Question relating to the nopage handler and memory in general

[JJ Jordan]

Okay, I'm in the middle of developing a pseudo device driver under 
2.2.18.  Processes that use it generally mmap() it, and in the mmap 
handler, it sets up a nopage handler.  Here's the question: After the 
nopage handler has been called and pages have been mapped to client 
processes' spaces, how can I "unmap" certain pages from processes that 
memory has been mapped to, say from the ioctl handler?  If not unmap, then 
at least create a condition where the nopage handler would have to be 
called again for particular pages..

Any help would be appreciated.

Thanks,
John Jordan

PS- I did look briefly through the list archives but couldn't find 
anything.. and this is my first post to the list; if I sound like an idiot, 
well.. it's to be expected.