[merged mm-stable] mm-memcontrol-fix-data-race-on-reading-jiffies_64.patch removed from -mm tree

[merged mm-stable] mm-memcontrol-fix-data-race-on-reading-jiffies_64.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/memcontrol: fix data-race on reading jiffies_64
has been removed from the -mm tree.  Its filename was
     mm-memcontrol-fix-data-race-on-reading-jiffies_64.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Jiayuan Chen <jiayuan.chen@linux.dev>
Subject: mm/memcontrol: fix data-race on reading jiffies_64
Date: Thu, 27 Aug 2026 10:54:56 +0800

KCSAN reported a data-race between tick_do_update_jiffies64() updating
jiffies_64 and mem_cgroup_flush_stats_ratelimited() reading it directly.

Unlike jiffies, jiffies_64 is not volatile, so raw reads are plain
accesses and can even be torn on 32-bit.  Use get_jiffies_64() instead,
and fix the same pattern in mem_cgroup_flush_foreign().

Link: https://lore.kernel.org/20260827025457.116191-1-jiayuan.chen@linux.dev
Fixes: 508bed884767 ("mm: memcg: change flush_next_time to flush_last_time")
Fixes: 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing")
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: syzbot+ced4d9a8cadb5ef3adae@syzkaller.appspotmail.com
Acked-by: Muchun Song <muchun.song@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
---

 mm/memcontrol.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/memcontrol.c~mm-memcontrol-fix-data-race-on-reading-jiffies_64
+++ a/mm/memcontrol.c
@@ -757,7 +757,7 @@ static void __mem_cgroup_flush_stats(str
 		return;
 
 	if (mem_cgroup_is_root(memcg))
-		WRITE_ONCE(flush_last_time, jiffies_64);
+		WRITE_ONCE(flush_last_time, get_jiffies_64());
 
 	css_rstat_flush(&memcg->css);
 }
@@ -785,7 +785,7 @@ void mem_cgroup_flush_stats(struct mem_c
 void mem_cgroup_flush_stats_ratelimited(struct mem_cgroup *memcg)
 {
 	/* Only flush if the periodic flusher is one full cycle late */
-	if (time_after64(jiffies_64, READ_ONCE(flush_last_time) + 2*FLUSH_TIME))
+	if (time_after64(get_jiffies_64(), READ_ONCE(flush_last_time) + 2 * FLUSH_TIME))
 		mem_cgroup_flush_stats(memcg);
 }
 
@@ -3946,7 +3946,7 @@ void mem_cgroup_flush_foreign(struct bdi
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css);
 	unsigned long intv = msecs_to_jiffies(dirty_expire_interval * 10);
-	u64 now = jiffies_64;
+	u64 now = get_jiffies_64();
 	int i;
 
 	for (i = 0; i < MEMCG_CGWB_FRN_CNT; i++) {
_

Patches currently in -mm which might be from jiayuan.chen@linux.dev are