block: Add check on mirror target

Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Message-id: 1450932306-13717-4-git-send-email-famz@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

blockdev.c

@@ -3342,6 +3342,9 @@ static void blockdev_mirror_common(BlockDriverState *bs,
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_MIRROR_SOURCE, errp)) {
         return;
     }
+    if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_MIRROR_TARGET, errp)) {
+        return;
+    }
 
     if (!bs->backing && sync == MIRROR_SYNC_MODE_TOP) {
         sync = MIRROR_SYNC_MODE_FULL;

include/block/block.h

@@ -170,6 +170,7 @@ typedef enum BlockOpType {
     BLOCK_OP_TYPE_INTERNAL_SNAPSHOT,
     BLOCK_OP_TYPE_INTERNAL_SNAPSHOT_DELETE,
     BLOCK_OP_TYPE_MIRROR_SOURCE,
+    BLOCK_OP_TYPE_MIRROR_TARGET,
     BLOCK_OP_TYPE_RESIZE,
     BLOCK_OP_TYPE_STREAM,
     BLOCK_OP_TYPE_REPLACE,