[PATCH v8 07/11] migration: control whether snapshots are ovewritten

From: "Daniel P. Berrangé" <berrange@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Kevin Wolf" <kwolf@redhat.com>,
	"Peter Krempa" <pkrempa@redhat.com>,
	"Daniel P. Berrangé" <berrange@redhat.com>,
	"Denis V. Lunev" <den@virtuozzo.com>,
	qemu-block@nongnu.org, "Juan Quintela" <quintela@redhat.com>,
	"Philippe Mathieu-Daudé" <philmd@redhat.com>,
	"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	"Max Reitz" <mreitz@redhat.com>,
	"Pavel Dovgalyuk" <pavel.dovgaluk@ispras.ru>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"John Snow" <jsnow@redhat.com>,
	"Markus Armbruster" <armbru@redhat.com>
Subject: [PATCH v8 07/11] migration: control whether snapshots are ovewritten
Date: Thu, 26 Nov 2020 17:35:17 +0000	[thread overview]
Message-ID: <20201126173521.137580-8-berrange@redhat.com> (raw)
In-Reply-To: <20201126173521.137580-1-berrange@redhat.com>

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>
---
 include/migration/snapshot.h |  3 ++-
 migration/savevm.c           | 19 ++++++++++++++++---
 monitor/hmp-cmds.c           |  2 +-
 replay/replay-debugging.c    |  2 +-
 replay/replay-snapshot.c     |  2 +-
 5 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/include/migration/snapshot.h b/include/migration/snapshot.h
index d7d210820c..d8c22d343c 100644
--- 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 18275aef2c..3ced05459d 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2725,7 +2725,7 @@ 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, old_sn1, *old_sn = &old_sn1;
@@ -2753,8 +2753,21 @@ 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 a5e2de5947..4e1e775007 100644
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -1140,7 +1140,7 @@ 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 0fdf643c7b..8847b2e218 100644
--- a/replay/replay-debugging.c
+++ b/replay/replay-debugging.c
@@ -328,7 +328,7 @@ 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 b289365937..31c5a8702b 100644
--- 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);
-- 
2.28.0


