linux-kernel - [PATCH v3 19/30] mm: workingset: prevent lruvec release in workingset

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Message-ID: <cf64f5c0563a3fba9994d45bda5027f00afbed3f.1768389889.git.zhengqi.arch@bytedance.com>
Date: Wed, 14 Jan 2026 19:32:46 +0800
From: Qi Zheng <qi.zheng@...ux.dev>
To: hannes@...xchg.org,
	hughd@...gle.com,
	mhocko@...e.com,
	roman.gushchin@...ux.dev,
	shakeel.butt@...ux.dev,
	muchun.song@...ux.dev,
	david@...nel.org,
	lorenzo.stoakes@...cle.com,
	ziy@...dia.com,
	harry.yoo@...cle.com,
	yosry.ahmed@...ux.dev,
	imran.f.khan@...cle.com,
	kamalesh.babulal@...cle.com,
	axelrasmussen@...gle.com,
	yuanchu@...gle.com,
	weixugc@...gle.com,
	chenridong@...weicloud.com,
	mkoutny@...e.com,
	akpm@...ux-foundation.org,
	hamzamahfooz@...ux.microsoft.com,
	apais@...ux.microsoft.com,
	lance.yang@...ux.dev
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org,
	Muchun Song <songmuchun@...edance.com>,
	Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH v3 19/30] mm: workingset: prevent lruvec release in workingset_refault()

From: Muchun Song <songmuchun@...edance.com>

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 workingset_refault().

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

Signed-off-by: Muchun Song <songmuchun@...edance.com>
Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
Reviewed-by: Harry Yoo <harry.yoo@...cle.com>
---
 mm/workingset.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/workingset.c b/mm/workingset.c
index 79b40f058cd48..5fbf316fb0e71 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -539,6 +539,7 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset,
 void workingset_refault(struct folio *folio, void *shadow)
 {
 	bool file = folio_is_file_lru(folio);
+	struct mem_cgroup *memcg;
 	struct lruvec *lruvec;
 	bool workingset;
 	long nr;
@@ -560,11 +561,12 @@ void workingset_refault(struct folio *folio, void *shadow)
 	 * locked to guarantee folio_memcg() stability throughout.
 	 */
 	nr = folio_nr_pages(folio);
-	lruvec = folio_lruvec(folio);
+	memcg = get_mem_cgroup_from_folio(folio);
+	lruvec = mem_cgroup_lruvec(memcg, folio_pgdat(folio));
 	mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file, nr);
 
 	if (!workingset_test_recent(shadow, file, &workingset, true))
-		return;
+		goto out;
 
 	folio_set_active(folio);
 	workingset_age_nonresident(lruvec, nr);
@@ -580,6 +582,8 @@ void workingset_refault(struct folio *folio, void *shadow)
 		lru_note_cost_refault(folio);
 		mod_lruvec_state(lruvec, WORKINGSET_RESTORE_BASE + file, nr);
 	}
+out:
+	mem_cgroup_put(memcg);
 }
 
 /**
-- 
2.20.1