nfsd: fix courtesy client with deny mode handling in nfs4_upgrade_open

The nested if statements here make no sense, as you can never reach
"else" branch in the nested statement. Fix the error handling for
when there is a courtesy client that holds a conflicting deny mode.

Fixes: 3d694271 ("NFSD: add support for share reservation conflict to courteous server")
Reported-by: 張智諺 <cc85nod@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4state.c

@@ -5282,16 +5282,17 @@ nfs4_upgrade_open(struct svc_rqst *rqstp, struct nfs4_file *fp,
 	/* test and set deny mode */
 	spin_lock(&fp->fi_lock);
 	status = nfs4_file_check_deny(fp, open->op_share_deny);
-	if (status == nfs_ok) {
-		if (status != nfserr_share_denied) {
+	switch (status) {
+	case nfs_ok:
 		set_deny(open->op_share_deny, stp);
 		fp->fi_share_deny |=
 			(open->op_share_deny & NFS4_SHARE_DENY_BOTH);
-		} else {
+		break;
+	case nfserr_share_denied:
 		if (nfs4_resolve_deny_conflicts_locked(fp, false,
 				stp, open->op_share_deny, false))
 			status = nfserr_jukebox;
-		}
+		break;
 	}
 	spin_unlock(&fp->fi_lock);