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Date: Thu, 11 Dec 2008 13:00:56 +0200
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] [5860] Cleanup {alloc|get}_cluster_offset() (Gleb
	Natapov)
Message-ID: <20081211110056.GJ5555@redhat.com>
References: <E1L7bah-00055e-I4@cvs.savannah.gnu.org>
	<493FD45B.5010500@codemonkey.ws>
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>

On Wed, Dec 10, 2008 at 08:38:19AM -0600, Anthony Liguori wrote:
> Hi Gleb,
>
> Anthony Liguori wrote:
>> Revision: 5860
>>           http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=5860
>> Author:   aliguori
>> Date:     2008-12-02 20:11:27 +0000 (Tue, 02 Dec 2008)
>>   
>
> According to https://bugzilla.novell.com/show_bug.cgi?id=457957, this  
> changeset breaks compressed qcow2 on write and savevm.
>
> Can you please look into this?
>
Alexander, can you try the patch below?


diff --git a/block-qcow2.c b/block-qcow2.c
index b3b5f8f..d8ac647 100644
--- a/block-qcow2.c
+++ b/block-qcow2.c
@@ -620,6 +620,9 @@ static int count_contiguous_clusters(uint64_t nb_clusters, int cluster_size,
     int i;
     uint64_t offset = be64_to_cpu(l2_table[0]) & ~mask;
 
+    if (!offset)
+        return 0;
+
     for (i = 0; i < nb_clusters; i++)
         if (offset + i * cluster_size != (be64_to_cpu(l2_table[i]) & ~mask))
             break;
@@ -981,6 +984,12 @@ static uint64_t alloc_cluster_offset(BlockDriverState *bs,
     /* how many available clusters ? */
 
     while (i < nb_clusters) {
+        i += count_contiguous_clusters(nb_clusters - i, s->cluster_size,
+                &l2_table[l2_index + i], 0);
+
+        if(be64_to_cpu(l2_table[l2_index + i]))
+            break;
+
         i += count_contiguous_free_clusters(nb_clusters - i,
                 &l2_table[l2_index + i]);
 
@@ -989,12 +998,6 @@ static uint64_t alloc_cluster_offset(BlockDriverState *bs,
         if ((cluster_offset & QCOW_OFLAG_COPIED) ||
                 (cluster_offset & QCOW_OFLAG_COMPRESSED))
             break;
-
-        i += count_contiguous_clusters(nb_clusters - i, s->cluster_size,
-                &l2_table[l2_index + i], 0);
-
-        if(be64_to_cpu(l2_table[l2_index + i]))
-            break;
     }
     nb_clusters = i;
 
--
			Gleb.