Message-ID: <471F5804.30305@garzik.org>
Date: Wed, 24 Oct 2007 10:34:44 -0400
From: Jeff Garzik <jeff@garzik.org>
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To: FUJITA Tomonori <tomof@acm.org>
CC: jens.axboe@oracle.com, akpm@linux-foundation.org,
       linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
       James.Bottomley@SteelEye.com, fujita.tomonori@lab.ntt.co.jp
Subject: Re: [PATCH -mm 09/11] call blk_queue_segment_boundary in __scsi_alloc_queue
References: <67bb10d9f4e9473ddc84d9839114602c1966f19f.tomof@acm.org>	<20071024172611B.tomof@acm.org>	<471F2EE4.5000309@garzik.org> <20071024231724T.tomof@acm.org>
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FUJITA Tomonori wrote:
> On Wed, 24 Oct 2007 07:39:16 -0400
> Jeff Garzik <jeff@garzik.org> wrote:
> 
>> FUJITA Tomonori wrote:
>>> request_queue and device struct must have the same value of a segment
>>> size limit. This patch adds blk_queue_segment_boundary in
>>> __scsi_alloc_queue so LLDs don't need to call both
>>> blk_queue_segment_boundary and set_dma_max_seg_size. A LLD can change
>>> the default value (64KB) can call device_dma_parameters accessors like
>>> pci_set_dma_max_seg_size when allocating scsi_host.
>>>
>>> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
>>> ---
>>>  drivers/scsi/scsi_lib.c |    3 +++
>>>  1 files changed, 3 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
>>> index 61fdaf0..23a30ab 100644
>>> --- a/drivers/scsi/scsi_lib.c
>>> +++ b/drivers/scsi/scsi_lib.c
>>> @@ -1645,6 +1645,7 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
>>>  					 request_fn_proc *request_fn)
>>>  {
>>>  	struct request_queue *q;
>>> +	struct device *dev = shost->shost_gendev.parent;
>>>  
>>>  	q = blk_init_queue(request_fn, NULL);
>>>  	if (!q)
>>> @@ -1673,6 +1674,8 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
>>>  	blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
>>>  	blk_queue_segment_boundary(q, shost->dma_boundary);
>>>  
>>> +	blk_queue_max_segment_size(q, dma_get_max_seg_size(dev));
>>> +
>> it would be nice to have something more general that's useable in 
>> drivers/block/sx8.c (for example), something like
>>
>> 	static inline void
>> 	dev_blk_associate(struct device *dev, request_queue *q)
>> 	{
>> 		blk_queue_max_segment_size(q,
>> 					dma_get_max_seg_size(dev));
>> 	}
>>
>> still, I will ACK the above patch (#9) in case you wish that to become a 
>> future cleanup, or others dislike this suggestion
> 
> Yeah, I thought about something like that. But I can't find many
> non-scsi drivers (ide, sx8, mmc/card/, anymore?) doing dma and having
> the restrictions so I just call blk_queue_max_segment_size here.

My main idea was that request_queue will eventually want to know struct 
device details directly, if it can.


> Either is ok with me. I'll modify the patch if Jens prefers such
> function. Jens?

I have no strong opinion... it was just a thought.

	Jeff


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