| Seq | Timestamp | Type | Name | Duration |
|---|---|---|---|---|
| 0/0 | 2026/09/10 08:41 | flow | patch-triage |
1mArgs:null Results: {
"EnableConfigs": [
"MEMCG",
"TRANSPARENT_HUGEPAGE",
"ZSWAP"
],
"FocusSymbols": [
"memcg_reparent_list_lrus",
"__memcg_list_lru_alloc",
"memcg_list_lru_alloc",
"folio_memcg_list_lru_alloc",
"list_lru_count_one",
"mem_cgroup_css_online",
"mem_cgroup_css_offline"
],
"KMSANReasoning": "The patch refactors the memcg LRU list indexing by eliminating the redundant `kmemcg_id` field from `struct mem_cgroup` in favor of `mem_cgroup_id()`, and marks THP deferred split and zswap shrinkers with `SHRINKER_NONSLAB`.\n\nNo new uninitialized memory allocations, conditional branches on uninitialized values, or data structures exported to user space are introduced. Any potential lifetime, concurrency, or pointer indexing issues related to xarray or memcg reparenting are within the domain of KASAN, LOCKDEP, and standard kernel debugging tools. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
"NeedsKMSAN": false,
"Reasoning": "The patch refactors list_lru indexing and lifetime management across memory cgroups by replacing kmemcg_id with mem_cgroup_id and unifying the reparenting paths during memcg offline. It also enables SHRINKER_NONSLAB on THP deferred split and zswap shrinkers. These changes touch reachable core mm and cgroup code paths executed during cgroup lifecycles and memory reclaim.",
"WorthFuzzing": true
} |
| 1/1 | 2026/09/10 08:41 | action | read-patch-diff |
0mArgs:null Results: {
"PatchDiff": "commit 42e91a5e11a6f41178b648ecc9bf8424ab0023e2\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Thu Sep 10 08:41:10 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h\nindex a03b6e3e54707..3463d2c52c628 100644\n--- a/include/linux/memcontrol.h\n+++ b/include/linux/memcontrol.h\n@@ -253,7 +253,6 @@ struct mem_cgroup {\n #if BITS_PER_LONG \u003c 64\n \tseqlock_t\t\tsocket_pressure_seqlock;\n #endif\n-\tint kmemcg_id;\n \n #ifdef CONFIG_CGROUP_WRITEBACK\n \tstruct list_head cgwb_list;\n@@ -1775,15 +1774,6 @@ static inline void memcg_kmem_uncharge_page(struct page *page, int order)\n \t\t__memcg_kmem_uncharge_page(page, order);\n }\n \n-/*\n- * A helper for accessing memcg's kmem_id, used for getting\n- * corresponding LRU lists.\n- */\n-static inline int memcg_kmem_id(struct mem_cgroup *memcg)\n-{\n-\treturn memcg ? memcg-\u003ekmemcg_id : -1;\n-}\n-\n struct mem_cgroup *mem_cgroup_from_virt(void *p);\n \n static inline void count_objcg_events(struct obj_cgroup *objcg,\n@@ -1851,11 +1841,6 @@ static inline bool memcg_kmem_online(void)\n \treturn false;\n }\n \n-static inline int memcg_kmem_id(struct mem_cgroup *memcg)\n-{\n-\treturn -1;\n-}\n-\n static inline struct mem_cgroup *mem_cgroup_from_virt(void *p)\n {\n \treturn NULL;\ndiff --git a/mm/huge_memory.c b/mm/huge_memory.c\nindex dd66c6ad5af13..d1ce061601bcd 100644\n--- a/mm/huge_memory.c\n+++ b/mm/huge_memory.c\n@@ -1064,7 +1064,8 @@ int folio_memcg_alloc_deferred(struct folio *folio)\n static int __init thp_shrinker_init(void)\n {\n \tdeferred_split_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE |\n-\t\t\t\t\t\t SHRINKER_MEMCG_AWARE,\n+\t\t\t\t\t\t SHRINKER_MEMCG_AWARE |\n+\t\t\t\t\t\t SHRINKER_NONSLAB,\n \t\t\t\t\t\t \"thp-deferred_split\");\n \tif (!deferred_split_shrinker)\n \t\treturn -ENOMEM;\ndiff --git a/mm/list_lru.c b/mm/list_lru.c\nindex 8a6dd0a489e12..f1968f02be3b3 100644\n--- a/mm/list_lru.c\n+++ b/mm/list_lru.c\n@@ -72,10 +72,11 @@ static int lru_shrinker_id(struct list_lru *lru)\n }\n \n static inline struct list_lru_one *\n-list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)\n+list_lru_from_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg)\n {\n-\tif (list_lru_memcg_aware(lru) \u0026\u0026 idx \u003e= 0) {\n-\t\tstruct list_lru_memcg *mlru = xa_load(\u0026lru-\u003exa, idx);\n+\tif (list_lru_memcg_aware(lru) \u0026\u0026 memcg \u0026\u0026 !mem_cgroup_is_root(memcg)) {\n+\t\tstruct list_lru_memcg *mlru =\n+\t\t\txa_load(\u0026lru-\u003exa, mem_cgroup_id(memcg));\n \n \t\treturn mlru ? \u0026mlru-\u003enode[nid] : NULL;\n \t}\n@@ -91,7 +92,7 @@ lock_list_lru_of_memcg(struct list_lru *lru, int nid,\n \n \trcu_read_lock();\n again:\n-\tl = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(*memcg));\n+\tl = list_lru_from_memcg(lru, nid, *memcg);\n \tif (likely(l)) {\n \t\tlock_list_lru(l, irq, irq_flags);\n \t\tif (likely(READ_ONCE(l-\u003enr_items) != LONG_MIN)) {\n@@ -132,7 +133,7 @@ static inline bool list_lru_memcg_aware(struct list_lru *lru)\n }\n \n static inline struct list_lru_one *\n-list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)\n+list_lru_from_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg)\n {\n \treturn \u0026lru-\u003enode[nid].lru;\n }\n@@ -313,7 +314,7 @@ unsigned long list_lru_count_one(struct list_lru *lru,\n \tlong count;\n \n \trcu_read_lock();\n-\tl = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));\n+\tl = list_lru_from_memcg(lru, nid, memcg);\n \tcount = l ? READ_ONCE(l-\u003enr_items) : 0;\n \trcu_read_unlock();\n \n@@ -502,11 +503,10 @@ static void memcg_reparent_list_lru_one(struct list_lru *lru, int nid,\n \t\t\t\t\tstruct list_lru_one *src,\n \t\t\t\t\tstruct mem_cgroup *dst_memcg)\n {\n-\tint dst_idx = dst_memcg-\u003ekmemcg_id;\n \tstruct list_lru_one *dst;\n \n \tspin_lock_irq(\u0026src-\u003elock);\n-\tdst = list_lru_from_memcg_idx(lru, nid, dst_idx);\n+\tdst = list_lru_from_memcg(lru, nid, dst_memcg);\n \tspin_lock_nested(\u0026dst-\u003elock, SINGLE_DEPTH_NESTING);\n \n \tlist_splice_init(\u0026src-\u003elist, \u0026dst-\u003elist);\n@@ -536,7 +536,7 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren\n \t\t * allocating a new mlru since CSS_DYING is already set for this\n \t\t * memcg a rcu grace period ago.\n \t\t */\n-\t\tmlru = xa_load(\u0026lru-\u003exa, memcg-\u003ekmemcg_id);\n+\t\tmlru = xa_load(\u0026lru-\u003exa, mem_cgroup_id(memcg));\n \t\tif (!mlru)\n \t\t\tcontinue;\n \n@@ -551,7 +551,7 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren\n \t\tfor_each_node(i)\n \t\t\tmemcg_reparent_list_lru_one(lru, i, \u0026mlru-\u003enode[i], parent);\n \n-\t\txa_erase_irq(\u0026lru-\u003exa, memcg-\u003ekmemcg_id);\n+\t\txa_erase_irq(\u0026lru-\u003exa, mem_cgroup_id(memcg));\n \n \t\t/*\n \t\t * Here all list_lrus corresponding to the cgroup are guaranteed\n@@ -566,9 +566,10 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren\n static inline bool memcg_list_lru_allocated(struct mem_cgroup *memcg,\n \t\t\t\t\t struct list_lru *lru)\n {\n-\tint idx = memcg-\u003ekmemcg_id;\n+\tif (!memcg || mem_cgroup_is_root(memcg))\n+\t\treturn true;\n \n-\treturn idx \u003c 0 || xa_load(\u0026lru-\u003exa, idx);\n+\treturn xa_load(\u0026lru-\u003exa, mem_cgroup_id(memcg));\n }\n \n static int __memcg_list_lru_alloc(struct mem_cgroup *memcg,\n@@ -602,7 +603,7 @@ static int __memcg_list_lru_alloc(struct mem_cgroup *memcg,\n \t\t\tif (!mlru)\n \t\t\t\treturn -ENOMEM;\n \t\t}\n-\t\txas_set(\u0026xas, pos-\u003ekmemcg_id);\n+\t\txas_set(\u0026xas, mem_cgroup_id(pos));\n \t\tdo {\n \t\t\txas_lock_irqsave(\u0026xas, flags);\n \t\t\tif (!xas_load(\u0026xas) \u0026\u0026 !css_is_dying(\u0026pos-\u003ecss)) {\n@@ -676,7 +677,9 @@ int __list_lru_init(struct list_lru *lru, bool memcg_aware, struct shrinker *shr\n \telse\n \t\tlru-\u003eshrinker_id = -1;\n \n-\tif (mem_cgroup_disabled() || mem_cgroup_kmem_disabled())\n+\tif (mem_cgroup_disabled() ||\n+\t (mem_cgroup_kmem_disabled() \u0026\u0026\n+\t (!shrinker || !(shrinker-\u003eflags \u0026 SHRINKER_NONSLAB))))\n \t\tmemcg_aware = false;\n #endif\n \ndiff --git a/mm/memcontrol.c b/mm/memcontrol.c\nindex 4cb2db8c0923a..ae2d6d9cfa742 100644\n--- a/mm/memcontrol.c\n+++ b/mm/memcontrol.c\n@@ -3763,33 +3763,6 @@ void folio_split_memcg_refs(struct folio *folio, unsigned old_order,\n \tobj_cgroup_get_many(folio_objcg(folio), new_refs);\n }\n \n-static void memcg_online_kmem(struct mem_cgroup *memcg)\n-{\n-\tif (mem_cgroup_kmem_disabled())\n-\t\treturn;\n-\n-\tif (unlikely(mem_cgroup_is_root(memcg)))\n-\t\treturn;\n-\n-\tstatic_branch_enable(\u0026memcg_kmem_online_key);\n-\n-\tmemcg-\u003ekmemcg_id = memcg-\u003eid.id;\n-}\n-\n-static void memcg_offline_kmem(struct mem_cgroup *memcg)\n-{\n-\tstruct mem_cgroup *parent;\n-\n-\tif (mem_cgroup_kmem_disabled())\n-\t\treturn;\n-\n-\tif (unlikely(mem_cgroup_is_root(memcg)))\n-\t\treturn;\n-\n-\tparent = parent_mem_cgroup(memcg);\n-\tmemcg_reparent_list_lrus(memcg, parent);\n-}\n-\n #ifdef CONFIG_CGROUP_WRITEBACK\n \n #include \u003ctrace/events/writeback.h\u003e\n@@ -4216,7 +4189,6 @@ static struct mem_cgroup *mem_cgroup_alloc(struct mem_cgroup *parent)\n \tseqlock_init(\u0026memcg-\u003esocket_pressure_seqlock);\n #endif\n \tmemcg1_memcg_init(memcg);\n-\tmemcg-\u003ekmemcg_id = -1;\n #ifdef CONFIG_CGROUP_WRITEBACK\n \tINIT_LIST_HEAD(\u0026memcg-\u003ecgwb_list);\n \tfor (i = 0; i \u003c MEMCG_CGWB_FRN_CNT; i++)\n@@ -4290,7 +4262,8 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)\n \tstruct obj_cgroup *objcg;\n \tint nid;\n \n-\tmemcg_online_kmem(memcg);\n+\tif (!mem_cgroup_kmem_disabled() \u0026\u0026 likely(!mem_cgroup_is_root(memcg)))\n+\t\tstatic_branch_enable(\u0026memcg_kmem_online_key);\n \n \t/*\n \t * A memcg must be visible for expand_shrinker_info()\n@@ -4298,7 +4271,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)\n \t * here, when mem_cgroup_iter() can't skip it.\n \t */\n \tif (alloc_shrinker_info(memcg))\n-\t\tgoto offline_kmem;\n+\t\tgoto reparent_lrus;\n \n \tfor_each_node(nid) {\n \t\tobjcg = obj_cgroup_alloc();\n@@ -4355,8 +4328,8 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)\n \t\t}\n \t}\n \tfree_shrinker_info(memcg);\n-offline_kmem:\n-\tmemcg_offline_kmem(memcg);\n+reparent_lrus:\n+\tmemcg_reparent_list_lrus(memcg, parent_mem_cgroup(memcg));\n \tmem_cgroup_private_id_remove(memcg);\n \treturn -ENOMEM;\n }\n@@ -4372,11 +4345,11 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)\n \n \tzswap_memcg_offline_cleanup(memcg);\n \n-\tmemcg_offline_kmem(memcg);\n+\tmemcg_reparent_list_lrus(memcg, parent_mem_cgroup(memcg));\n \t/*\n \t * The reparenting of objcg must be after the reparenting of\n-\t * the list_lru in memcg_offline_kmem(), which ensures that\n-\t * they will not mistakenly get the parent list_lru.\n+\t * the list_lru above, which ensures that they will not\n+\t * mistakenly get the parent list_lru.\n \t */\n \tmemcg_reparent_objcgs(memcg);\n \treparent_shrinker_deferred(memcg);\ndiff --git a/mm/zswap.c b/mm/zswap.c\nindex cd7b0b621bda8..afc6c8d03d231 100644\n--- a/mm/zswap.c\n+++ b/mm/zswap.c\n@@ -1255,8 +1255,8 @@ static struct shrinker *zswap_alloc_shrinker(void)\n {\n \tstruct shrinker *shrinker;\n \n-\tshrinker =\n-\t\tshrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE, \"mm-zswap\");\n+\tshrinker = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |\n+\t\t\t\t SHRINKER_NONSLAB, \"mm-zswap\");\n \tif (!shrinker)\n \t\treturn NULL;\n \n"
} |
| 2/1 | 2026/09/10 08:41 | agent | patch-evaluator |
0mModel:core Args: null Results: {
"EnableConfigs": [
"MEMCG",
"TRANSPARENT_HUGEPAGE",
"ZSWAP"
],
"FocusSymbols": [
"memcg_reparent_list_lrus",
"__memcg_list_lru_alloc",
"memcg_list_lru_alloc",
"folio_memcg_list_lru_alloc",
"list_lru_count_one",
"mem_cgroup_css_online",
"mem_cgroup_css_offline"
],
"Reasoning": "The patch refactors list_lru indexing and lifetime management across memory cgroups by replacing kmemcg_id with mem_cgroup_id and unifying the reparenting paths during memcg offline. It also enables SHRINKER_NONSLAB on THP deferred split and zswap shrinkers. These changes touch reachable core mm and cgroup code paths executed during cgroup lifecycles and memory reclaim.",
"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 42e91a5e11a6f41178b648ecc9bf8424ab0023e2
Author: syz-cluster <triage@syzkaller.com>
Date: Thu Sep 10 08:41:10 2026 +0000
syz-cluster: applied patch under review
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index a03b6e3e54707..3463d2c52c628 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -253,7 +253,6 @@ struct mem_cgroup {
#if BITS_PER_LONG < 64
seqlock_t socket_pressure_seqlock;
#endif
- int kmemcg_id;
#ifdef CONFIG_CGROUP_WRITEBACK
struct list_head cgwb_list;
@@ -1775,15 +1774,6 @@ static inline void memcg_kmem_uncharge_page(struct page *page, int order)
__memcg_kmem_uncharge_page(page, order);
}
-/*
- * A helper for accessing memcg's kmem_id, used for getting
- * corresponding LRU lists.
