AI Trajectory

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Seq	Timestamp	Type	Name	Duration
0/0	2026/07/28 02:13	flow	patch-triage	4m Args: null Results: { "EnableConfigs": [ "MEMCG", "MEM_ALLOC_PROFILING", "KFENCE" ], "FocusSymbols": [ "alloc_slab_obj_exts", "__memcg_slab_post_alloc_hook", "__memcg_slab_free_hook", "__kmem_cache_create_args", "kmem_cache_charge" ], "Reasoning": "The patch modifies the memory allocation profiling and memcg accounting logic in the SLUB allocator. It changes how `slabobj_ext` structures are allocated, accessed, and managed, particularly when both `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING` are enabled. It introduces `SLAB_MAY_ACCOUNT` and changes the layout of `slabobj_ext`. These are core kernel memory management changes that should be fuzzed to ensure no memory corruption, leaks, or accounting errors occur.", "WorthFuzzing": true }
1/1	2026/07/28 02:13	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 48f84032d1bd908e46149ccacdb9013ee3369920\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Tue Jul 28 02:13:15 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/Documentation/mm/allocation-profiling.rst b/Documentation/mm/allocation-profiling.rst\nindex 5389d241176a8a..d02eb54ee8f2c6 100644\n--- a/Documentation/mm/allocation-profiling.rst\n+++ b/Documentation/mm/allocation-profiling.rst\n@@ -112,3 +112,10 @@ To do so:\n \n - Then, use the following form for your allocations:\n alloc_hooks_tag(ht-\u003eyour_saved_tag, kmalloc_noprof(...))\n+\n+Notes\n+=====\n+\n+- When a slab object is allocated from KFENCE, its accounting is skipped.\n+ KFENCE allocations are rare and limited to a small number, so this omission\n+ is negligible.\ndiff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h\nindex e1f46a0016fcfd..93869cc35c25bc 100644\n--- a/include/linux/memcontrol.h\n+++ b/include/linux/memcontrol.h\n@@ -1440,19 +1440,6 @@ static inline void mem_cgroup_flush_workqueue(void) { }\n static inline int mem_cgroup_init(void) { return 0; }\n #endif /* CONFIG_MEMCG /\n \n-/\n- * Extended information for slab objects stored as an array in page-\u003ememcg_data\n- * if MEMCG_DATA_OBJEXTS is set.\n- /\n-struct slabobj_ext {\n-#ifdef CONFIG_MEMCG\n-\tstruct obj_cgroup objcg;\n-#endif\n-#ifdef CONFIG_MEM_ALLOC_PROFILING\n-\tunion codetag_ref ref;\n-#endif\n-} __aligned(8);\n-\n static inline struct lruvec parent_lruvec(struct lruvec lruvec)\n {\n \tstruct mem_cgroup memcg;\ndiff --git a/include/linux/slab.h b/include/linux/slab.h\nindex 32c9f8ed7ae205..e1915026e03040 100644\n--- a/include/linux/slab.h\n+++ b/include/linux/slab.h\n@@ -45,6 +45,7 @@ enum _slab_flag_bits {\n #endif\n #ifdef CONFIG_MEMCG\n \t_SLAB_ACCOUNT,\n+\t_SLAB_MAY_ACCOUNT,\n #endif\n #ifdef CONFIG_KASAN_GENERIC\n \t_SLAB_KASAN,\n@@ -204,8 +205,10 @@ enum _slab_flag_bits {\n /\n #ifdef CONFIG_MEMCG\n # define SLAB_ACCOUNT\t\t__SLAB_FLAG_BIT(_SLAB_ACCOUNT)\n+# define SLAB_MAY_ACCOUNT\t__SLAB_FLAG_BIT(_SLAB_MAY_ACCOUNT)\n #else\n # define SLAB_ACCOUNT\t\t__SLAB_FLAG_UNUSED\n+# define SLAB_MAY_ACCOUNT\t__SLAB_FLAG_UNUSED\n #endif\n \n #ifdef CONFIG_KASAN_GENERIC\ndiff --git a/mm/kfence/core.c b/mm/kfence/core.c\nindex 6577bd76954eb4..90925c646c4c24 100644\n--- a/mm/kfence/core.c\n+++ b/mm/kfence/core.c\n@@ -636,11 +636,6 @@ static unsigned long kfence_init_pool(void)\n \n \t\tpage = pfn_to_page(start_pfn + i);\n \t\t__SetPageSlab(page);\n-#ifdef CONFIG_MEMCG\n-\t\tstruct slab slab = page_slab(page);\n-\t\tslab-\u003eobj_exts = (unsigned long)\u0026kfence_metadata_init[i / 2 - 1].obj_exts \|\n-\t\t\t\t MEMCG_DATA_OBJEXTS;\n-#endif\n \t}\n \n \t/\n@@ -704,10 +699,6 @@ static unsigned long kfence_init_pool(void)\n \t\t\tcontinue;\n \n \t\tpage = pfn_to_page(start_pfn + i);\n-#ifdef CONFIG_MEMCG\n-\t\tstruct slab slab = page_slab(page);\n-\t\tslab-\u003eobj_exts = 0;\n-#endif\n \t\t__ClearPageSlab(page);\n \t}\n \n@@ -1248,9 +1239,6 @@ void __kfence_free(void addr)\n {\n \tstruct kfence_metadata meta = addr_to_metadata((unsigned long)addr);\n \n-#ifdef CONFIG_MEMCG\n-\tKFENCE_WARN_ON(meta-\u003eobj_exts.objcg);\n-#endif\n \t/\n \t * If the objects of the cache are SLAB_TYPESAFE_BY_RCU, defer freeing\n \t * the object, as the object page may be recycled for other-typed\ndiff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h\nindex 1f618f9b0d12d9..e6b4bf349ff730 100644\n--- a/mm/kfence/kfence.h\n+++ b/mm/kfence/kfence.h\n@@ -102,9 +102,6 @@ struct kfence_metadata {\n \tstruct kfence_track free_track __guarded_by(\u0026lock);\n \t/* For updating alloc_covered on frees. /\n \tu32 alloc_stack_hash __guarded_by(\u0026lock);\n-#ifdef CONFIG_MEMCG\n-\tstruct slabobj_ext obj_exts;\n-#endif\n };\n \n #define KFENCE_METADATA_SIZE PAGE_ALIGN(sizeof(struct kfence_metadata) \\\ndiff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c\nindex de2d0f7d62b15e..9867c03ef0ae3d 100644\n--- a/mm/kfence/kfence_test.c\n+++ b/mm/kfence/kfence_test.c\n@@ -295,7 +295,7 @@ static void test_alloc(struct kunit test, size_t size, gfp_t gfp, enum allocat\n \t\t\t * memcg accounting works correctly.\n \t\t\t /\n \t\t\tKUNIT_EXPECT_EQ(test, obj_to_index(s, slab, alloc), 0U);\n-\t\t\tKUNIT_EXPECT_EQ(test, objs_per_slab(s, slab), 1);\n+\t\t\tKUNIT_EXPECT_EQ(test, ((unsigned int)slab-\u003eobjects), 1);\n \n \t\t\tif (policy == ALLOCATE_ANY)\n \t\t\t\treturn alloc;\ndiff --git a/mm/memcontrol.c b/mm/memcontrol.c\nindex 6dc4888a90f3fd..6b51ddf6dfe022 100644\n--- a/mm/memcontrol.c\n+++ b/mm/memcontrol.c\n@@ -2865,18 +2865,19 @@ struct mem_cgroup mem_cgroup_from_obj_slab(struct slab slab, void p)\n \t /\n \tunsigned long obj_exts;\n \tstruct slabobj_ext obj_ext;\n-\tunsigned int off;\n+\tstruct obj_cgroup objcg;\n \n \tobj_exts = slab_obj_exts(slab);\n \tif (!obj_exts)\n \t\treturn NULL;\n \n-\tget_slab_obj_exts(obj_exts);\n-\toff = obj_to_index(slab-\u003eslab_cache, slab, p);\n-\tobj_ext = slab_obj_ext(slab, obj_exts, off);\n-\tif (obj_ext-\u003eobjcg) {\n-\t\tstruct obj_cgroup objcg = obj_ext-\u003eobjcg;\n+\tif (!slab_needs_objcg(slab))\n+\t\treturn NULL;\n \n+\tget_slab_obj_exts(obj_exts);\n+\tobj_ext = slab_obj_ext(slab-\u003eslab_cache, slab, obj_exts, p);\n+\tobjcg = slab_obj_ext_objcg(obj_ext);\n+\tif (objcg) {\n \t\tput_slab_obj_exts(obj_exts);\n \t\treturn obj_cgroup_memcg(objcg);\n \t}\n@@ -3541,7 +3542,6 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache s, struct list_lru lru,\n \tsize_t obj_size = obj_full_size(s);\n \tstruct obj_cgroup objcg;\n \tstruct slab slab;\n-\tunsigned long off;\n \tsize_t i;\n \n \t/\n@@ -3583,11 +3583,16 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache s, struct list_lru lru,\n \n \t\tslab = virt_to_slab(p[i]);\n \n-\t\tif (!slab_obj_exts(slab) \u0026\u0026\n-\t\t alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags)) {\n-\t\t\tcontinue;\n+\t\tif (!slab_obj_exts(slab)) {\n+\t\t\tif (is_kfence_address(p[i]))\n+\t\t\t\tcontinue;\n+\t\t\tif (alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags))\n+\t\t\t\tcontinue;\n \t\t}\n \n+\t\tif (IS_ENABLED(CONFIG_DEBUG_VM) \u0026\u0026 WARN_ON_ONCE(!slab_needs_objcg(slab)))\n+\t\t\tcontinue;\n+\n \t\t/\n \t\t * if we fail and size is 1, memcg_alloc_abort_single() will\n \t\t * just free the object, which is ok as we have not assigned\n@@ -3616,10 +3621,11 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache s, struct list_lru lru,\n \n \t\tobj_exts = slab_obj_exts(slab);\n \t\tget_slab_obj_exts(obj_exts);\n-\t\toff = obj_to_index(s, slab, p[i]);\n-\t\tobj_ext = slab_obj_ext(slab, obj_exts, off);\n+\t\tobj_ext = slab_obj_ext(s, slab, obj_exts, p[i]);\n+\n \t\tobj_cgroup_get(objcg);\n-\t\tobj_ext-\u003eobjcg = objcg;\n+\t\tslab_obj_ext_set_objcg(obj_ext, objcg);\n+\n \t\tput_slab_obj_exts(obj_exts);\n \t}\n \n@@ -3635,15 +3641,13 @@ void __memcg_slab_free_hook(struct kmem_cache s, struct slab slab,\n \t\tstruct obj_cgroup objcg;\n \t\tstruct slabobj_ext obj_ext;\n \t\tstruct obj_stock_pcp stock;\n-\t\tunsigned int off;\n \n-\t\toff = obj_to_index(s, slab, p[i]);\n-\t\tobj_ext = slab_obj_ext(slab, obj_exts, off);\n-\t\tobjcg = obj_ext-\u003eobjcg;\n+\t\tobj_ext = slab_obj_ext(s, slab, obj_exts, p[i]);\n+\t\tobjcg = slab_obj_ext_objcg(obj_ext);\n \t\tif (!objcg)\n \t\t\tcontinue;\n \n-\t\tobj_ext-\u003eobjcg = NULL;\n+\t\tslab_obj_ext_set_objcg(obj_ext, NULL);\n \n \t\tstock = trylock_stock();\n \t\t__refill_obj_stock(objcg, stock, obj_size, true);\ndiff --git a/mm/slab.h b/mm/slab.h\nindex f5e336b6b6b04c..04600f57b40146 100644\n--- a/mm/slab.h\n+++ b/mm/slab.h\n@@ -81,10 +81,11 @@ struct freelist_counters {\n #ifdef CONFIG_64BIT\n \t\t\t\t\t/\n \t\t\t\t\t * Some optimizations use free bits in 'counters' field\n-\t\t\t\t\t * to save memory. In case -\u003estride field is not available,\n-\t\t\t\t\t * such optimizations are disabled.\n+\t\t\t\t\t * to save memory or CPU. If these free bits are not\n+\t\t\t\t\t * available, such optimizations are disabled.\n \t\t\t\t\t /\n-\t\t\t\t\tunsigned int stride;\n+\t\t\t\t\tunsigned obj_exts_in_object:1;\n+\t\t\t\t\tunsigned obj_exts_needs_objcg:1;\n #endif\n \t\t\t\t};\n \t\t\t};\n@@ -330,12 +331,6 @@ static inline unsigned int obj_to_index(const struct kmem_cache cache,\n \treturn __obj_to_index(cache, slab_address(slab), obj);\n }\n \n-static inline int objs_per_slab(const struct kmem_cache cache,\n-\t\t\t\tconst struct slab slab)\n-{\n-\treturn slab-\u003eobjects;\n-}\n-\n /\n State of the slab allocator.\n \n@@ -555,6 +550,93 @@ static inline bool need_kmalloc_no_objext(void)\n \treturn false;\n }\n \n+/\n+ * Extended information for slab objects stored as a pointer to an array in\n+ * slab-\u003eobj_exts (aliasing page-\u003ememcg_data) if MEMCG_DATA_OBJEXTS is set.\n+ /\n+struct slabobj_ext {\n+\t/\n+\t * All elements of the union should be pointer-sized to avoid memory\n+\t * waste\n+\t /\n+\tunion {\n+#ifdef CONFIG_MEMCG\n+\t\tstruct obj_cgroup _objcg;\n+#endif\n+#ifdef CONFIG_MEM_ALLOC_PROFILING\n+\t\tunion codetag_ref _ctref;\n+#endif\n+\t};\n+} __aligned(8);\n+\n+#ifdef CONFIG_MEM_ALLOC_PROFILING\n+DECLARE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\n+\t\t\t slab_obj_ext_has_codetag_key);\n+\n+static inline bool slab_obj_ext_has_codetag(void)\n+{\n+\treturn static_branch_maybe(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\n+\t\t\t\t \u0026slab_obj_ext_has_codetag_key);\n+}\n+#else\n+static inline bool slab_obj_ext_has_codetag(void)\n+{\n+\treturn false;\n+}\n+#endif\n+\n+#ifdef CONFIG_MEMCG\n+static inline bool cache_needs_objcg(struct kmem_cache cache)\n+{\n+\treturn (cache-\u003eflags \u0026 SLAB_MAY_ACCOUNT);\n+}\n+\n+static inline bool slab_needs_objcg(struct slab slab)\n+{\n+#ifdef CONFIG_64BIT\n+\treturn slab-\u003eobj_exts_needs_objcg;\n+#else\n+\treturn cache_needs_objcg(slab-\u003eslab_cache);\n+#endif\n+}\n+#else\n+static inline bool cache_needs_objcg(struct kmem_cache cache)\n+{\n+\treturn false;\n+}\n+\n+static inline bool slab_needs_objcg(struct slab slab)\n+{\n+\treturn false;\n+}\n+#endif\n+\n+static inline size_t cache_obj_ext_size(struct kmem_cache s)\n+{\n+\tsize_t sz = 0;\n+\n+\tif (cache_needs_objcg(s))\n+\t\tsz += 1;\n+\n+\tif (slab_obj_ext_has_codetag())\n+\t\tsz += 1;\n+\n+\treturn sizeof(struct slabobj_ext) sz;\n+}\n+\n+static inline size_t slab_obj_ext_size(struct slab slab)\n+{\n+\tsize_t sz = 0;\n+\n+\tif (slab_needs_objcg(slab))\n+\t\tsz += 1;\n+\n+\tif (slab_obj_ext_has_codetag())\n+\t\tsz += 1;\n+\n+\treturn sizeof(struct slabobj_ext) sz;\n+}\n+\n #ifdef CONFIG_SLAB_OBJ_EXT\n \n /\n@@ -572,7 +654,7 @@ static inline bool need_kmalloc_no_objext(void)\n obj_exts = slab_obj_exts(slab);\n * if (obj_exts) {\n * get_slab_obj_exts(obj_exts);\n- * obj_ext = slab_obj_ext(slab, obj_exts, obj_to_index(s, slab, obj));\n+ * obj_ext = slab_obj_ext(s, slab, obj_exts, obj);\n * // do something with obj_ext\n * put_slab_obj_exts(obj_exts);\n * }\n@@ -610,48 +692,86 @@ static inline void put_slab_obj_exts(unsigned long obj_exts)\n }\n \n #ifdef CONFIG_64BIT\n-static inline void slab_set_stride(struct slab slab, unsigned int stride)\n+static inline bool obj_exts_in_object(struct slab slab)\n {\n-\tslab-\u003estride = stride;\n-}\n-static inline unsigned int slab_get_stride(struct slab slab)\n-{\n-\treturn slab-\u003estride;\n+\t/\n+\t * Note we cannot rely on the SLAB_OBJ_EXT_IN_OBJ flag here and need to\n+\t * check the per-slab bit. A cache can have SLAB_OBJ_EXT_IN_OBJ set, but\n+\t * allocations within_slab_leftover are preferred. And those may be\n+\t * possible or not depending on the particular slab's size.\n+\t /\n+\treturn slab-\u003eobj_exts_in_object;\n }\n #else\n-static inline void slab_set_stride(struct slab slab, unsigned int stride)\n-{\n-\tVM_WARN_ON_ONCE(stride != sizeof(struct slabobj_ext));\n-}\n-static inline unsigned int slab_get_stride(struct slab slab)\n+static inline bool obj_exts_in_object(struct slab slab)\n {\n-\treturn sizeof(struct slabobj_ext);\n+\treturn false;\n }\n #endif\n \n /\n slab_obj_ext - get the pointer to the slab object extension metadata\n * associated with an object in a slab.\n+ * @s: cache that the slab belongs to\n * @slab: a pointer to the slab struct\n * @obj_exts: a pointer to the object extension vector\n- * @index: an index of the object\n+ * @obj: a pointer to the object\n \n Returns a pointer to the object extension associated with the object.\n * Must be called within a section covered by get/put_slab_obj_exts().\n /\n-static inline struct slabobj_ext slab_obj_ext(struct slab slab,\n-\t\t\t\t\t unsigned long obj_exts,\n-\t\t\t\t\t unsigned int index)\n+static inline struct slabobj_ext \n+slab_obj_ext(struct kmem_cache s, struct slab slab, unsigned long obj_exts,\n+\t const void obj)\n {\n \tstruct slabobj_ext obj_ext;\n+\tunsigned int index;\n+\tunsigned int stride;\n \n \tVM_WARN_ON_ONCE(obj_exts != slab_obj_exts(slab));\n \n-\tobj_ext = (struct slabobj_ext )(obj_exts +\n-\t\t\t\t\t slab_get_stride(slab) index);\n+\t/\n+\t KFENCE objects have NULL obj_exts and thus can't reach this\n+\t * and we don't need obj_to_index()\n+\t /\n+\tindex = __obj_to_index(s, slab_address(slab), obj);\n+\n+\tif (!obj_exts_in_object(slab))\n+\t\tstride = slab_obj_ext_size(slab);\n+\telse\n+\t\tstride = s-\u003esize;\n+\n+\tobj_ext = (struct slabobj_ext )(obj_exts + index * stride);\n+\n \treturn kasan_reset_tag(obj_ext);\n }\n \n+#ifdef CONFIG_MEMCG\n+static inline struct obj_cgroup slab_obj_ext_objcg(struct slabobj_ext obj_ext)\n+{\n+\t/* if objcg exists, it comes first, so we don't need to do anything /\n+\treturn obj_ext-\u003e_objcg;\n+}\n+\n+static inline void slab_obj_ext_set_objcg(struct slabobj_ext obj_ext,\n+\t\t\t\t\t struct obj_cgroup objcg)\n+{\n+\t/ if objcg exists, it comes first, so we don't need to do anything /\n+\tobj_ext-\u003e_objcg = objcg;\n+}\n+#endif\n+\n+#ifdef CONFIG_MEM_ALLOC_PROFILING\n+static inline union codetag_ref \n+slab_obj_ext_codetag_ref(struct slab slab, struct slabobj_ext obj_ext)\n+{\n+\tif (slab_needs_objcg(slab))\n+\t\tobj_ext += 1;\n+\n+\treturn \u0026obj_ext-\u003e_ctref;\n+}\n+#endif\n+\n int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s,\n \t\t\tgfp_t gfp, unsigned int alloc_flags);\n \n@@ -662,16 +782,17 @@ static inline unsigned long slab_obj_exts(struct slab slab)\n \treturn 0;\n }\n \n-static inline struct slabobj_ext slab_obj_ext(struct slab slab,\n-\t\t\t\t\t unsigned long obj_exts,\n-\t\t\t\t\t unsigned int index)\n+static inline struct slabobj_ext \n+slab_obj_ext(struct kmem_cache s, struct slab slab, unsigned long obj_exts,\n+\t const void obj)\n {\n \treturn NULL;\n }\n \n-static inline void slab_set_stride(struct slab slab, unsigned int stride) { }\n-static inline unsigned int slab_get_stride(struct slab slab) { return 0; }\n-\n+static inline bool obj_exts_in_object(struct slab slab)\n+{\n+\treturn false;\n+}\n \n #endif /* CONFIG_SLAB_OBJ_EXT /\n \ndiff --git a/mm/slab_common.c b/mm/slab_common.c\nindex 03ecac12cd865f..1e1d3feec3535b 100644\n--- a/mm/slab_common.c\n+++ b/mm/slab_common.c\n@@ -52,7 +52,7 @@ struct kmem_cache kmem_cache;\n \t\tSLAB_OBJ_EXT_IN_OBJ)\n \n #define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT \| SLAB_CACHE_DMA \| \\\n-\t\t\t SLAB_CACHE_DMA32 \| SLAB_ACCOUNT)\n+\t\t\t SLAB_CACHE_DMA32 \| SLAB_ACCOUNT \| SLAB_MAY_ACCOUNT)\n \n /\n Merge control. If this is set then no merging of slab caches will occur.\n@@ -359,6 +359,13 @@ struct kmem_cache __kmem_cache_create_args(const char name,\n \t\tgoto out_unlock;\n \t}\n \n+\t/\n+\t For now we assume any cache can be used with __GFP_ACCOUNT and thus\n+\t * may need to store objcg pointers for objects\n+\t /\n+\tif (!mem_cgroup_kmem_disabled())\n+\t\tflags \|= SLAB_MAY_ACCOUNT;\n+\n \t/ Fail closed on bad usersize of useroffset values. /\n \tif (!IS_ENABLED(CONFIG_HARDENED_USERCOPY) \|\|\n \t WARN_ON(!args-\u003eusersize \u0026\u0026 args-\u003euseroffset) \|\|\n@@ -984,11 +991,20 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type)\n #endif\n \n \t/\n-\t * If CONFIG_MEMCG is enabled, disable cache merging for\n-\t * KMALLOC_NORMAL caches.\n+\t * If memcg_kmem is enabled and this is a KMALLOC_NORMAL cache and not\n+\t * aliased with any other type, make sure it's never merged with any other\n+\t * cache.\n+\t \n+\t In other cases the kmalloc cache may end up being used for a\n+\t * __GFP_ACCOUNT allocation so mark it as such. The exception is a\n+\t * KMALLOC_NO_OBJ_EXT cache.\n \t /\n-\tif (IS_ENABLED(CONFIG_MEMCG) \u0026\u0026 (type == KMALLOC_NORMAL))\n-\t\tflags \|= SLAB_NO_MERGE;\n+\tif (!mem_cgroup_kmem_disabled()) {\n+\t\tif (type == KMALLOC_NORMAL \u0026\u0026 KMALLOC_RECLAIM != KMALLOC_NORMAL)\n+\t\t\tflags \|= SLAB_NO_MERGE;\n+\t\telse if (!(flags \u0026 SLAB_NO_OBJ_EXT))\n+\t\t\tflags \|= SLAB_MAY_ACCOUNT;\n+\t}\n \n \tif (minalign \u003e ARCH_KMALLOC_MINALIGN) {\n \t\taligned_size = ALIGN(aligned_size, minalign);\ndiff --git a/mm/slub.c b/mm/slub.c\nindex 0337e60db5ace0..94b744e5ac7919 100644\n--- a/mm/slub.c\n+++ b/mm/slub.c\n@@ -213,6 +213,11 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);\n static DEFINE_STATIC_KEY_FALSE(strict_numa);\n #endif\n \n+#ifdef CONFIG_MEM_ALLOC_PROFILING\n+DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\n+\t\t\tslab_obj_ext_has_codetag_key);\n+#endif\n+\n / Structure holding extra parameters for slab allocations /\n struct slab_alloc_context {\n \tunsigned long caller_addr;\n@@ -803,7 +808,7 @@ static inline bool need_slab_obj_exts(struct kmem_cache s)\n \n static inline unsigned int obj_exts_size_in_slab(struct slab slab)\n {\n-\treturn sizeof(struct slabobj_ext) slab-\u003eobjects;\n+\treturn slab_obj_ext_size(slab) * slab-\u003eobjects;\n }\n \n static inline unsigned long obj_exts_offset_in_slab(struct kmem_cache s,\n@@ -870,18 +875,6 @@ static inline bool obj_exts_in_slab(struct kmem_cache s, struct slab slab)\n #endif\n \n #if defined(CONFIG_SLAB_OBJ_EXT) \u0026\u0026 defined(CONFIG_64BIT)\n-static bool obj_exts_in_object(struct kmem_cache s, struct slab slab)\n-{\n-\t/\n-\t * Note we cannot rely on the SLAB_OBJ_EXT_IN_OBJ flag here and need to\n-\t * check the stride. A cache can have SLAB_OBJ_EXT_IN_OBJ set, but\n-\t * allocations within_slab_leftover are preferred. And those may be\n-\t * possible or not depending on the particular slab's size.\n-\t /\n-\treturn obj_exts_in_slab(s, slab) \u0026\u0026\n-\t (slab_get_stride(slab) == s-\u003esize);\n-}\n-\n static unsigned int obj_exts_offset_in_object(struct kmem_cache s)\n {\n \tunsigned int offset = get_info_end(s);\n@@ -896,16 +889,20 @@ static unsigned int obj_exts_offset_in_object(struct kmem_cache s)\n \n \treturn offset;\n }\n-#else\n-static inline bool obj_exts_in_object(struct kmem_cache s, struct slab slab)\n+\n+static inline void slab_set_obj_exts_in_object(struct slab slab)\n {\n-\treturn false;\n+\tslab-\u003eobj_exts_in_object = 1;\n }\n-\n+#else\n static inline unsigned int obj_exts_offset_in_object(struct kmem_cache s)\n {\n \treturn 0;\n }\n+\n+static inline void slab_set_obj_exts_in_object(struct slab slab)\n+{\n+}\n #endif\n \n #ifdef CONFIG_SLUB_DEBUG\n@@ -1206,8 +1203,8 @@ static void print_trailer(struct kmem_cache s, struct slab slab, u8 p)\n \n \toff += kasan_metadata_size(s, false);\n \n-\tif (obj_exts_in_object(s, slab))\n-\t\toff += sizeof(struct slabobj_ext);\n+\tif (obj_exts_in_object(slab))\n+\t\toff += slab_obj_ext_size(slab);\n \n \tif (off != size_from_object(s))\n \t\t/ Beginning of the filler is the free pointer /\n@@ -1411,8 +1408,8 @@ static int check_pad_bytes(struct kmem_cache s, struct slab slab, u8 p)\n \n \toff += kasan_metadata_size(s, false);\n \n-\tif (obj_exts_in_object(s, slab))\n-\t\toff += sizeof(struct slabobj_ext);\n+\tif (obj_exts_in_object(slab))\n+\t\toff += slab_obj_ext_size(slab);\n \n \tif (size_from_object(s) == off)\n \t\treturn 1;\n@@ -1439,7 +1436,7 @@ slab_pad_check(struct kmem_cache s, struct slab slab)\n \tlength = slab_size(slab);\n \tend = start + length;\n \n-\tif (obj_exts_in_slab(s, slab) \u0026\u0026 !obj_exts_in_object(s, slab)) {\n+\tif (obj_exts_in_slab(s, slab) \u0026\u0026 !obj_exts_in_object(slab)) {\n \t\tremainder = length;\n \t\tremainder -= obj_exts_offset_in_slab(s, slab);\n \t\tremainder -= obj_exts_size_in_slab(slab);\n@@ -2070,20 +2067,21 @@ static inline void mark_obj_codetag_empty(const void obj)\n \tobj_slab = virt_to_slab(obj);\n \tslab_exts = slab_obj_exts(obj_slab);\n \tif (slab_exts) {\n+\t\tstruct slabobj_ext ext;\n+\t\tunion codetag_ref ref;\n+\n \t\tget_slab_obj_exts(slab_exts);\n-\t\tunsigned int offs = obj_to_index(obj_slab-\u003eslab_cache,\n-\t\t\t\t\t\t obj_slab, obj);\n-\t\tstruct slabobj_ext ext = slab_obj_ext(obj_slab,\n-\t\t\t\t\t\t slab_exts, offs);\n+\t\text = slab_obj_ext(obj_slab-\u003eslab_cache, obj_slab, slab_exts, obj);\n+\t\tref = slab_obj_ext_codetag_ref(obj_slab, ext);\n \n-\t\tif (unlikely(is_codetag_empty(\u0026ext-\u003eref))) {\n+\t\tif (unlikely(is_codetag_empty(ref))) {\n \t\t\tput_slab_obj_exts(slab_exts);\n \t\t\treturn;\n \t\t}\n \n \t\t/* codetag should be NULL here /\n-\t\tWARN_ON(ext-\u003eref.ct);\n-\t\tset_codetag_empty(\u0026ext-\u003eref);\n+\t\tWARN_ON(ref-\u003ect);\n+\t\tset_codetag_empty(ref);\n \t\tput_slab_obj_exts(slab_exts);\n \t}\n }\n@@ -2093,19 +2091,29 @@ static inline bool mark_failed_objexts_alloc(struct slab slab)\n \treturn cmpxchg(\u0026slab-\u003eobj_exts, 0, OBJEXTS_ALLOC_FAIL) == 0;\n }\n \n-static inline void handle_failed_objexts_alloc(unsigned long obj_exts,\n-\t\t\tstruct slabobj_ext vec, unsigned int objects)\n+static inline void handle_failed_objexts_alloc(struct slab slab,\n+\t\tunsigned long obj_exts, struct slabobj_ext vec)\n {\n+\tunsigned int stride;\n+\n+\tif (!slab_obj_ext_has_codetag())\n+\t\treturn;\n+\n \t/\n \t * If vector previously failed to allocate then we have live\n \t * objects with no tag reference. Mark all references in this\n \t * vector as empty to avoid warnings later on.\n \t /\n-\tif (obj_exts == OBJEXTS_ALLOC_FAIL) {\n-\t\tunsigned int i;\n+\tif (obj_exts != OBJEXTS_ALLOC_FAIL)\n+\t\treturn;\n+\n+\tstride = slab_obj_ext_size(slab) / sizeof(vec);\n+\n+\tfor (unsigned int i = 0; i \u003c slab-\u003eobjects; i++) {\n+\t\tunion codetag_ref ref = slab_obj_ext_codetag_ref(slab, vec);\n \n-\t\tfor (i = 0; i \u003c objects; i++)\n-\t\t\tset_codetag_empty(\u0026vec[i].ref);\n+\t\tset_codetag_empty(ref);\n+\t\tvec += stride;\n \t}\n }\n \n@@ -2113,8 +2121,8 @@ static inline void handle_failed_objexts_alloc(unsigned long obj_exts,\n \n static inline void mark_obj_codetag_empty(const void obj) {}\n static inline bool mark_failed_objexts_alloc(struct slab slab) { return false; }\n-static inline void handle_failed_objexts_alloc(unsigned long obj_exts,\n-\t\t\tstruct slabobj_ext vec, unsigned int objects) {}\n+static inline void handle_failed_objexts_alloc(struct slab slab,\n+\t\tunsigned long obj_exts, struct slabobj_ext vec) {}\n \n #endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG /\n \n@@ -2127,12 +2135,11 @@ int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s,\n \t\t\tgfp_t gfp, unsigned int alloc_flags)\n {\n \tconst bool allow_spin = alloc_flags_allow_spinning(alloc_flags);\n-\tunsigned int objects = objs_per_slab(s, slab);\n \tbool new_slab = alloc_flags \u0026 SLAB_ALLOC_NEW_SLAB;\n \tunsigned long new_exts;\n \tunsigned long old_exts;\n \tstruct slabobj_ext vec;\n-\tsize_t sz = sizeof(struct slabobj_ext) * slab-\u003eobjects;\n+\tsize_t sz = slab_obj_ext_size(slab) * slab-\u003eobjects;\n \n \tgfp \u0026= ~OBJCGS_CLEAR_MASK;\n \t/\n@@ -2183,7 +2190,7 @@ int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s,\n #endif\n retry:\n \told_exts = READ_ONCE(slab-\u003eobj_exts);\n-\thandle_failed_objexts_alloc(old_exts, vec, objects);\n+\thandle_failed_objexts_alloc(slab, old_exts, vec);\n \n \tif (new_slab) {\n \t\t/\n@@ -2250,9 +2257,6 @@ static void alloc_slab_obj_exts_early(struct kmem_cache s, struct slab slab)\n \tvoid addr;\n \tunsigned long obj_exts;\n \n-\t/ Initialize stride early to avoid memory ordering issues /\n-\tslab_set_stride(slab, sizeof(struct slabobj_ext));\n-\n \tif (!need_slab_obj_exts(s))\n \t\treturn;\n \n@@ -2278,15 +2282,14 @@ static void alloc_slab_obj_exts_early(struct kmem_cache s, struct slab slab)\n \n \t\tget_slab_obj_exts(obj_exts);\n \t\tfor_each_object(addr, s, slab_address(slab), slab-\u003eobjects)\n-\t\t\tmemset(kasan_reset_tag(addr) + offset, 0,\n-\t\t\t sizeof(struct slabobj_ext));\n+\t\t\tmemset(kasan_reset_tag(addr) + offset, 0, slab_obj_ext_size(slab));\n \t\tput_slab_obj_exts(obj_exts);\n \n #ifdef CONFIG_MEMCG\n \t\tobj_exts \|= MEMCG_DATA_OBJEXTS;\n #endif\n \t\tslab-\u003eobj_exts = obj_exts;\n-\t\tslab_set_stride(slab, s-\u003esize);\n+\t\tslab_set_obj_exts_in_object(slab);\n \t}\n }\n \n@@ -2323,11 +2326,15 @@ static inline unsigned long\n prepare_slab_obj_exts_hook(struct kmem_cache s, struct slab slab,\n \t\t\t gfp_t flags, unsigned int alloc_flags, void p)\n {\n-\tif (!slab_obj_exts(slab) \u0026\u0026\n-\t alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {\n-\t\tpr_warn_once(\"%s, %s: Failed to create slab extension vector!\\n\",\n-\t\t\t __func__, s-\u003ename);\n-\t\treturn 0;\n+\tif (!slab_obj_exts(slab)) {\n+\t\tif (is_kfence_address(p))\n+\t\t\treturn 0;\n+\n+\t\tif (alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {\n+\t\t\tpr_warn_once(\"%s, %s: Failed to create slab extension vector!\\n\",\n+\t\t\t\t __func__, s-\u003ename);\n+\t\t\treturn 0;\n+\t\t}\n \t}\n \n \treturn slab_obj_exts(slab);\n@@ -2360,14 +2367,24 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache s, void object, gfp_t flags,\n \t * check should be added before alloc_tag_add().\n \t /\n \tif (obj_exts) {\n-\t\tunsigned int obj_idx = obj_to_index(s, slab, object);\n+\t\tunion codetag_ref ref;\n \n \t\tget_slab_obj_exts(obj_exts);\n-\t\tobj_ext = slab_obj_ext(slab, obj_exts, obj_idx);\n-\t\talloc_tag_add(\u0026obj_ext-\u003eref, current-\u003ealloc_tag, s-\u003esize);\n+\n+\t\tobj_ext = slab_obj_ext(s, slab, obj_exts, object);\n+\t\tref = slab_obj_ext_codetag_ref(slab, obj_ext);\n+\n+\t\talloc_tag_add(ref, current-\u003ealloc_tag, s-\u003esize);\n+\n \t\tput_slab_obj_exts(obj_exts);\n \t} else {\n-\t\talloc_tag_set_inaccurate(current-\u003ealloc_tag);\n+\t\t/\n+\t\t KFENCE allocations are rare and the amount of outstanding\n+\t\t * ones is limited to a small number so it's not worth setting\n+\t\t * tags as inaccurate because of them.\n+\t\t /\n+\t\tif (!is_kfence_address(object))\n+\t\t\talloc_tag_set_inaccurate(current-\u003ealloc_tag);\n \t}\n }\n \n@@ -2384,7 +2401,6 @@ static noinline void\n __alloc_tagging_slab_free_hook(struct kmem_cache s, struct slab slab, void p,\n \t\t\t int objects)\n {\n-\tint i;\n \tunsigned long obj_exts;\n \n \t/ slab-\u003eobj_exts might not be NULL if it was created for MEMCG accounting. /\n@@ -2396,10 +2412,11 @@ __alloc_tagging_slab_free_hook(struct kmem_cache s, struct slab slab, void p\n \t\treturn;\n \n \tget_slab_obj_exts(obj_exts);\n-\tfor (i = 0; i \u003c objects; i++) {\n-\t\tunsigned int off = obj_to_index(s, slab, p[i]);\n+\tfor (int i = 0; i \u003c objects; i++) {\n+\t\tstruct slabobj_ext ext;\n \n-\t\talloc_tag_sub(\u0026slab_obj_ext(slab, obj_exts, off)-\u003eref, s-\u003esize);\n+\t\text = slab_obj_ext(s, slab, obj_exts, p[i]);\n+\t\talloc_tag_sub(slab_obj_ext_codetag_ref(slab, ext), s-\u003esize);\n \t}\n \tput_slab_obj_exts(obj_exts);\n }\n@@ -2412,6 +2429,25 @@ alloc_tagging_slab_free_hook(struct kmem_cache s, struct slab slab, void *p,\n \t\t__alloc_tagging_slab_free_hook(s, slab, p, objects);\n }\n \n+/\n+ * Make sure the static key used by slab_obj_ext_has_codetag() reflects the\n+ * value of !mem_alloc_profiling_permanently_disabled()\n+ \n+ Any later mem alloc profiling shutdown won't be reflected in the static key\n+ * because obj_exts with codetags might already exist.\n+ /\n+static void __init slab_obj_ext_has_codetag_init(void)\n+{\n+\tbool need_codetag = !mem_alloc_profiling_permanently_disabled();\n+\n+\tif (need_codetag != static_key_enabled(\u0026slab_obj_ext_has_codetag_key)) {\n+\t\tif (need_codetag)\n+\t\t\tstatic_branch_enable(\u0026slab_obj_ext_has_codetag_key);\n+\t\telse\n+\t\t\tstatic_branch_disable(\u0026slab_obj_ext_has_codetag_key);\n+\t}\n+}\n+\n #else / CONFIG_MEM_ALLOC_PROFILING /\n \n static inline void\n@@ -2426,6 +2462,10 @@ alloc_tagging_slab_free_hook(struct kmem_cache s, struct slab slab, void p,\n {\n }\n \n+static inline void slab_obj_ext_has_codetag_init(void)\n+{\n+}\n+\n #endif / CONFIG_MEM_ALLOC_PROFILING /\n \n \n@@ -2471,6 +2511,9 @@ void memcg_slab_free_hook(struct kmem_cache s, struct slab slab, void p,\n \tif (likely(!obj_exts))\n \t\treturn;\n \n+\tif (!slab_needs_objcg(slab))\n+\t\treturn;\n+\n \tget_slab_obj_exts(obj_exts);\n \t__memcg_slab_free_hook(s, slab, p, objects, obj_exts);\n \tput_slab_obj_exts(obj_exts);\n@@ -2484,7 +2527,6 @@ bool memcg_slab_post_charge(void p, gfp_t flags)\n \tstruct kmem_cache s;\n \tstruct page page;\n \tstruct slab slab;\n-\tunsigned long off;\n \n \tpage = virt_to_page(p);\n \tif (PageLargeKmalloc(page)) {\n@@ -2517,16 +2559,15 @@ bool memcg_slab_post_charge(void p, gfp_t flags)\n \t * of slab_obj_exts being allocated from the same slab and thus the slab\n \t * becoming effectively unfreeable.\n \t /\n-\tif (is_kmalloc_normal(s))\n+\tif (!cache_needs_objcg(s))\n \t\treturn true;\n \n \t/ Ignore already charged objects. /\n \tobj_exts = slab_obj_exts(slab);\n \tif (obj_exts) {\n \t\tget_slab_obj_exts(obj_exts);\n-\t\toff = obj_to_index(s, slab, p);\n-\t\tobj_ext = slab_obj_ext(slab, obj_exts, off);\n-\t\tif (unlikely(obj_ext-\u003eobjcg)) {\n+\t\tobj_ext = slab_obj_ext(s, slab, obj_exts, p);\n+\t\tif (unlikely(slab_obj_ext_objcg(obj_ext))) {\n \t\t\tput_slab_obj_exts(obj_exts);\n \t\t\treturn true;\n \t\t}\n@@ -3391,10 +3432,15 @@ static struct slab allocate_slab(struct kmem_cache s, gfp_t flags,\n \t\tstat(s, ORDER_FALLBACK);\n \t}\n \n+\t/ Initializes frozen, inuse, and any extra 64bit-only flags /\n+\tslab-\u003ecounters = 0;\n+\n \tslab-\u003eobjects = oo_objects(oo);\n-\tslab-\u003einuse = 0;\n-\tslab-\u003efrozen = 0;\n \n+#ifdef CONFIG_64BIT\n+\tif (cache_needs_objcg(s))\n+\t\tslab-\u003eobj_exts_needs_objcg = 1;\n+#endif\n \tslab-\u003eslab_cache = s;\n \n \tkasan_poison_slab(slab);\n@@ -6526,7 +6572,7 @@ static inline size_t slab_ksize(struct slab slab)\n \t /\n \tif (s-\u003eflags \u0026 (SLAB_TYPESAFE_BY_RCU \| SLAB_STORE_USER))\n \t\treturn s-\u003einuse;\n-\telse if (obj_exts_in_object(s, slab))\n+\telse if (obj_exts_in_object(slab))\n \t\treturn s-\u003einuse;\n \t/\n \t * Else we can use all the padding etc for the allocation\n@@ -7929,7 +7975,7 @@ static int calculate_sizes(struct kmem_cache_args args, struct kmem_cache s)\n \taligned_size = ALIGN(size, s-\u003ealign);\n #if defined(CONFIG_SLAB_OBJ_EXT) \u0026\u0026 defined(CONFIG_64BIT)\n \tif (slab_args_unmergeable(args, s-\u003eflags) \u0026\u0026\n-\t\t\t(aligned_size - size \u003e= sizeof(struct slabobj_ext)))\n+\t\t\t(aligned_size - size \u003e= cache_obj_ext_size(s)))\n \t\ts-\u003eflags \|= SLAB_OBJ_EXT_IN_OBJ;\n #endif\n \tsize = aligned_size;\n@@ -8539,6 +8585,8 @@ void __init kmem_cache_init(void)\n \t\tboot_kmem_cache_node;\n \tint node;\n \n+\tslab_obj_ext_has_codetag_init();\n+\n \tif (debug_guardpage_minorder())\n \t\tslub_max_order = 0;\n \n" }
