To: Christoph Hellwig <hch@lst.de>
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 <20170414083921.GC25471@lst.de>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
        Sagi Grimberg <sagi@grimberg.me>, Jens Axboe <axboe@kernel.dk>,
        Tejun Heo <tj@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Ross Zwisler <ross.zwisler@linux.intel.com>,
        Matthew Wilcox <mawilcox@microsoft.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        Ming Lin <ming.l@ssi.samsung.com>, linux-kernel@vger.kernel.org,
        linux-crypto@vger.kernel.org, linux-media@vger.kernel.org,
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        devel@driverdev.osuosl.org, target-devel@vger.kernel.org,
        netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
        rds-devel@oss.oracle.com, Steve Wise <swise@opengridcomputing.com>,
        Stephen Bates <sbates@raithlin.com>
From: Logan Gunthorpe <logang@deltatee.com>
Message-ID: <302ae5ab-d515-5427-2e54-d58a9cdb8241@deltatee.com>
Date: Fri, 14 Apr 2017 10:03:43 -0600
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Subject: Re: [PATCH 09/22] dm-crypt: Make use of the new sg_map helper in 4
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On 14/04/17 02:39 AM, Christoph Hellwig wrote:
> On Thu, Apr 13, 2017 at 04:05:22PM -0600, Logan Gunthorpe wrote:
>> Very straightforward conversion to the new function in all four spots.
> 
> I think the right fix here is to switch dm-crypt to the ahash API
> that takes a scatterlist.

Hmm, well I'm not sure I understand the code enough to make that
conversion. But I was looking at it. One tricky bit seems to be that
crypt_iv_lmk_one adds a seed, skips the first 16 bytes in the page and
then hashes another 16 bytes from other data. What would you do
construct a new sgl for it and pass it to the ahash api?

The other thing is crypt_iv_lmk_post also seems to modify the page after
the hash with a  crypto_xor so you'd still need at least one kmap in there.

Logan