dm: use bio_clone_fast in alloc_io/alloc_tio

Replace open coded bio_clone_fast implementations with the actual helper.
Note that the bio allocated as part of the dm_io structure in alloc_io
will only actually be used later in alloc_tio, making this earlier
cloning of the information safe.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20220202160109.108149-12-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/dm.c

@@ -520,7 +520,7 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
 	struct dm_target_io *tio;
 	struct bio *clone;
 
-	clone = bio_alloc_bioset(NULL, 0, 0, GFP_NOIO, &md->io_bs);
+	clone = bio_clone_fast(bio, GFP_NOIO, &md->io_bs);
 
 	tio = clone_to_tio(clone);
 	tio->inside_dm_io = true;
@@ -553,8 +553,8 @@ static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti,
 		/* the dm_target_io embedded in ci->io is available */
 		tio = &ci->io->tio;
 	} else {
-		struct bio *clone = bio_alloc_bioset(NULL, 0, 0, gfp_mask,
-						     &ci->io->md->bs);
+		struct bio *clone = bio_clone_fast(ci->bio, gfp_mask,
+						   &ci->io->md->bs);
 		if (!clone)
 			return NULL;
 
@@ -562,12 +562,6 @@ static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti,
 		tio->inside_dm_io = false;
 	}
 
-	if (__bio_clone_fast(&tio->clone, ci->bio, gfp_mask) < 0) {
-		if (ci->io->tio.io)
-			bio_put(&tio->clone);
-		return NULL;
-	}
-
 	tio->magic = DM_TIO_MAGIC;
 	tio->io = ci->io;
 	tio->ti = ti;