AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/08/13 09:35	flow	patch-triage	1m Args: null Results: { "EnableConfigs": [ "MEMCG", "MEMCG_V1", "SWAP" ], "FocusSymbols": [ "mem_cgroup_from_private_id", "mem_cgroup_from_private_id_online", "mem_cgroup_private_id_get", "mem_cgroup_swapin_charge_folio", "__mem_cgroup_try_charge_swap", "__mem_cgroup_uncharge_swap", "__memcg1_swapout", "list_lru_walk_node", "workingset_test_recent" ], "KMSANReasoning": "The patch modifies the lifecycle and reference counting of `mem_cgroup` private IDs, introducing `id_objcg` to `struct mem_cgroup` and `id_ref` to `struct obj_cgroup`. It changes how memcgs are looked up from these IDs and how their references are managed, particularly during swap and workingset operations.\n\nThese changes are purely internal state management and do not introduce any new structures or buffers that are copied to user space. The `mem_cgroup` structure itself is allocated using `kmem_cache_zalloc` (as seen in `mem_cgroup_alloc`), ensuring it is fully zero-initialized.\n\nAny bugs introduced by these changes would likely be use-after-free, NULL pointer dereferences, or memory leaks due to incorrect reference counting. These types of bugs are effectively caught by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory reads or info-leaks that would necessitate a dedicated KMSAN fuzzing session.", "NeedsKMSAN": false, "Reasoning": "The patch modifies the memory control group (memcg) subsystem, specifically how private memcg IDs are managed and referenced. It moves the ID reference counting to `struct obj_cgroup` and updates several core memory management paths (swap, workingset, list_lru) to use the new ID management logic. These are reachable core kernel changes with functional impact.", "WorthFuzzing": true }
1/1	2026/08/13 09:35	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 1195f55d527ed44cf22d6593972ac8628e82ce29\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Thu Aug 13 09:34:59 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h\nindex 8170bb8066a22..fef8a1c4191b1 100644\n--- a/include/linux/memcontrol.h\n+++ b/include/linux/memcontrol.h\n@@ -191,6 +191,7 @@ struct obj_cgroup {\n \t\tstruct rcu_head rcu;\n \t};\n \tbool is_root;\n+\trefcount_t id_ref;\n };\n \n /\n@@ -202,8 +203,8 @@ struct obj_cgroup {\n struct mem_cgroup {\n \tstruct cgroup_subsys_state css;\n \n-\t/ Private memcg ID. Used to ID objects that outlive the cgroup /\n-\tstruct mem_cgroup_private_id id;\n+\t/ The objcg holding private memcg ID. /\n+\tstruct obj_cgroup id_objcg;\n \n \t/* Accounted resources /\n \tstruct page_counter memory;\t\t/ Both v1 \u0026 v2 /\n@@ -270,6 +271,9 @@ struct mem_cgroup {\n #endif\n \tint kmemcg_id;\n \n+\t/ Private memcg ID. Used to ID objects that outlive the cgroup /\n+\tint id;\n+\n \tstruct memcg_vmstats_percpu __percpu vmstats_percpu;\n \n #ifdef CONFIG_CGROUP_WRITEBACK\n@@ -820,9 +824,10 @@ static inline unsigned short mem_cgroup_private_id(struct mem_cgroup memcg)\n \tif (mem_cgroup_disabled())\n \t\treturn 0;\n \n-\treturn memcg-\u003eid.id;\n+\treturn memcg-\u003eid;\n }\n struct mem_cgroup mem_cgroup_from_private_id(unsigned short id);\n+struct mem_cgroup mem_cgroup_from_private_id_online(unsigned short id);\n \n static inline u64 mem_cgroup_id(struct mem_cgroup memcg)\n {\ndiff --git a/mm/list_lru.c b/mm/list_lru.c\nindex 36662d02ff963..bc956267f6835 100644\n--- a/mm/list_lru.c\n+++ b/mm/list_lru.c\n@@ -428,7 +428,7 @@ unsigned long list_lru_walk_node(struct list_lru lru, int nid,\n \t\txa_for_each(\u0026lru-\u003exa, index, mlru) {\n \t\t\trcu_read_lock();\n \t\t\tmemcg = mem_cgroup_from_private_id(index);\n-\t\t\tif (!mem_cgroup_tryget(memcg)) {\n+\t\t\tif (!memcg \|\| !mem_cgroup_tryget(memcg)) {\n \t\t\t\trcu_read_unlock();\n \t\t\t\tcontinue;\n \t\t\t}\ndiff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c\nindex 2dc599484d006..e5161e061bd11 100644\n--- a/mm/memcontrol-v1.c\n+++ b/mm/memcontrol-v1.c\n@@ -618,7 +618,7 @@ void memcg1_commit_charge(struct folio folio, struct mem_cgroup memcg)\n /\n void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci)\n {\n-\tstruct mem_cgroup memcg, swap_memcg;\n+\tstruct mem_cgroup memcg;\n \tstruct obj_cgroup objcg;\n \tunsigned int nr_entries;\n \n@@ -638,19 +638,20 @@ void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci)\n \tif (!objcg)\n \t\treturn;\n \n-\trcu_read_lock();\n-\tmemcg = obj_cgroup_memcg(objcg);\n \t/\n \t In case the memcg owning these pages has been offlined and doesn't\n \t * have an ID allocated to it anymore, charge the closest online\n-\t * ancestor for the swap instead and transfer the memory+swap charge.\n+\t * ancestor for the swap instead.\n \t /\n+\tmemcg = get_mem_cgroup_from_objcg(objcg);\n \tnr_entries = folio_nr_pages(folio);\n-\tswap_memcg = mem_cgroup_private_id_get_online(memcg, nr_entries);\n-\tmod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);\n+\tmod_memcg_state(memcg, MEMCG_SWAP, nr_entries);\n+\n+\t/ we have a reference to it, so we should get exact memcg itself /\n+\tmem_cgroup_private_id_get(memcg, nr_entries);\n \n \t__swap_cgroup_set(ci, swp_cluster_offset(folio-\u003eswap), nr_entries,\n-\t\t\t mem_cgroup_private_id(swap_memcg));\n+\t\t\t mem_cgroup_private_id(memcg));\n \n \tfolio_unqueue_deferred_split(folio);\n \tfolio-\u003ememcg_data = 0;\n@@ -658,12 +659,6 @@ void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci)\n \tif (!obj_cgroup_is_root(objcg))\n \t\tpage_counter_uncharge(\u0026memcg-\u003ememory, nr_entries);\n \n-\tif (memcg != swap_memcg) {\n-\t\tif (!mem_cgroup_is_root(swap_memcg))\n-\t\t\tpage_counter_charge(\u0026swap_memcg-\u003ememsw, nr_entries);\n-\t\tpage_counter_uncharge(\u0026memcg-\u003ememsw, nr_entries);\n-\t}\n-\n \t/\n \t * The caller must hold the swap cluster lock with IRQ off. It is\n \t * important here to have the interrupts disabled because it is the\n@@ -675,7 +670,7 @@ void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci)\n \tpreempt_enable_nested();\n \tmemcg1_check_events(memcg, folio_nid(folio));\n \n-\trcu_read_unlock();\n+\tmem_cgroup_put(memcg);\n \tobj_cgroup_put(objcg);\n }\n \ndiff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h\nindex 0f703f239c80f..9c74400aa7ddb 100644\n--- a/mm/memcontrol-v1.h\n+++ b/mm/memcontrol-v1.h\n@@ -21,8 +21,7 @@ void drain_all_stock(struct mem_cgroup root_memcg);\n \n int memory_stat_show(struct seq_file m, void v);\n \n-struct mem_cgroup mem_cgroup_private_id_get_online(struct mem_cgroup memcg,\n-\t\t\t\t\t\t unsigned int n);\n+void mem_cgroup_private_id_get(struct mem_cgroup memcg, unsigned int n);\n \n /* Cgroup v1-specific declarations /\n #ifdef CONFIG_MEMCG_V1\ndiff --git a/mm/memcontrol.c b/mm/memcontrol.c\nindex 8319ad8c5c23a..e7555eca77019 100644\n--- a/mm/memcontrol.c\n+++ b/mm/memcontrol.c\n@@ -3697,7 +3697,7 @@ static void memcg_online_kmem(struct mem_cgroup memcg)\n \n \tstatic_branch_enable(\u0026memcg_kmem_online_key);\n \n-\tmemcg-\u003ekmemcg_id = memcg-\u003eid.id;\n+\tmemcg-\u003ekmemcg_id = memcg-\u003eid;\n }\n \n static void memcg_offline_kmem(struct mem_cgroup memcg)\n@@ -3956,36 +3956,42 @@ static DEFINE_XARRAY_ALLOC1(mem_cgroup_private_ids);\n \n static void mem_cgroup_private_id_remove(struct mem_cgroup memcg)\n {\n-\tif (memcg-\u003eid.id \u003e 0) {\n-\t\txa_erase(\u0026mem_cgroup_private_ids, memcg-\u003eid.id);\n-\t\tmemcg-\u003eid.id = 0;\n+\tif (memcg-\u003eid \u003e 0) {\n+\t\txa_erase(\u0026mem_cgroup_private_ids, memcg-\u003eid);\n+\t\tmemcg-\u003eid = 0;\n \t}\n }\n \n-static inline void mem_cgroup_private_id_put(struct mem_cgroup memcg, unsigned int n)\n+/\n+ @objcg: the objcg returned by mem_cgroup_private_id_objcg\n+ * @id: the corresponding memcg private id\n+ /\n+static void __mem_cgroup_private_id_put(struct obj_cgroup objcg,\n+\t\tunsigned short id, unsigned int n)\n {\n-\tif (refcount_sub_and_test(n, \u0026memcg-\u003eid.ref)) {\n-\t\tmem_cgroup_private_id_remove(memcg);\n+\tstruct obj_cgroup objcg_free;\n \n-\t\t/ Memcg ID pins CSS /\n-\t\tcss_put(\u0026memcg-\u003ecss);\n+\tif (refcount_sub_and_test(n, \u0026objcg-\u003eid_ref)) {\n+\t\tobjcg_free = xa_erase(\u0026mem_cgroup_private_ids, id);\n+\t\tVM_WARN_ON(objcg_free != objcg);\n+\n+\t\t/ Memcg ID pins the objcg /\n+\t\tobj_cgroup_put(objcg);\n \t}\n }\n \n-struct mem_cgroup mem_cgroup_private_id_get_online(struct mem_cgroup memcg, unsigned int n)\n+static inline void mem_cgroup_private_id_put(struct mem_cgroup memcg, unsigned int n)\n {\n-\twhile (!refcount_add_not_zero(n, \u0026memcg-\u003eid.ref)) {\n-\t\t/\n-\t\t The root cgroup cannot be destroyed, so it's refcount must\n-\t\t * always be \u003e= 1.\n-\t\t /\n-\t\tif (WARN_ON_ONCE(mem_cgroup_is_root(memcg))) {\n-\t\t\tVM_BUG_ON(1);\n-\t\t\tbreak;\n-\t\t}\n-\t\tmemcg = parent_mem_cgroup(memcg);\n-\t}\n-\treturn memcg;\n+\t__mem_cgroup_private_id_put(memcg-\u003eid_objcg, memcg-\u003eid, n);\n+}\n+\n+void mem_cgroup_private_id_get(struct mem_cgroup memcg, unsigned int n)\n+{\n+\tbool success;\n+\tstruct obj_cgroup objcg = memcg-\u003eid_objcg;\n+\n+\tsuccess = refcount_add_not_zero(n, \u0026objcg-\u003eid_ref);\n+\tVM_WARN_ON(!success);\n }\n \n /\n@@ -3993,11 +3999,55 @@ struct mem_cgroup mem_cgroup_private_id_get_online(struct mem_cgroup memcg, un\n @id: the memcg id to look up\n \n Caller must hold rcu_read_lock().\n+ \n+ @return: the memcg, or NULL if the memcg is already reparented.\n /\n struct mem_cgroup mem_cgroup_from_private_id(unsigned short id)\n {\n+\tstruct obj_cgroup objcg;\n+\tstruct mem_cgroup memcg;\n \tWARN_ON_ONCE(!rcu_read_lock_held());\n-\treturn xa_load(\u0026mem_cgroup_private_ids, id);\n+\n+\tobjcg = xa_load(\u0026mem_cgroup_private_ids, id);\n+\tif (!objcg)\n+\t\treturn NULL;\n+\n+\tmemcg = obj_cgroup_memcg(objcg);\n+\tif (mem_cgroup_private_id(memcg) != id)\n+\t\treturn NULL;\n+\n+\treturn memcg;\n+}\n+\n+/*\n+ mem_cgroup_from_private_id - look up an online memcg from a memcg id\n+ * and get a reference.\n+ * @id: the memcg id to look up\n+ /\n+struct mem_cgroup mem_cgroup_from_private_id_online(unsigned short id)\n+{\n+\tstruct obj_cgroup objcg;\n+\n+\tobjcg = xa_load(\u0026mem_cgroup_private_ids, id);\n+\tif (!objcg)\n+\t\treturn NULL;\n+\n+\treturn get_mem_cgroup_from_objcg(objcg);\n+}\n+\n+static struct mem_cgroup mem_cgroup_take_from_private_id(unsigned short id, unsigned int n)\n+{\n+\tstruct obj_cgroup objcg;\n+\tstruct mem_cgroup memcg;\n+\n+\tobjcg = xa_load(\u0026mem_cgroup_private_ids, id);\n+\tif (!objcg)\n+\t\treturn NULL;\n+\n+\tmemcg = get_mem_cgroup_from_objcg(objcg);\n+\n+\t__mem_cgroup_private_id_put(objcg, id, n);\n+\treturn memcg;\n }\n \n struct mem_cgroup mem_cgroup_get_from_id(u64 id)\n@@ -4098,7 +4148,7 @@ static struct mem_cgroup mem_cgroup_alloc(struct mem_cgroup parent)\n \tif (!memcg)\n \t\treturn ERR_PTR(-ENOMEM);\n \n-\terror = xa_alloc(\u0026mem_cgroup_private_ids, \u0026memcg-\u003eid.id, NULL,\n+\terror = xa_alloc(\u0026mem_cgroup_private_ids, \u0026memcg-\u003eid, NULL,\n \t\t\t XA_LIMIT(1, MEM_CGROUP_ID_MAX), GFP_KERNEL);\n \tif (error)\n \t\tgoto fail;\n@@ -4243,9 +4293,10 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state css)\n \t\t\t\t FLUSH_TIME);\n \tlru_gen_online_memcg(memcg);\n \n-\t/* Online state pins memcg ID, memcg ID pins CSS /\n-\trefcount_set(\u0026memcg-\u003eid.ref, 1);\n-\tcss_get(css);\n+\t/ CSS pins memcg ID, memcg ID pins obj cgroup /\n+\tmemcg-\u003eid_objcg = memcg-\u003enodeinfo[0]-\u003eobjcg;\n+\trefcount_set(\u0026memcg-\u003eid_objcg-\u003eid_ref, 1);\n+\tobj_cgroup_get(memcg-\u003eid_objcg);\n \n \t/\n \t * Ensure mem_cgroup_from_private_id() works once we're fully online.\n@@ -4257,7 +4308,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state css)\n \t publish it here at the end of onlining. This matches the\n \t * regular ID destruction during offlining.