| Seq | Timestamp | Type | Name | Duration |
|---|---|---|---|---|
| 0/0 | 2026/09/12 03:37 | flow | patch-triage |
1mArgs:null Results: {
"EnableConfigs": [
"NUMA",
"NUMA_MIGRATION"
],
"FocusSymbols": [
"find_next_best_node_in",
"next_demotion_node",
"build_all_zonelists"
],
"KMSANReasoning": "The patch refactors NUMA zonelist generation and node fallback calculation by introducing `find_next_best_node_in()` with a `candidates` nodemask parameter and merging `build_zonelists_in_node_order()` into `build_node_zonelist()`.\n\n- No kernel memory is copied to userspace (no info-leaks).\n- No new heap or stack allocations with uninitialized fields are introduced.\n- All variables (such as `used_mask = NODE_MASK_NONE`) and zoneref terminations (`zonerefs-\u003ezone = NULL`, `zonerefs-\u003ezone_idx = 0`) are properly initialized.\n- Any potential memory safety issues introduced by zonelist indexing or traversal would be out-of-bounds accesses or pointer errors, which are detectable by KASAN. KMSAN uninitialized memory detection is not applicable.",
"NeedsKMSAN": false,
"Reasoning": "The patch refactors find_next_best_node() into find_next_best_node_in(), allowing callers to specify eligible candidate nodes via a nodemask. It also restructures zonelist building in mm/page_alloc.c (build_node_zonelist) and updates demotion target resolution in mm/memory-tiers.c (next_demotion_node and establish_demotion_targets). This modifies core memory management logic reachable during NUMA zonelist generation (e.g. boot and memory hotplug/rebuild) and folio demotion during memory reclamation.",
"WorthFuzzing": true
} |
| 1/1 | 2026/09/12 03:37 | action | read-patch-diff |
0mArgs:null Results: {
"PatchDiff": "commit 1ba2d4f1791db873600f0a12ff73d299abdd3bd7\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Sat Sep 12 03:37:02 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/mm/internal.h b/mm/internal.h\nindex da14c56fb24e1..1519dd21a900f 100644\n--- a/mm/internal.h\n+++ b/mm/internal.h\n@@ -1133,7 +1133,8 @@ extern int node_reclaim_mode;\n \n extern unsigned long node_reclaim(struct pglist_data *pgdat,\n \t\t\t\t gfp_t gfp_mask, unsigned int order);\n-extern int find_next_best_node(int node, nodemask_t *used_node_mask);\n+int find_next_best_node_in(int node, nodemask_t *used_node_mask,\n+\t\tconst nodemask_t *candidates);\n #else\n #define node_reclaim_mode 0\n \n@@ -1142,7 +1143,8 @@ static inline unsigned long node_reclaim(struct pglist_data *pgdat,\n {\n \treturn 0;\n }\n-static inline int find_next_best_node(int node, nodemask_t *used_node_mask)\n+static inline int find_next_best_node_in(int node, nodemask_t *used_node_mask,\n+\t\tconst nodemask_t *candidates)\n {\n \treturn NUMA_NO_NODE;\n }\ndiff --git a/mm/memory-tiers.c b/mm/memory-tiers.c\nindex 54851d8a195b0..25e121851b586 100644\n--- a/mm/memory-tiers.c\n+++ b/mm/memory-tiers.c\n@@ -370,7 +370,7 @@ int next_demotion_node(int node, const nodemask_t *allowed_mask)\n \t * closest demotion target.\n \t */\n \tnodes_complement(mask, *allowed_mask);\n-\treturn find_next_best_node(node, \u0026mask);\n+\treturn find_next_best_node_in(node, \u0026mask, \u0026node_states[N_MEMORY]);\n }\n \n static void disable_all_demotion_targets(void)\n@@ -450,7 +450,7 @@ static void establish_demotion_targets(void)\n \t\tmemtier = list_next_entry(memtier, list);\n \t\ttier_nodes = get_memtier_nodemask(memtier);\n \t\t/*\n-\t\t * find_next_best_node, use 'used' nodemask as a skip list.\n+\t\t * find_next_best_node_in, use 'used' nodemask as a skip list.\n \t\t * Add all memory nodes except the selected memory tier\n \t\t * nodelist to skip list so that we find the best node from the\n \t\t * memtier nodelist.\n@@ -463,7 +463,8 @@ static void establish_demotion_targets(void)\n \t\t * in the preferred mask when allocating pages during demotion.\n \t\t */\n \t\tdo {\n-\t\t\ttarget = find_next_best_node(node, \u0026tier_nodes);\n+\t\t\ttarget = find_next_best_node_in(node, \u0026tier_nodes,\n+\t\t\t\t\t\t\t\u0026node_states[N_MEMORY]);\n \t\t\tif (target == NUMA_NO_NODE)\n \t\t\t\tbreak;\n \ndiff --git a/mm/page_alloc.c b/mm/page_alloc.c\nindex 1cfbd0582a10a..d1888d5630e0a 100644\n--- a/mm/page_alloc.c\n+++ b/mm/page_alloc.c\n@@ -5793,9 +5793,10 @@ static int numa_zonelist_order_handler(const struct ctl_table *table, int write,\n static int node_load[MAX_NUMNODES];\n \n /**\n- * find_next_best_node - find the next node that should appear in a given node's fallback list\n+ * find_next_best_node_in - find the next node that should appear in a given node's fallback list\n * @node: node whose fallback list we're appending\n * @used_node_mask: nodemask_t of already used nodes\n+ * @candidates: nodemask_t of nodes eligible for selection\n *\n * We use a number of factors to determine which is the next node that should\n * appear on a given node's fallback list. The node should not have appeared\n@@ -5807,7 +5808,8 @@ static int node_load[MAX_NUMNODES];\n *\n * Return: node id of the found node or %NUMA_NO_NODE if no node is found.\n */\n-int find_next_best_node(int node, nodemask_t *used_node_mask)\n+int find_next_best_node_in(int node, nodemask_t *used_node_mask,\n+\t\t\t const nodemask_t *candidates)\n {\n \tint n, val;\n \tint min_val = INT_MAX;\n@@ -5817,12 +5819,12 @@ int find_next_best_node(int node, nodemask_t *used_node_mask)\n \t * Use the local node if we haven't already, but for memoryless local\n \t * node, we should skip it and fall back to other nodes.\n \t */\n-\tif (!node_isset(node, *used_node_mask) \u0026\u0026 node_state(node, N_MEMORY)) {\n+\tif (!node_isset(node, *used_node_mask) \u0026\u0026 node_isset(node, *candidates)) {\n \t\tnode_set(node, *used_node_mask);\n \t\treturn node;\n \t}\n \n-\tfor_each_node_state(n, N_MEMORY) {\n+\tfor_each_node_mask(n, *candidates) {\n \n \t\t/* Don't want a node to appear more than once */\n \t\tif (node_isset(n, *used_node_mask))\n@@ -5855,31 +5857,6 @@ int find_next_best_node(int node, nodemask_t *used_node_mask)\n }\n \n \n-/*\n- * Build zonelists ordered by node and zones within node.\n- * This results in maximum locality--normal zone overflows into local\n- * DMA zone, if any--but risks exhausting DMA zone.\n- */\n-static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order,\n-\t\tunsigned nr_nodes)\n-{\n-\tstruct zoneref *zonerefs;\n-\tint i;\n-\n-\tzonerefs = pgdat-\u003enode_zonelists[ZONELIST_FALLBACK]._zonerefs;\n-\n-\tfor (i = 0; i \u003c nr_nodes; i++) {\n-\t\tint nr_zones;\n-\n-\t\tpg_data_t *node = NODE_DATA(node_order[i]);\n-\n-\t\tnr_zones = build_zonerefs_node(node, zonerefs);\n-\t\tzonerefs += nr_zones;\n-\t}\n-\tzonerefs-\u003ezone = NULL;\n-\tzonerefs-\u003ezone_idx = 0;\n-}\n-\n /*\n * Build __GFP_THISNODE zonelists\n */\n@@ -5895,19 +5872,24 @@ static void build_thisnode_zonelists(pg_data_t *pgdat)\n \tzonerefs-\u003ezone_idx = 0;\n }\n \n-static void build_zonelists(pg_data_t *pgdat)\n+/*\n+ * Build one zonelist ordered by node and zones within node. This results in\n+ * maximum locality--normal zone overflows into local DMA zone, if any--but\n+ * risks exhausting DMA zone.\n+ */\n+static void build_node_zonelist(pg_data_t *pgdat, const nodemask_t *candidates,\n+\t\t\t\tint zlidx)\n {\n-\tstatic int node_order[MAX_NUMNODES];\n-\tint node, nr_nodes = 0;\n+\tstruct zoneref *zonerefs = pgdat-\u003enode_zonelists[zlidx]._zonerefs;\n \tnodemask_t used_mask = NODE_MASK_NONE;\n-\tint local_node, prev_node;\n+\tint local_node = pgdat-\u003enode_id;\n+\tint prev_node = local_node;\n+\tint node;\n \n-\t/* NUMA-aware ordering of nodes */\n-\tlocal_node = pgdat-\u003enode_id;\n-\tprev_node = local_node;\n+\tpr_info(\"Fallback order for Node %d: \", local_node);\n \n-\tmemset(node_order, 0, sizeof(node_order));\n-\twhile ((node = find_next_best_node(local_node, \u0026used_mask)) \u003e= 0) {\n+\twhile ((node = find_next_best_node_in(local_node, \u0026used_mask,\n+\t\t\t\t\t candidates)) \u003e= 0) {\n \t\t/*\n \t\t * We don't want to pressure a particular node.\n \t\t * So adding penalty to the first node in same\n@@ -5917,18 +5899,22 @@ static void build_zonelists(pg_data_t *pgdat)\n \t\t node_distance(local_node, prev_node))\n \t\t\tnode_load[node] += 1;\n \n-\t\tnode_order[nr_nodes++] = node;\n+\t\tzonerefs += build_zonerefs_node(NODE_DATA(node), zonerefs);\n+\t\tpr_cont(\"%d \", node);\n \t\tprev_node = node;\n \t}\n \n-\tbuild_zonelists_in_node_order(pgdat, node_order, nr_nodes);\n-\tbuild_thisnode_zonelists(pgdat);\n-\tpr_info(\"Fallback order for Node %d: \", local_node);\n-\tfor (node = 0; node \u003c nr_nodes; node++)\n-\t\tpr_cont(\"%d \", node_order[node]);\n+\tzonerefs-\u003ezone = NULL;\n+\tzonerefs-\u003ezone_idx = 0;\n \tpr_cont(\"\\n\");\n }\n \n+static void build_zonelists(pg_data_t *pgdat)\n+{\n+\tbuild_node_zonelist(pgdat, \u0026node_states[N_MEMORY], ZONELIST_FALLBACK);\n+\tbuild_thisnode_zonelists(pgdat);\n+}\n+\n #ifdef CONFIG_HAVE_MEMORYLESS_NODES\n /*\n * Return node id of node used for \"local\" allocations.\n"
} |
| 2/1 | 2026/09/12 03:37 | agent | patch-evaluator |
1mModel:core Args: null Results: {
"EnableConfigs": [
"NUMA",
"NUMA_MIGRATION"
],
"FocusSymbols": [
"find_next_best_node_in",
"next_demotion_node",
"build_all_zonelists"
],
"Reasoning": "The patch refactors find_next_best_node() into find_next_best_node_in(), allowing callers to specify eligible candidate nodes via a nodemask. It also restructures zonelist building in mm/page_alloc.c (build_node_zonelist) and updates demotion target resolution in mm/memory-tiers.c (next_demotion_node and establish_demotion_targets). This modifies core memory management logic reachable during NUMA zonelist generation (e.g. boot and memory hotplug/rebuild) and folio demotion during memory reclamation.",
"WorthFuzzing": true
}Instruction: 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.
Prompt: Target architecture: amd64
For your convenience, here is the diff of the changes:
commit 1ba2d4f1791db873600f0a12ff73d299abdd3bd7
Author: syz-cluster <triage@syzkaller.com>
Date: Sat Sep 12 03:37:02 2026 +0000
syz-cluster: applied patch under review
diff --git a/mm/internal.h b/mm/internal.h
index da14c56fb24e1..1519dd21a900f 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1133,7 +1133,8 @@ extern int node_reclaim_mode;
extern unsigned long node_reclaim(struct pglist_data *pgdat,
gfp_t gfp_mask, unsigned int order);
-extern int find_next_best_node(int node, nodemask_t *used_node_mask);
+int find_next_best_node_in(int node, nodemask_t *used_node_mask,
+ const nodemask_t *candidates);
#else
#define node_reclaim_mode 0
@@ -1142,7 +1143,8 @@ static inline unsigned long node_reclaim(struct pglist_data *pgdat,
{
return 0;
}
-static inline int find_next_best_node(int node, nodemask_t *used_node_mask)
+static inline int find_next_best_node_in(int node, nodemask_t *used_node_mask,
+ const nodemask_t *candidates)
{
return NUMA_NO_NODE;
}
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 54851d8a195b0..25e121851b586 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -370,7 +370,7 @@ int next_demotion_node(int node, const nodemask_t *allowed_mask)
* closest demotion target.
*/
nodes_complement(mask, *allowed_mask);
- return find_next_best_node(node, &mask);
+ return find_next_best_node_in(node, &mask, &node_states[N_MEMORY]);
}
static void disable_all_demotion_targets(void)
@@ -450,7 +450,7 @@ static void establish_demotion_targets(void)
memtier = list_next_entry(memtier, list);
tier_nodes = get_memtier_nodemask(memtier);
/*
- * find_next_best_node, use 'used' nodemask as a skip list.
+ * find_next_best_node_in, use 'used' nodemask as a skip list.
* Add all memory nodes except the selected memory tier
* nodelist to skip list so that we find the best node from the
* memtier nodelist.
@@ -463,7 +463,8 @@ static void establish_demotion_targets(void)
* in the preferred mask when allocating pages during demotion.
*/
do {
- target = find_next_best_node(node, &tier_nodes);
+ target = find_next_best_node_in(node, &tier_nodes,
+ &node_states[N_MEMORY]);
if (target == NUMA_NO_NODE)
break;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1cfbd0582a10a..d1888d5630e0a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5793,9 +5793,10 @@ static int numa_zonelist_order_handler(const struct ctl_table *table, int write,
static int node_load[MAX_NUMNODES];
/**
- * find_next_best_node - find the next node that should appear in a given node's fallback list
+ * find_next_best_node_in - find the next node that should appear in a given node's fallback list
* @node: node whose fallback list we're appending
* @used_node_mask: nodemask_t of already used nodes
+ * @candidates: nodemask_t of nodes eligible for selection
*
* We use a number of factors to determine which is the next node that should
* appear on a given node's fallback list. The node should not have appeared
@@ -5807,7 +5808,8 @@ static int node_load[MAX_NUMNODES];
*
* Return: node id of the found node or %NUMA_NO_NODE if no node is found.
*/
-int find_next_best_node(int node, nodemask_t *used_node_mask)
+int find_next_best_node_in(int node, nodemask_t *used_node_mask,
+ const nodemask_t *candidates)
{
int n, val;
int min_val = INT_MAX;
@@ -5817,12 +5819,12 @@ int find_next_best_node(int node, nodemask_t *used_node_mask)
* Use the local node if we haven't already, but for memoryless local
* node, we should skip it and fall back to other nodes.
*/
- if (!node_isset(node, *used_node_mask) && node_state(node, N_MEMORY)) {
+ if (!node_isset(node, *used_node_mask) && node_isset(node, *candidates)) {
node_set(node, *used_node_mask);
return node;
}
- for_each_node_state(n, N_MEMORY) {
+ for_each_node_mask(n, *candidates) {
/* Don't want a node to appear more than once */
if (node_isset(n, *used_node_mask))
@@ -5855,31 +5857,6 @@ int find_next_best_node(int node, nodemask_t *used_node_mask)
}
-/*
- * Build zonelists ordered by node and zones within node.
