qcow2: Support reading zero clusters

This adds support for reading zero clusters in version 3 images.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index 3e1482fa7e..9a8b354d0e 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -536,6 +536,14 @@ 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, 512 * cur_nr_sectors);
+            break;
+
         case QCOW2_CLUSTER_COMPRESSED:
             /* add AIO support for compressed blocks ? */
             ret = qcow2_decompress_cluster(bs, cluster_offset);