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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 Mikulas,
> 
> I get 'Invalid argument' with 'iflag=direct' option when I try to read 
> from a verity device using dd.

If you use iflag=direct, block size and offset must be aligned on physical 
block size boundary (usually 4k). If they are not aligned, you get invalid 
argument error.

> Before I read from the device, I also did 'echo 3 > 
> /proc/sys/vm/drop_caches' to make sure caches are dropped.

If the filesystem is mounted, it doesn't drop some buffers (those that are 
used by the filesystem). Unmount the filesystem first.

> But as I said before, some locations always fail with I/O error when 
> read and others don't.

If you still get misbehavior, even if you bypass the cache with 
iflag=direct or with filesystem unmount, create a script that reproduces 
it and send it to us.

> Regards,
> Chaitra

Mikulas


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