block: avoid double io accounting for flush request

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@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: John Garry <john.garry@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210511152236.763464-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-flush.c b/block/blk-flush.c
index 7942ca6..1002f6c 100644 (file)
--- 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