- */
-static inline int memcg_kmem_id(struct mem_cgroup *memcg)
-{
- return memcg ? memcg->kmemcg_id : -1;
-}
-
struct mem_cgroup *mem_cgroup_from_virt(void *p);
static inline void count_objcg_events(struct obj_cgroup *objcg,
@@ -1851,11 +1841,6 @@ static inline bool memcg_kmem_online(void)
return false;
}
-static inline int memcg_kmem_id(struct mem_cgroup *memcg)
-{
- return -1;
-}
-
static inline struct mem_cgroup *mem_cgroup_from_virt(void *p)
{
return NULL;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index dd66c6ad5af13..d1ce061601bcd 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1064,7 +1064,8 @@ int folio_memcg_alloc_deferred(struct folio *folio)
static int __init thp_shrinker_init(void)
{
deferred_split_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE |
- SHRINKER_MEMCG_AWARE,
+ SHRINKER_MEMCG_AWARE |
+ SHRINKER_NONSLAB,
"thp-deferred_split");
if (!deferred_split_shrinker)
return -ENOMEM;
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 8a6dd0a489e12..f1968f02be3b3 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -72,10 +72,11 @@ static int lru_shrinker_id(struct list_lru *lru)
}
static inline struct list_lru_one *
-list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)
+list_lru_from_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg)
{
- if (list_lru_memcg_aware(lru) && idx >= 0) {
- struct list_lru_memcg *mlru = xa_load(&lru->xa, idx);
+ if (list_lru_memcg_aware(lru) && memcg && !mem_cgroup_is_root(memcg)) {
+ struct list_lru_memcg *mlru =
+ xa_load(&lru->xa, mem_cgroup_id(memcg));
return mlru ? &mlru->node[nid] : NULL;
}
@@ -91,7 +92,7 @@ lock_list_lru_of_memcg(struct list_lru *lru, int nid,
rcu_read_lock();
again:
- l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(*memcg));
+ l = list_lru_from_memcg(lru, nid, *memcg);
if (likely(l)) {
lock_list_lru(l, irq, irq_flags);
if (likely(READ_ONCE(l->nr_items) != LONG_MIN)) {
@@ -132,7 +133,7 @@ static inline bool list_lru_memcg_aware(struct list_lru *lru)
}
static inline struct list_lru_one *
-list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)
+list_lru_from_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg)
{
return &lru->node[nid].lru;
}
@@ -313,7 +314,7 @@ unsigned long list_lru_count_one(struct list_lru *lru,
long count;
rcu_read_lock();
- l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
+ l = list_lru_from_memcg(lru, nid, memcg);
count = l ? READ_ONCE(l->nr_items) : 0;
rcu_read_unlock();
@@ -502,11 +503,10 @@ static void memcg_reparent_list_lru_one(struct list_lru *lru, int nid,
struct list_lru_one *src,
struct mem_cgroup *dst_memcg)
{
- int dst_idx = dst_memcg->kmemcg_id;
struct list_lru_one *dst;
spin_lock_irq(&src->lock);
- dst = list_lru_from_memcg_idx(lru, nid, dst_idx);
+ dst = list_lru_from_memcg(lru, nid, dst_memcg);
spin_lock_nested(&dst->lock, SINGLE_DEPTH_NESTING);
list_splice_init(&src->list, &dst->list);
@@ -536,7 +536,7 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren
* allocating a new mlru since CSS_DYING is already set for this
* memcg a rcu grace period ago.
*/
- mlru = xa_load(&lru->xa, memcg->kmemcg_id);
+ mlru = xa_load(&lru->xa, mem_cgroup_id(memcg));
if (!mlru)
continue;
@@ -551,7 +551,7 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren
for_each_node(i)
memcg_reparent_list_lru_one(lru, i, &mlru->node[i], parent);
- xa_erase_irq(&lru->xa, memcg->kmemcg_id);
+ xa_erase_irq(&lru->xa, mem_cgroup_id(memcg));
/*
* Here all list_lrus corresponding to the cgroup are guaranteed
@@ -566,9 +566,10 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren
static inline bool memcg_list_lru_allocated(struct mem_cgroup *memcg,
struct list_lru *lru)
{
- int idx = memcg->kmemcg_id;
+ if (!memcg || mem_cgroup_is_root(memcg))
+ return true;
- return idx < 0 || xa_load(&lru->xa, idx);
+ return xa_load(&lru->xa, mem_cgroup_id(memcg));
}
static int __memcg_list_lru_alloc(struct mem_cgroup *memcg,
@@ -602,7 +603,7 @@ static int __memcg_list_lru_alloc(struct mem_cgroup *memcg,
if (!mlru)
return -ENOMEM;
}
- xas_set(&xas, pos->kmemcg_id);
+ xas_set(&xas, mem_cgroup_id(pos));
do {
xas_lock_irqsave(&xas, flags);
if (!xas_load(&xas) && !css_is_dying(&pos->css)) {
@@ -676,7 +677,9 @@ int __list_lru_init(struct list_lru *lru, bool memcg_aware, struct shrinker *shr
else
lru->shrinker_id = -1;
- if (mem_cgroup_disabled() || mem_cgroup_kmem_disabled())
+ if (mem_cgroup_disabled() ||
+ (mem_cgroup_kmem_disabled() &&
+ (!shrinker || !(shrinker->flags & SHRINKER_NONSLAB))))
memcg_aware = false;
#endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4cb2db8c0923a..ae2d6d9cfa742 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3763,33 +3763,6 @@ void folio_split_memcg_refs(struct folio *folio, unsigned old_order,
obj_cgroup_get_many(folio_objcg(folio), new_refs);
}
-static void memcg_online_kmem(struct mem_cgroup *memcg)
-{
- if (mem_cgroup_kmem_disabled())
- return;
-
- if (unlikely(mem_cgroup_is_root(memcg)))
- return;
-
- static_branch_enable(&memcg_kmem_online_key);
-
- memcg->kmemcg_id = memcg->id.id;
-}
-
-static void memcg_offline_kmem(struct mem_cgroup *memcg)
-{
- struct mem_cgroup *parent;
-
- if (mem_cgroup_kmem_disabled())
- return;
-
- if (unlikely(mem_cgroup_is_root(memcg)))
- return;
-
- parent = parent_mem_cgroup(memcg);
- memcg_reparent_list_lrus(memcg, parent);
-}
-
#ifdef CONFIG_CGROUP_WRITEBACK
#include <trace/events/writeback.h>
@@ -4216,7 +4189,6 @@ static struct mem_cgroup *mem_cgroup_alloc(struct mem_cgroup *parent)
seqlock_init(&memcg->socket_pressure_seqlock);
#endif
memcg1_memcg_init(memcg);
- memcg->kmemcg_id = -1;
#ifdef CONFIG_CGROUP_WRITEBACK
INIT_LIST_HEAD(&memcg->cgwb_list);
for (i = 0; i < MEMCG_CGWB_FRN_CNT; i++)
@@ -4290,7 +4262,8 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
struct obj_cgroup *objcg;
int nid;
- memcg_online_kmem(memcg);
+ if (!mem_cgroup_kmem_disabled() && likely(!mem_cgroup_is_root(memcg)))
+ static_branch_enable(&memcg_kmem_online_key);
/*
* A memcg must be visible for expand_shrinker_info()
@@ -4298,7 +4271,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
* here, when mem_cgroup_iter() can't skip it.
*/
if (alloc_shrinker_info(memcg))
- goto offline_kmem;
+ goto reparent_lrus;
for_each_node(nid) {
objcg = obj_cgroup_alloc();
@@ -4355,8 +4328,8 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
}
}
free_shrinker_info(memcg);
-offline_kmem:
- memcg_offline_kmem(memcg);
+reparent_lrus:
+ memcg_reparent_list_lrus(memcg, parent_mem_cgroup(memcg));
mem_cgroup_private_id_remove(memcg);
return -ENOMEM;
}
@@ -4372,11 +4345,11 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
zswap_memcg_offline_cleanup(memcg);
- memcg_offline_kmem(memcg);
+ memcg_reparent_list_lrus(memcg, parent_mem_cgroup(memcg));
/*
* The reparenting of objcg must be after the reparenting of
- * the list_lru in memcg_offline_kmem(), which ensures that
- * they will not mistakenly get the parent list_lru.
+ * the list_lru above, which ensures that they will not
+ * mistakenly get the parent list_lru.
