gfs2: s64 cast for negative quota value

One-line fix to cast quota value to s64 before comparison.
By default the quantity is treated as u64.
Signed-off-by: Abhi Das <adas@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/quota.c

@@ -798,7 +798,7 @@ static int gfs2_adjust_quota(struct gfs2_inode *ip, loff_t loc,
 	loc -= sizeof(q); /* gfs2_internal_read would've advanced the loc ptr */
 	err = -EIO;
 	be64_add_cpu(&q.qu_value, change);
-	if (be64_to_cpu(q.qu_value) < 0)
+	if (((s64)be64_to_cpu(q.qu_value)) < 0)
 		q.qu_value = 0; /* Never go negative on quota usage */
 	qd->qd_qb.qb_value = q.qu_value;
 	if (fdq) {