AI Trajectory

null

{
  "EnableConfigs": [
    "TRANSPARENT_HUGEPAGE",
    "MIGRATION",
    "NUMA"
  ],
  "FocusSymbols": [
    "__alloc_pages_bulk_noprof",
    "alloc_migration_target",
    "collapse_run_pmd"
  ],
  "KMSANReasoning": "The patch refactors internal page allocator functions (`__folio_alloc_noprof` and `__alloc_pages_bulk_noprof`) to accept an `alloc_flags` argument rather than hardcoding `ALLOC_DEFAULT`. Existing callers (`khugepaged.c`, `migrate.c`) and wrappers (`alloc_pages_bulk_noprof`, `__folio_alloc_node_noprof`) are updated to explicitly pass `ALLOC_DEFAULT`. In `__alloc_pages_bulk_noprof`, `struct alloc_context ac` is initialized via designated initializer (`{ .alloc_flags = alloc_flags }`), which actually guarantees zero-initialization of remaining fields.\n\nNo kernel structures are copied or exposed to userspace, no conditional logic relies on uninitialized data, and page zeroing / init_on_alloc semantics are unchanged. Potential regressions from these changes (e.g. incorrect allocation watermarks, GFP flag handling, or NULL dereferences on allocation failure) are addressed by standard kernel debugging assertions, LOCKDEP, and KASAN. There are no uninitialized memory usage or info-leak risks requiring a dedicated KMSAN session.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch refactors core memory management functions in mm/page_alloc.c, mm/khugepaged.c, and mm/migrate.c. It extends __folio_alloc_noprof and alloc_pages_bulk_noprof to accept explicit alloc_flags, altering watermark checking and fallback allocation in __alloc_pages_bulk_noprof. These paths are reachable from userspace via page migration syscalls (e.g. migrate_pages, move_pages), madvise(MADV_COLLAPSE), and bulk allocation operations (e.g. splice).",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 4517e1ab346bb79c2dedf83e439ae3553b6c3a1d\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Mon Sep 14 20:22:44 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/include/linux/gfp.h b/include/linux/gfp.h\nindex 872bc53f32ec8..a327e58c313f8 100644\n--- a/include/linux/gfp.h\n+++ b/include/linux/gfp.h\n@@ -204,10 +204,6 @@ static inline void arch_free_page(struct page *page, int order) { }\n static inline void arch_alloc_page(struct page *page, int order) { }\n #endif\n \n-struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n-\t\tnodemask_t *nodemask);\n-#define __folio_alloc(...)\t\t\talloc_hooks(__folio_alloc_noprof(__VA_ARGS__))\n-\n unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n \t\t\t\tnodemask_t *nodemask, int nr_pages,\n \t\t\t\tstruct page **page_array);\n@@ -252,14 +248,7 @@ static inline void warn_if_node_offline(int this_node, gfp_t gfp_mask)\n \tdump_stack();\n }\n \n-static inline\n-struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid)\n-{\n-\twarn_if_node_offline(nid, gfp);\n-\n-\treturn __folio_alloc_noprof(gfp, order, nid, NULL);\n-}\n-\n+struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid);\n #define  __folio_alloc_node(...)\t\talloc_hooks(__folio_alloc_node_noprof(__VA_ARGS__))\n \n /*\ndiff --git a/mm/khugepaged.c b/mm/khugepaged.c\nindex 0d8cd44b14c57..431c2e610b392 100644\n--- a/mm/khugepaged.c\n+++ b/mm/khugepaged.c\n@@ -1193,7 +1193,7 @@ static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_stru\n \tint node = collapse_find_target_node(cc);\n \tstruct folio *folio;\n \n-\tfolio = __folio_alloc(gfp, order, node, \u0026cc-\u003ealloc_nmask);\n+\tfolio = __folio_alloc(gfp, order, node, \u0026cc-\u003ealloc_nmask, ALLOC_DEFAULT);\n \tif (!folio) {\n \t\t*foliop = NULL;\n \t\tcount_collapse_event(order, THP_COLLAPSE_ALLOC_FAILED,\ndiff --git a/mm/migrate.c b/mm/migrate.c\nindex 7e3a81f069744..8e1c25a6f7505 100644\n--- a/mm/migrate.c\n+++ b/mm/migrate.c\n@@ -2229,7 +2229,7 @@ struct folio *alloc_migration_target(struct folio *src, unsigned long private)\n \tif (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE)\n \t\tgfp_mask |= __GFP_HIGHMEM;\n \n-\treturn __folio_alloc(gfp_mask, order, nid, mtc-\u003enmask);\n+\treturn __folio_alloc(gfp_mask, order, nid, mtc-\u003enmask, ALLOC_DEFAULT);\n }\n \n #ifdef CONFIG_NUMA_MIGRATION\ndiff --git a/mm/page_alloc.c b/mm/page_alloc.c\nindex d977b8bf7245a..f4ceec8cf77e0 100644\n--- a/mm/page_alloc.c\n+++ b/mm/page_alloc.c\n@@ -5151,8 +5151,8 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\n  * @page_array were set to %NULL on entry, the slots from 0 to the return value\n  * - 1 will be filled.\n  */\n-unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n-\t\t\tnodemask_t *nodemask, int nr_pages,\n+unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\n+\t\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n \t\t\tstruct page **page_array)\n {\n \tstruct page *page;\n@@ -5160,8 +5160,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n \tstruct zoneref *z;\n \tstruct per_cpu_pages *pcp;\n \tstruct list_head *pcp_list;\n-\tstruct alloc_context ac;\n-\tunsigned int alloc_flags = ALLOC_WMARK_LOW;\n+\tstruct alloc_context ac = { .alloc_flags = alloc_flags };\n+\tunsigned int fastpath_alloc_flags = alloc_flags | ALLOC_WMARK_LOW;\n \tint nr_populated = 0, nr_account = 0;\n \n \t/*\n@@ -5202,7 +5202,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n \t/* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */\n \tgfp \u0026= gfp_allowed_mask;\n \tgfp = current_gfp_context(gfp);\n-\tif (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, \u0026ac, \u0026gfp, \u0026alloc_flags))\n+\tif (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, \u0026ac, \u0026gfp, \u0026fastpath_alloc_flags))\n \t\tgoto out;\n \n \t/* Find an allowed local zone that meets the low watermark. */\n@@ -5210,7 +5210,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n \tfor_next_zone_zonelist_nodemask(zone, z, ac.highest_zoneidx, ac.nodemask) {\n \t\tunsigned long mark;\n \n-\t\tif (cpusets_enabled() \u0026\u0026 (alloc_flags \u0026 ALLOC_CPUSET) \u0026\u0026\n+\t\tif (cpusets_enabled() \u0026\u0026 (fastpath_alloc_flags \u0026 ALLOC_CPUSET) \u0026\u0026\n \t\t    !__cpuset_zone_allowed(zone, gfp)) {\n \t\t\tcontinue;\n \t\t}\n@@ -5220,16 +5220,17 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n \t\t\tgoto failed;\n \t\t}\n \n-\t\tcond_accept_memory(zone, 0, alloc_flags);\n+\t\tcond_accept_memory(zone, 0, fastpath_alloc_flags);\n retry_this_zone:\n-\t\tmark = wmark_pages(zone, alloc_flags \u0026 ALLOC_WMARK_MASK) + nr_pages - nr_populated;\n+\t\tmark = wmark_pages(zone, fastpath_alloc_flags \u0026 ALLOC_WMARK_MASK) +\n+\t\t       nr_pages - nr_populated;\n \t\tif (zone_watermark_fast(zone, 0,  mark,\n \t\t\t\tzonelist_zone_idx(ac.preferred_zoneref),\n-\t\t\t\talloc_flags, gfp)) {\n+\t\t\t\tfastpath_alloc_flags, gfp)) {\n \t\t\tbreak;\n \t\t}\n \n-\t\tif (cond_accept_memory(zone, 0, alloc_flags))\n+\t\tif (cond_accept_memory(zone, 0, fastpath_alloc_flags))\n \t\t\tgoto retry_this_zone;\n \n \t\t/* Try again if zone has deferred pages */\n@@ -5261,7 +5262,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n \t\t\tcontinue;\n \t\t}\n \n-\t\tpage = __rmqueue_pcplist(zone, 0, ac.migratetype, alloc_flags,\n+\t\tpage = __rmqueue_pcplist(zone, 0, ac.migratetype, fastpath_alloc_flags,\n \t\t\t\t\t\t\t\tpcp, pcp_list);\n \t\tif (unlikely(!page)) {\n \t\t\t/* Try and allocate at least one page */\n@@ -5289,11 +5290,19 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n \treturn nr_populated;\n \n failed:\n-\tpage = __alloc_pages_noprof(gfp, 0, preferred_nid, nodemask, ALLOC_DEFAULT);\n+\tpage = __alloc_pages_noprof(gfp, 0, preferred_nid, nodemask, alloc_flags);\n \tif (page)\n \t\tpage_array[nr_populated++] = page;\n \tgoto out;\n }\n+\n+unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n+\t\t\tnodemask_t *nodemask, int nr_pages,\n+\t\t\tstruct page **page_array)\n+{\n+\treturn __alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid,\n+\t\t\t\t\t nodemask, nr_pages, page_array);\n+}\n EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);\n \n /*\n@@ -5484,13 +5493,20 @@ struct page *alloc_pages_node_noprof(int nid, gfp_t gfp_mask, unsigned int order\n EXPORT_SYMBOL(alloc_pages_node_noprof);\n \n struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n-\t\tnodemask_t *nodemask)\n+\t\tnodemask_t *nodemask, unsigned int alloc_flags)\n {\n \tstruct page *page = __alloc_pages_noprof(gfp | __GFP_COMP, order,\n-\t\t\t\t\tpreferred_nid, nodemask, ALLOC_DEFAULT);\n+\t\t\t\t\tpreferred_nid, nodemask, alloc_flags);\n \treturn page_rmappable_folio(page);\n }\n-EXPORT_SYMBOL(__folio_alloc_noprof);\n+\n+struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid)\n+{\n+\twarn_if_node_offline(nid, gfp);\n+\n+\treturn __folio_alloc_noprof(gfp, order, nid, NULL, ALLOC_DEFAULT);\n+}\n+EXPORT_SYMBOL(__folio_alloc_node_noprof);\n \n /*\n  * Common helper functions. Never use with __GFP_HIGHMEM because the returned\ndiff --git a/mm/page_alloc.h b/mm/page_alloc.h\nindex b9259deddb59d..23fc79ce97b60 100644\n--- a/mm/page_alloc.h\n+++ b/mm/page_alloc.h\n@@ -258,6 +258,14 @@ struct page *__alloc_pages_noprof(gfp_t gfp, unsigned int order, int preferred_n\n \t\tnodemask_t *nodemask, unsigned int alloc_flags);\n #define __alloc_pages(...)\t\t\talloc_hooks(__alloc_pages_noprof(__VA_ARGS__))\n \n+struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n+\t\tnodemask_t *nodemask, unsigned int alloc_flags);\n+#define __folio_alloc(...)\t\t\talloc_hooks(__folio_alloc_noprof(__VA_ARGS__))\n+\n+unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\n+\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n+\t\tstruct page **page_array);\n+\n extern void zone_pcp_reset(struct zone *zone);\n extern void zone_pcp_disable(struct zone *zone);\n extern void zone_pcp_enable(struct zone *zone);\n"
}

core

null

{
  "EnableConfigs": [
    "TRANSPARENT_HUGEPAGE",
    "MIGRATION",
    "NUMA"
  ],
  "FocusSymbols": [
    "__alloc_pages_bulk_noprof",
    "alloc_migration_target",
    "collapse_run_pmd"
  ],
  "Reasoning": "The patch refactors core memory management functions in mm/page_alloc.c, mm/khugepaged.c, and mm/migrate.c. It extends __folio_alloc_noprof and alloc_pages_bulk_noprof to accept explicit alloc_flags, altering watermark checking and fallback allocation in __alloc_pages_bulk_noprof. These paths are reachable from userspace via page migration syscalls (e.g. migrate_pages, move_pages), madvise(MADV_COLLAPSE), and bulk allocation operations (e.g. splice).",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer and security engineer.
Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on internal assumptions. You must actively use your code access
tools to inspect the actual source code, callers, and surrounding context.

================================================================================
1. CORE TRIAGE PHILOSOPHY
================================================================================
The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs,
and newly triggered assertions introduced by the patch series.

- REACHABILITY IS THE PRIMARY GATE:
  Fuzzing can only discover bugs in code that can actually execute in standard virtualized
  environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap).
  If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed,
  regardless of whether it adds assertions or complex logic.

- DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS:
  Patch authors routinely label changes as "cleanups", "refactorings", or state
  "No functional change intended". Do NOT take these claims at face value.
  Code refactorings that rearrange logic, introduce helper functions, or alter state management
  in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs.
  If reachable executable code is modified or refactored, it MUST be fuzzed.

- NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED:
  When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON*, VM_WARN_ON*,
  BUG_ON*, lockdep_assert*) in reachable code paths, it enforces new or stricter invariants.
  Even if the author believes the invariant always holds, fuzzing is essential to verify whether
  an unusual sequence of operations can violate it.

================================================================================
2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA)
================================================================================
Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories:

- Non-kernel and non-executable changes:
  * Modifications to Documentation/, comments, or spelling fixes.
  * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/)
    that do not affect the compiled kernel image (vmlinux) or kernel modules.
  * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints
    that do not alter control flow or data structures.
  * Build system or Kconfig changes that do not alter compiled C logic.
- Structurally unreachable hardware:
  * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed,
    ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU.
- Unreachable execution paths:
  * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during
    physical PCI hot-unplug or manual sysfs driver unbinding.
  * Code paths exclusive to architectures other than the target architecture.

================================================================================
3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA)
================================================================================
Return WorthFuzzing=true whenever the patch touches reachable executable code, including:
- Core Subsystems:
  * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/),
    BPF, scheduler, core networking, VFS, or syscall handling.
- Refactorings and Code Cleanups:
  * Any restructuring of reachable data structures, helper abstractions, or algorithm flows.
- Runtime Assertions and Defensive Checks:
  * Any introduction or alteration of assertions (WARN_ON*, VM_WARN_ON*, BUG_ON*, etc.) in reachable paths.
- Reachable Drivers and Protocols:
  * Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.).

================================================================================
4. EXTRACTING FocusSymbols (PREVENTING DILUTION)
================================================================================
When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer:

- AVOID UBIQUITOUS LIFECYCLE HOT-PATHS:
  Do NOT list generic, ubiquitous functions called by almost every program in the corpus
  (including, but not limited to: general memory allocators and deallocators, page fault
  and trap handlers, or core synchronization primitives; this is not an exhaustive list).
  Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused",
  which severely dilutes fuzzing effort away from the actual changes.

- TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS:
  List functions that specifically implement the logic being added or altered, or direct API entrypoints
  for the subsystem feature under review.

- HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h):
  Compiler-inlined static functions (such as static inlines in mm/*.h or include/linux/*.h) lack
  distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters.
  If the changes are primarily in static inline helpers, identify non-static, feature-specific caller
  functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers).

================================================================================
5. IDENTIFYING EnableConfigs
================================================================================
Identify any specific CONFIG_ options required to properly compile and reach the modified code:
- Inspect Kconfig files and #ifdef guards; do not make assumptions.
- Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed.
- Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit 4517e1ab346bb79c2dedf83e439ae3553b6c3a1d
Author: syz-cluster <triage@syzkaller.com>
Date:   Mon Sep 14 20:22:44 2026 +0000

    syz-cluster: applied patch under review

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 872bc53f32ec8..a327e58c313f8 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -204,10 +204,6 @@ static inline void arch_free_page(struct page *page, int order) { }
 static inline void arch_alloc_page(struct page *page, int order) { }
 #endif
 
-struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,
-		nodemask_t *nodemask);
-#define __folio_alloc(...)			alloc_hooks(__folio_alloc_noprof(__VA_ARGS__))
-
 unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 				nodemask_t *nodemask, int nr_pages,
 				struct page **page_array);
@@ -252,14 +248,7 @@ static inline void warn_if_node_offline(int this_node, gfp_t gfp_mask)
 	dump_stack();
 }
 
-static inline
-struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid)
-{
-	warn_if_node_offline(nid, gfp);
-
-	return __folio_alloc_noprof(gfp, order, nid, NULL);
-}
-
+struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid);
 #define  __folio_alloc_node(...)		alloc_hooks(__folio_alloc_node_noprof(__VA_ARGS__))
 
 /*
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 0d8cd44b14c57..431c2e610b392 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1193,7 +1193,7 @@ static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_stru
 	int node = collapse_find_target_node(cc);
 	struct folio *folio;
 
-	folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask);
+	folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask, ALLOC_DEFAULT);
 	if (!folio) {
 		*foliop = NULL;
 		count_collapse_event(order, THP_COLLAPSE_ALLOC_FAILED,
diff --git a/mm/migrate.c b/mm/migrate.c
index 7e3a81f069744..8e1c25a6f7505 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2229,7 +2229,7 @@ struct folio *alloc_migration_target(struct folio *src, unsigned long private)
 	if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE)
 		gfp_mask |= __GFP_HIGHMEM;
 
-	return __folio_alloc(gfp_mask, order, nid, mtc->nmask);
+	return __folio_alloc(gfp_mask, order, nid, mtc->nmask, ALLOC_DEFAULT);
 }
 
 #ifdef CONFIG_NUMA_MIGRATION
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d977b8bf7245a..f4ceec8cf77e0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5151,8 +5151,8 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
  * @page_array were set to %NULL on entry, the slots from 0 to the return value
  * - 1 will be filled.
  */
-unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
-			nodemask_t *nodemask, int nr_pages,
+unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,
+			int preferred_nid, nodemask_t *nodemask, int nr_pages,
 			struct page **page_array)
 {
 	struct page *page;
@@ -5160,8 +5160,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	struct zoneref *z;
 	struct per_cpu_pages *pcp;
 	struct list_head *pcp_list;
-	struct alloc_context ac;
-	unsigned int alloc_flags = ALLOC_WMARK_LOW;
+	struct alloc_context ac = { .alloc_flags = alloc_flags };
+	unsigned int fastpath_alloc_flags = alloc_flags | ALLOC_WMARK_LOW;
 	int nr_populated = 0, nr_account = 0;
 
 	/*
@@ -5202,7 +5202,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	/* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */
 	gfp &= gfp_allowed_mask;
 	gfp = current_gfp_context(gfp);
-	if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &gfp, &alloc_flags))
+	if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &gfp, &fastpath_alloc_flags))
 		goto out;
 
 	/* Find an allowed local zone that meets the low watermark. */
@@ -5210,7 +5210,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	for_next_zone_zonelist_nodemask(zone, z, ac.highest_zoneidx, ac.nodemask) {
 		unsigned long mark;
 
-		if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) &&
+		if (cpusets_enabled() && (fastpath_alloc_flags & ALLOC_CPUSET) &&
 		    !__cpuset_zone_allowed(zone, gfp)) {
 			continue;
 		}
@@ -5220,16 +5220,17 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 			goto failed;
 		}
 
-		cond_accept_memory(zone, 0, alloc_flags);
+		cond_accept_memory(zone, 0, fastpath_alloc_flags);
 retry_this_zone:
-		mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages - nr_populated;
+		mark = wmark_pages(zone, fastpath_alloc_flags & ALLOC_WMARK_MASK) +
+		       nr_pages - nr_populated;
 		if (zone_watermark_fast(zone, 0,  mark,
 				zonelist_zone_idx(ac.preferred_zoneref),
-				alloc_flags, gfp)) {
+				fastpath_alloc_flags, gfp)) {
 			break;
 		}
 
-		if (cond_accept_memory(zone, 0, alloc_flags))
+		if (cond_accept_memory(zone, 0, fastpath_alloc_flags))
 			goto retry_this_zone;
 
 		/* Try again if zone has deferred pages */
@@ -5261,7 +5262,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 			continue;
 		}
 
-		page = __rmqueue_pcplist(zone, 0, ac.migratetype, alloc_flags,
+		page = __rmqueue_pcplist(zone, 0, ac.migratetype, fastpath_alloc_flags,
 								pcp, pcp_list);
 		if (unlikely(!page)) {
 			/* Try and allocate at least one page */
@@ -5289,11 +5290,19 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	return nr_populated;
 
 failed:
-	page = __alloc_pages_noprof(gfp, 0, preferred_nid, nodemask, ALLOC_DEFAULT);
+	page = __alloc_pages_noprof(gfp, 0, preferred_nid, nodemask, alloc_flags);
 	if (page)
 		page_array[nr_populated++] = page;
 	goto out;
 }
+
+unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
+			nodemask_t *nodemask, int nr_pages,
+			struct page **page_array)
+{
+	return __alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid,
+					 nodemask, nr_pages, page_array);
+}
 EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
 
 /*
@@ -5484,13 +5493,20 @@ struct page *alloc_pages_node_noprof(int nid, gfp_t gfp_mask, unsigned int order
 EXPORT_SYMBOL(alloc_pages_node_noprof);
 
 struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,
-		nodemask_t *nodemask)
+		nodemask_t *nodemask, unsigned int alloc_flags)
 {
 	struct page *page = __alloc_pages_noprof(gfp | __GFP_COMP, order,
-					preferred_nid, nodemask, ALLOC_DEFAULT);
+					preferred_nid, nodemask, alloc_flags);
 	return page_rmappable_folio(page);
 }
-EXPORT_SYMBOL(__folio_alloc_noprof);
+
+struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid)
+{
+	warn_if_node_offline(nid, gfp);
+
+	return __folio_alloc_noprof(gfp, order, nid, NULL, ALLOC_DEFAULT);
+}
+EXPORT_SYMBOL(__folio_alloc_node_noprof);
 
 /*
  * Common helper functions. Never use with __GFP_HIGHMEM because the returned
diff --git a/mm/page_alloc.h b/mm/page_alloc.h
index b9259deddb59d..23fc79ce97b60 100644
--- a/mm/page_alloc.h
+++ b/mm/page_alloc.h
@@ -258,6 +258,14 @@ struct page *__alloc_pages_noprof(gfp_t gfp, unsigned int order, int preferred_n
 		nodemask_t *nodemask, unsigned int alloc_flags);
 #define __alloc_pages(...)			alloc_hooks(__alloc_pages_noprof(__VA_ARGS__))
 
+struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,
+		nodemask_t *nodemask, unsigned int alloc_flags);
+#define __folio_alloc(...)			alloc_hooks(__folio_alloc_noprof(__VA_ARGS__))
+
+unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,
+		int preferred_nid, nodemask_t *nodemask, int nr_pages,
+		struct page **page_array);
+
 extern void zone_pcp_reset(struct zone *zone);
 extern void zone_pcp_disable(struct zone *zone);
 extern void zone_pcp_enable(struct zone *zone);

gemini-3.8-flash

null

null

							input: 5786
							output: 24
							thoughts: 220
						

**Analyzing a Kernel Patch Series**

Okay, so I'm presented with a patch series integrated as a HEAD commit in the kernel workspace. My immediate instinct, of course, is to dive in and understand the impact. First, I need to get a handle on the changes themselves. I can’t just blindly accept this.

Let's start by inspecting the provided diff, which, from the looks of it, touches `include/linux/gfp.h`, `mm/khugepaged.c`, `mm/migrate.c`, `mm/page_alloc.c`, and `mm/page_alloc.h`. That alone tells me we're looking at memory management code, which is always interesting. This involves potentially complex interdependencies. Now, I need more context.

The next thing I would do is examine the commit log. I would ideally use `git log -1` to view the most recent commit. I think I'll try using grepper, or read-file. I'll need to figure out which tool is most appropriate here to retrieve the message; let's see which tools are actually available. Looks like I have grepper, codesearch-dir-index, read-file, and set-results at my disposal. Great.

I need to understand *why* these changes were made. So, I will use `grepper` or maybe `read-file` to search within the commit message and within the changed files to see if I can understand the purpose of these alterations, along with any relevant rationale. This will give me a proper starting point for a deeper analysis.

{
  "Expression": "__alloc_pages_bulk_noprof"
}

{
  "Output": "mm/page_alloc.c=5085=static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-5153- */\nmm/page_alloc.c:5154:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.c-5155-\t\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n--\nmm/page_alloc.c=5299=unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n--\nmm/page_alloc.c-5302-{\nmm/page_alloc.c:5303:\treturn __alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid,\nmm/page_alloc.c-5304-\t\t\t\t\t nodemask, nr_pages, page_array);\n--\nmm/page_alloc.h=261=struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n--\nmm/page_alloc.h-264-\nmm/page_alloc.h:265:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.h-266-\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n"
}

gemini-3.8-flash

null

null

							input: 6761
							output: 20
							thoughts: 25
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Investigating Memory Allocation Callers**

Alright, a moment of curiosity has struck. I'm wondering about the upstream callers of `__alloc_pages_bulk` and `__folio_alloc`. These are pretty fundamental memory allocation functions, and knowing *who* is requesting this level of allocation is crucial for understanding memory management behavior and potential bottlenecks. Time to delve into the code and trace the call paths. Let's see what the audit reveals.

{
  "Expression": "__alloc_pages_bulk"
}

{
  "Output": "include/linux/gfp.h=207=unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n--\ninclude/linux/gfp.h-209-\t\t\t\tstruct page **page_array);\ninclude/linux/gfp.h:210:#define __alloc_pages_bulk(...)\t\t\talloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-211-\n--\ninclude/linux/gfp.h=214=unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\n--\ninclude/linux/gfp.h-221-#define alloc_pages_bulk(_gfp, _nr_pages, _page_array)\t\t\\\ninclude/linux/gfp.h:222:\t__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _page_array)\ninclude/linux/gfp.h-223-\n--\nmm/kasan/shadow.c=327=static void ___free_pages_bulk(struct page **pages, int nr_pages)\n--\nmm/kasan/shadow.c-338-\nmm/kasan/shadow.c:339:static int ___alloc_pages_bulk(struct page **pages, int nr_pages, gfp_t gfp_mask)\nmm/kasan/shadow.c-340-{\n--\nmm/kasan/shadow.c=357=static int __kasan_populate_vmalloc_do(unsigned long start, unsigned long end, gfp_t gfp_mask)\n--\nmm/kasan/shadow.c-369-\t\tnr_pages = min(nr_total, PAGE_SIZE / sizeof(data.pages[0]));\nmm/kasan/shadow.c:370:\t\tret = ___alloc_pages_bulk(data.pages, nr_pages, gfp_mask);\nmm/kasan/shadow.c-371-\t\tif (ret)\n--\nmm/mempolicy.c=2659=static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,\n--\nmm/mempolicy.c-2697-\t\tnode_pages = min(rem_pages, weight);\nmm/mempolicy.c:2698:\t\tnr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,\nmm/mempolicy.c-2699-\t\t\t\t\t\t  page_array);\n--\nmm/mempolicy.c-2727-\t/*\nmm/mempolicy.c:2728:\t * Calculate rounds/partial rounds to minimize __alloc_pages_bulk calls.\nmm/mempolicy.c-2729-\t * Track which node weighted interleave should resume from.\n--\nmm/mempolicy.c-2761-\t\tnode_pages = min(node_pages, nr_pages - total_allocated);\nmm/mempolicy.c:2762:\t\tnr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,\nmm/mempolicy.c-2763-\t\t\t\t\t\t  page_array);\n--\nmm/page_alloc.c=5085=static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-5133-/*\nmm/page_alloc.c:5134: * __alloc_pages_bulk - Allocate a number of order-0 pages to an array\nmm/page_alloc.c-5135- * @gfp: GFP flags for the allocation\n--\nmm/page_alloc.c-5153- */\nmm/page_alloc.c:5154:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.c-5155-\t\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n--\nmm/page_alloc.c=5299=unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n--\nmm/page_alloc.c-5302-{\nmm/page_alloc.c:5303:\treturn __alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid,\nmm/page_alloc.c-5304-\t\t\t\t\t nodemask, nr_pages, page_array);\n--\nmm/page_alloc.h=261=struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n--\nmm/page_alloc.h-264-\nmm/page_alloc.h:265:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.h-266-\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n"
}

gemini-3.8-flash

null

null

							input: 8165
							output: 36
							thoughts: 75
						

Here's my summary, as though I'm thinking through this code:

**Diving into `alloc_pages_bulk`**

Okay, hold on a second. Something doesn't feel quite right about this. Let's dig deeper. I need to understand exactly what `alloc_pages_bulk` is doing behind the scenes. Right, the macro expansion. First things first, let's pull up `include/linux/gfp.h`, specifically around lines 200-240. I'm guessing there's some cleverness here with the allocation hooks. I need to understand if there is a use of the `__alloc_pages_bulk` macro here, how it is expanded, and any overhead the `alloc_hooks` macro might introduce in terms of performance. It will also be worthwhile to understand what `alloc_pages_bulk_noprof` is doing. This might expose some interesting optimization opportunities if the hooks prove to be the bottleneck.

{
  "File": "include/linux/gfp.h",
  "FirstLine": 195,
  "LineCount": 50
}

{
  "Contents": " 195:\tstatic inline struct zonelist *node_zonelist(int nid, gfp_t flags)\n 196:\t{\n 197:\t\treturn NODE_DATA(nid)-\u003enode_zonelists + gfp_zonelist(flags);\n 198:\t}\n 199:\t\n 200:\t#ifndef HAVE_ARCH_FREE_PAGE\n 201:\tstatic inline void arch_free_page(struct page *page, int order) { }\n 202:\t#endif\n 203:\t#ifndef HAVE_ARCH_ALLOC_PAGE\n 204:\tstatic inline void arch_alloc_page(struct page *page, int order) { }\n 205:\t#endif\n 206:\t\n 207:\tunsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n 208:\t\t\t\t\tnodemask_t *nodemask, int nr_pages,\n 209:\t\t\t\t\tstruct page **page_array);\n 210:\t#define __alloc_pages_bulk(...)\t\t\talloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))\n 211:\t\n 212:\tvoid free_pages_bulk(struct page **page_array, unsigned long nr_pages);\n 213:\t\n 214:\tunsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\n 215:\t\t\t\t\tunsigned long nr_pages,\n 216:\t\t\t\t\tstruct page **page_array);\n 217:\t#define  alloc_pages_bulk_mempolicy(...)\t\t\t\t\\\n 218:\t\talloc_hooks(alloc_pages_bulk_mempolicy_noprof(__VA_ARGS__))\n 219:\t\n 220:\t/* Bulk allocate order-0 pages */\n 221:\t#define alloc_pages_bulk(_gfp, _nr_pages, _page_array)\t\t\\\n 222:\t\t__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _page_array)\n 223:\t\n 224:\tstatic inline unsigned long\n 225:\talloc_pages_bulk_node_noprof(gfp_t gfp, int nid, unsigned long nr_pages,\n 226:\t\t\t\t\t   struct page **page_array)\n 227:\t{\n 228:\t\tif (nid == NUMA_NO_NODE)\n 229:\t\t\tnid = numa_mem_id();\n 230:\t\n 231:\t\treturn alloc_pages_bulk_noprof(gfp, nid, NULL, nr_pages, page_array);\n 232:\t}\n 233:\t\n 234:\t#define alloc_pages_bulk_node(...)\t\t\t\t\\\n 235:\t\talloc_hooks(alloc_pages_bulk_node_noprof(__VA_ARGS__))\n 236:\t\n 237:\tstatic inline void warn_if_node_offline(int this_node, gfp_t gfp_mask)\n 238:\t{\n 239:\t\tgfp_t warn_gfp = gfp_mask \u0026 (__GFP_THISNODE|__GFP_NOWARN);\n 240:\t\n 241:\t\tif (warn_gfp != (__GFP_THISNODE|__GFP_NOWARN))\n 242:\t\t\treturn;\n 243:\t\n 244:\t\tif (node_online(this_node))\n"
}

gemini-3.8-flash

null

null

							input: 9375
							output: 36
							thoughts: 25
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Diving into gfp.h**

Okay, I need a deeper understanding of memory allocation flags in the Linux kernel for this. Let's dig into the `include/linux/gfp.h` file, specifically lines 240-280. I expect to find some fundamental definitions and probably some critical context on how different memory zones and allocation strategies are handled. I'm hoping to refresh my memory on the interactions of allocation flags. I suspect this section will provide a concise overview.

{
  "File": "include/linux/gfp.h",
  "FirstLine": 240,
  "LineCount": 40
}

{
  "Contents": " 240:\t\n 241:\t\tif (warn_gfp != (__GFP_THISNODE|__GFP_NOWARN))\n 242:\t\t\treturn;\n 243:\t\n 244:\t\tif (node_online(this_node))\n 245:\t\t\treturn;\n 246:\t\n 247:\t\tpr_warn(\"%pGg allocation from offline node %d\\n\", \u0026gfp_mask, this_node);\n 248:\t\tdump_stack();\n 249:\t}\n 250:\t\n 251:\tstruct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid);\n 252:\t#define  __folio_alloc_node(...)\t\talloc_hooks(__folio_alloc_node_noprof(__VA_ARGS__))\n 253:\t\n 254:\t/*\n 255:\t * Allocate pages, preferring the node given as nid. When nid == NUMA_NO_NODE,\n 256:\t * prefer the current CPU's closest node. Otherwise node must be valid and\n 257:\t * online.\n 258:\t */\n 259:\tstruct page *alloc_pages_node_noprof(int nid, gfp_t gfp_mask, unsigned int order);\n 260:\t\n 261:\t#define  alloc_pages_node(...)\t\t\talloc_hooks(alloc_pages_node_noprof(__VA_ARGS__))\n 262:\t\n 263:\t#ifdef CONFIG_NUMA\n 264:\tstruct page *alloc_pages_noprof(gfp_t gfp, unsigned int order);\n 265:\tstruct folio *folio_alloc_noprof(gfp_t gfp, unsigned int order);\n 266:\tstruct folio *folio_alloc_mpol_noprof(gfp_t gfp, unsigned int order,\n 267:\t\t\tstruct mempolicy *mpol, pgoff_t ilx, int nid);\n 268:\tstruct folio *vma_alloc_folio_noprof(gfp_t gfp, int order, struct vm_area_struct *vma,\n 269:\t\t\tunsigned long addr);\n 270:\t#else\n 271:\tstatic inline struct page *alloc_pages_noprof(gfp_t gfp_mask, unsigned int order)\n 272:\t{\n 273:\t\treturn alloc_pages_node_noprof(numa_node_id(), gfp_mask, order);\n 274:\t}\n 275:\tstatic inline struct folio *folio_alloc_noprof(gfp_t gfp, unsigned int order)\n 276:\t{\n 277:\t\treturn __folio_alloc_node_noprof(gfp, order, numa_node_id());\n 278:\t}\n 279:\tstatic inline struct folio *folio_alloc_mpol_noprof(gfp_t gfp, unsigned int order,\n"
}

gemini-3.8-flash

null

null

							input: 10335
							output: 19
							thoughts: 371
						

**Analyzing the Folio Allocation Change**

Okay, let's dive in. I'm seeing a change in `include/linux/gfp.h`. Specifically, the removal of `__folio_alloc_noprof` and its associated macro `__folio_alloc`. Hmm, it looks like they've been moved, I see `mm/page_alloc.h`. That's an internal mm header, so I need to understand why this move was necessary.

Looking at `mm/page_alloc.h`, I immediately see the re-defined function and macro. But there's a crucial difference: `__folio_alloc_noprof` now takes an additional argument, `alloc_flags`!  The signature changed from four arguments to five. That's a key detail. What's `alloc_flags` used for, and how will that affect existing callers?

To understand the full impact, I need to know where `__folio_alloc` was used *before* this change. I'll need to run a grep across the entire codebase to identify all the calls to `__folio_alloc(`. That will show me everything that's affected by the change in the argument list and the move. This should give me a better understanding of the rationale behind the change and what modifications need to be made to ensure compatibility and that there are no regressions.

{
  "Expression": "__folio_alloc\\("
}

{
  "Output": "mm/khugepaged.c=1189=static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,\n--\nmm/khugepaged.c-1195-\nmm/khugepaged.c:1196:\tfolio = __folio_alloc(gfp, order, node, \u0026cc-\u003ealloc_nmask, ALLOC_DEFAULT);\nmm/khugepaged.c-1197-\tif (!folio) {\n--\nmm/migrate.c=2196=struct folio *alloc_migration_target(struct folio *src, unsigned long private)\n--\nmm/migrate.c-2231-\nmm/migrate.c:2232:\treturn __folio_alloc(gfp_mask, order, nid, mtc-\u003enmask, ALLOC_DEFAULT);\nmm/migrate.c-2233-}\n--\nmm/page_alloc.h=261=struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\nmm/page_alloc.h-262-\t\tnodemask_t *nodemask, unsigned int alloc_flags);\nmm/page_alloc.h:263:#define __folio_alloc(...)\t\t\talloc_hooks(__folio_alloc_noprof(__VA_ARGS__))\nmm/page_alloc.h-264-\n"
}

gemini-3.8-flash

null

null

							input: 11366
							output: 20
							thoughts: 73
						

Here's my thinking process:

**Diving Deep into Folio Allocation**

Okay, so `__folio_alloc` is definitely a key function. My initial thought is, "Where the heck is this used?" I remember seeing it primarily in `mm/khugepaged.c` and `mm/migrate.c`. And, of course, the ever-present `mm/page_alloc.c`, specifically the `__folio_alloc_node_noprof` variant. That's a good starting point, but I need to be absolutely thorough.

This prompts a deeper dive. I have to verify that that's *all* of the places it's used. The natural next step is to use my tools to comprehensively check *all* the callers of `__folio_alloc_node` . Gotta make sure I'm not missing any subtle uses or edge cases that might be tucked away somewhere unexpected. This will give me the complete picture, and then I can really start to understand its complete role.

{
  "Expression": "__folio_alloc_node"
}

{
  "Output": "drivers/iommu/iommu-pages.c=43=void *iommu_alloc_pages_node_sz(int nid, gfp_t gfp, size_t size)\n--\ndrivers/iommu/iommu-pages.c-59-\t/*\ndrivers/iommu/iommu-pages.c:60:\t * __folio_alloc_node() does not handle NUMA_NO_NODE like\ndrivers/iommu/iommu-pages.c-61-\t * alloc_pages_node() did.\n--\ndrivers/iommu/iommu-pages.c-65-\ndrivers/iommu/iommu-pages.c:66:\tfolio = __folio_alloc_node(gfp | __GFP_ZERO, order, nid);\ndrivers/iommu/iommu-pages.c-67-\tif (unlikely(!folio))\n--\ndrivers/irqchip/irq-loongarch-ir.c=381=static int redirect_table_init(struct redirect_desc *irde)\n--\ndrivers/irqchip/irq-loongarch-ir.c-386-\ndrivers/irqchip/irq-loongarch-ir.c:387:\tfolio = __folio_alloc_node(GFP_KERNEL | __GFP_ZERO, IRD_TABLE_PAGE_ORDER, irde-\u003enode);\ndrivers/irqchip/irq-loongarch-ir.c-388-\tif (!folio) {\n--\ndrivers/irqchip/irq-loongarch-ir.c=408=static int redirect_queue_init(struct redirect_desc *irde)\n--\ndrivers/irqchip/irq-loongarch-ir.c-412-\ndrivers/irqchip/irq-loongarch-ir.c:413:\tfolio = __folio_alloc_node(GFP_KERNEL | __GFP_ZERO, INV_QUEUE_PAGE_ORDER, irde-\u003enode);\ndrivers/irqchip/irq-loongarch-ir.c-414-\tif (!folio) {\n--\ninclude/linux/gfp.h=237=static inline void warn_if_node_offline(int this_node, gfp_t gfp_mask)\n--\ninclude/linux/gfp.h-250-\ninclude/linux/gfp.h:251:struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid);\ninclude/linux/gfp.h:252:#define  __folio_alloc_node(...)\t\talloc_hooks(__folio_alloc_node_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-253-\n--\ninclude/linux/gfp.h=275=static inline struct folio *folio_alloc_noprof(gfp_t gfp, unsigned int order)\ninclude/linux/gfp.h-276-{\ninclude/linux/gfp.h:277:\treturn __folio_alloc_node_noprof(gfp, order, numa_node_id());\ninclude/linux/gfp.h-278-}\n--\nmm/filemap.c=999=struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order,\n--\nmm/filemap.c-1013-\t\t\tn = cpuset_mem_spread_node();\nmm/filemap.c:1014:\t\t\tfolio = __folio_alloc_node_noprof(gfp, order, n);\nmm/filemap.c-1015-\t\t} while (!folio \u0026\u0026 read_mems_allowed_retry(cpuset_mems_cookie));\n--\nmm/migrate.c=2668=static struct folio *alloc_misplaced_dst_folio(struct folio *src,\n--\nmm/migrate.c-2681-\t}\nmm/migrate.c:2682:\treturn __folio_alloc_node(gfp, order, nid);\nmm/migrate.c-2683-}\n--\nmm/page_alloc.c=5495=struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n--\nmm/page_alloc.c-5502-\nmm/page_alloc.c:5503:struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid)\nmm/page_alloc.c-5504-{\n--\nmm/page_alloc.c-5508-}\nmm/page_alloc.c:5509:EXPORT_SYMBOL(__folio_alloc_node_noprof);\nmm/page_alloc.c-5510-\n--\nnet/sunrpc/svc.c=623=svc_prepare_thread(struct svc_serv *serv, struct svc_pool *pool, int node)\n--\nnet/sunrpc/svc.c-635-\nnet/sunrpc/svc.c:636:\trqstp-\u003erq_scratch_folio = __folio_alloc_node(GFP_KERNEL, 0,\nnet/sunrpc/svc.c-637-\t\t\t\t\t\t     node == NUMA_NO_NODE ?\n"
}

gemini-3.8-flash

null

null

							input: 12977
							output: 36
							thoughts: 1201
						

**Analyzing the Memory Allocation Changes**

Okay, let's break down these memory allocation changes methodically. First, I need to understand the scope and implications here because there seem to be several subtle but important modifications.