*/
memcg_reparent_objcgs(memcg);
reparent_shrinker_deferred(memcg);
diff --git a/mm/zswap.c b/mm/zswap.c
index cd7b0b621bda8..afc6c8d03d231 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1255,8 +1255,8 @@ static struct shrinker *zswap_alloc_shrinker(void)
{
struct shrinker *shrinker;
- shrinker =
- shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE, "mm-zswap");
+ shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
+ SHRINKER_NONSLAB, "mm-zswap");
if (!shrinker)
return NULL;
|
| 3/2 | 2026/09/10 08:41 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 6541 output: 22 thoughts: 497 Thoughts: **Analyzing the Memory Controller Patch** Okay, let's break this down. First, I'm diving into this patch and its implications for the memory controller, since that's my area of expertise. It looks like we're streamlining the memory cgroup (memcg) kmem tracking and list_lru management. The initial scan shows the core changes: `include/linux/memcontrol.h` is shedding the `kmemcg_id` field and the associated `memcg_kmem_id()` function. This likely means we're moving away from the integer-based ID and adopting a direct pointer approach to reference the `mem_cgroup` struct itself. Good, potentially less overhead and a more direct data access. The `mm/huge_memory.c` addition of `SHRINKER_NONSLAB` to `deferred_split_shrinker` in `thp_shrinker_init()` is interesting. This points towards improved interaction with the THP (Transparent Huge Pages) shrinker and likely optimization around non-slab memory reclaim. I'll need to dig deeper into the shrinker flags to fully understand the impact here. The changes in `mm/list_lru.c` are more substantial. We're clearly shifting from an indexed approach (`list_lru_from_memcg_idx`) to a direct `mem_cgroup` pointer (`list_lru_from_memcg`). Replacing uses of `kmemcg_id` with `mem_cgroup_id(memcg)` solidifies this pointer-based approach. We also see updates to the memcg reparenting logic for list_lrus. This is key, especially if we're dealing with nested cgroups, and I need to understand how the new logic handles rebalancing of resources. The change in `__list_lru_init` with the `SHRINKER_NONSLAB` flag seems important. If I understand correctly, it is related to the configuration of memcg-aware list_lrus. The removal of `memcg_online_kmem` and `memcg_offline_kmem` in `mm/memcontrol.c` and the inlining of `memcg_reparent_list_lrus` within `mem_cgroup_css_online` and `mem_cgroup_css_offline` suggests that these operations are being simplified. This inlining and direct reparenting will be good for performance. The fact it's handled directly in online and offline implies an intention to optimize the common path and avoid function call overhead. Finally, the `mm/zswap.c` addition of `SHRINKER_NONSLAB` to `zswap_alloc_shrinker()` means zswap is also being configured to interact differently with the shrinker. This further points to improvements in how we handle non-slab memory pressure and reclaim within the memory cgroup framework. I'll need to use grepper and read the relevant source files to get the bigger picture. I need to understand the implications on memory reclaim, NUMA interactions, and overall cgroup performance. I'm especially interested in whether these changes break any assumptions I've relied on in my own work on the subject, or whether the new approach introduces opportunities for better optimizations. |
| 4/2 | 2026/09/10 08:41 | tool | grepper |
0mArgs:{
"Expression": "SHRINKER_NONSLAB"
}Results: {
"Output": "fs/btrfs/compression.c=1129=int __init btrfs_init_compress(void)\n--\nfs/btrfs/compression.c-1135-\nfs/btrfs/compression.c:1136:\tcompr_pool.shrinker = shrinker_alloc(SHRINKER_NONSLAB, \"btrfs-compr-pages\");\nfs/btrfs/compression.c-1137-\tif (!compr_pool.shrinker)\n--\nfs/xfs/xfs_icache.c=2335=xfs_inodegc_register_shrinker(\n--\nfs/xfs/xfs_icache.c-2337-{\nfs/xfs/xfs_icache.c:2338:\tmp-\u003em_inodegc_shrinker = shrinker_alloc(SHRINKER_NONSLAB,\nfs/xfs/xfs_icache.c-2339-\t\t\t\t\t\t\"xfs-inodegc:%s\",\n--\ninclude/linux/shrinker.h=82=struct shrinker {\n--\ninclude/linux/shrinker.h-131- */\ninclude/linux/shrinker.h:132:#define SHRINKER_NONSLAB\tBIT(4)\ninclude/linux/shrinker.h-133-\n--\nmm/huge_memory.c=1064=static int __init thp_shrinker_init(void)\n--\nmm/huge_memory.c-1067-\t\t\t\t\t\t SHRINKER_MEMCG_AWARE |\nmm/huge_memory.c:1068:\t\t\t\t\t\t SHRINKER_NONSLAB,\nmm/huge_memory.c-1069-\t\t\t\t\t\t \"thp-deferred_split\");\n--\nmm/list_lru.c=665=int __list_lru_init(struct list_lru *lru, bool memcg_aware, struct shrinker *shrinker)\n--\nmm/list_lru.c-681-\t (mem_cgroup_kmem_disabled() \u0026\u0026\nmm/list_lru.c:682:\t (!shrinker || !(shrinker-\u003eflags \u0026 SHRINKER_NONSLAB))))\nmm/list_lru.c-683-\t\tmemcg_aware = false;\n--\nmm/shrinker.c=226=static int shrinker_memcg_alloc(struct shrinker *shrinker)\n--\nmm/shrinker.c-233-\t\treturn -ENOSYS;\nmm/shrinker.c:234:\tif (mem_cgroup_kmem_disabled() \u0026\u0026 !(shrinker-\u003eflags \u0026 SHRINKER_NONSLAB))\nmm/shrinker.c-235-\t\treturn -ENOSYS;\n--\nmm/shrinker.c=478=static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,\n--\nmm/shrinker.c-555-\t\t\tif (!memcg_kmem_online() \u0026\u0026\nmm/shrinker.c:556:\t\t\t !(shrinker-\u003eflags \u0026 SHRINKER_NONSLAB)) {\nmm/shrinker.c-557-\t\t\t\tclear_bit(offset, unit-\u003emap);\n--\nmm/zswap.c=1254=static struct shrinker *zswap_alloc_shrinker(void)\n--\nmm/zswap.c-1258-\tshrinker = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |\nmm/zswap.c:1259:\t\t\t\t SHRINKER_NONSLAB, \"mm-zswap\");\nmm/zswap.c-1260-\tif (!shrinker)\n"
} |
| 5/2 | 2026/09/10 08:41 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 8695 output: 35 thoughts: 27 Thoughts: Here's my take on the code changes, from my perspective as an expert: **Diving into the Memory Management Core** Alright, time to dig into those recent commits. I'm starting with `mm/list_lru.c` and `mm/memcontrol.c`. These are fundamental areas; any change here has the potential to ripple through the entire memory management subsystem. I need to understand the *why* behind these alterations, not just the *what*. My initial focus will be on the impact to overall system performance and stability. I'll need to look closely for any lock ordering issues, potential race conditions, or changes to LRU behavior that might negatively impact caching or swapping. I will also be looking to see if any new features are exposed, or if any existing capabilities are deprecated. Ultimately, I want to determine if there are optimizations or performance improvements. |
| 6/2 | 2026/09/10 08:41 | tool | read-file |
0mArgs:{
"File": "mm/list_lru.c",
"FirstLine": 60,
"LineCount": 60
}Results: {
"Contents": " 60:\t{\n 61:\t\tif (!list_lru_memcg_aware(lru))\n 62:\t\t\treturn;\n 63:\t\n 64:\t\tmutex_lock(\u0026list_lrus_mutex);\n 65:\t\tlist_del(\u0026lru-\u003elist);\n 66:\t\tmutex_unlock(\u0026list_lrus_mutex);\n 67:\t}\n 68:\t\n 69:\tstatic int lru_shrinker_id(struct list_lru *lru)\n 70:\t{\n 71:\t\treturn lru-\u003eshrinker_id;\n 72:\t}\n 73:\t\n 74:\tstatic inline struct list_lru_one *\n 75:\tlist_lru_from_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg)\n 76:\t{\n 77:\t\tif (list_lru_memcg_aware(lru) \u0026\u0026 memcg \u0026\u0026 !mem_cgroup_is_root(memcg)) {\n 78:\t\t\tstruct list_lru_memcg *mlru =\n 79:\t\t\t\txa_load(\u0026lru-\u003exa, mem_cgroup_id(memcg));\n 80:\t\n 81:\t\t\treturn mlru ? \u0026mlru-\u003enode[nid] : NULL;\n 82:\t\t}\n 83:\t\treturn \u0026lru-\u003enode[nid].lru;\n 84:\t}\n 85:\t\n 86:\tstatic inline struct list_lru_one *\n 87:\tlock_list_lru_of_memcg(struct list_lru *lru, int nid,\n 88:\t\t\t struct mem_cgroup **memcg, bool irq,\n 89:\t\t\t unsigned long *irq_flags, bool skip_empty)\n 90:\t{\n 91:\t\tstruct list_lru_one *l;\n 92:\t\n 93:\t\trcu_read_lock();\n 94:\tagain:\n 95:\t\tl = list_lru_from_memcg(lru, nid, *memcg);\n 96:\t\tif (likely(l)) {\n 97:\t\t\tlock_list_lru(l, irq, irq_flags);\n 98:\t\t\tif (likely(READ_ONCE(l-\u003enr_items) != LONG_MIN)) {\n 99:\t\t\t\trcu_read_unlock();\n 100:\t\t\t\treturn l;\n 101:\t\t\t}\n 102:\t\t\tunlock_list_lru(l, irq, irq_flags);\n 103:\t\t}\n 104:\t\t/*\n 105:\t\t * Caller may simply bail out if raced with reparenting or\n 106:\t\t * may iterate through the list_lru and expect empty slots.\n 107:\t\t */\n 108:\t\tif (skip_empty) {\n 109:\t\t\trcu_read_unlock();\n 110:\t\t\treturn NULL;\n 111:\t\t}\n 112:\t\tVM_WARN_ON(!css_is_dying(\u0026(*memcg)-\u003ecss));\n 113:\t\t*memcg = parent_mem_cgroup(*memcg);\n 114:\t\tgoto again;\n 115:\t}\n 116:\t#else\n 117:\tstatic void list_lru_register(struct list_lru *lru)\n 118:\t{\n 119:\t}\n"
} |
| 7/2 | 2026/09/10 08:41 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 9830 output: 36 thoughts: 32 Thoughts: Here's my thought process, summarized as you requested: **Investigating `list_lru_from_memcg` and Related Functions** Alright, time to dig into `mm/list_lru.c`. My immediate focus is to understand how `list_lru_from_memcg` is being used within this module. I need to trace its call sites to grasp the contexts in which it's invoked. More broadly, I want a good overview of the function's interactions within the `list_lru` subsystem. Understanding the surrounding code, especially the functions that interact with this particular LRU implementation will be crucial. I'm looking for the "who," "what," and "where" to gain insight into the overall design and any potential performance implications within a memcg context. Let's start the analysis. |
| 8/2 | 2026/09/10 08:41 | tool | read-file |
0mArgs:{
"File": "mm/list_lru.c",
"FirstLine": 500,
"LineCount": 80
}Results: {
