block: Fix multiwrite error handling

When two requests of the same multiwrite batch fail, the callback of all
requests in that batch were called twice. This could have any kind of nasty
effects, in my case it lead to use after free and eventually a segfault.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/block.c b/block.c
index e891544dd1..06ed08ad88 100644
--- a/block.c
+++ b/block.c
@@ -1740,7 +1740,7 @@ static void multiwrite_cb(void *opaque, int ret)
 {
     MultiwriteCB *mcb = opaque;
 
-    if (ret < 0) {
+    if (ret < 0 && !mcb->error) {
         mcb->error = ret;
         multiwrite_user_cb(mcb);
     }