1.  **`include/linux/gfp.h` and `mm/page_alloc.h`:** It looks like the commit moved `__folio_alloc_noprof` and `#define __folio_alloc` from `gfp.h` to `page_alloc.h`. That makes sense; these functions are fundamentally about page allocation, so centralizing them in `page_alloc.h` is logical for maintainability and clarity. The change to `__folio_alloc_node_noprof` is also interesting. It was previously inlined, but now it's declared in `gfp.h` and defined in `page_alloc.c`. And it now accepts additional `ALLOC_DEFAULT` argument when calling `__folio_alloc_noprof` and also has been `EXPORT_SYMBOL`

2.  **`mm/page_alloc.c` and `__folio_alloc_noprof`:** This is where things get more interesting. The introduction of `unsigned int alloc_flags` to `__folio_alloc_noprof` is a significant change. It looks like `__alloc_pages_noprof` will have the ability to receive the argument. Also, `EXPORT_SYMBOL(__folio_alloc_noprof)` was removed. This means the symbol is no longer visible outside the `mm` subsystem, likely indicating an intention to make it more internal. The calls in `khugepaged.c` and `migrate.c` now pass `ALLOC_DEFAULT`, which makes sense as it had been hardcoded inside `__folio_alloc_noprof` previously.

3.  **`mm/page_alloc.c` and `alloc_pages_bulk_noprof`:** Okay, here's another key area. `alloc_pages_bulk_noprof` is now a wrapper that calls `__alloc_pages_bulk_noprof`. It appears that `alloc_flags` is being introduced here, and a `struct alloc_context ac = { .alloc_flags = alloc_flags };` is now used within the function. Looking back, I need to confirm the change to `ac.alloc_flags`. Previously, `ac` was uninitialized before `prepare_alloc_pages`! This change might introduce subtle bugs if the logic surrounding its initialization and use hasn't been carefully considered. I definitely need to understand what `prepare_alloc_pages` is doing now and how it interacts with the newly introduced `alloc_flags`. Time to go read the code in `mm/page_alloc.c`.

{
  "File": "mm/page_alloc.c",
  "FirstLine": 5085,
  "LineCount": 55
}

{
  "Contents": "5085:\tstatic inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\n5086:\t\t\tint preferred_nid, nodemask_t *nodemask,\n5087:\t\t\tstruct alloc_context *ac, gfp_t *alloc_gfp,\n5088:\t\t\tunsigned int *alloc_flags)\n5089:\t{\n5090:\t\tac-\u003ehighest_zoneidx = gfp_zone(gfp_mask);\n5091:\t\tac-\u003ezonelist = node_zonelist(preferred_nid, gfp_mask);\n5092:\t\tac-\u003enodemask = nodemask;\n5093:\t\tac-\u003emigratetype = gfp_migratetype(gfp_mask);\n5094:\t\n5095:\t\tif (cpusets_enabled()) {\n5096:\t\t\t*alloc_gfp |= __GFP_HARDWALL;\n5097:\t\t\t/*\n5098:\t\t\t * When we are in the interrupt context, it is irrelevant\n5099:\t\t\t * to the current task context. It means that any node ok.\n5100:\t\t\t */\n5101:\t\t\tif (in_task() \u0026\u0026 !ac-\u003enodemask)\n5102:\t\t\t\tac-\u003enodemask = \u0026cpuset_current_mems_allowed;\n5103:\t\t\telse\n5104:\t\t\t\t*alloc_flags |= ALLOC_CPUSET;\n5105:\t\t}\n5106:\t\n5107:\t\tmight_alloc(gfp_mask);\n5108:\t\n5109:\t\t/*\n5110:\t\t * Don't invoke should_fail logic, since it may call\n5111:\t\t * get_random_u32() and printk() which need to spin_lock.\n5112:\t\t */\n5113:\t\tif (!(*alloc_flags \u0026 ALLOC_NOLOCK) \u0026\u0026\n5114:\t\t    should_fail_alloc_page(gfp_mask, order))\n5115:\t\t\treturn false;\n5116:\t\n5117:\t\t*alloc_flags |= alloc_flags_cma(gfp_mask);\n5118:\t\n5119:\t\t/* Dirty zone balancing only done in the fast path */\n5120:\t\tac-\u003espread_dirty_pages = (gfp_mask \u0026 __GFP_WRITE);\n5121:\t\n5122:\t\t/*\n5123:\t\t * The preferred zone is used for statistics but crucially it is\n5124:\t\t * also used as the starting point for the zonelist iterator. It\n5125:\t\t * may get reset for allocations that ignore memory policies.\n5126:\t\t */\n5127:\t\tac-\u003epreferred_zoneref = first_zones_zonelist(ac-\u003ezonelist,\n5128:\t\t\t\t\t\tac-\u003ehighest_zoneidx, ac-\u003enodemask);\n5129:\t\n5130:\t\treturn true;\n5131:\t}\n5132:\t\n5133:\t/*\n5134:\t * __alloc_pages_bulk - Allocate a number of order-0 pages to an array\n5135:\t * @gfp: GFP flags for the allocation\n5136:\t * @preferred_nid: The preferred NUMA node ID to allocate from\n5137:\t * @nodemask: Set of nodes to allocate from, may be NULL\n5138:\t * @nr_pages: The number of pages desired in the array\n5139:\t * @page_array: Array to store the pages\n"
}

gemini-3.8-flash

null

null

							input: 15716
							output: 19
							thoughts: 67
						

**Analyzing Allocation Context Flags**

Okay, let's break this down. I'm looking at `prepare_alloc_pages` and trying to understand its behavior regarding allocation flags. Specifically, I'm trying to figure out if it's setting `ac->alloc_flags`. From my knowledge, it *shouldn't* necessarily be doing that directly. I have to verify that. And, of course, the key question is whether or not `alloc_flags` even *exists* as a member of the `alloc_context` struct. This feels like an important detail I need to confirm; it would seem odd for the code to try and set a field that doesn't exist, and yet, it is a possibility. Time to consult the definition of `struct alloc_context`. I'll need to check the header files for its declaration, either `mm/internal.h` or `mm/page_alloc.h`. I'll confirm the structure and see what's actually going on. This is where the root of the problem will be uncovered!

bad expression: fatal: -e option, 'struct alloc_context {': Unmatched \{

{
  "Expression": "struct alloc_context {"
}

{
  "error": "bad expression: fatal: -e option, 'struct alloc_context {': Unmatched \\{"
}

gemini-3.8-flash

null

null

							input: 16057
							output: 18
							thoughts: 15
						

Here's my attempt at summarizing those thoughts, considering I'm an expert:

**Navigating the Allocation Labyrinth**

Okay, so I'm looking at something, probably some C or C++ code dealing with memory allocation. The immediate goal is to understand how allocations are happening, or perhaps trace a specific allocation failure. The brackets, `{`, are a common debugging signifier, and I often use them for searching inside of code, and that's likely where my mind went first, or is that not the right starting point, I should just go straight for the alloc_context struct search. Now I need to decide, what's a more effective search key word to get me where I need to go. Escape `{`... What am I trying to do, and is that the right path? Or just search `struct alloc_context`. I've got a specific idea, and I need to figure out the fastest way to the answer.

{
  "Expression": "struct alloc_context"
}

{
  "Output": "include/linux/compaction.h=23=enum compact_result {\n--\ninclude/linux/compaction.h-59-\ninclude/linux/compaction.h:60:struct alloc_context; /* in mm/internal.h */\ninclude/linux/compaction.h-61-struct capture_control; /* in mm/internal.h */\n--\ninclude/linux/compaction.h=89=extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,\ninclude/linux/compaction.h-90-\t\tunsigned int order, unsigned int alloc_flags,\ninclude/linux/compaction.h:91:\t\tconst struct alloc_context *ac, enum compact_priority prio,\ninclude/linux/compaction.h-92-\t\tstruct capture_control *capc);\n--\ninclude/linux/compaction.h=97=extern void compaction_defer_reset(struct zone *zone, int order,\n--\ninclude/linux/compaction.h-99-\ninclude/linux/compaction.h:100:bool compaction_zonelist_suitable(struct alloc_context *ac, int order,\ninclude/linux/compaction.h-101-\t\t\t\t\tint alloc_flags, gfp_t gfp_mask);\n--\nmm/compaction.c=2434=bool compaction_suitable(struct zone *zone, int order, unsigned long watermark,\n--\nmm/compaction.c-2478-/* Used by direct reclaimers */\nmm/compaction.c:2479:bool compaction_zonelist_suitable(struct alloc_context *ac, int order,\nmm/compaction.c-2480-\t\tint alloc_flags, gfp_t gfp_mask)\n--\nmm/compaction.c=2834=enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,\nmm/compaction.c:2835:\t\tunsigned int alloc_flags, const struct alloc_context *ac,\nmm/compaction.c-2836-\t\tenum compact_priority prio, struct capture_control *capc)\n--\nmm/page_alloc.c=3429=static void reserve_highatomic_pageblock(struct page *page, int order,\n--\nmm/page_alloc.c-3477- */\nmm/page_alloc.c:3478:static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,\nmm/page_alloc.c-3479-\t\t\t\t\t\tbool force)\n--\nmm/page_alloc.c=3782=get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,\nmm/page_alloc.c:3783:\t\t\t\t\t\tconst struct alloc_context *ac)\nmm/page_alloc.c-3784-{\n--\nmm/page_alloc.c=4007=__alloc_pages_cpuset_fallback(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c-4008-\t\t\t      unsigned int alloc_flags,\nmm/page_alloc.c:4009:\t\t\t      const struct alloc_context *ac)\nmm/page_alloc.c-4010-{\n--\nmm/page_alloc.c=4026=__alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4027:\tconst struct alloc_context *ac, unsigned long *did_some_progress)\nmm/page_alloc.c-4028-{\n--\nmm/page_alloc.c=4121=__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4122:\t\tunsigned int alloc_flags, const struct alloc_context *ac,\nmm/page_alloc.c-4123-\t\tenum compact_priority prio, enum compact_result *compact_result)\n--\nmm/page_alloc.c=4229=static inline bool\nmm/page_alloc.c:4230:should_compact_retry(gfp_t gfp_mask, struct alloc_context *ac, int order,\nmm/page_alloc.c-4231-\t\t     int alloc_flags,\n--\nmm/page_alloc.c=4298=__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4299:\t\tunsigned int alloc_flags, const struct alloc_context *ac,\nmm/page_alloc.c-4300-\t\tenum compact_priority prio, enum compact_result *compact_result)\n--\nmm/page_alloc.c=4306=static inline bool\nmm/page_alloc.c:4307:should_compact_retry(gfp_t gfp_mask, struct alloc_context *ac, int order,\nmm/page_alloc.c-4308-\t\t     int alloc_flags,\n--\nmm/page_alloc.c=4420=__perform_reclaim(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4421:\t\t\t\t\tconst struct alloc_context *ac)\nmm/page_alloc.c-4422-{\n--\nmm/page_alloc.c=4446=__alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4447:\t\tunsigned int alloc_flags, const struct alloc_context *ac,\nmm/page_alloc.c-4448-\t\tunsigned long *did_some_progress)\n--\nmm/page_alloc.c=4484=static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask,\nmm/page_alloc.c:4485:\t\t\t     const struct alloc_context *ac)\nmm/page_alloc.c-4486-{\n--\nmm/page_alloc.c=4622=should_reclaim_retry(gfp_t gfp_mask, unsigned order,\nmm/page_alloc.c:4623:\t\t     struct alloc_context *ac, int alloc_flags,\nmm/page_alloc.c-4624-\t\t     bool did_some_progress, int *no_progress_loops)\n--\nmm/page_alloc.c=4698=static inline bool\nmm/page_alloc.c:4699:check_retry_cpuset(int cpuset_mems_cookie, struct alloc_context *ac)\nmm/page_alloc.c-4700-{\n--\nmm/page_alloc.c=4766=__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4767:\t\t\t\t\t\tstruct alloc_context *ac)\nmm/page_alloc.c-4768-{\n--\nmm/page_alloc.c=5085=static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c-5086-\t\tint preferred_nid, nodemask_t *nodemask,\nmm/page_alloc.c:5087:\t\tstruct alloc_context *ac, gfp_t *alloc_gfp,\nmm/page_alloc.c-5088-\t\tunsigned int *alloc_flags)\n--\nmm/page_alloc.c=5154=unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\n--\nmm/page_alloc.c-5162-\tstruct list_head *pcp_list;\nmm/page_alloc.c:5163:\tstruct alloc_context ac = { .alloc_flags = alloc_flags };\nmm/page_alloc.c-5164-\tunsigned int fastpath_alloc_flags = alloc_flags | ALLOC_WMARK_LOW;\n--\nmm/page_alloc.c=5389=struct page *__alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order,\n--\nmm/page_alloc.c-5393-\tgfp_t alloc_gfp; /* The gfp_t that was actually used for allocation */\nmm/page_alloc.c:5394:\tstruct alloc_context ac = {\nmm/page_alloc.c-5395-\t\t.alloc_flags = alloc_flags,\n--\nmm/page_alloc.h-75- */\nmm/page_alloc.h:76:struct alloc_context {\nmm/page_alloc.h-77-\tstruct zonelist *zonelist;\n"
}

gemini-3.8-flash

null

null

							input: 18446
							output: 36
							thoughts: 51
						

Here's my summary, as if I were thinking it:

**Diving into the Page Allocation Code**

Okay, time to get my hands dirty. I want to understand how this page allocation is happening under the hood, so I'm heading straight for the source. Specifically, I need to check out `mm/page_alloc.c`, lines 5385 through 5420. That should give me a good look at `__alloc_frozen_pages_noprof` and `__alloc_pages_noprof`. I know these are key allocation functions, and the "noprof" suffix likely indicates they're optimized to bypass certain profiling or accounting overhead. I'm hoping to get a clearer picture of the core allocation logic in this path, likely related to performance-sensitive areas, possibly a boot-time function. The goal is to see how they're handling page flags, order, and potential NUMA considerations and understand how they're interacting with the zone management. I'm keen to see if this is handling direct or deferred allocation; a dive into this code is precisely what is needed to understand the current behavior.

{
  "File": "mm/page_alloc.c",
  "FirstLine": 5385,
  "LineCount": 40
}

{
  "Contents": "5385:\t\n5386:\t/*\n5387:\t * This is the 'heart' of the zoned buddy allocator.\n5388:\t */\n5389:\tstruct page *__alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order,\n5390:\t\t\tint preferred_nid, nodemask_t *nodemask, unsigned int alloc_flags)\n5391:\t{\n5392:\t\tstruct page *page;\n5393:\t\tgfp_t alloc_gfp; /* The gfp_t that was actually used for allocation */\n5394:\t\tstruct alloc_context ac = {\n5395:\t\t\t.alloc_flags = alloc_flags,\n5396:\t\t};\n5397:\t\tunsigned int fastpath_alloc_flags = alloc_flags;\n5398:\t\n5399:\t\t/* Other flags could be supported later if needed. */\n5400:\t\tif (WARN_ON(alloc_flags \u0026 ~(ALLOC_NOLOCK | ALLOC_NO_CODETAG)))\n5401:\t\t\treturn NULL;\n5402:\t\n5403:\t\tif (!alloc_order_allowed(gfp, order, alloc_flags))\n5404:\t\t\treturn NULL;\n5405:\t\n5406:\t\tif (alloc_flags \u0026 ALLOC_NOLOCK) {\n5407:\t\t\t/* Certain other flags could be supported later if needed. */\n5408:\t\t\tVM_WARN_ON_ONCE(gfp \u0026 ~(__GFP_ACCOUNT | gfp_nolock));\n5409:\t\t\tif (!alloc_nolock_allowed())\n5410:\t\t\t\treturn NULL;\n5411:\t\t\tgfp |= gfp_nolock;\n5412:\t\t\tfastpath_alloc_flags |= ALLOC_WMARK_MIN;\n5413:\t\t} else {\n5414:\t\t\tfastpath_alloc_flags |= ALLOC_WMARK_LOW;\n5415:\t\t}\n5416:\t\n5417:\t\tgfp \u0026= gfp_allowed_mask;\n5418:\t\t/*\n5419:\t\t * Apply scoped allocation constraints. This is mainly about GFP_NOFS\n5420:\t\t * resp. GFP_NOIO which has to be inherited for all allocation requests\n5421:\t\t * from a particular context which has been marked by\n5422:\t\t * memalloc_no{fs,io}_{save,restore}. And PF_MEMALLOC_PIN which ensures\n5423:\t\t * movable zones are not used during allocation.\n5424:\t\t */\n"
}

gemini-3.8-flash

null

null

							input: 19438
							output: 36
							thoughts: 90
						

Okay, let me dive in and analyze this code.

**Diving into Memory Allocation**

Alright, my focus is immediately drawn to `__alloc_frozen_pages_noprof`. I see an allocation context `struct alloc_context ac = { .alloc_flags = alloc_flags };` being established, a pretty standard procedure. I'm noting the immediate setting of `fastpath_alloc_flags = alloc_flags | ALLOC_WMARK_LOW;` – that's a quick optimization using bitwise operations, likely for a faster memory allocation path. I need to keep an eye on how that's used.

Let's not forget to check `__alloc_pages_noprof`! Specifically, I want to get a look at the code between lines 5440 and 5500. This area will likely shed some light on the core allocation logic and how it interacts with the flags that were just set. I need to see how the overall process works and how it might be optimized, or where there might be some bottlenecks.

{
  "File": "mm/page_alloc.c",
  "FirstLine": 5440,
  "LineCount": 60
}

{
  "Contents": "5440:\t\n5441:\t\t/* First allocation attempt (or, for nolock, only attempt) */\n5442:\t\tpage = get_page_from_freelist(alloc_gfp, order, fastpath_alloc_flags, \u0026ac);\n5443:\t\tif (likely(page) || (alloc_flags \u0026 ALLOC_NOLOCK))\n5444:\t\t\tgoto out;\n5445:\t\n5446:\t\talloc_gfp = gfp;\n5447:\t\tac.spread_dirty_pages = false;\n5448:\t\n5449:\t\t/*\n5450:\t\t * Restore the original nodemask if it was potentially replaced with\n5451:\t\t * \u0026cpuset_current_mems_allowed to optimize the fast-path attempt.\n5452:\t\t */\n5453:\t\tac.nodemask = nodemask;\n5454:\t\n5455:\t\tpage = __alloc_pages_slowpath(alloc_gfp, order, \u0026ac);\n5456:\t\n5457:\tout:\n5458:\t\tif (memcg_kmem_online() \u0026\u0026 (gfp \u0026 __GFP_ACCOUNT) \u0026\u0026 page \u0026\u0026\n5459:\t\t    unlikely(__memcg_kmem_charge_page(page, gfp, order) != 0)) {\n5460:\t\t\t__free_frozen_pages(page, order,\n5461:\t\t\t\t\t    alloc_flags \u0026 ALLOC_NOLOCK ? FPI_NOLOCK : 0);\n5462:\t\t\tpage = NULL;\n5463:\t\t}\n5464:\t\n5465:\t\ttrace_mm_page_alloc(page, order, alloc_gfp, ac.migratetype);\n5466:\t\tkmsan_alloc_page(page, order, alloc_gfp);\n5467:\t\n5468:\t\treturn page;\n5469:\t}\n5470:\tEXPORT_SYMBOL(__alloc_frozen_pages_noprof);\n5471:\t\n5472:\tstruct page *__alloc_pages_noprof(gfp_t gfp, unsigned int order,\n5473:\t\t\tint preferred_nid, nodemask_t *nodemask, unsigned int alloc_flags)\n5474:\t{\n5475:\t\tstruct page *page;\n5476:\t\n5477:\t\tpage = __alloc_frozen_pages_noprof(gfp, order, preferred_nid, nodemask,\n5478:\t\t\t\t\t\t   alloc_flags);\n5479:\t\tif (page)\n5480:\t\t\tset_page_refcounted(page);\n5481:\t\treturn page;\n5482:\t}\n5483:\t\n5484:\tstruct page *alloc_pages_node_noprof(int nid, gfp_t gfp_mask, unsigned int order)\n5485:\t{\n5486:\t\tif (nid == NUMA_NO_NODE)\n5487:\t\t\tnid = numa_mem_id();\n5488:\t\n5489:\t\twarn_if_node_offline(nid, gfp_mask);\n5490:\t\n5491:\t\treturn __alloc_pages_noprof(gfp_mask, order, nid, NULL, ALLOC_DEFAULT);\n5492:\t}\n5493:\tEXPORT_SYMBOL(alloc_pages_node_noprof);\n5494:\t\n5495:\tstruct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n5496:\t\t\tnodemask_t *nodemask, unsigned int alloc_flags)\n5497:\t{\n5498:\t\tstruct page *page = __alloc_pages_noprof(gfp | __GFP_COMP, order,\n5499:\t\t\t\t\t\tpreferred_nid, nodemask, alloc_flags);\n"
}

gemini-3.8-flash

null

null

							input: 20800
							output: 22
							thoughts: 1931
						

**Fuzzing Decision for a Memory Management Patch**

Okay, let's break this down. First, I need to understand the context of this commit, so I'll check its log.  The commit's about an automated syz-cluster patch. Now, looking at the diff, it appears to be a modification to page allocation: `__folio_alloc_noprof`, `__folio_alloc`, and `__folio_alloc_node_noprof` are being moved around and modified, including the introduction of an `alloc_flags` parameter. Specifically, `__alloc_pages_bulk_noprof` is being added. These changes are in `mm/page_alloc.c`, `mm/khugepaged.c`, and `mm/migrate.c`, and associated headers.

Now, the important question: is this reachable code? Yes, this is core memory management, so the changes *are* reachable. Does syzkaller fuzz these specific areas? That's what I have to determine.

Time to consult the fuzzing guidelines. Reachability is the primary gate: if it's reachable, then consider fuzzing.  And, don't automatically trust "no functional change" or "refactoring" claims; subtle semantic shifts are common.  Also, new or modified assertions need to be fuzzed.

According to the guidelines, I only avoid fuzzing if the code modifications are non-kernel, structurally unreachable (like specialized hardware), or unreachable execution paths. This is *not* the case here, as this is core memory management.  Therefore, I'm leaning toward fuzzing.  This is a core subsystem refactoring and is touching code that is *definitely* reachable.  This is a clear "WorthFuzzing=true".

Now, let's figure out what the *focus* of fuzzing should be. We want to avoid diluting the effort.  We don't want to focus on "ubiquitous lifecycle hot-paths" like general allocators and deallocators. Instead, we need to target specific feature logic and entry points.

The core modified functions here are `__folio_alloc_node_noprof`, `__folio_alloc`, and `__alloc_pages_bulk_noprof`.  I need to be careful with `__folio_alloc_node_noprof`. Is that a ubiquitous allocator? No, it's defined within `folio_alloc_noprof`, which is likely called often. I need to trace back from here and see if it's indeed ubiquitous, or specific enough to warrant focus. I need to check the callers of `folio_alloc_noprof` and `__folio_alloc_node_noprof` more carefully, especially under `CONFIG_NUMA`, where `folio_alloc_noprof` is defined in `mm/page_alloc.c` or `mm/mempolicy.c`.

{
  "Expression": "folio_alloc_noprof\\("
}

{
  "Output": "include/linux/gfp.h=264=struct page *alloc_pages_noprof(gfp_t gfp, unsigned int order);\ninclude/linux/gfp.h:265:struct folio *folio_alloc_noprof(gfp_t gfp, unsigned int order);\ninclude/linux/gfp.h-266-struct folio *folio_alloc_mpol_noprof(gfp_t gfp, unsigned int order,\n--\ninclude/linux/gfp.h=271=static inline struct page *alloc_pages_noprof(gfp_t gfp_mask, unsigned int order)\n--\ninclude/linux/gfp.h-274-}\ninclude/linux/gfp.h:275:static inline struct folio *folio_alloc_noprof(gfp_t gfp, unsigned int order)\ninclude/linux/gfp.h-276-{\n--\ninclude/linux/gfp.h=279=static inline struct folio *folio_alloc_mpol_noprof(gfp_t gfp, unsigned int order,\n--\ninclude/linux/gfp.h-281-{\ninclude/linux/gfp.h:282:\treturn folio_alloc_noprof(gfp, order);\ninclude/linux/gfp.h-283-}\ninclude/linux/gfp.h=284=static inline struct folio *vma_alloc_folio_noprof(gfp_t gfp, int order,\n--\ninclude/linux/gfp.h-286-{\ninclude/linux/gfp.h:287:\treturn folio_alloc_noprof(gfp, order);\ninclude/linux/gfp.h-288-}\n--\ninclude/linux/gfp.h-291-#define alloc_pages(...)\t\t\talloc_hooks(alloc_pages_noprof(__VA_ARGS__))\ninclude/linux/gfp.h:292:#define folio_alloc(...)\t\t\talloc_hooks(folio_alloc_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-293-#define folio_alloc_mpol(...)\t\t\talloc_hooks(folio_alloc_mpol_noprof(__VA_ARGS__))\n--\ninclude/linux/pagemap.h=653=static inline struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order,\n--\ninclude/linux/pagemap.h-655-{\ninclude/linux/pagemap.h:656:\treturn folio_alloc_noprof(gfp, order);\ninclude/linux/pagemap.h-657-}\n--\nmm/filemap.c=999=struct folio *filemap_alloc_folio_noprof(gfp_t gfp, unsigned int order,\n--\nmm/filemap.c-1018-\t}\nmm/filemap.c:1019:\treturn folio_alloc_noprof(gfp, order);\nmm/filemap.c-1020-}\n--\nmm/mempolicy.c=2606=EXPORT_SYMBOL(alloc_pages_noprof);\nmm/mempolicy.c-2607-\nmm/mempolicy.c:2608:struct folio *folio_alloc_noprof(gfp_t gfp, unsigned int order)\nmm/mempolicy.c-2609-{\n--\nmm/page_alloc.c=5493=EXPORT_SYMBOL(alloc_pages_node_noprof);\nmm/page_alloc.c-5494-\nmm/page_alloc.c:5495:struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\nmm/page_alloc.c-5496-\t\tnodemask_t *nodemask, unsigned int alloc_flags)\n--\nmm/page_alloc.c=5503=struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid)\n--\nmm/page_alloc.c-5506-\nmm/page_alloc.c:5507:\treturn __folio_alloc_noprof(gfp, order, nid, NULL, ALLOC_DEFAULT);\nmm/page_alloc.c-5508-}\n--\nmm/page_alloc.h=257=struct page *__alloc_pages_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n--\nmm/page_alloc.h-260-\nmm/page_alloc.h:261:struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\nmm/page_alloc.h-262-\t\tnodemask_t *nodemask, unsigned int alloc_flags);\nmm/page_alloc.h:263:#define __folio_alloc(...)\t\t\talloc_hooks(__folio_alloc_noprof(__VA_ARGS__))\nmm/page_alloc.h-264-\n"
}

gemini-3.8-flash

null

null

							input: 24628
							output: 35
							thoughts: 48
						

Okay, let's dive into this. I'm curious about the function `folio_alloc_noprof` and its behavior. I know it's defined within `mm/mempolicy.c`, so that's where I'll need to look. I'll zero in on the vicinity of line 2608 in that file; that should give me a good starting point to understand its function and how it fits into the broader memory management framework. Let's see what that code reveals.

{
  "File": "mm/mempolicy.c",
  "FirstLine": 2605,
  "LineCount": 25
}

{
  "Contents": "2605:\t}\n2606:\tEXPORT_SYMBOL(alloc_pages_noprof);\n2607:\t\n2608:\tstruct folio *folio_alloc_noprof(gfp_t gfp, unsigned int order)\n2609:\t{\n2610:\t\treturn page_rmappable_folio(alloc_pages_noprof(gfp | __GFP_COMP, order));\n2611:\t}\n2612:\tEXPORT_SYMBOL(folio_alloc_noprof);\n2613:\t\n2614:\tstatic unsigned long alloc_pages_bulk_interleave(gfp_t gfp,\n2615:\t\t\tstruct mempolicy *pol, unsigned long nr_pages,\n2616:\t\t\tstruct page **page_array)\n2617:\t{\n2618:\t\tunsigned int cpuset_mems_cookie;\n2619:\t\tint nodes;\n2620:\t\tunsigned long nr_pages_per_node;\n2621:\t\tint delta;\n2622:\t\tint i;\n2623:\t\tunsigned long nr_allocated;\n2624:\t\tunsigned long total_allocated = 0;\n2625:\t\n2626:\t\t/* count the nodes, retry if a rebind happened during the read */\n2627:\t\tdo {\n2628:\t\t\tcpuset_mems_cookie = read_mems_allowed_begin();\n2629:\t\t\tnodes = nodes_weight(pol-\u003enodes);\n"
}

gemini-3.8-flash

null

null

							input: 25210
							output: 19
							thoughts: 303
						

**Analyzing Commit Changes and Avoiding Ubiquitous Functions**

Okay, let's break down this commit. It looks like we've got some new or modified functions across a few files. Specifically, in `mm/page_alloc.c`, I'm seeing changes to `__alloc_pages_bulk_noprof`, `alloc_pages_bulk_noprof`, `__folio_alloc_noprof`, and `__folio_alloc_node_noprof`. Then, in `mm/khugepaged.c`, there's `alloc_charge_folio` which calls `__folio_alloc`, and similarly, `alloc_migration_target` in `mm/migrate.c`, which also uses `__folio_alloc`.

Hold on a second... the instructions emphasize avoiding ubiquitous lifecycle hot-paths. It explicitly says to avoid listing general memory allocators. I need to be careful here. The instructions are very clear: Listing ubiquitous functions dilutes the focus of the fuzzer.

Are those bulk allocators in `mm/page_alloc.c` considered ubiquitous general memory allocators? I need to check. To make an informed decision, I need to see who calls `alloc_pages_bulk`, which will inform me if it is indeed a ubiquitous function. I will need to determine if it is best to leave those functions off the list.

{
  "Expression": "alloc_pages_bulk"
}

{
  "Output": "block/blk-crypto-fallback.c=172=static struct bio *blk_crypto_alloc_enc_bio(struct bio *bio_src,\n--\nblock/blk-crypto-fallback.c-204-\t *\nblock/blk-crypto-fallback.c:205:\t * Note: alloc_pages_bulk needs the array to be zeroed, as it assumes\nblock/blk-crypto-fallback.c-206-\t * any non-zero slot already contains a valid allocation.\n--\nblock/blk-crypto-fallback.c-208-\tmemset(pages, 0, sizeof(struct page *) * nr_segs);\nblock/blk-crypto-fallback.c:209:\tnr_allocated = alloc_pages_bulk(GFP_KERNEL, nr_segs, pages);\nblock/blk-crypto-fallback.c-210-\tif (nr_allocated \u003c nr_segs)\n--\ndrivers/firewire/core-iso.c=31=int fw_iso_buffer_alloc(struct fw_iso_buffer *buffer, int page_count)\n--\ndrivers/firewire/core-iso.c-41-\t// convenience to map them into virtual address space of user process.\ndrivers/firewire/core-iso.c:42:\tunsigned long nr_populated = alloc_pages_bulk(GFP_KERNEL | GFP_DMA32 | __GFP_ZERO,\ndrivers/firewire/core-iso.c-43-\t\t\t\t\t\t      page_count, page_array);\n--\ndrivers/firewire/ohci.c=848=static int ar_context_init(struct ar_context *ctx, struct fw_ohci *ohci,\n--\ndrivers/firewire/ohci.c-864-\t// address range in kernel virtual address space.\ndrivers/firewire/ohci.c:865:\tunsigned long nr_populated = alloc_pages_bulk(GFP_KERNEL | GFP_DMA32, AR_BUFFERS, pages);\ndrivers/firewire/ohci.c-866-\n--\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c=621=static int alloc_private_pages(struct hmm_buffer_object *bo)\n--\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c-626-\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c:627:\tnr_allocated = alloc_pages_bulk(GFP_KERNEL, bo-\u003epgnr, bo-\u003epages);\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c-628-\t/*\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c:629:\t * alloc_pages_bulk() does not try very hard to get pages under memory\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c-630-\t * pressure. If necessary fall back to alloc_page().\n--\ndrivers/vfio/pci/mlx5/cmd.c=466=static void free_page_list(u32 npages, struct page **page_list)\n--\ndrivers/vfio/pci/mlx5/cmd.c-469-\ndrivers/vfio/pci/mlx5/cmd.c:470:\t/* Undo alloc_pages_bulk() */\ndrivers/vfio/pci/mlx5/cmd.c-471-\tfor (i = npages - 1; i \u003e= 0; i--)\n--\ndrivers/vfio/pci/mlx5/cmd.c=496=static int mlx5vf_add_pages(struct page ***page_list, unsigned int npages)\n--\ndrivers/vfio/pci/mlx5/cmd.c-506-\tfor (;;) {\ndrivers/vfio/pci/mlx5/cmd.c:507:\t\tfilled = alloc_pages_bulk(GFP_KERNEL_ACCOUNT, npages - done,\ndrivers/vfio/pci/mlx5/cmd.c-508-\t\t\t\t\t  *page_list + done);\n--\ndrivers/vfio/pci/virtio/migrate.c=63=static int virtiovf_add_migration_pages(struct virtiovf_data_buffer *buf,\n--\ndrivers/vfio/pci/virtio/migrate.c-78-\tdo {\ndrivers/vfio/pci/virtio/migrate.c:79:\t\tfilled = alloc_pages_bulk(GFP_KERNEL_ACCOUNT, to_fill,\ndrivers/vfio/pci/virtio/migrate.c-80-\t\t\t\t\t  page_list);\n--\ndrivers/vfio/pci/virtio/migrate.c=110=static void virtiovf_free_data_buffer(struct virtiovf_data_buffer *buf)\n--\ndrivers/vfio/pci/virtio/migrate.c-113-\ndrivers/vfio/pci/virtio/migrate.c:114:\t/* Undo alloc_pages_bulk() */\ndrivers/vfio/pci/virtio/migrate.c-115-\tfor_each_sgtable_page(\u0026buf-\u003etable.sgt, \u0026sg_iter, 0)\n--\nfs/btrfs/extent_io.c=684=int btrfs_alloc_page_array(unsigned int nr_pages, struct page **page_array, gfp_t gfp)\n--\nfs/btrfs/extent_io.c-690-\nfs/btrfs/extent_io.c:691:\t\tallocated = alloc_pages_bulk(gfp, nr_pages, page_array);\nfs/btrfs/extent_io.c-692-\t\tif (unlikely(allocated == last)) {\n--\nfs/erofs/zutil.c=65=int z_erofs_gbuf_growsize(unsigned int nrpages)\n--\nfs/erofs/zutil.c-89-\t\t\tlast = j;\nfs/erofs/zutil.c:90:\t\t\tj = alloc_pages_bulk(GFP_KERNEL, nrpages, tmp_pages);\nfs/erofs/zutil.c-91-\t\t\tif (last == j)\n--\nfs/fuse/readdir.c=336=static struct page **fuse_readdir_alloc_buf(struct fuse_args_pages *ap, size_t *bufsize)\n--\nfs/fuse/readdir.c-343-\nfs/fuse/readdir.c:344:\tnr_alloc = alloc_pages_bulk(GFP_KERNEL, nr_pages, pages);\nfs/fuse/readdir.c-345-\tif (!nr_alloc)\n--\nfs/nfsd/nfs4state.c=1326=alloc_init_dir_deleg(struct nfs4_client *clp, struct nfs4_file *fp)\n--\nfs/nfsd/nfs4state.c-1337-\nfs/nfsd/nfs4state.c:1338:\tnpages = alloc_pages_bulk(GFP_KERNEL, NOTIFY4_PAGE_ARRAY_SIZE, ncn-\u003encn_pages);\nfs/nfsd/nfs4state.c-1339-\tif (npages != NOTIFY4_PAGE_ARRAY_SIZE) {\n--\nfs/splice.c=318=ssize_t copy_splice_read(struct file *in, loff_t *ppos,\n--\nfs/splice.c-341-\tpages = (struct page **)(bv + npages);\nfs/splice.c:342:\tnpages = alloc_pages_bulk(GFP_USER, npages, pages);\nfs/splice.c-343-\tif (!npages) {\n--\ninclude/linux/gfp.h=204=static inline void arch_alloc_page(struct page *page, int order) { }\n--\ninclude/linux/gfp.h-206-\ninclude/linux/gfp.h:207:unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\ninclude/linux/gfp.h-208-\t\t\t\tnodemask_t *nodemask, int nr_pages,\ninclude/linux/gfp.h-209-\t\t\t\tstruct page **page_array);\ninclude/linux/gfp.h:210:#define __alloc_pages_bulk(...)\t\t\talloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-211-\ninclude/linux/gfp.h=212=void free_pages_bulk(struct page **page_array, unsigned long nr_pages);\ninclude/linux/gfp.h-213-\ninclude/linux/gfp.h:214:unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\ninclude/linux/gfp.h-215-\t\t\t\tunsigned long nr_pages,\ninclude/linux/gfp.h-216-\t\t\t\tstruct page **page_array);\ninclude/linux/gfp.h:217:#define  alloc_pages_bulk_mempolicy(...)\t\t\t\t\\\ninclude/linux/gfp.h:218:\talloc_hooks(alloc_pages_bulk_mempolicy_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-219-\ninclude/linux/gfp.h-220-/* Bulk allocate order-0 pages */\ninclude/linux/gfp.h:221:#define alloc_pages_bulk(_gfp, _nr_pages, _page_array)\t\t\\\ninclude/linux/gfp.h:222:\t__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _page_array)\ninclude/linux/gfp.h-223-\ninclude/linux/gfp.h=224=static inline unsigned long\ninclude/linux/gfp.h:225:alloc_pages_bulk_node_noprof(gfp_t gfp, int nid, unsigned long nr_pages,\ninclude/linux/gfp.h-226-\t\t\t\t   struct page **page_array)\n--\ninclude/linux/gfp.h-230-\ninclude/linux/gfp.h:231:\treturn alloc_pages_bulk_noprof(gfp, nid, NULL, nr_pages, page_array);\ninclude/linux/gfp.h-232-}\ninclude/linux/gfp.h-233-\ninclude/linux/gfp.h:234:#define alloc_pages_bulk_node(...)\t\t\t\t\\\ninclude/linux/gfp.h:235:\talloc_hooks(alloc_pages_bulk_node_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-236-\n--\nio_uring/memmap.c=174=static int io_region_allocate_pages(struct io_mapped_region *mr,\n--\nio_uring/memmap.c-192-\nio_uring/memmap.c:193:\tnr_allocated = alloc_pages_bulk_node(gfp, NUMA_NO_NODE,\nio_uring/memmap.c-194-\t\t\t\t\t     mr-\u003enr_pages, pages);\n--\nkernel/bpf/arena.c=668=static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt, int node_id,\n--\nkernel/bpf/arena.c-732-\nkernel/bpf/arena.c:733:\t\t/* zeroing is needed, since alloc_pages_bulk() only fills in non-zero entries */\nkernel/bpf/arena.c-734-\t\tmemset(pages, 0, this_batch * sizeof(struct page *));\n--\nlib/test_vmalloc.c=391=vm_map_ram_test(void)\n--\nlib/test_vmalloc.c-403-\nlib/test_vmalloc.c:404:\tnr_allocated = alloc_pages_bulk(GFP_KERNEL, map_nr_pages, pages);\nlib/test_vmalloc.c-405-\tif (nr_allocated != map_nr_pages)\n--\nlib/tests/kunit_iov_iter.c=51=static void *__init iov_kunit_create_buffer(struct kunit *test,\n--\nlib/tests/kunit_iov_iter.c-66-\t\tlast = got;\nlib/tests/kunit_iov_iter.c:67:\t\tgot = alloc_pages_bulk(GFP_KERNEL, npages, pages);\nlib/tests/kunit_iov_iter.c-68-\n--\nmm/alloc_tag.c=785=static int vm_module_tags_populate(void)\n--\nmm/alloc_tag.c-801-\nmm/alloc_tag.c:802:\t\t\tallocated = alloc_pages_bulk_node(GFP_KERNEL | __GFP_NOWARN,\nmm/alloc_tag.c-803-\t\t\t\tNUMA_NO_NODE, more_pages - nr, next_page + nr);\n--\nmm/kasan/shadow.c=327=static void ___free_pages_bulk(struct page **pages, int nr_pages)\n--\nmm/kasan/shadow.c-338-\nmm/kasan/shadow.c:339:static int ___alloc_pages_bulk(struct page **pages, int nr_pages, gfp_t gfp_mask)\nmm/kasan/shadow.c-340-{\n--\nmm/kasan/shadow.c-344-\twhile (nr_pages) {\nmm/kasan/shadow.c:345:\t\tnr_populated = alloc_pages_bulk(gfp_mask, nr_pages, pages);\nmm/kasan/shadow.c-346-\t\tif (!nr_populated) {\n--\nmm/kasan/shadow.c=357=static int __kasan_populate_vmalloc_do(unsigned long start, unsigned long end, gfp_t gfp_mask)\n--\nmm/kasan/shadow.c-369-\t\tnr_pages = min(nr_total, PAGE_SIZE / sizeof(data.pages[0]));\nmm/kasan/shadow.c:370:\t\tret = ___alloc_pages_bulk(data.pages, nr_pages, gfp_mask);\nmm/kasan/shadow.c-371-\t\tif (ret)\n--\nmm/mempolicy.c=2612=EXPORT_SYMBOL(folio_alloc_noprof);\nmm/mempolicy.c-2613-\nmm/mempolicy.c:2614:static unsigned long alloc_pages_bulk_interleave(gfp_t gfp,\nmm/mempolicy.c-2615-\t\tstruct mempolicy *pol, unsigned long nr_pages,\n--\nmm/mempolicy.c-2640-\t\tif (delta) {\nmm/mempolicy.c:2641:\t\t\tnr_allocated = alloc_pages_bulk_noprof(gfp,\nmm/mempolicy.c-2642-\t\t\t\t\tinterleave_nodes(pol), NULL,\n--\nmm/mempolicy.c-2646-\t\t} else {\nmm/mempolicy.c:2647:\t\t\tnr_allocated = alloc_pages_bulk_noprof(gfp,\nmm/mempolicy.c-2648-\t\t\t\t\tinterleave_nodes(pol), NULL,\n--\nmm/mempolicy.c-2658-\nmm/mempolicy.c:2659:static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,\nmm/mempolicy.c-2660-\t\tstruct mempolicy *pol, unsigned long nr_pages,\n--\nmm/mempolicy.c-2697-\t\tnode_pages = min(rem_pages, weight);\nmm/mempolicy.c:2698:\t\tnr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,\nmm/mempolicy.c-2699-\t\t\t\t\t\t  page_array);\n--\nmm/mempolicy.c-2727-\t/*\nmm/mempolicy.c:2728:\t * Calculate rounds/partial rounds to minimize __alloc_pages_bulk calls.\nmm/mempolicy.c-2729-\t * Track which node weighted interleave should resume from.\n--\nmm/mempolicy.c-2761-\t\tnode_pages = min(node_pages, nr_pages - total_allocated);\nmm/mempolicy.c:2762:\t\tnr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,\nmm/mempolicy.c-2763-\t\t\t\t\t\t  page_array);\n--\nmm/mempolicy.c-2776-\nmm/mempolicy.c:2777:static unsigned long alloc_pages_bulk_preferred_many(gfp_t gfp, int nid,\nmm/mempolicy.c-2778-\t\tstruct mempolicy *pol, unsigned long nr_pages,\n--\nmm/mempolicy.c-2786-\nmm/mempolicy.c:2787:\tnr_allocated  = alloc_pages_bulk_noprof(preferred_gfp, nid, \u0026pol-\u003enodes,\nmm/mempolicy.c-2788-\t\t\t\t\t   nr_pages, page_array);\n--\nmm/mempolicy.c-2790-\tif (nr_allocated \u003c nr_pages)\nmm/mempolicy.c:2791:\t\tnr_allocated += alloc_pages_bulk_noprof(gfp, numa_node_id(), NULL,\nmm/mempolicy.c-2792-\t\t\t\tnr_pages - nr_allocated,\n--\nmm/mempolicy.c-2802- */\nmm/mempolicy.c:2803:unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\nmm/mempolicy.c-2804-\t\tunsigned long nr_pages, struct page **page_array)\n--\nmm/mempolicy.c-2813-\tif (pol-\u003emode == MPOL_INTERLEAVE)\nmm/mempolicy.c:2814:\t\treturn alloc_pages_bulk_interleave(gfp, pol,\nmm/mempolicy.c-2815-\t\t\t\t\t\t\t nr_pages, page_array);\n--\nmm/mempolicy.c-2817-\tif (pol-\u003emode == MPOL_WEIGHTED_INTERLEAVE)\nmm/mempolicy.c:2818:\t\treturn alloc_pages_bulk_weighted_interleave(\nmm/mempolicy.c-2819-\t\t\t\t  gfp, pol, nr_pages, page_array);\n--\nmm/mempolicy.c-2821-\tif (pol-\u003emode == MPOL_PREFERRED_MANY)\nmm/mempolicy.c:2822:\t\treturn alloc_pages_bulk_preferred_many(gfp,\nmm/mempolicy.c-2823-\t\t\t\tnuma_node_id(), pol, nr_pages, page_array);\n--\nmm/mempolicy.c-2826-\tnodemask = policy_nodemask(gfp, pol, NO_INTERLEAVE_INDEX, \u0026nid);\nmm/mempolicy.c:2827:\treturn alloc_pages_bulk_noprof(gfp, nid, nodemask,\nmm/mempolicy.c-2828-\t\t\t\t       nr_pages, page_array);\n--\nmm/page_alloc.c=5085=static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-5133-/*\nmm/page_alloc.c:5134: * __alloc_pages_bulk - Allocate a number of order-0 pages to an array\nmm/page_alloc.c-5135- * @gfp: GFP flags for the allocation\n--\nmm/page_alloc.c-5153- */\nmm/page_alloc.c:5154:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.c-5155-\t\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n--\nmm/page_alloc.c-5298-\nmm/page_alloc.c:5299:unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\nmm/page_alloc.c-5300-\t\t\tnodemask_t *nodemask, int nr_pages,\n--\nmm/page_alloc.c-5302-{\nmm/page_alloc.c:5303:\treturn __alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid,\nmm/page_alloc.c-5304-\t\t\t\t\t nodemask, nr_pages, page_array);\nmm/page_alloc.c-5305-}\nmm/page_alloc.c:5306:EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);\nmm/page_alloc.c-5307-\n--\nmm/page_alloc.h=261=struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n--\nmm/page_alloc.h-264-\nmm/page_alloc.h:265:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.h-266-\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n--\nmm/slub.c=7426=static bool __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,\n--\nmm/slub.c-7470- *\nmm/slub.c:7471: * Unlike alloc_pages_bulk(), this function does not check for already allocated\nmm/slub.c-7472- * objects in @p, and thus the caller does not need to zero it.\n--\nmm/vmalloc.c=3686=vm_area_alloc_pages(gfp_t gfp, int nid,\n--\nmm/vmalloc.c-3753-\t\t\tif (IS_ENABLED(CONFIG_NUMA) \u0026\u0026 nid == NUMA_NO_NODE)\nmm/vmalloc.c:3754:\t\t\t\tnr = alloc_pages_bulk_mempolicy_noprof(gfp,\nmm/vmalloc.c-3755-\t\t\t\t\t\t\tnr_pages_request,\n--\nmm/vmalloc.c-3757-\t\t\telse\nmm/vmalloc.c:3758:\t\t\t\tnr = alloc_pages_bulk_node_noprof(gfp, nid,\nmm/vmalloc.c-3759-\t\t\t\t\t\t\tnr_pages_request,\n--\nnet/core/page_pool.c=611=static noinline netmem_ref __page_pool_alloc_netmems_slow(struct page_pool *pool,\n--\nnet/core/page_pool.c-633-\nnet/core/page_pool.c:634:\t/* Mark empty alloc.cache slots \"empty\" for alloc_pages_bulk */\nnet/core/page_pool.c-635-\tmemset(\u0026pool-\u003ealloc.cache, 0, sizeof(void *) * bulk);\nnet/core/page_pool.c-636-\nnet/core/page_pool.c:637:\tnr_pages = alloc_pages_bulk_node(gfp, pool-\u003ep.nid, bulk,\nnet/core/page_pool.c-638-\t\t\t\t\t (struct page **)pool-\u003ealloc.cache);\n--\nnet/sunrpc/svc_xprt.c=687=static bool svc_fill_pages(struct svc_rqst *rqstp, struct page **pages,\n--\nnet/sunrpc/svc_xprt.c-692-\tfor (filled = 0; filled \u003c npages; filled = ret) {\nnet/sunrpc/svc_xprt.c:693:\t\tret = alloc_pages_bulk(GFP_KERNEL, npages, pages);\nnet/sunrpc/svc_xprt.c-694-\t\tif (ret \u003e filled)\n"
}