"Contents": " 500:\t}\n 501:\t\n 502:\tstatic void memcg_reparent_list_lru_one(struct list_lru *lru, int nid,\n 503:\t\t\t\t\t\tstruct list_lru_one *src,\n 504:\t\t\t\t\t\tstruct mem_cgroup *dst_memcg)\n 505:\t{\n 506:\t\tstruct list_lru_one *dst;\n 507:\t\n 508:\t\tspin_lock_irq(\u0026src-\u003elock);\n 509:\t\tdst = list_lru_from_memcg(lru, nid, dst_memcg);\n 510:\t\tspin_lock_nested(\u0026dst-\u003elock, SINGLE_DEPTH_NESTING);\n 511:\t\n 512:\t\tlist_splice_init(\u0026src-\u003elist, \u0026dst-\u003elist);\n 513:\t\tif (src-\u003enr_items) {\n 514:\t\t\tWARN_ON(src-\u003enr_items \u003c 0);\n 515:\t\t\tdst-\u003enr_items += src-\u003enr_items;\n 516:\t\t\tset_shrinker_bit(dst_memcg, nid, lru_shrinker_id(lru));\n 517:\t\t}\n 518:\t\t/* Mark the list_lru_one dead */\n 519:\t\tsrc-\u003enr_items = LONG_MIN;\n 520:\t\n 521:\t\tspin_unlock(\u0026dst-\u003elock);\n 522:\t\tspin_unlock_irq(\u0026src-\u003elock);\n 523:\t}\n 524:\t\n 525:\tvoid memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent)\n 526:\t{\n 527:\t\tstruct list_lru *lru;\n 528:\t\tint i;\n 529:\t\n 530:\t\tmutex_lock(\u0026list_lrus_mutex);\n 531:\t\tlist_for_each_entry(lru, \u0026memcg_list_lrus, list) {\n 532:\t\t\tstruct list_lru_memcg *mlru;\n 533:\t\n 534:\t\t\t/*\n 535:\t\t\t * css_is_dying() check in memcg_list_lru_alloc() avoids\n 536:\t\t\t * allocating a new mlru since CSS_DYING is already set for this\n 537:\t\t\t * memcg a rcu grace period ago.\n 538:\t\t\t */\n 539:\t\t\tmlru = xa_load(\u0026lru-\u003exa, mem_cgroup_id(memcg));\n 540:\t\t\tif (!mlru)\n 541:\t\t\t\tcontinue;\n 542:\t\n 543:\t\t\t/*\n 544:\t\t\t * Reparent each per-node list and mark the child dead\n 545:\t\t\t * (LONG_MIN) before clearing xarray entry otherwise a\n 546:\t\t\t * concurrent list_lru_del() may corrupt the list if it arrives\n 547:\t\t\t * after xarray clear but before reparenting as\n 548:\t\t\t * lock_list_lru_of_memcg will acquire parent's lock while the\n 549:\t\t\t * item is still on child's list.\n 550:\t\t\t */\n 551:\t\t\tfor_each_node(i)\n 552:\t\t\t\tmemcg_reparent_list_lru_one(lru, i, \u0026mlru-\u003enode[i], parent);\n 553:\t\n 554:\t\t\txa_erase_irq(\u0026lru-\u003exa, mem_cgroup_id(memcg));\n 555:\t\n 556:\t\t\t/*\n 557:\t\t\t * Here all list_lrus corresponding to the cgroup are guaranteed\n 558:\t\t\t * to remain empty, we can safely free this lru, any further\n 559:\t\t\t * memcg_list_lru_alloc() call will simply bail out.\n 560:\t\t\t */\n 561:\t\t\tkvfree_rcu(mlru, rcu);\n 562:\t\t}\n 563:\t\tmutex_unlock(\u0026list_lrus_mutex);\n 564:\t}\n 565:\t\n 566:\tstatic inline bool memcg_list_lru_allocated(struct mem_cgroup *memcg,\n 567:\t\t\t\t\t\t struct list_lru *lru)\n 568:\t{\n 569:\t\tif (!memcg || mem_cgroup_is_root(memcg))\n 570:\t\t\treturn true;\n 571:\t\n 572:\t\treturn xa_load(\u0026lru-\u003exa, mem_cgroup_id(memcg));\n 573:\t}\n 574:\t\n 575:\tstatic int __memcg_list_lru_alloc(struct mem_cgroup *memcg,\n 576:\t\t\t\t\t struct list_lru *lru, gfp_t gfp)\n 577:\t{\n 578:\t\tunsigned long flags;\n 579:\t\tstruct list_lru_memcg *mlru = NULL;\n"
} |
| 9/2 | 2026/09/10 08:41 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 11388 output: 36 thoughts: 73 Thoughts: Here's my take on the thought process, as requested: **Diving Deep into `__memcg_list_lru_alloc` and Related Functions** Okay, so I'm thinking, before I go any further, I need to thoroughly understand how `__memcg_list_lru_alloc` works and, crucially, how everything *uses* it. My next move is going to be tracing the call path – specifically, I need to investigate not just the direct callers of `__memcg_list_lru_alloc`, but also the functions that subsequently use what it allocates. I'm talking about any function that interacts with that returned data in a meaningful way. This means a methodical search for anything calling `memcg_list_lru_alloc` or any of the fundamental list_lru functions. I'm focusing on the core list manipulation: `list_lru_add`, `list_lru_del`, `list_lru_count_one`, and `list_lru_walk_one`. By examining these, I can get a complete picture of the allocation's lifetime, its purpose, and how it is ultimately being used. This should give me a solid foundation for any further analysis or optimization. I need to understand all the usage patterns before I can make any informed decisions. |
| 10/2 | 2026/09/10 08:41 | tool | read-file |
0mArgs:{
"File": "mm/list_lru.c",
"FirstLine": 580,
"LineCount": 90
}Results: {
"Contents": " 580:\t\tstruct mem_cgroup *pos, *parent;\n 581:\t\tXA_STATE(xas, \u0026lru-\u003exa, 0);\n 582:\t\n 583:\t\tgfp \u0026= GFP_RECLAIM_MASK;\n 584:\t\t/*\n 585:\t\t * Because the list_lru can be reparented to the parent cgroup's\n 586:\t\t * list_lru, we should make sure that this cgroup and all its\n 587:\t\t * ancestors have allocated list_lru_memcg.\n 588:\t\t */\n 589:\t\tdo {\n 590:\t\t\t/*\n 591:\t\t\t * Keep finding the farest parent that wasn't populated\n 592:\t\t\t * until found memcg itself.\n 593:\t\t\t */\n 594:\t\t\tpos = memcg;\n 595:\t\t\tparent = parent_mem_cgroup(pos);\n 596:\t\t\twhile (!memcg_list_lru_allocated(parent, lru)) {\n 597:\t\t\t\tpos = parent;\n 598:\t\t\t\tparent = parent_mem_cgroup(pos);\n 599:\t\t\t}\n 600:\t\n 601:\t\t\tif (!mlru) {\n 602:\t\t\t\tmlru = memcg_init_list_lru_one(lru, gfp);\n 603:\t\t\t\tif (!mlru)\n 604:\t\t\t\t\treturn -ENOMEM;\n 605:\t\t\t}\n 606:\t\t\txas_set(\u0026xas, mem_cgroup_id(pos));\n 607:\t\t\tdo {\n 608:\t\t\t\txas_lock_irqsave(\u0026xas, flags);\n 609:\t\t\t\tif (!xas_load(\u0026xas) \u0026\u0026 !css_is_dying(\u0026pos-\u003ecss)) {\n 610:\t\t\t\t\txas_store(\u0026xas, mlru);\n 611:\t\t\t\t\tif (!xas_error(\u0026xas))\n 612:\t\t\t\t\t\tmlru = NULL;\n 613:\t\t\t\t}\n 614:\t\t\t\txas_unlock_irqrestore(\u0026xas, flags);\n 615:\t\t\t} while (xas_nomem(\u0026xas, gfp));\n 616:\t\t} while (pos != memcg \u0026\u0026 !css_is_dying(\u0026pos-\u003ecss));\n 617:\t\n 618:\t\tif (unlikely(mlru))\n 619:\t\t\tkfree(mlru);\n 620:\t\n 621:\t\treturn xas_error(\u0026xas);\n 622:\t}\n 623:\t\n 624:\tint memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,\n 625:\t\t\t\t gfp_t gfp)\n 626:\t{\n 627:\t\tif (!list_lru_memcg_aware(lru) || memcg_list_lru_allocated(memcg, lru))\n 628:\t\t\treturn 0;\n 629:\t\treturn __memcg_list_lru_alloc(memcg, lru, gfp);\n 630:\t}\n 631:\t\n 632:\tint folio_memcg_list_lru_alloc(struct folio *folio, struct list_lru *lru,\n 633:\t\t\t\t gfp_t gfp)\n 634:\t{\n 635:\t\tstruct mem_cgroup *memcg;\n 636:\t\tint res;\n 637:\t\n 638:\t\tif (!list_lru_memcg_aware(lru))\n 639:\t\t\treturn 0;\n 640:\t\n 641:\t\t/* Fast path when list_lru heads already exist */\n 642:\t\trcu_read_lock();\n 643:\t\tmemcg = folio_memcg(folio);\n 644:\t\tres = memcg_list_lru_allocated(memcg, lru);\n 645:\t\trcu_read_unlock();\n 646:\t\tif (likely(res))\n 647:\t\t\treturn 0;\n 648:\t\n 649:\t\t/* Allocation may block, pin the memcg */\n 650:\t\tmemcg = get_mem_cgroup_from_folio(folio);\n 651:\t\tres = __memcg_list_lru_alloc(memcg, lru, gfp);\n 652:\t\tmem_cgroup_put(memcg);\n 653:\t\treturn res;\n 654:\t}\n 655:\t#else\n 656:\tstatic inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)\n 657:\t{\n 658:\t}\n 659:\t\n 660:\tstatic void memcg_destroy_list_lru(struct list_lru *lru)\n 661:\t{\n 662:\t}\n 663:\t#endif /* CONFIG_MEMCG */\n 664:\t\n 665:\tint __list_lru_init(struct list_lru *lru, bool memcg_aware, struct shrinker *shrinker)\n 666:\t{\n 667:\t\tint i;\n 668:\t\n 669:\t#ifdef CONFIG_MEMCG\n"
} |
| 11/2 | 2026/09/10 08:41 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 13153 output: 25 thoughts: 414 Thoughts: **My Analysis of this Memory Management Patch** Okay, let's break this down. This patch is clearly digging deep into core memory management territory – we're talking about changes to `mm/list_lru.c`, `mm/memcontrol.c`, `mm/huge_memory.c`, and `mm/zswap.c`. That tells me this is important! The core change revolves around how `list_lru` indexes those per-memcg LRU lists. Before, it was using `kmemcg_id`, but now it's switching to directly using `mem_cgroup_id(memcg)`. Okay, so they're moving away from the initialization-based `kmemcg_id` and directly referencing the `memcg->id.id` allocated during the css initialization process. This suggests a potential performance or correctness improvement in how these LRU lists are managed within the memory control group framework. I also see modifications related to the THP deferred split shrinker and the zswap shrinker, with `SHRINKER_NONSLAB` being added. And a tweak to `__list_lru_init` to keep it `memcg_aware` even if `mem_cgroup_kmem_disabled()` when `shrinker->flags & SHRINKER_NONSLAB`. This seems like they're simplifying some logic and likely ensuring more robust memcg integration in the shrinking process. The simplification of `mem_cgroup_css_online` and `mem_cgroup_css_offline` to remove `memcg_online_kmem` and `memcg_offline_kmem` by directly reparenting list_lrus further corroborates this. Is this code path actually *reachable*? Absolutely. Core memory management, cgroups/memcg, list_lru, THP shrinker, and zswap shrinker are all intertwined. This is definitely `WorthFuzzing=true`. The potential for subtle interactions and edge cases within this code makes it a prime candidate for fuzzing. Now, I need to check the configurations. What CONFIG options are we looking at? `CONFIG_MEMCG`, obviously, plus `CONFIG_TRANSPARENT_HUGEPAGE`, and `CONFIG_ZSWAP`. I should double-check the `CONFIG_MEMCG_KMEM` situation... is that still around, or has it been merged into just `CONFIG_MEMCG`? I'll run a quick grepper search to confirm. Gotta make sure our fuzzing builds are configured correctly. |
| 12/2 | 2026/09/10 08:41 | tool | grepper |
0mError:no matches Args: {
"Expression": "config MEMCG",
"PathPrefix": "mm/"
}Results: {
"error": "no matches"
} |
| 13/2 | 2026/09/10 08:41 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 14151 output: 17 thoughts: 18 Thoughts: Here's my thought process, as if I were considering those Kconfig files: **Finding the Right Configuration Location** Okay, so I need to figure out where a specific configuration option is defined, right? My first instinct is to check the most common places for kernel configuration options. Since this is related to memory management, I'd immediately lean towards looking in `init/Kconfig` and `mm/Kconfig`. `init/Kconfig` is often a good starting point for general system initialization options, and `mm/Kconfig` is, of course, the obvious choice for anything related to memory management. I'll start with those two and see what I can find! They're likely the most relevant and efficient places to begin my search. |
| 14/2 | 2026/09/10 08:41 | tool | grepper |
0mArgs:{
"Expression": "config MEMCG"
}Results: {
"Output": "init/Kconfig=1076=config CGROUP_FAVOR_DYNMODS\n--\ninit/Kconfig-1085-\ninit/Kconfig:1086:config MEMCG\ninit/Kconfig-1087-\tbool \"Memory controller\"\n--\ninit/Kconfig-1094-\ninit/Kconfig:1095:config MEMCG_NMI_UNSAFE\ninit/Kconfig-1096-\tbool\n--\ninit/Kconfig-1101-\ninit/Kconfig:1102:config MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\ninit/Kconfig-1103-\tbool\n--\ninit/Kconfig-1108-\ninit/Kconfig:1109:config MEMCG_V1\ninit/Kconfig-1110-\tbool \"Legacy cgroup v1 memory controller\"\n"
} |
| 15/2 | 2026/09/10 08:41 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 14572 output: 22 thoughts: 27 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: **Checking Kernel Memory Configuration** Right, let's just quickly confirm a couple of critical memory-related configurations in the kernel. I need to double-check the settings for `TRANSPARENT_HUGEPAGE` and `ZSWAP` within `mm/Kconfig`. These are fundamental for how the kernel handles memory. The impact of `TRANSPARENT_HUGEPAGE` is pretty direct on memory fragmentation and overall performance, especially under heavier workloads, and I need to ensure it's set appropriately for the specific hardware and application profile in mind. Then I need to confirm `ZSWAP`. This is for swap space compression. I should consider whether the performance benefits of compression outweigh the CPU overhead, especially on systems with sufficient physical RAM. Gotta make sure both configurations align with the design goals and the system’s resource constraints. Time to dive into that Kconfig file. |
