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From: Daniel Phillips <phillips@arcor.de>
To: Andrew Morton <akpm@digeo.com>, Rik van Riel <riel@conectiva.com.br>
Subject: Re: invalidate_inode_pages in 2.5.32/3
Date: Mon, 9 Sep 2002 23:44:08 +0200
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Cc: trond.myklebust@fys.uio.no, Chuck Lever <cel@citi.umich.edu>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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> I'm very unkeen about using the inaccurate invalidate_inode_pages
> for anything which matters, really.   And the consistency of pagecache
> data matters.
> 
> NFS should be using something stronger.  And that's basically
> vmtruncate() without the i_size manipulation.

Yes, that looks good.  Semantics are basically "and don't come back
until every damm page is gone" which is enforced by the requirement
that we hold the mapping->page_lock though one entire scan of the
truncated region.  (Yes, I remember sweating this one out a year
or two ago so it doesn't eat 100% CPU on regular occasions.)

So, specifically, we want:

void invalidate_inode_pages(struct inode *inode)
{
	truncate_inode_pages(mapping, 0);
}

Is it any harder than that?

By the way, now that we're all happy with the radix tree, we might
as well just go traverse that instead of all the mapping->*_pages.
(Not that I'm seriously suggesting rocking the boat that way just
now, but it might yield some interesting de-crufting possibilities.)

> Hold i_sem,
> vmtruncate_list() for assured pagetable takedown, proper page
> locking to take the pages out of pagecache, etc.
> 
> Sure, we could replace the page_count() heuristic with a
> page->pte.direct heuristic.  Which would work just as well.  Or
> better.  Or worse.  Who knows?
> 
> Guys, can we sort out the NFS locking so that it is possible to
> take the correct locks to get the 100% behaviour?

Trond, will the above work?

Now, what is this invalidate_inode_pages2 seepage about?  Called from
one place.  Sheesh.

-- 
Daniel
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