2/1	2026/07/28 02:13	agent	patch-evaluator	4m Model: best-expensive Args: null Results: { "EnableConfigs": [ "MEMCG", "MEM_ALLOC_PROFILING", "KFENCE" ], "FocusSymbols": [ "alloc_slab_obj_exts", "__memcg_slab_post_alloc_hook", "__memcg_slab_free_hook", "__kmem_cache_create_args", "kmem_cache_charge" ], "Reasoning": "The patch modifies the memory allocation profiling and memcg accounting logic in the SLUB allocator. It changes how `slabobj_ext` structures are allocated, accessed, and managed, particularly when both `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING` are enabled. It introduces `SLAB_MAY_ACCOUNT` and changes the layout of `slabobj_ext`. These are core kernel memory management changes that should be fuzzed to ensure no memory corruption, leaks, or accounting errors occur.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer. Your job is to review a provided patch series and determine if it makes functional changes to the kernel that should be fuzzed. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively use your code access tools to examine the actual source code and confirm any assumptions. Return WorthFuzzing=false if the patch only contains: - Modifications to Documentation/, Kconfig files, or code comments. - Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints. - Changes to numeric constants or macros that do not functionally alter execution flow. - Code paths that are impossible to reach in virtualized environments like GCE or QEMU, even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim). - Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU. - Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove) that are executed only during PCI hot-unplug or sysfs driver unbind operations. If it modifies reachable core kernel logic, drivers, or architectures, use your code search tools to verify the code can be executed, then return WorthFuzzing=true. When returning WorthFuzzing=true, you MUST ALSO: 1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols. Avoid listing generic hot-path functions to prevent skewed test distributions. Prefer non-static, non-inlined API entrypoint functions over internal static helper functions (which are inlined by the compiler and do not have distinct symbol addresses). 2. Identify any specific CONFIG_ options required to properly test this new/modified feature. Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions. Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs output array, and DO NOT add a '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: For your convenience, here is the diff of the changes: commit 48f84032d1bd908e46149ccacdb9013ee3369920 Author: syz-cluster <triage@syzkaller.com> Date: Tue Jul 28 02:13:15 2026 +0000 syz-cluster: applied patch under review diff --git a/Documentation/mm/allocation-profiling.rst b/Documentation/mm/allocation-profiling.rst index 5389d241176a8a..d02eb54ee8f2c6 100644 --- a/Documentation/mm/allocation-profiling.rst +++ b/Documentation/mm/allocation-profiling.rst @@ -112,3 +112,10 @@ To do so: - Then, use the following form for your allocations: alloc_hooks_tag(ht->your_saved_tag, kmalloc_noprof(...)) + +Notes +===== + +- When a slab object is allocated from KFENCE, its accounting is skipped. + KFENCE allocations are rare and limited to a small number, so this omission + is negligible. diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index e1f46a0016fcfd..93869cc35c25bc 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1440,19 +1440,6 @@ static inline void mem_cgroup_flush_workqueue(void) { } static inline int mem_cgroup_init(void) { return 0; } #endif /* CONFIG_MEMCG / -/ - * Extended information for slab objects stored as an array in page->memcg_data - * if MEMCG_DATA_OBJEXTS is set. - / -struct slabobj_ext { -#ifdef CONFIG_MEMCG - struct obj_cgroup objcg; -#endif -#ifdef CONFIG_MEM_ALLOC_PROFILING - union codetag_ref ref; -#endif -} __aligned(8); - static inline struct lruvec parent_lruvec(struct lruvec lruvec) { struct mem_cgroup memcg; diff --git a/include/linux/slab.h b/include/linux/slab.h index 32c9f8ed7ae205..e1915026e03040 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -45,6 +45,7 @@ enum _slab_flag_bits { #endif #ifdef CONFIG_MEMCG _SLAB_ACCOUNT, + _SLAB_MAY_ACCOUNT, #endif #ifdef CONFIG_KASAN_GENERIC _SLAB_KASAN, @@ -204,8 +205,10 @@ enum _slab_flag_bits { / #ifdef CONFIG_MEMCG # define SLAB_ACCOUNT __SLAB_FLAG_BIT(_SLAB_ACCOUNT) +# define SLAB_MAY_ACCOUNT __SLAB_FLAG_BIT(_SLAB_MAY_ACCOUNT) #else # define SLAB_ACCOUNT __SLAB_FLAG_UNUSED +# define SLAB_MAY_ACCOUNT __SLAB_FLAG_UNUSED #endif #ifdef CONFIG_KASAN_GENERIC diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 6577bd76954eb4..90925c646c4c24 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -636,11 +636,6 @@ static unsigned long kfence_init_pool(void) page = pfn_to_page(start_pfn + i); __SetPageSlab(page); -#ifdef CONFIG_MEMCG - struct slab slab = page_slab(page); - slab->obj_exts = (unsigned long)&kfence_metadata_init[i / 2 - 1].obj_exts \| - MEMCG_DATA_OBJEXTS; -#endif } / @@ -704,10 +699,6 @@ static unsigned long kfence_init_pool(void) continue; page = pfn_to_page(start_pfn + i); -#ifdef CONFIG_MEMCG - struct slab slab = page_slab(page); - slab->obj_exts = 0; -#endif __ClearPageSlab(page); } @@ -1248,9 +1239,6 @@ void __kfence_free(void addr) { struct kfence_metadata meta = addr_to_metadata((unsigned long)addr); -#ifdef CONFIG_MEMCG - KFENCE_WARN_ON(meta->obj_exts.objcg); -#endif / * If the objects of the cache are SLAB_TYPESAFE_BY_RCU, defer freeing * the object, as the object page may be recycled for other-typed diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h index 1f618f9b0d12d9..e6b4bf349ff730 100644 --- a/mm/kfence/kfence.h +++ b/mm/kfence/kfence.h @@ -102,9 +102,6 @@ struct kfence_metadata { struct kfence_track free_track __guarded_by(&lock); /* For updating alloc_covered on frees. / u32 alloc_stack_hash __guarded_by(&lock); -#ifdef CONFIG_MEMCG - struct slabobj_ext obj_exts; -#endif }; #define KFENCE_METADATA_SIZE PAGE_ALIGN(sizeof(struct kfence_metadata) \ diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c index de2d0f7d62b15e..9867c03ef0ae3d 100644 --- a/mm/kfence/kfence_test.c +++ b/mm/kfence/kfence_test.c @@ -295,7 +295,7 @@ static void test_alloc(struct kunit test, size_t size, gfp_t gfp, enum allocat * memcg accounting works correctly. / KUNIT_EXPECT_EQ(test, obj_to_index(s, slab, alloc), 0U); - KUNIT_EXPECT_EQ(test, objs_per_slab(s, slab), 1); + KUNIT_EXPECT_EQ(test, ((unsigned int)slab->objects), 1); if (policy == ALLOCATE_ANY) return alloc; diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 6dc4888a90f3fd..6b51ddf6dfe022 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2865,18 +2865,19 @@ struct mem_cgroup mem_cgroup_from_obj_slab(struct slab slab, void p) / unsigned long obj_exts; struct slabobj_ext obj_ext; - unsigned int off; + struct obj_cgroup objcg; obj_exts = slab_obj_exts(slab); if (!obj_exts) return NULL; - get_slab_obj_exts(obj_exts); - off = obj_to_index(slab->slab_cache, slab, p); - obj_ext = slab_obj_ext(slab, obj_exts, off); - if (obj_ext->objcg) { - struct obj_cgroup objcg = obj_ext->objcg; + if (!slab_needs_objcg(slab)) + return NULL; + get_slab_obj_exts(obj_exts); + obj_ext = slab_obj_ext(slab->slab_cache, slab, obj_exts, p); + objcg = slab_obj_ext_objcg(obj_ext); + if (objcg) { put_slab_obj_exts(obj_exts); return obj_cgroup_memcg(objcg); } @@ -3541,7 +3542,6 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache s, struct list_lru lru, size_t obj_size = obj_full_size(s); struct obj_cgroup objcg; struct slab slab; - unsigned long off; size_t i; /* @@ -3583,11 +3583,16 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache s, struct list_lru lru, slab = virt_to_slab(p[i]); - if (!slab_obj_exts(slab) && - alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags)) { - continue; + if (!slab_obj_exts(slab)) { + if (is_kfence_address(p[i])) + continue; + if (alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags)) + continue; } + if (IS_ENABLED(CONFIG_DEBUG_VM) && WARN_ON_ONCE(!slab_needs_objcg(slab))) + continue; + /* * if we fail and size is 1, memcg_alloc_abort_single() will * just free the object, which is ok as we have not assigned @@ -3616,10 +3621,11 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache s, struct list_lru lru, obj_exts = slab_obj_exts(slab); get_slab_obj_exts(obj_exts); - off = obj_to_index(s, slab, p[i]); - obj_ext = slab_obj_ext(slab, obj_exts, off); + obj_ext = slab_obj_ext(s, slab, obj_exts, p[i]); + obj_cgroup_get(objcg); - obj_ext->objcg = objcg; + slab_obj_ext_set_objcg(obj_ext, objcg); + put_slab_obj_exts(obj_exts); } @@ -3635,15 +3641,13 @@ void __memcg_slab_free_hook(struct kmem_cache s, struct slab slab, struct obj_cgroup objcg; struct slabobj_ext obj_ext; struct obj_stock_pcp stock; - unsigned int off; - off = obj_to_index(s, slab, p[i]); - obj_ext = slab_obj_ext(slab, obj_exts, off); - objcg = obj_ext->objcg; + obj_ext = slab_obj_ext(s, slab, obj_exts, p[i]); + objcg = slab_obj_ext_objcg(obj_ext); if (!objcg) continue; - obj_ext->objcg = NULL; + slab_obj_ext_set_objcg(obj_ext, NULL); stock = trylock_stock(); __refill_obj_stock(objcg, stock, obj_size, true); diff --git a/mm/slab.h b/mm/slab.h index f5e336b6b6b04c..04600f57b40146 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -81,10 +81,11 @@ struct freelist_counters { #ifdef CONFIG_64BIT / * Some optimizations use free bits in 'counters' field - * to save memory. In case ->stride field is not available, - * such optimizations are disabled. + * to save memory or CPU. If these free bits are not + * available, such optimizations are disabled. / - unsigned int stride; + unsigned obj_exts_in_object:1; + unsigned obj_exts_needs_objcg:1; #endif }; }; @@ -330,12 +331,6 @@ static inline unsigned int obj_to_index(const struct kmem_cache cache, return __obj_to_index(cache, slab_address(slab), obj); } -static inline int objs_per_slab(const struct kmem_cache cache, - const struct slab slab) -{ - return slab->objects; -} - /* * State of the slab allocator. * @@ -555,6 +550,93 @@ static inline bool need_kmalloc_no_objext(void) return false; } +/* + * Extended information for slab objects stored as a pointer to an array in + * slab->obj_exts (aliasing page->memcg_data) if MEMCG_DATA_OBJEXTS is set. + / +struct slabobj_ext { + / + * All elements of the union should be pointer-sized to avoid memory + * waste + / + union { +#ifdef CONFIG_MEMCG + struct obj_cgroup _objcg; +#endif +#ifdef CONFIG_MEM_ALLOC_PROFILING + union codetag_ref _ctref; +#endif + }; +} __aligned(8); + +#ifdef CONFIG_MEM_ALLOC_PROFILING +DECLARE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT, + slab_obj_ext_has_codetag_key); + +static inline bool slab_obj_ext_has_codetag(void) +{ + return static_branch_maybe(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT, + &slab_obj_ext_has_codetag_key); +} +#else +static inline bool slab_obj_ext_has_codetag(void) +{ + return false; +} +#endif + +#ifdef CONFIG_MEMCG +static inline bool cache_needs_objcg(struct kmem_cache cache) +{ + return (cache->flags & SLAB_MAY_ACCOUNT); +} + +static inline bool slab_needs_objcg(struct slab slab) +{ +#ifdef CONFIG_64BIT + return slab->obj_exts_needs_objcg; +#else + return cache_needs_objcg(slab->slab_cache); +#endif +} +#else +static inline bool cache_needs_objcg(struct kmem_cache cache) +{ + return false; +} + +static inline bool slab_needs_objcg(struct slab slab) +{ + return false; +} +#endif + +static inline size_t cache_obj_ext_size(struct kmem_cache s) +{ + size_t sz = 0; + + if (cache_needs_objcg(s)) + sz += 1; + + if (slab_obj_ext_has_codetag()) + sz += 1; + + return sizeof(struct slabobj_ext) sz; +} + +static inline size_t slab_obj_ext_size(struct slab slab) +{ + size_t sz = 0; + + if (slab_needs_objcg(slab)) + sz += 1; + + if (slab_obj_ext_has_codetag()) + sz += 1; + + return sizeof(struct slabobj_ext) sz; +} + #ifdef CONFIG_SLAB_OBJ_EXT /* @@ -572,7 +654,7 @@ static inline bool need_kmalloc_no_objext(void) * obj_exts = slab_obj_exts(slab); * if (obj_exts) { * get_slab_obj_exts(obj_exts); - * obj_ext = slab_obj_ext(slab, obj_exts, obj_to_index(s, slab, obj)); + * obj_ext = slab_obj_ext(s, slab, obj_exts, obj); * // do something with obj_ext * put_slab_obj_exts(obj_exts); * } @@ -610,48 +692,86 @@ static inline void put_slab_obj_exts(unsigned long obj_exts) } #ifdef CONFIG_64BIT -static inline void slab_set_stride(struct slab slab, unsigned int stride) +static inline bool obj_exts_in_object(struct slab slab) { - slab->stride = stride; -} -static inline unsigned int slab_get_stride(struct slab slab) -{ - return slab->stride; + / + * Note we cannot rely on the SLAB_OBJ_EXT_IN_OBJ flag here and need to + * check the per-slab bit. A cache can have SLAB_OBJ_EXT_IN_OBJ set, but + * allocations within_slab_leftover are preferred. And those may be + * possible or not depending on the particular slab's size. + / + return slab->obj_exts_in_object; } #else -static inline void slab_set_stride(struct slab slab, unsigned int stride) -{ - VM_WARN_ON_ONCE(stride != sizeof(struct slabobj_ext)); -} -static inline unsigned int slab_get_stride(struct slab slab) +static inline bool obj_exts_in_object(struct slab slab) { - return sizeof(struct slabobj_ext); + return false; } #endif /* * slab_obj_ext - get the pointer to the slab object extension metadata * associated with an object in a slab. + * @s: cache that the slab belongs to * @slab: a pointer to the slab struct * @obj_exts: a pointer to the object extension vector - * @index: an index of the object + * @obj: a pointer to the object * * Returns a pointer to the object extension associated with the object. * Must be called within a section covered by get/put_slab_obj_exts(). / -static inline struct slabobj_ext slab_obj_ext(struct slab slab, - unsigned long obj_exts, - unsigned int index) +static inline struct slabobj_ext +slab_obj_ext(struct kmem_cache s, struct slab slab, unsigned long obj_exts, + const void obj) { struct slabobj_ext obj_ext; + unsigned int index; + unsigned int stride; VM_WARN_ON_ONCE(obj_exts != slab_obj_exts(slab)); - obj_ext = (struct slabobj_ext )(obj_exts + - slab_get_stride(slab) index); + /* + * KFENCE objects have NULL obj_exts and thus can't reach this + * and we don't need obj_to_index() + / + index = __obj_to_index(s, slab_address(slab), obj); + + if (!obj_exts_in_object(slab)) + stride = slab_obj_ext_size(slab); + else + stride = s->size; + + obj_ext = (struct slabobj_ext )(obj_exts + index * stride); + return kasan_reset_tag(obj_ext); } +#ifdef CONFIG_MEMCG +static inline struct obj_cgroup slab_obj_ext_objcg(struct slabobj_ext obj_ext) +{ + /* if objcg exists, it comes first, so we don't need to do anything / + return obj_ext->_objcg; +} + +static inline void slab_obj_ext_set_objcg(struct slabobj_ext obj_ext, + struct obj_cgroup objcg) +{ + / if objcg exists, it comes first, so we don't need to do anything / + obj_ext->_objcg = objcg; +} +#endif + +#ifdef CONFIG_MEM_ALLOC_PROFILING +static inline union codetag_ref +slab_obj_ext_codetag_ref(struct slab slab, struct slabobj_ext obj_ext) +{ + if (slab_needs_objcg(slab)) + obj_ext += 1; + + return &obj_ext->_ctref; +} +#endif + int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s, gfp_t gfp, unsigned int alloc_flags); @@ -662,16 +782,17 @@ static inline unsigned long slab_obj_exts(struct slab slab) return 0; } -static inline struct slabobj_ext slab_obj_ext(struct slab slab, - unsigned long obj_exts, - unsigned int index) +static inline struct slabobj_ext +slab_obj_ext(struct kmem_cache s, struct slab slab, unsigned long obj_exts, + const void obj) { return NULL; } -static inline void slab_set_stride(struct slab slab, unsigned int stride) { } -static inline unsigned int slab_get_stride(struct slab slab) { return 0; } - +static inline bool obj_exts_in_object(struct slab slab) +{ + return false; +} #endif /* CONFIG_SLAB_OBJ_EXT / diff --git a/mm/slab_common.c b/mm/slab_common.c index 03ecac12cd865f..1e1d3feec3535b 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -52,7 +52,7 @@ struct kmem_cache kmem_cache; SLAB_OBJ_EXT_IN_OBJ) #define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT \| SLAB_CACHE_DMA \| \ - SLAB_CACHE_DMA32 \| SLAB_ACCOUNT) + SLAB_CACHE_DMA32 \| SLAB_ACCOUNT \| SLAB_MAY_ACCOUNT) /* * Merge control. If this is set then no merging of slab caches will occur. @@ -359,6 +359,13 @@ struct kmem_cache __kmem_cache_create_args(const char name, goto out_unlock; } + /* + * For now we assume any cache can be used with __GFP_ACCOUNT and thus + * may need to store objcg pointers for objects + / + if (!mem_cgroup_kmem_disabled()) + flags \|= SLAB_MAY_ACCOUNT; + / Fail closed on bad usersize of useroffset values. / if (!IS_ENABLED(CONFIG_HARDENED_USERCOPY) \|\| WARN_ON(!args->usersize && args->useroffset) \|\| @@ -984,11 +991,20 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type) #endif / - * If CONFIG_MEMCG is enabled, disable cache merging for - * KMALLOC_NORMAL caches. + * If memcg_kmem is enabled and this is a KMALLOC_NORMAL cache and not + * aliased with any other type, make sure it's never merged with any other + * cache. + * + * In other cases the kmalloc cache may end up being used for a + * __GFP_ACCOUNT allocation so mark it as such. The exception is a + * KMALLOC_NO_OBJ_EXT cache. / - if (IS_ENABLED(CONFIG_MEMCG) && (type == KMALLOC_NORMAL)) - flags \|= SLAB_NO_MERGE; + if (!mem_cgroup_kmem_disabled()) { + if (type == KMALLOC_NORMAL && KMALLOC_RECLAIM != KMALLOC_NORMAL) + flags \|= SLAB_NO_MERGE; + else if (!(flags & SLAB_NO_OBJ_EXT)) + flags \|= SLAB_MAY_ACCOUNT; + } if (minalign > ARCH_KMALLOC_MINALIGN) { aligned_size = ALIGN(aligned_size, minalign); diff --git a/mm/slub.c b/mm/slub.c index 0337e60db5ace0..94b744e5ac7919 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -213,6 +213,11 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled); static DEFINE_STATIC_KEY_FALSE(strict_numa); #endif +#ifdef CONFIG_MEM_ALLOC_PROFILING +DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT, + slab_obj_ext_has_codetag_key); +#endif + / Structure holding extra parameters for slab allocations / struct slab_alloc_context { unsigned long caller_addr; @@ -803,7 +808,7 @@ static inline bool need_slab_obj_exts(struct kmem_cache s) static inline unsigned int obj_exts_size_in_slab(struct slab slab) { - return sizeof(struct slabobj_ext) slab->objects; + return slab_obj_ext_size(slab) * slab->objects; } static inline unsigned long obj_exts_offset_in_slab(struct kmem_cache s, @@ -870,18 +875,6 @@ static inline bool obj_exts_in_slab(struct kmem_cache s, struct slab slab) #endif #if defined(CONFIG_SLAB_OBJ_EXT) && defined(CONFIG_64BIT) -static bool obj_exts_in_object(struct kmem_cache s, struct slab slab) -{ - / - * Note we cannot rely on the SLAB_OBJ_EXT_IN_OBJ flag here and need to - * check the stride. A cache can have SLAB_OBJ_EXT_IN_OBJ set, but - * allocations within_slab_leftover are preferred. And those may be - * possible or not depending on the particular slab's size. - / - return obj_exts_in_slab(s, slab) && - (slab_get_stride(slab) == s->size); -} - static unsigned int obj_exts_offset_in_object(struct kmem_cache s) { unsigned int offset = get_info_end(s); @@ -896,16 +889,20 @@ static unsigned int obj_exts_offset_in_object(struct kmem_cache s) return offset; } -#else -static inline bool obj_exts_in_object(struct kmem_cache s, struct slab slab) + +static inline void slab_set_obj_exts_in_object(struct slab slab) { - return false; + slab->obj_exts_in_object = 1; } - +#else static inline unsigned int obj_exts_offset_in_object(struct kmem_cache s) { return 0; } + +static inline void slab_set_obj_exts_in_object(struct slab slab) +{ +} #endif #ifdef CONFIG_SLUB_DEBUG @@ -1206,8 +1203,8 @@ static void print_trailer(struct kmem_cache s, struct slab slab, u8 p) off += kasan_metadata_size(s, false); - if (obj_exts_in_object(s, slab)) - off += sizeof(struct slabobj_ext); + if (obj_exts_in_object(slab)) + off += slab_obj_ext_size(slab); if (off != size_from_object(s)) / Beginning of the filler is the free pointer / @@ -1411,8 +1408,8 @@ static int check_pad_bytes(struct kmem_cache s, struct slab slab, u8 p) off += kasan_metadata_size(s, false); - if (obj_exts_in_object(s, slab)) - off += sizeof(struct slabobj_ext); + if (obj_exts_in_object(slab)) + off += slab_obj_ext_size(slab); if (size_from_object(s) == off) return 1; @@ -1439,7 +1436,7 @@ slab_pad_check(struct kmem_cache s, struct slab slab) length = slab_size(slab); end = start + length; - if (obj_exts_in_slab(s, slab) && !obj_exts_in_object(s, slab)) { + if (obj_exts_in_slab(s, slab) && !obj_exts_in_object(slab)) { remainder = length; remainder -= obj_exts_offset_in_slab(s, slab); remainder -= obj_exts_size_in_slab(slab); @@ -2070,20 +2067,21 @@ static inline void mark_obj_codetag_empty(const void obj) obj_slab = virt_to_slab(obj); slab_exts = slab_obj_exts(obj_slab); if (slab_exts) { + struct slabobj_ext ext; + union codetag_ref ref; + get_slab_obj_exts(slab_exts); - unsigned int offs = obj_to_index(obj_slab->slab_cache, - obj_slab, obj); - struct slabobj_ext ext = slab_obj_ext(obj_slab, - slab_exts, offs); + ext = slab_obj_ext(obj_slab->slab_cache, obj_slab, slab_exts, obj); + ref = slab_obj_ext_codetag_ref(obj_slab, ext); - if (unlikely(is_codetag_empty(&ext->ref))) { + if (unlikely(is_codetag_empty(ref))) { put_slab_obj_exts(slab_exts); return; } /* codetag should be NULL here / - WARN_ON(ext->ref.ct); - set_codetag_empty(&ext->ref); + WARN_ON(ref->ct); + set_codetag_empty(ref); put_slab_obj_exts(slab_exts); } } @@ -2093,19 +2091,29 @@ static inline bool mark_failed_objexts_alloc(struct slab slab) return cmpxchg(&slab->obj_exts, 0, OBJEXTS_ALLOC_FAIL) == 0; } -static inline void handle_failed_objexts_alloc(unsigned long obj_exts, - struct slabobj_ext vec, unsigned int objects) +static inline void handle_failed_objexts_alloc(struct slab slab, + unsigned long obj_exts, struct slabobj_ext vec) { + unsigned int stride; + + if (!slab_obj_ext_has_codetag()) + return; + / * If vector previously failed to allocate then we have live * objects with no tag reference. Mark all references in this * vector as empty to avoid warnings later on. / - if (obj_exts == OBJEXTS_ALLOC_FAIL) { - unsigned int i; + if (obj_exts != OBJEXTS_ALLOC_FAIL) + return; + + stride = slab_obj_ext_size(slab) / sizeof(vec); + + for (unsigned int i = 0; i < slab->objects; i++) { + union codetag_ref ref = slab_obj_ext_codetag_ref(slab, vec); - for (i = 0; i < objects; i++) - set_codetag_empty(&vec[i].ref); + set_codetag_empty(ref); + vec += stride; } } @@ -2113,8 +2121,8 @@ static inline void handle_failed_objexts_alloc(unsigned long obj_exts, static inline void mark_obj_codetag_empty(const void obj) {} static inline bool mark_failed_objexts_alloc(struct slab slab) { return false; } -static inline void handle_failed_objexts_alloc(unsigned long obj_exts, - struct slabobj_ext vec, unsigned int objects) {} +static inline void handle_failed_objexts_alloc(struct slab slab, + unsigned long obj_exts, struct slabobj_ext vec) {} #endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG / @@ -2127,12 +2135,11 @@ int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s, gfp_t gfp, unsigned int alloc_flags) { const bool allow_spin = alloc_flags_allow_spinning(alloc_flags); - unsigned int objects = objs_per_slab(s, slab); bool new_slab = alloc_flags & SLAB_ALLOC_NEW_SLAB; unsigned long new_exts; unsigned long old_exts; struct slabobj_ext vec; - size_t sz = sizeof(struct slabobj_ext) * slab->objects; + size_t sz = slab_obj_ext_size(slab) * slab->objects; gfp &= ~OBJCGS_CLEAR_MASK; /* @@ -2183,7 +2190,7 @@ int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s, #endif retry: old_exts = READ_ONCE(slab->obj_exts); - handle_failed_objexts_alloc(old_exts, vec, objects); + handle_failed_objexts_alloc(slab, old_exts, vec); if (new_slab) { /* @@ -2250,9 +2257,6 @@ static void alloc_slab_obj_exts_early(struct kmem_cache s, struct slab slab) void addr; unsigned long obj_exts; - / Initialize stride early to avoid memory ordering issues / - slab_set_stride(slab, sizeof(struct slabobj_ext)); - if (!need_slab_obj_exts(s)) return; @@ -2278,15 +2282,14 @@ static void alloc_slab_obj_exts_early(struct kmem_cache s, struct slab slab) get_slab_obj_exts(obj_exts); for_each_object(addr, s, slab_address(slab), slab->objects) - memset(kasan_reset_tag(addr) + offset, 0, - sizeof(struct slabobj_ext)); + memset(kasan_reset_tag(addr) + offset, 0, slab_obj_ext_size(slab)); put_slab_obj_exts(obj_exts); #ifdef CONFIG_MEMCG obj_exts \|= MEMCG_DATA_OBJEXTS; #endif slab->obj_exts = obj_exts; - slab_set_stride(slab, s->size); + slab_set_obj_exts_in_object(slab); } } @@ -2323,11 +2326,15 @@ static inline unsigned long prepare_slab_obj_exts_hook(struct kmem_cache s, struct slab slab, gfp_t flags, unsigned int alloc_flags, void p) { - if (!slab_obj_exts(slab) && - alloc_slab_obj_exts(slab, s, flags, alloc_flags)) { - pr_warn_once("%s, %s: Failed to create slab extension vector!\n", - __func__, s->name); - return 0; + if (!slab_obj_exts(slab)) { + if (is_kfence_address(p)) + return 0; + + if (alloc_slab_obj_exts(slab, s, flags, alloc_flags)) { + pr_warn_once("%s, %s: Failed to create slab extension vector!\n", + __func__, s->name); + return 0; + } } return slab_obj_exts(slab); @@ -2360,14 +2367,24 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache s, void object, gfp_t flags, * check should be added before alloc_tag_add(). / if (obj_exts) { - unsigned int obj_idx = obj_to_index(s, slab, object); + union codetag_ref ref; get_slab_obj_exts(obj_exts); - obj_ext = slab_obj_ext(slab, obj_exts, obj_idx); - alloc_tag_add(&obj_ext->ref, current->alloc_tag, s->size); + + obj_ext = slab_obj_ext(s, slab, obj_exts, object); + ref = slab_obj_ext_codetag_ref(slab, obj_ext); + + alloc_tag_add(ref, current->alloc_tag, s->size); + put_slab_obj_exts(obj_exts); } else { - alloc_tag_set_inaccurate(current->alloc_tag); + /* + * KFENCE allocations are rare and the amount of outstanding + * ones is limited to a small number so it's not worth setting + * tags as inaccurate because of them. + / + if (!is_kfence_address(object)) + alloc_tag_set_inaccurate(current->alloc_tag); } } @@ -2384,7 +2401,6 @@ static noinline void __alloc_tagging_slab_free_hook(struct kmem_cache s, struct slab slab, void p, int objects) { - int i; unsigned long obj_exts; / slab->obj_exts might not be NULL if it was created for MEMCG accounting. / @@ -2396,10 +2412,11 @@ __alloc_tagging_slab_free_hook(struct kmem_cache s, struct slab slab, void p return; get_slab_obj_exts(obj_exts); - for (i = 0; i < objects; i++) { - unsigned int off = obj_to_index(s, slab, p[i]); + for (int i = 0; i < objects; i++) { + struct slabobj_ext ext; - alloc_tag_sub(&slab_obj_ext(slab, obj_exts, off)->ref, s->size); + ext = slab_obj_ext(s, slab, obj_exts, p[i]); + alloc_tag_sub(slab_obj_ext_codetag_ref(slab, ext), s->size); } put_slab_obj_exts(obj_exts); } @@ -2412,6 +2429,25 @@ alloc_tagging_slab_free_hook(struct kmem_cache s, struct slab slab, void *p, __alloc_tagging_slab_free_hook(s, slab, p, objects); } +/ + * Make sure the static key used by slab_obj_ext_has_codetag() reflects the + * value of !mem_alloc_profiling_permanently_disabled() + * + * Any later mem alloc profiling shutdown won't be reflected in the static key + * because obj_exts with codetags might already exist. + / +static void __init slab_obj_ext_has_codetag_init(void) +{ + bool need_codetag = !mem_alloc_profiling_permanently_disabled(); + + if (need_codetag != static_key_enabled(&slab_obj_ext_has_codetag_key)) { + if (need_codetag) + static_branch_enable(&slab_obj_ext_has_codetag_key); + else + static_branch_disable(&slab_obj_ext_has_codetag_key); + } +} + #else / CONFIG_MEM_ALLOC_PROFILING / static inline void @@ -2426,6 +2462,10 @@ alloc_tagging_slab_free_hook(struct kmem_cache s, struct slab slab, void p, { } +static inline void slab_obj_ext_has_codetag_init(void) +{ +} + #endif / CONFIG_MEM_ALLOC_PROFILING / @@ -2471,6 +2511,9 @@ void memcg_slab_free_hook(struct kmem_cache s, struct slab slab, void p, if (likely(!obj_exts)) return; + if (!slab_needs_objcg(slab)) + return; + get_slab_obj_exts(obj_exts); __memcg_slab_free_hook(s, slab, p, objects, obj_exts); put_slab_obj_exts(obj_exts); @@ -2484,7 +2527,6 @@ bool memcg_slab_post_charge(void p, gfp_t flags) struct kmem_cache s; struct page page; struct slab slab; - unsigned long off; page = virt_to_page(p); if (PageLargeKmalloc(page)) { @@ -2517,16 +2559,15 @@ bool memcg_slab_post_charge(void p, gfp_t flags) * of slab_obj_exts being allocated from the same slab and thus the slab * becoming effectively unfreeable. / - if (is_kmalloc_normal(s)) + if (!cache_needs_objcg(s)) return true; / Ignore already charged objects. / obj_exts = slab_obj_exts(slab); if (obj_exts) { get_slab_obj_exts(obj_exts); - off = obj_to_index(s, slab, p); - obj_ext = slab_obj_ext(slab, obj_exts, off); - if (unlikely(obj_ext->objcg)) { + obj_ext = slab_obj_ext(s, slab, obj_exts, p); + if (unlikely(slab_obj_ext_objcg(obj_ext))) { put_slab_obj_exts(obj_exts); return true; } @@ -3391,10 +3432,15 @@ static struct slab allocate_slab(struct kmem_cache s, gfp_t flags, stat(s, ORDER_FALLBACK); } + / Initializes frozen, inuse, and any extra 64bit-only flags / + slab->counters = 0; + slab->objects = oo_objects(oo); - slab->inuse = 0; - slab->frozen = 0; +#ifdef CONFIG_64BIT + if (cache_needs_objcg(s)) + slab->obj_exts_needs_objcg = 1; +#endif slab->slab_cache = s; kasan_poison_slab(slab); @@ -6526,7 +6572,7 @@ static inline size_t slab_ksize(struct slab slab) / if (s->flags & (SLAB_TYPESAFE_BY_RCU \| SLAB_STORE_USER)) return s->inuse; - else if (obj_exts_in_object(s, slab)) + else if (obj_exts_in_object(slab)) return s->inuse; / * Else we can use all the padding etc for the allocation @@ -7929,7 +7975,7 @@ static int calculate_sizes(struct kmem_cache_args args, struct kmem_cache s) aligned_size = ALIGN(size, s->align); #if defined(CONFIG_SLAB_OBJ_EXT) && defined(CONFIG_64BIT) if (slab_args_unmergeable(args, s->flags) && - (aligned_size - size >= sizeof(struct slabobj_ext))) + (aligned_size - size >= cache_obj_ext_size(s))) s->flags \|= SLAB_OBJ_EXT_IN_OBJ; #endif size = aligned_size; @@ -8539,6 +8585,8 @@ void __init kmem_cache_init(void) boot_kmem_cache_node; int node; + slab_obj_ext_has_codetag_init(); + if (debug_guardpage_minorder()) slub_max_order = 0;
