linux-ext4 - Re: [PATCH v3 1/2] block: skip elevator data initialization for flush requests

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Message-ID: <20110203133820.GF2570@htj.dyndns.org>
Date:	Thu, 3 Feb 2011 14:38:20 +0100
From:	Tejun Heo <tj@...nel.org>
To:	Jens Axboe <jaxboe@...ionio.com>
Cc:	Mike Snitzer <snitzer@...hat.com>, "tytso@....edu" <tytso@....edu>,
	"djwong@...ibm.com" <djwong@...ibm.com>,
	"shli@...nel.org" <shli@...nel.org>,
	"neilb@...e.de" <neilb@...e.de>,
	"adilger.kernel@...ger.ca" <adilger.kernel@...ger.ca>,
	"jack@...e.cz" <jack@...e.cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kmannth@...ibm.com" <kmannth@...ibm.com>,
	"cmm@...ibm.com" <cmm@...ibm.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"rwheeler@...hat.com" <rwheeler@...hat.com>,
	"hch@....de" <hch@....de>, "josef@...hat.com" <josef@...hat.com>,
	"jmoyer@...hat.com" <jmoyer@...hat.com>,
	"vgoyal@...hat.com" <vgoyal@...hat.com>
Subject: Re: [PATCH v3 1/2] block: skip elevator data initialization for
 flush requests

Hey, Jens.

On Thu, Feb 03, 2011 at 02:24:42PM +0100, Jens Axboe wrote:
> On 2011-02-02 23:55, Mike Snitzer wrote:
> > REQ_SORTED is not set for flush requests because they are never put on
> > the IO scheduler.
> 
> That looks very wrong. REQ_SORTED gets set _when_ the request is sorted
> into the IO scheduler. This is gross misuse, a bad hack.

The rationale behind suggesting was that it indicates to the allocator
that the request may be sorted as how the request will be used is
communicated using @rw_flags to the allocator.  The patch is buggy
that the flag actually ends up on the request.  Any better idea how to
communicate it?

Thanks.

-- 
tejun
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