[PATCH 19/20] block: shortcut __submit_bio_noacct for blk-mq drivers

[Christoph Hellwig]

For blk-mq drivers bios can only be inserted for the same queue.  So
bypass the complicated sorting logic in __submit_bio_noacct with
a blk-mq simpler submission helper.

Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 block/blk-core.c | 50 +++++++++++++++++++++++++++++++++---------------
 1 file changed, 35 insertions(+), 15 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index b82f48c86e6f7a..46e3c0a37cc377 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1071,20 +1071,6 @@ static noinline_for_stack bool submit_bio_checks(struct 
bio *bio)
        return false;
 }
 
-static blk_qc_t do_make_request(struct bio *bio)
-{
-       struct gendisk *disk = bio->bi_disk;
-       blk_qc_t ret = BLK_QC_T_NONE;
-
-       if (blk_crypto_bio_prep(&bio)) {
-               if (!disk->fops->submit_bio)
-                       return blk_mq_submit_bio(bio);
-               ret = disk->fops->submit_bio(bio);
-       }
-       blk_queue_exit(disk->queue);
-       return ret;
-}
-
 /*
  * The loop in this function may be a bit non-obvious, and so deserves some
  * explanation:
@@ -1127,7 +1113,11 @@ static blk_qc_t __submit_bio_noacct(struct bio *bio)
                bio_list_on_stack[1] = bio_list_on_stack[0];
                bio_list_init(&bio_list_on_stack[0]);
 
-               ret = do_make_request(bio);
+               if (blk_crypto_bio_prep(&bio))
+                       ret = bio->bi_disk->fops->submit_bio(bio);
+               else
+                       ret = BLK_QC_T_NONE;
+               blk_queue_exit(q);
 
                /*
                 * Sort new bios into those for a lower level and those for the
@@ -1153,6 +1143,34 @@ static blk_qc_t __submit_bio_noacct(struct bio *bio)
        return ret;
 }
 
+static blk_qc_t __submit_bio_noacct_mq(struct bio *bio)
+{
+       struct gendisk *disk = bio->bi_disk;
+       struct bio_list bio_list;
+       blk_qc_t ret = BLK_QC_T_NONE;
+
+       bio_list_init(&bio_list);
+       current->bio_list = &bio_list;
+
+       do {
+               WARN_ON_ONCE(bio->bi_disk != disk);
+
+               if (unlikely(bio_queue_enter(bio) != 0))
+                       continue;
+
+               if (!blk_crypto_bio_prep(&bio)) {
+                       blk_queue_exit(disk->queue);
+                       ret = BLK_QC_T_NONE;
+                       continue;
+               }
+
+               ret = blk_mq_submit_bio(bio);
+       } while ((bio = bio_list_pop(&bio_list)));
+
+       current->bio_list = NULL;
+       return ret;
+}
+
 /**
  * submit_bio_noacct - re-submit a bio to the block device layer for I/O
  * @bio:  The bio describing the location in memory and on the device.
@@ -1182,6 +1200,8 @@ blk_qc_t submit_bio_noacct(struct bio *bio)
                return BLK_QC_T_NONE;
        }
 
+       if (bio->bi_disk->queue->mq_ops)
+               return __submit_bio_noacct_mq(bio);
        return __submit_bio_noacct(bio);
 }
 EXPORT_SYMBOL(submit_bio_noacct);
-- 
2.26.2