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mm: swap: prevent lruvec release in lru_gen_clear_refs()

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In the near future, a folio will no longer pin its corresponding memory
cgroup.  So an lruvec returned by folio_lruvec() could be released without
the rcu read lock or a reference to its memory cgroup.

In the current patch, the rcu read lock is employed to safeguard against
the release of the lruvec in lru_gen_clear_refs().

This serves as a preparatory measure for the reparenting of the LRU pages.

Link: https://lore.kernel.org/986cd26227191a48a7c34a2a15812d361f4ebd53.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Allen Pais <apais@linux.microsoft.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chen Ridong <chenridong@huawei.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yosry Ahmed <yosry@kernel.org>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Muchun Song
2026-03-05 19:52:39 +08:00
committed by Andrew Morton
parent d5ddaf4341
commit 74e225ffaa
1 changed files with 5 additions and 3 deletions
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8
mm/swap.c
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@@ -412,18 +412,20 @@ static void lru_gen_inc_refs(struct folio *folio)
static bool lru_gen_clear_refs(struct folio *folio)
{
struct lru_gen_folio *lrugen;
int gen = folio_lru_gen(folio);
int type = folio_is_file_lru(folio);
unsigned long seq;
if (gen < 0)
return true;
set_mask_bits(&folio->flags.f, LRU_REFS_FLAGS | BIT(PG_workingset), 0);
lrugen = &folio_lruvec(folio)->lrugen;
rcu_read_lock();
seq = READ_ONCE(folio_lruvec(folio)->lrugen.min_seq[type]);
rcu_read_unlock();
/* whether can do without shuffling under the LRU lock */
return gen == lru_gen_from_seq(READ_ONCE(lrugen->min_seq[type]));
return gen == lru_gen_from_seq(seq);
}
#else /* !CONFIG_LRU_GEN */