Subject: Re: [PATCH 06/43] FS-Cache: Recruit a couple of page flags for
 cache management [ver #46]
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: David Howells <dhowells@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>, viro@zeniv.linux.org.uk,
       nfsv4@linux-nfs.org, linux-kernel@vger.kernel.org,
       linux-fsdevel@vger.kernel.org
In-Reply-To: <7516.1238694057@redhat.com>
References: <200904030431.04079.nickpiggin@yahoo.com.au>
	 <200904030353.17713.nickpiggin@yahoo.com.au>
	 <200904030315.03606.nickpiggin@yahoo.com.au> <7249.1238692155@redhat.com>
	 <7516.1238694057@redhat.com>
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Date: Thu, 02 Apr 2009 15:19:47 -0400
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On Thu, 2009-04-02 at 18:40 +0100, David Howells wrote:
> Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
> > Well in theory I still think it would be cleanest to modify buffer to
> > play more nicely with it. But maybe that ends up being harder to
> > distinguish the 3 cases of attached metadata on the page. I don't know,
> > you haven't posted any isofs code so either way it is inappropriate to
> > use up this extra page flag here.
> > 
> > Is isofs cache worth a page flag?
> 
> Well, isofs was something I wanted at the time.
> 
> Besides, as I said NFS uses PG_private for its own purposes, and entangling
> the two wasn't the most fun I've had.  Trond didn't like it either.

We use it for exactly the same purpose as everyone else: to signal that
we need a callback to ->releasepage() if the VM wants to truncate the
page.

Trond

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