gemini-3.8-flash

null

null

							input: 31832
							output: 36
							thoughts: 615
						

**Analyzing the New `__alloc_pages_bulk_noprof` Function**

Okay, let's dive into this `alloc_pages_bulk` situation. I see it's used across a lot of key subsystems – btrfs, splice, io_uring, bpf arena, vmalloc, page_pool, you name it. But wait, what's this `__alloc_pages_bulk_noprof` thing? It looks like it's the core of the bulk allocation logic now. And it's *new* and *non-static*, which is a pretty significant change. Before this patch, `alloc_pages_bulk_noprof` *was* the function.

Now, the core logic is in `__alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags, int preferred_nid, nodemask_t *nodemask, int nr_pages, struct page **page_array)`. Curious. Who's calling it? Just `alloc_pages_bulk_noprof`! So it appears the only use of `__alloc_pages_bulk_noprof` is the one provided by `alloc_pages_bulk_noprof` calling `__alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid, nodemask, nr_pages, page_array)`. What's the point of this abstraction?

And that `alloc_flags` parameter… why introduce that? Let's check `mm/page_alloc.h`. Ah, I see a similar pattern with `__folio_alloc_noprof`. It looks like this is a patch series adding `alloc_flags` support to `__folio_alloc` and `__alloc_pages_bulk`. That's interesting.

Let's look for how `alloc_flags` is being used. And, here we are in `__alloc_frozen_pages_noprof`:

```c
	/* Other flags could be supported later if needed. */
	if (WARN_ON(alloc_flags & ~(ALLOC_NOLOCK | ALLOC_NO_CODETAG)))
		return NULL;
```

So far, it seems like only `ALLOC_NOLOCK` and `ALLOC_NO_CODETAG` are being used. Okay.

Now, back to `__alloc_pages_bulk_noprof`. Does it actually *do* anything with `alloc_flags`? Time to dig into lines 5160-5205 of `mm/page_alloc.c` and find out!

{
  "File": "mm/page_alloc.c",
  "FirstLine": 5150,
  "LineCount": 55
}

{
  "Contents": "5150:\t * but all empty slots are filled from the beginning.  I.e., if all slots in\n5151:\t * @page_array were set to %NULL on entry, the slots from 0 to the return value\n5152:\t * - 1 will be filled.\n5153:\t */\n5154:\tunsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\n5155:\t\t\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n5156:\t\t\t\tstruct page **page_array)\n5157:\t{\n5158:\t\tstruct page *page;\n5159:\t\tstruct zone *zone;\n5160:\t\tstruct zoneref *z;\n5161:\t\tstruct per_cpu_pages *pcp;\n5162:\t\tstruct list_head *pcp_list;\n5163:\t\tstruct alloc_context ac = { .alloc_flags = alloc_flags };\n5164:\t\tunsigned int fastpath_alloc_flags = alloc_flags | ALLOC_WMARK_LOW;\n5165:\t\tint nr_populated = 0, nr_account = 0;\n5166:\t\n5167:\t\t/*\n5168:\t\t * Skip populated array elements to determine if any pages need\n5169:\t\t * to be allocated before disabling IRQs.\n5170:\t\t */\n5171:\t\twhile (nr_populated \u003c nr_pages \u0026\u0026 page_array[nr_populated])\n5172:\t\t\tnr_populated++;\n5173:\t\n5174:\t\t/* No pages requested? */\n5175:\t\tif (unlikely(nr_pages \u003c= 0))\n5176:\t\t\tgoto out;\n5177:\t\n5178:\t\t/* Already populated array? */\n5179:\t\tif (unlikely(nr_pages - nr_populated == 0))\n5180:\t\t\tgoto out;\n5181:\t\n5182:\t\t/* Bulk allocator does not support memcg accounting. */\n5183:\t\tif (memcg_kmem_online() \u0026\u0026 (gfp \u0026 __GFP_ACCOUNT))\n5184:\t\t\tgoto failed;\n5185:\t\n5186:\t\t/* Use the single page allocator for one page. */\n5187:\t\tif (nr_pages - nr_populated == 1)\n5188:\t\t\tgoto failed;\n5189:\t\n5190:\t#ifdef CONFIG_PAGE_OWNER\n5191:\t\t/*\n5192:\t\t * PAGE_OWNER may recurse into the allocator to allocate space to\n5193:\t\t * save the stack with pagesets.lock held. Releasing/reacquiring\n5194:\t\t * removes much of the performance benefit of bulk allocation so\n5195:\t\t * force the caller to allocate one page at a time as it'll have\n5196:\t\t * similar performance to added complexity to the bulk allocator.\n5197:\t\t */\n5198:\t\tif (static_branch_unlikely(\u0026page_owner_inited))\n5199:\t\t\tgoto failed;\n5200:\t#endif\n5201:\t\n5202:\t\t/* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */\n5203:\t\tgfp \u0026= gfp_allowed_mask;\n5204:\t\tgfp = current_gfp_context(gfp);\n"
}

gemini-3.8-flash

null

null

							input: 33939
							output: 20
							thoughts: 595
						

**Analyzing the Bulk Page Allocation Optimization**

Okay, let's break this down. I'm looking at the changes in `alloc_pages_bulk_noprof` and how the flags are being handled. Before the patch, it looks like `ALLOC_WMARK_LOW` was the initial `alloc_flags` in `alloc_pages_bulk_noprof`. Then, those flags were potentially modified by `prepare_alloc_pages`, and used directly in the loop with calls to `cond_accept_memory`, `wmark_pages`, and `zone_watermark_fast`, and ultimately used when calling `__rmqueue_pcplist`. If those initial attempts failed, it would fall back to allocating with `__alloc_pages_noprof` using `ALLOC_DEFAULT`.

Now, the code has changed significantly.  We now have an `__alloc_pages_bulk_noprof` that takes an `alloc_flags` parameter directly. An `alloc_context` struct is initialized with that. There's a new `fastpath_alloc_flags` that is derived by adding `ALLOC_WMARK_LOW` to `alloc_flags`, which seems to be the primary flag passed around and used in the same functions as before. I see that the same logic path that previously used the modified `alloc_flags` now uses `fastpath_alloc_flags` within the loop, and the fallback still seems to use the original `alloc_flags`.

Interesting. I'm seeing that the original `alloc_pages_bulk_noprof` now calls this internal function with a flag called `ALLOC_DEFAULT`. I need to check what `ALLOC_DEFAULT` is defined as. I'm off to look at `mm/page_alloc.h`.

{
  "Expression": "#define ALLOC_DEFAULT"
}

{
  "Output": "mm/page_alloc.h-13-\nmm/page_alloc.h:14:#define ALLOC_DEFAULT\t\t0\nmm/page_alloc.h-15-/* The ALLOC_WMARK bits are used as an index to zone-\u003ewatermark */\n"
}

gemini-3.8-flash

null

null

							input: 35006
							output: 19
							thoughts: 920
						

**Analyzing the Recent Changes to Folio Allocation**

Okay, so I'm looking at this patch and trying to understand the implications. The key change seems to revolve around adding an `alloc_flags` argument to `__folio_alloc_noprof` and creating `__alloc_pages_bulk_noprof`. Right now, my initial thought is that `ALLOC_DEFAULT` (which is 0) is being passed in every instance.

My initial thought process is:
1.  **Understand the Baseline:**  `ALLOC_DEFAULT` is zero. Therefore, when a function passes in `ALLOC_DEFAULT`, it's effectively passing zero.  The `fastpath_alloc_flags` seems to be set to `ALLOC_WMARK_LOW` after a bitwise OR operation. Then, `prepare_alloc_pages` modifies `fastpath_alloc_flags`.
2.  **Locate key functions:**  I notice that `__folio_alloc_noprof` now accepts an `alloc_flags` argument.  Previously, it was calling `__alloc_pages_noprof` with `ALLOC_DEFAULT`. Now, it's explicitly passing along the `alloc_flags` parameter. The same thing is true for `__folio_alloc_node_noprof` which, by the way, has been transformed from an inline to a non-inline function, that now has the `alloc_flags` argument in its call to `__folio_alloc_noprof`.
3.  **Check for call sites:** I've confirmed that `__folio_alloc_noprof` is also called in `khugepaged.c` and `migrate.c`, and again, `ALLOC_DEFAULT` is being passed in.
4.  **Confirm the Scope:** The files modified in this diff are limited to `include/linux/gfp.h`, `mm/khugepaged.c`, `mm/migrate.c`, `mm/page_alloc.c` and `mm/page_alloc.h`. This is a relatively focused set of changes.
5.  **Reasoning and Hypothesis:** The puzzling part is *why* this change? Adding an `alloc_flags` argument and creating `__alloc_pages_bulk_noprof` seems like a preparation for something, but in this commit itself, it seems like an unnecessary change since only `ALLOC_DEFAULT` is used in all the calls. It's almost as if this is a "refactoring" or preparatory patch. My hypothesis is that this patch is laying the groundwork for future functionality, possibly related to something like `ALLOC_NOLOCK`, `ALLOC_NO_CODETAG`, or some other flag that will influence page allocation behavior. This could be a cleanup or a preparation for a larger feature.
6. **Next Steps:** I will now scan the git history for the project and see if there are any recent commits or references to flags such as `ALLOC_NOLOCK`.

{
  "Expression": "ALLOC_NOLOCK"
}

{
  "Output": "mm/page_alloc.c=2517=static int rmqueue_bulk(struct zone *zone, unsigned int order,\n--\nmm/page_alloc.c-2524-\nmm/page_alloc.c:2525:\tif (unlikely(alloc_flags \u0026 ALLOC_NOLOCK)) {\nmm/page_alloc.c-2526-\t\tif (!spin_trylock_irqsave(\u0026zone-\u003elock, flags))\n--\nmm/page_alloc.c=3203=struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone,\n--\nmm/page_alloc.c-3211-\t\tpage = NULL;\nmm/page_alloc.c:3212:\t\tif (unlikely(alloc_flags \u0026 ALLOC_NOLOCK)) {\nmm/page_alloc.c-3213-\t\t\tif (!spin_trylock_irqsave(\u0026zone-\u003elock, flags))\n--\nmm/page_alloc.c=5085=static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-5112-\t */\nmm/page_alloc.c:5113:\tif (!(*alloc_flags \u0026 ALLOC_NOLOCK) \u0026\u0026\nmm/page_alloc.c-5114-\t    should_fail_alloc_page(gfp_mask, order))\n--\nmm/page_alloc.c=5336=static inline bool alloc_order_allowed(gfp_t gfp, unsigned int order,\n--\nmm/page_alloc.c-5338-{\nmm/page_alloc.c:5339:\tif (alloc_flags \u0026 ALLOC_NOLOCK)\nmm/page_alloc.c-5340-\t\treturn pcp_allowed_order(order);\n--\nmm/page_alloc.c=5349=static inline bool alloc_nolock_allowed(void)\n--\nmm/page_alloc.c-5361-/*\nmm/page_alloc.c:5362: * GFP flags to set for ALLOC_NOLOCK i.e. alloc_pages_nolock().\nmm/page_alloc.c-5363- *\n--\nmm/page_alloc.c=5389=struct page *__alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order,\n--\nmm/page_alloc.c-5399-\t/* Other flags could be supported later if needed. */\nmm/page_alloc.c:5400:\tif (WARN_ON(alloc_flags \u0026 ~(ALLOC_NOLOCK | ALLOC_NO_CODETAG)))\nmm/page_alloc.c-5401-\t\treturn NULL;\n--\nmm/page_alloc.c-5405-\nmm/page_alloc.c:5406:\tif (alloc_flags \u0026 ALLOC_NOLOCK) {\nmm/page_alloc.c-5407-\t\t/* Certain other flags could be supported later if needed. */\n--\nmm/page_alloc.c-5430-\nmm/page_alloc.c:5431:\tif (!(alloc_flags \u0026 ALLOC_NOLOCK)) {\nmm/page_alloc.c-5432-\t\t/*\n--\nmm/page_alloc.c-5442-\tpage = get_page_from_freelist(alloc_gfp, order, fastpath_alloc_flags, \u0026ac);\nmm/page_alloc.c:5443:\tif (likely(page) || (alloc_flags \u0026 ALLOC_NOLOCK))\nmm/page_alloc.c-5444-\t\tgoto out;\n--\nmm/page_alloc.c-5460-\t\t__free_frozen_pages(page, order,\nmm/page_alloc.c:5461:\t\t\t\t    alloc_flags \u0026 ALLOC_NOLOCK ? FPI_NOLOCK : 0);\nmm/page_alloc.c-5462-\t\tpage = NULL;\n--\nmm/page_alloc.c=7962=static bool cond_accept_memory(struct zone *zone, unsigned int order,\n--\nmm/page_alloc.c-7971-\t/* Bailout, since try_to_accept_memory_one() needs to take a lock */\nmm/page_alloc.c:7972:\tif (alloc_flags \u0026 ALLOC_NOLOCK)\nmm/page_alloc.c-7973-\t\treturn false;\n--\nmm/page_alloc.c=8040=struct page *alloc_frozen_pages_nolock_noprof(gfp_t gfp_flags, int nid, unsigned int order)\n--\nmm/page_alloc.c-8044-\nmm/page_alloc.c:8045:\treturn __alloc_frozen_pages_noprof(gfp_flags, order, nid, NULL, ALLOC_NOLOCK);\nmm/page_alloc.c-8046-}\n--\nmm/page_alloc.h-49-#define ALLOC_HIGHATOMIC\t0x200 /* Allows access to MIGRATE_HIGHATOMIC */\nmm/page_alloc.h:50:#define ALLOC_NOLOCK\t\t0x400 /* Only use spin_trylock in allocation path */\nmm/page_alloc.h-51-#define ALLOC_KSWAPD\t\t0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */\n--\nmm/slab.h-21-#define SLAB_ALLOC_DEFAULT\t0x00 /* no flags */\nmm/slab.h:22:#define SLAB_ALLOC_NOLOCK\t0x01 /* a kmalloc_nolock() allocation */\nmm/slab.h-23-#define SLAB_ALLOC_NEW_SLAB\t0x02 /* a flag for alloc_slab_obj_exts() */\n--\nmm/slab.h=30=static inline unsigned int to_alloc_flags(unsigned int free_flags)\n--\nmm/slab.h-32-\tif (free_flags \u0026 SLAB_FREE_NOLOCK)\nmm/slab.h:33:\t\treturn SLAB_ALLOC_NOLOCK;\nmm/slab.h-34-\telse\n--\nmm/slab.h=38=static inline bool alloc_flags_allow_spinning(const unsigned int alloc_flags)\nmm/slab.h-39-{\nmm/slab.h:40:\treturn !(alloc_flags \u0026 SLAB_ALLOC_NOLOCK);\nmm/slab.h-41-}\n--\nmm/slub.c=5523=void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, int node)\n--\nmm/slub.c-5527-\t\t.orig_size = size,\nmm/slub.c:5528:\t\t.alloc_flags = SLAB_ALLOC_NOLOCK,\nmm/slub.c-5529-\t};\n"
}

gemini-3.8-flash

null

null

							input: 38326
							output: 35
							thoughts: 3634
						

**Analysis of Memory Allocation Patch for Fuzzing**

Okay, this looks like a good one. I'm seeing changes to several core memory allocation functions. The main focus seems to be on allowing more granular control over page allocation flags. Specifically, I'm noticing modifications around `ALLOC_NOLOCK`, `alloc_frozen_pages_nolock_noprof`, and `SLAB_ALLOC_NOLOCK`. This patch introduces `alloc_flags` to `__folio_alloc_noprof`, `__alloc_pages_bulk_noprof`, and de-inlines `__folio_alloc_node_noprof`.

The change in `alloc_pages_bulk_noprof` is particularly interesting. Previously, it directly used `ALLOC_DEFAULT`, but now it seems the `alloc_flags` are passed through more consistently. I see a `fastpath_alloc_flags` now being used in the `prepare_alloc_pages` calls. And the code path at `failed:` now also passes `alloc_flags` to `__alloc_pages_noprof` (when called from `alloc_pages_bulk_noprof`).

This touches code that is absolutely reachable, used by many programs allocating memory, using page cache, migration, khugepaged collapse, `alloc_pages_bulk` in `splice`, `fs`, `net` etc.

This patch clearly meets the criteria for "WorthFuzzing=true". It's modifying reachable executable code within core memory management and related subsystems. No negative criteria are met. It's a clear yes.

Now, to determine the "FocusSymbols". I need to avoid listing ubiquitous functions that are called by almost every program. Functions like `__folio_alloc_noprof`, `__folio_alloc_node_noprof`, while essential, are *very* general. However, I should focus on the specific feature logic and entry points.

Given the changes, I'd say the following functions are good `FocusSymbols`:

1.  `__alloc_pages_bulk_noprof`: This is the core bulk allocator refactored and modified. It is the key change.
2.  `alloc_pages_bulk_noprof`: This is the wrapper calling `__alloc_pages_bulk_noprof`
3. `alloc_charge_folio`: In khugepaged.c. This is a *specific* entrypoint to THP (transparent huge pages) collapse logic, a specific use case of folio allocation.
4. `alloc_migration_target`: In migrate.c, which is a specific entrypoint for page migration allocation.

By focusing on these, I can avoid diluting the fuzzing effort.

{
  "File": "mm/vmalloc.c",
  "FirstLine": 3745,
  "LineCount": 25
}

{
  "Contents": "3745:\t\t\t\t */\n3746:\t\t\t\tnr_pages_request = min(100UL, nr_pages - nr_allocated);\n3747:\t\n3748:\t\t\t\t/* memory allocation should consider mempolicy, we can't\n3749:\t\t\t\t * wrongly use nearest node when nid == NUMA_NO_NODE,\n3750:\t\t\t\t * otherwise memory may be allocated in only one node,\n3751:\t\t\t\t * but mempolicy wants to alloc memory by interleaving.\n3752:\t\t\t\t */\n3753:\t\t\t\tif (IS_ENABLED(CONFIG_NUMA) \u0026\u0026 nid == NUMA_NO_NODE)\n3754:\t\t\t\t\tnr = alloc_pages_bulk_mempolicy_noprof(gfp,\n3755:\t\t\t\t\t\t\t\tnr_pages_request,\n3756:\t\t\t\t\t\t\t\tpages + nr_allocated);\n3757:\t\t\t\telse\n3758:\t\t\t\t\tnr = alloc_pages_bulk_node_noprof(gfp, nid,\n3759:\t\t\t\t\t\t\t\tnr_pages_request,\n3760:\t\t\t\t\t\t\t\tpages + nr_allocated);\n3761:\t\n3762:\t\t\t\tfor (i = nr_allocated; i \u003c nr_allocated + nr; i++)\n3763:\t\t\t\t\tmod_lruvec_page_state(pages[i], NR_VMALLOC, 1);\n3764:\t\n3765:\t\t\t\tnr_allocated += nr;\n3766:\t\n3767:\t\t\t\t/*\n3768:\t\t\t\t * If zero or pages were obtained partly,\n3769:\t\t\t\t * fallback to a single page allocator.\n"
}

gemini-3.8-flash

null

null

							input: 42987
							output: 19
							thoughts: 1005
						

**Focus Symbol Selection: A Deep Dive into Memory Allocation**

Okay, here's what's running through my head as I review this: I need to pick the right focus symbols, so I can't just throw everything in there.  Let's start with `vmalloc` – it's crucial to understand how it allocates memory, but a quick look reveals that every call to `vmalloc()` traces back through `alloc_pages_bulk_mempolicy_noprof`, `alloc_pages_bulk_node_noprof`, and ultimately `alloc_pages_bulk_noprof`, which then calls `__alloc_pages_bulk_noprof`.  The page pool itself uses `alloc_pages_bulk_node`, which also hits `alloc_pages_bulk_noprof`. I see similar calls via `folio_alloc` and `__folio_alloc_node_noprof`.

My gut tells me this is too broad. Is `__folio_alloc_node_noprof` ubiquitous? Let's trace it and find out. Bingo. It's called by `filemap_alloc_folio_noprof` in `mm/filemap.c`, which tells me the page cache allocation in filemap is calling `__folio_alloc_node_noprof`. And, when `!CONFIG_NUMA`, `folio_alloc_noprof` calls `__folio_alloc_node_noprof`. Then, to make it even more obvious, `__folio_alloc_noprof` is called by `__folio_alloc_node_noprof`. This is exactly the kind of thing the guidance is warning against: "AVOID UBIQUITOUS LIFECYCLE HOT-PATHS." It is explicitly stated: "general memory allocators and deallocators". If I put this in FocusSymbols, practically every program would be considered focused.

So, the challenge is finding the *specific* entrypoints, the feature logic. I need to dig deeper. I'm focusing on the *modified* functionality, here. Let's look at `mm/khugepaged.c` and `mm/migrate.c`. Ah, here's something: `alloc_charge_folio`.

Now, is `alloc_charge_folio` static? Let's check the code... Yep, it is. But, can static functions *in a .c file* be FocusSymbols? Let's double-check the documentation. The guidance is clear about *static inlines in headers*, but it states "identify non-static, feature-specific *caller* functions in .c files that exercise them". So, can *static functions in .c files* be used as FocusSymbols? Static functions in .c files usually *do* have symbols in `vmlinux` unless they're inlined by the compiler. But, who is calling it? I need to check the call sites for `alloc_charge_folio` in `mm/khugepaged.c` to see if that works.

{
  "Expression": "alloc_charge_folio"
}

{
  "Output": "mm/khugepaged.c=1098=static enum scan_result __collapse_huge_page_swapin(struct mm_struct *mm,\n--\nmm/khugepaged.c-1188-\nmm/khugepaged.c:1189:static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,\nmm/khugepaged.c-1190-\t\tstruct collapse_control *cc, unsigned int order)\n--\nmm/khugepaged.c=1225=static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long start_addr,\n--\nmm/khugepaged.c-1241-\nmm/khugepaged.c:1242:\tresult = alloc_charge_folio(\u0026folio, mm, cc, order);\nmm/khugepaged.c-1243-\tif (result != SCAN_SUCCEED)\n--\nmm/khugepaged.c=2189=static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,\n--\nmm/khugepaged.c-2212-\nmm/khugepaged.c:2213:\tresult = alloc_charge_folio(\u0026new_folio, mm, cc, HPAGE_PMD_ORDER);\nmm/khugepaged.c-2214-\tif (result != SCAN_SUCCEED)\n"
}

gemini-3.8-flash

null

null

							input: 45030
							output: 19
							thoughts: 74
						

**Investigating Memory Allocation Dependencies**

Okay, so I'm digging into memory management, specifically within the kernel. I see that `alloc_charge_folio` is used by both `collapse_huge_page` and `collapse_file` – that seems straightforward enough, both are located within `mm/khugepaged.c`. But my mind immediately jumps to other related functions, and I'm curious about how `alloc_migration_target` in `mm/migrate.c` fits into the picture. A key question in these investigations is always: What about the scope of that call? I should check if `alloc_migration_target` is declared as a static function or not. That will help me understand its reach and potential impact in the wider system. I need to nail that down.

{
  "Expression": "alloc_migration_target"
}

{
  "Output": "include/linux/migrate.h=59=int migrate_pages(struct list_head *l, new_folio_t new, free_folio_t free,\n--\ninclude/linux/migrate.h-62-\t\tunsigned int *ret_succeeded);\ninclude/linux/migrate.h:63:struct folio *alloc_migration_target(struct folio *src, unsigned long private);\ninclude/linux/migrate.h-64-bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode);\n--\ninclude/linux/migrate.h=79=static inline int migrate_pages(struct list_head *l, new_folio_t new,\n--\ninclude/linux/migrate.h-83-\t{ return -ENOSYS; }\ninclude/linux/migrate.h:84:static inline struct folio *alloc_migration_target(struct folio *src,\ninclude/linux/migrate.h-85-\t\tunsigned long private)\n--\nmm/damon/ops-common.c=395=static unsigned int __damon_migrate_folio_list(\n--\nmm/damon/ops-common.c-417-\t/* Migration ignores all cpuset and mempolicy settings */\nmm/damon/ops-common.c:418:\tmigrate_pages(migrate_folios, alloc_migration_target, NULL,\nmm/damon/ops-common.c-419-\t\t      (unsigned long)\u0026mtc, MIGRATE_ASYNC, MR_DAMON,\n--\nmm/gup.c=2323=migrate_longterm_unpinnable_folios(struct list_head *movable_folio_list,\n--\nmm/gup.c-2367-\nmm/gup.c:2368:\t\tif (migrate_pages(movable_folio_list, alloc_migration_target,\nmm/gup.c-2369-\t\t\t\t  NULL, (unsigned long)\u0026mtc, MIGRATE_SYNC,\n--\nmm/memory-failure.c=2849=static int soft_offline_in_use_page(struct page *page)\n--\nmm/memory-failure.c-2917-\tif (isolated) {\nmm/memory-failure.c:2918:\t\tret = migrate_pages(\u0026pagelist, alloc_migration_target, NULL,\nmm/memory-failure.c-2919-\t\t\t(unsigned long)\u0026mtc, MIGRATE_SYNC, MR_MEMORY_FAILURE, NULL);\n--\nmm/memory_hotplug.c=1879=static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)\n--\nmm/memory_hotplug.c-1952-\t\t\tnode_set(mtc.nid, nmask);\nmm/memory_hotplug.c:1953:\t\tret = migrate_pages(\u0026source, alloc_migration_target, NULL,\nmm/memory_hotplug.c-1954-\t\t\t(unsigned long)\u0026mtc, MIGRATE_SYNC, MR_MEMORY_HOTPLUG, NULL);\n--\nmm/mempolicy.c=629=static bool strictly_unmovable(unsigned long flags)\n--\nmm/mempolicy.c-638-\nmm/mempolicy.c:639:struct migration_mpol {\t\t/* for alloc_migration_target_by_mpol() */\nmm/mempolicy.c-640-\tstruct mempolicy *pol;\n--\nmm/mempolicy.c=1306=static long migrate_to_node(struct mm_struct *mm, int source, int dest,\n--\nmm/mempolicy.c-1342-\tif (!list_empty(\u0026pagelist)) {\nmm/mempolicy.c:1343:\t\terr = migrate_pages(\u0026pagelist, alloc_migration_target, NULL,\nmm/mempolicy.c-1344-\t\t\t(unsigned long)\u0026mtc, MIGRATE_SYNC, MR_SYSCALL, NULL);\n--\nmm/mempolicy.c=1360=int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,\n--\nmm/mempolicy.c-1457- */\nmm/mempolicy.c:1458:static struct folio *alloc_migration_target_by_mpol(struct folio *src,\nmm/mempolicy.c-1459-\t\t\t\t\t\t    unsigned long private)\n--\nmm/mempolicy.c=1497=int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,\n--\nmm/mempolicy.c-1502-\nmm/mempolicy.c:1503:static struct folio *alloc_migration_target_by_mpol(struct folio *src,\nmm/mempolicy.c-1504-\t\t\t\t\t\t    unsigned long private)\n--\nmm/mempolicy.c=1510=static long do_mbind(unsigned long start, unsigned long len,\n--\nmm/mempolicy.c-1638-\t\tnr_failed |= migrate_pages(\u0026pagelist,\nmm/mempolicy.c:1639:\t\t\t\talloc_migration_target_by_mpol, NULL,\nmm/mempolicy.c-1640-\t\t\t\t(unsigned long)\u0026mmpol, MIGRATE_SYNC,\n--\nmm/migrate.c=2099=int migrate_pages(struct list_head *from, new_folio_t get_new_folio,\n--\nmm/migrate.c-2195-\nmm/migrate.c:2196:struct folio *alloc_migration_target(struct folio *src, unsigned long private)\nmm/migrate.c-2197-{\n--\nmm/migrate.c=2247=static int do_move_pages_to_node(struct list_head *pagelist, int node)\n--\nmm/migrate.c-2255-\nmm/migrate.c:2256:\terr = migrate_pages(pagelist, alloc_migration_target, NULL,\nmm/migrate.c-2257-\t\t(unsigned long)\u0026mtc, MIGRATE_SYNC, MR_SYSCALL, NULL);\n--\nmm/page_alloc.c=7135=static int __alloc_contig_migrate_range(struct compact_control *cc,\n--\nmm/page_alloc.c-7172-\nmm/page_alloc.c:7173:\t\tret = migrate_pages(\u0026cc-\u003emigratepages, alloc_migration_target,\nmm/page_alloc.c-7174-\t\t\tNULL, (unsigned long)\u0026mtc, cc-\u003emode, MR_CONTIG_RANGE, NULL);\n--\nmm/vmscan.c=1040=static struct folio *alloc_demote_folio(struct folio *src,\n--\nmm/vmscan.c-1059-\ttarget_nid_mtc.gfp_mask |= __GFP_THISNODE;\nmm/vmscan.c:1060:\tdst = alloc_migration_target(src, (unsigned long)\u0026target_nid_mtc);\nmm/vmscan.c-1061-\tif (dst)\n--\nmm/vmscan.c-1063-\nmm/vmscan.c:1064:\treturn alloc_migration_target(src, (unsigned long)mtc);\nmm/vmscan.c-1065-}\n"
}

gemini-3.8-flash

null

null

							input: 47082
							output: 34
							thoughts: 267
						

**My Assessment of the Code**

Okay, so `alloc_migration_target` is a globally accessible symbol, declared in `include/linux/migrate.h` and defined in `mm/migrate.c`. This patch actually changes its behavior. And from the looks of it, it is used for page migration specifically – meaning it is not a core function called continuously, which is good.

My immediate thought, though, is about the potential for other similar functions. Is `alloc_charge_folio` in `mm/khugepaged.c` a problem? Wait, nope. It's static, so it's not globally visible and therefore not exposed as an issue. Similarly, `collapse_huge_page` and `collapse_file` in `mm/khugepaged.c` are also static, so they should be safe.

However, I need to know if there are *non*-static functions in `mm/khugepaged.c` that *call* those static functions or other khugepaged functions. Those would be the next things to examine for any potential issues or interaction points that could trigger this kind of behaviour. Let's dig into `mm/khugepaged.c` itself and see what's going on in there.

no matches

{
  "Expression": "^int khugepaged",
  "PathPrefix": "mm/khugepaged.c"
}

{
  "error": "no matches"
}

gemini-3.8-flash

null

null

							input: 47667
							output: 33
							thoughts: 32
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Investigating `madvise_collapse` in `mm/khugepaged.c`**

Okay, so the code is telling me `madvise_collapse` isn't static within `mm/khugepaged.c`. Let me just confirm that. I need to be absolutely sure because... well, let's just make sure I'm not missing something fundamental about its scope or how it's being accessed. A non-static function here raises certain considerations regarding potential external calls or usage patterns I'll need to account for in my analysis. Good, let's take a look.

no matches

{
  "Expression": "madvise_collapse",
  "PathPrefix": "mm/khugepaged.c"
}

{
  "error": "no matches"
}

gemini-3.8-flash

null

null

							input: 47895
							output: 35
							thoughts: 19
						

Here's my take on those thoughts:

**Khugepaged Function Investigation**

Alright, let's dive into the `mm/khugepaged.c` file. My first port of call is always the non-static functions. They're the entry points, the public interface, the parts of the kernel that other modules are *meant* to interact with. Static functions are, by their nature, more tightly coupled and contained within that file's specific implementation details. The non-static functions are, therefore, the key to understanding how khugepaged is *used* and *interacts* with the rest of the memory management subsystem. I need to get a high-level view of the API and the core behaviors that other components can trigger, and I'll find that in the non-static functions.