- * This results in maximum locality--normal zone overflows into local
- * DMA zone, if any--but risks exhausting DMA zone.
- */
-static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order,
- unsigned nr_nodes)
-{
- struct zoneref *zonerefs;
- int i;
-
- zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
-
- for (i = 0; i < nr_nodes; i++) {
- int nr_zones;
-
- pg_data_t *node = NODE_DATA(node_order[i]);
-
- nr_zones = build_zonerefs_node(node, zonerefs);
- zonerefs += nr_zones;
- }
- zonerefs->zone = NULL;
- zonerefs->zone_idx = 0;
-}
-
/*
* Build __GFP_THISNODE zonelists
*/
@@ -5895,19 +5872,24 @@ static void build_thisnode_zonelists(pg_data_t *pgdat)
zonerefs->zone_idx = 0;
}
-static void build_zonelists(pg_data_t *pgdat)
+/*
+ * Build one zonelist ordered by node and zones within node. This results in
+ * maximum locality--normal zone overflows into local DMA zone, if any--but
+ * risks exhausting DMA zone.
+ */
+static void build_node_zonelist(pg_data_t *pgdat, const nodemask_t *candidates,
+ int zlidx)
{
- static int node_order[MAX_NUMNODES];
- int node, nr_nodes = 0;
+ struct zoneref *zonerefs = pgdat->node_zonelists[zlidx]._zonerefs;
nodemask_t used_mask = NODE_MASK_NONE;
- int local_node, prev_node;
+ int local_node = pgdat->node_id;
+ int prev_node = local_node;
+ int node;
- /* NUMA-aware ordering of nodes */
- local_node = pgdat->node_id;
- prev_node = local_node;
+ pr_info("Fallback order for Node %d: ", local_node);
- memset(node_order, 0, sizeof(node_order));
- while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
+ while ((node = find_next_best_node_in(local_node, &used_mask,
+ candidates)) >= 0) {
/*
* We don't want to pressure a particular node.
* So adding penalty to the first node in same
@@ -5917,18 +5899,22 @@ static void build_zonelists(pg_data_t *pgdat)
node_distance(local_node, prev_node))
node_load[node] += 1;
- node_order[nr_nodes++] = node;
+ zonerefs += build_zonerefs_node(NODE_DATA(node), zonerefs);
+ pr_cont("%d ", node);
prev_node = node;
}
- build_zonelists_in_node_order(pgdat, node_order, nr_nodes);
- build_thisnode_zonelists(pgdat);
- pr_info("Fallback order for Node %d: ", local_node);
- for (node = 0; node < nr_nodes; node++)
- pr_cont("%d ", node_order[node]);
+ zonerefs->zone = NULL;
+ zonerefs->zone_idx = 0;
pr_cont("\n");
}
+static void build_zonelists(pg_data_t *pgdat)
+{
+ build_node_zonelist(pgdat, &node_states[N_MEMORY], ZONELIST_FALLBACK);
+ build_thisnode_zonelists(pgdat);
+}
+
#ifdef CONFIG_HAVE_MEMORYLESS_NODES
/*
* Return node id of node used for "local" allocations.
|
| 3/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 5308 output: 34 thoughts: 425 Thoughts: **Analyzing the Memory Management Patch** Okay, let's dive into this patch. My initial thought is to identify the scope of the changes. The diff touches `mm/internal.h`, `mm/memory-tiers.c`, and `mm/page_alloc.c`. This suggests it's likely related to memory node selection or zone management within NUMA systems, my spidey senses are tingling. I'll probably grab `grepper` or `read-file` to get a quick overview of the code, maybe look at function calls. First things first, I need a high-level understanding of what this patch actually *does*. 1. **`mm/internal.h`**: It looks like `find_next_best_node` is getting a signature change, being renamed to `find_next_best_node_in`. I also see a static inline fallback when `CONFIG_NUMA` (or something similar) isn't defined. Seems like they're trying to generalize a node selection function and handle non-NUMA cases gracefully. 2. **`mm/memory-tiers.c`**: The `next_demotion_node()` and `establish_demotion_targets()` functions, now calling `find_next_best_node_in()`. I'm guessing this relates to memory tiering policies or demotion/promotion decisions within the memory hierarchy. The `&node_states[N_MEMORY]` argument is immediately interesting. 3. **`mm/page_alloc.c`**: This is where things get interesting. The original `find_next_best_node()` is gone, and now calling `find_next_best_node_in()`, taking a `candidates` nodemask instead of hardcoding node-state calls. This suggests a more flexible node selection mechanism. Also, the removal/merging of `build_zonelists_in_node_order()` into `build_node_zonelist()` is interesting. The `build_zonelists()` now calls `build_node_zonelist()` with different nodemasks. This is all about zone ordering during page allocation. I'm starting to see a pattern here: generalization and a potential shift in how nodemasks are handled within the core memory management. This is about making node selection more flexible, potentially for better NUMA awareness or perhaps to integrate it better with memory tiering. I'm thinking I should check around lines 1130-1150 in `mm/internal.h` to see what conditional compilation guards are in place. This will give me a better understanding of how the code behaves in different configurations. |
| 4/2 | 2026/09/12 03:37 | tool | read-file |
0mArgs:{
"File": "mm/internal.h",
"FirstLine": 1125,
"LineCount": 35
}Results: {
"Contents": "1125:\tstatic inline void mlock_new_folio(struct folio *folio) { }\n1126:\tstatic inline bool need_mlock_drain(int cpu) { return false; }\n1127:\tstatic inline void mlock_drain_local(void) { }\n1128:\tstatic inline void mlock_drain_remote(int cpu) { }\n1129:\t#endif /* !CONFIG_MMU */\n1130:\t\n1131:\t#ifdef CONFIG_NUMA\n1132:\textern int node_reclaim_mode;\n1133:\t\n1134:\textern unsigned long node_reclaim(struct pglist_data *pgdat,\n1135:\t\t\t\t\t gfp_t gfp_mask, unsigned int order);\n1136:\tint find_next_best_node_in(int node, nodemask_t *used_node_mask,\n1137:\t\t\tconst nodemask_t *candidates);\n1138:\t#else\n1139:\t#define node_reclaim_mode 0\n1140:\t\n1141:\tstatic inline unsigned long node_reclaim(struct pglist_data *pgdat,\n1142:\t\t\t\t\t\t gfp_t mask, unsigned int order)\n1143:\t{\n1144:\t\treturn 0;\n1145:\t}\n1146:\tstatic inline int find_next_best_node_in(int node, nodemask_t *used_node_mask,\n1147:\t\t\tconst nodemask_t *candidates)\n1148:\t{\n1149:\t\treturn NUMA_NO_NODE;\n1150:\t}\n1151:\t#endif\n1152:\t\n1153:\tstatic inline bool node_reclaim_enabled(void)\n1154:\t{\n1155:\t\t/* Is any node_reclaim_mode bit set? */\n1156:\t\treturn node_reclaim_mode \u0026 (RECLAIM_ZONE|RECLAIM_WRITE|RECLAIM_UNMAP);\n1157:\t}\n1158:\t\n1159:\t/*\n"
} |
| 5/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 6893 output: 35 thoughts: 74 Thoughts: **Investigating NUMA Configuration in Memory Management** Alright, so `CONFIG_NUMA` is the key configuration guard we're dealing with here, specifically defined within `mm/internal.h`. My immediate focus shifts to how this impacts the memory management components, and I'm particularly interested in `mm/memory-tiers.c` and `mm/page_alloc.c`. I need to understand the compilation conditions and how this `CONFIG_NUMA` flag influences the code paths within those files. I'll zero in on `mm/memory-tiers.c`, specifically scrutinizing the code between lines 360 and 480. That seems like a likely region to find the relevant conditional compilation logic, which should illuminate how NUMA-aware memory tiering is actually implemented. Let's dig in and see what we find. |
| 6/2 | 2026/09/12 03:37 | tool | read-file |
0mArgs:{
"File": "mm/memory-tiers.c",
"FirstLine": 360,
"LineCount": 40
}Results: {
"Contents": " 360:\t\t * last target node. Or introducing per-cpu data to avoid\n 361:\t\t * caching issue, which seems more complicated. So selecting\n 362:\t\t * target node randomly seems better until now.\n 363:\t\t */\n 364:\t\tif (!nodes_empty(mask))\n 365:\t\t\treturn node_random(\u0026mask);\n 366:\t\n 367:\t\t/*\n 368:\t\t * Preferred nodes are not in allowed_mask. Flip bits in\n 369:\t\t * allowed_mask as used node mask. Then, use it to get the\n 370:\t\t * closest demotion target.\n 371:\t\t */\n 372:\t\tnodes_complement(mask, *allowed_mask);\n 373:\t\treturn find_next_best_node_in(node, \u0026mask, \u0026node_states[N_MEMORY]);\n 374:\t}\n 375:\t\n 376:\tstatic void disable_all_demotion_targets(void)\n 377:\t{\n 378:\t\tstruct memory_tier *memtier;\n 379:\t\tint node;\n 380:\t\n 381:\t\tfor_each_node_state(node, N_MEMORY) {\n 382:\t\t\tnode_demotion[node].preferred = NODE_MASK_NONE;\n 383:\t\t\t/*\n 384:\t\t\t * We are holding memory_tier_lock, it is safe\n 385:\t\t\t * to access pgda-\u003ememtier.\n 386:\t\t\t */\n 387:\t\t\tmemtier = __node_get_memory_tier(node);\n 388:\t\t\tif (memtier)\n 389:\t\t\t\tmemtier-\u003elower_tier_mask = NODE_MASK_NONE;\n 390:\t\t}\n 391:\t\t/*\n 392:\t\t * Ensure that the \"disable\" is visible across the system.\n 393:\t\t * Readers will see either a combination of before+disable\n 394:\t\t * state or disable+after. They will never see before and\n 395:\t\t * after state together.\n 396:\t\t */\n 397:\t\tsynchronize_rcu();\n 398:\t}\n 399:\t\n"
} |
| 7/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 7763 output: 24 thoughts: 28 Thoughts: Here's my take on the thought process, as if it were my own: **Investigating the Memory Tiers Implementation** Okay, so I need to dig into the `mm/memory-tiers.c` implementation. The logical starting point is always the build system, so let's check the Kconfig and Makefile for that particular file. The key here is to understand how it's configured and built, which will tell me a lot about the dependencies and any associated feature flags. Now, to quickly locate the relevant sections, I'll use `grep`. I'll search specifically for "memory-tiers" within those configuration files. This should quickly highlight the relevant configuration options and how the module is incorporated into the build. This approach is efficient – starting at the build system gives me context and makes sure I don't miss anything that enables or disables it. |
| 8/2 | 2026/09/12 03:37 | tool | grepper |
0mArgs:{
"Expression": "memory-tiers",
"PathPrefix": "mm"
}Results: {
"Output": "mm/Makefile=99=obj-$(CONFIG_MIGRATION) += migrate.o\nmm/Makefile:100:obj-$(CONFIG_NUMA) += memory-tiers.o\nmm/Makefile-101-obj-$(CONFIG_DEVICE_MIGRATION) += migrate_device.o\n--\nmm/damon/paddr.c-12-#include \u003clinux/swap.h\u003e\nmm/damon/paddr.c:13:#include \u003clinux/memory-tiers.h\u003e\nmm/damon/paddr.c-14-#include \u003clinux/mm_inline.h\u003e\n--\nmm/huge_memory.c-38-#include \u003clinux/sched/sysctl.h\u003e\nmm/huge_memory.c:39:#include \u003clinux/memory-tiers.h\u003e\nmm/huge_memory.c-40-#include \u003clinux/compat.h\u003e\n--\nmm/memory-tiers.c-6-#include \u003clinux/memory.h\u003e\nmm/memory-tiers.c:7:#include \u003clinux/memory-tiers.h\u003e\nmm/memory-tiers.c-8-#include \u003clinux/notifier.h\u003e\n--\nmm/memory-tiers.c=747=int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,\n--\nmm/memory-tiers.c-779-\t\tpr_info(\nmm/memory-tiers.c:780:\"memory-tiers: the performance of DRAM node %d mismatches that of the reference\\n\"\nmm/memory-tiers.c-781-\"DRAM node %d.\\n\", nid, default_dram_perf_ref_nid);\n--\nmm/memory.c-68-#include \u003clinux/shmem_fs.h\u003e\nmm/memory.c:69:#include \u003clinux/memory-tiers.h\u003e\nmm/memory.c-70-#include \u003clinux/debugfs.h\u003e\n--\nmm/mempolicy.c-102-#include \u003clinux/proc_fs.h\u003e\nmm/mempolicy.c:103:#include \u003clinux/memory-tiers.h\u003e\nmm/mempolicy.c-104-#include \u003clinux/migrate.h\u003e\n--\nmm/migrate.c-43-#include \u003clinux/sched/sysctl.h\u003e\nmm/migrate.c:44:#include \u003clinux/memory-tiers.h\u003e\nmm/migrate.c-45-#include \u003clinux/pagewalk.h\u003e\n--\nmm/vmscan.c-44-#include \u003clinux/sysctl.h\u003e\nmm/vmscan.c:45:#include \u003clinux/memory-tiers.h\u003e\nmm/vmscan.c-46-#include \u003clinux/oom.h\u003e\n"
} |
| 9/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 8654 output: 20 thoughts: 80 Thoughts: Here's my thought process, as an expert in this area: **Investigating NUMA and Memory Demotion** Okay, so `memory-tiers.o` is only brought into the picture when NUMA support is enabled. That makes sense, as memory tiering is a core NUMA-related optimization. My next step is to understand the control flow, so I'll trace a few key functions. I want to see how the demotion process is kicked off and managed. Specifically, I need to know where `next_demotion_node` and `establish_demotion_targets` are *called*. These are clearly critical to the actual demotion decisions and target setup. And, let's not forget how these zones get set up - I should look into where `build_zonelists` is called. It's time to get down and dirty with some `grep` action to find those call sites. This should give me a good handle on the overall execution path. |
| 10/2 | 2026/09/12 03:37 | tool | grepper |
0mArgs:{
"Expression": "next_demotion_node"
}Results: {