3/2	2026/07/28 02:13	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 13750 output: 54 thoughts: 1033 Thoughts: Analyzing the SLUB Object Extension Patch Okay, so I'm looking at this kernel patch, and it's making some substantial changes to how `slabobj_ext` is handled in the SLUB allocator. My first thought is: this looks like a significant functional change to the core memory management. We're dealing with how object extensions are allocated, accessed, and managed, so this absolutely needs fuzzing. The changes are centered around `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING`. The way `slabobj_ext` is defined initially confused me, as the union structure seemed to suggest that if both features were enabled, they would share the same memory. But, no, it looks like it's actually an array of `slabobj_ext` elements per object. If `CONFIG_MEMCG` is enabled, the first element will be used for `objcg`, and then `codetag_ref` goes in the second. The size of `slabobj_ext` is 8 bytes, and `slab_obj_ext_size` returns `sizeof(struct slabobj_ext) * sz` where `sz` is either 1 or 2 depending on the need. This implies that there's a good amount of extra memory use if `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING` are both enabled. Let's identify the key functions that are modified or newly introduced. I'm focusing on the exposed symbols – things that other parts of the kernel might be calling. We've got `alloc_slab_obj_exts`, the inline `slab_obj_ext`, `prepare_slab_obj_exts_hook`, `__alloc_tagging_slab_alloc_hook`, `__alloc_tagging_slab_free_hook`, `memcg_slab_post_charge`, `__memcg_slab_post_alloc_hook`, `__memcg_slab_free_hook`, and `kmem_cache_create` (indirectly via `__kmem_cache_create_args`), plus `kmem_cache_alloc` and `kmem_cache_free` via hooks. Now, let's hunt for any non-static functions in relevant files. I'm checking `mm/slub.c`, `mm/slab_common.c`, and `mm/memcontrol.c`. I've confirmed that `alloc_slab_obj_exts` is non-static in `mm/slub.c`, and so are `memcg_slab_post_charge`, and the `__memcg_slab_post_alloc_hook` and `__memcg_slab_free_hook` hooks. We also need to check `mm/memcontrol.c` and confirm that `mem_cgroup_from_obj_slab` is non-static. Finally, `__kmem_cache_create_args` is non-static in `mm/slab_common.c`. Also to keep in mind are the configuration options: `CONFIG_MEMCG`, `CONFIG_MEM_ALLOC_PROFILING`, `CONFIG_SLAB_OBJ_EXT` (selected by the above), and `CONFIG_KFENCE`. I should verify these function names, and any other relevant names, later, but these are all starting points.
4/2	2026/07/28 02:13	tool	grepper	0m Args: { "Expression": "^(int\|void\|bool\|struct [a-z_]+ \\?) [a-zA-Z0-9_]+\\(", "PathPrefix": "mm/slub.c" } Results:* { "Output": "mm/slub.c=403=static inline\nmm/slub.c:404:void stat_add(const struct kmem_cache s, enum stat_item si, int v)\nmm/slub.c-405-{\n--\nmm/slub.c=935=static bool slab_add_kunit_errors(void)\n--\nmm/slub.c-950-\nmm/slub.c:951:bool slab_in_kunit_test(void)\nmm/slub.c-952-{\n--\nmm/slub.c=1093=static void print_track(const char s, struct track t, unsigned long pr_time)\n--\nmm/slub.c-1110-\nmm/slub.c:1111:void print_tracking(struct kmem_cache s, void object)\nmm/slub.c-1112-{\n--\nmm/slub.c=1121=static void print_slab_info(const struct slab slab)\n--\nmm/slub.c-1127-\nmm/slub.c:1128:void skip_orig_size_check(struct kmem_cache s, const void object)\nmm/slub.c-1129-{\n--\nmm/slub.c=1708=static\nmm/slub.c:1709:void setup_slab_debug(struct kmem_cache s, struct slab slab, void addr)\nmm/slub.c-1710-{\n--\nmm/slub.c=2010=static inline\nmm/slub.c:2011:void setup_slab_debug(struct kmem_cache s, struct slab slab, void addr) {}\nmm/slub.c-2012-\n--\nmm/slub.c=2129=static inline void init_slab_obj_exts(struct slab slab)\n--\nmm/slub.c-2133-\nmm/slub.c:2134:int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s,\nmm/slub.c-2135-\t\t\tgfp_t gfp, unsigned int alloc_flags)\n--\nmm/slub.c=2476=static __fastpath_inline\nmm/slub.c:2477:bool memcg_slab_post_alloc_hook(struct kmem_cache s, gfp_t flags,\nmm/slub.c-2478-\t\t\t\tsize_t size, void *p,\n--\nmm/slub.c=2501=static __fastpath_inline\nmm/slub.c:2502:void memcg_slab_free_hook(struct kmem_cache s, struct slab slab, void p,\nmm/slub.c-2503-\t\t\t int objects)\n--\nmm/slub.c=2522=static __fastpath_inline\nmm/slub.c:2523:bool memcg_slab_post_charge(void p, gfp_t flags)\nmm/slub.c-2524-{\n--\nmm/slub.c=2636=static __always_inline\nmm/slub.c:2637:bool slab_free_hook(struct kmem_cache s, void x, bool init,\nmm/slub.c-2638-\t\t bool after_rcu_delay)\n--\nmm/slub.c=2721=static __fastpath_inline\nmm/slub.c:2722:bool slab_free_freelist_hook(struct kmem_cache s, void head, void tail,\nmm/slub.c-2723-\t\t\t int cnt)\n--\nmm/slub.c=4067=static void flush_rcu_sheaf(struct work_struct w)\n--\nmm/slub.c-4090-/ needed for kvfree_rcu_barrier() /\nmm/slub.c:4091:void flush_rcu_sheaves_on_cache(struct kmem_cache s)\nmm/slub.c-4092-{\n--\nmm/slub.c-4121-\nmm/slub.c:4122:void flush_all_rcu_sheaves(void)\nmm/slub.c-4123-{\n--\nmm/slub.c=4591=static __fastpath_inline\nmm/slub.c:4592:bool slab_post_alloc_hook(struct kmem_cache s, gfp_t flags, size_t size,\nmm/slub.c-4593-\t\t\t void p, const struct slab_alloc_context ac)\n--\nmm/slub.c=5002=EXPORT_SYMBOL(kmem_cache_alloc_lru_noprof);\nmm/slub.c-5003-\nmm/slub.c:5004:bool kmem_cache_charge(void objp, gfp_t gfpflags)\nmm/slub.c-5005-{\n--\nmm/slub.c=5078=kmem_cache_prefill_sheaf(struct kmem_cache s, gfp_t gfp, unsigned int size)\n--\nmm/slub.c-5160- /\nmm/slub.c:5161:void kmem_cache_return_sheaf(struct kmem_cache s, gfp_t gfp,\nmm/slub.c-5162-\t\t\t struct slab_sheaf sheaf)\n--\nmm/slub.c-5218- /\nmm/slub.c:5219:int kmem_cache_refill_sheaf(struct kmem_cache s, gfp_t gfp,\nmm/slub.c-5220-\t\t\t struct slab_sheaf sheafp, unsigned int size)\n--\nmm/slub.c=5977=static __fastpath_inline\nmm/slub.c:5978:bool free_to_pcs(struct kmem_cache s, void object, bool allow_spin)\nmm/slub.c-5979-{\n--\nmm/slub.c=6071=static DEFINE_WAIT_OVERRIDE_MAP(kfree_rcu_sheaf_map, LD_WAIT_CONFIG);\nmm/slub.c-6072-\nmm/slub.c:6073:bool __kfree_rcu_sheaf(struct kmem_cache s, void obj)\nmm/slub.c-6074-{\n--\nmm/slub.c=6395=static void defer_free(struct kmem_cache s, void head)\n--\nmm/slub.c-6407-\nmm/slub.c:6408:void defer_free_barrier(void)\nmm/slub.c-6409-{\n--\nmm/slub.c=6416=static __fastpath_inline\nmm/slub.c:6417:void slab_free(struct kmem_cache s, struct slab slab, void object,\nmm/slub.c-6418-\t unsigned long addr)\n--\nmm/slub.c=6435=static noinline\nmm/slub.c:6436:void memcg_alloc_abort_single(struct kmem_cache s, void object)\nmm/slub.c-6437-{\n--\nmm/slub.c=6447=static __fastpath_inline\nmm/slub.c:6448:void slab_free_bulk(struct kmem_cache s, struct slab slab, void head,\nmm/slub.c-6449-\t\t void tail, void *p, int cnt, unsigned long addr)\n--\nmm/slub.c=6464=static void slab_free_after_rcu_debug(struct rcu_head rcu_head)\n--\nmm/slub.c-6492-#ifdef CONFIG_KASAN_GENERIC\nmm/slub.c:6493:void ___cache_free(struct kmem_cache cache, void x, unsigned long addr)\nmm/slub.c-6494-{\n--\nmm/slub.c=6500=static noinline void warn_free_bad_obj(struct kmem_cache s, void obj)\n--\nmm/slub.c-6529- /\nmm/slub.c:6530:void kmem_cache_free(struct kmem_cache s, void x)\nmm/slub.c-6531-{\n--\nmm/slub.c=6644=static void free_large_kmalloc(struct page page, void object)\n--\nmm/slub.c-6669- /\nmm/slub.c:6670:void kvfree_rcu_cb(struct rcu_head head)\nmm/slub.c-6671-{\n--\nmm/slub.c-6716- /\nmm/slub.c:6717:void kfree(const void object)\nmm/slub.c-6718-{\n--\nmm/slub.c=6740=EXPORT_SYMBOL(kfree);\n--\nmm/slub.c-6750- /\nmm/slub.c:6751:void kfree_nolock(const void object)\nmm/slub.c-6752-{\n--\nmm/slub.c=6983=EXPORT_SYMBOL(__kvmalloc_node_noprof);\n--\nmm/slub.c-6994- /\nmm/slub.c:6995:void kvfree(const void addr)\nmm/slub.c-6996-{\n--\nmm/slub.c=7002=EXPORT_SYMBOL(kvfree);\n--\nmm/slub.c-7010- /\nmm/slub.c:7011:void kvfree_atomic(const void addr)\nmm/slub.c-7012-{\n--\nmm/slub.c=7018=EXPORT_SYMBOL(kvfree_atomic);\n--\nmm/slub.c-7028- /\nmm/slub.c:7029:void kvfree_sensitive(const void addr, size_t len)\nmm/slub.c-7030-{\n--\nmm/slub.c=7087=static inline\nmm/slub.c:7088:int build_detached_freelist(struct kmem_cache s, size_t size,\nmm/slub.c-7089-\t\t\t void *p, struct detached_freelist df)\n--\nmm/slub.c=7152=static void __kmem_cache_free_bulk(struct kmem_cache s, size_t size, void p)\n--\nmm/slub.c-7172-/ Note that interrupts must be enabled when calling this function. /\nmm/slub.c:7173:void kmem_cache_free_bulk(struct kmem_cache s, size_t size, void *p)\nmm/slub.c-7174-{\n--\nmm/slub.c=7372=static bool __kmem_cache_alloc_bulk(struct kmem_cache s, gfp_t flags,\n--\nmm/slub.c-7421- /\nmm/slub.c:7422:bool kmem_cache_alloc_bulk_noprof(struct kmem_cache s, gfp_t flags,\nmm/slub.c-7423-\t\tsize_t size, void *p)\n--\nmm/slub.c=7738=static void free_kmem_cache_nodes(struct kmem_cache s)\n--\nmm/slub.c-7760-\nmm/slub.c:7761:void __kmem_cache_release(struct kmem_cache s)\nmm/slub.c-7762-{\n--\nmm/slub.c=8049=static void free_partial(struct kmem_cache s, struct kmem_cache_node n)\n--\nmm/slub.c-8069-\nmm/slub.c:8070:bool __kmem_cache_empty(struct kmem_cache s)\nmm/slub.c-8071-{\n--\nmm/slub.c-8083- /\nmm/slub.c:8084:int __kmem_cache_shutdown(struct kmem_cache s)\nmm/slub.c-8085-{\n--\nmm/slub.c-8111-#ifdef CONFIG_PRINTK\nmm/slub.c:8112:void __kmem_obj_info(struct kmem_obj_info kpp, void object, struct slab slab)\nmm/slub.c-8113-{\n--\nmm/slub.c=8236=__core_param_cb(slab_strict_numa, \u0026param_ops_slab_strict_numa, NULL, 0);\n--\nmm/slub.c-8248- /\nmm/slub.c:8249:void __check_heap_object(const void ptr, unsigned long n,\nmm/slub.c-8250-\t\t\t const struct slab slab, bool to_user)\n--\nmm/slub.c=8301=static int __kmem_cache_do_shrink(struct kmem_cache s)\n--\nmm/slub.c-8369-\nmm/slub.c:8370:int __kmem_cache_shrink(struct kmem_cache s)\nmm/slub.c-8371-{\n--\nmm/slub.c=8646=void __init kmem_cache_init_late(void)\n--\nmm/slub.c-8655-\nmm/slub.c:8656:int do_kmem_cache_create(struct kmem_cache s, const char name,\nmm/slub.c-8657-\t\t\t unsigned int size, struct kmem_cache_args args,\n--\nmm/slub.c=9689=static int sysfs_slab_add(struct kmem_cache s)\n--\nmm/slub.c-9732-\nmm/slub.c:9733:void sysfs_slab_unlink(struct kmem_cache s)\nmm/slub.c-9734-{\n--\nmm/slub.c-9738-\nmm/slub.c:9739:void sysfs_slab_release(struct kmem_cache s)\nmm/slub.c-9740-{\n--\nmm/slub.c=9754=static struct saved_alias alias_list;\nmm/slub.c-9755-\nmm/slub.c:9756:int sysfs_slab_alias(struct kmem_cache s, const char name)\nmm/slub.c-9757-{\n--\nmm/slub.c=9997=static void debugfs_slab_add(struct kmem_cache s)\n--\nmm/slub.c-10012-\nmm/slub.c:10013:void debugfs_slab_release(struct kmem_cache s)\nmm/slub.c-10014-{\n--\nmm/slub.c=10031=__initcall(slab_debugfs_init);\n--\nmm/slub.c-10036-#ifdef CONFIG_SLUB_DEBUG\nmm/slub.c:10037:void get_slabinfo(struct kmem_cache s, struct slabinfo *sinfo)\nmm/slub.c-10038-{\n" }
5/2	2026/07/28 02:13	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 19622 output: 55 thoughts: 122 Thoughts: Navigating the Slub Memory Management Landscape Okay, so I'm diving into this `slub.c` code and trying to get a handle on how these memory accounting functions interact. My initial understanding was that `alloc_slab_obj_exts`, `memcg_slab_post_charge`, and `memcg_slab_free_hook` are all housed neatly within `mm/slub.c`. But hold on... something feels off about that `memcg_slab_post_charge` location... It is in `mm/slub.c`, isn't it? Oh right, I'm forgetting about the patch I'm looking at. Yes, it's modified within `mm/slub.c`, that makes sense. Now I'm questioning whether I have the full picture. Let me quickly check `mm/slab_common.c` to see if there are any related functions or crucial dependencies lurking there that I might be overlooking. It's always smart to have a wider view when dealing with such core memory management components. I need to be thorough.
6/2	2026/07/28 02:13	tool	grepper	0m Args: { "Expression": "^(int\|void\|bool\|struct [a-z_]+ \\?) [a-zA-Z0-9_]+\\(", "PathPrefix": "mm/slab_common.c" } Results:* { "Output": "mm/slab_common.c=128=static unsigned int calculate_alignment(slab_flags_t flags,\n--\nmm/slab_common.c-154- /\nmm/slab_common.c:155:int slab_unmergeable(struct kmem_cache s)\nmm/slab_common.c-156-{\n--\nmm/slab_common.c-176-\nmm/slab_common.c:177:bool slab_args_unmergeable(struct kmem_cache_args args, slab_flags_t flags)\nmm/slab_common.c-178-{\n--\nmm/slab_common.c=518=static void kmem_cache_release(struct kmem_cache s)\n--\nmm/slab_common.c-526-\nmm/slab_common.c:527:void slab_kmem_cache_release(struct kmem_cache s)\nmm/slab_common.c-528-{\n--\nmm/slab_common.c-533-\nmm/slab_common.c:534:void kmem_cache_destroy(struct kmem_cache s)\nmm/slab_common.c-535-{\n--\nmm/slab_common.c=598=EXPORT_SYMBOL(kmem_cache_destroy);\n--\nmm/slab_common.c-608- /\nmm/slab_common.c:609:int kmem_cache_shrink(struct kmem_cache cachep)\nmm/slab_common.c-610-{\n--\nmm/slab_common.c=615=EXPORT_SYMBOL(kmem_cache_shrink);\nmm/slab_common.c-616-\nmm/slab_common.c:617:bool slab_is_available(void)\nmm/slab_common.c-618-{\n--\nmm/slab_common.c=623=static void kmem_obj_info(struct kmem_obj_info kpp, void object, struct slab slab)\n--\nmm/slab_common.c-644- /\nmm/slab_common.c:645:bool kmem_dump_obj(void object)\nmm/slab_common.c-646-{\n--\nmm/slab_common.c=1073=static void freelist_randomize(unsigned int list,\n--\nmm/slab_common.c-1089-/* Create a random sequence per cache /\nmm/slab_common.c:1090:int cache_random_seq_create(struct kmem_cache cachep, unsigned int count,\nmm/slab_common.c-1091-\t\t\t\t gfp_t gfp)\n--\nmm/slab_common.c-1105-/* Destroy the per-cache random freelist sequence /\nmm/slab_common.c:1106:void cache_random_seq_destroy(struct kmem_cache cachep)\nmm/slab_common.c-1107-{\n--\nmm/slab_common.c=1163=static int slab_show(struct seq_file m, void p)\n--\nmm/slab_common.c-1172-\nmm/slab_common.c:1173:void dump_unreclaimable_slab(void)\nmm/slab_common.c-1174-{\n--\nmm/slab_common.c=1245=module_init(slab_proc_init);\n--\nmm/slab_common.c-1259- /\nmm/slab_common.c:1260:void kfree_sensitive(const void p)\nmm/slab_common.c-1261-{\n--\nmm/slab_common.c=1297=EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);\n--\nmm/slab_common.c-1300-\nmm/slab_common.c:1301:void kvfree_call_rcu(struct rcu_head head, void ptr)\nmm/slab_common.c-1302-{\n--\nmm/slab_common.c=1950=void __init kfree_rcu_scheduler_running(void)\n--\nmm/slab_common.c-1973- /\nmm/slab_common.c:1974:void kvfree_call_rcu(struct rcu_head head, void ptr)\nmm/slab_common.c-1975-{\n--\nmm/slab_common.c=2050=static inline void __kvfree_rcu_barrier(void)\n--\nmm/slab_common.c-2128- /\nmm/slab_common.c:2129:void kvfree_rcu_barrier(void)\nmm/slab_common.c-2130-{\n--\nmm/slab_common.c=2134=EXPORT_SYMBOL_GPL(kvfree_rcu_barrier);\n--\nmm/slab_common.c-2142- /\nmm/slab_common.c:2143:void kvfree_rcu_barrier_on_cache(struct kmem_cache s)\nmm/slab_common.c-2144-{\n" }
7/2	2026/07/28 02:13	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 21333 output: 54 thoughts: 26 Thoughts: Here's my thought process, as if I were reviewing this patch: Analyzing the Scope of Changes Okay, so this patch touches `mm/memcontrol.c`. That's significant. The memory control subsystem is a critical piece, and any changes there warrant a very close look. I need to be sure the rationale behind this modification is sound, and I understand how it interacts with the existing memory management structures. My initial focus will be on understanding why this file was chosen for modification. I'll need to assess if the changes are logically related to the primary intent of the patch or if they represent a potentially risky side effect or unrelated refactoring. A deep dive into `mm/memcontrol.c` is definitely required.
8/2	2026/07/28 02:13	tool	grepper	0m Args: { "Expression": "^(int\|void\|bool\|struct [a-z_]+ \\?) [a-zA-Z0-9_]+\\(", "PathPrefix": "mm/memcontrol.c" } Results:* { "Output": "mm/memcontrol.c=131=static DEFINE_SPINLOCK(objcg_lock);\nmm/memcontrol.c-132-\nmm/memcontrol.c:133:bool mem_cgroup_kmem_disabled(void)\nmm/memcontrol.c-134-{\n--\nmm/memcontrol.c=529=static void __mod_memcg_lruvec_state(struct mem_cgroup_per_node pn,\n--\nmm/memcontrol.c-531-\nmm/memcontrol.c:532:void reparent_memcg_lruvec_state_local(struct mem_cgroup memcg,\nmm/memcontrol.c-533-\t\t\t\t struct mem_cgroup parent, int idx)\n--\nmm/memcontrol.c=704=static void __mem_cgroup_flush_stats(struct mem_cgroup memcg, bool force)\n--\nmm/memcontrol.c-728- /\nmm/memcontrol.c:729:void mem_cgroup_flush_stats(struct mem_cgroup memcg)\nmm/memcontrol.c-730-{\n--\nmm/memcontrol.c-739-\nmm/memcontrol.c:740:void mem_cgroup_flush_stats_ratelimited(struct mem_cgroup memcg)\nmm/memcontrol.c-741-{\n--\nmm/memcontrol.c=757=unsigned long memcg_page_state(struct mem_cgroup memcg, int idx)\n--\nmm/memcontrol.c-772-\nmm/memcontrol.c:773:bool memcg_stat_item_valid(int idx)\nmm/memcontrol.c-774-{\n--\nmm/memcontrol.c=845=static void __mod_memcg_state(struct mem_cgroup memcg,\n--\nmm/memcontrol.c-870- /\nmm/memcontrol.c:871:void mod_memcg_state(struct mem_cgroup memcg, enum memcg_stat_item idx,\nmm/memcontrol.c-872-\t\t int val)\n--\nmm/memcontrol.c=886=unsigned long memcg_page_state_local(struct mem_cgroup memcg, int idx)\n--\nmm/memcontrol.c-901-\nmm/memcontrol.c:902:void reparent_memcg_state_local(struct mem_cgroup memcg,\nmm/memcontrol.c-903-\t\t\t\tstruct mem_cgroup parent, int idx)\n--\nmm/memcontrol.c=937=static void mod_memcg_lruvec_state(struct lruvec lruvec,\n--\nmm/memcontrol.c-964- /\nmm/memcontrol.c:965:void mod_lruvec_state(struct lruvec lruvec, enum node_stat_item idx,\nmm/memcontrol.c-966-\t\t\tint val)\n--\nmm/memcontrol.c-975-\nmm/memcontrol.c:976:void lruvec_stat_mod_folio(struct folio folio, enum node_stat_item idx,\nmm/memcontrol.c-977-\t\t\t int val)\n--\nmm/memcontrol.c=996=EXPORT_SYMBOL(lruvec_stat_mod_folio);\nmm/memcontrol.c-997-\nmm/memcontrol.c:998:void mod_lruvec_kmem_state(void p, enum node_stat_item idx, int val)\nmm/memcontrol.c-999-{\n--\nmm/memcontrol.c-1027- /\nmm/memcontrol.c:1028:void count_memcg_events(struct mem_cgroup memcg, enum vm_event_item idx,\nmm/memcontrol.c-1029-\t\t\t unsigned long count)\n--\nmm/memcontrol.c=1049=unsigned long memcg_events(struct mem_cgroup memcg, int event)\n--\nmm/memcontrol.c-1058-\nmm/memcontrol.c:1059:bool memcg_vm_event_item_valid(enum vm_event_item idx)\nmm/memcontrol.c-1060-{\n--\nmm/memcontrol.c=1213=struct mem_cgroup mem_cgroup_iter(struct mem_cgroup root,\n--\nmm/memcontrol.c-1304- /\nmm/memcontrol.c:1305:void mem_cgroup_iter_break(struct mem_cgroup root,\nmm/memcontrol.c-1306-\t\t\t struct mem_cgroup prev)\n--\nmm/memcontrol.c=1328=static void invalidate_reclaim_iterators(struct mem_cgroup dead_memcg)\n--\nmm/memcontrol.c-1361- /\nmm/memcontrol.c:1362:void mem_cgroup_scan_tasks(struct mem_cgroup memcg,\nmm/memcontrol.c-1363-\t\t\t int (fn)(struct task_struct , void ), void arg)\n--\nmm/memcontrol.c=1456=struct lruvec folio_lruvec_lock_irqsave(struct folio folio,\n--\nmm/memcontrol.c-1482- /\nmm/memcontrol.c:1483:void mem_cgroup_update_lru_size(struct lruvec lruvec, enum lru_list lru,\nmm/memcontrol.c-1484-\t\t\t\tint zid, long nr_pages)\n--\nmm/memcontrol.c=1751=static void memory_stat_format(struct mem_cgroup memcg, struct seq_buf s)\n--\nmm/memcontrol.c-1769- /\nmm/memcontrol.c:1770:void mem_cgroup_print_oom_context(struct mem_cgroup memcg, struct task_struct p)\nmm/memcontrol.c-1771-{\n--\nmm/memcontrol.c-1790- /\nmm/memcontrol.c:1791:void mem_cgroup_print_oom_meminfo(struct mem_cgroup memcg)\nmm/memcontrol.c-1792-{\n--\nmm/memcontrol.c=1835=unsigned long mem_cgroup_get_max(struct mem_cgroup memcg)\n--\nmm/memcontrol.c-1853-\nmm/memcontrol.c:1854:void __memcg_memory_event(struct mem_cgroup memcg,\nmm/memcontrol.c-1855-\t\t\t enum memcg_memory_event event, bool allow_spinning)\n--\nmm/memcontrol.c=1947=struct mem_cgroup mem_cgroup_get_oom_group(struct task_struct victim,\n--\nmm/memcontrol.c-1993-\nmm/memcontrol.c:1994:void mem_cgroup_print_oom_group(struct mem_cgroup memcg)\nmm/memcontrol.c-1995-{\n--\nmm/memcontrol.c=2259=static void schedule_drain_work(int cpu, struct work_struct work)\n--\nmm/memcontrol.c-2275- /\nmm/memcontrol.c:2276:void drain_all_stock(struct mem_cgroup root_memcg)\nmm/memcontrol.c-2277-{\n--\nmm/memcontrol.c=2468=static unsigned long calculate_high_delay(struct mem_cgroup memcg,\n--\nmm/memcontrol.c-2504- /\nmm/memcontrol.c:2505:void __mem_cgroup_handle_over_high(gfp_t gfp_mask)\nmm/memcontrol.c-2506-{\n--\nmm/memcontrol.c=3122=static void page_set_objcg(struct page page, const struct obj_cgroup objcg)\n--\nmm/memcontrol.c-3134- /\nmm/memcontrol.c:3135:int __memcg_kmem_charge_page(struct page page, gfp_t gfp, int order)\nmm/memcontrol.c-3136-{\n--\nmm/memcontrol.c-3156- /\nmm/memcontrol.c:3157:void __memcg_kmem_uncharge_page(struct page page, int order)\nmm/memcontrol.c-3158-{\n--\nmm/memcontrol.c=3472=static int __obj_cgroup_charge(struct obj_cgroup objcg, gfp_t gfp,\n--\nmm/memcontrol.c-3485-\nmm/memcontrol.c:3486:int obj_cgroup_charge(struct obj_cgroup objcg, gfp_t gfp, size_t size)\nmm/memcontrol.c-3487-{\n--\nmm/memcontrol.c-3523-\nmm/memcontrol.c:3524:void obj_cgroup_uncharge(struct obj_cgroup objcg, size_t size)\nmm/memcontrol.c-3525-{\n--\nmm/memcontrol.c=3529=static inline size_t obj_full_size(struct kmem_cache s)\n--\nmm/memcontrol.c-3537-\nmm/memcontrol.c:3538:bool __memcg_slab_post_alloc_hook(struct kmem_cache s, struct list_lru lru,\nmm/memcontrol.c-3539-\t\t\t\t gfp_t flags, unsigned int slab_alloc_flags,\n--\nmm/memcontrol.c-3634-\nmm/memcontrol.c:3635:void __memcg_slab_free_hook(struct kmem_cache s, struct slab slab,\nmm/memcontrol.c-3636-\t\t\t void p, int objects, unsigned long obj_exts)\n--\nmm/memcontrol.c-3665- /\nmm/memcontrol.c:3666:void split_page_memcg(struct page page, unsigned order)\nmm/memcontrol.c-3667-{\n--\nmm/memcontrol.c-3679-\nmm/memcontrol.c:3680:void folio_split_memcg_refs(struct folio folio, unsigned old_order,\nmm/memcontrol.c-3681-\t\tunsigned new_order)\n--\nmm/memcontrol.c=3738=struct wb_domain mem_cgroup_wb_domain(struct bdi_writeback wb)\n--\nmm/memcontrol.c-3765- /\nmm/memcontrol.c:3766:void mem_cgroup_wb_stats(struct bdi_writeback wb, unsigned long pfilepages,\nmm/memcontrol.c-3767-\t\t\t unsigned long pheadroom, unsigned long pdirty,\n--\nmm/memcontrol.c-3834- /\nmm/memcontrol.c:3835:void mem_cgroup_track_foreign_dirty_slowpath(struct folio folio,\nmm/memcontrol.c-3836-\t\t\t\t\t struct bdi_writeback wb)\n--\nmm/memcontrol.c-3887-/* issue foreign writeback flushes for recorded foreign dirtying events /\nmm/memcontrol.c:3888:void mem_cgroup_flush_foreign(struct bdi_writeback wb)\nmm/memcontrol.c-3889-{\n--\nmm/memcontrol.c=4901=static int memory_events_local_show(struct seq_file m, void v)\n--\nmm/memcontrol.c-4908-\nmm/memcontrol.c:4909:int memory_stat_show(struct seq_file m, void v)\nmm/memcontrol.c-4910-{\n--\nmm/memcontrol.c=5080=struct cgroup_subsys memory_cgrp_subsys = {\n--\nmm/memcontrol.c-5105- /\nmm/memcontrol.c:5106:void mem_cgroup_calculate_protection(struct mem_cgroup root,\nmm/memcontrol.c-5107-\t\t\t\t struct mem_cgroup memcg)\n--\nmm/memcontrol.c=5121=static int charge_memcg(struct folio folio, struct mem_cgroup memcg,\n--\nmm/memcontrol.c-5140-\nmm/memcontrol.c:5141:int __mem_cgroup_charge(struct folio folio, struct mm_struct mm, gfp_t gfp)\nmm/memcontrol.c-5142-{\n--\nmm/memcontrol.c-5164- /\nmm/memcontrol.c:5165:int mem_cgroup_charge_hugetlb(struct folio folio, gfp_t gfp)\nmm/memcontrol.c-5166-{\n--\nmm/memcontrol.c-5198- /\nmm/memcontrol.c:5199:int mem_cgroup_swapin_charge_folio(struct folio folio, unsigned short id,\nmm/memcontrol.c-5200-\t\t\t\t struct mm_struct mm, gfp_t gfp)\n--\nmm/memcontrol.c=5255=static void uncharge_folio(struct folio folio, struct uncharge_gather ug)\n--\nmm/memcontrol.c-5300-\nmm/memcontrol.c:5301:void __mem_cgroup_uncharge(struct folio folio)\nmm/memcontrol.c-5302-{\n--\nmm/memcontrol.c-5313-\nmm/memcontrol.c:5314:void __mem_cgroup_uncharge_folios(struct folio_batch folios)\nmm/memcontrol.c-5315-{\n--\nmm/memcontrol.c-5335- /\nmm/memcontrol.c:5336:void mem_cgroup_replace_folio(struct folio old, struct folio new)\nmm/memcontrol.c-5337-{\n--\nmm/memcontrol.c-5384- /\nmm/memcontrol.c:5385:void mem_cgroup_migrate(struct folio old, struct folio new)\nmm/memcontrol.c-5386-{\n--\nmm/memcontrol.c=5417=EXPORT_SYMBOL(memcg_sockets_enabled_key);\nmm/memcontrol.c-5418-\nmm/memcontrol.c:5419:void mem_cgroup_sk_alloc(struct sock sk)\nmm/memcontrol.c-5420-{\n--\nmm/memcontrol.c-5441-\nmm/memcontrol.c:5442:void mem_cgroup_sk_free(struct sock sk)\nmm/memcontrol.c-5443-{\n--\nmm/memcontrol.c-5449-\nmm/memcontrol.c:5450:void mem_cgroup_sk_inherit(const struct sock sk, struct sock newsk)\nmm/memcontrol.c-5451-{\n--\nmm/memcontrol.c-5474- /\nmm/memcontrol.c:5475:bool mem_cgroup_sk_charge(const struct sock sk, unsigned int nr_pages,\nmm/memcontrol.c-5476-\t\t\t gfp_t gfp_mask)\n--\nmm/memcontrol.c-5495- /\nmm/memcontrol.c:5496:void mem_cgroup_sk_uncharge(const struct sock sk, unsigned int nr_pages)\nmm/memcontrol.c-5497-{\n--\nmm/memcontrol.c-5509-\nmm/memcontrol.c:5510:void mem_cgroup_flush_workqueue(void)\nmm/memcontrol.c-5511-{\n--\nmm/memcontrol.c=5541=int __init mem_cgroup_init(void)\n--\nmm/memcontrol.c-5585- /\nmm/memcontrol.c:5586:int __mem_cgroup_try_charge_swap(struct folio folio)\nmm/memcontrol.c-5587-{\n--\nmm/memcontrol.c-5635- /\nmm/memcontrol.c:5636:void __mem_cgroup_uncharge_swap(unsigned short id, unsigned int nr_pages)\nmm/memcontrol.c-5637-{\n--\nmm/memcontrol.c=5655=long mem_cgroup_get_nr_swap_pages(struct mem_cgroup memcg)\n--\nmm/memcontrol.c-5667-\nmm/memcontrol.c:5668:bool mem_cgroup_swap_full(struct folio folio)\nmm/memcontrol.c-5669-{\n--\nmm/memcontrol.c=5793=static struct cftype swap_files[] = {\n--\nmm/memcontrol.c-5840- /\nmm/memcontrol.c:5841:bool obj_cgroup_may_zswap(struct obj_cgroup objcg)\nmm/memcontrol.c-5842-{\n--\nmm/memcontrol.c-5881- /\nmm/memcontrol.c:5882:void obj_cgroup_charge_zswap(struct obj_cgroup objcg, size_t size)\nmm/memcontrol.c-5883-{\n--\nmm/memcontrol.c-5913- /\nmm/memcontrol.c:5914:void obj_cgroup_uncharge_zswap(struct obj_cgroup objcg, size_t size)\nmm/memcontrol.c-5915-{\n--\nmm/memcontrol.c-5934-\nmm/memcontrol.c:5935:bool mem_cgroup_zswap_writeback_enabled(struct mem_cgroup memcg)\nmm/memcontrol.c-5936-{\n--\nmm/memcontrol.c=6040=subsys_initcall(mem_cgroup_swap_init);\n--\nmm/memcontrol.c-6043-\nmm/memcontrol.c:6044:void mem_cgroup_node_filter_allowed(struct mem_cgroup memcg, nodemask_t mask)\nmm/memcontrol.c-6045-{\n--\nmm/memcontrol.c-6060-\nmm/memcontrol.c:6061:void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg)\nmm/memcontrol.c-6062-{\n" }
9/2	2026/07/28 02:13	llm	patch-evaluator	1m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 26317 output: 36 thoughts: 43 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Memory Control Module Deep Dive Hmm, let me think... I was under the impression that the function `mem_cgroup_from_obj_slab` was situated in a different part of the kernel, probably related to the slab allocator itself. But wait a minute... that doesn't quite sit right. Let's revisit the `mm/memcontrol.c` file again. I should have a clear understanding of its functions. It is important to know the precise location of memory cgroup functionalities. I need to refresh my memory regarding all of the functions associated.
10/2	2026/07/28 02:14	tool	grepper	0m Args: { "Expression": "mem_cgroup_from_obj_slab", "PathPrefix": "mm/memcontrol.c" } Results: { "Output": "mm/memcontrol.c=2858=static __always_inline\nmm/memcontrol.c:2859:struct mem_cgroup mem_cgroup_from_obj_slab(struct slab slab, void p)\nmm/memcontrol.c-2860-{\n--\nmm/memcontrol.c=2898=struct mem_cgroup mem_cgroup_from_virt(void *p)\n--\nmm/memcontrol.c-2906-\tif (slab)\nmm/memcontrol.c:2907:\t\treturn mem_cgroup_from_obj_slab(slab, p);\nmm/memcontrol.c-2908-\treturn folio_memcg_check(virt_to_folio(p));\n" }
11/2	2026/07/28 02:14	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 26729 output: 36 thoughts: 109 Thoughts: Slab Cache Hook Conundrum Okay, so I'm looking at this `mem_cgroup_from_obj_slab` function, and it's marked `static __always_inline`. That's standard and expected for performance reasons within the module. But then my mind jumps to the hooks, and I see a potential inconsistency here, I’m thinking, why aren’t the slab cache allocation and free hook functions static? `__memcg_slab_post_alloc_hook` and `__memcg_slab_free_hook` are not static, which gives me pause. And then there’s `alloc_slab_obj_exts`, also not static. This suggests a more global intent with their scope than the `static` declaration suggests for `mem_cgroup_from_obj_slab`. This isn't necessarily a problem, but it warrants closer inspection for how these hook functions are intended to interact with the larger slab allocator architecture. I need to refresh my memory and check the definition of `__kmem_cache_create_args` in `mm/slab_common.c` to remind myself of the full context and see how these pieces are really intended to fit together.
12/2	2026/07/28 02:14	tool	grepper	0m Args: { "Expression": "__kmem_cache_create_args", "PathPrefix": "mm/slab_common.c" } Results: { "Output": "mm/slab_common.c=267=__kmem_cache_alias(const char name, unsigned int size, slab_flags_t flags,\n--\nmm/slab_common.c-291-/\nmm/slab_common.c:292: __kmem_cache_create_args - Create a kmem cache.\nmm/slab_common.c-293- * @name: A string which is used in /proc/slabinfo to identify this cache.\n--\nmm/slab_common.c-317- /\nmm/slab_common.c:318:struct kmem_cache __kmem_cache_create_args(const char *name,\nmm/slab_common.c-319-\t\t\t\t\t unsigned int object_size,\n--\nmm/slab_common.c-408-}\nmm/slab_common.c:409:EXPORT_SYMBOL(__kmem_cache_create_args);\nmm/slab_common.c-410-\n" }
13/2	2026/07/28 02:14	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 27388 output: 34 thoughts: 174 Thoughts: Analyzing SLUB Object Extension Allocation Okay, so `__kmem_cache_create_args` is exported, that's straightforward. But, hold on a second... `alloc_slab_obj_exts` isn't explicitly exported, though it isn't static either. This seems a little unusual. Now, let me think... Aha! `alloc_slab_obj_exts` is called from `prepare_slab_obj_exts_hook`, which is inline within `mm/slub.c`. Right, that explains the access. I need to confirm where `alloc_slab_obj_exts` is defined. Is it in `mm/slub.c` or perhaps hiding in `mm/slab_common.c`? Okay, I've checked... it's definitely in `mm/slub.c`. But, wait a minute, I just realized, `alloc_slab_obj_exts` is declared in `mm/slab.h`. Hmm, that's a key detail. Time to thoroughly examine the implementation of `alloc_slab_obj_exts` within `mm/slub.c`.
14/2	2026/07/28 02:14	tool	grepper	0m Args: { "Expression": "alloc_slab_obj_exts", "PathPrefix": "mm/slub.c" } Results: { "Output": "mm/slub.c=2129=static inline void init_slab_obj_exts(struct slab slab)\n--\nmm/slub.c-2133-\nmm/slub.c:2134:int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s,\nmm/slub.c-2135-\t\t\tgfp_t gfp, unsigned int alloc_flags)\n--\nmm/slub.c=2223=static inline void free_slab_obj_exts(struct slab slab, bool allow_spin)\n--\nmm/slub.c-2254- /\nmm/slub.c:2255:static void alloc_slab_obj_exts_early(struct kmem_cache s, struct slab slab)\nmm/slub.c-2256-{\n--\nmm/slub.c=2302=static inline void init_slab_obj_exts(struct slab slab)\n--\nmm/slub.c-2305-\nmm/slub.c:2306:static int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s,\nmm/slub.c-2307-\t\t\t gfp_t gfp, unsigned int alloc_flags)\n--\nmm/slub.c=2312=static inline void free_slab_obj_exts(struct slab slab, bool allow_spin)\n--\nmm/slub.c-2315-\nmm/slub.c:2316:static inline void alloc_slab_obj_exts_early(struct kmem_cache s,\nmm/slub.c-2317-\t\t\t\t\t\t struct slab slab)\n--\nmm/slub.c=2326=prepare_slab_obj_exts_hook(struct kmem_cache s, struct slab slab,\n--\nmm/slub.c-2332-\nmm/slub.c:2333:\t\tif (alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {\nmm/slub.c-2334-\t\t\tpr_warn_once(\"%s, %s: Failed to create slab extension vector!\\n\",\n--\nmm/slub.c=3371=static __always_inline void account_slab(struct slab slab, int order,\n--\nmm/slub.c-3377-\t\t\t!slab_obj_exts(slab))\nmm/slub.c:3378:\t\talloc_slab_obj_exts(slab, s, gfp,\nmm/slub.c-3379-\t\t\t\t alloc_flags \| SLAB_ALLOC_NEW_SLAB);\n--\nmm/slub.c=3400=static struct slab allocate_slab(struct kmem_cache s, gfp_t flags,\n--\nmm/slub.c-3455-\t */\nmm/slub.c:3456:\talloc_slab_obj_exts_early(s, slab);\nmm/slub.c-3457-\taccount_slab(slab, oo_order(oo), s, flags, alloc_flags);\n" }
15/2	2026/07/28 02:14	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 28650 output: 34 thoughts: 129 Thoughts: Investigating the Scope of `alloc_slab_obj_exts` Okay, so I'm digging into the kernel's slab allocator code, specifically around extended object features. My initial thought is that `alloc_slab_obj_exts` is likely non-static if `CONFIG_SLAB_OBJ_EXT` is enabled. Seems logical, given the dependency on the configuration option. But hold on... I'm looking at the definition now, and it's defined in `mm/slub.c` as a non-static function. Now, that immediately raises a red flag. If it's not static, I'd expect it to be used more broadly, but the code scan suggests that it's only used within `mm/slub.c` itself, and in `mm/memcontrol.c`. That's not the usual pattern. Usually, if a function isn't static it will be visible outside of its file. Aha! `mm/memcontrol.c` does call `alloc_slab_obj_exts`! Excellent, that answers a bit of the puzzle, but let's go check `mm/memcontrol.c` to see exactly how that function is being called in there. This is where the real nuance is. Understanding the calling context is key.
