blk-mq: cleanup blk_mq_submit_bio

Move the blk_mq_alloc_data stack allocation only into the branch
that actually needs it, and use rq->mq_hctx instead of data.hctx
to refer to the hctx.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211012104045.658051-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 98a5d08..87dc2de 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2216,10 +2216,6 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio)
        struct request_queue *q = bio->bi_bdev->bd_disk->queue;
        const int is_sync = op_is_sync(bio->bi_opf);
        const int is_flush_fua = op_is_flush(bio->bi_opf);
-       struct blk_mq_alloc_data data = {
-               .q              = q,
-               .nr_tags        = 1,
-       };
        struct request *rq;
        struct blk_plug *plug;
        struct request *same_queue_rq = NULL;
@@ -2250,9 +2246,13 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio)
                rq = plug->cached_rq;
                plug->cached_rq = rq->rq_next;
                INIT_LIST_HEAD(&rq->queuelist);
-               data.hctx = rq->mq_hctx;
        } else {
-               data.cmd_flags = bio->bi_opf;
+               struct blk_mq_alloc_data data = {
+                       .q              = q,
+                       .nr_tags        = 1,
+                       .cmd_flags      = bio->bi_opf,
+               };
+
                if (plug) {
                        data.nr_tags = plug->nr_ios;
                        plug->nr_ios = 1;
@@ -2271,7 +2271,7 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio)
 
        rq_qos_track(q, rq, bio);
 
-       cookie = request_to_qc_t(data.hctx, rq);
+       cookie = request_to_qc_t(rq->mq_hctx, rq);
 
        blk_mq_bio_to_request(rq, bio, nr_segs);
 
@@ -2286,7 +2286,7 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio)
        if (unlikely(is_flush_fua)) {
                /* Bypass scheduler for flush requests */
                blk_insert_flush(rq);
-               blk_mq_run_hw_queue(data.hctx, true);
+               blk_mq_run_hw_queue(rq->mq_hctx, true);
        } else if (plug && (q->nr_hw_queues == 1 ||
                   blk_mq_is_shared_tags(rq->mq_hctx->flags) ||
                   q->mq_ops->commit_rqs || !blk_queue_nonrot(q))) {
@@ -2333,18 +2333,17 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio)
                trace_block_plug(q);
 
                if (same_queue_rq) {
-                       data.hctx = same_queue_rq->mq_hctx;
                        trace_block_unplug(q, 1, true);
-                       blk_mq_try_issue_directly(data.hctx, same_queue_rq,
-                                       &cookie);
+                       blk_mq_try_issue_directly(same_queue_rq->mq_hctx,
+                                                 same_queue_rq, &cookie);
                }
        } else if ((q->nr_hw_queues > 1 && is_sync) ||
-                       !data.hctx->dispatch_busy) {
+                  !rq->mq_hctx->dispatch_busy) {
                /*
                 * There is no scheduler and we can try to send directly
                 * to the hardware.
                 */
-               blk_mq_try_issue_directly(data.hctx, rq, &cookie);
+               blk_mq_try_issue_directly(rq->mq_hctx, rq, &cookie);
        } else {
                /* Default case. */
                blk_mq_sched_insert_request(rq, false, true, true);