blk-mq: really fix plug list flushing for nomerge queues

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>

1 files 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))