"Output": "include/linux/memory-tiers.h=54=void mt_put_memory_types(struct list_head *memory_types);\ninclude/linux/memory-tiers.h-55-#ifdef CONFIG_NUMA_MIGRATION\ninclude/linux/memory-tiers.h:56:int next_demotion_node(int node, const nodemask_t *allowed_mask);\ninclude/linux/memory-tiers.h-57-void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);\ninclude/linux/memory-tiers.h=58=bool node_is_toptier(int node);\ninclude/linux/memory-tiers.h-59-#else\ninclude/linux/memory-tiers.h:60:static inline int next_demotion_node(int node, const nodemask_t *allowed_mask)\ninclude/linux/memory-tiers.h-61-{\n--\ninclude/linux/memory-tiers.h=99=static inline void clear_node_memory_type(int node, struct memory_dev_type *memtype)\n--\ninclude/linux/memory-tiers.h-103-\ninclude/linux/memory-tiers.h:104:static inline int next_demotion_node(int node, const nodemask_t *allowed_mask)\ninclude/linux/memory-tiers.h-105-{\n--\nmm/memory-tiers.c=302=void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets)\n--\nmm/memory-tiers.c-320-/**\nmm/memory-tiers.c:321: * next_demotion_node() - Get the next node in the demotion path\nmm/memory-tiers.c-322- * @node: The starting node to lookup the next node\n--\nmm/memory-tiers.c-329- */\nmm/memory-tiers.c:330:int next_demotion_node(int node, const nodemask_t *allowed_mask)\nmm/memory-tiers.c-331-{\n--\nmm/vmscan.c=1071=static unsigned int demote_folio_list(struct list_head *demote_folios,\n--\nmm/vmscan.c-1098-\nmm/vmscan.c:1099:\ttarget_nid = next_demotion_node(pgdat-\u003enode_id, \u0026allowed_mask);\nmm/vmscan.c-1100-\tif (target_nid == NUMA_NO_NODE)\n"
} |
| 11/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 9599 output: 36 thoughts: 88 Thoughts: **Investigating `next_demotion_node` in the VMscan Context** Okay, so I've spotted that `next_demotion_node` is invoked within `demote_folio_list` inside `mm/vmscan.c`. Immediately, my expert brain is firing off potential dependencies. I need to quickly ascertain the prerequisites. The question that has sprung to mind is whether `CONFIG_NUMA_MIGRATION` is a requirement for the `next_demotion_node` function. I *believe* it’s defined in `include/linux/memory-tiers.h` but I need to quickly verify that. Let's jump over to that header file, specifically around line 50, to confirm. Time to dig in and clarify this quickly. |
| 12/2 | 2026/09/12 03:37 | tool | read-file |
0mArgs:{
"File": "include/linux/memory-tiers.h",
"FirstLine": 40,
"LineCount": 40
}Results: {
"Contents": " 40:\textern struct memory_dev_type *default_dram_type;\n 41:\textern nodemask_t default_dram_nodes;\n 42:\tstruct memory_dev_type *alloc_memory_type(int adistance);\n 43:\tvoid put_memory_type(struct memory_dev_type *memtype);\n 44:\tvoid init_node_memory_type(int node, struct memory_dev_type *default_type);\n 45:\tvoid clear_node_memory_type(int node, struct memory_dev_type *memtype);\n 46:\tint register_mt_adistance_algorithm(struct notifier_block *nb);\n 47:\tint unregister_mt_adistance_algorithm(struct notifier_block *nb);\n 48:\tint mt_calc_adistance(int node, int *adist);\n 49:\tint mt_set_default_dram_perf(int nid, struct access_coordinate *perf,\n 50:\t\t\t\t const char *source);\n 51:\tint mt_perf_to_adistance(struct access_coordinate *perf, int *adist);\n 52:\tstruct memory_dev_type *mt_find_alloc_memory_type(int adist,\n 53:\t\t\t\t\t\t\t struct list_head *memory_types);\n 54:\tvoid mt_put_memory_types(struct list_head *memory_types);\n 55:\t#ifdef CONFIG_NUMA_MIGRATION\n 56:\tint next_demotion_node(int node, const nodemask_t *allowed_mask);\n 57:\tvoid node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);\n 58:\tbool node_is_toptier(int node);\n 59:\t#else\n 60:\tstatic inline int next_demotion_node(int node, const nodemask_t *allowed_mask)\n 61:\t{\n 62:\t\treturn NUMA_NO_NODE;\n 63:\t}\n 64:\t\n 65:\tstatic inline void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets)\n 66:\t{\n 67:\t\t*targets = NODE_MASK_NONE;\n 68:\t}\n 69:\t\n 70:\tstatic inline bool node_is_toptier(int node)\n 71:\t{\n 72:\t\treturn true;\n 73:\t}\n 74:\t#endif\n 75:\t\n 76:\t#else\n 77:\t\n 78:\t#define numa_demotion_enabled\tfalse\n 79:\t#define default_dram_type\tNULL\n"
} |
| 13/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 10586 output: 35 thoughts: 56 Thoughts: Here's my thought process, as if I were analyzing that code snippet: **Diving into memory-tiers.c** Okay, so I need to figure out how a specific piece of code in `mm/memory-tiers.c` is handled. Specifically, I'm trying to determine the conditions under which it's active. My initial hypothesis is that it's governed by the `CONFIG_NUMA_MIGRATION` preprocessor define. To confirm this, I need to pinpoint the relevant section. I recall the discussion around this area, so let's start by zeroing in on lines 300 to 480 in `mm/memory-tiers.c`. That chunk should contain the critical logic I'm interested in, and hopefully, the preprocessor directives that control its execution are clearly visible within that range. From there, I can quickly determine whether my initial thought about `CONFIG_NUMA_MIGRATION` is correct or if another conditional is at play. This information is key to understanding the specific behaviour in question, especially in this context, so I'll double check the results. |
| 14/2 | 2026/09/12 03:37 | tool | read-file |
0mArgs:{
"File": "mm/memory-tiers.c",
"FirstLine": 300,
"LineCount": 40
}Results: {
"Contents": " 300:\t}\n 301:\t\n 302:\tvoid node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets)\n 303:\t{\n 304:\t\tstruct memory_tier *memtier;\n 305:\t\n 306:\t\t/*\n 307:\t\t * pg_data_t.memtier updates includes a synchronize_rcu()\n 308:\t\t * which ensures that we either find NULL or a valid memtier\n 309:\t\t * in NODE_DATA. protect the access via rcu_read_lock();\n 310:\t\t */\n 311:\t\trcu_read_lock();\n 312:\t\tmemtier = rcu_dereference(pgdat-\u003ememtier);\n 313:\t\tif (memtier)\n 314:\t\t\t*targets = memtier-\u003elower_tier_mask;\n 315:\t\telse\n 316:\t\t\t*targets = NODE_MASK_NONE;\n 317:\t\trcu_read_unlock();\n 318:\t}\n 319:\t\n 320:\t/**\n 321:\t * next_demotion_node() - Get the next node in the demotion path\n 322:\t * @node: The starting node to lookup the next node\n 323:\t * @allowed_mask: The pointer to allowed node mask\n 324:\t *\n 325:\t * Return: node id for next memory node in the demotion path hierarchy\n 326:\t * from @node; NUMA_NO_NODE if @node is terminal. This does not keep\n 327:\t * @node online or guarantee that it *continues* to be the next demotion\n 328:\t * target.\n 329:\t */\n 330:\tint next_demotion_node(int node, const nodemask_t *allowed_mask)\n 331:\t{\n 332:\t\tstruct demotion_nodes *nd;\n 333:\t\tnodemask_t mask;\n 334:\t\n 335:\t\tif (!node_demotion)\n 336:\t\t\treturn NUMA_NO_NODE;\n 337:\t\n 338:\t\tnd = \u0026node_demotion[node];\n 339:\t\n"
} |
| 15/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 11515 output: 35 thoughts: 35 Thoughts: Okay, let's dive into this. **Investigating Memory Tier Guards** Alright, I need to understand what's happening around line 330 in `mm/memory-tiers.c`. That function call, or whatever logic resides there, seems significant enough to warrant a deeper look. Before I jump *directly* to 330 though, let's give myself some context. I'll take a peek at the surrounding code, say lines 280 through 300. Knowing the *what* around the *where* is always a smart move to understand the *why*. This quick scan should give me a better understanding of the overall flow and any surrounding guard conditions or logic that might be relevant. It's time to get a feel for the neighborhood around line 330. |
| 16/2 | 2026/09/12 03:37 | tool | read-file |
0mArgs:{
"File": "mm/memory-tiers.c",
"FirstLine": 280,
"LineCount": 25
}Results: {
"Contents": " 280:\t\tpg_data_t *pgdat;\n 281:\t\tstruct memory_tier *memtier;\n 282:\t\n 283:\t\tpgdat = NODE_DATA(node);\n 284:\t\tif (!pgdat)\n 285:\t\t\treturn false;\n 286:\t\n 287:\t\trcu_read_lock();\n 288:\t\tmemtier = rcu_dereference(pgdat-\u003ememtier);\n 289:\t\tif (!memtier) {\n 290:\t\t\ttoptier = true;\n 291:\t\t\tgoto out;\n 292:\t\t}\n 293:\t\tif (memtier-\u003eadistance_start \u003c= top_tier_adistance)\n 294:\t\t\ttoptier = true;\n 295:\t\telse\n 296:\t\t\ttoptier = false;\n 297:\tout:\n 298:\t\trcu_read_unlock();\n 299:\t\treturn toptier;\n 300:\t}\n 301:\t\n 302:\tvoid node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets)\n 303:\t{\n 304:\t\tstruct memory_tier *memtier;\n"
} |
| 17/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 12097 output: 35 thoughts: 22 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: **Investigating Memory Tier Guardrails** Okay, let's dive in. My focus right now is on the memory tiering implementation within the kernel, specifically around line 270 of `mm/memory-tiers.c`. I'm going to carefully scrutinize the guard conditions surrounding that particular point in the code. I need to understand what protections are in place to prevent potential issues, like out-of-bounds accesses, race conditions, or incorrect tier assignments. My primary goal here is to identify any potential weaknesses or areas where optimizations might be possible. I'll need to consider how these guards interact with other parts of the memory management subsystem, taking into account any relevant locking mechanisms, cache coherency protocols, and concurrent access patterns. |
| 18/2 | 2026/09/12 03:37 | tool | read-file |
0mArgs:{
"File": "mm/memory-tiers.c",
"FirstLine": 260,
"LineCount": 25
}Results: {
"Contents": " 260:\tstatic struct memory_tier *__node_get_memory_tier(int node)\n 261:\t{\n 262:\t\tpg_data_t *pgdat;\n 263:\t\n 264:\t\tpgdat = NODE_DATA(node);\n 265:\t\tif (!pgdat)\n 266:\t\t\treturn NULL;\n 267:\t\t/*\n 268:\t\t * Since we hold memory_tier_lock, we can avoid\n 269:\t\t * RCU read locks when accessing the details. No\n 270:\t\t * parallel updates are possible here.\n 271:\t\t */\n 272:\t\treturn rcu_dereference_check(pgdat-\u003ememtier,\n 273:\t\t\t\t\t lockdep_is_held(\u0026memory_tier_lock));\n 274:\t}\n 275:\t\n 276:\t#ifdef CONFIG_NUMA_MIGRATION\n 277:\tbool node_is_toptier(int node)\n 278:\t{\n 279:\t\tbool toptier;\n 280:\t\tpg_data_t *pgdat;\n 281:\t\tstruct memory_tier *memtier;\n 282:\t\n 283:\t\tpgdat = NODE_DATA(node);\n 284:\t\tif (!pgdat)\n"
} |
| 19/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 12681 output: 35 thoughts: 52 Thoughts: **Investigating NUMA Migration in `mm/memory-tiers.c`** Okay, so I'm looking at this code and I see this `#ifdef CONFIG_NUMA_MIGRATION` guard around a block of code, starting around line 276. I need to understand the scope of this preprocessor directive. Where does it end in `mm/memory-tiers.c`? It's essential to understand which parts of the code are conditionally compiled based on the NUMA migration configuration. Let me quickly jump to lines 480-530 to find the corresponding `#endif` or the next defining `ifdef` or `ifndef`, or `else`. That should clarify what falls within the conditional compilation scope. |
| 20/2 | 2026/09/12 03:37 | tool | read-file |
0mArgs:{
"File": "mm/memory-tiers.c",
"FirstLine": 480,
"LineCount": 40
}Results: {
"Contents": " 480:\t\t/*\n 481:\t\t * Promotion is allowed from a memory tier to higher\n 482:\t\t * memory tier only if the memory tier doesn't include\n 483:\t\t * compute. We want to skip promotion from a memory tier,\n 484:\t\t * if any node that is part of the memory tier have CPUs.\n 485:\t\t * Once we detect such a memory tier, we consider that tier\n 486:\t\t * as top tiper from which promotion is not allowed.\n 487:\t\t */\n 488:\t\tlist_for_each_entry_reverse(memtier, \u0026memory_tiers, list) {\n 489:\t\t\ttier_nodes = get_memtier_nodemask(memtier);\n 490:\t\t\tif (nodes_and(tier_nodes, node_states[N_CPU], tier_nodes)) {\n 491:\t\t\t\t/*\n 492:\t\t\t\t * abstract distance below the max value of this memtier\n 493:\t\t\t\t * is considered toptier.\n 494:\t\t\t\t */\n 495:\t\t\t\ttop_tier_adistance = memtier-\u003eadistance_start +\n 496:\t\t\t\t\t\t\tMEMTIER_CHUNK_SIZE - 1;\n 497:\t\t\t\tbreak;\n 498:\t\t\t}\n 499:\t\t}\n 500:\t\t/*\n 501:\t\t * Now build the lower_tier mask for each node collecting node mask from\n 502:\t\t * all memory tier below it. This allows us to fallback demotion page\n 503:\t\t * allocation to a set of nodes that is closer the above selected\n 504:\t\t * preferred node.\n 505:\t\t */\n 506:\t\tlower_tier = node_states[N_MEMORY];\n 507:\t\tlist_for_each_entry(memtier, \u0026memory_tiers, list) {\n 508:\t\t\t/*\n 509:\t\t\t * Keep removing current tier from lower_tier nodes,\n 510:\t\t\t * This will remove all nodes in current and above\n 511:\t\t\t * memory tier from the lower_tier mask.\n 512:\t\t\t */\n 513:\t\t\ttier_nodes = get_memtier_nodemask(memtier);\n 514:\t\t\tnodes_andnot(lower_tier, lower_tier, tier_nodes);\n 515:\t\t\tmemtier-\u003elower_tier_mask = lower_tier;\n 516:\t\t}\n 517:\t\n 518:\t\tdump_demotion_targets();\n 519:\t}\n"
} |
| 21/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 13570 output: 35 thoughts: 16 Thoughts: Okay, I'm ready to dive into this. Let's see what's being asked here... I need to summarize a text as if it's *my* thought process, as an expert in my field. Okay, so I should be thinking about the information from a position of deep understanding and experience, interpreting it as I would naturally. Got it. I should also start with a bolded header and speak in the first person. Alright, here we go. **Navigating the Nuances: Lines 520-560** Right, so let's get down to the brass tacks and take a look at lines 520 through 560. I immediately think that these lines probably hold crucial details, and based on the prompt, it would be advantageous to examine this section closely. I know the intricacies of this subject; it's practically second nature. I'll read with that perspective. I should be able to deduce the implications of these lines relatively quickly. Let's see how this text unfolds. |
| 22/2 | 2026/09/12 03:37 | tool | read-file |
0mArgs:{
"File": "mm/memory-tiers.c",
"FirstLine": 520,
"LineCount": 40
}Results: {
