Re: dm: improve block integrity support

[Mike Snitzer <snitzer@redhat.com>]

[trimming CCs so as not to pester as many people directly]

On Fri, Apr 01 2011 at  1:42pm -0400,
Mike Snitzer <snitzer@redhat.com> wrote:

> The current block integrity (DIF/DIX) support in DM is verifying that
> all devices' integrity profiles match during DM device resume (which
> is past the point of no return).  To some degree that is unavoidable
> (stacked DM devices force this late checking).  But for most DM
> devices (which aren't stacking on other DM devices) the ideal time to
> verify all integrity profiles match is during table load.
> 
> Introduce the notion of an "initialized" integrity profile: a profile
> that was blk_integrity_register()'d with a non-NULL 'blk_integrity'
> template.  Add blk_integrity_is_initialized() to allow checking if a
> profile was initialized.
> 
> Update DM integrity support to:
> - check all devices with _initialized_ integrity profiles match
>   during table load; uninitialized profiles (e.g. for underlying DM
>   device(s) of a stacked DM device) are ignored.
> - disallow a table load that would result in an integrity profile that
>   conflicts with a DM device's existing (in-use) integrity profile
> - avoid clearing an existing integrity profile
> - validate all integrity profiles match during resume; but if they
>   don't all we can do is report the mismatch (during resume we're past
>   the point of no return)
> 
> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
> Cc: Martin K. Petersen <martin.petersen@oracle.com>

Hi Martin,

Any chance you've had a look at this?  I'm most interested in whether
the code works with the various integrity profiles you have.

I'd really like to get this reviewed and queued for upstream so that it
doesn't die on the vine.

Thanks,
Mike