[PATCH] block: fix double account of flush request's driver tag

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

In case of none scheduler, we share data request's driver tag for
flush request, so have to mark the flush request as INFLIGHT for
avoiding double account of this driver tag.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Fixes: 568f27006577 ("blk-mq: centralise related handling into blk_mq_get_driver_tag")
Reported-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
---
 block/blk-flush.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/block/blk-flush.c b/block/blk-flush.c
index 6e1543c10493..53abb5c73d99 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -308,9 +308,16 @@ static void blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq,
 	flush_rq->mq_ctx = first_rq->mq_ctx;
 	flush_rq->mq_hctx = first_rq->mq_hctx;
 
-	if (!q->elevator)
+	if (!q->elevator) {
 		flush_rq->tag = first_rq->tag;
-	else
+
+		/*
+		 * We borrow data request's driver tag, so have to mark
+		 * this flush request as INFLIGHT for avoiding double
+		 * account of this driver tag
+		 */
+		flush_rq->rq_flags |= RQF_MQ_INFLIGHT;
+	} else
 		flush_rq->internal_tag = first_rq->internal_tag;
 
 	flush_rq->cmd_flags = REQ_OP_FLUSH | REQ_PREFLUSH;
-- 
2.25.2