linux-kernel - Re: [PATCH 0/2] block layer filter and block device snapshot module

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 21 Oct 2020 17:10:44 +0300
From:   Sergei Shtepa <sergei.shtepa@...am.com>
To:     Hannes Reinecke <hare@...e.de>
CC:     "axboe@...nel.dk" <axboe@...nel.dk>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "hch@...radead.org" <hch@...radead.org>,
        "darrick.wong@...cle.com" <darrick.wong@...cle.com>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "len.brown@...el.com" <len.brown@...el.com>,
        "pavel@....cz" <pavel@....cz>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "johannes.thumshirn@....com" <johannes.thumshirn@....com>,
        "ming.lei@...hat.com" <ming.lei@...hat.com>,
        "jack@...e.cz" <jack@...e.cz>, "tj@...nel.org" <tj@...nel.org>,
        "gustavo@...eddedor.com" <gustavo@...eddedor.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "osandov@...com" <osandov@...com>,
        "koct9i@...il.com" <koct9i@...il.com>,
        "damien.lemoal@....com" <damien.lemoal@....com>,
        "steve@....org" <steve@....org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 0/2] block layer filter and block device snapshot module

The 10/21/2020 16:31, Hannes Reinecke wrote:
> I do understand where you are coming from, but then we already have a 
> dm-snap which does exactly what you want to achieve.
> Of course, that would require a reconfiguration of the storage stack on 
> the machine, which is not always possible (or desired).

Yes, reconfiguring the storage stack on a machine is almost impossible.

> 
> What I _could_ imagine would be a 'dm-intercept' thingie, which 
> redirects the current submit_bio() function for any block device, and 
> re-routes that to a linear device-mapper device pointing back to the 
> original block device.
> 
> That way you could attach it to basically any block device, _and_ can 
> use the existing device-mapper functionality to do fancy stuff once the 
> submit_io() callback has been re-routed.
> 
> And it also would help in other scenarios, too; with such a 
> functionality we could seamlessly clone devices without having to move 
> the whole setup to device-mapper first.

Hm... 
Did I understand correctly that the filter itself can be left approximately
as it is, but the blk-snap module can be replaced with 'dm-intercept',
which would use the re-route mechanism from the dm?
I think I may be able to implement it, if you describe your idea in more
detail.


-- 
Sergei Shtepa
Veeam Software developer.