vm_pageout: rewrite cluster()

[dougm]

Summary

Implement vm_pageout_cluster using iterators instead of vm_page_next() and vm_page_prev().

[kib]

sys/vm/vm_pageout.c

399

Could we please avoid jumping into the loop body from outside? Wouldn't the code work same if the 'more' label is left at the old position, before the reverse scan while() loop, by checking the true condition?

[dougm]

Modify vm_pageout_cluster() to avoid labels and gotos.