[PATCH 2/2] block: allow passing a NULL bdev to bio_alloc_clone/bio_init_clone

[Christoph Hellwig <hch@xxxxxx>]

Device mapper wants to allocate a bio before knowing the device it
gets send to, so add explicit support for that.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 block/bio.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 3cffc01e6377f..23a6838cb97e0 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -732,13 +732,15 @@ static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp)
 	bio_set_flag(bio, BIO_CLONED);
 	if (bio_flagged(bio_src, BIO_THROTTLED))
 		bio_set_flag(bio, BIO_THROTTLED);
-	if (bio->bi_bdev == bio_src->bi_bdev &&
-	    bio_flagged(bio_src, BIO_REMAPPED))
-		bio_set_flag(bio, BIO_REMAPPED);
 	bio->bi_ioprio = bio_src->bi_ioprio;
 	bio->bi_iter = bio_src->bi_iter;
 
-	bio_clone_blkg_association(bio, bio_src);
+	if (bio->bi_bdev) {
+		if (bio->bi_bdev == bio_src->bi_bdev &&
+		    bio_flagged(bio_src, BIO_REMAPPED))
+			bio_set_flag(bio, BIO_REMAPPED);
+		bio_clone_blkg_association(bio, bio_src);
+	}
 
 	if (bio_crypt_clone(bio, bio_src, gfp) < 0)
 		return -ENOMEM;
-- 
2.30.2