[V9,02/14] block: distinguish id and name in bdrv_find_snapshot()

diff --git a/block/snapshot.c b/block/snapshot.c
index 8de73b4..1449b3d 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -13,8 +13,20 @@ 
 
 #include "block/snapshot.h"
 
+/*
+ * Try find an internal snapshot with @id or @name, @id have higher priority
+ * in searching.
+ *
+ * @bs: block device to search on, must not be NULL.
+ * @sn_info: snapshot information to be filled in, must not be NULL.
+ * @id: snapshot id to search with, can be NULL.
+ * @name: snapshot name to search with, can be NULL.
+ *
+ * returns 0 and @sn_info is filled with related information if found,
+ * otherwise it returns negative value.
+ */
 int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
-                       const char *name)
+                       const char *id, const char *name)
 {
     QEMUSnapshotInfo *sn_tab, *sn;
     int nb_sns, i, ret;
@@ -22,16 +34,34 @@  int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
     ret = -ENOENT;
     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
     if (nb_sns < 0) {
-        return ret;
+        return nb_sns;
     }
-    for (i = 0; i < nb_sns; i++) {
-        sn = &sn_tab[i];
-        if (!strcmp(sn->id_str, name) || !strcmp(sn->name, name)) {
-            *sn_info = *sn;
-            ret = 0;
-            break;
+
+    /* search by id */
+    if (id) {
+        for (i = 0; i < nb_sns; i++) {
+            sn = &sn_tab[i];
+            if (!strcmp(sn->id_str, id)) {
+                *sn_info = *sn;
+                ret = 0;
+                goto out;
+            }
         }
     }
+
+    /* search by name */
+    if (name) {
+        for (i = 0; i < nb_sns; i++) {
+            sn = &sn_tab[i];
+            if (!strcmp(sn->name, name)) {
+                *sn_info = *sn;
+                ret = 0;
+                goto out;
+            }
+        }
+    }
+
+ out:
     g_free(sn_tab);
     return ret;
 }
diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index 86891d1..fc9be7b 100644
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -22,5 +22,5 @@ 
 #include "block.h"
 
 int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
-                       const char *name);
+                       const char *id, const char *name);
 #endif
diff --git a/savevm.c b/savevm.c
index 95f19ca..6557750 100644
--- a/savevm.c
+++ b/savevm.c
@@ -2073,7 +2073,7 @@  static int del_existing_snapshots(Monitor *mon, const char *name)
     bs = NULL;
     while ((bs = bdrv_next(bs))) {
         if (bdrv_can_snapshot(bs) &&
-            bdrv_snapshot_find(bs, snapshot, name) >= 0)
+            bdrv_snapshot_find(bs, snapshot, name, name) >= 0)
         {
             ret = bdrv_snapshot_delete(bs, name);
             if (ret < 0) {
@@ -2133,7 +2133,7 @@  void do_savevm(Monitor *mon, const QDict *qdict)
     sn->vm_clock_nsec = qemu_get_clock_ns(vm_clock);
 
     if (name) {
-        ret = bdrv_snapshot_find(bs, old_sn, name);
+        ret = bdrv_snapshot_find(bs, old_sn, name, 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);
@@ -2224,7 +2224,7 @@  int load_vmstate(const char *name)
     }
 
     /* Don't even try to load empty VM states */
-    ret = bdrv_snapshot_find(bs_vm_state, &sn, name);
+    ret = bdrv_snapshot_find(bs_vm_state, &sn, name, name);
     if (ret < 0) {
         return ret;
     } else if (sn.vm_state_size == 0) {
@@ -2248,7 +2248,7 @@  int load_vmstate(const char *name)
             return -ENOTSUP;
         }
 
-        ret = bdrv_snapshot_find(bs, &sn, name);
+        ret = bdrv_snapshot_find(bs, &sn, name, name);
         if (ret < 0) {
             error_report("Device '%s' does not have the requested snapshot '%s'",
                            bdrv_get_device_name(bs), name);
@@ -2354,7 +2354,7 @@  void do_info_snapshots(Monitor *mon, const QDict *qdict)
 
         while ((bs1 = bdrv_next(bs1))) {
             if (bdrv_can_snapshot(bs1) && bs1 != bs) {
-                ret = bdrv_snapshot_find(bs1, sn_info, sn->id_str);
+                ret = bdrv_snapshot_find(bs1, sn_info, sn->id_str, NULL);
                 if (ret < 0) {
                     available = 0;
                     break;