From: Johannes Weiner <hannes@cmpxchg.org>
Date: Wed, 27 May 2026 20:45:11 +0000 (-0400)
Subject: mm: list_lru: move list dead check to lock_list_lru_of_memcg()
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=8b98cfe2c52d7492a024b655e0978545845646cb;p=thirdparty%2Fkernel%2Fstable.git

mm: list_lru: move list dead check to lock_list_lru_of_memcg()

Only the MEMCG variant of lock_list_lru() needs to check if there is a
race with cgroup deletion and list reparenting.  Move the check to the
caller, so that the next patch can unify the lock_list_lru() variants.

Link: https://lore.kernel.org/20260527204757.2544958-5-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Liam R. Howlett (Oracle) <liam@infradead.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Lance Yang <lance.yang@linux.dev>
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: 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>
---

diff --git a/mm/list_lru.c b/mm/list_lru.c
index 5497034e80f3..7d0523e44010 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -68,17 +68,12 @@ list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)
 	return &lru->node[nid].lru;
 }
 
-static inline bool lock_list_lru(struct list_lru_one *l, bool irq)
+static inline void lock_list_lru(struct list_lru_one *l, bool irq)
 {
 	if (irq)
 		spin_lock_irq(&l->lock);
 	else
 		spin_lock(&l->lock);
-	if (unlikely(READ_ONCE(l->nr_items) == LONG_MIN)) {
-		unlock_list_lru(l, irq);
-		return false;
-	}
-	return true;
 }
 
 static inline struct list_lru_one *
@@ -90,9 +85,13 @@ lock_list_lru_of_memcg(struct list_lru *lru, int nid,
 	rcu_read_lock();
 again:
 	l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(*memcg));
-	if (likely(l) && lock_list_lru(l, irq)) {
-		rcu_read_unlock();
-		return l;
+	if (likely(l)) {
+		lock_list_lru(l, irq);
+		if (likely(READ_ONCE(l->nr_items) != LONG_MIN)) {
+			rcu_read_unlock();
+			return l;
+		}
+		unlock_list_lru(l, irq);
 	}
 	/*
 	 * Caller may simply bail out if raced with reparenting or