btrfs-progs: btrfstune: add ability to restore unfinished fsid change

Now change_uuid() can auto detected unfinished fsid change and restore
it.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>

diff --git a/btrfstune.c b/btrfstune.c
index 36d7a00..9bf06c2 100644 (file)
--- a/btrfstune.c
+++ b/btrfstune.c
@@ -267,7 +267,9 @@ out:
 
 static int change_fsid_prepare(struct btrfs_fs_info *fs_info)
 {
+       struct btrfs_root *tree_root = fs_info->tree_root;
        u64 flags = btrfs_super_flags(fs_info->super_copy);
+       int ret = 0;
 
        if (!fs_info->new_fsid && !fs_info->new_chunk_tree_uuid)
                return 0;
@@ -276,7 +278,16 @@ static int change_fsid_prepare(struct btrfs_fs_info *fs_info)
                flags |= BTRFS_SUPER_FLAG_CHANGING_FSID;
        btrfs_set_super_flags(fs_info->super_copy, flags);
 
-       return write_all_supers(fs_info->tree_root);
+       memcpy(fs_info->super_copy->fsid, fs_info->new_fsid, BTRFS_FSID_SIZE);
+       ret = write_all_supers(tree_root);
+       if (ret < 0)
+               return ret;
+
+       /* also restore new chunk_tree_id into tree_root for restore */
+       write_extent_buffer(tree_root->node, fs_info->new_chunk_tree_uuid,
+                           btrfs_header_chunk_tree_uuid(tree_root->node),
+                           BTRFS_UUID_SIZE);
+       return write_tree_block(NULL, tree_root, tree_root->node);
 }
 
 static int change_fsid_done(struct btrfs_fs_info *fs_info)
@@ -294,9 +305,31 @@ static int change_fsid_done(struct btrfs_fs_info *fs_info)
 }
 
 /*
+ * Return 0 for no unfinished fsid change.
+ * Return >0 for unfinished fsid change, and restore unfinished fsid/
+ * chunk_tree_id into fsid_ret/chunk_id_ret.
+ */
+static int check_unfinished_fsid_change(struct btrfs_fs_info *fs_info,
+                                       uuid_t fsid_ret, uuid_t chunk_id_ret)
+{
+       struct btrfs_root *tree_root = fs_info->tree_root;
+       u64 flags = btrfs_super_flags(fs_info->super_copy);
+
+       if (flags & BTRFS_SUPER_FLAG_CHANGING_FSID) {
+               memcpy(fsid_ret, fs_info->super_copy->fsid, BTRFS_FSID_SIZE);
+               read_extent_buffer(tree_root->node, chunk_id_ret,
+                               btrfs_header_chunk_tree_uuid(tree_root->node),
+                               BTRFS_UUID_SIZE);
+               return 1;
+       }
+       return 0;
+}
+
+/*
  * Change fsid of a given fs.
  *
  * If new_fsid_str is not given, use a random generated UUID.
+ * Caller should check new_fsid_str is valid
  */
 static int change_uuid(struct btrfs_fs_info *fs_info, const char *new_fsid_str)
 {
@@ -305,13 +338,26 @@ static int change_uuid(struct btrfs_fs_info *fs_info, const char *new_fsid_str)
        char uuid_buf[BTRFS_UUID_UNPARSED_SIZE];
        int ret = 0;
 
-       /* caller should do extra check on passed uuid */
-       if (new_fsid_str)
-               uuid_parse(new_fsid_str, new_fsid);
-       else
-               uuid_generate(new_fsid);
+       if (check_unfinished_fsid_change(fs_info, new_fsid, new_chunk_id)) {
+               if (new_fsid_str) {
+                       uuid_t tmp;
 
-       uuid_generate(new_chunk_id);
+                       uuid_parse(new_fsid_str, tmp);
+                       if (memcmp(tmp, new_fsid, BTRFS_FSID_SIZE)) {
+                               fprintf(stderr,
+               "ERROR: New fsid %s is not the same with unfinished fsid change\n",
+                                       new_fsid_str);
+                               return -EINVAL;
+                       }
+               }
+       } else {
+               if (new_fsid_str)
+                       uuid_parse(new_fsid_str, new_fsid);
+               else
+                       uuid_generate(new_fsid);
+
+               uuid_generate(new_chunk_id);
+       }
        fs_info->new_fsid = new_fsid;
        fs_info->new_chunk_tree_uuid = new_chunk_id;