On Thu, Jun 2, 2016 at 1:18 PM, Omar Sandoval <osandov@xxxxxxxxxxx> wrote:
> From: Omar Sandoval <osandov@xxxxxx>
>
> Commit 0809e3ac6231 ("block: fix plug list flushing for nomerge queues")
> updated blk_mq_make_request() to set request_count even when
> blk_queue_nomerges() returns true. However, blk_mq_make_request() only
> does limited plugging and doesn't use request_count;
> blk_sq_make_request() is the one that should have been fixed. Do that
> and get rid of the unnecessary work in the mq version.
>
> Fixes: 0809e3ac6231 ("block: fix plug list flushing for nomerge queues")
> Signed-off-by: Omar Sandoval <osandov@xxxxxx>
Looks good catch.
Reviewed-by: Ming Lei <tom.leiming@xxxxxxxxx>
> ---
> Applies to v4.7-rc1.
>
> block/blk-mq.c | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 29cbc1b5fbdb..f9b9049b1284 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1262,12 +1262,9 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
>
> blk_queue_split(q, &bio, q->bio_split);
>
> - if (!is_flush_fua && !blk_queue_nomerges(q)) {
> - if (blk_attempt_plug_merge(q, bio, &request_count,
> - &same_queue_rq))
> - return BLK_QC_T_NONE;
> - } else
> - request_count = blk_plug_queued_count(q);
> + if (!is_flush_fua && !blk_queue_nomerges(q) &&
> + blk_attempt_plug_merge(q, bio, &request_count, &same_queue_rq))
> + return BLK_QC_T_NONE;
>
> rq = blk_mq_map_request(q, bio, &data);
> if (unlikely(!rq))
> @@ -1358,9 +1355,11 @@ static blk_qc_t blk_sq_make_request(struct request_queue *q, struct bio *bio)
>
> blk_queue_split(q, &bio, q->bio_split);
>
> - if (!is_flush_fua && !blk_queue_nomerges(q) &&
> - blk_attempt_plug_merge(q, bio, &request_count, NULL))
> - return BLK_QC_T_NONE;
> + if (!is_flush_fua && !blk_queue_nomerges(q)) {
> + if (blk_attempt_plug_merge(q, bio, &request_count, NULL))
> + return BLK_QC_T_NONE;
> + } else
> + request_count = blk_plug_queued_count(q);
>
> rq = blk_mq_map_request(q, bio, &data);
> if (unlikely(!rq))
> --
> 2.8.3
>
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--
Ming Lei
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