AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/09/09 09:05	flow	patch-triage	1m Args: null Results: { "EnableConfigs": [ "MEMCG", "MEMCG_V1", "CGROUP_DMEM", "CGROUP_HUGETLB" ], "FocusSymbols": [ "page_counter_set_min", "page_counter_set_low", "page_counter_calculate_protection", "mem_cgroup_calculate_protection", "mem_cgroup_css_alloc", "memory_min_write", "memory_low_write", "dmem_cgroup_state_evict_valuable", "dmem_cgroup_below_min", "dmem_cgroup_below_low", "dmem_cgroup_region_min_write", "dmem_cgroup_region_low_write", "hugetlb_cgroup_css_alloc" ], "KMSANReasoning": "The patch refactors hierarchical protection tracking fields (emin, elow, min, low, and usage counters) out of `struct page_counter` into a separate `struct page_counter_protection` structure.\n\n1. Memory Initialization: All instances of `struct page_counter_protection` are embedded within `struct mem_cgroup` and `struct dmem_cgroup_pool_state`, which are allocated via zero-allocating APIs (`kmem_cache_zalloc` and `kzalloc_obj`). `page_counter_init()` explicitly clears `prot = NULL`, and `page_counter_init_protection()` initializes the protection pointers and limits.\n2. User-space Boundary: No uninitialized bytes, structs with uninitialized padding, or uninitialized buffers are exposed or copied to user space. Only scalar values formatted through seq_file helpers or numerical returns are read.\n3. Bug Detection Suitability: Potential risks in this refactoring would involve NULL pointer dereferences or control flow issues, which are caught by standard kernel checks and KASAN. There are no risks of uninitialized memory reads or information leaks.\n\nTherefore, a dedicated KMSAN fuzzing session is not required.", "NeedsKMSAN": false, "Reasoning": "The patch refactors the memory protection fields (memory.min, memory.low, emin, elow, and associated usages) out of struct page_counter into a dedicated struct page_counter_protection. It modifies core page counter initialization and protection calculations, memcg cgroup v1/v2 control files and calculations, and dmem cgroup pool protection logic. These reachable memory management and cgroup subsystem paths warrant fuzzing to verify against null pointer dereferences, incorrect protection calculations, and state inconsistencies.", "WorthFuzzing": true }
1/1	2026/09/09 09:05	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit a44d7a8c0d593e8dd444819f3e172e4d44299d5b\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Wed Sep 9 09:05:15 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h\nindex 058ebd73ff160..44065001a66ac 100644\n--- a/include/linux/memcontrol.h\n+++ b/include/linux/memcontrol.h\n@@ -195,6 +195,13 @@ struct mem_cgroup {\n \t/* Accounted resources /\n \tstruct page_counter memory;\t\t/ Both v1 \u0026 v2 /\n \n+\t/\n+\t * Hierarchical memory.min/memory.low protection tracking for the\n+\t * memory page counter. swap/memsw, kmem and tcpmem counters do not\n+\t * support protection and have no such context.\n+\t /\n+\tstruct page_counter_protection memory_prot;\n+\n \tunion {\n \t\tstruct page_counter swap;\t/ v2 only /\n \t\tstruct page_counter memsw;\t/ v1 only /\n@@ -584,8 +591,8 @@ static inline void mem_cgroup_protection(struct mem_cgroup root,\n \tif (root == memcg)\n \t\treturn;\n \n-\tmin = READ_ONCE(memcg-\u003ememory.emin);\n-\tlow = READ_ONCE(memcg-\u003ememory.elow);\n+\tmin = READ_ONCE(memcg-\u003ememory_prot.emin);\n+\tlow = READ_ONCE(memcg-\u003ememory_prot.elow);\n }\n \n void mem_cgroup_calculate_protection(struct mem_cgroup root,\n@@ -609,7 +616,7 @@ static inline bool mem_cgroup_below_low(struct mem_cgroup target,\n \tif (mem_cgroup_unprotected(target, memcg))\n \t\treturn false;\n \n-\treturn READ_ONCE(memcg-\u003ememory.elow) \u003e=\n+\treturn READ_ONCE(memcg-\u003ememory_prot.elow) \u003e=\n \t\tpage_counter_read(\u0026memcg-\u003ememory);\n }\n \n@@ -619,7 +626,7 @@ static inline bool mem_cgroup_below_min(struct mem_cgroup target,\n \tif (mem_cgroup_unprotected(target, memcg))\n \t\treturn false;\n \n-\treturn READ_ONCE(memcg-\u003ememory.emin) \u003e=\n+\treturn READ_ONCE(memcg-\u003ememory_prot.emin) \u003e=\n \t\tpage_counter_read(\u0026memcg-\u003ememory);\n }\n \ndiff --git a/include/linux/page_counter.h b/include/linux/page_counter.h\nindex 07b7cb12249c7..a4dd461523af2 100644\n--- a/include/linux/page_counter.h\n+++ b/include/linux/page_counter.h\n@@ -7,15 +7,17 @@\n #include \u003clinux/limits.h\u003e\n #include \u003casm/page.h\u003e\n \n-struct page_counter {\n-\t/\n-\t * Make sure 'usage' does not share cacheline with any other field in\n-\t * v2. The memcg-\u003ememory.usage is a hot member of struct mem_cgroup.\n-\t /\n-\tatomic_long_t usage;\n-\tunsigned long failcnt; / v1-only field /\n-\n-\tCACHELINE_PADDING(_pad1_);\n+/\n+ * Hierarchical protection (memory.min / memory.low) tracking.\n+ \n+ Only the memory page counter (and dmem pools) participate in protection.\n+ * swap/memsw, kmem and tcpmem page counters never do, so the protection\n+ * fields are kept out of struct page_counter in this separate structure to\n+ * save space in the common case. struct page_counter links to it via -\u003eprot,\n+ * which is NULL for counters without protection support.\n+ /\n+struct page_counter_protection {\n+\tstruct page_counter_protection parent;\n \n \t/* effective memory.min and memory.min usage tracking /\n \tunsigned long emin;\n@@ -27,20 +29,37 @@ struct page_counter {\n \tatomic_long_t low_usage;\n \tatomic_long_t children_low_usage;\n \n+\tunsigned long min;\n+\tunsigned long low;\n+};\n+\n+struct page_counter {\n+\t/\n+\t * Make sure 'usage' does not share cacheline with any other field in\n+\t * v2. The memcg-\u003ememory.usage is a hot member of struct mem_cgroup.\n+\t /\n+\tatomic_long_t usage;\n+\tunsigned long failcnt; / v1-only field /\n+\n+\tCACHELINE_PADDING(_pad1_);\n+\n \tunsigned long watermark;\n \t/ Latest cg2 reset watermark /\n \tunsigned long local_watermark;\n \n-\t/ Keep all the read most fields in a separete cacheline. /\n-\tCACHELINE_PADDING(_pad2_);\n-\n-\tbool protection_support;\n \tbool track_failcnt;\n-\tunsigned long min;\n-\tunsigned long low;\n \tunsigned long high;\n \tunsigned long max;\n \tstruct page_counter parent;\n+\n+\t/\n+\t Hierarchical protection context, NULL for counters that do not\n+\t * support memory.min/memory.low (swap, memsw, kmem, tcpmem, ...).\n+\t /\n+\tstruct page_counter_protection prot;\n+\n+\t/* Keep all the read most fields in a separete cacheline. /\n+\tCACHELINE_PADDING(_pad2_);\n } ____cacheline_internodealigned_in_smp;\n \n #if BITS_PER_LONG == 32\n@@ -49,18 +68,33 @@ struct page_counter {\n #define PAGE_COUNTER_MAX (LONG_MAX / PAGE_SIZE)\n #endif\n \n-/\n- * Protection is supported only for the first counter (with id 0).\n- /\n static inline void page_counter_init(struct page_counter counter,\n-\t\t\t\t struct page_counter parent,\n-\t\t\t\t bool protection_support)\n+\t\t\t\t struct page_counter parent)\n {\n \tcounter-\u003eusage = (atomic_long_t)ATOMIC_LONG_INIT(0);\n \tcounter-\u003emax = PAGE_COUNTER_MAX;\n \tcounter-\u003eparent = parent;\n-\tcounter-\u003eprotection_support = protection_support;\n \tcounter-\u003etrack_failcnt = false;\n+\tcounter-\u003eprot = NULL;\n+}\n+\n+/\n+ Enable hierarchical protection (memory.min/memory.low) on @counter.\n+ * @prot and @parent are the protection contexts of @counter and its\n+ * parent page counter respectively. Only the memory page counter (and\n+ * dmem pools) call this.\n+ \n+ The remaining members of @prot (emin, elow and the usage counters) are\n+ * expected to be zero already, so @prot must come from zeroed memory.\n+ /\n+static inline void page_counter_init_protection(struct page_counter counter,\n+\t\t\t\t\t\tstruct page_counter_protection prot,\n+\t\t\t\t\t\tstruct page_counter_protection parent)\n+{\n+\tcounter-\u003eprot = prot;\n+\tprot-\u003eparent = parent;\n+\tprot-\u003emin = 0;\n+\tprot-\u003elow = 0;\n }\n \n static inline unsigned long page_counter_read(struct page_counter counter)\ndiff --git a/kernel/cgroup/dmem.c b/kernel/cgroup/dmem.c\nindex 4683f3d680226..10321f1f03308 100644\n--- a/kernel/cgroup/dmem.c\n+++ b/kernel/cgroup/dmem.c\n@@ -88,6 +88,7 @@ struct dmem_cgroup_pool_state {\n \tstruct rcu_head rcu;\n \n \tstruct page_counter cnt;\n+\tstruct page_counter_protection prot;\n \tstruct dmem_cgroup_pool_state parent;\n \n \trefcount_t ref;\n@@ -211,12 +212,12 @@ set_resource_max(struct dmem_cgroup_pool_state pool, u64 val, bool nonblock)\n \n static u64 get_resource_low(struct dmem_cgroup_pool_state pool)\n {\n-\treturn pool ? READ_ONCE(pool-\u003ecnt.low) : 0;\n+\treturn pool ? READ_ONCE(pool-\u003ecnt.prot-\u003elow) : 0;\n }\n \n static u64 get_resource_min(struct dmem_cgroup_pool_state pool)\n {\n-\treturn pool ? READ_ONCE(pool-\u003ecnt.min) : 0;\n+\treturn pool ? READ_ONCE(pool-\u003ecnt.prot-\u003emin) : 0;\n }\n \n static u64 get_resource_max(struct dmem_cgroup_pool_state pool)\n@@ -387,13 +388,13 @@ bool dmem_cgroup_state_evict_valuable(struct dmem_cgroup_pool_state limit_pool,\n \tdmem_cgroup_calculate_protection(limit_pool, test_pool);\n \n \tused = page_counter_read(ctest);\n-\tmin = READ_ONCE(ctest-\u003eemin);\n+\tmin = READ_ONCE(ctest-\u003eprot-\u003eemin);\n \n \tif (used \u003c= min)\n \t\treturn false;\n \n \tif (!ignore_low) {\n-\t\tlow = READ_ONCE(ctest-\u003eelow);\n+\t\tlow = READ_ONCE(ctest-\u003eprot-\u003eelow);\n \t\tif (used \u003e low)\n \t\t\treturn true;\n \n@@ -426,8 +427,9 @@ alloc_pool_single(struct dmemcg_state dmemcs, struct dmem_cgroup_region region\n \tif (parent)\n \t\tppool = find_cg_pool_locked(parent, region);\n \n-\tpage_counter_init(\u0026pool-\u003ecnt,\n-\t\t\t ppool ? \u0026ppool-\u003ecnt : NULL, true);\n+\tpage_counter_init(\u0026pool-\u003ecnt, ppool ? \u0026ppool-\u003ecnt : NULL);\n+\tpage_counter_init_protection(\u0026pool-\u003ecnt, \u0026pool-\u003eprot,\n+\t\t\t\t ppool ? \u0026ppool-\u003eprot : NULL);\n \treset_all_resource_limits(pool);\n \trefcount_set(\u0026pool-\u003eref, 1);\n \tkref_get(\u0026region-\u003eref);\n@@ -784,7 +786,7 @@ bool dmem_cgroup_below_min(struct dmem_cgroup_pool_state root,\n \t * here.\n \t /\n \tdmem_cgroup_calculate_protection(root, test);\n-\treturn page_counter_read(\u0026test-\u003ecnt) \u003c= READ_ONCE(test-\u003ecnt.emin);\n+\treturn page_counter_read(\u0026test-\u003ecnt) \u003c= READ_ONCE(test-\u003ecnt.prot-\u003eemin);\n }\n EXPORT_SYMBOL_GPL(dmem_cgroup_below_min);\n \n@@ -815,7 +817,7 @@ bool dmem_cgroup_below_low(struct dmem_cgroup_pool_state root,\n \t * here.\n \t /\n \tdmem_cgroup_calculate_protection(root, test);\n-\treturn page_counter_read(\u0026test-\u003ecnt) \u003c= READ_ONCE(test-\u003ecnt.elow);\n+\treturn page_counter_read(\u0026test-\u003ecnt) \u003c= READ_ONCE(test-\u003ecnt.prot-\u003eelow);\n }\n EXPORT_SYMBOL_GPL(dmem_cgroup_below_low);\n \ndiff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c\nindex ecb6e0b7819a0..7fdae504cfc6f 100644\n--- a/mm/hugetlb_cgroup.c\n+++ b/mm/hugetlb_cgroup.c\n@@ -108,8 +108,8 @@ static void hugetlb_cgroup_init(struct hugetlb_cgroup h_cgroup,\n \t\tfault = hugetlb_cgroup_counter_from_cgroup(h_cgroup, idx);\n \t\trsvd = hugetlb_cgroup_counter_from_cgroup_rsvd(h_cgroup, idx);\n \n-\t\tpage_counter_init(fault, fault_parent, false);\n-\t\tpage_counter_init(rsvd, rsvd_parent, false);\n+\t\tpage_counter_init(fault, fault_parent);\n+\t\tpage_counter_init(rsvd, rsvd_parent);\n \n \t\tif (!cgroup_subsys_on_dfl(hugetlb_cgrp_subsys)) {\n \t\t\tfault-\u003etrack_failcnt = true;\ndiff --git a/mm/memcontrol.c b/mm/memcontrol.c\nindex 86ff580c70183..b4c01a0dfd4f6 100644\n--- a/mm/memcontrol.c\n+++ b/mm/memcontrol.c\n@@ -4267,25 +4267,30 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state parent_css)\n #endif\n \tpage_counter_set_high(\u0026memcg-\u003eswap, PAGE_COUNTER_MAX);\n \tif (parent) {\n-\t\tpage_counter_init(\u0026memcg-\u003ememory, \u0026parent-\u003ememory, memcg_on_dfl);\n-\t\tpage_counter_init(\u0026memcg-\u003eswap, \u0026parent-\u003eswap, false);\n+\t\tpage_counter_init(\u0026memcg-\u003ememory, \u0026parent-\u003ememory);\n+\t\tif (memcg_on_dfl)\n+\t\t\tpage_counter_init_protection(\u0026memcg-\u003ememory, \u0026memcg-\u003ememory_prot,\n+\t\t\t\t\t\t \u0026parent-\u003ememory_prot);\n+\t\tpage_counter_init(\u0026memcg-\u003eswap, \u0026parent-\u003eswap);\n #ifdef CONFIG_MEMCG_V1\n \t\tWRITE_ONCE(memcg-\u003eswappiness, mem_cgroup_swappiness(parent));\n \t\tmemcg-\u003ememory.track_failcnt = !memcg_on_dfl;\n \t\tmemcg-\u003ememsw.track_failcnt = !memcg_on_dfl;\n \t\tWRITE_ONCE(memcg-\u003eoom_kill_disable, READ_ONCE(parent-\u003eoom_kill_disable));\n-\t\tpage_counter_init(\u0026memcg-\u003ekmem, \u0026parent-\u003ekmem, false);\n-\t\tpage_counter_init(\u0026memcg-\u003etcpmem, \u0026parent-\u003etcpmem, false);\n+\t\tpage_counter_init(\u0026memcg-\u003ekmem, \u0026parent-\u003ekmem);\n+\t\tpage_counter_init(\u0026memcg-\u003etcpmem, \u0026parent-\u003etcpmem);\n \t\tmemcg-\u003etcpmem.track_failcnt = !memcg_on_dfl;\n #endif\n \t} else {\n \t\tinit_memcg_stats();\n \t\tinit_memcg_events();\n-\t\tpage_counter_init(\u0026memcg-\u003ememory, NULL, true);\n-\t\tpage_counter_init(\u0026memcg-\u003eswap, NULL, false);\n+\t\tpage_counter_init(\u0026memcg-\u003ememory, NULL);\n+\t\tpage_counter_init_protection(\u0026memcg-\u003ememory, \u0026memcg-\u003ememory_prot,\n+\t\t\t\t\t NULL);\n+\t\tpage_counter_init(\u0026memcg-\u003eswap, NULL);\n #ifdef CONFIG_MEMCG_V1\n-\t\tpage_counter_init(\u0026memcg-\u003ekmem, NULL, false);\n-\t\tpage_counter_init(\u0026memcg-\u003etcpmem, NULL, false);\n+\t\tpage_counter_init(\u0026memcg-\u003ekmem, NULL);\n+\t\tpage_counter_init(\u0026memcg-\u003etcpmem, NULL);\n #endif\n \t\troot_mem_cgroup = memcg;\n \t\treturn \u0026memcg-\u003ecss;\n@@ -4818,7 +4823,7 @@ static ssize_t memory_peak_write(struct kernfs_open_file of, char buf,\n static int memory_min_show(struct seq_file m, void v)\n {\n \treturn seq_puts_memcg_tunable(m,\n-\t\tREAD_ONCE(mem_cgroup_from_seq(m)-\u003ememory.min));\n+\t\tREAD_ONCE(mem_cgroup_from_seq(m)-\u003ememory_prot.min));\n }\n \n static ssize_t memory_min_write(struct kernfs_open_file of,\n@@ -4841,7 +4846,7 @@ static ssize_t memory_min_write(struct kernfs_open_file of,\n static int memory_low_show(struct seq_file m, void v)\n {\n \treturn seq_puts_memcg_tunable(m,\n-\t\tREAD_ONCE(mem_cgroup_from_seq(m)-\u003ememory.low));\n+\t\tREAD_ONCE(mem_cgroup_from_seq(m)-\u003ememory_prot.low));\n }\n \n static ssize_t memory_low_write(struct kernfs_open_file of,\n@@ -6266,6 +6271,6 @@ void mem_cgroup_show_protected_memory(struct mem_cgroup memcg)\n \t\tmemcg = root_mem_cgroup;\n \n \tpr_warn(\"Memory cgroup min protection %lukB -- low protection %lukB\",\n-\t\tK(atomic_long_read(\u0026memcg-\u003ememory.children_min_usage)),\n-\t\tK(atomic_long_read(\u0026memcg-\u003ememory.children_low_usage)));\n+\t\tK(atomic_long_read(\u0026memcg-\u003ememory_prot.children_min_usage)),\n+\t\tK(atomic_long_read(\u0026memcg-\u003ememory_prot.children_low_usage)));\n }\ndiff --git a/mm/page_counter.c b/mm/page_counter.c\nindex 450543f4b318b..401201c8e3902 100644\n--- a/mm/page_counter.c\n+++ b/mm/page_counter.c\n@@ -15,34 +15,35 @@\n \n static bool track_protection(struct page_counter c)\n {\n-\treturn c-\u003eprotection_support;\n+\treturn c-\u003eprot != NULL;\n }\n \n static void propagate_protected_usage(struct page_counter c,\n \t\t\t\t unsigned long usage)\n {\n+\tstruct page_counter_protection prot = c-\u003eprot;\n \tunsigned long protected, old_protected;\n \tlong delta;\n \n-\tif (!c-\u003eparent)\n+\tif (!prot \|\| !prot-\u003eparent)\n \t\treturn;\n \n-\tprotected = min(usage, READ_ONCE(c-\u003emin));\n-\told_protected = atomic_long_read(\u0026c-\u003emin_usage);\n+\tprotected = min(usage, READ_ONCE(prot-\u003emin));\n+\told_protected = atomic_long_read(\u0026prot-\u003emin_usage);\n \tif (protected != old_protected) {\n-\t\told_protected = atomic_long_xchg(\u0026c-\u003emin_usage, protected);\n+\t\told_protected = atomic_long_xchg(\u0026prot-\u003emin_usage, protected);\n \t\tdelta = protected - old_protected;\n \t\tif (delta)\n-\t\t\tatomic_long_add(delta, \u0026c-\u003eparent-\u003echildren_min_usage);\n+\t\t\tatomic_long_add(delta, \u0026prot-\u003eparent-\u003echildren_min_usage);\n \t}\n \n-\tprotected = min(usage, READ_ONCE(c-\u003elow));\n-\told_protected = atomic_long_read(\u0026c-\u003elow_usage);\n+\tprotected = min(usage, READ_ONCE(prot-\u003elow));\n+\told_protected = atomic_long_read(\u0026prot-\u003elow_usage);\n \tif (protected != old_protected) {\n-\t\told_protected = atomic_long_xchg(\u0026c-\u003elow_usage, protected);\n+\t\told_protected = atomic_long_xchg(\u0026prot-\u003elow_usage, protected);\n \t\tdelta = protected - old_protected;\n \t\tif (delta)\n-\t\t\tatomic_long_add(delta, \u0026c-\u003eparent-\u003echildren_low_usage);\n+\t\t\tatomic_long_add(delta, \u0026prot-\u003eparent-\u003echildren_low_usage);\n \t}\n }\n \n@@ -257,7 +258,10 @@ void page_counter_set_min(struct page_counter counter, unsigned long nr_pages)\n {\n \tstruct page_counter c;\n \n-\tWRITE_ONCE(counter-\u003emin, nr_pages);\n+\tif (!counter-\u003eprot)\n+\t\treturn;\n+\n+\tWRITE_ONCE(counter-\u003eprot-\u003emin, nr_pages);\n \n \tfor (c = counter; c; c = c-\u003eparent)\n \t\tpropagate_protected_usage(c, atomic_long_read(\u0026c-\u003eusage));\n@@ -274,7 +278,10 @@ void page_counter_set_low(struct page_counter counter, unsigned long nr_pages)\n {\n \tstruct page_counter c;\n \n-\tWRITE_ONCE(counter-\u003elow, nr_pages);\n+\tif (!counter-\u003eprot)\n+\t\treturn;\n+\n+\tWRITE_ONCE(counter-\u003eprot-\u003elow, nr_pages);\n \n \tfor (c = counter; c; c = c-\u003eparent)\n \t\tpropagate_protected_usage(c, atomic_long_read(\u0026c-\u003eusage));\n@@ -445,9 +452,18 @@ void page_counter_calculate_protection(struct page_counter root,\n \t\t\t\t struct page_counter counter,\n \t\t\t\t bool recursive_protection)\n {\n+\tstruct page_counter_protection prot = counter-\u003eprot;\n+\tstruct page_counter_protection parent_prot;\n \tunsigned long usage, parent_usage;\n \tstruct page_counter parent = counter-\u003eparent;\n \n+\t/\n+\t * Only counters with protection support (memory, dmem pools) are\n+\t * ever passed here, but guard anyway.\n+\t /\n+\tif (!prot)\n+\t\treturn;\n+\n \t/\n \t * Effective values of the reclaim targets are ignored so they\n \t * can be stale. Have a look at mem_cgroup_protection for more\n@@ -463,23 +479,24 @@ void page_counter_calculate_protection(struct page_counter root,\n \t\treturn;\n \n \tif (parent == root) {\n-\t\tcounter-\u003eemin = READ_ONCE(counter-\u003emin);\n-\t\tcounter-\u003eelow = READ_ONCE(counter-\u003elow);\n+\t\tprot-\u003eemin = READ_ONCE(prot-\u003emin);\n+\t\tprot-\u003eelow = READ_ONCE(prot-\u003elow);\n \t\treturn;\n \t}\n \n+\tparent_prot = parent-\u003eprot;\n \tparent_usage = page_counter_read(parent);\n \n-\tWRITE_ONCE(counter-\u003eemin, effective_protection(usage, parent_usage,\n-\t\t\tREAD_ONCE(counter-\u003emin),\n-\t\t\tREAD_ONCE(parent-\u003eemin),\n-\t\t\tatomic_long_read(\u0026parent-\u003echildren_min_usage),\n+\tWRITE_ONCE(prot-\u003eemin, effective_protection(usage, parent_usage,\n+\t\t\tREAD_ONCE(prot-\u003emin),\n+\t\t\tREAD_ONCE(parent_prot-\u003eemin),\n+\t\t\tatomic_long_read(\u0026parent_prot-\u003echildren_min_usage),\n \t\t\trecursive_protection));\n \n-\tWRITE_ONCE(counter-\u003eelow, effective_protection(usage, parent_usage,\n-\t\t\tREAD_ONCE(counter-\u003elow),\n-\t\t\tREAD_ONCE(parent-\u003eelow),\n-\t\t\tatomic_long_read(\u0026parent-\u003echildren_low_usage),\n+\tWRITE_ONCE(prot-\u003eelow, effective_protection(usage, parent_usage,\n+\t\t\tREAD_ONCE(prot-\u003elow),\n+\t\t\tREAD_ONCE(parent_prot-\u003eelow),\n+\t\t\tatomic_long_read(\u0026parent_prot-\u003echildren_low_usage),\n \t\t\trecursive_protection));\n }\n #endif / CONFIG_MEMCG \|\| CONFIG_CGROUP_DMEM */\n" }
2/1	2026/09/09 09:05	agent	patch-evaluator	0m Model: core Args: null Results: { "EnableConfigs": [ "MEMCG", "MEMCG_V1", "CGROUP_DMEM", "CGROUP_HUGETLB" ], "FocusSymbols": [ "page_counter_set_min", "page_counter_set_low", "page_counter_calculate_protection", "mem_cgroup_calculate_protection", "mem_cgroup_css_alloc", "memory_min_write", "memory_low_write", "dmem_cgroup_state_evict_valuable", "dmem_cgroup_below_min", "dmem_cgroup_below_low", "dmem_cgroup_region_min_write", "dmem_cgroup_region_low_write", "hugetlb_cgroup_css_alloc" ], "Reasoning": "The patch refactors the memory protection fields (memory.min, memory.low, emin, elow, and associated usages) out of struct page_counter into a dedicated struct page_counter_protection. It modifies core page counter initialization and protection calculations, memcg cgroup v1/v2 control files and calculations, and dmem cgroup pool protection logic. These reachable memory management and cgroup subsystem paths warrant fuzzing to verify against null pointer dereferences, incorrect protection calculations, and state inconsistencies.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer and security engineer. Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on internal assumptions. You must actively use your code access tools to inspect the actual source code, callers, and surrounding context. ================================================================================ 1. CORE TRIAGE PHILOSOPHY ================================================================================ The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs, and newly triggered assertions introduced by the patch series. - REACHABILITY IS THE PRIMARY GATE: Fuzzing can only discover bugs in code that can actually execute in standard virtualized environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap). If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed, regardless of whether it adds assertions or complex logic. - DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS: Patch authors routinely label changes as "cleanups", "refactorings", or state "No functional change intended". Do NOT take these claims at face value. Code refactorings that rearrange logic, introduce helper functions, or alter state management in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs. If reachable executable code is modified or refactored, it MUST be fuzzed. - NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED: When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON, VM_WARN_ON, BUG_ON, lockdep_assert) in reachable code paths, it enforces new or stricter invariants. Even if the author believes the invariant always holds, fuzzing is essential to verify whether an unusual sequence of operations can violate it. ================================================================================ 2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA) ================================================================================ Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories: - Non-kernel and non-executable changes: * Modifications to Documentation/, comments, or spelling fixes. * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/) that do not affect the compiled kernel image (vmlinux) or kernel modules. * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints that do not alter control flow or data structures. * Build system or Kconfig changes that do not alter compiled C logic. - Structurally unreachable hardware: * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU. - Unreachable execution paths: * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during physical PCI hot-unplug or manual sysfs driver unbinding. * Code paths exclusive to architectures other than the target architecture. ================================================================================ 3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA) ================================================================================ Return WorthFuzzing=true whenever the patch touches reachable executable code, including: - Core Subsystems: * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/), BPF, scheduler, core networking, VFS, or syscall handling. - Refactorings and Code Cleanups: * Any restructuring of reachable data structures, helper abstractions, or algorithm flows. - Runtime Assertions and Defensive Checks: * Any introduction or alteration of assertions (WARN_ON, VM_WARN_ON, BUG_ON, etc.) in reachable paths. - Reachable Drivers and Protocols: Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.). ================================================================================ 4. EXTRACTING FocusSymbols (PREVENTING DILUTION) ================================================================================ When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer: - AVOID UBIQUITOUS LIFECYCLE HOT-PATHS: Do NOT list generic, ubiquitous functions called by almost every program in the corpus (including, but not limited to: general memory allocators and deallocators, page fault and trap handlers, or core synchronization primitives; this is not an exhaustive list). Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused", which severely dilutes fuzzing effort away from the actual changes. - TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS: List functions that specifically implement the logic being added or altered, or direct API entrypoints for the subsystem feature under review. - HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h): Compiler-inlined static functions (such as static inlines in mm/.h or include/linux/.h) lack distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters. If the changes are primarily in static inline helpers, identify non-static, feature-specific caller functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers). ================================================================================ 5. IDENTIFYING EnableConfigs ================================================================================ Identify any specific CONFIG_ options required to properly compile and reach the modified code: - Inspect Kconfig files and #ifdef guards; do not make assumptions. - Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed. - Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4"). Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit a44d7a8c0d593e8dd444819f3e172e4d44299d5b Author: syz-cluster <triage@syzkaller.com> Date: Wed Sep 9 09:05:15 2026 +0000 syz-cluster: applied patch under review diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 058ebd73ff160..44065001a66ac 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -195,6 +195,13 @@ struct mem_cgroup { /* Accounted resources / struct page_counter memory; / Both v1 & v2 / + / + * Hierarchical memory.min/memory.low protection tracking for the + * memory page counter. swap/memsw, kmem and tcpmem counters do not + * support protection and have no such context. + / + struct page_counter_protection memory_prot; + union { struct page_counter swap; / v2 only / struct page_counter memsw; / v1 only / @@ -584,8 +591,8 @@ static inline void mem_cgroup_protection(struct mem_cgroup root, if (root == memcg) return; - min = READ_ONCE(memcg->memory.emin); - low = READ_ONCE(memcg->memory.elow); + min = READ_ONCE(memcg->memory_prot.emin); + low = READ_ONCE(memcg->memory_prot.elow); } void mem_cgroup_calculate_protection(struct mem_cgroup root, @@ -609,7 +616,7 @@ static inline bool mem_cgroup_below_low(struct mem_cgroup target, if (mem_cgroup_unprotected(target, memcg)) return false; - return READ_ONCE(memcg->memory.elow) >= + return READ_ONCE(memcg->memory_prot.elow) >= page_counter_read(&memcg->memory); } @@ -619,7 +626,7 @@ static inline bool mem_cgroup_below_min(struct mem_cgroup target, if (mem_cgroup_unprotected(target, memcg)) return false; - return READ_ONCE(memcg->memory.emin) >= + return READ_ONCE(memcg->memory_prot.emin) >= page_counter_read(&memcg->memory); } diff --git a/include/linux/page_counter.h b/include/linux/page_counter.h index 07b7cb12249c7..a4dd461523af2 100644 --- a/include/linux/page_counter.h +++ b/include/linux/page_counter.h @@ -7,15 +7,17 @@ #include <linux/limits.h> #include <asm/page.h> -struct page_counter { - / - * Make sure 'usage' does not share cacheline with any other field in - * v2. The memcg->memory.usage is a hot member of struct mem_cgroup. - / - atomic_long_t usage; - unsigned long failcnt; / v1-only field / - - CACHELINE_PADDING(_pad1_); +/ + * Hierarchical protection (memory.min / memory.low) tracking. + * + * Only the memory page counter (and dmem pools) participate in protection. + * swap/memsw, kmem and tcpmem page counters never do, so the protection + * fields are kept out of struct page_counter in this separate structure to + * save space in the common case. struct page_counter links to it via ->prot, + * which is NULL for counters without protection support. + / +struct page_counter_protection { + struct page_counter_protection parent; /* effective memory.min and memory.min usage tracking / unsigned long emin; @@ -27,20 +29,37 @@ struct page_counter { atomic_long_t low_usage; atomic_long_t children_low_usage; + unsigned long min; + unsigned long low; +}; + +struct page_counter { + / + * Make sure 'usage' does not share cacheline with any other field in + * v2. The memcg->memory.usage is a hot member of struct mem_cgroup. + / + atomic_long_t usage; + unsigned long failcnt; / v1-only field / + + CACHELINE_PADDING(_pad1_); + unsigned long watermark; / Latest cg2 reset watermark / unsigned long local_watermark; - / Keep all the read most fields in a separete cacheline. / - CACHELINE_PADDING(_pad2_); - - bool protection_support; bool track_failcnt; - unsigned long min; - unsigned long low; unsigned long high; unsigned long max; struct page_counter parent; + + /* + * Hierarchical protection context, NULL for counters that do not + * support memory.min/memory.low (swap, memsw, kmem, tcpmem, ...). + / + struct page_counter_protection prot; + + /* Keep all the read most fields in a separete cacheline. / + CACHELINE_PADDING(_pad2_); } ____cacheline_internodealigned_in_smp; #if BITS_PER_LONG == 32 @@ -49,18 +68,33 @@ struct page_counter { #define PAGE_COUNTER_MAX (LONG_MAX / PAGE_SIZE) #endif -/ - * Protection is supported only for the first counter (with id 0). - / static inline void page_counter_init(struct page_counter counter, - struct page_counter parent, - bool protection_support) + struct page_counter parent) { counter->usage = (atomic_long_t)ATOMIC_LONG_INIT(0); counter->max = PAGE_COUNTER_MAX; counter->parent = parent; - counter->protection_support = protection_support; counter->track_failcnt = false; + counter->prot = NULL; +} + +/* + * Enable hierarchical protection (memory.min/memory.low) on @counter. + * @prot and @parent are the protection contexts of @counter and its + * parent page counter respectively. Only the memory page counter (and + * dmem pools) call this. + * + * The remaining members of @prot (emin, elow and the usage counters) are + * expected to be zero already, so @prot must come from zeroed memory. + / +static inline void page_counter_init_protection(struct page_counter counter, + struct page_counter_protection prot, + struct page_counter_protection parent) +{ + counter->prot = prot; + prot->parent = parent; + prot->min = 0; + prot->low = 0; } static inline unsigned long page_counter_read(struct page_counter counter) diff --git a/kernel/cgroup/dmem.c b/kernel/cgroup/dmem.c index 4683f3d680226..10321f1f03308 100644 --- a/kernel/cgroup/dmem.c +++ b/kernel/cgroup/dmem.c @@ -88,6 +88,7 @@ struct dmem_cgroup_pool_state { struct rcu_head rcu; struct page_counter cnt; + struct page_counter_protection prot; struct dmem_cgroup_pool_state parent; refcount_t ref; @@ -211,12 +212,12 @@ set_resource_max(struct dmem_cgroup_pool_state pool, u64 val, bool nonblock) static u64 get_resource_low(struct dmem_cgroup_pool_state pool) { - return pool ? READ_ONCE(pool->cnt.low) : 0; + return pool ? READ_ONCE(pool->cnt.prot->low) : 0; } static u64 get_resource_min(struct dmem_cgroup_pool_state pool) { - return pool ? READ_ONCE(pool->cnt.min) : 0; + return pool ? READ_ONCE(pool->cnt.prot->min) : 0; } static u64 get_resource_max(struct dmem_cgroup_pool_state pool) @@ -387,13 +388,13 @@ bool dmem_cgroup_state_evict_valuable(struct dmem_cgroup_pool_state limit_pool, dmem_cgroup_calculate_protection(limit_pool, test_pool); used = page_counter_read(ctest); - min = READ_ONCE(ctest->emin); + min = READ_ONCE(ctest->prot->emin); if (used <= min) return false; if (!ignore_low) { - low = READ_ONCE(ctest->elow); + low = READ_ONCE(ctest->prot->elow); if (used > low) return true; @@ -426,8 +427,9 @@ alloc_pool_single(struct dmemcg_state dmemcs, struct dmem_cgroup_region region if (parent) ppool = find_cg_pool_locked(parent, region); - page_counter_init(&pool->cnt, - ppool ? &ppool->cnt : NULL, true); + page_counter_init(&pool->cnt, ppool ? &ppool->cnt : NULL); + page_counter_init_protection(&pool->cnt, &pool->prot, + ppool ? &ppool->prot : NULL); reset_all_resource_limits(pool); refcount_set(&pool->ref, 1); kref_get(&region->ref); @@ -784,7 +786,7 @@ bool dmem_cgroup_below_min(struct dmem_cgroup_pool_state root, * here. / dmem_cgroup_calculate_protection(root, test); - return page_counter_read(&test->cnt) <= READ_ONCE(test->cnt.emin); + return page_counter_read(&test->cnt) <= READ_ONCE(test->cnt.prot->emin); } EXPORT_SYMBOL_GPL(dmem_cgroup_below_min); @@ -815,7 +817,7 @@ bool dmem_cgroup_below_low(struct dmem_cgroup_pool_state root, * here. / dmem_cgroup_calculate_protection(root, test); - return page_counter_read(&test->cnt) <= READ_ONCE(test->cnt.elow); + return page_counter_read(&test->cnt) <= READ_ONCE(test->cnt.prot->elow); } EXPORT_SYMBOL_GPL(dmem_cgroup_below_low); diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c index ecb6e0b7819a0..7fdae504cfc6f 100644 --- a/mm/hugetlb_cgroup.c +++ b/mm/hugetlb_cgroup.c @@ -108,8 +108,8 @@ static void hugetlb_cgroup_init(struct hugetlb_cgroup h_cgroup, fault = hugetlb_cgroup_counter_from_cgroup(h_cgroup, idx); rsvd = hugetlb_cgroup_counter_from_cgroup_rsvd(h_cgroup, idx); - page_counter_init(fault, fault_parent, false); - page_counter_init(rsvd, rsvd_parent, false); + page_counter_init(fault, fault_parent); + page_counter_init(rsvd, rsvd_parent); if (!cgroup_subsys_on_dfl(hugetlb_cgrp_subsys)) { fault->track_failcnt = true; diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 86ff580c70183..b4c01a0dfd4f6 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4267,25 +4267,30 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state parent_css) #endif page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX); if (parent) { - page_counter_init(&memcg->memory, &parent->memory, memcg_on_dfl); - page_counter_init(&memcg->swap, &parent->swap, false); + page_counter_init(&memcg->memory, &parent->memory); + if (memcg_on_dfl) + page_counter_init_protection(&memcg->memory, &memcg->memory_prot, + &parent->memory_prot); + page_counter_init(&memcg->swap, &parent->swap); #ifdef CONFIG_MEMCG_V1 WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent)); memcg->memory.track_failcnt = !memcg_on_dfl; memcg->memsw.track_failcnt = !memcg_on_dfl; WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable)); - page_counter_init(&memcg->kmem, &parent->kmem, false); - page_counter_init(&memcg->tcpmem, &parent->tcpmem, false); + page_counter_init(&memcg->kmem, &parent->kmem); + page_counter_init(&memcg->tcpmem, &parent->tcpmem); memcg->tcpmem.track_failcnt = !memcg_on_dfl; #endif } else { init_memcg_stats(); init_memcg_events(); - page_counter_init(&memcg->memory, NULL, true); - page_counter_init(&memcg->swap, NULL, false); + page_counter_init(&memcg->memory, NULL); + page_counter_init_protection(&memcg->memory, &memcg->memory_prot, + NULL); + page_counter_init(&memcg->swap, NULL); #ifdef CONFIG_MEMCG_V1 - page_counter_init(&memcg->kmem, NULL, false); - page_counter_init(&memcg->tcpmem, NULL, false); + page_counter_init(&memcg->kmem, NULL); + page_counter_init(&memcg->tcpmem, NULL); #endif root_mem_cgroup = memcg; return &memcg->css; @@ -4818,7 +4823,7 @@ static ssize_t memory_peak_write(struct kernfs_open_file of, char buf, static int memory_min_show(struct seq_file m, void v) { return seq_puts_memcg_tunable(m, - READ_ONCE(mem_cgroup_from_seq(m)->memory.min)); + READ_ONCE(mem_cgroup_from_seq(m)->memory_prot.min)); } static ssize_t memory_min_write(struct kernfs_open_file of, @@ -4841,7 +4846,7 @@ static ssize_t memory_min_write(struct kernfs_open_file of, static int memory_low_show(struct seq_file m, void v) { return seq_puts_memcg_tunable(m, - READ_ONCE(mem_cgroup_from_seq(m)->memory.low)); + READ_ONCE(mem_cgroup_from_seq(m)->memory_prot.low)); } static ssize_t memory_low_write(struct kernfs_open_file of, @@ -6266,6 +6271,6 @@ void mem_cgroup_show_protected_memory(struct mem_cgroup memcg) memcg = root_mem_cgroup; pr_warn("Memory cgroup min protection %lukB -- low protection %lukB", - K(atomic_long_read(&memcg->memory.children_min_usage)), - K(atomic_long_read(&memcg->memory.children_low_usage))); + K(atomic_long_read(&memcg->memory_prot.children_min_usage)), + K(atomic_long_read(&memcg->memory_prot.children_low_usage))); } diff --git a/mm/page_counter.c b/mm/page_counter.c index 450543f4b318b..401201c8e3902 100644 --- a/mm/page_counter.c +++ b/mm/page_counter.c @@ -15,34 +15,35 @@ static bool track_protection(struct page_counter c) { - return c->protection_support; + return c->prot != NULL; } static void propagate_protected_usage(struct page_counter c, unsigned long usage) { + struct page_counter_protection prot = c->prot; unsigned long protected, old_protected; long delta; - if (!c->parent) + if (!prot \|\| !prot->parent) return; - protected = min(usage, READ_ONCE(c->min)); - old_protected = atomic_long_read(&c->min_usage); + protected = min(usage, READ_ONCE(prot->min)); + old_protected = atomic_long_read(&prot->min_usage); if (protected != old_protected) { - old_protected = atomic_long_xchg(&c->min_usage, protected); + old_protected = atomic_long_xchg(&prot->min_usage, protected); delta = protected - old_protected; if (delta) - atomic_long_add(delta, &c->parent->children_min_usage); + atomic_long_add(delta, &prot->parent->children_min_usage); } - protected = min(usage, READ_ONCE(c->low)); - old_protected = atomic_long_read(&c->low_usage); + protected = min(usage, READ_ONCE(prot->low)); + old_protected = atomic_long_read(&prot->low_usage); if (protected != old_protected) { - old_protected = atomic_long_xchg(&c->low_usage, protected); + old_protected = atomic_long_xchg(&prot->low_usage, protected); delta = protected - old_protected; if (delta) - atomic_long_add(delta, &c->parent->children_low_usage); + atomic_long_add(delta, &prot->parent->children_low_usage); } } @@ -257,7 +258,10 @@ void page_counter_set_min(struct page_counter counter, unsigned long nr_pages) { struct page_counter c; - WRITE_ONCE(counter->min, nr_pages); + if (!counter->prot) + return; + + WRITE_ONCE(counter->prot->min, nr_pages); for (c = counter; c; c = c->parent) propagate_protected_usage(c, atomic_long_read(&c->usage)); @@ -274,7 +278,10 @@ void page_counter_set_low(struct page_counter counter, unsigned long nr_pages) { struct page_counter c; - WRITE_ONCE(counter->low, nr_pages); + if (!counter->prot) + return; + + WRITE_ONCE(counter->prot->low, nr_pages); for (c = counter; c; c = c->parent) propagate_protected_usage(c, atomic_long_read(&c->usage)); @@ -445,9 +452,18 @@ void page_counter_calculate_protection(struct page_counter root, struct page_counter counter, bool recursive_protection) { + struct page_counter_protection prot = counter->prot; + struct page_counter_protection parent_prot; unsigned long usage, parent_usage; struct page_counter parent = counter->parent; + / + * Only counters with protection support (memory, dmem pools) are + * ever passed here, but guard anyway. + / + if (!prot) + return; + / * Effective values of the reclaim targets are ignored so they * can be stale. Have a look at mem_cgroup_protection for more @@ -463,23 +479,24 @@ void page_counter_calculate_protection(struct page_counter root, return; if (parent == root) { - counter->emin = READ_ONCE(counter->min); - counter->elow = READ_ONCE(counter->low); + prot->emin = READ_ONCE(prot->min); + prot->elow = READ_ONCE(prot->low); return; } + parent_prot = parent->prot; parent_usage = page_counter_read(parent); - WRITE_ONCE(counter->emin, effective_protection(usage, parent_usage, - READ_ONCE(counter->min), - READ_ONCE(parent->emin), - atomic_long_read(&parent->children_min_usage), + WRITE_ONCE(prot->emin, effective_protection(usage, parent_usage, + READ_ONCE(prot->min), + READ_ONCE(parent_prot->emin), + atomic_long_read(&parent_prot->children_min_usage), recursive_protection)); - WRITE_ONCE(counter->elow, effective_protection(usage, parent_usage, - READ_ONCE(counter->low), - READ_ONCE(parent->elow), - atomic_long_read(&parent->children_low_usage), + WRITE_ONCE(prot->elow, effective_protection(usage, parent_usage, + READ_ONCE(prot->low), + READ_ONCE(parent_prot->elow), + atomic_long_read(&parent_prot->children_low_usage), recursive_protection)); } #endif / CONFIG_MEMCG \|\| CONFIG_CGROUP_DMEM */
3/2	2026/09/09 09:05	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 8637 output: 36 thoughts: 669 Thoughts: Analyzing a Memory Management Patch Okay, let's dive into this patch and review the request. My initial assessment is that it looks like a targeted refactoring within the memory management and cgroup subsystems. I see touches on `memcontrol.h`, `page_counter.h`, `dmem.c`, `hugetlb_cgroup.c`, `memcontrol.c`, and `page_counter.c`, which immediately flags this as potentially significant. My understanding is that this patch is aimed at isolating protection-related fields within `struct page_counter` into a dedicated `struct page_counter_protection`. From what I can tell, we're seeing this new protection struct surfacing as `memory_prot` within `struct mem_cgroup` and `prot` in `struct dmem_cgroup_pool_state`. Furthermore, it seems that the initialization flow is changing, with the `protection_support` argument being removed from `page_counter_init` in favor of an explicit call to `page_counter_init_protection` only when protection is needed. This looks like a good step towards improved code clarity and perhaps reduces some unnecessary overhead. Looking at the code changes, `mm/memcontrol.c` seems to be the most impacted, with modifications across `mem_cgroup_css_alloc`, `memory_min_show`, `memory_low_show`, and `mem_cgroup_show_protected_memory`. Also, `include/linux/memcontrol.h`, sees new helper functions for assessing memory protection states. The `page_counter` code in `mm/page_counter.c` is being updated to use and manage the protection structure in a more targeted way, including functions like `track_protection`, `propagate_protected_usage`, and the `page_counter_set_` family of functions. `kernel/cgroup/dmem.c` is also touched, with changes in resource limit/usage functions and the cgroup state management. Finally, `mm/hugetlb_cgroup.c` is receiving updates to incorporate this new structure. This is definitely core subsystem territory – memory management, cgroups, and their interplay. I'm thinking this means the patch is very likely reachable with standard QEMU/GCE fuzzing setups involving memcg, cgroup v2, page counter interaction, and memory.min/low configurations. Given the fundamental nature of the changes, this seems like it's absolutely* worth fuzzing. I'll need to double-check the Kconfig dependencies – specifically, the configurations for MEMCG, CGROUP_DMEM, and HUGETLB_CGROUP – to be sure we have the right test setup. I'll need to consult the Kconfig files directly to confirm these are all enabled.
4/2	2026/09/09 09:05	tool	grepper	0m Args: { "Expression": "config (MEMCG\|CGROUP_DMEM)", "PathPrefix": "init/Kconfig" } Results: { "Output": "init/Kconfig=1075=config CGROUP_FAVOR_DYNMODS\n--\ninit/Kconfig-1084-\ninit/Kconfig:1085:config MEMCG\ninit/Kconfig-1086-\tbool \"Memory controller\"\n--\ninit/Kconfig-1093-\ninit/Kconfig:1094:config MEMCG_NMI_UNSAFE\ninit/Kconfig-1095-\tbool\n--\ninit/Kconfig-1100-\ninit/Kconfig:1101:config MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\ninit/Kconfig-1102-\tbool\n--\ninit/Kconfig-1107-\ninit/Kconfig:1108:config MEMCG_V1\ninit/Kconfig-1109-\tbool \"Legacy cgroup v1 memory controller\"\n--\ninit/Kconfig=1262=config CGROUP_RDMA\n--\ninit/Kconfig-1271-\ninit/Kconfig:1272:config CGROUP_DMEM\ninit/Kconfig-1273-\tbool \"Device memory controller (DMEM)\"\n" }
5/2	2026/09/09 09:05	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 10236 output: 29 thoughts: 24 Thoughts: Here's my summary, as though I'm thinking through this process: Diving into the Page Counter Logic Okay, so I need to understand how these page counter modifications were handled. My first move is to head straight into `mm/page_counter.c`. It's the most logical place to start – this file is dedicated to page counter implementations. I need to quickly scan the file for any preprocessor directives, specifically `#ifdef`, surrounding the functions that were touched. These directives will tell me how the code's behavior changes depending on the configuration. This approach will allow me to quickly determine if there are any conditional compilation behaviors at play.
6/2	2026/09/09 09:05	tool	grepper	0m Args: { "Expression": "CONFIG_", "PathPrefix": "mm/page_counter.c" } Results: { "Output": "mm/page_counter.c=299=int page_counter_memparse(const char buf, const char max,\n--\nmm/page_counter.c-319-\nmm/page_counter.c:320:#if IS_ENABLED(CONFIG_MEMCG) \|\| IS_ENABLED(CONFIG_CGROUP_DMEM)\nmm/page_counter.c-321-/\n--\nmm/page_counter.c=451=void page_counter_calculate_protection(struct page_counter root,\n--\nmm/page_counter.c-501-}\nmm/page_counter.c:502:#endif /* CONFIG_MEMCG \|\| CONFIG_CGROUP_DMEM */\n" }
7/2	2026/09/09 09:05	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 10611 output: 28 thoughts: 48 Thoughts: Okay, let's dive into this. Here's how I'd approach this task: Investigating `dmem.c` and Related Configuration Right, so I need to understand how dynamic memory cgroups are handled. My first move is to directly inspect `kernel/cgroup/dmem.c`. I need to see if there are any specific configuration options within that file itself that might control its behavior, or if the code is conditionally compiled or guarded by a specific Kconfig option – probably something like `CONFIG_CGROUP_DMEM`, though I'll need to confirm that. Looking for conditional compilation is crucial, as it will tell me if the code is enabled under certain circumstances and what those circumstances are. After that, I would then check the Makefile of the cgroup directory, since it often indicates the build targets, and any conditional build dependencies or compilation flags. This will give me further clues about how this part of the kernel is integrated and configured. By checking these files, I'll gain a good understanding of how to enable or disable the dmem module, and how it is configured and managed at compile time.
8/2	2026/09/09 09:05	tool	grepper	0m Args: { "Expression": "dmem", "PathPrefix": "kernel/cgroup/Makefile" } Results: { "Output": "kernel/cgroup/Makefile=9=obj-$(CONFIG_CGROUP_MISC) += misc.o\nkernel/cgroup/Makefile:10:obj-$(CONFIG_CGROUP_DMEM) += dmem.o\nkernel/cgroup/Makefile-11-obj-$(CONFIG_CGROUP_DEBUG) += debug.o\n" }
9/2	2026/09/09 09:05	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 11017 output: 28 thoughts: 22 Thoughts: Here's my summary, as if I were thinking these thoughts: Examining the Memory Management Subsystem Alright, I'm deep diving into this memory management aspect again. It's time to double-check that I haven't missed anything in the build configuration for `hugetlb_cgroup`. Specifically, I need to make sure the relevant settings are properly defined in the `Makefile` and `Kconfig` files associated with `mm/hugetlb_cgroup.c`. There could be dependency or enablement issues lurking there that I need to address. This module's behavior and build setup is key, let's take a look.