16/2	2026/07/28 02:14	tool	grepper	0m Args: { "Expression": "alloc_slab_obj_exts", "PathPrefix": "mm/memcontrol.c" } Results: { "Output": "mm/memcontrol.c=3538=bool __memcg_slab_post_alloc_hook(struct kmem_cache s, struct list_lru lru,\n--\nmm/memcontrol.c-3588-\t\t\t\tcontinue;\nmm/memcontrol.c:3589:\t\t\tif (alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags))\nmm/memcontrol.c-3590-\t\t\t\tcontinue;\n" }
17/2	2026/07/28 02:14	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 29229 output: 37 thoughts: 143 Thoughts: Analyzing Memory Control Hooks Okay, so I've identified `alloc_slab_obj_exts` as a key function, seeing as it's called directly from `mm/memcontrol.c`. That makes it a solid starting point for investigation. And, of course, the `__memcg_slab_post_alloc_hook` and `__memcg_slab_free_hook` functions also warrant close attention within that context. Wait a second, though; I recall now that `__memcg_slab_post_alloc_hook` is called from `memcg_slab_post_alloc_hook`, which is actually inlined from `mm/slub.c`. I need to be careful with that one. Let's make sure I'm looking at the correct definition. Best to double-check the implementation of `__memcg_slab_post_alloc_hook` within `mm/memcontrol.c` directly to confirm.
18/2	2026/07/28 02:15	tool	grepper	0m Args: { "Expression": "__memcg_slab_post_alloc_hook", "PathPrefix": "mm/memcontrol.c" } Results: { "Output": "mm/memcontrol.c=3529=static inline size_t obj_full_size(struct kmem_cache s)\n--\nmm/memcontrol.c-3537-\nmm/memcontrol.c:3538:bool __memcg_slab_post_alloc_hook(struct kmem_cache s, struct list_lru *lru,\nmm/memcontrol.c-3539-\t\t\t\t gfp_t flags, unsigned int slab_alloc_flags,\n" }
19/2	2026/07/28 02:15	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 29745 output: 35 thoughts: 35 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: Hook Investigation Right, so `__memcg_slab_post_alloc_hook` is definitely not a static function. That's a key observation. Now, that's useful, that means it's available for modification or intervention, likely from external modules or perhaps even in a system-wide or core way. I need to keep that in mind when tracing calls through the allocation/free path. What about the counterpart? I need to check `__memcg_slab_free_hook`. Is it static as well? Is there any similar behavior with the free hook? Because the post-allocation one is non static it will have serious implications for further analysis.
20/2	2026/07/28 02:15	tool	grepper	0m Args: { "Expression": "__memcg_slab_free_hook", "PathPrefix": "mm/memcontrol.c" } Results: { "Output": "mm/memcontrol.c=3538=bool __memcg_slab_post_alloc_hook(struct kmem_cache s, struct list_lru lru,\n--\nmm/memcontrol.c-3634-\nmm/memcontrol.c:3635:void __memcg_slab_free_hook(struct kmem_cache s, struct slab slab,\nmm/memcontrol.c-3636-\t\t\t void **p, int objects, unsigned long obj_exts)\n" }
21/2	2026/07/28 02:15	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 30113 output: 34 thoughts: 44 Thoughts: Okay, here's my take on those thoughts, framed as my own: Investigating Memory Control Group Interaction with SLUB Allocator Right, so I'm digging into how memory control groups (memcgs) interact with the SLUB allocator. Let me see, `__memcg_slab_free_hook`… Yup, that’s confirmed, it's definitely not declared static. Good, that helps clarify a specific point. Now, what about the other side of this? Let me check… ah, yes, `memcg_slab_post_charge`. That looks interesting, and it lives over in `mm/slub.c`. I need to review that file and understand how `memcg_slab_post_charge` is used and how it interacts with the rest of the SLUB code. Gotta dive deeper to understand the complete picture.
22/2	2026/07/28 02:15	tool	grepper	0m Args: { "Expression": "memcg_slab_post_charge", "PathPrefix": "mm/slub.c" } Results: { "Output": "mm/slub.c=2522=static __fastpath_inline\nmm/slub.c:2523:bool memcg_slab_post_charge(void p, gfp_t flags)\nmm/slub.c-2524-{\n--\nmm/slub.c=2590=static inline void memcg_slab_free_hook(struct kmem_cache s, struct slab slab,\n--\nmm/slub.c-2594-\nmm/slub.c:2595:static inline bool memcg_slab_post_charge(void p, gfp_t flags)\nmm/slub.c-2596-{\n--\nmm/slub.c=5004=bool kmem_cache_charge(void *objp, gfp_t gfpflags)\n--\nmm/slub.c-5008-\nmm/slub.c:5009:\treturn memcg_slab_post_charge(objp, gfpflags);\nmm/slub.c-5010-}\n" }
23/2	2026/07/28 02:15	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 30652 output: 32 thoughts: 60 Thoughts: Diving into Slab Allocation Okay, so I'm looking at this `memcg_slab_post_charge` function. I see it's defined as `static __fastpath_inline` within `mm/slub.c`. Hmm, that suggests it's optimized for speed and intended for internal use only within that file. But then I remember `kmem_cache_charge`. That's not static; it's exported, meaning other parts of the kernel can call it. Right, I need to understand the relationship between these two. It's time to dig into the implementation of `kmem_cache_charge` and see how it interacts with `memcg_slab_post_charge`. I need to figure out where the connection between these two lies, and what's driving the logic.
24/2	2026/07/28 02:15	tool	grepper	0m Args: { "Expression": "kmem_cache_charge", "PathPrefix": "mm/slub.c" } Results: { "Output": "mm/slub.c=5002=EXPORT_SYMBOL(kmem_cache_alloc_lru_noprof);\nmm/slub.c-5003-\nmm/slub.c:5004:bool kmem_cache_charge(void *objp, gfp_t gfpflags)\nmm/slub.c-5005-{\n--\nmm/slub.c-5010-}\nmm/slub.c:5011:EXPORT_SYMBOL(kmem_cache_charge);\nmm/slub.c-5012-\n" }
25/2	2026/07/28 02:15	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 31074 output: 36 thoughts: 43 Thoughts: Okay, here's my take on those thoughts, framed as my own: Investigating Slab Allocator Internals Right, so I'm digging into this slab allocator stuff. `kmem_cache_charge` seems like a solid starting point for tracing allocation costs, right? It's a key function in the process. Now, I should probably also check out `__kmem_cache_create_args`. It looks like that one's the heart of how these caches are actually made, I see that it's in `mm/slab_common.c`. I need to figure out how these are working, and this looks like a good next step.
26/2	2026/07/28 02:15	tool	grepper	0m Args: { "Expression": "__kmem_cache_create_args", "PathPrefix": "mm/slab_common.c" } Results: { "Output": "mm/slab_common.c=267=__kmem_cache_alias(const char name, unsigned int size, slab_flags_t flags,\n--\nmm/slab_common.c-291-/\nmm/slab_common.c:292: __kmem_cache_create_args - Create a kmem cache.\nmm/slab_common.c-293- * @name: A string which is used in /proc/slabinfo to identify this cache.\n--\nmm/slab_common.c-317- /\nmm/slab_common.c:318:struct kmem_cache __kmem_cache_create_args(const char *name,\nmm/slab_common.c-319-\t\t\t\t\t unsigned int object_size,\n--\nmm/slab_common.c-408-}\nmm/slab_common.c:409:EXPORT_SYMBOL(__kmem_cache_create_args);\nmm/slab_common.c-410-\n" }
27/2	2026/07/28 02:15	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 31549 output: 37 thoughts: 73 Thoughts: Okay, let's see... Analyzing Potential Focus Symbols Right, `__kmem_cache_create_args` seems like a solid candidate to center on. It's a key function in cache creation, making it a natural starting point. But wait... what about `alloc_tagging_slab_free_hook`? That's right, it's defined inline, so its behavior is intimately tied to the surrounding code. Interesting... now, hang on a second. Isn't `__alloc_tagging_slab_free_hook` not a static function? That's unexpected, I should confirm that in `mm/slub.c` right away. I need to understand its scope fully.
28/2	2026/07/28 02:15	tool	grepper	0m Args: { "Expression": "__alloc_tagging_slab_free_hook", "PathPrefix": "mm/slub.c" } Results: { "Output": "mm/slub.c=2400=static noinline void\nmm/slub.c:2401:__alloc_tagging_slab_free_hook(struct kmem_cache s, struct slab slab, void *p,\nmm/slub.c-2402-\t\t\t int objects)\n--\nmm/slub.c=2425=alloc_tagging_slab_free_hook(struct kmem_cache s, struct slab slab, void *p,\n--\nmm/slub.c-2428-\tif (mem_alloc_profiling_enabled())\nmm/slub.c:2429:\t\t__alloc_tagging_slab_free_hook(s, slab, p, objects);\nmm/slub.c-2430-}\n" }
29/2	2026/07/28 02:15	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 32021 output: 37 thoughts: 31 Thoughts: Okay, here's my interpretation of those thoughts, presented as a summary from my expert perspective: Deciphering the Function Declaration Alright, let's break this down. The function signature is `static noinline void`. This immediately tells me a few critical things. It's `static`, meaning its scope is restricted to this specific compilation unit – it's not meant to be accessed from outside this module. The `noinline` attribute is a directive to the compiler, specifically instructing it not to inline this function's code into any call sites. This might be due to size constraints, debugging considerations, or perhaps because we want precise control over where the function's code resides in memory. Now, that name. `__alloc_tagging_slab_alloc_hook`... That naming convention clearly suggests a hook related to memory allocation, specifically within a slab allocator. The double underscore at the beginning is a strong indicator of an internal or private function. The presence of "tagging" is also important, as this hints at metadata or instrumentation. The "alloc hook" piece is the most obvious part. It sounds like this function is designed to be called during the slab allocation process. I need to understand what this hook does, to better understand how allocation behaves at a lower level.
30/2	2026/07/28 02:15	tool	grepper	0m Args: { "Expression": "__alloc_tagging_slab_alloc_hook", "PathPrefix": "mm/slub.c" } Results: { "Output": "mm/slub.c=2345=static noinline void\nmm/slub.c:2346:__alloc_tagging_slab_alloc_hook(struct kmem_cache s, void object, gfp_t flags,\nmm/slub.c-2347-\t\t\t\tunsigned int alloc_flags)\n--\nmm/slub.c=2392=alloc_tagging_slab_alloc_hook(struct kmem_cache s, void object, gfp_t flags,\n--\nmm/slub.c-2395-\tif (mem_alloc_profiling_enabled())\nmm/slub.c:2396:\t\t__alloc_tagging_slab_alloc_hook(s, object, flags, alloc_flags);\nmm/slub.c-2397-}\n" }
31/2	2026/07/28 02:15	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 32572 output: 34 thoughts: 24 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person: Revisiting Slab Allocator Internals Alright, let's circle back to that `alloc_slab_obj_exts` function again. I want to make sure I haven't missed anything crucial in my mental model of the slab allocator. Considering its role in object allocation, particularly when extended metadata is involved, a closer inspection is warranted. And, I need to remind myself to take note of why the function is declared `static noinline void`. Is it for inlining, or is it because it needs to be accessible only within a specific translation unit, or is the intention to prevent the compiler from making a call across functions? I need to think through the implications of this. I should ensure that any assumptions about its behavior are validated.
32/2	2026/07/28 02:15	tool	grepper	0m Args: { "Expression": "alloc_slab_obj_exts", "PathPrefix": "mm/slub.c" } Results: { "Output": "mm/slub.c=2129=static inline void init_slab_obj_exts(struct slab slab)\n--\nmm/slub.c-2133-\nmm/slub.c:2134:int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s,\nmm/slub.c-2135-\t\t\tgfp_t gfp, unsigned int alloc_flags)\n--\nmm/slub.c=2223=static inline void free_slab_obj_exts(struct slab slab, bool allow_spin)\n--\nmm/slub.c-2254- /\nmm/slub.c:2255:static void alloc_slab_obj_exts_early(struct kmem_cache s, struct slab slab)\nmm/slub.c-2256-{\n--\nmm/slub.c=2302=static inline void init_slab_obj_exts(struct slab slab)\n--\nmm/slub.c-2305-\nmm/slub.c:2306:static int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s,\nmm/slub.c-2307-\t\t\t gfp_t gfp, unsigned int alloc_flags)\n--\nmm/slub.c=2312=static inline void free_slab_obj_exts(struct slab slab, bool allow_spin)\n--\nmm/slub.c-2315-\nmm/slub.c:2316:static inline void alloc_slab_obj_exts_early(struct kmem_cache s,\nmm/slub.c-2317-\t\t\t\t\t\t struct slab slab)\n--\nmm/slub.c=2326=prepare_slab_obj_exts_hook(struct kmem_cache s, struct slab slab,\n--\nmm/slub.c-2332-\nmm/slub.c:2333:\t\tif (alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {\nmm/slub.c-2334-\t\t\tpr_warn_once(\"%s, %s: Failed to create slab extension vector!\\n\",\n--\nmm/slub.c=3371=static __always_inline void account_slab(struct slab slab, int order,\n--\nmm/slub.c-3377-\t\t\t!slab_obj_exts(slab))\nmm/slub.c:3378:\t\talloc_slab_obj_exts(slab, s, gfp,\nmm/slub.c-3379-\t\t\t\t alloc_flags \| SLAB_ALLOC_NEW_SLAB);\n--\nmm/slub.c=3400=static struct slab allocate_slab(struct kmem_cache s, gfp_t flags,\n--\nmm/slub.c-3455-\t */\nmm/slub.c:3456:\talloc_slab_obj_exts_early(s, slab);\nmm/slub.c-3457-\taccount_slab(slab, oo_order(oo), s, flags, alloc_flags);\n" }
33/2	2026/07/28 02:15	llm	patch-evaluator	1m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 33613 output: 38 thoughts: 150 Thoughts: Examining the Slab Object Extension Allocation Function Okay, hold on a second. I'm looking at `alloc_slab_obj_exts`. If `CONFIG_SLAB_OBJ_EXT` is active, it's defined as a regular `int alloc_slab_obj_exts`, not a static one, right? Let me double-check... Yes, line 2134 is the non-static definition, and line 2306 is the static dummy version used when the configuration option is disabled. So, that means the `alloc_slab_obj_exts` function isn't static when the extension is enabled, meaning it's visible outside the current compilation unit. That means it isn't strictly exported for use by other modules, but it is non-static and thus visible, making its use a bit...interesting. Hmm, let me just confirm whether or not it actually gets exported in the build system. I need to make sure I'm not missing something subtle here.
34/2	2026/07/28 02:16	tool	grepper	0m Error: no matches Args: { "Expression": "EXPORT_SYMBOL.alloc_slab_obj_exts", "PathPrefix": "mm/slub.c" } Results:* { "error": "no matches" }
35/2	2026/07/28 02:16	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 34034 output: 41 thoughts: 52 Thoughts: Okay, here's my take on those thoughts, framed as my own reasoning: Analyzing the Potential for Fuzzing Right, so this thing isn't explicitly exported, which is a good initial sign from a security perspective. However, it's non-static – that's the key. That means it's accessible within the module or potentially even from a different module, so fuzzing it is definitely on the table. We need to figure out how. My first thought is to dig into `__memcg_slab_post_alloc_hook` and `__memcg_slab_free_hook`. These sound like likely candidates for interacting with whatever's going on here. They probably are hooks associated with memory control groups (memcgs) and slab allocation/deallocation. We can examine the code surrounding these and see how they are called and what arguments are passed. That should reveal how this non-static function can be reached and how we might manipulate its input for fuzzing. It's a good starting point to identify a potential vulnerability.
36/2	2026/07/28 02:16	tool	grepper	0m Error: no matches Args: { "Expression": "EXPORT_SYMBOL.__memcg_slab_post_alloc_hook", "PathPrefix": "mm/memcontrol.c" } Results:* { "error": "no matches" }
37/2	2026/07/28 02:16	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 34367 output: 33 thoughts: 31 Thoughts: Okay, here's my take on those thoughts, framed as an expert's inner monologue: Investigating Non-Exported, Non-Static Function Usage Alright, so the clue is something that's not exported, but it's also not static. That immediately piques my interest. It implies a function potentially used internally within a module, or perhaps indirectly via a function pointer or other less obvious mechanism. It's not something meant for direct external consumption, but it is accessible within the compilation unit, or perhaps, within the kernel. Let's dig in a bit. The most likely place to start looking for this will be within the code related to memory management, I'll go straight to `mm/kfence/core.c`. Let me see what `__kfence_free` does, and what it might tell us about how this non-static function is intended to be used. I wonder if there are any interesting patterns or design choices reflected there. Let's see how deep this rabbit hole goes.
38/2	2026/07/28 02:16	tool	grepper	0m Args: { "Expression": "__kfence_free", "PathPrefix": "mm/kfence/core.c" } Results: { "Output": "mm/kfence/core.c=1227=void kfence_object_start(const void addr)\n--\nmm/kfence/core.c-1237-\nmm/kfence/core.c:1238:void __kfence_free(void *addr)\nmm/kfence/core.c-1239-{\n" }
39/2	2026/07/28 02:16	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 34751 output: 33 thoughts: 439 Thoughts: Analyzing Kernel Slab Object Extension and KFENCE Integration Okay, so the initial concern was the non-static nature of `__kfence_free`, which is good to confirm. Now, I want to map out the key symbols involved in this area. `kmem_cache_charge` is also exported, so it's relevant, and I'm seeing other important symbols related to memcg and slab object extensions. Let's see: `alloc_slab_obj_exts`, `__memcg_slab_post_alloc_hook`, `__memcg_slab_free_hook`, `__kmem_cache_create_args` and `kmem_cache_charge`. And of course `__kfence_free`. Wait, there's a minor change in `__kfence_free` with that `KFENCE_WARN_ON` removal, but the significant modifications are primarily focused on `alloc_slab_obj_exts` and `__memcg_slab_post_alloc_hook`. Now I need to eliminate some irrelevant pieces and focus on the important ones. `mem_cgroup_from_obj_slab` is `static inline`, so not directly relevant. Also `slab_obj_ext_has_codetag_init` is `static __init` and `alloc_slab_obj_exts_early` is `static void`, so I won't need to focus on them as much. So, taking all that into consideration, the most critical symbols to zero in on are: `alloc_slab_obj_exts`, `__memcg_slab_post_alloc_hook`, `__memcg_slab_free_hook` and `__kmem_cache_create_args`. Finally, to understand the build requirements I need to check the relevant configuration options. `CONFIG_MEMCG`, obviously, `CONFIG_MEM_ALLOC_PROFILING`, `CONFIG_SLAB_OBJ_EXT` which is selected by the above, and, importantly, `CONFIG_KFENCE` since we've seen it modified. Now to check the header file and make sure I haven't missed anything.
40/2	2026/07/28 02:16	tool	grepper	0m Args: { "Expression": "CONFIG_SLAB_OBJ_EXT", "PathPrefix": "mm/slab.h" } Results: { "Output": "mm/slab.h=100=struct slab {\n--\nmm/slab.h-114-\tatomic_t __page_refcount;\nmm/slab.h:115:#ifdef CONFIG_SLAB_OBJ_EXT\nmm/slab.h-116-\tunsigned long obj_exts;\n--\nmm/slab.h=126=SLAB_MATCH(memcg_data, obj_exts);\nmm/slab.h:127:#elif defined(CONFIG_SLAB_OBJ_EXT)\nmm/slab.h-128-SLAB_MATCH(_unused_slab_obj_exts, obj_exts);\n--\nmm/slab.h=627=static inline size_t slab_obj_ext_size(struct slab slab)\n--\nmm/slab.h-639-\nmm/slab.h:640:#ifdef CONFIG_SLAB_OBJ_EXT\nmm/slab.h-641-\n--\nmm/slab.h=775=int alloc_slab_obj_exts(struct slab slab, struct kmem_cache s,\n--\nmm/slab.h-777-\nmm/slab.h:778:#else / CONFIG_SLAB_OBJ_EXT /\nmm/slab.h-779-\n--\nmm/slab.h=792=static inline bool obj_exts_in_object(struct slab slab)\n--\nmm/slab.h-796-\nmm/slab.h:797:#endif /* CONFIG_SLAB_OBJ_EXT */\nmm/slab.h-798-\n" }
41/2	2026/07/28 02:16	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 36088 output: 27 thoughts: 59 Thoughts: Here's my summary, as the thought process unfolds: Digging into `CONFIG_SLAB_OBJ_EXT` Okay, so `CONFIG_SLAB_OBJ_EXT`... that rings a bell. It's definitely an internal config option; I'm pretty sure it's not something you'd manually enable. My gut says it's likely selected based on other, broader features. Perhaps something like `MEMCG` (memory control groups) or maybe even `MEM_ALLOC_PROFILING`. I need to figure out the context. My next step is to drill down to where this thing is defined and, more importantly, why it's defined. Time to go hunting in the Kconfig files. The most obvious places to start would be `init/Kconfig` and, more likely, `mm/Kconfig`. Those are the usual suspects for memory management options. I'll check those files, and hopefully, I'll find the dependencies and get a clearer picture of what this `SLAB_OBJ_EXT` is all about. This should be a quick one, just a matter of tracing the config.
42/2	2026/07/28 02:16	tool	grepper	0m Args: { "Expression": "config SLAB_OBJ_EXT", "PathPrefix": "" } Results: { "Output": "init/Kconfig=1033=config NUMA_BALANCING_DEFAULT_ENABLED\n--\ninit/Kconfig-1040-\ninit/Kconfig:1041:config SLAB_OBJ_EXT\ninit/Kconfig-1042-\tbool\n" }
43/2	2026/07/28 02:16	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 36496 output: 28 thoughts: 56 Thoughts: Uncovering the Boolean Labyrinth Okay, so there's a hidden boolean flag lurking somewhere. My initial instinct tells me we're looking at something related to memory management and allocation. Specifically, I'm thinking about `MEMCG`, `MEM_ALLOC_PROFILING`, and `KFENCE`. Those three often dance together in this space. Now, let's not get ahead of ourselves. Before we dive deeper, I need to understand the dependencies of `MEM_ALLOC_PROFILING`. Does it rely on other configurations? Does it have any implications that might impact the system? Gotta make sure we're considering the whole picture before chasing a specific path.
44/2	2026/07/28 02:16	tool	grepper	0m Args: { "Expression": "config MEM_ALLOC_PROFILING", "PathPrefix": "" } Results: { "Output": "lib/Kconfig.debug=1047=config CODE_TAGGING\n--\nlib/Kconfig.debug-1050-\nlib/Kconfig.debug:1051:config MEM_ALLOC_PROFILING\nlib/Kconfig.debug-1052-\tbool \"Enable memory allocation profiling\"\n--\nlib/Kconfig.debug-1064-\nlib/Kconfig.debug:1065:config MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT\nlib/Kconfig.debug-1066-\tbool \"Enable memory allocation profiling by default\"\n--\nlib/Kconfig.debug-1069-\nlib/Kconfig.debug:1070:config MEM_ALLOC_PROFILING_DEBUG\nlib/Kconfig.debug-1071-\tbool \"Memory allocation profiler debugging\"\n" }
45/2	2026/07/28 02:16	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 36933 output: 35 thoughts: 20 Thoughts: Here's my summary, as though I'm thinking through this process: Diving into Debugging Configuration Okay, so I need to understand something related to the debugging configuration of this project. My first instinct is to zero in on the relevant Kconfig file – which, as I recall, is usually where these settings are defined. I'll start with `lib/Kconfig.debug`. I seem to remember there was a configuration I was interested in around line 1051, so I'll go straight there. Let me see what that reveals about the specifics I'm looking for... I'm already anticipating what to expect, but need the hard data to make a useful determination.
46/2	2026/07/28 02:17	tool	read-file	0m Args: { "File": "lib/Kconfig.debug", "FirstLine": 1045, "LineCount": 20 } Results: { "Contents": "1045:\t\t If in doubt, say \"N\".\n1046:\t\n1047:\tconfig CODE_TAGGING\n1048:\t\tbool\n1049:\t\tselect KALLSYMS\n1050:\t\n1051:\tconfig MEM_ALLOC_PROFILING\n1052:\t\tbool \"Enable memory allocation profiling\"\n1053:\t\tdefault n\n1054:\t\tdepends on MMU\n1055:\t\tdepends on PROC_FS\n1056:\t\tdepends on !DEBUG_FORCE_WEAK_PER_CPU\n1057:\t\tselect CODE_TAGGING\n1058:\t\tselect PAGE_EXTENSION\n1059:\t\tselect SLAB_OBJ_EXT\n1060:\t\thelp\n1061:\t\t Track allocation source code and record total allocation size\n1062:\t\t initiated at that code location. The mechanism can be used to track\n1063:\t\t memory leaks with a low performance and memory impact.\n1064:\t\n" }
47/2	2026/07/28 02:17	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 37400 output: 23 thoughts: 52 Thoughts: Okay, here's my interpretation of that thought process, from an expert's perspective: Deciphering the Configuration Dependencies Alright, let me break this down. My initial thought process revolves around the dependencies of `MEM_ALLOC_PROFILING`. I see that it requires the presence of an `MMU`, the `PROC_FS`, and importantly, the negation of `DEBUG_FORCE_WEAK_PER_CPU`. These are fairly standard dependencies; profiling often needs a mature memory management unit and access to the process filesystem for introspection. The exclusion of `DEBUG_FORCE_WEAK_PER_CPU` suggests that a different, potentially more robust, debug mechanism is at play when we're profiling. Then, there's the automatic selection of `SLAB_OBJ_EXT`. Hmm, that's interesting. `SLAB_OBJ_EXT` is likely selected to provide additional metadata or extended object support needed for the profiling. It provides extended data to each slab object. I would need to double-check, but that's a reasonable assumption, given the context. My next thought, and this is where I start to drill down, is about `MEMCG`. I need to consider whether memory cgroups (MEMCG) play a role here. Memory cgroups offer more granular resource tracking, which might be critical for a more accurate and useful memory allocation profile. Does `MEM_ALLOC_PROFILING` work well with memory cgroups, or are there compatibility issues, or even better, does it leverage them in some way? This is an important question to address, as integrating with MEMCG would make the profiling much more valuable in a controlled environment. I would need to check the relationships and configurations for that.
48/2	2026/07/28 02:17	tool	grepper	0m Args: { "Expression": "config MEMCG", "PathPrefix": "" } Results: { "Output": "init/Kconfig=1063=config CGROUP_FAVOR_DYNMODS\n--\ninit/Kconfig-1072-\ninit/Kconfig:1073:config MEMCG\ninit/Kconfig-1074-\tbool \"Memory controller\"\n--\ninit/Kconfig-1081-\ninit/Kconfig:1082:config MEMCG_NMI_UNSAFE\ninit/Kconfig-1083-\tbool\n--\ninit/Kconfig-1088-\ninit/Kconfig:1089:config MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\ninit/Kconfig-1090-\tbool\n--\ninit/Kconfig-1095-\ninit/Kconfig:1096:config MEMCG_V1\ninit/Kconfig-1097-\tbool \"Legacy cgroup v1 memory controller\"\n" }
49/2	2026/07/28 02:17	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 38065 output: 33 thoughts: 18 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Diving into the Kernel Configuration Landscape Okay, so I need to understand something related to kernel configuration. Let's see... the most likely place to find information about this, especially if it's a core option, is the `init/Kconfig` file. Given the typical structure of the kernel source, I'm going to start my investigation there. Specifically, my intuition is telling me that the relevant section is around line 1073. It's a broad starting point, but experience has taught me that the initial configuration definitions are often grouped together somewhat logically, and that line number seems like a sensible place to begin. Time to pull up the file and take a look. I'll need to rapidly scan the surrounding code, identify the relevant Kconfig syntax, and then extrapolate the specific configuration options it defines and how it may be affecting the kernel's behaviour in the specific area I'm interested in.
50/2	2026/07/28 02:17	tool	read-file	0m Args: { "File": "init/Kconfig", "FirstLine": 1070, "LineCount": 20 } Results: { "Contents": "1070:\t\n1071:\t\t Say N if unsure.\n1072:\t\n1073:\tconfig MEMCG\n1074:\t\tbool \"Memory controller\"\n1075:\t\tselect PAGE_COUNTER\n1076:\t\tselect EVENTFD\n1077:\t\tselect SLAB_OBJ_EXT\n1078:\t\tselect VM_EVENT_COUNTERS\n1079:\t\thelp\n1080:\t\t Provides control over the memory footprint of tasks in a cgroup.\n1081:\t\n1082:\tconfig MEMCG_NMI_UNSAFE\n1083:\t\tbool\n1084:\t\tdepends on MEMCG\n1085:\t\tdepends on HAVE_NMI\n1086:\t\tdepends on !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS \u0026\u0026 !ARCH_HAVE_NMI_SAFE_CMPXCHG\n1087:\t\tdefault y\n1088:\t\n1089:\tconfig MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\n" }
51/2	2026/07/28 02:17	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 38599 output: 214 thoughts: 803 Thoughts: Analyzing the SLUB Allocator Patch Okay, so this patch is clearly making some significant changes, particularly around `SLAB_OBJ_EXT`. Right off the bat, I see that it's going to require that we enable `MEMCG`, `MEM_ALLOC_PROFILING`, and `KFENCE`. This is crucial context for understanding the scope of the modifications. I've confirmed that the patch is functional and definitely touches core slab behavior. I need to zero in on the key symbols that are being modified here. I've identified: `alloc_slab_obj_exts`, `__memcg_slab_post_alloc_hook`, `__memcg_slab_free_hook`, `__kmem_cache_create_args`, and `kmem_cache_charge`. I also noticed that the change to `__kfence_free` seems minor—just removing a `KFENCE_WARN_ON`, so I will discount that symbol. Initially, I considered adding `memcg_slab_post_charge`, but then I remembered it's inline, so it's not a relevant symbol to focus on. But I still need to make sure I focus on `kmem_cache_charge`. Let's quickly verify my focus symbols. `__kmem_cache_create_args`, in `mm/slab_common.c`, looks right. Okay, moving on. `alloc_slab_obj_exts` looks correct. `__memcg_slab_post_alloc_hook` seems right. `__memcg_slab_free_hook` looks good. And, yes, `kmem_cache_charge` seems like it should be included. Based on the code changes and the configurations it impacts ( `MEMCG`, `MEM_ALLOC_PROFILING`, `KFENCE`), the patch seems to be modifying memory allocation profiling and memcg accounting logic within the SLUB allocator. It is changing how `slabobj_ext` structures are managed and accessed. It looks like `SLAB_MAY_ACCOUNT` is introduced and the `slabobj_ext` layout is changed to an array of pointers or a union, depending on the configuration. Given these core kernel memory management changes, I need to focus on fuzzing these changes to look for any memory corruption, leaks, or accounting errors. I'm going to call `set-results` tool now.
52/2	2026/07/28 02:17	tool	set-results	0m Args: { "EnableConfigs": [ "MEMCG", "MEM_ALLOC_PROFILING", "KFENCE" ], "FocusSymbols": [ "alloc_slab_obj_exts", "__memcg_slab_post_alloc_hook", "__memcg_slab_free_hook", "__kmem_cache_create_args", "kmem_cache_charge" ], "Reasoning": "The patch modifies the memory allocation profiling and memcg accounting logic in the SLUB allocator. It changes how `slabobj_ext` structures are allocated, accessed, and managed, particularly when both `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING` are enabled. It introduces `SLAB_MAY_ACCOUNT` and changes the layout of `slabobj_ext`. These are core kernel memory management changes that should be fuzzed to ensure no memory corruption, leaks, or accounting errors occur.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "MEMCG", "MEM_ALLOC_PROFILING", "KFENCE" ], "FocusSymbols": [ "alloc_slab_obj_exts", "__memcg_slab_post_alloc_hook", "__memcg_slab_free_hook", "__kmem_cache_create_args", "kmem_cache_charge" ], "Reasoning": "The patch modifies the memory allocation profiling and memcg accounting logic in the SLUB allocator. It changes how `slabobj_ext` structures are allocated, accessed, and managed, particularly when both `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING` are enabled. It introduces `SLAB_MAY_ACCOUNT` and changes the layout of `slabobj_ext`. These are core kernel memory management changes that should be fuzzed to ensure no memory corruption, leaks, or accounting errors occur.", "WorthFuzzing": true }

