diff --git a/[refs] b/[refs]
index 70ede398209d..1b9d9423d524 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c84a301d4a4b1cc382a6549b4e7881ce5b796d63
+refs/heads/master: 1d6165851cd8e3f919d446cd6da35dee44e8837e
diff --git a/trunk/fs/bio.c b/trunk/fs/bio.c
index 12429c9553eb..88094afc29ea 100644
--- a/trunk/fs/bio.c
+++ b/trunk/fs/bio.c
@@ -542,13 +542,18 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
 
 		if (page == prev->bv_page &&
 		    offset == prev->bv_offset + prev->bv_len) {
+			unsigned int prev_bv_len = prev->bv_len;
 			prev->bv_len += len;
 
 			if (q->merge_bvec_fn) {
 				struct bvec_merge_data bvm = {
+					/* prev_bvec is already charged in
+					   bi_size, discharge it in order to
+					   simulate merging updated prev_bvec
+					   as new bvec. */
 					.bi_bdev = bio->bi_bdev,
 					.bi_sector = bio->bi_sector,
-					.bi_size = bio->bi_size,
+					.bi_size = bio->bi_size - prev_bv_len,
 					.bi_rw = bio->bi_rw,
 				};