FAILED: patch "[PATCH] block: get the 1st and last bvec via helpers" failed to apply to 4.4-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 25e71a99f10e444cd00bb2ebccb11e1c9fb672b1 Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@canonical.com>
Date: Fri, 26 Feb 2016 23:40:52 +0800
Subject: [PATCH] block: get the 1st and last bvec via helpers

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

Cc: stable@vger.kernel.org
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>

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index cd06a41581b3..d7f6bca707ef 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1394,11 +1394,16 @@ static inline bool bvec_gap_to_prev(struct request_queue *q,
 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;
+
+		bio_get_last_bvec(prev, &pb);
+		bio_get_first_bvec(next, &nb);
 
-	return __bvec_gap_to_prev(q, &prev->bi_io_vec[prev->bi_vcnt - 1],
-				  next->bi_io_vec[0].bv_offset);
+		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)