{
  "EnableConfigs": [
    "MEMCG",
    "MEM_ALLOC_PROFILING",
    "KFENCE"
  ],
  "FocusSymbols": [
    "alloc_slab_obj_exts",
    "__memcg_slab_post_alloc_hook",
    "__memcg_slab_free_hook",
    "__kmem_cache_create_args",
    "kmem_cache_charge"
  ],
  "Reasoning": "The patch modifies the memory allocation profiling and memcg accounting logic in the SLUB allocator. It changes how `slabobj_ext` structures are allocated, accessed, and managed, particularly when both `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING` are enabled. It introduces `SLAB_MAY_ACCOUNT` and changes the layout of `slabobj_ext`. These are core kernel memory management changes that should be fuzzed to ensure no memory corruption, leaks, or accounting errors occur.",
  "WorthFuzzing": true
}

{
  "PatchDiff": "commit 48f84032d1bd908e46149ccacdb9013ee3369920\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Tue Jul 28 02:13:15 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/Documentation/mm/allocation-profiling.rst b/Documentation/mm/allocation-profiling.rst\nindex 5389d241176a8a..d02eb54ee8f2c6 100644\n--- a/Documentation/mm/allocation-profiling.rst\n+++ b/Documentation/mm/allocation-profiling.rst\n@@ -112,3 +112,10 @@ To do so:\n \n - Then, use the following form for your allocations:\n   alloc_hooks_tag(ht-\u003eyour_saved_tag, kmalloc_noprof(...))\n+\n+Notes\n+=====\n+\n+- When a slab object is allocated from KFENCE, its accounting is skipped.\n+  KFENCE allocations are rare and limited to a small number, so this omission\n+  is negligible.\ndiff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h\nindex e1f46a0016fcfd..93869cc35c25bc 100644\n--- a/include/linux/memcontrol.h\n+++ b/include/linux/memcontrol.h\n@@ -1440,19 +1440,6 @@ static inline void mem_cgroup_flush_workqueue(void) { }\n static inline int mem_cgroup_init(void) { return 0; }\n #endif /* CONFIG_MEMCG */\n \n-/*\n- * Extended information for slab objects stored as an array in page-\u003ememcg_data\n- * if MEMCG_DATA_OBJEXTS is set.\n- */\n-struct slabobj_ext {\n-#ifdef CONFIG_MEMCG\n-\tstruct obj_cgroup *objcg;\n-#endif\n-#ifdef CONFIG_MEM_ALLOC_PROFILING\n-\tunion codetag_ref ref;\n-#endif\n-} __aligned(8);\n-\n static inline struct lruvec *parent_lruvec(struct lruvec *lruvec)\n {\n \tstruct mem_cgroup *memcg;\ndiff --git a/include/linux/slab.h b/include/linux/slab.h\nindex 32c9f8ed7ae205..e1915026e03040 100644\n--- a/include/linux/slab.h\n+++ b/include/linux/slab.h\n@@ -45,6 +45,7 @@ enum _slab_flag_bits {\n #endif\n #ifdef CONFIG_MEMCG\n \t_SLAB_ACCOUNT,\n+\t_SLAB_MAY_ACCOUNT,\n #endif\n #ifdef CONFIG_KASAN_GENERIC\n \t_SLAB_KASAN,\n@@ -204,8 +205,10 @@ enum _slab_flag_bits {\n  */\n #ifdef CONFIG_MEMCG\n # define SLAB_ACCOUNT\t\t__SLAB_FLAG_BIT(_SLAB_ACCOUNT)\n+# define SLAB_MAY_ACCOUNT\t__SLAB_FLAG_BIT(_SLAB_MAY_ACCOUNT)\n #else\n # define SLAB_ACCOUNT\t\t__SLAB_FLAG_UNUSED\n+# define SLAB_MAY_ACCOUNT\t__SLAB_FLAG_UNUSED\n #endif\n \n #ifdef CONFIG_KASAN_GENERIC\ndiff --git a/mm/kfence/core.c b/mm/kfence/core.c\nindex 6577bd76954eb4..90925c646c4c24 100644\n--- a/mm/kfence/core.c\n+++ b/mm/kfence/core.c\n@@ -636,11 +636,6 @@ static unsigned long kfence_init_pool(void)\n \n \t\tpage = pfn_to_page(start_pfn + i);\n \t\t__SetPageSlab(page);\n-#ifdef CONFIG_MEMCG\n-\t\tstruct slab *slab = page_slab(page);\n-\t\tslab-\u003eobj_exts = (unsigned long)\u0026kfence_metadata_init[i / 2 - 1].obj_exts |\n-\t\t\t\t MEMCG_DATA_OBJEXTS;\n-#endif\n \t}\n \n \t/*\n@@ -704,10 +699,6 @@ static unsigned long kfence_init_pool(void)\n \t\t\tcontinue;\n \n \t\tpage = pfn_to_page(start_pfn + i);\n-#ifdef CONFIG_MEMCG\n-\t\tstruct slab *slab = page_slab(page);\n-\t\tslab-\u003eobj_exts = 0;\n-#endif\n \t\t__ClearPageSlab(page);\n \t}\n \n@@ -1248,9 +1239,6 @@ void __kfence_free(void *addr)\n {\n \tstruct kfence_metadata *meta = addr_to_metadata((unsigned long)addr);\n \n-#ifdef CONFIG_MEMCG\n-\tKFENCE_WARN_ON(meta-\u003eobj_exts.objcg);\n-#endif\n \t/*\n \t * If the objects of the cache are SLAB_TYPESAFE_BY_RCU, defer freeing\n \t * the object, as the object page may be recycled for other-typed\ndiff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h\nindex 1f618f9b0d12d9..e6b4bf349ff730 100644\n--- a/mm/kfence/kfence.h\n+++ b/mm/kfence/kfence.h\n@@ -102,9 +102,6 @@ struct kfence_metadata {\n \tstruct kfence_track free_track __guarded_by(\u0026lock);\n \t/* For updating alloc_covered on frees. */\n \tu32 alloc_stack_hash __guarded_by(\u0026lock);\n-#ifdef CONFIG_MEMCG\n-\tstruct slabobj_ext obj_exts;\n-#endif\n };\n \n #define KFENCE_METADATA_SIZE PAGE_ALIGN(sizeof(struct kfence_metadata) * \\\ndiff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c\nindex de2d0f7d62b15e..9867c03ef0ae3d 100644\n--- a/mm/kfence/kfence_test.c\n+++ b/mm/kfence/kfence_test.c\n@@ -295,7 +295,7 @@ static void *test_alloc(struct kunit *test, size_t size, gfp_t gfp, enum allocat\n \t\t\t * memcg accounting works correctly.\n \t\t\t */\n \t\t\tKUNIT_EXPECT_EQ(test, obj_to_index(s, slab, alloc), 0U);\n-\t\t\tKUNIT_EXPECT_EQ(test, objs_per_slab(s, slab), 1);\n+\t\t\tKUNIT_EXPECT_EQ(test, ((unsigned int)slab-\u003eobjects), 1);\n \n \t\t\tif (policy == ALLOCATE_ANY)\n \t\t\t\treturn alloc;\ndiff --git a/mm/memcontrol.c b/mm/memcontrol.c\nindex 6dc4888a90f3fd..6b51ddf6dfe022 100644\n--- a/mm/memcontrol.c\n+++ b/mm/memcontrol.c\n@@ -2865,18 +2865,19 @@ struct mem_cgroup *mem_cgroup_from_obj_slab(struct slab *slab, void *p)\n \t */\n \tunsigned long obj_exts;\n \tstruct slabobj_ext *obj_ext;\n-\tunsigned int off;\n+\tstruct obj_cgroup *objcg;\n \n \tobj_exts = slab_obj_exts(slab);\n \tif (!obj_exts)\n \t\treturn NULL;\n \n-\tget_slab_obj_exts(obj_exts);\n-\toff = obj_to_index(slab-\u003eslab_cache, slab, p);\n-\tobj_ext = slab_obj_ext(slab, obj_exts, off);\n-\tif (obj_ext-\u003eobjcg) {\n-\t\tstruct obj_cgroup *objcg = obj_ext-\u003eobjcg;\n+\tif (!slab_needs_objcg(slab))\n+\t\treturn NULL;\n \n+\tget_slab_obj_exts(obj_exts);\n+\tobj_ext = slab_obj_ext(slab-\u003eslab_cache, slab, obj_exts, p);\n+\tobjcg = slab_obj_ext_objcg(obj_ext);\n+\tif (objcg) {\n \t\tput_slab_obj_exts(obj_exts);\n \t\treturn obj_cgroup_memcg(objcg);\n \t}\n@@ -3541,7 +3542,6 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,\n \tsize_t obj_size = obj_full_size(s);\n \tstruct obj_cgroup *objcg;\n \tstruct slab *slab;\n-\tunsigned long off;\n \tsize_t i;\n \n \t/*\n@@ -3583,11 +3583,16 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,\n \n \t\tslab = virt_to_slab(p[i]);\n \n-\t\tif (!slab_obj_exts(slab) \u0026\u0026\n-\t\t    alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags)) {\n-\t\t\tcontinue;\n+\t\tif (!slab_obj_exts(slab)) {\n+\t\t\tif (is_kfence_address(p[i]))\n+\t\t\t\tcontinue;\n+\t\t\tif (alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags))\n+\t\t\t\tcontinue;\n \t\t}\n \n+\t\tif (IS_ENABLED(CONFIG_DEBUG_VM) \u0026\u0026 WARN_ON_ONCE(!slab_needs_objcg(slab)))\n+\t\t\tcontinue;\n+\n \t\t/*\n \t\t * if we fail and size is 1, memcg_alloc_abort_single() will\n \t\t * just free the object, which is ok as we have not assigned\n@@ -3616,10 +3621,11 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,\n \n \t\tobj_exts = slab_obj_exts(slab);\n \t\tget_slab_obj_exts(obj_exts);\n-\t\toff = obj_to_index(s, slab, p[i]);\n-\t\tobj_ext = slab_obj_ext(slab, obj_exts, off);\n+\t\tobj_ext = slab_obj_ext(s, slab, obj_exts, p[i]);\n+\n \t\tobj_cgroup_get(objcg);\n-\t\tobj_ext-\u003eobjcg = objcg;\n+\t\tslab_obj_ext_set_objcg(obj_ext, objcg);\n+\n \t\tput_slab_obj_exts(obj_exts);\n \t}\n \n@@ -3635,15 +3641,13 @@ void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,\n \t\tstruct obj_cgroup *objcg;\n \t\tstruct slabobj_ext *obj_ext;\n \t\tstruct obj_stock_pcp *stock;\n-\t\tunsigned int off;\n \n-\t\toff = obj_to_index(s, slab, p[i]);\n-\t\tobj_ext = slab_obj_ext(slab, obj_exts, off);\n-\t\tobjcg = obj_ext-\u003eobjcg;\n+\t\tobj_ext = slab_obj_ext(s, slab, obj_exts, p[i]);\n+\t\tobjcg = slab_obj_ext_objcg(obj_ext);\n \t\tif (!objcg)\n \t\t\tcontinue;\n \n-\t\tobj_ext-\u003eobjcg = NULL;\n+\t\tslab_obj_ext_set_objcg(obj_ext, NULL);\n \n \t\tstock = trylock_stock();\n \t\t__refill_obj_stock(objcg, stock, obj_size, true);\ndiff --git a/mm/slab.h b/mm/slab.h\nindex f5e336b6b6b04c..04600f57b40146 100644\n--- a/mm/slab.h\n+++ b/mm/slab.h\n@@ -81,10 +81,11 @@ struct freelist_counters {\n #ifdef CONFIG_64BIT\n \t\t\t\t\t/*\n \t\t\t\t\t * Some optimizations use free bits in 'counters' field\n-\t\t\t\t\t * to save memory. In case -\u003estride field is not available,\n-\t\t\t\t\t * such optimizations are disabled.\n+\t\t\t\t\t * to save memory or CPU. If these free bits are not\n+\t\t\t\t\t * available, such optimizations are disabled.\n \t\t\t\t\t */\n-\t\t\t\t\tunsigned int stride;\n+\t\t\t\t\tunsigned obj_exts_in_object:1;\n+\t\t\t\t\tunsigned obj_exts_needs_objcg:1;\n #endif\n \t\t\t\t};\n \t\t\t};\n@@ -330,12 +331,6 @@ static inline unsigned int obj_to_index(const struct kmem_cache *cache,\n \treturn __obj_to_index(cache, slab_address(slab), obj);\n }\n \n-static inline int objs_per_slab(const struct kmem_cache *cache,\n-\t\t\t\tconst struct slab *slab)\n-{\n-\treturn slab-\u003eobjects;\n-}\n-\n /*\n  * State of the slab allocator.\n  *\n@@ -555,6 +550,93 @@ static inline bool need_kmalloc_no_objext(void)\n \treturn false;\n }\n \n+/*\n+ * Extended information for slab objects stored as a pointer to an array in\n+ * slab-\u003eobj_exts (aliasing page-\u003ememcg_data) if MEMCG_DATA_OBJEXTS is set.\n+ */\n+struct slabobj_ext {\n+\t/*\n+\t * All elements of the union should be pointer-sized to avoid memory\n+\t * waste\n+\t */\n+\tunion {\n+#ifdef CONFIG_MEMCG\n+\t\tstruct obj_cgroup *_objcg;\n+#endif\n+#ifdef CONFIG_MEM_ALLOC_PROFILING\n+\t\tunion codetag_ref _ctref;\n+#endif\n+\t};\n+} __aligned(8);\n+\n+#ifdef CONFIG_MEM_ALLOC_PROFILING\n+DECLARE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\n+\t\t\t slab_obj_ext_has_codetag_key);\n+\n+static inline bool slab_obj_ext_has_codetag(void)\n+{\n+\treturn static_branch_maybe(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\n+\t\t\t\t   \u0026slab_obj_ext_has_codetag_key);\n+}\n+#else\n+static inline bool slab_obj_ext_has_codetag(void)\n+{\n+\treturn false;\n+}\n+#endif\n+\n+#ifdef CONFIG_MEMCG\n+static inline bool cache_needs_objcg(struct kmem_cache *cache)\n+{\n+\treturn (cache-\u003eflags \u0026 SLAB_MAY_ACCOUNT);\n+}\n+\n+static inline bool slab_needs_objcg(struct slab *slab)\n+{\n+#ifdef CONFIG_64BIT\n+\treturn slab-\u003eobj_exts_needs_objcg;\n+#else\n+\treturn cache_needs_objcg(slab-\u003eslab_cache);\n+#endif\n+}\n+#else\n+static inline bool cache_needs_objcg(struct kmem_cache *cache)\n+{\n+\treturn false;\n+}\n+\n+static inline bool slab_needs_objcg(struct slab *slab)\n+{\n+\treturn false;\n+}\n+#endif\n+\n+static inline size_t cache_obj_ext_size(struct kmem_cache *s)\n+{\n+\tsize_t sz = 0;\n+\n+\tif (cache_needs_objcg(s))\n+\t\tsz += 1;\n+\n+\tif (slab_obj_ext_has_codetag())\n+\t\tsz += 1;\n+\n+\treturn sizeof(struct slabobj_ext) * sz;\n+}\n+\n+static inline size_t slab_obj_ext_size(struct slab *slab)\n+{\n+\tsize_t sz = 0;\n+\n+\tif (slab_needs_objcg(slab))\n+\t\tsz += 1;\n+\n+\tif (slab_obj_ext_has_codetag())\n+\t\tsz += 1;\n+\n+\treturn sizeof(struct slabobj_ext) * sz;\n+}\n+\n #ifdef CONFIG_SLAB_OBJ_EXT\n \n /*\n@@ -572,7 +654,7 @@ static inline bool need_kmalloc_no_objext(void)\n  * obj_exts = slab_obj_exts(slab);\n  * if (obj_exts) {\n  *         get_slab_obj_exts(obj_exts);\n- *         obj_ext = slab_obj_ext(slab, obj_exts, obj_to_index(s, slab, obj));\n+ *         obj_ext = slab_obj_ext(s, slab, obj_exts, obj);\n  *         // do something with obj_ext\n  *         put_slab_obj_exts(obj_exts);\n  * }\n@@ -610,48 +692,86 @@ static inline void put_slab_obj_exts(unsigned long obj_exts)\n }\n \n #ifdef CONFIG_64BIT\n-static inline void slab_set_stride(struct slab *slab, unsigned int stride)\n+static inline bool obj_exts_in_object(struct slab *slab)\n {\n-\tslab-\u003estride = stride;\n-}\n-static inline unsigned int slab_get_stride(struct slab *slab)\n-{\n-\treturn slab-\u003estride;\n+\t/*\n+\t * Note we cannot rely on the SLAB_OBJ_EXT_IN_OBJ flag here and need to\n+\t * check the per-slab bit. A cache can have SLAB_OBJ_EXT_IN_OBJ set, but\n+\t * allocations within_slab_leftover are preferred. And those may be\n+\t * possible or not depending on the particular slab's size.\n+\t */\n+\treturn slab-\u003eobj_exts_in_object;\n }\n #else\n-static inline void slab_set_stride(struct slab *slab, unsigned int stride)\n-{\n-\tVM_WARN_ON_ONCE(stride != sizeof(struct slabobj_ext));\n-}\n-static inline unsigned int slab_get_stride(struct slab *slab)\n+static inline bool obj_exts_in_object(struct slab *slab)\n {\n-\treturn sizeof(struct slabobj_ext);\n+\treturn false;\n }\n #endif\n \n /*\n  * slab_obj_ext - get the pointer to the slab object extension metadata\n  * associated with an object in a slab.\n+ * @s: cache that the slab belongs to\n  * @slab: a pointer to the slab struct\n  * @obj_exts: a pointer to the object extension vector\n- * @index: an index of the object\n+ * @obj: a pointer to the object\n  *\n  * Returns a pointer to the object extension associated with the object.\n  * Must be called within a section covered by get/put_slab_obj_exts().\n  */\n-static inline struct slabobj_ext *slab_obj_ext(struct slab *slab,\n-\t\t\t\t\t       unsigned long obj_exts,\n-\t\t\t\t\t       unsigned int index)\n+static inline struct slabobj_ext *\n+slab_obj_ext(struct kmem_cache *s, struct slab *slab, unsigned long obj_exts,\n+\t     const void *obj)\n {\n \tstruct slabobj_ext *obj_ext;\n+\tunsigned int index;\n+\tunsigned int stride;\n \n \tVM_WARN_ON_ONCE(obj_exts != slab_obj_exts(slab));\n \n-\tobj_ext = (struct slabobj_ext *)(obj_exts +\n-\t\t\t\t\t slab_get_stride(slab) * index);\n+\t/*\n+\t * KFENCE objects have NULL obj_exts and thus can't reach this\n+\t * and we don't need obj_to_index()\n+\t */\n+\tindex = __obj_to_index(s, slab_address(slab), obj);\n+\n+\tif (!obj_exts_in_object(slab))\n+\t\tstride = slab_obj_ext_size(slab);\n+\telse\n+\t\tstride = s-\u003esize;\n+\n+\tobj_ext = (struct slabobj_ext *)(obj_exts + index * stride);\n+\n \treturn kasan_reset_tag(obj_ext);\n }\n \n+#ifdef CONFIG_MEMCG\n+static inline struct obj_cgroup *slab_obj_ext_objcg(struct slabobj_ext *obj_ext)\n+{\n+\t/* if objcg exists, it comes first, so we don't need to do anything */\n+\treturn obj_ext-\u003e_objcg;\n+}\n+\n+static inline void slab_obj_ext_set_objcg(struct slabobj_ext *obj_ext,\n+\t\t\t\t\t  struct obj_cgroup *objcg)\n+{\n+\t/* if objcg exists, it comes first, so we don't need to do anything */\n+\tobj_ext-\u003e_objcg = objcg;\n+}\n+#endif\n+\n+#ifdef CONFIG_MEM_ALLOC_PROFILING\n+static inline union codetag_ref *\n+slab_obj_ext_codetag_ref(struct slab *slab, struct slabobj_ext *obj_ext)\n+{\n+\tif (slab_needs_objcg(slab))\n+\t\tobj_ext += 1;\n+\n+\treturn \u0026obj_ext-\u003e_ctref;\n+}\n+#endif\n+\n int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,\n \t\t\tgfp_t gfp, unsigned int alloc_flags);\n \n@@ -662,16 +782,17 @@ static inline unsigned long slab_obj_exts(struct slab *slab)\n \treturn 0;\n }\n \n-static inline struct slabobj_ext *slab_obj_ext(struct slab *slab,\n-\t\t\t\t\t       unsigned long obj_exts,\n-\t\t\t\t\t       unsigned int index)\n+static inline struct slabobj_ext *\n+slab_obj_ext(struct kmem_cache *s, struct slab *slab, unsigned long obj_exts,\n+\t     const void *obj)\n {\n \treturn NULL;\n }\n \n-static inline void slab_set_stride(struct slab *slab, unsigned int stride) { }\n-static inline unsigned int slab_get_stride(struct slab *slab) { return 0; }\n-\n+static inline bool obj_exts_in_object(struct slab *slab)\n+{\n+\treturn false;\n+}\n \n #endif /* CONFIG_SLAB_OBJ_EXT */\n \ndiff --git a/mm/slab_common.c b/mm/slab_common.c\nindex 03ecac12cd865f..1e1d3feec3535b 100644\n--- a/mm/slab_common.c\n+++ b/mm/slab_common.c\n@@ -52,7 +52,7 @@ struct kmem_cache *kmem_cache;\n \t\tSLAB_OBJ_EXT_IN_OBJ)\n \n #define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | \\\n-\t\t\t SLAB_CACHE_DMA32 | SLAB_ACCOUNT)\n+\t\t\t SLAB_CACHE_DMA32 | SLAB_ACCOUNT | SLAB_MAY_ACCOUNT)\n \n /*\n  * Merge control. If this is set then no merging of slab caches will occur.\n@@ -359,6 +359,13 @@ struct kmem_cache *__kmem_cache_create_args(const char *name,\n \t\tgoto out_unlock;\n \t}\n \n+\t/*\n+\t * For now we assume any cache can be used with __GFP_ACCOUNT and thus\n+\t * may need to store objcg pointers for objects\n+\t */\n+\tif (!mem_cgroup_kmem_disabled())\n+\t\tflags |= SLAB_MAY_ACCOUNT;\n+\n \t/* Fail closed on bad usersize of useroffset values. */\n \tif (!IS_ENABLED(CONFIG_HARDENED_USERCOPY) ||\n \t    WARN_ON(!args-\u003eusersize \u0026\u0026 args-\u003euseroffset) ||\n@@ -984,11 +991,20 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type)\n #endif\n \n \t/*\n-\t * If CONFIG_MEMCG is enabled, disable cache merging for\n-\t * KMALLOC_NORMAL caches.\n+\t * If memcg_kmem is enabled and this is a KMALLOC_NORMAL cache and not\n+\t * aliased with any other type, make sure it's never merged with any other\n+\t * cache.\n+\t *\n+\t * In other cases the kmalloc cache may end up being used for a\n+\t * __GFP_ACCOUNT allocation so mark it as such. The exception is a\n+\t * KMALLOC_NO_OBJ_EXT cache.\n \t */\n-\tif (IS_ENABLED(CONFIG_MEMCG) \u0026\u0026 (type == KMALLOC_NORMAL))\n-\t\tflags |= SLAB_NO_MERGE;\n+\tif (!mem_cgroup_kmem_disabled()) {\n+\t\tif (type == KMALLOC_NORMAL \u0026\u0026 KMALLOC_RECLAIM != KMALLOC_NORMAL)\n+\t\t\tflags |= SLAB_NO_MERGE;\n+\t\telse if (!(flags \u0026 SLAB_NO_OBJ_EXT))\n+\t\t\tflags |= SLAB_MAY_ACCOUNT;\n+\t}\n \n \tif (minalign \u003e ARCH_KMALLOC_MINALIGN) {\n \t\taligned_size = ALIGN(aligned_size, minalign);\ndiff --git a/mm/slub.c b/mm/slub.c\nindex 0337e60db5ace0..94b744e5ac7919 100644\n--- a/mm/slub.c\n+++ b/mm/slub.c\n@@ -213,6 +213,11 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);\n static DEFINE_STATIC_KEY_FALSE(strict_numa);\n #endif\n \n+#ifdef CONFIG_MEM_ALLOC_PROFILING\n+DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\n+\t\t\tslab_obj_ext_has_codetag_key);\n+#endif\n+\n /* Structure holding extra parameters for slab allocations */\n struct slab_alloc_context {\n \tunsigned long caller_addr;\n@@ -803,7 +808,7 @@ static inline bool need_slab_obj_exts(struct kmem_cache *s)\n \n static inline unsigned int obj_exts_size_in_slab(struct slab *slab)\n {\n-\treturn sizeof(struct slabobj_ext) * slab-\u003eobjects;\n+\treturn slab_obj_ext_size(slab) * slab-\u003eobjects;\n }\n \n static inline unsigned long obj_exts_offset_in_slab(struct kmem_cache *s,\n@@ -870,18 +875,6 @@ static inline bool obj_exts_in_slab(struct kmem_cache *s, struct slab *slab)\n #endif\n \n #if defined(CONFIG_SLAB_OBJ_EXT) \u0026\u0026 defined(CONFIG_64BIT)\n-static bool obj_exts_in_object(struct kmem_cache *s, struct slab *slab)\n-{\n-\t/*\n-\t * Note we cannot rely on the SLAB_OBJ_EXT_IN_OBJ flag here and need to\n-\t * check the stride. A cache can have SLAB_OBJ_EXT_IN_OBJ set, but\n-\t * allocations within_slab_leftover are preferred. And those may be\n-\t * possible or not depending on the particular slab's size.\n-\t */\n-\treturn obj_exts_in_slab(s, slab) \u0026\u0026\n-\t       (slab_get_stride(slab) == s-\u003esize);\n-}\n-\n static unsigned int obj_exts_offset_in_object(struct kmem_cache *s)\n {\n \tunsigned int offset = get_info_end(s);\n@@ -896,16 +889,20 @@ static unsigned int obj_exts_offset_in_object(struct kmem_cache *s)\n \n \treturn offset;\n }\n-#else\n-static inline bool obj_exts_in_object(struct kmem_cache *s, struct slab *slab)\n+\n+static inline void slab_set_obj_exts_in_object(struct slab *slab)\n {\n-\treturn false;\n+\tslab-\u003eobj_exts_in_object = 1;\n }\n-\n+#else\n static inline unsigned int obj_exts_offset_in_object(struct kmem_cache *s)\n {\n \treturn 0;\n }\n+\n+static inline void slab_set_obj_exts_in_object(struct slab *slab)\n+{\n+}\n #endif\n \n #ifdef CONFIG_SLUB_DEBUG\n@@ -1206,8 +1203,8 @@ static void print_trailer(struct kmem_cache *s, struct slab *slab, u8 *p)\n \n \toff += kasan_metadata_size(s, false);\n \n-\tif (obj_exts_in_object(s, slab))\n-\t\toff += sizeof(struct slabobj_ext);\n+\tif (obj_exts_in_object(slab))\n+\t\toff += slab_obj_ext_size(slab);\n \n \tif (off != size_from_object(s))\n \t\t/* Beginning of the filler is the free pointer */\n@@ -1411,8 +1408,8 @@ static int check_pad_bytes(struct kmem_cache *s, struct slab *slab, u8 *p)\n \n \toff += kasan_metadata_size(s, false);\n \n-\tif (obj_exts_in_object(s, slab))\n-\t\toff += sizeof(struct slabobj_ext);\n+\tif (obj_exts_in_object(slab))\n+\t\toff += slab_obj_ext_size(slab);\n \n \tif (size_from_object(s) == off)\n \t\treturn 1;\n@@ -1439,7 +1436,7 @@ slab_pad_check(struct kmem_cache *s, struct slab *slab)\n \tlength = slab_size(slab);\n \tend = start + length;\n \n-\tif (obj_exts_in_slab(s, slab) \u0026\u0026 !obj_exts_in_object(s, slab)) {\n+\tif (obj_exts_in_slab(s, slab) \u0026\u0026 !obj_exts_in_object(slab)) {\n \t\tremainder = length;\n \t\tremainder -= obj_exts_offset_in_slab(s, slab);\n \t\tremainder -= obj_exts_size_in_slab(slab);\n@@ -2070,20 +2067,21 @@ static inline void mark_obj_codetag_empty(const void *obj)\n \tobj_slab = virt_to_slab(obj);\n \tslab_exts = slab_obj_exts(obj_slab);\n \tif (slab_exts) {\n+\t\tstruct slabobj_ext *ext;\n+\t\tunion codetag_ref *ref;\n+\n \t\tget_slab_obj_exts(slab_exts);\n-\t\tunsigned int offs = obj_to_index(obj_slab-\u003eslab_cache,\n-\t\t\t\t\t\t obj_slab, obj);\n-\t\tstruct slabobj_ext *ext = slab_obj_ext(obj_slab,\n-\t\t\t\t\t\t       slab_exts, offs);\n+\t\text = slab_obj_ext(obj_slab-\u003eslab_cache, obj_slab, slab_exts, obj);\n+\t\tref = slab_obj_ext_codetag_ref(obj_slab, ext);\n \n-\t\tif (unlikely(is_codetag_empty(\u0026ext-\u003eref))) {\n+\t\tif (unlikely(is_codetag_empty(ref))) {\n \t\t\tput_slab_obj_exts(slab_exts);\n \t\t\treturn;\n \t\t}\n \n \t\t/* codetag should be NULL here */\n-\t\tWARN_ON(ext-\u003eref.ct);\n-\t\tset_codetag_empty(\u0026ext-\u003eref);\n+\t\tWARN_ON(ref-\u003ect);\n+\t\tset_codetag_empty(ref);\n \t\tput_slab_obj_exts(slab_exts);\n \t}\n }\n@@ -2093,19 +2091,29 @@ static inline bool mark_failed_objexts_alloc(struct slab *slab)\n \treturn cmpxchg(\u0026slab-\u003eobj_exts, 0, OBJEXTS_ALLOC_FAIL) == 0;\n }\n \n-static inline void handle_failed_objexts_alloc(unsigned long obj_exts,\n-\t\t\tstruct slabobj_ext *vec, unsigned int objects)\n+static inline void handle_failed_objexts_alloc(struct slab *slab,\n+\t\tunsigned long obj_exts, struct slabobj_ext *vec)\n {\n+\tunsigned int stride;\n+\n+\tif (!slab_obj_ext_has_codetag())\n+\t\treturn;\n+\n \t/*\n \t * If vector previously failed to allocate then we have live\n \t * objects with no tag reference. Mark all references in this\n \t * vector as empty to avoid warnings later on.\n \t */\n-\tif (obj_exts == OBJEXTS_ALLOC_FAIL) {\n-\t\tunsigned int i;\n+\tif (obj_exts != OBJEXTS_ALLOC_FAIL)\n+\t\treturn;\n+\n+\tstride = slab_obj_ext_size(slab) / sizeof(*vec);\n+\n+\tfor (unsigned int i = 0; i \u003c slab-\u003eobjects; i++) {\n+\t\tunion codetag_ref *ref = slab_obj_ext_codetag_ref(slab, vec);\n \n-\t\tfor (i = 0; i \u003c objects; i++)\n-\t\t\tset_codetag_empty(\u0026vec[i].ref);\n+\t\tset_codetag_empty(ref);\n+\t\tvec += stride;\n \t}\n }\n \n@@ -2113,8 +2121,8 @@ static inline void handle_failed_objexts_alloc(unsigned long obj_exts,\n \n static inline void mark_obj_codetag_empty(const void *obj) {}\n static inline bool mark_failed_objexts_alloc(struct slab *slab) { return false; }\n-static inline void handle_failed_objexts_alloc(unsigned long obj_exts,\n-\t\t\tstruct slabobj_ext *vec, unsigned int objects) {}\n+static inline void handle_failed_objexts_alloc(struct slab *slab,\n+\t\tunsigned long obj_exts, struct slabobj_ext *vec) {}\n \n #endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */\n \n@@ -2127,12 +2135,11 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,\n \t\t\tgfp_t gfp, unsigned int alloc_flags)\n {\n \tconst bool allow_spin = alloc_flags_allow_spinning(alloc_flags);\n-\tunsigned int objects = objs_per_slab(s, slab);\n \tbool new_slab = alloc_flags \u0026 SLAB_ALLOC_NEW_SLAB;\n \tunsigned long new_exts;\n \tunsigned long old_exts;\n \tstruct slabobj_ext *vec;\n-\tsize_t sz = sizeof(struct slabobj_ext) * slab-\u003eobjects;\n+\tsize_t sz = slab_obj_ext_size(slab) * slab-\u003eobjects;\n \n \tgfp \u0026= ~OBJCGS_CLEAR_MASK;\n \t/*\n@@ -2183,7 +2190,7 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,\n #endif\n retry:\n \told_exts = READ_ONCE(slab-\u003eobj_exts);\n-\thandle_failed_objexts_alloc(old_exts, vec, objects);\n+\thandle_failed_objexts_alloc(slab, old_exts, vec);\n \n \tif (new_slab) {\n \t\t/*\n@@ -2250,9 +2257,6 @@ static void alloc_slab_obj_exts_early(struct kmem_cache *s, struct slab *slab)\n \tvoid *addr;\n \tunsigned long obj_exts;\n \n-\t/* Initialize stride early to avoid memory ordering issues */\n-\tslab_set_stride(slab, sizeof(struct slabobj_ext));\n-\n \tif (!need_slab_obj_exts(s))\n \t\treturn;\n \n@@ -2278,15 +2282,14 @@ static void alloc_slab_obj_exts_early(struct kmem_cache *s, struct slab *slab)\n \n \t\tget_slab_obj_exts(obj_exts);\n \t\tfor_each_object(addr, s, slab_address(slab), slab-\u003eobjects)\n-\t\t\tmemset(kasan_reset_tag(addr) + offset, 0,\n-\t\t\t       sizeof(struct slabobj_ext));\n+\t\t\tmemset(kasan_reset_tag(addr) + offset, 0, slab_obj_ext_size(slab));\n \t\tput_slab_obj_exts(obj_exts);\n \n #ifdef CONFIG_MEMCG\n \t\tobj_exts |= MEMCG_DATA_OBJEXTS;\n #endif\n \t\tslab-\u003eobj_exts = obj_exts;\n-\t\tslab_set_stride(slab, s-\u003esize);\n+\t\tslab_set_obj_exts_in_object(slab);\n \t}\n }\n \n@@ -2323,11 +2326,15 @@ static inline unsigned long\n prepare_slab_obj_exts_hook(struct kmem_cache *s, struct slab *slab,\n \t\t\t   gfp_t flags, unsigned int alloc_flags, void *p)\n {\n-\tif (!slab_obj_exts(slab) \u0026\u0026\n-\t    alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {\n-\t\tpr_warn_once(\"%s, %s: Failed to create slab extension vector!\\n\",\n-\t\t\t     __func__, s-\u003ename);\n-\t\treturn 0;\n+\tif (!slab_obj_exts(slab)) {\n+\t\tif (is_kfence_address(p))\n+\t\t\treturn 0;\n+\n+\t\tif (alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {\n+\t\t\tpr_warn_once(\"%s, %s: Failed to create slab extension vector!\\n\",\n+\t\t\t\t     __func__, s-\u003ename);\n+\t\t\treturn 0;\n+\t\t}\n \t}\n \n \treturn slab_obj_exts(slab);\n@@ -2360,14 +2367,24 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags,\n \t * check should be added before alloc_tag_add().\n \t */\n \tif (obj_exts) {\n-\t\tunsigned int obj_idx = obj_to_index(s, slab, object);\n+\t\tunion codetag_ref *ref;\n \n \t\tget_slab_obj_exts(obj_exts);\n-\t\tobj_ext = slab_obj_ext(slab, obj_exts, obj_idx);\n-\t\talloc_tag_add(\u0026obj_ext-\u003eref, current-\u003ealloc_tag, s-\u003esize);\n+\n+\t\tobj_ext = slab_obj_ext(s, slab, obj_exts, object);\n+\t\tref = slab_obj_ext_codetag_ref(slab, obj_ext);\n+\n+\t\talloc_tag_add(ref, current-\u003ealloc_tag, s-\u003esize);\n+\n \t\tput_slab_obj_exts(obj_exts);\n \t} else {\n-\t\talloc_tag_set_inaccurate(current-\u003ealloc_tag);\n+\t\t/*\n+\t\t * KFENCE allocations are rare and the amount of outstanding\n+\t\t * ones is limited to a small number so it's not worth setting\n+\t\t * tags as inaccurate because of them.\n+\t\t */\n+\t\tif (!is_kfence_address(object))\n+\t\t\talloc_tag_set_inaccurate(current-\u003ealloc_tag);\n \t}\n }\n \n@@ -2384,7 +2401,6 @@ static noinline void\n __alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,\n \t\t\t       int objects)\n {\n-\tint i;\n \tunsigned long obj_exts;\n \n \t/* slab-\u003eobj_exts might not be NULL if it was created for MEMCG accounting. */\n@@ -2396,10 +2412,11 @@ __alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p\n \t\treturn;\n \n \tget_slab_obj_exts(obj_exts);\n-\tfor (i = 0; i \u003c objects; i++) {\n-\t\tunsigned int off = obj_to_index(s, slab, p[i]);\n+\tfor (int i = 0; i \u003c objects; i++) {\n+\t\tstruct slabobj_ext *ext;\n \n-\t\talloc_tag_sub(\u0026slab_obj_ext(slab, obj_exts, off)-\u003eref, s-\u003esize);\n+\t\text = slab_obj_ext(s, slab, obj_exts, p[i]);\n+\t\talloc_tag_sub(slab_obj_ext_codetag_ref(slab, ext), s-\u003esize);\n \t}\n \tput_slab_obj_exts(obj_exts);\n }\n@@ -2412,6 +2429,25 @@ alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,\n \t\t__alloc_tagging_slab_free_hook(s, slab, p, objects);\n }\n \n+/*\n+ * Make sure the static key used by slab_obj_ext_has_codetag() reflects the\n+ * value of !mem_alloc_profiling_permanently_disabled()\n+ *\n+ * Any later mem alloc profiling shutdown won't be reflected in the static key\n+ * because obj_exts with codetags might already exist.\n+ */\n+static void __init slab_obj_ext_has_codetag_init(void)\n+{\n+\tbool need_codetag = !mem_alloc_profiling_permanently_disabled();\n+\n+\tif (need_codetag != static_key_enabled(\u0026slab_obj_ext_has_codetag_key)) {\n+\t\tif (need_codetag)\n+\t\t\tstatic_branch_enable(\u0026slab_obj_ext_has_codetag_key);\n+\t\telse\n+\t\t\tstatic_branch_disable(\u0026slab_obj_ext_has_codetag_key);\n+\t}\n+}\n+\n #else /* CONFIG_MEM_ALLOC_PROFILING */\n \n static inline void\n@@ -2426,6 +2462,10 @@ alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,\n {\n }\n \n+static inline void slab_obj_ext_has_codetag_init(void)\n+{\n+}\n+\n #endif /* CONFIG_MEM_ALLOC_PROFILING */\n \n \n@@ -2471,6 +2511,9 @@ void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,\n \tif (likely(!obj_exts))\n \t\treturn;\n \n+\tif (!slab_needs_objcg(slab))\n+\t\treturn;\n+\n \tget_slab_obj_exts(obj_exts);\n \t__memcg_slab_free_hook(s, slab, p, objects, obj_exts);\n \tput_slab_obj_exts(obj_exts);\n@@ -2484,7 +2527,6 @@ bool memcg_slab_post_charge(void *p, gfp_t flags)\n \tstruct kmem_cache *s;\n \tstruct page *page;\n \tstruct slab *slab;\n-\tunsigned long off;\n \n \tpage = virt_to_page(p);\n \tif (PageLargeKmalloc(page)) {\n@@ -2517,16 +2559,15 @@ bool memcg_slab_post_charge(void *p, gfp_t flags)\n \t * of slab_obj_exts being allocated from the same slab and thus the slab\n \t * becoming effectively unfreeable.\n \t */\n-\tif (is_kmalloc_normal(s))\n+\tif (!cache_needs_objcg(s))\n \t\treturn true;\n \n \t/* Ignore already charged objects. */\n \tobj_exts = slab_obj_exts(slab);\n \tif (obj_exts) {\n \t\tget_slab_obj_exts(obj_exts);\n-\t\toff = obj_to_index(s, slab, p);\n-\t\tobj_ext = slab_obj_ext(slab, obj_exts, off);\n-\t\tif (unlikely(obj_ext-\u003eobjcg)) {\n+\t\tobj_ext = slab_obj_ext(s, slab, obj_exts, p);\n+\t\tif (unlikely(slab_obj_ext_objcg(obj_ext))) {\n \t\t\tput_slab_obj_exts(obj_exts);\n \t\t\treturn true;\n \t\t}\n@@ -3391,10 +3432,15 @@ static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags,\n \t\tstat(s, ORDER_FALLBACK);\n \t}\n \n+\t/* Initializes frozen, inuse, and any extra 64bit-only flags */\n+\tslab-\u003ecounters = 0;\n+\n \tslab-\u003eobjects = oo_objects(oo);\n-\tslab-\u003einuse = 0;\n-\tslab-\u003efrozen = 0;\n \n+#ifdef CONFIG_64BIT\n+\tif (cache_needs_objcg(s))\n+\t\tslab-\u003eobj_exts_needs_objcg = 1;\n+#endif\n \tslab-\u003eslab_cache = s;\n \n \tkasan_poison_slab(slab);\n@@ -6526,7 +6572,7 @@ static inline size_t slab_ksize(struct slab *slab)\n \t */\n \tif (s-\u003eflags \u0026 (SLAB_TYPESAFE_BY_RCU | SLAB_STORE_USER))\n \t\treturn s-\u003einuse;\n-\telse if (obj_exts_in_object(s, slab))\n+\telse if (obj_exts_in_object(slab))\n \t\treturn s-\u003einuse;\n \t/*\n \t * Else we can use all the padding etc for the allocation\n@@ -7929,7 +7975,7 @@ static int calculate_sizes(struct kmem_cache_args *args, struct kmem_cache *s)\n \taligned_size = ALIGN(size, s-\u003ealign);\n #if defined(CONFIG_SLAB_OBJ_EXT) \u0026\u0026 defined(CONFIG_64BIT)\n \tif (slab_args_unmergeable(args, s-\u003eflags) \u0026\u0026\n-\t\t\t(aligned_size - size \u003e= sizeof(struct slabobj_ext)))\n+\t\t\t(aligned_size - size \u003e= cache_obj_ext_size(s)))\n \t\ts-\u003eflags |= SLAB_OBJ_EXT_IN_OBJ;\n #endif\n \tsize = aligned_size;\n@@ -8539,6 +8585,8 @@ void __init kmem_cache_init(void)\n \t\tboot_kmem_cache_node;\n \tint node;\n \n+\tslab_obj_ext_has_codetag_init();\n+\n \tif (debug_guardpage_minorder())\n \t\tslub_max_order = 0;\n \n"
}

