diff options
| -rw-r--r-- | blockdev.c | 14 | ||||
| -rw-r--r-- | tests/qemu-iotests/085.out | 4 |
2 files changed, 10 insertions, 8 deletions
diff --git a/blockdev.c b/blockdev.c index 257cb37682..ea89896f27 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1471,6 +1471,7 @@ static void external_snapshot_prepare(BlkActionState *common, TransactionAction *action = common->action; AioContext *aio_context; AioContext *old_context; + uint64_t perm, shared; int ret; /* 'blockdev-snapshot' and 'blockdev-snapshot-sync' have similar @@ -1586,16 +1587,17 @@ static void external_snapshot_prepare(BlkActionState *common, goto out; } - if (bdrv_has_blk(state->new_bs)) { + /* + * Allow attaching a backing file to an overlay that's already in use only + * if the parents don't assume that they are already seeing a valid image. + * (Specifically, allow it as a mirror target, which is write-only access.) + */ + bdrv_get_cumulative_perm(state->new_bs, &perm, &shared); + if (perm & BLK_PERM_CONSISTENT_READ) { error_setg(errp, "The overlay is already in use"); goto out; } - if (bdrv_op_is_blocked(state->new_bs, BLOCK_OP_TYPE_EXTERNAL_SNAPSHOT, - errp)) { - goto out; - } - if (state->new_bs->backing != NULL) { error_setg(errp, "The overlay already has a backing image"); goto out; diff --git a/tests/qemu-iotests/085.out b/tests/qemu-iotests/085.out index d94ad22f70..fd11aae678 100644 --- a/tests/qemu-iotests/085.out +++ b/tests/qemu-iotests/085.out @@ -82,7 +82,7 @@ Formatting 'TEST_DIR/12-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_f === Invalid command - cannot create a snapshot using a file BDS === { 'execute': 'blockdev-snapshot', 'arguments': { 'node':'virtio0', 'overlay':'file_12' } } -{"error": {"class": "GenericError", "desc": "The overlay does not support backing images"}} +{"error": {"class": "GenericError", "desc": "The overlay is already in use"}} === Invalid command - snapshot node used as active layer === @@ -96,7 +96,7 @@ Formatting 'TEST_DIR/12-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_f === Invalid command - snapshot node used as backing hd === { 'execute': 'blockdev-snapshot', 'arguments': { 'node': 'virtio0', 'overlay':'snap_11' } } -{"error": {"class": "GenericError", "desc": "Node 'snap_11' is busy: node is used as backing hd of 'snap_12'"}} +{"error": {"class": "GenericError", "desc": "The overlay is already in use"}} === Invalid command - snapshot node has a backing image === |