commit 381b487d54ba18c73df9db8452028a330058c505
author Paolo Bonzini <pbonzini@redhat.com> Wed Mar 06 18:02:01 2013 +0100
committer Stefan Hajnoczi <stefanha@redhat.com> Fri Mar 15 16:07:50 2013 +0100
tree ba501d114bd2f5010366e67c306ac08843186c77
parent 3647917919dfce5f731755f0ac5955a64bc12570

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>

block/qcow2-cluster.c

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index ff9ae18..d72d063 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -454,6 +454,9 @@
         *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);

block/qcow2.c

diff --git a/block/qcow2.c b/block/qcow2.c
index ad43a13..1f99866 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -621,7 +621,7 @@
         *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 @@
             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;