\n \t /\n-\txa_store(\u0026mem_cgroup_private_ids, memcg-\u003eid.id, memcg, GFP_KERNEL);\n+\txa_store(\u0026mem_cgroup_private_ids, memcg-\u003eid, objcg, GFP_KERNEL);\n \n \treturn 0;\n free_objcg:\n@@ -4308,8 +4359,6 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state css)\n \tlru_gen_offline_memcg(memcg);\n \n \tdrain_all_stock(memcg);\n-\n-\tmem_cgroup_private_id_put(memcg, 1);\n }\n \n static void mem_cgroup_css_released(struct cgroup_subsys_state css)\n@@ -4318,6 +4367,9 @@ static void mem_cgroup_css_released(struct cgroup_subsys_state css)\n \n \tinvalidate_reclaim_iterators(memcg);\n \tlru_gen_release_memcg(memcg);\n+\n+\tmem_cgroup_private_id_put(memcg, 1);\n+\tmemcg-\u003eid_objcg = NULL;\n }\n \n static void mem_cgroup_css_free(struct cgroup_subsys_state css)\n@@ -5219,11 +5271,9 @@ int mem_cgroup_swapin_charge_folio(struct folio folio, unsigned short id,\n \tif (mem_cgroup_disabled())\n \t\treturn 0;\n \n-\trcu_read_lock();\n-\tmemcg = mem_cgroup_from_private_id(id);\n-\tif (!memcg \|\| !css_tryget_online(\u0026memcg-\u003ecss))\n+\tmemcg = mem_cgroup_from_private_id_online(id);\n+\tif (!memcg)\n \t\tmemcg = get_mem_cgroup_from_mm(mm);\n-\trcu_read_unlock();\n \n \tret = charge_memcg(folio, memcg, gfp);\n \n@@ -5621,24 +5671,27 @@ int __mem_cgroup_try_charge_swap(struct folio folio)\n \t\treturn 0;\n \t}\n \n-\tmemcg = mem_cgroup_private_id_get_online(memcg, nr_pages);\n-\t/ memcg is pined by memcg ID. /\n+\tmemcg = get_mem_cgroup_from_objcg(objcg);\n \trcu_read_unlock();\n \n \tif (!mem_cgroup_is_root(memcg) \u0026\u0026\n \t !page_counter_try_charge(\u0026memcg-\u003eswap, nr_pages, \u0026counter)) {\n \t\tmemcg_memory_event(memcg, MEMCG_SWAP_MAX);\n \t\tmemcg_memory_event(memcg, MEMCG_SWAP_FAIL);\n-\t\tmem_cgroup_private_id_put(memcg, nr_pages);\n+\t\tmem_cgroup_put(memcg);\n \t\treturn -ENOMEM;\n \t}\n \tmod_memcg_state(memcg, MEMCG_SWAP, nr_pages);\n \n+\t/ we have a reference to it, so we should get exact memcg itself /\n+\tmem_cgroup_private_id_get(memcg, nr_pages);\n+\n \tci = swap_cluster_get_and_lock(folio);\n \t__swap_cgroup_set(ci, swp_cluster_offset(folio-\u003eswap), nr_pages,\n \t\t\t mem_cgroup_private_id(memcg));\n \tswap_cluster_unlock(ci);\n \n+\tmem_cgroup_put(memcg);\n \treturn 0;\n }\n \n@@ -5651,19 +5704,19 @@ void __mem_cgroup_uncharge_swap(unsigned short id, unsigned int nr_pages)\n {\n \tstruct mem_cgroup memcg;\n \n-\trcu_read_lock();\n-\tmemcg = mem_cgroup_from_private_id(id);\n-\tif (memcg) {\n-\t\tif (!mem_cgroup_is_root(memcg)) {\n-\t\t\tif (do_memsw_account())\n-\t\t\t\tpage_counter_uncharge(\u0026memcg-\u003ememsw, nr_pages);\n-\t\t\telse\n-\t\t\t\tpage_counter_uncharge(\u0026memcg-\u003eswap, nr_pages);\n-\t\t}\n-\t\tmod_memcg_state(memcg, MEMCG_SWAP, -nr_pages);\n-\t\tmem_cgroup_private_id_put(memcg, nr_pages);\n+\tmemcg = mem_cgroup_take_from_private_id(id, nr_pages);\n+\tif (!memcg)\n+\t\treturn;\n+\n+\tif (!mem_cgroup_is_root(memcg)) {\n+\t\tif (do_memsw_account())\n+\t\t\tpage_counter_uncharge(\u0026memcg-\u003ememsw, nr_pages);\n+\t\telse\n+\t\t\tpage_counter_uncharge(\u0026memcg-\u003eswap, nr_pages);\n \t}\n-\trcu_read_unlock();\n+\tmod_memcg_state(memcg, MEMCG_SWAP, -nr_pages);\n+\n+\tmem_cgroup_put(memcg);\n }\n \n long mem_cgroup_get_nr_swap_pages(struct mem_cgroup memcg)\ndiff --git a/mm/workingset.c b/mm/workingset.c\nindex f351798e723ac..b6e22536a5240 100644\n--- a/mm/workingset.c\n+++ b/mm/workingset.c\n@@ -283,6 +283,10 @@ static bool lru_gen_test_recent(void shadow, struct lruvec *lruvec,\n \tmemcg = mem_cgroup_from_private_id(memcg_id);\n \tlruvec = mem_cgroup_lruvec(memcg, pgdat);\n \n+\t/* reparented memcg loses its max_seq /\n+\tif (!memcg)\n+\t\treturn false;\n+\n \tmax_seq = READ_ONCE((lruvec)-\u003elrugen.max_seq);\n \tmax_seq \u0026= (file ? EVICTION_MASK : EVICTION_MASK_ANON) \u003e\u003e LRU_REFS_WIDTH;\n \n@@ -470,7 +474,7 @@ bool workingset_test_recent(void shadow, bool file, bool workingset,\n \t * configurations instead.\n \t */\n \teviction_memcg = mem_cgroup_from_private_id(memcgid);\n-\tif (!mem_cgroup_tryget(eviction_memcg))\n+\tif (!eviction_memcg \|\| !mem_cgroup_tryget(eviction_memcg))\n \t\teviction_memcg = NULL;\n \trcu_read_unlock();\n \n" }
2/1	2026/08/13 09:35	agent	patch-evaluator	1m Model: best-expensive Args: null Results: { "EnableConfigs": [ "MEMCG", "MEMCG_V1", "SWAP" ], "FocusSymbols": [ "mem_cgroup_from_private_id", "mem_cgroup_from_private_id_online", "mem_cgroup_private_id_get", "mem_cgroup_swapin_charge_folio", "__mem_cgroup_try_charge_swap", "__mem_cgroup_uncharge_swap", "__memcg1_swapout", "list_lru_walk_node", "workingset_test_recent" ], "Reasoning": "The patch modifies the memory control group (memcg) subsystem, specifically how private memcg IDs are managed and referenced. It moves the ID reference counting to `struct obj_cgroup` and updates several core memory management paths (swap, workingset, list_lru) to use the new ID management logic. These are reachable core kernel changes with functional impact.", "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 1195f55d527ed44cf22d6593972ac8628e82ce29 Author: syz-cluster <triage@syzkaller.com> Date: Thu Aug 13 09:34:59 2026 +0000 syz-cluster: applied patch under review diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 8170bb8066a22..fef8a1c4191b1 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -191,6 +191,7 @@ struct obj_cgroup { struct rcu_head rcu; }; bool is_root; + refcount_t id_ref; }; /* @@ -202,8 +203,8 @@ struct obj_cgroup { struct mem_cgroup { struct cgroup_subsys_state css; - /* Private memcg ID. Used to ID objects that outlive the cgroup / - struct mem_cgroup_private_id id; + / The objcg holding private memcg ID. / + struct obj_cgroup id_objcg; /* Accounted resources / struct page_counter memory; / Both v1 & v2 / @@ -270,6 +271,9 @@ struct mem_cgroup { #endif int kmemcg_id; + / Private memcg ID. Used to ID objects that outlive the cgroup / + int id; + struct memcg_vmstats_percpu __percpu vmstats_percpu; #ifdef CONFIG_CGROUP_WRITEBACK @@ -820,9 +824,10 @@ static inline unsigned short mem_cgroup_private_id(struct mem_cgroup memcg) if (mem_cgroup_disabled()) return 0; - return memcg->id.id; + return memcg->id; } struct mem_cgroup mem_cgroup_from_private_id(unsigned short id); +struct mem_cgroup mem_cgroup_from_private_id_online(unsigned short id); static inline u64 mem_cgroup_id(struct mem_cgroup memcg) { diff --git a/mm/list_lru.c b/mm/list_lru.c index 36662d02ff963..bc956267f6835 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -428,7 +428,7 @@ unsigned long list_lru_walk_node(struct list_lru lru, int nid, xa_for_each(&lru->xa, index, mlru) { rcu_read_lock(); memcg = mem_cgroup_from_private_id(index); - if (!mem_cgroup_tryget(memcg)) { + if (!memcg \|\| !mem_cgroup_tryget(memcg)) { rcu_read_unlock(); continue; } diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c index 2dc599484d006..e5161e061bd11 100644 --- a/mm/memcontrol-v1.c +++ b/mm/memcontrol-v1.c @@ -618,7 +618,7 @@ void memcg1_commit_charge(struct folio folio, struct mem_cgroup memcg) / void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci) { - struct mem_cgroup memcg, swap_memcg; + struct mem_cgroup memcg; struct obj_cgroup objcg; unsigned int nr_entries; @@ -638,19 +638,20 @@ void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci) if (!objcg) return; - rcu_read_lock(); - memcg = obj_cgroup_memcg(objcg); /* * In case the memcg owning these pages has been offlined and doesn't * have an ID allocated to it anymore, charge the closest online - * ancestor for the swap instead and transfer the memory+swap charge. + * ancestor for the swap instead. / + memcg = get_mem_cgroup_from_objcg(objcg); nr_entries = folio_nr_pages(folio); - swap_memcg = mem_cgroup_private_id_get_online(memcg, nr_entries); - mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries); + mod_memcg_state(memcg, MEMCG_SWAP, nr_entries); + + / we have a reference to it, so we should get exact memcg itself / + mem_cgroup_private_id_get(memcg, nr_entries); __swap_cgroup_set(ci, swp_cluster_offset(folio->swap), nr_entries, - mem_cgroup_private_id(swap_memcg)); + mem_cgroup_private_id(memcg)); folio_unqueue_deferred_split(folio); folio->memcg_data = 0; @@ -658,12 +659,6 @@ void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci) if (!obj_cgroup_is_root(objcg)) page_counter_uncharge(&memcg->memory, nr_entries); - if (memcg != swap_memcg) { - if (!mem_cgroup_is_root(swap_memcg)) - page_counter_charge(&swap_memcg->memsw, nr_entries); - page_counter_uncharge(&memcg->memsw, nr_entries); - } - / * The caller must hold the swap cluster lock with IRQ off. It is * important here to have the interrupts disabled because it is the @@ -675,7 +670,7 @@ void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci) preempt_enable_nested(); memcg1_check_events(memcg, folio_nid(folio)); - rcu_read_unlock(); + mem_cgroup_put(memcg); obj_cgroup_put(objcg); } diff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h index 0f703f239c80f..9c74400aa7ddb 100644 --- a/mm/memcontrol-v1.h +++ b/mm/memcontrol-v1.h @@ -21,8 +21,7 @@ void drain_all_stock(struct mem_cgroup root_memcg); int memory_stat_show(struct seq_file m, void v); -struct mem_cgroup mem_cgroup_private_id_get_online(struct mem_cgroup memcg, - unsigned int n); +void mem_cgroup_private_id_get(struct mem_cgroup memcg, unsigned int n); /* Cgroup v1-specific declarations / #ifdef CONFIG_MEMCG_V1 diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8319ad8c5c23a..e7555eca77019 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3697,7 +3697,7 @@ static void memcg_online_kmem(struct mem_cgroup memcg) static_branch_enable(&memcg_kmem_online_key); - memcg->kmemcg_id = memcg->id.id; + memcg->kmemcg_id = memcg->id; } static void memcg_offline_kmem(struct mem_cgroup memcg) @@ -3956,36 +3956,42 @@ static DEFINE_XARRAY_ALLOC1(mem_cgroup_private_ids); static void mem_cgroup_private_id_remove(struct mem_cgroup memcg) { - if (memcg->id.id > 0) { - xa_erase(&mem_cgroup_private_ids, memcg->id.id); - memcg->id.id = 0; + if (memcg->id > 0) { + xa_erase(&mem_cgroup_private_ids, memcg->id); + memcg->id = 0; } } -static inline void mem_cgroup_private_id_put(struct mem_cgroup memcg, unsigned int n) +/* + * @objcg: the objcg returned by mem_cgroup_private_id_objcg + * @id: the corresponding memcg private id + / +static void __mem_cgroup_private_id_put(struct obj_cgroup objcg, + unsigned short id, unsigned int n) { - if (refcount_sub_and_test(n, &memcg->id.ref)) { - mem_cgroup_private_id_remove(memcg); + struct obj_cgroup objcg_free; - / Memcg ID pins CSS / - css_put(&memcg->css); + if (refcount_sub_and_test(n, &objcg->id_ref)) { + objcg_free = xa_erase(&mem_cgroup_private_ids, id); + VM_WARN_ON(objcg_free != objcg); + + / Memcg ID pins the objcg / + obj_cgroup_put(objcg); } } -struct mem_cgroup mem_cgroup_private_id_get_online(struct mem_cgroup memcg, unsigned int n) +static inline void mem_cgroup_private_id_put(struct mem_cgroup memcg, unsigned int n) { - while (!refcount_add_not_zero(n, &memcg->id.ref)) { - /* - * The root cgroup cannot be destroyed, so it's refcount must - * always be >= 1. - / - if (WARN_ON_ONCE(mem_cgroup_is_root(memcg))) { - VM_BUG_ON(1); - break; - } - memcg = parent_mem_cgroup(memcg); - } - return memcg; + __mem_cgroup_private_id_put(memcg->id_objcg, memcg->id, n); +} + +void mem_cgroup_private_id_get(struct mem_cgroup memcg, unsigned int n) +{ + bool success; + struct obj_cgroup objcg = memcg->id_objcg; + + success = refcount_add_not_zero(n, &objcg->id_ref); + VM_WARN_ON(!success); } /* @@ -3993,11 +3999,55 @@ struct mem_cgroup mem_cgroup_private_id_get_online(struct mem_cgroup memcg, un * @id: the memcg id to look up * * Caller must hold rcu_read_lock(). + * + * @return: the memcg, or NULL if the memcg is already reparented. / struct mem_cgroup mem_cgroup_from_private_id(unsigned short id) { + struct obj_cgroup objcg; + struct mem_cgroup memcg; WARN_ON_ONCE(!rcu_read_lock_held()); - return xa_load(&mem_cgroup_private_ids, id); + + objcg = xa_load(&mem_cgroup_private_ids, id); + if (!objcg) + return NULL; + + memcg = obj_cgroup_memcg(objcg); + if (mem_cgroup_private_id(memcg) != id) + return NULL; + + return memcg; +} + +/** + * mem_cgroup_from_private_id - look up an online memcg from a memcg id + * and get a reference. + * @id: the memcg id to look up + / +struct mem_cgroup mem_cgroup_from_private_id_online(unsigned short id) +{ + struct obj_cgroup objcg; + + objcg = xa_load(&mem_cgroup_private_ids, id); + if (!objcg) + return NULL; + + return get_mem_cgroup_from_objcg(objcg); +} + +static struct mem_cgroup mem_cgroup_take_from_private_id(unsigned short