AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/08/12 12:41	flow	patch-triage	2m Args: null Results: { "EnableConfigs": [ "LRU_GEN", "LRU_GEN_ENABLED" ], "FocusSymbols": [ "lru_gen_soft_reclaim", "max_lru_gen_memcg", "try_to_free_mem_cgroup_pages" ], "KMSANReasoning": "The patch modifies the Multi-Gen LRU (MGLRU) page reclaim logic in `mm/vmscan.c`. It introduces batching for LRU list operations, modifies the swappiness-based type selection with a quadratic boost, and adjusts the aging and isolation heuristics. These changes manipulate internal kernel structures (`struct folio`, LRU lists) and do not introduce new allocations, user-space copies, or complex data structures where uninitialized memory could be exposed. Any potential bugs introduced by this patch would be logic errors, use-after-free, out-of-bounds accesses, or list corruptions, which are effectively detected by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory usage or info-leaks that would require KMSAN.", "NeedsKMSAN": false, "Reasoning": "The patch modifies the core Multi-Gen LRU (MGLRU) memory reclaim logic, specifically the eviction path, folio scanning, and aging heuristics. It introduces batching in `inc_min_seq` and changes how `get_type_to_scan` calculates the preferred reclaim type based on swappiness. These are significant functional changes to memory management that should be fuzzed to ensure stability under memory pressure.", "WorthFuzzing": true }
1/1	2026/08/12 12:41	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 943b18674ea159c14b89773e488c8d73e383fad9\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Wed Aug 12 12:41:48 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/mm/vmscan.c b/mm/vmscan.c\nindex be6bd26e8c578..09535d9bded5c 100644\n--- a/mm/vmscan.c\n+++ b/mm/vmscan.c\n@@ -191,8 +191,20 @@ struct scan_control {\n \t\t\tprefetchw(\u0026prev-\u003e_field);\t\t\t\\\n \t\t}\t\t\t\t\t\t\t\\\n \t} while (0)\n+#define prefetchw_next_lru_folio(_folio, _base, _field)\t\t\t\\\n+\tdo {\t\t\t\t\t\t\t\t\\\n+\t\tif ((_folio)-\u003elru.next != _base) {\t\t\t\\\n+\t\t\tstruct folio next;\t\t\t\t\\\n+\t\t\t\t\t\t\t\t\t\\\n+\t\t\tnext = list_entry((_folio)-\u003elru.next,\t\t\\\n+\t\t\t\t\tstruct folio, lru);\t\t\\\n+\t\t\tprefetchw(\u0026next-\u003e_field);\t\t\t\\\n+\t\t}\t\t\t\t\t\t\t\\\n+\t} while (0)\n+\n #else\n #define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0)\n+#define prefetchw_next_lru_folio(_folio, _base, _field) do { } while (0)\n #endif\n \n /\n@@ -270,6 +282,13 @@ static inline bool is_exec_file_folio(const struct folio folio,\n \treturn vma_flags_test(vma_flags, VMA_EXEC_BIT) \u0026\u0026 folio_is_file_lru(folio);\n }\n \n+/ See get_type_to_scan(): these values always select FILE or ANON /\n+static inline bool is_extreme_swappiness(int swappiness)\n+{\n+\treturn swappiness \u003c= MIN_SWAPPINESS + 1 \|\|\n+\t swappiness \u003e= MAX_SWAPPINESS;\n+}\n+\n static void set_task_reclaim_state(struct task_struct task,\n \t\t\t\t struct reclaim_state rs)\n {\n@@ -3296,20 +3315,21 @@ static int folio_update_gen(struct folio folio, int gen, const vma_flags_t vma\n }\n \n / protect pages accessed multiple times through file descriptors /\n-static int folio_inc_gen(struct lruvec lruvec, struct folio folio)\n+static int __folio_inc_gen(struct folio folio, int old_gen, bool increased)\n {\n-\tint type = folio_is_file_lru(folio);\n-\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\n-\tint new_gen, old_gen = lru_gen_from_seq(lrugen-\u003emin_seq[type]);\n \tunsigned long new_flags, old_flags = READ_ONCE(folio-\u003eflags.f);\n+\tint new_gen;\n \n \tVM_WARN_ON_ONCE_FOLIO(!(old_flags \u0026 LRU_GEN_MASK), folio);\n \n \tdo {\n \t\tnew_gen = ((old_flags \u0026 LRU_GEN_MASK) \u003e\u003e LRU_GEN_PGOFF) - 1;\n \t\t/* folio_update_gen() has promoted this page? /\n-\t\tif (new_gen \u003e= 0 \u0026\u0026 new_gen != old_gen)\n+\t\tif (new_gen \u003e= 0 \u0026\u0026 new_gen != old_gen) {\n+\t\t\tif (increased)\n+\t\t\t\tincreased = false;\n \t\t\treturn new_gen;\n+\t\t}\n \n \t\tnew_gen = (old_gen + 1) % MAX_NR_GENS;\n \n@@ -3317,8 +3337,21 @@ static int folio_inc_gen(struct lruvec lruvec, struct folio folio)\n \t\tnew_flags \|= (new_gen + 1UL) \u003c\u003c LRU_GEN_PGOFF;\n \t} while (!try_cmpxchg(\u0026folio-\u003eflags.f, \u0026old_flags, new_flags));\n \n-\tlru_gen_update_size(lruvec, folio, old_gen, new_gen);\n+\tif (increased)\n+\t\tincreased = true;\n+\treturn new_gen;\n+}\n+\n+static int folio_inc_gen(struct lruvec lruvec, struct folio folio)\n+{\n+\tint type = folio_is_file_lru(folio);\n+\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\n+\tint new_gen, old_gen = lru_gen_from_seq(lrugen-\u003emin_seq[type]);\n+\tbool gen_increased;\n \n+\tnew_gen = __folio_inc_gen(folio, old_gen, \u0026gen_increased);\n+\tif (gen_increased)\n+\t\tlru_gen_update_size(lruvec, folio, old_gen, new_gen);\n \treturn new_gen;\n }\n \n@@ -3897,13 +3930,27 @@ static void clear_mm_walk(void)\n \t\tkfree(walk);\n }\n \n+static inline void flush_lru_batch(struct list_head head, struct list_head batch_end,\n+\t\t\t\t struct list_head dst)\n+{\n+\tLIST_HEAD(movable);\n+\n+\tif (!batch_end)\n+\t\treturn;\n+\n+\tlist_cut_position(\u0026movable, head, batch_end);\n+\tlist_splice_tail_init(\u0026movable, dst);\n+\tbatch_end = NULL;\n+}\n+\n static bool inc_min_seq(struct lruvec lruvec, int type, int swappiness)\n {\n \tint zone;\n-\tint remaining = MAX_LRU_BATCH;\n+\tint remaining = MAX_LRU_BATCH / (is_extreme_swappiness(swappiness) ? 2 : 8);\n \tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\n \tint hist = lru_hist_from_seq(lrugen-\u003emin_seq[type]);\n \tint new_gen, old_gen = lru_gen_from_seq(lrugen-\u003emin_seq[type]);\n+\tint target_gen = (old_gen + 1) % MAX_NR_GENS;\n \n \t/ For file type, skip the check if swappiness is anon only /\n \tif (type \u0026\u0026 (swappiness == SWAPPINESS_ANON_ONLY))\n@@ -3915,33 +3962,55 @@ static bool inc_min_seq(struct lruvec lruvec, int type, int swappiness)\n \n \t/* prevent cold/hot inversion if the type is evictable /\n \tfor (zone = 0; zone \u003c MAX_NR_ZONES; zone++) {\n+\t\tstruct list_head target_list = \u0026lrugen-\u003efolios[target_gen][type][zone];\n \t\tstruct list_head head = \u0026lrugen-\u003efolios[old_gen][type][zone];\n+\t\tunsigned long protected[MAX_NR_TIERS] = {}, delta = 0;\n+\t\tstruct list_head pos = head-\u003enext;\n+\t\tstruct list_head batch_end = NULL;\n \n-\t\twhile (!list_empty(head)) {\n-\t\t\tstruct folio folio = lru_to_folio(head);\n+\t\twhile (pos != head) {\n+\t\t\tstruct folio folio = list_entry(pos, struct folio, lru);\n+\t\t\tlong nr_pages = folio_nr_pages(folio);\n \t\t\tint refs = folio_lru_refs(folio);\n \t\t\tbool workingset = folio_test_workingset(folio);\n+\t\t\tbool gen_increased;\n \n \t\t\tVM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio);\n \t\t\tVM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);\n \t\t\tVM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);\n \t\t\tVM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);\n \n-\t\t\tnew_gen = folio_inc_gen(lruvec, folio);\n-\t\t\tlist_move_tail(\u0026folio-\u003elru, \u0026lrugen-\u003efolios[new_gen][type][zone]);\n+\t\t\tprefetchw_next_lru_folio(folio, head, flags);\n+\t\t\tpos = pos-\u003enext;\n+\t\t\tnew_gen = __folio_inc_gen(folio, old_gen, \u0026gen_increased);\n+\t\t\tif (gen_increased) {\n+\t\t\t\tdelta += nr_pages;\n+\t\t\t\tbatch_end = \u0026folio-\u003elru;\n \n-\t\t\t/ don't count the workingset being lazily promoted /\n-\t\t\tif (refs + workingset != BIT(LRU_REFS_WIDTH) + 1) {\n-\t\t\t\tint tier = lru_tier_from_refs(refs, workingset);\n-\t\t\t\tint delta = folio_nr_pages(folio);\n+\t\t\t\t/ don't count the workingset being lazily promoted /\n+\t\t\t\tif (refs + workingset != BIT(LRU_REFS_WIDTH) + 1) {\n+\t\t\t\t\tint tier = lru_tier_from_refs(refs, workingset);\n \n-\t\t\t\tWRITE_ONCE(lrugen-\u003eprotected[hist][type][tier],\n-\t\t\t\t\t lrugen-\u003eprotected[hist][type][tier] + delta);\n+\t\t\t\t\tprotected[tier] += nr_pages;\n+\t\t\t\t}\n+\t\t\t} else {\n+\t\t\t\tflush_lru_batch(head, \u0026batch_end, target_list);\n+\t\t\t\tlist_move(\u0026folio-\u003elru, \u0026lrugen-\u003efolios[new_gen][type][zone]);\n \t\t\t}\n-\n \t\t\tif (!--remaining)\n-\t\t\t\treturn false;\n+\t\t\t\tbreak;\n \t\t}\n+\t\tflush_lru_batch(head, \u0026batch_end, target_list);\n+\n+\t\tWRITE_ONCE(lrugen-\u003enr_pages[old_gen][type][zone],\n+\t\t\t lrugen-\u003enr_pages[old_gen][type][zone] - delta);\n+\t\tWRITE_ONCE(lrugen-\u003enr_pages[target_gen][type][zone],\n+\t\t\t lrugen-\u003enr_pages[target_gen][type][zone] + delta);\n+\t\tfor (int tier = 0; tier \u003c MAX_NR_TIERS; tier++)\n+\t\t\tWRITE_ONCE(lrugen-\u003eprotected[hist][type][tier],\n+\t\t\t\t lrugen-\u003eprotected[hist][type][tier] + protected[tier]);\n+\t\tif (!remaining)\n+\t\t\treturn false;\n \t}\n done:\n \treset_ctrl_pos(lruvec, type, true);\n@@ -4151,20 +4220,28 @@ static void set_initial_priority(struct pglist_data pgdat, struct scan_control\n \tsc-\u003epriority = clamp(priority, DEF_PRIORITY / 2, DEF_PRIORITY);\n }\n \n+static inline unsigned long lruvec_gen_size(struct lru_gen_folio lrugen,\n+\t\tint type, unsigned long seq)\n+{\n+\tint gen = lru_gen_from_seq(seq);\n+\tunsigned long size = 0;\n+\n+\tfor (int zone = 0; zone \u003c MAX_NR_ZONES; zone++)\n+\t\tsize += max(READ_ONCE(lrugen-\u003enr_pages[gen][type][zone]), 0L);\n+\treturn size;\n+}\n+\n static unsigned long lruvec_evictable_size(struct lruvec lruvec, int swappiness)\n {\n-\tint gen, type, zone;\n+\tint type;\n \tunsigned long seq, total = 0;\n \tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\n \tDEFINE_MAX_SEQ(lruvec);\n \tDEFINE_MIN_SEQ(lruvec);\n \n \tfor_each_evictable_type(type, swappiness) {\n-\t\tfor (seq = min_seq[type]; seq \u003c= max_seq; seq++) {\n-\t\t\tgen = lru_gen_from_seq(seq);\n-\t\t\tfor (zone = 0; zone \u003c MAX_NR_ZONES; zone++)\n-\t\t\t\ttotal += max(READ_ONCE(lrugen-\u003enr_pages[gen][type][zone]), 0L);\n-\t\t}\n+\t\tfor (seq = min_seq[type]; seq \u003c= max_seq; seq++)\n+\t\t\ttotal += lruvec_gen_size(lrugen, type, seq);\n \t}\n \n \treturn total;\n@@ -4728,7 +4805,8 @@ static bool isolate_folio(struct lruvec lruvec, struct folio folio, struct sca\n \n static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec,\n \t\t struct scan_control sc, int type, int tier,\n-\t\t struct list_head list, int isolatedp)\n+\t\t struct list_head list, int isolatedp,\n+\t\t bool exhausted)\n {\n \tint i;\n \tint gen;\n@@ -4739,12 +4817,15 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec,\n \tint skipped = 0;\n \tunsigned long remaining = nr_to_scan;\n \tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\n+\tbool early_stop = false;\n \n \tVM_WARN_ON_ONCE(nr_to_scan \u003e MAX_LRU_BATCH);\n \tVM_WARN_ON_ONCE(!list_empty(list));\n \n-\tif (get_nr_gens(lruvec, type) == MIN_NR_GENS)\n+\tif (get_nr_gens(lruvec, type) == MIN_NR_GENS) {\n+\t\texhausted = true;\n \t\treturn 0;\n+\t}\n \n \tgen = lru_gen_from_seq(lrugen-\u003emin_seq[type]);\n \n@@ -4775,8 +4856,10 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec,\n \t\t\t\tskipped_zone += delta;\n \t\t\t}\n \n-\t\t\tif (!--remaining \|\| max(isolated, skipped_zone) \u003e= MIN_LRU_BATCH)\n+\t\t\tif (!--remaining \|\| max(isolated, skipped_zone) \u003e= MIN_LRU_BATCH) {\n+\t\t\t\tearly_stop = true;\n \t\t\t\tbreak;\n+\t\t\t}\n \t\t}\n \n \t\tif (skipped_zone) {\n@@ -4785,8 +4868,10 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec,\n \t\t\tskipped += skipped_zone;\n \t\t}\n \n-\t\tif (!remaining \|\| isolated \u003e= MIN_LRU_BATCH)\n+\t\tif (!remaining \|\| isolated \u003e= MIN_LRU_BATCH) {\n+\t\t\tearly_stop = true;\n \t\t\tbreak;\n+\t\t}\n \t}\n \n \titem = PGSCAN_KSWAPD + reclaimer_offset(sc);\n@@ -4797,6 +4882,13 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec,\n \t\t\t\tscanned, skipped, isolated,\n \t\t\t\ttype ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);\n \n+\t/\n+\t If we didn't stop early, all reclaimable folios in the current\n+\t * generation have been scanned. We are exhausted if this is the last\n+\t * reclaimable generation.\n+\t /\n+\texhausted = !early_stop \u0026\u0026\n+\t\t lrugen-\u003emin_seq[type] + MIN_NR_GENS == lrugen-\u003emax_seq;\n \tisolatedp = isolated;\n \treturn scanned;\n }\n@@ -4824,51 +4916,90 @@ static int get_tier_idx(struct lruvec lruvec, int type)\n static int get_type_to_scan(struct lruvec lruvec, int swappiness)\n {\n \tstruct ctrl_pos sp, pv = {};\n+\tint anon_gain, file_gain;\n \n \tif (swappiness \u003c= MIN_SWAPPINESS + 1)\n \t\treturn LRU_GEN_FILE;\n \n \tif (swappiness \u003e= MAX_SWAPPINESS)\n \t\treturn LRU_GEN_ANON;\n+\n+\t/\n+\t * Apply a quadratic boost based on the distance from the neutral\n+\t * balance point (swappiness = MAX_SWAPPINESS / 2).\n+\t \n+\t A linear weight is easily overwhelmed by historical refault cost\n+\t * when swappiness deviates from neutral. The quadratic scaling\n+\t * amplifies the weight of the preferred type smoothly.\n+\t /\n+\tif (swappiness \u003c MAX_SWAPPINESS / 2) {\n+\t\tint delta = (MAX_SWAPPINESS / 2) - swappiness;\n+\t\tint boost = (delta delta) \u003e\u003e 4;\n+\n+\t\tanon_gain = swappiness;\n+\t\tfile_gain = (MAX_SWAPPINESS - swappiness) + boost;\n+\t} else {\n+\t\tint delta = swappiness - (MAX_SWAPPINESS / 2);\n+\t\tint boost = (delta * delta) \u003e\u003e 4;\n+\n+\t\tanon_gain = swappiness + boost;\n+\t\tfile_gain = MAX_SWAPPINESS - swappiness;\n+\t}\n+\n \t/\n \t Compare the sum of all tiers of anon with that of file to determine\n \t * which type to scan.\n \t /\n-\tread_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, swappiness, \u0026sp);\n-\tread_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, MAX_SWAPPINESS - swappiness, \u0026pv);\n+\tread_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, anon_gain, \u0026sp);\n+\tread_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, file_gain, \u0026pv);\n \n \treturn positive_ctrl_err(\u0026sp, \u0026pv);\n }\n \n+static inline bool is_single_type_reclaim(int swappiness)\n+{\n+\treturn swappiness == MIN_SWAPPINESS \|\|\n+\t swappiness == SWAPPINESS_ANON_ONLY;\n+}\n+\n static int isolate_folios(unsigned long nr_to_scan, struct lruvec lruvec,\n \t\t\t struct scan_control sc, int swappiness,\n \t\t\t struct list_head list, int isolated,\n \t\t\t int isolate_type, int isolate_scanned)\n {\n-\tint i;\n-\tint total_scanned = 0;\n+\tbool type_fallback_allowed = !is_single_type_reclaim(swappiness);\n \tint type = get_type_to_scan(lruvec, swappiness);\n+\tint total_scanned = 0, scanned, tier;\n+\tbool exhausted, tried = false;\n \n-\tfor_each_evictable_type(i, swappiness) {\n-\t\tint scanned;\n-\t\tint tier = get_tier_idx(lruvec, type);\n+retry:\n+\ttier = get_tier_idx(lruvec, type);\n+\tscanned = scan_folios(nr_to_scan, lruvec, sc,\n+\t\t\t type, tier, list, isolated, \u0026exhausted);\n \n-\t\tscanned = scan_folios(nr_to_scan, lruvec, sc,\n-\t\t\t\t type, tier, list, isolated);\n+\ttotal_scanned += scanned;\n+\tif (isolated) {\n+\t\tisolate_type = type;\n+\t\tisolate_scanned = scanned;\n+\t\treturn total_scanned;\n+\t}\n \n-\t\ttotal_scanned += scanned;\n-\t\tif (isolated) {\n-\t\t\tisolate_type = type;\n-\t\t\tisolate_scanned = scanned;\n-\t\t\tbreak;\n-\t\t}\n-\t\t/\n-\t\t * If scanned \u003e 0 and isolated == 0, avoid falling back to the\n-\t\t * other type, as this type remains sufficient. Falling back\n-\t\t * too readily can disrupt the positive_ctrl_err() bias.\n-\t\t /\n-\t\tif (!scanned)\n-\t\t\ttype = !type;\n+\t/\n+\t * We are running out of the current reclaim type. Fall back to\n+\t * the other type if allowed.\n+\t /\n+\tif (exhausted \u0026\u0026 type_fallback_allowed) {\n+\t\ttype = !type;\n+\t\ttype_fallback_allowed = false;\n+\t\tgoto retry;\n+\t}\n+\t/\n+\t * We are not exhausted, but failed to isolate any folios due to\n+\t * races. Give this type one more chance to avoid a larger loop.