[Qemu-devel] [PATCH] savevm: create snapshot failed when id_str already exits

[Yi Wang]

>From b119164ba6715f53594facfc4d1022c198852e9d Mon Sep 17 00:00:00 2001
From: Yi Wang <address@hidden>
Date: Mon, 12 Jan 2015 00:05:40 +0800
Subject: [PATCH] savevm: create snapshot failed when id_str already exits

Create snapshot failed in this case:
1) vm has two or more qcow2 disks;
2) the first disk has snapshot with id_str 1, and the second disk has
snapshots with id_str 2 and 3, for example;
3) create snapshot using virsh snapshot-create/snapshot-create-as will
fail, 'cause id_str 2 has already existed in disk two.

The reason is that do_savevm() didn't check id_str before create
bdrv_snapshot_create(), and this patch fixed this.

Signed-off-by: Yi Wang <address@hidden>
---
 block/snapshot.c         |   32 ++++++++++++++++++++++++++++++++
 include/block/snapshot.h |    1 +
 savevm.c                 |    7 +++++++
 3 files changed, 40 insertions(+), 0 deletions(-)

diff --git a/block/snapshot.c b/block/snapshot.c
index 698e1a1..f2757ab 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -66,6 +66,38 @@ int bdrv_snapshot_find(BlockDriverState *bs,
QEMUSnapshotInfo *sn_info,
     return ret;
 }

+int bdrv_snapshot_get_id_str(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
+{
+    QEMUSnapshotInfo *sn_tab, *sn;
+    int nb_sns, i, ret;
+    int max = 0, temp_max;
+    bool need_max = false;
+
+    ret = -ENOENT;
+    nb_sns = bdrv_snapshot_list(bs, &sn_tab);
+    if (nb_sns < 0) {
+        return ret;
+    }
+
+    for (i = 0; i < nb_sns; i++) {
+        sn = &sn_tab[i];
+        temp_max = atoi(sn->id_str);
+        if (max < temp_max) {
+            max = temp_max;
+        }
+        if (!need_max && !strcmp(sn->id_str, sn_info->id_str)) {
+            need_max = true;
+        }
+        if (need_max) {
+            snprintf(sn_info->id_str, 128*sizeof(char), "%d", max+1);
+        }
+
+    }
+    g_free(sn_tab);
+    ret = 0;
+    return ret;
+}
+
 /**
  * Look up an internal snapshot by @id and @name.
  * @bs: block device to search
diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index 770d9bb..047ed7b 100644
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -49,6 +49,7 @@ typedef struct QEMUSnapshotInfo {

 int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
                        const char *name);
+int bdrv_snapshot_get_id_str(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);
 bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
                                        const char *id,
                                        const char *name,
diff --git a/savevm.c b/savevm.c
index 08ec678..f2edc13 100644
--- a/savevm.c
+++ b/savevm.c
@@ -1123,6 +1123,13 @@ void do_savevm(Monitor *mon, const QDict *qdict)
         if (bdrv_can_snapshot(bs1)) {
             /* Write VM state size only to the image that contains the state */
             sn->vm_state_size = (bs == bs1 ? vm_state_size : 0);
+
+            /* To avoid sn->id_str already exists */
+            if (bdrv_snapshot_get_id_str(bs1, sn) < 0) {
+                monitor_printf(mon, "Error when get id str.\n");
+                goto the_end;
+            }
+
             ret = bdrv_snapshot_create(bs1, sn);
             if (ret < 0) {
                 monitor_printf(mon, "Error while creating snapshot on '%s'\n",
-- 
1.7.1


-- 
Best Regards
Yi Wang