[PATCH] blk-mq: don't grab rq's refcount in blk_mq_check_expired()

[Ming Lei <ming.lei@redhat.com>]

Inside blk_mq_queue_tag_busy_iter() we already grabbed request's
refcount before calling ->fn(), so needn't to grab it one more time
in blk_mq_check_expired().

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq.c | 25 +++++++------------------
 1 file changed, 7 insertions(+), 18 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index d2725f94491d..4d3457d2957f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -917,6 +917,10 @@ void blk_mq_put_rq_ref(struct request *rq)
 		__blk_mq_free_request(rq);
 }
 
+/*
+ * This request won't be re-allocated because its refcount is held when
+ * calling this callback.
+ */
 static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
 		struct request *rq, void *priv, bool reserved)
 {
@@ -930,27 +934,12 @@ static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
 		return true;
 
 	/*
-	 * We have reason to believe the request may be expired. Take a
-	 * reference on the request to lock this request lifetime into its
-	 * currently allocated context to prevent it from being reallocated in
-	 * the event the completion by-passes this timeout handler.
-	 *
-	 * If the reference was already released, then the driver beat the
-	 * timeout handler to posting a natural completion.
-	 */
-	if (!refcount_inc_not_zero(&rq->ref))
-		return true;
-
-	/*
-	 * The request is now locked and cannot be reallocated underneath the
-	 * timeout handler's processing. Re-verify this exact request is truly
-	 * expired; if it is not expired, then the request was completed and
-	 * reallocated as a new request.
+	 * Re-verify this exact request is truly expired; if it is not expired,
+	 * then the request was completed and reallocated as a new request
+	 * after returning from blk_mq_check_expired().
 	 */
 	if (blk_mq_req_expired(rq, next))
 		blk_mq_rq_timed_out(rq, reserved);
-
-	blk_mq_put_rq_ref(rq);
 	return true;
 }
 
-- 
2.31.1