{
  "Expression": "^[a-z].*\\)",
  "PathPrefix": "mm/khugepaged.c"
}

{
  "Output": "mm/khugepaged.c=37=static struct task_struct *khugepaged_thread __read_mostly;\nmm/khugepaged.c:38:static DEFINE_MUTEX(khugepaged_mutex);\nmm/khugepaged.c-39-\n--\nmm/khugepaged.c=50=static unsigned long khugepaged_sleep_expire;\nmm/khugepaged.c:51:static DEFINE_SPINLOCK(khugepaged_mm_lock);\nmm/khugepaged.c:52:static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);\nmm/khugepaged.c-53-/*\n--\nmm/khugepaged.c=62=static unsigned int khugepaged_max_ptes_shared __read_mostly;\n--\nmm/khugepaged.c-64-#define MM_SLOTS_HASH_BITS 10\nmm/khugepaged.c:65:static DEFINE_READ_MOSTLY_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);\nmm/khugepaged.c-66-\n--\nmm/khugepaged.c=292=struct attribute_group khugepaged_attr_group = {\n--\nmm/khugepaged.c-297-\nmm/khugepaged.c:298:static bool pte_none_or_zero(pte_t pte)\nmm/khugepaged.c-299-{\n--\nmm/khugepaged.c=383=int hugepage_madvise(struct vm_area_struct *vma,\n--\nmm/khugepaged.c-404-\nmm/khugepaged.c:405:int __init khugepaged_init(void)\nmm/khugepaged.c-406-{\n--\nmm/khugepaged.c-418-\nmm/khugepaged.c:419:void __init khugepaged_destroy(void)\nmm/khugepaged.c-420-{\n--\nmm/khugepaged.c-423-\nmm/khugepaged.c:424:static inline int collapse_test_exit(struct mm_struct *mm)\nmm/khugepaged.c-425-{\n--\nmm/khugepaged.c-428-\nmm/khugepaged.c:429:static inline int collapse_test_exit_or_disable(struct mm_struct *mm)\nmm/khugepaged.c-430-{\n--\nmm/khugepaged.c-434-\nmm/khugepaged.c:435:static inline bool anon_hpage_enabled(void)\nmm/khugepaged.c-436-{\n--\nmm/khugepaged.c-446-\nmm/khugepaged.c:447:static bool hugepage_enabled(void)\nmm/khugepaged.c-448-{\n--\nmm/khugepaged.c-464-\nmm/khugepaged.c:465:void __khugepaged_enter(struct mm_struct *mm)\nmm/khugepaged.c-466-{\n--\nmm/khugepaged.c=515=void khugepaged_enter_vma(struct vm_area_struct *vma,\n--\nmm/khugepaged.c-522-\nmm/khugepaged.c:523:void __khugepaged_exit(struct mm_struct *mm)\nmm/khugepaged.c-524-{\n--\nmm/khugepaged.c-552-\nmm/khugepaged.c:553:static void collapse_scan_reset(struct collapse_control *cc)\nmm/khugepaged.c-554-{\n--\nmm/khugepaged.c-559-\nmm/khugepaged.c:560:static void release_pte_folio(struct folio *folio)\nmm/khugepaged.c-561-{\n--\nmm/khugepaged.c=872=static enum scan_result __collapse_huge_page_copy(pte_t *pte, struct folio *folio,\n--\nmm/khugepaged.c-910-\nmm/khugepaged.c:911:static void khugepaged_alloc_sleep(void)\nmm/khugepaged.c-912-{\n--\nmm/khugepaged.c=921=static struct collapse_control khugepaged_collapse_control;\nmm/khugepaged.c-922-\nmm/khugepaged.c:923:static bool collapse_scan_abort(int nid, struct collapse_control *cc)\nmm/khugepaged.c-924-{\n--\nmm/khugepaged.c-951-/* Defrag for khugepaged will enter direct reclaim/compaction if necessary */\nmm/khugepaged.c:952:static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)\nmm/khugepaged.c-953-{\n--\nmm/khugepaged.c-957-/* khugepaged collapses on its own initiative, so it obeys its own settings */\nmm/khugepaged.c:958:static void collapse_policy_khugepaged(struct collapse_policy *p)\nmm/khugepaged.c-959-{\n--\nmm/khugepaged.c-972-#ifdef CONFIG_NUMA\nmm/khugepaged.c:973:static int collapse_find_target_node(struct collapse_control *cc)\nmm/khugepaged.c-974-{\n--\nmm/khugepaged.c-991-#else\nmm/khugepaged.c:992:static int collapse_find_target_node(struct collapse_control *cc)\nmm/khugepaged.c-993-{\n--\nmm/khugepaged.c=1004=enum scan_result collapse_vma_revalidate(struct mm_struct *mm, unsigned long address,\n--\nmm/khugepaged.c-1040-\nmm/khugepaged.c:1041:static inline enum scan_result check_pmd_state(pmd_t *pmd)\nmm/khugepaged.c-1042-{\n--\nmm/khugepaged.c=1225=static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long start_addr,\n--\nmm/khugepaged.c-1410-/* Return the highest naturally aligned order that fits at @offset within a PMD. */\nmm/khugepaged.c:1411:static unsigned int max_order_from_offset(unsigned int offset)\nmm/khugepaged.c-1412-{\n--\nmm/khugepaged.c=1538=static enum scan_result collapse_scan_anon_pmd(struct vm_area_struct *vma,\n--\nmm/khugepaged.c-1731-\nmm/khugepaged.c:1732:static void collect_mm_slot(struct mm_slot *slot)\nmm/khugepaged.c-1733-{\n--\nmm/khugepaged.c=2036=void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,\n--\nmm/khugepaged.c-2042-/* Can we retract page tables for this file-backed VMA? */\nmm/khugepaged.c:2043:static bool file_backed_vma_is_retractable(struct vm_area_struct *vma)\nmm/khugepaged.c-2044-{\n--\nmm/khugepaged.c-2079-\nmm/khugepaged.c:2080:static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)\nmm/khugepaged.c-2081-{\n--\nmm/khugepaged.c=2645=static enum scan_result collapse_scan_file(struct mm_struct *mm,\n--\nmm/khugepaged.c-2752-\nmm/khugepaged.c:2753:void collapse_control_init(struct collapse_control *cc)\nmm/khugepaged.c-2754-{\n--\nmm/khugepaged.c-2758-\nmm/khugepaged.c:2759:void collapse_control_release(struct collapse_control *cc)\nmm/khugepaged.c-2760-{\n--\nmm/khugepaged.c=2865=static void collapse_scan_mm_slot(unsigned int progress_max,\n--\nmm/khugepaged.c-2994-\nmm/khugepaged.c:2995:static int khugepaged_has_work(void)\nmm/khugepaged.c-2996-{\n--\nmm/khugepaged.c-2999-\nmm/khugepaged.c:3000:static int khugepaged_wait_event(void)\nmm/khugepaged.c-3001-{\n--\nmm/khugepaged.c-3005-\nmm/khugepaged.c:3006:static void khugepaged_do_scan(struct collapse_control *cc)\nmm/khugepaged.c-3007-{\n--\nmm/khugepaged.c-3052-\nmm/khugepaged.c:3053:static bool khugepaged_should_wakeup(void)\nmm/khugepaged.c-3054-{\n--\nmm/khugepaged.c-3058-\nmm/khugepaged.c:3059:static void khugepaged_wait_work(void)\nmm/khugepaged.c-3060-{\n--\nmm/khugepaged.c-3078-\nmm/khugepaged.c:3079:static int khugepaged(void *none)\nmm/khugepaged.c-3080-{\n--\nmm/khugepaged.c-3099-\nmm/khugepaged.c:3100:void set_recommended_min_free_kbytes(void)\nmm/khugepaged.c-3101-{\n--\nmm/khugepaged.c-3150-\nmm/khugepaged.c:3151:int start_stop_khugepaged(void)\nmm/khugepaged.c-3152-{\n--\nmm/khugepaged.c-3177-\nmm/khugepaged.c:3178:void khugepaged_min_free_kbytes_update(void)\nmm/khugepaged.c-3179-{\n--\nmm/khugepaged.c-3184-\nmm/khugepaged.c:3185:bool current_is_khugepaged(void)\nmm/khugepaged.c-3186-{\n"
}

gemini-3.8-flash

null

null

							input: 50967
							output: 20
							thoughts: 56
						

Okay, here's my take on those thoughts, framed as my own mental process:

**Diving into the Kernel's Memory Management**

Alright, I'm digging into `mm/khugepaged.c`. I'm focusing on that `alloc_charge_folio` function. It's declared static, which immediately flags it as something potentially important only within that module. But, I've got a specific concern in mind: madvise collapse. I need to refresh my memory, where is `madvise_collapse` actually implemented? It's been a little while since I've been deep in this area, and while I *know* it's involved with that madvise flag, I need to jog my memory.

Time to reach for grep and search for `MADV_COLLAPSE`. That should give me a good handle on where that interaction is defined.

{
  "Expression": "MADV_COLLAPSE"
}

{
  "Output": "Documentation/admin-guide/mm/transhuge.rst=121=for which vary by system.\n--\nDocumentation/admin-guide/mm/transhuge.rst-124-          Transparent Huge Pages globally. This is because ``madvise(...,\nDocumentation/admin-guide/mm/transhuge.rst:125:          MADV_COLLAPSE)`` ignores these settings and collapses ranges to\nDocumentation/admin-guide/mm/transhuge.rst-126-          PMD-sized huge pages unconditionally.\n--\nDocumentation/admin-guide/mm/transhuge.rst=195=never\nDocumentation/admin-guide/mm/transhuge.rst-196-\tshould be self-explanatory. Note that ``madvise(...,\nDocumentation/admin-guide/mm/transhuge.rst:197:\tMADV_COLLAPSE)`` can still cause transparent huge pages to be\nDocumentation/admin-guide/mm/transhuge.rst-198-\tobtained even if this mode is specified everywhere.\n--\nDocumentation/admin-guide/mm/transhuge.rst=235=support the following arguments::\n--\nDocumentation/admin-guide/mm/transhuge.rst-238-\t\tThis will disable THPs completely for the process, irrespective\nDocumentation/admin-guide/mm/transhuge.rst:239:\t\tof global THP controls or madvise(..., MADV_COLLAPSE) being used.\nDocumentation/admin-guide/mm/transhuge.rst-240-\n--\nDocumentation/admin-guide/mm/transhuge.rst-244-\t\t- Global THP controls are set to \"always\" or \"madvise\" and\nDocumentation/admin-guide/mm/transhuge.rst:245:\t\t  madvise(..., MADV_HUGEPAGE) or madvise(..., MADV_COLLAPSE) is used.\nDocumentation/admin-guide/mm/transhuge.rst:246:\t\t- Global THP controls are set to \"never\" and madvise(..., MADV_COLLAPSE)\nDocumentation/admin-guide/mm/transhuge.rst-247-\t\t  is used. This is the same behavior as if THPs would not be disabled on\nDocumentation/admin-guide/mm/transhuge.rst-248-\t\t  a process level.\nDocumentation/admin-guide/mm/transhuge.rst:249:\t\tNote that MADV_COLLAPSE is currently always rejected if\nDocumentation/admin-guide/mm/transhuge.rst-250-\t\tmadvise(..., MADV_NOHUGEPAGE) is set on an area.\n--\nDocumentation/admin-guide/mm/transhuge.rst=447=never\nDocumentation/admin-guide/mm/transhuge.rst:448:    Do not allocate huge pages. Note that ``madvise(..., MADV_COLLAPSE)``\nDocumentation/admin-guide/mm/transhuge.rst-449-    can still cause transparent huge pages to be obtained even if this mode\n--\nDocumentation/admin-guide/mm/transhuge.rst=507=never\nDocumentation/admin-guide/mm/transhuge.rst-508-    Do not allocate \u003csize\u003e huge pages. Note that ``madvise(...,\nDocumentation/admin-guide/mm/transhuge.rst:509:    MADV_COLLAPSE)`` can still cause transparent huge pages to be obtained\nDocumentation/admin-guide/mm/transhuge.rst-510-    even if this mode is specified everywhere;\n--\nDocumentation/mm/damon/design.rst=544=that supports each action are as below.\n--\nDocumentation/mm/damon/design.rst-559-   fail.\nDocumentation/mm/damon/design.rst:560: - ``collapse``: Call ``madvise()`` for the region with ``MADV_COLLAPSE``.\nDocumentation/mm/damon/design.rst-561-   Supported by ``vaddr`` and ``fvaddr`` operations set. When\n--\nDocumentation/mm/process_addrs.rst=568=are extra requirements for accessing them:\n--\nDocumentation/mm/process_addrs.rst-574-  In particular, this happens in :c:func:`!retract_page_tables` when handling\nDocumentation/mm/process_addrs.rst:575:  :c:macro:`!MADV_COLLAPSE`.\nDocumentation/mm/process_addrs.rst-576-  So accessing PTE-level page tables requires at least holding an RCU read lock;\n--\nDocumentation/mm/process_addrs.rst-585-  the requirements. In particular, this also happens in :c:func:`!retract_page_tables`\nDocumentation/mm/process_addrs.rst:586:  when handling :c:macro:`!MADV_COLLAPSE`.\nDocumentation/mm/process_addrs.rst-587-\n--\narch/alpha/include/uapi/asm/mman.h-78-\narch/alpha/include/uapi/asm/mman.h:79:#define MADV_COLLAPSE\t25\t\t/* Synchronous hugepage collapse */\narch/alpha/include/uapi/asm/mman.h-80-\n--\narch/mips/include/uapi/asm/mman.h-105-\narch/mips/include/uapi/asm/mman.h:106:#define MADV_COLLAPSE\t25\t\t/* Synchronous hugepage collapse */\narch/mips/include/uapi/asm/mman.h-107-\n--\narch/parisc/include/uapi/asm/mman.h-72-\narch/parisc/include/uapi/asm/mman.h:73:#define MADV_COLLAPSE\t25\t\t/* Synchronous hugepage collapse */\narch/parisc/include/uapi/asm/mman.h-74-\n--\narch/parisc/kernel/sys_parisc.c=394=asmlinkage notrace long parisc_madvise(unsigned long start, size_t len_in, int behavior)\n--\narch/parisc/kernel/sys_parisc.c-404-\tcase 72: behavior = MADV_KEEPONFORK;\tbreak;\narch/parisc/kernel/sys_parisc.c:405:\tcase 73: behavior = MADV_COLLAPSE;\tbreak;\narch/parisc/kernel/sys_parisc.c-406-\t}\n--\narch/xtensa/include/uapi/asm/mman.h-113-\narch/xtensa/include/uapi/asm/mman.h:114:#define MADV_COLLAPSE\t25\t\t/* Synchronous hugepage collapse */\narch/xtensa/include/uapi/asm/mman.h-115-\n--\ninclude/linux/damon.h=93=struct damon_target {\n--\ninclude/linux/damon.h-113- * @DAMOS_NOHUGEPAGE:\tCall ``madvise()`` for the region with MADV_NOHUGEPAGE.\ninclude/linux/damon.h:114: * @DAMOS_COLLAPSE:\tCall ``madvise()`` for the region with MADV_COLLAPSE.\ninclude/linux/damon.h-115- * @DAMOS_LRU_PRIO:\tPrioritize the region on its LRU lists.\n--\ninclude/linux/huge_mm.h=97=enum tva_type {\n--\ninclude/linux/huge_mm.h-100-\tTVA_KHUGEPAGED,\t\t/* Khugepaged collapse. */\ninclude/linux/huge_mm.h:101:\tTVA_FORCED_COLLAPSE,\t/* Forced collapse (e.g. MADV_COLLAPSE). */\ninclude/linux/huge_mm.h-102-};\n--\ninclude/uapi/asm-generic/mman-common.h-79-\ninclude/uapi/asm-generic/mman-common.h:80:#define MADV_COLLAPSE\t25\t\t/* Synchronous hugepage collapse */\ninclude/uapi/asm-generic/mman-common.h-81-\n--\ninclude/uapi/linux/prctl.h=134=struct prctl_mm_map {\n--\ninclude/uapi/linux/prctl.h-187- * Don't disable THPs when explicitly advised (e.g., MADV_HUGEPAGE /\ninclude/uapi/linux/prctl.h:188: * VM_HUGEPAGE, MADV_COLLAPSE).\ninclude/uapi/linux/prctl.h-189- */\n--\nmm/Kconfig=881=choice\n--\nmm/Kconfig-896-\t  'transparent_hugepage_shmem=' option or at runtime via sysfs\nmm/Kconfig:897:\t  knob. Note that madvise(MADV_COLLAPSE) can still cause\nmm/Kconfig-898-\t  transparent huge pages to be obtained even if this mode is\n--\nmm/Kconfig=926=choice\n--\nmm/Kconfig-941-\t  'transparent_hugepage_tmpfs=' option. Note that\nmm/Kconfig:942:\t  madvise(MADV_COLLAPSE) can still cause transparent huge pages\nmm/Kconfig-943-\t  to be obtained even if this mode is specified.\n--\nmm/damon/vaddr.c=1085=static unsigned long damon_va_apply_scheme(struct damon_ctx *ctx,\n--\nmm/damon/vaddr.c-1107-\tcase DAMOS_COLLAPSE:\nmm/damon/vaddr.c:1108:\t\tmadv_action = MADV_COLLAPSE;\nmm/damon/vaddr.c-1109-\t\tbreak;\n--\nmm/huge_memory.c=121=static bool vma_file_bypass_thp_tuneables(const struct vm_area_struct *vma,\n--\nmm/huge_memory.c-125-\nmm/huge_memory.c:126:\t/* MADV_COLLAPSE ignores tuneables. */\nmm/huge_memory.c-127-\tif (type == TVA_FORCED_COLLAPSE)\n--\nmm/khugepaged.c=2189=static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,\n--\nmm/khugepaged.c-2204-\t/*\nmm/khugepaged.c:2205:\t * MADV_COLLAPSE ignores shmem huge config, so do not check shmem\nmm/khugepaged.c-2206-\t *\n--\nmm/madvise.c=878=bool madvise_dontneed_free_valid_vma(struct madvise_behavior *madv_behavior)\n--\nmm/madvise.c-910-\nmm/madvise.c:911:/* MADV_COLLAPSE was asked for explicitly, so it is not held to those */\nmm/madvise.c-912-static void collapse_policy_forced(struct collapse_policy *p)\n--\nmm/madvise.c=926=static int madvise_collapse_errno(enum scan_result r)\n--\nmm/madvise.c-928-\t/*\nmm/madvise.c:929:\t * MADV_COLLAPSE breaks from existing madvise(2) conventions to provide\nmm/madvise.c-930-\t * actionable feedback to caller, so they may take an appropriate\n--\nmm/madvise.c=1516=static int madvise_vma_behavior(struct madvise_behavior *madv_behavior)\n--\nmm/madvise.c-1539-\t\treturn madvise_dontneed_free(madv_behavior);\nmm/madvise.c:1540:\tcase MADV_COLLAPSE:\nmm/madvise.c-1541-\t\treturn madvise_collapse(madv_behavior);\n--\nmm/madvise.c=1695=madvise_behavior_valid(int behavior)\n--\nmm/madvise.c-1718-\tcase MADV_NOHUGEPAGE:\nmm/madvise.c:1719:\tcase MADV_COLLAPSE:\nmm/madvise.c-1720-#endif\n--\nmm/madvise.c=1739=static bool process_madvise_remote_valid(int behavior)\n--\nmm/madvise.c-1744-\tcase MADV_WILLNEED:\nmm/madvise.c:1745:\tcase MADV_COLLAPSE:\nmm/madvise.c-1746-\t\treturn true;\n--\nmm/madvise.c=1919=static enum madvise_lock_mode get_lock_mode(struct madvise_behavior *madv_behavior)\n--\nmm/madvise.c-1930-\tcase MADV_POPULATE_WRITE:\nmm/madvise.c:1931:\tcase MADV_COLLAPSE:\nmm/madvise.c-1932-\t\treturn MADVISE_MMAP_READ_LOCK;\n--\nmm/madvise.c=2064=static int madvise_do_behavior(unsigned long start, size_t len_in,\n--\nmm/madvise.c-2132- *\t\tcoalesced into THP and new pages will not be allocated as THP.\nmm/madvise.c:2133: *  MADV_COLLAPSE - synchronously coalesce pages into new THP.\nmm/madvise.c-2134- *  MADV_DONTDUMP - the application wants to prevent pages in the given range\n--\ntools/include/uapi/asm-generic/mman-common.h-79-\ntools/include/uapi/asm-generic/mman-common.h:80:#define MADV_COLLAPSE\t25\t\t/* Synchronous hugepage collapse */\ntools/include/uapi/asm-generic/mman-common.h-81-\n--\ntools/perf/trace/beauty/include/uapi/linux/prctl.h=134=struct prctl_mm_map {\n--\ntools/perf/trace/beauty/include/uapi/linux/prctl.h-187- * Don't disable THPs when explicitly advised (e.g., MADV_HUGEPAGE /\ntools/perf/trace/beauty/include/uapi/linux/prctl.h:188: * VM_HUGEPAGE, MADV_COLLAPSE).\ntools/perf/trace/beauty/include/uapi/linux/prctl.h-189- */\n--\ntools/testing/selftests/kvm/guest_memfd_test.c=174=static void test_collapse(int fd, u64 flags)\n--\ntools/testing/selftests/kvm/guest_memfd_test.c-218-\t */\ntools/testing/selftests/kvm/guest_memfd_test.c:219:\tTEST_ASSERT_EQ(madvise(mem, pmd_size, MADV_COLLAPSE), -1);\ntools/testing/selftests/kvm/guest_memfd_test.c-220-\tTEST_ASSERT_EQ(errno, EINVAL);\n--\ntools/testing/selftests/mm/cow.c=1276=static void do_test_anon_thp_collapse(char *mem, size_t size,\n--\ntools/testing/selftests/mm/cow.c-1308-\t\t/* Collapse before actually COW-sharing the page. */\ntools/testing/selftests/mm/cow.c:1309:\t\tret = madvise(mem, size, MADV_COLLAPSE);\ntools/testing/selftests/mm/cow.c-1310-\t\tif (ret) {\ntools/testing/selftests/mm/cow.c:1311:\t\t\tksft_perror(\"MADV_COLLAPSE failed\");\ntools/testing/selftests/mm/cow.c-1312-\t\t\tlog_test_result(KSFT_SKIP);\n--\ntools/testing/selftests/mm/cow.c-1386-\t\t/* Collapse before anyone modified the COW-shared page. */\ntools/testing/selftests/mm/cow.c:1387:\t\tret = madvise(mem, size, MADV_COLLAPSE);\ntools/testing/selftests/mm/cow.c-1388-\t\tif (ret) {\ntools/testing/selftests/mm/cow.c:1389:\t\t\tksft_perror(\"MADV_COLLAPSE failed\");\ntools/testing/selftests/mm/cow.c-1390-\t\t\tlog_test_result(KSFT_SKIP);\n--\ntools/testing/selftests/mm/guard-regions.c=2195=TEST_F(guard_regions, collapse)\n--\ntools/testing/selftests/mm/guard-regions.c-2237-\t */\ntools/testing/selftests/mm/guard-regions.c:2238:\tEXPECT_NE(madvise(ptr, size, MADV_COLLAPSE), 0);\ntools/testing/selftests/mm/guard-regions.c-2239-\n--\ntools/testing/selftests/mm/hmm-tests.c=2080=TEST_F(hmm, migrate_anon_huge_fault)\n--\ntools/testing/selftests/mm/hmm-tests.c-2110-\ntools/testing/selftests/mm/hmm-tests.c:2111:\tret = madvise(map, size, MADV_COLLAPSE);\ntools/testing/selftests/mm/hmm-tests.c-2112-\tASSERT_EQ(ret, 0);\n--\ntools/testing/selftests/mm/khugepaged.c=235=static void fill_memory(int *p, unsigned long start, unsigned long end)\n--\ntools/testing/selftests/mm/khugepaged.c-243-/*\ntools/testing/selftests/mm/khugepaged.c:244: * MADV_COLLAPSE is a best-effort request and may fail if an internal\ntools/testing/selftests/mm/khugepaged.c-245- * resource is temporarily unavailable, in which case it will set errno to\n--\ntools/testing/selftests/mm/khugepaged.c=249=static int madvise_collapse_retry(void *p, unsigned long size)\n--\ntools/testing/selftests/mm/khugepaged.c-254-retry:\ntools/testing/selftests/mm/khugepaged.c:255:\tret = madvise(p, size, MADV_COLLAPSE);\ntools/testing/selftests/mm/khugepaged.c-256-\tif (ret \u0026\u0026 errno == EAGAIN \u0026\u0026 retry) {\n--\ntools/testing/selftests/mm/khugepaged.c=267=static void *alloc_hpage(struct mem_ops *ops)\n--\ntools/testing/selftests/mm/khugepaged.c-274-\t * VMA should be neither VM_HUGEPAGE nor VM_NOHUGEPAGE.\ntools/testing/selftests/mm/khugepaged.c:275:\t * The latter is ineligible for collapse by MADV_COLLAPSE\ntools/testing/selftests/mm/khugepaged.c:276:\t * while the former might cause MADV_COLLAPSE to race with\ntools/testing/selftests/mm/khugepaged.c-277-\t * khugepaged on low-load system (like a test machine), which\ntools/testing/selftests/mm/khugepaged.c:278:\t * would cause MADV_COLLAPSE to fail with EAGAIN.\ntools/testing/selftests/mm/khugepaged.c-279-\t */\n--\ntools/testing/selftests/mm/khugepaged.c-281-\tif (madvise_collapse_retry(p, hpage_pmd_size))\ntools/testing/selftests/mm/khugepaged.c:282:\t\tksft_exit_fail_perror(\"madvise(MADV_COLLAPSE)\");\ntools/testing/selftests/mm/khugepaged.c-283-\tif (!ops-\u003echeck_huge(p, hpage_pmd_size, 1, hpage_pmd_size))\ntools/testing/selftests/mm/khugepaged.c:284:\t\tksft_exit_fail_perror(\"madvise(MADV_COLLAPSE)\");\ntools/testing/selftests/mm/khugepaged.c-285-\tif (madvise(p, hpage_pmd_size, MADV_HUGEPAGE))\n--\ntools/testing/selftests/mm/khugepaged.c=510=static void __madvise_collapse(const char *msg, char *p, int nr_hpages,\n--\ntools/testing/selftests/mm/khugepaged.c-518-\t/*\ntools/testing/selftests/mm/khugepaged.c:519:\t * read\u0026write file collapse succeeds for MADV_COLLAPSE because dirty\ntools/testing/selftests/mm/khugepaged.c-520-\t * folios are written back after collapse fails for dirty folios and\n--\ntools/testing/selftests/mm/khugepaged.c-524-\t/*\ntools/testing/selftests/mm/khugepaged.c:525:\t * Prevent khugepaged interference and tests that MADV_COLLAPSE\ntools/testing/selftests/mm/khugepaged.c-526-\t * ignores /sys/kernel/mm/transparent_hugepage/enabled\n--\ntools/testing/selftests/mm/pagemap_ioctl.c=1077=static void unpopulated_written_test(const char *name, char *mem, size_t size,\n--\ntools/testing/selftests/mm/pagemap_ioctl.c-1088-\tif (use_thp \u0026\u0026\ntools/testing/selftests/mm/pagemap_ioctl.c:1089:\t    (madvise(mem, size, MADV_COLLAPSE) ||\ntools/testing/selftests/mm/pagemap_ioctl.c-1090-\t     !check_huge_anon(mem, size, size / hpage_size, hpage_size))) {\n--\ntools/testing/selftests/mm/prctl_thp_disable.c=24=enum thp_collapse_type {\n--\ntools/testing/selftests/mm/prctl_thp_disable.c-27-\tTHP_COLLAPSE_MADV_HUGEPAGE,\t/* MADV_HUGEPAGE before access */\ntools/testing/selftests/mm/prctl_thp_disable.c:28:\tTHP_COLLAPSE_MADV_COLLAPSE,\t/* MADV_COLLAPSE after access */\ntools/testing/selftests/mm/prctl_thp_disable.c-29-};\n--\ntools/testing/selftests/mm/prctl_thp_disable.c-32- * Function to mmap a buffer, fault it in, madvise it appropriately (before\ntools/testing/selftests/mm/prctl_thp_disable.c:33: * page fault for MADV_HUGE, and after for MADV_COLLAPSE), and check if the\ntools/testing/selftests/mm/prctl_thp_disable.c-34- * mmap region is huge.\n--\ntools/testing/selftests/mm/prctl_thp_disable.c=40=static int test_mmap_thp(enum thp_collapse_type madvise_buf, size_t pmdsize)\n--\ntools/testing/selftests/mm/prctl_thp_disable.c-63-\ntools/testing/selftests/mm/prctl_thp_disable.c:64:\tif (madvise_buf == THP_COLLAPSE_MADV_COLLAPSE)\ntools/testing/selftests/mm/prctl_thp_disable.c:65:\t\tmadvise(mem, pmdsize, MADV_COLLAPSE);\ntools/testing/selftests/mm/prctl_thp_disable.c-66-\n--\ntools/testing/selftests/mm/prctl_thp_disable.c=75=static void prctl_thp_disable_completely_test(struct __test_metadata *const _metadata,\n--\ntools/testing/selftests/mm/prctl_thp_disable.c-87-\ntools/testing/selftests/mm/prctl_thp_disable.c:88:\tASSERT_EQ(test_mmap_thp(THP_COLLAPSE_MADV_COLLAPSE, pmdsize), 0);\ntools/testing/selftests/mm/prctl_thp_disable.c-89-\n--\ntools/testing/selftests/mm/prctl_thp_disable.c-101-\ntools/testing/selftests/mm/prctl_thp_disable.c:102:\tASSERT_EQ(test_mmap_thp(THP_COLLAPSE_MADV_COLLAPSE, pmdsize), 1);\ntools/testing/selftests/mm/prctl_thp_disable.c-103-}\n--\ntools/testing/selftests/mm/prctl_thp_disable.c=182=static void prctl_thp_disable_except_madvise_test(struct __test_metadata *const _metadata,\n--\ntools/testing/selftests/mm/prctl_thp_disable.c-195-\ntools/testing/selftests/mm/prctl_thp_disable.c:196:\tASSERT_EQ(test_mmap_thp(THP_COLLAPSE_MADV_COLLAPSE, pmdsize), 1);\ntools/testing/selftests/mm/prctl_thp_disable.c-197-\n--\ntools/testing/selftests/mm/prctl_thp_disable.c-209-\ntools/testing/selftests/mm/prctl_thp_disable.c:210:\tASSERT_EQ(test_mmap_thp(THP_COLLAPSE_MADV_COLLAPSE, pmdsize), 1);\ntools/testing/selftests/mm/prctl_thp_disable.c-211-}\n--\ntools/testing/selftests/mm/process_madv.c=60=TEST_F(process_madvise, basic)\n--\ntools/testing/selftests/mm/process_madv.c-123-/*\ntools/testing/selftests/mm/process_madv.c:124: * This test deterministically validates process_madvise() with MADV_COLLAPSE\ntools/testing/selftests/mm/process_madv.c-125- * on a remote process, other advices are difficult to verify reliably.\n--\ntools/testing/selftests/mm/process_madv.c-128- * focus on process_madv remote result, only check addresses and lengths.\ntools/testing/selftests/mm/process_madv.c:129: * The correctness of the MADV_COLLAPSE can be found in the relevant test examples in khugepaged.\ntools/testing/selftests/mm/process_madv.c-130- */\ntools/testing/selftests/mm/process_madv.c=131=TEST_F(process_madvise, remote_collapse)\n--\ntools/testing/selftests/mm/process_madv.c-195-\ntools/testing/selftests/mm/process_madv.c:196:\tret = sys_process_madvise(self-\u003eremote_pidfd, \u0026vec, 1, MADV_COLLAPSE,\ntools/testing/selftests/mm/process_madv.c-197-\t\t\t\t  0);\n--\ntools/testing/selftests/mm/uffd-unit-tests.c=551=static void uffd_minor_test_common(uffd_global_test_opts_t *gopts, bool test_collapse, bool test_wp)\n--\ntools/testing/selftests/mm/uffd-unit-tests.c-561-\t/*\ntools/testing/selftests/mm/uffd-unit-tests.c:562:\t * NOTE: MADV_COLLAPSE is not yet compatible with WP, so testing\ntools/testing/selftests/mm/uffd-unit-tests.c-563-\t * both do not make much sense.\n--\ntools/testing/selftests/mm/uffd-unit-tests.c-567-\tif (uffd_register(gopts-\u003euffd, gopts-\u003earea_dst_alias, gopts-\u003enr_pages * gopts-\u003epage_size,\ntools/testing/selftests/mm/uffd-unit-tests.c:568:\t\t\t  /* NOTE! MADV_COLLAPSE may not work with uffd-wp */\ntools/testing/selftests/mm/uffd-unit-tests.c-569-\t\t\t  false, test_wp, true))\n--\ntools/testing/selftests/mm/uffd-unit-tests.c-591-\ntools/testing/selftests/mm/uffd-unit-tests.c:592:\t\t/* MADV_COLLAPSE might return EINVAL for uffd-minor VMAs. */\ntools/testing/selftests/mm/uffd-unit-tests.c-593-\t\tmadvise(gopts-\u003earea_dst_alias, gopts-\u003enr_pages * gopts-\u003epage_size,\ntools/testing/selftests/mm/uffd-unit-tests.c:594:\t\t\tMADV_COLLAPSE);\ntools/testing/selftests/mm/uffd-unit-tests.c-595-\t\t/*\n--\ntools/testing/selftests/mm/uffd-unit-tests.c-631-\t\t/*\ntools/testing/selftests/mm/uffd-unit-tests.c:632:\t\t * MADV_COLLAPSE will fail unless userfaultfd-minor is\ntools/testing/selftests/mm/uffd-unit-tests.c-633-\t\t * unregistered.\n--\ntools/testing/selftests/mm/uffd-unit-tests.c-636-\t\t\t\t    gopts-\u003enr_pages * gopts-\u003epage_size))\ntools/testing/selftests/mm/uffd-unit-tests.c:637:\t\t\terr(\"uffd_unregister before MADV_COLLAPSE failed\");\ntools/testing/selftests/mm/uffd-unit-tests.c-638-\ntools/testing/selftests/mm/uffd-unit-tests.c:639:\t\t/* MADV_COLLAPSE should succeed with userfaultfd unregistered. */\ntools/testing/selftests/mm/uffd-unit-tests.c-640-\t\tif (madvise(gopts-\u003earea_dst_alias, gopts-\u003enr_pages * gopts-\u003epage_size,\ntools/testing/selftests/mm/uffd-unit-tests.c:641:\t\t\t    MADV_COLLAPSE)) {\ntools/testing/selftests/mm/uffd-unit-tests.c:642:\t\t\tuffd_test_fail(\"MADV_COLLAPSE failed\");\ntools/testing/selftests/mm/uffd-unit-tests.c-643-\t\t\treturn;\n--\ntools/testing/selftests/mm/uffd-unit-tests.c=2383=uffd_test_case_t uffd_tests[] = {\n--\ntools/testing/selftests/mm/uffd-unit-tests.c-2485-\t\t.uffd_fn = uffd_minor_collapse_test,\ntools/testing/selftests/mm/uffd-unit-tests.c:2486:\t\t/* MADV_COLLAPSE only works with shmem */\ntools/testing/selftests/mm/uffd-unit-tests.c-2487-\t\t.mem_targets = MEM_SHMEM,\ntools/testing/selftests/mm/uffd-unit-tests.c:2488:\t\t/* We can't test MADV_COLLAPSE, so try our luck */\ntools/testing/selftests/mm/uffd-unit-tests.c-2489-\t\t.uffd_feature_required = UFFD_FEATURE_MINOR_SHMEM,\n"
}

gemini-3.8-flash

null

null

							input: 59422
							output: 20
							thoughts: 92
						

**Investigating the `madvise_collapse` Function**

Okay, so I'm digging into `mm/madvise.c`, specifically looking at how `madvise_collapse` works. It seems like this function is key, as it calls either `collapse_huge_page` or `collapse_file`, depending on the situation. Now, the real question is, where is `madvise_collapse` defined? I need to understand its logic, and the natural place to start looking is `mm/khugepaged.c`. But hold on, I don't see it directly. Time to fire up the grep and search for `madvise_collapse(` to track down its definition and see what's really going on under the hood. Hopefully, that will give me the context I need.

{
  "Expression": "madvise_collapse\\("
}

{
  "Output": "mm/madvise.c=926=static int madvise_collapse_errno(enum scan_result r)\n--\nmm/madvise.c-957-\nmm/madvise.c:958:static int madvise_collapse(struct madvise_behavior *madv_behavior)\nmm/madvise.c-959-{\n--\nmm/madvise.c-1066-\nmm/madvise.c:1067:static int madvise_collapse(struct madvise_behavior *madv_behavior)\nmm/madvise.c-1068-{\n--\nmm/madvise.c=1516=static int madvise_vma_behavior(struct madvise_behavior *madv_behavior)\n--\nmm/madvise.c-1540-\tcase MADV_COLLAPSE:\nmm/madvise.c:1541:\t\treturn madvise_collapse(madv_behavior);\nmm/madvise.c-1542-\tcase MADV_GUARD_INSTALL:\n--\ntools/testing/selftests/mm/khugepaged.c=505=static bool is_anon(struct mem_ops *ops)\n--\ntools/testing/selftests/mm/khugepaged.c-509-\ntools/testing/selftests/mm/khugepaged.c:510:static void __madvise_collapse(const char *msg, char *p, int nr_hpages,\ntools/testing/selftests/mm/khugepaged.c-511-\t\t\t       struct mem_ops *ops, bool expect)\n--\ntools/testing/selftests/mm/khugepaged.c-544-\ntools/testing/selftests/mm/khugepaged.c:545:static void madvise_collapse(const char *msg, char *p, int nr_hpages,\ntools/testing/selftests/mm/khugepaged.c-546-\t\t\t     struct mem_ops *ops, bool expect)\n--\ntools/testing/selftests/mm/khugepaged.c-550-\t\tksft_exit_fail_msg(\"Unexpected huge page\\n\");\ntools/testing/selftests/mm/khugepaged.c:551:\t__madvise_collapse(msg, p, nr_hpages, ops, expect);\ntools/testing/selftests/mm/khugepaged.c-552-}\n--\ntools/testing/selftests/mm/khugepaged.c=1128=static void madvise_collapse_existing_thps(struct collapse_context *c,\n--\ntools/testing/selftests/mm/khugepaged.c-1138-\t/* c-\u003ecollapse() will find a hugepage and complain - call directly. */\ntools/testing/selftests/mm/khugepaged.c:1139:\t__madvise_collapse(\"Re-collapse PMD-mapped hugepage\", p, 1, ops, true);\ntools/testing/selftests/mm/khugepaged.c-1140-\tvalidate_memory(p, 0, hpage_pmd_size);\n"
}

gemini-3.8-flash

null

null

							input: 60506
							output: 35
							thoughts: 43
						

Okay, let's break this down.

**Investigating a `madvise` Call**

Right, so I'm trying to trace the execution path and I see a reference to `mm/madvise.c:958`. That tells me the specific file and line number within the kernel source code related to memory management, specifically with the `madvise` system call. Now, the next logical step is to understand what that line is actually *doing*. To do that, I need to know what function is being called from that line. I'm going to quickly look up `madvise_collapse` in `mm/madvise.c` to see how it's used. This should give me some context about what happens, and what the flow is.

{
  "File": "mm/madvise.c",
  "FirstLine": 958,
  "LineCount": 45
}

{
  "Contents": " 958:\tstatic int madvise_collapse(struct madvise_behavior *madv_behavior)\n 959:\t{\n 960:\t\tstruct madvise_behavior_range *range = \u0026madv_behavior-\u003erange;\n 961:\t\tstruct vm_area_struct *vma = madv_behavior-\u003evma;\n 962:\t\tstruct mm_struct *mm = madv_behavior-\u003emm;\n 963:\t\tstruct collapse_control *cc;\n 964:\t\tunsigned long hstart, hend, addr, orders;\n 965:\t\tenum scan_result last_fail = SCAN_FAIL;\n 966:\t\tint thps = 0;\n 967:\t\n 968:\t\tBUG_ON(vma-\u003evm_start \u003e range-\u003estart);\n 969:\t\tBUG_ON(vma-\u003evm_end \u003c range-\u003eend);\n 970:\t\n 971:\t\torders = collapse_possible_orders(vma, vma-\u003evm_flags,\n 972:\t\t\t\t\t\t  TVA_FORCED_COLLAPSE);\n 973:\t\tif (!orders)\n 974:\t\t\treturn -EINVAL;\n 975:\t\n 976:\t\thstart = ALIGN(range-\u003estart, HPAGE_PMD_SIZE);\n 977:\t\thend = ALIGN_DOWN(range-\u003eend, HPAGE_PMD_SIZE);\n 978:\t\n 979:\t\tif (hstart \u003e= hend)\n 980:\t\t\treturn 0;\n 981:\t\n 982:\t\tcc = kmalloc_obj(*cc);\n 983:\t\tif (!cc)\n 984:\t\t\treturn -ENOMEM;\n 985:\t\tcollapse_control_init(cc);\n 986:\t\tcollapse_policy_forced(\u0026cc-\u003epolicy);\n 987:\t\n 988:\t\tlru_add_drain_all();\n 989:\t\n 990:\t\tfor (addr = hstart; addr \u003c hend; addr += HPAGE_PMD_SIZE) {\n 991:\t\t\tstruct vm_area_struct *found;\n 992:\t\t\tenum scan_result result;\n 993:\t\n 994:\t\t\t/*\n 995:\t\t\t * A collapse gives the lock up, so the VMA has to be found\n 996:\t\t\t * again after one: it can shrink while nothing is held.  A scan\n 997:\t\t\t * that finds nothing to collapse leaves the lock alone, so a\n 998:\t\t\t * range that is already collapsed walks on without relocking.\n 999:\t\t\t */\n1000:\t\t\tif (!vma) {\n1001:\t\t\t\tcond_resched();\n1002:\t\t\t\tmmap_read_lock(mm);\n"
}

gemini-3.8-flash

null

null

							input: 61463
							output: 36
							thoughts: 31
						

Here's my summary, as if I were thinking these thoughts:

**Dissecting `madvise_collapse`'s Inner Workings**

Okay, let's dive into this. The objective is clear: to understand what `madvise_collapse` is actually calling within that loop. I need to pinpoint the critical lines of code, specifically within the region 1000-1040. My deep understanding of memory management and system calls tells me that this function is likely orchestrating something significant related to memory regions. It's time to follow the trail. I'll focus on the calls made in the context of the loop to see how this function is optimizing or changing the memory mapping, specifically by looking for a function that handles that kind of task. My expert knowledge helps me, as I already have a suspicion about what I should find.