id, unsigned int n) +{ + struct obj_cgroup objcg; + struct mem_cgroup memcg; + + objcg = xa_load(&mem_cgroup_private_ids, id); + if (!objcg) + return NULL; + + memcg = get_mem_cgroup_from_objcg(objcg); + + __mem_cgroup_private_id_put(objcg, id, n); + return memcg; } struct mem_cgroup mem_cgroup_get_from_id(u64 id) @@ -4098,7 +4148,7 @@ static struct mem_cgroup mem_cgroup_alloc(struct mem_cgroup parent) if (!memcg) return ERR_PTR(-ENOMEM); - error = xa_alloc(&mem_cgroup_private_ids, &memcg->id.id, NULL, + error = xa_alloc(&mem_cgroup_private_ids, &memcg->id, NULL, XA_LIMIT(1, MEM_CGROUP_ID_MAX), GFP_KERNEL); if (error) goto fail; @@ -4243,9 +4293,10 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state css) FLUSH_TIME); lru_gen_online_memcg(memcg); - /* Online state pins memcg ID, memcg ID pins CSS / - refcount_set(&memcg->id.ref, 1); - css_get(css); + / CSS pins memcg ID, memcg ID pins obj cgroup / + memcg->id_objcg = memcg->nodeinfo[0]->objcg; + refcount_set(&memcg->id_objcg->id_ref, 1); + obj_cgroup_get(memcg->id_objcg); / * Ensure mem_cgroup_from_private_id() works once we're fully online. @@ -4257,7 +4308,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state css) publish it here at the end of onlining. This matches the * regular ID destruction during offlining. / - xa_store(&mem_cgroup_private_ids, memcg->id.id, memcg, GFP_KERNEL); + xa_store(&mem_cgroup_private_ids, memcg->id, objcg, GFP_KERNEL); return 0; free_objcg: @@ -4308,8 +4359,6 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state css) lru_gen_offline_memcg(memcg); drain_all_stock(memcg); - - mem_cgroup_private_id_put(memcg, 1); } static void mem_cgroup_css_released(struct cgroup_subsys_state css) @@ -4318,6 +4367,9 @@ static void mem_cgroup_css_released(struct cgroup_subsys_state css) invalidate_reclaim_iterators(memcg); lru_gen_release_memcg(memcg); + + mem_cgroup_private_id_put(memcg, 1); + memcg->id_objcg = NULL; } static void mem_cgroup_css_free(struct cgroup_subsys_state css) @@ -5219,11 +5271,9 @@ int mem_cgroup_swapin_charge_folio(struct folio folio, unsigned short id, if (mem_cgroup_disabled()) return 0; - rcu_read_lock(); - memcg = mem_cgroup_from_private_id(id); - if (!memcg \|\| !css_tryget_online(&memcg->css)) + memcg = mem_cgroup_from_private_id_online(id); + if (!memcg) memcg = get_mem_cgroup_from_mm(mm); - rcu_read_unlock(); ret = charge_memcg(folio, memcg, gfp); @@ -5621,24 +5671,27 @@ int __mem_cgroup_try_charge_swap(struct folio folio) return 0; } - memcg = mem_cgroup_private_id_get_online(memcg, nr_pages); - / memcg is pined by memcg ID. / + memcg = get_mem_cgroup_from_objcg(objcg); rcu_read_unlock(); if (!mem_cgroup_is_root(memcg) && !page_counter_try_charge(&memcg->swap, nr_pages, &counter)) { memcg_memory_event(memcg, MEMCG_SWAP_MAX); memcg_memory_event(memcg, MEMCG_SWAP_FAIL); - mem_cgroup_private_id_put(memcg, nr_pages); + mem_cgroup_put(memcg); return -ENOMEM; } mod_memcg_state(memcg, MEMCG_SWAP, nr_pages); + / we have a reference to it, so we should get exact memcg itself / + mem_cgroup_private_id_get(memcg, nr_pages); + ci = swap_cluster_get_and_lock(folio); __swap_cgroup_set(ci, swp_cluster_offset(folio->swap), nr_pages, mem_cgroup_private_id(memcg)); swap_cluster_unlock(ci); + mem_cgroup_put(memcg); return 0; } @@ -5651,19 +5704,19 @@ void __mem_cgroup_uncharge_swap(unsigned short id, unsigned int nr_pages) { struct mem_cgroup memcg; - rcu_read_lock(); - memcg = mem_cgroup_from_private_id(id); - if (memcg) { - if (!mem_cgroup_is_root(memcg)) { - if (do_memsw_account()) - page_counter_uncharge(&memcg->memsw, nr_pages); - else - page_counter_uncharge(&memcg->swap, nr_pages); - } - mod_memcg_state(memcg, MEMCG_SWAP, -nr_pages); - mem_cgroup_private_id_put(memcg, nr_pages); + memcg = mem_cgroup_take_from_private_id(id, nr_pages); + if (!memcg) + return; + + if (!mem_cgroup_is_root(memcg)) { + if (do_memsw_account()) + page_counter_uncharge(&memcg->memsw, nr_pages); + else + page_counter_uncharge(&memcg->swap, nr_pages); } - rcu_read_unlock(); + mod_memcg_state(memcg, MEMCG_SWAP, -nr_pages); + + mem_cgroup_put(memcg); } long mem_cgroup_get_nr_swap_pages(struct mem_cgroup memcg) diff --git a/mm/workingset.c b/mm/workingset.c index f351798e723ac..b6e22536a5240 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -283,6 +283,10 @@ static bool lru_gen_test_recent(void shadow, struct lruvec *lruvec, memcg = mem_cgroup_from_private_id(memcg_id); lruvec = mem_cgroup_lruvec(memcg, pgdat); + /* reparented memcg loses its max_seq / + if (!memcg) + return false; + max_seq = READ_ONCE((lruvec)->lrugen.max_seq); max_seq &= (file ? EVICTION_MASK : EVICTION_MASK_ANON) >> LRU_REFS_WIDTH; @@ -470,7 +474,7 @@ bool workingset_test_recent(void shadow, bool file, bool workingset, * configurations instead. */ eviction_memcg = mem_cgroup_from_private_id(memcgid); - if (!mem_cgroup_tryget(eviction_memcg)) + if (!eviction_memcg \|\| !mem_cgroup_tryget(eviction_memcg)) eviction_memcg = NULL; rcu_read_unlock();
3/2	2026/08/13 09:35	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 7465 output: 128 thoughts: 673 Thoughts: Fuzzing Focus: Memcg ID Management Patch Okay, here's what I'm thinking. We've got a patch that's fundamentally altering how the `memcg->id` is handled within the Linux kernel, specifically within the memory control group subsystem (memcg). It's a pretty substantial change, moving the `refcount_t id_ref` from `memcg` to `struct obj_cgroup`. We're talking about refactoring how the ID is managed, essentially. This also involves renaming a few things; `memcg->id.id` is now simply `memcg->id`, and the reference count is now handled through `memcg->id_objcg->id_ref`. This patch is touching core memory management and cgroup code, meaning it has significant functional implications. It's definitely reachable, especially in virtualized environments. Because of that, and knowing the potential for subtle bugs in refcounting changes like this, I'm confident we need to mark this for fuzzing (WorthFuzzing=true, no question). My main focus right now is to identify the specific areas to target with our fuzzers. Based on the diff, these functions are modified or added: `mem_cgroup_from_private_id`, `mem_cgroup_from_private_id_online`, `mem_cgroup_private_id_get`, `__mem_cgroup_private_id_put`, `mem_cgroup_take_from_private_id`, `mem_cgroup_css_online`, `mem_cgroup_css_offline`, `mem_cgroup_css_released`, `mem_cgroup_swapin_charge_folio`, `__mem_cgroup_try_charge_swap`, `__mem_cgroup_uncharge_swap`, `__memcg1_swapout`, `list_lru_walk_node`, `workingset_test_recent`, and `lru_gen_test_recent`. Now, the next step is to prioritize based on accessibility. I need to figure out which of these are the public entrypoints. I'm taking a look at `mm/memcontrol.c` and `mm/memcontrol-v1.c` since the diff touches those files directly. I've already confirmed `mem_cgroup_from_private_id`, `mem_cgroup_from_private_id_online`, `mem_cgroup_private_id_get`, `mem_cgroup_swapin_charge_folio`, `__mem_cgroup_try_charge_swap`, `__mem_cgroup_uncharge_swap`, `__memcg1_swapout`, `list_lru_walk_node`, and `workingset_test_recent` are non-static functions, which makes them likely entry points. I’m thinking I will utilize `grepper` to pull up these definitions. That should give me the function signatures and likely give us the information to find test harness entry points. I should be able to go from there, and construct an effective fuzzing strategy.
4/2	2026/08/13 09:35	tool	grepper	0m Args: { "Expression": "^(void\|struct mem_cgroup \\\|int\|unsigned long\|bool) (mem_cgroup_from_private_id\|mem_cgroup_from_private_id_online\|mem_cgroup_private_id_get\|mem_cgroup_swapin_charge_folio\|__mem_cgroup_try_charge_swap\|__mem_cgroup_uncharge_swap\|__memcg1_swapout\|list_lru_walk_node\|workingset_test_recent)\\(" } Results:* { "Output": "include/linux/list_lru.h=320=unsigned long list_lru_walk_one_irq(struct list_lru lru,\n--\ninclude/linux/list_lru.h-323-\t\t\t\t unsigned long nr_to_walk);\ninclude/linux/list_lru.h:324:unsigned long list_lru_walk_node(struct list_lru lru, int nid,\ninclude/linux/list_lru.h-325-\t\t\t\t list_lru_walk_cb isolate, void cb_arg,\n--\ninclude/linux/memcontrol.h=664=int mem_cgroup_charge_hugetlb(struct folio* folio, gfp_t gfp);\ninclude/linux/memcontrol.h-665-\ninclude/linux/memcontrol.h:666:int mem_cgroup_swapin_charge_folio(struct folio folio, unsigned short id,\ninclude/linux/memcontrol.h-667-\t\t\t\t struct mm_struct mm, gfp_t gfp);\n--\ninclude/linux/memcontrol.h=1973=static inline void mem_cgroup_exit_user_fault(void)\n--\ninclude/linux/memcontrol.h-1980-\ninclude/linux/memcontrol.h:1981:void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci);\ninclude/linux/memcontrol.h-1982-void memcg1_swapin(struct folio folio);\n--\ninclude/linux/swap.h=501=static inline void folio_throttle_swaprate(struct folio folio, gfp_t gfp)\n--\ninclude/linux/swap.h-506-#if defined(CONFIG_MEMCG) \u0026\u0026 defined(CONFIG_SWAP)\ninclude/linux/swap.h:507:int __mem_cgroup_try_charge_swap(struct folio folio);\ninclude/linux/swap.h-508-static inline int mem_cgroup_try_charge_swap(struct folio folio)\n--\nmm/internal.h=28=struct huge_bootmem_page {\n--\nmm/internal.h-34-/* mm/workingset.c /\nmm/internal.h:35:bool workingset_test_recent(void shadow, bool file, bool workingset,\nmm/internal.h-36-\t\t\t bool flush);\n--\nmm/list_lru.c=405=list_lru_walk_one_irq(struct list_lru lru, int nid, struct mem_cgroup memcg,\n--\nmm/list_lru.c-412-\nmm/list_lru.c:413:unsigned long list_lru_walk_node(struct list_lru lru, int nid,\nmm/list_lru.c-414-\t\t\t\t list_lru_walk_cb isolate, void cb_arg,\n--\nmm/memcontrol-v1.c=597=void memcg1_commit_charge(struct folio folio, struct mem_cgroup memcg)\n--\nmm/memcontrol-v1.c-618- /\nmm/memcontrol-v1.c:619:void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci)\nmm/memcontrol-v1.c-620-{\n--\nmm/memcontrol-v1.h=22=int memory_stat_show(struct seq_file m, void v);\nmm/memcontrol-v1.h-23-\nmm/memcontrol-v1.h:24:void mem_cgroup_private_id_get(struct mem_cgroup memcg, unsigned int n);\nmm/memcontrol-v1.h-25-\n--\nmm/memcontrol.c=3983=static inline void mem_cgroup_private_id_put(struct mem_cgroup memcg, unsigned int n)\n--\nmm/memcontrol.c-3987-\nmm/memcontrol.c:3988:void mem_cgroup_private_id_get(struct mem_cgroup memcg, unsigned int n)\nmm/memcontrol.c-3989-{\n--\nmm/memcontrol.c=5231=int mem_cgroup_charge_hugetlb(struct folio folio, gfp_t gfp)\n--\nmm/memcontrol.c-5264- /\nmm/memcontrol.c:5265:int mem_cgroup_swapin_charge_folio(struct folio folio, unsigned short id,\nmm/memcontrol.c-5266-\t\t\t\t struct mm_struct mm, gfp_t gfp)\n--\nmm/memcontrol.c=5605=int __init mem_cgroup_init(void)\n--\nmm/memcontrol.c-5649- /\nmm/memcontrol.c:5650:int __mem_cgroup_try_charge_swap(struct folio folio)\nmm/memcontrol.c-5651-{\n--\nmm/memcontrol.c-5702- /\nmm/memcontrol.c:5703:void __mem_cgroup_uncharge_swap(unsigned short id, unsigned int nr_pages)\nmm/memcontrol.c-5704-{\n--\nmm/workingset.c=396=void workingset_eviction(struct folio folio, struct mem_cgroup target_memcg)\n--\nmm/workingset.c-433- /\nmm/workingset.c:434:bool workingset_test_recent(void shadow, bool file, bool workingset,\nmm/workingset.c-435-\t\t\t\tbool flush)\n" }
5/2	2026/08/13 09:35	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 10375 output: 30 thoughts: 181 Thoughts: Analyzing Memory Cgroup Functions Okay, so I've been looking at this code, and the first thing I noticed is that my regex didn't catch `mem_cgroup_from_private_id`. Hmm, I wonder why... Ah, right, it returns a `struct mem_cgroup *`. That's why the regex missed it. Let's make sure we include that one in our evaluation. I've also identified a few other potentially relevant functions: `mem_cgroup_from_private_id_online`, `mem_cgroup_private_id_get`, `mem_cgroup_swapin_charge_folio`, `__mem_cgroup_try_charge_swap`, `__mem_cgroup_uncharge_swap`, `__memcg1_swapout`, `list_lru_walk_node`, and `workingset_test_recent`. Seems like a pretty good list to start with for exploring this particular area of memory cgroups. Now, let's dive into the details of `mem_cgroup_from_private_id` and `mem_cgroup_from_private_id_online`. I need to understand how these functions retrieve the memory cgroup based on a private ID.