\n+\t /\n+\tif (!exhausted \u0026\u0026 !tried) {\n+\t\ttried = true;\n+\t\tgoto retry;\n \t}\n \n \treturn total_scanned;\n@@ -4970,21 +5101,67 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec lruvec,\n \treturn scanned;\n }\n \n+static bool lru_gen_imbalanced(struct lruvec lruvec, unsigned long max_seq,\n+\t\tstruct scan_control sc, int type, int swappiness)\n+{\n+\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\n+\tunsigned long young = 0, old = 0, lag = 0;\n+\tunsigned long inactive_ratio, gb;\n+\tDEFINE_MIN_SEQ(lruvec);\n+\n+\t/ we still have enough generations to reclaim /\n+\tif (min_seq[type] + MIN_NR_GENS \u003c max_seq)\n+\t\treturn false;\n+\n+\t/\n+\t * Trigger aging if the preferred type is running low on reclaimable\n+\t * folios, provided the generation lag of the other type remains small\n+\t * enough that inc_min_seq() introduces negligible overhead\n+\t /\n+\tfor (unsigned long seq = min_seq[type]; seq \u003c= max_seq; seq++) {\n+\t\tunsigned long size = lruvec_gen_size(lrugen, type, seq);\n+\n+\t\tif (seq + MIN_NR_GENS \u003e max_seq)\n+\t\t\tyoung += size;\n+\t\telse\n+\t\t\told += size;\n+\t}\n+\tif (min_seq[!type] + MAX_NR_GENS == max_seq + 1)\n+\t\tlag += lruvec_gen_size(lrugen, !type, min_seq[!type]);\n+\n+\t/\n+\t * Borrow the adaptive ratio from inactive_is_low(), and scale\n+\t * it by sqrt(MAX_NR_GENS) to make aging less aggressive\n+\t /\n+\tgb = (young + old) \u003e\u003e (30 - PAGE_SHIFT);\n+\tinactive_ratio = gb ? int_sqrt(10 gb * MAX_NR_GENS) : MAX_NR_GENS;\n+\treturn young \u003e old * inactive_ratio \u0026\u0026 (lag \u003c MAX_LRU_BATCH \|\|\n+\t (is_extreme_swappiness(swappiness) \u0026\u0026 sc-\u003epriority \u003e 2));\n+}\n+\n static bool should_run_aging(struct lruvec lruvec, unsigned long max_seq,\n \t\t\t struct scan_control sc, int swappiness)\n {\n+\tint type = get_type_to_scan(lruvec, swappiness);\n \tDEFINE_MIN_SEQ(lruvec);\n \n-\t/* have to run aging, since eviction is not possible anymore /\n-\tif (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS \u003e max_seq)\n+\t/ run aging if the preferred type is exhausted /\n+\tif (min_seq[type] + MIN_NR_GENS \u003e max_seq)\n \t\treturn true;\n \n-\t/ try to avoid aging, do gentle reclaim at the default priority /\n-\tif (sc-\u003epriority == DEF_PRIORITY)\n+\t/\n+\t * Try to avoid aging by doing gentle reclaim at the default\n+\t * priority. Skip gentle reclaim for extreme swappiness.\n+\t /\n+\tif (sc-\u003epriority == DEF_PRIORITY \u0026\u0026 !is_extreme_swappiness(swappiness))\n \t\treturn false;\n \n \t/ better to run aging even though eviction is still possible /\n-\treturn evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq;\n+\tif (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq)\n+\t\treturn true;\n+\n+\t/ Run aging if the preferred type is severely imbalanced across gens /\n+\treturn lru_gen_imbalanced(lruvec, max_seq, sc, type, swappiness);\n }\n \n static long get_nr_to_scan(struct lruvec lruvec, struct scan_control *sc,\n" }
2/1	2026/08/12 12:41	agent	patch-evaluator	2m Model: best-expensive Args: null Results: { "EnableConfigs": [ "LRU_GEN", "LRU_GEN_ENABLED" ], "FocusSymbols": [ "lru_gen_soft_reclaim", "max_lru_gen_memcg", "try_to_free_mem_cgroup_pages" ], "Reasoning": "The patch modifies the core Multi-Gen LRU (MGLRU) memory reclaim logic, specifically the eviction path, folio scanning, and aging heuristics. It introduces batching in `inc_min_seq` and changes how `get_type_to_scan` calculates the preferred reclaim type based on swappiness. These are significant functional changes to memory management that should be fuzzed to ensure stability under memory pressure.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer. Your job is to review a provided patch series and determine if it makes functional changes to the kernel that should be fuzzed. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively use your code access tools to examine the actual source code and confirm any assumptions. Return WorthFuzzing=false if the patch only contains: - Modifications to Documentation/, Kconfig files, or code comments. - Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints. - Changes to numeric constants or macros that do not functionally alter execution flow. - Code paths that are impossible to reach in virtualized environments like GCE or QEMU, even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim). - Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU. - Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove) that are executed only during PCI hot-unplug or sysfs driver unbind operations. If it modifies reachable core kernel logic, drivers, or architectures, use your code search tools to verify the code can be executed, then return WorthFuzzing=true. When returning WorthFuzzing=true, you MUST ALSO: 1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols. Avoid listing generic hot-path functions to prevent skewed test distributions. Prefer non-static, non-inlined API entrypoint functions over internal static helper functions (which are inlined by the compiler and do not have distinct symbol addresses). 2. Identify any specific CONFIG_ options required to properly test this new/modified feature. Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions. Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs output array, and DO NOT add a 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4"). Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: For your convenience, here is the diff of the changes: commit 943b18674ea159c14b89773e488c8d73e383fad9 Author: syz-cluster <triage@syzkaller.com> Date: Wed Aug 12 12:41:48 2026 +0000 syz-cluster: applied patch under review diff --git a/mm/vmscan.c b/mm/vmscan.c index be6bd26e8c578..09535d9bded5c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -191,8 +191,20 @@ struct scan_control { prefetchw(&prev->_field); \ } \ } while (0) +#define prefetchw_next_lru_folio(_folio, _base, _field) \ + do { \ + if ((_folio)->lru.next != _base) { \ + struct folio next; \ + \ + next = list_entry((_folio)->lru.next, \ + struct folio, lru); \ + prefetchw(&next->_field); \ + } \ + } while (0) + #else #define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0) +#define prefetchw_next_lru_folio(_folio, _base, _field) do { } while (0) #endif / @@ -270,6 +282,13 @@ static inline bool is_exec_file_folio(const struct folio folio, return vma_flags_test(vma_flags, VMA_EXEC_BIT) && folio_is_file_lru(folio); } +/ See get_type_to_scan(): these values always select FILE or ANON / +static inline bool is_extreme_swappiness(int swappiness) +{ + return swappiness <= MIN_SWAPPINESS + 1 \|\| + swappiness >= MAX_SWAPPINESS; +} + static void set_task_reclaim_state(struct task_struct task, struct reclaim_state rs) { @@ -3296,20 +3315,21 @@ static int folio_update_gen(struct folio folio, int gen, const vma_flags_t vma } / protect pages accessed multiple times through file descriptors / -static int folio_inc_gen(struct lruvec lruvec, struct folio folio) +static int __folio_inc_gen(struct folio folio, int old_gen, bool increased) { - int type = folio_is_file_lru(folio); - struct lru_gen_folio lrugen = &lruvec->lrugen; - int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); unsigned long new_flags, old_flags = READ_ONCE(folio->flags.f); + int new_gen; VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio); do { new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; /* folio_update_gen() has promoted this page? / - if (new_gen >= 0 && new_gen != old_gen) + if (new_gen >= 0 && new_gen != old_gen) { + if (increased) + increased = false; return new_gen; + } new_gen = (old_gen + 1) % MAX_NR_GENS; @@ -3317,8 +3337,21 @@ static int folio_inc_gen(struct lruvec lruvec, struct folio folio) new_flags \|= (new_gen + 1UL) << LRU_GEN_PGOFF; } while (!try_cmpxchg(&folio->flags.f, &old_flags, new_flags)); - lru_gen_update_size(lruvec, folio, old_gen, new_gen); + if (increased) + increased = true; + return new_gen; +} + +static int folio_inc_gen(struct lruvec lruvec, struct folio folio) +{ + int type = folio_is_file_lru(folio); + struct lru_gen_folio lrugen = &lruvec->lrugen; + int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); + bool gen_increased; + new_gen = __folio_inc_gen(folio, old_gen, &gen_increased); + if (gen_increased) + lru_gen_update_size(lruvec, folio, old_gen, new_gen); return new_gen; } @@ -3897,13 +3930,27 @@ static void clear_mm_walk(void) kfree(walk); } +static inline void flush_lru_batch(struct list_head head, struct list_head batch_end, + struct list_head dst) +{ + LIST_HEAD(movable); + + if (!batch_end) + return; + + list_cut_position(&movable, head, batch_end); + list_splice_tail_init(&movable, dst); + batch_end = NULL; +} + static bool inc_min_seq(struct lruvec lruvec, int type, int swappiness) { int zone; - int remaining = MAX_LRU_BATCH; + int remaining = MAX_LRU_BATCH / (is_extreme_swappiness(swappiness) ? 2 : 8); struct lru_gen_folio lrugen = &lruvec->lrugen; int hist = lru_hist_from_seq(lrugen->min_seq[type]); int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); + int target_gen = (old_gen + 1) % MAX_NR_GENS; / For file type, skip the check if swappiness is anon only / if (type && (swappiness == SWAPPINESS_ANON_ONLY)) @@ -3915,33 +3962,55 @@ static bool inc_min_seq(struct lruvec lruvec, int type, int swappiness) /* prevent cold/hot inversion if the type is evictable / for (zone = 0; zone < MAX_NR_ZONES; zone++) { + struct list_head target_list = &lrugen->folios[target_gen][type][zone]; struct list_head head = &lrugen->folios[old_gen][type][zone]; + unsigned long protected[MAX_NR_TIERS] = {}, delta = 0; + struct list_head pos = head->next; + struct list_head batch_end = NULL; - while (!list_empty(head)) { - struct folio folio = lru_to_folio(head); + while (pos != head) { + struct folio folio = list_entry(pos, struct folio, lru); + long nr_pages = folio_nr_pages(folio); int refs = folio_lru_refs(folio); bool workingset = folio_test_workingset(folio); + bool gen_increased; VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio); VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio); VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio); VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio); - new_gen = folio_inc_gen(lruvec, folio); - list_move_tail(&folio->lru, &lrugen->folios[new_gen][type][zone]); + prefetchw_next_lru_folio(folio, head, flags); + pos = pos->next; + new_gen = __folio_inc_gen(folio, old_gen, &gen_increased); + if (gen_increased) { + delta += nr_pages; + batch_end = &folio->lru; - / don't count the workingset being lazily promoted / - if (refs + workingset != BIT(LRU_REFS_WIDTH) + 1) { - int tier = lru_tier_from_refs(refs, workingset); - int delta = folio_nr_pages(folio); + / don't count the workingset being lazily promoted / + if (refs + workingset != BIT(LRU_REFS_WIDTH) + 1) { + int tier = lru_tier_from_refs(refs, workingset); - WRITE_ONCE(lrugen->protected[hist][type][tier], - lrugen->protected[hist][type][tier] + delta); + protected[tier] += nr_pages; + } + } else { + flush_lru_batch(head, &batch_end, target_list); + list_move(&folio->lru, &lrugen->folios[new_gen][type][zone]); } - if (!--remaining) - return false; + break; } + flush_lru_batch(head, &batch_end, target_list); + + WRITE_ONCE(lrugen->nr_pages[old_gen][type][zone], + lrugen->nr_pages[old_gen][type][zone] - delta); + WRITE_ONCE(lrugen->nr_pages[target_gen][type][zone], + lrugen->nr_pages[target_gen][type][zone] + delta); + for (int tier = 0; tier < MAX_NR_TIERS; tier++) + WRITE_ONCE(lrugen->protected[hist][type][tier], + lrugen->protected[hist][type][tier] + protected[tier]); + if (!remaining) + return false; } done: reset_ctrl_pos(lruvec, type, true); @@ -4151,20 +4220,28 @@ static void set_initial_priority(struct pglist_data pgdat, struct scan_control sc->priority = clamp(priority, DEF_PRIORITY / 2, DEF_PRIORITY); } +static inline unsigned long lruvec_gen_size(struct lru_gen_folio lrugen, + int type, unsigned long seq) +{ + int gen = lru_gen_from_seq(seq); + unsigned long size = 0; + + for (int zone = 0; zone < MAX_NR_ZONES; zone++) + size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L); + return size; +} + static unsigned long lruvec_evictable_size(struct lruvec lruvec, int swappiness) { - int gen, type, zone; + int type; unsigned long seq, total = 0; struct lru_gen_folio lrugen = &lruvec->lrugen; DEFINE_MAX_SEQ(lruvec); DEFINE_MIN_SEQ(lruvec); for_each_evictable_type(type, swappiness) { - for (seq = min_seq[type]; seq <= max_seq; seq++) { - gen = lru_gen_from_seq(seq); - for (zone = 0; zone < MAX_NR_ZONES; zone++) - total += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L); - } + for (seq = min_seq[type]; seq <= max_seq; seq++) + total += lruvec_gen_size(lrugen, type, seq); } return total; @@ -4728,7 +4805,8 @@ static bool isolate_folio(struct lruvec lruvec, struct folio folio, struct sca static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec, struct scan_control sc, int type, int tier, - struct list_head list, int isolatedp) + struct list_head list, int isolatedp, + bool exhausted) { int i; int gen; @@ -4739,12 +4817,15 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec, int skipped = 0; unsigned long remaining = nr_to_scan; struct lru_gen_folio lrugen = &lruvec->lrugen; + bool early_stop = false; VM_WARN_ON_ONCE(nr_to_scan > MAX_LRU_BATCH); VM_WARN_ON_ONCE(!list_empty(list)); - if (get_nr_gens(lruvec, type) == MIN_NR_GENS) + if (get_nr_gens(lruvec, type) == MIN_NR_GENS) { + exhausted = true; return 0; + } gen = lru_gen_from_seq(lrugen->min_seq[type]); @@ -4775,8 +4856,10 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec, skipped_zone += delta; } - if (!--remaining \|\| max(isolated, skipped_zone) >= MIN_LRU_BATCH) + if (!