linux-kernel - Re: [PATCH 1/7] block: Add block_flush

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Message-ID: <49D2B8B5.9040602@kernel.org>
Date:	Wed, 01 Apr 2009 09:43:33 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Jens Axboe <jens.axboe@...cle.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ric Wheeler <rwheeler@...hat.com>,
	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>, Jeff Garzik <jeff@...zik.org>,
	Christoph Hellwig <hch@...radead.org>,
	Theodore Tso <tytso@....edu>, Ingo Molnar <mingo@...e.hu>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arjan van de Ven <arjan@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...e.de>, David Rees <drees76@...il.com>,
	Jesper Krogh <jesper@...gh.cc>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	chris.mason@...cle.com, david@...morbit.com
Subject: Re: [PATCH 1/7] block: Add block_flush_device()

Jens Axboe wrote:
> On Tue, Mar 31 2009, Jens Axboe wrote:
>> On Tue, Mar 31 2009, Linus Torvalds wrote:
>>>
>>> On Tue, 31 Mar 2009, Ric Wheeler wrote:
>>>> The question is really what we do when you have a storage device in your box
>>>> with a volatile write cache that does support flush or fua or similar.
>>> Ok. Then you are talking about a different case - not EOPNOTSUPP.
>> So here's a test patch that attempts to just ignore such a failure to
>> flush the caches. It will still flag the bio as BIO_EOPNOTSUPP, but
>> that's merely maintaining the information in case the caller does want
>> to see if that barrier failed or not. It may not actually be useful, in
>> which case we can just kill that flag.
> 
> Updated version, the previous missed most of the buffer_eopnotsupp()
> checking. So this one also gets rid of the file system retry logic.
> Thanks to gfs2 Steve for pointing out that I missed gfs2, made me
> realize that I missed a lot more as well.

Wouldn't it be cleaner to simply finish with success status from
blk_do_ordered()?  That is the single place that all flush/barrier ops
go through and semantically better place too.

Thanks.

-- 
tejun
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