How can TUX user module get notified when a page is removed from cache?

Hi,

We can use path_walk() to query Linux kernel file system whether a specific
file
is in the memory cache or not, but now we want our TUX user space module to
get notified regularly from Linux kernel when a page is removed  from memory
cache or a page is added to the memory cache? The purpose of this is we try
to
maintain a table in user module to record the status of files which are once
accessed.
It seems we need to install a callback function in TUX user module for this
event.
How can we do that?

BTW, which function can we use to get the information of all cached files in
Linux
kernel so that we can know which files are cached currently?

Thank you.

Liang