From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 6 Mar 2013 17:02:01 +0000 (+0100)
Subject: qcow2: make is_allocated return true for zero clusters
X-Git-Tag: v1.5.0-rc0~467^2~13
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=381b487d54ba18c73df9db8452028a330058c505;p=thirdparty%2Fqemu.git

qcow2: make is_allocated return true for zero clusters

Otherwise, live migration of the top layer will miss zero clusters and
let the backing file show through.  This also matches what is done in qed.

QCOW2_CLUSTER_ZERO clusters are invalid in v2 image files.  Check this
directly in qcow2_get_cluster_offset instead of replicating the test
everywhere.

Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index ff9ae18e4a3..d72d063e6d6 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -454,6 +454,9 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
         *cluster_offset &= L2E_COMPRESSED_OFFSET_SIZE_MASK;
         break;
     case QCOW2_CLUSTER_ZERO:
+        if (s->qcow_version < 3) {
+            return -EIO;
+        }
         c = count_contiguous_clusters(nb_clusters, s->cluster_size,
                 &l2_table[l2_index], 0,
                 QCOW_OFLAG_COMPRESSED | QCOW_OFLAG_ZERO);
diff --git a/block/qcow2.c b/block/qcow2.c
index ad43a13cb0a..1f99866cf49 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -621,7 +621,7 @@ static int coroutine_fn qcow2_co_is_allocated(BlockDriverState *bs,
         *pnum = 0;
     }
 
-    return (cluster_offset != 0);
+    return (cluster_offset != 0) || (ret == QCOW2_CLUSTER_ZERO);
 }
 
 /* handle reading after the end of the backing file */
@@ -702,10 +702,6 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
             break;
 
         case QCOW2_CLUSTER_ZERO:
-            if (s->qcow_version < 3) {
-                ret = -EIO;
-                goto fail;
-            }
             qemu_iovec_memset(&hd_qiov, 0, 0, 512 * cur_nr_sectors);
             break;