6/2	2026/08/13 09:35	tool	grepper	0m Args: { "Expression": "struct mem_cgroup \\mem_cgroup_from_private_id" } Results:* { "Output": "include/linux/memcontrol.h=822=static inline unsigned short mem_cgroup_private_id(struct mem_cgroup memcg)\n--\ninclude/linux/memcontrol.h-828-}\ninclude/linux/memcontrol.h:829:struct mem_cgroup mem_cgroup_from_private_id(unsigned short id);\ninclude/linux/memcontrol.h:830:struct mem_cgroup mem_cgroup_from_private_id_online(unsigned short id);\ninclude/linux/memcontrol.h-831-\n--\ninclude/linux/memcontrol.h=1297=static inline unsigned short mem_cgroup_private_id(struct mem_cgroup memcg)\n--\ninclude/linux/memcontrol.h-1301-\ninclude/linux/memcontrol.h:1302:static inline struct mem_cgroup mem_cgroup_from_private_id(unsigned short id)\ninclude/linux/memcontrol.h-1303-{\n--\nmm/memcontrol.c=3988=void mem_cgroup_private_id_get(struct mem_cgroup memcg, unsigned int n)\n--\nmm/memcontrol.c-4004- /\nmm/memcontrol.c:4005:struct mem_cgroup mem_cgroup_from_private_id(unsigned short id)\nmm/memcontrol.c-4006-{\n--\nmm/memcontrol.c-4026- /\nmm/memcontrol.c:4027:struct mem_cgroup mem_cgroup_from_private_id_online(unsigned short id)\nmm/memcontrol.c-4028-{\n" }
7/2	2026/08/13 09:35	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 11284 output: 73 thoughts: 204 Thoughts: Analyzing the `mem_cgroup_from_private_id` and Related Functions Okay, so these two functions, `mem_cgroup_from_private_id` and its online counterpart, are exported, which means they're accessible outside their immediate scope. But they primarily seem to function as helper routines, which raises a question of their wider impact and how they are used. The key entry points that rely on them appear to be `mem_cgroup_swapin_charge_folio`, `__mem_cgroup_try_charge_swap`, `__mem_cgroup_uncharge_swap`, `__memcg1_swapout`, `list_lru_walk_node`, and `workingset_test_recent`. This gives me some direction as to where to look to investigate the context of their use. My next step is to figure out their configuration dependencies. Clearly, `CONFIG_MEMCG` is a fundamental requirement. What I'm less certain about is the dependency on `CONFIG_SWAP`. Given that a significant portion of the entry points appear to be swap-related, there is a strong possibility that `CONFIG_SWAP` will also be a dependency. I'll need to go through the source to see what I can find. I'm going to look at both `mm/memcontrol.c` and `mm/memcontrol-v1.c` and look for any `#ifdef` directives that might provide clues about conditional compilation and configuration dependencies. Let's see what the code reveals.
8/2	2026/08/13 09:35	tool	grepper	0m Args: { "Expression": "^(#ifdef\|#ifndef) CONFIG_", "PathPrefix": "mm/memcontrol.c" } Results: { "Output": "mm/memcontrol.c=102=static struct kmem_cache memcg_pn_cachep;\nmm/memcontrol.c-103-\nmm/memcontrol.c:104:#ifdef CONFIG_CGROUP_WRITEBACK\nmm/memcontrol.c-105-static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq);\n--\nmm/memcontrol.c=214=static inline struct obj_cgroup __memcg_reparent_objcgs(struct mem_cgroup memcg,\n--\nmm/memcontrol.c-233-\nmm/memcontrol.c:234:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-235-static void __mem_cgroup_flush_stats(struct mem_cgroup memcg, bool force);\n--\nmm/memcontrol.c=377=static const unsigned int memcg_node_stat_items[] = {\n--\nmm/memcontrol.c-404-\tNR_SECONDARY_PAGETABLE,\nmm/memcontrol.c:405:#ifdef CONFIG_SWAP\nmm/memcontrol.c-406-\tNR_SWAPCACHE,\nmm/memcontrol.c-407-#endif\nmm/memcontrol.c:408:#ifdef CONFIG_NUMA_BALANCING\nmm/memcontrol.c-409-\tPGPROMOTE_SUCCESS,\n--\nmm/memcontrol.c-427-\tPGREFILL,\nmm/memcontrol.c:428:#ifdef CONFIG_HUGETLB_PAGE\nmm/memcontrol.c-429-\tNR_HUGETLB,\n--\nmm/memcontrol.c=488=unsigned long lruvec_page_state(struct lruvec lruvec, enum node_stat_item idx)\n--\nmm/memcontrol.c-502-\tx = READ_ONCE(pn-\u003elruvec_stats-\u003estate[i]);\nmm/memcontrol.c:503:#ifdef CONFIG_SMP\nmm/memcontrol.c-504-\tif (x \u003c 0)\n--\nmm/memcontrol.c=510=unsigned long lruvec_page_state_local(struct lruvec lruvec,\n--\nmm/memcontrol.c-525-\tx = READ_ONCE(pn-\u003elruvec_stats-\u003estate_local[i]);\nmm/memcontrol.c:526:#ifdef CONFIG_SMP\nmm/memcontrol.c-527-\tif (x \u003c 0)\n--\nmm/memcontrol.c-532-\nmm/memcontrol.c:533:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-534-static void __mod_memcg_lruvec_state(struct mem_cgroup_per_node pn,\n--\nmm/memcontrol.c=558=static const unsigned int memcg_vm_event_stat[] = {\nmm/memcontrol.c:559:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-560-\tPGPGIN,\n--\nmm/memcontrol.c-570-\tPGLAZYFREED,\nmm/memcontrol.c:571:#ifdef CONFIG_SWAP\nmm/memcontrol.c-572-\tSWPIN_ZERO,\n--\nmm/memcontrol.c-574-#endif\nmm/memcontrol.c:575:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-576-\tZSWPIN,\n--\nmm/memcontrol.c-579-#endif\nmm/memcontrol.c:580:#ifdef CONFIG_TRANSPARENT_HUGEPAGE\nmm/memcontrol.c-581-\tTHP_FAULT_ALLOC,\n--\nmm/memcontrol.c-585-#endif\nmm/memcontrol.c:586:#ifdef CONFIG_NUMA_BALANCING\nmm/memcontrol.c-587-\tNUMA_PAGE_MIGRATE,\n--\nmm/memcontrol.c=762=unsigned long memcg_page_state(struct mem_cgroup memcg, int idx)\n--\nmm/memcontrol.c-770-\tx = READ_ONCE(memcg-\u003evmstats-\u003estate[i]);\nmm/memcontrol.c:771:#ifdef CONFIG_SMP\nmm/memcontrol.c-772-\tif (x \u003c 0)\n--\nmm/memcontrol.c=792=static long memcg_state_val_in_pages(int idx, long val)\n--\nmm/memcontrol.c-807-\nmm/memcontrol.c:808:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-809-/\n--\nmm/memcontrol.c=876=void mod_memcg_state(struct mem_cgroup memcg, enum memcg_stat_item idx,\n--\nmm/memcontrol.c-888-\nmm/memcontrol.c:889:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-890-/* idx can be of type enum memcg_stat_item or node_stat_item. /\nmm/memcontrol.c=891=unsigned long memcg_page_state_local(struct mem_cgroup memcg, int idx)\n--\nmm/memcontrol.c-899-\tx = READ_ONCE(memcg-\u003evmstats-\u003estate_local[i]);\nmm/memcontrol.c:900:#ifdef CONFIG_SMP\nmm/memcontrol.c-901-\tif (x \u003c 0)\n--\nmm/memcontrol.c=1064=bool memcg_vm_event_item_valid(enum vm_event_item idx)\n--\nmm/memcontrol.c-1071-\nmm/memcontrol.c:1072:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-1073-unsigned long memcg_events_local(struct mem_cgroup memcg, int event)\n--\nmm/memcontrol.c=1551=static const struct memory_stat memory_stats[] = {\n--\nmm/memcontrol.c-1561-\t{ \"shmem\",\t\t\tNR_SHMEM\t\t\t},\nmm/memcontrol.c:1562:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-1563-\t{ \"zswap\",\t\t\tMEMCG_ZSWAP_B\t\t\t},\n--\nmm/memcontrol.c-1569-\t{ \"file_writeback\",\t\tNR_WRITEBACK\t\t\t},\nmm/memcontrol.c:1570:#ifdef CONFIG_SWAP\nmm/memcontrol.c-1571-\t{ \"swapcached\",\t\t\tNR_SWAPCACHE\t\t\t},\nmm/memcontrol.c-1572-#endif\nmm/memcontrol.c:1573:#ifdef CONFIG_TRANSPARENT_HUGEPAGE\nmm/memcontrol.c-1574-\t{ \"anon_thp\",\t\t\tNR_ANON_THPS\t\t\t},\n--\nmm/memcontrol.c-1584-\t{ \"slab_unreclaimable\",\t\tNR_SLAB_UNRECLAIMABLE_B\t\t},\nmm/memcontrol.c:1585:#ifdef CONFIG_HUGETLB_PAGE\nmm/memcontrol.c-1586-\t{ \"hugetlb\",\t\t\tNR_HUGETLB\t\t\t},\n--\nmm/memcontrol.c-1610-\t{ \"pgrefill\",\t\t\tPGREFILL\t\t},\nmm/memcontrol.c:1611:#ifdef CONFIG_NUMA_BALANCING\nmm/memcontrol.c-1612-\t{ \"pgpromote_success\",\t\tPGPROMOTE_SUCCESS\t},\n--\nmm/memcontrol.c=1633=static int memcg_page_state_output_unit(int item)\n--\nmm/memcontrol.c-1662-\tcase PGREFILL:\nmm/memcontrol.c:1663:#ifdef CONFIG_NUMA_BALANCING\nmm/memcontrol.c-1664-\tcase PGPROMOTE_SUCCESS:\n--\nmm/memcontrol.c=1672=unsigned long memcg_page_state_output(struct mem_cgroup memcg, int item)\n--\nmm/memcontrol.c-1677-\nmm/memcontrol.c:1678:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-1679-unsigned long memcg_page_state_local_output(struct mem_cgroup memcg, int item)\n--\nmm/memcontrol.c-1685-\nmm/memcontrol.c:1686:#ifdef CONFIG_HUGETLB_PAGE\nmm/memcontrol.c-1687-static bool memcg_accounts_hugetlb(void)\n--\nmm/memcontrol.c=1698=static void memcg_stat_format(struct mem_cgroup memcg, struct seq_buf s)\n--\nmm/memcontrol.c-1716-\nmm/memcontrol.c:1717:#ifdef CONFIG_HUGETLB_PAGE\nmm/memcontrol.c-1718-\t\tif (unlikely(memory_stats[i].idx == NR_HUGETLB) \u0026\u0026\n--\nmm/memcontrol.c-1744-\tfor (i = 0; i \u003c ARRAY_SIZE(memcg_vm_event_stat); i++) {\nmm/memcontrol.c:1745:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-1746-\t\tif (memcg_vm_event_stat[i] == PGPGIN \|\|\n--\nmm/memcontrol.c=1796=void mem_cgroup_print_oom_meminfo(struct mem_cgroup memcg)\n--\nmm/memcontrol.c-1817-\t\t\tatomic_long_read(\u0026memcg-\u003ememory_events[MEMCG_SWAP_MAX]));\nmm/memcontrol.c:1818:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-1819-\telse {\n--\nmm/memcontrol.c=2805=static void commit_charge(struct folio folio, struct obj_cgroup objcg)\n--\nmm/memcontrol.c-2817-\nmm/memcontrol.c:2818:#ifdef CONFIG_MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\nmm/memcontrol.c-2819-static inline void account_slab_nmi_safe(struct mem_cgroup memcg,\n--\nmm/memcontrol.c=3037=struct obj_cgroup get_obj_cgroup_from_folio(struct folio folio)\n--\nmm/memcontrol.c-3047-\nmm/memcontrol.c:3048:#ifdef CONFIG_MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\nmm/memcontrol.c-3049-static inline void account_kmem_nmi_safe(struct mem_cgroup memcg, int val)\n--\nmm/memcontrol.c=3703=static void memcg_offline_kmem(struct mem_cgroup memcg)\n--\nmm/memcontrol.c-3716-\nmm/memcontrol.c:3717:#ifdef CONFIG_CGROUP_WRITEBACK\nmm/memcontrol.c-3718-\n--\nmm/memcontrol.c=4138=static struct mem_cgroup mem_cgroup_alloc(struct mem_cgroup parent)\n--\nmm/memcontrol.c-4193-\tmemcg-\u003ekmemcg_id = -1;\nmm/memcontrol.c:4194:#ifdef CONFIG_CGROUP_WRITEBACK\nmm/memcontrol.c-4195-\tINIT_LIST_HEAD(\u0026memcg-\u003ecgwb_list);\n--\nmm/memcontrol.c=4209=mem_cgroup_css_alloc(struct cgroup_subsys_state parent_css)\n--\nmm/memcontrol.c-4222-\tmemcg1_soft_limit_reset(memcg);\nmm/memcontrol.c:4223:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-4224-\tmemcg-\u003ezswap_max = PAGE_COUNTER_MAX;\n--\nmm/memcontrol.c-4232-\t\tpage_counter_init(\u0026memcg-\u003eswap, \u0026parent-\u003eswap, false);\nmm/memcontrol.c:4233:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-4234-\t\tmemcg-\u003ememory.track_failcnt = !memcg_on_dfl;\n--\nmm/memcontrol.c-4243-\t\tpage_counter_init(\u0026memcg-\u003eswap, NULL, false);\nmm/memcontrol.c:4244:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-4245-\t\tpage_counter_init(\u0026memcg-\u003ekmem, NULL, false);\n--\nmm/memcontrol.c=4375=static void mem_cgroup_css_free(struct cgroup_subsys_state css)\n--\nmm/memcontrol.c-4379-\nmm/memcontrol.c:4380:#ifdef CONFIG_CGROUP_WRITEBACK\nmm/memcontrol.c-4381-\tfor (i = 0; i \u003c MEMCG_CGWB_FRN_CNT; i++)\n--\nmm/memcontrol.c=4413=static void mem_cgroup_css_reset(struct cgroup_subsys_state css)\n--\nmm/memcontrol.c-4419-\tWRITE_ONCE(memcg-\u003eoom_group, false);\nmm/memcontrol.c:4420:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-4421-\tWRITE_ONCE(memcg-\u003ezswap_max, PAGE_COUNTER_MAX);\n--\nmm/memcontrol.c-4423-#endif\nmm/memcontrol.c:4424:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-4425-\tpage_counter_set_max(\u0026memcg-\u003ekmem, PAGE_COUNTER_MAX);\n--\nmm/memcontrol.c=4453=static void mem_cgroup_stat_aggregate(struct aggregate_control ac)\n--\nmm/memcontrol.c-4488-\nmm/memcontrol.c:4489:#ifdef CONFIG_MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\nmm/memcontrol.c-4490-static void flush_nmi_stats(struct mem_cgroup memcg, struct mem_cgroup parent)\n--\nmm/memcontrol.c=4619=static void mem_cgroup_exit(struct task_struct task)\n--\nmm/memcontrol.c-4635-\nmm/memcontrol.c:4636:#ifdef CONFIG_LRU_GEN\nmm/memcontrol.c-4637-static void mem_cgroup_lru_gen_attach(struct cgroup_taskset tset)\n--\nmm/memcontrol.c=4975=int memory_stat_show(struct seq_file m, void v)\n--\nmm/memcontrol.c-4989-\nmm/memcontrol.c:4990:#ifdef CONFIG_NUMA\nmm/memcontrol.c-4991-static inline unsigned long lruvec_page_state_output(struct lruvec lruvec,\n--\nmm/memcontrol.c=5072=static struct cftype memory_files[] = {\n--\nmm/memcontrol.c-5125-\t},\nmm/memcontrol.c:5126:#ifdef CONFIG_NUMA\nmm/memcontrol.c-5127-\t{\n--\nmm/memcontrol.c=5146=struct cgroup_subsys memory_cgrp_subsys = {\n--\nmm/memcontrol.c-5157-\t.dfl_cftypes = memory_files,\nmm/memcontrol.c:5158:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-5159-\t.legacy_cftypes = mem_cgroup_legacy_files,\n--\nmm/memcontrol.c=5605=int __init mem_cgroup_init(void)\n--\nmm/memcontrol.c-5640-\nmm/memcontrol.c:5641:#ifdef CONFIG_SWAP\nmm/memcontrol.c-5642-/\n--\nmm/memcontrol.c=5860=static struct cftype swap_files[] = {\n--\nmm/memcontrol.c-5894-\nmm/memcontrol.c:5895:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-5896-/\n--\nmm/memcontrol.c=6093=static int __init mem_cgroup_swap_init(void)\n--\nmm/memcontrol.c-6098-\tWARN_ON(cgroup_add_dfl_cftypes(\u0026memory_cgrp_subsys, swap_files));\nmm/memcontrol.c:6099:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-6100-\tWARN_ON(cgroup_add_legacy_cftypes(\u0026memory_cgrp_subsys, memsw_files));\nmm/memcontrol.c-6101-#endif\nmm/memcontrol.c:6102:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-6103-\tWARN_ON(cgroup_add_dfl_cftypes(\u0026memory_cgrp_subsys, zswap_files));\n" }