| 16/2 | 2026/09/10 08:41 | tool | grepper |
0mArgs:{
"Expression": "config TRANSPARENT_HUGEPAGE"
}Results: {
"Output": "mm/Kconfig=827=config MM_ID\n--\nmm/Kconfig-829-\nmm/Kconfig:830:menuconfig TRANSPARENT_HUGEPAGE\nmm/Kconfig-831-\tbool \"Transparent Hugepage Support\"\n--\nmm/Kconfig=848=choice\n--\nmm/Kconfig-853-\nmm/Kconfig:854:\tconfig TRANSPARENT_HUGEPAGE_ALWAYS\nmm/Kconfig-855-\t\tbool \"always\"\n--\nmm/Kconfig-860-\nmm/Kconfig:861:\tconfig TRANSPARENT_HUGEPAGE_MADVISE\nmm/Kconfig-862-\t\tbool \"madvise\"\n--\nmm/Kconfig-869-\nmm/Kconfig:870:\tconfig TRANSPARENT_HUGEPAGE_NEVER\nmm/Kconfig-871-\t\tbool \"never\"\n--\nmm/Kconfig=877=choice\n--\nmm/Kconfig-886-\nmm/Kconfig:887:\tconfig TRANSPARENT_HUGEPAGE_SHMEM_HUGE_NEVER\nmm/Kconfig-888-\t\tbool \"never\"\n--\nmm/Kconfig-896-\nmm/Kconfig:897:\tconfig TRANSPARENT_HUGEPAGE_SHMEM_HUGE_ALWAYS\nmm/Kconfig-898-\t\tbool \"always\"\n--\nmm/Kconfig-904-\nmm/Kconfig:905:\tconfig TRANSPARENT_HUGEPAGE_SHMEM_HUGE_WITHIN_SIZE\nmm/Kconfig-906-\t\tbool \"within_size\"\n--\nmm/Kconfig-912-\nmm/Kconfig:913:\tconfig TRANSPARENT_HUGEPAGE_SHMEM_HUGE_ADVISE\nmm/Kconfig-914-\t\tbool \"advise\"\n--\nmm/Kconfig=922=choice\n--\nmm/Kconfig-931-\nmm/Kconfig:932:\tconfig TRANSPARENT_HUGEPAGE_TMPFS_HUGE_NEVER\nmm/Kconfig-933-\t\tbool \"never\"\n--\nmm/Kconfig-940-\nmm/Kconfig:941:\tconfig TRANSPARENT_HUGEPAGE_TMPFS_HUGE_ALWAYS\nmm/Kconfig-942-\t\tbool \"always\"\n--\nmm/Kconfig-948-\nmm/Kconfig:949:\tconfig TRANSPARENT_HUGEPAGE_TMPFS_HUGE_WITHIN_SIZE\nmm/Kconfig-950-\t\tbool \"within_size\"\n--\nmm/Kconfig-956-\nmm/Kconfig:957:\tconfig TRANSPARENT_HUGEPAGE_TMPFS_HUGE_ADVISE\nmm/Kconfig-958-\t\tbool \"advise\"\n"
} |
| 17/2 | 2026/09/10 08:41 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 15539 output: 18 thoughts: 9 Thoughts: Okay, here's my attempt at summarizing the thought process, tailored for an expert audience, and written in the first person: **Let's Dive into `ZSWAP`** Alright, time to circle back to `ZSWAP`. This isn't just a casual glance; I need to quickly assess its current state and any potential impacts. My initial thought process is likely to be driven by a few key questions: What triggered this review? Is it performance-related, a bug report, or perhaps a general architectural consideration? My mind is already running through a mental checklist: What's the implementation? How is it integrated within the broader swap subsystem? Are we talking about a simple LRU-based swapping implementation, or something more advanced like demand paging with compression or encryption? I need to quickly recall the relevant kernel documentation and any recent patches related to `ZSWAP`. I'll be looking for any indications of increased usage, potential bottlenecks, or recent changes that might need my attention. I'll be mentally parsing the code, focusing on areas like page allocation and deallocation, data compression and decompression, and the interactions with the backing store (typically disk or a dedicated swap partition). I'll want to see how the system handles page fault handling and the overall swapping algorithm, to quickly understand how it can affect the overall performance. The main thing is to find if there are any current areas of concern, or if anything looks particularly unusual at the moment. |
| 18/2 | 2026/09/10 08:41 | tool | grepper |
0mArgs:{
"Expression": "config ZSWAP"
}Results: {
"Output": "mm/Kconfig=12=menuconfig SWAP\n--\nmm/Kconfig-21-\nmm/Kconfig:22:config ZSWAP\nmm/Kconfig-23-\tbool \"Compressed cache for swap pages\"\n--\nmm/Kconfig-34-\nmm/Kconfig:35:config ZSWAP_DEFAULT_ON\nmm/Kconfig-36-\tbool \"Enable the compressed cache for swap pages by default\"\n--\nmm/Kconfig-44-\nmm/Kconfig:45:config ZSWAP_SHRINKER_DEFAULT_ON\nmm/Kconfig-46-\tbool \"Shrink the zswap pool on memory pressure\"\n--\nmm/Kconfig=59=choice\n--\nmm/Kconfig-76-\nmm/Kconfig:77:config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE\nmm/Kconfig-78-\tbool \"Deflate\"\n--\nmm/Kconfig-82-\nmm/Kconfig:83:config ZSWAP_COMPRESSOR_DEFAULT_LZO\nmm/Kconfig-84-\tbool \"LZO\"\n--\nmm/Kconfig-88-\nmm/Kconfig:89:config ZSWAP_COMPRESSOR_DEFAULT_842\nmm/Kconfig-90-\tbool \"842\"\n--\nmm/Kconfig-94-\nmm/Kconfig:95:config ZSWAP_COMPRESSOR_DEFAULT_LZ4\nmm/Kconfig-96-\tbool \"LZ4\"\n--\nmm/Kconfig-100-\nmm/Kconfig:101:config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC\nmm/Kconfig-102-\tbool \"LZ4HC\"\n--\nmm/Kconfig-106-\nmm/Kconfig:107:config ZSWAP_COMPRESSOR_DEFAULT_ZSTD\nmm/Kconfig-108-\tbool \"zstd\"\n--\nmm/Kconfig=112=endchoice\nmm/Kconfig-113-\nmm/Kconfig:114:config ZSWAP_COMPRESSOR_DEFAULT\nmm/Kconfig-115- string\n"
} |
| 19/2 | 2026/09/10 08:41 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 16409 output: 41 thoughts: 423 Thoughts: **My Analysis of Relevant Kernel Configurations and Functions** Okay, let's break this down. My initial focus is on the kernel configurations – specifically, `CONFIG_MEMCG`, `CONFIG_TRANSPARENT_HUGEPAGE`, and `CONFIG_ZSWAP`. These are the key variables that define the playing field for the code I'm analyzing. Now, I need to identify the crucial functions. My goal is to pinpoint the most specific, non-ubiquitous functions that have been modified or that directly call the changed logic. I want to avoid anything overly general. I see a concentrated set of these in `mm/list_lru.c`. Looking at the functions listed, I'll need to examine: * `list_lru_count_one` * `list_lru_add` * `list_lru_del` * `lock_list_lru_of_memcg` (this one's static inline, so there may be a symbol check) I'll need to confirm which symbols in this file are non-static/exported or static using read-file or grepper. * `memcg_reparent_list_lrus` * `memcg_reparent_list_lru_one` * `memcg_list_lru_alloc` * `folio_memcg_list_lru_alloc` * `__memcg_list_lru_alloc` * `__list_lru_init` Then, moving to `mm/memcontrol.c`, the functions of interest are: * `mem_cgroup_css_online` * `mem_cgroup_css_offline` And, in `mm/huge_memory.c`, the list includes: * `thp_shrinker_init` (this is an init function, so it's only run at boot, right?) * `folio_memcg_alloc_deferred` or `deferred_split_scan` / `deferred_split_count` / `deferred_split_folio` Finally, from `mm/zswap.c`: * `zswap_alloc_shrinker` / `zswap_shrinker_scan` / `zswap_shrinker_count` Now, to refine this further, I'll need to use `read-file` or `grepper` on `mm/list_lru.c` to look at those symbol names and make sure I know how they're being used. |
| 20/2 | 2026/09/10 08:41 | tool | grepper |
0mArgs:{
"Expression": "^[a-zA-Z_0-9]+ .*\\(",
"PathPrefix": "mm/list_lru.c"
}Results: {
"Output": "mm/list_lru.c-17-\nmm/list_lru.c:18:static inline void lock_list_lru(struct list_lru_one *l, bool irq,\nmm/list_lru.c-19-\t\t\t\t unsigned long *irq_flags)\n--\nmm/list_lru.c-28-\nmm/list_lru.c:29:static inline void unlock_list_lru(struct list_lru_one *l, bool irq_off,\nmm/list_lru.c-30-\t\t\t\t unsigned long *irq_flags)\n--\nmm/list_lru.c-40-#ifdef CONFIG_MEMCG\nmm/list_lru.c:41:static LIST_HEAD(memcg_list_lrus);\nmm/list_lru.c:42:static DEFINE_MUTEX(list_lrus_mutex);\nmm/list_lru.c-43-\nmm/list_lru.c:44:static inline bool list_lru_memcg_aware(struct list_lru *lru)\nmm/list_lru.c-45-{\n--\nmm/list_lru.c-48-\nmm/list_lru.c:49:static void list_lru_register(struct list_lru *lru)\nmm/list_lru.c-50-{\n--\nmm/list_lru.c-58-\nmm/list_lru.c:59:static void list_lru_unregister(struct list_lru *lru)\nmm/list_lru.c-60-{\n--\nmm/list_lru.c-68-\nmm/list_lru.c:69:static int lru_shrinker_id(struct list_lru *lru)\nmm/list_lru.c-70-{\n--\nmm/list_lru.c=87=lock_list_lru_of_memcg(struct list_lru *lru, int nid,\n--\nmm/list_lru.c-116-#else\nmm/list_lru.c:117:static void list_lru_register(struct list_lru *lru)\nmm/list_lru.c-118-{\n--\nmm/list_lru.c-120-\nmm/list_lru.c:121:static void list_lru_unregister(struct list_lru *lru)\nmm/list_lru.c-122-{\n--\nmm/list_lru.c-124-\nmm/list_lru.c:125:static int lru_shrinker_id(struct list_lru *lru)\nmm/list_lru.c-126-{\n--\nmm/list_lru.c-129-\nmm/list_lru.c:130:static inline bool list_lru_memcg_aware(struct list_lru *lru)\nmm/list_lru.c-131-{\n--\nmm/list_lru.c=142=lock_list_lru_of_memcg(struct list_lru *lru, int nid,\n--\nmm/list_lru.c-153-\nmm/list_lru.c:154:struct list_lru_one *list_lru_lock(struct list_lru *lru, int nid,\nmm/list_lru.c-155-\t\t\t\t struct mem_cgroup **memcg)\n--\nmm/list_lru.c-160-\nmm/list_lru.c:161:void list_lru_unlock(struct list_lru_one *l)\nmm/list_lru.c-162-{\n--\nmm/list_lru.c-165-\nmm/list_lru.c:166:struct list_lru_one *list_lru_lock_irq(struct list_lru *lru, int nid,\nmm/list_lru.c-167-\t\t\t\t struct mem_cgroup **memcg)\n--\nmm/list_lru.c-172-\nmm/list_lru.c:173:void list_lru_unlock_irq(struct list_lru_one *l)\nmm/list_lru.c-174-{\n--\nmm/list_lru.c-177-\nmm/list_lru.c:178:struct list_lru_one *list_lru_lock_irqsave(struct list_lru *lru, int nid,\nmm/list_lru.c-179-\t\t\t\t\t struct mem_cgroup **memcg,\n--\nmm/list_lru.c-185-\nmm/list_lru.c:186:void list_lru_unlock_irqrestore(struct list_lru_one *l, unsigned long *flags)\nmm/list_lru.c-187-{\n--\nmm/list_lru.c-190-\nmm/list_lru.c:191:bool __list_lru_add(struct list_lru *lru, struct list_lru_one *l,\nmm/list_lru.c-192-\t\t struct list_head *item, int nid,\n--\nmm/list_lru.c=209=EXPORT_SYMBOL_GPL(list_lru_add);\nmm/list_lru.c-210-\nmm/list_lru.c:211:bool __list_lru_del(struct list_lru *lru, struct list_lru_one *l,\nmm/list_lru.c-212-\t\t struct list_head *item, int nid)\n--\nmm/list_lru.c-223-/* The caller must ensure the memcg lifetime. */\nmm/list_lru.c:224:bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid,\nmm/list_lru.c-225-\t\t struct mem_cgroup *memcg)\n--\nmm/list_lru.c-235-\nmm/list_lru.c:236:bool list_lru_add_irq(struct list_lru *lru, struct list_head *item,\nmm/list_lru.c-237-\t\t int nid, struct mem_cgroup *memcg)\n--\nmm/list_lru.c-247-\nmm/list_lru.c:248:bool list_lru_add_obj(struct list_lru *lru, struct list_head *item)\nmm/list_lru.c-249-{\n--\nmm/list_lru.c=263=EXPORT_SYMBOL_GPL(list_lru_add_obj);\n--\nmm/list_lru.c-265-/* The caller must ensure the memcg lifetime. */\nmm/list_lru.c:266:bool list_lru_del(struct list_lru *lru, struct list_head *item, int nid,\nmm/list_lru.c-267-\t\t struct mem_cgroup *memcg)\n--\nmm/list_lru.c-277-\nmm/list_lru.c:278:bool list_lru_del_obj(struct list_lru *lru, struct list_head *item)\nmm/list_lru.c-279-{\n--\nmm/list_lru.c=293=EXPORT_SYMBOL_GPL(list_lru_del_obj);\nmm/list_lru.c-294-\nmm/list_lru.c:295:void