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Cc: Jens Axboe <jens.axboe@oracle.com>, rusty@rustcorp.com.au,
       linux-kernel@vger.kernel.org
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From: Divyesh Shah <dpshah@google.com>
Subject: Re: request->ioprio
Date: Wed, 6 Aug 2008 10:22:30 -0700
To: =?ISO-8859-1?Q?Fernando_Luis_V=E1zquez_Cao?= 
	<fernando@oss.ntt.co.jp>
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On Aug 6, 2008, at 2:32 AM, Fernando Luis V?zquez Cao wrote:

> (CCing LKML)
>
> Hi Jens, Rusty,
>
> Trying to implement i/o tracking all the way up to the page cache (so
> that cfq and the future cgroup-based I/O controllers can schedule
> buffered I/O properly) I noticed that struct request's ioprio is
> initialized but never used for I/O scheduling purposes. Indeed there
> seems to be one single user of this member: virtio_blk. Virtio uses
> struct request's ioprio in the request() function of the virtio block
> driver, which just copies the ioprio value to the output header of
> virtblk_req.
>
> Is this the intended use of struct request's ioprio? Is it OK for  
> device
> drivers to use it? If the answer two the previous to questions is no I
> would like to send some clean-up patches.

Naveen Gupta sent a priority-based anticipatory IO scheduler patchset  
earlier which uses request->ioprio and the struct request seems to be  
the logical place to keep the ioprio. So, please don't cleanup the  
ioprio from there.

Thanks,
Divyesh

>
> - Fernando
>


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