"Contents": " 520:\t\n 521:\t#else\n 522:\tstatic inline void establish_demotion_targets(void) {}\n 523:\t#endif /* CONFIG_NUMA_MIGRATION */\n 524:\t\n 525:\tstatic inline void __init_node_memory_type(int node, struct memory_dev_type *memtype)\n 526:\t{\n 527:\t\tif (!node_memory_types[node].memtype)\n 528:\t\t\tnode_memory_types[node].memtype = memtype;\n 529:\t\t/*\n 530:\t\t * for each device getting added in the same NUMA node\n 531:\t\t * with this specific memtype, bump the map count. We\n 532:\t\t * Only take memtype device reference once, so that\n 533:\t\t * changing a node memtype can be done by dropping the\n 534:\t\t * only reference count taken here.\n 535:\t\t */\n 536:\t\n 537:\t\tif (node_memory_types[node].memtype == memtype) {\n 538:\t\t\tif (!node_memory_types[node].map_count++)\n 539:\t\t\t\tkref_get(\u0026memtype-\u003ekref);\n 540:\t\t}\n 541:\t}\n 542:\t\n 543:\tstatic struct memory_tier *set_node_memory_tier(int node)\n 544:\t{\n 545:\t\tstruct memory_tier *memtier;\n 546:\t\tstruct memory_dev_type *memtype = default_dram_type;\n 547:\t\tint adist = MEMTIER_ADISTANCE_DRAM;\n 548:\t\tpg_data_t *pgdat = NODE_DATA(node);\n 549:\t\n 550:\t\n 551:\t\tlockdep_assert_held_once(\u0026memory_tier_lock);\n 552:\t\n 553:\t\tif (!node_state(node, N_MEMORY))\n 554:\t\t\treturn ERR_PTR(-EINVAL);\n 555:\t\n 556:\t\tmt_calc_adistance(node, \u0026adist);\n 557:\t\tif (!node_memory_types[node].memtype) {\n 558:\t\t\tmemtype = mt_find_alloc_memory_type(adist, \u0026default_memory_types);\n 559:\t\t\tif (IS_ERR(memtype)) {\n"
} |
| 23/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 14481 output: 23 thoughts: 75 Thoughts: **Diving into `mm/page_alloc.c`** Okay, let's get down to brass tacks and dissect `mm/page_alloc.c`. My immediate focus is on the function `find_next_best_node_in`. I need to understand its role in the grand scheme of things. So, the first question that pops into my head is: who is calling this particular function? What are its dependencies? I'm going to fire up grep and scan the entire kernel source tree, looking for all instances of `find_next_best_node_in`. That's the best way to determine its callers and, by extension, its context. Knowing where it's used is the first critical step to understanding its purpose and potential impact. |
| 24/2 | 2026/09/12 03:37 | tool | grepper |
0mArgs:{
"Expression": "find_next_best_node_in"
}Results: {
"Output": "mm/internal.h=1134=extern unsigned long node_reclaim(struct pglist_data *pgdat,\nmm/internal.h-1135-\t\t\t\t gfp_t gfp_mask, unsigned int order);\nmm/internal.h:1136:int find_next_best_node_in(int node, nodemask_t *used_node_mask,\nmm/internal.h-1137-\t\tconst nodemask_t *candidates);\n--\nmm/internal.h=1141=static inline unsigned long node_reclaim(struct pglist_data *pgdat,\n--\nmm/internal.h-1145-}\nmm/internal.h:1146:static inline int find_next_best_node_in(int node, nodemask_t *used_node_mask,\nmm/internal.h-1147-\t\tconst nodemask_t *candidates)\n--\nmm/memory-tiers.c=330=int next_demotion_node(int node, const nodemask_t *allowed_mask)\n--\nmm/memory-tiers.c-372-\tnodes_complement(mask, *allowed_mask);\nmm/memory-tiers.c:373:\treturn find_next_best_node_in(node, \u0026mask, \u0026node_states[N_MEMORY]);\nmm/memory-tiers.c-374-}\n--\nmm/memory-tiers.c=425=static void establish_demotion_targets(void)\n--\nmm/memory-tiers.c-452-\t\t/*\nmm/memory-tiers.c:453:\t\t * find_next_best_node_in, use 'used' nodemask as a skip list.\nmm/memory-tiers.c-454-\t\t * Add all memory nodes except the selected memory tier\n--\nmm/memory-tiers.c-465-\t\tdo {\nmm/memory-tiers.c:466:\t\t\ttarget = find_next_best_node_in(node, \u0026tier_nodes,\nmm/memory-tiers.c-467-\t\t\t\t\t\t\t\u0026node_states[N_MEMORY]);\n--\nmm/page_alloc.c=5793=static int node_load[MAX_NUMNODES];\n--\nmm/page_alloc.c-5795-/**\nmm/page_alloc.c:5796: * find_next_best_node_in - find the next node that should appear in a given node's fallback list\nmm/page_alloc.c-5797- * @node: node whose fallback list we're appending\n--\nmm/page_alloc.c-5810- */\nmm/page_alloc.c:5811:int find_next_best_node_in(int node, nodemask_t *used_node_mask,\nmm/page_alloc.c-5812-\t\t\t const nodemask_t *candidates)\n--\nmm/page_alloc.c=5880=static void build_node_zonelist(pg_data_t *pgdat, const nodemask_t *candidates,\n--\nmm/page_alloc.c-5890-\nmm/page_alloc.c:5891:\twhile ((node = find_next_best_node_in(local_node, \u0026used_mask,\nmm/page_alloc.c-5892-\t\t\t\t\t candidates)) \u003e= 0) {\n"
} |
| 25/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 15584 output: 26 thoughts: 48 Thoughts: Okay, let's break this down. **Analyzing Function Call Graphs** Alright, first things first. I need to make sure I haven't missed anything related to `find_next_best_node`. The implication is that I've been tracing the lineage of that function, probably to optimize or understand its usage. Good! Looks like no further instances of it are being called. That's a clean break point. Now, my focus shifts. I need to understand the dependencies around `build_zonelists` and `build_all_zonelists`. Who relies on these functions? Knowing their callers is crucial to understanding the data flow and any potential bottlenecks or areas for refactoring. I'm going to follow the call graph up to see what functions are affected by changes to these functions. |
| 26/2 | 2026/09/12 03:37 | tool | grepper |
0mArgs:{
"Expression": "build_zonelists",
"PathPrefix": "mm"
}Results: {
"Output": "mm/page_alloc.c=5880=static void build_node_zonelist(pg_data_t *pgdat, const nodemask_t *candidates,\n--\nmm/page_alloc.c-5911-\nmm/page_alloc.c:5912:static void build_zonelists(pg_data_t *pgdat)\nmm/page_alloc.c-5913-{\n--\nmm/page_alloc.c=5937=static void setup_min_slab_ratio(void);\n--\nmm/page_alloc.c-5939-\nmm/page_alloc.c:5940:static void build_zonelists(pg_data_t *pgdat)\nmm/page_alloc.c-5941-{\n--\nmm/page_alloc.c=5977=static void __build_all_zonelists(void *data)\n--\nmm/page_alloc.c-6005-\tif (self \u0026\u0026 !node_online(self-\u003enode_id)) {\nmm/page_alloc.c:6006:\t\tbuild_zonelists(self);\nmm/page_alloc.c-6007-\t} else {\n--\nmm/page_alloc.c-6014-\nmm/page_alloc.c:6015:\t\t\tbuild_zonelists(pgdat);\nmm/page_alloc.c-6016-\t\t}\n"
} |
| 27/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 16192 output: 21 thoughts: 46 Thoughts: Okay, let's break this down. **Investigating the Call Hierarchy of `__build_all_zonelists`** Right, so I see `__build_all_zonelists` is directly called by `build_all_zonelists`. That's the immediate relationship. Now, the real question is, where does `build_all_zonelists` itself fit into the larger picture? I need to understand the upstream dependencies. Where are *its* calling points? I need to trace back from `build_all_zonelists` to understand the bigger architecture it plays a role in. Let's find those calls. I expect to find some interesting things. |
| 28/2 | 2026/09/12 03:37 | tool | grepper |
0mArgs:{
"Expression": "build_all_zonelists"
}Results: {
"Output": "arch/x86/mm/numa.c=232=void __init x86_numa_init(void)\n--\narch/x86/mm/numa.c-256- * memoryless CPU nodes have already been brought online, and before the\narch/x86/mm/numa.c:257: * node_data[nid] is needed for zone list setup in build_all_zonelists().\narch/x86/mm/numa.c-258- *\n--\ninclude/linux/mmzone.h=1620=static inline unsigned long pgdat_end_pfn(pg_data_t *pgdat)\n--\ninclude/linux/mmzone.h-1626-\ninclude/linux/mmzone.h:1627:void build_all_zonelists(pg_data_t *pgdat);\ninclude/linux/mmzone.h-1628-bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,\n--\nmm/memory_hotplug.c=1140=int online_pages(unsigned long pfn, unsigned long nr_pages,\n--\nmm/memory_hotplug.c-1215-\tif (need_zonelists_rebuild)\nmm/memory_hotplug.c:1216:\t\tbuild_all_zonelists(NULL);\nmm/memory_hotplug.c-1217-\n--\nmm/memory_hotplug.c=1256=static pg_data_t *hotadd_init_pgdat(int nid)\n--\nmm/memory_hotplug.c-1275-\t */\nmm/memory_hotplug.c:1276:\tbuild_all_zonelists(pgdat);\nmm/memory_hotplug.c-1277-\n--\nmm/memory_hotplug.c=1986=int offline_pages(unsigned long start_pfn, unsigned long nr_pages,\n--\nmm/memory_hotplug.c-2170-\t\tzone_pcp_reset(zone);\nmm/memory_hotplug.c:2171:\t\tbuild_all_zonelists(NULL);\nmm/memory_hotplug.c-2172-\t}\n--\nmm/mm_init.c=2697=void __init mm_core_init(void)\n--\nmm/mm_init.c-2703-\tBUILD_BUG_ON(MAX_ZONELISTS \u003e 2);\nmm/mm_init.c:2704:\tbuild_all_zonelists(NULL);\nmm/mm_init.c-2705-\tpage_alloc_init_cpuhp();\n--\nmm/page_alloc.c=5975=static DEFINE_PER_CPU(struct per_cpu_zonestat, boot_zonestats);\nmm/page_alloc.c-5976-\nmm/page_alloc.c:5977:static void __build_all_zonelists(void *data)\nmm/page_alloc.c-5978-{\n--\nmm/page_alloc.c=6036=static noinline void __init\nmm/page_alloc.c:6037:build_all_zonelists_init(void)\nmm/page_alloc.c-6038-{\n--\nmm/page_alloc.c-6040-\nmm/page_alloc.c:6041:\t__build_all_zonelists(NULL);\nmm/page_alloc.c-6042-\n--\nmm/page_alloc.c-6065- *\nmm/page_alloc.c:6066: * __ref due to call of __init annotated helper build_all_zonelists_init\nmm/page_alloc.c-6067- * [protected by SYSTEM_BOOTING].\nmm/page_alloc.c-6068- */\nmm/page_alloc.c:6069:void __ref build_all_zonelists(pg_data_t *pgdat)\nmm/page_alloc.c-6070-{\n--\nmm/page_alloc.c-6073-\tif (system_state == SYSTEM_BOOTING) {\nmm/page_alloc.c:6074:\t\tbuild_all_zonelists_init();\nmm/page_alloc.c-6075-\t} else {\nmm/page_alloc.c:6076:\t\t__build_all_zonelists(pgdat);\nmm/page_alloc.c-6077-\t\t/* cpuset refresh routine should be here */\n"
} |
| 29/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 17556 output: 20 thoughts: 84 Thoughts: Here's my thought process, summarized as if I were considering the code: **Thinking Through Zonelist Initialization and Demotion** Okay, so `build_all_zonelists` is a critical function, clearly. It's called not just during the initial boot sequence via `mm_core_init`, but also dynamically when we're dealing with memory hotplug events: `online_pages`, `hotadd_init_pgdat`, and `offline_pages`. That makes sense; the zonelist structure has to be updated whenever the memory topology changes. But, I need to understand the full picture. My immediate question is about `establish_demotion_targets`. Where does *that* fit into the memory management lifecycle? When is *that* function being called? Given its name, it must play a part, and its execution context is important to analyze. Time to reach for the trusty `grep`. I'll run a quick search for `establish_demotion_targets` and see where it's being used within the kernel source. Knowing that should give me a more complete understanding of how memory demotion is set up. |
| 30/2 | 2026/09/12 03:37 | tool | grepper |
0mArgs:{
"Expression": "establish_demotion_targets"
}Results: {
"Output": "mm/memory-tiers.c=400=static void dump_demotion_targets(void)\n--\nmm/memory-tiers.c-424- */\nmm/memory-tiers.c:425:static void establish_demotion_targets(void)\nmm/memory-tiers.c-426-{\n--\nmm/memory-tiers.c-521-#else\nmm/memory-tiers.c:522:static inline void establish_demotion_targets(void) {}\nmm/memory-tiers.c-523-#endif /* CONFIG_NUMA_MIGRATION */\n--\nmm/memory-tiers.c=708=static int __init memory_tier_late_init(void)\n--\nmm/memory-tiers.c-731-\nmm/memory-tiers.c:732:\testablish_demotion_targets();\nmm/memory-tiers.c-733-\tput_online_mems();\n--\nmm/memory-tiers.c=882=static int __meminit memtier_hotplug_callback(struct notifier_block *self,\n--\nmm/memory-tiers.c-891-\t\tif (clear_node_memory_tier(nn-\u003enid))\nmm/memory-tiers.c:892:\t\t\testablish_demotion_targets();\nmm/memory-tiers.c-893-\t\tmutex_unlock(\u0026memory_tier_lock);\n--\nmm/memory-tiers.c-898-\t\tif (!IS_ERR(memtier))\nmm/memory-tiers.c:899:\t\t\testablish_demotion_targets();\nmm/memory-tiers.c-900-\t\tmutex_unlock(\u0026memory_tier_lock);\n"
} |
| 31/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 18321 output: 35 thoughts: 72 Thoughts: Here's my summary, as though I'm thinking through this myself: **Tracing Down `next_demotion_node`** Okay, so I'm digging into this memory management stuff, and I've hit a point where I need to understand `next_demotion_node`. Where does this get called, exactly? Let's see... Aha! It looks like `next_demotion_node` is invoked from `demote_folio_list`. Right, and that function lives in `mm/vmscan.c`. Now we're getting somewhere. I need to understand the context of the call to `next_demotion_node`, so I'm going to jump into `demote_folio_list` in `mm/vmscan.c` and see how *it* is used. That will give me the broader picture of why `next_demotion_node` is relevant here. Let's see what we find! |
| 32/2 | 2026/09/12 03:37 | tool | read-file |
0mArgs:{
"File": "mm/vmscan.c",
"FirstLine": 1070,
"LineCount": 40
}Results: {
"Contents": "1070:\t */\n1071:\tstatic unsigned int demote_folio_list(struct list_head *demote_folios,\n1072:\t\t\t\t\t struct pglist_data *pgdat,\n1073:\t\t\t\t\t struct mem_cgroup *memcg)\n1074:\t{\n1075:\t\tint target_nid;\n1076:\t\tunsigned int nr_succeeded;\n1077:\t\tnodemask_t allowed_mask;\n1078:\t\n1079:\t\tstruct migration_target_control mtc = {\n1080:\t\t\t/*\n1081:\t\t\t * Allocate from 'node', or fail quickly and quietly.\n1082:\t\t\t * When this happens, 'page' will likely just be discarded\n1083:\t\t\t * instead of migrated.\n1084:\t\t\t */\n1085:\t\t\t.gfp_mask = (GFP_HIGHUSER_MOVABLE \u0026 ~__GFP_RECLAIM) |\n1086:\t\t\t\t__GFP_NOMEMALLOC | GFP_NOWAIT,\n1087:\t\t\t.nmask = \u0026allowed_mask,\n1088:\t\t\t.reason = MR_DEMOTION,\n1089:\t\t};\n1090:\t\n1091:\t\tif (list_empty(demote_folios))\n1092:\t\t\treturn 0;\n1093:\t\n1094:\t\tnode_get_allowed_targets(pgdat, \u0026allowed_mask);\n1095:\t\tmem_cgroup_node_filter_allowed(memcg, \u0026allowed_mask);\n1096:\t\tif (nodes_empty(allowed_mask))\n1097:\t\t\treturn 0;\n1098:\t\n1099:\t\ttarget_nid = next_demotion_node(pgdat-\u003enode_id, \u0026allowed_mask);\n1100:\t\tif (target_nid == NUMA_NO_NODE)\n1101:\t\t\t/* No lower-tier nodes or nodes were hot-unplugged. */\n1102:\t\t\treturn 0;\n1103:\t\n1104:\t\tmtc.nid = target_nid;\n1105:\t\n1106:\t\t/* Demotion ignores all cpuset and mempolicy settings */\n1107:\t\tmigrate_pages(demote_folios, alloc_demote_folio, NULL,\n1108:\t\t\t (unsigned long)\u0026mtc, MIGRATE_ASYNC, MR_DEMOTION,\n1109:\t\t\t \u0026nr_succeeded);\n"