--remaining \|\| max(isolated, skipped_zone) >= MIN_LRU_BATCH) { + early_stop = true; break; + } } if (skipped_zone) { @@ -4785,8 +4868,10 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec, skipped += skipped_zone; } - if (!remaining \|\| isolated >= MIN_LRU_BATCH) + if (!remaining \|\| isolated >= MIN_LRU_BATCH) { + early_stop = true; break; + } } item = PGSCAN_KSWAPD + reclaimer_offset(sc); @@ -4797,6 +4882,13 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec, scanned, skipped, isolated, type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON); + /* + * If we didn't stop early, all reclaimable folios in the current + * generation have been scanned. We are exhausted if this is the last + * reclaimable generation. + / + exhausted = !early_stop && + lrugen->min_seq[type] + MIN_NR_GENS == lrugen->max_seq; isolatedp = isolated; return scanned; } @@ -4824,51 +4916,90 @@ static int get_tier_idx(struct lruvec lruvec, int type) static int get_type_to_scan(struct lruvec lruvec, int swappiness) { struct ctrl_pos sp, pv = {}; + int anon_gain, file_gain; if (swappiness <= MIN_SWAPPINESS + 1) return LRU_GEN_FILE; if (swappiness >= MAX_SWAPPINESS) return LRU_GEN_ANON; + + / + * Apply a quadratic boost based on the distance from the neutral + * balance point (swappiness = MAX_SWAPPINESS / 2). + * + * A linear weight is easily overwhelmed by historical refault cost + * when swappiness deviates from neutral. The quadratic scaling + * amplifies the weight of the preferred type smoothly. + / + if (swappiness < MAX_SWAPPINESS / 2) { + int delta = (MAX_SWAPPINESS / 2) - swappiness; + int boost = (delta delta) >> 4; + + anon_gain = swappiness; + file_gain = (MAX_SWAPPINESS - swappiness) + boost; + } else { + int delta = swappiness - (MAX_SWAPPINESS / 2); + int boost = (delta * delta) >> 4; + + anon_gain = swappiness + boost; + file_gain = MAX_SWAPPINESS - swappiness; + } + /* * Compare the sum of all tiers of anon with that of file to determine * which type to scan. / - read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, swappiness, &sp); - read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, MAX_SWAPPINESS - swappiness, &pv); + read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, anon_gain, &sp); + read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, file_gain, &pv); return positive_ctrl_err(&sp, &pv); } +static inline bool is_single_type_reclaim(int swappiness) +{ + return swappiness == MIN_SWAPPINESS \|\| + swappiness == SWAPPINESS_ANON_ONLY; +} + static int isolate_folios(unsigned long nr_to_scan, struct lruvec lruvec, struct scan_control sc, int swappiness, struct list_head list, int isolated, int isolate_type, int isolate_scanned) { - int i; - int total_scanned = 0; + bool type_fallback_allowed = !is_single_type_reclaim(swappiness); int type = get_type_to_scan(lruvec, swappiness); + int total_scanned = 0, scanned, tier; + bool exhausted, tried = false; - for_each_evictable_type(i, swappiness) { - int scanned; - int tier = get_tier_idx(lruvec, type); +retry: + tier = get_tier_idx(lruvec, type); + scanned = scan_folios(nr_to_scan, lruvec, sc, + type, tier, list, isolated, &exhausted); - scanned = scan_folios(nr_to_scan, lruvec, sc, - type, tier, list, isolated); + total_scanned += scanned; + if (isolated) { + isolate_type = type; + isolate_scanned = scanned; + return total_scanned; + } - total_scanned += scanned; - if (isolated) { - isolate_type = type; - isolate_scanned = scanned; - break; - } - / - * If scanned > 0 and isolated == 0, avoid falling back to the - * other type, as this type remains sufficient. Falling back - * too readily can disrupt the positive_ctrl_err() bias. - / - if (!scanned) - type = !type; + / + * We are running out of the current reclaim type. Fall back to + * the other type if allowed. + / + if (exhausted && type_fallback_allowed) { + type = !type; + type_fallback_allowed = false; + goto retry; + } + / + * We are not exhausted, but failed to isolate any folios due to + * races. Give this type one more chance to avoid a larger loop. + / + if (!exhausted && !tried) { + tried = true; + goto retry; } return total_scanned; @@ -4970,21 +5101,67 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec lruvec, return scanned; } +static bool lru_gen_imbalanced(struct lruvec lruvec, unsigned long max_seq, + struct scan_control sc, int type, int swappiness) +{ + struct lru_gen_folio lrugen = &lruvec->lrugen; + unsigned long young = 0, old = 0, lag = 0; + unsigned long inactive_ratio, gb; + DEFINE_MIN_SEQ(lruvec); + + / we still have enough generations to reclaim / + if (min_seq[type] + MIN_NR_GENS < max_seq) + return false; + + / + * Trigger aging if the preferred type is running low on reclaimable + * folios, provided the generation lag of the other type remains small + * enough that inc_min_seq() introduces negligible overhead + / + for (unsigned long seq = min_seq[type]; seq <= max_seq; seq++) { + unsigned long size = lruvec_gen_size(lrugen, type, seq); + + if (seq + MIN_NR_GENS > max_seq) + young += size; + else + old += size; + } + if (min_seq[!type] + MAX_NR_GENS == max_seq + 1) + lag += lruvec_gen_size(lrugen, !type, min_seq[!type]); + + / + * Borrow the adaptive ratio from inactive_is_low(), and scale + * it by sqrt(MAX_NR_GENS) to make aging less aggressive + / + gb = (young + old) >> (30 - PAGE_SHIFT); + inactive_ratio = gb ? int_sqrt(10 gb * MAX_NR_GENS) : MAX_NR_GENS; + return young > old * inactive_ratio && (lag < MAX_LRU_BATCH \|\| + (is_extreme_swappiness(swappiness) && sc->priority > 2)); +} + static bool should_run_aging(struct lruvec lruvec, unsigned long max_seq, struct scan_control sc, int swappiness) { + int type = get_type_to_scan(lruvec, swappiness); DEFINE_MIN_SEQ(lruvec); - /* have to run aging, since eviction is not possible anymore / - if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS > max_seq) + / run aging if the preferred type is exhausted / + if (min_seq[type] + MIN_NR_GENS > max_seq) return true; - / try to avoid aging, do gentle reclaim at the default priority / - if (sc->priority == DEF_PRIORITY) + / + * Try to avoid aging by doing gentle reclaim at the default + * priority. Skip gentle reclaim for extreme swappiness. + / + if (sc->priority == DEF_PRIORITY && !is_extreme_swappiness(swappiness)) return false; / better to run aging even though eviction is still possible / - return evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq; + if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq) + return true; + + / Run aging if the preferred type is severely imbalanced across gens / + return lru_gen_imbalanced(lruvec, max_seq, sc, type, swappiness); } static long get_nr_to_scan(struct lruvec lruvec, struct scan_control *sc,
3/2	2026/08/12 12:41	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 8052 output: 29 thoughts: 153 Thoughts: Analyzing the MGLRU Patch Okay, so I've got this patch here, and it's messing with `mm/vmscan.c`. Immediately, I see it's about MGLRU – Multi-Gen LRU. Let's get right into the specifics. It's touching a lot of key functions: `folio_inc_gen`, `inc_min_seq`, which I understand are fundamental to the gen-based LRU logic; `scan_folios`, `get_type_to_scan`, and `isolate_folios` -- all crucial for the scanning process; and `should_run_aging`, related to the aging mechanisms. Plus, it's adding these new functions, `lru_gen_imbalanced`, `lruvec_gen_size`, `flush_lru_batch`, and `is_extreme_swappiness`, which suggests potentially significant changes to the balancing and flush behavior, and how we handle extreme swapping. First things first, I need to understand the context. Is MGLRU enabled by default? Or is there some specific config option I need to look for? I can't just dive into the code blind. I'll hit `grepper` and search for `LRU_GEN` in `mm/Kconfig`. That'll give me the enabling conditions. From there, I can get a better feel for the patch's significance and intended use case. This gives a great overview and will help to guide further investigation.
4/2	2026/08/12 12:41	tool	grepper	0m Args: { "Expression": "config LRU_GEN", "PathPrefix": "mm/Kconfig" } Results: { "Output": "mm/Kconfig=1392=config PTE_MARKER_UFFD_WP\n--\nmm/Kconfig-1402-# multi-gen LRU {\nmm/Kconfig:1403:config LRU_GEN\nmm/Kconfig-1404-\tbool \"Multi-Gen LRU\"\n--\nmm/Kconfig-1411-\nmm/Kconfig:1412:config LRU_GEN_ENABLED\nmm/Kconfig-1413-\tbool \"Enable by default\"\n--\nmm/Kconfig-1417-\nmm/Kconfig:1418:config LRU_GEN_STATS\nmm/Kconfig-1419-\tbool \"Full stats for debugging\"\n--\nmm/Kconfig-1426-\nmm/Kconfig:1427:config LRU_GEN_WALKS_MMU\nmm/Kconfig-1428-\tdef_bool y\n" }
5/2	2026/08/12 12:41	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 8789 output: 29 thoughts: 22 Thoughts: Here's my take on those thoughts: Analyzing the Configuration Dependency Okay, so `LRU_GEN` is the piece of the config we're focusing on. My first step is to quickly determine its dependencies. I need to understand what other components or settings `LRU_GEN` relies on to function correctly. This is fundamental to understanding its behavior and any potential cascading effects of changes to it.
6/2	2026/08/12 12:41	tool	grepper	0m Args: { "Expression": "config LRU_GEN", "PathPrefix": "mm/Kconfig" } Results: { "Output": "mm/Kconfig=1392=config PTE_MARKER_UFFD_WP\n--\nmm/Kconfig-1402-# multi-gen LRU {\nmm/Kconfig:1403:config LRU_GEN\nmm/Kconfig-1404-\tbool \"Multi-Gen LRU\"\n--\nmm/Kconfig-1411-\nmm/Kconfig:1412:config LRU_GEN_ENABLED\nmm/Kconfig-1413-\tbool \"Enable by default\"\n--\nmm/Kconfig-1417-\nmm/Kconfig:1418:config LRU_GEN_STATS\nmm/Kconfig-1419-\tbool \"Full stats for debugging\"\n--\nmm/Kconfig-1426-\nmm/Kconfig:1427:config LRU_GEN_WALKS_MMU\nmm/Kconfig-1428-\tdef_bool y\n" }
7/2	2026/08/12 12:41	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 9165 output: 33 thoughts: 15 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience: Unpacking the `LRU_GEN` Dependencies Right, before I dive in, I need to get a handle on what `LRU_GEN` actually relies on. I can't just start tweaking or analyzing it without understanding its place in the broader architecture. What other components, libraries, or data structures does this thing depend on? Are there any upstream effects I need to be aware of? Are there specific versions or configurations? Understanding the dependency tree is fundamental before any serious analysis or modification can happen. I need to ensure I don't introduce unintended side effects by, for example, missing a critical library that's used somewhere. It all hangs together, so let's start with a solid foundation.
8/2	2026/08/12 12:42	tool	read-file	0m Args: { "File": "mm/Kconfig", "FirstLine": 1400, "LineCount": 30 } Results: { "Contents": "1400:\t\t file-backed memory types like shmem and hugetlbfs.\n1401:\t\n1402:\t# multi-gen LRU {\n1403:\tconfig LRU_GEN\n1404:\t\tbool \"Multi-Gen LRU\"\n1405:\t\tdepends on MMU\n1406:\t\t# make sure folio-\u003eflags has enough spare bits\n1407:\t\tdepends on 64BIT \|\| !SPARSEMEM \|\| SPARSEMEM_VMEMMAP\n1408:\t\thelp\n1409:\t\t A high performance LRU implementation to overcommit memory. See\n1410:\t\t Documentation/admin-guide/mm/multigen_lru.rst for details.\n1411:\t\n1412:\tconfig LRU_GEN_ENABLED\n1413:\t\tbool \"Enable by default\"\n1414:\t\tdepends on LRU_GEN\n1415:\t\thelp\n1416:\t\t This option enables the multi-gen LRU by default.\n1417:\t\n1418:\tconfig LRU_GEN_STATS\n1419:\t\tbool \"Full stats for debugging\"\n1420:\t\tdepends on LRU_GEN\n1421:\t\thelp\n1422:\t\t Do not enable this option unless you plan to look at historical stats\n1423:\t\t from evicted generations for debugging purpose.\n1424:\t\n1425:\t\t This option has a per-memcg and per-node memory overhead.\n1426:\t\n1427:\tconfig LRU_GEN_WALKS_MMU\n1428:\t\tdef_bool y\n1429:\t\tdepends on LRU_GEN \u0026\u0026 ARCH_HAS_HW_PTE_YOUNG\n" }
9/2	2026/08/12 12:42	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 9831 output: 60 thoughts: 175 Thoughts: Fuzzing MGLRU's Core Memory Management Alright, so `LRU_GEN` and `LRU_GEN_ENABLED` – those are the key configuration options, got it. Now, let's dive into the code. My initial thought is to map out which functions have been touched in this change, specifically. Looks like we're dealing with `folio_inc_gen`, `__folio_inc_gen`, `inc_min_seq`, `scan_folios`, `get_type_to_scan`, `isolate_folios`, `evict_folios`, `lru_gen_imbalanced`, and `should_run_aging`. These are all pretty critical – the heart of MGLRU's memory management, the ones that are likely to be reached during standard operation. Definitely worth fuzzing to see what we can shake loose. Now, the natural next step is to pinpoint entry points. I need to figure out which of these functions are directly accessible from elsewhere, ideally non-static ones. Aha, it seems they are all static functions, which is typically going to limit direct fuzzing opportunities. Not a deal breaker, but it means I need to adjust my approach. The next question is, are there any non-static functions within that file that call these core functions? That's where I need to focus my energy.
10/2	2026/08/12 12:42	tool	grepper	0m Args: { "Expression": "(inc_min_seq\|scan_folios\|get_type_to_scan\|isolate_folios\|evict_folios\|should_run_aging)", "PathPrefix": "mm/vmscan.c" } Results: { "Output": "mm/vmscan.c=279=static inline bool is_exec_file_folio(const struct folio folio,\n--\nmm/vmscan.c-284-\nmm/vmscan.c:285:/ See get_type_to_scan(): these values always select FILE or ANON /\nmm/vmscan.c-286-static inline bool is_extreme_swappiness(int swappiness)\n--\nmm/vmscan.c=3933=static inline void flush_lru_batch(struct list_head head, struct list_head *batch_end,\n--\nmm/vmscan.c-3945-\nmm/vmscan.c:3946:static bool inc_min_seq(struct lruvec lruvec, int type, int swappiness)\nmm/vmscan.c-3947-{\n--\nmm/vmscan.c-4021-\nmm/vmscan.c:4022:static void try_to_inc_min_seq(struct lruvec lruvec, int swappiness)\nmm/vmscan.c-4023-{\n--\nmm/vmscan.c=4074=static bool inc_max_seq(struct lruvec lruvec, unsigned long seq, int swappiness)\n--\nmm/vmscan.c-4095-\nmm/vmscan.c:4096:\t\tif (inc_min_seq(lruvec, type, swappiness))\nmm/vmscan.c-4097-\t\t\tcontinue;\n--\nmm/vmscan.c=4782=static bool isolate_folio(struct lruvec lruvec, struct folio folio, struct scan_control sc)\n--\nmm/vmscan.c-4805-\nmm/vmscan.c:4806:static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec,\nmm/vmscan.c-4807-\t\t struct scan_control sc, int type, int tier,\n--\nmm/vmscan.c=4896=static int get_tier_idx(struct lruvec lruvec, int type)\n--\nmm/vmscan.c-4915-\nmm/vmscan.c:4916:static int get_type_to_scan(struct lruvec lruvec, int swappiness)\nmm/vmscan.c-4917-{\n--\nmm/vmscan.c=4959=static inline bool is_single_type_reclaim(int swappiness)\n--\nmm/vmscan.c-4964-\nmm/vmscan.c:4965:static int isolate_folios(unsigned long nr_to_scan, struct lruvec lruvec,\nmm/vmscan.c-4966-\t\t\t struct scan_control sc, int swappiness,\n--\nmm/vmscan.c-4970-\tbool type_fallback_allowed = !is_single_type_reclaim(swappiness);\nmm/vmscan.c:4971:\tint type = get_type_to_scan(lruvec, swappiness);\nmm/vmscan.c-4972-\tint total_scanned = 0, scanned, tier;\n--\nmm/vmscan.c-4976-\ttier = get_tier_idx(lruvec, type);\nmm/vmscan.c:4977:\tscanned = scan_folios(nr_to_scan, lruvec, sc,\nmm/vmscan.c-4978-\t\t\t type, tier, list, isolated, \u0026exhausted);\n--\nmm/vmscan.c-5007-\nmm/vmscan.c:5008:static int evict_folios(unsigned long nr_to_scan, struct lruvec lruvec,\nmm/vmscan.c-5009-\t\t\tstruct scan_control sc, int swappiness)\n--\nmm/vmscan.c-5027-\t/ In case folio deletion left empty old gens, flush them /\nmm/vmscan.c:5028:\ttry_to_inc_min_seq(lruvec, swappiness);\nmm/vmscan.c-5029-\nmm/vmscan.c:5030:\tscanned = isolate_folios(nr_to_scan, lruvec, sc, swappiness,\nmm/vmscan.c-5031-\t\t\t\t \u0026list, \u0026isolated, \u0026type, \u0026type_scanned);\n--\nmm/vmscan.c-5035-\tif (scanned)\nmm/vmscan.c:5036:\t\ttry_to_inc_min_seq(lruvec, swappiness);\nmm/vmscan.c-5037-\n--\nmm/vmscan.c=5104=static bool lru_gen_imbalanced(struct lruvec lruvec, unsigned long max_seq,\n--\nmm/vmscan.c-5118-\t * folios, provided the generation lag of the other type remains small\nmm/vmscan.c:5119:\t * enough that inc_min_seq() introduces negligible overhead\nmm/vmscan.c-5120-\t /\n--\nmm/vmscan.c-5141-\nmm/vmscan.c:5142:static bool should_run_aging(struct lruvec lruvec, unsigned long max_seq,\nmm/vmscan.c-5143-\t\t\t struct scan_control sc, int swappiness)\nmm/vmscan.c-5144-{\nmm/vmscan.c:5145:\tint type = get_type_to_scan(lruvec, swappiness);\nmm/vmscan.c-5146-\tDEFINE_MIN_SEQ(lruvec);\n--\nmm/vmscan.c=5233=static bool try_to_shrink_lruvec(struct lruvec lruvec, struct scan_control sc)\n--\nmm/vmscan.c-5249-\nmm/vmscan.c:5250:\t\tif (should_run_aging(lruvec, max_seq, sc, swappiness)) {\nmm/vmscan.c-5251-\t\t\tif (try_to_inc_max_seq(lruvec, max_seq, swappiness, false))\n--\nmm/vmscan.c-5256-\t\tnr_batch = min(nr_to_scan, MIN_LRU_BATCH);\nmm/vmscan.c:5257:\t\tdelta = evict_folios(nr_batch, lruvec, sc, swappiness);\nmm/vmscan.c-5258-\t\tif (!delta)\n--\nmm/vmscan.c=5860=static int run_eviction(struct lruvec lruvec, unsigned long seq, struct scan_control *sc,\n--\nmm/vmscan.c-5880-\t\tnr_batch = min(nr_to_reclaim - sc-\u003enr_reclaimed, MAX_LRU_BATCH);\nmm/vmscan.c:5881:\t\tif (!evict_folios(nr_batch, lruvec, sc, swappiness))\nmm/vmscan.c-5882-\t\t\treturn 0;\n" }
11/2	2026/08/12 12:42	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 12168 output: 35 thoughts: 41 Thoughts: Okay, let's break this down. Investigating the LRU Vector Shrinkage Right, so I'm looking at `try_to_shrink_lruvec` and `run_eviction`, and I see they call some other functions. Now, my immediate thought is, I need to understand the call graph of `try_to_shrink_lruvec`. Where does it get called? Understanding its upstream dependencies is key to figuring out the bigger picture of how this LRU vector shrinkage is initiated within this system. It's a classic debugging and performance analysis technique: follow the call chain to understand the control flow. Let's see what's calling that function, shall we? I need to get a clear picture of the context in which it operates.
