VisionFive2 Linux kernel

StarFive Tech Linux Kernel for VisionFive (JH7110) boards (mirror)

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author: Ming Lei <ming.lei@redhat.com> 2021-08-11 23:52:02 +0800 committer: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 2021-09-03 10:23:03 +0200 commit: 65bafad4556d99074401cc4630027bee7b0dd09e parent: 1ae8c1e2dbd78a9c571c1ca4baa8cd68ed069e00
Commit Summary:
blk-mq: don't grab rq's refcount in blk_mq_check_expired()
Diffstat:
1 file changed, 5 insertions, 22 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index c732aa581124..6dfa572ac1fc 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -923,34 +923,14 @@ static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
 	unsigned long *next = priv;
 
 	/*
-	 * Just do a quick check if it is expired before locking the request in
-	 * so we're not unnecessarilly synchronizing across CPUs.
-	 */
-	if (!blk_mq_req_expired(rq, next))
-		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.
+	 * blk_mq_queue_tag_busy_iter() has locked the request, so it cannot
+	 * be reallocated underneath the timeout handler's processing, then
+	 * the expire check is reliable. If the request is not expired, then
+	 * it 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;
 }