gnttab_entry
gnttab_entry(ref) = gnttab_free_head;
gnttab_entry(*refs) = head;
gnttab_entry(tail) = gnttab_free_head;
while (gnttab_entry(ref) != GNTTAB_LIST_END) {
ref = gnttab_entry(ref);
gnttab_entry(ref) = gnttab_free_head;
*private_head = gnttab_entry(g);
gnttab_entry(release) = *private_head;
gnttab_entry(i) = i + 1;
gnttab_entry(i) = gnttab_free_head;
gnttab_entry(i) = i + 1;
gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END;
head = gnttab_entry(head);
gnttab_free_head = gnttab_entry(head);
gnttab_entry(head) = GNTTAB_LIST_END;