question on memory map cleanup stuff

[Chris Friesen <cfriesen@nortelnetworks.com>]

I've got a small feature that maps a page of kernel memory to userspace via a 
syscall, then uses that page for various things.

Currently, I'm marking the page reserved, then exporting it via 
remap_page_range().  This means that I need to clean up my mapping whenever the 
memory map is destroyed (process death, exec(), daemonize, etc.).

It appears that I should be able to put my cleanup code in exit_mmap().  Since 
the cleanup code calls do_munmap() on the address, I would want to call it 
before taking mm->page_table_lock, correct?

Also, normally I would hold mm->mmap_sem before calling do_munmap().  Would I 
still need this if I'm calling it from exit_mmap()?  Presumably nobody else can 
get at it anymore...

Thanks,

Chris