purging file cache

hi

i'm trying to find a way to purge file caching in a consistent way. i found 2 relevant function
invalidate_inode_pages()
truncate_inode_pages()

does truncate_inode_pages() remove the page_cache only or that it actually truncate the on-disk file?

can cache purging be done with a better granularity than the whole page, some thing like purge_inode_cache( mapping, start, length ) ?

i don't realy understand the new VM model in linux 2.4 and what level of consistancy exists between the page-cache and the file-buffers so i got a few more questions:

can i invalidate cache for mmaped file? ( the reason i'm asking this is that there is at least one os which doesn;t allow to purge cache from a mmaped file )

can i invalidate mmaped section of a file which some process own a READ-lock on it( so the next access to that section will cause page-fault) or that this will break the mmap semantic ?

are files marked for mandatory locking protected from mmap access, or that the file locks are checked only on the FS system_calls( read, write...) ?

hope that at least some of those many questions will be answers

please CC me for any answer

regards
Benhanokh Gabriel

-----------------------------------------------------------------------------
"If you think C++ is not overly complicated, just what is a
protected abstract virtual base class with a pure virtual private destructor,
and when was the last time you needed one?"
-- Tom Cargil, C++ Journal, Fall 1990. --

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