12/2	2026/08/12 12:42	tool	grepper	0m Args: { "Expression": "try_to_shrink_lruvec", "PathPrefix": "mm/vmscan.c" } Results: { "Output": "mm/vmscan.c=5198=static bool should_abort_scan(struct lruvec lruvec, struct scan_control sc)\n--\nmm/vmscan.c-5232- /\nmm/vmscan.c:5233:static bool try_to_shrink_lruvec(struct lruvec lruvec, struct scan_control sc)\nmm/vmscan.c-5234-{\n--\nmm/vmscan.c=5278=static int shrink_one(struct lruvec lruvec, struct scan_control sc)\n--\nmm/vmscan.c-5297-\nmm/vmscan.c:5298:\tneed_rotate = try_to_shrink_lruvec(lruvec, sc);\nmm/vmscan.c-5299-\n--\nmm/vmscan.c=5389=static void lru_gen_shrink_lruvec(struct lruvec lruvec, struct scan_control *sc)\n--\nmm/vmscan.c-5401-\nmm/vmscan.c:5402:\tif (try_to_shrink_lruvec(lruvec, sc))\nmm/vmscan.c-5403-\t\tlru_gen_rotate_memcg(lruvec, MEMCG_LRU_YOUNG);\n" }
13/2	2026/08/12 12:42	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 12757 output: 36 thoughts: 61 Thoughts: Okay, let's break this down. Diving into the LRU Shrinkage Process Right, so I'm trying to understand the flow within this LRU (Least Recently Used) cache shrinking mechanism. My initial thought is that `lru_gen_shrink_lruvec` and `shrink_one` both seem to eventually trigger `try_to_shrink_lruvec`. That suggests a shared responsibility, potentially a centralized control point for the actual shrinking operation. Now, where does `lru_gen_shrink_lruvec` originate? It's key to trace its call stack. My hunch is that it's probably called from `shrink_lruvec` or something analogous. I need to verify that connection. Knowing where the shrinking process begins is crucial for understanding its overall behaviour and identifying potential bottlenecks or areas for optimisation. Time to dig deeper and see if my assumption holds true. I'll need to examine the calling context of `lru_gen_shrink_lruvec` to confirm the initial trigger.
14/2	2026/08/12 12:42	tool	grepper	0m Args: { "Expression": "lru_gen_shrink_lruvec", "PathPrefix": "mm/vmscan.c" } Results: { "Output": "mm/vmscan.c=5319=static void shrink_many(struct pglist_data pgdat, struct scan_control sc)\n--\nmm/vmscan.c-5388-\nmm/vmscan.c:5389:static void lru_gen_shrink_lruvec(struct lruvec lruvec, struct scan_control sc)\nmm/vmscan.c-5390-{\n--\nmm/vmscan.c=6133=static void lru_gen_age_node(struct pglist_data pgdat, struct scan_control sc)\n--\nmm/vmscan.c-6137-\nmm/vmscan.c:6138:static void lru_gen_shrink_lruvec(struct lruvec lruvec, struct scan_control sc)\nmm/vmscan.c-6139-{\n--\nmm/vmscan.c=6150=static void shrink_lruvec(struct lruvec lruvec, struct scan_control sc)\n--\nmm/vmscan.c-6161-\tif ((lru_gen_enabled() \|\| lru_gen_switching()) \u0026\u0026 !root_reclaim(sc)) {\nmm/vmscan.c:6162:\t\tlru_gen_shrink_lruvec(lruvec, sc);\nmm/vmscan.c-6163-\n" }
15/2	2026/08/12 12:42	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 13432 output: 31 thoughts: 190 Thoughts: Analyzing `mm/vmscan.c` for MGLRU Entry Points Okay, so I'm looking at `mm/vmscan.c` and trying to figure out which functions are most relevant, particularly for MGLRU. The first thing I spot is `shrink_lruvec`, but wait, that's static! That probably means it's not a good candidate for `FocusSymbols`, as the instructions say to prioritize non-static entry points. Let's see… Okay, I see `shrink_node`, `shrink_zones`, `do_try_to_free_pages`, and `kswapd` – all classic hot-path functions. The instructions specifically caution against listing generic hot-path functions to avoid biasing the test distribution, so I need to be careful here. If the code modifications are happening inside one of these already heavily scrutinized functions, like `shrink_lruvec` for example, then including them in `FocusSymbols` might not be the best approach. My focus needs to be on identifying specific entry points related to MGLRU's unique functionalities. I need to check and ensure that there are specific functions associated with MGLRU's logic.
16/2	2026/08/12 12:42	tool	grepper	0m Args: { "Expression": "lru_gen_", "PathPrefix": "mm/vmscan.c" } Results: { "Output": "\nFull output is too long, showing 500 out of 744 lines.\nUse more precise expression if possible.\n\nmm/vmscan.c=846=enum folio_references {\n--\nmm/vmscan.c-858- /\nmm/vmscan.c:859:static bool lru_gen_set_refs(struct folio folio, const vma_flags_t vma_flags)\nmm/vmscan.c-860-{\n--\nmm/vmscan.c-880-#else\nmm/vmscan.c:881:static bool lru_gen_set_refs(struct folio folio, const vma_flags_t vma_flags)\nmm/vmscan.c-882-{\n--\nmm/vmscan.c=887=static enum folio_references folio_check_references(struct folio folio,\n--\nmm/vmscan.c-911-\nmm/vmscan.c:912:\tif (lru_gen_enabled() \u0026\u0026 !lru_gen_switching()) {\nmm/vmscan.c-913-\t\tif (!referenced_ptes)\n--\nmm/vmscan.c-915-\nmm/vmscan.c:916:\t\treturn lru_gen_set_refs(folio, \u0026vma_flags) ? FOLIOREF_ACTIVATE : FOLIOREF_KEEP;\nmm/vmscan.c-917-\t}\n--\nmm/vmscan.c=2299=static void prepare_scan_control(pg_data_t pgdat, struct scan_control sc)\n--\nmm/vmscan.c-2305-\nmm/vmscan.c:2306:\tif (lru_gen_enabled() \u0026\u0026 !lru_gen_switching())\nmm/vmscan.c-2307-\t\treturn;\n--\nmm/vmscan.c=2713=DEFINE_STATIC_KEY_FALSE(lru_switch);\nmm/vmscan.c-2714-#ifdef CONFIG_LRU_GEN_ENABLED\nmm/vmscan.c:2715:DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS);\nmm/vmscan.c:2716:#define get_cap(cap)\tstatic_branch_likely(\u0026lru_gen_caps[cap])\nmm/vmscan.c-2717-#else\nmm/vmscan.c:2718:DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS);\nmm/vmscan.c:2719:#define get_cap(cap)\tstatic_branch_unlikely(\u0026lru_gen_caps[cap])\nmm/vmscan.c-2720-#endif\n--\nmm/vmscan.c=2807=static bool __maybe_unused seq_is_valid(struct lruvec lruvec)\n--\nmm/vmscan.c-2836- walk_pmd_range(); the eviction also report them when walking the rmap\nmm/vmscan.c:2837: * in lru_gen_look_around().\nmm/vmscan.c-2838- \n--\nmm/vmscan.c=2854=static void get_item_key(void item, int key)\n--\nmm/vmscan.c-2863-\nmm/vmscan.c:2864:static bool test_bloom_filter(struct lru_gen_mm_state mm_state, unsigned long seq,\nmm/vmscan.c-2865-\t\t\t void item)\n--\nmm/vmscan.c-2879-\nmm/vmscan.c:2880:static void update_bloom_filter(struct lru_gen_mm_state mm_state, unsigned long seq,\nmm/vmscan.c-2881-\t\t\t\tvoid item)\n--\nmm/vmscan.c-2898-\nmm/vmscan.c:2899:static void reset_bloom_filter(struct lru_gen_mm_state mm_state, unsigned long seq)\nmm/vmscan.c-2900-{\n--\nmm/vmscan.c-2920-\nmm/vmscan.c:2921:static struct lru_gen_mm_list get_mm_list(struct mem_cgroup memcg)\nmm/vmscan.c-2922-{\nmm/vmscan.c:2923:\tstatic struct lru_gen_mm_list mm_list = {\nmm/vmscan.c-2924-\t\t.fifo = LIST_HEAD_INIT(mm_list.fifo),\n--\nmm/vmscan.c-2936-\nmm/vmscan.c:2937:static struct lru_gen_mm_state get_mm_state(struct lruvec lruvec)\nmm/vmscan.c-2938-{\n--\nmm/vmscan.c-2941-\nmm/vmscan.c:2942:static struct mm_struct get_next_mm(struct lru_gen_mm_walk walk)\nmm/vmscan.c-2943-{\n--\nmm/vmscan.c-2946-\tstruct pglist_data pgdat = lruvec_pgdat(walk-\u003elruvec);\nmm/vmscan.c:2947:\tstruct lru_gen_mm_state mm_state = get_mm_state(walk-\u003elruvec);\nmm/vmscan.c-2948-\n--\nmm/vmscan.c-2960-\nmm/vmscan.c:2961:void lru_gen_add_mm(struct mm_struct mm)\nmm/vmscan.c-2962-{\n--\nmm/vmscan.c-2964-\tstruct mem_cgroup memcg = get_mem_cgroup_from_mm(mm);\nmm/vmscan.c:2965:\tstruct lru_gen_mm_list mm_list = get_mm_list(memcg);\nmm/vmscan.c-2966-\n--\nmm/vmscan.c-2975-\t\tstruct lruvec lruvec = get_lruvec(memcg, nid);\nmm/vmscan.c:2976:\t\tstruct lru_gen_mm_state mm_state = get_mm_state(lruvec);\nmm/vmscan.c-2977-\n--\nmm/vmscan.c-2987-\nmm/vmscan.c:2988:void lru_gen_del_mm(struct mm_struct mm)\nmm/vmscan.c-2989-{\nmm/vmscan.c-2990-\tint nid;\nmm/vmscan.c:2991:\tstruct lru_gen_mm_list mm_list;\nmm/vmscan.c-2992-\tstruct mem_cgroup memcg = NULL;\n--\nmm/vmscan.c-3005-\t\tstruct lruvec lruvec = get_lruvec(memcg, nid);\nmm/vmscan.c:3006:\t\tstruct lru_gen_mm_state mm_state = get_mm_state(lruvec);\nmm/vmscan.c-3007-\n--\nmm/vmscan.c-3027-#ifdef CONFIG_MEMCG\nmm/vmscan.c:3028:void lru_gen_migrate_mm(struct mm_struct mm)\nmm/vmscan.c-3029-{\n--\nmm/vmscan.c-3051-\nmm/vmscan.c:3052:\tlru_gen_del_mm(mm);\nmm/vmscan.c:3053:\tlru_gen_add_mm(mm);\nmm/vmscan.c-3054-}\n--\nmm/vmscan.c-3058-\nmm/vmscan.c:3059:static struct lru_gen_mm_list get_mm_list(struct mem_cgroup memcg)\nmm/vmscan.c-3060-{\n--\nmm/vmscan.c-3063-\nmm/vmscan.c:3064:static struct lru_gen_mm_state get_mm_state(struct lruvec lruvec)\nmm/vmscan.c-3065-{\n--\nmm/vmscan.c-3068-\nmm/vmscan.c:3069:static struct mm_struct get_next_mm(struct lru_gen_mm_walk walk)\nmm/vmscan.c-3070-{\n--\nmm/vmscan.c-3075-\nmm/vmscan.c:3076:static void reset_mm_stats(struct lru_gen_mm_walk walk, bool last)\nmm/vmscan.c-3077-{\n--\nmm/vmscan.c-3080-\tstruct lruvec lruvec = walk-\u003elruvec;\nmm/vmscan.c:3081:\tstruct lru_gen_mm_state mm_state = get_mm_state(lruvec);\nmm/vmscan.c-3082-\n--\nmm/vmscan.c-3100-\nmm/vmscan.c:3101:static bool iterate_mm_list(struct lru_gen_mm_walk walk, struct mm_struct iter)\nmm/vmscan.c-3102-{\n--\nmm/vmscan.c-3107-\tstruct mem_cgroup memcg = lruvec_memcg(lruvec);\nmm/vmscan.c:3108:\tstruct lru_gen_mm_list mm_list = get_mm_list(memcg);\nmm/vmscan.c:3109:\tstruct lru_gen_mm_state mm_state = get_mm_state(lruvec);\nmm/vmscan.c-3110-\n--\nmm/vmscan.c=3165=static bool iterate_mm_list_nowalk(struct lruvec lruvec, unsigned long seq)\n--\nmm/vmscan.c-3168-\tstruct mem_cgroup memcg = lruvec_memcg(lruvec);\nmm/vmscan.c:3169:\tstruct lru_gen_mm_list mm_list = get_mm_list(memcg);\nmm/vmscan.c:3170:\tstruct lru_gen_mm_state mm_state = get_mm_state(lruvec);\nmm/vmscan.c-3171-\n--\nmm/vmscan.c=3217=static void read_ctrl_pos(struct lruvec lruvec, int type, int tier, int gain,\n--\nmm/vmscan.c-3220-\tint i;\nmm/vmscan.c:3221:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c-3222-\tint hist = lru_hist_from_seq(lrugen-\u003emin_seq[type]);\n--\nmm/vmscan.c=3236=static void reset_ctrl_pos(struct lruvec lruvec, int type, bool carryover)\n--\nmm/vmscan.c-3238-\tint hist, tier;\nmm/vmscan.c:3239:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c-3240-\tbool clear = carryover ? NR_HIST_GENS == 1 : NR_HIST_GENS \u003e 1;\n--\nmm/vmscan.c=3288=static int folio_update_gen(struct folio folio, int gen, const vma_flags_t vma_flags)\n--\nmm/vmscan.c-3305-\tdo {\nmm/vmscan.c:3306:\t\t/* lru_gen_del_folio() has isolated this page? /\nmm/vmscan.c-3307-\t\tif (!(old_flags \u0026 LRU_GEN_MASK))\n--\nmm/vmscan.c=3345=static int folio_inc_gen(struct lruvec lruvec, struct folio folio)\n--\nmm/vmscan.c-3347-\tint type = folio_is_file_lru(folio);\nmm/vmscan.c:3348:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c:3349:\tint new_gen, old_gen = lru_gen_from_seq(lrugen-\u003emin_seq[type]);\nmm/vmscan.c-3350-\tbool gen_increased;\n--\nmm/vmscan.c-3353-\tif (gen_increased)\nmm/vmscan.c:3354:\t\tlru_gen_update_size(lruvec, folio, old_gen, new_gen);\nmm/vmscan.c-3355-\treturn new_gen;\n--\nmm/vmscan.c-3357-\nmm/vmscan.c:3358:static void update_batch_size(struct lru_gen_mm_walk walk, struct folio folio,\nmm/vmscan.c-3359-\t\t\t int old_gen, int new_gen)\n--\nmm/vmscan.c-3373-\nmm/vmscan.c:3374:static void reset_batch_size(struct lru_gen_mm_walk walk)\nmm/vmscan.c-3375-{\n--\nmm/vmscan.c-3377-\tstruct lruvec lruvec = lruvec_live_lock_irq(walk-\u003elruvec);\nmm/vmscan.c:3378:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c-3379-\n--\nmm/vmscan.c-3392-\nmm/vmscan.c:3393:\t\tif (lru_gen_is_active(lruvec, gen))\nmm/vmscan.c-3394-\t\t\tlru += LRU_ACTIVE;\n--\nmm/vmscan.c=3401=static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk args)\n--\nmm/vmscan.c-3404-\tstruct vm_area_struct vma = args-\u003evma;\nmm/vmscan.c:3405:\tstruct lru_gen_mm_walk walk = args-\u003eprivate;\nmm/vmscan.c-3406-\n--\nmm/vmscan.c=3539=static bool suitable_to_scan(int total, int young)\n--\nmm/vmscan.c-3546-\nmm/vmscan.c:3547:static void walk_update_folio(struct lru_gen_mm_walk walk, struct vm_area_struct vma,\nmm/vmscan.c-3548-\t\tstruct folio folio, int new_gen, bool dirty)\n--\nmm/vmscan.c-3563-\t\t\tupdate_batch_size(walk, folio, old_gen, new_gen);\nmm/vmscan.c:3564:\t} else if (lru_gen_set_refs(folio, \u0026vma-\u003eflags)) {\nmm/vmscan.c-3565-\t\told_gen = folio_lru_gen(folio);\n--\nmm/vmscan.c=3571=static bool walk_pte_range(pmd_t pmd, unsigned long start, unsigned long end,\n--\nmm/vmscan.c-3581-\tstruct folio last = NULL;\nmm/vmscan.c:3582:\tstruct lru_gen_mm_walk walk = args-\u003eprivate;\nmm/vmscan.c-3583-\tstruct mem_cgroup memcg = lruvec_memcg(walk-\u003elruvec);\n--\nmm/vmscan.c-3585-\tDEFINE_MAX_SEQ(walk-\u003elruvec);\nmm/vmscan.c:3586:\tint gen = lru_gen_from_seq(max_seq);\nmm/vmscan.c-3587-\tunsigned int nr;\n--\nmm/vmscan.c=3662=static void walk_pmd_range_locked(pud_t pud, unsigned long addr, struct vm_area_struct vma,\n--\nmm/vmscan.c-3669-\tstruct folio last = NULL;\nmm/vmscan.c:3670:\tstruct lru_gen_mm_walk walk = args-\u003eprivate;\nmm/vmscan.c-3671-\tstruct mem_cgroup memcg = lruvec_memcg(walk-\u003elruvec);\n--\nmm/vmscan.c-3673-\tDEFINE_MAX_SEQ(walk-\u003elruvec);\nmm/vmscan.c:3674:\tint gen = lru_gen_from_seq(max_seq);\nmm/vmscan.c-3675-\n--\nmm/vmscan.c=3750=static void walk_pmd_range(pud_t pud, unsigned long start, unsigned long end,\n--\nmm/vmscan.c-3759-\tunsigned long first = -1;\nmm/vmscan.c:3760:\tstruct lru_gen_mm_walk walk = args-\u003eprivate;\nmm/vmscan.c:3761:\tstruct lru_gen_mm_state mm_state = get_mm_state(walk-\u003elruvec);\nmm/vmscan.c-3762-\n--\nmm/vmscan.c=3823=static int walk_pud_range(p4d_t p4d, unsigned long start, unsigned long end,\n--\nmm/vmscan.c-3829-\tunsigned long next;\nmm/vmscan.c:3830:\tstruct lru_gen_mm_walk walk = args-\u003eprivate;\nmm/vmscan.c-3831-\n--\nmm/vmscan.c-3864-\nmm/vmscan.c:3865:static void walk_mm(struct mm_struct mm, struct lru_gen_mm_walk walk)\nmm/vmscan.c-3866-{\n--\nmm/vmscan.c-3899-\nmm/vmscan.c:3900:static struct lru_gen_mm_walk set_mm_walk(struct pglist_data pgdat, bool force_alloc)\nmm/vmscan.c-3901-{\nmm/vmscan.c:3902:\tstruct lru_gen_mm_walk walk = current-\u003ereclaim_state-\u003emm_walk;\nmm/vmscan.c-3903-\n--\nmm/vmscan.c=3920=static void clear_mm_walk(void)\nmm/vmscan.c-3921-{\nmm/vmscan.c:3922:\tstruct lru_gen_mm_walk walk = current-\u003ereclaim_state-\u003emm_walk;\nmm/vmscan.c-3923-\n--\nmm/vmscan.c=3946=static bool inc_min_seq(struct lruvec lruvec, int type, int swappiness)\n--\nmm/vmscan.c-3949-\tint remaining = MAX_LRU_BATCH / (is_extreme_swappiness(swappiness) ? 