linux-kernel - Re: [PATCH 1/2] block: fix leaks associated with discard request payload

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Date:	Wed, 30 Jun 2010 13:25:01 +0300
From:	Boaz Harrosh <bharrosh@...asas.com>
To:	Christoph Hellwig <hch@....de>
CC:	James Bottomley <James.Bottomley@...e.de>,
	Mike Snitzer <snitzer@...hat.com>, axboe@...nel.dk,
	dm-devel@...hat.com, linux-kernel@...r.kernel.org,
	martin.petersen@...cle.com, akpm@...ux-foundation.org,
	linux-scsi@...r.kernel.org,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Subject: Re: [PATCH 1/2] block: fix leaks associated with discard request
 payload

On 06/30/2010 11:42 AM, Christoph Hellwig wrote:
> On Wed, Jun 30, 2010 at 11:32:43AM +0300, Boaz Harrosh wrote:
>> May I ask a silly question? Why the dynamic allocation?
>>
>> Why not have a const-static single global page at the block-layer somewhere
>> that will be used for all discard-type operations and be done with it once and
>> for all. A single page can be used for any size bio , any number of concurrent
>> discards, any ZERO needed operation. It can also be used by other operations
>> like padding and others. In fact isn't there one for the libsata padding?
> 
> for UNMAP we need to write into the payload.  And for ATA TRIM we need
> to write into the WRITE SAME payload.  

OK, Thanks, I see. Is it one of these operations, (like we have in OSD) where
the CDB information spills into the payload? like the scatter-gather and extent
lists and such. Do we actually use a WRITE_SAME which is not zero? for what use?

> That's another layering violation
> for those looking for them, btw..
> 

Agreed
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