+/*
+ * does all the dirty work required for changing file system's UUID.
+ */
+static int btrfs_prepare_sprout(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root)
+{
+ struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
+ struct btrfs_fs_devices *old_devices;
+ struct btrfs_super_block *disk_super = &root->fs_info->super_copy;
+ struct btrfs_device *device;
+ u64 super_flags;
+
+ BUG_ON(!mutex_is_locked(&uuid_mutex));
+ if (!fs_devices->seeding || fs_devices->opened != 1)
+ return -EINVAL;
+
+ old_devices = kzalloc(sizeof(*fs_devices), GFP_NOFS);
+ if (!old_devices)
+ return -ENOMEM;
+
+ memcpy(old_devices, fs_devices, sizeof(*old_devices));
+ old_devices->opened = 1;
+ old_devices->sprouted = 1;
+ INIT_LIST_HEAD(&old_devices->devices);
+ INIT_LIST_HEAD(&old_devices->alloc_list);
+ list_splice_init(&fs_devices->devices, &old_devices->devices);
+ list_splice_init(&fs_devices->alloc_list, &old_devices->alloc_list);
+ list_for_each_entry(device, &old_devices->devices, dev_list) {
+ device->fs_devices = old_devices;
+ }
+ list_add(&old_devices->list, &fs_uuids);
+
+ fs_devices->seeding = 0;
+ fs_devices->num_devices = 0;
+ fs_devices->open_devices = 0;
+ fs_devices->seed = old_devices;
+
+ generate_random_uuid(fs_devices->fsid);
+ memcpy(root->fs_info->fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
+ memcpy(disk_super->fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
+ super_flags = btrfs_super_flags(disk_super) &
+ ~BTRFS_SUPER_FLAG_SEEDING;
+ btrfs_set_super_flags(disk_super, super_flags);
+
+ return 0;
+}
+
+/*
+ * strore the expected generation for seed devices in device items.
+ */
+static int btrfs_finish_sprout(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root)
+{
+ struct btrfs_path *path;
+ struct extent_buffer *leaf;
+ struct btrfs_dev_item *dev_item;
+ struct btrfs_device *device;
+ struct btrfs_key key;
+ u8 fs_uuid[BTRFS_UUID_SIZE];
+ u8 dev_uuid[BTRFS_UUID_SIZE];
+ u64 devid;
+ int ret;
+
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+
+ root = root->fs_info->chunk_root;
+ key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
+ key.offset = 0;
+ key.type = BTRFS_DEV_ITEM_KEY;
+
+ while (1) {
+ ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+ if (ret < 0)
+ goto error;
+
+ leaf = path->nodes[0];
+next_slot:
+ if (path->slots[0] >= btrfs_header_nritems(leaf)) {
+ ret = btrfs_next_leaf(root, path);
+ if (ret > 0)
+ break;
+ if (ret < 0)
+ goto error;
+ leaf = path->nodes[0];
+ btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+ btrfs_release_path(root, path);
+ continue;
+ }
+
+ btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+ if (key.objectid != BTRFS_DEV_ITEMS_OBJECTID ||
+ key.type != BTRFS_DEV_ITEM_KEY)
+ break;
+
+ dev_item = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_dev_item);
+ devid = btrfs_device_id(leaf, dev_item);
+ read_extent_buffer(leaf, dev_uuid,
+ (unsigned long)btrfs_device_uuid(dev_item),
+ BTRFS_UUID_SIZE);
+ read_extent_buffer(leaf, fs_uuid,
+ (unsigned long)btrfs_device_fsid(dev_item),
+ BTRFS_UUID_SIZE);
+ device = btrfs_find_device(root, devid, dev_uuid, fs_uuid);
+ BUG_ON(!device);
+
+ if (device->fs_devices->seeding) {
+ btrfs_set_device_generation(leaf, dev_item,
+ device->generation);
+ btrfs_mark_buffer_dirty(leaf);
+ }
+
+ path->slots[0]++;
+ goto next_slot;
+ }
+ ret = 0;
+error:
+ btrfs_free_path(path);
+ return ret;
+}
+