[PATCH 3.16.y-ckt 092/144] Fix bug in blk_rq_merge_ok

[Luis Henriques]

3.16.7-ckt10 -stable review patch.  If anyone has any objections, please let me know.

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

From: Wenbo Wang <wenbo.wang at memblaze.com>

commit 7ee8e4f3983c4ff700958a6099c8fd212ea67b94 upstream.

Use the right array index to reference the last
element of rq->biotail->bi_io_vec[]

Signed-off-by: Wenbo Wang <wenbo.wang at memblaze.com>
Reviewed-by: Chong Yuan <chong.yuan at memblaze.com>
Fixes: 66cb45aa41315 ("block: add support for limiting gaps in SG lists")
Signed-off-by: Jens Axboe <axboe at fb.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 block/blk-merge.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 54535831f1e1..25db382fd2c2 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -596,7 +596,7 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 	if (q->queue_flags & (1 << QUEUE_FLAG_SG_GAPS)) {
 		struct bio_vec *bprev;
 
-		bprev = &rq->biotail->bi_io_vec[bio->bi_vcnt - 1];
+		bprev = &rq->biotail->bi_io_vec[rq->biotail->bi_vcnt - 1];
 		if (bvec_gap_to_prev(bprev, bio->bi_io_vec[0].bv_offset))
 			return false;
 	}