} |
| 33/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 19271 output: 28 thoughts: 1441 Thoughts: **Analyzing Zonelist Changes for Memory Management and Fuzzing Relevance** Okay, so I'm looking at this patch and immediately, my expert mind flags `demote_folio_list` as part of page reclamation—specifically, the demotion process when memory pressure hits. Pages get shuffled down the memory hierarchy. The core of this seems to be how the fallback order for `node_zonelists[ZONELIST_FALLBACK]._zonerefs` is constructed, mainly through `build_node_zonelist` and the broader `build_zonelists` functions. This `ZONELIST_FALLBACK` is *crucial* because it's used by every allocation that needs to fall back across NUMA nodes. I see a clear shift here. The old `build_zonelists_in_node_order` was pretty straightforward, iterating over nodes in a set order. Now, `build_node_zonelist` is using `find_next_best_node_in()` and a `candidates` nodemask. This `candidates` mask is *key*. Before, it used `N_MEMORY`. It looks like we're being far more precise about *which* nodes are considered, which is a big change! I need to dive into `find_next_best_node_in()`. The difference is that it now uses that `candidates` mask, which is great because callers can now pass in a restricted nodemask. I see this happening in the `memory-tiers` code, in `next_demotion_node()` and `establish_demotion_targets()`. The previous code was more of a blunt instrument, and this is far more targeted. Okay, now let's apply the fuzzing criteria. This patch is *definitely* in `mm/` – memory management. It's changing core zonelist building logic, specifically how we're calculating which node to use in page reclaim (and in particular, demotion). This directly affects `build_node_zonelist` and the `find_next_best_node_in` function in `mm/page_alloc.c`, along with updates to the demotion target calculation in `mm/memory-tiers.c`. Those are *exactly* the kind of core subsystem and algorithm flow changes that the fuzzing criteria flag. The question then becomes, is this patch code reachable in a fuzzer friendly environment? And the answer is absolutely yes! I can easily configure NUMA nodes in QEMU (I use it all the time). Syzkaller often runs with NUMA enabled, too. And crucially, memory hotplug/mempolicy syscalls (e.g., `set_mempolicy`, `mbind`, `migrate_pages`, `move_pages`) and page reclaim demotion definitely run this code. So this is great! Finally, I need to double-check something – is the `numa_zonelist_order_handler` sysctl still around? I'd expect it is as `build_all_zonelists` will use its order. I'll need to double check that. But everything so far strongly suggests this patch is *highly* fuzzable. |
| 34/2 | 2026/09/12 03:37 | tool | grepper |
0mArgs:{
"Expression": "numa_zonelist_order",
"PathPrefix": "mm"
}Results: {
"Output": "mm/page_alloc.c=5745=static int build_zonerefs_node(pg_data_t *pgdat, struct zoneref *zonerefs)\n--\nmm/page_alloc.c-5764-\nmm/page_alloc.c:5765:static int __parse_numa_zonelist_order(char *s)\nmm/page_alloc.c-5766-{\n--\nmm/page_alloc.c-5773-\tif (!(*s == 'd' || *s == 'D' || *s == 'n' || *s == 'N')) {\nmm/page_alloc.c:5774:\t\tpr_warn(\"Ignoring unsupported numa_zonelist_order value: %s\\n\", s);\nmm/page_alloc.c-5775-\t\treturn -EINVAL;\n--\nmm/page_alloc.c-5779-\nmm/page_alloc.c:5780:static char numa_zonelist_order[] = \"Node\";\nmm/page_alloc.c-5781-#define NUMA_ZONELIST_ORDER_LEN\t16\nmm/page_alloc.c-5782-/*\nmm/page_alloc.c:5783: * sysctl handler for numa_zonelist_order\nmm/page_alloc.c-5784- */\nmm/page_alloc.c:5785:static int numa_zonelist_order_handler(const struct ctl_table *table, int write,\nmm/page_alloc.c-5786-\t\tvoid *buffer, size_t *length, loff_t *ppos)\n--\nmm/page_alloc.c-5788-\tif (write)\nmm/page_alloc.c:5789:\t\treturn __parse_numa_zonelist_order(buffer);\nmm/page_alloc.c-5790-\treturn proc_dostring(table, write, buffer, length, ppos);\n--\nmm/page_alloc.c=6918=static const struct ctl_table page_alloc_sysctl_table[] = {\n--\nmm/page_alloc.c-6970-\t{\nmm/page_alloc.c:6971:\t\t.procname\t= \"numa_zonelist_order\",\nmm/page_alloc.c:6972:\t\t.data\t\t= \u0026numa_zonelist_order,\nmm/page_alloc.c-6973-\t\t.maxlen\t\t= NUMA_ZONELIST_ORDER_LEN,\nmm/page_alloc.c-6974-\t\t.mode\t\t= 0644,\nmm/page_alloc.c:6975:\t\t.proc_handler\t= numa_zonelist_order_handler,\nmm/page_alloc.c-6976-\t},\n"
} |
| 35/2 | 2026/09/12 03:37 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 22121 output: 21 thoughts: 214 Thoughts: **My Analysis of Zonelist Construction and Configuration** Okay, so I need to understand what's kicking off this `build_all_zonelists` function. My initial thought is it's tied to changes in the memory topology, right? Like, sysfs entries for online/offline memory pages – the usual suspects at `/sys/devices/system/memory/...`. Also, it's gotta be involved with hot-add memory operations, obviously. And, of course, the `next_demotion_node` function, which I know is a key part of memory reclaim, specifically when we're demoting pages within `demote_folio_list`. Then there's `establish_demotion_targets`, called when there's a shift in memory tiers, or also on hotplug events. Finally, zonelists get a build at boot, too, which makes sense. Right, so what configurations are absolutely essential for this whole process? Let me check the code. Alright, looking at `mm/memory-tiers.c`, I see a clear dependency: `obj-$(CONFIG_NUMA) += memory-tiers.o`. Makes sense, we need NUMA support. And *crucially*, it looks like the presence of `#ifdef CONFIG_NUMA_MIGRATION` in `mm/memory-tiers.c` is what guards both `next_demotion_node` and `establish_demotion_targets`. That's the linchpin. So, the key is going to be `CONFIG_NUMA_MIGRATION`, and, of course, `CONFIG_NUMA`. Let me go check Kconfig to be sure I understand the full scope of these. |
| 36/2 | 2026/09/12 03:38 | tool | grepper |
0mArgs:{
"Expression": "config NUMA_MIGRATION"
}Results: {
"Output": "mm/Kconfig=660=config PAGE_REPORTING\n--\nmm/Kconfig-667-\nmm/Kconfig:668:config NUMA_MIGRATION\nmm/Kconfig-669-\tbool \"NUMA page migration\"\n"
} |
| 37/2 | 2026/09/12 03:38 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 22789 output: 32 thoughts: 29 Thoughts: Here's my thinking process: **Diving into the NUMA_MIGRATION Configuration** Alright, let's get down to brass tacks. I need to understand the configuration dependencies of `NUMA_MIGRATION`. My immediate thought is to check the `mm/Kconfig` file, specifically around line 668. That's usually where the relevant Kconfig options reside. By examining that section, I should be able to unravel the conditions under which `NUMA_MIGRATION` is enabled or disabled. Hopefully, this will give me a clear picture of what other features or options need to be in place for this particular NUMA migration functionality to be available. I'm expecting to see dependencies on the NUMA architecture itself, and potentially on other memory management features. I'll need to pay close attention to the `depends on` statements to get the full picture. |
| 38/2 | 2026/09/12 03:38 | tool | read-file |
0mArgs:{
"File": "mm/Kconfig",
"FirstLine": 665,
"LineCount": 20
}Results: {
"Contents": " 665:\t\t those pages to another entity, such as a hypervisor, so that the\n 666:\t\t memory can be freed within the host for other uses.\n 667:\t\n 668:\tconfig NUMA_MIGRATION\n 669:\t\tbool \"NUMA page migration\"\n 670:\t\tdefault y\n 671:\t\tdepends on NUMA \u0026\u0026 MMU\n 672:\t\tselect MIGRATION\n 673:\t\thelp\n 674:\t\t Support the migration of pages to other NUMA nodes, available to\n 675:\t\t user space through interfaces like migrate_pages(), move_pages(),\n 676:\t\t and mbind(). Selecting this option also enables support for page\n 677:\t\t demotion for memory tiering.\n 678:\t\n 679:\tconfig MIGRATION\n 680:\t\tbool\n 681:\t\tdepends on MMU\n 682:\t\n 683:\tconfig DEVICE_MIGRATION\n 684:\t\tdef_bool MIGRATION \u0026\u0026 ZONE_DEVICE\n"
} |
| 39/2 | 2026/09/12 03:38 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 23321 output: 36 thoughts: 74 Thoughts: **Delving into NUMA Migration Dependencies** Okay, so I'm thinking about `NUMA_MIGRATION` and, naturally, it leans on both `NUMA` and the `MMU`. That makes sense, right? It wouldn't be able to migrate without those underlying structures. But now my mind is starting to wander a bit. I need to make sure I understand the full context here. That's when I wonder about `find_next_best_node_in` within `mm/page_alloc.c`. I have a feeling I need to circle back to what gates that function. Let's see what guards that function in `mm/page_alloc.c`. |
| 40/2 | 2026/09/12 03:38 | tool | read-file |
0mArgs:{
"File": "mm/page_alloc.c",
"FirstLine": 5790,
"LineCount": 25
}Results: {
"Contents": "5790:\t\treturn proc_dostring(table, write, buffer, length, ppos);\n5791:\t}\n5792:\t\n5793:\tstatic int node_load[MAX_NUMNODES];\n5794:\t\n5795:\t/**\n5796:\t * find_next_best_node_in - find the next node that should appear in a given node's fallback list\n5797:\t * @node: node whose fallback list we're appending\n5798:\t * @used_node_mask: nodemask_t of already used nodes\n5799:\t * @candidates: nodemask_t of nodes eligible for selection\n5800:\t *\n5801:\t * We use a number of factors to determine which is the next node that should\n5802:\t * appear on a given node's fallback list. The node should not have appeared\n5803:\t * already in @node's fallback list, and it should be the next closest node\n5804:\t * according to the distance array (which contains arbitrary distance values\n5805:\t * from each node to each node in the system), and should also prefer nodes\n5806:\t * with no CPUs, since presumably they'll have very little allocation pressure\n5807:\t * on them otherwise.\n5808:\t *\n5809:\t * Return: node id of the found node or %NUMA_NO_NODE if no node is found.\n5810:\t */\n5811:\tint find_next_best_node_in(int node, nodemask_t *used_node_mask,\n5812:\t\t\t\t const nodemask_t *candidates)\n5813:\t{\n5814:\t\tint n, val;\n"
} |
| 41/2 | 2026/09/12 03:38 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 24036 output: 30 thoughts: 50 Thoughts: **Investigating the Conditional Compilation in `mm/page_alloc.c`** Okay, so I need to figure out what preprocessor directives are controlling line 5790 in `mm/page_alloc.c`. This is a pretty common debugging step; understanding the conditional compilation can be crucial. My first thought is to just dive into the file. I’ll search backwards from line 5790, looking for the relevant `#if` or `#ifdef` statement that encloses it. Hopefully, it's a relatively short span to identify the relevant condition. |
| 42/2 | 2026/09/12 03:38 | tool | grepper |
0mArgs:{
"Expression": "^#if",
"PathPrefix": "mm/page_alloc.c"
}Results: {
"Output": "mm/page_alloc.c=99=static DEFINE_MUTEX(pcp_batch_high_lock);\n--\nmm/page_alloc.c-109- */\nmm/page_alloc.c:110:#ifndef CONFIG_PREEMPT_RT\nmm/page_alloc.c-111-#define pcpu_task_pin()\t\tpreempt_disable()\n--\nmm/page_alloc.c-122- */\nmm/page_alloc.c:123:#ifdef CONFIG_SMP\nmm/page_alloc.c-124-#define pcp_spin_trylock(ptr)\t\t\t\t\t\t\\\n--\nmm/page_alloc.c-164-\nmm/page_alloc.c:165:#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID\nmm/page_alloc.c-166-DEFINE_PER_CPU(int, numa_node);\nmm/page_alloc.c=167=EXPORT_PER_CPU_SYMBOL(numa_node);\n--\nmm/page_alloc.c-169-\nmm/page_alloc.c:170:#ifdef CONFIG_NUMA\nmm/page_alloc.c-171-DEFINE_STATIC_KEY_TRUE(vm_numa_stat_key);\n--\nmm/page_alloc.c-173-\nmm/page_alloc.c:174:#ifdef CONFIG_HAVE_MEMORYLESS_NODES\nmm/page_alloc.c-175-/*\n--\nmm/page_alloc.c=185=static DEFINE_MUTEX(pcpu_drain_mutex);\nmm/page_alloc.c-186-\nmm/page_alloc.c:187:#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY\nmm/page_alloc.c-188-volatile unsigned long latent_entropy __latent_entropy;\n--\nmm/page_alloc.c=195=nodemask_t node_states[NR_NODE_STATES] __read_mostly = {\n--\nmm/page_alloc.c-197-\t[N_ONLINE] = { { [0] = 1UL } },\nmm/page_alloc.c:198:#ifndef CONFIG_NUMA\nmm/page_alloc.c-199-\t[N_NORMAL_MEMORY] = { { [0] = 1UL } },\nmm/page_alloc.c:200:#ifdef CONFIG_HIGHMEM\nmm/page_alloc.c-201-\t[N_HIGH_MEMORY] = { { [0] = 1UL } },\n--\nmm/page_alloc.c=209=gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;\nmm/page_alloc.c-210-\nmm/page_alloc.c:211:#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE\nmm/page_alloc.c-212-unsigned int pageblock_order __read_mostly;\n--\nmm/page_alloc.c=231=static int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES] = {\nmm/page_alloc.c:232:#ifdef CONFIG_ZONE_DMA\nmm/page_alloc.c-233-\t[ZONE_DMA] = 256,\nmm/page_alloc.c-234-#endif\nmm/page_alloc.c:235:#ifdef CONFIG_ZONE_DMA32\nmm/page_alloc.c-236-\t[ZONE_DMA32] = 256,\n--\nmm/page_alloc.c-238-\t[ZONE_NORMAL] = 32,\nmm/page_alloc.c:239:#ifdef CONFIG_HIGHMEM\nmm/page_alloc.c-240-\t[ZONE_HIGHMEM] = 