[PATCH 4.4 03/25] blk-mq: really fix plug list flushing for nomerge queues

Greg Kroah-Hartman
2017-02-24T08:27:32Z

From: Omar Sandoval <osandov@fb.com>

commit 87c279e613f848c691111b29d49de8df3f4f56da upstream.

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@fb.com>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
block/blk-mq.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)

--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1259,12 +1259,9 @@ static blk_qc_t blk_mq_make_request(stru

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))
@@ -1355,9 +1352,11 @@ static blk_qc_t blk_sq_make_request(stru

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))