9/2	2026/08/13 09:35	tool	grepper	0m Args: { "Expression": "^(#ifdef\|#ifndef) CONFIG_", "PathPrefix": "mm/memcontrol-v1.c" } Results: { "Output": "mm/memcontrol-v1.c=94=enum {\n--\nmm/memcontrol-v1.c-101-\nmm/memcontrol-v1.c:102:#ifdef CONFIG_LOCKDEP\nmm/memcontrol-v1.c-103-static struct lockdep_map memcg_oom_lock_dep_map = {\n--\nmm/memcontrol-v1.c=405=static u64 mem_cgroup_move_charge_read(struct cgroup_subsys_state css,\n--\nmm/memcontrol-v1.c-410-\nmm/memcontrol-v1.c:411:#ifdef CONFIG_MMU\nmm/memcontrol-v1.c-412-static int mem_cgroup_move_charge_write(struct cgroup_subsys_state css,\n--\nmm/memcontrol-v1.c=597=void memcg1_commit_charge(struct folio folio, struct mem_cgroup memcg)\n--\nmm/memcontrol-v1.c-606-\nmm/memcontrol-v1.c:607:#ifdef CONFIG_SWAP\nmm/memcontrol-v1.c-608-/*\n--\nmm/memcontrol-v1.c=2033=static ssize_t mem_cgroup_reset(struct kernfs_open_file of, char buf,\n--\nmm/memcontrol-v1.c-2069-\nmm/memcontrol-v1.c:2070:#ifdef CONFIG_NUMA\nmm/memcontrol-v1.c-2071-\n--\nmm/memcontrol-v1.c=2160=static const unsigned int memcg1_stats[] = {\n--\nmm/memcontrol-v1.c-2162-\tNR_ANON_MAPPED,\nmm/memcontrol-v1.c:2163:#ifdef CONFIG_TRANSPARENT_HUGEPAGE\nmm/memcontrol-v1.c-2164-\tNR_ANON_THPS,\n--\nmm/memcontrol-v1.c-2171-\tWORKINGSET_REFAULT_FILE,\nmm/memcontrol-v1.c:2172:#ifdef CONFIG_SWAP\nmm/memcontrol-v1.c-2173-\tMEMCG_SWAP,\n--\nmm/memcontrol-v1.c=2178=static const char const memcg1_stat_names[] = {\n--\nmm/memcontrol-v1.c-2180-\t\"rss\",\nmm/memcontrol-v1.c:2181:#ifdef CONFIG_TRANSPARENT_HUGEPAGE\nmm/memcontrol-v1.c-2182-\t\"rss_huge\",\n--\nmm/memcontrol-v1.c-2189-\t\"workingset_refault_file\",\nmm/memcontrol-v1.c:2190:#ifdef CONFIG_SWAP\nmm/memcontrol-v1.c-2191-\t\"swap\",\n--\nmm/memcontrol-v1.c=2220=void memcg1_stat_format(struct mem_cgroup memcg, struct seq_buf s)\n--\nmm/memcontrol-v1.c-2274-\nmm/memcontrol-v1.c:2275:#ifdef CONFIG_DEBUG_VM\nmm/memcontrol-v1.c-2276-\t{\n--\nmm/memcontrol-v1.c=2331=static int mem_cgroup_oom_control_write(struct cgroup_subsys_state css,\n--\nmm/memcontrol-v1.c-2350-\nmm/memcontrol-v1.c:2351:#ifdef CONFIG_SLUB_DEBUG\nmm/memcontrol-v1.c-2352-static int mem_cgroup_slab_show(struct seq_file m, void *p)\n--\nmm/memcontrol-v1.c=2362=struct cftype mem_cgroup_legacy_files[] = {\n--\nmm/memcontrol-v1.c-2428-\t},\nmm/memcontrol-v1.c:2429:#ifdef CONFIG_NUMA\nmm/memcontrol-v1.c-2430-\t{\n--\nmm/memcontrol-v1.c-2457-\t},\nmm/memcontrol-v1.c:2458:#ifdef CONFIG_SLUB_DEBUG\nmm/memcontrol-v1.c-2459-\t{\n" }
10/2	2026/08/13 09:35	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 17399 output: 38 thoughts: 186 Thoughts: Analyzing Swap-Related Memory Cgroup Operations Okay, so I'm diving into this memory cgroup code, specifically looking at swap-related functions. I see `__mem_cgroup_try_charge_swap`, `__mem_cgroup_uncharge_swap`, and `__memcg1_swapout` are all clearly guarded by `CONFIG_SWAP`. Makes sense. But here's where it gets interesting: `mem_cgroup_swapin_charge_folio`. I initially thought it should also be under `CONFIG_SWAP` given its name, and that it's in `mm/memcontrol.c`. A quick check confirms it isn't directly under a `#ifdef CONFIG_SWAP` in that specific function, which is strange. I need to be sure. Alright, now I'm going to look at `mm/memcontrol.c` more broadly to see if `mem_cgroup_swapin_charge_folio` is defined under some other conditional. Ah, found it. Looking at line 5641 I can see that `#ifdef CONFIG_SWAP` is used. Now, let's see where the function `mem_cgroup_swapin_charge_folio` is actually defined.
11/2	2026/08/13 09:35	tool	grepper	0m Args: { "Expression": "int mem_cgroup_swapin_charge_folio", "PathPrefix": "mm/memcontrol.c" } Results: { "Output": "mm/memcontrol.c=5231=int mem_cgroup_charge_hugetlb(struct folio folio, gfp_t gfp)\n--\nmm/memcontrol.c-5264- /\nmm/memcontrol.c:5265:int mem_cgroup_swapin_charge_folio(struct folio folio, unsigned short id,\nmm/memcontrol.c-5266-\t\t\t\t struct mm_struct mm, gfp_t gfp)\n" }
12/2	2026/08/13 09:35	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 18025 output: 35 thoughts: 24 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: Checking Conditional Compilation of `mem_cgroup_swapin_charge_folio` Alright, before I dive too deep into this `mem_cgroup_swapin_charge_folio` function, I need to quickly establish its context. My immediate thought is, "Is this thing even always enabled? Or is it tucked away behind some preprocessor directive?" I need to figure out if it's potentially conditional, maybe only compiled in for specific kernel configurations, or perhaps a feature flag that's only active under certain circumstances. A quick scan for `#ifdef` statements around the definition or uses of this function is a necessary first step. That'll save me from chasing a ghost later, you know? It's a fundamental sanity check to see if it's conditionally compiled. Otherwise, I will have wasted my time.
13/2	2026/08/13 09:35	tool	grepper	0m Args: { "Expression": "^(#ifdef\|#ifndef) CONFIG_", "PathPrefix": "mm/memcontrol.c" } Results: { "Output": "mm/memcontrol.c=102=static struct kmem_cache memcg_pn_cachep;\nmm/memcontrol.c-103-\nmm/memcontrol.c:104:#ifdef CONFIG_CGROUP_WRITEBACK\nmm/memcontrol.c-105-static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq);\n--\nmm/memcontrol.c=214=static inline struct obj_cgroup __memcg_reparent_objcgs(struct mem_cgroup memcg,\n--\nmm/memcontrol.c-233-\nmm/memcontrol.c:234:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-235-static void __mem_cgroup_flush_stats(struct mem_cgroup memcg, bool force);\n--\nmm/memcontrol.c=377=static const unsigned int memcg_node_stat_items[] = {\n--\nmm/memcontrol.c-404-\tNR_SECONDARY_PAGETABLE,\nmm/memcontrol.c:405:#ifdef CONFIG_SWAP\nmm/memcontrol.c-406-\tNR_SWAPCACHE,\nmm/memcontrol.c-407-#endif\nmm/memcontrol.c:408:#ifdef CONFIG_NUMA_BALANCING\nmm/memcontrol.c-409-\tPGPROMOTE_SUCCESS,\n--\nmm/memcontrol.c-427-\tPGREFILL,\nmm/memcontrol.c:428:#ifdef CONFIG_HUGETLB_PAGE\nmm/memcontrol.c-429-\tNR_HUGETLB,\n--\nmm/memcontrol.c=488=unsigned long lruvec_page_state(struct lruvec lruvec, enum node_stat_item idx)\n--\nmm/memcontrol.c-502-\tx = READ_ONCE(pn-\u003elruvec_stats-\u003estate[i]);\nmm/memcontrol.c:503:#ifdef CONFIG_SMP\nmm/memcontrol.c-504-\tif (x \u003c 0)\n--\nmm/memcontrol.c=510=unsigned long lruvec_page_state_local(struct lruvec lruvec,\n--\nmm/memcontrol.c-525-\tx = READ_ONCE(pn-\u003elruvec_stats-\u003estate_local[i]);\nmm/memcontrol.c:526:#ifdef CONFIG_SMP\nmm/memcontrol.c-527-\tif (x \u003c 0)\n--\nmm/memcontrol.c-532-\nmm/memcontrol.c:533:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-534-static void __mod_memcg_lruvec_state(struct mem_cgroup_per_node pn,\n--\nmm/memcontrol.c=558=static const unsigned int memcg_vm_event_stat[] = {\nmm/memcontrol.c:559:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-560-\tPGPGIN,\n--\nmm/memcontrol.c-570-\tPGLAZYFREED,\nmm/memcontrol.c:571:#ifdef CONFIG_SWAP\nmm/memcontrol.c-572-\tSWPIN_ZERO,\n--\nmm/memcontrol.c-574-#endif\nmm/memcontrol.c:575:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-576-\tZSWPIN,\n--\nmm/memcontrol.c-579-#endif\nmm/memcontrol.c:580:#ifdef CONFIG_TRANSPARENT_HUGEPAGE\nmm/memcontrol.c-581-\tTHP_FAULT_ALLOC,\n--\nmm/memcontrol.c-585-#endif\nmm/memcontrol.c:586:#ifdef CONFIG_NUMA_BALANCING\nmm/memcontrol.c-587-\tNUMA_PAGE_MIGRATE,\n--\nmm/memcontrol.c=762=unsigned long memcg_page_state(struct mem_cgroup memcg, int idx)\n--\nmm/memcontrol.c-770-\tx = READ_ONCE(memcg-\u003evmstats-\u003estate[i]);\nmm/memcontrol.c:771:#ifdef CONFIG_SMP\nmm/memcontrol.c-772-\tif (x \u003c 0)\n--\nmm/memcontrol.c=792=static long memcg_state_val_in_pages(int idx, long val)\n--\nmm/memcontrol.c-807-\nmm/memcontrol.c:808:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-809-/\n--\nmm/memcontrol.c=876=void mod_memcg_state(struct mem_cgroup memcg, enum memcg_stat_item idx,\n--\nmm/memcontrol.c-888-\nmm/memcontrol.c:889:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-890-/* idx can be of type enum memcg_stat_item or node_stat_item. /\nmm/memcontrol.c=891=unsigned long memcg_page_state_local(struct mem_cgroup memcg, int idx)\n--\nmm/memcontrol.c-899-\tx = READ_ONCE(memcg-\u003evmstats-\u003estate_local[i]);\nmm/memcontrol.c:900:#ifdef CONFIG_SMP\nmm/memcontrol.c-901-\tif (x \u003c 0)\n--\nmm/memcontrol.c=1064=bool memcg_vm_event_item_valid(enum vm_event_item idx)\n--\nmm/memcontrol.c-1071-\nmm/memcontrol.c:1072:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-1073-unsigned long memcg_events_local(struct mem_cgroup memcg, int event)\n--\nmm/memcontrol.c=1551=static const struct memory_stat memory_stats[] = {\n--\nmm/memcontrol.c-1561-\t{ \"shmem\",\t\t\tNR_SHMEM\t\t\t},\nmm/memcontrol.c:1562:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-1563-\t{ \"zswap\",\t\t\tMEMCG_ZSWAP_B\t\t\t},\n--\nmm/memcontrol.c-1569-\t{ \"file_writeback\",\t\tNR_WRITEBACK\t\t\t},\nmm/memcontrol.c:1570:#ifdef CONFIG_SWAP\nmm/memcontrol.c-1571-\t{ \"swapcached\",\t\t\tNR_SWAPCACHE\t\t\t},\nmm/memcontrol.c-1572-#endif\nmm/memcontrol.c:1573:#ifdef CONFIG_TRANSPARENT_HUGEPAGE\nmm/memcontrol.c-1574-\t{ \"anon_thp\",\t\t\tNR_ANON_THPS\t\t\t},\n--\nmm/memcontrol.c-1584-\t{ \"slab_unreclaimable\",\t\tNR_SLAB_UNRECLAIMABLE_B\t\t},\nmm/memcontrol.c:1585:#ifdef CONFIG_HUGETLB_PAGE\nmm/memcontrol.c-1586-\t{ \"hugetlb\",\t\t\tNR_HUGETLB\t\t\t},\n--\nmm/memcontrol.c-1610-\t{ \"pgrefill\",\t\t\tPGREFILL\t\t},\nmm/memcontrol.c:1611:#ifdef CONFIG_NUMA_BALANCING\nmm/memcontrol.c-1612-\t{ \"pgpromote_success\",\t\tPGPROMOTE_SUCCESS\t},\n--\nmm/memcontrol.c=1633=static int memcg_page_state_output_unit(int item)\n--\nmm/memcontrol.c-1662-\tcase PGREFILL:\nmm/memcontrol.c:1663:#ifdef CONFIG_NUMA_BALANCING\nmm/memcontrol.c-1664-\tcase PGPROMOTE_SUCCESS:\n--\nmm/memcontrol.c=1672=unsigned long memcg_page_state_output(struct mem_cgroup memcg, int item)\n--\nmm/memcontrol.c-1677-\nmm/memcontrol.c:1678:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-1679-unsigned long memcg_page_state_local_output(struct mem_cgroup memcg, int item)\n--\nmm/memcontrol.c-1685-\nmm/memcontrol.c:1686:#ifdef CONFIG_HUGETLB_PAGE\nmm/memcontrol.c-1687-static bool memcg_accounts_hugetlb(void)\n--\nmm/memcontrol.c=1698=static void memcg_stat_format(struct mem_cgroup memcg, struct seq_buf s)\n--\nmm/memcontrol.c-1716-\nmm/memcontrol.c:1717:#ifdef CONFIG_HUGETLB_PAGE\nmm/memcontrol.c-1718-\t\tif (unlikely(memory_stats[i].idx == NR_HUGETLB) \u0026\u0026\n--\nmm/memcontrol.c-1744-\tfor (i = 0; i \u003c ARRAY_SIZE(memcg_vm_event_stat); i++) {\nmm/memcontrol.c:1745:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-1746-\t\tif (memcg_vm_event_stat[i] == PGPGIN \|\|\n--\nmm/memcontrol.c=1796=void mem_cgroup_print_oom_meminfo(struct mem_cgroup memcg)\n--\nmm/memcontrol.c-1817-\t\t\tatomic_long_read(\u0026memcg-\u003ememory_events[MEMCG_SWAP_MAX]));\nmm/memcontrol.c:1818:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-1819-\telse {\n--\nmm/memcontrol.c=2805=static void commit_charge(struct folio folio, struct obj_cgroup objcg)\n--\nmm/memcontrol.c-2817-\nmm/memcontrol.c:2818:#ifdef CONFIG_MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\nmm/memcontrol.c-2819-static inline void account_slab_nmi_safe(struct mem_cgroup memcg,\n--\nmm/memcontrol.c=3037=struct obj_cgroup get_obj_cgroup_from_folio(struct folio folio)\n--\nmm/memcontrol.c-3047-\nmm/memcontrol.c:3048:#ifdef CONFIG_MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\nmm/memcontrol.c-3049-static inline void account_kmem_nmi_safe(struct