{
  "File": "mm/madvise.c",
  "FirstLine": 1000,
  "LineCount": 40
}

{
  "Contents": "1000:\t\t\tif (!vma) {\n1001:\t\t\t\tcond_resched();\n1002:\t\t\t\tmmap_read_lock(mm);\n1003:\t\t\t\tresult = collapse_vma_revalidate(mm, addr, false, \u0026found,\n1004:\t\t\t\t\t\t\t\t cc, HPAGE_PMD_ORDER);\n1005:\t\t\t\tif (result != SCAN_SUCCEED) {\n1006:\t\t\t\t\tlast_fail = result;\n1007:\t\t\t\t\tgoto out_locked;\n1008:\t\t\t\t}\n1009:\t\t\t\tvma = found;\n1010:\t\t\t\thend = min(hend, vma-\u003evm_end \u0026 HPAGE_PMD_MASK);\n1011:\t\t\t\torders = collapse_possible_orders(vma, vma-\u003evm_flags,\n1012:\t\t\t\t\t\t\t\t  cc-\u003epolicy.tva_type);\n1013:\t\t\t}\n1014:\t\n1015:\t\t\tresult = collapse_scan_pmd(vma, addr, cc, orders);\n1016:\t\t\t/* Nothing to collapse here, and the lock is still ours */\n1017:\t\t\tif (result != SCAN_SUCCEED)\n1018:\t\t\t\tgoto tally;\n1019:\t\n1020:\t\t\t/* The collapse takes its own locks, so give this up */\n1021:\t\t\tmmap_read_unlock(mm);\n1022:\t\t\tmark_mmap_lock_dropped(madv_behavior);\n1023:\t\t\tvma = NULL;\n1024:\t\n1025:\t\t\tresult = collapse_run_pmd(mm, addr, cc);\n1026:\ttally:\n1027:\t\t\tswitch (result) {\n1028:\t\t\tcase SCAN_SUCCEED:\n1029:\t\t\tcase SCAN_PMD_MAPPED:\n1030:\t\t\t\t++thps;\n1031:\t\t\t\tbreak;\n1032:\t\t\t/* Whitelisted set of results where continuing OK */\n1033:\t\t\tcase SCAN_NO_PTE_TABLE:\n1034:\t\t\tcase SCAN_PTE_NON_PRESENT:\n1035:\t\t\tcase SCAN_PTE_UFFD:\n1036:\t\t\tcase SCAN_LACK_REFERENCED_PAGE:\n1037:\t\t\tcase SCAN_PAGE_NULL:\n1038:\t\t\tcase SCAN_PAGE_COUNT:\n1039:\t\t\tcase SCAN_PAGE_LOCK:\n"
}

gemini-3.8-flash

null

null

							input: 62333
							output: 20
							thoughts: 26
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Debugging a Potential PMD Collapse**

Alright, *collapse_run_pmd*! That's a flag that's set somewhere in the build process. I'm seeing it referenced in this context, so the first thing I need to figure out is its scope and definition. Where the hell is this thing defined? Let's trace it back to its source. Time to dive into the code! I need to quickly identify where this flag is set or unset to understand its behavior. It could be in a script, a configuration file, an environment variable, or even hardcoded somewhere. Let's start with a thorough search of the relevant source tree. I need to understand its intended purpose and how it's influencing the build.

{
  "Expression": "collapse_run_pmd"
}

{
  "Output": "mm/collapse.h=110=unsigned long collapse_possible_orders(struct vm_area_struct *vma,\n--\nmm/collapse.h-118- *     collapse_scan_pmd(vma, addr, ...) per table\nmm/collapse.h:119: *     collapse_run_pmd(mm, addr, cc)    when a scan found work\nmm/collapse.h-120- *     collapse_control_release(cc)      once, when done with the control\n--\nmm/collapse.h=143=enum scan_result collapse_scan_pmd(struct vm_area_struct *vma,\n--\nmm/collapse.h-145-\t\tunsigned long orders);\nmm/collapse.h:146:enum scan_result collapse_run_pmd(struct mm_struct *mm, unsigned long addr,\nmm/collapse.h-147-\t\tstruct collapse_control *cc);\n--\nmm/khugepaged.c=2768=enum scan_result collapse_scan_pmd(struct vm_area_struct *vma,\n--\nmm/khugepaged.c-2811-\nmm/khugepaged.c:2812:enum scan_result collapse_run_pmd(struct mm_struct *mm, unsigned long addr,\nmm/khugepaged.c-2813-\t\tstruct collapse_control *cc)\n--\nmm/khugepaged.c=2865=static void collapse_scan_mm_slot(unsigned int progress_max,\n--\nmm/khugepaged.c-2957-\t\t\tmmap_read_unlock(mm);\nmm/khugepaged.c:2958:\t\t\t*result = collapse_run_pmd(mm, addr, cc);\nmm/khugepaged.c-2959-\t\t\tif (*result == SCAN_SUCCEED)\n--\nmm/madvise.c=958=static int madvise_collapse(struct madvise_behavior *madv_behavior)\n--\nmm/madvise.c-1024-\nmm/madvise.c:1025:\t\tresult = collapse_run_pmd(mm, addr, cc);\nmm/madvise.c-1026-tally:\n"
}

gemini-3.8-flash

null

null

							input: 63116
							output: 37
							thoughts: 50
						

Here's my take on the thought process, as requested:

**Diving into `collapse_run_pmd`**

Okay, so `collapse_run_pmd` is *right there* in `mm/khugepaged.c`! And, interestingly, it's global. Not static, so potentially callable from elsewhere, though the implications will require further investigation. Let's dig into the code and see what this thing is *actually* doing. Understanding this function is going to be key to grasping how khugepaged is handling page collapse...

{
  "File": "mm/khugepaged.c",
  "FirstLine": 2810,
  "LineCount": 40
}

{
  "Contents": "2810:\t}\n2811:\t\n2812:\tenum scan_result collapse_run_pmd(struct mm_struct *mm, unsigned long addr,\n2813:\t\t\tstruct collapse_control *cc)\n2814:\t{\n2815:\t\tstruct file *file = cc-\u003escan_file;\n2816:\t\tbool triggered_wb = false;\n2817:\t\tenum scan_result result;\n2818:\t\tpgoff_t pgoff;\n2819:\t\n2820:\t\tif (!file)\n2821:\t\t\treturn mthp_collapse(mm, addr, cc-\u003escan_referenced,\n2822:\t\t\t\t\t     cc-\u003escan_unmapped, cc, cc-\u003escan_orders);\n2823:\t\n2824:\t\tcc-\u003escan_file = NULL;\n2825:\t\tpgoff = cc-\u003escan_pgoff;\n2826:\t\n2827:\t\tif (cc-\u003escan_retract_only) {\n2828:\t\t\tresult = SCAN_PTE_MAPPED_HUGEPAGE;\n2829:\t\t\tgoto retract;\n2830:\t\t}\n2831:\tretry:\n2832:\t\tresult = collapse_file(mm, addr, file, pgoff, cc);\n2833:\t\n2834:\t\t/* Dirty pages are worth a writeback and one more try, if asked for */\n2835:\t\tif (cc-\u003epolicy.writeback_dirty \u0026\u0026 result == SCAN_PAGE_DIRTY_OR_WRITEBACK \u0026\u0026\n2836:\t\t    !triggered_wb \u0026\u0026 mapping_can_writeback(file-\u003ef_mapping)) {\n2837:\t\t\tconst loff_t lstart = (loff_t)pgoff \u003c\u003c PAGE_SHIFT;\n2838:\t\t\tconst loff_t lend = lstart + HPAGE_PMD_SIZE - 1;\n2839:\t\n2840:\t\t\tfilemap_write_and_wait_range(file-\u003ef_mapping, lstart, lend);\n2841:\t\t\ttriggered_wb = true;\n2842:\t\t\tgoto retry;\n2843:\t\t}\n2844:\tretract:\n2845:\t\tfput(file);\n2846:\t\n2847:\t\t/*\n2848:\t\t * A PMD folio is in the page cache, whether the collapse just put it\n2849:\t\t * there or found it: retract the PTE table, and map the PMD if asked.\n"
}

gemini-3.8-flash

null

null

							input: 63969
							output: 34
							thoughts: 37
						

Okay, here's my interpretation of that thought process, as if it were my own:

**Analyzing the `collapse_run_pmd` Function**

Right, `collapse_run_pmd` is the key function here. My immediate thought is, okay, what's *actually* happening under the hood? It seems like it's a wrapper of sorts, which calls either `mthp_collapse` or `collapse_file`. So, the next logical step is to dive deeper. I need to understand the behaviour of those functions to grasp what the larger routine is intended to accomplish. Let's see what happens within `mthp_collapse`, and whether `collapse_file` should also be examined. I suspect that the true logic probably lies within these called methods.

{
  "Expression": "mthp_collapse\\(",
  "PathPrefix": "mm/khugepaged.c"
}

{
  "Output": "mm/khugepaged.c=1411=static unsigned int max_order_from_offset(unsigned int offset)\n--\nmm/khugepaged.c-1419-/*\nmm/khugepaged.c:1420: * mthp_collapse() consumes the bitmap that is generated during\nmm/khugepaged.c-1421- * collapse_scan_pmd() to determine what regions and mTHP orders fit best.\n--\nmm/khugepaged.c-1435- */\nmm/khugepaged.c:1436:static enum scan_result mthp_collapse(struct mm_struct *mm,\nmm/khugepaged.c-1437-\t\tunsigned long address, int referenced, int unmapped,\n--\nmm/khugepaged.c=1538=static enum scan_result collapse_scan_anon_pmd(struct vm_area_struct *vma,\n--\nmm/khugepaged.c-1570-\t * scan all pages to populate the bitmap for mTHP collapse. The bitmap\nmm/khugepaged.c:1571:\t * is then checked again in mthp_collapse() for each attempted order.\nmm/khugepaged.c-1572-\t */\n--\nmm/khugepaged.c=2812=enum scan_result collapse_run_pmd(struct mm_struct *mm, unsigned long addr,\n--\nmm/khugepaged.c-2820-\tif (!file)\nmm/khugepaged.c:2821:\t\treturn mthp_collapse(mm, addr, cc-\u003escan_referenced,\nmm/khugepaged.c-2822-\t\t\t\t     cc-\u003escan_unmapped, cc, cc-\u003escan_orders);\n"
}

gemini-3.8-flash

null

null

							input: 64659
							output: 21
							thoughts: 1802
						

**Focus Symbol Determination: A Deep Dive**

Okay, let's break this down. My goal is to identify suitable "FocusSymbols" for fuzzing, avoiding both ubiquitous functions and focusing on specific feature logic.

First, I see the calls: `mthp_collapse` calls `collapse_huge_page`, which calls `alloc_charge_folio`, which calls `__folio_alloc`. And `collapse_file` calls `alloc_charge_folio`, which also calls `__folio_alloc`. This suggests a clear call chain related to page collapse. The entrypoint in `mm/khugepaged.c` is `collapse_run_pmd`. This looks promising. The question is, can I also use a static function? Let me think.

Then, there's `alloc_migration_target`, exported in `mm/migrate.c`. I see that it is modified and calls `__folio_alloc`. This is interesting, `alloc_migration_target` itself can be a FocusSymbol because it's *directly* altered by the patch. I need to make sure this symbol isn't static. Okay, it's non-static. The code shows the function signature as `struct folio *alloc_migration_target(struct folio *src, unsigned long private);`, which confirms it's not static. And it's only called during page migration, so it's not ubiquitous. That's a good candidate.

Now, revisiting `mm/khugepaged.c`. `alloc_charge_folio` is static. Can that even be a FocusSymbol? Let me refer back to Section 4. It says "Compiler-inlined static functions... lack distinct symbol addresses" but not functions in .c files. The key distinction is in headers.  `alloc_charge_folio` *could* be inlined. But `collapse_run_pmd` is definitely a non-static symbol in `mm/khugepaged.c` and is a good candidate. I can include both `collapse_run_pmd` and/or `alloc_charge_folio`.

Finally, `mm/page_alloc.c` comes into play with the functions `__alloc_pages_bulk_noprof`, `alloc_pages_bulk_noprof`, `__folio_alloc_noprof`, and `__folio_alloc_node_noprof`. Now, the crucial question is whether these are *ubiquitous*. Section 4 explicitly says to avoid general memory allocators. Is `__folio_alloc_node_noprof` and `__folio_alloc_noprof` a general memory allocator? Yes, it's part of the core page allocation path.

What about `alloc_pages_bulk_noprof`? Does *almost every program* call `alloc_pages_bulk_noprof`? I need to think about syzkaller and what those programs do. Are there any programs in the corpus that call `alloc_pages_bulk`? It seems like it's used less frequently. `copy_splice_read`, `fuse_readdir_alloc_buf`, `btrfs_alloc_page_array`, and `z_erofs_gbuf_growsize` are all callers. Therefore, they aren't *ubiquitous*, or called by *almost every program*.

Therefore, based on this analysis, I have two very strong FocusSymbol candidates: `alloc_migration_target` and `collapse_run_pmd`. I might also include `alloc_charge_folio`. I am comfortable *not* listing `__folio_alloc_node_noprof`, `__folio_alloc_noprof`, `alloc_pages_bulk_noprof`, or `__alloc_pages_bulk_noprof` as FocusSymbols.

{
  "Expression": "alloc_pages_bulk_node"
}

{
  "Output": "include/linux/gfp.h=224=static inline unsigned long\ninclude/linux/gfp.h:225:alloc_pages_bulk_node_noprof(gfp_t gfp, int nid, unsigned long nr_pages,\ninclude/linux/gfp.h-226-\t\t\t\t   struct page **page_array)\n--\ninclude/linux/gfp.h-233-\ninclude/linux/gfp.h:234:#define alloc_pages_bulk_node(...)\t\t\t\t\\\ninclude/linux/gfp.h:235:\talloc_hooks(alloc_pages_bulk_node_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-236-\n--\nio_uring/memmap.c=174=static int io_region_allocate_pages(struct io_mapped_region *mr,\n--\nio_uring/memmap.c-192-\nio_uring/memmap.c:193:\tnr_allocated = alloc_pages_bulk_node(gfp, NUMA_NO_NODE,\nio_uring/memmap.c-194-\t\t\t\t\t     mr-\u003enr_pages, pages);\n--\nmm/alloc_tag.c=785=static int vm_module_tags_populate(void)\n--\nmm/alloc_tag.c-801-\nmm/alloc_tag.c:802:\t\t\tallocated = alloc_pages_bulk_node(GFP_KERNEL | __GFP_NOWARN,\nmm/alloc_tag.c-803-\t\t\t\tNUMA_NO_NODE, more_pages - nr, next_page + nr);\n--\nmm/vmalloc.c=3686=vm_area_alloc_pages(gfp_t gfp, int nid,\n--\nmm/vmalloc.c-3757-\t\t\telse\nmm/vmalloc.c:3758:\t\t\t\tnr = alloc_pages_bulk_node_noprof(gfp, nid,\nmm/vmalloc.c-3759-\t\t\t\t\t\t\tnr_pages_request,\n--\nnet/core/page_pool.c=611=static noinline netmem_ref __page_pool_alloc_netmems_slow(struct page_pool *pool,\n--\nnet/core/page_pool.c-636-\nnet/core/page_pool.c:637:\tnr_pages = alloc_pages_bulk_node(gfp, pool-\u003ep.nid, bulk,\nnet/core/page_pool.c-638-\t\t\t\t\t (struct page **)pool-\u003ealloc.cache);\n"
}

gemini-3.8-flash

null

null

							input: 67936
							output: 22
							thoughts: 19
						

Here's my take on those thoughts, tailored for an expert audience:

**Analyzing `alloc_pages_bulk_mempolicy_noprof`**

Okay, so we're looking at `alloc_pages_bulk_mempolicy_noprof`. Right, let's dive into this. The name itself is pretty descriptive, but let's break it down in terms of memory allocation: "bulk," implies a demand for multiple pages at once. The "mempolicy" part indicates we're working with NUMA or other memory policies, and that's critical given performance implications in NUMA systems.  The "noprof" suffix... hmm, that's interesting. It suggests that this allocation path avoids the overhead of profiling or instrumentation. It means there's a strong emphasis on performance, bypassing some of the standard checks or tracing that would normally be in place. I bet it's used in some very specific, latency-sensitive contexts. I wonder about the trade-offs there... are there potential implications for debugging or monitoring, or is this used in such a high throughput context that tracing is just a non-starter? I need to dig deeper into the call sites and see where it's being used. It's likely that it's designed to be fast, but that has consequences to understand, and where those consequences are acceptable is what I need to see.

{
  "Expression": "alloc_pages_bulk_mempolicy"
}

{
  "Output": "include/linux/gfp.h=212=void free_pages_bulk(struct page **page_array, unsigned long nr_pages);\ninclude/linux/gfp.h-213-\ninclude/linux/gfp.h:214:unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\ninclude/linux/gfp.h-215-\t\t\t\tunsigned long nr_pages,\ninclude/linux/gfp.h-216-\t\t\t\tstruct page **page_array);\ninclude/linux/gfp.h:217:#define  alloc_pages_bulk_mempolicy(...)\t\t\t\t\\\ninclude/linux/gfp.h:218:\talloc_hooks(alloc_pages_bulk_mempolicy_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-219-\n--\nmm/mempolicy.c=2777=static unsigned long alloc_pages_bulk_preferred_many(gfp_t gfp, int nid,\n--\nmm/mempolicy.c-2802- */\nmm/mempolicy.c:2803:unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\nmm/mempolicy.c-2804-\t\tunsigned long nr_pages, struct page **page_array)\n--\nmm/vmalloc.c=3686=vm_area_alloc_pages(gfp_t gfp, int nid,\n--\nmm/vmalloc.c-3753-\t\t\tif (IS_ENABLED(CONFIG_NUMA) \u0026\u0026 nid == NUMA_NO_NODE)\nmm/vmalloc.c:3754:\t\t\t\tnr = alloc_pages_bulk_mempolicy_noprof(gfp,\nmm/vmalloc.c-3755-\t\t\t\t\t\t\tnr_pages_request,\n"
}

gemini-3.8-flash

null

null

### 1. Approaches Tried and Results

* **Diff Inspection**:
  * Reviewed commit `4517e1ab346bb79c2dedf83e439ae3553b6c3a1d`.
  * Files touched:
    * `include/linux/gfp.h`
    * `mm/khugepaged.c`
    * `mm/migrate.c`
    * `mm/page_alloc.c`
    * `mm/page_alloc.h`
  * Changes identified:
    * `__folio_alloc_noprof` and `#define __folio_alloc` were moved from `include/linux/gfp.h` to internal header `mm/page_alloc.h`.
    * Signature of `__folio_alloc_noprof` modified to take an extra parameter: `unsigned int alloc_flags`.
    * Calls in `mm/khugepaged.c` (`alloc_charge_folio`) and `mm/migrate.c` (`alloc_migration_target`) updated to pass `ALLOC_DEFAULT`.
    * `__folio_alloc_node_noprof` converted from static inline in `include/linux/gfp.h` to an exported non-inline function in `mm/page_alloc.c`, passing `ALLOC_DEFAULT` into `__folio_alloc_noprof`.
    * `alloc_pages_bulk_noprof` in `mm/page_alloc.c` refactored into `__alloc_pages_bulk_noprof(gfp, alloc_flags, preferred_nid, nodemask, nr_pages, page_array)`, with `alloc_pages_bulk_noprof` acting as a wrapper passing `ALLOC_DEFAULT`.
    * In `__alloc_pages_bulk_noprof`, `struct alloc_context ac` is initialized with `.alloc_flags = alloc_flags`, and `fastpath_alloc_flags = alloc_flags | ALLOC_WMARK_LOW` is passed to `prepare_alloc_pages` and watermark checks, while the fallback path passes `alloc_flags` to `__alloc_pages_noprof`.

* **Caller and Reference Analysis**:
  * Searched callers of `__alloc_pages_bulk_noprof`: only called by `alloc_pages_bulk_noprof` in this patch.
  * Searched callers of `alloc_pages_bulk`: widely used across kernel (e.g. `fs/splice.c`, `fs/btrfs`, `io_uring`, `kernel/bpf/arena.c`, `mm/vmalloc.c`, `net/core/page_pool.c`).
  * Searched callers of `__folio_alloc`: only called in `mm/khugepaged.c` (`alloc_charge_folio`) and `mm/migrate.c` (`alloc_migration_target`).
  * Searched callers of `__folio_alloc_node`: used in `drivers/iommu/iommu-pages.c`, `mm/filemap.c` (`filemap_alloc_folio_noprof`), `mm/migrate.c` (`alloc_misplaced_dst_folio`), `net/sunrpc/svc.c`, and by `folio_alloc_noprof` when `!CONFIG_NUMA`.
  * Investigated `ALLOC_NOLOCK`: related to lockless page/slab allocations (`alloc_frozen_pages_nolock_noprof`, `_kmalloc_nolock_noprof`). The patch prepares `__folio_alloc` and `alloc_pages_bulk` infrastructure for passing arbitrary `alloc_flags` (such as `ALLOC_NOLOCK`).

* **FocusSymbols & Reachability Assessment**:
  * The patch touches core memory management (`mm/page_alloc.c`, `mm/khugepaged.c`, `mm/migrate.c`), which is fully reachable in standard virtualized environments.
  * WorthFuzzing is unambiguously `true`.
  * Evaluated candidates for `FocusSymbols`:
    * General memory allocators like `__folio_alloc_node_noprof` or general bulk wrappers (`alloc_pages_bulk_noprof`) risk diluting fuzzing effort because ubiquitous paths like page cache allocation (`filemap_alloc_folio_noprof`) or `vmalloc` call them.
    * `alloc_migration_target`: non-static function exported via `include/linux/migrate.h`, explicitly modified in `mm/migrate.c` to use new `__folio_alloc` signature with `ALLOC_DEFAULT`. Used in migration paths (`migrate_pages`, `do_move_pages_to_node`, `alloc_demote_folio`).
    * `alloc_charge_folio`: static in `mm/khugepaged.c`, called by `collapse_huge_page` and `collapse_file`.
    * `__alloc_pages_bulk_noprof`: new non-static entrypoint in `mm/page_alloc.c` containing the bulk allocation logic.

### 2. Current Hypotheses and Active Lines of Investigation

* **Evaluation Outcome**:
  * `WorthFuzzing=true`: Core memory management restructuring and flag plumbing directly reachable by userspace syscalls triggering page migration (`migrate_pages`, `move_pages`, `mbind`), compaction/khugepaged, and bulk page allocation (splice, btrfs, io_uring, bpf arena).
* **Focus Symbol Candidates**:
  * `__alloc_pages_bulk_noprof` (mm/page_alloc.c) - Contains the refactored bulk allocation loop and flag handling.
  * `alloc_migration_target` (mm/migrate.c) - Directly modified non-static function handling folio allocation for page migration.
  * Caller in `khugepaged.c`: `alloc_charge_folio` is static; khugepaged callers include `collapse_pte_mapped_thp` or caller entrypoint, but `alloc_migration_target` and `__alloc_pages_bulk_noprof` are specific non-static functions.
* **Config Requirements (`EnableConfigs`)**:
  * Transparent huge pages / khugepaged requires `TRANSPARENT_HUGEPAGE`.
  * Page migration requires `MIGRATION`.
  * General page allocation requires standard mm configs (NUMA optional but standard).

### 3. Key Files, Functions, and Code References

* `mm/page_alloc.c`:
  ```c
  unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,
              int preferred_nid, nodemask_t *nodemask, int nr_pages,
              struct page **page_array);
  unsigned long alloc_pages_bulk_noprof(...);
  struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,
          nodemask_t *nodemask, unsigned int alloc_flags);
  struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid);
  ```
* `mm/page_alloc.h`:
  ```c
  #define ALLOC_DEFAULT 0
  struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,
          nodemask_t *nodemask, unsigned int alloc_flags);
  #define __folio_alloc(...) alloc_hooks(__folio_alloc_noprof(__VA_ARGS__))
  unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,
          int preferred_nid, nodemask_t *nodemask, int nr_pages,
          struct page **page_array);
  ```
* `mm/migrate.c`:
  ```c
  struct folio *alloc_migration_target(struct folio *src, unsigned long private)
  {
      ...
      return __folio_alloc(gfp_mask, order, nid, mtc->nmask, ALLOC_DEFAULT);
  }
  ```
* `mm/khugepaged.c`:
  ```c
  static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,
          struct collapse_control *cc, unsigned int order)
  {
      ...
      folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask, ALLOC_DEFAULT);
      ...
  }
  ```

### 4. Watchouts / Dead-ends

* Do NOT use `folio_alloc_noprof` or `__folio_alloc_node_noprof` as primary FocusSymbols without consideration: they are hit by generic page cache allocations (`filemap_alloc_folio_noprof`), which would dilute coverage.
* Grepping for `struct alloc_context {` threw regex syntax errors due to unescaped `{`. Keep regex escaped when grepping kernel structs.
* `madvise_collapse` was not found in `mm/khugepaged.c`. Khugepaged functions are mostly static or prefixed differently (`hugepage_madvise`, `collapse_huge_page`).

							input: 41281
							output: 2092
							thoughts: 0
						

gemini-3.8-flash

null

null

							input: 23488
							output: 19
							thoughts: 0
						

{
  "Expression": "alloc_migration_target"
}

{
  "Output": "include/linux/migrate.h=59=int migrate_pages(struct list_head *l, new_folio_t new, free_folio_t free,\n--\ninclude/linux/migrate.h-62-\t\tunsigned int *ret_succeeded);\ninclude/linux/migrate.h:63:struct folio *alloc_migration_target(struct folio *src, unsigned long private);\ninclude/linux/migrate.h-64-bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode);\n--\ninclude/linux/migrate.h=79=static inline int migrate_pages(struct list_head *l, new_folio_t new,\n--\ninclude/linux/migrate.h-83-\t{ return -ENOSYS; }\ninclude/linux/migrate.h:84:static inline struct folio *alloc_migration_target(struct folio *src,\ninclude/linux/migrate.h-85-\t\tunsigned long private)\n--\nmm/damon/ops-common.c=395=static unsigned int __damon_migrate_folio_list(\n--\nmm/damon/ops-common.c-417-\t/* Migration ignores all cpuset and mempolicy settings */\nmm/damon/ops-common.c:418:\tmigrate_pages(migrate_folios, alloc_migration_target, NULL,\nmm/damon/ops-common.c-419-\t\t      (unsigned long)\u0026mtc, MIGRATE_ASYNC, MR_DAMON,\n--\nmm/gup.c=2323=migrate_longterm_unpinnable_folios(struct list_head *movable_folio_list,\n--\nmm/gup.c-2367-\nmm/gup.c:2368:\t\tif (migrate_pages(movable_folio_list, alloc_migration_target,\nmm/gup.c-2369-\t\t\t\t  NULL, (unsigned long)\u0026mtc, MIGRATE_SYNC,\n--\nmm/memory-failure.c=2849=static int soft_offline_in_use_page(struct page *page)\n--\nmm/memory-failure.c-2917-\tif (isolated) {\nmm/memory-failure.c:2918:\t\tret = migrate_pages(\u0026pagelist, alloc_migration_target, NULL,\nmm/memory-failure.c-2919-\t\t\t(unsigned long)\u0026mtc, MIGRATE_SYNC, MR_MEMORY_FAILURE, NULL);\n--\nmm/memory_hotplug.c=1879=static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)\n--\nmm/memory_hotplug.c-1952-\t\t\tnode_set(mtc.nid, nmask);\nmm/memory_hotplug.c:1953:\t\tret = migrate_pages(\u0026source, alloc_migration_target, NULL,\nmm/memory_hotplug.c-1954-\t\t\t(unsigned long)\u0026mtc, MIGRATE_SYNC, MR_MEMORY_HOTPLUG, NULL);\n--\nmm/mempolicy.c=629=static bool strictly_unmovable(unsigned long flags)\n--\nmm/mempolicy.c-638-\nmm/mempolicy.c:639:struct migration_mpol {\t\t/* for alloc_migration_target_by_mpol() */\nmm/mempolicy.c-640-\tstruct mempolicy *pol;\n--\nmm/mempolicy.c=1306=static long migrate_to_node(struct mm_struct *mm, int source, int dest,\n--\nmm/mempolicy.c-1342-\tif (!list_empty(\u0026pagelist)) {\nmm/mempolicy.c:1343:\t\terr = migrate_pages(\u0026pagelist, alloc_migration_target, NULL,\nmm/mempolicy.c-1344-\t\t\t(unsigned long)\u0026mtc, MIGRATE_SYNC, MR_SYSCALL, NULL);\n--\nmm/mempolicy.c=1360=int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,\n--\nmm/mempolicy.c-1457- */\nmm/mempolicy.c:1458:static struct folio *alloc_migration_target_by_mpol(struct folio *src,\nmm/mempolicy.c-1459-\t\t\t\t\t\t    unsigned long private)\n--\nmm/mempolicy.c=1497=int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,\n--\nmm/mempolicy.c-1502-\nmm/mempolicy.c:1503:static struct folio *alloc_migration_target_by_mpol(struct folio *src,\nmm/mempolicy.c-1504-\t\t\t\t\t\t    unsigned long private)\n--\nmm/mempolicy.c=1510=static long do_mbind(unsigned long start, unsigned long len,\n--\nmm/mempolicy.c-1638-\t\tnr_failed |= migrate_pages(\u0026pagelist,\nmm/mempolicy.c:1639:\t\t\t\talloc_migration_target_by_mpol, NULL,\nmm/mempolicy.c-1640-\t\t\t\t(unsigned long)\u0026mmpol, MIGRATE_SYNC,\n--\nmm/migrate.c=2099=int migrate_pages(struct list_head *from, new_folio_t get_new_folio,\n--\nmm/migrate.c-2195-\nmm/migrate.c:2196:struct folio *alloc_migration_target(struct folio *src, unsigned long private)\nmm/migrate.c-2197-{\n--\nmm/migrate.c=2247=static int do_move_pages_to_node(struct list_head *pagelist, int node)\n--\nmm/migrate.c-2255-\nmm/migrate.c:2256:\terr = migrate_pages(pagelist, alloc_migration_target, NULL,\nmm/migrate.c-2257-\t\t(unsigned long)\u0026mtc, MIGRATE_SYNC, MR_SYSCALL, NULL);\n--\nmm/page_alloc.c=7135=static int __alloc_contig_migrate_range(struct compact_control *cc,\n--\nmm/page_alloc.c-7172-\nmm/page_alloc.c:7173:\t\tret = migrate_pages(\u0026cc-\u003emigratepages, alloc_migration_target,\nmm/page_alloc.c-7174-\t\t\tNULL, (unsigned long)\u0026mtc, cc-\u003emode, MR_CONTIG_RANGE, NULL);\n--\nmm/vmscan.c=1040=static struct folio *alloc_demote_folio(struct folio *src,\n--\nmm/vmscan.c-1059-\ttarget_nid_mtc.gfp_mask |= __GFP_THISNODE;\nmm/vmscan.c:1060:\tdst = alloc_migration_target(src, (unsigned long)\u0026target_nid_mtc);\nmm/vmscan.c-1061-\tif (dst)\n--\nmm/vmscan.c-1063-\nmm/vmscan.c:1064:\treturn alloc_migration_target(src, (unsigned long)mtc);\nmm/vmscan.c-1065-}\n"
}

gemini-3.8-flash

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null

							input: 25298
							output: 20
							thoughts: 0
						

{
  "Expression": "__alloc_pages_bulk"
}

{
  "Output": "include/linux/gfp.h=207=unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n--\ninclude/linux/gfp.h-209-\t\t\t\tstruct page **page_array);\ninclude/linux/gfp.h:210:#define __alloc_pages_bulk(...)\t\t\talloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-211-\n--\ninclude/linux/gfp.h=214=unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\n--\ninclude/linux/gfp.h-221-#define alloc_pages_bulk(_gfp, _nr_pages, _page_array)\t\t\\\ninclude/linux/gfp.h:222:\t__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _page_array)\ninclude/linux/gfp.h-223-\n--\nmm/kasan/shadow.c=327=static void ___free_pages_bulk(struct page **pages, int nr_pages)\n--\nmm/kasan/shadow.c-338-\nmm/kasan/shadow.c:339:static int ___alloc_pages_bulk(struct page **pages, int nr_pages, gfp_t gfp_mask)\nmm/kasan/shadow.c-340-{\n--\nmm/kasan/shadow.c=357=static int __kasan_populate_vmalloc_do(unsigned long start, unsigned long end, gfp_t gfp_mask)\n--\nmm/kasan/shadow.c-369-\t\tnr_pages = min(nr_total, PAGE_SIZE / sizeof(data.pages[0]));\nmm/kasan/shadow.c:370:\t\tret = ___alloc_pages_bulk(data.pages, nr_pages, gfp_mask);\nmm/kasan/shadow.c-371-\t\tif (ret)\n--\nmm/mempolicy.c=2659=static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,\n--\nmm/mempolicy.c-2697-\t\tnode_pages = min(rem_pages, weight);\nmm/mempolicy.c:2698:\t\tnr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,\nmm/mempolicy.c-2699-\t\t\t\t\t\t  page_array);\n--\nmm/mempolicy.c-2727-\t/*\nmm/mempolicy.c:2728:\t * Calculate rounds/partial rounds to minimize __alloc_pages_bulk calls.\nmm/mempolicy.c-2729-\t * Track which node weighted interleave should resume from.\n--\nmm/mempolicy.c-2761-\t\tnode_pages = min(node_pages, nr_pages - total_allocated);\nmm/mempolicy.c:2762:\t\tnr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,\nmm/mempolicy.c-2763-\t\t\t\t\t\t  page_array);\n--\nmm/page_alloc.c=5085=static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-5133-/*\nmm/page_alloc.c:5134: * __alloc_pages_bulk - Allocate a number of order-0 pages to an array\nmm/page_alloc.c-5135- * @gfp: GFP flags for the allocation\n--\nmm/page_alloc.c-5153- */\nmm/page_alloc.c:5154:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.c-5155-\t\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n--\nmm/page_alloc.c=5299=unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n--\nmm/page_alloc.c-5302-{\nmm/page_alloc.c:5303:\treturn __alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid,\nmm/page_alloc.c-5304-\t\t\t\t\t nodemask, nr_pages, page_array);\n--\nmm/page_alloc.h=261=struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n--\nmm/page_alloc.h-264-\nmm/page_alloc.h:265:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.h-266-\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n"
}

gemini-3.8-flash

null

null

							input: 26565
							output: 33
							thoughts: 1103
						

**Analysis of the Memory Management Patch**

Okay, let's break this down. This patch is definitely interesting from a fuzzing perspective. It looks like we have some significant changes to core memory allocation functions and their calling sites.

First, I see some refactoring around folio allocation. We've got `__folio_alloc_noprof` being modified to accept `alloc_flags` and being replaced with a new `__folio_alloc_node_noprof` with an extern declaration. We also have `alloc_pages_bulk_noprof` being modified to `__alloc_pages_bulk_noprof` and also taking an `alloc_flags` argument. This signals a shift in how these functions behave and how they're used.

Looking at the commit diff, the modifications within `mm/khugepaged.c` and `mm/migrate.c` are particularly relevant. Specifically, `alloc_charge_folio` in `khugepaged` and `alloc_migration_target` in `migrate.c` are now directly calling the altered `__folio_alloc`. These aren't just generic functions; they're specific to their respective subsystems: `khugepaged` for transparent huge pages, and `migrate` for page migration. The fact that the changes touch code involved in memory collapse, migration, and allocation means we have several opportunities to explore potentially interesting states.

Given the fuzzing guidelines, the key is to identify *non-ubiquitous* and *feature-specific* functions. We need to avoid those general allocators that are called everywhere. The guideline to avoid the ubiquitous calls is essential.

I will focus on `alloc_migration_target` in `mm/migrate.c`. This isn't a general allocator; it's specific to the page migration process, which is exercised by multiple system calls like `migrate_pages`, `move_pages`, `mbind`, etc. The fact that `alloc_migration_target` was directly modified to call the altered `__folio_alloc` makes it a prime candidate for fuzzing.

For `khugepaged`, `alloc_charge_folio` is static. Now I must look for the non-static callers of this function. I will need to understand what specific logic in the khugepaged subsystem ultimately calls `alloc_charge_folio`. Understanding those callers is key to identifying appropriate focus symbols.

In summary, this patch is worth fuzzing because it touches core memory management functions, and especially because the changes propagate to subsystems like khugepaged and page migration. I need to now map the calling contexts for `alloc_charge_folio`.

{
  "Expression": "alloc_charge_folio",
  "PathPrefix": "mm/khugepaged.c"
}

{
  "Output": "mm/khugepaged.c=1098=static enum scan_result __collapse_huge_page_swapin(struct mm_struct *mm,\n--\nmm/khugepaged.c-1188-\nmm/khugepaged.c:1189:static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,\nmm/khugepaged.c-1190-\t\tstruct collapse_control *cc, unsigned int order)\n--\nmm/khugepaged.c=1225=static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long start_addr,\n--\nmm/khugepaged.c-1241-\nmm/khugepaged.c:1242:\tresult = alloc_charge_folio(\u0026folio, mm, cc, order);\nmm/khugepaged.c-1243-\tif (result != SCAN_SUCCEED)\n--\nmm/khugepaged.c=2189=static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,\n--\nmm/khugepaged.c-2212-\nmm/khugepaged.c:2213:\tresult = alloc_charge_folio(\u0026new_folio, mm, cc, HPAGE_PMD_ORDER);\nmm/khugepaged.c-2214-\tif (result != SCAN_SUCCEED)\n"
}

gemini-3.8-flash

null

null

							input: 28630
							output: 33
							thoughts: 53
						

**Investigating the `collapse_huge_page` and `collapse_file` Functions**

Okay, so I'm looking at `mm/khugepaged.c` again, and I'm focusing specifically on the static functions `collapse_huge_page` and `collapse_file`. The question immediately popping into my head is, "Where are these functions actually *used*?" I need to understand their call sites to truly grasp their role in the bigger picture of khugepaged. Time to track down the callers of both `collapse_huge_page` and `collapse_file`. That's where I need to start.

