btrfs-progs: Introduce change_extents_uuid function

This is the function which iterates all metadata extents and changes
their fsid.

This function also does it without transaction.

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 92837e6..b890011 100644 (file)
--- a/btrfstune.c
+++ b/btrfstune.c
@@ -130,6 +130,74 @@ static int change_header_uuid(struct btrfs_root *root, struct extent_buffer *eb)
        return ret;
 }
 
+static int change_extents_uuid(struct btrfs_fs_info *fs_info)
+{
+       struct btrfs_root *root = fs_info->extent_root;
+       struct btrfs_path *path;
+       struct btrfs_key key = {0, 0, 0};
+       int ret = 0;
+
+       if (!fs_info->new_fsid && !fs_info->new_chunk_tree_uuid)
+               return 0;
+
+       path = btrfs_alloc_path();
+       if (!path)
+               return -ENOMEM;
+
+       /*
+        * Here we don't use transaction as it will takes a lot of reserve
+        * space, and that will make a near-full btrfs unable to change uuid
+        */
+       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+       if (ret < 0)
+               goto out;
+
+       while (1) {
+               struct btrfs_extent_item *ei;
+               struct extent_buffer *eb;
+               u64 flags;
+               u64 bytenr;
+
+               btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+               if (key.type != BTRFS_EXTENT_ITEM_KEY &&
+                   key.type != BTRFS_METADATA_ITEM_KEY)
+                       goto next;
+               ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                   struct btrfs_extent_item);
+               flags = btrfs_extent_flags(path->nodes[0], ei);
+               if (!(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
+                       goto next;
+
+               bytenr = key.objectid;
+               eb = read_tree_block(root, bytenr, root->nodesize, 0);
+               if (IS_ERR(eb)) {
+                       fprintf(stderr, "Failed to read tree block: %llu\n",
+                               bytenr);
+                       ret = PTR_ERR(eb);
+                       goto out;
+               }
+               ret = change_header_uuid(root, eb);
+               free_extent_buffer(eb);
+               if (ret < 0) {
+                       fprintf(stderr, "Failed to change uuid of tree block: %llu\n",
+                               bytenr);
+                       goto out;
+               }
+next:
+               ret = btrfs_next_item(root, path);
+               if (ret < 0)
+                       goto out;
+               if (ret > 0) {
+                       ret = 0;
+                       goto out;
+               }
+       }
+
+out:
+       btrfs_free_path(path);
+       return ret;
+}
+
 static void print_usage(void)
 {
        fprintf(stderr, "usage: btrfstune [options] device\n");