10/2	2026/09/09 09:05	tool	grepper	0m Args: { "Expression": "hugetlb_cgroup", "PathPrefix": "mm/" } Results: { "Output": "\nFull output is too long, showing 500 out of 683 lines.\nUse more precise expression if possible.\n\nmm/Makefile=109=endif\nmm/Makefile:110:obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o\nmm/Makefile-111-obj-$(CONFIG_GUP_TEST) += gup_test.o\n--\nmm/hugetlb.c=473=get_file_region_entry_from_cache(struct resv_map resv, long from, long to)\n--\nmm/hugetlb.c-488-\nmm/hugetlb.c:489:static void copy_hugetlb_cgroup_uncharge_info(struct file_region nrg,\nmm/hugetlb.c-490-\t\t\t\t\t struct file_region rg)\n--\nmm/hugetlb.c-499-\nmm/hugetlb.c:500:/ Helper that records hugetlb_cgroup uncharge info. /\nmm/hugetlb.c:501:static void record_hugetlb_cgroup_uncharge_info(struct hugetlb_cgroup h_cg,\nmm/hugetlb.c-502-\t\t\t\t\t\tstruct hstate h,\n--\nmm/hugetlb.c=583=hugetlb_resv_map_add(struct resv_map map, struct list_head rg, long from,\nmm/hugetlb.c:584:\t\t long to, struct hstate h, struct hugetlb_cgroup cg,\nmm/hugetlb.c-585-\t\t long regions_needed)\n--\nmm/hugetlb.c-590-\t\tnrg = get_file_region_entry_from_cache(map, from, to);\nmm/hugetlb.c:591:\t\trecord_hugetlb_cgroup_uncharge_info(cg, h, map, nrg);\nmm/hugetlb.c-592-\t\tlist_add(\u0026nrg-\u003elink, rg);\n--\nmm/hugetlb.c=609=static long add_reservation_in_range(struct resv_map resv, long f, long t,\nmm/hugetlb.c:610:\t\t\t\t struct hugetlb_cgroup h_cg,\nmm/hugetlb.c-611-\t\t\t\t struct hstate h, long regions_needed)\n--\nmm/hugetlb.c=742=static long region_add(struct resv_map resv, long f, long t,\nmm/hugetlb.c-743-\t\t long in_regions_needed, struct hstate h,\nmm/hugetlb.c:744:\t\t struct hugetlb_cgroup h_cg)\nmm/hugetlb.c-745-{\n--\nmm/hugetlb.c=868=static long region_del(struct resv_map resv, long f, long t)\n--\nmm/hugetlb.c-913-\t\t\tdel += t - f;\nmm/hugetlb.c:914:\t\t\thugetlb_cgroup_uncharge_file_region(\nmm/hugetlb.c-915-\t\t\t\tresv, rg, t - f, false);\n--\nmm/hugetlb.c-920-\nmm/hugetlb.c:921:\t\t\tcopy_hugetlb_cgroup_uncharge_info(nrg, rg);\nmm/hugetlb.c-922-\n--\nmm/hugetlb.c-934-\t\t\tdel += rg-\u003eto - rg-\u003efrom;\nmm/hugetlb.c:935:\t\t\thugetlb_cgroup_uncharge_file_region(resv, rg,\nmm/hugetlb.c-936-\t\t\t\t\t\t\t rg-\u003eto - rg-\u003efrom, true);\n--\nmm/hugetlb.c-942-\t\tif (f \u003c= rg-\u003efrom) {\t/* Trim beginning of region /\nmm/hugetlb.c:943:\t\t\thugetlb_cgroup_uncharge_file_region(resv, rg,\nmm/hugetlb.c-944-\t\t\t\t\t\t\t t - rg-\u003efrom, false);\n--\nmm/hugetlb.c-948-\t\t} else {\t\t/ Trim end of region /\nmm/hugetlb.c:949:\t\t\thugetlb_cgroup_uncharge_file_region(resv, rg,\nmm/hugetlb.c-950-\t\t\t\t\t\t\t rg-\u003eto - f, false);\n--\nmm/hugetlb.c=1071=static void\nmm/hugetlb.c:1072:resv_map_set_hugetlb_cgroup_uncharge_info(struct resv_map resv_map,\nmm/hugetlb.c:1073:\t\t\t\t\t struct hugetlb_cgroup h_cg,\nmm/hugetlb.c-1074-\t\t\t\t\t struct hstate h)\n--\nmm/hugetlb.c=1090=struct resv_map resv_map_alloc(void)\n--\nmm/hugetlb.c-1112-\t /\nmm/hugetlb.c:1113:\tresv_map_set_hugetlb_cgroup_uncharge_info(resv_map, NULL, NULL);\nmm/hugetlb.c-1114-\n--\nmm/hugetlb.c=1224=void clear_vma_resv_huge_pages(struct vm_area_struct vma)\n--\nmm/hugetlb.c-1240-\tif (reservations \u0026\u0026 is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {\nmm/hugetlb.c:1241:\t\tresv_map_put_hugetlb_cgroup_uncharge_info(reservations);\nmm/hugetlb.c-1242-\t\tkref_put(\u0026reservations-\u003erefs, resv_map_release);\n--\nmm/hugetlb.c=1390=void remove_hugetlb_folio(struct hstate h, struct folio folio,\n--\nmm/hugetlb.c-1394-\nmm/hugetlb.c:1395:\tVM_BUG_ON_FOLIO(hugetlb_cgroup_from_folio(folio), folio);\nmm/hugetlb.c:1396:\tVM_BUG_ON_FOLIO(hugetlb_cgroup_from_folio_rsvd(folio), folio);\nmm/hugetlb.c-1397-\n--\nmm/hugetlb.c=1688=void free_huge_folio(struct folio folio)\n--\nmm/hugetlb.c-1730-\tfolio_clear_hugetlb_migratable(folio);\nmm/hugetlb.c:1731:\thugetlb_cgroup_uncharge_folio(hstate_index(h),\nmm/hugetlb.c-1732-\t\t\t\t pages_per_huge_page(h), folio);\nmm/hugetlb.c:1733:\thugetlb_cgroup_uncharge_folio_rsvd(hstate_index(h),\nmm/hugetlb.c-1734-\t\t\t\t\t pages_per_huge_page(h), folio);\n--\nmm/hugetlb.c=1766=void init_new_hugetlb_folio(struct folio folio)\n--\nmm/hugetlb.c-1770-\thugetlb_set_folio_subpool(folio, NULL);\nmm/hugetlb.c:1771:\tset_hugetlb_cgroup(folio, NULL);\nmm/hugetlb.c:1772:\tset_hugetlb_cgroup_rsvd(folio, NULL);\nmm/hugetlb.c-1773-}\n--\nmm/hugetlb.c=2856=struct folio hugetlb_alloc_folio(struct hstate h,\n--\nmm/hugetlb.c-2859-{\nmm/hugetlb.c:2860:\tbool charge_hugetlb_cgroup_rsvd = alloc_flags \u0026\nmm/hugetlb.c-2861-\t\t\t\t\t HUGETLB_ALLOC_CHARG_CGROUP_RSVD;\n--\nmm/hugetlb.c-2864-\tsize_t nr_pages = pages_per_huge_page(h);\nmm/hugetlb.c:2865:\tstruct hugetlb_cgroup h_cg_rsvd = NULL;\nmm/hugetlb.c:2866:\tstruct hugetlb_cgroup h_cg = NULL;\nmm/hugetlb.c-2867-\tgfp_t gfp = htlb_alloc_mask(h);\n--\nmm/hugetlb.c-2871-\nmm/hugetlb.c:2872:\tif (charge_hugetlb_cgroup_rsvd \u0026\u0026\nmm/hugetlb.c:2873:\t hugetlb_cgroup_charge_cgroup_rsvd(idx, nr_pages, \u0026h_cg_rsvd))\nmm/hugetlb.c-2874-\t\treturn ERR_PTR(-ENOSPC);\nmm/hugetlb.c-2875-\nmm/hugetlb.c:2876:\tif (hugetlb_cgroup_charge_cgroup(idx, nr_pages, \u0026h_cg)) {\nmm/hugetlb.c-2877-\t\tret = -ENOSPC;\nmm/hugetlb.c:2878:\t\tgoto err_uncharge_hugetlb_cgroup_rsvd;\nmm/hugetlb.c-2879-\t}\n--\nmm/hugetlb.c-2891-\t\t\tret = -ENOSPC;\nmm/hugetlb.c:2892:\t\t\tgoto err_uncharge_hugetlb_cgroup;\nmm/hugetlb.c-2893-\t\t}\n--\nmm/hugetlb.c-2903-\nmm/hugetlb.c:2904:\thugetlb_cgroup_commit_charge(idx, nr_pages, h_cg, folio);\nmm/hugetlb.c-2905-\nmm/hugetlb.c:2906:\tif (charge_hugetlb_cgroup_rsvd) {\nmm/hugetlb.c:2907:\t\thugetlb_cgroup_commit_charge_rsvd(idx, nr_pages, h_cg_rsvd,\nmm/hugetlb.c-2908-\t\t\t\t\t\t folio);\n--\nmm/hugetlb.c-2924-\t\t/\nmm/hugetlb.c:2925:\t\t * Skip uncharging hugetlb_cgroup since the charges\nmm/hugetlb.c-2926-\t\t * were committed to the folio and freeing the folio\n--\nmm/hugetlb.c-2944-\nmm/hugetlb.c:2945: err_uncharge_hugetlb_cgroup:\nmm/hugetlb.c:2946:\thugetlb_cgroup_uncharge_cgroup(idx, nr_pages, h_cg);\nmm/hugetlb.c:2947: err_uncharge_hugetlb_cgroup_rsvd:\nmm/hugetlb.c:2948:\tif (charge_hugetlb_cgroup_rsvd)\nmm/hugetlb.c:2949:\t\thugetlb_cgroup_uncharge_cgroup_rsvd(idx, nr_pages, h_cg_rsvd);\nmm/hugetlb.c-2950-\n--\nmm/hugetlb.c=2980=struct folio alloc_hugetlb_folio(struct vm_area_struct vma,\n--\nmm/hugetlb.c-3093-\t\t\tspin_lock_irq(\u0026hugetlb_lock);\nmm/hugetlb.c:3094:\t\t\thugetlb_cgroup_uncharge_folio_rsvd(\nmm/hugetlb.c-3095-\t\t\t hstate_index(h), pages_per_huge_page(h), folio);\n--\nmm/hugetlb.c=4167=static int __init hugetlb_init(void)\n--\nmm/hugetlb.c-4219-\thugetlb_sysfs_init();\nmm/hugetlb.c:4220:\thugetlb_cgroup_file_init();\nmm/hugetlb.c-4221-\thugetlb_sysctl_init();\n--\nmm/hugetlb.c=4729=static void hugetlb_vm_op_open(struct vm_area_struct vma)\n--\nmm/hugetlb.c-4742-\tif (resv \u0026\u0026 is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {\nmm/hugetlb.c:4743:\t\tresv_map_dup_hugetlb_cgroup_uncharge_info(resv);\nmm/hugetlb.c-4744-\t\tkref_get(\u0026resv-\u003erefs);\n--\nmm/hugetlb.c=4769=static void hugetlb_vm_op_close(struct vm_area_struct vma)\n--\nmm/hugetlb.c-4786-\treserve = (end - start) - region_count(resv, start, end);\nmm/hugetlb.c:4787:\thugetlb_cgroup_uncharge_counter(resv, start, end);\nmm/hugetlb.c-4788-\tif (reserve) {\n--\nmm/hugetlb.c=6719=long hugetlb_reserve_pages(struct inode inode,\n--\nmm/hugetlb.c-6727-\tstruct resv_map resv_map;\nmm/hugetlb.c:6728:\tstruct hugetlb_cgroup h_cg = NULL;\nmm/hugetlb.c-6729-\tlong gbl_reserve, regions_needed = 0;\n--\nmm/hugetlb.c-6786-\nmm/hugetlb.c:6787:\terr = hugetlb_cgroup_charge_cgroup_rsvd(hstate_index(h),\nmm/hugetlb.c-6788-\t\t\t\tchg pages_per_huge_page(h), \u0026h_cg);\n--\nmm/hugetlb.c-6792-\tif (vma \u0026\u0026 !vma_test(vma, VMA_MAYSHARE_BIT) \u0026\u0026 h_cg) {\nmm/hugetlb.c:6793:\t\t/* For private mappings, the hugetlb_cgroup uncharge info hangs\nmm/hugetlb.c-6794-\t\t * of the resv_map.\nmm/hugetlb.c-6795-\t\t /\nmm/hugetlb.c:6796:\t\tresv_map_set_hugetlb_cgroup_uncharge_info(resv_map, h_cg, h);\nmm/hugetlb.c-6797-\t}\n--\nmm/hugetlb.c-6846-\t\t\t/\nmm/hugetlb.c:6847:\t\t\t * hugetlb_cgroup_uncharge_cgroup_rsvd() will put the\nmm/hugetlb.c-6848-\t\t\t * reference to h_cg-\u003ecss. See comment below for detail.\nmm/hugetlb.c-6849-\t\t\t /\nmm/hugetlb.c:6850:\t\t\thugetlb_cgroup_uncharge_cgroup_rsvd(\nmm/hugetlb.c-6851-\t\t\t\thstate_index(h),\n--\nmm/hugetlb.c-6860-\t\t\t h_cg-\u003ecss. So we should release the reference held\nmm/hugetlb.c:6861:\t\t\t * via hugetlb_cgroup_charge_cgroup_rsvd() when we are\nmm/hugetlb.c-6862-\t\t\t * done.\nmm/hugetlb.c-6863-\t\t\t /\nmm/hugetlb.c:6864:\t\t\thugetlb_cgroup_put_rsvd_cgroup(h_cg);\nmm/hugetlb.c-6865-\t\t}\n--\nmm/hugetlb.c-6889-out_uncharge_cgroup:\nmm/hugetlb.c:6890:\thugetlb_cgroup_uncharge_cgroup_rsvd(hstate_index(h),\nmm/hugetlb.c-6891-\t\t\t\t\t chg pages_per_huge_page(h), h_cg);\n--\nmm/hugetlb.c=7363=void move_hugetlb_state(struct folio old_folio, struct folio new_folio,\n--\nmm/hugetlb.c-7367-\nmm/hugetlb.c:7368:\thugetlb_cgroup_migrate(old_folio, new_folio);\nmm/hugetlb.c-7369-\tfolio_set_owner_migrate_reason(new_folio, reason);\n--\nmm/hugetlb_cgroup.c-16-#include \u003clinux/hugetlb.h\u003e\nmm/hugetlb_cgroup.c:17:#include \u003clinux/hugetlb_cgroup.h\u003e\nmm/hugetlb_cgroup.c-18-\n--\nmm/hugetlb_cgroup.c-30-\nmm/hugetlb_cgroup.c:31:static struct hugetlb_cgroup root_h_cgroup __read_mostly;\nmm/hugetlb_cgroup.c-32-static struct cftype dfl_files;\n--\nmm/hugetlb_cgroup.c=35=static inline struct page_counter \nmm/hugetlb_cgroup.c:36:__hugetlb_cgroup_counter_from_cgroup(struct hugetlb_cgroup h_cg, int idx,\nmm/hugetlb_cgroup.c-37-\t\t\t\t bool rsvd)\n--\nmm/hugetlb_cgroup.c=44=static inline struct page_counter \nmm/hugetlb_cgroup.c:45:hugetlb_cgroup_counter_from_cgroup(struct hugetlb_cgroup h_cg, int idx)\nmm/hugetlb_cgroup.c-46-{\nmm/hugetlb_cgroup.c:47:\treturn __hugetlb_cgroup_counter_from_cgroup(h_cg, idx, false);\nmm/hugetlb_cgroup.c-48-}\n--\nmm/hugetlb_cgroup.c=50=static inline struct page_counter \nmm/hugetlb_cgroup.c:51:hugetlb_cgroup_counter_from_cgroup_rsvd(struct hugetlb_cgroup h_cg, int idx)\nmm/hugetlb_cgroup.c-52-{\nmm/hugetlb_cgroup.c:53:\treturn __hugetlb_cgroup_counter_from_cgroup(h_cg, idx, true);\nmm/hugetlb_cgroup.c-54-}\n--\nmm/hugetlb_cgroup.c=56=static inline\nmm/hugetlb_cgroup.c:57:struct hugetlb_cgroup hugetlb_cgroup_from_css(struct cgroup_subsys_state s)\nmm/hugetlb_cgroup.c-58-{\nmm/hugetlb_cgroup.c:59:\treturn s ? container_of(s, struct hugetlb_cgroup, css) : NULL;\nmm/hugetlb_cgroup.c-60-}\n--\nmm/hugetlb_cgroup.c=62=static inline\nmm/hugetlb_cgroup.c:63:struct hugetlb_cgroup hugetlb_cgroup_from_task(struct task_struct task)\nmm/hugetlb_cgroup.c-64-{\nmm/hugetlb_cgroup.c:65:\treturn hugetlb_cgroup_from_css(task_css(task, hugetlb_cgrp_id));\nmm/hugetlb_cgroup.c-66-}\nmm/hugetlb_cgroup.c-67-\nmm/hugetlb_cgroup.c:68:static inline bool hugetlb_cgroup_is_root(struct hugetlb_cgroup h_cg)\nmm/hugetlb_cgroup.c-69-{\n--\nmm/hugetlb_cgroup.c-72-\nmm/hugetlb_cgroup.c:73:static inline struct hugetlb_cgroup \nmm/hugetlb_cgroup.c:74:parent_hugetlb_cgroup(struct hugetlb_cgroup h_cg)\nmm/hugetlb_cgroup.c-75-{\nmm/hugetlb_cgroup.c:76:\treturn hugetlb_cgroup_from_css(h_cg-\u003ecss.parent);\nmm/hugetlb_cgroup.c-77-}\nmm/hugetlb_cgroup.c-78-\nmm/hugetlb_cgroup.c:79:static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup h_cg)\nmm/hugetlb_cgroup.c-80-{\n--\nmm/hugetlb_cgroup.c-84-\t\tif (page_counter_read(\nmm/hugetlb_cgroup.c:85:\t\t hugetlb_cgroup_counter_from_cgroup(h_cg, hstate_index(h))))\nmm/hugetlb_cgroup.c-86-\t\t\treturn true;\n--\nmm/hugetlb_cgroup.c-90-\nmm/hugetlb_cgroup.c:91:static void hugetlb_cgroup_init(struct hugetlb_cgroup h_cgroup,\nmm/hugetlb_cgroup.c:92:\t\t\t\tstruct hugetlb_cgroup parent_h_cgroup)\nmm/hugetlb_cgroup.c-93-{\n--\nmm/hugetlb_cgroup.c-102-\t\tif (parent_h_cgroup) {\nmm/hugetlb_cgroup.c:103:\t\t\tfault_parent = hugetlb_cgroup_counter_from_cgroup(\nmm/hugetlb_cgroup.c-104-\t\t\t\tparent_h_cgroup, idx);\nmm/hugetlb_cgroup.c:105:\t\t\trsvd_parent = hugetlb_cgroup_counter_from_cgroup_rsvd(\nmm/hugetlb_cgroup.c-106-\t\t\t\tparent_h_cgroup, idx);\nmm/hugetlb_cgroup.c-107-\t\t}\nmm/hugetlb_cgroup.c:108:\t\tfault = hugetlb_cgroup_counter_from_cgroup(h_cgroup, idx);\nmm/hugetlb_cgroup.c:109:\t\trsvd = hugetlb_cgroup_counter_from_cgroup_rsvd(h_cgroup, idx);\nmm/hugetlb_cgroup.c-110-\n--\nmm/hugetlb_cgroup.c-128-\nmm/hugetlb_cgroup.c:129:static void hugetlb_cgroup_free(struct hugetlb_cgroup h_cgroup)\nmm/hugetlb_cgroup.c-130-{\n--\nmm/hugetlb_cgroup.c=138=static struct cgroup_subsys_state \nmm/hugetlb_cgroup.c:139:hugetlb_cgroup_css_alloc(struct cgroup_subsys_state parent_css)\nmm/hugetlb_cgroup.c-140-{\nmm/hugetlb_cgroup.c:141:\tstruct hugetlb_cgroup parent_h_cgroup = hugetlb_cgroup_from_css(parent_css);\nmm/hugetlb_cgroup.c:142:\tstruct hugetlb_cgroup h_cgroup;\nmm/hugetlb_cgroup.c-143-\tint node;\n--\nmm/hugetlb_cgroup.c-162-\t\th_cgroup-\u003enodeinfo[node] =\nmm/hugetlb_cgroup.c:163:\t\t\tkzalloc_node(sizeof(struct hugetlb_cgroup_per_node),\nmm/hugetlb_cgroup.c-164-\t\t\t\t GFP_KERNEL, node_to_alloc);\n--\nmm/hugetlb_cgroup.c-168-\nmm/hugetlb_cgroup.c:169:\thugetlb_cgroup_init(h_cgroup, parent_h_cgroup);\nmm/hugetlb_cgroup.c-170-\treturn \u0026h_cgroup-\u003ecss;\n--\nmm/hugetlb_cgroup.c-172-fail_alloc_nodeinfo:\nmm/hugetlb_cgroup.c:173:\thugetlb_cgroup_free(h_cgroup);\nmm/hugetlb_cgroup.c-174-\treturn ERR_PTR(-ENOMEM);\n--\nmm/hugetlb_cgroup.c-176-\nmm/hugetlb_cgroup.c:177:static void hugetlb_cgroup_css_free(struct cgroup_subsys_state css)\nmm/hugetlb_cgroup.c-178-{\nmm/hugetlb_cgroup.c:179:\thugetlb_cgroup_free(hugetlb_cgroup_from_css(css));\nmm/hugetlb_cgroup.c-180-}\n--\nmm/hugetlb_cgroup.c-188- /\nmm/hugetlb_cgroup.c:189:static void hugetlb_cgroup_move_parent(int idx, struct hugetlb_cgroup h_cg,\nmm/hugetlb_cgroup.c-190-\t\t\t\t struct folio folio)\n--\nmm/hugetlb_cgroup.c-193-\tstruct page_counter counter;\nmm/hugetlb_cgroup.c:194:\tstruct hugetlb_cgroup hcg;\nmm/hugetlb_cgroup.c:195:\tstruct hugetlb_cgroup parent = parent_hugetlb_cgroup(h_cg);\nmm/hugetlb_cgroup.c-196-\nmm/hugetlb_cgroup.c:197:\thcg = hugetlb_cgroup_from_folio(folio);\nmm/hugetlb_cgroup.c-198-\t/\n--\nmm/hugetlb_cgroup.c-215-\nmm/hugetlb_cgroup.c:216:\tset_hugetlb_cgroup(folio, parent);\nmm/hugetlb_cgroup.c-217-out:\n--\nmm/hugetlb_cgroup.c-224- /\nmm/hugetlb_cgroup.c:225:static void hugetlb_cgroup_css_offline(struct cgroup_subsys_state css)\nmm/hugetlb_cgroup.c-226-{\nmm/hugetlb_cgroup.c:227:\tstruct hugetlb_cgroup h_cg = hugetlb_cgroup_from_css(css);\nmm/hugetlb_cgroup.c-228-\tstruct hstate h;\n--\nmm/hugetlb_cgroup.c-234-\t\t\tlist_for_each_entry(folio, \u0026h-\u003ehugepage_activelist, lru)\nmm/hugetlb_cgroup.c:235:\t\t\t\thugetlb_cgroup_move_parent(hstate_index(h), h_cg, folio);\nmm/hugetlb_cgroup.c-236-\n--\nmm/hugetlb_cgroup.c-239-\t\tcond_resched();\nmm/hugetlb_cgroup.c:240:\t} while (hugetlb_cgroup_have_usage(h_cg));\nmm/hugetlb_cgroup.c-241-}\nmm/hugetlb_cgroup.c-242-\nmm/hugetlb_cgroup.c:243:static inline void hugetlb_event(struct hugetlb_cgroup hugetlb, int idx,\nmm/hugetlb_cgroup.c-244-\t\t\t\t enum hugetlb_memory_event event)\n--\nmm/hugetlb_cgroup.c-251-\t\tcgroup_file_notify(\u0026hugetlb-\u003eevents_file[idx]);\nmm/hugetlb_cgroup.c:252:\t} while ((hugetlb = parent_hugetlb_cgroup(hugetlb)) \u0026\u0026\nmm/hugetlb_cgroup.c:253:\t\t !hugetlb_cgroup_is_root(hugetlb));\nmm/hugetlb_cgroup.c-254-}\nmm/hugetlb_cgroup.c-255-\nmm/hugetlb_cgroup.c:256:static int __hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c:257:\t\t\t\t\t struct hugetlb_cgroup *ptr,\nmm/hugetlb_cgroup.c-258-\t\t\t\t\t bool rsvd)\n--\nmm/hugetlb_cgroup.c-261-\tstruct page_counter counter;\nmm/hugetlb_cgroup.c:262:\tstruct hugetlb_cgroup h_cg = NULL;\nmm/hugetlb_cgroup.c-263-\nmm/hugetlb_cgroup.c:264:\tif (hugetlb_cgroup_disabled())\nmm/hugetlb_cgroup.c-265-\t\tgoto done;\n--\nmm/hugetlb_cgroup.c-267-\trcu_read_lock();\nmm/hugetlb_cgroup.c:268:\th_cg = hugetlb_cgroup_from_task(current);\nmm/hugetlb_cgroup.c-269-\tif (!css_tryget(\u0026h_cg-\u003ecss)) {\n--\nmm/hugetlb_cgroup.c-275-\tif (!page_counter_try_charge(\nmm/hugetlb_cgroup.c:276:\t\t __hugetlb_cgroup_counter_from_cgroup(h_cg, idx, rsvd),\nmm/hugetlb_cgroup.c-277-\t\t nr_pages, \u0026counter)) {\n--\nmm/hugetlb_cgroup.c-292-\nmm/hugetlb_cgroup.c:293:int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c:294:\t\t\t\t struct hugetlb_cgroup ptr)\nmm/hugetlb_cgroup.c-295-{\nmm/hugetlb_cgroup.c:296:\treturn __hugetlb_cgroup_charge_cgroup(idx, nr_pages, ptr, false);\nmm/hugetlb_cgroup.c-297-}\nmm/hugetlb_cgroup.c-298-\nmm/hugetlb_cgroup.c:299:int hugetlb_cgroup_charge_cgroup_rsvd(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c:300:\t\t\t\t struct hugetlb_cgroup ptr)\nmm/hugetlb_cgroup.c-301-{\nmm/hugetlb_cgroup.c:302:\treturn __hugetlb_cgroup_charge_cgroup(idx, nr_pages, ptr, true);\nmm/hugetlb_cgroup.c-303-}\n--\nmm/hugetlb_cgroup.c-305-/ Should be called with hugetlb_lock held /\nmm/hugetlb_cgroup.c:306:static void __hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c:307:\t\t\t\t\t struct hugetlb_cgroup h_cg,\nmm/hugetlb_cgroup.c-308-\t\t\t\t\t struct folio folio, bool rsvd)\nmm/hugetlb_cgroup.c-309-{\nmm/hugetlb_cgroup.c:310:\tif (hugetlb_cgroup_disabled() \|\| !h_cg)\nmm/hugetlb_cgroup.c-311-\t\treturn;\nmm/hugetlb_cgroup.c-312-\tlockdep_assert_held(\u0026hugetlb_lock);\nmm/hugetlb_cgroup.c:313:\t__set_hugetlb_cgroup(folio, h_cg, rsvd);\nmm/hugetlb_cgroup.c-314-\tif (!rsvd) {\n--\nmm/hugetlb_cgroup.c-326-\nmm/hugetlb_cgroup.c:327:void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c:328:\t\t\t\t struct hugetlb_cgroup h_cg,\nmm/hugetlb_cgroup.c-329-\t\t\t\t struct folio folio)\nmm/hugetlb_cgroup.c-330-{\nmm/hugetlb_cgroup.c:331:\t__hugetlb_cgroup_commit_charge(idx, nr_pages, h_cg, folio, false);\nmm/hugetlb_cgroup.c-332-}\nmm/hugetlb_cgroup.c-333-\nmm/hugetlb_cgroup.c:334:void hugetlb_cgroup_commit_charge_rsvd(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c:335:\t\t\t\t struct hugetlb_cgroup h_cg,\nmm/hugetlb_cgroup.c-336-\t\t\t\t struct folio folio)\nmm/hugetlb_cgroup.c-337-{\nmm/hugetlb_cgroup.c:338:\t__hugetlb_cgroup_commit_charge(idx, nr_pages, h_cg, folio, true);\nmm/hugetlb_cgroup.c-339-}\n--\nmm/hugetlb_cgroup.c-343- /\nmm/hugetlb_cgroup.c:344:static