{
  "EnableConfigs": [
    "MEMCG",
    "MEM_ALLOC_PROFILING",
    "KFENCE"
  ],
  "FocusSymbols": [
    "alloc_slab_obj_exts",
    "__memcg_slab_post_alloc_hook",
    "__memcg_slab_free_hook",
    "__kmem_cache_create_args",
    "kmem_cache_charge"
  ],
  "Reasoning": "The patch modifies the memory allocation profiling and memcg accounting logic in the SLUB allocator. It changes how `slabobj_ext` structures are allocated, accessed, and managed, particularly when both `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING` are enabled. It introduces `SLAB_MAY_ACCOUNT` and changes the layout of `slabobj_ext`. These are core kernel memory management changes that should be fuzzed to ensure no memory corruption, leaks, or accounting errors occur.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
  even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).
- Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed,
  ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU.
- Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove)
  that are executed only during PCI hot-unplug or sysfs driver unbind operations.

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
   Prefer non-static, non-inlined API entrypoint functions over internal static helper functions
   (which are inlined by the compiler and do not have distinct symbol addresses).
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs
   needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs
   output array, and DO NOT add a '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.

For your convenience, here is the diff of the changes:
commit 48f84032d1bd908e46149ccacdb9013ee3369920
Author: syz-cluster <triage@syzkaller.com>
Date:   Tue Jul 28 02:13:15 2026 +0000

    syz-cluster: applied patch under review

diff --git a/Documentation/mm/allocation-profiling.rst b/Documentation/mm/allocation-profiling.rst
index 5389d241176a8a..d02eb54ee8f2c6 100644
--- a/Documentation/mm/allocation-profiling.rst
+++ b/Documentation/mm/allocation-profiling.rst
@@ -112,3 +112,10 @@ To do so:
 
 - Then, use the following form for your allocations:
   alloc_hooks_tag(ht->your_saved_tag, kmalloc_noprof(...))
+
+Notes
+=====
+
+- When a slab object is allocated from KFENCE, its accounting is skipped.
+  KFENCE allocations are rare and limited to a small number, so this omission
+  is negligible.
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index e1f46a0016fcfd..93869cc35c25bc 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1440,19 +1440,6 @@ static inline void mem_cgroup_flush_workqueue(void) { }
 static inline int mem_cgroup_init(void) { return 0; }
 #endif /* CONFIG_MEMCG */
 
-/*
- * Extended information for slab objects stored as an array in page->memcg_data
- * if MEMCG_DATA_OBJEXTS is set.
- */
-struct slabobj_ext {
-#ifdef CONFIG_MEMCG
-	struct obj_cgroup *objcg;
-#endif
-#ifdef CONFIG_MEM_ALLOC_PROFILING
-	union codetag_ref ref;
-#endif
-} __aligned(8);
-
 static inline struct lruvec *parent_lruvec(struct lruvec *lruvec)
 {
 	struct mem_cgroup *memcg;
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 32c9f8ed7ae205..e1915026e03040 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -45,6 +45,7 @@ enum _slab_flag_bits {
 #endif
 #ifdef CONFIG_MEMCG
 	_SLAB_ACCOUNT,
+	_SLAB_MAY_ACCOUNT,
 #endif
 #ifdef CONFIG_KASAN_GENERIC
 	_SLAB_KASAN,
@@ -204,8 +205,10 @@ enum _slab_flag_bits {
  */
 #ifdef CONFIG_MEMCG
 # define SLAB_ACCOUNT		__SLAB_FLAG_BIT(_SLAB_ACCOUNT)
+# define SLAB_MAY_ACCOUNT	__SLAB_FLAG_BIT(_SLAB_MAY_ACCOUNT)
 #else
 # define SLAB_ACCOUNT		__SLAB_FLAG_UNUSED
+# define SLAB_MAY_ACCOUNT	__SLAB_FLAG_UNUSED
 #endif
 
 #ifdef CONFIG_KASAN_GENERIC
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 6577bd76954eb4..90925c646c4c24 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -636,11 +636,6 @@ static unsigned long kfence_init_pool(void)
 
 		page = pfn_to_page(start_pfn + i);
 		__SetPageSlab(page);
-#ifdef CONFIG_MEMCG
-		struct slab *slab = page_slab(page);
-		slab->obj_exts = (unsigned long)&kfence_metadata_init[i / 2 - 1].obj_exts |
-				 MEMCG_DATA_OBJEXTS;
-#endif
 	}
 
 	/*
@@ -704,10 +699,6 @@ static unsigned long kfence_init_pool(void)
 			continue;
 
 		page = pfn_to_page(start_pfn + i);
-#ifdef CONFIG_MEMCG
-		struct slab *slab = page_slab(page);
-		slab->obj_exts = 0;
-#endif
 		__ClearPageSlab(page);
 	}
 
@@ -1248,9 +1239,6 @@ void __kfence_free(void *addr)
 {
 	struct kfence_metadata *meta = addr_to_metadata((unsigned long)addr);
 
-#ifdef CONFIG_MEMCG
-	KFENCE_WARN_ON(meta->obj_exts.objcg);
-#endif
 	/*
 	 * If the objects of the cache are SLAB_TYPESAFE_BY_RCU, defer freeing
 	 * the object, as the object page may be recycled for other-typed
diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h
index 1f618f9b0d12d9..e6b4bf349ff730 100644
--- a/mm/kfence/kfence.h
+++ b/mm/kfence/kfence.h
@@ -102,9 +102,6 @@ struct kfence_metadata {
 	struct kfence_track free_track __guarded_by(&lock);
 	/* For updating alloc_covered on frees. */
 	u32 alloc_stack_hash __guarded_by(&lock);
-#ifdef CONFIG_MEMCG
-	struct slabobj_ext obj_exts;
-#endif
 };
 
 #define KFENCE_METADATA_SIZE PAGE_ALIGN(sizeof(struct kfence_metadata) * \
diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c
index de2d0f7d62b15e..9867c03ef0ae3d 100644
--- a/mm/kfence/kfence_test.c
+++ b/mm/kfence/kfence_test.c
@@ -295,7 +295,7 @@ static void *test_alloc(struct kunit *test, size_t size, gfp_t gfp, enum allocat
 			 * memcg accounting works correctly.
 			 */
 			KUNIT_EXPECT_EQ(test, obj_to_index(s, slab, alloc), 0U);
-			KUNIT_EXPECT_EQ(test, objs_per_slab(s, slab), 1);
+			KUNIT_EXPECT_EQ(test, ((unsigned int)slab->objects), 1);
 
 			if (policy == ALLOCATE_ANY)
 				return alloc;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6dc4888a90f3fd..6b51ddf6dfe022 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2865,18 +2865,19 @@ struct mem_cgroup *mem_cgroup_from_obj_slab(struct slab *slab, void *p)
 	 */
 	unsigned long obj_exts;
 	struct slabobj_ext *obj_ext;
-	unsigned int off;
+	struct obj_cgroup *objcg;
 
 	obj_exts = slab_obj_exts(slab);
 	if (!obj_exts)
 		return NULL;
 
-	get_slab_obj_exts(obj_exts);
-	off = obj_to_index(slab->slab_cache, slab, p);
-	obj_ext = slab_obj_ext(slab, obj_exts, off);
-	if (obj_ext->objcg) {
-		struct obj_cgroup *objcg = obj_ext->objcg;
+	if (!slab_needs_objcg(slab))
+		return NULL;
 
+	get_slab_obj_exts(obj_exts);
+	obj_ext = slab_obj_ext(slab->slab_cache, slab, obj_exts, p);
+	objcg = slab_obj_ext_objcg(obj_ext);
+	if (objcg) {
 		put_slab_obj_exts(obj_exts);
 		return obj_cgroup_memcg(objcg);
 	}
@@ -3541,7 +3542,6 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
 	size_t obj_size = obj_full_size(s);
 	struct obj_cgroup *objcg;
 	struct slab *slab;
-	unsigned long off;
 	size_t i;
 
 	/*
@@ -3583,11 +3583,16 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
 
 		slab = virt_to_slab(p[i]);
 
-		if (!slab_obj_exts(slab) &&
-		    alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags)) {
-			continue;
+		if (!slab_obj_exts(slab)) {
+			if (is_kfence_address(p[i]))
+				continue;
+			if (alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags))
+				continue;
 		}
 
+		if (IS_ENABLED(CONFIG_DEBUG_VM) && WARN_ON_ONCE(!slab_needs_objcg(slab)))
+			continue;
+
 		/*
 		 * if we fail and size is 1, memcg_alloc_abort_single() will
 		 * just free the object, which is ok as we have not assigned
@@ -3616,10 +3621,11 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
 
 		obj_exts = slab_obj_exts(slab);
 		get_slab_obj_exts(obj_exts);
-		off = obj_to_index(s, slab, p[i]);
-		obj_ext = slab_obj_ext(slab, obj_exts, off);
+		obj_ext = slab_obj_ext(s, slab, obj_exts, p[i]);
+
 		obj_cgroup_get(objcg);
-		obj_ext->objcg = objcg;
+		slab_obj_ext_set_objcg(obj_ext, objcg);
+
 		put_slab_obj_exts(obj_exts);
 	}
 
@@ -3635,15 +3641,13 @@ void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,
 		struct obj_cgroup *objcg;
 		struct slabobj_ext *obj_ext;
 		struct obj_stock_pcp *stock;
-		unsigned int off;
 
-		off = obj_to_index(s, slab, p[i]);
-		obj_ext = slab_obj_ext(slab, obj_exts, off);
-		objcg = obj_ext->objcg;
+		obj_ext = slab_obj_ext(s, slab, obj_exts, p[i]);
+		objcg = slab_obj_ext_objcg(obj_ext);
 		if (!objcg)
 			continue;
 
-		obj_ext->objcg = NULL;
+		slab_obj_ext_set_objcg(obj_ext, NULL);
 
 		stock = trylock_stock();
 		__refill_obj_stock(objcg, stock, obj_size, true);
diff --git a/mm/slab.h b/mm/slab.h
index f5e336b6b6b04c..04600f57b40146 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -81,10 +81,11 @@ struct freelist_counters {
 #ifdef CONFIG_64BIT
 					/*
 					 * Some optimizations use free bits in 'counters' field
-					 * to save memory. In case ->stride field is not available,
-					 * such optimizations are disabled.
+					 * to save memory or CPU. If these free bits are not
+					 * available, such optimizations are disabled.
 					 */
-					unsigned int stride;
+					unsigned obj_exts_in_object:1;
+					unsigned obj_exts_needs_objcg:1;
 #endif
 				};
 			};
@@ -330,12 +331,6 @@ static inline unsigned int obj_to_index(const struct kmem_cache *cache,
 	return __obj_to_index(cache, slab_address(slab), obj);
 }
 
-static inline int objs_per_slab(const struct kmem_cache *cache,
-				const struct slab *slab)
-{
-	return slab->objects;
-}
-
 /*
  * State of the slab allocator.
  *
@@ -555,6 +550,93 @@ static inline bool need_kmalloc_no_objext(void)
 	return false;
 }
 
+/*
+ * Extended information for slab objects stored as a pointer to an array in
+ * slab->obj_exts (aliasing page->memcg_data) if MEMCG_DATA_OBJEXTS is set.
+ */
+struct slabobj_ext {
+	/*
+	 * All elements of the union should be pointer-sized to avoid memory
+	 * waste
+	 */
+	union {
+#ifdef CONFIG_MEMCG
+		struct obj_cgroup *_objcg;
+#endif
+#ifdef CONFIG_MEM_ALLOC_PROFILING
+		union codetag_ref _ctref;
+#endif
+	};
+} __aligned(8);
+
+#ifdef CONFIG_MEM_ALLOC_PROFILING
+DECLARE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
+			 slab_obj_ext_has_codetag_key);
+
+static inline bool slab_obj_ext_has_codetag(void)
+{
+	return static_branch_maybe(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
+				   &slab_obj_ext_has_codetag_key);
+}
+#else
+static inline bool slab_obj_ext_has_codetag(void)
+{
+	return false;
+}
+#endif
+
+#ifdef CONFIG_MEMCG
+static inline bool cache_needs_objcg(struct kmem_cache *cache)
+{
+	return (cache->flags & SLAB_MAY_ACCOUNT);
+}
+
+static inline bool slab_needs_objcg(struct slab *slab)
+{
+#ifdef CONFIG_64BIT
+	return slab->obj_exts_needs_objcg;
+#else
+	return cache_needs_objcg(slab->slab_cache);
+#endif
+}
+#else
+static inline bool cache_needs_objcg(struct kmem_cache *cache)
+{
+	return false;
+}
+
+static inline bool slab_needs_objcg(struct slab *slab)
+{
+	return false;
+}
+#endif
+
+static inline size_t cache_obj_ext_size(struct kmem_cache *s)
+{
+	size_t sz = 0;
+
+	if (cache_needs_objcg(s))
+		sz += 1;
+
+	if (slab_obj_ext_has_codetag())
+		sz += 1;
+
+	return sizeof(struct slabobj_ext) * sz;
+}
+
+static inline size_t slab_obj_ext_size(struct slab *slab)
+{
+	size_t sz = 0;
+
+	if (slab_needs_objcg(slab))
+		sz += 1;
+
+	if (slab_obj_ext_has_codetag())
+		sz += 1;
+
+	return sizeof(struct slabobj_ext) * sz;
+}
+
 #ifdef CONFIG_SLAB_OBJ_EXT
 
 /*
@@ -572,7 +654,7 @@ static inline bool need_kmalloc_no_objext(void)
  * obj_exts = slab_obj_exts(slab);
  * if (obj_exts) {
  *         get_slab_obj_exts(obj_exts);
- *         obj_ext = slab_obj_ext(slab, obj_exts, obj_to_index(s, slab, obj));
+ *         obj_ext = slab_obj_ext(s, slab, obj_exts, obj);
  *         // do something with obj_ext
  *         put_slab_obj_exts(obj_exts);
  * }
@@ -610,48 +692,86 @@ static inline void put_slab_obj_exts(unsigned long obj_exts)
 }
 
 #ifdef CONFIG_64BIT
-static inline void slab_set_stride(struct slab *slab, unsigned int stride)
+static inline bool obj_exts_in_object(struct slab *slab)
 {
-	slab->stride = stride;
-}
-static inline unsigned int slab_get_stride(struct slab *slab)
-{
-	return slab->stride;
+	/*
+	 * Note we cannot rely on the SLAB_OBJ_EXT_IN_OBJ flag here and need to
+	 * check the per-slab bit. A cache can have SLAB_OBJ_EXT_IN_OBJ set, but
+	 * allocations within_slab_leftover are preferred. And those may be
+	 * possible or not depending on the particular slab's size.
+	 */
+	return slab->obj_exts_in_object;
 }
 #else
-static inline void slab_set_stride(struct slab *slab, unsigned int stride)
-{
-	VM_WARN_ON_ONCE(stride != sizeof(struct slabobj_ext));
-}
-static inline unsigned int slab_get_stride(struct slab *slab)
+static inline bool obj_exts_in_object(struct slab *slab)
 {
-	return sizeof(struct slabobj_ext);
+	return false;
 }
 #endif
 
 /*
  * slab_obj_ext - get the pointer to the slab object extension metadata
  * associated with an object in a slab.
+ * @s: cache that the slab belongs to
  * @slab: a pointer to the slab struct
  * @obj_exts: a pointer to the object extension vector
- * @index: an index of the object
+ * @obj: a pointer to the object
  *
  * Returns a pointer to the object extension associated with the object.
  * Must be called within a section covered by get/put_slab_obj_exts().
  */
-static inline struct slabobj_ext *slab_obj_ext(struct slab *slab,
-					       unsigned long obj_exts,
-					       unsigned int index)
+static inline struct slabobj_ext *
+slab_obj_ext(struct kmem_cache *s, struct slab *slab, unsigned long obj_exts,
+	     const void *obj)
 {
 	struct slabobj_ext *obj_ext;
+	unsigned int index;
+	unsigned int stride;
 
 	VM_WARN_ON_ONCE(obj_exts != slab_obj_exts(slab));
 
-	obj_ext = (struct slabobj_ext *)(obj_exts +
-					 slab_get_stride(slab) * index);
+	/*
+	 * KFENCE objects have NULL obj_exts and thus can't reach this
+	 * and we don't need obj_to_index()
+	 */
+	index = __obj_to_index(s, slab_address(slab), obj);
+
+	if (!obj_exts_in_object(slab))
+		stride = slab_obj_ext_size(slab);
+	else
+		stride = s->size;
+
+	obj_ext = (struct slabobj_ext *)(obj_exts + index * stride);
+
 	return kasan_reset_tag(obj_ext);
 }
 
+#ifdef CONFIG_MEMCG
+static inline struct obj_cgroup *slab_obj_ext_objcg(struct slabobj_ext *obj_ext)
+{
+	/* if objcg exists, it comes first, so we don't need to do anything */
+	return obj_ext->_objcg;
+}
+
+static inline void slab_obj_ext_set_objcg(struct slabobj_ext *obj_ext,
+					  struct obj_cgroup *objcg)
+{
+	/* if objcg exists, it comes first, so we don't need to do anything */
+	obj_ext->_objcg = objcg;
+}
+#endif
+
+#ifdef CONFIG_MEM_ALLOC_PROFILING
+static inline union codetag_ref *
+slab_obj_ext_codetag_ref(struct slab *slab, struct slabobj_ext *obj_ext)
+{
+	if (slab_needs_objcg(slab))
+		obj_ext += 1;
+
+	return &obj_ext->_ctref;
+}
+#endif
+
 int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 			gfp_t gfp, unsigned int alloc_flags);
 
@@ -662,16 +782,17 @@ static inline unsigned long slab_obj_exts(struct slab *slab)
 	return 0;
 }
 
-static inline struct slabobj_ext *slab_obj_ext(struct slab *slab,
-					       unsigned long obj_exts,
-					       unsigned int index)
+static inline struct slabobj_ext *
+slab_obj_ext(struct kmem_cache *s, struct slab *slab, unsigned long obj_exts,
+	     const void *obj)
 {
 	return NULL;
 }
 
-static inline void slab_set_stride(struct slab *slab, unsigned int stride) { }
-static inline unsigned int slab_get_stride(struct slab *slab) { return 0; }
-
+static inline bool obj_exts_in_object(struct slab *slab)
+{
+	return false;
+}
 
 #endif /* CONFIG_SLAB_OBJ_EXT */
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 03ecac12cd865f..1e1d3feec3535b 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -52,7 +52,7 @@ struct kmem_cache *kmem_cache;
 		SLAB_OBJ_EXT_IN_OBJ)
 
 #define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | \
-			 SLAB_CACHE_DMA32 | SLAB_ACCOUNT)
+			 SLAB_CACHE_DMA32 | SLAB_ACCOUNT | SLAB_MAY_ACCOUNT)
 
 /*
  * Merge control. If this is set then no merging of slab caches will occur.
@@ -359,6 +359,13 @@ struct kmem_cache *__kmem_cache_create_args(const char *name,
 		goto out_unlock;
 	}
 
+	/*
+	 * For now we assume any cache can be used with __GFP_ACCOUNT and thus
+	 * may need to store objcg pointers for objects
+	 */
+	if (!mem_cgroup_kmem_disabled())
+		flags |= SLAB_MAY_ACCOUNT;
+
 	/* Fail closed on bad usersize of useroffset values. */
 	if (!IS_ENABLED(CONFIG_HARDENED_USERCOPY) ||
 	    WARN_ON(!args->usersize && args->useroffset) ||
@@ -984,11 +991,20 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type)
 #endif
 
 	/*
-	 * If CONFIG_MEMCG is enabled, disable cache merging for
-	 * KMALLOC_NORMAL caches.
+	 * If memcg_kmem is enabled and this is a KMALLOC_NORMAL cache and not
+	 * aliased with any other type, make sure it's never merged with any other
+	 * cache.
+	 *
+	 * In other cases the kmalloc cache may end up being used for a
+	 * __GFP_ACCOUNT allocation so mark it as such. The exception is a
+	 * KMALLOC_NO_OBJ_EXT cache.
 	 */
-	if (IS_ENABLED(CONFIG_MEMCG) && (type == KMALLOC_NORMAL))
-		flags |= SLAB_NO_MERGE;
+	if (!mem_cgroup_kmem_disabled()) {
+		if (type == KMALLOC_NORMAL && KMALLOC_RECLAIM != KMALLOC_NORMAL)
+			flags |= SLAB_NO_MERGE;
+		else if (!(flags & SLAB_NO_OBJ_EXT))
+			flags |= SLAB_MAY_ACCOUNT;
+	}
 
 	if (minalign > ARCH_KMALLOC_MINALIGN) {
 		aligned_size = ALIGN(aligned_size, minalign);
diff --git a/mm/slub.c b/mm/slub.c
index 0337e60db5ace0..94b744e5ac7919 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -213,6 +213,11 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
 static DEFINE_STATIC_KEY_FALSE(strict_numa);
 #endif
 
+#ifdef CONFIG_MEM_ALLOC_PROFILING
+DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
+			slab_obj_ext_has_codetag_key);
+#endif
+
 /* Structure holding extra parameters for slab allocations */
 struct slab_alloc_context {
 	unsigned long caller_addr;
@@ -803,7 +808,7 @@ static inline bool need_slab_obj_exts(struct kmem_cache *s)
 
 static inline unsigned int obj_exts_size_in_slab(struct slab *slab)
 {
-	return sizeof(struct slabobj_ext) * slab->objects;
+	return slab_obj_ext_size(slab) * slab->objects;
 }
 
 static inline unsigned long obj_exts_offset_in_slab(struct kmem_cache *s,
@@ -870,18 +875,6 @@ static inline bool obj_exts_in_slab(struct kmem_cache *s, struct slab *slab)
 #endif
 
 #if defined(CONFIG_SLAB_OBJ_EXT) && defined(CONFIG_64BIT)
-static bool obj_exts_in_object(struct kmem_cache *s, struct slab *slab)
-{
-	/*
-	 * Note we cannot rely on the SLAB_OBJ_EXT_IN_OBJ flag here and need to
-	 * check the stride. A cache can have SLAB_OBJ_EXT_IN_OBJ set, but
-	 * allocations within_slab_leftover are preferred. And those may be
-	 * possible or not depending on the particular slab's size.
-	 */
-	return obj_exts_in_slab(s, slab) &&
-	       (slab_get_stride(slab) == s->size);
-}
-
 static unsigned int obj_exts_offset_in_object(struct kmem_cache *s)
 {
 	unsigned int offset = get_info_end(s);
@@ -896,16 +889,20 @@ static unsigned int obj_exts_offset_in_object(struct kmem_cache *s)
 
 	return offset;
 }
-#else
-static inline bool obj_exts_in_object(struct kmem_cache *s, struct slab *slab)
+
+static inline void slab_set_obj_exts_in_object(struct slab *slab)
 {
-	return false;
+	slab->obj_exts_in_object = 1;
 }
-
+#else
 static inline unsigned int obj_exts_offset_in_object(struct kmem_cache *s)
 {
 	return 0;
 }
+
+static inline void slab_set_obj_exts_in_object(struct slab *slab)
+{
+}
 #endif
 
 #ifdef CONFIG_SLUB_DEBUG
@@ -1206,8 +1203,8 @@ static void print_trailer(struct kmem_cache *s, struct slab *slab, u8 *p)
 
 	off += kasan_metadata_size(s, false);
 
-	if (obj_exts_in_object(s, slab))
-		off += sizeof(struct slabobj_ext);
+	if (obj_exts_in_object(slab))
+		off += slab_obj_ext_size(slab);
 
 	if (off != size_from_object(s))
 		/* Beginning of the filler is the free pointer */
@@ -1411,8 +1408,8 @@ static int check_pad_bytes(struct kmem_cache *s, struct slab *slab, u8 *p)
 
 	off += kasan_metadata_size(s, false);
 
-	if (obj_exts_in_object(s, slab))
-		off += sizeof(struct slabobj_ext);
+	if (obj_exts_in_object(slab))
+		off += slab_obj_ext_size(slab);
 
 	if (size_from_object(s) == off)
 		return 1;
@@ -1439,7 +1436,7 @@ slab_pad_check(struct kmem_cache *s, struct slab *slab)
 	length = slab_size(slab);
 	end = start + length;
 
-	if (obj_exts_in_slab(s, slab) && !obj_exts_in_object(s, slab)) {
+	if (obj_exts_in_slab(s, slab) && !obj_exts_in_object(slab)) {
 		remainder = length;
 		remainder -= obj_exts_offset_in_slab(s, slab);
 		remainder -= obj_exts_size_in_slab(slab);
@@ -2070,20 +2067,21 @@ static inline void mark_obj_codetag_empty(const void *obj)
 	obj_slab = virt_to_slab(obj);
 	slab_exts = slab_obj_exts(obj_slab);
 	if (slab_exts) {
+		struct slabobj_ext *ext;
+		union codetag_ref *ref;
+
 		get_slab_obj_exts(slab_exts);
-		unsigned int offs = obj_to_index(obj_slab->slab_cache,
-						 obj_slab, obj);
-		struct slabobj_ext *ext = slab_obj_ext(obj_slab,
-						       slab_exts, offs);
+		ext = slab_obj_ext(obj_slab->slab_cache, obj_slab, slab_exts, obj);
+		ref = slab_obj_ext_codetag_ref(obj_slab, ext);
 
-		if (unlikely(is_codetag_empty(&ext->ref))) {
+		if (unlikely(is_codetag_empty(ref))) {
 			put_slab_obj_exts(slab_exts);
 			return;
 		}
 
 		/* codetag should be NULL here */
-		WARN_ON(ext->ref.ct);
-		set_codetag_empty(&ext->ref);
+		WARN_ON(ref->ct);
+		set_codetag_empty(ref);
 		put_slab_obj_exts(slab_exts);
 	}
 }
@@ -2093,19 +2091,29 @@ static inline bool mark_failed_objexts_alloc(struct slab *slab)
 	return cmpxchg(&slab->obj_exts, 0, OBJEXTS_ALLOC_FAIL) == 0;
 }
 
-static inline void handle_failed_objexts_alloc(unsigned long obj_exts,
-			struct slabobj_ext *vec, unsigned int objects)
+static inline void handle_failed_objexts_alloc(struct slab *slab,
+		unsigned long obj_exts, struct slabobj_ext *vec)
 {
+	unsigned int stride;
+
+	if (!slab_obj_ext_has_codetag())
+		return;
+
 	/*
 	 * If vector previously failed to allocate then we have live
 	 * objects with no tag reference. Mark all references in this
 	 * vector as empty to avoid warnings later on.
 	 */
-	if (obj_exts == OBJEXTS_ALLOC_FAIL) {
-		unsigned int i;
+	if (obj_exts != OBJEXTS_ALLOC_FAIL)
+		return;
+
+	stride = slab_obj_ext_size(slab) / sizeof(*vec);
+
+	for (unsigned int i = 0; i < slab->objects; i++) {
+		union codetag_ref *ref = slab_obj_ext_codetag_ref(slab, vec);
 
-		for (i = 0; i < objects; i++)
-			set_codetag_empty(&vec[i].ref);
+		set_codetag_empty(ref);
+		vec += stride;
 	}
 }
 
@@ -2113,8 +2121,8 @@ static inline void handle_failed_objexts_alloc(unsigned long obj_exts,
 
 static inline void mark_obj_codetag_empty(const void *obj) {}
 static inline bool mark_failed_objexts_alloc(struct slab *slab) { return false; }
-static inline void handle_failed_objexts_alloc(unsigned long obj_exts,
-			struct slabobj_ext *vec, unsigned int objects) {}
+static inline void handle_failed_objexts_alloc(struct slab *slab,
+		unsigned long obj_exts, struct slabobj_ext *vec) {}
 
 #endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */
 
@@ -2127,12 +2135,11 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 			gfp_t gfp, unsigned int alloc_flags)
 {
 	const bool allow_spin = alloc_flags_allow_spinning(alloc_flags);
-	unsigned int objects = objs_per_slab(s, slab);
 	bool new_slab = alloc_flags & SLAB_ALLOC_NEW_SLAB;
 	unsigned long new_exts;
 	unsigned long old_exts;
 	struct slabobj_ext *vec;
-	size_t sz = sizeof(struct slabobj_ext) * slab->objects;
+	size_t sz = slab_obj_ext_size(slab) * slab->objects;
 
 	gfp &= ~OBJCGS_CLEAR_MASK;
 	/*
@@ -2183,7 +2190,7 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 #endif
 retry:
 	old_exts = READ_ONCE(slab->obj_exts);
-	handle_failed_objexts_alloc(old_exts, vec, objects);
+	handle_failed_objexts_alloc(slab, old_exts, vec);
 
 	if (new_slab) {
 		/*
@@ -2250,9 +2257,6 @@ static void alloc_slab_obj_exts_early(struct kmem_cache *s, struct slab *slab)
 	void *addr;
 	unsigned long obj_exts;
 
-	/* Initialize stride early to avoid memory ordering issues */
-	slab_set_stride(slab, sizeof(struct slabobj_ext));
-
 	if (!need_slab_obj_exts(s))
 		return;
 
@@ -2278,15 +2282,14 @@ static void alloc_slab_obj_exts_early(struct kmem_cache *s, struct slab *slab)
 
 		get_slab_obj_exts(obj_exts);
 		for_each_object(addr, s, slab_address(slab), slab->objects)
-			memset(kasan_reset_tag(addr) + offset, 0,
-			       sizeof(struct slabobj_ext));
+			memset(kasan_reset_tag(addr) + offset, 0, slab_obj_ext_size(slab));
 		put_slab_obj_exts(obj_exts);
 
 #ifdef CONFIG_MEMCG
 		obj_exts |= MEMCG_DATA_OBJEXTS;
 #endif
 		slab->obj_exts = obj_exts;
-		slab_set_stride(slab, s->size);
+		slab_set_obj_exts_in_object(slab);
 	}
 }
 
@@ -2323,11 +2326,15 @@ static inline unsigned long
 prepare_slab_obj_exts_hook(struct kmem_cache *s, struct slab *slab,
 			   gfp_t flags, unsigned int alloc_flags, void *p)
 {
-	if (!slab_obj_exts(slab) &&
-	    alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {
-		pr_warn_once("%s, %s: Failed to create slab extension vector!\n",
-			     __func__, s->name);
-		return 0;
+	if (!slab_obj_exts(slab)) {
+		if (is_kfence_address(p))
+			return 0;
+
+		if (alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {
+			pr_warn_once("%s, %s: Failed to create slab extension vector!\n",
+				     __func__, s->name);
+			return 0;
+		}
 	}
 
 	return slab_obj_exts(slab);
@@ -2360,14 +2367,24 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags,
 	 * check should be added before alloc_tag_add().
 	 */
 	if (obj_exts) {
-		unsigned int obj_idx = obj_to_index(s, slab, object);
+		union codetag_ref *ref;
 
 		get_slab_obj_exts(obj_exts);
-		obj_ext = slab_obj_ext(slab, obj_exts, obj_idx);
-		alloc_tag_add(&obj_ext->ref, current->alloc_tag, s->size);
+
+		obj_ext = slab_obj_ext(s, slab, obj_exts, object);
+		ref = slab_obj_ext_codetag_ref(slab, obj_ext);
+
+		alloc_tag_add(ref, current->alloc_tag, s->size);
+
 		put_slab_obj_exts(obj_exts);
 	} else {
-		alloc_tag_set_inaccurate(current->alloc_tag);
+		/*
+		 * KFENCE allocations are rare and the amount of outstanding
+		 * ones is limited to a small number so it's not worth setting
+		 * tags as inaccurate because of them.
+		 */
+		if (!is_kfence_address(object))
+			alloc_tag_set_inaccurate(current->alloc_tag);
 	}
 }
 
@@ -2384,7 +2401,6 @@ static noinline void
 __alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,
 			       int objects)
 {
-	int i;
 	unsigned long obj_exts;
 
 	/* slab->obj_exts might not be NULL if it was created for MEMCG accounting. */
@@ -2396,10 +2412,11 @@ __alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p
 		return;
 
 	get_slab_obj_exts(obj_exts);
-	for (i = 0; i < objects; i++) {
-		unsigned int off = obj_to_index(s, slab, p[i]);
+	for (int i = 0; i < objects; i++) {
+		struct slabobj_ext *ext;
 
-		alloc_tag_sub(&slab_obj_ext(slab, obj_exts, off)->ref, s->size);
+		ext = slab_obj_ext(s, slab, obj_exts, p[i]);
+		alloc_tag_sub(slab_obj_ext_codetag_ref(slab, ext), s->size);
 	}
 	put_slab_obj_exts(obj_exts);
 }
@@ -2412,6 +2429,25 @@ alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,
 		__alloc_tagging_slab_free_hook(s, slab, p, objects);
 }
 
+/*
+ * Make sure the static key used by slab_obj_ext_has_codetag() reflects the
+ * value of !mem_alloc_profiling_permanently_disabled()
+ *
+ * Any later mem alloc profiling shutdown won't be reflected in the static key
+ * because obj_exts with codetags might already exist.
+ */
+static void __init slab_obj_ext_has_codetag_init(void)
+{
+	bool need_codetag = !mem_alloc_profiling_permanently_disabled();
+
+	if (need_codetag != static_key_enabled(&slab_obj_ext_has_codetag_key)) {
+		if (need_codetag)
+			static_branch_enable(&slab_obj_ext_has_codetag_key);
+		else
+			static_branch_disable(&slab_obj_ext_has_codetag_key);
+	}
+}
+
 #else /* CONFIG_MEM_ALLOC_PROFILING */
 
 static inline void
@@ -2426,6 +2462,10 @@ alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,
 {
 }
 
+static inline void slab_obj_ext_has_codetag_init(void)
+{
+}
+
 #endif /* CONFIG_MEM_ALLOC_PROFILING */
 
 
@@ -2471,6 +2511,9 @@ void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,
 	if (likely(!obj_exts))
 		return;
 
+	if (!slab_needs_objcg(slab))
+		return;
+
 	get_slab_obj_exts(obj_exts);
 	__memcg_slab_free_hook(s, slab, p, objects, obj_exts);
 	put_slab_obj_exts(obj_exts);
@@ -2484,7 +2527,6 @@ bool memcg_slab_post_charge(void *p, gfp_t flags)
 	struct kmem_cache *s;
 	struct page *page;
 	struct slab *slab;
-	unsigned long off;
 
 	page = virt_to_page(p);
 	if (PageLargeKmalloc(page)) {
@@ -2517,16 +2559,15 @@ bool memcg_slab_post_charge(void *p, gfp_t flags)
 	 * of slab_obj_exts being allocated from the same slab and thus the slab
 	 * becoming effectively unfreeable.
 	 */
-	if (is_kmalloc_normal(s))
+	if (!cache_needs_objcg(s))
 		return true;
 
 	/* Ignore already charged objects. */
 	obj_exts = slab_obj_exts(slab);
 	if (obj_exts) {
 		get_slab_obj_exts(obj_exts);
-		off = obj_to_index(s, slab, p);
-		obj_ext = slab_obj_ext(slab, obj_exts, off);
-		if (unlikely(obj_ext->objcg)) {
+		obj_ext = slab_obj_ext(s, slab, obj_exts, p);
+		if (unlikely(slab_obj_ext_objcg(obj_ext))) {
 			put_slab_obj_exts(obj_exts);
 			return true;
 		}
@@ -3391,10 +3432,15 @@ static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags,
 		stat(s, ORDER_FALLBACK);
 	}
 
+	/* Initializes frozen, inuse, and any extra 64bit-only flags */
+	slab->counters = 0;
+
 	slab->objects = oo_objects(oo);
-	slab->inuse = 0;
-	slab->frozen = 0;
 
+#ifdef CONFIG_64BIT
+	if (cache_needs_objcg(s))
+		slab->obj_exts_needs_objcg = 1;
+#endif
 	slab->slab_cache = s;
 
 	kasan_poison_slab(slab);
@@ -6526,7 +6572,7 @@ static inline size_t slab_ksize(struct slab *slab)
 	 */
 	if (s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_STORE_USER))
 		return s->inuse;
-	else if (obj_exts_in_object(s, slab))
+	else if (obj_exts_in_object(slab))
 		return s->inuse;
 	/*
 	 * Else we can use all the padding etc for the allocation
@@ -7929,7 +7975,7 @@ static int calculate_sizes(struct kmem_cache_args *args, struct kmem_cache *s)
 	aligned_size = ALIGN(size, s->align);
 #if defined(CONFIG_SLAB_OBJ_EXT) && defined(CONFIG_64BIT)
 	if (slab_args_unmergeable(args, s->flags) &&
-			(aligned_size - size >= sizeof(struct slabobj_ext)))
+			(aligned_size - size >= cache_obj_ext_size(s)))
 		s->flags |= SLAB_OBJ_EXT_IN_OBJ;
 #endif
 	size = aligned_size;
@@ -8539,6 +8585,8 @@ void __init kmem_cache_init(void)
 		boot_kmem_cache_node;
 	int node;
 
+	slab_obj_ext_has_codetag_init();
+
 	if (debug_guardpage_minorder())
 		slub_max_order = 0;

gemini-3.1-pro-preview

							input: 13750
							output: 54
							thoughts: 1033

**Analyzing the SLUB Object Extension Patch**

Okay, so I'm looking at this kernel patch, and it's making some substantial changes to how `slabobj_ext` is handled in the SLUB allocator. My first thought is: this looks like a significant functional change to the core memory management. We're dealing with how object extensions are allocated, accessed, and managed, so this absolutely *needs* fuzzing.

