These functions handle the busying, unbusying and notification of the unbusying
of a page.
vm_page_busy ();
sets the
PG_BUSY
flag in the page.
vm_page_flash ();
checks to see if there is anybody waiting on the page
( PG_WANTED
will be set), and if so, clears the
PG_WANTED
flag and notifies whoever is waiting via
wakeup (.);
vm_page_wakeup ();
clears the
PG_BUSY
flag on the page, and calls
vm_page_flash ();
in case somebody has been waiting for it.