void __hugetlb_cgroup_uncharge_folio(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c-345-\t\t\t\t\t struct folio folio, bool rsvd)\nmm/hugetlb_cgroup.c-346-{\nmm/hugetlb_cgroup.c:347:\tstruct hugetlb_cgroup h_cg;\nmm/hugetlb_cgroup.c-348-\nmm/hugetlb_cgroup.c:349:\tif (hugetlb_cgroup_disabled())\nmm/hugetlb_cgroup.c-350-\t\treturn;\nmm/hugetlb_cgroup.c-351-\tlockdep_assert_held(\u0026hugetlb_lock);\nmm/hugetlb_cgroup.c:352:\th_cg = __hugetlb_cgroup_from_folio(folio, rsvd);\nmm/hugetlb_cgroup.c-353-\tif (unlikely(!h_cg))\nmm/hugetlb_cgroup.c-354-\t\treturn;\nmm/hugetlb_cgroup.c:355:\t__set_hugetlb_cgroup(folio, NULL, rsvd);\nmm/hugetlb_cgroup.c-356-\nmm/hugetlb_cgroup.c:357:\tpage_counter_uncharge(__hugetlb_cgroup_counter_from_cgroup(h_cg, idx,\nmm/hugetlb_cgroup.c-358-\t\t\t\t\t\t\t\t rsvd),\n--\nmm/hugetlb_cgroup.c-375-\nmm/hugetlb_cgroup.c:376:void hugetlb_cgroup_uncharge_folio(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c-377-\t\t\t\t struct folio folio)\nmm/hugetlb_cgroup.c-378-{\nmm/hugetlb_cgroup.c:379:\t__hugetlb_cgroup_uncharge_folio(idx, nr_pages, folio, false);\nmm/hugetlb_cgroup.c-380-}\nmm/hugetlb_cgroup.c-381-\nmm/hugetlb_cgroup.c:382:void hugetlb_cgroup_uncharge_folio_rsvd(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c-383-\t\t\t\t struct folio folio)\nmm/hugetlb_cgroup.c-384-{\nmm/hugetlb_cgroup.c:385:\t__hugetlb_cgroup_uncharge_folio(idx, nr_pages, folio, true);\nmm/hugetlb_cgroup.c-386-}\nmm/hugetlb_cgroup.c-387-\nmm/hugetlb_cgroup.c:388:static void __hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c:389:\t\t\t\t\t struct hugetlb_cgroup h_cg,\nmm/hugetlb_cgroup.c-390-\t\t\t\t\t bool rsvd)\nmm/hugetlb_cgroup.c-391-{\nmm/hugetlb_cgroup.c:392:\tif (hugetlb_cgroup_disabled() \|\| !h_cg)\nmm/hugetlb_cgroup.c-393-\t\treturn;\nmm/hugetlb_cgroup.c-394-\nmm/hugetlb_cgroup.c:395:\tpage_counter_uncharge(__hugetlb_cgroup_counter_from_cgroup(h_cg, idx,\nmm/hugetlb_cgroup.c-396-\t\t\t\t\t\t\t\t rsvd),\n--\nmm/hugetlb_cgroup.c-402-\nmm/hugetlb_cgroup.c:403:void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c:404:\t\t\t\t struct hugetlb_cgroup h_cg)\nmm/hugetlb_cgroup.c-405-{\nmm/hugetlb_cgroup.c:406:\t__hugetlb_cgroup_uncharge_cgroup(idx, nr_pages, h_cg, false);\nmm/hugetlb_cgroup.c-407-}\nmm/hugetlb_cgroup.c-408-\nmm/hugetlb_cgroup.c:409:void hugetlb_cgroup_uncharge_cgroup_rsvd(int idx, unsigned long nr_pages,\nmm/hugetlb_cgroup.c:410:\t\t\t\t\t struct hugetlb_cgroup h_cg)\nmm/hugetlb_cgroup.c-411-{\nmm/hugetlb_cgroup.c:412:\t__hugetlb_cgroup_uncharge_cgroup(idx, nr_pages, h_cg, true);\nmm/hugetlb_cgroup.c-413-}\nmm/hugetlb_cgroup.c-414-\nmm/hugetlb_cgroup.c:415:void hugetlb_cgroup_uncharge_counter(struct resv_map resv, unsigned long start,\nmm/hugetlb_cgroup.c-416-\t\t\t\t unsigned long end)\nmm/hugetlb_cgroup.c-417-{\nmm/hugetlb_cgroup.c:418:\tif (hugetlb_cgroup_disabled() \|\| !resv \|\| !resv-\u003ereservation_counter \|\|\nmm/hugetlb_cgroup.c-419-\t !resv-\u003ecss)\n--\nmm/hugetlb_cgroup.c-426-\nmm/hugetlb_cgroup.c:427:void hugetlb_cgroup_uncharge_file_region(struct resv_map resv,\nmm/hugetlb_cgroup.c-428-\t\t\t\t\t struct file_region rg,\n--\nmm/hugetlb_cgroup.c-431-{\nmm/hugetlb_cgroup.c:432:\tif (hugetlb_cgroup_disabled() \|\| !resv \|\| !rg \|\| !nr_pages)\nmm/hugetlb_cgroup.c-433-\t\treturn;\n--\nmm/hugetlb_cgroup.c=448=enum {\n--\nmm/hugetlb_cgroup.c-458-\nmm/hugetlb_cgroup.c:459:static int hugetlb_cgroup_read_numa_stat(struct seq_file seq, void dummy)\nmm/hugetlb_cgroup.c-460-{\n--\nmm/hugetlb_cgroup.c-464-\tbool legacy = !cgroup_subsys_on_dfl(hugetlb_cgrp_subsys);\nmm/hugetlb_cgroup.c:465:\tstruct hugetlb_cgroup h_cg = hugetlb_cgroup_from_css(seq_css(seq));\nmm/hugetlb_cgroup.c-466-\tstruct cgroup_subsys_state css;\n--\nmm/hugetlb_cgroup.c-498-\t\tcss_for_each_descendant_pre(css, \u0026h_cg-\u003ecss) {\nmm/hugetlb_cgroup.c:499:\t\t\tusage += READ_ONCE(hugetlb_cgroup_from_css(css)\nmm/hugetlb_cgroup.c-500-\t\t\t\t\t\t -\u003enodeinfo[nid]\n--\nmm/hugetlb_cgroup.c-511-\nmm/hugetlb_cgroup.c:512:static u64 hugetlb_cgroup_read_u64(struct cgroup_subsys_state css,\nmm/hugetlb_cgroup.c-513-\t\t\t\t struct cftype cft)\n--\nmm/hugetlb_cgroup.c-516-\tstruct page_counter rsvd_counter;\nmm/hugetlb_cgroup.c:517:\tstruct hugetlb_cgroup h_cg = hugetlb_cgroup_from_css(css);\nmm/hugetlb_cgroup.c-518-\n--\nmm/hugetlb_cgroup.c-543-\nmm/hugetlb_cgroup.c:544:static int hugetlb_cgroup_read_u64_max(struct seq_file seq, void v)\nmm/hugetlb_cgroup.c-545-{\n--\nmm/hugetlb_cgroup.c-550-\tstruct page_counter counter;\nmm/hugetlb_cgroup.c:551:\tstruct hugetlb_cgroup h_cg = hugetlb_cgroup_from_css(seq_css(seq));\nmm/hugetlb_cgroup.c-552-\n--\nmm/hugetlb_cgroup.c=584=static DEFINE_MUTEX(hugetlb_limit_mutex);\nmm/hugetlb_cgroup.c-585-\nmm/hugetlb_cgroup.c:586:static ssize_t hugetlb_cgroup_write(struct kernfs_open_file of,\nmm/hugetlb_cgroup.c-587-\t\t\t\t char buf, size_t nbytes, loff_t off,\n--\nmm/hugetlb_cgroup.c-591-\tunsigned long nr_pages;\nmm/hugetlb_cgroup.c:592:\tstruct hugetlb_cgroup h_cg = hugetlb_cgroup_from_css(of_css(of));\nmm/hugetlb_cgroup.c-593-\tbool rsvd = false;\nmm/hugetlb_cgroup.c-594-\nmm/hugetlb_cgroup.c:595:\tif (hugetlb_cgroup_is_root(h_cg)) / Can't set limit on root */\n\n" }
11/2	2026/09/09 09:05	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 22561 output: 35 thoughts: 22 Thoughts: Here's my take on the kernel module, as if it were my thought process: Diving into the Dynamic Memory Allocation in cgroups Alright, time to dig into this `kernel/cgroup/dmem.c` file. Let's see exactly what's happening under the hood with dynamic memory allocation within the context of cgroups. I'm especially interested in how it interacts with the broader memory management subsystem. I'm going to want to understand what kind of isolation and resource limiting it provides. I want to see how these functions hook into the core memory management facilities and whether they introduce any interesting complexities or optimizations. I’ll be looking for the key data structures and control paths. I want to build a mental map of this functionality and how it fits into the overall cgroup architecture.
12/2	2026/09/09 09:05	tool	read-file	0m Args: { "File": "kernel/cgroup/dmem.c", "FirstLine": 1, "LineCount": 60 } Results: { "Contents": " 1:\t// SPDX-License-Identifier: GPL-2.0\n 2:\t/\n 3:\t Copyright 2023-2024 Intel Corporation (Maarten Lankhorst \u003cdev@lankhorst.se\u003e)\n 4:\t * Copyright 2024 Red Hat (Maxime Ripard \u003cmripard@kernel.org\u003e)\n 5:\t * Partially based on the rdma and misc controllers, which bear the following copyrights:\n 6:\t \n 7:\t Copyright 2020 Google LLC\n 8:\t * Copyright (C) 2016 Parav Pandit \u003cpandit.parav@gmail.com\u003e\n 9:\t /\n 10:\t\n 11:\t#include \u003clinux/cgroup.h\u003e\n 12:\t#include \u003clinux/cgroup_dmem.h\u003e\n 13:\t#include \u003clinux/list.h\u003e\n 14:\t#include \u003clinux/mutex.h\u003e\n 15:\t#include \u003clinux/page_counter.h\u003e\n 16:\t#include \u003clinux/parser.h\u003e\n 17:\t#include \u003clinux/refcount.h\u003e\n 18:\t#include \u003clinux/rculist.h\u003e\n 19:\t#include \u003clinux/slab.h\u003e\n 20:\t#include \u003clinux/srcu.h\u003e\n 21:\t\n 22:\t/ Maximum reclaim attempts before giving up when lowering dmem.max. /\n 23:\t#define DMEM_MAX_RECLAIM_RETRIES 16\n 24:\t\n 25:\t/ SRCU domain serialising reclaim callbacks against region unregistration. /\n 26:\tDEFINE_STATIC_SRCU(dmemcg_srcu);\n 27:\t\n 28:\tstruct dmem_cgroup_region {\n 29:\t\t/\n 30:\t\t @ref: References keeping the region alive.\n 31:\t\t * Keeps the region reference alive after a succesful RCU lookup.\n 32:\t\t /\n 33:\t\tstruct kref ref;\n 34:\t\n 35:\t\t/* @rcu: RCU head for freeing /\n 36:\t\tstruct rcu_head rcu;\n 37:\t\n 38:\t\t/\n 39:\t\t @region_node: Linked into \u0026dmem_cgroup_regions list.\n 40:\t\t * Protected by RCU and global spinlock.\n 41:\t\t /\n 42:\t\tstruct list_head region_node;\n 43:\t\n 44:\t\t/\n 45:\t\t @pools: List of pools linked to this region.\n 46:\t\t * Protected by global spinlock only\n 47:\t\t /\n 48:\t\tstruct list_head pools;\n 49:\t\n 50:\t\t/* @size: Size of region, in bytes /\n 51:\t\tu64 size;\n 52:\t\n 53:\t\t/* @name: Name describing the node, set by dmem_cgroup_register_region /\n 54:\t\tchar name;\n 55:\t\n 56:\t\t/*\n 57:\t\t @unregistered: Whether the region is unregistered by its caller.\n 58:\t\t * No new pools should be added to the region afterwards, and no new\n 59:\t\t * reclaim callbacks should be invoked.\n 60:\t\t */\n" }
13/2	2026/09/09 09:05	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 23628 output: 34 thoughts: 24 Thoughts: Okay, let's dive into this. Here's how I'd approach this task, as if these were my internal thoughts: Analyzing dmem Pool Usage in the Kernel Right, time to get my hands dirty. I need to understand how the dynamic memory (dmem) pools are being utilized within the kernel's cgroup implementation. Specifically, I'm going to head straight for `kernel/cgroup/dmem.c`. That file is the most likely candidate to hold the core logic for managing these dmem pools within the cgroup framework. I need to understand the allocation and deallocation strategies, any accounting mechanisms, and how different processes or cgroups interact with the available dmem resources. I'll be looking for the fundamental building blocks of this feature.
14/2	2026/09/09 09:05	tool	grepper	0m Args: { "Expression": "dmem_cgroup", "PathPrefix": "kernel/cgroup/dmem.c" } Results: { "Output": "kernel/cgroup/dmem.c=26=DEFINE_STATIC_SRCU(dmemcg_srcu);\nkernel/cgroup/dmem.c-27-\nkernel/cgroup/dmem.c:28:struct dmem_cgroup_region {\nkernel/cgroup/dmem.c-29-\t/\n--\nkernel/cgroup/dmem.c-38-\t/\nkernel/cgroup/dmem.c:39:\t * @region_node: Linked into \u0026dmem_cgroup_regions list.\nkernel/cgroup/dmem.c-40-\t * Protected by RCU and global spinlock.\n--\nkernel/cgroup/dmem.c-52-\nkernel/cgroup/dmem.c:53:\t/** @name: Name describing the node, set by dmem_cgroup_register_region /\nkernel/cgroup/dmem.c-54-\tchar name;\n--\nkernel/cgroup/dmem.c-65-\t /\nkernel/cgroup/dmem.c:66:\tconst struct dmem_cgroup_ops ops;\nkernel/cgroup/dmem.c-67-\n--\nkernel/cgroup/dmem.c=72=struct dmemcg_state {\n--\nkernel/cgroup/dmem.c-77-\nkernel/cgroup/dmem.c:78:struct dmem_cgroup_pool_state {\nkernel/cgroup/dmem.c:79:\tstruct dmem_cgroup_region region;\nkernel/cgroup/dmem.c-80-\tstruct dmemcg_state cs;\n--\nkernel/cgroup/dmem.c-91-\tstruct page_counter_protection prot;\nkernel/cgroup/dmem.c:92:\tstruct dmem_cgroup_pool_state parent;\nkernel/cgroup/dmem.c-93-\n--\nkernel/cgroup/dmem.c-100- - Registering and unregistering region to/from list, requires global lock.\nkernel/cgroup/dmem.c:101: * - Adding a dmem_cgroup_pool_state to a CSS, removing when CSS is freed.\nkernel/cgroup/dmem.c:102: * - Adding a dmem_cgroup_pool_state to a region list.\nkernel/cgroup/dmem.c-103- \n--\nkernel/cgroup/dmem.c=108=static DEFINE_SPINLOCK(dmemcg_lock);\nkernel/cgroup/dmem.c:109:static LIST_HEAD(dmem_cgroup_regions);\nkernel/cgroup/dmem.c-110-\n--\nkernel/cgroup/dmem.c=125=static struct dmemcg_state parent_dmemcs(struct dmemcg_state cg)\n--\nkernel/cgroup/dmem.c-129-\nkernel/cgroup/dmem.c:130:static void dmemcg_pool_get(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-131-{\n--\nkernel/cgroup/dmem.c-134-\nkernel/cgroup/dmem.c:135:static bool dmemcg_pool_tryget(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-136-{\n--\nkernel/cgroup/dmem.c-139-\nkernel/cgroup/dmem.c:140:static void dmemcg_pool_put(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-141-{\n--\nkernel/cgroup/dmem.c=148=static void dmemcg_pool_free_rcu(struct rcu_head rcu)\nkernel/cgroup/dmem.c-149-{\nkernel/cgroup/dmem.c:150:\tstruct dmem_cgroup_pool_state pool = container_of(rcu, typeof(pool), rcu);\nkernel/cgroup/dmem.c-151-\n--\nkernel/cgroup/dmem.c-157-\nkernel/cgroup/dmem.c:158:static void free_cg_pool(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-159-{\n--\nkernel/cgroup/dmem.c=164=static void\nkernel/cgroup/dmem.c:165:set_resource_min(struct dmem_cgroup_pool_state pool, u64 val, bool nonblock)\nkernel/cgroup/dmem.c-166-{\n--\nkernel/cgroup/dmem.c=170=static void\nkernel/cgroup/dmem.c:171:set_resource_low(struct dmem_cgroup_pool_state pool, u64 val, bool nonblock)\nkernel/cgroup/dmem.c-172-{\n--\nkernel/cgroup/dmem.c=176=static void\nkernel/cgroup/dmem.c:177:set_resource_max(struct dmem_cgroup_pool_state pool, u64 val, bool nonblock)\nkernel/cgroup/dmem.c-178-{\nkernel/cgroup/dmem.c:179:\tstruct dmem_cgroup_region region = pool-\u003eregion;\nkernel/cgroup/dmem.c-180-\tunsigned long limit = (unsigned long)val;\n--\nkernel/cgroup/dmem.c-212-\nkernel/cgroup/dmem.c:213:static u64 get_resource_low(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-214-{\n--\nkernel/cgroup/dmem.c-217-\nkernel/cgroup/dmem.c:218:static u64 get_resource_min(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-219-{\n--\nkernel/cgroup/dmem.c-222-\nkernel/cgroup/dmem.c:223:static u64 get_resource_max(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-224-{\n--\nkernel/cgroup/dmem.c-227-\nkernel/cgroup/dmem.c:228:static u64 get_resource_current(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-229-{\n--\nkernel/cgroup/dmem.c-232-\nkernel/cgroup/dmem.c:233:static u64 get_resource_peak(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-234-{\n--\nkernel/cgroup/dmem.c-237-\nkernel/cgroup/dmem.c:238:static void reset_all_resource_limits(struct dmem_cgroup_pool_state rpool)\nkernel/cgroup/dmem.c-239-{\n--\nkernel/cgroup/dmem.c=246=static void dmemcs_offline(struct cgroup_subsys_state css)\n--\nkernel/cgroup/dmem.c-248-\tstruct dmemcg_state dmemcs = css_to_dmemcs(css);\nkernel/cgroup/dmem.c:249:\tstruct dmem_cgroup_pool_state pool;\nkernel/cgroup/dmem.c-250-\n--\nkernel/cgroup/dmem.c=257=static void dmemcs_free(struct cgroup_subsys_state css)\n--\nkernel/cgroup/dmem.c-259-\tstruct dmemcg_state dmemcs = css_to_dmemcs(css);\nkernel/cgroup/dmem.c:260:\tstruct dmem_cgroup_pool_state pool, next;\nkernel/cgroup/dmem.c-261-\n--\nkernel/cgroup/dmem.c=277=dmemcs_alloc(struct cgroup_subsys_state parent_css)\n--\nkernel/cgroup/dmem.c-286-\nkernel/cgroup/dmem.c:287:static struct dmem_cgroup_pool_state \nkernel/cgroup/dmem.c:288:find_cg_pool_locked(struct dmemcg_state dmemcs, struct dmem_cgroup_region region)\nkernel/cgroup/dmem.c-289-{\nkernel/cgroup/dmem.c:290:\tstruct dmem_cgroup_pool_state pool;\nkernel/cgroup/dmem.c-291-\n--\nkernel/cgroup/dmem.c-298-\nkernel/cgroup/dmem.c:299:static struct dmem_cgroup_pool_state pool_parent(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-300-{\n--\nkernel/cgroup/dmem.c=307=static void\nkernel/cgroup/dmem.c:308:dmem_cgroup_calculate_protection(struct dmem_cgroup_pool_state limit_pool,\nkernel/cgroup/dmem.c:309:\t\t\t\t struct dmem_cgroup_pool_state test_pool)\nkernel/cgroup/dmem.c-310-{\n--\nkernel/cgroup/dmem.c-313-\tstruct dmemcg_state dmemcg_iter;\nkernel/cgroup/dmem.c:314:\tstruct dmem_cgroup_pool_state pool, found_pool;\nkernel/cgroup/dmem.c-315-\n--\nkernel/cgroup/dmem.c-342-/\nkernel/cgroup/dmem.c:343: dmem_cgroup_state_evict_valuable() - Check if we should evict from test_pool\nkernel/cgroup/dmem.c-344- * @limit_pool: The pool for which we hit limits\n--\nkernel/cgroup/dmem.c-355- /\nkernel/cgroup/dmem.c:356:bool dmem_cgroup_state_evict_valuable(struct dmem_cgroup_pool_state limit_pool,\nkernel/cgroup/dmem.c:357:\t\t\t\t struct dmem_cgroup_pool_state test_pool,\nkernel/cgroup/dmem.c-358-\t\t\t\t bool ignore_low, bool ret_hit_low)\nkernel/cgroup/dmem.c-359-{\nkernel/cgroup/dmem.c:360:\tstruct dmem_cgroup_pool_state pool = test_pool;\nkernel/cgroup/dmem.c-361-\tstruct page_counter ctest;\n--\nkernel/cgroup/dmem.c-387-\nkernel/cgroup/dmem.c:388:\tdmem_cgroup_calculate_protection(limit_pool, test_pool);\nkernel/cgroup/dmem.c-389-\n--\nkernel/cgroup/dmem.c-405-}\nkernel/cgroup/dmem.c:406:EXPORT_SYMBOL_GPL(dmem_cgroup_state_evict_valuable);\nkernel/cgroup/dmem.c-407-\nkernel/cgroup/dmem.c:408:static struct dmem_cgroup_pool_state \nkernel/cgroup/dmem.c:409:alloc_pool_single(struct dmemcg_state dmemcs, struct dmem_cgroup_region region,\nkernel/cgroup/dmem.c:410:\t\t struct dmem_cgroup_pool_state allocpool)\nkernel/cgroup/dmem.c-411-{\nkernel/cgroup/dmem.c-412-\tstruct dmemcg_state parent = parent_dmemcs(dmemcs);\nkernel/cgroup/dmem.c:413:\tstruct dmem_cgroup_pool_state pool, ppool = NULL;\nkernel/cgroup/dmem.c-414-\n--\nkernel/cgroup/dmem.c-450-\nkernel/cgroup/dmem.c:451:static struct dmem_cgroup_pool_state \nkernel/cgroup/dmem.c:452:get_cg_pool_locked(struct dmemcg_state dmemcs, struct dmem_cgroup_region region,\nkernel/cgroup/dmem.c:453:\t\t struct dmem_cgroup_pool_state allocpool)\nkernel/cgroup/dmem.c-454-{\nkernel/cgroup/dmem.c:455:\tstruct dmem_cgroup_pool_state pool, ppool, retpool;\nkernel/cgroup/dmem.c-456-\tstruct dmemcg_state p, pp;\n--\nkernel/cgroup/dmem.c=499=static void dmemcg_free_rcu(struct rcu_head rcu)\nkernel/cgroup/dmem.c-500-{\nkernel/cgroup/dmem.c:501:\tstruct dmem_cgroup_region region = container_of(rcu, typeof(region), rcu);\nkernel/cgroup/dmem.c:502:\tstruct dmem_cgroup_pool_state pool, next;\nkernel/cgroup/dmem.c-503-\n--\nkernel/cgroup/dmem.c=510=static void dmemcg_free_region(struct kref ref)\nkernel/cgroup/dmem.c-511-{\nkernel/cgroup/dmem.c:512:\tstruct dmem_cgroup_region cgregion = container_of(ref, typeof(cgregion), ref);\nkernel/cgroup/dmem.c-513-\n--\nkernel/cgroup/dmem.c-517-/*\nkernel/cgroup/dmem.c:518: dmem_cgroup_unregister_region() - Unregister a previously registered region.\nkernel/cgroup/dmem.c-519- * @region: The region to unregister.\nkernel/cgroup/dmem.c-520- \nkernel/cgroup/dmem.c:521: This function undoes dmem_cgroup_register_region. It drains any\nkernel/cgroup/dmem.c-522- * in-flight reclaim callbacks before returning, so the caller may safely\n--\nkernel/cgroup/dmem.c-525- /\nkernel/cgroup/dmem.c:526:void dmem_cgroup_unregister_region(struct dmem_cgroup_region region)\nkernel/cgroup/dmem.c-527-{\nkernel/cgroup/dmem.c:528:\tstruct dmem_cgroup_pool_state pool, next;\nkernel/cgroup/dmem.c-529-\n--\nkernel/cgroup/dmem.c-555-}\nkernel/cgroup/dmem.c:556:EXPORT_SYMBOL_GPL(dmem_cgroup_unregister_region);\nkernel/cgroup/dmem.c-557-\nkernel/cgroup/dmem.c-558-/*\nkernel/cgroup/dmem.c:559: dmem_cgroup_register_region() - Register a regions for dev cgroup.\nkernel/cgroup/dmem.c-560- * @init: Initialization parameters for the region.