From 997dd8df3e95b2fdbd1f30b3deefaad4e9efd14a Mon Sep 17 00:00:00 2001
From: Liu Yuan <namei.unix@gmail.com>
Date: Thu, 11 Sep 2014 13:41:21 +0800
Subject: [PATCH] quorum: fix quorum_aio_cancel()

For a fifo read pattern, we only have one running aio (possible other cases that
has less number than num_children in the future), so we need to check if
.acb is NULL against bdrv_aio_cancel() to avoid segfault.

Cc: Eric Blake <eblake@redhat.com>
Cc: Benoit Canet <benoit@irqsave.net>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/quorum.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/quorum.c b/block/quorum.c
index 093382e8f5..41c4249547 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -138,7 +138,9 @@ static void quorum_aio_cancel(BlockDriverAIOCB *blockacb)
 
     /* cancel all callbacks */
     for (i = 0; i < s->num_children; i++) {
-        bdrv_aio_cancel(acb->qcrs[i].aiocb);
+        if (acb->qcrs[i].aiocb) {
+            bdrv_aio_cancel(acb->qcrs[i].aiocb);
+        }
     }
 
     g_free(acb->qcrs);