UPSTREAM: blk-cgroup: fix list corruption from reorder of WRITE ->lqueued

[ Upstream commit d0aac236 ]

__blkcg_rstat_flush() can be run anytime, especially when blk_cgroup_bio_start
is being executed.

If WRITE of `->lqueued` is re-ordered with READ of 'bisc->lnode.next' in
the loop of __blkcg_rstat_flush(), `next_bisc` can be assigned with one
stat instance being added in blk_cgroup_bio_start(), then the local
list in __blkcg_rstat_flush() could be corrupted.

Fix the issue by adding one barrier.

Bug: 377605240
Bug: 381955521

Cc: Tejun Heo <tj@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Fixes: 3b8cc629 ("blk-cgroup: Optimize blkcg_rstat_flush()")
Change-Id: Ia61ffc39009c44ba3e1b065640b27f3c6e659026
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20240515013157.443672-3-ming.lei@redhat.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 714e59b5)