+ mm-switch-deferred-split-shrinker-to-list_lru-fix-2.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: switch deferred split shrinker to list_lru fix
has been added to the -mm mm-unstable branch.  Its filename is
     mm-switch-deferred-split-shrinker-to-list_lru-fix-2.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-switch-deferred-split-shrinker-to-list_lru-fix-2.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Johannes Weiner <hannes@cmpxchg.org>
Subject: switch deferred split shrinker to list_lru fix
Date: Tue, 2 Jun 2026 17:11:46 -0400

Lance Yang points out a weirdness in the list_lru code with
cgroup.memory=nokmem: in this mode, list_lru collapses to a shared
per-node list that holds the folios, but __list_lru_add() still sets the
shrinker bit on the owning memcg.

Usually this is fine, because the generic shrinker code ignores these
random bits when !memcg_kmem_online().  But the THP shrinker still has the
SHRINKER_NONSLAB flag set, which specifically declares an independence
from kmem.  As a result, the shrinker fires twice per reclaim cycle: one
during the regular root cgroup scan, and then one more time triggered from
whichever memcg got the shrinker bit.

Drop the flag, since it's no longer true.  The deferred_split shrinker
then behaves like every other list_lru-backed shrinker under nokmem,
including the non-kmem ones (zswap, workingset shadow_nodes): skipped from
memcg-internal reclaim, driven by global reclaim only.

This needs proper cleaning up on the shrinker and list_lru side, but
that's scope for a follow-up series.  Just make it consistent now.

Link: https://lore.kernel.org/ah9PGv12mqai84ES@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Lance Yang <lance.yang@linux.dev>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nico Pache <npache@redhat.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/huge_memory.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/mm/huge_memory.c~mm-switch-deferred-split-shrinker-to-list_lru-fix-2
+++ a/mm/huge_memory.c
@@ -945,8 +945,7 @@ int folio_memcg_alloc_deferred(struct fo
 static int __init thp_shrinker_init(void)
 {
 	deferred_split_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE |
-						 SHRINKER_MEMCG_AWARE |
-						 SHRINKER_NONSLAB,
+						 SHRINKER_MEMCG_AWARE,
 						 "thp-deferred_split");
 	if (!deferred_split_shrinker)
 		return -ENOMEM;
_

Patches currently in -mm which might be from hannes@cmpxchg.org are

mm-list_lru-fix-set_shrinker_bit-call-during-race-with-cgroup-deletion.patch
mm-list_lru-lock_list_lru_of_memcg-cannot-return-null-if-skip_empty.patch
mm-list_lru-deduplicate-unlock_list_lru.patch
mm-list_lru-move-list-dead-check-to-lock_list_lru_of_memcg.patch
mm-list_lru-deduplicate-lock_list_lru.patch
mm-list_lru-introduce-caller-locking-for-additions-and-deletions.patch
mm-list_lru-introduce-folio_memcg_list_lru_alloc.patch
mm-memory-flatten-alloc_anon_folio-retry-loop.patch
mm-switch-deferred-split-shrinker-to-list_lru.patch
mm-switch-deferred-split-shrinker-to-list_lru-fix-2.patch