list_lru_isolate(struct list_lru_one *list, struct list_head *item)\nmm/list_lru.c-296-{\n--\nmm/list_lru.c=300=EXPORT_SYMBOL_GPL(list_lru_isolate);\nmm/list_lru.c-301-\nmm/list_lru.c:302:void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,\nmm/list_lru.c-303-\t\t\t struct list_head *head)\n--\nmm/list_lru.c=308=EXPORT_SYMBOL_GPL(list_lru_isolate_move);\nmm/list_lru.c-309-\nmm/list_lru.c:310:unsigned long list_lru_count_one(struct list_lru *lru,\nmm/list_lru.c-311-\t\t\t\t int nid, struct mem_cgroup *memcg)\n--\nmm/list_lru.c=326=EXPORT_SYMBOL_GPL(list_lru_count_one);\nmm/list_lru.c-327-\nmm/list_lru.c:328:unsigned long list_lru_count_node(struct list_lru *lru, int nid)\nmm/list_lru.c-329-{\n--\nmm/list_lru.c=406=list_lru_walk_one_irq(struct list_lru *lru, int nid, struct mem_cgroup *memcg,\n--\nmm/list_lru.c-413-\nmm/list_lru.c:414:unsigned long list_lru_walk_node(struct list_lru *lru, int nid,\nmm/list_lru.c-415-\t\t\t\t list_lru_walk_cb isolate, void *cb_arg,\n--\nmm/list_lru.c=450=EXPORT_SYMBOL_GPL(list_lru_walk_node);\nmm/list_lru.c-451-\nmm/list_lru.c:452:static void init_one_lru(struct list_lru *lru, struct list_lru_one *l)\nmm/list_lru.c-453-{\n--\nmm/list_lru.c-463-#ifdef CONFIG_MEMCG\nmm/list_lru.c:464:static struct list_lru_memcg *memcg_init_list_lru_one(struct list_lru *lru, gfp_t gfp)\nmm/list_lru.c-465-{\n--\nmm/list_lru.c-478-\nmm/list_lru.c:479:static inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)\nmm/list_lru.c-480-{\n--\nmm/list_lru.c-485-\nmm/list_lru.c:486:static void memcg_destroy_list_lru(struct list_lru *lru)\nmm/list_lru.c-487-{\n--\nmm/list_lru.c-501-\nmm/list_lru.c:502:static void memcg_reparent_list_lru_one(struct list_lru *lru, int nid,\nmm/list_lru.c-503-\t\t\t\t\tstruct list_lru_one *src,\n--\nmm/list_lru.c-524-\nmm/list_lru.c:525:void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent)\nmm/list_lru.c-526-{\n--\nmm/list_lru.c-565-\nmm/list_lru.c:566:static inline bool memcg_list_lru_allocated(struct mem_cgroup *memcg,\nmm/list_lru.c-567-\t\t\t\t\t struct list_lru *lru)\n--\nmm/list_lru.c-574-\nmm/list_lru.c:575:static int __memcg_list_lru_alloc(struct mem_cgroup *memcg,\nmm/list_lru.c-576-\t\t\t\t struct list_lru *lru, gfp_t gfp)\n--\nmm/list_lru.c-623-\nmm/list_lru.c:624:int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,\nmm/list_lru.c-625-\t\t\t gfp_t gfp)\n--\nmm/list_lru.c-631-\nmm/list_lru.c:632:int folio_memcg_list_lru_alloc(struct folio *folio, struct list_lru *lru,\nmm/list_lru.c-633-\t\t\t gfp_t gfp)\n--\nmm/list_lru.c-655-#else\nmm/list_lru.c:656:static inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)\nmm/list_lru.c-657-{\n--\nmm/list_lru.c-659-\nmm/list_lru.c:660:static void memcg_destroy_list_lru(struct list_lru *lru)\nmm/list_lru.c-661-{\n--\nmm/list_lru.c-664-\nmm/list_lru.c:665:int __list_lru_init(struct list_lru *lru, bool memcg_aware, struct shrinker *shrinker)\nmm/list_lru.c-666-{\n--\nmm/list_lru.c=698=EXPORT_SYMBOL_GPL(__list_lru_init);\nmm/list_lru.c-699-\nmm/list_lru.c:700:void list_lru_destroy(struct list_lru *lru)\nmm/list_lru.c-701-{\n"
} |
| 21/2 | 2026/09/10 08:41 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 20980 output: 221 thoughts: 407 Thoughts: **Analyzing a Memory Cgroup Refactoring Patch** Okay, let's break this down. First, I need to identify the key symbols affected by this patch. I've got a list here: `memcg_reparent_list_lrus`, `__memcg_list_lru_alloc`, `memcg_list_lru_alloc`, `folio_memcg_list_lru_alloc`, `list_lru_count_one`, `mem_cgroup_css_online`, and `mem_cgroup_css_offline`. These seem like the primary entry points or data structures involved in the changes. Now, let's confirm the reasoning and impact. The patch series is fundamentally about refactoring how memory cgroups handle `list_lru` instances. It's moving from `kmemcg_id` to `mem_cgroup_id` which is a significant architectural shift. It also removes those lifecycle hooks, `memcg_online_kmem` and `memcg_offline_kmem`, simplifying things. And the addition of `SHRINKER_NONSLAB` is important, making sure memcg awareness is present even when kmem accounting is disabled. This is a pretty core change affecting memory management and cgroup reparenting, meaning it's reachable through user-space interactions like cgroup creation, memory allocation, and reclaim pressure. Definitely a significant area. Finally, I have to ensure the necessary kernel configurations are enabled. We're looking at `MEMCG`, `TRANSPARENT_HUGEPAGE`, and `ZSWAP`. Makes sense, as these features are directly involved in the memory management and cgroup interaction being refactored. Alright, with all that validated, it's time to 'set-results' and move on. |
| 22/2 | 2026/09/10 08:42 | tool | set-results |
0mArgs:{
"EnableConfigs": [
"MEMCG",
"TRANSPARENT_HUGEPAGE",
"ZSWAP"
],
"FocusSymbols": [
"memcg_reparent_list_lrus",
"__memcg_list_lru_alloc",
"memcg_list_lru_alloc",
"folio_memcg_list_lru_alloc",
"list_lru_count_one",
"mem_cgroup_css_online",
"mem_cgroup_css_offline"
],
"Reasoning": "The patch refactors list_lru indexing and lifetime management across memory cgroups by replacing kmemcg_id with mem_cgroup_id and unifying the reparenting paths during memcg offline. It also enables SHRINKER_NONSLAB on THP deferred split and zswap shrinkers. These changes touch reachable core mm and cgroup code paths executed during cgroup lifecycles and memory reclaim.",
"WorthFuzzing": true
}Results: {
"EnableConfigs": [
"MEMCG",
"TRANSPARENT_HUGEPAGE",
"ZSWAP"
],
"FocusSymbols": [
"memcg_reparent_list_lrus",
"__memcg_list_lru_alloc",
"memcg_list_lru_alloc",
"folio_memcg_list_lru_alloc",
"list_lru_count_one",
"mem_cgroup_css_online",
"mem_cgroup_css_offline"
],
"Reasoning": "The patch refactors list_lru indexing and lifetime management across memory cgroups by replacing kmemcg_id with mem_cgroup_id and unifying the reparenting paths during memcg offline. It also enables SHRINKER_NONSLAB on THP deferred split and zswap shrinkers. These changes touch reachable core mm and cgroup code paths executed during cgroup lifecycles and memory reclaim.",
"WorthFuzzing": true
} |
| 23/1 | 2026/09/10 08:42 | action | If |
0mArgs:{
"WorthFuzzing": true
}Results: null |
| 24/2 | 2026/09/10 08:42 | agent | kmsan-evaluator |
0mModel:core Args: null Results: {
"KMSANReasoning": "The patch refactors the memcg LRU list indexing by eliminating the redundant `kmemcg_id` field from `struct mem_cgroup` in favor of `mem_cgroup_id()`, and marks THP deferred split and zswap shrinkers with `SHRINKER_NONSLAB`.\n\nNo new uninitialized memory allocations, conditional branches on uninitialized values, or data structures exported to user space are introduced. Any potential lifetime, concurrency, or pointer indexing issues related to xarray or memcg reparenting are within the domain of KASAN, LOCKDEP, and standard kernel debugging tools. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
"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 42e91a5e11a6f41178b648ecc9bf8424ab0023e2
Author: syz-cluster <triage@syzkaller.com>
Date: Thu Sep 10 08:41:10 2026 +0000
syz-cluster: applied patch under review
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index a03b6e3e54707..3463d2c52c628 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -253,7 +253,6 @@ struct mem_cgroup {
#if BITS_PER_LONG < 64
seqlock_t socket_pressure_seqlock;
#endif
- int kmemcg_id;
#ifdef CONFIG_CGROUP_WRITEBACK
struct list_head cgwb_list;
@@ -1775,15 +1774,6 @@ static inline void memcg_kmem_uncharge_page(struct page *page, int order)
__memcg_kmem_uncharge_page(page, order);
}
-/*
- * A helper for accessing memcg's kmem_id, used for getting
- * corresponding LRU lists.
- */
-static inline int memcg_kmem_id(struct mem_cgroup *memcg)
-{
- return memcg ? memcg->kmemcg_id : -1;
-}
-
struct mem_cgroup *mem_cgroup_from_virt(void *p);
static inline void count_objcg_events(struct obj_cgroup *objcg,
@@ -1851,11 +1841,6 @@ static inline bool memcg_kmem_online(void)
return false;
}
-static inline int memcg_kmem_id(struct mem_cgroup *memcg)
-{
- return -1;
-}
-
static inline struct mem_cgroup *mem_cgroup_from_virt(void *p)
{
return NULL;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index dd66c6ad5af13..d1ce061601bcd 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1064,7 +1064,8 @@ int folio_memcg_alloc_deferred(struct folio *folio)
static int __init thp_shrinker_init(void)
{
deferred_split_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE |
- SHRINKER_MEMCG_AWARE,
+ SHRINKER_MEMCG_AWARE |
+ SHRINKER_NONSLAB,
"thp-deferred_split");
if (!deferred_split_shrinker)
return -ENOMEM;
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 8a6dd0a489e12..f1968f02be3b3 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -72,10 +72,11 @@ static int lru_shrinker_id(struct list_lru *lru)
}
static inline struct list_lru_one *
-list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)
+list_lru_from_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg)
{
- if (list_lru_memcg_aware(lru) && idx >= 0) {
- struct list_lru_memcg *mlru = xa_load(&lru->xa, idx);
+ if (list_lru_memcg_aware(lru) && memcg && !mem_cgroup_is_root(memcg)) {
+ struct list_lru_memcg *mlru =
+ xa_load(&lru->xa, mem_cgroup_id(memcg));
return mlru ? &mlru->node[nid] : NULL;
}
@@ -91,7 +92,7 @@ lock_list_lru_of_memcg(struct list_lru *lru, int nid,
rcu_read_lock();
again:
- l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(*memcg));
+ l = list_lru_from_memcg(lru, nid, *memcg);
if (likely(l)) {
lock_list_lru(l, irq, irq_flags);
if (likely(READ_ONCE(l->nr_items) != LONG_MIN)) {
@@ -132,7 +133,7 @@ static inline bool list_lru_memcg_aware(struct list_lru *lru)
}
static inline struct list_lru_one *
-list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)
+list_lru_from_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg)
{
return &lru->node[nid].lru;
}
@@ -313,7 +314,7 @@ unsigned long list_lru_count_one(struct list_lru *lru,
long count;
rcu_read_lock();
- l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
+ l = list_lru_from_memcg(lru, nid, memcg);
count = l ? READ_ONCE(l->nr_items) : 0;
rcu_read_unlock();
@@ -502,11 +503,10 @@ static void memcg_reparent_list_lru_one(struct list_lru *lru, int nid,
struct list_lru_one *src,
struct mem_cgroup *dst_memcg)
{
- int dst_idx = dst_memcg->kmemcg_id;
struct list_lru_one *dst;
spin_lock_irq(&src->lock);
- dst = list_lru_from_memcg_idx(lru, nid, dst_idx);
+ dst = list_lru_from_memcg(lru, nid, dst_memcg);
spin_lock_nested(&dst->lock, SINGLE_DEPTH_NESTING);
list_splice_init(&src->list, &dst->list);
@@ -536,7 +536,7 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren
* allocating a new mlru since CSS_DYING is already set for this
* memcg a rcu grace period ago.