2 : 8);\nmm/vmscan.c:3950:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c-3951-\tint hist = lru_hist_from_seq(lrugen-\u003emin_seq[type]);\nmm/vmscan.c:3952:\tint new_gen, old_gen = lru_gen_from_seq(lrugen-\u003emin_seq[type]);\nmm/vmscan.c-3953-\tint target_gen = (old_gen + 1) % MAX_NR_GENS;\n--\nmm/vmscan.c=4022=static void try_to_inc_min_seq(struct lruvec lruvec, int swappiness)\n--\nmm/vmscan.c-4025-\tbool seq_inc_flag = false;\nmm/vmscan.c:4026:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c-4027-\tDEFINE_MIN_SEQ(lruvec);\n--\nmm/vmscan.c-4033-\t\twhile (min_seq[type] + MIN_NR_GENS \u003c= lrugen-\u003emax_seq) {\nmm/vmscan.c:4034:\t\t\tgen = lru_gen_from_seq(min_seq[type]);\nmm/vmscan.c-4035-\n--\nmm/vmscan.c-4054-\nmm/vmscan.c:4055:\t/ see the comment on lru_gen_folio /\nmm/vmscan.c-4056-\tif (swappiness \u0026\u0026 swappiness \u003c= MAX_SWAPPINESS) {\n--\nmm/vmscan.c=4074=static bool inc_max_seq(struct lruvec lruvec, unsigned long seq, int swappiness)\n--\nmm/vmscan.c-4078-\tint type, zone;\nmm/vmscan.c:4079:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c-4080-restart:\n--\nmm/vmscan.c-4109-\t /\nmm/vmscan.c:4110:\tprev = lru_gen_from_seq(lrugen-\u003emax_seq - 1);\nmm/vmscan.c:4111:\tnext = lru_gen_from_seq(lrugen-\u003emax_seq + 1);\nmm/vmscan.c-4112-\n--\nmm/vmscan.c=4139=static bool try_to_inc_max_seq(struct lruvec lruvec, unsigned long seq,\n--\nmm/vmscan.c-4142-\tbool success;\nmm/vmscan.c:4143:\tstruct lru_gen_mm_walk walk;\nmm/vmscan.c-4144-\tstruct mm_struct mm = NULL;\nmm/vmscan.c:4145:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c:4146:\tstruct lru_gen_mm_state mm_state = get_mm_state(lruvec);\nmm/vmscan.c-4147-\n--\nmm/vmscan.c-4158-\t If the hardware doesn't automatically set the accessed bit, fallback\nmm/vmscan.c:4159:\t * to lru_gen_look_around(), which only clears the accessed bit in a\nmm/vmscan.c-4160-\t * handful of PTEs. Spreading the work out over a period of time usually\n--\nmm/vmscan.c=4197=static void set_initial_priority(struct pglist_data pgdat, struct scan_control sc)\n--\nmm/vmscan.c-4222-\nmm/vmscan.c:4223:static inline unsigned long lruvec_gen_size(struct lru_gen_folio lrugen,\nmm/vmscan.c-4224-\t\tint type, unsigned long seq)\nmm/vmscan.c-4225-{\nmm/vmscan.c:4226:\tint gen = lru_gen_from_seq(seq);\nmm/vmscan.c-4227-\tunsigned long size = 0;\n--\nmm/vmscan.c=4234=static unsigned long lruvec_evictable_size(struct lruvec lruvec, int swappiness)\n--\nmm/vmscan.c-4237-\tunsigned long seq, total = 0;\nmm/vmscan.c:4238:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c-4239-\tDEFINE_MAX_SEQ(lruvec);\n--\nmm/vmscan.c=4262=static bool lruvec_is_reclaimable(struct lruvec lruvec, struct scan_control sc,\n--\nmm/vmscan.c-4276-\nmm/vmscan.c:4277:\tgen = lru_gen_from_seq(evictable_min_seq(min_seq, swappiness));\nmm/vmscan.c-4278-\tbirth = READ_ONCE(lruvec-\u003elrugen.timestamps[gen]);\n--\nmm/vmscan.c-4283-/ to protect the working set of the last N jiffies /\nmm/vmscan.c:4284:static unsigned long lru_gen_min_ttl __read_mostly;\nmm/vmscan.c-4285-\nmm/vmscan.c:4286:static void lru_gen_age_node(struct pglist_data pgdat, struct scan_control sc)\nmm/vmscan.c-4287-{\nmm/vmscan.c-4288-\tstruct mem_cgroup memcg;\nmm/vmscan.c:4289:\tunsigned long min_ttl = READ_ONCE(lru_gen_min_ttl);\nmm/vmscan.c-4290-\tbool reclaimable = !min_ttl;\n--\nmm/vmscan.c-4332- /\nmm/vmscan.c:4333:bool lru_gen_look_around(struct page_vma_mapped_walk pvmw, unsigned int nr)\nmm/vmscan.c-4334-{\n--\nmm/vmscan.c-4338-\tunsigned long end;\nmm/vmscan.c:4339:\tstruct lru_gen_mm_walk walk;\nmm/vmscan.c-4340-\tstruct folio last = NULL;\n--\nmm/vmscan.c-4348-\tstruct lruvec lruvec;\nmm/vmscan.c:4349:\tstruct lru_gen_mm_state mm_state;\nmm/vmscan.c-4350-\tunsigned long max_seq;\n--\nmm/vmscan.c-4388-\tmax_seq = READ_ONCE((lruvec)-\u003elrugen.max_seq);\nmm/vmscan.c:4389:\tgen = lru_gen_from_seq(max_seq);\nmm/vmscan.c-4390-\tmm_state = get_mm_state(lruvec);\n--\nmm/vmscan.c=4451=enum {\n--\nmm/vmscan.c-4458-\nmm/vmscan.c:4459:static void lru_gen_rotate_memcg(struct lruvec lruvec, int op)\nmm/vmscan.c-4460-{\n--\nmm/vmscan.c-4506-\nmm/vmscan.c:4507:void lru_gen_online_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-4508-{\n--\nmm/vmscan.c-4531-\nmm/vmscan.c:4532:void lru_gen_offline_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-4533-{\n--\nmm/vmscan.c-4538-\nmm/vmscan.c:4539:\t\tlru_gen_rotate_memcg(lruvec, MEMCG_LRU_OLD);\nmm/vmscan.c-4540-\t}\n--\nmm/vmscan.c-4542-\nmm/vmscan.c:4543:void lru_gen_release_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-4544-{\n--\nmm/vmscan.c-4568-\nmm/vmscan.c:4569:void lru_gen_soft_reclaim(struct mem_cgroup memcg, int nid)\nmm/vmscan.c-4570-{\n--\nmm/vmscan.c-4574-\tif (READ_ONCE(lruvec-\u003elrugen.seg) != MEMCG_LRU_HEAD)\nmm/vmscan.c:4575:\t\tlru_gen_rotate_memcg(lruvec, MEMCG_LRU_HEAD);\nmm/vmscan.c-4576-}\nmm/vmscan.c-4577-\nmm/vmscan.c:4578:bool recheck_lru_gen_max_memcg(struct mem_cgroup memcg, int nid)\nmm/vmscan.c-4579-{\n--\nmm/vmscan.c=4591=static void try_to_inc_max_seq_nowalk(struct mem_cgroup memcg,\n--\nmm/vmscan.c-4593-{\nmm/vmscan.c:4594:\tstruct lru_gen_mm_list mm_list = get_mm_list(memcg);\nmm/vmscan.c:4595:\tstruct lru_gen_mm_state mm_state = get_mm_state(lruvec);\nmm/vmscan.c-4596-\tint swappiness = mem_cgroup_swappiness(memcg);\n--\nmm/vmscan.c-4624- /\nmm/vmscan.c:4625:void max_lru_gen_memcg(struct mem_cgroup memcg, int nid)\nmm/vmscan.c-4626-{\n--\nmm/vmscan.c-4651- generations on an LRU list.\nmm/vmscan.c:4652: * 4. In lru_gen_del_folio(), the generation to which the folio belongs is\nmm/vmscan.c-4653- * found based on the generation information in folio-\u003eflags, and the\n--\nmm/vmscan.c-4655- * the lru size correctly during reparenting, otherwise the lru size may\nmm/vmscan.c:4656: * be updated incorrectly in lru_gen_del_folio().\nmm/vmscan.c-4657- \n--\nmm/vmscan.c-4665- /\nmm/vmscan.c:4666:static void __lru_gen_reparent_memcg(struct lruvec child_lruvec, struct lruvec parent_lruvec,\nmm/vmscan.c-4667-\t\t\t\t int zone, int type)\nmm/vmscan.c-4668-{\nmm/vmscan.c:4669:\tstruct lru_gen_folio child_lrugen, parent_lrugen;\nmm/vmscan.c-4670-\tenum lru_list lru = type * LRU_INACTIVE_FILE;\n--\nmm/vmscan.c-4676-\tfor (i = 0; i \u003c get_nr_gens(child_lruvec, type); i++) {\nmm/vmscan.c:4677:\t\tint gen = lru_gen_from_seq(child_lrugen-\u003emax_seq - i);\nmm/vmscan.c-4678-\t\tlong nr_pages = child_lrugen-\u003enr_pages[gen][type][zone];\nmm/vmscan.c:4679:\t\tint child_lru_active = lru_gen_is_active(child_lruvec, gen) ? LRU_ACTIVE : 0;\nmm/vmscan.c:4680:\t\tint parent_lru_active = lru_gen_is_active(parent_lruvec, gen) ? LRU_ACTIVE : 0;\nmm/vmscan.c-4681-\n--\nmm/vmscan.c-4689-\nmm/vmscan.c:4690:\t\tif (lru_gen_is_active(child_lruvec, gen) != lru_gen_is_active(parent_lruvec, gen)) {\nmm/vmscan.c-4691-\t\t\t__update_lru_size(child_lruvec, lru + child_lru_active, zone, -nr_pages);\n--\nmm/vmscan.c-4696-\nmm/vmscan.c:4697:void lru_gen_reparent_memcg(struct mem_cgroup memcg, struct mem_cgroup parent, int nid)\nmm/vmscan.c-4698-{\n--\nmm/vmscan.c-4708-\t\tfor (type = 0; type \u003c ANON_AND_FILE; type++)\nmm/vmscan.c:4709:\t\t\t__lru_gen_reparent_memcg(child_lruvec, parent_lruvec, zid, type);\nmm/vmscan.c-4710-\n--\nmm/vmscan.c=4726=static bool sort_folio(struct lruvec lruvec, struct folio folio, struct scan_control sc,\n--\nmm/vmscan.c-4736-\tint tier = lru_tier_from_refs(refs, workingset);\nmm/vmscan.c:4737:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c-4738-\n--\nmm/vmscan.c-4742-\tif (!folio_evictable(folio)) {\nmm/vmscan.c:4743:\t\tsuccess = lru_gen_del_folio(lruvec, folio, true);\nmm/vmscan.c-4744-\t\tVM_WARN_ON_ONCE_FOLIO(!success, folio);\n--\nmm/vmscan.c-4751-\t/* promoted /\nmm/vmscan.c:4752:\tif (gen != lru_gen_from_seq(lrugen-\u003emin_seq[type])) {\nmm/vmscan.c-4753-\t\tlist_move(\u0026folio-\u003elru, \u0026lrugen-\u003efolios[gen][type][zone]);\n--\nmm/vmscan.c=4782=static bool isolate_folio(struct lruvec lruvec, struct folio folio, struct scan_control sc)\n--\nmm/vmscan.c-4799-\nmm/vmscan.c:4800:\tsuccess = lru_gen_del_folio(lruvec, folio, true);\nmm/vmscan.c-4801-\tVM_WARN_ON_ONCE_FOLIO(!success, folio);\n--\nmm/vmscan.c=4806=static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec,\n--\nmm/vmscan.c-4818-\tunsigned long remaining = nr_to_scan;\nmm/vmscan.c:4819:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c-4820-\tbool early_stop = false;\n--\nmm/vmscan.c-4829-\nmm/vmscan.c:4830:\tgen = lru_gen_from_seq(lrugen-\u003emin_seq[type]);\nmm/vmscan.c-4831-\n--\nmm/vmscan.c=5008=static int evict_folios(unsigned long nr_to_scan, struct lruvec lruvec,\n--\nmm/vmscan.c-5016-\tstruct reclaim_stat stat;\nmm/vmscan.c:5017:\tstruct lru_gen_mm_walk walk;\nmm/vmscan.c-5018-\tint scanned, reclaimed;\n--\nmm/vmscan.c-5069-\t\t/* don't add rejected folios to the oldest generation /\nmm/vmscan.c:5070:\t\tif (lru_gen_folio_seq(lruvec, folio, false) == min_seq[type])\nmm/vmscan.c-5071-\t\t\tset_mask_bits(\u0026folio-\u003eflags.f, LRU_REFS_FLAGS, BIT(PG_active));\n--\nmm/vmscan.c-5103-\nmm/vmscan.c:5104:static bool lru_gen_imbalanced(struct lruvec lruvec, unsigned long max_seq,\nmm/vmscan.c-5105-\t\tstruct scan_control sc, int type, int swappiness)\nmm/vmscan.c-5106-{\nmm/vmscan.c:5107:\tstruct lru_gen_folio lrugen = \u0026lruvec-\u003elrugen;\nmm/vmscan.c-5108-\tunsigned long young = 0, old = 0, lag = 0;\n--\nmm/vmscan.c=5142=static bool should_run_aging(struct lruvec lruvec, unsigned long max_seq,\n--\nmm/vmscan.c-5163-\t/ Run aging if the preferred type is severely imbalanced across gens /\nmm/vmscan.c:5164:\treturn lru_gen_imbalanced(lruvec, max_seq, sc, type, swappiness);\nmm/vmscan.c-5165-}\n--\nmm/vmscan.c=5278=static int shrink_one(struct lruvec lruvec, struct scan_control sc)\n--\nmm/vmscan.c-5285-\nmm/vmscan.c:5286:\t/ lru_gen_age_node() called mem_cgroup_calculate_protection() /\nmm/vmscan.c-5287-\tif (mem_cgroup_below_min(NULL, memcg))\n--\nmm/vmscan.c=5319=static void shrink_many(struct pglist_data pgdat, struct scan_control sc)\n--\nmm/vmscan.c-5325-\tstruct lruvec lruvec;\nmm/vmscan.c:5326:\tstruct lru_gen_folio lrugen;\nmm/vmscan.c-5327-\tstruct mem_cgroup memcg;\n--\nmm/vmscan.c-5339-\t\tif (op) {\nmm/vmscan.c:5340:\t\t\tlru_gen_rotate_memcg(lruvec, op);\nmm/vmscan.c-5341-\t\t\top = 0;\n--\nmm/vmscan.c-5353-\t\tif (!mem_cgroup_tryget(memcg)) {\nmm/vmscan.c:5354:\t\t\tlru_gen_release_memcg(memcg);\nmm/vmscan.c-5355-\t\t\tmemcg = NULL;\n--\nmm/vmscan.c-5371-\tif (op)\nmm/vmscan.c:5372:\t\tlru_gen_rotate_memcg(lruvec, op);\nmm/vmscan.c-5373-\n--\nmm/vmscan.c-5378-\nmm/vmscan.c:5379:\t/* restart if raced with lru_gen_rotate_memcg() */\nmm/vmscan.c-5380-\tif (gen != get_nulls_value(pos))\n\n" }
17/2	2026/08/12 12:42	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 23950 output: 43 thoughts: 926 Thoughts: Focusing Fuzzing Efforts on MGLRU Reclaim Paths Okay, so I'm thinking about how to effectively fuzz the MGLRU code, specifically the reclaim paths. The goal is to identify the crucial functions that trigger the reclaim and aging logic and target those. The initial approach involves understanding which functions are actually responsible for the reclaim process. We have a set of non-static functions like `lru_gen_add_mm`, `lru_gen_del_mm`, etc., but these aren't the primary drivers. The real reclaim work is initiated by memory pressure, which calls a sequence: `shrink_lruvec` -> `lru_gen_shrink_lruvec` -> `try_to_shrink_lruvec` and so on, eventually leading to `__folio_inc_gen`. Aging is triggered in a similar manner, from `try_to_shrink_lruvec` down to `lru_gen_imbalanced`. Given that these paths are activated by memory allocation, particularly through syscalls like `alloc_pages` or `mmap`, Syzkaller seems like the obvious tool for the job. To make it effective, I need to provide `FocusSymbols` that are specific kernel functions and not just generic syscalls. My first impulse was to list out the internal helper functions: `lru_gen_shrink_lruvec`, `lru_gen_age_node`, etc. However, the instructions highlighted something important: prioritize non-static, non-inlined API entrypoints because static helpers are often inlined and don't have distinct symbol addresses. This is a crucial distinction. So, I started checking the listed functions. `lru_gen_shrink_lruvec` is static, as is `shrink_lruvec`, `shrink_node`, and `do_try_to_free_pages`. However, `try_to_free_pages` is non-static. The same goes for `kswapd`, `lru_gen_look_around`, `lru_gen_add_mm`, and `lru_gen_del_mm`. `try_to_free_pages` sounds generic and might not be the most targeted. Now, considering the changes, the more relevant functions seem to be those involved in increasing the sequence number, scanning folios, isolating and evicting them, and the aging logic, such as `lru_gen_imbalanced`, and so on. These all feed into `try_to_shrink_lruvec` or `run_eviction`, which is then called by `lru_gen_soft_reclaim` and `max_lru_gen_memcg`. The question is, which of these is the most effective entry point? `lru_gen_soft_reclaim` and `max_lru_gen_memcg` are non-static. That seems like a good place to start. I need to investigate them further to see if they are a good fit for my `FocusSymbols`.
