[Qemu-devel] [PATCH 3/3] savevm: prevent snapshot overwriting

[Miguel Di Ciurcio Filho <miguel.filho@gmail.com>]

When savevm is run using an previously saved snapshot id or name, it will
delete the original and create a new one, using the same id and name and not
prompting the user of what just happened.

This behaviour is not good, IMHO.

We add a '-f' parameter to savevm, to really force that to happen, in case the
user really wants to.

New behavior:
(qemu) savevm snap1
An snapshot named 'snap1' already exists

(qemu) savevm -f snap1

We do better error reporting in case '-f' is used too than before and don't
reuse the previous id.

Note: This patch depends on "savevm: Generate a name when run without one"

Signed-off-by: Miguel Di Ciurcio Filho <miguel.filho@gmail.com>
---
 qemu-monitor.hx |    7 ++++---
 savevm.c        |   19 ++++++++++++++-----
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/qemu-monitor.hx b/qemu-monitor.hx
index 2af3de6..683ac73 100644
--- a/qemu-monitor.hx
+++ b/qemu-monitor.hx
@@ -275,9 +275,10 @@ ETEXI
 
     {
         .name       = "savevm",
-        .args_type  = "name:s?",
-        .params     = "[tag|id]",
-        .help       = "save a VM snapshot. If no tag or id are provided, a new snapshot is created",
+        .args_type  = "force:-f,name:s?",
+        .params     = "[-f] [tag|id]",
+        .help       = "save a VM snapshot. If no tag is provided, a new one is created"
+                    "\n\t\t\t -f to overwrite an snapshot if it already exists",
         .mhandler.cmd = do_savevm,
     },
 
diff --git a/savevm.c b/savevm.c
index 025bee6..f0a4b78 100644
--- a/savevm.c
+++ b/savevm.c
@@ -1805,6 +1805,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
     struct tm tm;
 #endif
     const char *name = qdict_get_try_str(qdict, "name");
+    int force = qdict_get_try_bool(qdict, "force", 0);
 
     /* Verify if there is a device that doesn't support snapshots and is writable */
     bs = NULL;
@@ -1848,12 +1849,20 @@ void do_savevm(Monitor *mon, const QDict *qdict)
 
     if (name) {
         ret = bdrv_snapshot_find(bs, old_sn, name);
-        if (ret >= 0) {
-            pstrcpy(sn->name, sizeof(sn->name), old_sn->name);
-            pstrcpy(sn->id_str, sizeof(sn->id_str), old_sn->id_str);
-        } else {
-            pstrcpy(sn->name, sizeof(sn->name), name);
+        if (ret == 0) {
+            if (force) {
+                ret = del_existing_snapshots(mon, name);
+                if (ret < 0) {
+                    monitor_printf(mon, "Error deleting snapshot '%s', error: %d\n", name, ret);
+                    goto the_end;
+                }
+            } else {
+                monitor_printf(mon, "An snapshot named '%s' already exists\n", name);
+                goto the_end;
+            }
         }
+
+        pstrcpy(sn->name, sizeof(sn->name), name);
     } else {
 #ifdef _WIN32
         ptm = localtime(&tb.time);
-- 
1.7.1