From 6c5a42ac344306bb3711140a3267c61276c1567b Mon Sep 17 00:00:00 2001
From: Peter Lieven <pl@kamp.de>
Date: Mon, 27 Oct 2014 10:18:46 +0100
Subject: [PATCH] block: avoid creating oversized writes in multiwrite_merge

Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block.c b/block.c
index 76fcc1d6d3..41793419d8 100644
--- a/block.c
+++ b/block.c
@@ -4446,6 +4446,11 @@ static int multiwrite_merge(BlockDriverState *bs, BlockRequest *reqs,
             merge = 0;
         }
 
+        if (bs->bl.max_transfer_length && reqs[outidx].nb_sectors +
+            reqs[i].nb_sectors > bs->bl.max_transfer_length) {
+            merge = 0;
+        }
+
         if (merge) {
             size_t size;
             QEMUIOVector *qiov = g_malloc0(sizeof(*qiov));