[PATCH 5.12 325/700] block: avoid double io accounting for flush request

[Greg Kroah-Hartman]

From: Ming Lei <ming.lei@xxxxxxxxxx>

[ Upstream commit 84da7acc3ba53af26f15c4b0ada446127b7a7836 ]

For flush request, rq->end_io() may be called two times, one is from
timeout handling(blk_mq_check_expired()), another is from normal
completion(__blk_mq_end_request()).

Move blk_account_io_flush() after flush_rq->ref drops to zero, so
io accounting can be done just once for flush request.

Fixes: b68663186577 ("block: add iostat counters for flush requests")
Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Tested-by: John Garry <john.garry@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210511152236.763464-2-ming.lei@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 block/blk-flush.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/block/blk-flush.c b/block/blk-flush.c
index 7942ca6ed321..1002f6c58181 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -219,8 +219,6 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error)
 	unsigned long flags = 0;
 	struct blk_flush_queue *fq = blk_get_flush_queue(q, flush_rq->mq_ctx);
 
-	blk_account_io_flush(flush_rq);
-
 	/* release the tag's ownership to the req cloned from */
 	spin_lock_irqsave(&fq->mq_flush_lock, flags);
 
@@ -230,6 +228,7 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error)
 		return;
 	}
 
+	blk_account_io_flush(flush_rq);
 	/*
 	 * Flush request has to be marked as IDLE when it is really ended
 	 * because its .end_io() is called from timeout code path too for
-- 
2.30.2