From: Tejun Heo Date: Thu, 14 Oct 2021 23:20:22 +0000 (-1000) Subject: blk-cgroup: blk_cgroup_bio_start() should use irq-safe operations on blkg->iostat_cpu X-Git-Tag: v5.19~2010^2~140 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=3c08b0931eedd04c530040499fadeccab50ed646;p=mirror_ubuntu-kernels.git blk-cgroup: blk_cgroup_bio_start() should use irq-safe operations on blkg->iostat_cpu 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 Link: https://lore.kernel.org/r/YWi7NrQdVlxD6J9W@slm.duckdns.org Signed-off-by: Jens Axboe --- diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 38b9f7684952..9a1c5839dd46 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1897,10 +1897,11 @@ void blk_cgroup_bio_start(struct bio *bio) { 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 @@ -1912,7 +1913,7 @@ void blk_cgroup_bio_start(struct bio *bio) } 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();