linux-kernel - Re: [RFC PATCH v4] IV Generation algorithms for dm-crypt

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Date:   Wed, 1 Mar 2017 14:04:47 +0100
From:   Milan Broz <gmazyland@...il.com>
To:     Gilad Ben-Yossef <gilad@...yossef.com>,
        Milan Broz <gmazyland@...il.com>
Cc:     Binoy Jayan <binoy.jayan@...aro.org>, Oded <oded.golombek@....com>,
        Ofir <Ofir.Drang@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        Shaohua Li <shli@...nel.org>, linux-raid@...r.kernel.org,
        Rajendra <rnayak@...eaurora.org>,
        Ondrej Mosnacek <omosnace@...hat.com>
Subject: Re: [RFC PATCH v4] IV Generation algorithms for dm-crypt

On 03/01/2017 01:42 PM, Gilad Ben-Yossef wrote:
...

> I can certainly understand if you don't wont to take the patch until
> we have results with
> dm-crypt itself but the difference between 8 separate invocation of
> the engine for 512
> bytes of XTS and a single invocation for 4KB are pretty big.

Yes, I know it. But the same can be achieved if we just implement
4k sector encryption in dmcrypt. It is incompatible with LUKS1
(but next LUKS version will support it) but I think this is not
a problem for now.

If the underlying device supports atomic write of 4k sectors, then
there should not be a problem.

This is one of the speed-up I would like to compare with the IV approach,
because everyone should benefit from 4k sectors in the end.
And no crypto API changes are needed here.

(I have an old patch for this, so I will try to revive it.)

Milan