At present, flush_cache_page() is used to handle the case where we
unmap a page or alter the page permissions on the target page with
one exception - access_process_vm().  Based upon the former, the
decision to implement this function is:

        do we need to flush the cache when we unmap or change
        the mapping permissions?

However, kernel/ptrace.c: access_process_vm() also includes into this:

        or we need to ensure cache coherency between the kernel
        and user space mapping of this page.

I argue that the use of flush_cache_page() here in the generic
code is wrong, and if an architecture wishes to use it for this
purpose, it should do so within it's architecture private
implementation of copy_to_user_page() and copy_from_user_page().

So this patch removes the flush_cache_page() from kernel/ptrace.c,
adding it to the arch-specific copy_{to,from}_user_page() where
flush_cache_page is non-empty.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>