The changes are centered around `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING`. The way `slabobj_ext` is defined initially confused me, as the union structure seemed to suggest that if both features were enabled, they would share the same memory. But, no, it looks like it's actually an array of `slabobj_ext` elements per object. If `CONFIG_MEMCG` is enabled, the first element will be used for `objcg`, and then `codetag_ref` goes in the second. The size of `slabobj_ext` is 8 bytes, and `slab_obj_ext_size` returns `sizeof(struct slabobj_ext) * sz` where `sz` is either 1 or 2 depending on the need.

This implies that there's a good amount of extra memory use if `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING` are both enabled.

Let's identify the key functions that are modified or newly introduced. I'm focusing on the exposed symbols – things that other parts of the kernel might be calling. We've got `alloc_slab_obj_exts`, the inline `slab_obj_ext`, `prepare_slab_obj_exts_hook`, `__alloc_tagging_slab_alloc_hook`, `__alloc_tagging_slab_free_hook`, `memcg_slab_post_charge`, `__memcg_slab_post_alloc_hook`, `__memcg_slab_free_hook`, and `kmem_cache_create` (indirectly via `__kmem_cache_create_args`), plus `kmem_cache_alloc` and `kmem_cache_free` via hooks.

Now, let's hunt for any non-static functions in relevant files. I'm checking `mm/slub.c`, `mm/slab_common.c`, and `mm/memcontrol.c`. I've confirmed that `alloc_slab_obj_exts` is non-static in `mm/slub.c`, and so are `memcg_slab_post_charge`, and the `__memcg_slab_post_alloc_hook` and `__memcg_slab_free_hook` hooks. We also need to check `mm/memcontrol.c` and confirm that `mem_cgroup_from_obj_slab` is non-static. Finally, `__kmem_cache_create_args` is non-static in `mm/slab_common.c`.

Also to keep in mind are the configuration options: `CONFIG_MEMCG`, `CONFIG_MEM_ALLOC_PROFILING`, `CONFIG_SLAB_OBJ_EXT` (selected by the above), and `CONFIG_KFENCE`. I should verify these function names, and any other relevant names, later, but these are all starting points.

{
  "Expression": "^(int|void|bool|struct [a-z_]+ \\*?) [a-zA-Z0-9_]+\\(",
  "PathPrefix": "mm/slub.c"
}

{
  "Output": "mm/slub.c=403=static inline\nmm/slub.c:404:void stat_add(const struct kmem_cache *s, enum stat_item si, int v)\nmm/slub.c-405-{\n--\nmm/slub.c=935=static bool slab_add_kunit_errors(void)\n--\nmm/slub.c-950-\nmm/slub.c:951:bool slab_in_kunit_test(void)\nmm/slub.c-952-{\n--\nmm/slub.c=1093=static void print_track(const char *s, struct track *t, unsigned long pr_time)\n--\nmm/slub.c-1110-\nmm/slub.c:1111:void print_tracking(struct kmem_cache *s, void *object)\nmm/slub.c-1112-{\n--\nmm/slub.c=1121=static void print_slab_info(const struct slab *slab)\n--\nmm/slub.c-1127-\nmm/slub.c:1128:void skip_orig_size_check(struct kmem_cache *s, const void *object)\nmm/slub.c-1129-{\n--\nmm/slub.c=1708=static\nmm/slub.c:1709:void setup_slab_debug(struct kmem_cache *s, struct slab *slab, void *addr)\nmm/slub.c-1710-{\n--\nmm/slub.c=2010=static inline\nmm/slub.c:2011:void setup_slab_debug(struct kmem_cache *s, struct slab *slab, void *addr) {}\nmm/slub.c-2012-\n--\nmm/slub.c=2129=static inline void init_slab_obj_exts(struct slab *slab)\n--\nmm/slub.c-2133-\nmm/slub.c:2134:int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,\nmm/slub.c-2135-\t\t\tgfp_t gfp, unsigned int alloc_flags)\n--\nmm/slub.c=2476=static __fastpath_inline\nmm/slub.c:2477:bool memcg_slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,\nmm/slub.c-2478-\t\t\t\tsize_t size, void **p,\n--\nmm/slub.c=2501=static __fastpath_inline\nmm/slub.c:2502:void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,\nmm/slub.c-2503-\t\t\t  int objects)\n--\nmm/slub.c=2522=static __fastpath_inline\nmm/slub.c:2523:bool memcg_slab_post_charge(void *p, gfp_t flags)\nmm/slub.c-2524-{\n--\nmm/slub.c=2636=static __always_inline\nmm/slub.c:2637:bool slab_free_hook(struct kmem_cache *s, void *x, bool init,\nmm/slub.c-2638-\t\t    bool after_rcu_delay)\n--\nmm/slub.c=2721=static __fastpath_inline\nmm/slub.c:2722:bool slab_free_freelist_hook(struct kmem_cache *s, void **head, void **tail,\nmm/slub.c-2723-\t\t\t     int *cnt)\n--\nmm/slub.c=4067=static void flush_rcu_sheaf(struct work_struct *w)\n--\nmm/slub.c-4090-/* needed for kvfree_rcu_barrier() */\nmm/slub.c:4091:void flush_rcu_sheaves_on_cache(struct kmem_cache *s)\nmm/slub.c-4092-{\n--\nmm/slub.c-4121-\nmm/slub.c:4122:void flush_all_rcu_sheaves(void)\nmm/slub.c-4123-{\n--\nmm/slub.c=4591=static __fastpath_inline\nmm/slub.c:4592:bool slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags, size_t size,\nmm/slub.c-4593-\t\t\t  void **p, const struct slab_alloc_context *ac)\n--\nmm/slub.c=5002=EXPORT_SYMBOL(kmem_cache_alloc_lru_noprof);\nmm/slub.c-5003-\nmm/slub.c:5004:bool kmem_cache_charge(void *objp, gfp_t gfpflags)\nmm/slub.c-5005-{\n--\nmm/slub.c=5078=kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size)\n--\nmm/slub.c-5160- */\nmm/slub.c:5161:void kmem_cache_return_sheaf(struct kmem_cache *s, gfp_t gfp,\nmm/slub.c-5162-\t\t\t     struct slab_sheaf *sheaf)\n--\nmm/slub.c-5218- */\nmm/slub.c:5219:int kmem_cache_refill_sheaf(struct kmem_cache *s, gfp_t gfp,\nmm/slub.c-5220-\t\t\t    struct slab_sheaf **sheafp, unsigned int size)\n--\nmm/slub.c=5977=static __fastpath_inline\nmm/slub.c:5978:bool free_to_pcs(struct kmem_cache *s, void *object, bool allow_spin)\nmm/slub.c-5979-{\n--\nmm/slub.c=6071=static DEFINE_WAIT_OVERRIDE_MAP(kfree_rcu_sheaf_map, LD_WAIT_CONFIG);\nmm/slub.c-6072-\nmm/slub.c:6073:bool __kfree_rcu_sheaf(struct kmem_cache *s, void *obj)\nmm/slub.c-6074-{\n--\nmm/slub.c=6395=static void defer_free(struct kmem_cache *s, void *head)\n--\nmm/slub.c-6407-\nmm/slub.c:6408:void defer_free_barrier(void)\nmm/slub.c-6409-{\n--\nmm/slub.c=6416=static __fastpath_inline\nmm/slub.c:6417:void slab_free(struct kmem_cache *s, struct slab *slab, void *object,\nmm/slub.c-6418-\t       unsigned long addr)\n--\nmm/slub.c=6435=static noinline\nmm/slub.c:6436:void memcg_alloc_abort_single(struct kmem_cache *s, void *object)\nmm/slub.c-6437-{\n--\nmm/slub.c=6447=static __fastpath_inline\nmm/slub.c:6448:void slab_free_bulk(struct kmem_cache *s, struct slab *slab, void *head,\nmm/slub.c-6449-\t\t    void *tail, void **p, int cnt, unsigned long addr)\n--\nmm/slub.c=6464=static void slab_free_after_rcu_debug(struct rcu_head *rcu_head)\n--\nmm/slub.c-6492-#ifdef CONFIG_KASAN_GENERIC\nmm/slub.c:6493:void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr)\nmm/slub.c-6494-{\n--\nmm/slub.c=6500=static noinline void warn_free_bad_obj(struct kmem_cache *s, void *obj)\n--\nmm/slub.c-6529- */\nmm/slub.c:6530:void kmem_cache_free(struct kmem_cache *s, void *x)\nmm/slub.c-6531-{\n--\nmm/slub.c=6644=static void free_large_kmalloc(struct page *page, void *object)\n--\nmm/slub.c-6669- */\nmm/slub.c:6670:void kvfree_rcu_cb(struct rcu_head *head)\nmm/slub.c-6671-{\n--\nmm/slub.c-6716- */\nmm/slub.c:6717:void kfree(const void *object)\nmm/slub.c-6718-{\n--\nmm/slub.c=6740=EXPORT_SYMBOL(kfree);\n--\nmm/slub.c-6750- */\nmm/slub.c:6751:void kfree_nolock(const void *object)\nmm/slub.c-6752-{\n--\nmm/slub.c=6983=EXPORT_SYMBOL(__kvmalloc_node_noprof);\n--\nmm/slub.c-6994- */\nmm/slub.c:6995:void kvfree(const void *addr)\nmm/slub.c-6996-{\n--\nmm/slub.c=7002=EXPORT_SYMBOL(kvfree);\n--\nmm/slub.c-7010- */\nmm/slub.c:7011:void kvfree_atomic(const void *addr)\nmm/slub.c-7012-{\n--\nmm/slub.c=7018=EXPORT_SYMBOL(kvfree_atomic);\n--\nmm/slub.c-7028- */\nmm/slub.c:7029:void kvfree_sensitive(const void *addr, size_t len)\nmm/slub.c-7030-{\n--\nmm/slub.c=7087=static inline\nmm/slub.c:7088:int build_detached_freelist(struct kmem_cache *s, size_t size,\nmm/slub.c-7089-\t\t\t    void **p, struct detached_freelist *df)\n--\nmm/slub.c=7152=static void __kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)\n--\nmm/slub.c-7172-/* Note that interrupts must be enabled when calling this function. */\nmm/slub.c:7173:void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)\nmm/slub.c-7174-{\n--\nmm/slub.c=7372=static bool __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,\n--\nmm/slub.c-7421- */\nmm/slub.c:7422:bool kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags,\nmm/slub.c-7423-\t\tsize_t size, void **p)\n--\nmm/slub.c=7738=static void free_kmem_cache_nodes(struct kmem_cache *s)\n--\nmm/slub.c-7760-\nmm/slub.c:7761:void __kmem_cache_release(struct kmem_cache *s)\nmm/slub.c-7762-{\n--\nmm/slub.c=8049=static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)\n--\nmm/slub.c-8069-\nmm/slub.c:8070:bool __kmem_cache_empty(struct kmem_cache *s)\nmm/slub.c-8071-{\n--\nmm/slub.c-8083- */\nmm/slub.c:8084:int __kmem_cache_shutdown(struct kmem_cache *s)\nmm/slub.c-8085-{\n--\nmm/slub.c-8111-#ifdef CONFIG_PRINTK\nmm/slub.c:8112:void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)\nmm/slub.c-8113-{\n--\nmm/slub.c=8236=__core_param_cb(slab_strict_numa, \u0026param_ops_slab_strict_numa, NULL, 0);\n--\nmm/slub.c-8248- */\nmm/slub.c:8249:void __check_heap_object(const void *ptr, unsigned long n,\nmm/slub.c-8250-\t\t\t const struct slab *slab, bool to_user)\n--\nmm/slub.c=8301=static int __kmem_cache_do_shrink(struct kmem_cache *s)\n--\nmm/slub.c-8369-\nmm/slub.c:8370:int __kmem_cache_shrink(struct kmem_cache *s)\nmm/slub.c-8371-{\n--\nmm/slub.c=8646=void __init kmem_cache_init_late(void)\n--\nmm/slub.c-8655-\nmm/slub.c:8656:int do_kmem_cache_create(struct kmem_cache *s, const char *name,\nmm/slub.c-8657-\t\t\t unsigned int size, struct kmem_cache_args *args,\n--\nmm/slub.c=9689=static int sysfs_slab_add(struct kmem_cache *s)\n--\nmm/slub.c-9732-\nmm/slub.c:9733:void sysfs_slab_unlink(struct kmem_cache *s)\nmm/slub.c-9734-{\n--\nmm/slub.c-9738-\nmm/slub.c:9739:void sysfs_slab_release(struct kmem_cache *s)\nmm/slub.c-9740-{\n--\nmm/slub.c=9754=static struct saved_alias *alias_list;\nmm/slub.c-9755-\nmm/slub.c:9756:int sysfs_slab_alias(struct kmem_cache *s, const char *name)\nmm/slub.c-9757-{\n--\nmm/slub.c=9997=static void debugfs_slab_add(struct kmem_cache *s)\n--\nmm/slub.c-10012-\nmm/slub.c:10013:void debugfs_slab_release(struct kmem_cache *s)\nmm/slub.c-10014-{\n--\nmm/slub.c=10031=__initcall(slab_debugfs_init);\n--\nmm/slub.c-10036-#ifdef CONFIG_SLUB_DEBUG\nmm/slub.c:10037:void get_slabinfo(struct kmem_cache *s, struct slabinfo *sinfo)\nmm/slub.c-10038-{\n"
}

gemini-3.1-pro-preview

							input: 19622
							output: 55
							thoughts: 122

**Navigating the Slub Memory Management Landscape**

Okay, so I'm diving into this `slub.c` code and trying to get a handle on how these memory accounting functions interact. My initial understanding was that `alloc_slab_obj_exts`, `memcg_slab_post_charge`, and `memcg_slab_free_hook` are all housed neatly within `mm/slub.c`. But hold on... something feels off about that `memcg_slab_post_charge` location... It *is* in `mm/slub.c`, isn't it? Oh right, I'm forgetting about the patch I'm looking at. Yes, it's modified within `mm/slub.c`, that makes sense.

Now I'm questioning whether I have the full picture. Let me quickly check `mm/slab_common.c` to see if there are any related functions or crucial dependencies lurking there that I might be overlooking. It's always smart to have a wider view when dealing with such core memory management components. I need to be thorough.

{
  "Expression": "^(int|void|bool|struct [a-z_]+ \\*?) [a-zA-Z0-9_]+\\(",
  "PathPrefix": "mm/slab_common.c"
}

{
  "Output": "mm/slab_common.c=128=static unsigned int calculate_alignment(slab_flags_t flags,\n--\nmm/slab_common.c-154- */\nmm/slab_common.c:155:int slab_unmergeable(struct kmem_cache *s)\nmm/slab_common.c-156-{\n--\nmm/slab_common.c-176-\nmm/slab_common.c:177:bool slab_args_unmergeable(struct kmem_cache_args *args, slab_flags_t flags)\nmm/slab_common.c-178-{\n--\nmm/slab_common.c=518=static void kmem_cache_release(struct kmem_cache *s)\n--\nmm/slab_common.c-526-\nmm/slab_common.c:527:void slab_kmem_cache_release(struct kmem_cache *s)\nmm/slab_common.c-528-{\n--\nmm/slab_common.c-533-\nmm/slab_common.c:534:void kmem_cache_destroy(struct kmem_cache *s)\nmm/slab_common.c-535-{\n--\nmm/slab_common.c=598=EXPORT_SYMBOL(kmem_cache_destroy);\n--\nmm/slab_common.c-608- */\nmm/slab_common.c:609:int kmem_cache_shrink(struct kmem_cache *cachep)\nmm/slab_common.c-610-{\n--\nmm/slab_common.c=615=EXPORT_SYMBOL(kmem_cache_shrink);\nmm/slab_common.c-616-\nmm/slab_common.c:617:bool slab_is_available(void)\nmm/slab_common.c-618-{\n--\nmm/slab_common.c=623=static void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)\n--\nmm/slab_common.c-644- */\nmm/slab_common.c:645:bool kmem_dump_obj(void *object)\nmm/slab_common.c-646-{\n--\nmm/slab_common.c=1073=static void freelist_randomize(unsigned int *list,\n--\nmm/slab_common.c-1089-/* Create a random sequence per cache */\nmm/slab_common.c:1090:int cache_random_seq_create(struct kmem_cache *cachep, unsigned int count,\nmm/slab_common.c-1091-\t\t\t\t    gfp_t gfp)\n--\nmm/slab_common.c-1105-/* Destroy the per-cache random freelist sequence */\nmm/slab_common.c:1106:void cache_random_seq_destroy(struct kmem_cache *cachep)\nmm/slab_common.c-1107-{\n--\nmm/slab_common.c=1163=static int slab_show(struct seq_file *m, void *p)\n--\nmm/slab_common.c-1172-\nmm/slab_common.c:1173:void dump_unreclaimable_slab(void)\nmm/slab_common.c-1174-{\n--\nmm/slab_common.c=1245=module_init(slab_proc_init);\n--\nmm/slab_common.c-1259- */\nmm/slab_common.c:1260:void kfree_sensitive(const void *p)\nmm/slab_common.c-1261-{\n--\nmm/slab_common.c=1297=EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);\n--\nmm/slab_common.c-1300-\nmm/slab_common.c:1301:void kvfree_call_rcu(struct rcu_head *head, void *ptr)\nmm/slab_common.c-1302-{\n--\nmm/slab_common.c=1950=void __init kfree_rcu_scheduler_running(void)\n--\nmm/slab_common.c-1973- */\nmm/slab_common.c:1974:void kvfree_call_rcu(struct rcu_head *head, void *ptr)\nmm/slab_common.c-1975-{\n--\nmm/slab_common.c=2050=static inline void __kvfree_rcu_barrier(void)\n--\nmm/slab_common.c-2128- */\nmm/slab_common.c:2129:void kvfree_rcu_barrier(void)\nmm/slab_common.c-2130-{\n--\nmm/slab_common.c=2134=EXPORT_SYMBOL_GPL(kvfree_rcu_barrier);\n--\nmm/slab_common.c-2142- */\nmm/slab_common.c:2143:void kvfree_rcu_barrier_on_cache(struct kmem_cache *s)\nmm/slab_common.c-2144-{\n"
}

gemini-3.1-pro-preview

							input: 21333
							output: 54
							thoughts: 26

Here's my thought process, as if I were reviewing this patch:

**Analyzing the Scope of Changes**

Okay, so this patch touches `mm/memcontrol.c`. That's significant. The memory control subsystem is a critical piece, and any changes there warrant a *very* close look. I need to be sure the rationale behind this modification is sound, and I understand how it interacts with the existing memory management structures. My initial focus will be on understanding *why* this file was chosen for modification. I'll need to assess if the changes are logically related to the primary intent of the patch or if they represent a potentially risky side effect or unrelated refactoring. A deep dive into `mm/memcontrol.c` is definitely required.

{
  "Expression": "^(int|void|bool|struct [a-z_]+ \\*?) [a-zA-Z0-9_]+\\(",
  "PathPrefix": "mm/memcontrol.c"
}

{
  "Output": "mm/memcontrol.c=131=static DEFINE_SPINLOCK(objcg_lock);\nmm/memcontrol.c-132-\nmm/memcontrol.c:133:bool mem_cgroup_kmem_disabled(void)\nmm/memcontrol.c-134-{\n--\nmm/memcontrol.c=529=static void __mod_memcg_lruvec_state(struct mem_cgroup_per_node *pn,\n--\nmm/memcontrol.c-531-\nmm/memcontrol.c:532:void reparent_memcg_lruvec_state_local(struct mem_cgroup *memcg,\nmm/memcontrol.c-533-\t\t\t\t       struct mem_cgroup *parent, int idx)\n--\nmm/memcontrol.c=704=static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force)\n--\nmm/memcontrol.c-728- */\nmm/memcontrol.c:729:void mem_cgroup_flush_stats(struct mem_cgroup *memcg)\nmm/memcontrol.c-730-{\n--\nmm/memcontrol.c-739-\nmm/memcontrol.c:740:void mem_cgroup_flush_stats_ratelimited(struct mem_cgroup *memcg)\nmm/memcontrol.c-741-{\n--\nmm/memcontrol.c=757=unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)\n--\nmm/memcontrol.c-772-\nmm/memcontrol.c:773:bool memcg_stat_item_valid(int idx)\nmm/memcontrol.c-774-{\n--\nmm/memcontrol.c=845=static void __mod_memcg_state(struct mem_cgroup *memcg,\n--\nmm/memcontrol.c-870- */\nmm/memcontrol.c:871:void mod_memcg_state(struct mem_cgroup *memcg, enum memcg_stat_item idx,\nmm/memcontrol.c-872-\t\t       int val)\n--\nmm/memcontrol.c=886=unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx)\n--\nmm/memcontrol.c-901-\nmm/memcontrol.c:902:void reparent_memcg_state_local(struct mem_cgroup *memcg,\nmm/memcontrol.c-903-\t\t\t\tstruct mem_cgroup *parent, int idx)\n--\nmm/memcontrol.c=937=static void mod_memcg_lruvec_state(struct lruvec *lruvec,\n--\nmm/memcontrol.c-964- */\nmm/memcontrol.c:965:void mod_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx,\nmm/memcontrol.c-966-\t\t\tint val)\n--\nmm/memcontrol.c-975-\nmm/memcontrol.c:976:void lruvec_stat_mod_folio(struct folio *folio, enum node_stat_item idx,\nmm/memcontrol.c-977-\t\t\t     int val)\n--\nmm/memcontrol.c=996=EXPORT_SYMBOL(lruvec_stat_mod_folio);\nmm/memcontrol.c-997-\nmm/memcontrol.c:998:void mod_lruvec_kmem_state(void *p, enum node_stat_item idx, int val)\nmm/memcontrol.c-999-{\n--\nmm/memcontrol.c-1027- */\nmm/memcontrol.c:1028:void count_memcg_events(struct mem_cgroup *memcg, enum vm_event_item idx,\nmm/memcontrol.c-1029-\t\t\t  unsigned long count)\n--\nmm/memcontrol.c=1049=unsigned long memcg_events(struct mem_cgroup *memcg, int event)\n--\nmm/memcontrol.c-1058-\nmm/memcontrol.c:1059:bool memcg_vm_event_item_valid(enum vm_event_item idx)\nmm/memcontrol.c-1060-{\n--\nmm/memcontrol.c=1213=struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,\n--\nmm/memcontrol.c-1304- */\nmm/memcontrol.c:1305:void mem_cgroup_iter_break(struct mem_cgroup *root,\nmm/memcontrol.c-1306-\t\t\t   struct mem_cgroup *prev)\n--\nmm/memcontrol.c=1328=static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg)\n--\nmm/memcontrol.c-1361- */\nmm/memcontrol.c:1362:void mem_cgroup_scan_tasks(struct mem_cgroup *memcg,\nmm/memcontrol.c-1363-\t\t\t   int (*fn)(struct task_struct *, void *), void *arg)\n--\nmm/memcontrol.c=1456=struct lruvec *folio_lruvec_lock_irqsave(struct folio *folio,\n--\nmm/memcontrol.c-1482- */\nmm/memcontrol.c:1483:void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,\nmm/memcontrol.c-1484-\t\t\t\tint zid, long nr_pages)\n--\nmm/memcontrol.c=1751=static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)\n--\nmm/memcontrol.c-1769- */\nmm/memcontrol.c:1770:void mem_cgroup_print_oom_context(struct mem_cgroup *memcg, struct task_struct *p)\nmm/memcontrol.c-1771-{\n--\nmm/memcontrol.c-1790- */\nmm/memcontrol.c:1791:void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)\nmm/memcontrol.c-1792-{\n--\nmm/memcontrol.c=1835=unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg)\n--\nmm/memcontrol.c-1853-\nmm/memcontrol.c:1854:void __memcg_memory_event(struct mem_cgroup *memcg,\nmm/memcontrol.c-1855-\t\t\t  enum memcg_memory_event event, bool allow_spinning)\n--\nmm/memcontrol.c=1947=struct mem_cgroup *mem_cgroup_get_oom_group(struct task_struct *victim,\n--\nmm/memcontrol.c-1993-\nmm/memcontrol.c:1994:void mem_cgroup_print_oom_group(struct mem_cgroup *memcg)\nmm/memcontrol.c-1995-{\n--\nmm/memcontrol.c=2259=static void schedule_drain_work(int cpu, struct work_struct *work)\n--\nmm/memcontrol.c-2275- */\nmm/memcontrol.c:2276:void drain_all_stock(struct mem_cgroup *root_memcg)\nmm/memcontrol.c-2277-{\n--\nmm/memcontrol.c=2468=static unsigned long calculate_high_delay(struct mem_cgroup *memcg,\n--\nmm/memcontrol.c-2504- */\nmm/memcontrol.c:2505:void __mem_cgroup_handle_over_high(gfp_t gfp_mask)\nmm/memcontrol.c-2506-{\n--\nmm/memcontrol.c=3122=static void page_set_objcg(struct page *page, const struct obj_cgroup *objcg)\n--\nmm/memcontrol.c-3134- */\nmm/memcontrol.c:3135:int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)\nmm/memcontrol.c-3136-{\n--\nmm/memcontrol.c-3156- */\nmm/memcontrol.c:3157:void __memcg_kmem_uncharge_page(struct page *page, int order)\nmm/memcontrol.c-3158-{\n--\nmm/memcontrol.c=3472=static int __obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp,\n--\nmm/memcontrol.c-3485-\nmm/memcontrol.c:3486:int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size)\nmm/memcontrol.c-3487-{\n--\nmm/memcontrol.c-3523-\nmm/memcontrol.c:3524:void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size)\nmm/memcontrol.c-3525-{\n--\nmm/memcontrol.c=3529=static inline size_t obj_full_size(struct kmem_cache *s)\n--\nmm/memcontrol.c-3537-\nmm/memcontrol.c:3538:bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,\nmm/memcontrol.c-3539-\t\t\t\t  gfp_t flags, unsigned int slab_alloc_flags,\n--\nmm/memcontrol.c-3634-\nmm/memcontrol.c:3635:void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,\nmm/memcontrol.c-3636-\t\t\t    void **p, int objects, unsigned long obj_exts)\n--\nmm/memcontrol.c-3665- */\nmm/memcontrol.c:3666:void split_page_memcg(struct page *page, unsigned order)\nmm/memcontrol.c-3667-{\n--\nmm/memcontrol.c-3679-\nmm/memcontrol.c:3680:void folio_split_memcg_refs(struct folio *folio, unsigned old_order,\nmm/memcontrol.c-3681-\t\tunsigned new_order)\n--\nmm/memcontrol.c=3738=struct wb_domain *mem_cgroup_wb_domain(struct bdi_writeback *wb)\n--\nmm/memcontrol.c-3765- */\nmm/memcontrol.c:3766:void mem_cgroup_wb_stats(struct bdi_writeback *wb, unsigned long *pfilepages,\nmm/memcontrol.c-3767-\t\t\t unsigned long *pheadroom, unsigned long *pdirty,\n--\nmm/memcontrol.c-3834- */\nmm/memcontrol.c:3835:void mem_cgroup_track_foreign_dirty_slowpath(struct folio *folio,\nmm/memcontrol.c-3836-\t\t\t\t\t     struct bdi_writeback *wb)\n--\nmm/memcontrol.c-3887-/* issue foreign writeback flushes for recorded foreign dirtying events */\nmm/memcontrol.c:3888:void mem_cgroup_flush_foreign(struct bdi_writeback *wb)\nmm/memcontrol.c-3889-{\n--\nmm/memcontrol.c=4901=static int memory_events_local_show(struct seq_file *m, void *v)\n--\nmm/memcontrol.c-4908-\nmm/memcontrol.c:4909:int memory_stat_show(struct seq_file *m, void *v)\nmm/memcontrol.c-4910-{\n--\nmm/memcontrol.c=5080=struct cgroup_subsys memory_cgrp_subsys = {\n--\nmm/memcontrol.c-5105- */\nmm/memcontrol.c:5106:void mem_cgroup_calculate_protection(struct mem_cgroup *root,\nmm/memcontrol.c-5107-\t\t\t\t     struct mem_cgroup *memcg)\n--\nmm/memcontrol.c=5121=static int charge_memcg(struct folio *folio, struct mem_cgroup *memcg,\n--\nmm/memcontrol.c-5140-\nmm/memcontrol.c:5141:int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp)\nmm/memcontrol.c-5142-{\n--\nmm/memcontrol.c-5164- */\nmm/memcontrol.c:5165:int mem_cgroup_charge_hugetlb(struct folio *folio, gfp_t gfp)\nmm/memcontrol.c-5166-{\n--\nmm/memcontrol.c-5198- */\nmm/memcontrol.c:5199:int mem_cgroup_swapin_charge_folio(struct folio *folio, unsigned short id,\nmm/memcontrol.c-5200-\t\t\t\t   struct mm_struct *mm, gfp_t gfp)\n--\nmm/memcontrol.c=5255=static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug)\n--\nmm/memcontrol.c-5300-\nmm/memcontrol.c:5301:void __mem_cgroup_uncharge(struct folio *folio)\nmm/memcontrol.c-5302-{\n--\nmm/memcontrol.c-5313-\nmm/memcontrol.c:5314:void __mem_cgroup_uncharge_folios(struct folio_batch *folios)\nmm/memcontrol.c-5315-{\n--\nmm/memcontrol.c-5335- */\nmm/memcontrol.c:5336:void mem_cgroup_replace_folio(struct folio *old, struct folio *new)\nmm/memcontrol.c-5337-{\n--\nmm/memcontrol.c-5384- */\nmm/memcontrol.c:5385:void mem_cgroup_migrate(struct folio *old, struct folio *new)\nmm/memcontrol.c-5386-{\n--\nmm/memcontrol.c=5417=EXPORT_SYMBOL(memcg_sockets_enabled_key);\nmm/memcontrol.c-5418-\nmm/memcontrol.c:5419:void mem_cgroup_sk_alloc(struct sock *sk)\nmm/memcontrol.c-5420-{\n--\nmm/memcontrol.c-5441-\nmm/memcontrol.c:5442:void mem_cgroup_sk_free(struct sock *sk)\nmm/memcontrol.c-5443-{\n--\nmm/memcontrol.c-5449-\nmm/memcontrol.c:5450:void mem_cgroup_sk_inherit(const struct sock *sk, struct sock *newsk)\nmm/memcontrol.c-5451-{\n--\nmm/memcontrol.c-5474- */\nmm/memcontrol.c:5475:bool mem_cgroup_sk_charge(const struct sock *sk, unsigned int nr_pages,\nmm/memcontrol.c-5476-\t\t\t  gfp_t gfp_mask)\n--\nmm/memcontrol.c-5495- */\nmm/memcontrol.c:5496:void mem_cgroup_sk_uncharge(const struct sock *sk, unsigned int nr_pages)\nmm/memcontrol.c-5497-{\n--\nmm/memcontrol.c-5509-\nmm/memcontrol.c:5510:void mem_cgroup_flush_workqueue(void)\nmm/memcontrol.c-5511-{\n--\nmm/memcontrol.c=5541=int __init mem_cgroup_init(void)\n--\nmm/memcontrol.c-5585- */\nmm/memcontrol.c:5586:int __mem_cgroup_try_charge_swap(struct folio *folio)\nmm/memcontrol.c-5587-{\n--\nmm/memcontrol.c-5635- */\nmm/memcontrol.c:5636:void __mem_cgroup_uncharge_swap(unsigned short id, unsigned int nr_pages)\nmm/memcontrol.c-5637-{\n--\nmm/memcontrol.c=5655=long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)\n--\nmm/memcontrol.c-5667-\nmm/memcontrol.c:5668:bool mem_cgroup_swap_full(struct folio *folio)\nmm/memcontrol.c-5669-{\n--\nmm/memcontrol.c=5793=static struct cftype swap_files[] = {\n--\nmm/memcontrol.c-5840- */\nmm/memcontrol.c:5841:bool obj_cgroup_may_zswap(struct obj_cgroup *objcg)\nmm/memcontrol.c-5842-{\n--\nmm/memcontrol.c-5881- */\nmm/memcontrol.c:5882:void obj_cgroup_charge_zswap(struct obj_cgroup *objcg, size_t size)\nmm/memcontrol.c-5883-{\n--\nmm/memcontrol.c-5913- */\nmm/memcontrol.c:5914:void obj_cgroup_uncharge_zswap(struct obj_cgroup *objcg, size_t size)\nmm/memcontrol.c-5915-{\n--\nmm/memcontrol.c-5934-\nmm/memcontrol.c:5935:bool mem_cgroup_zswap_writeback_enabled(struct mem_cgroup *memcg)\nmm/memcontrol.c-5936-{\n--\nmm/memcontrol.c=6040=subsys_initcall(mem_cgroup_swap_init);\n--\nmm/memcontrol.c-6043-\nmm/memcontrol.c:6044:void mem_cgroup_node_filter_allowed(struct mem_cgroup *memcg, nodemask_t *mask)\nmm/memcontrol.c-6045-{\n--\nmm/memcontrol.c-6060-\nmm/memcontrol.c:6061:void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg)\nmm/memcontrol.c-6062-{\n"
}

gemini-3.1-pro-preview

							input: 26317
							output: 36
							thoughts: 43

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

**Memory Control Module Deep Dive**

Hmm, let me think... I was under the impression that the function `mem_cgroup_from_obj_slab` was situated in a different part of the kernel, probably related to the slab allocator itself. But wait a minute... that doesn't quite sit right. Let's revisit the `mm/memcontrol.c` file again. I should have a clear understanding of its functions. It is important to know the precise location of memory cgroup functionalities. I need to refresh my memory regarding all of the functions associated.

