From a88d32af18b8a6616128c971f766eaf545966405 Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@canonical.com>
Date: Mon, 30 Nov 2015 16:05:49 +0800
Subject: blk-merge: fix computing bio->bi_seg_front_size in case of single
 segment

When bio has only one physical segment, we should set bio's
bi_seg_front_size as the real(final) size of the single segment.

Fixes: 02e707424c2ea(blk-merge: fix blk_bio_segment_split)
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
---
 block/blk-merge.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 41a55ba..e01405a 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -103,6 +103,9 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
 			bvprv = bv;
 			bvprvp = &bvprv;
 			sectors += bv.bv_len >> 9;
+
+			if (nsegs == 1 && seg_size > front_seg_size)
+				front_seg_size = seg_size;
 			continue;
 		}
 new_segment:
-- 
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