[PATCH] kNFSd: Improve idmapper behaviour on failure.

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.

fs/nfsd/nfs4idmap.c

@@ -543,6 +543,8 @@ idmap_name_to_id(struct svc_rqst *rqstp, int type, const char *name, u32 namelen
 	key.name[namelen] = '\0';
 	strlcpy(key.authname, rqstp->rq_client->name, sizeof(key.authname));
 	ret = idmap_lookup(rqstp, nametoid_lookup, &key, &nametoid_cache, &item);
+	if (ret == -ENOENT)
+		ret = -ESRCH; /* nfserr_badname */
 	if (ret)
 		return ret;
 	*id = item->id;
@@ -561,6 +563,8 @@ idmap_id_to_name(struct svc_rqst *rqstp, int type, uid_t id, char *name)
 
 	strlcpy(key.authname, rqstp->rq_client->name, sizeof(key.authname));
 	ret = idmap_lookup(rqstp, idtoname_lookup, &key, &idtoname_cache, &item);
+	if (ret == -ENOENT)
+		return sprintf(name, "%u", id);
 	if (ret)
 		return ret;
 	ret = strlen(item->name);

fs/nfsd/nfsproc.c

@@ -589,6 +589,7 @@ nfserrno (int errno)
 		{ nfserr_jukebox, -ETIMEDOUT },
 		{ nfserr_dropit, -EAGAIN },
 		{ nfserr_dropit, -ENOMEM },
+		{ nfserr_badname, -ESRCH },
 		{ -1, -EIO }
 	};
 	int	i;

include/linux/nfsd/nfsd.h

@@ -199,6 +199,7 @@ void		nfsd_lockd_shutdown(void);
 #define	nfserr_grace		__constant_htonl(NFSERR_GRACE)
 #define	nfserr_no_grace		__constant_htonl(NFSERR_NO_GRACE)
 #define	nfserr_reclaim_bad	__constant_htonl(NFSERR_RECLAIM_BAD)
+#define	nfserr_badname		__constant_htonl(NFSERR_BADNAME)
 
 /* error codes for internal use */
 /* if a request fails due to kmalloc failure, it gets dropped.