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: [email protected] # 4.16+
Signed-off-by: Mike Snitzer <[email protected]>
---
 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

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