mem_cgroup memcg, int val)\n--\nmm/memcontrol.c=3703=static void memcg_offline_kmem(struct mem_cgroup memcg)\n--\nmm/memcontrol.c-3716-\nmm/memcontrol.c:3717:#ifdef CONFIG_CGROUP_WRITEBACK\nmm/memcontrol.c-3718-\n--\nmm/memcontrol.c=4138=static struct mem_cgroup mem_cgroup_alloc(struct mem_cgroup parent)\n--\nmm/memcontrol.c-4193-\tmemcg-\u003ekmemcg_id = -1;\nmm/memcontrol.c:4194:#ifdef CONFIG_CGROUP_WRITEBACK\nmm/memcontrol.c-4195-\tINIT_LIST_HEAD(\u0026memcg-\u003ecgwb_list);\n--\nmm/memcontrol.c=4209=mem_cgroup_css_alloc(struct cgroup_subsys_state parent_css)\n--\nmm/memcontrol.c-4222-\tmemcg1_soft_limit_reset(memcg);\nmm/memcontrol.c:4223:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-4224-\tmemcg-\u003ezswap_max = PAGE_COUNTER_MAX;\n--\nmm/memcontrol.c-4232-\t\tpage_counter_init(\u0026memcg-\u003eswap, \u0026parent-\u003eswap, false);\nmm/memcontrol.c:4233:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-4234-\t\tmemcg-\u003ememory.track_failcnt = !memcg_on_dfl;\n--\nmm/memcontrol.c-4243-\t\tpage_counter_init(\u0026memcg-\u003eswap, NULL, false);\nmm/memcontrol.c:4244:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-4245-\t\tpage_counter_init(\u0026memcg-\u003ekmem, NULL, false);\n--\nmm/memcontrol.c=4375=static void mem_cgroup_css_free(struct cgroup_subsys_state css)\n--\nmm/memcontrol.c-4379-\nmm/memcontrol.c:4380:#ifdef CONFIG_CGROUP_WRITEBACK\nmm/memcontrol.c-4381-\tfor (i = 0; i \u003c MEMCG_CGWB_FRN_CNT; i++)\n--\nmm/memcontrol.c=4413=static void mem_cgroup_css_reset(struct cgroup_subsys_state css)\n--\nmm/memcontrol.c-4419-\tWRITE_ONCE(memcg-\u003eoom_group, false);\nmm/memcontrol.c:4420:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-4421-\tWRITE_ONCE(memcg-\u003ezswap_max, PAGE_COUNTER_MAX);\n--\nmm/memcontrol.c-4423-#endif\nmm/memcontrol.c:4424:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-4425-\tpage_counter_set_max(\u0026memcg-\u003ekmem, PAGE_COUNTER_MAX);\n--\nmm/memcontrol.c=4453=static void mem_cgroup_stat_aggregate(struct aggregate_control ac)\n--\nmm/memcontrol.c-4488-\nmm/memcontrol.c:4489:#ifdef CONFIG_MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\nmm/memcontrol.c-4490-static void flush_nmi_stats(struct mem_cgroup memcg, struct mem_cgroup parent)\n--\nmm/memcontrol.c=4619=static void mem_cgroup_exit(struct task_struct task)\n--\nmm/memcontrol.c-4635-\nmm/memcontrol.c:4636:#ifdef CONFIG_LRU_GEN\nmm/memcontrol.c-4637-static void mem_cgroup_lru_gen_attach(struct cgroup_taskset tset)\n--\nmm/memcontrol.c=4975=int memory_stat_show(struct seq_file m, void v)\n--\nmm/memcontrol.c-4989-\nmm/memcontrol.c:4990:#ifdef CONFIG_NUMA\nmm/memcontrol.c-4991-static inline unsigned long lruvec_page_state_output(struct lruvec lruvec,\n--\nmm/memcontrol.c=5072=static struct cftype memory_files[] = {\n--\nmm/memcontrol.c-5125-\t},\nmm/memcontrol.c:5126:#ifdef CONFIG_NUMA\nmm/memcontrol.c-5127-\t{\n--\nmm/memcontrol.c=5146=struct cgroup_subsys memory_cgrp_subsys = {\n--\nmm/memcontrol.c-5157-\t.dfl_cftypes = memory_files,\nmm/memcontrol.c:5158:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-5159-\t.legacy_cftypes = mem_cgroup_legacy_files,\n--\nmm/memcontrol.c=5605=int __init mem_cgroup_init(void)\n--\nmm/memcontrol.c-5640-\nmm/memcontrol.c:5641:#ifdef CONFIG_SWAP\nmm/memcontrol.c-5642-/\n--\nmm/memcontrol.c=5860=static struct cftype swap_files[] = {\n--\nmm/memcontrol.c-5894-\nmm/memcontrol.c:5895:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-5896-/\n--\nmm/memcontrol.c=6093=static int __init mem_cgroup_swap_init(void)\n--\nmm/memcontrol.c-6098-\tWARN_ON(cgroup_add_dfl_cftypes(\u0026memory_cgrp_subsys, swap_files));\nmm/memcontrol.c:6099:#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c-6100-\tWARN_ON(cgroup_add_legacy_cftypes(\u0026memory_cgrp_subsys, memsw_files));\nmm/memcontrol.c-6101-#endif\nmm/memcontrol.c:6102:#ifdef CONFIG_ZSWAP\nmm/memcontrol.c-6103-\tWARN_ON(cgroup_add_dfl_cftypes(\u0026memory_cgrp_subsys, zswap_files));\n" }
14/2	2026/08/13 09:35	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 22656 output: 28 thoughts: 93 Thoughts: Examining Memory Control and Swap Integration Okay, so I'm looking at `mm/memcontrol.c` and specifically at `mem_cgroup_swapin_charge_folio`. It's immediately apparent that this function isn't guarded by an `#ifdef CONFIG_SWAP` preprocessor directive, which is interesting. I would have expected a direct connection to the swap functionality. Now, that's making me reconsider the architecture. Hmm, wait a second... If I'm remembering correctly, the actual swapout function for memory cgroups, `__memcg1_swapout`, is actually defined in `mm/memcontrol-v1.c`. And that file's conditional compilation is tied to `CONFIG_MEMCG_V1`. I'm starting to put the pieces together. The v1 memory cgroup implementation might handle this swap interaction differently or encapsulate related logic. Alright, let's back up a step. To confirm this line of thinking and get the whole picture, I need to check the `mm/Makefile`. That will give me a clear view of how these files and configurations are interconnected at the build level. Let me quickly examine how everything is built.
15/2	2026/08/13 09:35	tool	grepper	0m Args: { "Expression": "memcontrol-v1", "PathPrefix": "mm/Makefile" } Results: { "Output": "mm/Makefile=28=KCOV_INSTRUMENT_memcontrol.o := n\nmm/Makefile:29:KCOV_INSTRUMENT_memcontrol-v1.o := n\nmm/Makefile-30-KCOV_INSTRUMENT_mmzone.o := n\n--\nmm/Makefile=103=obj-$(CONFIG_LIVEUPDATE_MEMFD) += memfd_luo.o\nmm/Makefile:104:obj-$(CONFIG_MEMCG_V1) += memcontrol-v1.o\nmm/Makefile-105-obj-$(CONFIG_MEMCG) += memcontrol.o vmpressure.o\n" }
16/2	2026/08/13 09:35	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 23193 output: 35 thoughts: 207 Thoughts: Analyzing Kernel Configuration Dependencies Okay, so I'm looking at these kernel symbols and their configuration dependencies. It seems pretty straightforward: `CONFIG_MEMCG_V1` is essential for the function `__memcg1_swapout`. Then, we need `CONFIG_SWAP` for both `__mem_cgroup_try_charge_swap` and `__mem_cgroup_uncharge_swap`. And, as expected, `CONFIG_MEMCG` is fundamental for `mem_cgroup_swapin_charge_folio`, as well as `list_lru_walk_node` and `workingset_test_recent`. Now, I want to confirm that `list_lru_walk_node` and `workingset_test_recent` are always included or at least conditionally compiled under reasonable circumstances. Let's see... `list_lru_walk_node` resides in `mm/list_lru.c` and `workingset_test_recent` is in `mm/workingset.c`. I'll quickly check the `mm/Makefile` to make sure `list_lru.o` and `workingset.o` are getting built, to confirm no unexpected config requirements are present.
17/2	2026/08/13 09:35	tool	grepper	0m Args: { "Expression": "list_lru\\.o\|workingset\\.o", "PathPrefix": "mm/Makefile" } Results: { "Output": "mm/Makefile=51=obj-y\t\t\t:= filemap.o mempool.o oom_kill.o fadvise.o \\\n--\nmm/Makefile-56-\t\t\t compaction.o show_mem.o \\\nmm/Makefile:57:\t\t\t interval_tree.o list_lru.o workingset.o \\\nmm/Makefile-58-\t\t\t debug.o gup.o mmap_lock.o vma_init.o $(mmu-y)\n" }
18/2	2026/08/13 09:35	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 23834 output: 28 thoughts: 412 Thoughts: My Current Thinking on Focusing Symbols and Configurations Okay, so I'm putting together a list of focus symbols, and this process is pretty straightforward; I'm compiling the information unconditionally. This means I'm not making any assumptions, and I'm looking at everything. I've got my configurations defined, which are `MEMCG`, `MEMCG_V1`, and `SWAP`. That's the baseline. Right now, my initial focus symbols are: `mem_cgroup_swapin_charge_folio`, `__mem_cgroup_try_charge_swap`, `__mem_cgroup_uncharge_swap`, `__memcg1_swapout`, `list_lru_walk_node`, and `workingset_test_recent`. Solid start, but I need to be thorough. Now, I'm thinking about including some smaller helper functions. Specifically, I'm considering `mem_cgroup_from_private_id` and `mem_cgroup_from_private_id_online`. They're non-static, they're exported, and while fuzzing them directly might not yield the most interesting results compared to fuzzing the functions that use them, it doesn't hurt. Might as well include them for broader coverage. Actually, hold on. I see `mem_cgroup_private_id_get` and `mem_cgroup_take_from_private_id`, which are static and related, so let's include those too. This is expanding the scope a bit. Okay, let's update that list: - `mem_cgroup_from_private_id` - `mem_cgroup_from_private_id_online` - `mem_cgroup_private_id_get` - `mem_cgroup_swapin_charge_folio` - `__mem_cgroup_try_charge_swap` - `__mem_cgroup_uncharge_swap` - `__memcg1_swapout` - `list_lru_walk_node` - `workingset_test_recent` Now, just a quick sanity check… I know `mem_cgroup_from_private_id` is non-static and in `mm/memcontrol.c`, but let me double-check it's actually exported. It's easy to overlook something in these sorts of evaluations.
19/2	2026/08/13 09:36	tool	grepper	0m Error: no matches Args: { "Expression": "EXPORT_SYMBOL.mem_cgroup_from_private_id" } Results:* { "error": "no matches" }
20/2	2026/08/13 09:36	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 24825 output: 29 thoughts: 44 Thoughts: Okay, here's my take on those thoughts, framed as my own: Investigating a Symbol's Visibility Alright, so I'm looking at this function, and I see it's not explicitly exported, but it's not `static` either. That's interesting, because it means it has a globally unique symbol address. This suggests it could be used outside its compilation unit. The question is, can it actually be accessed from other modules? I need to know if `mem_cgroup_swapin_charge_folio` is actually made available for external use. Let's dig into whether it's exported or not, and how we can determine this information.
21/2	2026/08/13 09:36	tool	grepper	0m Error: no matches Args: { "Expression": "EXPORT_SYMBOL.mem_cgroup_swapin_charge_folio" } Results:* { "error": "no matches" }
22/2	2026/08/13 09:36	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 25060 output: 26 thoughts: 30 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Analyzing Potential Non-Static, Non-Exported Function Behavior Alright, so the function in question isn't explicitly exported, but it's also not static. That immediately piques my interest. Non-exported, non-static functions can be tricky, depending on the compiler and linker environment. They might be subject to internal linkage or, depending on the build process, potentially accessible within the same compilation unit or linked object files in ways that aren't immediately obvious from a standard header examination. This situation raises questions about potential unintended side effects or dependency concerns during refactoring or future modifications. The lack of static scoping implies a specific build configuration. Without more context, there are implications to this. Is the function potentially used through a more complex linkage mechanism, perhaps with a shared library or DLL? Or is there a specific design pattern in play? I need to dig deeper to understand its purpose and scope. To get a better understanding of its calling context, my next step is to examine `list_lru_walk_node`. Examining this particular function will likely provide insight into how this one is used, which can provide a clearer picture of its potential impact. It will indicate the data structures or methods being used and how the function fits into a larger system context.
23/2	2026/08/13 09:36	tool	grepper	0m Args: { "Expression": "EXPORT_SYMBOL.list_lru_walk_node" } Results:* { "Output": "mm/list_lru.c=413=unsigned long list_lru_walk_node(struct list_lru *lru, int nid,\n--\nmm/list_lru.c-448-}\nmm/list_lru.c:449:EXPORT_SYMBOL_GPL(list_lru_walk_node);\nmm/list_lru.c-450-\n" }
24/2	2026/08/13 09:36	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 25506 output: 25 thoughts: 18 Thoughts: Okay, here's my interpretation of those thoughts, crafted with the understanding that I'm speaking to a fellow expert: Assessment of Current Status & Initial Approach Alright, so the data is exported. That's the baseline. Now, let's get down to the brass tacks. My immediate thought is to zero in on `workingset_test_recent`. That's where I need to start, to check the recent data. It sounds like the most relevant area for analysis at this point.