18/2	2026/08/12 12:43	tool	grepper	0m Args: { "Expression": "(lru_gen_soft_reclaim\|max_lru_gen_memcg)", "PathPrefix": "mm/" } Results: { "Output": "mm/memcontrol-v1.c=180=static void memcg1_update_tree(struct mem_cgroup memcg, int nid)\n--\nmm/memcontrol-v1.c-187-\t\tif (soft_limit_excess(memcg))\nmm/memcontrol-v1.c:188:\t\t\tlru_gen_soft_reclaim(memcg, nid);\nmm/memcontrol-v1.c-189-\t\treturn;\n--\nmm/memcontrol.c=277=static void memcg_reparent_objcgs(struct mem_cgroup memcg)\n--\nmm/memcontrol.c-285-\t\tif (lru_gen_enabled())\nmm/memcontrol.c:286:\t\t\tmax_lru_gen_memcg(parent, nid);\nmm/memcontrol.c-287-\n--\nmm/vmscan.c=4543=void lru_gen_release_memcg(struct mem_cgroup memcg)\n--\nmm/vmscan.c-4568-\nmm/vmscan.c:4569:void lru_gen_soft_reclaim(struct mem_cgroup memcg, int nid)\nmm/vmscan.c-4570-{\n--\nmm/vmscan.c=4591=static void try_to_inc_max_seq_nowalk(struct mem_cgroup memcg,\n--\nmm/vmscan.c-4624- /\nmm/vmscan.c:4625:void max_lru_gen_memcg(struct mem_cgroup *memcg, int nid)\nmm/vmscan.c-4626-{\n" }
19/2	2026/08/12 12:43	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 25999 output: 29 thoughts: 61 Thoughts: Here's my summary, as though I'm thinking through this process: Diving into Memory Management Interdependencies Okay, so I'm tracing some memory reclaim logic here. I see that `lru_gen_soft_reclaim` is triggered by `memcg1_update_tree`. That's important – it tells me how soft reclaim, presumably related to generational LRU, gets initiated during memory control group updates. Now, I have to remember the specifics of that call and its implications for how memcg pressure is addressed. Then I note `max_lru_gen_memcg` is invoked from `memcg_reparent_objcgs`, which makes sense. Reparenting object cgroups probably involves readjusting limits and, by extension, maximum generational LRU values for a memcg. So I need to go over the nuances of that interaction too. I'm wondering if there's any complex interactions with page ownership happening here. Now, a critical question arises: What about `try_to_free_pages`? Where does that fit in this whole picture? Is this being called directly, or is there a layer of abstraction? It might be the core page freeing mechanism, but I need to understand its role and how it interacts with the calls I've just identified. I should probably review the call chain and understand where this comes in. What are the conditions that trigger it? What are the implications of its success or failure?
20/2	2026/08/12 12:43	tool	grepper	0m Args: { "Expression": "try_to_free_pages", "PathPrefix": "mm/" } Results: { "Output": "mm/internal.h=69=unsigned long zone_reclaimable_pages(struct zone zone);\nmm/internal.h:70:unsigned long try_to_free_pages(struct zonelist zonelist, int order,\nmm/internal.h-71-\t\t\t\tgfp_t gfp_mask, const nodemask_t mask);\n--\nmm/page_alloc.c=4438=__perform_reclaim(gfp_t gfp_mask, unsigned int order,\n--\nmm/page_alloc.c-4450-\nmm/page_alloc.c:4451:\tprogress = try_to_free_pages(ac-\u003ezonelist, order, gfp_mask,\nmm/page_alloc.c-4452-\t\t\t\t\t\t\t\tac-\u003enodemask);\n--\nmm/vmscan.c=6697=static void snapshot_refaults(struct mem_cgroup target_memcg, pg_data_t pgdat)\n--\nmm/vmscan.c-6727- /\nmm/vmscan.c:6728:static unsigned long do_try_to_free_pages(struct zonelist zonelist,\nmm/vmscan.c-6729-\t\t\t\t\t struct scan_control sc)\n--\nmm/vmscan.c=6870=static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist zonelist,\n--\nmm/vmscan.c-6949-\nmm/vmscan.c:6950:unsigned long try_to_free_pages(struct zonelist zonelist, int order,\nmm/vmscan.c-6951-\t\t\t\tgfp_t gfp_mask, const nodemask_t nodemask)\n--\nmm/vmscan.c-6984-\nmm/vmscan.c:6985:\tnr_reclaimed = do_try_to_free_pages(zonelist, \u0026sc);\nmm/vmscan.c-6986-\n--\nmm/vmscan.c=7036=unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup memcg,\n--\nmm/vmscan.c-7067-\nmm/vmscan.c:7068:\tnr_reclaimed = do_try_to_free_pages(zonelist, \u0026sc);\nmm/vmscan.c-7069-\n--\nmm/vmscan.c=7834=unsigned long shrink_all_memory(unsigned long nr_to_reclaim)\n--\nmm/vmscan.c-7853-\nmm/vmscan.c:7854:\tnr_reclaimed = do_try_to_free_pages(zonelist, \u0026sc);\nmm/vmscan.c-7855-\n" }
21/2	2026/08/12 12:43	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 27098 output: 33 thoughts: 77 Thoughts: Okay, here's my understanding, tailored for an expert audience, as if it were my own thought process: Direct & Background Reclaim Entry Points & Exploring Further MGLRU Connections Alright, so `try_to_free_pages` and `try_to_free_mem_cgroup_pages` – those are the key functions I'd reach for when thinking about direct memory reclaim. They represent a good starting point for triggering immediate freeing of pages. Then, as expected, we have `kswapd` for background reclaim, the one that runs in the background. Now, I need to zoom in on `mm/vmscan.c`. I need to figure out which other functions within that module might be relevant to MGLRU. The intent is to see if any other function is not static and may be related to the MGLRU code. It makes sense to see how these different pieces interconnect. I need to make sure I don't miss anything that has a potential impact on, or implication for, MGLRU's behavior.
22/2	2026/08/12 12:43	tool	grepper	0m Args: { "Expression": "^void lru_gen_", "PathPrefix": "mm/vmscan.c" } Results: { "Output": "mm/vmscan.c=2942=static struct mm_struct get_next_mm(struct lru_gen_mm_walk walk)\n--\nmm/vmscan.c-2960-\nmm/vmscan.c:2961:void lru_gen_add_mm(struct mm_struct mm)\nmm/vmscan.c-2962-{\n--\nmm/vmscan.c-2987-\nmm/vmscan.c:2988:void lru_gen_del_mm(struct mm_struct mm)\nmm/vmscan.c-2989-{\n--\nmm/vmscan.c-3027-#ifdef CONFIG_MEMCG\nmm/vmscan.c:3028:void lru_gen_migrate_mm(struct mm_struct mm)\nmm/vmscan.c-3029-{\n--\nmm/vmscan.c=4459=static void lru_gen_rotate_memcg(struct lruvec lruvec, int op)\n--\nmm/vmscan.c-4506-\nmm/vmscan.c:4507:void lru_gen_online_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-4508-{\n--\nmm/vmscan.c-4531-\nmm/vmscan.c:4532:void lru_gen_offline_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-4533-{\n--\nmm/vmscan.c-4542-\nmm/vmscan.c:4543:void lru_gen_release_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-4544-{\n--\nmm/vmscan.c-4568-\nmm/vmscan.c:4569:void lru_gen_soft_reclaim(struct mem_cgroup memcg, int nid)\nmm/vmscan.c-4570-{\n--\nmm/vmscan.c=4666=static void __lru_gen_reparent_memcg(struct lruvec child_lruvec, struct lruvec parent_lruvec,\n--\nmm/vmscan.c-4696-\nmm/vmscan.c:4697:void lru_gen_reparent_memcg(struct mem_cgroup memcg, struct mem_cgroup parent, int nid)\nmm/vmscan.c-4698-{\n--\nmm/vmscan.c=6029=static const struct file_operations lru_gen_ro_fops = {\n--\nmm/vmscan.c-6039-\nmm/vmscan.c:6040:void lru_gen_init_pgdat(struct pglist_data pgdat)\nmm/vmscan.c-6041-{\n--\nmm/vmscan.c-6051-\nmm/vmscan.c:6052:void lru_gen_init_lruvec(struct lruvec lruvec)\nmm/vmscan.c-6053-{\n--\nmm/vmscan.c-6073-\nmm/vmscan.c:6074:void lru_gen_init_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-6075-{\n--\nmm/vmscan.c-6084-\nmm/vmscan.c:6085:void lru_gen_exit_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-6086-{\n" }
23/2	2026/08/12 12:43	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 28350 output: 33 thoughts: 16 Thoughts: Okay, here's my interpretation of that thought, expressed as if it were my own: Analyzing the Scope of `lru_gen_look_around` Hmm, `lru_gen_look_around`... right, it's not a static function. That's an important point. Knowing it's non-static immediately expands the possibilities for its usage. It means it's likely part of a larger class or module, and therefore its scope isn't limited to a single file. I need to consider where it's visible and how that might affect its interaction with other components within the system. Is it `public`, `protected`, or `private`? That's the next critical piece of information. This isn't just about implementation details, it's about the architectural implications and how this function can be leveraged or potentially modified later. I should be keeping track of all the calls to this function. Understanding its non-static nature will be important to grasp the wider context of this function's purpose.
24/2	2026/08/12 12:43	tool	grepper	0m Args: { "Expression": "^bool lru_gen_", "PathPrefix": "mm/vmscan.c" } Results: { "Output": "mm/vmscan.c=4286=static void lru_gen_age_node(struct pglist_data pgdat, struct scan_control sc)\n--\nmm/vmscan.c-4332- /\nmm/vmscan.c:4333:bool lru_gen_look_around(struct page_vma_mapped_walk pvmw, unsigned int nr)\nmm/vmscan.c-4334-{\n" }
25/2	2026/08/12 12:43	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 28741 output: 30 thoughts: 18 Thoughts: Here's my take on those thoughts: Tracing the Footsteps of `lru_gen_look_around` Okay, so I need to understand the lifecycle of `lru_gen_look_around`. My first step is to figure out everywhere this function is called. Where does the execution path begin? I need to build a mental map of how it fits into the broader architecture. Understanding its dependencies will tell me a lot. Essentially, I'm going to start with the source code, trace the usage, and see how it is working, hoping to paint a picture of the overall design and architecture.
26/2	2026/08/12 12:43	tool	grepper	0m Args: { "Expression": "lru_gen_look_around", "PathPrefix": "mm/" } Results: { "Output": "mm/rmap.c=918=static bool folio_referenced_one(struct folio folio,\n--\nmm/rmap.c-982-\t\tif (lru_gen_enabled() \u0026\u0026 !lru_gen_switching() \u0026\u0026 pvmw.pte) {\nmm/rmap.c:983:\t\t\tif (lru_gen_look_around(\u0026pvmw, nr))\nmm/rmap.c-984-\t\t\t\treferenced++;\n--\nmm/vmscan.c=2807=static bool __maybe_unused seq_is_valid(struct lruvec lruvec)\n--\nmm/vmscan.c-2836- * walk_pmd_range(); the eviction also report them when walking the rmap\nmm/vmscan.c:2837: * in lru_gen_look_around().\nmm/vmscan.c-2838- \n--\nmm/vmscan.c=4139=static bool try_to_inc_max_seq(struct lruvec lruvec, unsigned long seq,\n--\nmm/vmscan.c-4158-\t * If the hardware doesn't automatically set the accessed bit, fallback\nmm/vmscan.c:4159:\t * to lru_gen_look_around(), which only clears the accessed bit in a\nmm/vmscan.c-4160-\t * handful of PTEs. Spreading the work out over a period of time usually\n--\nmm/vmscan.c=4286=static void lru_gen_age_node(struct pglist_data pgdat, struct scan_control sc)\n--\nmm/vmscan.c-4332- /\nmm/vmscan.c:4333:bool lru_gen_look_around(struct page_vma_mapped_walk pvmw, unsigned int nr)\nmm/vmscan.c-4334-{\n" }
27/2	2026/08/12 12:43	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 29393 output: 33 thoughts: 1514 Thoughts: Analyzing MGLRU Eviction Path Entry Points Okay, so I'm digging into this MGLRU patch, and it seems like the core changes are centered around eviction and aging within `mm/vmscan.c`. The initial call stack points to `lru_gen_look_around` from `folio_referenced_one` in `mm/rmap.c`, but the meat of the modified functions—`folio_inc_gen`, `__folio_inc_gen`, `inc_min_seq`, `scan_folios`, `get_type_to_scan`, `isolate_folios`, `evict_folios`, `lru_gen_imbalanced`, and `should_run_aging`—are all deeply involved in the eviction process. The eviction path itself is triggered by `try_to_shrink_lruvec` and `run_eviction`, and it looks like `run_eviction` is the critical function here, being called by `lru_gen_soft_reclaim` (for cgroup v1 soft limit reclaim) and `max_lru_gen_memcg` (when a memcg is offlined). `try_to_shrink_lruvec` is called from `lru_gen_shrink_lruvec` which is then called from `shrink_lruvec`, `shrink_node`, which finally are called from `do_try_to_free_pages` and `kswapd`. Therefore, the main entry points I'm focusing on are initially: `try_to_free_pages`, `try_to_free_mem_cgroup_pages`, `lru_gen_soft_reclaim`, and `max_lru_gen_memcg`. `try_to_free_pages` and `try_to_free_mem_cgroup_pages` are the obvious direct reclaim entry points, but the others are MGLRU-specific. I've also considered other entry points, such as `kswapd`, but it seems like a kernel thread that's not easily triggered via an interface. `shrink_all_memory` is also a possibility, but it looks like that is related to hibernation. However, `try_to_free_pages` is a hot-path function. The instructions say to avoid listing those to prevent skewed tests, which makes me think that, given the depth of these changes in the reclaim logic, it's not the ideal focus. Then, I thought about whether there are other MGLRU-specific entry points, such as `lru_gen_add_mm`, `lru_gen_del_mm`, etc., but it seems that these are mainly setup-related and don't directly kick off eviction. So, the cleanest options are `lru_gen_soft_reclaim` and `max_lru_gen_memcg`. Looking through the patch more closely, it's all static functions. If there are no other, non-static, non-inlined API entrypoint functions specific to this change, the best choice is to either list those triggering the logic, or omit the `FocusSymbols` entry. I still think `lru_gen_soft_reclaim` and `max_lru_gen_memcg` are pretty good. They're non-static and they're specific to MGLRU. They both call `run_eviction`, which in turn, calls the modified functions, specifically `evict_folios`. I'll double-check `mm/vmscan.c` one more time to make sure I haven't missed any other exported or non-static functions related to MGLRU. But for now, I'm confident that `lru_gen_soft_reclaim` and `max_lru_gen_memcg` are the best choices for testing these MGLRU changes.
