linux-kernel - Re: [RFC v2 2/3] crypto: Introduce CRYPTO_ALG

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Date:	Fri, 3 Jun 2016 18:47:57 +0800
From:	Baolin Wang <baolin.wang@...aro.org>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Jens Axboe <axboe@...nel.dk>, Alasdair G Kergon <agk@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>,
	"open list:DEVICE-MAPPER (LVM)" <dm-devel@...hat.com>,
	David Miller <davem@...emloft.net>,
	Eric Biggers <ebiggers3@...il.com>,
	Joonsoo Kim <js1304@...il.com>, tadeusz.struk@...el.com,
	smueller@...onox.de, Masanari Iida <standby24x7@...il.com>,
	Shaohua Li <shli@...nel.org>,
	Dan Williams <dan.j.williams@...el.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Sagi Grimberg <sagig@...lanox.com>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Keith Busch <keith.busch@...el.com>, Tejun Heo <tj@...nel.org>,
	Ming Lei <ming.lei@...onical.com>,
	Mark Brown <broonie@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	linux-crypto@...r.kernel.org, linux-block@...r.kernel.org,
	"open list:SOFTWARE RAID (Multiple Disks) SUPPORT" 
	<linux-raid@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v2 2/3] crypto: Introduce CRYPTO_ALG_BULK flag

On 3 June 2016 at 18:09, Herbert Xu <herbert@...dor.apana.org.au> wrote:
> On Fri, Jun 03, 2016 at 05:23:59PM +0800, Baolin Wang wrote:
>>
>> Assuming one 64K size bio coming, we can map the whole bio with one sg
>> table in crypt_convert_bulk_block() function. But if we send this bulk
>> request to crypto layer, we should divide the bulk request into small
>> requests, and each small request should be one sector size (512 bytes)
>> with assuming the correct IV, but we need to allocate small requests
>> memory for the division, which will not good for IO mapping, and how
>> each small request connect to dm-crypt (how to notify the request is
>> done?)?
>
> Why won't it be good? The actual AES block size is 16 and yet we

Like I said, we should avoid memory allocation to improve efficiency
in the IO path. Another hand is how the divided small requests
(allocate request memory at crypt layer) connect with dm-crypt? Since
dm-crypt just send one bulk request to crypt layer, but it will be
divided into small requests at crypt layer.

> have no trouble when you feed it a block of 512 bytes.

That's right.

-- 
Baolin.wang
Best Regards