COW callback

i am very new to linux kernel world. so please excuse me for any trivial queries. but i am looking for some callback/signal mechanism so that the driver is notified when a page is COWed (in handle_pte_fault).

i have wriiten a simple driver which support mmap. i want to keep track of the modified pages so that when the user calls msync (but does not explicitely provide the start offset and lenght), the modified pages are flushed to disk. now, is there a mechanism to do that in 2.4 and onward ?

thanks,
pavan