\n--\nkernel/cgroup/dmem.c-568- /\nkernel/cgroup/dmem.c:569:struct dmem_cgroup_region \nkernel/cgroup/dmem.c:570:dmem_cgroup_register_region(const struct dmem_cgroup_init init,\nkernel/cgroup/dmem.c-571-\t\t\t const char fmt, ...)\nkernel/cgroup/dmem.c-572-{\nkernel/cgroup/dmem.c:573:\tstruct dmem_cgroup_region ret;\nkernel/cgroup/dmem.c-574-\tchar region_name;\n--\nkernel/cgroup/dmem.c-599-\tspin_lock(\u0026dmemcg_lock);\nkernel/cgroup/dmem.c:600:\tlist_add_tail_rcu(\u0026ret-\u003eregion_node, \u0026dmem_cgroup_regions);\nkernel/cgroup/dmem.c-601-\tspin_unlock(\u0026dmemcg_lock);\n--\nkernel/cgroup/dmem.c-604-}\nkernel/cgroup/dmem.c:605:EXPORT_SYMBOL_GPL(dmem_cgroup_register_region);\nkernel/cgroup/dmem.c-606-\nkernel/cgroup/dmem.c:607:static struct dmem_cgroup_region dmemcg_get_region_by_name(const char name)\nkernel/cgroup/dmem.c-608-{\nkernel/cgroup/dmem.c:609:\tstruct dmem_cgroup_region region;\nkernel/cgroup/dmem.c-610-\nkernel/cgroup/dmem.c:611:\tlist_for_each_entry_rcu(region, \u0026dmem_cgroup_regions, region_node, spin_is_locked(\u0026dmemcg_lock))\nkernel/cgroup/dmem.c-612-\t\tif (!strcmp(name, region-\u003ename) \u0026\u0026\n--\nkernel/cgroup/dmem.c-619-/\nkernel/cgroup/dmem.c:620: dmem_cgroup_pool_state_put() - Drop a reference to a dmem_cgroup_pool_state\nkernel/cgroup/dmem.c:621: * @pool: \u0026dmem_cgroup_pool_state\nkernel/cgroup/dmem.c-622- \nkernel/cgroup/dmem.c-623- Called to drop a reference to the limiting pool returned by\nkernel/cgroup/dmem.c:624: * dmem_cgroup_try_charge().\nkernel/cgroup/dmem.c-625- /\nkernel/cgroup/dmem.c:626:void dmem_cgroup_pool_state_put(struct dmem_cgroup_pool_state pool)\nkernel/cgroup/dmem.c-627-{\n--\nkernel/cgroup/dmem.c-632-}\nkernel/cgroup/dmem.c:633:EXPORT_SYMBOL_GPL(dmem_cgroup_pool_state_put);\nkernel/cgroup/dmem.c-634-\nkernel/cgroup/dmem.c:635:static struct dmem_cgroup_pool_state \nkernel/cgroup/dmem.c:636:get_cg_pool_unlocked(struct dmemcg_state cg, struct dmem_cgroup_region region)\nkernel/cgroup/dmem.c-637-{\nkernel/cgroup/dmem.c:638:\tstruct dmem_cgroup_pool_state pool, allocpool = NULL;\nkernel/cgroup/dmem.c-639-\n--\nkernel/cgroup/dmem.c-677-/\nkernel/cgroup/dmem.c:678: dmem_cgroup_uncharge() - Uncharge a pool.\nkernel/cgroup/dmem.c-679- * @pool: Pool to uncharge.\n--\nkernel/cgroup/dmem.c-681- \nkernel/cgroup/dmem.c:682: Undoes the effects of dmem_cgroup_try_charge.\nkernel/cgroup/dmem.c-683- * Must be called with the returned pool as argument,\n--\nkernel/cgroup/dmem.c-685- /\nkernel/cgroup/dmem.c:686:void dmem_cgroup_uncharge(struct dmem_cgroup_pool_state pool, u64 size)\nkernel/cgroup/dmem.c-687-{\n--\nkernel/cgroup/dmem.c-694-}\nkernel/cgroup/dmem.c:695:EXPORT_SYMBOL_GPL(dmem_cgroup_uncharge);\nkernel/cgroup/dmem.c-696-\nkernel/cgroup/dmem.c-697-/*\nkernel/cgroup/dmem.c:698: dmem_cgroup_try_charge() - Try charging a new allocation to a region.\nkernel/cgroup/dmem.c-699- * @region: dmem region to charge\n--\nkernel/cgroup/dmem.c-706- * If the function succeeds, @ret_pool is set, which must be passed to\nkernel/cgroup/dmem.c:707: * dmem_cgroup_uncharge() when undoing the allocation.\nkernel/cgroup/dmem.c-708- \n--\nkernel/cgroup/dmem.c-710- will be set to the pool for which the limit is hit. This can be used for\nkernel/cgroup/dmem.c:711: * eviction as argument to dmem_cgroup_evict_valuable(). This reference must be freed\nkernel/cgroup/dmem.c:712: * with @dmem_cgroup_pool_state_put().\nkernel/cgroup/dmem.c-713- \n--\nkernel/cgroup/dmem.c-715- /\nkernel/cgroup/dmem.c:716:int dmem_cgroup_try_charge(struct dmem_cgroup_region region, u64 size,\nkernel/cgroup/dmem.c:717:\t\t\t struct dmem_cgroup_pool_state ret_pool,\nkernel/cgroup/dmem.c:718:\t\t\t struct dmem_cgroup_pool_state ret_limit_pool)\nkernel/cgroup/dmem.c-719-{\nkernel/cgroup/dmem.c-720-\tstruct dmemcg_state cg;\nkernel/cgroup/dmem.c:721:\tstruct dmem_cgroup_pool_state pool;\nkernel/cgroup/dmem.c-722-\tstruct page_counter fail;\n--\nkernel/cgroup/dmem.c-742-\t\tif (ret_limit_pool) {\nkernel/cgroup/dmem.c:743:\t\t\tret_limit_pool = container_of(fail, struct dmem_cgroup_pool_state, cnt);\nkernel/cgroup/dmem.c-744-\t\t\tcss_get(\u0026(ret_limit_pool)-\u003ecs-\u003ecss);\n--\nkernel/cgroup/dmem.c-759-}\nkernel/cgroup/dmem.c:760:EXPORT_SYMBOL_GPL(dmem_cgroup_try_charge);\nkernel/cgroup/dmem.c-761-\nkernel/cgroup/dmem.c-762-/*\nkernel/cgroup/dmem.c:763: dmem_cgroup_below_min() - Tests whether current usage is within min limit.\nkernel/cgroup/dmem.c-764- \n--\nkernel/cgroup/dmem.c-769- /\nkernel/cgroup/dmem.c:770:bool dmem_cgroup_below_min(struct dmem_cgroup_pool_state root,\nkernel/cgroup/dmem.c:771:\t\t\t struct dmem_cgroup_pool_state test)\nkernel/cgroup/dmem.c-772-{\n--\nkernel/cgroup/dmem.c-787-\t /\nkernel/cgroup/dmem.c:788:\tdmem_cgroup_calculate_protection(root, test);\nkernel/cgroup/dmem.c-789-\treturn page_counter_read(\u0026test-\u003ecnt) \u003c= READ_ONCE(test-\u003ecnt.prot-\u003eemin);\nkernel/cgroup/dmem.c-790-}\nkernel/cgroup/dmem.c:791:EXPORT_SYMBOL_GPL(dmem_cgroup_below_min);\nkernel/cgroup/dmem.c-792-\nkernel/cgroup/dmem.c-793-/\nkernel/cgroup/dmem.c:794: dmem_cgroup_below_low() - Tests whether current usage is within low limit.\nkernel/cgroup/dmem.c-795- \n--\nkernel/cgroup/dmem.c-800- /\nkernel/cgroup/dmem.c:801:bool dmem_cgroup_below_low(struct dmem_cgroup_pool_state root,\nkernel/cgroup/dmem.c:802:\t\t\t struct dmem_cgroup_pool_state test)\nkernel/cgroup/dmem.c-803-{\n--\nkernel/cgroup/dmem.c-818-\t /\nkernel/cgroup/dmem.c:819:\tdmem_cgroup_calculate_protection(root, test);\nkernel/cgroup/dmem.c-820-\treturn page_counter_read(\u0026test-\u003ecnt) \u003c= READ_ONCE(test-\u003ecnt.prot-\u003eelow);\nkernel/cgroup/dmem.c-821-}\nkernel/cgroup/dmem.c:822:EXPORT_SYMBOL_GPL(dmem_cgroup_below_low);\nkernel/cgroup/dmem.c-823-\nkernel/cgroup/dmem.c-824-/\nkernel/cgroup/dmem.c:825: dmem_cgroup_get_common_ancestor(): Find the first common ancestor of two pools.\nkernel/cgroup/dmem.c-826- * @a: First pool to find the common ancestor of.\n--\nkernel/cgroup/dmem.c-832- /\nkernel/cgroup/dmem.c:833:struct dmem_cgroup_pool_state dmem_cgroup_get_common_ancestor(struct dmem_cgroup_pool_state a,\nkernel/cgroup/dmem.c:834:\t\t\t\t\t\t\t struct dmem_cgroup_pool_state b)\nkernel/cgroup/dmem.c-835-{\n--\nkernel/cgroup/dmem.c-838-\tstruct dmemcg_state ancestor_dmemcs = NULL;\nkernel/cgroup/dmem.c:839:\tstruct dmem_cgroup_pool_state pool = NULL;\nkernel/cgroup/dmem.c-840-\n--\nkernel/cgroup/dmem.c-863-}\nkernel/cgroup/dmem.c:864:EXPORT_SYMBOL_GPL(dmem_cgroup_get_common_ancestor);\nkernel/cgroup/dmem.c-865-\nkernel/cgroup/dmem.c:866:static int dmem_cgroup_region_capacity_show(struct seq_file sf, void v)\nkernel/cgroup/dmem.c-867-{\nkernel/cgroup/dmem.c:868:\tstruct dmem_cgroup_region region;\nkernel/cgroup/dmem.c-869-\nkernel/cgroup/dmem.c-870-\trcu_read_lock();\nkernel/cgroup/dmem.c:871:\tlist_for_each_entry_rcu(region, \u0026dmem_cgroup_regions, region_node) {\nkernel/cgroup/dmem.c-872-\t\tseq_puts(sf, region-\u003ename);\n--\nkernel/cgroup/dmem.c=895=static ssize_t dmemcg_limit_write(struct kernfs_open_file of,\nkernel/cgroup/dmem.c-896-\t\t\t\t char buf, size_t nbytes, loff_t off,\nkernel/cgroup/dmem.c:897:\t\t\t\t void (apply)(struct dmem_cgroup_pool_state , u64, bool))\nkernel/cgroup/dmem.c-898-{\nkernel/cgroup/dmem.c-899-\tstruct dmemcg_state dmemcs = css_to_dmemcs(of_css(of));\nkernel/cgroup/dmem.c:900:\tstruct dmem_cgroup_pool_state pool;\nkernel/cgroup/dmem.c:901:\tstruct dmem_cgroup_region region;\nkernel/cgroup/dmem.c-902-\tbool nonblock = of-\u003efile-\u003ef_flags \u0026 O_NONBLOCK;\n--\nkernel/cgroup/dmem.c=937=static int dmemcg_limit_show(struct seq_file sf, void v,\nkernel/cgroup/dmem.c:938:\t\t\t u64 (fn)(struct dmem_cgroup_pool_state ))\nkernel/cgroup/dmem.c-939-{\nkernel/cgroup/dmem.c-940-\tstruct dmemcg_state dmemcs = css_to_dmemcs(seq_css(sf));\nkernel/cgroup/dmem.c:941:\tstruct dmem_cgroup_region region;\nkernel/cgroup/dmem.c-942-\nkernel/cgroup/dmem.c-943-\trcu_read_lock();\nkernel/cgroup/dmem.c:944:\tlist_for_each_entry_rcu(region, \u0026dmem_cgroup_regions, region_node) {\nkernel/cgroup/dmem.c:945:\t\tstruct dmem_cgroup_pool_state pool = find_cg_pool_locked(dmemcs, region);\nkernel/cgroup/dmem.c-946-\t\tu64 val;\n--\nkernel/cgroup/dmem.c-960-\nkernel/cgroup/dmem.c:961:static int dmem_cgroup_region_peak_show(struct seq_file sf, void v)\nkernel/cgroup/dmem.c-962-{\n--\nkernel/cgroup/dmem.c-965-\nkernel/cgroup/dmem.c:966:static int dmem_cgroup_region_current_show(struct seq_file sf, void v)\nkernel/cgroup/dmem.c-967-{\n--\nkernel/cgroup/dmem.c-970-\nkernel/cgroup/dmem.c:971:static int dmem_cgroup_region_min_show(struct seq_file sf, void v)\nkernel/cgroup/dmem.c-972-{\n--\nkernel/cgroup/dmem.c-975-\nkernel/cgroup/dmem.c:976:static ssize_t dmem_cgroup_region_min_write(struct kernfs_open_file of,\nkernel/cgroup/dmem.c-977-\t\t\t\t char buf, size_t nbytes, loff_t off)\n--\nkernel/cgroup/dmem.c-981-\nkernel/cgroup/dmem.c:982:static int dmem_cgroup_region_low_show(struct seq_file sf, void v)\nkernel/cgroup/dmem.c-983-{\n--\nkernel/cgroup/dmem.c-986-\nkernel/cgroup/dmem.c:987:static ssize_t dmem_cgroup_region_low_write(struct kernfs_open_file of,\nkernel/cgroup/dmem.c-988-\t\t\t\t char buf, size_t nbytes, loff_t off)\n--\nkernel/cgroup/dmem.c-992-\nkernel/cgroup/dmem.c:993:static int dmem_cgroup_region_max_show(struct seq_file sf, void v)\nkernel/cgroup/dmem.c-994-{\n--\nkernel/cgroup/dmem.c-997-\nkernel/cgroup/dmem.c:998:static ssize_t dmem_cgroup_region_max_write(struct kernfs_open_file of,\nkernel/cgroup/dmem.c-999-\t\t\t\t char *buf, size_t nbytes, loff_t off)\n--\nkernel/cgroup/dmem.c=1004=static struct cftype files[] = {\n--\nkernel/cgroup/dmem.c-1006-\t\t.name = \"capacity\",\nkernel/cgroup/dmem.c:1007:\t\t.seq_show = dmem_cgroup_region_capacity_show,\nkernel/cgroup/dmem.c-1008-\t\t.flags = CFTYPE_ONLY_ON_ROOT,\n--\nkernel/cgroup/dmem.c-1011-\t\t.name = \"current\",\nkernel/cgroup/dmem.c:1012:\t\t.seq_show = dmem_cgroup_region_current_show,\nkernel/cgroup/dmem.c-1013-\t},\n--\nkernel/cgroup/dmem.c-1015-\t\t.name = \"peak\",\nkernel/cgroup/dmem.c:1016:\t\t.seq_show = dmem_cgroup_region_peak_show,\nkernel/cgroup/dmem.c-1017-\t\t.flags = CFTYPE_NOT_ON_ROOT,\n--\nkernel/cgroup/dmem.c-1020-\t\t.name = \"min\",\nkernel/cgroup/dmem.c:1021:\t\t.write = dmem_cgroup_region_min_write,\nkernel/cgroup/dmem.c:1022:\t\t.seq_show = dmem_cgroup_region_min_show,\nkernel/cgroup/dmem.c-1023-\t\t.flags = CFTYPE_NOT_ON_ROOT,\n--\nkernel/cgroup/dmem.c-1026-\t\t.name = \"low\",\nkernel/cgroup/dmem.c:1027:\t\t.write = dmem_cgroup_region_low_write,\nkernel/cgroup/dmem.c:1028:\t\t.seq_show = dmem_cgroup_region_low_show,\nkernel/cgroup/dmem.c-1029-\t\t.flags = CFTYPE_NOT_ON_ROOT,\n--\nkernel/cgroup/dmem.c-1032-\t\t.name = \"max\",\nkernel/cgroup/dmem.c:1033:\t\t.write = dmem_cgroup_region_max_write,\nkernel/cgroup/dmem.c:1034:\t\t.seq_show = dmem_cgroup_region_max_show,\nkernel/cgroup/dmem.c-1035-\t\t.flags = CFTYPE_NOT_ON_ROOT,\n" }
15/2	2026/09/09 09:05	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 32714 output: 32 thoughts: 121 Thoughts: Analyzing Focus Symbols and Configurations Okay, let's break this down. My immediate task is to figure out the right focus symbols and configurations needed here. We're dealing with memory management, likely within a containerized environment, given the "cgroup" references. I need to be precise about which configurations are in play. I see several key configurations listed: `MEMCG`, which is the core memory cgroup config, that's fundamental. Then there's `MEMCG_V1`, likely addressing legacy aspects of memcg page counters that were handled by a change in `memcontrol.c`. I'll need to keep that in mind as I go forward. We also have `CGROUP_DMEM`, which indicates a device memory controller—this suggests potential hardware interactions, which I'll have to watch carefully. And finally, `CGROUP_HUGETLB`, clearly related to HugeTLB cgroup support, handled by `hugetlb_cgroup.c`. Right, that seems logical. I should start by checking the `CONFIG_CGROUP_HUGETLB` configuration within the Kconfig files to confirm its presence and understand its context within the broader system. I anticipate this will provide insight into other potential dependencies.
16/2	2026/09/09 09:05	tool	grepper	0m Args: { "Expression": "config CGROUP_HUGETLB", "PathPrefix": "init/Kconfig" } Results: { "Output": "init/Kconfig=1282=config CGROUP_FREEZER\n--\ninit/Kconfig-1292-\ninit/Kconfig:1293:config CGROUP_HUGETLB\ninit/Kconfig-1294-\tbool \"HugeTLB controller\"\n" }
17/2	2026/09/09 09:05	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 33211 output: 30 thoughts: 611 Thoughts: Analyzing Memory Management Related Symbols and Their Context Okay, let's break this down. First, I need to get a clear picture of the relevant symbols, focusing on those involved with page counters, memory cgroups, and direct memory access (dmem). The goal here is to identify key areas to investigate further or potentially optimize. My initial scan focuses on what's modified or relevant in `mm/page_counter.c`. I'm specifically looking at: `page_counter_set_min`, `page_counter_set_low`, `page_counter_calculate_protection`, and `propagate_protected_usage`. `propagate_protected_usage` is static within `page_counter.c`, so that's something to keep in mind. Next, I'm checking `mm/memcontrol.c`. This is crucial. I'm noting `mem_cgroup_css_alloc`, then functions related to setting and showing memory limits: `memory_min_show`, `memory_min_write` (and the all-important call to `page_counter_set_min`), `memory_low_show`, `memory_low_write` (calling `page_counter_set_low`), and then things related to protection: `mem_cgroup_show_protected_memory`, and `mem_cgroup_calculate_protection` (which in turn calls `page_counter_calculate_protection`). These are all key areas. Moving on to `kernel/cgroup/dmem.c`, I'm looking at how dmem interacts with these concepts. I see `dmem_cgroup_state_evict_valuable`, `dmem_cgroup_below_min`, `dmem_cgroup_below_low`, and `alloc_pool_single`. Also, the related show/write functions for dmem regions and low/min limits: `dmem_cgroup_region_min_show`, `dmem_cgroup_region_min_write`, `dmem_cgroup_region_low_show`, and `dmem_cgroup_region_low_write`. Finally, I glanced at `mm/hugetlb_cgroup.c` to see how huge pages are handled with memory cgroups: `hugetlb_cgroup_init` and `hugetlb_cgroup_css_alloc`. Now, the important part. I need to figure out which functions are frequently called or are bottlenecks. I'm deliberately avoiding generic page allocation and fault handling functions like `alloc_pages` or `do_anonymous_page`. That's a red herring. The interesting stuff is in these specialized subsystem features that seem to be on the critical path, so I've highlighted them: `page_counter_set_min`, `page_counter_set_low`, `page_counter_calculate_protection`, `mem_cgroup_calculate_protection`, `memory_min_show`, `memory_min_write`, `memory_low_show`, `memory_low_write`, `dmem_cgroup_state_evict_valuable`, `dmem_cgroup_below_min`, `dmem_cgroup_below_low`, `dmem_cgroup_region_min_write`, `dmem_cgroup_region_low_write`, and `hugetlb_cgroup_css_alloc`. I will try to confirm the location of `mem_cgroup_calculate_protection` in either `mm/memcontrol.c` or as static inline.
18/2	2026/09/09 09:05	tool	grepper	0m Args: { "Expression": "mem_cgroup_calculate_protection", "PathPrefix": "mm/" } Results: { "Output": "mm/memcontrol.c=5197=struct cgroup_subsys memory_cgrp_subsys = {\n--\nmm/memcontrol.c-5215-/*\nmm/memcontrol.c:5216: mem_cgroup_calculate_protection - check if memory consumption is in the normal range\nmm/memcontrol.c-5217- * @root: the top ancestor of the sub-tree being checked\n--\nmm/memcontrol.c-5222- /\nmm/memcontrol.c:5223:void mem_cgroup_calculate_protection(struct mem_cgroup root,\nmm/memcontrol.c-5224-\t\t\t\t struct mem_cgroup memcg)\n--\nmm/vmscan.c=4290=static void lru_gen_age_node(struct pglist_data pgdat, struct scan_control sc)\n--\nmm/vmscan.c-4303-\nmm/vmscan.c:4304:\t\tmem_cgroup_calculate_protection(NULL, memcg);\nmm/vmscan.c-4305-\n--\nmm/vmscan.c=5182=static int shrink_one(struct lruvec lruvec, struct scan_control sc)\n--\nmm/vmscan.c-5189-\nmm/vmscan.c:5190:\t/ lru_gen_age_node() called mem_cgroup_calculate_protection() /\nmm/vmscan.c-5191-\tif (mem_cgroup_below_min(NULL, memcg))\n--\nmm/vmscan.c=6259=static void shrink_node_memcgs(pg_data_t pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-6293-\nmm/vmscan.c:6294:\t\tmem_cgroup_calculate_protection(target_memcg, memcg);\nmm/vmscan.c-6295-\n" }
19/2	2026/09/09 09:05	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 35120 output: 313 thoughts: 429 Thoughts: My Assessment of the Proposed Patch Okay, so `mem_cgroup_calculate_protection` is definitely an exported symbol in `mm/memcontrol.c`. Good, that's what I expected. Now, let's just quickly review the required kernel configurations to make sure we're covering all our bases: We've got `MEMCG` for the memory cgroup controller, `MEMCG_V1` for legacy support, `CGROUP_DMEM` for the device memory cgroup, and `CGROUP_HUGETLB` for the huge pages stuff. Yep, looks like we're good there. Alright, next up, the core symbols this patch is touching: `page_counter_set_min`, `page_counter_set_low`, `page_counter_calculate_protection`, `mem_cgroup_calculate_protection`, and then the CSS allocation functions for memcg and hugetlb. We've also got `memory_min_write`, `memory_low_write`, plus the device memory specific logic: `dmem_cgroup_state_evict_valuable`, `dmem_cgroup_below_min`, `dmem_cgroup_below_low`, and region writes. Okay, yes, it's touching quite a bit of the core. Now, let's recap the reasoning behind this patch. It sounds like they're refactoring the page counter protection fields into a dedicated `struct page_counter_protection`, which makes sense for cleaner organization. This will affect `memcg`, `dmemcg`, and `hugetlb_cgroup`, which is pretty significant. And that's impacting the core protection tracking and propagation logic, including those sysfs interfaces like `memory.min` and `memory.low`, and the dmemcg eviction and limits. Yep, it's a deep dive into core memory management and cgroup logic. So, this patch is changing quite a bit of critical code. Given that, fuzzing this is absolutely the right call to flush out any null pointer dereferences, calculation errors, or synchronization regressions. All the relevant parts are addressed. I think it meets all criteria, let's call `set-results`.