*/
- mlru = xa_load(&lru->xa, memcg->kmemcg_id);
+ mlru = xa_load(&lru->xa, mem_cgroup_id(memcg));
if (!mlru)
continue;
@@ -551,7 +551,7 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren
for_each_node(i)
memcg_reparent_list_lru_one(lru, i, &mlru->node[i], parent);
- xa_erase_irq(&lru->xa, memcg->kmemcg_id);
+ xa_erase_irq(&lru->xa, mem_cgroup_id(memcg));
/*
* Here all list_lrus corresponding to the cgroup are guaranteed
@@ -566,9 +566,10 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren
static inline bool memcg_list_lru_allocated(struct mem_cgroup *memcg,
struct list_lru *lru)
{
- int idx = memcg->kmemcg_id;
+ if (!memcg || mem_cgroup_is_root(memcg))
+ return true;
- return idx < 0 || xa_load(&lru->xa, idx);
+ return xa_load(&lru->xa, mem_cgroup_id(memcg));
}
static int __memcg_list_lru_alloc(struct mem_cgroup *memcg,
@@ -602,7 +603,7 @@ static int __memcg_list_lru_alloc(struct mem_cgroup *memcg,
if (!mlru)
return -ENOMEM;
}
- xas_set(&xas, pos->kmemcg_id);
+ xas_set(&xas, mem_cgroup_id(pos));
do {
xas_lock_irqsave(&xas, flags);
if (!xas_load(&xas) && !css_is_dying(&pos->css)) {
@@ -676,7 +677,9 @@ int __list_lru_init(struct list_lru *lru, bool memcg_aware, struct shrinker *shr
else
lru->shrinker_id = -1;
- if (mem_cgroup_disabled() || mem_cgroup_kmem_disabled())
+ if (mem_cgroup_disabled() ||
+ (mem_cgroup_kmem_disabled() &&
+ (!shrinker || !(shrinker->flags & SHRINKER_NONSLAB))))
memcg_aware = false;
#endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4cb2db8c0923a..ae2d6d9cfa742 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3763,33 +3763,6 @@ void folio_split_memcg_refs(struct folio *folio, unsigned old_order,
obj_cgroup_get_many(folio_objcg(folio), new_refs);
}
-static void memcg_online_kmem(struct mem_cgroup *memcg)
-{
- if (mem_cgroup_kmem_disabled())
- return;
-
- if (unlikely(mem_cgroup_is_root(memcg)))
- return;
-
- static_branch_enable(&memcg_kmem_online_key);
-
- memcg->kmemcg_id = memcg->id.id;
-}
-
-static void memcg_offline_kmem(struct mem_cgroup *memcg)
-{
- struct mem_cgroup *parent;
-
- if (mem_cgroup_kmem_disabled())
- return;
-
- if (unlikely(mem_cgroup_is_root(memcg)))
- return;
-
- parent = parent_mem_cgroup(memcg);
- memcg_reparent_list_lrus(memcg, parent);
-}
-
#ifdef CONFIG_CGROUP_WRITEBACK
#include <trace/events/writeback.h>
@@ -4216,7 +4189,6 @@ static struct mem_cgroup *mem_cgroup_alloc(struct mem_cgroup *parent)
seqlock_init(&memcg->socket_pressure_seqlock);
#endif
memcg1_memcg_init(memcg);
- memcg->kmemcg_id = -1;
#ifdef CONFIG_CGROUP_WRITEBACK
INIT_LIST_HEAD(&memcg->cgwb_list);
for (i = 0; i < MEMCG_CGWB_FRN_CNT; i++)
@@ -4290,7 +4262,8 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
struct obj_cgroup *objcg;
int nid;
- memcg_online_kmem(memcg);
+ if (!mem_cgroup_kmem_disabled() && likely(!mem_cgroup_is_root(memcg)))
+ static_branch_enable(&memcg_kmem_online_key);
/*
* A memcg must be visible for expand_shrinker_info()
@@ -4298,7 +4271,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
* here, when mem_cgroup_iter() can't skip it.
*/
if (alloc_shrinker_info(memcg))
- goto offline_kmem;
+ goto reparent_lrus;
for_each_node(nid) {
objcg = obj_cgroup_alloc();
@@ -4355,8 +4328,8 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
}
}
free_shrinker_info(memcg);
-offline_kmem:
- memcg_offline_kmem(memcg);
+reparent_lrus:
+ memcg_reparent_list_lrus(memcg, parent_mem_cgroup(memcg));
mem_cgroup_private_id_remove(memcg);
return -ENOMEM;
}
@@ -4372,11 +4345,11 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
zswap_memcg_offline_cleanup(memcg);
- memcg_offline_kmem(memcg);
+ memcg_reparent_list_lrus(memcg, parent_mem_cgroup(memcg));
/*
* The reparenting of objcg must be after the reparenting of
- * the list_lru in memcg_offline_kmem(), which ensures that
- * they will not mistakenly get the parent list_lru.
+ * the list_lru above, which ensures that they will not
+ * mistakenly get the parent list_lru.
*/
memcg_reparent_objcgs(memcg);
reparent_shrinker_deferred(memcg);
diff --git a/mm/zswap.c b/mm/zswap.c
index cd7b0b621bda8..afc6c8d03d231 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1255,8 +1255,8 @@ static struct shrinker *zswap_alloc_shrinker(void)
{
struct shrinker *shrinker;
- shrinker =
- shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE, "mm-zswap");
+ shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
+ SHRINKER_NONSLAB, "mm-zswap");
if (!shrinker)
return NULL;
|
| 25/3 | 2026/09/10 08:42 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 5753 output: 21 thoughts: 501 Thoughts: **Analyzing the Memory Management Patch** Okay, let's dive into this patch and assess the potential for uninitialized memory exposure. My immediate focus is on whether this warrants a KMSAN session. First, I need a detailed breakdown. Alright, it seems we're primarily dealing with the removal of `kmemcg_id` and related functions within the memory control subsystem. The patch touches several files: * `include/linux/memcontrol.h`: The most significant change is the removal of the `kmemcg_id` field from the `mem_cgroup` struct and the associated helper function. This is a red flag, as this is something that I am intimately familiar with and I will be looking closely at how this is being handled. * `mm/huge_memory.c` and `mm/zswap.c`: Here, the `SHRINKER_NONSLAB` flag is being added to the allocation of certain shrinkers. Interesting; this change suggests we are migrating away from slab-based allocations. * `mm/list_lru.c`: This file is where things get interesting. `list_lru_from_memcg_idx` is replaced by `list_lru_from_memcg`. The code is using `mem_cgroup_id(memcg)` instead of the old `kmemcg_id` methods. The flag checking for `memcg_aware` when `mem_cgroup_kmem_disabled()` looks like it might change something. * `mm/memcontrol.c`: We're seeing the removal of `memcg_online_kmem()`, `memcg_offline_kmem()`, and the initialization of `kmemcg_id`. Instead of initializing it, it looks like it is enabling the static branch. Now, the crucial question is whether `mem_cgroup_id(memcg)` is safe. What's the implementation? How does this function work? I'll use `grepper` to quickly find its definition and understand exactly how it's being used and, critically, initialized. I need to make absolutely sure there's no subtle initialization issue here, especially with the removal of `kmemcg_id`. I also need to verify that this refactoring doesn't create any new race conditions. |
| 26/3 | 2026/09/10 08:42 | tool | grepper |
0mArgs:{
"Expression": "mem_cgroup_id\\("
}Results: {
"Output": "include/linux/memcontrol.h=815=struct mem_cgroup *mem_cgroup_from_private_id(unsigned short id);\ninclude/linux/memcontrol.h-816-\ninclude/linux/memcontrol.h:817:static inline u64 mem_cgroup_id(struct mem_cgroup *memcg)\ninclude/linux/memcontrol.h-818-{\n--\ninclude/linux/memcontrol.h=1300=static inline struct mem_cgroup *mem_cgroup_from_private_id(unsigned short id)\n--\ninclude/linux/memcontrol.h-1306-\ninclude/linux/memcontrol.h:1307:static inline u64 mem_cgroup_id(struct mem_cgroup *memcg)\ninclude/linux/memcontrol.h-1308-{\n--\ninclude/trace/events/vmscan.h=177=DECLARE_EVENT_CLASS(mm_vmscan_direct_reclaim_begin_template,\n--\ninclude/trace/events/vmscan.h-191-\t\t__entry-\u003eorder\t\t= order;\ninclude/trace/events/vmscan.h:192:\t\t__entry-\u003ememcg_id\t= mem_cgroup_id(memcg);\ninclude/trace/events/vmscan.h-193-\t),\n--\ninclude/trace/events/vmscan.h=219=DECLARE_EVENT_CLASS(mm_vmscan_direct_reclaim_end_template,\n--\ninclude/trace/events/vmscan.h-231-\t\t__entry-\u003enr_reclaimed\t= nr_reclaimed;\ninclude/trace/events/vmscan.h:232:\t\t__entry-\u003ememcg_id\t= mem_cgroup_id(memcg);\ninclude/trace/events/vmscan.h-233-\t),\n--\ninclude/trace/events/vmscan.h=258=TRACE_EVENT(mm_shrink_slab_start,\n--\ninclude/trace/events/vmscan.h-289-\t\t__entry-\u003enid = sc-\u003enid;\ninclude/trace/events/vmscan.h:290:\t\t__entry-\u003ememcg_id = mem_cgroup_id(memcg);\ninclude/trace/events/vmscan.h-291-\t),\n--\ninclude/trace/events/vmscan.h=308=TRACE_EVENT(mm_shrink_slab_end,\n--\ninclude/trace/events/vmscan.h-333-\t\t__entry-\u003eretval = shrinker_retval;\ninclude/trace/events/vmscan.h:334:\t\t__entry-\u003ememcg_id = mem_cgroup_id(memcg);\ninclude/trace/events/vmscan.h-335-\t),\n--\nmm/damon/ops-common.c=266=bool damos_folio_filter_match(struct damos_filter *filter, struct folio *folio)\n--\nmm/damon/ops-common.c-284-\t\telse\nmm/damon/ops-common.c:285:\t\t\tmatched = filter-\u003ememcg_id == mem_cgroup_id(memcg);\nmm/damon/ops-common.c-286-\t\trcu_read_unlock();\n--\nmm/damon/paddr.c=142=static bool damon_pa_filter_match(struct damon_filter *filter,\n--\nmm/damon/paddr.c-165-\t\telse\nmm/damon/paddr.c:166:\t\t\tmatched = filter-\u003ememcg_id == mem_cgroup_id(memcg);\nmm/damon/paddr.c-167-\t\trcu_read_unlock();\n--\nmm/damon/sysfs-common.c=117=int damon_sysfs_memcg_path_to_id(char *memcg_path, u64 *id)\n--\nmm/damon/sysfs-common.c-135-\t\tif (damon_sysfs_memcg_path_eq(memcg, path, memcg_path)) {\nmm/damon/sysfs-common.c:136:\t\t\t*id = mem_cgroup_id(memcg);\nmm/damon/sysfs-common.c-137-\t\t\tfound = true;\n--\nmm/list_lru.c=75=list_lru_from_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg)\n--\nmm/list_lru.c-78-\t\tstruct list_lru_memcg *mlru =\nmm/list_lru.c:79:\t\t\txa_load(\u0026lru-\u003exa, mem_cgroup_id(memcg));\nmm/list_lru.c-80-\n--\nmm/list_lru.c=525=void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent)\n--\nmm/list_lru.c-538-\t\t */\nmm/list_lru.c:539:\t\tmlru = xa_load(\u0026lru-\u003exa, mem_cgroup_id(memcg));\nmm/list_lru.c-540-\t\tif (!mlru)\n--\nmm/list_lru.c-553-\nmm/list_lru.c:554:\t\txa_erase_irq(\u0026lru-\u003exa, mem_cgroup_id(memcg));\nmm/list_lru.c-555-\n--\nmm/list_lru.c=566=static inline bool memcg_list_lru_allocated(struct mem_cgroup *memcg,\n--\nmm/list_lru.c-571-\nmm/list_lru.c:572:\treturn xa_load(\u0026lru-\u003exa, mem_cgroup_id(memcg));\nmm/list_lru.c-573-}\n--\nmm/list_lru.c=575=static int __memcg_list_lru_alloc(struct mem_cgroup *memcg,\n--\nmm/list_lru.c-605-\t\t}\nmm/list_lru.c:606:\t\txas_set(\u0026xas, mem_cgroup_id(pos));\nmm/list_lru.c-607-\t\tdo {\n--\nmm/shrinker_debug.c=47=static int shrinker_debugfs_count_show(struct seq_file *m, void *v)\n--\nmm/shrinker_debug.c-70-\t\tif (total) {\nmm/shrinker_debug.c:71:\t\t\tseq_printf(m, \"%llu\", mem_cgroup_id(memcg));\nmm/shrinker_debug.c-72-\t\t\tfor_each_node(nid)\n--\nmm/vmscan.c=5710=static int lru_gen_seq_show(struct seq_file *m, void *v)\n--\nmm/vmscan.c-5727-#endif\nmm/vmscan.c:5728:\t\tseq_printf(m, \"memcg %llu %s\\n\", mem_cgroup_id(memcg), path);\nmm/vmscan.c-5729-\t}\n--\nmm/vmscan.c=5814=static int run_cmd(char cmd, u64 memcg_id, int nid, unsigned long seq,\n--\nmm/vmscan.c-5829-\nmm/vmscan.c:5830:\tif (memcg_id != mem_cgroup_id(memcg))\nmm/vmscan.c-5831-\t\tgoto done;\n"
} |
| 27/3 | 2026/09/10 08:42 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 8676 output: 36 thoughts: 24 Thoughts: Here's my take on those thoughts: **Peering into the Memory Management Depths** Okay, so I need to understand what this `mem_cgroup_id` actually *is*. Time to dive into the core. Let's start with the standard practice, as always: the official definition. I'll head straight for `include/linux/memcontrol.h`. That's where I'd expect to find the authoritative source, the definitive declaration of this beast. Hopefully, the comments are clear and concise. Knowing the declaration and comments will ensure an accurate understanding of its purpose within the wider memory control landscape of the kernel. I'm hoping it's well-documented, because, let's face it, memory management is complex, and accurate documentation is key to even the most basic understanding. Let's see what gems are in there! |
