From: Tejun Heo tj@kernel.org
commit 5370b0f49078203acf3c064b634a09707167a864 upstream.
c3df5fb57fe8 ("cgroup: rstat: fix A-A deadlock on 32bit around u64_stats_sync") made u64_stats updates irq-safe to avoid A-A deadlocks. Unfortunately, the conversion missed one in blk_cgroup_bio_start(). Fix it.
Fixes: 2d146aa3aa84 ("mm: memcontrol: switch to rstat") Cc: stable@vger.kernel.org # v5.13+ Reported-by: syzbot+9738c8815b375ce482a1@syzkaller.appspotmail.com Signed-off-by: Tejun Heo tj@kernel.org Link: https://lore.kernel.org/r/YWi7NrQdVlxD6J9W@slm.duckdns.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/blk-cgroup.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1916,10 +1916,11 @@ void blk_cgroup_bio_start(struct bio *bi { int rwd = blk_cgroup_io_type(bio), cpu; struct blkg_iostat_set *bis; + unsigned long flags;
cpu = get_cpu(); bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu); - u64_stats_update_begin(&bis->sync); + flags = u64_stats_update_begin_irqsave(&bis->sync);
/* * If the bio is flagged with BIO_CGROUP_ACCT it means this is a split @@ -1931,7 +1932,7 @@ void blk_cgroup_bio_start(struct bio *bi } bis->cur.ios[rwd]++;
- u64_stats_update_end(&bis->sync); + u64_stats_update_end_irqrestore(&bis->sync, flags); if (cgroup_subsys_on_dfl(io_cgrp_subsys)) cgroup_rstat_updated(bio->bi_blkg->blkcg->css.cgroup, cpu); put_cpu();