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From: Milan Broz <>
Subject: Re: dm-verity design question
Date: Tue, 12 Apr 2022 11:47:07 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi Jasper,

if it is question about kernel code, the best is to ask on list
(you can cc cryptsetup list too).

Not all device-mapper kernel developers are here (dm-devel is official list
for kernel device-mapper subsystem; this one mainly for userspace cryptsetup tools).


On 12/04/2022 11:38, Jasper Surmont wrote:
> Hey,
> After going through the dm-verity source code for a while I think I
> kind of figured out the general design; on a read:
> 1. Multiple possible problems get checked like alignment, out of range
> etc. Also variables get set based on the request
> 2. The request is prefetched to the cache
> 3. The actual integrity check is done when the bio ends (bi_end_io
> points to verity_end_io which submits the work to verify digest etc
> If this is correct, I have 2 questions:
> 1. What is the main benefit of prefetching here? We know the remapped
> request is going to be executed very soon, so I don't really see why
> we prefetch.
> 2. In verity_end_io(...), we only submit the work to verify the digest
> if FEC is enabled. Why? Can't we check integrity without using FEC?
> I hope my questions are clear.
> Thanks a lot!
> Sincerely, Jasper Surmont

      reply	other threads:[~2022-04-12  9:47 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-12  9:38 dm-verity design question Jasper Surmont
2022-04-12  9:47 ` Milan Broz [this message]

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