Re: invalidate_inode_pages2

[Andrea Arcangeli <andrea@suse.de>]

On Tue, May 18, 2004 at 06:00:28PM -0700, Andrew Morton wrote:
> OK.  Can we do a full pte invalidation and force a major fault?

we'd need to take the page_table_lock to do that from there, I find
safer to stay at the pagecache layer at that point inside the nfs
filesystem routines. the semantics of invalidate_inode_pages2 doesn't
require a synchronous invalidate with major fault, both O_DIRECT and nfs
cannot provide distributed shared memory anyways, all it matters is that
_future_ reads will trigger readpage again to provide inode invalidate
semantics.

> > > It's currently the case that pages which are mapped into process pagetables
> > > are always up to date, which sounds like a good invariant to have.  This
> > 
> > I already intentionally broke that invariant in 2.4 just to make exactly
> > this thing work safely, this is needed for correct O_DIRECT semantics
> > too.
> > 
> > All it matters is that the pages are re-read after munmap+mmap.
> > 
> > > changes that rule.  I dunno if it'll break anything though.
> > 
> > It didn't break anything in 2.4 AFIK.
> 
> It might have caused some of the debug checks in fs/buffer.c to get angry
> when it's used by direct-IO.  But they're gone now anyway...

sounds good then ;)