linux-kernel - Re: [PATCH] dm verity fec: Don't add data

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Date:   Thu, 9 Apr 2020 15:40:07 +0900
From:   Sunwook Eom <speed.eom@...sung.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        device-mapper development <dm-devel@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>, sunwook5492@...il.com
Subject: Re: [PATCH] dm verity fec: Don't add data_blocks to block


On 20. 4. 8. 오전 12:55, Sami Tolvanen wrote:
> On Mon, Apr 6, 2020 at 11:54 PM Sunwook Eom <speed.eom@...sung.com> wrote:
>> Even if block type is metadata,
>> block in verity_fec_decode() has already the right block number.
>> So there is no need to add data_blocks to block.
> Is this also true if the hashes are on a separate block device?
>
> The idea here is that the error correction data was computed over both
> data and hash blocks, as if they were concatenated, and we want to
> calculate the logical block number based on that. I agree that the
> code doesn't look quite right though. Should we use something like
> this instead?
>
>      if (type == DM_VERITY_BLOCK_TYPE_METADATA)
>              block = block - v->hash_start + v->data_blocks;
>
> Sami
>
>
You're right. I missed the case that hashes are on a separate block device.

And, the code you wrote seems to be correct.

If you don't mind, I'll send a new version of this patch.

Thank you for the review.


Sunwook