Internal snapshots and an external data file are incompatible because
snapshots require refcounting and non-linear mapping. Return an error
for all of the snapshot operations if an external data file is in use.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2-snapshot.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 5ae3407f68..a6ffae89a6 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -353,6 +353,10 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
         return -EFBIG;
     }
 
+    if (has_data_file(bs)) {
+        return -ENOTSUP;
+    }
+
     memset(sn, 0, sizeof(*sn));
 
     /* Generate an ID */
@@ -466,6 +470,10 @@ int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
     int ret;
     uint64_t *sn_l1_table = NULL;
 
+    if (has_data_file(bs)) {
+        return -ENOTSUP;
+    }
+
     /* Search the snapshot */
     snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
     if (snapshot_index < 0) {
@@ -599,6 +607,10 @@ int qcow2_snapshot_delete(BlockDriverState *bs,
     QCowSnapshot sn;
     int snapshot_index, ret;
 
+    if (has_data_file(bs)) {
+        return -ENOTSUP;
+    }
+
     /* Search the snapshot */
     snapshot_index = find_snapshot_by_id_and_name(bs, snapshot_id, name);
     if (snapshot_index < 0) {
@@ -670,6 +682,9 @@ int qcow2_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
     QCowSnapshot *sn;
     int i;
 
+    if (has_data_file(bs)) {
+        return -ENOTSUP;
+    }
     if (!s->nb_snapshots) {
         *psn_tab = NULL;
         return s->nb_snapshots;
-- 
2.20.1