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mm/shrinker: fix refcount leak in shrink_slab_memcg()

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When kmem is disabled for memcg, slab-backed shrinkers are skipped. 
However, shrink_slab_memcg() doesn't drop the reference acquired via
shrinker_try_get() before continuing.

Add the missing shrinker_put().

Also, since memcg_kmem_online() and shrinker flags cannot change
dynamically, remove the shrinker from the bitmap to avoid unnecessary
future scans.

Link: https://lkml.kernel.org/r/20260204033553.50039-1-ahacigu.linux@gmail.com
Fixes: 50d09da8e1 ("mm: shrinker: make memcg slab shrink lockless")
Signed-off-by: Altan Hacigumus <ahacigu.linux@gmail.com>
Acked-by: Qi Zheng <zhengqi.arch@bytedance.com>
  Link: https://lore.kernel.org/r/20260203073757.135088-1-ahacigu.linux@gmail.com
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Altan Hacigumus 2026-02-03 19:35:53 -08:00 committed by Andrew Morton
parent b8a4b08838
commit 260d70819c
1 changed files with 4 additions and 1 deletions
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5
mm/shrinker.c
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@ -544,8 +544,11 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
/* Call non-slab shrinkers even though kmem is disabled */
if (!memcg_kmem_online() &&
!(shrinker->flags & SHRINKER_NONSLAB))
!(shrinker->flags & SHRINKER_NONSLAB)) {
clear_bit(offset, unit->map);
shrinker_put(shrinker);
continue;
}
ret = do_shrink_slab(&sc, shrinker, priority);
if (ret == SHRINK_EMPTY) {