| 28/3 | 2026/09/10 08:42 | tool | read-file |
0mArgs:{
"File": "include/linux/memcontrol.h",
"FirstLine": 810,
"LineCount": 20
}Results: {
"Contents": " 810:\t\tif (mem_cgroup_disabled())\n 811:\t\t\treturn 0;\n 812:\t\n 813:\t\treturn memcg-\u003eid.id;\n 814:\t}\n 815:\tstruct mem_cgroup *mem_cgroup_from_private_id(unsigned short id);\n 816:\t\n 817:\tstatic inline u64 mem_cgroup_id(struct mem_cgroup *memcg)\n 818:\t{\n 819:\t\treturn memcg ? cgroup_id(memcg-\u003ecss.cgroup) : 0;\n 820:\t}\n 821:\t\n 822:\tstruct mem_cgroup *mem_cgroup_get_from_id(u64 id);\n 823:\t\n 824:\tstatic inline struct mem_cgroup *mem_cgroup_from_seq(struct seq_file *m)\n 825:\t{\n 826:\t\treturn mem_cgroup_from_css(seq_css(m));\n 827:\t}\n 828:\t\n 829:\tstatic inline struct mem_cgroup *lruvec_memcg(struct lruvec *lruvec)\n"
} |
| 29/3 | 2026/09/10 08:42 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 9245 output: 19 thoughts: 416 Thoughts: **My Analysis of the `memcg->kmemcg_id` Removal and `list_lru` Adaptation** Okay, so the `memcg->kmemcg_id` has been reworked. Previously, it was an index assigned during kmem onlining, essentially the old `memcg->id.id`. Now, `list_lru` is using `mem_cgroup_id(memcg)` which resolves to `cgroup_id(memcg->css.cgroup)`. That makes sense; it streamlines things. Plus, the `SHRINKER_NONSLAB` flag is being introduced. This is smart, it allows non-slab shrinkers like deferred_split (THP) and zswap to leverage the memcg-aware `list_lru` even when kmem isn't active or in the general case. Now, my main concern is always potential issues when making this type of change. I need to make sure we haven't introduced any bugs. First things first, I need to check for uninitialized variable usage, info leaks to user space, or unintended memory reads. Let's apply the usual criteria. 1. **Kernel-to-User Space Exposure:** Are there any kernel structures being passed to user space (through `copy_to_user`, `put_user`, Netlink attributes, ioctl output arguments, socket options, or BPF buffers), where uninitialized fields or structure padding might cause problems? Not in this specific change, as far as I can tell. 2. **Conditional Logic:** Is there any conditional logic or branching that might rely on potentially uninitialized variables or struct fields? The variables being used (`memcg`, `pos`, `lru`, `nid`) are standard pointers or integers that are passed in. That's good. 3. **Complex Data Structure Initialization:** Any allocation or initialization of complex data structures where uninitialized fields could be read later? The deletion of `kmemcg_id` from `struct mem_cgroup` is the main thing here, effectively removing a field. Then, `list_lru_from_memcg` has a sanity check: `if (list_lru_memcg_aware(lru) && memcg && !mem_cgroup_is_root(memcg))`. Seems safe. 4. **Buffer Bounds & Uninitialized Memory Access:** Are we changing any bounds checks, lengths, or logic that could potentially allow surrounding code to access uninitialized bytes of existing buffers? No changes to buffer access. That's a relief. Finally, I need to do a broader check. I should look through the rest of the code base. Let's make sure there isn't any code lingering out there that might still be referencing `kmemcg_id`. It's a classic gotcha. |
| 30/3 | 2026/09/10 08:42 | tool | grepper |
0mError:no matches Args: {
"Expression": "kmemcg_id"
}Results: {
"error": "no matches"
} |
| 31/3 | 2026/09/10 08:42 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 10299 output: 21 thoughts: 28 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Memory Controller IDs: A Quick Audit** Right, so it looks like we've successfully purged any instances of `kmemcg_id` in the code, which is good news. However, we all know how these things can sometimes hide in plain sight or have naming inconsistencies. Before we declare victory, I think it's prudent to quickly check for any occurrences of `memcg_kmem_id` as well. Double-checking related variables or potentially similar naming conventions is always time well-spent in these situations. Let's make sure we've covered our bases and haven't introduced any subtle regressions by overlooking anything. |
| 32/3 | 2026/09/10 08:42 | tool | grepper |
0mError:no matches Args: {
"Expression": "memcg_kmem_id"
}Results: {
"error": "no matches"
} |
| 33/3 | 2026/09/10 08:42 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 10513 output: 22 thoughts: 18 Thoughts: Here's a summary of my thought process, as if I were analyzing that prompt: **Analyzing the Query: SHRINKER_NONSLAB** Okay, so the prompt wants me to analyze something related to "SHRINKER_NONSLAB". That specific term suggests it's likely a configuration setting, a macro, or a variable name, almost certainly within a codebase. The use of all caps reinforces that it’s probably a constant. The "SHRINKER" part hints at memory management, garbage collection, or something related to reducing the footprint of data structures. The "NONSLAB" part is interesting; it contrasts with something called "SLAB", which immediately brings to mind Linux kernel memory management. Therefore, I'm already anticipating this might relate to how a system manages memory allocation for specific kinds of objects. The prompt explicitly tells me to check the *definition* and *usage* of this term. That means I need to look for where this `SHRINKER_NONSLAB` is declared, and then trace all instances where it's used. This suggests the query might involve understanding its scope and its influence on system behavior. The instruction to summarize the process, suggests this involves explaining the process from beginning to end. |
| 34/3 | 2026/09/10 08:42 | tool | grepper |
0mArgs:{
"Expression": "SHRINKER_NONSLAB"
}Results: {
"Output": "fs/btrfs/compression.c=1129=int __init btrfs_init_compress(void)\n--\nfs/btrfs/compression.c-1135-\nfs/btrfs/compression.c:1136:\tcompr_pool.shrinker = shrinker_alloc(SHRINKER_NONSLAB, \"btrfs-compr-pages\");\nfs/btrfs/compression.c-1137-\tif (!compr_pool.shrinker)\n--\nfs/xfs/xfs_icache.c=2335=xfs_inodegc_register_shrinker(\n--\nfs/xfs/xfs_icache.c-2337-{\nfs/xfs/xfs_icache.c:2338:\tmp-\u003em_inodegc_shrinker = shrinker_alloc(SHRINKER_NONSLAB,\nfs/xfs/xfs_icache.c-2339-\t\t\t\t\t\t\"xfs-inodegc:%s\",\n--\ninclude/linux/shrinker.h=82=struct shrinker {\n--\ninclude/linux/shrinker.h-131- */\ninclude/linux/shrinker.h:132:#define SHRINKER_NONSLAB\tBIT(4)\ninclude/linux/shrinker.h-133-\n--\nmm/huge_memory.c=1064=static int __init thp_shrinker_init(void)\n--\nmm/huge_memory.c-1067-\t\t\t\t\t\t SHRINKER_MEMCG_AWARE |\nmm/huge_memory.c:1068:\t\t\t\t\t\t SHRINKER_NONSLAB,\nmm/huge_memory.c-1069-\t\t\t\t\t\t \"thp-deferred_split\");\n--\nmm/list_lru.c=665=int __list_lru_init(struct list_lru *lru, bool memcg_aware, struct shrinker *shrinker)\n--\nmm/list_lru.c-681-\t (mem_cgroup_kmem_disabled() \u0026\u0026\nmm/list_lru.c:682:\t (!shrinker || !(shrinker-\u003eflags \u0026 SHRINKER_NONSLAB))))\nmm/list_lru.c-683-\t\tmemcg_aware = false;\n--\nmm/shrinker.c=226=static int shrinker_memcg_alloc(struct shrinker *shrinker)\n--\nmm/shrinker.c-233-\t\treturn -ENOSYS;\nmm/shrinker.c:234:\tif (mem_cgroup_kmem_disabled() \u0026\u0026 !(shrinker-\u003eflags \u0026 SHRINKER_NONSLAB))\nmm/shrinker.c-235-\t\treturn -ENOSYS;\n--\nmm/shrinker.c=478=static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,\n--\nmm/shrinker.c-555-\t\t\tif (!memcg_kmem_online() \u0026\u0026\nmm/shrinker.c:556:\t\t\t !(shrinker-\u003eflags \u0026 SHRINKER_NONSLAB)) {\nmm/shrinker.c-557-\t\t\t\tclear_bit(offset, unit-\u003emap);\n--\nmm/zswap.c=1254=static struct shrinker *zswap_alloc_shrinker(void)\n--\nmm/zswap.c-1258-\tshrinker = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |\nmm/zswap.c:1259:\t\t\t\t SHRINKER_NONSLAB, \"mm-zswap\");\nmm/zswap.c-1260-\tif (!shrinker)\n"
} |
| 35/3 | 2026/09/10 08:42 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 11744 output: 167 thoughts: 242 Thoughts: **My Assessment of the Refactoring Changes** Okay, so I've been reviewing the changes, specifically the refactoring of `list_lru` and memcg shrinker indexing. My initial thoughts are centered on ensuring the changes are sound and don't introduce any regressions, particularly around memory safety. The key changes involve: * Replacing `kmemcg_id` with `mem_cgroup_id(memcg)`. This direct use of the cgroup ID seems cleaner and more straightforward. * Tagging the THP split and zswap shrinkers with `SHRINKER_NONSLAB`. This is standard practice to help KMSAN and KASAN find problems. * Updating all `list_lru` interactions – lookups, reparenting, and allocations – to align with `mem_cgroup_id(memcg)`. Now, the critical question: are we opening the door to uninitialized memory reads or any potential information leaks to userspace? I've carefully considered this. I've confirmed: * We're not copying stack or heap structures to userspace without ensuring they're properly initialized. * We're not introducing any new uninitialized allocations. * In fact, we've gone the other way – the `kmemcg_id` field has been *removed* from `struct mem_cgroup`, which is a good thing. Given this, any memory safety issues in this particular area would likely manifest as null pointer dereferences, use-after-free conditions, or concurrency problems within the xarray lookup mechanism. Fortunately, we have KASAN, LOCKDEP, and our standard bug detectors in place to catch those issues. Therefore, my assessment is that KMSAN isn't strictly necessary for this set of changes. `NeedsKMSAN = false` is the right call. Alright, with that done, it's time to call the `set-results` tool and move on. |
| 36/3 | 2026/09/10 08:42 | tool | set-results |
0mArgs:{
"KMSANReasoning": "The patch refactors the memcg LRU list indexing by eliminating the redundant `kmemcg_id` field from `struct mem_cgroup` in favor of `mem_cgroup_id()`, and marks THP deferred split and zswap shrinkers with `SHRINKER_NONSLAB`.\n\nNo new uninitialized memory allocations, conditional branches on uninitialized values, or data structures exported to user space are introduced. Any potential lifetime, concurrency, or pointer indexing issues related to xarray or memcg reparenting are within the domain of KASAN, LOCKDEP, and standard kernel debugging tools. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
"NeedsKMSAN": false
}Results: {
"KMSANReasoning": "The patch refactors the memcg LRU list indexing by eliminating the redundant `kmemcg_id` field from `struct mem_cgroup` in favor of `mem_cgroup_id()`, and marks THP deferred split and zswap shrinkers with `SHRINKER_NONSLAB`.\n\nNo new uninitialized memory allocations, conditional branches on uninitialized values, or data structures exported to user space are introduced. Any potential lifetime, concurrency, or pointer indexing issues related to xarray or memcg reparenting are within the domain of KASAN, LOCKDEP, and standard kernel debugging tools. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
"NeedsKMSAN": false
} |
| Total Calls | Total Tokens | Avg Tokens | Total Duration (Seconds) | Avg Duration (Seconds) |
|---|
| Total Calls | Total Duration (Seconds) | Avg Duration (Seconds) |
|---|