[dm-devel] [PATCH 9/9] dm-integrity: recalculate checksums

Milan Broz gmazyland at gmail.com
Tue Jul 3 14:53:33 UTC 2018


On 07/03/2018 03:21 PM, Mike Snitzer wrote:
>>
>> Should we even have the possibility to stop recalculating?
>>
>> If the device was recalculating and we activate it without the 
>> "recalculate" flag, what should it do? If the user reads data that haven't 
>> been recalculated yet, we could:
>> 1. return an error
>> 2. ignore the non-recalculated checksum and return data
>> 3. continue with recalculating even if the flag "recalculate" is not present
>>
>> In my opinion, the option 3 is the best. Option 1 makes the device 
>> unreliable and option 2 makes the device silently lose the integrity 
>> protection.
> 
> Yes, option 3.  But you could even error out on table load; though that
> may be too unforgiving.. reality is userspace needs to account for
> staying in recalculating mode until it is complete.

I do not think table load error is the way to go.

Can we activate dmintegrity read-only (for example with read-only backend device)
that is not yet fully recalculated?

This can needed in some recovery scenarios... (But her we can use recovery mode).

> But to do that they'd need to monitor (similar to how snapshot-merge
> polls progress?)

For veritysetup I will just add this to "status" command output.

Milan




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