Messages in this thread Patch in this message | | | Date | Sat, 16 Aug 2014 08:02:24 -0400 | From | Tejun Heo <> | Subject | [PATCH] 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> --- Hello, Ming, Jens.
I think something like this is the correct solution. Freezing should be nestable after all. Ming, can you please verify whether this fixes the issue you're seeing?
Thanks.
block/blk-mq.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c index 5189cb1..5978088 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;
| |