Re: dm vdo: add optional Intel IAA-backed compression support

On Wed, 29 Apr 2026, Matthew Sakai wrote:

> 
> 
> On 4/29/26 11:24 AM, Mikulas Patocka wrote:
> > Hi
> > 
> > I think the best way how to support it would be to modify the VDO target
> > to use the asynchronous compression API (so that it could use arbitrary
> > algorithms). Then, the support for IAA could be plugged in easily with
> > little or no extra code.
> 
> I agree that this is the right approach, but supporting arbitrary compression
> algorithms will require some significant changes on its own. dm-vdo currently
> has nowhere to store information about what algorithm is used for which
> blocks, so it would require reworking the metadata. (We would probably store

You can store the algorithm in the superblock and use it for all blocks on 
the device. This would be not as flexible as per-block algorithm 
specification, but it should be relatively easy to implement - and it 
would allow you to evaluate whether different algorithms improve 
performance or compression ratio.

> the extra compression information in the compression block header.) This
> metadata rework in turn will require some effort to make sure we can continue
> to support existing users who will want to continue to use dm-vdo volumes in
> the current format.

Mikulas