linux-kernel - Re: [dm-devel] [PATCH v2 0/2] Introduce the bulk IV mode for improving the crypto engine efficiency

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Date:	Wed, 13 Jan 2016 08:01:01 +0100
From:	Milan Broz <gmazyland@...il.com>
To:	Arnd Bergmann <arnd@...db.de>,
	Mikulas Patocka <mpatocka@...hat.com>
Cc:	device-mapper development <dm-devel@...hat.com>,
	Mark Brown <broonie@...nel.org>,
	Milan Broz <gmazyland@...il.com>, Jens Axboe <axboe@...nel.dk>,
	keith.busch@...el.com, linux-raid@...r.kernel.org,
	martin.petersen@...cle.com, Mike Snitzer <snitzer@...hat.com>,
	Baolin Wang <baolin.wang@...aro.org>,
	linux-block@...r.kernel.org, neilb@...e.com,
	LKML <linux-kernel@...r.kernel.org>, sagig@...lanox.com,
	tj@...nel.org, dan.j.williams@...el.com,
	Kent Overstreet <kent.overstreet@...il.com>,
	Alasdair G Kergon <agk@...hat.com>
Subject: Re: [dm-devel] [PATCH v2 0/2] Introduce the bulk IV mode for
 improving the crypto engine efficiency

On 01/13/2016 12:38 AM, Arnd Bergmann wrote:
> On Tuesday 12 January 2016 18:31:19 Mikulas Patocka wrote:
>>
>> Another possibility is to use dm-crypt block size 4k and use a filesystem 
>> with 4k blocksize on it (it will never send requests not aligned on 4k 
>> boundary, so we could reject such requests with an error).
> 
> Is there ever a reason to use something other than 4K block size on
> dm-crypt?

Most existing sw FDE systems use 512bytes blocks. I would like to see
configurable block size (at least up to 4k) but as Mikulas pointed out
it opens several new problems. 

Anyway, I do not see reason why crypto accelerators should not process
these small sectors better - just hw must be designed for it.

Milan