btrfs: assert that send is not in progres before root deletion

CC: Miao Xie <miaox@cn.fujitsu.com>
CC: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/ioctl.c

@@ -2424,6 +2424,7 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
 		shrink_dcache_sb(root->fs_info->sb);
 		btrfs_invalidate_inodes(dest);
 		d_delete(dentry);
+		ASSERT(dest->send_in_progress == 0);
 
 		/* the last ref */
 		if (dest->cache_inode) {

fs/btrfs/transaction.c

@@ -1984,19 +1984,6 @@ int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
 	}
 	root = list_first_entry(&fs_info->dead_roots,
 			struct btrfs_root, root_list);
-	/*
-	 * Make sure root is not involved in send,
-	 * if we fail with first root, we return
-	 * directly rather than continue.
-	 */
-	spin_lock(&root->root_item_lock);
-	if (root->send_in_progress) {
-		spin_unlock(&fs_info->trans_lock);
-		spin_unlock(&root->root_item_lock);
-		return 0;
-	}
-	spin_unlock(&root->root_item_lock);
-
 	list_del_init(&root->root_list);
 	spin_unlock(&fs_info->trans_lock);