From: Kevin Wolf <kwolf@redhat.com>
Date: Wed, 20 Jan 2010 14:03:05 +0000 (+0100)
Subject: qcow2: Allow updating no refcounts
X-Git-Tag: v0.12.3~30
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=afa328b1b25a624517d0c7c461571c49c6ffcf63;p=thirdparty%2Fqemu.git

qcow2: Allow updating no refcounts

There's absolutely no problem with updating the refcounts of 0 clusters.
At least snapshot code is doing this and would fail once the result of
update_refcount isn't ignored any more.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit 7322afe7eaa7211285a38ccfb754a0a52911e394)
---

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index a28acc00f2e..08e67361f10 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -284,8 +284,12 @@ static int update_refcount(BlockDriverState *bs,
     printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n",
            offset, length, addend);
 #endif
-    if (length <= 0)
+    if (length < 0) {
         return -EINVAL;
+    } else if (length == 0) {
+        return 0;
+    }
+
     start = offset & ~(s->cluster_size - 1);
     last = (offset + length - 1) & ~(s->cluster_size - 1);
     for(cluster_offset = start; cluster_offset <= last;