btrfs: free-space-cache, clean up unnecessary root arguments

The free space cache APIs accept a root but always use the tree root.

Also, btrfs_truncate_free_space_cache accepts a root AND an inode but
the inode always points to the root anyway, so let's just pass the inode.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index e2cf65c..ddbde0f 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3543,7 +3543,7 @@
 		goto out;
 	}
 
-	ret = btrfs_truncate_free_space_cache(root, trans, block_group, inode);
+	ret = btrfs_truncate_free_space_cache(trans, block_group, inode);
 
 	btrfs_end_transaction(trans);
 	btrfs_btree_balance_dirty(fs_info);
@@ -4347,8 +4347,7 @@
 		goto out;
 	}
 
-	inode = lookup_free_space_inode(fs_info->tree_root, rc->block_group,
-					path);
+	inode = lookup_free_space_inode(fs_info, rc->block_group, path);
 	btrfs_free_path(path);
 
 	if (!IS_ERR(inode))