From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: block mapping
Date: Thu, 29 Sep 2011 09:55:18 -0400
Message-ID: <20110929135518.GA3639@infradead.org>
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On Thu, Sep 29, 2011 at 04:35:44PM +0300, Kasatkin, Dmitry wrote:
> Hello All,
> 
> I would like to implement such block device, which can store
> additional information along with the block data.
> For example. so if file system has 4k block, I would like to store
> 4k+256b of additional information...
> 
> Can such block device be implemented with device mapper?

Given your other recent posts you probably want to take a look at
dm-verity:

	http://selinuxproject.org/~jmorris/lss2011_slides/LSS_11_Integrity_checked_block_devices.pdf

(even if that's not strictly what you are asking for here)