linux-kernel - Re: [PATCH v1 0/5] dm: dm-user: New target that proxies BIOs to userspace

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]

Message-ID: <20201222143616.GB12885@redhat.com>
Date:   Tue, 22 Dec 2020 09:36:16 -0500
From:   Mike Snitzer <snitzer@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Palmer Dabbelt <palmer@...belt.com>, josef@...icpanda.com,
        bvanassche@....org, corbet@....net, kernel-team@...roid.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, song@...nel.org, dm-devel@...hat.com,
        linux-kselftest@...r.kernel.org, shuah@...nel.org, agk@...hat.com,
        michael.christie@...cle.com
Subject: Re: [PATCH v1 0/5] dm: dm-user: New target that proxies BIOs to
 userspace

On Tue, Dec 22 2020 at  8:32am -0500,
Christoph Hellwig <hch@...radead.org> wrote:

> On Mon, Dec 14, 2020 at 07:00:57PM -0800, Palmer Dabbelt wrote:
> > I haven't gotten a whole lot of feedback, so I'm inclined to at least have some
> > reasonable performance numbers before bothering with a v2.
> 
> FYI, my other main worry beside duplicating nbd is that device mapper
> really is a stacked interface that sits on top of other block device.
> Turning this into something else that just pipes data to userspace
> seems very strange.

I agree.  Only way I'd be interested is if it somehow tackled enabling
much more efficient IO.  Earlier discussion in this thread mentioned
that zero-copy and low overhead wasn't a priority (because it is hard,
etc).  But the hard work has already been done with io_uring.  If
dm-user had a prereq of leaning heavily on io_uring and also enabled IO
polling for bio-based then there may be a win to supporting it.

But unless lower latency (or some other more significant win) is made
possible I just don't care to prop up an unnatural DM bolt-on.

Mike