From: Jeff Cody <jcody@redhat.com>
Date: Wed, 23 Jul 2014 21:22:57 +0000 (-0400)
Subject: block: allow bdrv_unref() to be passed NULL pointers
X-Git-Tag: qemu-xen-4.6.0-rc1~264^2~28
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=9a4d5ca60772e09d0cbac01f1b4778aa68e00eaa;p=qemu-xen.git

block: allow bdrv_unref() to be passed NULL pointers

If bdrv_unref() is passed a NULL BDS pointer, it is safe to
exit with no operation.  This will allow cleanup code to blindly
call bdrv_unref() on a BDS that has been initialized to NULL.

Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---

diff --git a/block.c b/block.c
index 6b29285381..d7cb7d48fa 100644
--- a/block.c
+++ b/block.c
@@ -5381,6 +5381,9 @@ void bdrv_ref(BlockDriverState *bs)
  * deleted. */
 void bdrv_unref(BlockDriverState *bs)
 {
+    if (!bs) {
+        return;
+    }
     assert(bs->refcnt > 0);
     if (--bs->refcnt == 0) {
         bdrv_delete(bs);