[PATCH 4.4 70/74] block: get the 1st and last bvec via helpers

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ming Lei <ming.lei@canonical.com>

commit 25e71a99f10e444cd00bb2ebccb11e1c9fb672b1 upstream.

This patch applies the two introduced helpers to
figure out the 1st and last bvec, and fixes the
original way after bio splitting.

Reported-by: Sagi Grimberg <sagig@dev.mellanox.co.il>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 include/linux/blkdev.h |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1389,11 +1389,16 @@ static inline bool bvec_gap_to_prev(stru
 static inline bool bio_will_gap(struct request_queue *q, struct bio *prev,
 			 struct bio *next)
 {
-	if (!bio_has_data(prev) || !queue_virt_boundary(q))
-		return false;
+	if (bio_has_data(prev) && queue_virt_boundary(q)) {
+		struct bio_vec pb, nb;
 
-	return __bvec_gap_to_prev(q, &prev->bi_io_vec[prev->bi_vcnt - 1],
-				  next->bi_io_vec[0].bv_offset);
+		bio_get_last_bvec(prev, &pb);
+		bio_get_first_bvec(next, &nb);
+
+		return __bvec_gap_to_prev(q, &pb, nb.bv_offset);
+	}
+
+	return false;
 }
 
 static inline bool req_gap_back_merge(struct request *req, struct bio *bio)