28/2	2026/08/12 12:43	tool	grepper	0m Args: { "Expression": "^void lru_gen_", "PathPrefix": "mm/vmscan.c" } Results: { "Output": "mm/vmscan.c=2942=static struct mm_struct get_next_mm(struct lru_gen_mm_walk walk)\n--\nmm/vmscan.c-2960-\nmm/vmscan.c:2961:void lru_gen_add_mm(struct mm_struct mm)\nmm/vmscan.c-2962-{\n--\nmm/vmscan.c-2987-\nmm/vmscan.c:2988:void lru_gen_del_mm(struct mm_struct mm)\nmm/vmscan.c-2989-{\n--\nmm/vmscan.c-3027-#ifdef CONFIG_MEMCG\nmm/vmscan.c:3028:void lru_gen_migrate_mm(struct mm_struct mm)\nmm/vmscan.c-3029-{\n--\nmm/vmscan.c=4459=static void lru_gen_rotate_memcg(struct lruvec lruvec, int op)\n--\nmm/vmscan.c-4506-\nmm/vmscan.c:4507:void lru_gen_online_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-4508-{\n--\nmm/vmscan.c-4531-\nmm/vmscan.c:4532:void lru_gen_offline_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-4533-{\n--\nmm/vmscan.c-4542-\nmm/vmscan.c:4543:void lru_gen_release_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-4544-{\n--\nmm/vmscan.c-4568-\nmm/vmscan.c:4569:void lru_gen_soft_reclaim(struct mem_cgroup memcg, int nid)\nmm/vmscan.c-4570-{\n--\nmm/vmscan.c=4666=static void __lru_gen_reparent_memcg(struct lruvec child_lruvec, struct lruvec parent_lruvec,\n--\nmm/vmscan.c-4696-\nmm/vmscan.c:4697:void lru_gen_reparent_memcg(struct mem_cgroup memcg, struct mem_cgroup parent, int nid)\nmm/vmscan.c-4698-{\n--\nmm/vmscan.c=6029=static const struct file_operations lru_gen_ro_fops = {\n--\nmm/vmscan.c-6039-\nmm/vmscan.c:6040:void lru_gen_init_pgdat(struct pglist_data pgdat)\nmm/vmscan.c-6041-{\n--\nmm/vmscan.c-6051-\nmm/vmscan.c:6052:void lru_gen_init_lruvec(struct lruvec lruvec)\nmm/vmscan.c-6053-{\n--\nmm/vmscan.c-6073-\nmm/vmscan.c:6074:void lru_gen_init_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-6075-{\n--\nmm/vmscan.c-6084-\nmm/vmscan.c:6085:void lru_gen_exit_memcg(struct mem_cgroup memcg)\nmm/vmscan.c-6086-{\n" }
29/2	2026/08/12 12:43	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 32688 output: 30 thoughts: 347 Thoughts: My Analysis of the Code Modification and Testing Strategy Okay, so I'm thinking that `lru_gen_soft_reclaim` and `max_lru_gen_memcg` seem like solid entry points for understanding the modified code's execution, especially since `try_to_free_pages` and `try_to_free_mem_cgroup_pages` are where the direct reclaim actions are happening. Even though they're performance-critical, and the instructions told me to avoid those types of functions, those are the functions where I'll see my code running. I might also need to consider `lru_gen_look_around`. Wait a minute, let me not jump the gun and remember the instructions: I need to check the Kconfig files for any specific `CONFIG_` options that are critical for testing this feature properly. I shouldn't make any assumptions; I need to look for ifdefs around the code. Also, I need to check the "depends on" lines in the Kconfig files. The instructions said not to add the "CONFIG_" prefix. Alright, let's look at the dependencies of `LRU_GEN`. I see it depends on `MMU` and either `64BIT` or `!SPARSEMEM` or `SPARSEMEM_VMEMMAP`. Those are pretty standard, so I don't think they're anything special to worry about. So, `LRU_GEN` and `LRU_GEN_ENABLED` are the configurations I need to focus on. I should double-check to make sure there aren't any other configurations that could be necessary.
30/2	2026/08/12 12:43	tool	grepper	0m Args: { "Expression": "#ifdef CONFIG_", "PathPrefix": "mm/vmscan.c" } Results: { "Output": "mm/vmscan.c=215=static int sc_swappiness(struct scan_control sc, struct mem_cgroup memcg)\n--\nmm/vmscan.c-221-\nmm/vmscan.c:222:#ifdef CONFIG_MEMCG\nmm/vmscan.c-223-\n--\nmm/vmscan.c=252=static bool writeback_throttling_sane(struct scan_control sc)\n--\nmm/vmscan.c-255-\t\treturn true;\nmm/vmscan.c:256:#ifdef CONFIG_CGROUP_WRITEBACK\nmm/vmscan.c-257-\tif (cgroup_subsys_on_dfl(memory_cgrp_subsys))\n--\nmm/vmscan.c=846=enum folio_references {\n--\nmm/vmscan.c-851-\nmm/vmscan.c:852:#ifdef CONFIG_LRU_GEN\nmm/vmscan.c-853-/\n--\nmm/vmscan.c=1077=static unsigned int shrink_folio_list(struct list_head folio_list,\n--\nmm/vmscan.c-1306-\t\t\t\t\tgoto activate_locked;\nmm/vmscan.c:1307:#ifdef CONFIG_TRANSPARENT_HUGEPAGE\nmm/vmscan.c-1308-\t\t\t\tif (nr_pages \u003e= HPAGE_PMD_NR) {\n--\nmm/vmscan.c=2699=static bool can_age_anon_pages(struct lruvec lruvec,\n--\nmm/vmscan.c-2710-\nmm/vmscan.c:2711:#ifdef CONFIG_LRU_GEN\nmm/vmscan.c-2712-\nmm/vmscan.c=2713=DEFINE_STATIC_KEY_FALSE(lru_switch);\nmm/vmscan.c:2714:#ifdef CONFIG_LRU_GEN_ENABLED\nmm/vmscan.c-2715-DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS);\n--\nmm/vmscan.c=2763=static struct lruvec get_lruvec(struct mem_cgroup memcg, int nid)\n--\nmm/vmscan.c-2766-\nmm/vmscan.c:2767:#ifdef CONFIG_MEMCG\nmm/vmscan.c-2768-\tif (memcg) {\n--\nmm/vmscan.c=2899=static void reset_bloom_filter(struct lru_gen_mm_state mm_state, unsigned long seq)\n--\nmm/vmscan.c-2918-\nmm/vmscan.c:2919:#ifdef CONFIG_LRU_GEN_WALKS_MMU\nmm/vmscan.c-2920-\nmm/vmscan.c=2921=static struct lru_gen_mm_list get_mm_list(struct mem_cgroup memcg)\n--\nmm/vmscan.c-2927-\nmm/vmscan.c:2928:#ifdef CONFIG_MEMCG\nmm/vmscan.c-2929-\tif (memcg)\n--\nmm/vmscan.c=2961=void lru_gen_add_mm(struct mm_struct mm)\n--\nmm/vmscan.c-2967-\tVM_WARN_ON_ONCE(!list_empty(\u0026mm-\u003elru_gen.list));\nmm/vmscan.c:2968:#ifdef CONFIG_MEMCG\nmm/vmscan.c-2969-\tVM_WARN_ON_ONCE(mm-\u003elru_gen.memcg);\n--\nmm/vmscan.c=2988=void lru_gen_del_mm(struct mm_struct mm)\n--\nmm/vmscan.c-2996-\nmm/vmscan.c:2997:#ifdef CONFIG_MEMCG\nmm/vmscan.c-2998-\tmemcg = mm-\u003elru_gen.memcg;\n--\nmm/vmscan.c-3020-\nmm/vmscan.c:3021:#ifdef CONFIG_MEMCG\nmm/vmscan.c-3022-\tmem_cgroup_put(mm-\u003elru_gen.memcg);\n--\nmm/vmscan.c-3026-\nmm/vmscan.c:3027:#ifdef CONFIG_MEMCG\nmm/vmscan.c-3028-void lru_gen_migrate_mm(struct mm_struct mm)\n--\nmm/vmscan.c=4459=static void lru_gen_rotate_memcg(struct lruvec lruvec, int op)\n--\nmm/vmscan.c-4504-\nmm/vmscan.c:4505:#ifdef CONFIG_MEMCG\nmm/vmscan.c-4506-\n--\nmm/vmscan.c=5786=static int lru_gen_seq_show(struct seq_file m, void v)\n--\nmm/vmscan.c-5799-\nmm/vmscan.c:5800:#ifdef CONFIG_MEMCG\nmm/vmscan.c-5801-\t\tif (memcg)\n--\nmm/vmscan.c=6052=void lru_gen_init_lruvec(struct lruvec lruvec)\n--\nmm/vmscan.c-6071-\nmm/vmscan.c:6072:#ifdef CONFIG_MEMCG\nmm/vmscan.c-6073-\n--\nmm/vmscan.c=6950=unsigned long try_to_free_pages(struct zonelist zonelist, int order,\n--\nmm/vmscan.c-6992-\nmm/vmscan.c:6993:#ifdef CONFIG_MEMCG\nmm/vmscan.c-6994-\n--\nmm/vmscan.c=7820=bool kswapd_test_hopeless(pg_data_t pgdat)\n--\nmm/vmscan.c-7824-\nmm/vmscan.c:7825:#ifdef CONFIG_HIBERNATION\nmm/vmscan.c-7826-/\n--\nmm/vmscan.c=7905=static const struct ctl_table vmscan_sysctl_table[] = {\n--\nmm/vmscan.c-7914-\t},\nmm/vmscan.c:7915:#ifdef CONFIG_NUMA\nmm/vmscan.c-7916-\t{\n--\nmm/vmscan.c=7937=module_init(kswapd_init)\nmm/vmscan.c-7938-\nmm/vmscan.c:7939:#ifdef CONFIG_NUMA\nmm/vmscan.c-7940-/\n" }
31/2	2026/08/12 12:43	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 35145 output: 171 thoughts: 1282 Thoughts: Fuzzing Configuration for MGLRU Patch Alright, let's nail down the fuzzing config for this MGLRU patch. I've got a handle on the key aspects. First, the `EnableConfigs`. It's pretty straightforward. We're dealing with `LRU_GEN` and `LRU_GEN_ENABLED`. Initially, I thought about not enabling `LRU_GEN_ENABLED` by default to give some sysfs control, but it's better for fuzzing to just enable it from the get-go. So `EnableConfigs` will be `["LRU_GEN", "LRU_GEN_ENABLED"]`. Next, I considered whether `MEMCG` is strictly required. The code touches functions used by both global and memcg reclaim. `MEMCG` isn't strictly necessary, but it's a good idea to have it enabled in fuzzing kernels anyway. No further action needed here. Now, the `FocusSymbols`. That's where it gets interesting. I initially listed `lru_gen_soft_reclaim`, `max_lru_gen_memcg`, `lru_gen_look_around`, `try_to_free_pages`, and `try_to_free_mem_cgroup_pages`. However, I have to be careful not to pick generic hot-path functions. I realized `lru_gen_look_around` isn't actually modified by the patch, even though it's related to MGLRU. The instructions are clear: prefer non-static, non-inlined API entrypoints over internal helpers. So, although the code modified might be in static functions, I should list the non-static functions that call them. I identified the calls: - `lru_gen_soft_reclaim` and `max_lru_gen_memcg` call `run_eviction` which calls `evict_folios`. - `try_to_free_pages` and `try_to_free_mem_cgroup_pages` call `do_try_to_free_pages` which calls `shrink_zones` -> `shrink_node` -> `shrink_lruvec` -> `lru_gen_shrink_lruvec` -> `try_to_shrink_lruvec` -> `evict_folios`. So, it seemed `try_to_free_pages` and `try_to_free_mem_cgroup_pages` were important. However, I paused. Is `try_to_free_pages` too generic? It's the main entry point for direct reclaim and is called from `__alloc_pages_slowpath`. It's a hot-path function when memory is low. If I include it, I might skew the fuzzing towards memory allocation, which is a common scenario. However, the only way to trigger direct reclaim is through memory allocation. After careful consideration, I decided to simplify. I'll focus the fuzzing on the core MGLRU and memcg aspects. Also, `lru_gen_soft_reclaim` is called from `memcg1_update_tree` for cgroup v1 and `max_lru_gen_memcg` is called from `memcg_reparent_objcgs` for cgroup v2, so these focus symbols will cover the key parts of the new patch. Therefore, I will include only `lru_gen_soft_reclaim` and `max_lru_gen_memcg`. I also briefly reviewed other configs. `LRU_GEN_WALKS_MMU` is a `def_bool y` and depends on `LRU_GEN && ARCH_HAS_HW_PTE_YOUNG`. `LRU_GEN_STATS` is only for debugging. Let's do a quick patch review to ensure the fuzzing is worth it. This patch does make some big changes. It modifies MGLRU eviction, how folios are scanned and isolated, and the minimum sequence number incrementing. It adds batching, and changes swappiness. These are significant changes to the memory management logic. Therefore, the final `FocusSymbols` will be `["lru_gen_soft_reclaim", "max_lru_gen_memcg"]`. I'm confident in these settings. Now, I'll go ahead and execute `set-results`.
