xfs: failure mapping nfs fh to inode should return ESTALE

On xfs exports, nfsd is incorrectly returning ENOENT instead of
ESTALE on attempts to use a filehandle of a deleted file (spotted
with pynfs test PUTFH3).  The ENOENT was coming from xfs_iget.

(It's tempting to wonder whether we should just map all xfs_iget
errors to ESTALE, but I don't believe so--xfs_iget can also return
ENOMEM at least, which we wouldn't want mapped to ESTALE.)

While we're at it, the other return of ENOENT in xfs_nfs_get_inode()
also looks wrong.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/linux-2.6/xfs_export.c

@@ -151,14 +151,14 @@ xfs_nfs_get_inode(
 		 * We don't use ESTALE directly down the chain to not
 		 * confuse applications using bulkstat that expect EINVAL.
 		 */
-		if (error == EINVAL)
+		if (error == EINVAL || error == ENOENT)
 			error = ESTALE;
 		return ERR_PTR(-error);
 	}
 
 	if (ip->i_d.di_gen != generation) {
 		IRELE(ip);
-		return ERR_PTR(-ENOENT);
+		return ERR_PTR(-ESTALE);
 	}
 
 	return VFS_I(ip);