{
  "Expression": "mem_cgroup_from_obj_slab",
  "PathPrefix": "mm/memcontrol.c"
}

{
  "Output": "mm/memcontrol.c=2858=static __always_inline\nmm/memcontrol.c:2859:struct mem_cgroup *mem_cgroup_from_obj_slab(struct slab *slab, void *p)\nmm/memcontrol.c-2860-{\n--\nmm/memcontrol.c=2898=struct mem_cgroup *mem_cgroup_from_virt(void *p)\n--\nmm/memcontrol.c-2906-\tif (slab)\nmm/memcontrol.c:2907:\t\treturn mem_cgroup_from_obj_slab(slab, p);\nmm/memcontrol.c-2908-\treturn folio_memcg_check(virt_to_folio(p));\n"
}

gemini-3.1-pro-preview

							input: 26729
							output: 36
							thoughts: 109

**Slab Cache Hook Conundrum**

Okay, so I'm looking at this `mem_cgroup_from_obj_slab` function, and it's marked `static __always_inline`. That's standard and expected for performance reasons within the module. But then my mind jumps to the hooks, and I see a potential inconsistency here, I’m thinking, why aren’t the slab cache allocation and free hook functions static?  `__memcg_slab_post_alloc_hook` and `__memcg_slab_free_hook` are *not* static, which gives me pause. And then there’s `alloc_slab_obj_exts`, also not static. This suggests a more global intent with their scope than the `static` declaration suggests for `mem_cgroup_from_obj_slab`. This isn't necessarily a *problem*, but it warrants closer inspection for how these hook functions are intended to interact with the larger slab allocator architecture. I need to refresh my memory and check the definition of `__kmem_cache_create_args` in `mm/slab_common.c` to remind myself of the full context and see how these pieces are really intended to fit together.

{
  "Expression": "__kmem_cache_create_args",
  "PathPrefix": "mm/slab_common.c"
}

{
  "Output": "mm/slab_common.c=267=__kmem_cache_alias(const char *name, unsigned int size, slab_flags_t flags,\n--\nmm/slab_common.c-291-/**\nmm/slab_common.c:292: * __kmem_cache_create_args - Create a kmem cache.\nmm/slab_common.c-293- * @name: A string which is used in /proc/slabinfo to identify this cache.\n--\nmm/slab_common.c-317- */\nmm/slab_common.c:318:struct kmem_cache *__kmem_cache_create_args(const char *name,\nmm/slab_common.c-319-\t\t\t\t\t    unsigned int object_size,\n--\nmm/slab_common.c-408-}\nmm/slab_common.c:409:EXPORT_SYMBOL(__kmem_cache_create_args);\nmm/slab_common.c-410-\n"
}

gemini-3.1-pro-preview

							input: 27388
							output: 34
							thoughts: 174

**Analyzing SLUB Object Extension Allocation**

Okay, so `__kmem_cache_create_args` is exported, that's straightforward. But, hold on a second... `alloc_slab_obj_exts` isn't explicitly exported, though it isn't static either. This seems a little unusual. Now, let me think... Aha! `alloc_slab_obj_exts` is called from `prepare_slab_obj_exts_hook`, which is inline within `mm/slub.c`. Right, that explains the access. I need to confirm where `alloc_slab_obj_exts` is defined. Is it in `mm/slub.c` or perhaps hiding in `mm/slab_common.c`? Okay, I've checked... it's definitely in `mm/slub.c`. But, wait a minute, I just realized, `alloc_slab_obj_exts` is *declared* in `mm/slab.h`. Hmm, that's a key detail. Time to thoroughly examine the implementation of `alloc_slab_obj_exts` within `mm/slub.c`.

{
  "Expression": "alloc_slab_obj_exts",
  "PathPrefix": "mm/slub.c"
}

{
  "Output": "mm/slub.c=2129=static inline void init_slab_obj_exts(struct slab *slab)\n--\nmm/slub.c-2133-\nmm/slub.c:2134:int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,\nmm/slub.c-2135-\t\t\tgfp_t gfp, unsigned int alloc_flags)\n--\nmm/slub.c=2223=static inline void free_slab_obj_exts(struct slab *slab, bool allow_spin)\n--\nmm/slub.c-2254- */\nmm/slub.c:2255:static void alloc_slab_obj_exts_early(struct kmem_cache *s, struct slab *slab)\nmm/slub.c-2256-{\n--\nmm/slub.c=2302=static inline void init_slab_obj_exts(struct slab *slab)\n--\nmm/slub.c-2305-\nmm/slub.c:2306:static int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,\nmm/slub.c-2307-\t\t\t       gfp_t gfp, unsigned int alloc_flags)\n--\nmm/slub.c=2312=static inline void free_slab_obj_exts(struct slab *slab, bool allow_spin)\n--\nmm/slub.c-2315-\nmm/slub.c:2316:static inline void alloc_slab_obj_exts_early(struct kmem_cache *s,\nmm/slub.c-2317-\t\t\t\t\t\t       struct slab *slab)\n--\nmm/slub.c=2326=prepare_slab_obj_exts_hook(struct kmem_cache *s, struct slab *slab,\n--\nmm/slub.c-2332-\nmm/slub.c:2333:\t\tif (alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {\nmm/slub.c-2334-\t\t\tpr_warn_once(\"%s, %s: Failed to create slab extension vector!\\n\",\n--\nmm/slub.c=3371=static __always_inline void account_slab(struct slab *slab, int order,\n--\nmm/slub.c-3377-\t\t\t!slab_obj_exts(slab))\nmm/slub.c:3378:\t\talloc_slab_obj_exts(slab, s, gfp,\nmm/slub.c-3379-\t\t\t\t    alloc_flags | SLAB_ALLOC_NEW_SLAB);\n--\nmm/slub.c=3400=static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags,\n--\nmm/slub.c-3455-\t */\nmm/slub.c:3456:\talloc_slab_obj_exts_early(s, slab);\nmm/slub.c-3457-\taccount_slab(slab, oo_order(oo), s, flags, alloc_flags);\n"
}

gemini-3.1-pro-preview

							input: 28650
							output: 34
							thoughts: 129

**Investigating the Scope of `alloc_slab_obj_exts`**

Okay, so I'm digging into the kernel's slab allocator code, specifically around extended object features. My initial thought is that `alloc_slab_obj_exts` is likely non-static if `CONFIG_SLAB_OBJ_EXT` is enabled. Seems logical, given the dependency on the configuration option. But hold on... I'm looking at the definition now, and it's defined in `mm/slub.c` as a non-static function.

Now, that immediately raises a red flag. If it's *not* static, I'd expect it to be used more broadly, but the code scan suggests that it's *only* used within `mm/slub.c` itself, and in `mm/memcontrol.c`. That's not the usual pattern. Usually, if a function isn't static it will be visible outside of its file.

Aha! `mm/memcontrol.c` *does* call `alloc_slab_obj_exts`! Excellent, that answers a bit of the puzzle, but let's go check `mm/memcontrol.c` to see exactly *how* that function is being called in there. This is where the real nuance is. Understanding the calling context is key.

{
  "Expression": "alloc_slab_obj_exts",
  "PathPrefix": "mm/memcontrol.c"
}

{
  "Output": "mm/memcontrol.c=3538=bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,\n--\nmm/memcontrol.c-3588-\t\t\t\tcontinue;\nmm/memcontrol.c:3589:\t\t\tif (alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags))\nmm/memcontrol.c-3590-\t\t\t\tcontinue;\n"
}

gemini-3.1-pro-preview

							input: 29229
							output: 37
							thoughts: 143

**Analyzing Memory Control Hooks**

Okay, so I've identified `alloc_slab_obj_exts` as a key function, seeing as it's called directly from `mm/memcontrol.c`. That makes it a solid starting point for investigation. And, of course, the `__memcg_slab_post_alloc_hook` and `__memcg_slab_free_hook` functions also warrant close attention within that context. Wait a second, though; I recall now that `__memcg_slab_post_alloc_hook` is called from `memcg_slab_post_alloc_hook`, which is actually inlined from `mm/slub.c`. I need to be careful with that one. Let's make sure I'm looking at the correct definition. Best to double-check the implementation of `__memcg_slab_post_alloc_hook` within `mm/memcontrol.c` directly to confirm.

{
  "Expression": "__memcg_slab_post_alloc_hook",
  "PathPrefix": "mm/memcontrol.c"
}

{
  "Output": "mm/memcontrol.c=3529=static inline size_t obj_full_size(struct kmem_cache *s)\n--\nmm/memcontrol.c-3537-\nmm/memcontrol.c:3538:bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,\nmm/memcontrol.c-3539-\t\t\t\t  gfp_t flags, unsigned int slab_alloc_flags,\n"
}

gemini-3.1-pro-preview

							input: 29745
							output: 35
							thoughts: 35

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

**Hook Investigation**

Right, so `__memcg_slab_post_alloc_hook` is definitely not a static function. That's a key observation. Now, that's useful, that means it's available for modification or intervention, likely from external modules or perhaps even in a system-wide or core way. I need to keep that in mind when tracing calls through the allocation/free path. What about the counterpart? I need to check `__memcg_slab_free_hook`. Is it static as well? Is there any similar behavior with the free hook? Because the post-allocation one is non static it will have serious implications for further analysis.

{
  "Expression": "__memcg_slab_free_hook",
  "PathPrefix": "mm/memcontrol.c"
}

{
  "Output": "mm/memcontrol.c=3538=bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,\n--\nmm/memcontrol.c-3634-\nmm/memcontrol.c:3635:void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,\nmm/memcontrol.c-3636-\t\t\t    void **p, int objects, unsigned long obj_exts)\n"
}

gemini-3.1-pro-preview

							input: 30113
							output: 34
							thoughts: 44

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

**Investigating Memory Control Group Interaction with SLUB Allocator**

Right, so I'm digging into how memory control groups (memcgs) interact with the SLUB allocator. Let me see, `__memcg_slab_free_hook`… Yup, that’s confirmed, it's definitely *not* declared static. Good, that helps clarify a specific point. Now, what about the other side of this? Let me check… ah, yes, `memcg_slab_post_charge`. That looks interesting, and it lives over in `mm/slub.c`. I need to review that file and understand how `memcg_slab_post_charge` is used and how it interacts with the rest of the SLUB code. Gotta dive deeper to understand the complete picture.

{
  "Expression": "memcg_slab_post_charge",
  "PathPrefix": "mm/slub.c"
}

{
  "Output": "mm/slub.c=2522=static __fastpath_inline\nmm/slub.c:2523:bool memcg_slab_post_charge(void *p, gfp_t flags)\nmm/slub.c-2524-{\n--\nmm/slub.c=2590=static inline void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,\n--\nmm/slub.c-2594-\nmm/slub.c:2595:static inline bool memcg_slab_post_charge(void *p, gfp_t flags)\nmm/slub.c-2596-{\n--\nmm/slub.c=5004=bool kmem_cache_charge(void *objp, gfp_t gfpflags)\n--\nmm/slub.c-5008-\nmm/slub.c:5009:\treturn memcg_slab_post_charge(objp, gfpflags);\nmm/slub.c-5010-}\n"
}

gemini-3.1-pro-preview

							input: 30652
							output: 32
							thoughts: 60

**Diving into Slab Allocation**

Okay, so I'm looking at this `memcg_slab_post_charge` function. I see it's defined as `static __fastpath_inline` within `mm/slub.c`. Hmm, that suggests it's optimized for speed and intended for internal use only within that file. But then I remember `kmem_cache_charge`. That's not static; it's exported, meaning other parts of the kernel can call it.  Right, I need to understand the relationship between these two. It's time to dig into the implementation of `kmem_cache_charge` and see how it interacts with `memcg_slab_post_charge`. I need to figure out where the connection between these two lies, and what's driving the logic.

{
  "Expression": "kmem_cache_charge",
  "PathPrefix": "mm/slub.c"
}

{
  "Output": "mm/slub.c=5002=EXPORT_SYMBOL(kmem_cache_alloc_lru_noprof);\nmm/slub.c-5003-\nmm/slub.c:5004:bool kmem_cache_charge(void *objp, gfp_t gfpflags)\nmm/slub.c-5005-{\n--\nmm/slub.c-5010-}\nmm/slub.c:5011:EXPORT_SYMBOL(kmem_cache_charge);\nmm/slub.c-5012-\n"
}

gemini-3.1-pro-preview

							input: 31074
							output: 36
							thoughts: 43

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

**Investigating Slab Allocator Internals**

Right, so I'm digging into this slab allocator stuff. `kmem_cache_charge` seems like a solid starting point for tracing allocation costs, right? It's a key function in the process. Now, I should probably also check out `__kmem_cache_create_args`. It looks like that one's the heart of how these caches are actually made, I see that it's in `mm/slab_common.c`. I need to figure out how these are working, and this looks like a good next step.

{
  "Expression": "__kmem_cache_create_args",
  "PathPrefix": "mm/slab_common.c"
}

{
  "Output": "mm/slab_common.c=267=__kmem_cache_alias(const char *name, unsigned int size, slab_flags_t flags,\n--\nmm/slab_common.c-291-/**\nmm/slab_common.c:292: * __kmem_cache_create_args - Create a kmem cache.\nmm/slab_common.c-293- * @name: A string which is used in /proc/slabinfo to identify this cache.\n--\nmm/slab_common.c-317- */\nmm/slab_common.c:318:struct kmem_cache *__kmem_cache_create_args(const char *name,\nmm/slab_common.c-319-\t\t\t\t\t    unsigned int object_size,\n--\nmm/slab_common.c-408-}\nmm/slab_common.c:409:EXPORT_SYMBOL(__kmem_cache_create_args);\nmm/slab_common.c-410-\n"
}

gemini-3.1-pro-preview

							input: 31549
							output: 37
							thoughts: 73

Okay, let's see...

**Analyzing Potential Focus Symbols**

Right, `__kmem_cache_create_args` seems like a solid candidate to center on. It's a key function in cache creation, making it a natural starting point. But wait... what about `alloc_tagging_slab_free_hook`? That's right, it's defined inline, so its behavior is intimately tied to the surrounding code. Interesting... now, hang on a second. Isn't `__alloc_tagging_slab_free_hook` *not* a static function? That's unexpected, I should confirm that in `mm/slub.c` right away. I need to understand its scope fully.

{
  "Expression": "__alloc_tagging_slab_free_hook",
  "PathPrefix": "mm/slub.c"
}

{
  "Output": "mm/slub.c=2400=static noinline void\nmm/slub.c:2401:__alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,\nmm/slub.c-2402-\t\t\t       int objects)\n--\nmm/slub.c=2425=alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,\n--\nmm/slub.c-2428-\tif (mem_alloc_profiling_enabled())\nmm/slub.c:2429:\t\t__alloc_tagging_slab_free_hook(s, slab, p, objects);\nmm/slub.c-2430-}\n"
}

gemini-3.1-pro-preview

							input: 32021
							output: 37
							thoughts: 31

Okay, here's my interpretation of those thoughts, presented as a summary from my expert perspective:

**Deciphering the Function Declaration**

Alright, let's break this down. The function signature is `static noinline void`. This immediately tells me a few critical things. It's `static`, meaning its scope is restricted to this specific compilation unit – it's not meant to be accessed from outside this module. The `noinline` attribute is a directive to the compiler, specifically instructing it *not* to inline this function's code into any call sites. This might be due to size constraints, debugging considerations, or perhaps because we want precise control over where the function's code resides in memory.

Now, that name. `__alloc_tagging_slab_alloc_hook`... That naming convention clearly suggests a hook related to memory allocation, specifically within a slab allocator. The double underscore at the beginning is a strong indicator of an internal or private function. The presence of "tagging" is also important, as this hints at metadata or instrumentation. The "alloc hook" piece is the most obvious part. It sounds like this function is designed to be called during the slab allocation process. I need to understand what this hook does, to better understand how allocation behaves at a lower level.

{
  "Expression": "__alloc_tagging_slab_alloc_hook",
  "PathPrefix": "mm/slub.c"
}

{
  "Output": "mm/slub.c=2345=static noinline void\nmm/slub.c:2346:__alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags,\nmm/slub.c-2347-\t\t\t\tunsigned int alloc_flags)\n--\nmm/slub.c=2392=alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags,\n--\nmm/slub.c-2395-\tif (mem_alloc_profiling_enabled())\nmm/slub.c:2396:\t\t__alloc_tagging_slab_alloc_hook(s, object, flags, alloc_flags);\nmm/slub.c-2397-}\n"
}

gemini-3.1-pro-preview

							input: 32572
							output: 34
							thoughts: 24

Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person:

**Revisiting Slab Allocator Internals**

Alright, let's circle back to that `alloc_slab_obj_exts` function again. I want to make sure I haven't missed anything crucial in my mental model of the slab allocator. Considering its role in object allocation, particularly when extended metadata is involved, a closer inspection is warranted. And, I need to remind myself to take note of why the function is declared `static noinline void`. Is it for inlining, or is it because it needs to be accessible only within a specific translation unit, or is the intention to prevent the compiler from making a call across functions? I need to think through the implications of this. I should ensure that any assumptions about its behavior are validated.

{
  "Expression": "alloc_slab_obj_exts",
  "PathPrefix": "mm/slub.c"
}

{
  "Output": "mm/slub.c=2129=static inline void init_slab_obj_exts(struct slab *slab)\n--\nmm/slub.c-2133-\nmm/slub.c:2134:int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,\nmm/slub.c-2135-\t\t\tgfp_t gfp, unsigned int alloc_flags)\n--\nmm/slub.c=2223=static inline void free_slab_obj_exts(struct slab *slab, bool allow_spin)\n--\nmm/slub.c-2254- */\nmm/slub.c:2255:static void alloc_slab_obj_exts_early(struct kmem_cache *s, struct slab *slab)\nmm/slub.c-2256-{\n--\nmm/slub.c=2302=static inline void init_slab_obj_exts(struct slab *slab)\n--\nmm/slub.c-2305-\nmm/slub.c:2306:static int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,\nmm/slub.c-2307-\t\t\t       gfp_t gfp, unsigned int alloc_flags)\n--\nmm/slub.c=2312=static inline void free_slab_obj_exts(struct slab *slab, bool allow_spin)\n--\nmm/slub.c-2315-\nmm/slub.c:2316:static inline void alloc_slab_obj_exts_early(struct kmem_cache *s,\nmm/slub.c-2317-\t\t\t\t\t\t       struct slab *slab)\n--\nmm/slub.c=2326=prepare_slab_obj_exts_hook(struct kmem_cache *s, struct slab *slab,\n--\nmm/slub.c-2332-\nmm/slub.c:2333:\t\tif (alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {\nmm/slub.c-2334-\t\t\tpr_warn_once(\"%s, %s: Failed to create slab extension vector!\\n\",\n--\nmm/slub.c=3371=static __always_inline void account_slab(struct slab *slab, int order,\n--\nmm/slub.c-3377-\t\t\t!slab_obj_exts(slab))\nmm/slub.c:3378:\t\talloc_slab_obj_exts(slab, s, gfp,\nmm/slub.c-3379-\t\t\t\t    alloc_flags | SLAB_ALLOC_NEW_SLAB);\n--\nmm/slub.c=3400=static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags,\n--\nmm/slub.c-3455-\t */\nmm/slub.c:3456:\talloc_slab_obj_exts_early(s, slab);\nmm/slub.c-3457-\taccount_slab(slab, oo_order(oo), s, flags, alloc_flags);\n"
}

gemini-3.1-pro-preview

							input: 33613
							output: 38
							thoughts: 150

**Examining the Slab Object Extension Allocation Function**

Okay, hold on a second. I'm looking at `alloc_slab_obj_exts`. If `CONFIG_SLAB_OBJ_EXT` is active, it's defined as a regular `int alloc_slab_obj_exts`, not a static one, right? Let me double-check... Yes, line 2134 is the non-static definition, and line 2306 is the static dummy version used when the configuration option is disabled. So, that means the `alloc_slab_obj_exts` function *isn't* static when the extension is enabled, meaning it's visible outside the current compilation unit. That means it isn't strictly exported for use by other modules, but it *is* non-static and thus visible, making its use a bit...interesting. Hmm, let me just confirm whether or not it actually gets exported in the build system. I need to make sure I'm not missing something subtle here.

{
  "Expression": "EXPORT_SYMBOL.*alloc_slab_obj_exts",
  "PathPrefix": "mm/slub.c"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

							input: 34034
							output: 41
							thoughts: 52

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

**Analyzing the Potential for Fuzzing**

Right, so this thing isn't explicitly exported, which is a good initial sign from a security perspective. However, it's *non-static* – that's the key. That means it's accessible within the module or potentially even from a different module, so fuzzing it is definitely on the table. We need to figure out how.

My first thought is to dig into `__memcg_slab_post_alloc_hook` and `__memcg_slab_free_hook`. These sound like likely candidates for interacting with whatever's going on here. They probably are hooks associated with memory control groups (memcgs) and slab allocation/deallocation. We can examine the code surrounding these and see how they are called and what arguments are passed. That should reveal how this non-static function can be reached and how we might manipulate its input for fuzzing. It's a good starting point to identify a potential vulnerability.

{
  "Expression": "EXPORT_SYMBOL.*__memcg_slab_post_alloc_hook",
  "PathPrefix": "mm/memcontrol.c"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

							input: 34367
							output: 33
							thoughts: 31

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

**Investigating Non-Exported, Non-Static Function Usage**

Alright, so the clue is something that's not exported, but it's *also* not static. That immediately piques my interest. It implies a function potentially used internally within a module, or perhaps indirectly via a function pointer or other less obvious mechanism. It's not something meant for direct external consumption, but it *is* accessible within the compilation unit, or perhaps, within the kernel. Let's dig in a bit.

The most likely place to start looking for this will be within the code related to memory management, I'll go straight to `mm/kfence/core.c`. Let me see what `__kfence_free` does, and what it might tell us about how this non-static function is intended to be used. I wonder if there are any interesting patterns or design choices reflected there. Let's see how deep this rabbit hole goes.

{
  "Expression": "__kfence_free",
  "PathPrefix": "mm/kfence/core.c"
}

{
  "Output": "mm/kfence/core.c=1227=void *kfence_object_start(const void *addr)\n--\nmm/kfence/core.c-1237-\nmm/kfence/core.c:1238:void __kfence_free(void *addr)\nmm/kfence/core.c-1239-{\n"
}

gemini-3.1-pro-preview

							input: 34751
							output: 33
							thoughts: 439

**Analyzing Kernel Slab Object Extension and KFENCE Integration**

Okay, so the initial concern was the non-static nature of `__kfence_free`, which is good to confirm. Now, I want to map out the key symbols involved in this area. `kmem_cache_charge` is also exported, so it's relevant, and I'm seeing other important symbols related to memcg and slab object extensions.

Let's see: `alloc_slab_obj_exts`, `__memcg_slab_post_alloc_hook`, `__memcg_slab_free_hook`, `__kmem_cache_create_args` and `kmem_cache_charge`. And of course `__kfence_free`. Wait, there's a minor change in `__kfence_free` with that `KFENCE_WARN_ON` removal, but the *significant* modifications are primarily focused on `alloc_slab_obj_exts` and `__memcg_slab_post_alloc_hook`.

Now I need to eliminate some irrelevant pieces and focus on the important ones. `mem_cgroup_from_obj_slab` is `static inline`, so not directly relevant. Also `slab_obj_ext_has_codetag_init` is `static __init` and `alloc_slab_obj_exts_early` is `static void`, so I won't need to focus on them as much.

So, taking all that into consideration, the most critical symbols to zero in on are: `alloc_slab_obj_exts`, `__memcg_slab_post_alloc_hook`, `__memcg_slab_free_hook` and `__kmem_cache_create_args`.

Finally, to understand the build requirements I need to check the relevant configuration options. `CONFIG_MEMCG`, obviously, `CONFIG_MEM_ALLOC_PROFILING`, `CONFIG_SLAB_OBJ_EXT` which is selected by the above, and, importantly, `CONFIG_KFENCE` since we've seen it modified. Now to check the header file and make sure I haven't missed anything.

{
  "Expression": "CONFIG_SLAB_OBJ_EXT",
  "PathPrefix": "mm/slab.h"
}

{
  "Output": "mm/slab.h=100=struct slab {\n--\nmm/slab.h-114-\tatomic_t __page_refcount;\nmm/slab.h:115:#ifdef CONFIG_SLAB_OBJ_EXT\nmm/slab.h-116-\tunsigned long obj_exts;\n--\nmm/slab.h=126=SLAB_MATCH(memcg_data, obj_exts);\nmm/slab.h:127:#elif defined(CONFIG_SLAB_OBJ_EXT)\nmm/slab.h-128-SLAB_MATCH(_unused_slab_obj_exts, obj_exts);\n--\nmm/slab.h=627=static inline size_t slab_obj_ext_size(struct slab *slab)\n--\nmm/slab.h-639-\nmm/slab.h:640:#ifdef CONFIG_SLAB_OBJ_EXT\nmm/slab.h-641-\n--\nmm/slab.h=775=int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,\n--\nmm/slab.h-777-\nmm/slab.h:778:#else /* CONFIG_SLAB_OBJ_EXT */\nmm/slab.h-779-\n--\nmm/slab.h=792=static inline bool obj_exts_in_object(struct slab *slab)\n--\nmm/slab.h-796-\nmm/slab.h:797:#endif /* CONFIG_SLAB_OBJ_EXT */\nmm/slab.h-798-\n"
}

gemini-3.1-pro-preview

							input: 36088
							output: 27
							thoughts: 59

Here's my summary, as the thought process unfolds:

**Digging into `CONFIG_SLAB_OBJ_EXT`**

Okay, so `CONFIG_SLAB_OBJ_EXT`... that rings a bell. It's definitely an internal config option; I'm pretty sure it's not something you'd manually enable. My gut says it's likely selected based on other, broader features. Perhaps something like `MEMCG` (memory control groups) or maybe even `MEM_ALLOC_PROFILING`. I need to figure out the context.

My next step is to drill down to where this thing is defined and, more importantly, *why* it's defined. Time to go hunting in the Kconfig files. The most obvious places to start would be `init/Kconfig` and, more likely, `mm/Kconfig`. Those are the usual suspects for memory management options. I'll check those files, and hopefully, I'll find the dependencies and get a clearer picture of what this `SLAB_OBJ_EXT` is all about. This should be a quick one, just a matter of tracing the config.

{
  "Expression": "config SLAB_OBJ_EXT",
  "PathPrefix": ""
}

{
  "Output": "init/Kconfig=1033=config NUMA_BALANCING_DEFAULT_ENABLED\n--\ninit/Kconfig-1040-\ninit/Kconfig:1041:config SLAB_OBJ_EXT\ninit/Kconfig-1042-\tbool\n"
}

gemini-3.1-pro-preview

							input: 36496
							output: 28
							thoughts: 56

**Uncovering the Boolean Labyrinth**

Okay, so there's a hidden boolean flag lurking somewhere. My initial instinct tells me we're looking at something related to memory management and allocation. Specifically, I'm thinking about `MEMCG`, `MEM_ALLOC_PROFILING`, and `KFENCE`. Those three often dance together in this space. Now, let's not get ahead of ourselves. Before we dive deeper, I need to understand the dependencies of `MEM_ALLOC_PROFILING`. Does it rely on other configurations? Does it have any implications that might impact the system? Gotta make sure we're considering the whole picture before chasing a specific path.

{
  "Expression": "config MEM_ALLOC_PROFILING",
  "PathPrefix": ""
}

{
  "Output": "lib/Kconfig.debug=1047=config CODE_TAGGING\n--\nlib/Kconfig.debug-1050-\nlib/Kconfig.debug:1051:config MEM_ALLOC_PROFILING\nlib/Kconfig.debug-1052-\tbool \"Enable memory allocation profiling\"\n--\nlib/Kconfig.debug-1064-\nlib/Kconfig.debug:1065:config MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT\nlib/Kconfig.debug-1066-\tbool \"Enable memory allocation profiling by default\"\n--\nlib/Kconfig.debug-1069-\nlib/Kconfig.debug:1070:config MEM_ALLOC_PROFILING_DEBUG\nlib/Kconfig.debug-1071-\tbool \"Memory allocation profiler debugging\"\n"
}

gemini-3.1-pro-preview

							input: 36933
							output: 35
							thoughts: 20

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

**Diving into Debugging Configuration**

Okay, so I need to understand something related to the debugging configuration of this project. My first instinct is to zero in on the relevant Kconfig file – which, as I recall, is usually where these settings are defined. I'll start with `lib/Kconfig.debug`. I seem to remember there was a configuration I was interested in around line 1051, so I'll go straight there. Let me see what that reveals about the specifics I'm looking for... I'm already anticipating what to expect, but need the hard data to make a useful determination.

{
  "File": "lib/Kconfig.debug",
  "FirstLine": 1045,
  "LineCount": 20
}

{
  "Contents": "1045:\t\t  If in doubt, say \"N\".\n1046:\t\n1047:\tconfig CODE_TAGGING\n1048:\t\tbool\n1049:\t\tselect KALLSYMS\n1050:\t\n1051:\tconfig MEM_ALLOC_PROFILING\n1052:\t\tbool \"Enable memory allocation profiling\"\n1053:\t\tdefault n\n1054:\t\tdepends on MMU\n1055:\t\tdepends on PROC_FS\n1056:\t\tdepends on !DEBUG_FORCE_WEAK_PER_CPU\n1057:\t\tselect CODE_TAGGING\n1058:\t\tselect PAGE_EXTENSION\n1059:\t\tselect SLAB_OBJ_EXT\n1060:\t\thelp\n1061:\t\t  Track allocation source code and record total allocation size\n1062:\t\t  initiated at that code location. The mechanism can be used to track\n1063:\t\t  memory leaks with a low performance and memory impact.\n1064:\t\n"
}

gemini-3.1-pro-preview

							input: 37400
							output: 23
							thoughts: 52

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

**Deciphering the Configuration Dependencies**

Alright, let me break this down. My initial thought process revolves around the dependencies of `MEM_ALLOC_PROFILING`. I see that it requires the presence of an `MMU`, the `PROC_FS`, and importantly, the negation of `DEBUG_FORCE_WEAK_PER_CPU`. These are fairly standard dependencies; profiling often needs a mature memory management unit and access to the process filesystem for introspection. The exclusion of `DEBUG_FORCE_WEAK_PER_CPU` suggests that a different, potentially more robust, debug mechanism is at play when we're profiling.

Then, there's the automatic selection of `SLAB_OBJ_EXT`. Hmm, that's interesting. `SLAB_OBJ_EXT` is likely selected to provide additional metadata or extended object support needed for the profiling. It provides extended data to each slab object. I would need to double-check, but that's a reasonable assumption, given the context.

My next thought, and this is where I start to drill down, is about `MEMCG`. I need to consider whether memory cgroups (MEMCG) play a role here. Memory cgroups offer more granular resource tracking, which might be critical for a more accurate and useful memory allocation profile. Does `MEM_ALLOC_PROFILING` work well with memory cgroups, or are there compatibility issues, or even better, does it leverage them in some way? This is an important question to address, as integrating with MEMCG would make the profiling much more valuable in a controlled environment. I would need to check the relationships and configurations for that.

{
  "Expression": "config MEMCG",
  "PathPrefix": ""
}

{
  "Output": "init/Kconfig=1063=config CGROUP_FAVOR_DYNMODS\n--\ninit/Kconfig-1072-\ninit/Kconfig:1073:config MEMCG\ninit/Kconfig-1074-\tbool \"Memory controller\"\n--\ninit/Kconfig-1081-\ninit/Kconfig:1082:config MEMCG_NMI_UNSAFE\ninit/Kconfig-1083-\tbool\n--\ninit/Kconfig-1088-\ninit/Kconfig:1089:config MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\ninit/Kconfig-1090-\tbool\n--\ninit/Kconfig-1095-\ninit/Kconfig:1096:config MEMCG_V1\ninit/Kconfig-1097-\tbool \"Legacy cgroup v1 memory controller\"\n"
}

gemini-3.1-pro-preview

							input: 38065
							output: 33
							thoughts: 18

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

**Diving into the Kernel Configuration Landscape**

Okay, so I need to understand something related to kernel configuration. Let's see... the most likely place to find information about this, especially if it's a core option, is the `init/Kconfig` file. Given the typical structure of the kernel source, I'm going to start my investigation there. Specifically, my intuition is telling me that the relevant section is around line 1073. It's a broad starting point, but experience has taught me that the initial configuration definitions are often grouped together somewhat logically, and that line number seems like a sensible place to begin. Time to pull up the file and take a look. I'll need to rapidly scan the surrounding code, identify the relevant Kconfig syntax, and then extrapolate the specific configuration options it defines and how it may be affecting the kernel's behaviour in the specific area I'm interested in.

{
  "File": "init/Kconfig",
  "FirstLine": 1070,
  "LineCount": 20
}

{
  "Contents": "1070:\t\n1071:\t\t  Say N if unsure.\n1072:\t\n1073:\tconfig MEMCG\n1074:\t\tbool \"Memory controller\"\n1075:\t\tselect PAGE_COUNTER\n1076:\t\tselect EVENTFD\n1077:\t\tselect SLAB_OBJ_EXT\n1078:\t\tselect VM_EVENT_COUNTERS\n1079:\t\thelp\n1080:\t\t  Provides control over the memory footprint of tasks in a cgroup.\n1081:\t\n1082:\tconfig MEMCG_NMI_UNSAFE\n1083:\t\tbool\n1084:\t\tdepends on MEMCG\n1085:\t\tdepends on HAVE_NMI\n1086:\t\tdepends on !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS \u0026\u0026 !ARCH_HAVE_NMI_SAFE_CMPXCHG\n1087:\t\tdefault y\n1088:\t\n1089:\tconfig MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\n"
}

gemini-3.1-pro-preview

							input: 38599
							output: 214
							thoughts: 803

**Analyzing the SLUB Allocator Patch**

Okay, so this patch is clearly making some significant changes, particularly around `SLAB_OBJ_EXT`. Right off the bat, I see that it's going to require that we enable `MEMCG`, `MEM_ALLOC_PROFILING`, and `KFENCE`. This is crucial context for understanding the scope of the modifications.

I've confirmed that the patch is functional and definitely touches core slab behavior. I need to zero in on the key symbols that are being modified here. I've identified: `alloc_slab_obj_exts`, `__memcg_slab_post_alloc_hook`, `__memcg_slab_free_hook`, `__kmem_cache_create_args`, and `kmem_cache_charge`. I also noticed that the change to `__kfence_free` seems minor—just removing a `KFENCE_WARN_ON`, so I will discount that symbol.

Initially, I considered adding `memcg_slab_post_charge`, but then I remembered it's inline, so it's not a relevant symbol to focus on. But I still need to make sure I focus on `kmem_cache_charge`.

Let's quickly verify my focus symbols. `__kmem_cache_create_args`, in `mm/slab_common.c`, looks right. Okay, moving on. `alloc_slab_obj_exts` looks correct. `__memcg_slab_post_alloc_hook` seems right. `__memcg_slab_free_hook` looks good. And, yes, `kmem_cache_charge` seems like it should be included.

Based on the code changes and the configurations it impacts ( `MEMCG`, `MEM_ALLOC_PROFILING`, `KFENCE`), the patch seems to be modifying memory allocation profiling and memcg accounting logic within the SLUB allocator. It is changing how `slabobj_ext` structures are managed and accessed. It looks like `SLAB_MAY_ACCOUNT` is introduced and the `slabobj_ext` layout is changed to an array of pointers or a union, depending on the configuration. Given these core kernel memory management changes, I need to focus on fuzzing these changes to look for any memory corruption, leaks, or accounting errors.

I'm going to call `set-results` tool now.

{
  "EnableConfigs": [
    "MEMCG",
    "MEM_ALLOC_PROFILING",
    "KFENCE"
  ],
  "FocusSymbols": [
    "alloc_slab_obj_exts",
    "__memcg_slab_post_alloc_hook",
    "__memcg_slab_free_hook",
    "__kmem_cache_create_args",
    "kmem_cache_charge"
  ],
  "Reasoning": "The patch modifies the memory allocation profiling and memcg accounting logic in the SLUB allocator. It changes how `slabobj_ext` structures are allocated, accessed, and managed, particularly when both `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING` are enabled. It introduces `SLAB_MAY_ACCOUNT` and changes the layout of `slabobj_ext`. These are core kernel memory management changes that should be fuzzed to ensure no memory corruption, leaks, or accounting errors occur.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "MEMCG",
    "MEM_ALLOC_PROFILING",
    "KFENCE"
  ],
  "FocusSymbols": [
    "alloc_slab_obj_exts",
    "__memcg_slab_post_alloc_hook",
    "__memcg_slab_free_hook",
    "__kmem_cache_create_args",
    "kmem_cache_charge"
  ],
  "Reasoning": "The patch modifies the memory allocation profiling and memcg accounting logic in the SLUB allocator. It changes how `slabobj_ext` structures are allocated, accessed, and managed, particularly when both `CONFIG_MEMCG` and `CONFIG_MEM_ALLOC_PROFILING` are enabled. It introduces `SLAB_MAY_ACCOUNT` and changes the layout of `slabobj_ext`. These are core kernel memory management changes that should be fuzzed to ensure no memory corruption, leaks, or accounting errors occur.",
  "WorthFuzzing": true
}

LLM Calls Summary:
Total Calls	Total Tokens	Avg Tokens	Total Duration (Seconds)	Avg Duration (Seconds)

Tool Calls Summary:
Total Calls	Total Duration (Seconds)	Avg Duration (Seconds)