[PATCH] dm: pass origin bio's bdev to bio_alloc_clone

[Zhihao Cheng]

The origin bio carries blk-cgroup information which could be set from
foreground(task_css(css) - wbc->wb->blkcg_css), so the blkcg won't
control buffer io since commit ca522482e3eaf ("dm: pass NULL bdev to
bio_alloc_clone"). The synchronous io is still under control by blkcg,
because 'bio->bi_blkg' is set by io submitting task which has been
added into 'cgroup.procs'.

Fix it by passing origin bio's bdev to bio_alloc_clone.

Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=220985
Fixes: ca522482e3eaf ("dm: pass NULL bdev to bio_alloc_clone")
Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
---
 drivers/md/dm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index b63279202260..e763e3b02a9f 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -574,7 +574,8 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio, gfp_t g
 	struct dm_target_io *tio;
 	struct bio *clone;
 
-	clone = bio_alloc_clone(NULL, bio, gfp_mask, &md->mempools->io_bs);
+	clone = bio_alloc_clone(bio->bi_bdev, bio,
+				gfp_mask, &md->mempools->io_bs);
 	if (unlikely(!clone))
 		return NULL;
 	tio = clone_to_tio(clone);
@@ -623,7 +624,7 @@ static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti,
 		/* alloc_io() already initialized embedded clone */
 		clone = &tio->clone;
 	} else {
-		clone = bio_alloc_clone(NULL, ci->bio, gfp_mask,
+		clone = bio_alloc_clone(ci->bio->bi_bdev, ci->bio, gfp_mask,
 					&md->mempools->bs);
 		if (!clone)
 			return NULL;
-- 
2.52.0