blk-merge: don't compute bi_phys_segments from bi_vcnt for cloned bio

It isn't correct to figure out req->bi_phys_segments from bio->bi_vcnt
if the bio is cloned.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Tested-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/block/blk-merge.c b/block/blk-merge.c
index f71bad35b4cc..ba99351c0f58 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -97,14 +97,18 @@ void blk_recalc_rq_segments(struct request *rq)
 
 void blk_recount_segments(struct request_queue *q, struct bio *bio)
 {
-        if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
+        bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
+                        &q->queue_flags);
+
+        if (no_sg_merge && !bio_flagged(bio, BIO_CLONED) &&
                         bio->bi_vcnt < queue_max_segments(q))
                 bio->bi_phys_segments = bio->bi_vcnt;
         else {
                 struct bio *nxt = bio->bi_next;
 
                 bio->bi_next = NULL;
-                bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
+                bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio,
+                                no_sg_merge);
                 bio->bi_next = nxt;
         }