NFSD: restore EINVAL error translation in nfsd_commit()

commit 8a9ffb8 upstream.

commit 555dbf1 ("nfsd: Replace use of rwsem with errseq_t")
incidentally broke translation of -EINVAL to nfserr_notsupp.
The patch restores that.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Fixes: 555dbf1 ("nfsd: Replace use of rwsem with errseq_t")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/nfsd/vfs.c

@@ -1156,15 +1156,16 @@ nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp,
 						nfsd_net_id));
 			err2 = filemap_check_wb_err(nf->nf_file->f_mapping,
 						    since);
+			err = nfserrno(err2);
 			break;
 		case -EINVAL:
 			err = nfserr_notsupp;
 			break;
 		default:
 			nfsd_reset_boot_verifier(net_generic(nf->nf_net,
 						 nfsd_net_id));
+			err = nfserrno(err2);
 		}
-		err = nfserrno(err2);
 	} else
 		nfsd_copy_boot_verifier(verf, net_generic(nf->nf_net,
 					nfsd_net_id));