linux-kernel - [PATCH 19/20] block: shortcut __submit_bio

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Date:   Mon, 29 Jun 2020 21:39:46 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     dm-devel@...hat.com, linux-kernel@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-xtensa@...ux-xtensa.org,
        drbd-dev@...ts.linbit.com, linuxppc-dev@...ts.ozlabs.org,
        linux-bcache@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-nvme@...ts.infradead.org,
        linux-s390@...r.kernel.org
Subject: [PATCH 19/20] block: shortcut __submit_bio_noacct for blk-mq drivers

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 <hch@....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