{
  "Expression": "collapse_huge_page",
  "PathPrefix": "mm/khugepaged.c"
}

{
  "Output": "mm/khugepaged.c=606=static void count_collapse_event(unsigned int order, enum vm_event_item vm_event,\n--\nmm/khugepaged.c-613-\nmm/khugepaged.c:614:static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma,\nmm/khugepaged.c-615-\t\tunsigned long start_addr, pte_t *pte, struct collapse_control *cc,\n--\nmm/khugepaged.c-758-\t\tresult = SCAN_SUCCEED;\nmm/khugepaged.c:759:\t\ttrace_mm_collapse_huge_page_isolate(folio, none_or_zero,\nmm/khugepaged.c-760-\t\t\t\t\t\t    referenced, result, order);\n--\nmm/khugepaged.c-764-\trelease_pte_pages(pte, _pte, compound_pagelist);\nmm/khugepaged.c:765:\ttrace_mm_collapse_huge_page_isolate(folio, none_or_zero,\nmm/khugepaged.c-766-\t\t\t\t\t    referenced, result, order);\n--\nmm/khugepaged.c-769-\nmm/khugepaged.c:770:static void __collapse_huge_page_copy_succeeded(pte_t *pte,\nmm/khugepaged.c-771-\t\tstruct vm_area_struct *vma, unsigned long address,\n--\nmm/khugepaged.c-833-\nmm/khugepaged.c:834:static void __collapse_huge_page_copy_failed(pte_t *pte,\nmm/khugepaged.c-835-\t\tpmd_t *pmd, pmd_t orig_pmd, struct vm_area_struct *vma,\n--\nmm/khugepaged.c-851-\t * Release both raw and compound pages isolated\nmm/khugepaged.c:852:\t * in __collapse_huge_page_isolate.\nmm/khugepaged.c-853-\t */\n--\nmm/khugepaged.c-857-/*\nmm/khugepaged.c:858: * __collapse_huge_page_copy - attempts to copy memory contents from raw\nmm/khugepaged.c-859- * pages to a hugepage. Cleans up the raw pages if copying succeeds;\n--\nmm/khugepaged.c-871- */\nmm/khugepaged.c:872:static enum scan_result __collapse_huge_page_copy(pte_t *pte, struct folio *folio,\nmm/khugepaged.c-873-\t\tpmd_t *pmd, pmd_t orig_pmd, struct vm_area_struct *vma,\n--\nmm/khugepaged.c-901-\tif (likely(result == SCAN_SUCCEED))\nmm/khugepaged.c:902:\t\t__collapse_huge_page_copy_succeeded(pte, vma, address, ptl,\nmm/khugepaged.c-903-\t\t\t\t\t\t    order, compound_pagelist);\nmm/khugepaged.c-904-\telse\nmm/khugepaged.c:905:\t\t__collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,\nmm/khugepaged.c-906-\t\t\t\t\t\t order, compound_pagelist);\n--\nmm/khugepaged.c=1074=static enum scan_result check_pmd_still_valid(struct mm_struct *mm,\n--\nmm/khugepaged.c-1097- */\nmm/khugepaged.c:1098:static enum scan_result __collapse_huge_page_swapin(struct mm_struct *mm,\nmm/khugepaged.c-1099-\t\tstruct vm_area_struct *vma, unsigned long start_addr,\n--\nmm/khugepaged.c-1183-out:\nmm/khugepaged.c:1184:\ttrace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, result,\nmm/khugepaged.c-1185-\t\t\t\t\t   order);\n--\nmm/khugepaged.c=1189=static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,\n--\nmm/khugepaged.c-1219-/*\nmm/khugepaged.c:1220: * collapse_huge_page() expects the mmap_lock to be unlocked before entering and\nmm/khugepaged.c-1221- * will always return with the lock unlocked, to avoid holding the mmap_lock\n--\nmm/khugepaged.c-1224- */\nmm/khugepaged.c:1225:static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long start_addr,\nmm/khugepaged.c-1226-\t\tint referenced, int unmapped, struct collapse_control *cc,\n--\nmm/khugepaged.c-1266-\t\t/*\nmm/khugepaged.c:1267:\t\t * __collapse_huge_page_swapin() will return with mmap_lock\nmm/khugepaged.c-1268-\t\t * released when it fails. So we jump out_nolock directly in\n--\nmm/khugepaged.c-1270-\t\t */\nmm/khugepaged.c:1271:\t\tresult = __collapse_huge_page_swapin(mm, vma, start_addr, pmd,\nmm/khugepaged.c-1272-\t\t\t\t\t\t     referenced, order);\n--\nmm/khugepaged.c-1326-\tif (pte) {\nmm/khugepaged.c:1327:\t\tresult = __collapse_huge_page_isolate(vma, start_addr, pte, cc,\nmm/khugepaged.c-1328-\t\t\t\t\t\t      order, \u0026compound_pagelist);\n--\nmm/khugepaged.c-1358-\nmm/khugepaged.c:1359:\tresult = __collapse_huge_page_copy(pte, folio, pmd, _pmd,\nmm/khugepaged.c-1360-\t\t\t\t\t   vma, start_addr, pte_ptl,\n--\nmm/khugepaged.c-1405-\t\tfolio_put(folio);\nmm/khugepaged.c:1406:\ttrace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result, order);\nmm/khugepaged.c-1407-\treturn result;\n--\nmm/khugepaged.c=1436=static enum scan_result mthp_collapse(struct mm_struct *mm,\n--\nmm/khugepaged.c-1469-\t\t\tcollapse_address = address + offset * PAGE_SIZE;\nmm/khugepaged.c:1470:\t\t\tret = collapse_huge_page(mm, collapse_address, referenced,\nmm/khugepaged.c-1471-\t\t\t\t\t\t unmapped, cc, order);\n"
}

gemini-3.8-flash

null

null

							input: 30693
							output: 19
							thoughts: 478
						

**Analyzing Memory Allocation Paths**

Okay, let's break this down. First, I'm zeroing in on `collapse_run_pmd`. This function, defined in `mm/collapse.h` but implemented in `mm/khugepaged.c`, looks like a good starting point. I see that it's called by `madvise_collapse`, triggered by `madvise(..., MADV_COLLAPSE)`, and crucially, by `collapse_scan_mm_slot` within the khugepaged thread. This suggests a direct involvement in huge page management and potential allocation during memory collapsing operations. It calls `mthp_collapse` which calls `collapse_huge_page` or `collapse_file`, which in both cases calls `alloc_charge_folio`. This, in turn, calls `__folio_alloc(..., ALLOC_DEFAULT)`. Therefore `collapse_run_pmd` is a decent symbol to examine.

Next up, `alloc_migration_target` in `mm/migrate.c`. The patch alters this function: `struct folio *alloc_migration_target(struct folio *src, unsigned long private) { ... return __folio_alloc(gfp_mask, order, nid, mtc->nmask, ALLOC_DEFAULT); }`. This function is directly tied to page migration, specifically the movement of pages, triggered by syscalls like `move_pages(2)`, `migrate_pages(2)`, and `mbind(2)` with the `MPOL_MF_MOVE` flag. Unlike the previous function, this one is much more targeted; it's not ubiquitous. Normal processes that aren't actively migrating pages won't be hitting this code path.

Finally, I'm curious about `__alloc_pages_bulk_noprof`. I need to figure out how widespread this is. Does `alloc_pages_bulk` have a wide reach? I need to analyze its call graph to understand its ubiquity and therefore how useful it would be to examine.

{
  "Expression": "alloc_pages_bulk"
}

{
  "Output": "block/blk-crypto-fallback.c=172=static struct bio *blk_crypto_alloc_enc_bio(struct bio *bio_src,\n--\nblock/blk-crypto-fallback.c-204-\t *\nblock/blk-crypto-fallback.c:205:\t * Note: alloc_pages_bulk needs the array to be zeroed, as it assumes\nblock/blk-crypto-fallback.c-206-\t * any non-zero slot already contains a valid allocation.\n--\nblock/blk-crypto-fallback.c-208-\tmemset(pages, 0, sizeof(struct page *) * nr_segs);\nblock/blk-crypto-fallback.c:209:\tnr_allocated = alloc_pages_bulk(GFP_KERNEL, nr_segs, pages);\nblock/blk-crypto-fallback.c-210-\tif (nr_allocated \u003c nr_segs)\n--\ndrivers/firewire/core-iso.c=31=int fw_iso_buffer_alloc(struct fw_iso_buffer *buffer, int page_count)\n--\ndrivers/firewire/core-iso.c-41-\t// convenience to map them into virtual address space of user process.\ndrivers/firewire/core-iso.c:42:\tunsigned long nr_populated = alloc_pages_bulk(GFP_KERNEL | GFP_DMA32 | __GFP_ZERO,\ndrivers/firewire/core-iso.c-43-\t\t\t\t\t\t      page_count, page_array);\n--\ndrivers/firewire/ohci.c=848=static int ar_context_init(struct ar_context *ctx, struct fw_ohci *ohci,\n--\ndrivers/firewire/ohci.c-864-\t// address range in kernel virtual address space.\ndrivers/firewire/ohci.c:865:\tunsigned long nr_populated = alloc_pages_bulk(GFP_KERNEL | GFP_DMA32, AR_BUFFERS, pages);\ndrivers/firewire/ohci.c-866-\n--\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c=621=static int alloc_private_pages(struct hmm_buffer_object *bo)\n--\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c-626-\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c:627:\tnr_allocated = alloc_pages_bulk(GFP_KERNEL, bo-\u003epgnr, bo-\u003epages);\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c-628-\t/*\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c:629:\t * alloc_pages_bulk() does not try very hard to get pages under memory\ndrivers/staging/media/atomisp/pci/hmm/hmm_bo.c-630-\t * pressure. If necessary fall back to alloc_page().\n--\ndrivers/vfio/pci/mlx5/cmd.c=466=static void free_page_list(u32 npages, struct page **page_list)\n--\ndrivers/vfio/pci/mlx5/cmd.c-469-\ndrivers/vfio/pci/mlx5/cmd.c:470:\t/* Undo alloc_pages_bulk() */\ndrivers/vfio/pci/mlx5/cmd.c-471-\tfor (i = npages - 1; i \u003e= 0; i--)\n--\ndrivers/vfio/pci/mlx5/cmd.c=496=static int mlx5vf_add_pages(struct page ***page_list, unsigned int npages)\n--\ndrivers/vfio/pci/mlx5/cmd.c-506-\tfor (;;) {\ndrivers/vfio/pci/mlx5/cmd.c:507:\t\tfilled = alloc_pages_bulk(GFP_KERNEL_ACCOUNT, npages - done,\ndrivers/vfio/pci/mlx5/cmd.c-508-\t\t\t\t\t  *page_list + done);\n--\ndrivers/vfio/pci/virtio/migrate.c=63=static int virtiovf_add_migration_pages(struct virtiovf_data_buffer *buf,\n--\ndrivers/vfio/pci/virtio/migrate.c-78-\tdo {\ndrivers/vfio/pci/virtio/migrate.c:79:\t\tfilled = alloc_pages_bulk(GFP_KERNEL_ACCOUNT, to_fill,\ndrivers/vfio/pci/virtio/migrate.c-80-\t\t\t\t\t  page_list);\n--\ndrivers/vfio/pci/virtio/migrate.c=110=static void virtiovf_free_data_buffer(struct virtiovf_data_buffer *buf)\n--\ndrivers/vfio/pci/virtio/migrate.c-113-\ndrivers/vfio/pci/virtio/migrate.c:114:\t/* Undo alloc_pages_bulk() */\ndrivers/vfio/pci/virtio/migrate.c-115-\tfor_each_sgtable_page(\u0026buf-\u003etable.sgt, \u0026sg_iter, 0)\n--\nfs/btrfs/extent_io.c=684=int btrfs_alloc_page_array(unsigned int nr_pages, struct page **page_array, gfp_t gfp)\n--\nfs/btrfs/extent_io.c-690-\nfs/btrfs/extent_io.c:691:\t\tallocated = alloc_pages_bulk(gfp, nr_pages, page_array);\nfs/btrfs/extent_io.c-692-\t\tif (unlikely(allocated == last)) {\n--\nfs/erofs/zutil.c=65=int z_erofs_gbuf_growsize(unsigned int nrpages)\n--\nfs/erofs/zutil.c-89-\t\t\tlast = j;\nfs/erofs/zutil.c:90:\t\t\tj = alloc_pages_bulk(GFP_KERNEL, nrpages, tmp_pages);\nfs/erofs/zutil.c-91-\t\t\tif (last == j)\n--\nfs/fuse/readdir.c=336=static struct page **fuse_readdir_alloc_buf(struct fuse_args_pages *ap, size_t *bufsize)\n--\nfs/fuse/readdir.c-343-\nfs/fuse/readdir.c:344:\tnr_alloc = alloc_pages_bulk(GFP_KERNEL, nr_pages, pages);\nfs/fuse/readdir.c-345-\tif (!nr_alloc)\n--\nfs/nfsd/nfs4state.c=1326=alloc_init_dir_deleg(struct nfs4_client *clp, struct nfs4_file *fp)\n--\nfs/nfsd/nfs4state.c-1337-\nfs/nfsd/nfs4state.c:1338:\tnpages = alloc_pages_bulk(GFP_KERNEL, NOTIFY4_PAGE_ARRAY_SIZE, ncn-\u003encn_pages);\nfs/nfsd/nfs4state.c-1339-\tif (npages != NOTIFY4_PAGE_ARRAY_SIZE) {\n--\nfs/splice.c=318=ssize_t copy_splice_read(struct file *in, loff_t *ppos,\n--\nfs/splice.c-341-\tpages = (struct page **)(bv + npages);\nfs/splice.c:342:\tnpages = alloc_pages_bulk(GFP_USER, npages, pages);\nfs/splice.c-343-\tif (!npages) {\n--\ninclude/linux/gfp.h=204=static inline void arch_alloc_page(struct page *page, int order) { }\n--\ninclude/linux/gfp.h-206-\ninclude/linux/gfp.h:207:unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\ninclude/linux/gfp.h-208-\t\t\t\tnodemask_t *nodemask, int nr_pages,\ninclude/linux/gfp.h-209-\t\t\t\tstruct page **page_array);\ninclude/linux/gfp.h:210:#define __alloc_pages_bulk(...)\t\t\talloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-211-\ninclude/linux/gfp.h=212=void free_pages_bulk(struct page **page_array, unsigned long nr_pages);\ninclude/linux/gfp.h-213-\ninclude/linux/gfp.h:214:unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\ninclude/linux/gfp.h-215-\t\t\t\tunsigned long nr_pages,\ninclude/linux/gfp.h-216-\t\t\t\tstruct page **page_array);\ninclude/linux/gfp.h:217:#define  alloc_pages_bulk_mempolicy(...)\t\t\t\t\\\ninclude/linux/gfp.h:218:\talloc_hooks(alloc_pages_bulk_mempolicy_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-219-\ninclude/linux/gfp.h-220-/* Bulk allocate order-0 pages */\ninclude/linux/gfp.h:221:#define alloc_pages_bulk(_gfp, _nr_pages, _page_array)\t\t\\\ninclude/linux/gfp.h:222:\t__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _page_array)\ninclude/linux/gfp.h-223-\ninclude/linux/gfp.h=224=static inline unsigned long\ninclude/linux/gfp.h:225:alloc_pages_bulk_node_noprof(gfp_t gfp, int nid, unsigned long nr_pages,\ninclude/linux/gfp.h-226-\t\t\t\t   struct page **page_array)\n--\ninclude/linux/gfp.h-230-\ninclude/linux/gfp.h:231:\treturn alloc_pages_bulk_noprof(gfp, nid, NULL, nr_pages, page_array);\ninclude/linux/gfp.h-232-}\ninclude/linux/gfp.h-233-\ninclude/linux/gfp.h:234:#define alloc_pages_bulk_node(...)\t\t\t\t\\\ninclude/linux/gfp.h:235:\talloc_hooks(alloc_pages_bulk_node_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-236-\n--\nio_uring/memmap.c=174=static int io_region_allocate_pages(struct io_mapped_region *mr,\n--\nio_uring/memmap.c-192-\nio_uring/memmap.c:193:\tnr_allocated = alloc_pages_bulk_node(gfp, NUMA_NO_NODE,\nio_uring/memmap.c-194-\t\t\t\t\t     mr-\u003enr_pages, pages);\n--\nkernel/bpf/arena.c=668=static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt, int node_id,\n--\nkernel/bpf/arena.c-732-\nkernel/bpf/arena.c:733:\t\t/* zeroing is needed, since alloc_pages_bulk() only fills in non-zero entries */\nkernel/bpf/arena.c-734-\t\tmemset(pages, 0, this_batch * sizeof(struct page *));\n--\nlib/test_vmalloc.c=391=vm_map_ram_test(void)\n--\nlib/test_vmalloc.c-403-\nlib/test_vmalloc.c:404:\tnr_allocated = alloc_pages_bulk(GFP_KERNEL, map_nr_pages, pages);\nlib/test_vmalloc.c-405-\tif (nr_allocated != map_nr_pages)\n--\nlib/tests/kunit_iov_iter.c=51=static void *__init iov_kunit_create_buffer(struct kunit *test,\n--\nlib/tests/kunit_iov_iter.c-66-\t\tlast = got;\nlib/tests/kunit_iov_iter.c:67:\t\tgot = alloc_pages_bulk(GFP_KERNEL, npages, pages);\nlib/tests/kunit_iov_iter.c-68-\n--\nmm/alloc_tag.c=785=static int vm_module_tags_populate(void)\n--\nmm/alloc_tag.c-801-\nmm/alloc_tag.c:802:\t\t\tallocated = alloc_pages_bulk_node(GFP_KERNEL | __GFP_NOWARN,\nmm/alloc_tag.c-803-\t\t\t\tNUMA_NO_NODE, more_pages - nr, next_page + nr);\n--\nmm/kasan/shadow.c=327=static void ___free_pages_bulk(struct page **pages, int nr_pages)\n--\nmm/kasan/shadow.c-338-\nmm/kasan/shadow.c:339:static int ___alloc_pages_bulk(struct page **pages, int nr_pages, gfp_t gfp_mask)\nmm/kasan/shadow.c-340-{\n--\nmm/kasan/shadow.c-344-\twhile (nr_pages) {\nmm/kasan/shadow.c:345:\t\tnr_populated = alloc_pages_bulk(gfp_mask, nr_pages, pages);\nmm/kasan/shadow.c-346-\t\tif (!nr_populated) {\n--\nmm/kasan/shadow.c=357=static int __kasan_populate_vmalloc_do(unsigned long start, unsigned long end, gfp_t gfp_mask)\n--\nmm/kasan/shadow.c-369-\t\tnr_pages = min(nr_total, PAGE_SIZE / sizeof(data.pages[0]));\nmm/kasan/shadow.c:370:\t\tret = ___alloc_pages_bulk(data.pages, nr_pages, gfp_mask);\nmm/kasan/shadow.c-371-\t\tif (ret)\n--\nmm/mempolicy.c=2612=EXPORT_SYMBOL(folio_alloc_noprof);\nmm/mempolicy.c-2613-\nmm/mempolicy.c:2614:static unsigned long alloc_pages_bulk_interleave(gfp_t gfp,\nmm/mempolicy.c-2615-\t\tstruct mempolicy *pol, unsigned long nr_pages,\n--\nmm/mempolicy.c-2640-\t\tif (delta) {\nmm/mempolicy.c:2641:\t\t\tnr_allocated = alloc_pages_bulk_noprof(gfp,\nmm/mempolicy.c-2642-\t\t\t\t\tinterleave_nodes(pol), NULL,\n--\nmm/mempolicy.c-2646-\t\t} else {\nmm/mempolicy.c:2647:\t\t\tnr_allocated = alloc_pages_bulk_noprof(gfp,\nmm/mempolicy.c-2648-\t\t\t\t\tinterleave_nodes(pol), NULL,\n--\nmm/mempolicy.c-2658-\nmm/mempolicy.c:2659:static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,\nmm/mempolicy.c-2660-\t\tstruct mempolicy *pol, unsigned long nr_pages,\n--\nmm/mempolicy.c-2697-\t\tnode_pages = min(rem_pages, weight);\nmm/mempolicy.c:2698:\t\tnr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,\nmm/mempolicy.c-2699-\t\t\t\t\t\t  page_array);\n--\nmm/mempolicy.c-2727-\t/*\nmm/mempolicy.c:2728:\t * Calculate rounds/partial rounds to minimize __alloc_pages_bulk calls.\nmm/mempolicy.c-2729-\t * Track which node weighted interleave should resume from.\n--\nmm/mempolicy.c-2761-\t\tnode_pages = min(node_pages, nr_pages - total_allocated);\nmm/mempolicy.c:2762:\t\tnr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,\nmm/mempolicy.c-2763-\t\t\t\t\t\t  page_array);\n--\nmm/mempolicy.c-2776-\nmm/mempolicy.c:2777:static unsigned long alloc_pages_bulk_preferred_many(gfp_t gfp, int nid,\nmm/mempolicy.c-2778-\t\tstruct mempolicy *pol, unsigned long nr_pages,\n--\nmm/mempolicy.c-2786-\nmm/mempolicy.c:2787:\tnr_allocated  = alloc_pages_bulk_noprof(preferred_gfp, nid, \u0026pol-\u003enodes,\nmm/mempolicy.c-2788-\t\t\t\t\t   nr_pages, page_array);\n--\nmm/mempolicy.c-2790-\tif (nr_allocated \u003c nr_pages)\nmm/mempolicy.c:2791:\t\tnr_allocated += alloc_pages_bulk_noprof(gfp, numa_node_id(), NULL,\nmm/mempolicy.c-2792-\t\t\t\tnr_pages - nr_allocated,\n--\nmm/mempolicy.c-2802- */\nmm/mempolicy.c:2803:unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\nmm/mempolicy.c-2804-\t\tunsigned long nr_pages, struct page **page_array)\n--\nmm/mempolicy.c-2813-\tif (pol-\u003emode == MPOL_INTERLEAVE)\nmm/mempolicy.c:2814:\t\treturn alloc_pages_bulk_interleave(gfp, pol,\nmm/mempolicy.c-2815-\t\t\t\t\t\t\t nr_pages, page_array);\n--\nmm/mempolicy.c-2817-\tif (pol-\u003emode == MPOL_WEIGHTED_INTERLEAVE)\nmm/mempolicy.c:2818:\t\treturn alloc_pages_bulk_weighted_interleave(\nmm/mempolicy.c-2819-\t\t\t\t  gfp, pol, nr_pages, page_array);\n--\nmm/mempolicy.c-2821-\tif (pol-\u003emode == MPOL_PREFERRED_MANY)\nmm/mempolicy.c:2822:\t\treturn alloc_pages_bulk_preferred_many(gfp,\nmm/mempolicy.c-2823-\t\t\t\tnuma_node_id(), pol, nr_pages, page_array);\n--\nmm/mempolicy.c-2826-\tnodemask = policy_nodemask(gfp, pol, NO_INTERLEAVE_INDEX, \u0026nid);\nmm/mempolicy.c:2827:\treturn alloc_pages_bulk_noprof(gfp, nid, nodemask,\nmm/mempolicy.c-2828-\t\t\t\t       nr_pages, page_array);\n--\nmm/page_alloc.c=5085=static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-5133-/*\nmm/page_alloc.c:5134: * __alloc_pages_bulk - Allocate a number of order-0 pages to an array\nmm/page_alloc.c-5135- * @gfp: GFP flags for the allocation\n--\nmm/page_alloc.c-5153- */\nmm/page_alloc.c:5154:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.c-5155-\t\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n--\nmm/page_alloc.c-5298-\nmm/page_alloc.c:5299:unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\nmm/page_alloc.c-5300-\t\t\tnodemask_t *nodemask, int nr_pages,\n--\nmm/page_alloc.c-5302-{\nmm/page_alloc.c:5303:\treturn __alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid,\nmm/page_alloc.c-5304-\t\t\t\t\t nodemask, nr_pages, page_array);\nmm/page_alloc.c-5305-}\nmm/page_alloc.c:5306:EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);\nmm/page_alloc.c-5307-\n--\nmm/page_alloc.h=261=struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n--\nmm/page_alloc.h-264-\nmm/page_alloc.h:265:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.h-266-\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n--\nmm/slub.c=7426=static bool __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,\n--\nmm/slub.c-7470- *\nmm/slub.c:7471: * Unlike alloc_pages_bulk(), this function does not check for already allocated\nmm/slub.c-7472- * objects in @p, and thus the caller does not need to zero it.\n--\nmm/vmalloc.c=3686=vm_area_alloc_pages(gfp_t gfp, int nid,\n--\nmm/vmalloc.c-3753-\t\t\tif (IS_ENABLED(CONFIG_NUMA) \u0026\u0026 nid == NUMA_NO_NODE)\nmm/vmalloc.c:3754:\t\t\t\tnr = alloc_pages_bulk_mempolicy_noprof(gfp,\nmm/vmalloc.c-3755-\t\t\t\t\t\t\tnr_pages_request,\n--\nmm/vmalloc.c-3757-\t\t\telse\nmm/vmalloc.c:3758:\t\t\t\tnr = alloc_pages_bulk_node_noprof(gfp, nid,\nmm/vmalloc.c-3759-\t\t\t\t\t\t\tnr_pages_request,\n--\nnet/core/page_pool.c=611=static noinline netmem_ref __page_pool_alloc_netmems_slow(struct page_pool *pool,\n--\nnet/core/page_pool.c-633-\nnet/core/page_pool.c:634:\t/* Mark empty alloc.cache slots \"empty\" for alloc_pages_bulk */\nnet/core/page_pool.c-635-\tmemset(\u0026pool-\u003ealloc.cache, 0, sizeof(void *) * bulk);\nnet/core/page_pool.c-636-\nnet/core/page_pool.c:637:\tnr_pages = alloc_pages_bulk_node(gfp, pool-\u003ep.nid, bulk,\nnet/core/page_pool.c-638-\t\t\t\t\t (struct page **)pool-\u003ealloc.cache);\n--\nnet/sunrpc/svc_xprt.c=687=static bool svc_fill_pages(struct svc_rqst *rqstp, struct page **pages,\n--\nnet/sunrpc/svc_xprt.c-692-\tfor (filled = 0; filled \u003c npages; filled = ret) {\nnet/sunrpc/svc_xprt.c:693:\t\tret = alloc_pages_bulk(GFP_KERNEL, npages, pages);\nnet/sunrpc/svc_xprt.c-694-\t\tif (ret \u003e filled)\n"
}

gemini-3.8-flash

null

null

							input: 37632
							output: 26
							thoughts: 1592
						

**Analyzing Focus Symbols in a Kernel Patch**

Okay, so I'm diving into this patch and trying to figure out the best symbols to focus fuzzing efforts. The goal is to identify specific feature logic or entry points, and avoid the noise of ubiquitous functions. I immediately notice `alloc_pages_bulk`, and I'm thinking, "Is this it?". It's not a generic allocator like `kmalloc` or page fault handlers.  It's used in these specific batch operations: splice, Btrfs, FUSE, mempolicy, io_uring, and BPF arena allocations, and vmalloc. That's a strong indicator.

Then I see `__alloc_pages_bulk_noprof`, which is the core logic directly modified in the patch. Its non-`noprof` counterpart calls `alloc_pages_bulk`, which is used in the above listed batch operations. It was *introduced* in this patch, which makes it a very strong candidate.

The guideline's "ubiquitous lifecycle hot-paths" warning is ringing in my head though. But is `__alloc_pages_bulk_noprof` truly ubiquitous? No. It's not called by every program, it's specific to bulk allocations. Unlike `__alloc_pages_noprof` or `kfree`.

However, `alloc_pages_bulk_mempolicy_noprof` and `alloc_migration_target`, and `collapse_run_pmd` sound even more specific. So I will add them as focus symbols. I also confirmed that `alloc_pages_bulk_mempolicy_noprof` is used in specific syscalls and vmalloc.

Now, let's explore `alloc_migration_target`. It's right there in the patch code. It calls `__folio_alloc`. That seems good, too, but I need to make sure I am not including something I should not.

I check `mm/khugepaged.c` for any other relevant symbols. I find `collapse_run_pmd`, which calls `alloc_charge_folio`.

Now, I look for more symbols modified in the patch, and find `__folio_alloc_noprof` and `__folio_alloc_node_noprof`. WAIT! `__folio_alloc_noprof` is called by `__folio_alloc_node_noprof`, which in turn, is called by `folio_alloc_noprof` and then `filemap_alloc_folio` - which is a generic memory allocator called during file read/write! So I have to be careful not to list these as focus symbols!

Therefore, the ones I want to focus on are:

*   `__alloc_pages_bulk_noprof`
*   `alloc_migration_target`
*   `collapse_run_pmd`

Now, Kconfig dependencies, real quick.  `alloc_migration_target` has a `CONFIG_MIGRATION` check. I need to make sure the fuzzing config enables that. Looks like it does by default.

Alright, that's the list.  `__alloc_pages_bulk_noprof`, `alloc_migration_target` and `collapse_run_pmd` are the key entry points for this patch's core logic. The others are too ubiquitous, and would cause dilution. Time to submit this.

{
  "Expression": "migrate\\.o",
  "PathPrefix": "mm/Makefile"
}

{
  "Output": "mm/Makefile=98=obj-$(CONFIG_MEMTEST)\t\t+= memtest.o\nmm/Makefile:99:obj-$(CONFIG_MIGRATION) += migrate.o\nmm/Makefile-100-obj-$(CONFIG_NUMA) += memory-tiers.o\n"
}

gemini-3.8-flash

null

null

							input: 40059
							output: 28
							thoughts: 33
						

Okay, here's my take on those thoughts, framed as an expert's internal monologue:

**Investigating the Migration Configuration**

Right, so `CONFIG_MIGRATION` appears to be the key to enabling or disabling `migrate.o`. That's not entirely surprising, but it's always good to be certain. Time to dive into `mm/Kconfig` and verify the exact implications of that configuration option. I need to understand how it's defined, any dependencies it might have, and what other components are potentially impacted when it's enabled or disabled. This will give me a better understanding of the implications to the overall kernel configuration.

{
  "Expression": "config MIGRATION",
  "PathPrefix": "mm/Kconfig"
}

{
  "Output": "mm/Kconfig=672=config NUMA_MIGRATION\n--\nmm/Kconfig-682-\nmm/Kconfig:683:config MIGRATION\nmm/Kconfig-684-\tbool\n"
}

gemini-3.8-flash

null

null

							input: 40325
							output: 32
							thoughts: 17
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Diving into the Kernel Configuration Landscape**

Okay, so I need to get a handle on how this particular feature is being configured within the kernel. My instincts tell me the best place to start is the core Kconfig files, specifically `mm/Kconfig`. That's where a lot of the memory management options are typically defined. I’m thinking line 683 is a likely spot. It’s usually around that area where more specific options branch out, or major sections are delineated. Let's see if this hunch is correct, or if I need to adjust my search.

{
  "File": "mm/Kconfig",
  "FirstLine": 670,
  "LineCount": 35
}

{
  "Contents": " 670:\t\t  memory can be freed within the host for other uses.\n 671:\t\n 672:\tconfig NUMA_MIGRATION\n 673:\t\tbool \"NUMA page migration\"\n 674:\t\tdefault y\n 675:\t\tdepends on NUMA \u0026\u0026 MMU\n 676:\t\tselect MIGRATION\n 677:\t\thelp\n 678:\t\t  Support the migration of pages to other NUMA nodes, available to\n 679:\t\t  user space through interfaces like migrate_pages(), move_pages(),\n 680:\t\t  and mbind(). Selecting this option also enables support for page\n 681:\t\t  demotion for memory tiering.\n 682:\t\n 683:\tconfig MIGRATION\n 684:\t\tbool\n 685:\t\tdepends on MMU\n 686:\t\n 687:\tconfig DEVICE_MIGRATION\n 688:\t\tdef_bool MIGRATION \u0026\u0026 ZONE_DEVICE\n 689:\t\n 690:\tconfig ARCH_ENABLE_HUGEPAGE_MIGRATION\n 691:\t\tbool\n 692:\t\n 693:\tconfig ARCH_HAS_PMD_SOFTLEAVES\n 694:\t\tbool\n 695:\t\n 696:\tconfig HUGETLB_PAGE_SIZE_VARIABLE\n 697:\t\tdef_bool n\n 698:\t\thelp\n 699:\t\t  Allows the pageblock_order value to be dynamic instead of just standard\n 700:\t\t  HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available\n 701:\t\t  on a platform.\n 702:\t\n 703:\t\t  Note that the pageblock_order cannot exceed MAX_PAGE_ORDER and will be\n 704:\t\t  clamped down to MAX_PAGE_ORDER.\n"
}

gemini-3.8-flash

null

null

							input: 40994
							output: 18
							thoughts: 50
						

**Investigating the Dependencies of `MIGRATION`**

Okay, so `MIGRATION` is obviously a key feature, and it looks like a whole host of other configurations – `NUMA_MIGRATION`, `TRANSPARENT_HUGEPAGE`, `CMA`, `MEMORY_HOTREMOVE`, the list goes on – are pulling it in. That suggests it's a fundamental building block.  My next step is clear: I need to quickly identify *precisely* which of these selectors are responsible for enabling `MIGRATION`. Understanding the direct dependencies is crucial. I need to trace this back. This level of granularity will tell me the fundamental dependencies so I can reason about design trade-offs and potentially optimize configurations. Let's see what the Kconfig files reveal.

{
  "Expression": "select MIGRATION"
}

{
  "Output": "mm/Kconfig=581=config MEMORY_HOTREMOVE\nmm/Kconfig-582-\tbool \"Allow for memory hot remove\"\nmm/Kconfig:583:\tselect MIGRATION\nmm/Kconfig-584-\n--\nmm/Kconfig=641=config COMPACTION\n--\nmm/Kconfig-643-\tdefault y\nmm/Kconfig:644:\tselect MIGRATION\nmm/Kconfig-645-\tdepends on MMU\n--\nmm/Kconfig=672=config NUMA_MIGRATION\n--\nmm/Kconfig-675-\tdepends on NUMA \u0026\u0026 MMU\nmm/Kconfig:676:\tselect MIGRATION\nmm/Kconfig-677-\thelp\n--\nmm/Kconfig=764=config MEMORY_FAILURE\n--\nmm/Kconfig-768-\tselect INTERVAL_TREE\nmm/Kconfig:769:\tselect MIGRATION\nmm/Kconfig-770-\thelp\n--\nmm/Kconfig=1055=config CMA\n--\nmm/Kconfig-1057-\tdepends on MMU\nmm/Kconfig:1058:\tselect MIGRATION\nmm/Kconfig-1059-\tselect MEMORY_ISOLATION\n"
}

gemini-3.8-flash

null

null

							input: 41554
							output: 29
							thoughts: 50
						

Okay, here's my interpretation of that thought process, from an expert's perspective:

**Kernel Memory Management – Thinking Through Khugepaged Compilation**

Right, so I'm focusing on memory management, specifically looking at how the kernel handles page migration. My immediate thought is that `COMPACTION` and `NUMA_MIGRATION` ultimately trigger `MIGRATION`. This is pretty standard; those two features are fundamentally related to the need for moving pages around.

Now, my mind shifts to `mm/khugepaged.c`. I need to figure out how this plays into the bigger picture. I'm wondering, how is this crucial file, `khugepaged.c`, *compiled* into the kernel? What conditions govern its inclusion? Knowing this is vital to understanding how transparent huge pages are managed. Is it always compiled in, or is it conditional based on other kernel configurations or compile-time options? This information is essential for analyzing its behavior during runtime and determining how it interacts with other features like compaction or NUMA migration. I need to understand its build environment to assess its behavior and troubleshoot issues.

{
  "Expression": "khugepaged\\.o",
  "PathPrefix": "mm/Makefile"
}

{
  "Output": "mm/Makefile=101=obj-$(CONFIG_DEVICE_MIGRATION) += migrate_device.o\nmm/Makefile:102:obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o\nmm/Makefile-103-obj-$(CONFIG_PAGE_COUNTER) += page_counter.o\n"
}

gemini-3.8-flash

null

null

							input: 41966
							output: 34
							thoughts: 161
						

**Kernel Configuration Dependency Deep Dive**

Okay, so I'm digging into these kernel config options and dependencies again. Right, first things first, it's clear that `TRANSPARENT_HUGEPAGE` *absolutely* needs to be enabled for `khugepaged.o` to function. That's a fundamental link I need to keep in mind. Then, it's equally crucial to recognize that either `NUMA_MIGRATION` or just plain `MIGRATION` is essential for `migrate.o` to work. The user-prompted description for `NUMA_MIGRATION`, "NUMA page migration," is a good reminder of its specific purpose.

My next step is to get a handle on the relationships between `MIGRATION`, `NUMA_MIGRATION`, and, especially, `TRANSPARENT_HUGEPAGE`. Are there any additional configurations that influence `mm/page_alloc.c`? Ah, but I need to remember that `page_alloc.c` is always compiled; it's a core memory management component. So, I shouldn't expect *those* configs to be gating it.

Hang on... what are the actual dependencies or configurations that *control* `TRANSPARENT_HUGEPAGE` itself? I need to drill down into the finer details there. Let's start by looking specifically at `CONFIG_TRANSPARENT_HUGEPAGE`. That should provide the key to understanding the underlying implications of enabling it.

{
  "Expression": "config TRANSPARENT_HUGEPAGE\\b",
  "PathPrefix": "mm/Kconfig"
}

{
  "Output": "mm/Kconfig=831=config MM_ID\n--\nmm/Kconfig-833-\nmm/Kconfig:834:menuconfig TRANSPARENT_HUGEPAGE\nmm/Kconfig-835-\tbool \"Transparent Hugepage Support\"\n"
}

gemini-3.8-flash

null

null

							input: 42555
							output: 32
							thoughts: 17
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Diving into the Kernel Configuration Landscape**

Okay, so I need to zero in on a specific area within the kernel configuration system. I'm thinking I need to investigate the `mm/Kconfig` file, specifically around line 834. This likely indicates I'm troubleshooting, debugging, or perhaps extending a memory management-related feature or option. Knowing the typical layout of `Kconfig` files, line numbers are a pretty solid indicator of what I might find there - possibly a complex conditional block for a feature, or an important dependency definition. It's time to get hands on and see what's what.

{
  "File": "mm/Kconfig",
  "FirstLine": 834,
  "LineCount": 20
}

{
  "Contents": " 834:\tmenuconfig TRANSPARENT_HUGEPAGE\n 835:\t\tbool \"Transparent Hugepage Support\"\n 836:\t\tdepends on HAVE_ARCH_TRANSPARENT_HUGEPAGE \u0026\u0026 !PREEMPT_RT\n 837:\t\tselect COMPACTION\n 838:\t\tselect XARRAY_MULTI\n 839:\t\tselect MM_ID\n 840:\t\thelp\n 841:\t\t  Transparent Hugepages allows the kernel to use huge pages and\n 842:\t\t  huge tlb transparently to the applications whenever possible.\n 843:\t\t  This feature can improve computing performance to certain\n 844:\t\t  applications by speeding up page faults during memory\n 845:\t\t  allocation, by reducing the number of tlb misses and by speeding\n 846:\t\t  up the pagetable walking.\n 847:\t\n 848:\t\t  If memory constrained on embedded, you may want to say N.\n 849:\t\n 850:\tif TRANSPARENT_HUGEPAGE\n 851:\t\n 852:\tchoice\n 853:\t\tprompt \"Transparent Hugepage Support sysfs defaults\"\n"
}

gemini-3.8-flash

null

null

							input: 43051
							output: 205
							thoughts: 1360
						

**Analyzing Fuzzing Focus: Memory Allocation and Migration**

Okay, let's break this down. First, I see that `TRANSPARENT_HUGEPAGE` triggers `COMPACTION`, which then triggers `MIGRATION`. And, `NUMA_MIGRATION` relies on `NUMA && MMU` and *also* selects `MIGRATION`. Got it. Now, let's zoom in on the specific functions we're considering for fuzzing.

My primary goal here is to identify and list functions *directly* modified by the patch, or critical callers that exercise the patched logic. But, I need to avoid including functions that are simply generic, ubiquitous memory allocators called by almost *everything* in the kernel. That would just be noise in the fuzzing results.

So, let's start with what the patch directly touches. The functions `alloc_migration_target` (non-static, `mm/migrate.c`, called by `migrate_pages`) and `collapse_run_pmd` (non-static, `mm/khugepaged.c`, which calls `alloc_charge_folio`) are certainly good candidates. `alloc_migration_target` is directly modified in the patch. `collapse_run_pmd` is also great; it's the non-static caller that executes the collapse logic and calls the modified `alloc_charge_folio`.

Now, the interesting one: `__alloc_pages_bulk_noprof` (introduced and modified in `mm/page_alloc.c`). Is this function a *ubiquitous* memory allocator, or is it specific enough to warrant inclusion? Checking `vmlinux`, `__alloc_pages_bulk_noprof` *is* a global symbol (declared in `mm/page_alloc.h`), and `alloc_pages_bulk_noprof` (which calls it) is exported as well. But is it ubiquitous? The instruction says to avoid the usual suspects. While *some* code, such as `kmalloc` and page faults, is universal, bulk allocation is only used in specific subsystems. It's used in bulk I/O and specific subsystems like splice, btrfs, io_uring, bpf arena, vmalloc, page pool. Thus it is NOT a generic, ubiquitous function. But what about the related folio allocation functions `__folio_alloc_noprof` and `__folio_alloc_node_noprof`? `folio_alloc` calls them, and `folio_alloc` *is* used everywhere for page cache, anonymous pages, pipes, etc. So definitely *no* to those. They're too general. However, `__alloc_pages_bulk_noprof` appears to be a good fit. It's the function where the core logic was added/modified (specifically, the `fastpath_alloc_flags` handling, watermark checks, and fallback paths). Therefore, `__alloc_pages_bulk_noprof` is worth including.

Let's double-check other candidates. Static functions are out, so `collapse_huge_page`, `collapse_file`, and `alloc_charge_folio` in `mm/khugepaged.c` are not candidates. Similarly, `madvise_collapse` in `mm/madvise.c` is static, so it's not a direct focus. Thus `collapse_run_pmd` remains the only candidate from that file.

For the configurations, it's clear: `TRANSPARENT_HUGEPAGE` for `mm/khugepaged.c`, `MIGRATION` (or `NUMA_MIGRATION`) for `mm/migrate.c`, and `NUMA` for NUMA migration and bulk allocation.

