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authorTejun Heo <tj@kernel.org>2014-08-16 08:02:24 -0400
committerJens Axboe <axboe@fb.com>2014-08-21 20:37:51 -0500
commitcddd5d17642cc6881352732693c2ae6930e9ce65 (patch)
tree5fad9444dbe5b3d2347d43c2bfe77383573b9031
parenta68aafa5b297d99c2d0c38689089a752126e9e79 (diff)
downloadlinux-cddd5d17642cc6881352732693c2ae6930e9ce65.tar.bz2
blk-mq: blk_mq_freeze_queue() should allow nesting
While converting to percpu_ref for freezing, add703fda981 ("blk-mq: use percpu_ref for mq usage count") incorrectly made blk_mq_freeze_queue() misbehave when freezing is nested due to percpu_ref_kill() being invoked on an already killed ref. Fix it by making blk_mq_freeze_queue() kill and kick the queue only for the outermost freeze attempt. All the nested ones can simply wait for the ref to reach zero. While at it, remove unnecessary @wake initialization from blk_mq_unfreeze_queue(). Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Ming Lei <ming.lei@canonical.com> Signed-off-by: Jens Axboe <axboe@fb.com>
-rw-r--r--block/blk-mq.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index a0565bb20fd5..7950f8d7c1bb 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -112,18 +112,22 @@ static void blk_mq_usage_counter_release(struct percpu_ref *ref)
*/
void blk_mq_freeze_queue(struct request_queue *q)
{
+ bool freeze;
+
spin_lock_irq(q->queue_lock);
- q->mq_freeze_depth++;
+ freeze = !q->mq_freeze_depth++;
spin_unlock_irq(q->queue_lock);
- percpu_ref_kill(&q->mq_usage_counter);
- blk_mq_run_queues(q, false);
+ if (freeze) {
+ percpu_ref_kill(&q->mq_usage_counter);
+ blk_mq_run_queues(q, false);
+ }
wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter));
}
static void blk_mq_unfreeze_queue(struct request_queue *q)
{
- bool wake = false;
+ bool wake;
spin_lock_irq(q->queue_lock);
wake = !--q->mq_freeze_depth;