20/2	2026/09/09 09:05	tool	set-results	0m Args: { "EnableConfigs": [ "MEMCG", "MEMCG_V1", "CGROUP_DMEM", "CGROUP_HUGETLB" ], "FocusSymbols": [ "page_counter_set_min", "page_counter_set_low", "page_counter_calculate_protection", "mem_cgroup_calculate_protection", "mem_cgroup_css_alloc", "memory_min_write", "memory_low_write", "dmem_cgroup_state_evict_valuable", "dmem_cgroup_below_min", "dmem_cgroup_below_low", "dmem_cgroup_region_min_write", "dmem_cgroup_region_low_write", "hugetlb_cgroup_css_alloc" ], "Reasoning": "The patch refactors the memory protection fields (memory.min, memory.low, emin, elow, and associated usages) out of struct page_counter into a dedicated struct page_counter_protection. It modifies core page counter initialization and protection calculations, memcg cgroup v1/v2 control files and calculations, and dmem cgroup pool protection logic. These reachable memory management and cgroup subsystem paths warrant fuzzing to verify against null pointer dereferences, incorrect protection calculations, and state inconsistencies.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "MEMCG", "MEMCG_V1", "CGROUP_DMEM", "CGROUP_HUGETLB" ], "FocusSymbols": [ "page_counter_set_min", "page_counter_set_low", "page_counter_calculate_protection", "mem_cgroup_calculate_protection", "mem_cgroup_css_alloc", "memory_min_write", "memory_low_write", "dmem_cgroup_state_evict_valuable", "dmem_cgroup_below_min", "dmem_cgroup_below_low", "dmem_cgroup_region_min_write", "dmem_cgroup_region_low_write", "hugetlb_cgroup_css_alloc" ], "Reasoning": "The patch refactors the memory protection fields (memory.min, memory.low, emin, elow, and associated usages) out of struct page_counter into a dedicated struct page_counter_protection. It modifies core page counter initialization and protection calculations, memcg cgroup v1/v2 control files and calculations, and dmem cgroup pool protection logic. These reachable memory management and cgroup subsystem paths warrant fuzzing to verify against null pointer dereferences, incorrect protection calculations, and state inconsistencies.", "WorthFuzzing": true }
21/1	2026/09/09 09:05	action	If	1m Args: { "WorthFuzzing": true } Results: null
22/2	2026/09/09 09:05	agent	kmsan-evaluator	1m Model: core Args: null Results: { "KMSANReasoning": "The patch refactors hierarchical protection tracking fields (emin, elow, min, low, and usage counters) out of `struct page_counter` into a separate `struct page_counter_protection` structure.\n\n1. Memory Initialization: All instances of `struct page_counter_protection` are embedded within `struct mem_cgroup` and `struct dmem_cgroup_pool_state`, which are allocated via zero-allocating APIs (`kmem_cache_zalloc` and `kzalloc_obj`). `page_counter_init()` explicitly clears `prot = NULL`, and `page_counter_init_protection()` initializes the protection pointers and limits.\n2. User-space Boundary: No uninitialized bytes, structs with uninitialized padding, or uninitialized buffers are exposed or copied to user space. Only scalar values formatted through seq_file helpers or numerical returns are read.\n3. Bug Detection Suitability: Potential risks in this refactoring would involve NULL pointer dereferences or control flow issues, which are caught by standard kernel checks and KASAN. There are no risks of uninitialized memory reads or information leaks.\n\nTherefore, a dedicated KMSAN fuzzing session is not required.", "NeedsKMSAN": false } Instruction: You are an expert Linux kernel security engineer specializing in kernel memory error detectors (KASAN and KMSAN). Your job is to review the provided patch series and determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer) fuzzing session in addition to standard KASAN fuzzing. CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN: - Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable a comprehensive suite of debugging tools and sanitizers, including KASAN (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks. - KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap, or page allocations) and kernel-to-user memory info-leaks. Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS. A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks that are detected ONLY by KMSAN. Look holistically at the patch series and surrounding code. Even if no direct uninitialized field accesses or new buffer allocations are added in the diff itself, a patch may alter control flow, bounds checking, or data length calculations in ways that change how the rest of the code operates on existing buffers (e.g. allowing uninitialized stack/heap memory to be read, copied to user space, or used in control flow). Do not hesitate to use your code access tools to inspect the surrounding code, called functions, and callers. Set NeedsKMSAN=true ONLY IF the patch introduces or modifies: 1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb attributes, ioctl output arguments, socket options, or BPF buffers) where fields or structure padding might not be fully initialized/zeroed. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. Set NeedsKMSAN=false IF: - The code changes primarily risk out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (these are already caught by KASAN, LOCKDEP, or standard bug detectors). - All stack/heap structures touched or introduced by the patch are fully zeroed or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied. - The patch does not introduce any risk of uninitialized memory usage or info-leaks. Use your code access tools to inspect the surrounding code if necessary, then provide detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit a44d7a8c0d593e8dd444819f3e172e4d44299d5b Author: syz-cluster <triage@syzkaller.com> Date: Wed Sep 9 09:05:15 2026 +0000 syz-cluster: applied patch under review diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 058ebd73ff160..44065001a66ac 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -195,6 +195,13 @@ struct mem_cgroup { /* Accounted resources / struct page_counter memory; / Both v1 & v2 / + / + * Hierarchical memory.min/memory.low protection tracking for the + * memory page counter. swap/memsw, kmem and tcpmem counters do not + * support protection and have no such context. + / + struct page_counter_protection memory_prot; + union { struct page_counter swap; / v2 only / struct page_counter memsw; / v1 only / @@ -584,8 +591,8 @@ static inline void mem_cgroup_protection(struct mem_cgroup root, if (root == memcg) return; - min = READ_ONCE(memcg->memory.emin); - low = READ_ONCE(memcg->memory.elow); + min = READ_ONCE(memcg->memory_prot.emin); + low = READ_ONCE(memcg->memory_prot.elow); } void mem_cgroup_calculate_protection(struct mem_cgroup root, @@ -609,7 +616,7 @@ static inline bool mem_cgroup_below_low(struct mem_cgroup target, if (mem_cgroup_unprotected(target, memcg)) return false; - return READ_ONCE(memcg->memory.elow) >= + return READ_ONCE(memcg->memory_prot.elow) >= page_counter_read(&memcg->memory); } @@ -619,7 +626,7 @@ static inline bool mem_cgroup_below_min(struct mem_cgroup target, if (mem_cgroup_unprotected(target, memcg)) return false; - return READ_ONCE(memcg->memory.emin) >= + return READ_ONCE(memcg->memory_prot.emin) >= page_counter_read(&memcg->memory); } diff --git a/include/linux/page_counter.h b/include/linux/page_counter.h index 07b7cb12249c7..a4dd461523af2 100644 --- a/include/linux/page_counter.h +++ b/include/linux/page_counter.h @@ -7,15 +7,17 @@ #include <linux/limits.h> #include <asm/page.h> -struct page_counter { - / - * Make sure 'usage' does not share cacheline with any other field in - * v2. The memcg->memory.usage is a hot member of struct mem_cgroup. - / - atomic_long_t usage; - unsigned long failcnt; / v1-only field / - - CACHELINE_PADDING(_pad1_); +/ + * Hierarchical protection (memory.min / memory.low) tracking. + * + * Only the memory page counter (and dmem pools) participate in protection. + * swap/memsw, kmem and tcpmem page counters never do, so the protection + * fields are kept out of struct page_counter in this separate structure to + * save space in the common case. struct page_counter links to it via ->prot, + * which is NULL for counters without protection support. + / +struct page_counter_protection { + struct page_counter_protection parent; /* effective memory.min and memory.min usage tracking / unsigned long emin; @@ -27,20 +29,37 @@ struct page_counter { atomic_long_t low_usage; atomic_long_t children_low_usage; + unsigned long min; + unsigned long low; +}; + +struct page_counter { + / + * Make sure 'usage' does not share cacheline with any other field in + * v2. The memcg->memory.usage is a hot member of struct mem_cgroup. + / + atomic_long_t usage; + unsigned long failcnt; / v1-only field / + + CACHELINE_PADDING(_pad1_); + unsigned long watermark; / Latest cg2 reset watermark / unsigned long local_watermark; - / Keep all the read most fields in a separete cacheline. / - CACHELINE_PADDING(_pad2_); - - bool protection_support; bool track_failcnt; - unsigned long min; - unsigned long low; unsigned long high; unsigned long max; struct page_counter parent; + + /* + * Hierarchical protection context, NULL for counters that do not + * support memory.min/memory.low (swap, memsw, kmem, tcpmem, ...). + / + struct page_counter_protection prot; + + /* Keep all the read most fields in a separete cacheline. / + CACHELINE_PADDING(_pad2_); } ____cacheline_internodealigned_in_smp; #if BITS_PER_LONG == 32 @@ -49,18 +68,33 @@ struct page_counter { #define PAGE_COUNTER_MAX (LONG_MAX / PAGE_SIZE) #endif -/ - * Protection is supported only for the first counter (with id 0). - / static inline void page_counter_init(struct page_counter counter, - struct page_counter parent, - bool protection_support) + struct page_counter parent) { counter->usage = (atomic_long_t)ATOMIC_LONG_INIT(0); counter->max = PAGE_COUNTER_MAX; counter->parent = parent; - counter->protection_support = protection_support; counter->track_failcnt = false; + counter->prot = NULL; +} + +/* + * Enable hierarchical protection (memory.min/memory.low) on @counter. + * @prot and @parent are the protection contexts of @counter and its + * parent page counter respectively. Only the memory page counter (and + * dmem pools) call this. + * + * The remaining members of @prot (emin, elow and the usage counters) are + * expected to be zero already, so @prot must come from zeroed memory. + / +static inline void page_counter_init_protection(struct page_counter counter, + struct page_counter_protection prot, + struct page_counter_protection parent) +{ + counter->prot = prot; + prot->parent = parent; + prot->min = 0; + prot->low = 0; } static inline unsigned long page_counter_read(struct page_counter counter) diff --git a/kernel/cgroup/dmem.c b/kernel/cgroup/dmem.c index 4683f3d680226..10321f1f03308 100644 --- a/kernel/cgroup/dmem.c +++ b/kernel/cgroup/dmem.c @@ -88,6 +88,7 @@ struct dmem_cgroup_pool_state { struct rcu_head rcu; struct page_counter cnt; + struct page_counter_protection prot; struct dmem_cgroup_pool_state parent; refcount_t ref; @@ -211,12 +212,12 @@ set_resource_max(struct dmem_cgroup_pool_state pool, u64 val, bool nonblock) static u64 get_resource_low(struct dmem_cgroup_pool_state pool) { - return pool ? READ_ONCE(pool->cnt.low) : 0; + return pool ? READ_ONCE(pool->cnt.prot->low) : 0; } static u64 get_resource_min(struct dmem_cgroup_pool_state pool) { - return pool ? READ_ONCE(pool->cnt.min) : 0; + return pool ? READ_ONCE(pool->cnt.prot->min) : 0; } static u64 get_resource_max(struct dmem_cgroup_pool_state pool) @@ -387,13 +388,13 @@ bool dmem_cgroup_state_evict_valuable(struct dmem_cgroup_pool_state limit_pool, dmem_cgroup_calculate_protection(limit_pool, test_pool); used = page_counter_read(ctest); - min = READ_ONCE(ctest->emin); + min = READ_ONCE(ctest->prot->emin); if (used <= min) return false; if (!ignore_low) { - low = READ_ONCE(ctest->elow); + low = READ_ONCE(ctest->prot->elow); if (used > low) return true; @@ -426,8 +427,9 @@ alloc_pool_single(struct dmemcg_state dmemcs, struct dmem_cgroup_region region if (parent) ppool = find_cg_pool_locked(parent, region); - page_counter_init(&pool->cnt, - ppool ? &ppool->cnt : NULL, true); + page_counter_init(&pool->cnt, ppool ? &ppool->cnt : NULL); + page_counter_init_protection(&pool->cnt, &pool->prot, + ppool ? &ppool->prot : NULL); reset_all_resource_limits(pool); refcount_set(&pool->ref, 1); kref_get(&region->ref); @@ -784,7 +786,7 @@ bool dmem_cgroup_below_min(struct dmem_cgroup_pool_state root, * here. / dmem_cgroup_calculate_protection(root, test); - return page_counter_read(&test->cnt) <= READ_ONCE(test->cnt.emin); + return page_counter_read(&test->cnt) <= READ_ONCE(test->cnt.prot->emin); } EXPORT_SYMBOL_GPL(dmem_cgroup_below_min); @@ -815,7 +817,7 @@ bool dmem_cgroup_below_low(struct dmem_cgroup_pool_state root, * here. / dmem_cgroup_calculate_protection(root, test); - return page_counter_read(&test->cnt) <= READ_ONCE(test->cnt.elow); + return page_counter_read(&test->cnt) <= READ_ONCE(test->cnt.prot->elow); } EXPORT_SYMBOL_GPL(dmem_cgroup_below_low); diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c index ecb6e0b7819a0..7fdae504cfc6f 100644 --- a/mm/hugetlb_cgroup.c +++ b/mm/hugetlb_cgroup.c @@ -108,8 +108,8 @@ static void hugetlb_cgroup_init(struct hugetlb_cgroup h_cgroup, fault = hugetlb_cgroup_counter_from_cgroup(h_cgroup, idx); rsvd = hugetlb_cgroup_counter_from_cgroup_rsvd(h_cgroup, idx); - page_counter_init(fault, fault_parent, false); - page_counter_init(rsvd, rsvd_parent, false); + page_counter_init(fault, fault_parent); + page_counter_init(rsvd, rsvd_parent); if (!cgroup_subsys_on_dfl(hugetlb_cgrp_subsys)) { fault->track_failcnt = true; diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 86ff580c70183..b4c01a0dfd4f6 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4267,25 +4267,30 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state parent_css) #endif page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX); if (parent) { - page_counter_init(&memcg->memory, &parent->memory, memcg_on_dfl); - page_counter_init(&memcg->swap, &parent->swap, false); + page_counter_init(&memcg->memory, &parent->memory); + if (memcg_on_dfl) + page_counter_init_protection(&memcg->memory, &memcg->memory_prot, + &parent->memory_prot); + page_counter_init(&memcg->swap, &parent->swap); #ifdef CONFIG_MEMCG_V1 WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent)); memcg->memory.track_failcnt = !memcg_on_dfl; memcg->memsw.track_failcnt = !memcg_on_dfl; WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable)); - page_counter_init(&memcg->kmem, &parent->kmem, false); - page_counter_init(&memcg->tcpmem, &parent->tcpmem, false); + page_counter_init(&memcg->kmem, &parent->kmem); + page_counter_init(&memcg->tcpmem, &parent->tcpmem); memcg->tcpmem.track_failcnt = !memcg_on_dfl; #endif } else { init_memcg_stats(); init_memcg_events(); - page_counter_init(&memcg->memory, NULL, true); - page_counter_init(&memcg->swap, NULL, false); + page_counter_init(&memcg->memory, NULL); + page_counter_init_protection(&memcg->memory, &memcg->memory_prot, + NULL); + page_counter_init(&memcg->swap, NULL); #ifdef CONFIG_MEMCG_V1 - page_counter_init(&memcg->kmem, NULL, false); - page_counter_init(&memcg->tcpmem, NULL, false); + page_counter_init(&memcg->kmem, NULL); + page_counter_init(&memcg->tcpmem, NULL); #endif root_mem_cgroup = memcg; return &memcg->css; @@ -4818,7 +4823,7 @@ static ssize_t memory_peak_write(struct kernfs_open_file of, char buf, static int memory_min_show(struct seq_file m, void v) { return seq_puts_memcg_tunable(m, - READ_ONCE(mem_cgroup_from_seq(m)->memory.min)); + READ_ONCE(mem_cgroup_from_seq(m)->memory_prot.min)); } static ssize_t memory_min_write(struct kernfs_open_file of, @@ -4841,7 +4846,7 @@ static ssize_t memory_min_write(struct kernfs_open_file of, static int memory_low_show(struct seq_file m, void v) { return seq_puts_memcg_tunable(m, - READ_ONCE(mem_cgroup_from_seq(m)->memory.low)); + READ_ONCE(mem_cgroup_from_seq(m)->memory_prot.low)); } static ssize_t memory_low_write(struct kernfs_open_file of, @@ -6266,6 +6271,6 @@ void mem_cgroup_show_protected_memory(struct mem_cgroup memcg) memcg = root_mem_cgroup; pr_warn("Memory cgroup min protection %lukB -- low protection %lukB", - K(atomic_long_read(&memcg->memory.children_min_usage)), - K(atomic_long_read(&memcg->memory.children_low_usage))); + K(atomic_long_read(&memcg->memory_prot.children_min_usage)), + K(atomic_long_read(&memcg->memory_prot.children_low_usage))); } diff --git a/mm/page_counter.c b/mm/page_counter.c index 450543f4b318b..401201c8e3902 100644 --- a/mm/page_counter.c +++ b/mm/page_counter.c @@ -15,34 +15,35 @@ static bool track_protection(struct page_counter c) { - return c->protection_support; + return c->prot != NULL; } static void propagate_protected_usage(struct page_counter c, unsigned long usage) { + struct page_counter_protection prot = c->prot; unsigned long protected, old_protected; long delta; - if (!c->parent) + if (!prot \|\| !prot->parent) return; - protected = min(usage, READ_ONCE(c->min)); - old_protected = atomic_long_read(&c->min_usage); + protected = min(usage, READ_ONCE(prot->min)); + old_protected = atomic_long_read(&prot->min_usage); if (protected != old_protected) { - old_protected = atomic_long_xchg(&c->min_usage, protected); + old_protected = atomic_long_xchg(&prot->min_usage, protected); delta = protected - old_protected; if (delta) - atomic_long_add(delta, &c->parent->children_min_usage); + atomic_long_add(delta, &prot->parent->children_min_usage); } - protected = min(usage, READ_ONCE(c->low)); - old_protected = atomic_long_read(&c->low_usage); + protected = min(usage, READ_ONCE(prot->low)); + old_protected = atomic_long_read(&prot->low_usage); if (protected != old_protected) { - old_protected = atomic_long_xchg(&c->low_usage, protected); + old_protected = atomic_long_xchg(&prot->low_usage, protected); delta = protected - old_protected; if (delta) - atomic_long_add(delta, &c->parent->children_low_usage); + atomic_long_add(delta, &prot->parent->children_low_usage); } } @@ -257,7 +258,10 @@ void page_counter_set_min(struct page_counter counter, unsigned long nr_pages) { struct page_counter c; - WRITE_ONCE(counter->min, nr_pages); + if (!counter->prot) + return; + + WRITE_ONCE(counter->prot->min, nr_pages); for (c = counter; c; c = c->parent) propagate_protected_usage(c, atomic_long_read(&c->usage)); @@ -274,7 +278,10 @@ void page_counter_set_low(struct page_counter counter, unsigned long nr_pages) { struct page_counter c; - WRITE_ONCE(counter->low, nr_pages); + if (!counter->prot) + return; + + WRITE_ONCE(counter->prot->low, nr_pages); for (c = counter; c; c = c->parent) propagate_protected_usage(c, atomic_long_read(&c->usage)); @@ -445,9 +452,18 @@ void page_counter_calculate_protection(struct page_counter root, struct page_counter counter, bool recursive_protection) { + struct page_counter_protection prot = counter->prot; + struct page_counter_protection parent_prot; unsigned long usage, parent_usage; struct page_counter parent = counter->parent; + / + * Only counters with protection support (memory, dmem pools) are + * ever passed here, but guard anyway. + / + if (!prot) + return; + / * Effective values of the reclaim targets are ignored so they * can be stale. Have a look at mem_cgroup_protection for more @@ -463,23 +479,24 @@ void page_counter_calculate_protection(struct page_counter root, return; if (parent == root) { - counter->emin = READ_ONCE(counter->min); - counter->elow = READ_ONCE(counter->low); + prot->emin = READ_ONCE(prot->min); + prot->elow = READ_ONCE(prot->low); return; } + parent_prot = parent->prot; parent_usage = page_counter_read(parent); - WRITE_ONCE(counter->emin, effective_protection(usage, parent_usage, - READ_ONCE(counter->min), - READ_ONCE(parent->emin), - atomic_long_read(&parent->children_min_usage), + WRITE_ONCE(prot->emin, effective_protection(usage, parent_usage, + READ_ONCE(prot->min), + READ_ONCE(parent_prot->emin), + atomic_long_read(&parent_prot->children_min_usage), recursive_protection)); - WRITE_ONCE(counter->elow, effective_protection(usage, parent_usage, - READ_ONCE(counter->low), - READ_ONCE(parent->elow), - atomic_long_read(&parent->children_low_usage), + WRITE_ONCE(prot->elow, effective_protection(usage, parent_usage, + READ_ONCE(prot->low), + READ_ONCE(parent_prot->elow), + atomic_long_read(&parent_prot->children_low_usage), recursive_protection)); } #endif / CONFIG_MEMCG \|\| CONFIG_CGROUP_DMEM */
23/3	2026/09/09 09:05	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 7849 output: 36 thoughts: 295 Thoughts: Analyzing the Patch for Uninitialized Memory Risks Okay, let's dive into this patch and see if we have any KMSAN-related concerns stemming from potential uninitialized memory exposures. First, I need to grasp the changes the patch introduces. It seems like it's primarily refactoring how page counter protection fields are handled. Here's what I've got: 1. It's pulling those protection-related fields ( `emin`, `elow`, `min_usage`, `children_min_usage`, `low_usage`, `children_low_usage`, `min`, `low`) out of `struct page_counter` and into a brand new struct, `struct page_counter_protection`. This suggests some sort of logical grouping or separation of concerns. 2. Then, it's adding a `struct page_counter_protection memory_prot;` field within the `struct mem_cgroup` structure. 3. Similarly, a `struct page_counter_protection prot;` is added to `struct dmem_cgroup_pool_state`. 4. The `page_counter_init` function signature is simplified, removing the `bool protection_support` parameter. 5. And then, `page_counter_init_protection` initializes the `prot` field with values: `counter->prot = prot; prot->parent = parent; prot->min = 0; prot->low = 0;`. This is where I need to focus. I have to look carefully at initialization of `prot`. 6. Now, I have to figure out the allocations of `struct mem_cgroup` and `struct dmem_cgroup_pool_state`. I need to track down the allocations, so I will search the code for `mem_cgroup_css_alloc` or any allocation of `struct mem_cgroup`, as well as `alloc_pool_single` or any direct allocation of `dmem_cgroup_pool_state` to see if those structures are properly initialized. I need to make sure that these new `struct page_counter_protection` fields are correctly initialized during these allocations and that there's no way for uninitialized memory to be exposed. KMSAN will love to find such bugs!
