From: NeilBrown <neilb@cse.unsw.edu.au>

From: "J. Bruce Fields" <bfields@fieldses.org>

Slightly better behavior on failed mapping (which may happen either because
idmapd is not running, or because there it has told us it doesn't know the
mapping.):

	on name->id (setattr), return BADNAME.  (I used ESRCH to
		communicate BADNAME, just because it was the first error in
		include/asm-generic/errno-base.h that had something to
		do with nonexistance of something, and that we weren't
		already using.)

	id->name (getattr), return a string representation of the numerical
		id.  This is probably useless to the client, especially
		since we're unlikely to accept such a string on a setattr,
		but perhaps some client will find it mildly helpful.