32/2	2026/08/12 12:44	tool	set-results	0m Args: { "EnableConfigs": [ "LRU_GEN", "LRU_GEN_ENABLED" ], "FocusSymbols": [ "lru_gen_soft_reclaim", "max_lru_gen_memcg", "try_to_free_mem_cgroup_pages" ], "Reasoning": "The patch modifies the core Multi-Gen LRU (MGLRU) memory reclaim logic, specifically the eviction path, folio scanning, and aging heuristics. It introduces batching in `inc_min_seq` and changes how `get_type_to_scan` calculates the preferred reclaim type based on swappiness. These are significant functional changes to memory management that should be fuzzed to ensure stability under memory pressure.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "LRU_GEN", "LRU_GEN_ENABLED" ], "FocusSymbols": [ "lru_gen_soft_reclaim", "max_lru_gen_memcg", "try_to_free_mem_cgroup_pages" ], "Reasoning": "The patch modifies the core Multi-Gen LRU (MGLRU) memory reclaim logic, specifically the eviction path, folio scanning, and aging heuristics. It introduces batching in `inc_min_seq` and changes how `get_type_to_scan` calculates the preferred reclaim type based on swappiness. These are significant functional changes to memory management that should be fuzzed to ensure stability under memory pressure.", "WorthFuzzing": true }
33/1	2026/08/12 12:44	action	If	0m Args: { "WorthFuzzing": true } Results: null
34/2	2026/08/12 12:44	agent	kmsan-evaluator	0m Model: best-expensive Args: null Results: { "KMSANReasoning": "The patch modifies the Multi-Gen LRU (MGLRU) page reclaim logic in `mm/vmscan.c`. It introduces batching for LRU list operations, modifies the swappiness-based type selection with a quadratic boost, and adjusts the aging and isolation heuristics. These changes manipulate internal kernel structures (`struct folio`, LRU lists) and do not introduce new allocations, user-space copies, or complex data structures where uninitialized memory could be exposed. Any potential bugs introduced by this patch would be logic errors, use-after-free, out-of-bounds accesses, or list corruptions, which are effectively detected by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory usage or info-leaks that would require KMSAN.", "NeedsKMSAN": false } Instruction: You are an expert Linux kernel security engineer specializing in kernel memory error detectors (KASAN and KMSAN). Your job is to review the provided patch series and determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer) fuzzing session in addition to standard KASAN fuzzing. CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN: - Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable a comprehensive suite of debugging tools and sanitizers, including KASAN (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks. - KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap, or page allocations) and kernel-to-user memory info-leaks. Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS. A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks that are detected ONLY by KMSAN. Look holistically at the patch series and surrounding code. Even if no direct uninitialized field accesses or new buffer allocations are added in the diff itself, a patch may alter control flow, bounds checking, or data length calculations in ways that change how the rest of the code operates on existing buffers (e.g. allowing uninitialized stack/heap memory to be read, copied to user space, or used in control flow). Do not hesitate to use your code access tools to inspect the surrounding code, called functions, and callers. Set NeedsKMSAN=true ONLY IF the patch introduces or modifies: 1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb attributes, ioctl output arguments, socket options, or BPF buffers) where fields or structure padding might not be fully initialized/zeroed. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. Set NeedsKMSAN=false IF: - The code changes primarily risk out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (these are already caught by KASAN, LOCKDEP, or standard bug detectors). - All stack/heap structures touched or introduced by the patch are fully zeroed or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied. - The patch does not introduce any risk of uninitialized memory usage or info-leaks. Use your code access tools to inspect the surrounding code if necessary, then provide detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: For your convenience, here is the diff of the changes: commit 943b18674ea159c14b89773e488c8d73e383fad9 Author: syz-cluster <triage@syzkaller.com> Date: Wed Aug 12 12:41:48 2026 +0000 syz-cluster: applied patch under review diff --git a/mm/vmscan.c b/mm/vmscan.c index be6bd26e8c578..09535d9bded5c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -191,8 +191,20 @@ struct scan_control { prefetchw(&prev->_field); \ } \ } while (0) +#define prefetchw_next_lru_folio(_folio, _base, _field) \ + do { \ + if ((_folio)->lru.next != _base) { \ + struct folio next; \ + \ + next = list_entry((_folio)->lru.next, \ + struct folio, lru); \ + prefetchw(&next->_field); \ + } \ + } while (0) + #else #define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0) +#define prefetchw_next_lru_folio(_folio, _base, _field) do { } while (0) #endif / @@ -270,6 +282,13 @@ static inline bool is_exec_file_folio(const struct folio folio, return vma_flags_test(vma_flags, VMA_EXEC_BIT) && folio_is_file_lru(folio); } +/ See get_type_to_scan(): these values always select FILE or ANON / +static inline bool is_extreme_swappiness(int swappiness) +{ + return swappiness <= MIN_SWAPPINESS + 1 \|\| + swappiness >= MAX_SWAPPINESS; +} + static void set_task_reclaim_state(struct task_struct task, struct reclaim_state rs) { @@ -3296,20 +3315,21 @@ static int folio_update_gen(struct folio folio, int gen, const vma_flags_t vma } / protect pages accessed multiple times through file descriptors / -static int folio_inc_gen(struct lruvec lruvec, struct folio folio) +static int __folio_inc_gen(struct folio folio, int old_gen, bool increased) { - int type = folio_is_file_lru(folio); - struct lru_gen_folio lrugen = &lruvec->lrugen; - int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); unsigned long new_flags, old_flags = READ_ONCE(folio->flags.f); + int new_gen; VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio); do { new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; /* folio_update_gen() has promoted this page? / - if (new_gen >= 0 && new_gen != old_gen) + if (new_gen >= 0 && new_gen != old_gen) { + if (increased) + increased = false; return new_gen; + } new_gen = (old_gen + 1) % MAX_NR_GENS; @@ -3317,8 +3337,21 @@ static int folio_inc_gen(struct lruvec lruvec, struct folio folio) new_flags \|= (new_gen + 1UL) << LRU_GEN_PGOFF; } while (!try_cmpxchg(&folio->flags.f, &old_flags, new_flags)); - lru_gen_update_size(lruvec, folio, old_gen, new_gen); + if (increased) + increased = true; + return new_gen; +} + +static int folio_inc_gen(struct lruvec lruvec, struct folio folio) +{ + int type = folio_is_file_lru(folio); + struct lru_gen_folio lrugen = &lruvec->lrugen; + int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); + bool gen_increased; + new_gen = __folio_inc_gen(folio, old_gen, &gen_increased); + if (gen_increased) + lru_gen_update_size(lruvec, folio, old_gen, new_gen); return new_gen; } @@ -3897,13 +3930,27 @@ static void clear_mm_walk(void) kfree(walk); } +static inline void flush_lru_batch(struct list_head head, struct list_head batch_end, + struct list_head dst) +{ + LIST_HEAD(movable); + + if (!batch_end) + return; + + list_cut_position(&movable, head, batch_end); + list_splice_tail_init(&movable, dst); + batch_end = NULL; +} + static bool inc_min_seq(struct lruvec lruvec, int type, int swappiness) { int zone; - int remaining = MAX_LRU_BATCH; + int remaining = MAX_LRU_BATCH / (is_extreme_swappiness(swappiness) ? 2 : 8); struct lru_gen_folio lrugen = &lruvec->lrugen; int hist = lru_hist_from_seq(lrugen->min_seq[type]); int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); + int target_gen = (old_gen + 1) % MAX_NR_GENS; / For file type, skip the check if swappiness is anon only / if (type && (swappiness == SWAPPINESS_ANON_ONLY)) @@ -3915,33 +3962,55 @@ static bool inc_min_seq(struct lruvec lruvec, int type, int swappiness) /* prevent cold/hot inversion if the type is evictable / for (zone = 0; zone < MAX_NR_ZONES; zone++) { + struct list_head target_list = &lrugen->folios[target_gen][type][zone]; struct list_head head = &lrugen->folios[old_gen][type][zone]; + unsigned long protected[MAX_NR_TIERS] = {}, delta = 0; + struct list_head pos = head->next; + struct list_head batch_end = NULL; - while (!list_empty(head)) { - struct folio folio = lru_to_folio(head); + while (pos != head) { + struct folio folio = list_entry(pos, struct folio, lru); + long nr_pages = folio_nr_pages(folio); int refs = folio_lru_refs(folio); bool workingset = folio_test_workingset(folio); + bool gen_increased; VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio); VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio); VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio); VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio); - new_gen = folio_inc_gen(lruvec, folio); - list_move_tail(&folio->lru, &lrugen->folios[new_gen][type][zone]); + prefetchw_next_lru_folio(folio, head, flags); + pos = pos->next; + new_gen = __folio_inc_gen(folio, old_gen, &gen_increased); + if (gen_increased) { + delta += nr_pages; + batch_end = &folio->lru; - / don't count the workingset being lazily promoted / - if (refs + workingset != BIT(LRU_REFS_WIDTH) + 1) { - int tier = lru_tier_from_refs(refs, workingset); - int delta = folio_nr_pages(folio); + / don't count the workingset being lazily promoted / + if (refs + workingset != BIT(LRU_REFS_WIDTH) + 1) { + int tier = lru_tier_from_refs(refs, workingset); - WRITE_ONCE(lrugen->protected[hist][type][tier], - lrugen->protected[hist][type][tier] + delta); + protected[tier] += nr_pages; + } + } else { + flush_lru_batch(head, &batch_end, target_list); + list_move(&folio->lru, &lrugen->folios[new_gen][type][zone]); } - if (!--remaining) - return false; + break; } + flush_lru_batch(head, &batch_end, target_list); + + WRITE_ONCE(lrugen->nr_pages[old_gen][type][zone], + lrugen->nr_pages[old_gen][type][zone] - delta); + WRITE_ONCE(lrugen->nr_pages[target_gen][type][zone], + lrugen->nr_pages[target_gen][type][zone] + delta); + for (int tier = 0; tier < MAX_NR_TIERS; tier++) + WRITE_ONCE(lrugen->protected[hist][type][tier], + lrugen->protected[hist][type][tier] + protected[tier]); + if (!remaining) + return false; } done: reset_ctrl_pos(lruvec, type, true); @@ -4151,20 +4220,28 @@ static void set_initial_priority(struct pglist_data pgdat, struct scan_control sc->priority = clamp(priority, DEF_PRIORITY / 2, DEF_PRIORITY); } +static inline unsigned long lruvec_gen_size(struct lru_gen_folio lrugen, + int type, unsigned long seq) +{ + int gen = lru_gen_from_seq(seq); + unsigned long size = 0; + + for (int zone = 0; zone < MAX_NR_ZONES; zone++) + size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L); + return size; +} + static unsigned long lruvec_evictable_size(struct lruvec lruvec, int swappiness) { - int gen, type, zone; + int type; unsigned long seq, total = 0; struct lru_gen_folio lrugen = &lruvec->lrugen; DEFINE_MAX_SEQ(lruvec); DEFINE_MIN_SEQ(lruvec); for_each_evictable_type(type, swappiness) { - for (seq = min_seq[type]; seq <= max_seq; seq++) { - gen = lru_gen_from_seq(seq); - for (zone = 0; zone < MAX_NR_ZONES; zone++) - total += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L); - } + for (seq = min_seq[type]; seq <= max_seq; seq++) + total += lruvec_gen_size(lrugen, type, seq); } return total; @@ -4728,7 +4805,8 @@ static bool isolate_folio(struct lruvec lruvec, struct folio folio, struct sca static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec, struct scan_control sc, int type, int tier, - struct list_head list, int isolatedp) + struct list_head list, int isolatedp, + bool exhausted) { int i; int gen; @@ -4739,12 +4817,15 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec, int skipped = 0; unsigned long remaining = nr_to_scan; struct lru_gen_folio lrugen = &lruvec->lrugen; + bool early_stop = false; VM_WARN_ON_ONCE(nr_to_scan > MAX_LRU_BATCH); VM_WARN_ON_ONCE(!list_empty(list)); - if (get_nr_gens(lruvec, type) == MIN_NR_GENS) + if (get_nr_gens(lruvec, type) == MIN_NR_GENS) { + exhausted = true; return 0; + } gen = lru_gen_from_seq(lrugen->min_seq[type]); @@ -4775,8 +4856,10 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec, skipped_zone += delta; } - if (!--remaining \|\| max(isolated, skipped_zone) >= MIN_LRU_BATCH) + if (!--remaining \|\| max(isolated, skipped_zone) >= MIN_LRU_BATCH) { + early_stop = true; break; + } } if (skipped_zone) { @@ -4785,8 +4868,10 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec, skipped += skipped_zone; } - if (!remaining \|\| isolated >= MIN_LRU_BATCH) + if (!remaining \|\| isolated >= MIN_LRU_BATCH) { + early_stop = true; break; + } } item = PGSCAN_KSWAPD + reclaimer_offset(sc); @@ -4797,6 +4882,13 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec lruvec, scanned, skipped, isolated, type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON); + /* + * If we didn't stop early, all reclaimable folios in the current + * generation have been scanned. We are exhausted if this is the last + * reclaimable generation. + / + exhausted = !early_stop && + lrugen->min_seq[type] + MIN_NR_GENS == lrugen->max_seq; isolatedp = isolated; return scanned; } @@ -4824,51 +4916,90 @@ static int get_tier_idx(struct lruvec lruvec, int type) static int get_type_to_scan(struct lruvec lruvec, int swappiness) { struct ctrl_pos sp, pv = {}; + int anon_gain, file_gain; if (swappiness <= MIN_SWAPPINESS + 1) return LRU_GEN_FILE; if (swappiness >= MAX_SWAPPINESS) return LRU_GEN_ANON; + + / + * Apply a quadratic boost based on the distance from the neutral + * balance point (swappiness = MAX_SWAPPINESS / 2). + * + * A linear weight is easily overwhelmed by historical refault cost + * when swappiness deviates from neutral. The quadratic scaling + * amplifies the weight of the preferred type smoothly. + / + if (swappiness < MAX_SWAPPINESS / 2) { + int delta = (MAX_SWAPPINESS / 2) - swappiness; + int boost = (delta delta) >> 4; + + anon_gain = swappiness; + file_gain = (MAX_SWAPPINESS - swappiness) + boost; + } else { + int delta = swappiness - (MAX_SWAPPINESS / 2); + int boost = (delta * delta) >> 4; + + anon_gain = swappiness + boost; + file_gain = MAX_SWAPPINESS - swappiness; + } + /* * Compare the sum of all tiers of anon with that of file to determine * which type to scan. / - read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, swappiness, &sp); - read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, MAX_SWAPPINESS - swappiness, &pv); + read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, anon_gain, &sp); + read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, file_gain, &pv); return positive_ctrl_err(&sp, &pv); } +static inline bool is_single_type_reclaim(int swappiness) +{ + return swappiness == MIN_SWAPPINESS \|\| + swappiness == SWAPPINESS_ANON_ONLY; +} + static int isolate_folios(unsigned long nr_to_scan, struct lruvec lruvec, struct scan_control sc, int swappiness, struct list_head list, int isolated, int isolate_type, int isolate_scanned) { - int i; - int total_scanned = 0; + bool type_fallback_allowed = !is_single_type_reclaim(swappiness); int type = get_type_to_scan(lruvec, swappiness); + int total_scanned = 0, scanned, tier; + bool exhausted, tried = false; - for_each_evictable_type(i, swappiness) { - int scanned; - int tier = get_tier_idx(lruvec, type); +retry: + tier = get_tier_idx(lruvec, type); + scanned = scan_folios(nr_to_scan, lruvec, sc, + type, tier, list, isolated, &exhausted); - scanned = scan_folios(nr_to_scan, lruvec, sc, - type, tier, list, isolated); + total_scanned += scanned; + if (isolated) { + isolate_type = type; + isolate_scanned = scanned; + return total_scanned; + } - total_scanned += scanned; - if (isolated) { - isolate_type = type; - isolate_scanned = scanned; - break; - } - / - * If scanned > 0 and isolated == 0, avoid falling back to the - * other type, as this type remains sufficient. Falling back - * too readily can disrupt the positive_ctrl_err() bias. - / - if (!scanned) - type = !type; + / + * We are running out of the current reclaim type. Fall back to + * the other type if allowed. + / + if (exhausted && type_fallback_allowed) { + type = !type; + type_fallback_allowed = false; + goto retry; + } + / + * We are not exhausted, but failed to isolate any folios due to + * races. Give this type one more chance to avoid a larger loop. + / + if (!exhausted && !tried) { + tried = true; + goto retry; } return total_scanned; @@ -4970,21 +5101,67 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec lruvec, return scanned; } +static bool lru_gen_imbalanced(struct lruvec lruvec, unsigned long max_seq, + struct scan_control sc, int type, int swappiness) +{ + struct lru_gen_folio lrugen = &lruvec->lrugen; + unsigned long young = 0, old = 0, lag = 0; + unsigned long inactive_ratio, gb; + DEFINE_MIN_SEQ(lruvec); + + / we still have enough generations to reclaim / + if (min_seq[type] + MIN_NR_GENS < max_seq) + return false; + + / + * Trigger aging if the preferred type is running low on reclaimable + * folios, provided the generation lag of the other type remains small + * enough that inc_min_seq() introduces negligible overhead + / + for (unsigned long seq = min_seq[type]; seq <= max_seq; seq++) { + unsigned long size = lruvec_gen_size(lrugen, type, seq); + + if (seq + MIN_NR_GENS > max_seq) + young += size; + else + old += size; + } + if (min_seq[!type] + MAX_NR_GENS == max_seq + 1) + lag += lruvec_gen_size(lrugen, !type, min_seq[!type]); + + / + * Borrow the adaptive ratio from inactive_is_low(), and scale + * it by sqrt(MAX_NR_GENS) to make aging less aggressive + / + gb = (young + old) >> (30 - PAGE_SHIFT); + inactive_ratio = gb ? int_sqrt(10 gb * MAX_NR_GENS) : MAX_NR_GENS; + return young > old * inactive_ratio && (lag < MAX_LRU_BATCH \|\| + (is_extreme_swappiness(swappiness) && sc->priority > 2)); +} + static bool should_run_aging(struct lruvec lruvec, unsigned long max_seq, struct scan_control sc, int swappiness) { + int type = get_type_to_scan(lruvec, swappiness); DEFINE_MIN_SEQ(lruvec); - /* have to run aging, since eviction is not possible anymore / - if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS > max_seq) + / run aging if the preferred type is exhausted / + if (min_seq[type] + MIN_NR_GENS > max_seq) return true; - / try to avoid aging, do gentle reclaim at the default priority / - if (sc->priority == DEF_PRIORITY) + / + * Try to avoid aging by doing gentle reclaim at the default + * priority. Skip gentle reclaim for extreme swappiness. + / + if (sc->priority == DEF_PRIORITY && !is_extreme_swappiness(swappiness)) return false; / better to run aging even though eviction is still possible / - return evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq; + if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS == max_seq) + return true; + + / Run aging if the preferred type is severely imbalanced across gens / + return lru_gen_imbalanced(lruvec, max_seq, sc, type, swappiness); } static long get_nr_to_scan(struct lruvec lruvec, struct scan_control *sc,
35/3	2026/08/12 12:44	llm	kmsan-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 8049 output: 186 thoughts: 482 Thoughts: Assessing Uninitialized Memory Risks in the MGLRU Patch Alright, let's break down this MGLRU patch, focusing on potential uninitialized memory vulnerabilities. My initial scan of the code modifications to `mm/vmscan.c` immediately highlights the core areas: changes to LRU generation logic, specifically around `folio_inc_gen`, `inc_min_seq`, `scan_folios`, `get_type_to_scan`, `isolate_folios`, and `should_run_aging`. There's also this new `prefetchw_next_lru_folio` function. Now, my primary concern is always uninitialized memory, right? Let's see... the patch is all about optimizing page reclaim. It's working with the `struct folio` and LRU lists, core data structures for memory management. I'm not seeing any new structures being introduced that are exposed to userspace, which is a major red flag I can immediately dismiss. It's not allocating complex data structures with potentially uninitialized fields, nor does it appear to be handling any user-space copies or dealing with the risk of information leaks. This means there isn't anything directly introducing uninitialized memory dangers. Any bugs introduced here would more likely be logic errors within the page reclaim algorithms themselves, out-of-bounds accesses when manipulating folios, use-after-free conditions, or, potentially, deadlocks if concurrency isn't handled correctly. Thankfully, KASAN, LOCKDEP, and the usual suspects are in place to catch those types of issues. Since the changes are well-contained and focused on memory management, KMSAN isn't needed here. Just to be absolutely certain, let's take a quick second look. `flush_lru_batch` is using `list_cut_position` and `list_splice_tail_init`, which are standard list manipulation functions. `inc_min_seq` is using `prefetchw_next_lru_folio` – just a prefetching optimization. `__folio_inc_gen` updates `folio->flags`. `lruvec_gen_size` reads the existing `lrugen->nr_pages`. `get_type_to_scan` is calculating some gain factors based on swappiness. `isolate_folios` has a retry loop. And `lru_gen_imbalanced` calculates some ratios. Yep, all good. No uninitialized memory risks here. Moving on.
36/3	2026/08/12 12:44	tool	set-results	0m Args: { "KMSANReasoning": "The patch modifies the Multi-Gen LRU (MGLRU) page reclaim logic in `mm/vmscan.c`. It introduces batching for LRU list operations, modifies the swappiness-based type selection with a quadratic boost, and adjusts the aging and isolation heuristics. These changes manipulate internal kernel structures (`struct folio`, LRU lists) and do not introduce new allocations, user-space copies, or complex data structures where uninitialized memory could be exposed. Any potential bugs introduced by this patch would be logic errors, use-after-free, out-of-bounds accesses, or list corruptions, which are effectively detected by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory usage or info-leaks that would require KMSAN.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch modifies the Multi-Gen LRU (MGLRU) page reclaim logic in `mm/vmscan.c`. It introduces batching for LRU list operations, modifies the swappiness-based type selection with a quadratic boost, and adjusts the aging and isolation heuristics. These changes manipulate internal kernel structures (`struct folio`, LRU lists) and do not introduce new allocations, user-space copies, or complex data structures where uninitialized memory could be exposed. Any potential bugs introduced by this patch would be logic errors, use-after-free, out-of-bounds accesses, or list corruptions, which are effectively detected by KASAN and standard kernel debugging tools. There is no risk of uninitialized memory usage or info-leaks that would require KMSAN.", "NeedsKMSAN": false }

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

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