Date:   Thu, 11 Feb 2021 22:58:37 +0000
From:   Satya Tangirala <satyat@google.com>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        dm-devel@redhat.com, Jens Axboe <axboe@kernel.dk>,
        Mike Snitzer <snitzer@redhat.com>,
        Alasdair Kergon <agk@redhat.com>
Subject: Re: [PATCH v4 3/5] dm: add support for passing through inline crypto
 support
Message-ID: <YCW2nWmHCunU1DwV@google.com>
References: <20210201051019.1174983-1-satyat@google.com>
 <20210201051019.1174983-4-satyat@google.com>
 <YCQ/WjAsVA2gdb7d@gmail.com>
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On Wed, Feb 10, 2021 at 12:17:30PM -0800, Eric Biggers wrote:
> On Mon, Feb 01, 2021 at 05:10:17AM +0000, Satya Tangirala wrote:
> > Update the device-mapper core to support exposing the inline crypto
> > support of the underlying device(s) through the device-mapper device.
> > 
> > This works by creating a "passthrough keyslot manager" for the dm
> > device, which declares support for encryption settings which all
> > underlying devices support.  When a supported setting is used, the bio
> > cloning code handles cloning the crypto context to the bios for all the
> > underlying devices.  When an unsupported setting is used, the blk-crypto
> > fallback is used as usual.
> > 
> > Crypto support on each underlying device is ignored unless the
> > corresponding dm target opts into exposing it.  This is needed because
> > for inline crypto to semantically operate on the original bio, the data
> > must not be transformed by the dm target.  Thus, targets like dm-linear
> > can expose crypto support of the underlying device, but targets like
> > dm-crypt can't.  (dm-crypt could use inline crypto itself, though.)
> > 
> > A DM device's table can only be changed if the "new" inline encryption
> > capabilities are a (*not* necessarily strict) superset of the "old" inline
> > encryption capabilities.  Attempts to make changes to the table that result
> > in some inline encryption capability becoming no longer supported will be
> > rejected.
> > 
> > For the sake of clarity, key eviction from underlying devices will be
> > handled in a future patch.
> > 
> > Co-developed-by: Eric Biggers <ebiggers@google.com>
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > Signed-off-by: Satya Tangirala <satyat@google.com>
> 
> I don't see any obvious issues with this latest version.  I assume you've tested
> it on real hardware?
> 
> If it's needed despite my Co-developed-by, feel free to add:
> 
> Reviewed-by: Eric Biggers <ebiggers@google.com>
> 
> A few nits about comments, in case you resend:
> 
Thanks! I addressed the nits, added acked/reviewed-bys and resent v5.