migration: control whether snapshots are ovewritten

The traditional HMP "savevm" command will overwrite an existing snapshot
if it already exists with the requested name. This new flag allows this
to be controlled allowing for safer behaviour with a future QMP command.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210204124834.774401-8-berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

diff --git a/include/migration/snapshot.h b/include/migration/snapshot.h
index d7d210820c7937918016b39b4ae868b127631d5b..d8c22d343c9fc34d400f8dfcfcb593c01c5ecd6a 100644 (file)
--- a/include/migration/snapshot.h
+++ b/include/migration/snapshot.h
@@ -18,11 +18,12 @@
 /**
  * save_snapshot: Save an internal snapshot.
  * @name: name of internal snapshot
+ * @overwrite: replace existing snapshot with @name
  * @errp: pointer to error object
  * On success, return %true.
  * On failure, store an error through @errp and return %false.
  */
-bool save_snapshot(const char *name, Error **errp);
+bool save_snapshot(const char *name, bool overwrite, Error **errp);
 
 /**
  * load_snapshot: Load an internal snapshot.

diff --git a/migration/savevm.c b/migration/savevm.c
index a2a842d067cc634fa8a4550828db51864cdd4281..0ae8e4798c175fcee201812616789463a175828d 100644 (file)
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2764,7 +2764,7 @@ int qemu_load_device_state(QEMUFile *f)
     return 0;
 }
 
-bool save_snapshot(const char *name, Error **errp)
+bool save_snapshot(const char *name, bool overwrite, Error **errp)
 {
     BlockDriverState *bs;
     QEMUSnapshotInfo sn1, *sn = &sn1;
@@ -2792,8 +2792,21 @@ bool save_snapshot(const char *name, Error **errp)
 
     /* Delete old snapshots of the same name */
     if (name) {
-        if (bdrv_all_delete_snapshot(name, false, NULL, errp) < 0) {
-            return false;
+        if (overwrite) {
+            if (bdrv_all_delete_snapshot(name, false, NULL, errp) < 0) {
+                return false;
+            }
+        } else {
+            ret2 = bdrv_all_has_snapshot(name, false, NULL, errp);
+            if (ret2 < 0) {
+                return false;
+            }
+            if (ret2 == 1) {
+                error_setg(errp,
+                           "Snapshot '%s' already exists in one or more devices",
+                           name);
+                return false;
+            }
         }
     }
 

diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index f795261f77401cae803ffec9d60da7a1d6b170b4..1fff33f14a94ce501b633b16437d9e136c3e3555 100644 (file)
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -1149,7 +1149,7 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
 {
     Error *err = NULL;
 
-    save_snapshot(qdict_get_try_str(qdict, "name"), &err);
+    save_snapshot(qdict_get_try_str(qdict, "name"), true, &err);
     hmp_handle_error(mon, err);
 }
 

diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c
index 098ef8e0f55d41ea7b8ce9d6ad5d7b6bec8ca83e..0ae6785b3b2d4e806de8eafffa8f0d27b5a24151 100644 (file)
--- a/replay/replay-debugging.c
+++ b/replay/replay-debugging.c
@@ -327,7 +327,7 @@ void replay_gdb_attached(void)
      */
     if (replay_mode == REPLAY_MODE_PLAY
         && !replay_snapshot) {
-        if (!save_snapshot("start_debugging", NULL)) {
+        if (!save_snapshot("start_debugging", true, NULL)) {
             /* Can't create the snapshot. Continue conventional debugging. */
         }
     }

diff --git a/replay/replay-snapshot.c b/replay/replay-snapshot.c
index b2893659370d141214d449c4fc6f2f1430a9f153..31c5a8702b7eab75583e4dbf98419c2b4f4587ab 100644 (file)
--- a/replay/replay-snapshot.c
+++ b/replay/replay-snapshot.c
@@ -77,7 +77,7 @@ void replay_vmstate_init(void)
 
     if (replay_snapshot) {
         if (replay_mode == REPLAY_MODE_RECORD) {
-            if (!save_snapshot(replay_snapshot, &err)) {
+            if (!save_snapshot(replay_snapshot, true, &err)) {
                 error_report_err(err);
                 error_report("Could not create snapshot for icount record");
                 exit(1);