For a cloned bio, bi_vcnt should not be initialized since the bio_vec
array is shared and owned by the original bio. Instead, initialize
bi_iter.bi_idx to 0 to properly start iteration from the beginning
of the shared bio_vec array.

This also avoids to touch iov_iter.nr_segs, which belongs to iov_iter
implementation detail.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/bio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index e726c0e280a8..79d1fef8ad0f 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1162,8 +1162,8 @@ void bio_iov_bvec_set(struct bio *bio, const struct iov_iter *iter)
 {
 	WARN_ON_ONCE(bio->bi_max_vecs);
 
-	bio->bi_vcnt = iter->nr_segs;
 	bio->bi_io_vec = (struct bio_vec *)iter->bvec;
+	bio->bi_iter.bi_idx = 0;
 	bio->bi_iter.bi_bvec_done = iter->iov_offset;
 	bio->bi_iter.bi_size = iov_iter_count(iter);
 	bio_set_flag(bio, BIO_CLONED);
-- 
2.47.0