24/3	2026/09/09 09:05	tool	grepper	0m Args: { "Expression": "struct mem_cgroup \\memcg.=", "PathPrefix": "mm/memcontrol.c" } Results: { "Output": "mm/memcontrol.c=957=static void __mod_memcg_lruvec_state(struct mem_cgroup_per_node pn,\n--\nmm/memcontrol.c-959-{\nmm/memcontrol.c:960:\tstruct mem_cgroup memcg = pn-\u003ememcg;\nmm/memcontrol.c-961-\tint i = memcg_stats_index(idx);\n--\nmm/memcontrol.c=1373=static void invalidate_reclaim_iterators(struct mem_cgroup dead_memcg)\nmm/memcontrol.c-1374-{\nmm/memcontrol.c:1375:\tstruct mem_cgroup memcg = dead_memcg;\nmm/memcontrol.c-1376-\tstruct mem_cgroup last;\n--\nmm/memcontrol.c=3828=struct wb_domain mem_cgroup_wb_domain(struct bdi_writeback wb)\nmm/memcontrol.c-3829-{\nmm/memcontrol.c:3830:\tstruct mem_cgroup memcg = mem_cgroup_from_css(wb-\u003ememcg_css);\nmm/memcontrol.c-3831-\n--\nmm/memcontrol.c=3856=void mem_cgroup_wb_stats(struct bdi_writeback wb, unsigned long pfilepages,\n--\nmm/memcontrol.c-3859-{\nmm/memcontrol.c:3860:\tstruct mem_cgroup memcg = mem_cgroup_from_css(wb-\u003ememcg_css);\nmm/memcontrol.c-3861-\tstruct mem_cgroup parent;\n--\nmm/memcontrol.c=3925=void mem_cgroup_track_foreign_dirty_slowpath(struct folio folio,\n--\nmm/memcontrol.c-3927-{\nmm/memcontrol.c:3928:\tstruct mem_cgroup memcg = folio_memcg(folio);\nmm/memcontrol.c-3929-\tstruct memcg_cgwb_frn frn;\n--\nmm/memcontrol.c=3978=void mem_cgroup_flush_foreign(struct bdi_writeback wb)\nmm/memcontrol.c-3979-{\nmm/memcontrol.c:3980:\tstruct mem_cgroup memcg = mem_cgroup_from_css(wb-\u003ememcg_css);\nmm/memcontrol.c-3981-\tunsigned long intv = msecs_to_jiffies(dirty_expire_interval 10);\n--\nmm/memcontrol.c=4095=struct mem_cgroup mem_cgroup_get_from_id(u64 id)\n--\nmm/memcontrol.c-4098-\tstruct cgroup_subsys_state css;\nmm/memcontrol.c:4099:\tstruct mem_cgroup memcg = NULL;\nmm/memcontrol.c-4100-\n--\nmm/memcontrol.c=4308=static int mem_cgroup_css_online(struct cgroup_subsys_state css)\nmm/memcontrol.c-4309-{\nmm/memcontrol.c:4310:\tstruct mem_cgroup memcg = mem_cgroup_from_css(css);\nmm/memcontrol.c-4311-\tstruct obj_cgroup objcg;\n--\nmm/memcontrol.c=4385=static void mem_cgroup_css_offline(struct cgroup_subsys_state css)\nmm/memcontrol.c-4386-{\nmm/memcontrol.c:4387:\tstruct mem_cgroup memcg = mem_cgroup_from_css(css);\nmm/memcontrol.c-4388-\n--\nmm/memcontrol.c=4412=static void mem_cgroup_css_released(struct cgroup_subsys_state css)\nmm/memcontrol.c-4413-{\nmm/memcontrol.c:4414:\tstruct mem_cgroup memcg = mem_cgroup_from_css(css);\nmm/memcontrol.c-4415-\n--\nmm/memcontrol.c=4420=static void mem_cgroup_css_free(struct cgroup_subsys_state css)\nmm/memcontrol.c-4421-{\nmm/memcontrol.c:4422:\tstruct mem_cgroup memcg = mem_cgroup_from_css(css);\nmm/memcontrol.c-4423-\tint __maybe_unused i;\n--\nmm/memcontrol.c=4457=static void mem_cgroup_css_reset(struct cgroup_subsys_state css)\nmm/memcontrol.c-4458-{\nmm/memcontrol.c:4459:\tstruct mem_cgroup memcg = mem_cgroup_from_css(css);\nmm/memcontrol.c-4460-\n--\nmm/memcontrol.c=4588=static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state css, int cpu)\nmm/memcontrol.c-4589-{\nmm/memcontrol.c:4590:\tstruct mem_cgroup memcg = mem_cgroup_from_css(css);\nmm/memcontrol.c-4591-\tstruct mem_cgroup parent = parent_mem_cgroup(memcg);\n--\nmm/memcontrol.c=4728=static u64 memory_current_read(struct cgroup_subsys_state css,\n--\nmm/memcontrol.c-4730-{\nmm/memcontrol.c:4731:\tstruct mem_cgroup memcg = mem_cgroup_from_css(css);\nmm/memcontrol.c-4732-\n--\nmm/memcontrol.c=4753=static int memory_peak_show(struct seq_file sf, void v)\nmm/memcontrol.c-4754-{\nmm/memcontrol.c:4755:\tstruct mem_cgroup memcg = mem_cgroup_from_css(seq_css(sf));\nmm/memcontrol.c-4756-\n--\nmm/memcontrol.c=4769=static void peak_release(struct kernfs_open_file of)\nmm/memcontrol.c-4770-{\nmm/memcontrol.c:4771:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-4772-\tstruct cgroup_of_peak ofp = of_peak(of);\n--\nmm/memcontrol.c=4783=static ssize_t peak_write(struct kernfs_open_file of, char buf, size_t nbytes,\n--\nmm/memcontrol.c-4788-\tstruct cgroup_of_peak peer_ctx;\nmm/memcontrol.c:4789:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-4790-\tstruct cgroup_of_peak ofp = of_peak(of);\n--\nmm/memcontrol.c=4812=static ssize_t memory_peak_write(struct kernfs_open_file of, char buf,\n--\nmm/memcontrol.c-4814-{\nmm/memcontrol.c:4815:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-4816-\n--\nmm/memcontrol.c=4829=static ssize_t memory_min_write(struct kernfs_open_file of,\n--\nmm/memcontrol.c-4831-{\nmm/memcontrol.c:4832:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-4833-\tunsigned long min;\n--\nmm/memcontrol.c=4852=static ssize_t memory_low_write(struct kernfs_open_file of,\n--\nmm/memcontrol.c-4854-{\nmm/memcontrol.c:4855:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-4856-\tunsigned long low;\n--\nmm/memcontrol.c=4875=static ssize_t memory_high_write(struct kernfs_open_file of,\n--\nmm/memcontrol.c-4877-{\nmm/memcontrol.c:4878:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-4879-\tunsigned int nr_retries = MAX_RECLAIM_RETRIES;\n--\nmm/memcontrol.c=4934=static ssize_t memory_max_write(struct kernfs_open_file of,\n--\nmm/memcontrol.c-4936-{\nmm/memcontrol.c:4937:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-4938-\tunsigned int nr_reclaims = MAX_RECLAIM_RETRIES;\n--\nmm/memcontrol.c=5010=static int memory_events_show(struct seq_file m, void v)\nmm/memcontrol.c-5011-{\nmm/memcontrol.c:5012:\tstruct mem_cgroup memcg = mem_cgroup_from_seq(m);\nmm/memcontrol.c-5013-\n--\nmm/memcontrol.c=5018=static int memory_events_local_show(struct seq_file m, void v)\nmm/memcontrol.c-5019-{\nmm/memcontrol.c:5020:\tstruct mem_cgroup memcg = mem_cgroup_from_seq(m);\nmm/memcontrol.c-5021-\n--\nmm/memcontrol.c=5026=int memory_stat_show(struct seq_file m, void v)\nmm/memcontrol.c-5027-{\nmm/memcontrol.c:5028:\tstruct mem_cgroup memcg = mem_cgroup_from_seq(m);\nmm/memcontrol.c-5029-\tchar buf = kmalloc(SEQ_BUF_SIZE, GFP_KERNEL);\n--\nmm/memcontrol.c=5049=static int memory_numa_stat_show(struct seq_file m, void v)\n--\nmm/memcontrol.c-5051-\tint i;\nmm/memcontrol.c:5052:\tstruct mem_cgroup memcg = mem_cgroup_from_seq(m);\nmm/memcontrol.c-5053-\n--\nmm/memcontrol.c=5079=static int memory_oom_group_show(struct seq_file m, void v)\nmm/memcontrol.c-5080-{\nmm/memcontrol.c:5081:\tstruct mem_cgroup memcg = mem_cgroup_from_seq(m);\nmm/memcontrol.c-5082-\n--\nmm/memcontrol.c=5088=static ssize_t memory_oom_group_write(struct kernfs_open_file of,\n--\nmm/memcontrol.c-5090-{\nmm/memcontrol.c:5091:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-5092-\tint ret, oom_group;\n--\nmm/memcontrol.c=5110=static ssize_t memory_reclaim(struct kernfs_open_file of, char buf,\n--\nmm/memcontrol.c-5112-{\nmm/memcontrol.c:5113:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-5114-\tint ret;\n--\nmm/memcontrol.c=5283=int mem_cgroup_charge_hugetlb(struct folio folio, struct mm_struct mm,\n--\nmm/memcontrol.c-5285-{\nmm/memcontrol.c:5286:\tstruct mem_cgroup memcg = get_mem_cgroup_from_mm(mm);\nmm/memcontrol.c-5287-\tint ret = 0;\n--\nmm/memcontrol.c=5625=void mem_cgroup_sk_free(struct sock sk)\nmm/memcontrol.c-5626-{\nmm/memcontrol.c:5627:\tstruct mem_cgroup memcg = mem_cgroup_from_sk(sk);\nmm/memcontrol.c-5628-\n--\nmm/memcontrol.c=5658=bool mem_cgroup_sk_charge(const struct sock sk, unsigned int nr_pages,\n--\nmm/memcontrol.c-5660-{\nmm/memcontrol.c:5661:\tstruct mem_cgroup memcg = mem_cgroup_from_sk(sk);\nmm/memcontrol.c-5662-\n--\nmm/memcontrol.c=5679=void mem_cgroup_sk_uncharge(const struct sock sk, unsigned int nr_pages)\nmm/memcontrol.c-5680-{\nmm/memcontrol.c:5681:\tstruct mem_cgroup memcg = mem_cgroup_from_sk(sk);\nmm/memcontrol.c-5682-\n--\nmm/memcontrol.c=5912=static u64 swap_current_read(struct cgroup_subsys_state css,\n--\nmm/memcontrol.c-5914-{\nmm/memcontrol.c:5915:\tstruct mem_cgroup memcg = mem_cgroup_from_css(css);\nmm/memcontrol.c-5916-\n--\nmm/memcontrol.c=5920=static int swap_peak_show(struct seq_file sf, void v)\nmm/memcontrol.c-5921-{\nmm/memcontrol.c:5922:\tstruct mem_cgroup memcg = mem_cgroup_from_css(seq_css(sf));\nmm/memcontrol.c-5923-\n--\nmm/memcontrol.c=5928=static ssize_t swap_peak_write(struct kernfs_open_file of, char buf,\n--\nmm/memcontrol.c-5930-{\nmm/memcontrol.c:5931:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-5932-\n--\nmm/memcontrol.c=5943=static ssize_t swap_high_write(struct kernfs_open_file of,\n--\nmm/memcontrol.c-5945-{\nmm/memcontrol.c:5946:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-5947-\tunsigned long high;\n--\nmm/memcontrol.c=5966=static ssize_t swap_max_write(struct kernfs_open_file of,\n--\nmm/memcontrol.c-5968-{\nmm/memcontrol.c:5969:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-5970-\tunsigned long max;\n--\nmm/memcontrol.c=5983=static int swap_events_show(struct seq_file m, void v)\nmm/memcontrol.c-5984-{\nmm/memcontrol.c:5985:\tstruct mem_cgroup memcg = mem_cgroup_from_seq(m);\nmm/memcontrol.c-5986-\n--\nmm/memcontrol.c=6152=static u64 zswap_current_read(struct cgroup_subsys_state css,\n--\nmm/memcontrol.c-6154-{\nmm/memcontrol.c:6155:\tstruct mem_cgroup memcg = mem_cgroup_from_css(css);\nmm/memcontrol.c-6156-\n--\nmm/memcontrol.c=6167=static ssize_t zswap_max_write(struct kernfs_open_file of,\n--\nmm/memcontrol.c-6169-{\nmm/memcontrol.c:6170:\tstruct mem_cgroup memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-6171-\tunsigned long max;\n--\nmm/memcontrol.c=6184=static int zswap_writeback_show(struct seq_file m, void v)\nmm/memcontrol.c-6185-{\nmm/memcontrol.c:6186:\tstruct mem_cgroup memcg = mem_cgroup_from_seq(m);\nmm/memcontrol.c-6187-\n--\nmm/memcontrol.c=6192=static ssize_t zswap_writeback_write(struct kernfs_open_file of,\n--\nmm/memcontrol.c-6194-{\nmm/memcontrol.c:6195:\tstruct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));\nmm/memcontrol.c-6196-\tint zswap_writeback;\n" }
25/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 13191 output: 35 thoughts: 35 Thoughts: Okay, let's dive into this. I need to understand how `memcg` is being allocated, specifically around the `mem_cgroup_css_alloc` function within `mm/memcontrol.c`. I'm going to grab 50 lines on either side of that call to get a good context. This isn't just about the allocation function itself; I want to see how it's called, what precedes it, and what follows. I'm looking for clues about the overall `memcg` lifecycle within memory management. Is it triggered on task creation, fork, or something else? Are there any potential concurrency issues I should be aware of? Are there specific initialization routines that occur before or after allocation? This will give me a better understanding of how the kernel manages memory control groups, and potentially where to begin my investigation to solve an interesting issue.
26/3	2026/09/09 09:06	tool	read-file	0m Args: { "File": "mm/memcontrol.c", "FirstLine": 4250, "LineCount": 50 } Results: { "Contents": "4250:\tstatic struct cgroup_subsys_state * __ref\n4251:\tmem_cgroup_css_alloc(struct cgroup_subsys_state parent_css)\n4252:\t{\n4253:\t\tstruct mem_cgroup parent = mem_cgroup_from_css(parent_css);\n4254:\t\tstruct mem_cgroup memcg, old_memcg;\n4255:\t\tbool memcg_on_dfl = cgroup_subsys_on_dfl(memory_cgrp_subsys);\n4256:\t\n4257:\t\told_memcg = set_active_memcg(parent);\n4258:\t\tmemcg = mem_cgroup_alloc(parent);\n4259:\t\tset_active_memcg(old_memcg);\n4260:\t\tif (IS_ERR(memcg))\n4261:\t\t\treturn ERR_CAST(memcg);\n4262:\t\n4263:\t\tpage_counter_set_high(\u0026memcg-\u003ememory, PAGE_COUNTER_MAX);\n4264:\t#ifdef CONFIG_ZSWAP\n4265:\t\tmemcg-\u003ezswap_max = PAGE_COUNTER_MAX;\n4266:\t\tWRITE_ONCE(memcg-\u003ezswap_writeback, true);\n4267:\t#endif\n4268:\t\tpage_counter_set_high(\u0026memcg-\u003eswap, PAGE_COUNTER_MAX);\n4269:\t\tif (parent) {\n4270:\t\t\tpage_counter_init(\u0026memcg-\u003ememory, \u0026parent-\u003ememory);\n4271:\t\t\tif (memcg_on_dfl)\n4272:\t\t\t\tpage_counter_init_protection(\u0026memcg-\u003ememory, \u0026memcg-\u003ememory_prot,\n4273:\t\t\t\t\t\t\t \u0026parent-\u003ememory_prot);\n4274:\t\t\tpage_counter_init(\u0026memcg-\u003eswap, \u0026parent-\u003eswap);\n4275:\t#ifdef CONFIG_MEMCG_V1\n4276:\t\t\tWRITE_ONCE(memcg-\u003eswappiness, mem_cgroup_swappiness(parent));\n4277:\t\t\tmemcg-\u003ememory.track_failcnt = !memcg_on_dfl;\n4278:\t\t\tmemcg-\u003ememsw.track_failcnt = !memcg_on_dfl;\n4279:\t\t\tWRITE_ONCE(memcg-\u003eoom_kill_disable, READ_ONCE(parent-\u003eoom_kill_disable));\n4280:\t\t\tpage_counter_init(\u0026memcg-\u003ekmem, \u0026parent-\u003ekmem);\n4281:\t\t\tpage_counter_init(\u0026memcg-\u003etcpmem, \u0026parent-\u003etcpmem);\n4282:\t\t\tmemcg-\u003etcpmem.track_failcnt = !memcg_on_dfl;\n4283:\t#endif\n4284:\t\t} else {\n4285:\t\t\tinit_memcg_stats();\n4286:\t\t\tinit_memcg_events();\n4287:\t\t\tpage_counter_init(\u0026memcg-\u003ememory, NULL);\n4288:\t\t\tpage_counter_init_protection(\u0026memcg-\u003ememory, \u0026memcg-\u003ememory_prot,\n4289:\t\t\t\t\t\t NULL);\n4290:\t\t\tpage_counter_init(\u0026memcg-\u003eswap, NULL);\n4291:\t#ifdef CONFIG_MEMCG_V1\n4292:\t\t\tpage_counter_init(\u0026memcg-\u003ekmem, NULL);\n4293:\t\t\tpage_counter_init(\u0026memcg-\u003etcpmem, NULL);\n4294:\t#endif\n4295:\t\t\troot_mem_cgroup = memcg;\n4296:\t\t\treturn \u0026memcg-\u003ecss;\n4297:\t\t}\n4298:\t\n4299:\t\tif (memcg_on_dfl \u0026\u0026 !cgroup_memory_nosocket)\n" }
27/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 14418 output: 33 thoughts: 12 Thoughts: Okay, here's my interpretation of that thought process, assuming I'm deep in the weeds of memory management, likely within a complex system: Checking `mem_cgroup_alloc` Alright, time to dive into `mem_cgroup_alloc`. I need to understand its current state. Is there an issue with memory allocation within a specific cgroup (control group)? The fact that I'm even thinking about this function implies a potential memory pressure situation or perhaps an investigation into resource limits. I might be looking for a bottleneck, a leak, or even just attempting to confirm that allocation is behaving as expected within the defined constraints. I probably have some key questions in mind: are there unexpected allocation spikes? Are the cgroup limits being respected? Are there any obvious errors being returned by the function? Is it behaving in an unexpected manner? The goal is a clear understanding of what’s happening, and whether it's the root of the problem I'm trying to solve, or just a symptom. I'll need to check related metrics to give myself full context.
28/3	2026/09/09 09:06	tool	grepper	0m Args: { "Expression": "mem_cgroup_alloc\\(", "PathPrefix": "mm/memcontrol.c" } Results: { "Output": "mm/memcontrol.c=4173=static void mem_cgroup_free(struct mem_cgroup memcg)\n--\nmm/memcontrol.c-4179-\nmm/memcontrol.c:4180:static struct mem_cgroup mem_cgroup_alloc(struct mem_cgroup parent)\nmm/memcontrol.c-4181-{\n--\nmm/memcontrol.c=4251=mem_cgroup_css_alloc(struct cgroup_subsys_state parent_css)\n--\nmm/memcontrol.c-4257-\told_memcg = set_active_memcg(parent);\nmm/memcontrol.c:4258:\tmemcg = mem_cgroup_alloc(parent);\nmm/memcontrol.c-4259-\tset_active_memcg(old_memcg);\n" }
29/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 14913 output: 35 thoughts: 12 Thoughts: Okay, let's dive into this code. Diving into `mem_cgroup_alloc` Right, let's get into this `mem_cgroup_alloc` function. I need to understand how memory allocation is managed within memory cgroups, so I need a clear view on what this particular function is doing. I'm assuming it's the core of the allocation process. I need to see how it interacts with the underlying kernel memory management, how it tracks resources, and any potential points of contention or optimization. I'm looking for where and how the cgroup accounting comes into play, and what checks are performed to prevent over-commitment or limit violations. I’ll be paying close attention to any locking mechanisms to see how concurrent access is handled, especially in a multi-threaded or multi-process environment. Any error handling or fallback strategies will be of interest too. Ultimately, I need to build a mental map of how this function fits into the overall memory cgroup architecture, and what implications it has for the performance and reliability of containerized workloads.
30/3	2026/09/09 09:06	tool	read-file	0m Args: { "File": "mm/memcontrol.c", "FirstLine": 4180, "LineCount": 40 } Results: { "Contents": "4180:\tstatic struct mem_cgroup mem_cgroup_alloc(struct mem_cgroup parent)\n4181:\t{\n4182:\t\tstruct memcg_vmstats_percpu statc;\n4183:\t\tstruct memcg_vmstats_percpu __percpu pstatc_pcpu;\n4184:\t\tstruct mem_cgroup *memcg;\n4185:\t\tint node, cpu;\n4186:\t\tint __maybe_unused i;\n4187:\t\tlong error;\n4188:\t\n4189:\t\tmemcg = kmem_cache_zalloc(memcg_cachep, GFP_KERNEL);\n4190:\t\tif (!memcg)\n4191:\t\t\treturn ERR_PTR(-ENOMEM);\n4192:\t\n4193:\t\terror = xa_alloc(\u0026mem_cgroup_private_ids, \u0026memcg-\u003eid.id, NULL,\n4194:\t\t\t\t XA_LIMIT(1, MEM_CGROUP_ID_MAX), GFP_KERNEL);\n4195:\t\tif (error)\n4196:\t\t\tgoto fail;\n4197:\t\terror = -ENOMEM;\n4198:\t\n4199:\t\tmemcg-\u003evmstats = kzalloc_obj(struct memcg_vmstats, GFP_KERNEL_ACCOUNT);\n4200:\t\tif (!memcg-\u003evmstats)\n4201:\t\t\tgoto fail;\n4202:\t\n4203:\t\tmemcg-\u003evmstats_percpu = alloc_percpu_gfp(struct memcg_vmstats_percpu,\n4204:\t\t\t\t\t\t\t GFP_KERNEL_ACCOUNT);\n4205:\t\tif (!memcg-\u003evmstats_percpu)\n4206:\t\t\tgoto fail;\n4207:\t\n4208:\t\tif (!memcg1_alloc_events(memcg))\n4209:\t\t\tgoto fail;\n4210:\t\n4211:\t\tpstatc_pcpu = parent ? parent-\u003evmstats_percpu : NULL;\n4212:\t\tfor_each_possible_cpu(cpu) {\n4213:\t\t\tstatc = per_cpu_ptr(memcg-\u003evmstats_percpu, cpu);\n4214:\t\t\tstatc-\u003eparent_pcpu = pstatc_pcpu;\n4215:\t\t\tstatc-\u003evmstats = memcg-\u003evmstats;\n4216:\t\t}\n4217:\t\n4218:\t\tfor_each_node(node)\n4219:\t\t\tif (!alloc_mem_cgroup_per_node_info(memcg, node))\n" }
31/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 15856 output: 37 thoughts: 64 Thoughts: My Initial Thoughts on Memcg Allocation Okay, so I'm looking at how `memcg` is allocated. The code's using `kmem_cache_zalloc` with `memcg_cachep` and `GFP_KERNEL`. That's good; it means the allocation is clean. Everything is zero-initialized right off the bat, which eliminates some potential initial garbage issues and sets a good foundation. Now I need to see how the single pool allocation is working, so I'll check `alloc_pool_single` in `kernel/cgroup/dmem.c`. Let's dig in.
32/3	2026/09/09 09:06	tool	read-file	0m Args: { "File": "kernel/cgroup/dmem.c", "FirstLine": 415, "LineCount": 40 } Results: { "Contents": " 415:\t\tif (!allocpool) {\n 416:\t\t\tpool = kzalloc_obj(pool, GFP_NOWAIT);\n 417:\t\t\tif (!pool)\n 418:\t\t\t\treturn ERR_PTR(-ENOMEM);\n 419:\t\t} else {\n 420:\t\t\tpool = allocpool;\n 421:\t\t\tallocpool = NULL;\n 422:\t\t}\n 423:\t\n 424:\t\tpool-\u003eregion = region;\n 425:\t\tpool-\u003ecs = dmemcs;\n 426:\t\n 427:\t\tif (parent)\n 428:\t\t\tppool = find_cg_pool_locked(parent, region);\n 429:\t\n 430:\t\tpage_counter_init(\u0026pool-\u003ecnt, ppool ? \u0026ppool-\u003ecnt : NULL);\n 431:\t\tpage_counter_init_protection(\u0026pool-\u003ecnt, \u0026pool-\u003eprot,\n 432:\t\t\t\t\t ppool ? \u0026ppool-\u003eprot : NULL);\n 433:\t\treset_all_resource_limits(pool);\n 434:\t\trefcount_set(\u0026pool-\u003eref, 1);\n 435:\t\tkref_get(\u0026region-\u003eref);\n 436:\t\tif (ppool \u0026\u0026 !pool-\u003eparent) {\n 437:\t\t\tpool-\u003eparent = ppool;\n 438:\t\t\tdmemcg_pool_get(ppool);\n 439:\t\t}\n 440:\t\n 441:\t\tlist_add_tail_rcu(\u0026pool-\u003ecss_node, \u0026dmemcs-\u003epools);\n 442:\t\tlist_add_tail(\u0026pool-\u003eregion_node, \u0026region-\u003epools);\n 443:\t\n 444:\t\tif (!parent)\n 445:\t\t\tpool-\u003einited = true;\n 446:\t\telse\n 447:\t\t\tpool-\u003einited = ppool ? ppool-\u003einited : false;\n 448:\t\treturn pool;\n 449:\t}\n 450:\t\n 451:\tstatic struct dmem_cgroup_pool_state \n 452:\tget_cg_pool_locked(struct dmemcg_state dmemcs, struct dmem_cgroup_region region,\n 453:\t\t\t struct dmem_cgroup_pool_state *allocpool)\n 454:\t{\n" }
33/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 16707 output: 34 thoughts: 18 Thoughts: Here's my thought process, as requested: Tracing `allocpool` in `dmem.c` Okay, so I need to figure out the origin of `allocpool` within the `dmem.c` file. This is a common debugging step, especially when dealing with memory management. I need to understand where this function or variable is defined, how it's used, and what its purpose is within the broader `dmem.c` context. My immediate focus is to pinpoint its declaration and any initializations or assignments. This will likely involve a quick scan of the code, looking for the keyword "allocpool" alongside declaration specifiers like `static`, `extern`, or a specific data type (if it's a variable), or as part of a function definition. I'll probably start with a simple search for the exact string within the file. Depending on the code's structure, I might have to consider preprocessor directives like `#define` or typedefs, too, if `allocpool` is being defined or aliased in some indirect way. Essentially, I'm trying to get a map of its usage in `dmem.c`.
34/3	2026/09/09 09:06	tool	grepper	0m Args: { "Expression": "kzalloc\|kmalloc", "PathPrefix": "kernel/cgroup/dmem.c" } Results: { "Output": "kernel/cgroup/dmem.c=277=dmemcs_alloc(struct cgroup_subsys_state parent_css)\nkernel/cgroup/dmem.c-278-{\nkernel/cgroup/dmem.c:279:\tstruct dmemcg_state dmemcs = kzalloc_obj(dmemcs);\nkernel/cgroup/dmem.c-280-\tif (!dmemcs)\n--\nkernel/cgroup/dmem.c=409=alloc_pool_single(struct dmemcg_state dmemcs, struct dmem_cgroup_region region,\n--\nkernel/cgroup/dmem.c-415-\tif (!allocpool) {\nkernel/cgroup/dmem.c:416:\t\tpool = kzalloc_obj(pool, GFP_NOWAIT);\nkernel/cgroup/dmem.c-417-\t\tif (!pool)\n--\nkernel/cgroup/dmem.c=570=dmem_cgroup_register_region(const struct dmem_cgroup_init init,\n--\nkernel/cgroup/dmem.c-585-\nkernel/cgroup/dmem.c:586:\tret = kzalloc_obj(ret);\nkernel/cgroup/dmem.c-587-\tif (!ret) {\n--\nkernel/cgroup/dmem.c=636=get_cg_pool_unlocked(struct dmemcg_state cg, struct dmem_cgroup_region region)\n--\nkernel/cgroup/dmem.c-663-\nkernel/cgroup/dmem.c:664:\t\t\tallocpool = kzalloc_obj(allocpool);\nkernel/cgroup/dmem.c-665-\t\t\tif (allocpool) {\n" }
35/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 17458 output: 46 thoughts: 37 Thoughts: Here's my take on those thoughts: Analyzing Memory Pool States and Hugetlb Considerations Okay, so the `dmem_cgroup_pool_state` structure, which is critical for tracking dynamic memory pool states within cgroups, gets allocated using `kzalloc_obj`. That's good, means it's guaranteed to be zero-initialized. Important for ensuring a clean slate and preventing unexpected behavior based on uninitialized memory. Need to keep that in mind when examining the memory management logic. Now, I should also shift focus and quickly glance at the hugetlb cgroup implementation. Considering the potential interaction between different memory management schemes, understanding how hugetlb fits into this ecosystem is vital. A quick review could provide valuable insights into any cross-dependencies or potential bottlenecks. This is a very targeted examination, looking for potentially shared data structures.
36/3	2026/09/09 09:06	tool	grepper	0m Args: { "Expression": "hugetlb_cgroup_init\|kzalloc\|kmem_cache", "PathPrefix": "mm/hugetlb_cgroup.c" } Results: { "Output": "mm/hugetlb_cgroup.c=79=static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup h_cg)\n--\nmm/hugetlb_cgroup.c-90-\nmm/hugetlb_cgroup.c:91:static void hugetlb_cgroup_init(struct hugetlb_cgroup h_cgroup,\nmm/hugetlb_cgroup.c-92-\t\t\t\tstruct hugetlb_cgroup parent_h_cgroup)\n--\nmm/hugetlb_cgroup.c=139=hugetlb_cgroup_css_alloc(struct cgroup_subsys_state parent_css)\n--\nmm/hugetlb_cgroup.c-144-\nmm/hugetlb_cgroup.c:145:\th_cgroup = kzalloc_flex(h_cgroup, nodeinfo, nr_node_ids);\nmm/hugetlb_cgroup.c-146-\n--\nmm/hugetlb_cgroup.c-162-\t\th_cgroup-\u003enodeinfo[node] =\nmm/hugetlb_cgroup.c:163:\t\t\tkzalloc_node(sizeof(struct hugetlb_cgroup_per_node),\nmm/hugetlb_cgroup.c-164-\t\t\t\t GFP_KERNEL, node_to_alloc);\n--\nmm/hugetlb_cgroup.c-168-\nmm/hugetlb_cgroup.c:169:\thugetlb_cgroup_init(h_cgroup, parent_h_cgroup);\nmm/hugetlb_cgroup.c-170-\treturn \u0026h_cgroup-\u003ecss;\n--\nmm/hugetlb_cgroup.c=857=static void __init __hugetlb_cgroup_file_pre_init(void)\n--\nmm/hugetlb_cgroup.c-861-\tcft_count = hugetlb_max_hstate DFL_TMPL_SIZE + 1; /* add terminator /\nmm/hugetlb_cgroup.c:862:\tdfl_files = kzalloc_objs(struct cftype, cft_count);\nmm/hugetlb_cgroup.c-863-\tBUG_ON(!dfl_files);\nmm/hugetlb_cgroup.c-864-\tcft_count = hugetlb_max_hstate LEGACY_TMPL_SIZE + 1; /* add terminator */\nmm/hugetlb_cgroup.c:865:\tlegacy_files = kzalloc_objs(struct cftype, cft_count);\nmm/hugetlb_cgroup.c-866-\tBUG_ON(!legacy_files);\n" }
37/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 18409 output: 20 thoughts: 31 Thoughts: Okay, here's my take on those thoughts, framed as my own: Thoroughly Reviewing `page_counter_init` Usage Alright, time to get this done right. I need to go through the entire kernel codebase, methodically, and identify every single place where `page_counter_init` is called. It's a critical function, so I can't afford to miss anything. This inspection will be especially focused on verifying how it's being used. Specifically, I'm looking for potential bugs or vulnerabilities resulting from missing the calls. Were there any cases where `page_counter_init` was skipped, leaving memory uninitialized? This needs to be checked. We absolutely cannot have any callers that are using uninitialized memory. That's just asking for trouble and a potentially security flaw. I'll make sure to get this done methodically so I'll be certain I've covered every call.
