Re: [RFC v2 2/3] crypto: Introduce CRYPTO_ALG_BULK flag

From: Baolin Wang
Date: Fri Jun 03 2016 - 06:48:07 EST

On 3 June 2016 at 18:09, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> 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.

Best Regards