25/2	2026/08/13 09:36	tool	grepper	0m Error: no matches Args: { "Expression": "EXPORT_SYMBOL.workingset_test_recent" } Results:* { "error": "no matches" }
26/2	2026/08/13 09:36	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 25673 output: 234 thoughts: 116 Thoughts: Okay, here's my interpretation of that thinking, phrased as a first-person summary, keeping in mind my field expertise: My Analysis of this Kernel Patch Alright, I'm looking at this patch and, off the bat, I see it's dealing with a core aspect of memory management within the kernel: specifically, the memory control group, or memcg, subsystem. And I'm seeing that the code is not exported, but it also is not static, which is interesting for later consideration. The key configurations this touches, and therefore depends upon, are pretty clear: `MEMCG`, `MEMCG_V1`, and `SWAP`. That's not unexpected; any significant memcg change is going to ripple out to the swap handling. The real meat of this seems to be the refactoring of how private memcg IDs are handled. It's moving the reference counting for these IDs into the `struct obj_cgroup`. This implies a fundamental shift in how the kernel tracks and manages these memcg IDs throughout the system. I'm noting this is a change to the ID management logic. That means, of course, that core memory management paths – swap, workingset, and list_lru – are all being updated to use this new ID management paradigm. These are foundational elements of memory management, and changes here can have cascading effects. It’s definitely something that's going to have a functional impact on the system. It's a fundamental change to memory management, not just a cosmetic one. Let's term this change as `set-results`.
27/2	2026/08/13 09:36	tool	set-results	0m Args: { "EnableConfigs": [ "MEMCG", "MEMCG_V1", "SWAP" ], "FocusSymbols": [ "mem_cgroup_from_private_id", "mem_cgroup_from_private_id_online", "mem_cgroup_private_id_get", "mem_cgroup_swapin_charge_folio", "__mem_cgroup_try_charge_swap", "__mem_cgroup_uncharge_swap", "__memcg1_swapout", "list_lru_walk_node", "workingset_test_recent" ], "Reasoning": "The patch modifies the memory control group (memcg) subsystem, specifically how private memcg IDs are managed and referenced. It moves the ID reference counting to `struct obj_cgroup` and updates several core memory management paths (swap, workingset, list_lru) to use the new ID management logic. These are reachable core kernel changes with functional impact.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "MEMCG", "MEMCG_V1", "SWAP" ], "FocusSymbols": [ "mem_cgroup_from_private_id", "mem_cgroup_from_private_id_online", "mem_cgroup_private_id_get", "mem_cgroup_swapin_charge_folio", "__mem_cgroup_try_charge_swap", "__mem_cgroup_uncharge_swap", "__memcg1_swapout", "list_lru_walk_node", "workingset_test_recent" ], "Reasoning": "The patch modifies the memory control group (memcg) subsystem, specifically how private memcg IDs are managed and referenced. It moves the ID reference counting to `struct obj_cgroup` and updates several core memory management paths (swap, workingset, list_lru) to use the new ID management logic. These are reachable core kernel changes with functional impact.", "WorthFuzzing": true }
28/1	2026/08/13 09:36	action	If	0m Args: { "WorthFuzzing": true } Results: null
29/2	2026/08/13 09:36	agent	kmsan-evaluator	0m Model: best-expensive Args: null Results: { "KMSANReasoning": "The patch modifies the lifecycle and reference counting of `mem_cgroup` private IDs, introducing `id_objcg` to `struct mem_cgroup` and `id_ref` to `struct obj_cgroup`. It changes how memcgs are looked up from these IDs and how their references are managed, particularly during swap and workingset operations.\n\nThese changes are purely internal state management and do not introduce any new structures or buffers that are copied to user space. The `mem_cgroup` structure itself is allocated using `kmem_cache_zalloc` (as seen in `mem_cgroup_alloc`), ensuring it is fully zero-initialized.\n\nAny bugs introduced by these changes would likely be use-after-free, NULL pointer dereferences, or memory leaks due to incorrect reference counting. These types of bugs are effectively caught by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory reads or info-leaks that would necessitate a dedicated KMSAN fuzzing session.", "NeedsKMSAN": false } Instruction: You are an expert Linux kernel security engineer specializing in kernel memory error detectors (KASAN and KMSAN). Your job is to review the provided patch series and determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer) fuzzing session in addition to standard KASAN fuzzing. CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN: - Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable a comprehensive suite of debugging tools and sanitizers, including KASAN (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks. - KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap, or page allocations) and kernel-to-user memory info-leaks. Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS. A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks that are detected ONLY by KMSAN. Look holistically at the patch series and surrounding code. Even if no direct uninitialized field accesses or new buffer allocations are added in the diff itself, a patch may alter control flow, bounds checking, or data length calculations in ways that change how the rest of the code operates on existing buffers (e.g. allowing uninitialized stack/heap memory to be read, copied to user space, or used in control flow). Do not hesitate to use your code access tools to inspect the surrounding code, called functions, and callers. Set NeedsKMSAN=true ONLY IF the patch introduces or modifies: 1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb attributes, ioctl output arguments, socket options, or BPF buffers) where fields or structure padding might not be fully initialized/zeroed. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. Set NeedsKMSAN=false IF: - The code changes primarily risk out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (these are already caught by KASAN, LOCKDEP, or standard bug detectors). - All stack/heap structures touched or introduced by the patch are fully zeroed or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied. - The patch does not introduce any risk of uninitialized memory usage or info-leaks. Use your code access tools to inspect the surrounding code if necessary, then provide detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: For your convenience, here is the diff of the changes: commit 1195f55d527ed44cf22d6593972ac8628e82ce29 Author: syz-cluster <triage@syzkaller.com> Date: Thu Aug 13 09:34:59 2026 +0000 syz-cluster: applied patch under review diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 8170bb8066a22..fef8a1c4191b1 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -191,6 +191,7 @@ struct obj_cgroup { struct rcu_head rcu; }; bool is_root; + refcount_t id_ref; }; /* @@ -202,8 +203,8 @@ struct obj_cgroup { struct mem_cgroup { struct cgroup_subsys_state css; - /* Private memcg ID. Used to ID objects that outlive the cgroup / - struct mem_cgroup_private_id id; + / The objcg holding private memcg ID. / + struct obj_cgroup id_objcg; /* Accounted resources / struct page_counter memory; / Both v1 & v2 / @@ -270,6 +271,9 @@ struct mem_cgroup { #endif int kmemcg_id; + / Private memcg ID. Used to ID objects that outlive the cgroup / + int id; + struct memcg_vmstats_percpu __percpu vmstats_percpu; #ifdef CONFIG_CGROUP_WRITEBACK @@ -820,9 +824,10 @@ static inline unsigned short mem_cgroup_private_id(struct mem_cgroup memcg) if (mem_cgroup_disabled()) return 0; - return memcg->id.id; + return memcg->id; } struct mem_cgroup mem_cgroup_from_private_id(unsigned short id); +struct mem_cgroup mem_cgroup_from_private_id_online(unsigned short id); static inline u64 mem_cgroup_id(struct mem_cgroup memcg) { diff --git a/mm/list_lru.c b/mm/list_lru.c index 36662d02ff963..bc956267f6835 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -428,7 +428,7 @@ unsigned long list_lru_walk_node(struct list_lru lru, int nid, xa_for_each(&lru->xa, index, mlru) { rcu_read_lock(); memcg = mem_cgroup_from_private_id(index); - if (!mem_cgroup_tryget(memcg)) { + if (!memcg \|\| !mem_cgroup_tryget(memcg)) { rcu_read_unlock(); continue; } diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c index 2dc599484d006..e5161e061bd11 100644 --- a/mm/memcontrol-v1.c +++ b/mm/memcontrol-v1.c @@ -618,7 +618,7 @@ void memcg1_commit_charge(struct folio folio, struct mem_cgroup memcg) / void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci) { - struct mem_cgroup memcg, swap_memcg; + struct mem_cgroup memcg; struct obj_cgroup objcg; unsigned int nr_entries; @@ -638,19 +638,20 @@ void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci) if (!objcg) return; - rcu_read_lock(); - memcg = obj_cgroup_memcg(objcg); /* * In case the memcg owning these pages has been offlined and doesn't * have an ID allocated to it anymore, charge the closest online - * ancestor for the swap instead and transfer the memory+swap charge. + * ancestor for the swap instead. / + memcg = get_mem_cgroup_from_objcg(objcg); nr_entries = folio_nr_pages(folio); - swap_memcg = mem_cgroup_private_id_get_online(memcg, nr_entries); - mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries); + mod_memcg_state(memcg, MEMCG_SWAP, nr_entries); + + / we have a reference to it, so we should get exact memcg itself / + mem_cgroup_private_id_get(memcg, nr_entries); __swap_cgroup_set(ci, swp_cluster_offset(folio->swap), nr_entries, - mem_cgroup_private_id(swap_memcg)); + mem_cgroup_private_id(memcg)); folio_unqueue_deferred_split(folio); folio->memcg_data = 0; @@ -658,12 +659,6 @@ void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci) if (!obj_cgroup_is_root(objcg)) page_counter_uncharge(&memcg->memory, nr_entries); - if (memcg != swap_memcg) { - if (!mem_cgroup_is_root(swap_memcg)) - page_counter_charge(&swap_memcg->memsw, nr_entries); - page_counter_uncharge(&memcg->memsw, nr_entries); - } - / * The caller must hold the swap cluster lock with IRQ off. It is * important here to have the interrupts disabled because it is the @@ -675,7 +670,7 @@ void __memcg1_swapout(struct folio folio, struct swap_cluster_info ci) preempt_enable_nested(); memcg1_check_events(memcg, folio_nid(folio)); - rcu_read_unlock(); + mem_cgroup_put(memcg); obj_cgroup_put(objcg); } diff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h index 0f703f239c80f..9c74400aa7ddb 100644 --- a/mm/memcontrol-v1.h +++ b/mm/memcontrol-v1.h @@ -21,8 +21,7 @@ void drain_all_stock(struct mem_cgroup root_memcg); int memory_stat_show(struct seq_file m, void v); -struct mem_cgroup mem_cgroup_private_id_get_online(struct mem_cgroup memcg, - unsigned int n); +void mem_cgroup_private_id_get(struct mem_cgroup memcg, unsigned int n); /* Cgroup v1-specific declarations / #ifdef CONFIG_MEMCG_V1 diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8319ad8c5c23a..e7555eca77019 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3697,7 +3697,7 @@ static void memcg_online_kmem(struct mem_cgroup memcg) static_branch_enable(&memcg_kmem_online_key); - memcg->kmemcg_id = memcg->id.id; + memcg->kmemcg_id = memcg->id; } static void memcg_offline_kmem(struct mem_cgroup memcg) @@ -3956,36 +3956,42 @@ static DEFINE_XARRAY_ALLOC1(mem_cgroup_private_ids); static void mem_cgroup_private_id_remove(struct mem_cgroup memcg) { - if (memcg->id.id > 0) { - xa_erase(&mem_cgroup_private_ids, memcg->id.id); - memcg->id.id = 0; + if (memcg->id > 0) { + xa_erase(&mem_cgroup_private_ids, memcg->id); + memcg->id = 0; } } -static inline void mem_cgroup_private_id_put(struct mem_cgroup memcg, unsigned int n) +/* + * @objcg: the objcg returned by mem_cgroup_private_id_objcg + * @id: the corresponding memcg private id + / +static void __mem_cgroup_private_id_put(struct obj_cgroup objcg, + unsigned short id, unsigned int n) { - if (refcount_sub_and_test(n, &memcg->id.ref)) { - mem_cgroup_private_id_remove(memcg); + struct obj_cgroup objcg_free; - / Memcg ID pins CSS / - css_put(&memcg->css); + if (refcount_sub_and_test(n, &objcg->id_ref)) { + objcg_free = xa_erase(&mem_cgroup_private_ids, id); + VM_WARN_ON(objcg_free != objcg); + + / Memcg ID pins the objcg / + obj_cgroup_put(objcg); } } -struct mem_cgroup mem_cgroup_private_id_get_online(struct mem_cgroup memcg, unsigned int n) +static inline void mem_cgroup_private_id_put(struct mem_cgroup memcg, unsigned int n) { - while (!refcount_add_not_zero(n, &memcg->id.ref)) { - /* - * The root cgroup cannot be destroyed, so it's refcount must - * always be >= 1. - / - if (WARN_ON_ONCE(mem_cgroup_is_root(memcg))) { - VM_BUG_ON(1); - break; - } - memcg = parent_mem_cgroup(memcg); - } - return memcg; + __mem_cgroup_private_id_put(memcg->id_objcg, memcg->id, n); +} + +void mem_cgroup_private_id_get(struct mem_cgroup memcg, unsigned int n) +{ + bool success; + struct obj_cgroup objcg = memcg->id_objcg; + + success = refcount_add_not_zero(n, &objcg->id_ref); + VM_WARN_ON(!success); } /* @@ -3993,11 +3999,55 @@ struct mem_cgroup mem_cgroup_private_id_get_online(struct mem_cgroup memcg, un * @id: the memcg id to look up * * Caller must hold rcu_read_lock(). + * + * @return: the memcg, or NULL if the memcg is already reparented. / struct mem_cgroup mem_cgroup_from_private_id(unsigned short id) { + struct obj_cgroup objcg; + struct mem_cgroup memcg; WARN_ON_ONCE(!rcu_read_lock_held()); - return xa_load(&mem_cgroup_private_ids, id); + + objcg = xa_load(&mem_cgroup_private_ids, id); + if (!objcg) + return NULL; + + memcg = obj_cgroup_memcg(objcg); + if (mem_cgroup_private_id(memcg) != id) + return NULL; + + return memcg; +} + +/** + * mem_cgroup_from_private_id - look up an online memcg from a memcg id + * and get a reference. + * @id: the memcg id to look up + / +struct mem_cgroup mem_cgroup_from_private_id_online(unsigned short id) +{ + struct obj_cgroup objcg; + + objcg = xa_load(&mem_cgroup_private_ids, id); + if (!objcg) + return NULL; + + return get_mem_cgroup_from_objcg(objcg); +} + +static struct mem_cgroup mem_cgroup_take_from_private_id(unsigned short id, unsigned int n) +{ + struct obj_cgroup objcg; + struct mem_cgroup memcg; + + objcg = xa_load(&mem_cgroup_private_ids, id); + if (!objcg) + return NULL; + + memcg = get_mem_cgroup_from_objcg(objcg); + + __mem_cgroup_private_id_put(objcg, id, n); + return memcg; } struct mem_cgroup mem_cgroup_get_from_id(u64 id) @@ -4098,7 +4148,7 @@ static struct mem_cgroup mem_cgroup_alloc(struct mem_cgroup parent) if (!memcg) return ERR_PTR(-ENOMEM); - error = xa_alloc(&mem_cgroup_private_ids, &memcg->id.id, NULL, + error = xa_alloc(&mem_cgroup_private_ids, &memcg->id, NULL, XA_LIMIT(1, MEM_CGROUP_ID_MAX), GFP_KERNEL); if (error) goto fail; @@ -4243,9 +4293,10 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state css) FLUSH_TIME); lru_gen_online_memcg(memcg); - /* Online state pins memcg ID, memcg ID pins CSS / - refcount_set(&memcg->id.ref, 1); - css_get(css); + / CSS pins memcg ID, memcg ID pins obj cgroup / + memcg->id_objcg = memcg->nodeinfo[0]->objcg; + refcount_set(&memcg->id_objcg->id_ref, 1); + obj_cgroup_get(memcg->id_objcg); / * Ensure mem_cgroup_from_private_id() works once we're fully online. @@ -4257,7 +4308,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state css) publish it here at the end of onlining. This matches the * regular ID destruction during offlining. / - xa_store(&mem_cgroup_private_ids, memcg->id.id, memcg, GFP_KERNEL); + xa_store(&mem_cgroup_private_ids, memcg->id, objcg, GFP_KERNEL); return 0; free_objcg: @@ -4308,8 +4359,6 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state css) lru_gen_offline_memcg(memcg); drain_all_stock(memcg); - - mem_cgroup_private_id_put(memcg, 1); } static void mem_cgroup_css_released(struct cgroup_subsys_state css) @@ -4318,6 +4367,9 @@ static void mem_cgroup_css_released(struct cgroup_subsys_state css) invalidate_reclaim_iterators(memcg); lru_gen_release_memcg(memcg); + + mem_cgroup_private_id_put(memcg, 1); + memcg->id_objcg = NULL; } static void mem_cgroup_css_free(struct cgroup_subsys_state css) @@ -5219,11 +5271,9 @@ int mem_cgroup_swapin_charge_folio(struct folio folio, unsigned short id, if (mem_cgroup_disabled()) return 0; - rcu_read_lock(); - memcg = mem_cgroup_from_private_id(id); - if (!memcg \|\| !css_tryget_online(&memcg->css)) + memcg = mem_cgroup_from_private_id_online(id); + if (!memcg) memcg = get_mem_cgroup_from_mm(mm); - rcu_read_unlock(); ret = charge_memcg(folio, memcg, gfp); @@ -5621,24 +5671,27 @@ int __mem_cgroup_try_charge_swap(struct folio folio) return 0; } - memcg = mem_cgroup_private_id_get_online(memcg, nr_pages); - / memcg is pined by memcg ID. / + memcg = get_mem_cgroup_from_objcg(objcg); rcu_read_unlock(); if (!mem_cgroup_is_root(memcg) && !page_counter_try_charge(&memcg->swap, nr_pages, &counter)) { memcg_memory_event(memcg, MEMCG_SWAP_MAX); memcg_memory_event(memcg, MEMCG_SWAP_FAIL); - mem_cgroup_private_id_put(memcg, nr_pages); + mem_cgroup_put(memcg); return -ENOMEM; } mod_memcg_state(memcg, MEMCG_SWAP, nr_pages); + / we have a reference to it, so we should get exact memcg itself / + mem_cgroup_private_id_get(memcg, nr_pages); + ci = swap_cluster_get_and_lock(folio); __swap_cgroup_set(ci, swp_cluster_offset(folio->swap), nr_pages, mem_cgroup_private_id(memcg)); swap_cluster_unlock(ci); + mem_cgroup_put(memcg); return 0; } @@ -5651,19 +5704,19 @@ void __mem_cgroup_uncharge_swap(unsigned short id, unsigned int nr_pages) { struct mem_cgroup memcg; - rcu_read_lock(); - memcg = mem_cgroup_from_private_id(id); - if (memcg) { - if (!mem_cgroup_is_root(memcg)) { - if (do_memsw_account()) - page_counter_uncharge(&memcg->memsw, nr_pages); - else - page_counter_uncharge(&memcg->swap, nr_pages); - } - mod_memcg_state(memcg, MEMCG_SWAP, -nr_pages); - mem_cgroup_private_id_put(memcg, nr_pages); + memcg = mem_cgroup_take_from_private_id(id, nr_pages); + if (!memcg) + return; + + if (!mem_cgroup_is_root(memcg)) { + if (do_memsw_account()) + page_counter_uncharge(&memcg->memsw, nr_pages); + else + page_counter_uncharge(&memcg->swap, nr_pages); } - rcu_read_unlock(); + mod_memcg_state(memcg, MEMCG_SWAP, -nr_pages); + + mem_cgroup_put(memcg); } long mem_cgroup_get_nr_swap_pages(struct mem_cgroup memcg) diff --git a/mm/workingset.c b/mm/workingset.c index f351798e723ac..b6e22536a5240 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -283,6 +283,10 @@ static bool lru_gen_test_recent(void shadow, struct lruvec *lruvec, memcg = mem_cgroup_from_private_id(memcg_id); lruvec = mem_cgroup_lruvec(memcg, pgdat); + /* reparented memcg loses its max_seq / + if (!memcg) + return false; + max_seq = READ_ONCE((lruvec)->lrugen.max_seq); max_seq &= (file ? EVICTION_MASK : EVICTION_MASK_ANON) >> LRU_REFS_WIDTH; @@ -470,7 +474,7 @@ bool workingset_test_recent(void shadow, bool file, bool workingset, * configurations instead. */ eviction_memcg = mem_cgroup_from_private_id(memcgid); - if (!mem_cgroup_tryget(eviction_memcg)) + if (!eviction_memcg \|\| !mem_cgroup_tryget(eviction_memcg)) eviction_memcg = NULL; rcu_read_unlock();
30/3	2026/08/13 09:36	llm	kmsan-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 7462 output: 32 thoughts: 440 Thoughts: My Assessment of the Memcg Private ID Patch Okay, so this patch is digging into the guts of the memory control group (memcg) subsystem. Specifically, it's about how private IDs are handled and how memcgs are looked up using those IDs. I see it introduces `id_objcg` to `struct mem_cgroup` and `id_ref` to `struct obj_cgroup`, and it's tweaking a bunch of related functions like `mem_cgroup_private_id_get_online` and `mem_cgroup_from_private_id`. Mostly, it seems to be about reference counting and managing the lifecycle of memcgs and their private IDs, especially as it relates to swap and workingset. My initial thought is, let's nail down any potential security or stability issues. The big thing I always check is whether uninitialized memory is being exposed to userspace, or if it's potentially used in conditional logic, but looking at the modifications, it's purely internal. We're talking about changes to kernel data structures – `struct mem_cgroup` and `struct obj_cgroup`, but nothing new is being copied to userspace. There aren't any new buffers being allocated and passed back either. This is all internal state management, refcounts, pointers, and IDs. The types of bugs this is most likely to introduce are use-after-free, null pointer dereferences, or memory leaks. KASAN is the tool for catching those kinds of issues, which is great. The question is, does the patch introduce any risks of uninitialized memory reads, which KMSAN would catch? Alright, let's see. The patch does change how the ID is stored. `memcg->id` is now an `int`, replacing the old `struct mem_cgroup_private_id id`. And `memcg->id_objcg` is a pointer. It looks like these are initialized in `mem_cgroup_alloc` or `mem_cgroup_css_online`. And, if it's using standard memcg allocation functions, then we should be fine. I'll need to check `mem_cgroup_alloc` carefully, just to be sure, but it's likely using `kzalloc` or something similar, ensuring initialization. From what I can tell, I don't see any obvious uninitialized memory risks here that KMSAN would uniquely catch. The KASAN checks are going to be perfect for use-after-free or out-of-bounds accesses that could stem from screwed-up refcounting. Still, I should double-check `mem_cgroup_alloc` to be absolutely certain. I should never leave any stone unturned.
31/3	2026/08/13 09:36	tool	grepper	0m Args: { "Expression": "mem_cgroup_alloc", "PathPrefix": "mm/memcontrol.c" } Results: { "Output": "mm/memcontrol.c=4131=static void mem_cgroup_free(struct mem_cgroup memcg)\n--\nmm/memcontrol.c-4137-\nmm/memcontrol.c:4138:static struct mem_cgroup mem_cgroup_alloc(struct mem_cgroup parent)\nmm/memcontrol.c-4139-{\n--\nmm/memcontrol.c=4209=mem_cgroup_css_alloc(struct cgroup_subsys_state parent_css)\n--\nmm/memcontrol.c-4215-\told_memcg = set_active_memcg(parent);\nmm/memcontrol.c:4216:\tmemcg = mem_cgroup_alloc(parent);\nmm/memcontrol.c-4217-\tset_active_memcg(old_memcg);\n" }
32/3	2026/08/13 09:36	llm	kmsan-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 8744 output: 35 thoughts: 15 Thoughts: Here's a summary of my thought process regarding `mem_cgroup_alloc`, as an expert: Diving into `mem_cgroup_alloc` Okay, so let's get right into the guts of the `mem_cgroup_alloc` implementation. My initial focus is always on the fundamental mechanics. What are the key data structures involved here? I'm immediately thinking about the memory cgroup itself, the per-node accounting structures, and how they interact. Are we talking about a simple allocation check and accounting update, or is there a more complex balancing act going on? I'm anticipating interactions with the page allocator, NUMA considerations, and potentially even resource limits. I need to understand how this function fits into the larger picture of the memory cgroup subsystem. How does it interact with reclaim, swap, and OOM handling? What's the lock hierarchy like, and how is concurrency managed? Knowing that will provide insight into potential contention points, performance bottlenecks, or even deadlock scenarios. I'll need to trace the call paths to see how this function is called, under what conditions, and what the caller expects in return. I expect the details of the allocation to be interesting, so I'll want to review the implementation and identify any performance inefficiencies. I wonder how the function handles situations when the allocation fails due to memory limits.
33/3	2026/08/13 09:36	tool	read-file	0m Args: { "File": "mm/memcontrol.c", "FirstLine": 4138, "LineCount": 50 } Results: { "Contents": "4138:\tstatic struct mem_cgroup mem_cgroup_alloc(struct mem_cgroup parent)\n4139:\t{\n4140:\t\tstruct memcg_vmstats_percpu statc;\n4141:\t\tstruct memcg_vmstats_percpu __percpu pstatc_pcpu;\n4142:\t\tstruct mem_cgroup *memcg;\n4143:\t\tint node, cpu;\n4144:\t\tint __maybe_unused i;\n4145:\t\tlong error;\n4146:\t\n4147:\t\tmemcg = kmem_cache_zalloc(memcg_cachep, GFP_KERNEL);\n4148:\t\tif (!memcg)\n4149:\t\t\treturn ERR_PTR(-ENOMEM);\n4150:\t\n4151:\t\terror = xa_alloc(\u0026mem_cgroup_private_ids, \u0026memcg-\u003eid, NULL,\n4152:\t\t\t\t XA_LIMIT(1, MEM_CGROUP_ID_MAX), GFP_KERNEL);\n4153:\t\tif (error)\n4154:\t\t\tgoto fail;\n4155:\t\terror = -ENOMEM;\n4156:\t\n4157:\t\tmemcg-\u003evmstats = kzalloc_obj(struct memcg_vmstats, GFP_KERNEL_ACCOUNT);\n4158:\t\tif (!memcg-\u003evmstats)\n4159:\t\t\tgoto fail;\n4160:\t\n4161:\t\tmemcg-\u003evmstats_percpu = alloc_percpu_gfp(struct memcg_vmstats_percpu,\n4162:\t\t\t\t\t\t\t GFP_KERNEL_ACCOUNT);\n4163:\t\tif (!memcg-\u003evmstats_percpu)\n4164:\t\t\tgoto fail;\n4165:\t\n4166:\t\tif (!memcg1_alloc_events(memcg))\n4167:\t\t\tgoto fail;\n4168:\t\n4169:\t\tpstatc_pcpu = parent ? parent-\u003evmstats_percpu : NULL;\n4170:\t\tfor_each_possible_cpu(cpu) {\n4171:\t\t\tstatc = per_cpu_ptr(memcg-\u003evmstats_percpu, cpu);\n4172:\t\t\tstatc-\u003eparent_pcpu = pstatc_pcpu;\n4173:\t\t\tstatc-\u003evmstats = memcg-\u003evmstats;\n4174:\t\t}\n4175:\t\n4176:\t\tfor_each_node(node)\n4177:\t\t\tif (!alloc_mem_cgroup_per_node_info(memcg, node))\n4178:\t\t\t\tgoto fail;\n4179:\t\n4180:\t\tif (memcg_wb_domain_init(memcg, GFP_KERNEL))\n4181:\t\t\tgoto fail;\n4182:\t\n4183:\t\tINIT_WORK(\u0026memcg-\u003ehigh_work, high_work_func);\n4184:\t\tvmpressure_init(\u0026memcg-\u003evmpressure);\n4185:\t\tINIT_LIST_HEAD(\u0026memcg-\u003ememory_peaks);\n4186:\t\tINIT_LIST_HEAD(\u0026memcg-\u003eswap_peaks);\n4187:\t\tspin_lock_init(\u0026memcg-\u003epeaks_lock);\n" }
34/3	2026/08/13 09:36	llm	kmsan-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 9912 output: 237 thoughts: 334 Thoughts: My Assessment of the Patch's Safety Okay, let me break this down. My initial thought is that this patch, dealing with `memcg` lifecycle and reference counting, isn't going to require KMSAN. The core of the patch seems to be refining how we manage and track `mem_cgroup` private IDs, introducing `id_objcg` to `struct mem_cgroup` and `id_ref` to `struct obj_cgroup`. We're talking about internal bookkeeping, mainly centered around how memcgs are looked up using these IDs and how their references are handled, especially during swap and workingset operations. Crucially, the `mem_cgroup` is allocated using `kmem_cache_zalloc`, which means it's guaranteed to be zero-initialized. That alone significantly reduces the chances of exposing uninitialized memory. The modifications are focused on reference counting and object lifecycle. The primary risk from these changes would be classic memory management errors: use-after-free, double frees, or perhaps some subtle reference counting bugs leading to leaks or premature free-ing. Considering the types of changes and where the vulnerabilities would likely lie, KASAN seems perfectly suited to catch these types of errors. We're talking about classic kernel memory bugs, not the type of data leakage that KMSAN is designed to detect. There's no indication of user-space data copying or manipulation that would expose new, possibly uninitialized, memory areas to user processes. Given that KASAN's coverage of these types of issues is excellent and that the new fields are zero-initialized, I don't see any need to push for a KMSAN session. The standard kernel debugging tools and KASAN will be sufficient for this patch. Therefore, a `NeedsKMSAN` label seems unnecessary.
35/3	2026/08/13 09:36	tool	set-results	0m Args: { "KMSANReasoning": "The patch modifies the lifecycle and reference counting of `mem_cgroup` private IDs, introducing `id_objcg` to `struct mem_cgroup` and `id_ref` to `struct obj_cgroup`. It changes how memcgs are looked up from these IDs and how their references are managed, particularly during swap and workingset operations.\n\nThese changes are purely internal state management and do not introduce any new structures or buffers that are copied to user space. The `mem_cgroup` structure itself is allocated using `kmem_cache_zalloc` (as seen in `mem_cgroup_alloc`), ensuring it is fully zero-initialized.\n\nAny bugs introduced by these changes would likely be use-after-free, NULL pointer dereferences, or memory leaks due to incorrect reference counting. These types of bugs are effectively caught by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory reads or info-leaks that would necessitate a dedicated KMSAN fuzzing session.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch modifies the lifecycle and reference counting of `mem_cgroup` private IDs, introducing `id_objcg` to `struct mem_cgroup` and `id_ref` to `struct obj_cgroup`. It changes how memcgs are looked up from these IDs and how their references are managed, particularly during swap and workingset operations.\n\nThese changes are purely internal state management and do not introduce any new structures or buffers that are copied to user space. The `mem_cgroup` structure itself is allocated using `kmem_cache_zalloc` (as seen in `mem_cgroup_alloc`), ensuring it is fully zero-initialized.\n\nAny bugs introduced by these changes would likely be use-after-free, NULL pointer dereferences, or memory leaks due to incorrect reference counting. These types of bugs are effectively caught by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory reads or info-leaks that would necessitate a dedicated KMSAN fuzzing session.", "NeedsKMSAN": false }

LLM Calls Summary:
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Tool Calls Summary:
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