38/3	2026/09/09 09:06	tool	grepper	0m Args: { "Expression": "page_counter_init\\(" } Results: { "Output": "include/linux/page_counter.h=36=struct page_counter {\n--\ninclude/linux/page_counter.h-70-\ninclude/linux/page_counter.h:71:static inline void page_counter_init(struct page_counter counter,\ninclude/linux/page_counter.h-72-\t\t\t\t struct page_counter parent)\n--\nkernel/cgroup/dmem.c=409=alloc_pool_single(struct dmemcg_state dmemcs, struct dmem_cgroup_region region,\n--\nkernel/cgroup/dmem.c-429-\nkernel/cgroup/dmem.c:430:\tpage_counter_init(\u0026pool-\u003ecnt, ppool ? \u0026ppool-\u003ecnt : NULL);\nkernel/cgroup/dmem.c-431-\tpage_counter_init_protection(\u0026pool-\u003ecnt, \u0026pool-\u003eprot,\n--\nmm/hugetlb_cgroup.c=91=static void hugetlb_cgroup_init(struct hugetlb_cgroup h_cgroup,\n--\nmm/hugetlb_cgroup.c-110-\nmm/hugetlb_cgroup.c:111:\t\tpage_counter_init(fault, fault_parent);\nmm/hugetlb_cgroup.c:112:\t\tpage_counter_init(rsvd, rsvd_parent);\nmm/hugetlb_cgroup.c-113-\n--\nmm/memcontrol.c=4251=mem_cgroup_css_alloc(struct cgroup_subsys_state parent_css)\n--\nmm/memcontrol.c-4269-\tif (parent) {\nmm/memcontrol.c:4270:\t\tpage_counter_init(\u0026memcg-\u003ememory, \u0026parent-\u003ememory);\nmm/memcontrol.c-4271-\t\tif (memcg_on_dfl)\n--\nmm/memcontrol.c-4273-\t\t\t\t\t\t \u0026parent-\u003ememory_prot);\nmm/memcontrol.c:4274:\t\tpage_counter_init(\u0026memcg-\u003eswap, \u0026parent-\u003eswap);\nmm/memcontrol.c-4275-#ifdef CONFIG_MEMCG_V1\n--\nmm/memcontrol.c-4279-\t\tWRITE_ONCE(memcg-\u003eoom_kill_disable, READ_ONCE(parent-\u003eoom_kill_disable));\nmm/memcontrol.c:4280:\t\tpage_counter_init(\u0026memcg-\u003ekmem, \u0026parent-\u003ekmem);\nmm/memcontrol.c:4281:\t\tpage_counter_init(\u0026memcg-\u003etcpmem, \u0026parent-\u003etcpmem);\nmm/memcontrol.c-4282-\t\tmemcg-\u003etcpmem.track_failcnt = !memcg_on_dfl;\n--\nmm/memcontrol.c-4286-\t\tinit_memcg_events();\nmm/memcontrol.c:4287:\t\tpage_counter_init(\u0026memcg-\u003ememory, NULL);\nmm/memcontrol.c-4288-\t\tpage_counter_init_protection(\u0026memcg-\u003ememory, \u0026memcg-\u003ememory_prot,\nmm/memcontrol.c-4289-\t\t\t\t\t NULL);\nmm/memcontrol.c:4290:\t\tpage_counter_init(\u0026memcg-\u003eswap, NULL);\nmm/memcontrol.c-4291-#ifdef CONFIG_MEMCG_V1\nmm/memcontrol.c:4292:\t\tpage_counter_init(\u0026memcg-\u003ekmem, NULL);\nmm/memcontrol.c:4293:\t\tpage_counter_init(\u0026memcg-\u003etcpmem, NULL);\nmm/memcontrol.c-4294-#endif\n" }
39/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 19580 output: 24 thoughts: 84 Thoughts: Investigating Page Counter Initialization and Usage Okay, so I've pinpointed the initialization of these page counters. It seems all the `page_counter_init` calls are concentrated in three key areas: `kernel/cgroup/dmem.c`, `mm/hugetlb_cgroup.c`, and `mm/memcontrol.c`. That's a solid starting point. Now, my next move is to broaden the scope. I need to ensure I'm not missing any other potential usage scenarios or protection mechanisms related to these counters. Time to systematically expand the search. I'll thoroughly examine the broader code base, starting with the obvious place, `mm/page_counter.c`, and then branching out to catch any other functions or structures that might be using `page_counter` directly or indirectly. This comprehensive search is crucial to ensure I have a complete understanding of how these counters are employed throughout the memory management system.
40/3	2026/09/09 09:06	tool	grepper	0m Args: { "Expression": "prot-\u003e", "PathPrefix": "mm/" } Results: { "Output": "mm/page_counter.c=21=static void propagate_protected_usage(struct page_counter c,\n--\nmm/page_counter.c-27-\nmm/page_counter.c:28:\tif (!prot \|\| !prot-\u003eparent)\nmm/page_counter.c-29-\t\treturn;\nmm/page_counter.c-30-\nmm/page_counter.c:31:\tprotected = min(usage, READ_ONCE(prot-\u003emin));\nmm/page_counter.c:32:\told_protected = atomic_long_read(\u0026prot-\u003emin_usage);\nmm/page_counter.c-33-\tif (protected != old_protected) {\nmm/page_counter.c:34:\t\told_protected = atomic_long_xchg(\u0026prot-\u003emin_usage, protected);\nmm/page_counter.c-35-\t\tdelta = protected - old_protected;\nmm/page_counter.c-36-\t\tif (delta)\nmm/page_counter.c:37:\t\t\tatomic_long_add(delta, \u0026prot-\u003eparent-\u003echildren_min_usage);\nmm/page_counter.c-38-\t}\nmm/page_counter.c-39-\nmm/page_counter.c:40:\tprotected = min(usage, READ_ONCE(prot-\u003elow));\nmm/page_counter.c:41:\told_protected = atomic_long_read(\u0026prot-\u003elow_usage);\nmm/page_counter.c-42-\tif (protected != old_protected) {\nmm/page_counter.c:43:\t\told_protected = atomic_long_xchg(\u0026prot-\u003elow_usage, protected);\nmm/page_counter.c-44-\t\tdelta = protected - old_protected;\nmm/page_counter.c-45-\t\tif (delta)\nmm/page_counter.c:46:\t\t\tatomic_long_add(delta, \u0026prot-\u003eparent-\u003echildren_low_usage);\nmm/page_counter.c-47-\t}\n--\nmm/page_counter.c=257=void page_counter_set_min(struct page_counter counter, unsigned long nr_pages)\n--\nmm/page_counter.c-263-\nmm/page_counter.c:264:\tWRITE_ONCE(counter-\u003eprot-\u003emin, nr_pages);\nmm/page_counter.c-265-\n--\nmm/page_counter.c=277=void page_counter_set_low(struct page_counter counter, unsigned long nr_pages)\n--\nmm/page_counter.c-283-\nmm/page_counter.c:284:\tWRITE_ONCE(counter-\u003eprot-\u003elow, nr_pages);\nmm/page_counter.c-285-\n--\nmm/page_counter.c=451=void page_counter_calculate_protection(struct page_counter root,\n--\nmm/page_counter.c-481-\tif (parent == root) {\nmm/page_counter.c:482:\t\tprot-\u003eemin = READ_ONCE(prot-\u003emin);\nmm/page_counter.c:483:\t\tprot-\u003eelow = READ_ONCE(prot-\u003elow);\nmm/page_counter.c-484-\t\treturn;\n--\nmm/page_counter.c-489-\nmm/page_counter.c:490:\tWRITE_ONCE(prot-\u003eemin, effective_protection(usage, parent_usage,\nmm/page_counter.c:491:\t\t\tREAD_ONCE(prot-\u003emin),\nmm/page_counter.c:492:\t\t\tREAD_ONCE(parent_prot-\u003eemin),\nmm/page_counter.c:493:\t\t\tatomic_long_read(\u0026parent_prot-\u003echildren_min_usage),\nmm/page_counter.c-494-\t\t\trecursive_protection));\nmm/page_counter.c-495-\nmm/page_counter.c:496:\tWRITE_ONCE(prot-\u003eelow, effective_protection(usage, parent_usage,\nmm/page_counter.c:497:\t\t\tREAD_ONCE(prot-\u003elow),\nmm/page_counter.c:498:\t\t\tREAD_ONCE(parent_prot-\u003eelow),\nmm/page_counter.c:499:\t\t\tatomic_long_read(\u0026parent_prot-\u003echildren_low_usage),\nmm/page_counter.c-500-\t\t\trecursive_protection));\n" }
41/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 20991 output: 22 thoughts: 22 Thoughts: Here's my summary, as though I'm thinking through this process: Diving into Memory Protection Calculations Okay, so we've got a performance issue, and my gut tells me it's likely related to memory management somehow. Before I go too deep down a rabbit hole, let's start with a focused investigation. I need to zero in on areas where memory protection is calculated, specifically within the context of `mem_cgroup`. That feels like the most likely culprit given the system's behavior. I need to understand how the protection mechanisms are functioning and if there might be a bottleneck, inefficiency, or potential for miscalculation lurking within that code. I'll start with a methodical search for `mem_cgroup_calculate_protection` or anything else directly tied to memory protection calculations within the memory cgroup subsystem. I need to trace the flow, understand the inputs, the logic, and ultimately how this impacts overall memory allocation and performance. This is the right place to start.
42/3	2026/09/09 09:06	tool	grepper	0m Args: { "Expression": "mem_cgroup_calculate_protection" } Results: { "Output": "include/linux/memcontrol.h=546=static inline void mem_cgroup_protection(struct mem_cgroup root,\n--\ninclude/linux/memcontrol.h-560-\t We are special casing this specific case here because\ninclude/linux/memcontrol.h:561:\t * mem_cgroup_calculate_protection is not robust enough to keep\ninclude/linux/memcontrol.h-562-\t * the protection invariant for calculated effective values for\n--\ninclude/linux/memcontrol.h-597-\ninclude/linux/memcontrol.h:598:void mem_cgroup_calculate_protection(struct mem_cgroup root,\ninclude/linux/memcontrol.h-599-\t\t\t\t struct mem_cgroup memcg);\n--\ninclude/linux/memcontrol.h=601=static inline bool mem_cgroup_unprotected(struct mem_cgroup target,\n--\ninclude/linux/memcontrol.h-606-\t protection. The target memcg's protection is ignored, see\ninclude/linux/memcontrol.h:607:\t * mem_cgroup_calculate_protection() and mem_cgroup_protection()\ninclude/linux/memcontrol.h-608-\t /\n--\ninclude/linux/memcontrol.h=1120=static inline void mem_cgroup_protection(struct mem_cgroup root,\n--\ninclude/linux/memcontrol.h-1128-\ninclude/linux/memcontrol.h:1129:static inline void mem_cgroup_calculate_protection(struct mem_cgroup root,\ninclude/linux/memcontrol.h-1130-\t\t\t\t\t\t struct mem_cgroup memcg)\n--\nkernel/cgroup/dmem.c=307=static void\nkernel/cgroup/dmem.c:308:dmem_cgroup_calculate_protection(struct dmem_cgroup_pool_state limit_pool,\nkernel/cgroup/dmem.c-309-\t\t\t\t struct dmem_cgroup_pool_state test_pool)\n--\nkernel/cgroup/dmem.c=356=bool dmem_cgroup_state_evict_valuable(struct dmem_cgroup_pool_state limit_pool,\n--\nkernel/cgroup/dmem.c-387-\nkernel/cgroup/dmem.c:388:\tdmem_cgroup_calculate_protection(limit_pool, test_pool);\nkernel/cgroup/dmem.c-389-\n--\nkernel/cgroup/dmem.c=770=bool dmem_cgroup_below_min(struct dmem_cgroup_pool_state root,\n--\nkernel/cgroup/dmem.c-787-\t /\nkernel/cgroup/dmem.c:788:\tdmem_cgroup_calculate_protection(root, test);\nkernel/cgroup/dmem.c-789-\treturn page_counter_read(\u0026test-\u003ecnt) \u003c= READ_ONCE(test-\u003ecnt.prot-\u003eemin);\n--\nkernel/cgroup/dmem.c=801=bool dmem_cgroup_below_low(struct dmem_cgroup_pool_state root,\n--\nkernel/cgroup/dmem.c-818-\t /\nkernel/cgroup/dmem.c:819:\tdmem_cgroup_calculate_protection(root, test);\nkernel/cgroup/dmem.c-820-\treturn page_counter_read(\u0026test-\u003ecnt) \u003c= READ_ONCE(test-\u003ecnt.prot-\u003eelow);\n--\nmm/memcontrol.c=5197=struct cgroup_subsys memory_cgrp_subsys = {\n--\nmm/memcontrol.c-5215-/\nmm/memcontrol.c:5216: mem_cgroup_calculate_protection - check if memory consumption is in the normal range\nmm/memcontrol.c-5217- * @root: the top ancestor of the sub-tree being checked\n--\nmm/memcontrol.c-5222- /\nmm/memcontrol.c:5223:void mem_cgroup_calculate_protection(struct mem_cgroup root,\nmm/memcontrol.c-5224-\t\t\t\t struct mem_cgroup memcg)\n--\nmm/vmscan.c=4290=static void lru_gen_age_node(struct pglist_data pgdat, struct scan_control sc)\n--\nmm/vmscan.c-4303-\nmm/vmscan.c:4304:\t\tmem_cgroup_calculate_protection(NULL, memcg);\nmm/vmscan.c-4305-\n--\nmm/vmscan.c=5182=static int shrink_one(struct lruvec lruvec, struct scan_control sc)\n--\nmm/vmscan.c-5189-\nmm/vmscan.c:5190:\t/ lru_gen_age_node() called mem_cgroup_calculate_protection() /\nmm/vmscan.c-5191-\tif (mem_cgroup_below_min(NULL, memcg))\n--\nmm/vmscan.c=6259=static void shrink_node_memcgs(pg_data_t pgdat, struct scan_control *sc)\n--\nmm/vmscan.c-6293-\nmm/vmscan.c:6294:\t\tmem_cgroup_calculate_protection(target_memcg, memcg);\nmm/vmscan.c-6295-\n" }
43/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 22627 output: 35 thoughts: 24 Thoughts: Here's a first-person summary, tailored for an expert audience, as requested: Diving into `mem_cgroup_calculate_protection` Alright, time to dig into the guts of memory cgroup protection calculation. The function `mem_cgroup_calculate_protection` in `mm/memcontrol.c` is where the rubber meets the road. I need to understand exactly how the kernel determines the protection level for memory within a cgroup context. This is crucial for performance isolation and fairness, so a deep understanding is paramount. I'm going to start by walking through the code line by line, paying close attention to the variables being used and the logic behind the conditional statements. I need to see how factors like memory pressure, limits, and potentially, OOM scenarios factor into the protection strategy. My goal is to grasp the nuances and potential edge cases within this function. I'm especially keen to spot any potential bottlenecks or areas where further optimization or subtle bugs might exist. Let's see what we've got.
44/3	2026/09/09 09:06	tool	read-file	0m Args: { "File": "mm/memcontrol.c", "FirstLine": 5215, "LineCount": 25 } Results: { "Contents": "5215:\t/*\n5216:\t mem_cgroup_calculate_protection - check if memory consumption is in the normal range\n5217:\t * @root: the top ancestor of the sub-tree being checked\n5218:\t * @memcg: the memory cgroup to check\n5219:\t \n5220:\t WARNING: This function is not stateless! It can only be used as part\n5221:\t * of a top-down tree iteration, not for isolated queries.\n5222:\t /\n5223:\tvoid mem_cgroup_calculate_protection(struct mem_cgroup root,\n5224:\t\t\t\t\t struct mem_cgroup memcg)\n5225:\t{\n5226:\t\tbool recursive_protection =\n5227:\t\t\tcgrp_dfl_root.flags \u0026 CGRP_ROOT_MEMORY_RECURSIVE_PROT;\n5228:\t\n5229:\t\tif (mem_cgroup_disabled())\n5230:\t\t\treturn;\n5231:\t\n5232:\t\tif (!root)\n5233:\t\t\troot = root_mem_cgroup;\n5234:\t\n5235:\t\tpage_counter_calculate_protection(\u0026root-\u003ememory, \u0026memcg-\u003ememory, recursive_protection);\n5236:\t}\n5237:\t\n5238:\tstatic int charge_memcg(struct folio folio, struct mem_cgroup *memcg,\n5239:\t\t\t\tgfp_t gfp)\n" }
45/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 23303 output: 37 thoughts: 27 Thoughts: Here's my take on the thought process, summarized as you requested: Diving into `dmem_cgroup_calculate_protection` Alright, time to dig into the details. I need to understand how dynamic memory protection is calculated within the cgroup framework. Let's start by navigating to the source code for `dmem_cgroup_calculate_protection`. The function's likely definition is within `kernel/cgroup/dmem.c`. That's where I'll find the core logic for this aspect of dynamic memory management within cgroups. I expect this will be a critical piece to understanding the overall memory management strategy.
46/3	2026/09/09 09:06	tool	read-file	0m Args: { "File": "kernel/cgroup/dmem.c", "FirstLine": 305, "LineCount": 25 } Results: { "Contents": " 305:\t}\n 306:\t\n 307:\tstatic void\n 308:\tdmem_cgroup_calculate_protection(struct dmem_cgroup_pool_state limit_pool,\n 309:\t\t\t\t\t struct dmem_cgroup_pool_state test_pool)\n 310:\t{\n 311:\t\tstruct page_counter climit;\n 312:\t\tstruct cgroup_subsys_state css;\n 313:\t\tstruct dmemcg_state dmemcg_iter;\n 314:\t\tstruct dmem_cgroup_pool_state pool, *found_pool;\n 315:\t\n 316:\t\tclimit = \u0026limit_pool-\u003ecnt;\n 317:\t\n 318:\t\trcu_read_lock();\n 319:\t\n 320:\t\tcss_for_each_descendant_pre(css, \u0026limit_pool-\u003ecs-\u003ecss) {\n 321:\t\t\tdmemcg_iter = container_of(css, struct dmemcg_state, css);\n 322:\t\t\tfound_pool = NULL;\n 323:\t\n 324:\t\t\tlist_for_each_entry_rcu(pool, \u0026dmemcg_iter-\u003epools, css_node) {\n 325:\t\t\t\tif (pool-\u003eregion == limit_pool-\u003eregion) {\n 326:\t\t\t\t\tfound_pool = pool;\n 327:\t\t\t\t\tbreak;\n 328:\t\t\t\t}\n 329:\t\t\t}\n" }
47/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 23904 output: 37 thoughts: 18 Thoughts: Here's a summary of my thought process, as if I were analyzing that function: Diving Deeper into `dmem_cgroup_calculate_protection` Okay, so we're looking at the rest of `dmem_cgroup_calculate_protection`. My initial thought is, what are we trying to protect here? Memory, obviously, but what specific scenarios are we addressing? Are we preventing a single cgroup from exhausting shared memory resources, or are we ensuring fairness across multiple cgroups competing for limited resources? Understanding the problem domain is crucial before diving into the implementation details. I need to keep in mind the interaction of this function with other parts of the memory management system, particularly other cgroup-related mechanisms. How does this fit in with the overall protection scheme? Is this a hard limit, a soft limit, or something more nuanced? What other factors affect the protection level? Context is key. I'll need to remember any calls to this to understand the input variables being passed and where these variables originate. I want to look for the core logic within this function. What's the fundamental algorithm for calculating the protection level? Are there any heuristics or optimizations involved? Are there any potentially problematic edge cases, like division by zero or integer overflows, that I should be on the lookout for? I'll be specifically watching for anything that might lead to unexpected behavior in a heavily loaded system. Are there any locks involved? If so, what is the locking granularity, and could we potentially see contention? Is there any non-determinism involved, perhaps due to sampling or averaging, that could make the behavior unpredictable in a high-concurrency environment? I'll also keep an eye out for any calls to other functions or data structures. Are there any dependencies that might make this code difficult to maintain or reason about? Any external configuration or tunable parameters? Finally, I need to make sure I grasp the overall goal of the code to ensure it's doing what's intended.
48/3	2026/09/09 09:06	tool	read-file	0m Args: { "File": "kernel/cgroup/dmem.c", "FirstLine": 330, "LineCount": 25 } Results: { "Contents": " 330:\t\t\tif (!found_pool)\n 331:\t\t\t\tcontinue;\n 332:\t\n 333:\t\t\tpage_counter_calculate_protection(\n 334:\t\t\t\tclimit, \u0026found_pool-\u003ecnt, true);\n 335:\t\n 336:\t\t\tif (found_pool == test_pool)\n 337:\t\t\t\tbreak;\n 338:\t\t}\n 339:\t\trcu_read_unlock();\n 340:\t}\n 341:\t\n 342:\t/*\n 343:\t dmem_cgroup_state_evict_valuable() - Check if we should evict from test_pool\n 344:\t * @limit_pool: The pool for which we hit limits\n 345:\t * @test_pool: The pool for which to test\n 346:\t * @ignore_low: Whether we have to respect low watermarks.\n 347:\t * @ret_hit_low: Pointer to whether it makes sense to consider low watermark.\n 348:\t \n 349:\t This function returns true if we can evict from @test_pool, false if not.\n 350:\t * When returning false and @ignore_low is false, @ret_hit_low may\n 351:\t * be set to true to indicate this function can be retried with @ignore_low\n 352:\t * set to true.\n 353:\t \n 354:\t Return: bool\n" }
49/3	2026/09/09 09:06	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 24767 output: 275 thoughts: 1141 Thoughts: KMSAN Evaluation: Patch Analysis and Justification Okay, let's break this down. My initial assessment of this patch focuses on the core change: refactoring the `struct page_counter` and related structures to split out the protection-related fields into a separate `struct page_counter_protection`. The primary motivation, as I understand it, is memory optimization – specifically, reducing the footprint of page counters for those subsystems (like swap/memsw, kmem, tcpmem, and hugetlb) where protection tracking (the `emin`, `elow`, `min`, `low` fields and their associated atomics) isn't needed. First, I need to methodically check for memory safety issues. We need to be vigilant about uninitialized memory reads and potential information leaks. 1. Structure Field Analysis: `struct page_counter_protection` contains fields like `parent`, `emin`, `elow`, `min_usage`, `children_min_usage`, `low_usage`, `children_low_usage`, `min`, and `low`. 2. Embedding Structures: Where is `page_counter_protection` located? * In `struct mem_cgroup` as `memory_prot`. The key here is the allocation method for `struct mem_cgroup`: it uses `kmem_cache_zalloc`. This is crucial because `kmem_cache_zalloc` guarantees zero-initialization of all fields. * Also embedded in `struct dmem_cgroup_pool_state` as `prot`. Similarly, `struct dmem_cgroup_pool_state` is allocated via `kzalloc_obj` in `alloc_pool_single` / `get_cg_pool_unlocked`, which also initializes all fields to zero. 3. Initialization Process: Let's look at the initialization: * `page_counter_init` sets `counter->prot = NULL;`. * `page_counter_init_protection(&memcg->memory, &memcg->memory_prot, ...)` sets `counter->prot = &memcg->memory_prot`, and sets `prot->parent = parent_prot`, `prot->min = 0`, and `prot->low = 0`. This is the conditional protection setup. 4. User Space Interactions: The next step is examining any interactions with userspace: * `memory_min_show` and `memory_low_show` reads `memcg->memory_prot.min` and `memcg->memory_prot.low` respectively. They then format them as strings via `seq_puts_memcg_tunable`. * `get_resource_low` and `get_resource_min` in `dmem.c` return `u64`. * No direct copying of raw structs or uninitialized buffers to userspace, which is a good sign. 5. Uninitialized Field Reads: Are there cases where uninitialized fields could be read? * In memcg v1, protection is not utilized. This means v1 child cgroups will have protection turned off. The root cgroup calls `page_counter_init_protection` with a `NULL` parent, and for v1 children it's not called, meaning `memcg->memory.prot` remains `NULL`. * If `page_counter_set_min` or `page_counter_set_low` are called, there's a check `if (!counter->prot) return;`. * If `propagate_protected_usage` is called, there's a check `if (!prot \|\| !prot->parent) return;`. * Similarly, `page_counter_calculate_protection` has a check `if (!prot) return;`. * So, these checks are crucial to handle `NULL` cases. * We can see that all memory is zeroed out and initialized properly. 6. Information Leak, Uninitialized Variable Usage, or Padding Read: Is there any way this patch introduces a leak, use of an uninitialized variable, or uninitialized padding read? No, based on this thorough inspection. Now, let's evaluate the criteria from a KMSAN and KASAN perspective. * KASAN vs. KMSAN: Any potential vulnerabilities (e.g., NULL pointer dereferences if `counter->prot` were accidentally accessed when NULL, or out-of-bounds access) should be covered by standard bug detectors, like the KASAN tool. No uninitialized memory is being read or leaked. All allocated memory structures are explicitly zeroed out by allocation functions, guaranteeing that everything starts with a known, safe state
50/3	2026/09/09 09:07	tool	set-results	0m Args: { "KMSANReasoning": "The patch refactors hierarchical protection tracking fields (emin, elow, min, low, and usage counters) out of `struct page_counter` into a separate `struct page_counter_protection` structure.\n\n1. Memory Initialization: All instances of `struct page_counter_protection` are embedded within `struct mem_cgroup` and `struct dmem_cgroup_pool_state`, which are allocated via zero-allocating APIs (`kmem_cache_zalloc` and `kzalloc_obj`). `page_counter_init()` explicitly clears `prot = NULL`, and `page_counter_init_protection()` initializes the protection pointers and limits.\n2. User-space Boundary: No uninitialized bytes, structs with uninitialized padding, or uninitialized buffers are exposed or copied to user space. Only scalar values formatted through seq_file helpers or numerical returns are read.\n3. Bug Detection Suitability: Potential risks in this refactoring would involve NULL pointer dereferences or control flow issues, which are caught by standard kernel checks and KASAN. There are no risks of uninitialized memory reads or information leaks.\n\nTherefore, a dedicated KMSAN fuzzing session is not required.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch refactors hierarchical protection tracking fields (emin, elow, min, low, and usage counters) out of `struct page_counter` into a separate `struct page_counter_protection` structure.\n\n1. Memory Initialization: All instances of `struct page_counter_protection` are embedded within `struct mem_cgroup` and `struct dmem_cgroup_pool_state`, which are allocated via zero-allocating APIs (`kmem_cache_zalloc` and `kzalloc_obj`). `page_counter_init()` explicitly clears `prot = NULL`, and `page_counter_init_protection()` initializes the protection pointers and limits.\n2. User-space Boundary: No uninitialized bytes, structs with uninitialized padding, or uninitialized buffers are exposed or copied to user space. Only scalar values formatted through seq_file helpers or numerical returns are read.\n3. Bug Detection Suitability: Potential risks in this refactoring would involve NULL pointer dereferences or control flow issues, which are caught by standard kernel checks and KASAN. There are no risks of uninitialized memory reads or information leaks.\n\nTherefore, a dedicated KMSAN fuzzing session is not required.", "NeedsKMSAN": false }

LLM Calls Summary:
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Tool Calls Summary:
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