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Re: [dm-devel] dm-verity: Verification fails but do not see Input/Output Error on read




On Thu, 8 Aug 2013, Chaitra Bhat wrote:

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> 
> Hi Alasdair,
> 
> Thanks for your response.
> 
> But I am not convinced. Here is why...
>
> 1. I tried a bit-more and I was able to get Input/Output Error on 
> certain locations - everytime - I read that location. (But I still have 
> an open question that on some locations, though the verify reports 
> failure, I do not get an IO Error on read)
> 
> 2. I do not understand when you say device is live - do you mean 
> mounted? Because I thought that the whole idea of dm-verity was that 
> once the verity device is set-up, it would return EIO when something 
> gets corrupted in the data or hash partitions when that invalid data is 
> read.
> 
> Chaitra

It is possible that you are reading data from the buffer cache and not 
from the underlying device.

To not use the buffer cache, use iflag=direct parameter to dd.

Mikulas


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