From: Wei Xu weixugc@google.com
mainline inclusion from mainline-v6.13-rc1 commit f1001f3d3b6868998cab73d10fda1a5c99ddf963 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IBET92
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
--------------------------------
When a folio is activated, lru_gen_add_folio() moves the folio to the youngest generation. But unlike folio_update_gen()/folio_inc_gen(), lru_gen_add_folio() doesn't reset the folio lru tier bits (LRU_REFS_MASK | LRU_REFS_FLAGS). This inconsistency can affect how pages are aged via folio_mark_accessed() (e.g. fd accesses), though no user visible impact related to this has been detected yet.
Note that lru_gen_add_folio() cannot clear PG_workingset if the activation is due to workingset refault, otherwise PSI accounting will be skipped. So fix lru_gen_add_folio() to clear the lru tier bits other than PG_workingset when activating a folio, and also clear all the lru tier bits when a folio is activated via folio_activate() in lru_gen_look_around().
Link: https://lkml.kernel.org/r/20241017181528.3358821-1-weixugc@google.com Fixes: 018ee47f1489 ("mm: multi-gen LRU: exploit locality in rmap") Signed-off-by: Wei Xu weixugc@google.com Cc: Axel Rasmussen axelrasmussen@google.com Cc: Brian Geffon bgeffon@google.com Cc: Jan Alexander Steffens heftig@archlinux.org Cc: Suleiman Souhlal suleiman@google.com Cc: Yu Zhao yuzhao@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Kaixiong Yu yukaixiong@huawei.com --- include/linux/mm_inline.h | 15 ++++++++++++++- include/linux/mmzone.h | 2 ++ mm/vmscan.c | 8 ++++---- 3 files changed, 20 insertions(+), 5 deletions(-)
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index 386e1eaac1fa..24049f0124a5 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -155,6 +155,11 @@ static inline int folio_lru_refs(struct folio *folio) return ((flags & LRU_REFS_MASK) >> LRU_REFS_PGOFF) + workingset; }
+static inline void folio_clear_lru_refs(struct folio *folio) +{ + set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS, 0); +} + static inline int folio_lru_gen(struct folio *folio) { unsigned long flags = READ_ONCE(folio->flags); @@ -224,6 +229,7 @@ static inline bool lru_gen_add_folio(struct lruvec *lruvec, struct folio *folio, { unsigned long seq; unsigned long flags; + unsigned long mask; int gen = folio_lru_gen(folio); int type = folio_is_file_lru(folio); int zone = folio_zonenum(folio); @@ -259,7 +265,14 @@ static inline bool lru_gen_add_folio(struct lruvec *lruvec, struct folio *folio, gen = lru_gen_from_seq(seq); flags = (gen + 1UL) << LRU_GEN_PGOFF; /* see the comment on MIN_NR_GENS about PG_active */ - set_mask_bits(&folio->flags, LRU_GEN_MASK | BIT(PG_active), flags); + mask = LRU_GEN_MASK; + /* + * Don't clear PG_workingset here because it can affect PSI accounting + * if the activation is due to workingset refault. + */ + if (folio_test_active(folio)) + mask |= LRU_REFS_MASK | BIT(PG_referenced) | BIT(PG_active); + set_mask_bits(&folio->flags, mask, flags);
lru_gen_update_size(lruvec, folio, -1, gen); /* for folio_rotate_reclaimable() */ diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 3cee238de7c8..412167d6fb41 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -404,6 +404,8 @@ enum { NR_LRU_GEN_CAPS };
+#define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset)) + #define MIN_LRU_BATCH BITS_PER_LONG #define MAX_LRU_BATCH (MIN_LRU_BATCH * 64)
diff --git a/mm/vmscan.c b/mm/vmscan.c index 10acf5b339a7..63e6f72031e9 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3284,8 +3284,6 @@ static bool should_clear_pmd_young(void) * shorthand helpers ******************************************************************************/
-#define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset)) - #define DEFINE_MAX_SEQ(lruvec) \ unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq)
@@ -4787,8 +4785,10 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) old_gen = folio_lru_gen(folio); if (old_gen < 0) folio_set_referenced(folio); - else if (old_gen != new_gen) + else if (old_gen != new_gen) { + folio_clear_lru_refs(folio); folio_activate(folio); + } }
arch_leave_lazy_mmu_mode(); @@ -5040,7 +5040,7 @@ static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct sca
/* see the comment on MAX_NR_TIERS */ if (!folio_test_referenced(folio)) - set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS, 0); + folio_clear_lru_refs(folio);
/* for shrink_folio_list() */ folio_clear_reclaim(folio);