From 15552c4ad38b9ec66792b044cf5ae74538c32717 Mon Sep 17 00:00:00 2001
From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Date: Mon, 7 May 2012 16:51:03 +0800
Subject: [PATCH] qcow2: lock on prealloc

preallocate() will be locked. This is required because
qcow2_alloc_cluster_link_l2() assumes that it runs under a lock that it
can drop while COW is being performed.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/qcow2.c b/block/qcow2.c
index 8c60a6f061..ee4678f6ed 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1192,7 +1192,10 @@ static int qcow2_create2(const char *filename, int64_t total_size,
 
     /* And if we're supposed to preallocate metadata, do that now */
     if (prealloc) {
+        BDRVQcowState *s = bs->opaque;
+        qemu_co_mutex_lock(&s->lock);
         ret = preallocate(bs);
+        qemu_co_mutex_unlock(&s->lock);
         if (ret < 0) {
             goto out;
         }