From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH 2/3] dm: add support for passing through inline crypto support Date: Wed, 23 Sep 2020 21:14:39 -0400 Message-ID: <20200924011438.GD10500@redhat.com> References: <20200909234422.76194-1-satyat@google.com> <20200909234422.76194-3-satyat@google.com> <20200922003255.GC32959@sol.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20200922003255.GC32959@sol.localdomain> To: Eric Biggers Cc: Satya Tangirala , Jens Axboe , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, dm-devel@redhat.com, Alasdair Kergon List-Id: dm-devel.ids On Mon, Sep 21 2020 at 8:32pm -0400, Eric Biggers wrote: > On Wed, Sep 09, 2020 at 11:44:21PM +0000, Satya Tangirala wrote: > > From: Eric Biggers > > > > 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.) > > > > When a key is evicted from the dm device, it is evicted from all > > underlying devices. > > > > Signed-off-by: Eric Biggers > > Co-developed-by: Satya Tangirala > > Signed-off-by: Satya Tangirala > > Looks good as far as Satya's changes from my original patch are concerned. > > Can the device-mapper maintainers take a look at this? In general it looks like these changes were implemented very carefully and are reasonable if we _really_ want to enable passing through inline crypto. I do have concerns about the inability to handle changes at runtime (due to a table reload that introduces new devices without the encryption settings the existing devices in the table are using). But the fallback mechanism saves it from being a complete non-starter. Can you help me better understand the expected consumer of this code? If you have something _real_ please be explicit. It makes justifying supporting niche code like this more tolerable. Thanks, Mike