+extern char *setup_proto (char *fname);
+extern void parse_proto (xfs_mount_t *mp, struct fsxattr *fsx, char **pp);
+extern void res_failed (int err);

It might be worth to drop the externs, the spaces before the opening
braces and the xfs_mount_t typedef usage while you're at it.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>