Alright, the final assessment:

*   **WorthFuzzing: True.** This patch refactors core memory management allocation paths with significant change including `__alloc_pages_bulk_noprof`, `__folio_alloc_noprof`, and calls in `mm/migrate.c` and `mm/khugepaged.c`. It alters flag handling and fastpath watermarks in bulk allocation. The code is fully reachable via userspace syscalls including `madvise(MADV_COLLAPSE)`, `migrate_pages`, and splice/bulk allocation interfaces.
*   **FocusSymbols:**
    *   `__alloc_pages_bulk_noprof`
    *   `alloc_migration_target`
    *   `collapse_run_pmd`
*   **EnableConfigs:**
    *   `TRANSPARENT_HUGEPAGE`
    *   `MIGRATION`
    *   `NUMA`

All set. We're ready to

{
  "EnableConfigs": [
    "TRANSPARENT_HUGEPAGE",
    "MIGRATION",
    "NUMA"
  ],
  "FocusSymbols": [
    "__alloc_pages_bulk_noprof",
    "alloc_migration_target",
    "collapse_run_pmd"
  ],
  "Reasoning": "The patch refactors core memory management functions in mm/page_alloc.c, mm/khugepaged.c, and mm/migrate.c. It extends __folio_alloc_noprof and alloc_pages_bulk_noprof to accept explicit alloc_flags, altering watermark checking and fallback allocation in __alloc_pages_bulk_noprof. These paths are reachable from userspace via page migration syscalls (e.g. migrate_pages, move_pages), madvise(MADV_COLLAPSE), and bulk allocation operations (e.g. splice).",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "TRANSPARENT_HUGEPAGE",
    "MIGRATION",
    "NUMA"
  ],
  "FocusSymbols": [
    "__alloc_pages_bulk_noprof",
    "alloc_migration_target",
    "collapse_run_pmd"
  ],
  "Reasoning": "The patch refactors core memory management functions in mm/page_alloc.c, mm/khugepaged.c, and mm/migrate.c. It extends __folio_alloc_noprof and alloc_pages_bulk_noprof to accept explicit alloc_flags, altering watermark checking and fallback allocation in __alloc_pages_bulk_noprof. These paths are reachable from userspace via page migration syscalls (e.g. migrate_pages, move_pages), madvise(MADV_COLLAPSE), and bulk allocation operations (e.g. splice).",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

core

null

{
  "KMSANReasoning": "The patch refactors internal page allocator functions (`__folio_alloc_noprof` and `__alloc_pages_bulk_noprof`) to accept an `alloc_flags` argument rather than hardcoding `ALLOC_DEFAULT`. Existing callers (`khugepaged.c`, `migrate.c`) and wrappers (`alloc_pages_bulk_noprof`, `__folio_alloc_node_noprof`) are updated to explicitly pass `ALLOC_DEFAULT`. In `__alloc_pages_bulk_noprof`, `struct alloc_context ac` is initialized via designated initializer (`{ .alloc_flags = alloc_flags }`), which actually guarantees zero-initialization of remaining fields.\n\nNo kernel structures are copied or exposed to userspace, no conditional logic relies on uninitialized data, and page zeroing / init_on_alloc semantics are unchanged. Potential regressions from these changes (e.g. incorrect allocation watermarks, GFP flag handling, or NULL dereferences on allocation failure) are addressed by standard kernel debugging assertions, LOCKDEP, and KASAN. There are no uninitialized memory usage or info-leak risks requiring a dedicated KMSAN session.",
  "NeedsKMSAN": false
}

You are an expert Linux kernel security engineer specializing in kernel memory
error detectors (KASAN and KMSAN). Your job is to review the provided patch series and
determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer)
fuzzing session in addition to standard KASAN fuzzing.

CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN:
- Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable
  a comprehensive suite of debugging tools and sanitizers, including KASAN
  (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP
  (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks.
- KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap,
  or page allocations) and kernel-to-user memory info-leaks.

Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN,
LOCKDEP, OR OTHER STANDARD BUG DETECTORS.
A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY
set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks
that are detected ONLY by KMSAN.

Look holistically at the patch series and surrounding code. Even if no direct
uninitialized field accesses or new buffer allocations are added in the diff itself,
a patch may alter control flow, bounds checking, or data length calculations in ways
that change how the rest of the code operates on existing buffers (e.g. allowing
uninitialized stack/heap memory to be read, copied to user space, or used in control
flow). Do not hesitate to use your code access tools to inspect the surrounding code,
called functions, and callers.

Set NeedsKMSAN=true ONLY IF the patch introduces or modifies:
1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb
   attributes, ioctl output arguments, socket options, or BPF buffers) where fields
   or structure padding might not be fully initialized/zeroed.
2. Conditional logic or branching that depends on potentially uninitialized variables
   or struct fields.
3. Allocation or initialization of complex data structures where uninitialized fields
   could be read later in reachable code paths.
4. Bounds checks, lengths, or logic in a way that allows surrounding code to access
   uninitialized bytes of existing buffers.

Set NeedsKMSAN=false IF:
- The code changes primarily risk out-of-bounds access, array overflows, NULL pointer
  dereferences, locking deadlocks, or use-after-free bugs (these are already caught
  by KASAN, LOCKDEP, or standard bug detectors).
- All stack/heap structures touched or introduced by the patch are fully zeroed
  or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied.
- The patch does not introduce any risk of uninitialized memory usage or info-leaks.

Use your code access tools to inspect the surrounding code if necessary, then provide
detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch.
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit 4517e1ab346bb79c2dedf83e439ae3553b6c3a1d
Author: syz-cluster <triage@syzkaller.com>
Date:   Mon Sep 14 20:22:44 2026 +0000

    syz-cluster: applied patch under review

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 872bc53f32ec8..a327e58c313f8 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -204,10 +204,6 @@ static inline void arch_free_page(struct page *page, int order) { }
 static inline void arch_alloc_page(struct page *page, int order) { }
 #endif
 
-struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,
-		nodemask_t *nodemask);
-#define __folio_alloc(...)			alloc_hooks(__folio_alloc_noprof(__VA_ARGS__))
-
 unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 				nodemask_t *nodemask, int nr_pages,
 				struct page **page_array);
@@ -252,14 +248,7 @@ static inline void warn_if_node_offline(int this_node, gfp_t gfp_mask)
 	dump_stack();
 }
 
-static inline
-struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid)
-{
-	warn_if_node_offline(nid, gfp);
-
-	return __folio_alloc_noprof(gfp, order, nid, NULL);
-}
-
+struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid);
 #define  __folio_alloc_node(...)		alloc_hooks(__folio_alloc_node_noprof(__VA_ARGS__))
 
 /*
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 0d8cd44b14c57..431c2e610b392 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1193,7 +1193,7 @@ static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_stru
 	int node = collapse_find_target_node(cc);
 	struct folio *folio;
 
-	folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask);
+	folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask, ALLOC_DEFAULT);
 	if (!folio) {
 		*foliop = NULL;
 		count_collapse_event(order, THP_COLLAPSE_ALLOC_FAILED,
diff --git a/mm/migrate.c b/mm/migrate.c
index 7e3a81f069744..8e1c25a6f7505 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2229,7 +2229,7 @@ struct folio *alloc_migration_target(struct folio *src, unsigned long private)
 	if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE)
 		gfp_mask |= __GFP_HIGHMEM;
 
-	return __folio_alloc(gfp_mask, order, nid, mtc->nmask);
+	return __folio_alloc(gfp_mask, order, nid, mtc->nmask, ALLOC_DEFAULT);
 }
 
 #ifdef CONFIG_NUMA_MIGRATION
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d977b8bf7245a..f4ceec8cf77e0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5151,8 +5151,8 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
  * @page_array were set to %NULL on entry, the slots from 0 to the return value
  * - 1 will be filled.
  */
-unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
-			nodemask_t *nodemask, int nr_pages,
+unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,
+			int preferred_nid, nodemask_t *nodemask, int nr_pages,
 			struct page **page_array)
 {
 	struct page *page;
@@ -5160,8 +5160,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	struct zoneref *z;
 	struct per_cpu_pages *pcp;
 	struct list_head *pcp_list;
-	struct alloc_context ac;
-	unsigned int alloc_flags = ALLOC_WMARK_LOW;
+	struct alloc_context ac = { .alloc_flags = alloc_flags };
+	unsigned int fastpath_alloc_flags = alloc_flags | ALLOC_WMARK_LOW;
 	int nr_populated = 0, nr_account = 0;
 
 	/*
@@ -5202,7 +5202,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	/* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */
 	gfp &= gfp_allowed_mask;
 	gfp = current_gfp_context(gfp);
-	if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &gfp, &alloc_flags))
+	if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &gfp, &fastpath_alloc_flags))
 		goto out;
 
 	/* Find an allowed local zone that meets the low watermark. */
@@ -5210,7 +5210,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	for_next_zone_zonelist_nodemask(zone, z, ac.highest_zoneidx, ac.nodemask) {
 		unsigned long mark;
 
-		if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) &&
+		if (cpusets_enabled() && (fastpath_alloc_flags & ALLOC_CPUSET) &&
 		    !__cpuset_zone_allowed(zone, gfp)) {
 			continue;
 		}
@@ -5220,16 +5220,17 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 			goto failed;
 		}
 
-		cond_accept_memory(zone, 0, alloc_flags);
+		cond_accept_memory(zone, 0, fastpath_alloc_flags);
 retry_this_zone:
-		mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages - nr_populated;
+		mark = wmark_pages(zone, fastpath_alloc_flags & ALLOC_WMARK_MASK) +
+		       nr_pages - nr_populated;
 		if (zone_watermark_fast(zone, 0,  mark,
 				zonelist_zone_idx(ac.preferred_zoneref),
-				alloc_flags, gfp)) {
+				fastpath_alloc_flags, gfp)) {
 			break;
 		}
 
-		if (cond_accept_memory(zone, 0, alloc_flags))
+		if (cond_accept_memory(zone, 0, fastpath_alloc_flags))
 			goto retry_this_zone;
 
 		/* Try again if zone has deferred pages */
@@ -5261,7 +5262,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 			continue;
 		}
 
-		page = __rmqueue_pcplist(zone, 0, ac.migratetype, alloc_flags,
+		page = __rmqueue_pcplist(zone, 0, ac.migratetype, fastpath_alloc_flags,
 								pcp, pcp_list);
 		if (unlikely(!page)) {
 			/* Try and allocate at least one page */
@@ -5289,11 +5290,19 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	return nr_populated;
 
 failed:
-	page = __alloc_pages_noprof(gfp, 0, preferred_nid, nodemask, ALLOC_DEFAULT);
+	page = __alloc_pages_noprof(gfp, 0, preferred_nid, nodemask, alloc_flags);
 	if (page)
 		page_array[nr_populated++] = page;
 	goto out;
 }
+
+unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
+			nodemask_t *nodemask, int nr_pages,
+			struct page **page_array)
+{
+	return __alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid,
+					 nodemask, nr_pages, page_array);
+}
 EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
 
 /*
@@ -5484,13 +5493,20 @@ struct page *alloc_pages_node_noprof(int nid, gfp_t gfp_mask, unsigned int order
 EXPORT_SYMBOL(alloc_pages_node_noprof);
 
 struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,
-		nodemask_t *nodemask)
+		nodemask_t *nodemask, unsigned int alloc_flags)
 {
 	struct page *page = __alloc_pages_noprof(gfp | __GFP_COMP, order,
-					preferred_nid, nodemask, ALLOC_DEFAULT);
+					preferred_nid, nodemask, alloc_flags);
 	return page_rmappable_folio(page);
 }
-EXPORT_SYMBOL(__folio_alloc_noprof);
+
+struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid)
+{
+	warn_if_node_offline(nid, gfp);
+
+	return __folio_alloc_noprof(gfp, order, nid, NULL, ALLOC_DEFAULT);
+}
+EXPORT_SYMBOL(__folio_alloc_node_noprof);
 
 /*
  * Common helper functions. Never use with __GFP_HIGHMEM because the returned
diff --git a/mm/page_alloc.h b/mm/page_alloc.h
index b9259deddb59d..23fc79ce97b60 100644
--- a/mm/page_alloc.h
+++ b/mm/page_alloc.h
@@ -258,6 +258,14 @@ struct page *__alloc_pages_noprof(gfp_t gfp, unsigned int order, int preferred_n
 		nodemask_t *nodemask, unsigned int alloc_flags);
 #define __alloc_pages(...)			alloc_hooks(__alloc_pages_noprof(__VA_ARGS__))
 
+struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,
+		nodemask_t *nodemask, unsigned int alloc_flags);
+#define __folio_alloc(...)			alloc_hooks(__folio_alloc_noprof(__VA_ARGS__))
+
+unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,
+		int preferred_nid, nodemask_t *nodemask, int nr_pages,
+		struct page **page_array);
+
 extern void zone_pcp_reset(struct zone *zone);
 extern void zone_pcp_disable(struct zone *zone);
 extern void zone_pcp_enable(struct zone *zone);

gemini-3.8-flash

null

null

							input: 4998
							output: 19
							thoughts: 712
						

**KMSAN Risk Assessment for This Patch**

Okay, let's break this down. My main concern here is whether this patch introduces or exacerbates any uninitialized memory vulnerabilities that would justify running KMSAN. My expertise tells me that changes in memory allocation, especially those touching low-level functions, are prime candidates for such issues.

First, I see that the patch significantly alters some core allocation functions and macros. Specifically, it seems to be refactoring some folio allocation routines. I see the removal of `__folio_alloc_noprof` and `__folio_alloc` macros from `include/linux/gfp.h`, and a declaration change for `__folio_alloc_node_noprof`. The key change seems to be the introduction of an `alloc_flags` argument into a number of allocation functions.

Specifically, it looks like:
- `__folio_alloc` now gets a `ALLOC_DEFAULT` argument in `khugepaged.c` and `migrate.c`. This isn't that concerning, since it appears to simply be adding a constant, so long as the constant is initialized.
- `alloc_pages_bulk_noprof` is renamed to `__alloc_pages_bulk_noprof` and gains an `alloc_flags` argument. Now, this is interesting. I immediately noticed that the patch *corrects* a potential bug! The original code used to define `struct alloc_context ac;` *without* initialization before calling `prepare_alloc_pages`. The patch now explicitly initializes a `struct alloc_context ac` using the `alloc_flags`. This is a *good* change, and it reduces the potential for an uninitialized memory read! It's likely related to the overall purpose of `alloc_flags`.
- `__folio_alloc_noprof` also gets an `alloc_flags` argument, which it passes along to `__alloc_pages_noprof`. `__folio_alloc_node_noprof` now calls `__folio_alloc_noprof` with `ALLOC_DEFAULT`.

Now, I need to understand the *implications* of this `alloc_flags`. I need to dig deeper into the actual usage of this `alloc_flags` to see if there are any subtle risks. Are there situations where this flag isn't set correctly, and an uninitialized variable makes its way into the memory allocation? Does it impact the behavior of the allocator in ways that could expose uninitialized memory?

To get a clearer picture, I need to see *all* the callers of these modified functions, and understand the context in which they are used. I need to know how `prepare_alloc_pages` behaves now that `alloc_flags` is being passed around, and what's changed there. Time to fire up `grepper` and see what else this affects. Let's see if the broader changes make things better or worse.

{
  "Expression": "__folio_alloc\\("
}

{
  "Output": "mm/khugepaged.c=1189=static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,\n--\nmm/khugepaged.c-1195-\nmm/khugepaged.c:1196:\tfolio = __folio_alloc(gfp, order, node, \u0026cc-\u003ealloc_nmask, ALLOC_DEFAULT);\nmm/khugepaged.c-1197-\tif (!folio) {\n--\nmm/migrate.c=2196=struct folio *alloc_migration_target(struct folio *src, unsigned long private)\n--\nmm/migrate.c-2231-\nmm/migrate.c:2232:\treturn __folio_alloc(gfp_mask, order, nid, mtc-\u003enmask, ALLOC_DEFAULT);\nmm/migrate.c-2233-}\n--\nmm/page_alloc.h=261=struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\nmm/page_alloc.h-262-\t\tnodemask_t *nodemask, unsigned int alloc_flags);\nmm/page_alloc.h:263:#define __folio_alloc(...)\t\t\talloc_hooks(__folio_alloc_noprof(__VA_ARGS__))\nmm/page_alloc.h-264-\n"
}

gemini-3.8-flash

null

null

							input: 6703
							output: 32
							thoughts: 21
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Diving into `prepare_alloc_pages`**

Okay, time to get my hands dirty. I'm going to start digging into the memory allocation path, specifically the `prepare_alloc_pages` function. My gut tells me this is a key spot. I want to see what's happening *before* the actual page allocation occurs. What are the preconditions being checked? Are there any potential bottlenecks or contention points I should be aware of? I'm anticipating this function will involve some early checks, potential resource reservations, and likely some interaction with the NUMA architecture if the system is configured that way. Knowing this function's exact purpose, will help me troubleshoot any related memory performance issues. Let's see what the code reveals! I'll be looking for things like zone selection, order constraints, and any potential hints about the intended usage profile for the pages being requested. I anticipate this is going to be a crucial component in understanding the overall memory allocation flow.

{
  "Expression": "prepare_alloc_pages",
  "PathPrefix": "mm/page_alloc.c"
}

{
  "Output": "mm/page_alloc.c=4766=__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-5084-\nmm/page_alloc.c:5085:static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c-5086-\t\tint preferred_nid, nodemask_t *nodemask,\n--\nmm/page_alloc.c=5154=unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\n--\nmm/page_alloc.c-5204-\tgfp = current_gfp_context(gfp);\nmm/page_alloc.c:5205:\tif (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, \u0026ac, \u0026gfp, \u0026fastpath_alloc_flags))\nmm/page_alloc.c-5206-\t\tgoto out;\n--\nmm/page_alloc.c=5389=struct page *__alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order,\n--\nmm/page_alloc.c-5426-\talloc_gfp = gfp;\nmm/page_alloc.c:5427:\tif (!prepare_alloc_pages(gfp, order, preferred_nid, nodemask, \u0026ac,\nmm/page_alloc.c-5428-\t\t\t\u0026alloc_gfp, \u0026fastpath_alloc_flags))\n"
}

gemini-3.8-flash

null

null

							input: 7381
							output: 36
							thoughts: 29
						

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Diving into `prepare_alloc_pages`**

Okay, time to get my hands dirty and jump into the `mm/page_alloc.c` file. Let's head over to the `prepare_alloc_pages` function, specifically around line 5085. I'm keen to see exactly how the allocation process is prepped, before it gets down to the nitty-gritty of physically grabbing those pages. I need to refresh my memory on the subtle interactions before the allocation. It has been a while since I deeply reviewed this section. I recall some clever optimizations in the past around the NUMA balancing, and I want to refresh my memory. This function is a critical checkpoint for understanding the overall memory allocation flow, so this will be a good starting point.

{
  "File": "mm/page_alloc.c",
  "FirstLine": 5085,
  "LineCount": 60
}

{
  "Contents": "5085:\tstatic inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\n5086:\t\t\tint preferred_nid, nodemask_t *nodemask,\n5087:\t\t\tstruct alloc_context *ac, gfp_t *alloc_gfp,\n5088:\t\t\tunsigned int *alloc_flags)\n5089:\t{\n5090:\t\tac-\u003ehighest_zoneidx = gfp_zone(gfp_mask);\n5091:\t\tac-\u003ezonelist = node_zonelist(preferred_nid, gfp_mask);\n5092:\t\tac-\u003enodemask = nodemask;\n5093:\t\tac-\u003emigratetype = gfp_migratetype(gfp_mask);\n5094:\t\n5095:\t\tif (cpusets_enabled()) {\n5096:\t\t\t*alloc_gfp |= __GFP_HARDWALL;\n5097:\t\t\t/*\n5098:\t\t\t * When we are in the interrupt context, it is irrelevant\n5099:\t\t\t * to the current task context. It means that any node ok.\n5100:\t\t\t */\n5101:\t\t\tif (in_task() \u0026\u0026 !ac-\u003enodemask)\n5102:\t\t\t\tac-\u003enodemask = \u0026cpuset_current_mems_allowed;\n5103:\t\t\telse\n5104:\t\t\t\t*alloc_flags |= ALLOC_CPUSET;\n5105:\t\t}\n5106:\t\n5107:\t\tmight_alloc(gfp_mask);\n5108:\t\n5109:\t\t/*\n5110:\t\t * Don't invoke should_fail logic, since it may call\n5111:\t\t * get_random_u32() and printk() which need to spin_lock.\n5112:\t\t */\n5113:\t\tif (!(*alloc_flags \u0026 ALLOC_NOLOCK) \u0026\u0026\n5114:\t\t    should_fail_alloc_page(gfp_mask, order))\n5115:\t\t\treturn false;\n5116:\t\n5117:\t\t*alloc_flags |= alloc_flags_cma(gfp_mask);\n5118:\t\n5119:\t\t/* Dirty zone balancing only done in the fast path */\n5120:\t\tac-\u003espread_dirty_pages = (gfp_mask \u0026 __GFP_WRITE);\n5121:\t\n5122:\t\t/*\n5123:\t\t * The preferred zone is used for statistics but crucially it is\n5124:\t\t * also used as the starting point for the zonelist iterator. It\n5125:\t\t * may get reset for allocations that ignore memory policies.\n5126:\t\t */\n5127:\t\tac-\u003epreferred_zoneref = first_zones_zonelist(ac-\u003ezonelist,\n5128:\t\t\t\t\t\tac-\u003ehighest_zoneidx, ac-\u003enodemask);\n5129:\t\n5130:\t\treturn true;\n5131:\t}\n5132:\t\n5133:\t/*\n5134:\t * __alloc_pages_bulk - Allocate a number of order-0 pages to an array\n5135:\t * @gfp: GFP flags for the allocation\n5136:\t * @preferred_nid: The preferred NUMA node ID to allocate from\n5137:\t * @nodemask: Set of nodes to allocate from, may be NULL\n5138:\t * @nr_pages: The number of pages desired in the array\n5139:\t * @page_array: Array to store the pages\n5140:\t *\n5141:\t * This is a batched version of the page allocator that attempts to allocate\n5142:\t * @nr_pages quickly.  Pages are added to @page_array.\n5143:\t *\n5144:\t * Note that only the elements in @page_array that were cleared to %NULL on\n"
}

gemini-3.8-flash

null

null

							input: 8620
							output: 20
							thoughts: 90
						

**Examining the Memory Allocation Context**

Okay, let's dive into this `__alloc_pages_bulk_noprof` function. I see they've initialized the `alloc_context` struct now: `struct alloc_context ac = { .alloc_flags = alloc_flags };`. Interesting. I remember a time when `ac` was just declared without any initialization, like this: `struct alloc_context ac;`. That always made me a little uneasy.

Wait a second...I'm just quickly scanning the context here, does the `alloc_context` struct even *have* an `alloc_flags` member? Better confirm that. I need to make sure this initialization is actually doing what they think it's doing. Time to double-check the `struct alloc_context` definition. Can't be too careful!

{
  "Expression": "struct alloc_context\\b"
}

{
  "Output": "include/linux/compaction.h=23=enum compact_result {\n--\ninclude/linux/compaction.h-59-\ninclude/linux/compaction.h:60:struct alloc_context; /* in mm/internal.h */\ninclude/linux/compaction.h-61-struct capture_control; /* in mm/internal.h */\n--\ninclude/linux/compaction.h=89=extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,\ninclude/linux/compaction.h-90-\t\tunsigned int order, unsigned int alloc_flags,\ninclude/linux/compaction.h:91:\t\tconst struct alloc_context *ac, enum compact_priority prio,\ninclude/linux/compaction.h-92-\t\tstruct capture_control *capc);\n--\ninclude/linux/compaction.h=97=extern void compaction_defer_reset(struct zone *zone, int order,\n--\ninclude/linux/compaction.h-99-\ninclude/linux/compaction.h:100:bool compaction_zonelist_suitable(struct alloc_context *ac, int order,\ninclude/linux/compaction.h-101-\t\t\t\t\tint alloc_flags, gfp_t gfp_mask);\n--\nmm/compaction.c=2434=bool compaction_suitable(struct zone *zone, int order, unsigned long watermark,\n--\nmm/compaction.c-2478-/* Used by direct reclaimers */\nmm/compaction.c:2479:bool compaction_zonelist_suitable(struct alloc_context *ac, int order,\nmm/compaction.c-2480-\t\tint alloc_flags, gfp_t gfp_mask)\n--\nmm/compaction.c=2834=enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,\nmm/compaction.c:2835:\t\tunsigned int alloc_flags, const struct alloc_context *ac,\nmm/compaction.c-2836-\t\tenum compact_priority prio, struct capture_control *capc)\n--\nmm/page_alloc.c=3429=static void reserve_highatomic_pageblock(struct page *page, int order,\n--\nmm/page_alloc.c-3477- */\nmm/page_alloc.c:3478:static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,\nmm/page_alloc.c-3479-\t\t\t\t\t\tbool force)\n--\nmm/page_alloc.c=3782=get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,\nmm/page_alloc.c:3783:\t\t\t\t\t\tconst struct alloc_context *ac)\nmm/page_alloc.c-3784-{\n--\nmm/page_alloc.c=4007=__alloc_pages_cpuset_fallback(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c-4008-\t\t\t      unsigned int alloc_flags,\nmm/page_alloc.c:4009:\t\t\t      const struct alloc_context *ac)\nmm/page_alloc.c-4010-{\n--\nmm/page_alloc.c=4026=__alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4027:\tconst struct alloc_context *ac, unsigned long *did_some_progress)\nmm/page_alloc.c-4028-{\n--\nmm/page_alloc.c=4121=__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4122:\t\tunsigned int alloc_flags, const struct alloc_context *ac,\nmm/page_alloc.c-4123-\t\tenum compact_priority prio, enum compact_result *compact_result)\n--\nmm/page_alloc.c=4229=static inline bool\nmm/page_alloc.c:4230:should_compact_retry(gfp_t gfp_mask, struct alloc_context *ac, int order,\nmm/page_alloc.c-4231-\t\t     int alloc_flags,\n--\nmm/page_alloc.c=4298=__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4299:\t\tunsigned int alloc_flags, const struct alloc_context *ac,\nmm/page_alloc.c-4300-\t\tenum compact_priority prio, enum compact_result *compact_result)\n--\nmm/page_alloc.c=4306=static inline bool\nmm/page_alloc.c:4307:should_compact_retry(gfp_t gfp_mask, struct alloc_context *ac, int order,\nmm/page_alloc.c-4308-\t\t     int alloc_flags,\n--\nmm/page_alloc.c=4420=__perform_reclaim(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4421:\t\t\t\t\tconst struct alloc_context *ac)\nmm/page_alloc.c-4422-{\n--\nmm/page_alloc.c=4446=__alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4447:\t\tunsigned int alloc_flags, const struct alloc_context *ac,\nmm/page_alloc.c-4448-\t\tunsigned long *did_some_progress)\n--\nmm/page_alloc.c=4484=static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask,\nmm/page_alloc.c:4485:\t\t\t     const struct alloc_context *ac)\nmm/page_alloc.c-4486-{\n--\nmm/page_alloc.c=4622=should_reclaim_retry(gfp_t gfp_mask, unsigned order,\nmm/page_alloc.c:4623:\t\t     struct alloc_context *ac, int alloc_flags,\nmm/page_alloc.c-4624-\t\t     bool did_some_progress, int *no_progress_loops)\n--\nmm/page_alloc.c=4698=static inline bool\nmm/page_alloc.c:4699:check_retry_cpuset(int cpuset_mems_cookie, struct alloc_context *ac)\nmm/page_alloc.c-4700-{\n--\nmm/page_alloc.c=4766=__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c:4767:\t\t\t\t\t\tstruct alloc_context *ac)\nmm/page_alloc.c-4768-{\n--\nmm/page_alloc.c=5085=static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\nmm/page_alloc.c-5086-\t\tint preferred_nid, nodemask_t *nodemask,\nmm/page_alloc.c:5087:\t\tstruct alloc_context *ac, gfp_t *alloc_gfp,\nmm/page_alloc.c-5088-\t\tunsigned int *alloc_flags)\n--\nmm/page_alloc.c=5154=unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\n--\nmm/page_alloc.c-5162-\tstruct list_head *pcp_list;\nmm/page_alloc.c:5163:\tstruct alloc_context ac = { .alloc_flags = alloc_flags };\nmm/page_alloc.c-5164-\tunsigned int fastpath_alloc_flags = alloc_flags | ALLOC_WMARK_LOW;\n--\nmm/page_alloc.c=5389=struct page *__alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order,\n--\nmm/page_alloc.c-5393-\tgfp_t alloc_gfp; /* The gfp_t that was actually used for allocation */\nmm/page_alloc.c:5394:\tstruct alloc_context ac = {\nmm/page_alloc.c-5395-\t\t.alloc_flags = alloc_flags,\n--\nmm/page_alloc.h-75- */\nmm/page_alloc.h:76:struct alloc_context {\nmm/page_alloc.h-77-\tstruct zonelist *zonelist;\n"
}

gemini-3.8-flash

null

null

							input: 11068
							output: 34
							thoughts: 20
						

Here's my take on the thought process, as requested:

**Diving into `alloc_context`**

Alright, time to get to the heart of this. My focus is on memory allocation, so naturally, I'm heading straight for the core structures. Let's start by digging into `struct alloc_context`. It's defined in `mm/page_alloc.h`, and I need to refresh my memory on its fields and how it interacts with the overall allocation process. I need to understand its role within the larger framework. Is it used only when allocating pages? Does it impact other areas of memory management? Let's get to it. Time to explore this structure.

{
  "File": "mm/page_alloc.h",
  "FirstLine": 70,
  "LineCount": 40
}

{
  "Contents": "  70:\t *\n  71:\t * zonelist, preferred_zone and highest_zoneidx are set first in\n  72:\t * __alloc_pages() for the fast path, and might be later changed\n  73:\t * in __alloc_pages_slowpath(). All other functions pass the whole structure\n  74:\t * by a const pointer.\n  75:\t */\n  76:\tstruct alloc_context {\n  77:\t\tstruct zonelist *zonelist;\n  78:\t\tconst nodemask_t *nodemask;\n  79:\t\tstruct zoneref *preferred_zoneref;\n  80:\t\tint migratetype;\n  81:\t\n  82:\t\t/*\n  83:\t\t * highest_zoneidx represents highest usable zone index of\n  84:\t\t * the allocation request. Due to the nature of the zone,\n  85:\t\t * memory on lower zone than the highest_zoneidx will be\n  86:\t\t * protected by lowmem_reserve[highest_zoneidx].\n  87:\t\t *\n  88:\t\t * highest_zoneidx is also used by reclaim/compaction to limit\n  89:\t\t * the target zone since higher zone than this index cannot be\n  90:\t\t * usable for this allocation request.\n  91:\t\t */\n  92:\t\tenum zone_type highest_zoneidx;\n  93:\t\tbool spread_dirty_pages;\n  94:\t\t/* Only flags that are global to the whole allocation go here. */\n  95:\t\tunsigned int alloc_flags;\n  96:\t};\n  97:\t\n  98:\t/*\n  99:\t * This function returns the order of a free page in the buddy system. In\n 100:\t * general, page_zone(page)-\u003elock must be held by the caller to prevent the\n 101:\t * page from being allocated in parallel and returning garbage as the order.\n 102:\t * If a caller does not hold page_zone(page)-\u003elock, it must guarantee that the\n 103:\t * page cannot be allocated or merged in parallel. Alternatively, it must\n 104:\t * handle invalid values gracefully, and use buddy_order_unsafe() below.\n 105:\t */\n 106:\tstatic inline unsigned int buddy_order(struct page *page)\n 107:\t{\n 108:\t\t/* PageBuddy() must be checked by the caller */\n 109:\t\treturn page_private(page);\n"
}

gemini-3.8-flash

null

null

							input: 11881
							output: 20
							thoughts: 218
						

**Analyzing Allocation Context Initialization**

Okay, so I'm looking at this code and immediately something jumps out at me. We've got this `struct alloc_context`, which contains `unsigned int alloc_flags`. I see that in the past, in `alloc_pages_bulk_noprof`, they were setting up an `alloc_context` struct, let's call it `ac`. The confusing bit is that before, they were declaring a separate `unsigned int alloc_flags` and using it, but `ac.alloc_flags` itself wasn't initialized, or at least it wasn't explicitly zeroed. I need to go back and verify – did anything *actually* read from `ac.alloc_flags` in that function before this change?

Now, things are different. They're using a designated initializer: `struct alloc_context ac = { .alloc_flags = alloc_flags };`. Ah, that makes more sense! Using the designated initializer syntax like this means all the other fields of `ac` will be zero-initialized. That's a clean way to ensure a known state for the struct, which is good.

Also, I see the line `fastpath_alloc_flags = alloc_flags | ALLOC_WMARK_LOW;`. That's important to keep in mind, too.

So, the change seems to be to initialize the rest of the struct, not just the flag. Now, let me quickly glance at the callers of `__alloc_pages_bulk` and `alloc_pages_bulk`. I want to see if this pattern or a similar one is used elsewhere. Is this specific to `alloc_pages_bulk_noprof`, or is it a broader change? Let me see how far this goes and if there are any other examples I should be aware of.

{
  "Expression": "__alloc_pages_bulk"
}

{
  "Output": "include/linux/gfp.h=207=unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n--\ninclude/linux/gfp.h-209-\t\t\t\tstruct page **page_array);\ninclude/linux/gfp.h:210:#define __alloc_pages_bulk(...)\t\t\talloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))\ninclude/linux/gfp.h-211-\n--\ninclude/linux/gfp.h=214=unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\n--\ninclude/linux/gfp.h-221-#define alloc_pages_bulk(_gfp, _nr_pages, _page_array)\t\t\\\ninclude/linux/gfp.h:222:\t__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _page_array)\ninclude/linux/gfp.h-223-\n--\nmm/kasan/shadow.c=327=static void ___free_pages_bulk(struct page **pages, int nr_pages)\n--\nmm/kasan/shadow.c-338-\nmm/kasan/shadow.c:339:static int ___alloc_pages_bulk(struct page **pages, int nr_pages, gfp_t gfp_mask)\nmm/kasan/shadow.c-340-{\n--\nmm/kasan/shadow.c=357=static int __kasan_populate_vmalloc_do(unsigned long start, unsigned long end, gfp_t gfp_mask)\n--\nmm/kasan/shadow.c-369-\t\tnr_pages = min(nr_total, PAGE_SIZE / sizeof(data.pages[0]));\nmm/kasan/shadow.c:370:\t\tret = ___alloc_pages_bulk(data.pages, nr_pages, gfp_mask);\nmm/kasan/shadow.c-371-\t\tif (ret)\n--\nmm/mempolicy.c=2659=static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,\n--\nmm/mempolicy.c-2697-\t\tnode_pages = min(rem_pages, weight);\nmm/mempolicy.c:2698:\t\tnr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,\nmm/mempolicy.c-2699-\t\t\t\t\t\t  page_array);\n--\nmm/mempolicy.c-2727-\t/*\nmm/mempolicy.c:2728:\t * Calculate rounds/partial rounds to minimize __alloc_pages_bulk calls.\nmm/mempolicy.c-2729-\t * Track which node weighted interleave should resume from.\n--\nmm/mempolicy.c-2761-\t\tnode_pages = min(node_pages, nr_pages - total_allocated);\nmm/mempolicy.c:2762:\t\tnr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,\nmm/mempolicy.c-2763-\t\t\t\t\t\t  page_array);\n--\nmm/page_alloc.c=5085=static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-5133-/*\nmm/page_alloc.c:5134: * __alloc_pages_bulk - Allocate a number of order-0 pages to an array\nmm/page_alloc.c-5135- * @gfp: GFP flags for the allocation\n--\nmm/page_alloc.c-5153- */\nmm/page_alloc.c:5154:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.c-5155-\t\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n--\nmm/page_alloc.c=5299=unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n--\nmm/page_alloc.c-5302-{\nmm/page_alloc.c:5303:\treturn __alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid,\nmm/page_alloc.c-5304-\t\t\t\t\t nodemask, nr_pages, page_array);\n--\nmm/page_alloc.h=261=struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_nid,\n--\nmm/page_alloc.h-264-\nmm/page_alloc.h:265:unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\nmm/page_alloc.h-266-\t\tint preferred_nid, nodemask_t *nodemask, int nr_pages,\n"
}

gemini-3.8-flash

null

null

							input: 13752
							output: 36
							thoughts: 213
						

**Investigating a Potential Macro Conflict**

Okay, hold on a second. I'm looking at `include/linux/gfp.h`, specifically this macro definition:

```c
#define __alloc_pages_bulk(...)			alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
```

Right, so `include/linux/gfp.h` on line 210 defines `__alloc_pages_bulk(...)` as a call to `alloc_hooks` around `alloc_pages_bulk_noprof`.

Now, if I'm not mistaken, I also saw a declaration for something called `__alloc_pages_bulk_noprof` in `mm/page_alloc.h`:

```c
unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,
		int preferred_nid, nodemask_t *nodemask, int nr_pages,
		struct page **page_array);
```

Hmm... I have to ask myself, could this lead to some kind of conflict if both headers are included? They both define that same name, right? It might be tricky.

Let me just quickly re-examine `include/linux/gfp.h` around line 204 to make sure I'm not missing anything. Gotta be sure I haven't overlooked something obvious.

{
  "File": "include/linux/gfp.h",
  "FirstLine": 200,
  "LineCount": 35
}

{
  "Contents": " 200:\t#ifndef HAVE_ARCH_FREE_PAGE\n 201:\tstatic inline void arch_free_page(struct page *page, int order) { }\n 202:\t#endif\n 203:\t#ifndef HAVE_ARCH_ALLOC_PAGE\n 204:\tstatic inline void arch_alloc_page(struct page *page, int order) { }\n 205:\t#endif\n 206:\t\n 207:\tunsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n 208:\t\t\t\t\tnodemask_t *nodemask, int nr_pages,\n 209:\t\t\t\t\tstruct page **page_array);\n 210:\t#define __alloc_pages_bulk(...)\t\t\talloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))\n 211:\t\n 212:\tvoid free_pages_bulk(struct page **page_array, unsigned long nr_pages);\n 213:\t\n 214:\tunsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,\n 215:\t\t\t\t\tunsigned long nr_pages,\n 216:\t\t\t\t\tstruct page **page_array);\n 217:\t#define  alloc_pages_bulk_mempolicy(...)\t\t\t\t\\\n 218:\t\talloc_hooks(alloc_pages_bulk_mempolicy_noprof(__VA_ARGS__))\n 219:\t\n 220:\t/* Bulk allocate order-0 pages */\n 221:\t#define alloc_pages_bulk(_gfp, _nr_pages, _page_array)\t\t\\\n 222:\t\t__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _page_array)\n 223:\t\n 224:\tstatic inline unsigned long\n 225:\talloc_pages_bulk_node_noprof(gfp_t gfp, int nid, unsigned long nr_pages,\n 226:\t\t\t\t\t   struct page **page_array)\n 227:\t{\n 228:\t\tif (nid == NUMA_NO_NODE)\n 229:\t\t\tnid = numa_mem_id();\n 230:\t\n 231:\t\treturn alloc_pages_bulk_noprof(gfp, nid, NULL, nr_pages, page_array);\n 232:\t}\n 233:\t\n 234:\t#define alloc_pages_bulk_node(...)\t\t\t\t\\\n"
}

gemini-3.8-flash

null

null

							input: 14948
							output: 17
							thoughts: 222
						

**My Analysis of the Page Allocation Code**

Okay, so I'm digging into the page allocation internals again. It looks like the `__alloc_pages_bulk` macro, the workhorse of bulk page allocation, eventually calls `alloc_pages_bulk_noprof`. And *that* function takes the usual suspects: `gfp`, `preferred_nid`, `nodemask`, `nr_pages`, and the page array. Nothing particularly surprising there. But `alloc_pages_bulk_noprof` then calls `__alloc_pages_bulk_noprof`, with a surprising argument `ALLOC_DEFAULT`.

Now my expert intuition is tingling, because `ALLOC_DEFAULT` smells like some kind of internal allocation flag. I wonder about the relation between it and `__folio_alloc`. Memory suggests to me that there were some changes here; specifically, I *believe* I saw that `__folio_alloc_noprof` and the `__folio_alloc` macro have been shuffled around. Yes, my suspicion is confirmed; I remember that these were moved to `mm/page_alloc.h`. That makes sense. The real question is: *why*?

My guess is that this move is related to internal page allocator concepts, specifically, the `alloc_flags` structure. Since these flags, like `ALLOC_DEFAULT`, `ALLOC_WMARK_LOW`, and others, are probably defined in the internal `mm` headers like `mm/page_alloc.h` or `mm/internal.h`. I need to verify that `ALLOC_DEFAULT` is indeed defined there. I'll check it to be sure.

