From: Ming Lei <ming.lei@redhat.com>
Date: Mon, 10 Aug 2020 11:59:50 +0800
Subject: [PATCH] block: fix double account of flush request's driver tag
Git-commit: c1e2b8422bf946c80e832cee22b3399634f87a2c
Patch-Mainline: v5.9-rc1
References: bsc#1177434

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.

Fixes: 568f27006577 ("blk-mq: centralise related handling into blk_mq_get_driver_tag")
Reported-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 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;
-- 
2.16.4