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mm/migrate: copy all referenced state via folio_migrate_lru_refs

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folio_migrate_flags() copies PG_referenced separately from the MGLRU refs
counter, which folio_migrate_refs() transfers.  Yet under MGLRU,
PG_referenced and the refs counter bits together describe the referenced
status of a folio.

Consolidate the two: rename folio_migrate_refs() to
folio_migrate_lru_refs() and let it copy the complete referenced status,
i.e., the MGLRU refs count including PG_referenced, or just PG_referenced
for the active/inactive LRU.  Drop the open-coded PG_referenced copy so
the referenced status is transferred in one place.  No behavior change is
intended: under the active/inactive LRU the extra bits are unused, so
operating on them is a noop.

Transfer the reference state first, before the destination folio is marked
up to date, as a best effort to retain referenced status.

Link: https://lore.kernel.org/20260906-mglru-flags-cleanup-v6-3-9aacbd77d4ca@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Baoquan He <baoquan.he@linux.dev>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lian Wang <lianux.mm@gmail.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Ridong Chen <ridong.chen@linux.dev>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Qi Zheng <qi.zheng@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zi Yan <ziy@nvidia.com>
This commit is contained in:
Kairui Song 2026-09-06 00:51:08 +08:00 committed by Andrew Morton
parent 64169ceea5
commit d982ba0b97
2 changed files with 18 additions and 8 deletions
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20
include/linux/mm_inline.h
View File

@ -373,11 +373,19 @@ static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio,
return true;
}
static inline void folio_migrate_refs(struct folio *new, const struct folio *old)
/**
* folio_migrate_lru_refs - copy the reference state to a new folio
* @new: the destination folio
* @old: the source folio
*
* Transfer the reference state to @new during migration: the MGLRU
* refs count, including PG_referenced, or just PG_referenced for the
* active/inactive LRU.
*/
static inline void folio_migrate_lru_refs(struct folio *new, const struct folio *old)
{
unsigned long refs = READ_ONCE(old->flags.f) & LRU_REFS_MASK;
set_mask_bits(&new->flags.f, LRU_REFS_MASK, refs);
BUILD_BUG_ON(LRU_REFS_MASK & BIT(PG_referenced));
folio_set_lru_refs(new, folio_lru_refs(old));
}
#else /* !CONFIG_LRU_GEN */
@ -406,8 +414,10 @@ static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio,
return false;
}
static inline void folio_migrate_refs(struct folio *new, const struct folio *old)
static inline void folio_migrate_lru_refs(struct folio *new, const struct folio *old)
{
if (folio_test_referenced(old))
folio_set_referenced(new);
}
#endif /* CONFIG_LRU_GEN */

6
mm/migrate.c
View File

@ -776,8 +776,9 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
{
int cpupid;
if (folio_test_referenced(folio))
folio_set_referenced(newfolio);
/* Copy the reference state, including PG_referenced */
folio_migrate_lru_refs(newfolio, folio);
if (folio_test_uptodate(folio))
folio_mark_uptodate(newfolio);
if (folio_test_clear_active(folio)) {
@ -807,7 +808,6 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
if (folio_test_idle(folio))
folio_set_idle(newfolio);
folio_migrate_refs(newfolio, folio);
/*
* Copy NUMA information to the new page, to prevent over-eager
* future migrations of this same page.