A later patch will call blk_freeze_queue_start() followed by
blk_mq_unfreeze_queue() without waiting for q_usage_counter to drop
to zero. Make sure that this doesn't cause a kernel warning to appear
by switching from percpu_ref_reinit() to percpu_ref_resurrect(). The
former namely requires that the refcount it operates on is zero.

Signed-off-by: Bart Van Assche <bvanass...@acm.org>
Reviewed-by: Ming Lei <ming....@redhat.com>
Reviewed-by: Christoph Hellwig <h...@lst.de>
Cc: Jianchao Wang <jianchao.w.w...@oracle.com>
Cc: Hannes Reinecke <h...@suse.com>
Cc: Johannes Thumshirn <jthumsh...@suse.de>
---
 block/blk-mq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 85a1c1a59c72..96d501e8663c 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -198,7 +198,7 @@ void blk_mq_unfreeze_queue(struct request_queue *q)
        freeze_depth = atomic_dec_return(&q->mq_freeze_depth);
        WARN_ON_ONCE(freeze_depth < 0);
        if (!freeze_depth) {
-               percpu_ref_reinit(&q->q_usage_counter);
+               percpu_ref_resurrect(&q->q_usage_counter);
                wake_up_all(&q->mq_freeze_wq);
        }
 }
-- 
2.19.0.605.g01d371f741-goog

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