[PATCH 3/4] dm: fix missing bio_split() pattern code in __split_and_process_bio()

[Mike Snitzer <snitzer@redhat.com>]

Use the same BIO_QUEUE_ENTERED pattern that was established by commit
cd4a4ae4683dc ("block: don't use blocking queue entered for recursive
bio submits") by setting BIO_QUEUE_ENTERED after bio_split() and before
recursing via generic_make_request().

Also add trace_block_split() because it provides useful context about
bio splits in blktrace.

Depends-on: cd4a4ae4683dc ("block: don't use blocking queue entered for recursive bio submits")
Fixes: 18a25da84354 ("dm: ensure bio submission follows a depth-first tree walk")
Cc: stable@vger.kernel.org # 4.16+
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
 drivers/md/dm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index fbadda68e23b..6e29c2d99b99 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1654,7 +1654,9 @@ static blk_qc_t __split_and_process_bio(struct mapped_device *md,
 						   sectors[op_stat_group(bio_op(bio))], ci.sector_count);
 				part_stat_unlock();
 
+				bio_set_flag(bio, BIO_QUEUE_ENTERED);
 				bio_chain(b, bio);
+				trace_block_split(md->queue, b, bio->bi_iter.bi_sector);
 				ret = generic_make_request(bio);
 				break;
 			}
-- 
2.15.0