blk-mq: move more plug handling from blk_mq_submit_bio into blk_add_rq_to_plug

Keep all the functionality for adding a request to a plug in a single place.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211123160443.1315598-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 4a13900..3af88ff 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2662,21 +2662,6 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
                hctx->queue->mq_ops->commit_rqs(hctx);
 }
 
-static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
-{
-       if (!plug->multiple_queues) {
-               struct request *nxt = rq_list_peek(&plug->mq_list);
-
-               if (nxt && nxt->q != rq->q)
-                       plug->multiple_queues = true;
-       }
-       if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))
-               plug->has_elevator = true;
-       rq->rq_next = NULL;
-       rq_list_add(&plug->mq_list, rq);
-       plug->rq_count++;
-}
-
 /*
  * Allow 2x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
  * queues. This is important for md arrays to benefit from merging
@@ -2689,6 +2674,28 @@ static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
        return BLK_MAX_REQUEST_COUNT;
 }
 
+static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
+{
+       struct request *last = rq_list_peek(&plug->mq_list);
+
+       if (!plug->rq_count) {
+               trace_block_plug(rq->q);
+       } else if (plug->rq_count >= blk_plug_max_rq_count(plug) ||
+                  (!blk_queue_nomerges(rq->q) &&
+                   blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
+               blk_mq_flush_plug_list(plug, false);
+               trace_block_plug(rq->q);
+       }
+
+       if (!plug->multiple_queues && last && last->q != rq->q)
+               plug->multiple_queues = true;
+       if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))
+               plug->has_elevator = true;
+       rq->rq_next = NULL;
+       rq_list_add(&plug->mq_list, rq);
+       plug->rq_count++;
+}
+
 static bool blk_mq_attempt_bio_merge(struct request_queue *q,
                                     struct bio *bio, unsigned int nr_segs)
 {
@@ -2841,31 +2848,14 @@ void blk_mq_submit_bio(struct bio *bio)
                return;
        }
 
-       if (plug) {
-               unsigned int request_count = plug->rq_count;
-               struct request *last = NULL;
-
-               if (!request_count) {
-                       trace_block_plug(q);
-               } else if (!blk_queue_nomerges(q)) {
-                       last = rq_list_peek(&plug->mq_list);
-                       if (blk_rq_bytes(last) < BLK_PLUG_FLUSH_SIZE)
-                               last = NULL;
-               }
-
-               if (request_count >= blk_plug_max_rq_count(plug) || last) {
-                       blk_mq_flush_plug_list(plug, false);
-                       trace_block_plug(q);
-               }
-
+       if (plug)
                blk_add_rq_to_plug(plug, rq);
-       } else if ((rq->rq_flags & RQF_ELV) ||
-                  (rq->mq_hctx->dispatch_busy &&
-                   (q->nr_hw_queues == 1 || !is_sync))) {
+       else if ((rq->rq_flags & RQF_ELV) ||
+                (rq->mq_hctx->dispatch_busy &&
+                 (q->nr_hw_queues == 1 || !is_sync)))
                blk_mq_sched_insert_request(rq, false, true, true);
-       } else {
+       else
                blk_mq_try_issue_directly(rq->mq_hctx, rq);
-       }
 }
 
 /**