{
  "Expression": "ALLOC_DEFAULT"
}

{
  "Output": "Documentation/admin-guide/kernel-parameters.txt=98=Kernel parameters\n--\nDocumentation/admin-guide/kernel-parameters.txt-2469-\t\t\tFormat: 0 | 1\nDocumentation/admin-guide/kernel-parameters.txt:2470:\t\t\tDefault set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.\nDocumentation/admin-guide/kernel-parameters.txt-2471-\n--\narch/powerpc/configs/security.config=12=CONFIG_FORTIFY_SOURCE=y\narch/powerpc/configs/security.config:13:CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y\narch/powerpc/configs/security.config-14-\n--\narch/s390/boot/ipl_parm.c=32=int __bootdata_preserved(cmma_flag) = 1;\narch/s390/boot/ipl_parm.c-33-\narch/s390/boot/ipl_parm.c:34:unsigned long vmalloc_size = VMALLOC_DEFAULT_SIZE;\narch/s390/boot/ipl_parm.c-35-unsigned long memory_limit;\n--\narch/s390/include/asm/pgtable.h=80=extern unsigned long VMALLOC_END;\narch/s390/include/asm/pgtable.h:81:#define VMALLOC_DEFAULT_SIZE\t((512UL \u003c\u003c 30) - MODULES_LEN)\narch/s390/include/asm/pgtable.h-82-extern struct page *vmemmap;\n--\ndrivers/gpu/drm/amd/include/asic_reg/athub/athub_2_0_0_default.h-63-#define mmATHUB_PCIE_PAGE_REQ_CNTL_DEFAULT                                       0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/athub/athub_2_0_0_default.h:64:#define mmATHUB_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT                             0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/athub/athub_2_0_0_default.h-65-#define mmATHUB_COMMAND_DEFAULT                                                  0x00000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_1_0_default.h-3767-#define mmGE_STEREO_CNTL_DEFAULT                                                 0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_1_0_default.h:3768:#define mmGE_PC_ALLOC_DEFAULT                                                    0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_1_0_default.h-3769-#define mmVGT_TF_MEMORY_BASE_HI_UMD_DEFAULT                                      0x00000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_1_0_default.h-5845-#define ixSQ_WAVE_HW_ID_LEGACY_DEFAULT                                           0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_1_0_default.h:5846:#define ixSQ_WAVE_GPR_ALLOC_DEFAULT                                              0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_1_0_default.h:5847:#define ixSQ_WAVE_LDS_ALLOC_DEFAULT                                              0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_1_0_default.h-5848-#define ixSQ_WAVE_IB_STS_DEFAULT                                                 0x00000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_3_0_default.h-3592-#define mmGE_STEREO_CNTL_DEFAULT                                                 0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_3_0_default.h:3593:#define mmGE_PC_ALLOC_DEFAULT                                                    0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_3_0_default.h-3594-#define mmVGT_TF_MEMORY_BASE_HI_UMD_DEFAULT                                      0x00000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_3_0_default.h-7092-#define ixSQ_WAVE_HW_ID_LEGACY_DEFAULT                                           0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_3_0_default.h:7093:#define ixSQ_WAVE_GPR_ALLOC_DEFAULT                                              0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_3_0_default.h:7094:#define ixSQ_WAVE_LDS_ALLOC_DEFAULT                                              0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_10_3_0_default.h-7095-#define ixSQ_WAVE_IB_STS_DEFAULT                                                 0x00000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_default.h-1684-#define regSPI_SHADER_GS_MESHLET_DIM_DEFAULT                                      0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_default.h:1685:#define regSPI_SHADER_GS_MESHLET_EXP_ALLOC_DEFAULT                                0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_default.h-1686-#define regSPI_SHADER_REQ_CTRL_ESGS_DEFAULT                                       0x00000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_default.h-3346-#define regGE_STEREO_CNTL_DEFAULT                                                 0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_default.h:3347:#define regGE_PC_ALLOC_DEFAULT                                                    0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_default.h-3348-#define regVGT_TF_MEMORY_BASE_HI_DEFAULT                                          0x00000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_default.h-6078-#define ixSQ_WAVE_TRAPSTS_DEFAULT                                                0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_default.h:6079:#define ixSQ_WAVE_GPR_ALLOC_DEFAULT                                              0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_default.h:6080:#define ixSQ_WAVE_LDS_ALLOC_DEFAULT                                              0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_11_0_0_default.h-6081-#define ixSQ_WAVE_IB_STS_DEFAULT                                                 0x00000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_9_0_default.h-3688-#define ixSQ_WAVE_HW_ID_DEFAULT                                                  0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_9_0_default.h:3689:#define ixSQ_WAVE_GPR_ALLOC_DEFAULT                                              0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_9_0_default.h:3690:#define ixSQ_WAVE_LDS_ALLOC_DEFAULT                                              0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/gc/gc_9_0_default.h-3691-#define ixSQ_WAVE_IB_STS_DEFAULT                                                 0x00000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-780-#define cfgBIF_CFG_DEV0_EPF0_0_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h:781:#define cfgBIF_CFG_DEV0_EPF0_0_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-782-#define cfgBIF_CFG_DEV0_EPF0_0_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2f000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-1132-#define cfgBIF_CFG_DEV0_EPF1_0_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h:1133:#define cfgBIF_CFG_DEV0_EPF1_0_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-1134-#define cfgBIF_CFG_DEV0_EPF1_0_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2f000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-2604-#define smnINTR_LINE_ENABLE_DEFAULT                                               0x000000ff\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h:2605:#define smnOUTSTANDING_VC_ALLOC_DEFAULT                                           0x6f06c0cf\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-2606-#define smnBIFC_MISC_CTRL0_DEFAULT                                                0x08000024\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-2955-#define smnBIF_CFG_DEV0_EPF0_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT              0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h:2956:#define smnBIF_CFG_DEV0_EPF0_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT                 0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-2957-#define smnBIF_CFG_DEV0_EPF0_PCIE_PASID_ENH_CAP_LIST_DEFAULT                      0x2f000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-3307-#define smnBIF_CFG_DEV0_EPF1_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT              0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h:3308:#define smnBIF_CFG_DEV0_EPF1_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT                 0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-3309-#define smnBIF_CFG_DEV0_EPF1_PCIE_PASID_ENH_CAP_LIST_DEFAULT                      0x2f000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-14669-#define cfgBIF_CFG_DEV0_EPF0_1_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h:14670:#define cfgBIF_CFG_DEV0_EPF0_1_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-14671-#define cfgBIF_CFG_DEV0_EPF0_1_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2f000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-15021-#define cfgBIF_CFG_DEV0_EPF1_1_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h:15022:#define cfgBIF_CFG_DEV0_EPF1_1_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_2_3_default.h-15023-#define cfgBIF_CFG_DEV0_EPF1_1_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2f000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h-326-#define cfgBIF_CFG_DEV0_EPF0_0_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h:327:#define cfgBIF_CFG_DEV0_EPF0_0_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h-328-#define cfgBIF_CFG_DEV0_EPF0_0_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2e000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h-580-#define cfgBIF_CFG_DEV0_EPF1_0_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h:581:#define cfgBIF_CFG_DEV0_EPF1_0_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h-582-#define cfgBIF_CFG_DEV0_EPF1_0_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2e000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h-2970-#define smnINTR_LINE_ENABLE_DEFAULT                                               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h:2971:#define smnOUTSTANDING_VC_ALLOC_DEFAULT                                           0x6f06c0cf\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h-2972-#define smnBIFC_MISC_CTRL0_DEFAULT                                                0x08000004\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h-3254-#define smnBIF_CFG_DEV0_EPF0_1_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h:3255:#define smnBIF_CFG_DEV0_EPF0_1_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h-3256-#define smnBIF_CFG_DEV0_EPF0_1_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2e000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h-3508-#define smnBIF_CFG_DEV0_EPF1_1_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h:3509:#define smnBIF_CFG_DEV0_EPF1_1_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_6_1_default.h-3510-#define smnBIF_CFG_DEV0_EPF1_1_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2e000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-542-#define cfgPCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT                                0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h:543:#define cfgPCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT                                   0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-544-#define cfgPCIE_PASID_ENH_CAP_LIST_DEFAULT                                        0x2e000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-796-#define cfgBIF_CFG_DEV0_EPF1_0_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h:797:#define cfgBIF_CFG_DEV0_EPF1_0_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-798-#define cfgBIF_CFG_DEV0_EPF1_0_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2e000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-4357-#define smnINTR_LINE_ENABLE_DEFAULT                                               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h:4358:#define smnOUTSTANDING_VC_ALLOC_DEFAULT                                           0x6f06c0cf\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-4359-#define smnBIFC_MISC_CTRL0_DEFAULT                                                0x08000004\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-4779-#define smnBIF_CFG_DEV0_EPF0_2_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h:4780:#define smnBIF_CFG_DEV0_EPF0_2_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-4781-#define smnBIF_CFG_DEV0_EPF0_2_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2e000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-5033-#define smnBIF_CFG_DEV0_EPF1_1_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h:5034:#define smnBIF_CFG_DEV0_EPF1_1_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-5035-#define smnBIF_CFG_DEV0_EPF1_1_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2e000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-12753-#define smnBIF_CFG_DEV0_EPF0_3_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h:12754:#define smnBIF_CFG_DEV0_EPF0_3_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-12755-#define smnBIF_CFG_DEV0_EPF0_3_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2e000000\n--\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-13007-#define smnBIF_CFG_DEV0_EPF1_2_PCIE_OUTSTAND_PAGE_REQ_CAPACITY_DEFAULT            0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h:13008:#define smnBIF_CFG_DEV0_EPF1_2_PCIE_OUTSTAND_PAGE_REQ_ALLOC_DEFAULT               0x00000000\ndrivers/gpu/drm/amd/include/asic_reg/nbio/nbio_7_0_default.h-13009-#define smnBIF_CFG_DEV0_EPF1_2_PCIE_PASID_ENH_CAP_LIST_DEFAULT                    0x2e000000\n--\ndrivers/misc/lkdtm/heap.c=251=static void lkdtm_SLAB_INIT_ON_ALLOC(void)\n--\ndrivers/misc/lkdtm/heap.c-277-\t\tpr_err(\"FAIL: Slab was not initialized\\n\");\ndrivers/misc/lkdtm/heap.c:278:\t\tpr_expected_config_param(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, \"init_on_alloc\");\ndrivers/misc/lkdtm/heap.c-279-\t}\n--\ndrivers/misc/lkdtm/heap.c=283=static void lkdtm_BUDDY_INIT_ON_ALLOC(void)\n--\ndrivers/misc/lkdtm/heap.c-310-\t\tpr_err(\"FAIL: Slab was not initialized\\n\");\ndrivers/misc/lkdtm/heap.c:311:\t\tpr_expected_config_param(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, \"init_on_alloc\");\ndrivers/misc/lkdtm/heap.c-312-\t}\n--\ninclude/linux/mm.h=4922=static inline void kernel_unpoison_pages(struct page *page, int numpages) { }\n--\ninclude/linux/mm.h-4924-\ninclude/linux/mm.h:4925:DECLARE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, init_on_alloc);\ninclude/linux/mm.h-4926-static inline bool want_init_on_alloc(gfp_t flags)\ninclude/linux/mm.h-4927-{\ninclude/linux/mm.h:4928:\tif (static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON,\ninclude/linux/mm.h-4929-\t\t\t\t\u0026init_on_alloc))\n--\ninclude/linux/mm.h=5401=static inline bool user_alloc_needs_zeroing(void)\n--\ninclude/linux/mm.h-5409-\treturn cpu_dcache_is_aliasing() || cpu_icache_is_aliasing() ||\ninclude/linux/mm.h:5410:\t       !static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON,\ninclude/linux/mm.h-5411-\t\t\t\t   \u0026init_on_alloc);\n--\nkernel/configs/hardening.config=58=CONFIG_LIST_HARDENED=y\n--\nkernel/configs/hardening.config-60-# Initialize all heap variables to zero on allocation.\nkernel/configs/hardening.config:61:CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y\nkernel/configs/hardening.config-62-\n--\nmm/compaction.c=84=static struct page *mark_allocated_noprof(struct page *page, unsigned int order, gfp_t gfp_flags)\nmm/compaction.c-85-{\nmm/compaction.c:86:\tpost_alloc_hook(page, order, __GFP_MOVABLE, ALLOC_DEFAULT);\nmm/compaction.c-87-\tset_page_refcounted(page);\n--\nmm/compaction.c=1845=static struct folio *compaction_alloc_noprof(struct folio *src, unsigned long data)\n--\nmm/compaction.c-1882-\nmm/compaction.c:1883:\tpost_alloc_hook(\u0026dst-\u003epage, order, __GFP_MOVABLE, ALLOC_DEFAULT);\nmm/compaction.c-1884-\tset_page_refcounted(\u0026dst-\u003epage);\n--\nmm/hugetlb.c=1793=static struct folio *alloc_buddy_frozen_folio(int order, gfp_t gfp_mask,\n--\nmm/hugetlb.c-1811-\tfolio = (struct folio *)__alloc_frozen_pages(gfp_mask, order, nid, nmask,\nmm/hugetlb.c:1812:\t\t\t\t\t\t     ALLOC_DEFAULT);\nmm/hugetlb.c-1813-\n--\nmm/kasan/hw_tags.c=38=enum kasan_arg_vmalloc {\nmm/kasan/hw_tags.c:39:\tKASAN_ARG_VMALLOC_DEFAULT,\nmm/kasan/hw_tags.c-40-\tKASAN_ARG_VMALLOC_OFF,\n--\nmm/kasan/hw_tags.c=236=void __init kasan_init_hw_tags(void)\n--\nmm/kasan/hw_tags.c-261-\tswitch (kasan_arg_vmalloc) {\nmm/kasan/hw_tags.c:262:\tcase KASAN_ARG_VMALLOC_DEFAULT:\nmm/kasan/hw_tags.c-263-\t\t/* Default is specified by kasan_flag_vmalloc definition. */\n--\nmm/khugepaged.c=1189=static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,\n--\nmm/khugepaged.c-1195-\nmm/khugepaged.c:1196:\tfolio = __folio_alloc(gfp, order, node, \u0026cc-\u003ealloc_nmask, ALLOC_DEFAULT);\nmm/khugepaged.c-1197-\tif (!folio) {\n--\nmm/mempolicy.c=2431=static struct page *alloc_pages_preferred_many(gfp_t gfp, unsigned int order,\n--\nmm/mempolicy.c-2445-\tpage = __alloc_frozen_pages_noprof(preferred_gfp, order, nid, nodemask,\nmm/mempolicy.c:2446:\t\t\t\t\t   ALLOC_DEFAULT);\nmm/mempolicy.c-2447-\tif (!page)\nmm/mempolicy.c-2448-\t\tpage = __alloc_frozen_pages_noprof(gfp, order, nid, NULL,\nmm/mempolicy.c:2449:\t\t\t\t\t\t   ALLOC_DEFAULT);\nmm/mempolicy.c-2450-\n--\nmm/mempolicy.c=2464=static struct page *alloc_pages_mpol(gfp_t gfp, unsigned int order,\n--\nmm/mempolicy.c-2496-\t\t\t\tgfp | __GFP_THISNODE | __GFP_NORETRY, order,\nmm/mempolicy.c:2497:\t\t\t\tnid, NULL, ALLOC_DEFAULT);\nmm/mempolicy.c-2498-\t\t\tif (page || !(gfp \u0026 __GFP_DIRECT_RECLAIM))\n--\nmm/mempolicy.c-2508-\nmm/mempolicy.c:2509:\tpage = __alloc_frozen_pages_noprof(gfp, order, nid, nodemask, ALLOC_DEFAULT);\nmm/mempolicy.c-2510-\n--\nmm/migrate.c=2196=struct folio *alloc_migration_target(struct folio *src, unsigned long private)\n--\nmm/migrate.c-2231-\nmm/migrate.c:2232:\treturn __folio_alloc(gfp_mask, order, nid, mtc-\u003enmask, ALLOC_DEFAULT);\nmm/migrate.c-2233-}\n--\nmm/mm_init.c=2457=void __init memblock_free_pages(unsigned long pfn, unsigned int order)\n--\nmm/mm_init.c-2477-\nmm/mm_init.c:2478:DEFINE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, init_on_alloc);\nmm/mm_init.c-2479-EXPORT_SYMBOL(init_on_alloc);\n--\nmm/mm_init.c=2484=static bool _init_on_alloc_enabled_early __read_mostly\nmm/mm_init.c:2485:\t\t\t\t= IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON);\nmm/mm_init.c-2486-static int __init early_init_on_alloc(char *buf)\n--\nmm/page_alloc.c=3768=static inline unsigned int alloc_flags_cma(gfp_t gfp_mask)\n--\nmm/page_alloc.c-3773-#endif\nmm/page_alloc.c:3774:\treturn ALLOC_DEFAULT;\nmm/page_alloc.c-3775-}\n--\nmm/page_alloc.c=5154=unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\n--\nmm/page_alloc.c-5276-\nmm/page_alloc.c:5277:\t\tprep_new_page(page, 0, gfp, ALLOC_DEFAULT);\nmm/page_alloc.c-5278-\t\ttrace_mm_page_alloc(page, 0, gfp, ac.migratetype);\n--\nmm/page_alloc.c=5299=unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n--\nmm/page_alloc.c-5302-{\nmm/page_alloc.c:5303:\treturn __alloc_pages_bulk_noprof(gfp, ALLOC_DEFAULT, preferred_nid,\nmm/page_alloc.c-5304-\t\t\t\t\t nodemask, nr_pages, page_array);\n--\nmm/page_alloc.c=5484=struct page *alloc_pages_node_noprof(int nid, gfp_t gfp_mask, unsigned int order)\n--\nmm/page_alloc.c-5490-\nmm/page_alloc.c:5491:\treturn __alloc_pages_noprof(gfp_mask, order, nid, NULL, ALLOC_DEFAULT);\nmm/page_alloc.c-5492-}\n--\nmm/page_alloc.c=5503=struct folio *__folio_alloc_node_noprof(gfp_t gfp, unsigned int order, int nid)\n--\nmm/page_alloc.c-5506-\nmm/page_alloc.c:5507:\treturn __folio_alloc_noprof(gfp, order, nid, NULL, ALLOC_DEFAULT);\nmm/page_alloc.c-5508-}\n--\nmm/page_alloc.c=7194=static void split_free_frozen_pages(struct list_head *list, gfp_t gfp_mask)\n--\nmm/page_alloc.c-7204-\nmm/page_alloc.c:7205:\t\t\tpost_alloc_hook(page, order, gfp_mask, ALLOC_DEFAULT);\nmm/page_alloc.c-7206-\t\t\tif (!order)\n--\nmm/page_alloc.c=7282=int alloc_contig_frozen_range_noprof(unsigned long start, unsigned long end,\n--\nmm/page_alloc.c-7409-\t\tcheck_new_pages(head, order);\nmm/page_alloc.c:7410:\t\tprep_new_page(head, order, gfp_mask, ALLOC_DEFAULT);\nmm/page_alloc.c-7411-\t} else {\n--\nmm/page_alloc.h-13-\nmm/page_alloc.h:14:#define ALLOC_DEFAULT\t\t0\nmm/page_alloc.h-15-/* The ALLOC_WMARK bits are used as an index to zone-\u003ewatermark */\n--\nmm/page_alloc.h=242=static inline struct page *alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order)\n--\nmm/page_alloc.h-244-\treturn __alloc_frozen_pages_noprof(gfp, order, numa_node_id(), NULL,\nmm/page_alloc.h:245:\t\t\t\t\t   ALLOC_DEFAULT);\nmm/page_alloc.h-246-}\n--\nmm/page_frag_cache.c=49=static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,\n--\nmm/page_frag_cache.c-59-\tpage = __alloc_pages(gfp_mask, PAGE_FRAG_CACHE_MAX_ORDER,\nmm/page_frag_cache.c:60:\t\t\t     numa_mem_id(), NULL, ALLOC_DEFAULT);\nmm/page_frag_cache.c-61-#endif\nmm/page_frag_cache.c-62-\tif (unlikely(!page)) {\nmm/page_frag_cache.c:63:\t\tpage = __alloc_pages(gfp, 0, numa_mem_id(), NULL, ALLOC_DEFAULT);\nmm/page_frag_cache.c-64-\t\torder = 0;\n--\nmm/slab.h-20-/* slab's alloc_flags definitions */\nmm/slab.h:21:#define SLAB_ALLOC_DEFAULT\t0x00 /* no flags */\nmm/slab.h-22-#define SLAB_ALLOC_NOLOCK\t0x01 /* a kmalloc_nolock() allocation */\n--\nmm/slab.h=30=static inline unsigned int to_alloc_flags(unsigned int free_flags)\n--\nmm/slab.h-34-\telse\nmm/slab.h:35:\t\treturn SLAB_ALLOC_DEFAULT;\nmm/slab.h-36-}\n--\nmm/slab.h=903=static inline bool slab_want_init_on_alloc(gfp_t flags, struct kmem_cache *c)\nmm/slab.h-904-{\nmm/slab.h:905:\tif (static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON,\nmm/slab.h-906-\t\t\t\t\u0026init_on_alloc)) {\n--\nmm/slab_common.c=790=size_t kmalloc_size_roundup(size_t size)\n--\nmm/slab_common.c-799-\t\ts = kmalloc_slab(size, NULL, GFP_KERNEL, __kmalloc_token(0),\nmm/slab_common.c:800:\t\t\t\t SLAB_ALLOC_DEFAULT);\nmm/slab_common.c-801-\t\treturn s-\u003eobject_size;\n--\nmm/slub.c=2553=bool memcg_slab_post_charge(void *p, gfp_t flags)\n--\nmm/slub.c-2606-\nmm/slub.c:2607:\treturn __memcg_slab_post_alloc_hook(s, NULL, flags, SLAB_ALLOC_DEFAULT,\nmm/slub.c-2608-\t\t\t\t\t    1, \u0026p);\n--\nmm/slub.c=3333=static inline struct slab *alloc_slab_page(gfp_t flags, int node,\n--\nmm/slub.c-3347-\t\tpage = __alloc_frozen_pages(flags, order, node, NULL,\nmm/slub.c:3348:\t\t\t\t\t    ALLOC_DEFAULT);\nmm/slub.c-3349-\n--\nmm/slub.c=5001=void *kmem_cache_alloc_noprof(struct kmem_cache *s, gfp_t gfpflags)\n--\nmm/slub.c-5006-\t\t.orig_size = s-\u003eobject_size,\nmm/slub.c:5007:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-5008-\t};\n--\nmm/slub.c=5018=void *kmem_cache_alloc_lru_noprof(struct kmem_cache *s, struct list_lru *lru,\n--\nmm/slub.c-5024-\t\t.orig_size = s-\u003eobject_size,\nmm/slub.c:5025:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-5026-\t\t.lru = lru,\n--\nmm/slub.c=5059=void *kmem_cache_alloc_node_noprof(struct kmem_cache *s, gfp_t gfpflags, int node)\n--\nmm/slub.c-5064-\t\t.orig_size = s-\u003eobject_size,\nmm/slub.c:5065:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-5066-\t};\n--\nmm/slub.c=5111=kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size)\n--\nmm/slub.c-5121-\nmm/slub.c:5122:\t\tsheaf = __alloc_empty_sheaf(s, gfp, SLAB_ALLOC_DEFAULT, size);\nmm/slub.c-5123-\t\tif (!sheaf)\n--\nmm/slub.c-5166-\tif (!sheaf)\nmm/slub.c:5167:\t\tsheaf = alloc_empty_sheaf(s, gfp, SLAB_ALLOC_DEFAULT);\nmm/slub.c-5168-\n--\nmm/slub.c=5307=kmem_cache_alloc_from_sheaf_noprof(struct kmem_cache *s, gfp_t gfp,\n--\nmm/slub.c-5312-\t\t.orig_size = s-\u003eobject_size,\nmm/slub.c:5313:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-5314-\t};\n--\nmm/slub.c=5341=static void *___kmalloc_large_node(size_t size, gfp_t flags, int node)\n--\nmm/slub.c-5355-\t\tpage = __alloc_frozen_pages_noprof(flags, order, node, NULL,\nmm/slub.c:5356:\t\t\t\t\t\t   ALLOC_DEFAULT);\nmm/slub.c-5357-\n--\nmm/slub.c=5418=void *__kmalloc_node_noprof(DECL_KMALLOC_PARAMS(size, b, token), gfp_t flags, int node)\n--\nmm/slub.c-5422-\t\t.orig_size = size,\nmm/slub.c:5423:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-5424-\t};\n--\nmm/slub.c=5431=void *__kmalloc_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t flags)\n--\nmm/slub.c-5435-\t\t.orig_size = size,\nmm/slub.c:5436:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-5437-\t};\n--\nmm/slub.c=5536=void *__kmalloc_node_track_caller_noprof(DECL_KMALLOC_PARAMS(size, b, token), gfp_t flags,\n--\nmm/slub.c-5541-\t\t.orig_size = size,\nmm/slub.c:5542:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-5543-\t};\n--\nmm/slub.c=5550=void *__kmalloc_cache_noprof(struct kmem_cache *s, gfp_t gfpflags, size_t size)\n--\nmm/slub.c-5555-\t\t.orig_size = size,\nmm/slub.c:5556:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-5557-\t};\n--\nmm/slub.c=5568=void *__kmalloc_cache_node_noprof(struct kmem_cache *s, gfp_t gfpflags,\n--\nmm/slub.c-5574-\t\t.orig_size = size,\nmm/slub.c:5575:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-5576-\t};\n--\nmm/slub.c=5883=__pcs_replace_full_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs,\n--\nmm/slub.c-5963-\nmm/slub.c:5964:\tempty = alloc_empty_sheaf(s, GFP_NOWAIT, SLAB_ALLOC_DEFAULT);\nmm/slub.c-5965-\tif (empty)\n--\nmm/slub.c=6990=void *__kvmalloc_node_noprof(DECL_KMALLOC_PARAMS(size, b, token), unsigned long align,\n--\nmm/slub.c-6997-\t\t.orig_size = size,\nmm/slub.c:6998:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-6999-\t};\n--\nmm/slub.c=7390=refill_objects(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int min,\n--\nmm/slub.c-7409-\nmm/slub.c:7410:\tslab = new_slab(s, gfp, SLAB_ALLOC_DEFAULT, local_node);\nmm/slub.c-7411-\tif (!slab)\n--\nmm/slub.c=7426=static bool __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,\n--\nmm/slub.c-7434-\t\t\t.orig_size = s-\u003eobject_size,\nmm/slub.c:7435:\t\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-7436-\t\t};\n--\nmm/slub.c=7476=bool kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags,\n--\nmm/slub.c-7482-\t\t.orig_size = s-\u003eobject_size,\nmm/slub.c:7483:\t\t.alloc_flags = SLAB_ALLOC_DEFAULT,\nmm/slub.c-7484-\t};\n--\nmm/slub.c=7700=static int init_percpu_sheaves(struct kmem_cache *s)\n--\nmm/slub.c-7732-\t\telse\nmm/slub.c:7733:\t\t\tpcs-\u003emain = alloc_empty_sheaf(s, GFP_KERNEL, SLAB_ALLOC_DEFAULT);\nmm/slub.c-7734-\n--\nmm/slub.c=7753=static void early_kmem_cache_node_alloc(int node)\n--\nmm/slub.c-7760-\nmm/slub.c:7761:\tslab = new_slab(kmem_cache_node, GFP_NOWAIT, SLAB_ALLOC_DEFAULT, node);\nmm/slub.c-7762-\n--\nmm/slub.c=8567=static void __init bootstrap_cache_sheaves(struct kmem_cache *s)\n--\nmm/slub.c-8601-\t\tpcs-\u003emain = __alloc_empty_sheaf(s, GFP_KERNEL,\nmm/slub.c:8602:\t\t\t\tSLAB_ALLOC_DEFAULT, capacity);\nmm/slub.c-8603-\n--\nsecurity/Kconfig.hardening=151=config KSTACK_ERASE_RUNTIME_DISABLE\n--\nsecurity/Kconfig.hardening-158-\nsecurity/Kconfig.hardening:159:config INIT_ON_ALLOC_DEFAULT_ON\nsecurity/Kconfig.hardening-160-\tbool \"Enable heap memory zeroing on allocation by default\"\n--\ntools/testing/selftests/lkdtm/config=8=CONFIG_INIT_ON_FREE_DEFAULT_ON=y\ntools/testing/selftests/lkdtm/config:9:CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y\ntools/testing/selftests/lkdtm/config-10-CONFIG_UBSAN=y\n"
}

gemini-3.8-flash

null

null

							input: 28081
							output: 33
							thoughts: 898
						

**Analyzing the Refactoring Patch for Potential Risks**

Okay, let's break down this patch. It looks like we're refactoring page allocation internals to expose `alloc_flags`. So, it's a structural change, and the primary goal is probably to provide more granular control over page allocation, but we need to ensure this doesn't introduce any regressions. Let's start with the code changes: the patch moved around some functions and added an `alloc_flags` parameter to a few key allocation functions like `__folio_alloc_noprof` and `__alloc_pages_bulk_noprof`. It looks like some macros are being removed and some new parameters are being passed, including `ALLOC_DEFAULT`.

My main concern is whether this introduces any uninitialized memory vulnerabilities or changes the existing zeroing semantics. Let's go through the changes one by one.

First, the change in `alloc_pages_bulk_noprof`. Previously, `struct alloc_context ac` was uninitialized before `prepare_alloc_pages` got to it. Now, it's explicitly initialized with `.alloc_flags = alloc_flags`, which, crucially, zero-initializes all other fields of the struct. This is actually a *positive* change – it prevents potential uninitialized reads, which is a good thing!

Next, let's look at where these new `alloc_flags` are used. In `khugepaged.c` and `migrate.c`, the calls to `__folio_alloc` now explicitly pass `ALLOC_DEFAULT`, which is a constant zero. Similarly, `alloc_pages_bulk_noprof` calls `__alloc_pages_bulk_noprof` with `ALLOC_DEFAULT`, and `__folio_alloc_node_noprof` calls `__folio_alloc_noprof` with `ALLOC_DEFAULT`. Also, the updated `__folio_alloc_noprof` function receives the `alloc_flags` via value. So, there is no chance that uninitialized data gets passed around here.

Finally, we need to consider if this impacts memory zeroing. The patch doesn't seem to be touching the existing logic in `prep_new_page` or `post_alloc_hook`. Page initialization is still based on `gfp` flags (like `__GFP_ZERO`) and `init_on_alloc`. But wait, I'm second-guessing. Let's make sure that `ALLOC_DEFAULT` or `alloc_flags` doesn't somehow interfere with `prep_new_page`'s behavior. We need to check the code there.

{
  "Expression": "prep_new_page\\(",
  "PathPrefix": "mm/page_alloc.c"
}

{
  "Output": "mm/page_alloc.c=1803=inline void post_alloc_hook(struct page *page, unsigned int order,\n--\nmm/page_alloc.c-1857-\nmm/page_alloc.c:1858:static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,\nmm/page_alloc.c-1859-\t\t\t\t\t\t\tunsigned int alloc_flags)\n--\nmm/page_alloc.c=3782=get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,\n--\nmm/page_alloc.c-3924-\t\tif (page) {\nmm/page_alloc.c:3925:\t\t\tprep_new_page(page, order, gfp_mask, alloc_flags);\nmm/page_alloc.c-3926-\n--\nmm/page_alloc.c=4121=__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-4202-\tif (page)\nmm/page_alloc.c:4203:\t\tprep_new_page(page, order, gfp_mask, alloc_flags);\nmm/page_alloc.c-4204-\n--\nmm/page_alloc.c=5154=unsigned long __alloc_pages_bulk_noprof(gfp_t gfp, unsigned int alloc_flags,\n--\nmm/page_alloc.c-5276-\nmm/page_alloc.c:5277:\t\tprep_new_page(page, 0, gfp, ALLOC_DEFAULT);\nmm/page_alloc.c-5278-\t\ttrace_mm_page_alloc(page, 0, gfp, ac.migratetype);\n--\nmm/page_alloc.c=7282=int alloc_contig_frozen_range_noprof(unsigned long start, unsigned long end,\n--\nmm/page_alloc.c-7409-\t\tcheck_new_pages(head, order);\nmm/page_alloc.c:7410:\t\tprep_new_page(head, order, gfp_mask, ALLOC_DEFAULT);\nmm/page_alloc.c-7411-\t} else {\n"
}

gemini-3.8-flash

null

null

							input: 30159
							output: 36
							thoughts: 11
						

Okay, here's my attempt at summarizing the thought process, speaking as if they were my own, and assuming a high level of expertise:

**Checking `prep_new_page` Functionality**

Alright, let's dive into this `prep_new_page` function. Given my background, I'm expecting this to be the core logic that handles the initial setup for a new page within this system. Immediately, I'm thinking about the common pitfalls: ensuring unique identifiers, handling default content or templates, setting permissions appropriately, and, very importantly, managing any potential race conditions if this is a concurrent environment. Is this function atomic? What database transactions are involved? I need to quickly ascertain how resilient this is.

I'll be looking for how it interacts with the database – does it create entries in multiple tables, and if so, how are those operations orchestrated? I'm anticipating error handling to be robust; edge cases need to be managed elegantly. My radar's up for any assumptions baked into the design - assumptions about the content structure, user roles, or system configuration that might become problems down the line.

Finally, I'm already mentally forming a test plan. I'll need to stress-test it for concurrency, check for proper input validation, and make sure that a page is in the appropriate state after creation. The devil is in the details, so I'll be looking specifically at edge cases and boundary conditions.

{
  "File": "mm/page_alloc.c",
  "FirstLine": 1858,
  "LineCount": 25
}

{
  "Contents": "1858:\tstatic void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,\n1859:\t\t\t\t\t\t\t\tunsigned int alloc_flags)\n1860:\t{\n1861:\t\tpost_alloc_hook(page, order, gfp_flags, alloc_flags);\n1862:\t\n1863:\t\tif (order \u0026\u0026 (gfp_flags \u0026 __GFP_COMP))\n1864:\t\t\tprep_compound_page(page, order);\n1865:\t\n1866:\t\t/*\n1867:\t\t * page is set pfmemalloc when ALLOC_NO_WATERMARKS was necessary to\n1868:\t\t * allocate the page. The expectation is that the caller is taking\n1869:\t\t * steps that will free more memory. The caller should avoid the page\n1870:\t\t * being used for !PFMEMALLOC purposes.\n1871:\t\t */\n1872:\t\tif (alloc_flags \u0026 ALLOC_NO_WATERMARKS)\n1873:\t\t\tset_page_pfmemalloc(page);\n1874:\t\telse\n1875:\t\t\tclear_page_pfmemalloc(page);\n1876:\t}\n1877:\t\n1878:\t/*\n1879:\t * Go through the free lists for the given migratetype and remove\n1880:\t * the smallest available page from the freelists\n1881:\t */\n1882:\tstatic __always_inline\n"
}

gemini-3.8-flash

null

null

							input: 30894
							output: 36
							thoughts: 30
						

Here's my take on those thoughts, tailored for an expert audience:

**Diving into the Allocation Hook**

Alright, let's zero in on `post_alloc_hook` within `mm/page_alloc.c`, specifically at line 1803. I need to understand how this hook interacts with the overall allocation process. I'm keen to see the implementation details. Is it a function pointer? An inline call? What kind of arguments does it take? What does the return value signal? I suspect it's likely a mechanism to allow for additional, module-specific actions after a page has been successfully allocated, but before it's actually handed over to the requester. Things like initializing page flags, perhaps setting up some per-page data structures, or even potentially tracking the allocation for debugging purposes. I need to see if it allows for modifying the returned page, or if it is strictly observational. Time to dig in and see the details of its purpose!

{
  "File": "mm/page_alloc.c",
  "FirstLine": 1803,
  "LineCount": 40
}

{
  "Contents": "1803:\tinline void post_alloc_hook(struct page *page, unsigned int order,\n1804:\t\t\t\t\tgfp_t gfp_flags, unsigned int alloc_flags)\n1805:\t{\n1806:\t\tconst bool zero_tags = gfp_flags \u0026 __GFP_ZEROTAGS;\n1807:\t\tbool init = !want_init_on_free() \u0026\u0026 want_init_on_alloc(gfp_flags) \u0026\u0026\n1808:\t\t\t\t!should_skip_init(gfp_flags);\n1809:\t\tint i;\n1810:\t\n1811:\t\tset_page_private(page, 0);\n1812:\t\n1813:\t\tarch_alloc_page(page, order);\n1814:\t\tdebug_pagealloc_map_pages(page, 1 \u003c\u003c order);\n1815:\t\n1816:\t\t/*\n1817:\t\t * Page unpoisoning must happen before memory initialization.\n1818:\t\t * Otherwise, the poison pattern will be overwritten for __GFP_ZERO\n1819:\t\t * allocations and the page unpoisoning code will complain.\n1820:\t\t */\n1821:\t\tkernel_unpoison_pages(page, 1 \u003c\u003c order);\n1822:\t\n1823:\t\t/*\n1824:\t\t * As memory initialization might be integrated into KASAN,\n1825:\t\t * KASAN unpoisoning and memory initialization code must be\n1826:\t\t * kept together to avoid discrepancies in behavior.\n1827:\t\t */\n1828:\t\n1829:\t\t/*\n1830:\t\t * Clearing tags can efficiently clear the memory for us as well, if\n1831:\t\t * required.\n1832:\t\t */\n1833:\t\tif (zero_tags)\n1834:\t\t\tinit = tag_clear_highpages(page, 1 \u003c\u003c order, /* clear_pages= */init);\n1835:\t\n1836:\t\tif (!should_skip_kasan_unpoison(gfp_flags) \u0026\u0026\n1837:\t\t    kasan_unpoison_pages(page, order, init)) {\n1838:\t\t\t/* Take note that memory was initialized by KASAN. */\n1839:\t\t\tif (kasan_has_integrated_init())\n1840:\t\t\t\tinit = false;\n1841:\t\t} else {\n1842:\t\t\t/*\n"
}

gemini-3.8-flash

null

null

							input: 31792
							output: 270
							thoughts: 790
						

**KMSAN Assessment: A Clear "No"**

Okay, let's break this down. From what I'm seeing, this patch is all about tidying up how we pass `alloc_flags` around in these page allocation functions: `__folio_alloc_noprof`, `__folio_alloc`, and `__alloc_pages_bulk_noprof`. It's a refactoring, essentially. It looks like the goal is to make the code cleaner and more explicit about the allocation flags being used.

The key changes? Well, `__folio_alloc_noprof` and its callers now get `alloc_flags` passed through to `__alloc_pages_noprof`, explicitly passing `ALLOC_DEFAULT`.  And `__alloc_pages_bulk_noprof` now takes `alloc_flags` directly, initializing an `alloc_context ac` using a designated initializer.  Crucially, it's setting `fastpath_alloc_flags` correctly and passing `alloc_flags` to the fallback path. No `ALLOC_DEFAULT` hardcoded anywhere.

Now, does this touch anything that would trigger KMSAN? Let's go through the checklist.

1.  **Kernel structures to user space?** Nope. This patch isn't introducing any new data that's being copied to user space or exposed through any user-facing interfaces. No `copy_to_user`, no `put_user`, nothing. This is all internal.

2.  **Conditional logic based on uninitialized variables?** No. Everything is explicitly initialized or zeroed.

3.  **Complex data structures with uninitialized fields?** Not in a way that matters here. The `alloc_context ac` struct *was* potentially uninitialized, but it's now being initialized with a designated initializer - the result of which, combined with the zero initialization of the alloc flags, should ensure everything is zeroed.

4.  **Bounds checks or logic altering uninitialized buffer access?** Absolutely not. No buffer lengths or bounds are modified. This is all about allocation *parameters*, not the memory itself.

So, *definitely* `NeedsKMSAN = false`. This patch is about clarifying how allocation flags are used internally.  Any potential bugs introduced would be standard allocator problems. Standard KASAN coverage (and the existing testing) will be sufficient.  We are not opening any new attack vectors with memory leaks.

Time to call the `set-results` tool and move on.

{
  "KMSANReasoning": "The patch refactors internal page allocator functions (`__folio_alloc_noprof` and `__alloc_pages_bulk_noprof`) to accept an `alloc_flags` argument rather than hardcoding `ALLOC_DEFAULT`. Existing callers (`khugepaged.c`, `migrate.c`) and wrappers (`alloc_pages_bulk_noprof`, `__folio_alloc_node_noprof`) are updated to explicitly pass `ALLOC_DEFAULT`. In `__alloc_pages_bulk_noprof`, `struct alloc_context ac` is initialized via designated initializer (`{ .alloc_flags = alloc_flags }`), which actually guarantees zero-initialization of remaining fields.\n\nNo kernel structures are copied or exposed to userspace, no conditional logic relies on uninitialized data, and page zeroing / init_on_alloc semantics are unchanged. Potential regressions from these changes (e.g. incorrect allocation watermarks, GFP flag handling, or NULL dereferences on allocation failure) are addressed by standard kernel debugging assertions, LOCKDEP, and KASAN. There are no uninitialized memory usage or info-leak risks requiring a dedicated KMSAN session.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch refactors internal page allocator functions (`__folio_alloc_noprof` and `__alloc_pages_bulk_noprof`) to accept an `alloc_flags` argument rather than hardcoding `ALLOC_DEFAULT`. Existing callers (`khugepaged.c`, `migrate.c`) and wrappers (`alloc_pages_bulk_noprof`, `__folio_alloc_node_noprof`) are updated to explicitly pass `ALLOC_DEFAULT`. In `__alloc_pages_bulk_noprof`, `struct alloc_context ac` is initialized via designated initializer (`{ .alloc_flags = alloc_flags }`), which actually guarantees zero-initialization of remaining fields.\n\nNo kernel structures are copied or exposed to userspace, no conditional logic relies on uninitialized data, and page zeroing / init_on_alloc semantics are unchanged. Potential regressions from these changes (e.g. incorrect allocation watermarks, GFP flag handling, or NULL dereferences on allocation failure) are addressed by standard kernel debugging assertions, LOCKDEP, and KASAN. There are no uninitialized memory usage or info-leak risks requiring a dedicated KMSAN session.",
  "NeedsKMSAN": false
}