page_chain_next
for (; page && ({ prefetch(page_chain_next(page)); 1; }); \
page = page_chain_next(page))
for (; page && ({ n = page_chain_next(page); 1; }); page = n)
page_chain_next(page) ? MSG_MORE : 0);
page_chain_next(page) ? MSG_MORE : 0);
while ((tmp = page_chain_next(page))) {