Re: invalidate_inode_pages in 2.5.32/3

[Andrew Morton <akpm@digeo.com>]

Rik van Riel wrote:
> 
> On Thu, 12 Sep 2002, Andrew Morton wrote:
> 
> > Well the lazy invalidation would be OK - defer that to the next
> > userspace access,
> 
> I think I have an idea on how to do that, here's some pseudocode:
> 
> invalidate_page(struct page * page) {
>         SetPageInvalidated(page);
>         rmap_lock(page);
>         for_each_pte(pte, page) {
>                 make pte PROT_NONE;
>                 flush TLBs for this virtual address;
>         }
>         rmap_unlock(page);
> }
> 
> And in the page fault path:
> 
> if (pte_protection(pte) == PROT_NONE && PageInvalidated(pte_page_pte)) {
>         clear_pte(ptep);
>         page_cache_release(page);
>         mm->rss--;
> }
> 

That's the bottom-up approach.  The top-down (vmtruncate) approach
would also work, if the locking is suitable.

Look, idunnoigiveup.  Like scsi and USB, NFS is a black hole
where akpms fear to tread.  I think I'll sulk until someone
explains why this work has to be performed in the context of
a process which cannot do it.