Re: [patch] cache flush bug in mm/filemap.c (all kernels >= 2.5.30(at least))

[Andrew Morton <akpm@digeo.com>]

"Lothar Wassmann" <LW@KARO-electronics.de> wrote:
>
> Andrew Morton writes:
> > "Lothar Wassmann" <LW@KARO-electronics.de> wrote:
> > >
> > > And maybe because *every* other call to flush_page_to_ram() has been
> > >  replaced by one of the new interface macros except that one in
> > >  filemap_nopage() in 'mm/filemap.c'.
> > > 
> > 
> > flush_page_to_ram() has been deleted from the kernel.
> > 
> Yes, I know. But did you even read, what I have written?

Vaguely.  It never hurts to repeat things ;)

> Is 2.5.68 current enough?

yes.

filemap_nopage isn't the right place to be doing these things though.

Given that there was no page at the virtual address before filemap_nopage
was called I don't think any CPU cache writeback or invalidation need be
performed.  Perhaps a writeback or invalidate is missing somewhere in the
unmap paths, or there is a problem in arch/arm somewhere.

We have a no-op flush_icache_page() in do_no_page(), but I don't know what
that thing ever did, not what it's doing in there.  (What happens if you
replace it with a flush_cache_page(vma, address)?)

Someone who understands these things better than I is going to have to work
out where the bug really is, I'm afraid.