0,\n--\nmm/page_alloc.c=245=char * const zone_names[MAX_NR_ZONES] = {\nmm/page_alloc.c:246:#ifdef CONFIG_ZONE_DMA\nmm/page_alloc.c-247-\t \"DMA\",\nmm/page_alloc.c-248-#endif\nmm/page_alloc.c:249:#ifdef CONFIG_ZONE_DMA32\nmm/page_alloc.c-250-\t \"DMA32\",\n--\nmm/page_alloc.c-252-\t \"Normal\",\nmm/page_alloc.c:253:#ifdef CONFIG_HIGHMEM\nmm/page_alloc.c-254-\t \"HighMem\",\n--\nmm/page_alloc.c-256-\t \"Movable\",\nmm/page_alloc.c:257:#ifdef CONFIG_ZONE_DEVICE\nmm/page_alloc.c-258-\t \"Device\",\n--\nmm/page_alloc.c=262=const char * const migratetype_names[MIGRATE_TYPES] = {\n--\nmm/page_alloc.c-266-\t\"HighAtomic\",\nmm/page_alloc.c:267:#ifdef CONFIG_CMA\nmm/page_alloc.c-268-\t\"CMA\",\nmm/page_alloc.c-269-#endif\nmm/page_alloc.c:270:#ifdef CONFIG_MEMORY_ISOLATION\nmm/page_alloc.c-271-\t\"Isolate\",\n--\nmm/page_alloc.c=283=EXPORT_SYMBOL(movable_zone);\nmm/page_alloc.c-284-\nmm/page_alloc.c:285:#if MAX_NUMNODES \u003e 1\nmm/page_alloc.c-286-unsigned int nr_node_ids __read_mostly = MAX_NUMNODES;\n--\nmm/page_alloc.c=305=int page_group_by_mobility_disabled __read_mostly;\nmm/page_alloc.c-306-\nmm/page_alloc.c:307:#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT\nmm/page_alloc.c-308-/*\n--\nmm/page_alloc.c=334=static inline unsigned long *get_pageblock_bitmap(const struct page *page,\n--\nmm/page_alloc.c-336-{\nmm/page_alloc.c:337:#ifdef CONFIG_SPARSEMEM\nmm/page_alloc.c-338-\treturn section_to_usemap(__pfn_to_section(pfn));\n--\nmm/page_alloc.c=344=static inline int pfn_to_bitidx(const struct page *page, unsigned long pfn)\nmm/page_alloc.c-345-{\nmm/page_alloc.c:346:#ifdef CONFIG_SPARSEMEM\nmm/page_alloc.c-347-\tpfn \u0026= (PAGES_PER_SECTION-1);\n--\nmm/page_alloc.c=360=get_pfnblock_bitmap_bitidx(const struct page *page, unsigned long pfn,\n--\nmm/page_alloc.c-365-\nmm/page_alloc.c:366:#ifdef CONFIG_MEMORY_ISOLATION\nmm/page_alloc.c-367-\tBUILD_BUG_ON(NR_PAGEBLOCK_BITS != 8);\n--\nmm/page_alloc.c=442=get_pfnblock_migratetype(const struct page *page, unsigned long pfn)\n--\nmm/page_alloc.c-448-\nmm/page_alloc.c:449:#ifdef CONFIG_MEMORY_ISOLATION\nmm/page_alloc.c-450-\tif (flags \u0026 BIT(PB_migrate_isolate))\n--\nmm/page_alloc.c=526=static void set_pageblock_migratetype(struct page *page,\n--\nmm/page_alloc.c-532-\nmm/page_alloc.c:533:#ifdef CONFIG_MEMORY_ISOLATION\nmm/page_alloc.c-534-\tif (migratetype == MIGRATE_ISOLATE) {\n--\nmm/page_alloc.c=548=void __meminit init_pageblock_migratetype(struct page *page,\n--\nmm/page_alloc.c-559-\nmm/page_alloc.c:560:#ifdef CONFIG_MEMORY_ISOLATION\nmm/page_alloc.c-561-\tif (migratetype == MIGRATE_ISOLATE) {\n--\nmm/page_alloc.c-573-\nmm/page_alloc.c:574:#ifdef CONFIG_DEBUG_VM\nmm/page_alloc.c-575-static int page_outside_zone_boundaries(struct zone *zone, struct page *page)\n--\nmm/page_alloc.c=661=static inline bool pcp_allowed_order(unsigned int order)\n--\nmm/page_alloc.c-664-\t\treturn true;\nmm/page_alloc.c:665:#ifdef CONFIG_TRANSPARENT_HUGEPAGE\nmm/page_alloc.c-666-\tif (is_pmd_order(order))\n--\nmm/page_alloc.c=696=static inline void set_buddy_order(struct page *page, unsigned int order)\n--\nmm/page_alloc.c-701-\nmm/page_alloc.c:702:#ifdef CONFIG_COMPACTION\nmm/page_alloc.c-703-static inline struct capture_control *task_capc(struct zone *zone)\n--\nmm/page_alloc.c=1015=static inline bool page_expected_state(struct page *page,\n--\nmm/page_alloc.c-1022-\t\t\tpage_ref_count(page) |\nmm/page_alloc.c:1023:#ifdef CONFIG_MEMCG\nmm/page_alloc.c-1024-\t\t\tpage-\u003ememcg_data |\n--\nmm/page_alloc.c=1033=static const char *page_bad_reason(struct page *page, unsigned long flags)\n--\nmm/page_alloc.c-1048-\t}\nmm/page_alloc.c:1049:#ifdef CONFIG_MEMCG\nmm/page_alloc.c-1050-\tif (unlikely(page-\u003ememcg_data))\n--\nmm/page_alloc.c=1202=static void clear_highpages_kasan_tagged(struct page *page, int numpages)\n--\nmm/page_alloc.c-1216-\nmm/page_alloc.c:1217:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/page_alloc.c-1218-\n--\nmm/page_alloc.c=1298=static __always_inline bool __free_pages_prepare(struct page *page,\n--\nmm/page_alloc.c-1357-\t\t\tpage[1].flags.f \u0026= ~PAGE_FLAGS_SECOND;\nmm/page_alloc.c:1358:#ifdef NR_PAGES_IN_LARGE_FOLIO\nmm/page_alloc.c-1359-\t\t\tfolio-\u003e_nr_pages = 0;\n--\nmm/page_alloc.c=1915=static int fallbacks[MIGRATE_PCPTYPES][MIGRATE_PCPTYPES - 1] = {\n--\nmm/page_alloc.c-1920-\nmm/page_alloc.c:1921:#ifdef CONFIG_CMA\nmm/page_alloc.c-1922-static __always_inline struct page *__rmqueue_cma_fallback(struct zone *zone,\n--\nmm/page_alloc.c=2019=static int move_freepages_block(struct zone *zone, struct page *page,\n--\nmm/page_alloc.c-2034-\nmm/page_alloc.c:2035:#ifdef CONFIG_MEMORY_ISOLATION\nmm/page_alloc.c-2036-/* Look for a buddy that straddles start_pfn */\n--\nmm/page_alloc.c=2558=bool decay_pcp_high(struct zone *zone, struct per_cpu_pages *pcp)\n--\nmm/page_alloc.c-2590-\nmm/page_alloc.c:2591:#ifdef CONFIG_NUMA\nmm/page_alloc.c-2592-/*\n--\nmm/page_alloc.c=3179=static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,\n--\nmm/page_alloc.c-3181-{\nmm/page_alloc.c:3182:#ifdef CONFIG_NUMA\nmm/page_alloc.c-3183-\tenum numa_stat_item local_stat = NUMA_LOCAL;\n--\nmm/page_alloc.c=3553=static inline long __zone_watermark_unusable_free(struct zone *z,\n--\nmm/page_alloc.c-3564-\nmm/page_alloc.c:3565:#ifdef CONFIG_CMA\nmm/page_alloc.c-3566-\t/* If allocation can't use CMA areas don't use free CMA pages */\n--\nmm/page_alloc.c=3580=bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,\n--\nmm/page_alloc.c-3643-\nmm/page_alloc.c:3644:#ifdef CONFIG_CMA\nmm/page_alloc.c-3645-\t\tif ((alloc_flags \u0026 ALLOC_CMA) \u0026\u0026\n--\nmm/page_alloc.c=3665=static inline bool zone_watermark_fast(struct zone *z, unsigned int order,\n--\nmm/page_alloc.c-3709-\nmm/page_alloc.c:3710:#ifdef CONFIG_NUMA\nmm/page_alloc.c-3711-int __read_mostly node_reclaim_distance = RECLAIM_DISTANCE;\n--\nmm/page_alloc.c=3734=alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask)\n--\nmm/page_alloc.c-3745-\nmm/page_alloc.c:3746:#ifdef CONFIG_ZONE_DMA32\nmm/page_alloc.c-3747-\tif (!zone)\n--\nmm/page_alloc.c=3768=static inline unsigned int alloc_flags_cma(gfp_t gfp_mask)\nmm/page_alloc.c-3769-{\nmm/page_alloc.c:3770:#ifdef CONFIG_CMA\nmm/page_alloc.c-3771-\tif (gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)\n--\nmm/page_alloc.c=4026=__alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-4117-\nmm/page_alloc.c:4118:#ifdef CONFIG_COMPACTION\nmm/page_alloc.c-4119-/* Try memory compaction for high-order allocations before reclaim */\n--\nmm/page_alloc.c=4307=should_compact_retry(gfp_t gfp_mask, struct alloc_context *ac, int order,\n--\nmm/page_alloc.c-4334-\nmm/page_alloc.c:4335:#ifdef CONFIG_LOCKDEP\nmm/page_alloc.c-4336-static struct lockdep_map __fs_reclaim_map =\n--\nmm/page_alloc.c=4365=void fs_reclaim_acquire(gfp_t gfp_mask)\n--\nmm/page_alloc.c-4372-\nmm/page_alloc.c:4373:#ifdef CONFIG_MMU_NOTIFIER\nmm/page_alloc.c-4374-\t\tlock_map_acquire(\u0026__mmu_notifier_invalidate_range_start_map);\n--\nmm/page_alloc.c=5154=unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,\n--\nmm/page_alloc.c-5189-\nmm/page_alloc.c:5190:#ifdef CONFIG_PAGE_OWNER\nmm/page_alloc.c-5191-\t/*\n--\nmm/page_alloc.c=5745=static int build_zonerefs_node(pg_data_t *pgdat, struct zoneref *zonerefs)\n--\nmm/page_alloc.c-5762-\nmm/page_alloc.c:5763:#ifdef CONFIG_NUMA\nmm/page_alloc.c-5764-\n--\nmm/page_alloc.c=5912=static void build_zonelists(pg_data_t *pgdat)\n--\nmm/page_alloc.c-5917-\nmm/page_alloc.c:5918:#ifdef CONFIG_HAVE_MEMORYLESS_NODES\nmm/page_alloc.c-5919-/*\n--\nmm/page_alloc.c=5977=static void __build_all_zonelists(void *data)\n--\nmm/page_alloc.c-5996-\nmm/page_alloc.c:5997:#ifdef CONFIG_NUMA\nmm/page_alloc.c-5998-\tmemset(node_load, 0, sizeof(node_load));\n--\nmm/page_alloc.c-6017-\nmm/page_alloc.c:6018:#ifdef CONFIG_HAVE_MEMORYLESS_NODES\nmm/page_alloc.c-6019-\t\t/*\n--\nmm/page_alloc.c=6069=void __ref build_all_zonelists(pg_data_t *pgdat)\n--\nmm/page_alloc.c-6096-\t\tvm_total_pages);\nmm/page_alloc.c:6097:#ifdef CONFIG_NUMA\nmm/page_alloc.c-6098-\tpr_info(\"Policy zone: %s\\n\", zone_names[policy_zone]);\n--\nmm/page_alloc.c=6102=static int zone_batchsize(struct zone *zone)\nmm/page_alloc.c-6103-{\nmm/page_alloc.c:6104:#ifdef CONFIG_MMU\nmm/page_alloc.c-6105-\tint batch;\n--\nmm/page_alloc.c=6150=static int zone_highsize(struct zone *zone, int batch, int cpu_online,\n--\nmm/page_alloc.c-6152-{\nmm/page_alloc.c:6153:#ifdef CONFIG_MMU\nmm/page_alloc.c-6154-\tint high;\n--\nmm/page_alloc.c=6360=void __init setup_per_cpu_pageset(void)\n--\nmm/page_alloc.c-6368-\nmm/page_alloc.c:6369:#ifdef CONFIG_NUMA\nmm/page_alloc.c-6370-\t/*\n--\nmm/page_alloc.c=6723=int __meminit init_per_zone_wmark_min(void)\n--\nmm/page_alloc.c-6729-\nmm/page_alloc.c:6730:#ifdef CONFIG_NUMA\nmm/page_alloc.c-6731-\tsetup_min_unmapped_ratio();\n--\nmm/page_alloc.c=6762=static int watermark_scale_factor_sysctl_handler(const struct ctl_table *table, int write,\n--\nmm/page_alloc.c-6776-\nmm/page_alloc.c:6777:#ifdef CONFIG_NUMA\nmm/page_alloc.c-6778-static void setup_min_unmapped_ratio(void)\n--\nmm/page_alloc.c=6918=static const struct ctl_table page_alloc_sysctl_table[] = {\n--\nmm/page_alloc.c-6968-\t},\nmm/page_alloc.c:6969:#ifdef CONFIG_NUMA\nmm/page_alloc.c-6970-\t{\n--\nmm/page_alloc.c=7097=void __free_contig_range(unsigned long pfn, unsigned long nr_pages)\n--\nmm/page_alloc.c-7101-\nmm/page_alloc.c:7102:#ifdef CONFIG_CONTIG_ALLOC\nmm/page_alloc.c-7103-/* Usage: See admin-guide/dynamic-debug-howto.rst */\n--\nmm/page_alloc.c=7674=void zone_pcp_reset(struct zone *zone)\n--\nmm/page_alloc.c-7692-\nmm/page_alloc.c:7693:#ifdef CONFIG_MEMORY_HOTREMOVE\nmm/page_alloc.c-7694-/*\n--\nmm/page_alloc.c=7766=EXPORT_SYMBOL(is_free_buddy_page);\nmm/page_alloc.c-7767-\nmm/page_alloc.c:7768:#ifdef CONFIG_MEMORY_FAILURE\nmm/page_alloc.c-7769-static inline void add_to_free_list(struct page *page, struct zone *zone,\n--\nmm/page_alloc.c=7861=bool has_managed_zone(enum zone_type zone)\n--\nmm/page_alloc.c-7871-\nmm/page_alloc.c:7872:#ifdef CONFIG_UNACCEPTED_MEMORY\nmm/page_alloc.c-7873-\n"
} |
| 43/2 | 2026/09/12 03:38 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 29625 output: 36 thoughts: 53 Thoughts: **Investigating a Conditional Compilation Block** Okay, so line 5763 of this code has a `#ifdef CONFIG_NUMA` directive. My immediate thought is, "Right, I need to figure out the scope of that conditional compilation." It's crucial for understanding how the NUMA-aware memory allocation works in this specific context. The first thing I'm going to do is locate where that `#ifdef` block terminates. Given the likely structure of the code, I'll bet it's not far from the line. My focus now is on lines 5930-5945 within `mm/page_alloc.c`, I'll start there looking for the corresponding `#endif` statement and any intervening code that's conditionally compiled under the NUMA config. I need to understand what's *inside* that block to get a full picture of the impact of the NUMA configuration. |
| 44/2 | 2026/09/12 03:38 | tool | read-file |
0mArgs:{
"File": "mm/page_alloc.c",
"FirstLine": 5930,
"LineCount": 20
}Results: {
"Contents": "5930:\t\t\t\t\t gfp_zone(GFP_KERNEL),\n5931:\t\t\t\t\t NULL);\n5932:\t\treturn zonelist_node_idx(z);\n5933:\t}\n5934:\t#endif\n5935:\t\n5936:\tstatic void setup_min_unmapped_ratio(void);\n5937:\tstatic void setup_min_slab_ratio(void);\n5938:\t#else\t/* CONFIG_NUMA */\n5939:\t\n5940:\tstatic void build_zonelists(pg_data_t *pgdat)\n5941:\t{\n5942:\t\tstruct zoneref *zonerefs;\n5943:\t\tint nr_zones;\n5944:\t\n5945:\t\tzonerefs = pgdat-\u003enode_zonelists[ZONELIST_FALLBACK]._zonerefs;\n5946:\t\tnr_zones = build_zonerefs_node(pgdat, zonerefs);\n5947:\t\tzonerefs += nr_zones;\n5948:\t\n5949:\t\tzonerefs-\u003ezone = NULL;\n"
} |
| 45/2 | 2026/09/12 03:38 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 30210 output: 33 thoughts: 1237 Thoughts: **Focusing on NUMA Memory Management for Fuzzing** Alright, let's break this down. My initial thought is that the code in `mm/memory-tiers.c` and `mm/page_alloc.c` looks interesting, especially considering it's under `#ifdef CONFIG_NUMA` and specifically, `next_demotion_node` is protected by `#ifdef CONFIG_NUMA_MIGRATION`, which implies it's relevant to NUMA and memory migration. So, both `CONFIG_NUMA` and `CONFIG_NUMA_MIGRATION` are the relevant configurations. Now, is this code even worth fuzzing? Definitely. This is core memory management logic within the `mm/` subsystem. I've got changes to `find_next_best_node_in` and `build_node_zonelist` in `mm/page_alloc.c`, and `next_demotion_node` and `establish_demotion_targets` in `mm/memory-tiers.c`. Crucially, this code is reachable in a NUMA-enabled kernel running in QEMU because `build_node_zonelist` (or `build_zonelists`) is executed at boot, during memory hotplug and when triggered by memory pressure, the `next_demotion_node` will be called during memory reclaim. Furthermore, `establish_demotion_targets` is called at boot and on hotplug / sysfs memory tier operations. This directly impacts how NUMA zonelists are built and how we select nodes for fallback and demotion, which is exactly the kind of refactoring and logic change the fuzzing guidelines highlight as a high-value target. It's a clear 'WorthFuzzing=true'. So, let's get into the specifics of FocusSymbols. I'm following the guidelines, which says to avoid ubiquitous hot-paths and instead target specific feature logic and entrypoints. Here’s the current thinking: 1. `find_next_best_node_in` in `mm/page_alloc.c`. This is non-static (declared in `mm/internal.h` and defined in `mm/page_alloc.c`) and is only called when building zonelists or finding demotion targets, so it's not ubiquitous. Definitely a contender. 2. `build_node_zonelist` in `mm/page_alloc.c` is static, which might make it inlined, so potentially useless as a fuzzing symbol. But, it's called by `build_zonelists`, which in turn calls `__build_all_zonelists`, which is *also* called on boot and hotplug, so this *could* be good. Let's check if the definition is inlined... Oh, I see! `find_next_best_node_in` is *not* static, so it *is* an actual symbol. Good, good. 3. `next_demotion_node` in `mm/memory-tiers.c` is non-static. Again, not ubiquitous, only used in `demote_folio_list`, which is exactly what we want. This is a solid candidate. 4. `establish_demotion_targets` in `mm/memory-tiers.c` is static. I need to find the non-static functions that call it or are entrypoints to its functionality. Looking at the callers, I have `memory_tier_late_init` and `memtier_hotplug_callback` as candidates. I should also check within `mm/memory-tiers.c` itself. |
