From: Hao Zhang bio_set_dev() associates the bio with a blkg through bio_associate_blkg(). If the blkg lookup misses, blkg_tryget_closest() takes q->queue_lock with spin_lock_irq() and releases it with spin_unlock_irq(), which unconditionally enables local interrupts. Callers may call bio_set_dev() with interrupts already disabled, e.g. dm-thin's pool_map() does so while holding pool->lock taken with spin_lock_irq(). The nested spin_unlock_irq() then enables interrupts while pool->lock is still held, so an I/O completion softirq can run on the same CPU, re-acquire pool->lock (thin_endio(), or overwrite_endio() -> complete_mapping_preparation()) and deadlock. lockdep reports this as inconsistent SOFTIRQ-ON-W to IN-SOFTIRQ-W usage. Commit 3a762de55b4e ("block: save irq state in blkg_lookup_create()") fixed the same problem while the lock lived in blkg_lookup_create(), but commit 9327a865e395 ("blk-cgroup: don't nest queue_lock under rcu in blkg_lookup_create()") moved the locking into blkg_tryget_closest() and reverted it to spin_lock_irq(). Save and restore the caller's IRQ state instead. Fixes: 9327a865e395 ("blk-cgroup: don't nest queue_lock under rcu in blkg_lookup_create()") Cc: Ming Lei Signed-off-by: Hao Zhang --- block/blk-cgroup.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 2b5c29434e42..b56db1cc6778 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -2091,6 +2091,7 @@ static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio, struct request_queue *q = bio->bi_bdev->bd_queue; struct blkcg *blkcg = css_to_blkcg(css); struct blkcg_gq *blkg; + unsigned long flags; rcu_read_lock(); blkg = blkg_lookup(blkcg, q); @@ -2105,11 +2106,11 @@ static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio, * Fast path failed, we're probably issuing IO in this cgroup the first * time, hold lock to create new blkg. */ - spin_lock_irq(&q->queue_lock); + spin_lock_irqsave(&q->queue_lock, flags); blkg = blkg_lookup_create(blkcg, bio->bi_bdev->bd_disk); if (blkg) blkg = blkg_lookup_tryget(blkg); - spin_unlock_irq(&q->queue_lock); + spin_unlock_irqrestore(&q->queue_lock, flags); return blkg; } base-commit: 08df884136f1c1197bab2a27814404fd329d9aac -- 2.15.0