[V4,09/13] block: export function bdrv_find_snapshot()

diff --git a/block.c b/block.c
index 7c9727b..4313d1b 100644
--- a/block.c
+++ b/block.c
@@ -3381,6 +3381,57 @@  int bdrv_snapshot_load_tmp(BlockDriverState *bs,
     return -ENOTSUP;
 }
 
+/*
+ * 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, -ENOENT.
+ */
+int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
+                       const char *id, const char *name)
+{
+    QEMUSnapshotInfo *sn_tab, *sn;
+    int nb_sns, i, ret;
+
+    ret = -ENOENT;
+    nb_sns = bdrv_snapshot_list(bs, &sn_tab);
+    if (nb_sns < 0) {
+        return ret;
+    }
+
+    /* 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;
+}
+
 /* backing_file can either be relative, or absolute, or a protocol.  If it is
  * relative, it must be relative to the chain.  So, passing in bs->filename
  * from a BDS as backing_file should not be done, as that may be relative to
diff --git a/include/block/block.h b/include/block/block.h
index 9838c48..1e7f4a1 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -340,6 +340,8 @@  int bdrv_snapshot_list(BlockDriverState *bs,
 int bdrv_snapshot_load_tmp(BlockDriverState *bs,
                            const char *snapshot_name);
 char *bdrv_snapshot_dump(char *buf, int buf_size, QEMUSnapshotInfo *sn);
+int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
+                       const char *id, const char *name);
 
 char *get_human_readable_size(char *buf, int buf_size, int64_t size);
 int path_is_absolute(const char *path);
diff --git a/savevm.c b/savevm.c
index d9ff1d9..5607105 100644
--- a/savevm.c
+++ b/savevm.c
@@ -2027,28 +2027,6 @@  out:
     return ret;
 }
 
-static int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
-                              const char *name)
-{
-    QEMUSnapshotInfo *sn_tab, *sn;
-    int nb_sns, i, ret;
-
-    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];
-        if (!strcmp(sn->id_str, name) || !strcmp(sn->name, name)) {
-            *sn_info = *sn;
-            ret = 0;
-            break;
-        }
-    }
-    g_free(sn_tab);
-    return ret;
-}
-
 /*
  * Deletes snapshots of a given name in all opened images.
  */
@@ -2061,7 +2039,7 @@  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) {
@@ -2121,7 +2099,7 @@  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);
@@ -2212,7 +2190,7 @@  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) {
@@ -2236,7 +2214,7 @@  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);
@@ -2342,7 +2320,7 @@  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;