| 46/2 | 2026/09/12 03:38 | tool | grepper |
0mArgs:{
"Expression": "establish_demotion_targets",
"PathPrefix": "mm/memory-tiers.c"
}Results: {
"Output": "mm/memory-tiers.c=400=static void dump_demotion_targets(void)\n--\nmm/memory-tiers.c-424- */\nmm/memory-tiers.c:425:static void establish_demotion_targets(void)\nmm/memory-tiers.c-426-{\n--\nmm/memory-tiers.c-521-#else\nmm/memory-tiers.c:522:static inline void establish_demotion_targets(void) {}\nmm/memory-tiers.c-523-#endif /* CONFIG_NUMA_MIGRATION */\n--\nmm/memory-tiers.c=708=static int __init memory_tier_late_init(void)\n--\nmm/memory-tiers.c-731-\nmm/memory-tiers.c:732:\testablish_demotion_targets();\nmm/memory-tiers.c-733-\tput_online_mems();\n--\nmm/memory-tiers.c=882=static int __meminit memtier_hotplug_callback(struct notifier_block *self,\n--\nmm/memory-tiers.c-891-\t\tif (clear_node_memory_tier(nn-\u003enid))\nmm/memory-tiers.c:892:\t\t\testablish_demotion_targets();\nmm/memory-tiers.c-893-\t\tmutex_unlock(\u0026memory_tier_lock);\n--\nmm/memory-tiers.c-898-\t\tif (!IS_ERR(memtier))\nmm/memory-tiers.c:899:\t\t\testablish_demotion_targets();\nmm/memory-tiers.c-900-\t\tmutex_unlock(\u0026memory_tier_lock);\n"
} |
| 47/2 | 2026/09/12 03:38 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 32680 output: 197 thoughts: 907 Thoughts: **My Analysis of the Code Changes** Okay, let's break this down. From what I see, `build_all_zonelists` looks like the primary entry point for zonelist rebuilding, which is a good place to start. The real work seems to be happening in `find_next_best_node_in`, and the non-static function `next_demotion_node` used during demotion. I see a static function, `demote_folio_list`, as well but that may be less relevant here. `build_all_zonelists` is also non-static, so those are my key targets. I need to figure out how broadly these functions are used. `find_next_best_node_in` is involved in zonelist construction, demotion, and finding the best node, so potentially important. `next_demotion_node` appears limited to folio demotion, and `build_all_zonelists` kicks in during boot, memory hotplug/offlining, and zonelist rebuilds – not exactly *ubiquitous*, but definitely critical system events. Now, let's look at the configuration dependencies. I'm seeing `NUMA` as a requirement for the `find_next_best_node_in` implementation and compiling `mm/memory-tiers.c`. `NUMA_MIGRATION` requires `NUMA` and `MMU` (which is pretty much standard on amd64), specifically for `next_demotion_node` and `establish_demotion_targets` in `mm/memory-tiers.c`. So, `NUMA` and `NUMA_MIGRATION` are key config options. Drilling into the code, `mm/page_alloc.c` shows that `node_load`, `build_node_zonelist`, and `find_next_best_node_in` are all guarded by `#ifdef CONFIG_NUMA`. `mm/memory-tiers.c` is compiled under `obj-$(CONFIG_NUMA) += memory-tiers.o`. Within `mm/memory-tiers.c`, `next_demotion_node` and `establish_demotion_targets` are protected by `#ifdef CONFIG_NUMA_MIGRATION`. I've checked the `Makefile` and `memory-tiers.h` to confirm the dependencies. In summary: * The patch refactors `find_next_best_node` to `find_next_best_node_in` with a candidate nodemask. * It updates NUMA fallback zonelist construction in `mm/page_alloc.c` which streamlines zonelist generation directly into the node zonelist buffer. * It modifies demotion node selection in `mm/memory-tiers.c` to use the refactored `find_next_best_node_in` * The code touches fundamental MM logic, specifically NUMA zonelist construction and memory tiering (including demotion target calculations) triggered during boot, memory hotplug/offline, and memory reclaim if NUMA demotion is enabled. Therefore, this is a prime candidate for fuzzing. The key functions to target are `find_next_best_node_in`, `next_demotion_node`, and `build_all_zonelists`, and the configuration options I need to enable are `NUMA` and `NUMA_MIGRATION`. I'm comfortable with the analysis, so let's set the results. |
| 48/2 | 2026/09/12 03:38 | tool | set-results |
0mArgs:{
"EnableConfigs": [
"NUMA",
"NUMA_MIGRATION"
],
"FocusSymbols": [
"find_next_best_node_in",
"next_demotion_node",
"build_all_zonelists"
],
"Reasoning": "The patch refactors find_next_best_node() into find_next_best_node_in(), allowing callers to specify eligible candidate nodes via a nodemask. It also restructures zonelist building in mm/page_alloc.c (build_node_zonelist) and updates demotion target resolution in mm/memory-tiers.c (next_demotion_node and establish_demotion_targets). This modifies core memory management logic reachable during NUMA zonelist generation (e.g. boot and memory hotplug/rebuild) and folio demotion during memory reclamation.",
"WorthFuzzing": true
}Results: {
"EnableConfigs": [
"NUMA",
"NUMA_MIGRATION"
],
"FocusSymbols": [
"find_next_best_node_in",
"next_demotion_node",
"build_all_zonelists"
],
"Reasoning": "The patch refactors find_next_best_node() into find_next_best_node_in(), allowing callers to specify eligible candidate nodes via a nodemask. It also restructures zonelist building in mm/page_alloc.c (build_node_zonelist) and updates demotion target resolution in mm/memory-tiers.c (next_demotion_node and establish_demotion_targets). This modifies core memory management logic reachable during NUMA zonelist generation (e.g. boot and memory hotplug/rebuild) and folio demotion during memory reclamation.",
"WorthFuzzing": true
} |
| 49/1 | 2026/09/12 03:38 | action | If |
0mArgs:{
"WorthFuzzing": true
}Results: null |
| 50/2 | 2026/09/12 03:38 | agent | kmsan-evaluator |
0mModel:core Args: null Results: {
"KMSANReasoning": "The patch refactors NUMA zonelist generation and node fallback calculation by introducing `find_next_best_node_in()` with a `candidates` nodemask parameter and merging `build_zonelists_in_node_order()` into `build_node_zonelist()`.\n\n- No kernel memory is copied to userspace (no info-leaks).\n- No new heap or stack allocations with uninitialized fields are introduced.\n- All variables (such as `used_mask = NODE_MASK_NONE`) and zoneref terminations (`zonerefs-\u003ezone = NULL`, `zonerefs-\u003ezone_idx = 0`) are properly initialized.\n- Any potential memory safety issues introduced by zonelist indexing or traversal would be out-of-bounds accesses or pointer errors, which are detectable by KASAN. KMSAN uninitialized memory detection is not applicable.",
"NeedsKMSAN": false
}Instruction: 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.
Prompt: Target architecture: amd64
For your convenience, here is the diff of the changes:
commit 1ba2d4f1791db873600f0a12ff73d299abdd3bd7
Author: syz-cluster <triage@syzkaller.com>
Date: Sat Sep 12 03:37:02 2026 +0000
syz-cluster: applied patch under review
diff --git a/mm/internal.h b/mm/internal.h
index da14c56fb24e1..1519dd21a900f 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1133,7 +1133,8 @@ extern int node_reclaim_mode;
extern unsigned long node_reclaim(struct pglist_data *pgdat,
gfp_t gfp_mask, unsigned int order);
-extern int find_next_best_node(int node, nodemask_t *used_node_mask);
+int find_next_best_node_in(int node, nodemask_t *used_node_mask,
+ const nodemask_t *candidates);
#else
#define node_reclaim_mode 0
@@ -1142,7 +1143,8 @@ static inline unsigned long node_reclaim(struct pglist_data *pgdat,
{
return 0;
}
-static inline int find_next_best_node(int node, nodemask_t *used_node_mask)
+static inline int find_next_best_node_in(int node, nodemask_t *used_node_mask,
+ const nodemask_t *candidates)
{
return NUMA_NO_NODE;
}
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 54851d8a195b0..25e121851b586 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -370,7 +370,7 @@ int next_demotion_node(int node, const nodemask_t *allowed_mask)
* closest demotion target.
*/
nodes_complement(mask, *allowed_mask);
- return find_next_best_node(node, &mask);
+ return find_next_best_node_in(node, &mask, &node_states[N_MEMORY]);
}
static void disable_all_demotion_targets(void)
@@ -450,7 +450,7 @@ static void establish_demotion_targets(void)
memtier = list_next_entry(memtier, list);
tier_nodes = get_memtier_nodemask(memtier);
/*
- * find_next_best_node, use 'used' nodemask as a skip list.
+ * find_next_best_node_in, use 'used' nodemask as a skip list.
* Add all memory nodes except the selected memory tier
* nodelist to skip list so that we find the best node from the
* memtier nodelist.
@@ -463,7 +463,8 @@ static void establish_demotion_targets(void)
* in the preferred mask when allocating pages during demotion.
*/
do {
- target = find_next_best_node(node, &tier_nodes);
+ target = find_next_best_node_in(node, &tier_nodes,
+ &node_states[N_MEMORY]);
if (target == NUMA_NO_NODE)
break;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1cfbd0582a10a..d1888d5630e0a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5793,9 +5793,10 @@ static int numa_zonelist_order_handler(const struct ctl_table *table, int write,
static int node_load[MAX_NUMNODES];
/**
- * find_next_best_node - find the next node that should appear in a given node's fallback list
+ * find_next_best_node_in - find the next node that should appear in a given node's fallback list
* @node: node whose fallback list we're appending
* @used_node_mask: nodemask_t of already used nodes
+ * @candidates: nodemask_t of nodes eligible for selection
*
* We use a number of factors to determine which is the next node that should
* appear on a given node's fallback list. The node should not have appeared
@@ -5807,7 +5808,8 @@ static int node_load[MAX_NUMNODES];
*
* Return: node id of the found node or %NUMA_NO_NODE if no node is found.
*/
-int find_next_best_node(int node, nodemask_t *used_node_mask)
+int find_next_best_node_in(int node, nodemask_t *used_node_mask,
+ const nodemask_t *candidates)
{
int n, val;
int min_val = INT_MAX;
@@ -5817,12 +5819,12 @@ int find_next_best_node(int node, nodemask_t *used_node_mask)
* Use the local node if we haven't already, but for memoryless local
* node, we should skip it and fall back to other nodes.
*/
- if (!node_isset(node, *used_node_mask) && node_state(node, N_MEMORY)) {
+ if (!node_isset(node, *used_node_mask) && node_isset(node, *candidates)) {
node_set(node, *used_node_mask);
return node;
}
- for_each_node_state(n, N_MEMORY) {
+ for_each_node_mask(n, *candidates) {
/* Don't want a node to appear more than once */
if (node_isset(n, *used_node_mask))
@@ -5855,31 +5857,6 @@ int find_next_best_node(int node, nodemask_t *used_node_mask)
}
-/*
- * Build zonelists ordered by node and zones within node.
- * This results in maximum locality--normal zone overflows into local
- * DMA zone, if any--but risks exhausting DMA zone.
- */
-static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order,
- unsigned nr_nodes)
-{
- struct zoneref *zonerefs;
- int i;
-
- zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
-
- for (i = 0; i < nr_nodes; i++) {
- int nr_zones;
-
- pg_data_t *node = NODE_DATA(node_order[i]);
-
- nr_zones = build_zonerefs_node(node, zonerefs);
- zonerefs += nr_zones;
- }
- zonerefs->zone = NULL;
- zonerefs->zone_idx = 0;
-}
-
/*
* Build __GFP_THISNODE zonelists
*/
@@ -5895,19 +5872,24 @@ static void build_thisnode_zonelists(pg_data_t *pgdat)
zonerefs->zone_idx = 0;
}
-static void build_zonelists(pg_data_t *pgdat)
+/*
+ * Build one zonelist ordered by node and zones within node. This results in
+ * maximum locality--normal zone overflows into local DMA zone, if any--but
+ * risks exhausting DMA zone.
+ */
+static void build_node_zonelist(pg_data_t *pgdat, const nodemask_t *candidates,
+ int zlidx)
{
- static int node_order[MAX_NUMNODES];
- int node, nr_nodes = 0;
+ struct zoneref *zonerefs = pgdat->node_zonelists[zlidx]._zonerefs;
nodemask_t used_mask = NODE_MASK_NONE;
- int local_node, prev_node;
+ int local_node = pgdat->node_id;
+ int prev_node = local_node;
+ int node;
- /* NUMA-aware ordering of nodes */
- local_node = pgdat->node_id;
- prev_node = local_node;
+ pr_info("Fallback order for Node %d: ", local_node);
- memset(node_order, 0, sizeof(node_order));
- while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
+ while ((node = find_next_best_node_in(local_node, &used_mask,
+ candidates)) >= 0) {
/*
* We don't want to pressure a particular node.
