From: Minchan Kim <minchan.kim@gmail.com>
Subject: Re: [PATCH V3 0/8] Cleancache: overview
Date: Fri, 23 Jul 2010 17:16:47 +0900
Message-ID: <AANLkTikV6nypnLHjaidOyJPsP9xDawQ9ABOoRWKB-2+B@mail.gmail.com>
References: <20100621231809.GA11111@ca-server1.us.oracle.com>
	<4C49468B.40307@vflare.org>
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Cc: Dan Magenheimer <dan.magenheimer@oracle.com>, chris.mason@oracle.com,
	viro@zeniv.linux.org.uk, akpm@linux-foundation.org, adilger@sun.com,
	tytso@mit.edu, mfasheh@suse.com, joel.becker@oracle.com, matthew@wil.cx,
	linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	ocfs2-devel@oss.oracle.com, linux-mm@kvack.org, jeremy@goop.org,
	JBeulich@novell.com, kurt.hackel@oracle.com, npiggin@suse.de,
	dave.mccracken@oracle.com, riel@redhat.com, avi@redhat.com,
	konrad.wilk@oracle.com
To: ngupta@vflare.org
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On Fri, Jul 23, 2010 at 4:36 PM, Nitin Gupta <ngupta@vflare.org> wrote:
>
> 2. I think change in btrfs can be avoided by moving cleancache_get_page()
> from do_mpage_reapage() to filemap_fault() and this should work for all
> filesystems. See:
>
> handle_pte_fault() -> do_(non)linear_fault() -> __do_fault()
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0-> vma->vm_ops->fault()
>
> which is defined as filemap_fault() for all filesystems. If some future
> filesystem uses its own custom function (why?) then it will have to arran=
ge for
> call to cleancache_get_page(), if it wants this feature.


filemap fault works only in case of file-backed page which is mapped
but don't work not-mapped cache page.  So we could miss cache page by
read system call if we move it into filemap_fault.


--=20
Kind regards,
Minchan Kim

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