From: Boaz Harrosh <bharrosh@panasas.com>
Subject: Re: [PATCH V3 0/8] Cleancache: overview
Date: Tue, 03 Aug 2010 19:22:36 +0300
Message-ID: <4C58424C.1020208@panasas.com>
References: <20100621231809.GA11111@ca-server1.us.oracle.com4C49468B.40307@vflare.org> <840b32ff-a303-468e-9d4e-30fc92f629f8@default 20100723140440.GA12423@infradead.org 364c83bd-ccb2-48cc-920d-ffcf9ca7df19@default> <fc254547-5926-4cb9-98e1-7a79f7284e30@default>
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Cc: Christoph Hellwig <hch@infradead.org>, ngupta@vflare.org,
 akpm@linux-foundation.org, Chris Mason <chris.mason@oracle.com>,
 viro@zeniv.linux.org.uk, adilger@sun.com, tytso@mit.edu,
 mfasheh@suse.com, Joel Becker <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 <kurt.hackel@oracle.com>,
 npiggin@suse.de, Dave Mccracken <dave.mccracken@oracle.com>,
 riel@redhat.com, avi@redhat.com, Konrad Wilk <konrad.wilk@oracle.com>
To: Dan Magenheimer <dan.magenheimer@oracle.com>
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On 07/24/2010 12:17 AM, Dan Magenheimer wrote:
>>> On Fri, Jul 23, 2010 at 06:58:03AM -0700, Dan Magenheimer wrote:
>>>> CHRISTOPH AND ANDREW, if you disagree and your concerns have
>>>> not been resolved, please speak up.
>>
>> Hi Christoph --
>>
>> Thanks very much for the quick (instantaneous?) reply!
>>
>>> Anything that need modification of a normal non-shared fs is utterly
>>> broken and you'll get a clear NAK, so the propsal before is a good
>>> one.
>>
>> No, the per-fs opt-in is very sensible; and its design is
>> very minimal.
> 
> Not to belabor the point, but maybe the right way to think about
> this is:
> 
> Cleancache is a new optional feature provided by the VFS layer
> that potentially dramatically increases page cache effectiveness
> for many workloads in many environments at a negligible cost.
> 
> Filesystems that are well-behaved and conform to certain restrictions
> can utilize cleancache simply by making a call to cleancache_init_fs
> at mount time.  Unusual, misbehaving, or poorly layered filesystems
> must either add additional hooks and/or undergo extensive additional
> testing... or should just not enable the optional cleancache.

OK, So I maintain a filesystem in Kernel. How do I know if my FS
is not "Unusual, misbehaving, or poorly layered"

Thanks
Boaz

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