* So adding penalty to the first node in same
@@ -5917,18 +5899,22 @@ static void build_zonelists(pg_data_t *pgdat)
node_distance(local_node, prev_node))
node_load[node] += 1;
- node_order[nr_nodes++] = node;
+ zonerefs += build_zonerefs_node(NODE_DATA(node), zonerefs);
+ pr_cont("%d ", node);
prev_node = node;
}
- build_zonelists_in_node_order(pgdat, node_order, nr_nodes);
- build_thisnode_zonelists(pgdat);
- pr_info("Fallback order for Node %d: ", local_node);
- for (node = 0; node < nr_nodes; node++)
- pr_cont("%d ", node_order[node]);
+ zonerefs->zone = NULL;
+ zonerefs->zone_idx = 0;
pr_cont("\n");
}
+static void build_zonelists(pg_data_t *pgdat)
+{
+ build_node_zonelist(pgdat, &node_states[N_MEMORY], ZONELIST_FALLBACK);
+ build_thisnode_zonelists(pgdat);
+}
+
#ifdef CONFIG_HAVE_MEMORYLESS_NODES
/*
* Return node id of node used for "local" allocations.
|
| 51/3 | 2026/09/12 03:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 4520 output: 35 thoughts: 782 Thoughts: **Analyzing the Patch for KMSAN Fuzzing Needs** Okay, let's break down this patch and figure out if it warrants a dedicated KMSAN fuzzing session. My initial thought is to understand the changes first, then assess potential memory safety risks. So, here's what I see: the core of the patch revolves around the `find_next_best_node` function. It's been renamed to `find_next_best_node_in` and a `const nodemask_t *candidates` parameter has been added. The changes seem to be propagating this new function signature throughout the memory management code. Specifically, I see this function now being used in `mm/memory-tiers.c`, in both `next_demotion_node` and `establish_demotion_targets`. The crucial part here is how these `candidates` masks are being used; it's likely where any potential issues might hide. Further down the rabbit hole, `mm/page_alloc.c` contains the meat of the implementation. The key change here is how `find_next_best_node_in` now uses `node_isset` and `for_each_node_mask` with the provided `candidates` mask instead of the old `N_MEMORY` node state. The changes in `build_zonelists` seem significant as well. It looks like they've refactored the old node ordering logic to directly build zonelists based on the `candidates` mask within a new `build_node_zonelist` function. Instead of calling out to a function to build the zone list using node order, the new approach seems to be building it in the loop itself. Now, let's get down to brass tacks: uninitialized memory. Let's start with the basics; are there any newly allocated memory regions that aren't initialized? `nodemask_t used_mask` looks initialized, and `zonerefs` is pointing to an existing array in `pgdat`, which gets terminated with `zonerefs->zone = NULL; zonerefs->zone_idx = 0;`. Okay, that looks safe. Nothing is being copied to userspace, so that's one less concern. The most probable area of concern is reading uninitialized memory. `candidates` is the crucial pointer here, potentially. It's pointed to either `node_states[N_MEMORY]` or `&mask` / `&tier_nodes`. So, I'll need to check the initialization of `mask` and `tier_nodes` in `memory-tiers.c` around lines 370 and 450. I need to make sure those masks are properly initialized before they're passed to `find_next_best_node_in`. |
| 52/3 | 2026/09/12 03:38 | tool | read-file |
0mArgs:{
"File": "mm/memory-tiers.c",
"FirstLine": 360,
"LineCount": 40
}Results: {
"Contents": " 360:\t\t * last target node. Or introducing per-cpu data to avoid\n 361:\t\t * caching issue, which seems more complicated. So selecting\n 362:\t\t * target node randomly seems better until now.\n 363:\t\t */\n 364:\t\tif (!nodes_empty(mask))\n 365:\t\t\treturn node_random(\u0026mask);\n 366:\t\n 367:\t\t/*\n 368:\t\t * Preferred nodes are not in allowed_mask. Flip bits in\n 369:\t\t * allowed_mask as used node mask. Then, use it to get the\n 370:\t\t * closest demotion target.\n 371:\t\t */\n 372:\t\tnodes_complement(mask, *allowed_mask);\n 373:\t\treturn find_next_best_node_in(node, \u0026mask, \u0026node_states[N_MEMORY]);\n 374:\t}\n 375:\t\n 376:\tstatic void disable_all_demotion_targets(void)\n 377:\t{\n 378:\t\tstruct memory_tier *memtier;\n 379:\t\tint node;\n 380:\t\n 381:\t\tfor_each_node_state(node, N_MEMORY) {\n 382:\t\t\tnode_demotion[node].preferred = NODE_MASK_NONE;\n 383:\t\t\t/*\n 384:\t\t\t * We are holding memory_tier_lock, it is safe\n 385:\t\t\t * to access pgda-\u003ememtier.\n 386:\t\t\t */\n 387:\t\t\tmemtier = __node_get_memory_tier(node);\n 388:\t\t\tif (memtier)\n 389:\t\t\t\tmemtier-\u003elower_tier_mask = NODE_MASK_NONE;\n 390:\t\t}\n 391:\t\t/*\n 392:\t\t * Ensure that the \"disable\" is visible across the system.\n 393:\t\t * Readers will see either a combination of before+disable\n 394:\t\t * state or disable+after. They will never see before and\n 395:\t\t * after state together.\n 396:\t\t */\n 397:\t\tsynchronize_rcu();\n 398:\t}\n 399:\t\n"
} |
| 53/3 | 2026/09/12 03:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 6510 output: 35 thoughts: 30 Thoughts: Here's my take on those lines of code: **Diving into `establish_demotion_targets`** Okay, so we're talking memory tiers again. My intuition tells me to drill down into `mm/memory-tiers.c`, specifically around lines 440 to 480 within the `establish_demotion_targets` function. Given my expertise, I suspect this section is where the system is working out *which* memory regions are prime candidates for demotion – that is, moving data from a faster, more expensive tier down to a slower, cheaper one. I need to understand the criteria and logic being used. Are we looking at access frequency, overall footprint, recency, or some complex combination of these factors? This part of the code likely contains the core demotion decision-making process, and it's essential to analyze it with a fine-tooth comb to understand how effective the tiering is and how it might be improved. Let's see what gems we can find. |
| 54/3 | 2026/09/12 03:38 | tool | read-file |
0mArgs:{
"File": "mm/memory-tiers.c",
"FirstLine": 440,
"LineCount": 40
}Results: {
"Contents": " 440:\t\tfor_each_node_state(node, N_MEMORY) {\n 441:\t\t\tbest_distance = -1;\n 442:\t\t\tnd = \u0026node_demotion[node];\n 443:\t\n 444:\t\t\tmemtier = __node_get_memory_tier(node);\n 445:\t\t\tif (!memtier || list_is_last(\u0026memtier-\u003elist, \u0026memory_tiers))\n 446:\t\t\t\tcontinue;\n 447:\t\t\t/*\n 448:\t\t\t * Get the lower memtier to find the demotion node list.\n 449:\t\t\t */\n 450:\t\t\tmemtier = list_next_entry(memtier, list);\n 451:\t\t\ttier_nodes = get_memtier_nodemask(memtier);\n 452:\t\t\t/*\n 453:\t\t\t * find_next_best_node_in, use 'used' nodemask as a skip list.\n 454:\t\t\t * Add all memory nodes except the selected memory tier\n 455:\t\t\t * nodelist to skip list so that we find the best node from the\n 456:\t\t\t * memtier nodelist.\n 457:\t\t\t */\n 458:\t\t\tnodes_andnot(tier_nodes, node_states[N_MEMORY], tier_nodes);\n 459:\t\n 460:\t\t\t/*\n 461:\t\t\t * Find all the nodes in the memory tier node list of same best distance.\n 462:\t\t\t * add them to the preferred mask. We randomly select between nodes\n 463:\t\t\t * in the preferred mask when allocating pages during demotion.\n 464:\t\t\t */\n 465:\t\t\tdo {\n 466:\t\t\t\ttarget = find_next_best_node_in(node, \u0026tier_nodes,\n 467:\t\t\t\t\t\t\t\t\u0026node_states[N_MEMORY]);\n 468:\t\t\t\tif (target == NUMA_NO_NODE)\n 469:\t\t\t\t\tbreak;\n 470:\t\n 471:\t\t\t\tdistance = node_distance(node, target);\n 472:\t\t\t\tif (distance == best_distance || best_distance == -1) {\n 473:\t\t\t\t\tbest_distance = distance;\n 474:\t\t\t\t\tnode_set(target, nd-\u003epreferred);\n 475:\t\t\t\t} else {\n 476:\t\t\t\t\tbreak;\n 477:\t\t\t\t}\n 478:\t\t\t} while (1);\n 479:\t\t}\n"
} |
| 55/3 | 2026/09/12 03:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 7414 output: 36 thoughts: 20 Thoughts: Here's a summary of my thought process, as if I were considering the provided prompt: **Diving into `page_alloc.c` and Zonelists** Okay, so the prompt is asking me to think about a specific section of code, `page_alloc.c`, and specifically around the `build_node_zonelist` function. I immediately know this relates to the fundamental memory allocation mechanisms within the kernel, and the structuring of memory zones across NUMA nodes. My initial thought is to probably start by quickly reviewing `build_node_zonelist`'s purpose. I remember it's responsible for constructing the zonelist for each node. The zonelist dictates the order in which the kernel will attempt to allocate pages from different memory zones (e.g., DMA, Normal, HighMem) within a NUMA node and potentially across other nodes. I'd probably mentally reconstruct how the different zones on a node, and zones from other nodes, are added to that list. Then, I'd consider common scenarios: Are there any specific things I should be thinking about? Is this a standard scenario, is there something unusual about the prompt, or is this a trick question? The interplay with NUMA is key. I'll need to remember the impact of NUMA balancing, the impact of preferred nodes, and the effects of node interleave policies. I'd need to consider what configurations can significantly affect the zonelist construction. Finally, depending on context, I'd probably be thinking about performance impacts. How the zonelist is ordered directly affects allocation latency. Are there any known areas where suboptimal zonelist construction leads to performance issues? I might be thinking about how things are configured, because I recall that sometimes, the ideal zonelist ordering is a balance. |
| 56/3 | 2026/09/12 03:38 | tool | read-file |
0mArgs:{
"File": "mm/page_alloc.c",
"FirstLine": 5870,
"LineCount": 60
}Results: {
"Contents": "5870:\t\tzonerefs += nr_zones;\n5871:\t\tzonerefs-\u003ezone = NULL;\n5872:\t\tzonerefs-\u003ezone_idx = 0;\n5873:\t}\n5874:\t\n5875:\t/*\n5876:\t * Build one zonelist ordered by node and zones within node. This results in\n5877:\t * maximum locality--normal zone overflows into local DMA zone, if any--but\n5878:\t * risks exhausting DMA zone.\n5879:\t */\n5880:\tstatic void build_node_zonelist(pg_data_t *pgdat, const nodemask_t *candidates,\n5881:\t\t\t\t\tint zlidx)\n5882:\t{\n5883:\t\tstruct zoneref *zonerefs = pgdat-\u003enode_zonelists[zlidx]._zonerefs;\n5884:\t\tnodemask_t used_mask = NODE_MASK_NONE;\n5885:\t\tint local_node = pgdat-\u003enode_id;\n5886:\t\tint prev_node = local_node;\n5887:\t\tint node;\n5888:\t\n5889:\t\tpr_info(\"Fallback order for Node %d: \", local_node);\n5890:\t\n5891:\t\twhile ((node = find_next_best_node_in(local_node, \u0026used_mask,\n5892:\t\t\t\t\t\t candidates)) \u003e= 0) {\n5893:\t\t\t/*\n5894:\t\t\t * We don't want to pressure a particular node.\n5895:\t\t\t * So adding penalty to the first node in same\n5896:\t\t\t * distance group to make it round-robin.\n5897:\t\t\t */\n5898:\t\t\tif (node_distance(local_node, node) !=\n5899:\t\t\t node_distance(local_node, prev_node))\n5900:\t\t\t\tnode_load[node] += 1;\n5901:\t\n5902:\t\t\tzonerefs += build_zonerefs_node(NODE_DATA(node), zonerefs);\n5903:\t\t\tpr_cont(\"%d \", node);\n5904:\t\t\tprev_node = node;\n5905:\t\t}\n5906:\t\n5907:\t\tzonerefs-\u003ezone = NULL;\n5908:\t\tzonerefs-\u003ezone_idx = 0;\n5909:\t\tpr_cont(\"\\n\");\n5910:\t}\n5911:\t\n5912:\tstatic void build_zonelists(pg_data_t *pgdat)\n5913:\t{\n5914:\t\tbuild_node_zonelist(pgdat, \u0026node_states[N_MEMORY], ZONELIST_FALLBACK);\n5915:\t\tbuild_thisnode_zonelists(pgdat);\n5916:\t}\n5917:\t\n5918:\t#ifdef CONFIG_HAVE_MEMORYLESS_NODES\n5919:\t/*\n5920:\t * Return node id of node used for \"local\" allocations.\n5921:\t * I.e., first node id of first zone in arg node's generic zonelist.\n5922:\t * Used for initializing percpu 'numa_mem', which is used primarily\n5923:\t * for kernel allocations, so use GFP_KERNEL flags to locate zonelist.\n5924:\t */\n5925:\tint local_memory_node(int node)\n5926:\t{\n5927:\t\tstruct zoneref *z;\n5928:\t\n5929:\t\tz = first_zones_zonelist(node_zonelist(node, GFP_KERNEL),\n"
} |
| 57/3 | 2026/09/12 03:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 8790 output: 209 thoughts: 567 Thoughts: **KMSAN Assessment: This Patch is Safe** Okay, let's break this down. My primary concern is always uninitialized memory, right? Does this patch introduce a risk there? I've gone through it step by step. First, I checked: does any kernel memory leak into user space? Nope, nothing's copied out. Are there any uninitialized structs or buffers created or passed around? Again, no. The `candidates` parameter is a `const nodemask_t`, pointing to a global kernel variable, so that's covered. Inside the relevant functions like `find_next_best_node_in` and `build_node_zonelist`, I see bitwise operations on `candidates` and initialized variables. No red flags there. Then, I looked at allocations. Is this introducing new ones, stack or heap? No, actually, it *removed* allocations! That's a good sign. And no changes to any user-space interfaces like ioctl, netlink, or syscalls. This is all internal NUMA memory allocation logic. So, am I seeing *any* uninitialized memory bugs that KMSAN is designed to catch? No. Any bugs here would be logical errors, out-of-bounds zoneref access, which KASAN would catch, or potential infinite loops, which are not relevant to KMSAN. Therefore, no KMSAN is needed here. KASAN is sufficient to catch memory corruption or boundary issues that might arise. Now, let me double-check against the criteria: The requirements state that KMSAN isn't needed if the primary risks are out-of-bounds access, overflows, null dereferences, or use-after-free bugs (which are KASAN's domain), or if all structures are initialized. All structures touched or introduced are fully initialized. It also states the patch must not introduce any risk of uninitialized memory or info-leaks, and it doesn't. So, NeedsKMSAN = false. Case closed. I'm ready to write up the reasoning. |
| 58/3 | 2026/09/12 03:39 | tool | set-results |
0mArgs:{
"KMSANReasoning": "The patch refactors NUMA zonelist generation and node fallback calculation by introducing `find_next_best_node_in()` with a `candidates` nodemask parameter and merging `build_zonelists_in_node_order()` into `build_node_zonelist()`.\n\n- No kernel memory is copied to userspace (no info-leaks).\n- No new heap or stack allocations with uninitialized fields are introduced.\n- All variables (such as `used_mask = NODE_MASK_NONE`) and zoneref terminations (`zonerefs-\u003ezone = NULL`, `zonerefs-\u003ezone_idx = 0`) are properly initialized.\n- Any potential memory safety issues introduced by zonelist indexing or traversal would be out-of-bounds accesses or pointer errors, which are detectable by KASAN. KMSAN uninitialized memory detection is not applicable.",
"NeedsKMSAN": false
}Results: {
"KMSANReasoning": "The patch refactors NUMA zonelist generation and node fallback calculation by introducing `find_next_best_node_in()` with a `candidates` nodemask parameter and merging `build_zonelists_in_node_order()` into `build_node_zonelist()`.\n\n- No kernel memory is copied to userspace (no info-leaks).\n- No new heap or stack allocations with uninitialized fields are introduced.\n- All variables (such as `used_mask = NODE_MASK_NONE`) and zoneref terminations (`zonerefs-\u003ezone = NULL`, `zonerefs-\u003ezone_idx = 0`) are properly initialized.\n- Any potential memory safety issues introduced by zonelist indexing or traversal would be out-of-bounds accesses or pointer errors, which are detectable by KASAN. KMSAN uninitialized memory detection is not applicable.",
"NeedsKMSAN": false
} |
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