From: Octavian Purdila <octavian.purdila@intel.com>
To: Brian Foster <bfoster@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>,
Richard Weinberger <richard.weinberger@gmail.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>, xfs <xfs@oss.sgi.com>
Subject: Re: [RFC PATCH] xfs: support for non-mmu architectures
Date: Fri, 20 Nov 2015 17:31:59 +0200 [thread overview]
Message-ID: <CAE1zotK1Gjb_gzDjU_dnQoYQnP4azvsDtzi6f=RANH-wDOKhSA@mail.gmail.com> (raw)
In-Reply-To: <20151120152412.GC60886@bfoster.bfoster>
On Fri, Nov 20, 2015 at 5:24 PM, Brian Foster <bfoster@redhat.com> wrote:
> On Fri, Nov 20, 2015 at 04:26:28PM +0200, Octavian Purdila wrote:
>> On Fri, Nov 20, 2015 at 2:58 AM, Dave Chinner <david@fromorbit.com> wrote:
>> > On Fri, Nov 20, 2015 at 12:54:02AM +0100, Richard Weinberger wrote:
>> >> On Fri, Nov 20, 2015 at 12:24 AM, Dave Chinner <david@fromorbit.com> wrote:
>> >> > On Wed, Nov 18, 2015 at 12:46:21AM +0200, Octavian Purdila wrote:
>> >> >> Naive implementation for non-mmu architectures: allocate physically
>> >> >> contiguous xfs buffers with alloc_pages. Terribly inefficient with
>> >> >> memory and fragmentation on high I/O loads but it may be good enough
>> >> >> for basic usage (which most non-mmu architectures will need).
>> >> >
>> >> > Can you please explain why you want to use XFS on low end, basic
>> >> > non-MMU devices? XFS is a high performance, enterprise/HPC level
>> >> > filesystem - it's not a filesystem designed for small IoT level
>> >> > devices - so I'm struggling to see why we'd want to expend any
>> >> > effort to make XFS work on such devices....
>> >>
>> >> The use case is the Linux Kernel Library:
>> >> https://lkml.org/lkml/2015/11/3/706
>> >>
>> >> Using LKL and fuse you can mount any kernel filesystem using fuse
>> >> as non-root.
>> >
>> > IOWs, because we said no to unprivileged mounts, instead the
>> > proposal is to linking all the kernel code into userspace so you can
>> > do unprivielged mounts that way?
>> >
>>
>> LKL's goal is to make it easy for various applications to reuse Linux
>> kernel code instead of re-implementing it. Mounting filesystem images
>> is just one of the applications.
>>
>> > IOWs, you get to say "it secure because it's in userspace" and leave
>> > us filesystem people with all the shit that comes with allowing
>> > users to mount random untrusted filesystem images using code that
>> > was never designed to allow that to happen?
>> >
>>
>> It is already possible to mount arbitrary filesystem images in
>> userspace using VMs . LKL doesn't change that, it just reduces the
>> amount of dependencies you need to do so.
>>
>
> Perhaps a dumb question, but I'm not quite putting 2+2 together here.
> When I see nommu, I'm generally thinking hardware characteristics, but
> we're talking about a userspace kernel library here. So can you
> elaborate on how this relates to nommu? Does this library emulate kernel
> mechanisms in userspace via nommu mode or something of that nature?
>
LKL is currently implemented as a virtual non-mmu architecture. That
makes it simpler and it will also allow us to support environments
where it is not possible to emulate paging (e.g. bootloaders).
next prev parent reply other threads:[~2015-11-20 15:32 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-17 22:46 [RFC PATCH] xfs: support for non-mmu architectures Octavian Purdila
2015-11-19 15:55 ` Brian Foster
2015-11-19 20:54 ` Octavian Purdila
2015-11-20 15:11 ` Brian Foster
2015-11-19 23:35 ` Dave Chinner
2015-11-20 14:09 ` Octavian Purdila
2015-11-20 15:11 ` Brian Foster
2015-11-20 15:35 ` Octavian Purdila
2015-11-20 15:40 ` Brian Foster
2015-11-20 20:36 ` Dave Chinner
2015-11-20 22:47 ` Brian Foster
2015-11-22 22:04 ` Dave Chinner
2015-11-23 12:50 ` Brian Foster
2015-11-23 21:00 ` Dave Chinner
2015-11-19 23:24 ` Dave Chinner
2015-11-19 23:54 ` Richard Weinberger
2015-11-20 0:58 ` Dave Chinner
2015-11-20 14:26 ` Octavian Purdila
2015-11-20 15:24 ` Brian Foster
2015-11-20 15:31 ` Octavian Purdila [this message]
2015-11-20 15:43 ` Brian Foster
2015-11-20 20:07 ` Theodore Ts'o
2015-11-20 13:43 ` Octavian Purdila
2015-11-20 21:08 ` Dave Chinner
2015-11-20 22:26 ` Octavian Purdila
2015-11-22 22:44 ` Dave Chinner
2015-11-23 1:41 ` Octavian Purdila
2015-11-23 21:46 ` Dave Chinner
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAE1zotK1Gjb_gzDjU_dnQoYQnP4azvsDtzi6f=RANH-wDOKhSA@mail.gmail.com' \
--to=octavian.purdila@intel.com \
--cc=bfoster@redhat.com \
--cc=david@fromorbit.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=richard.weinberger@gmail.com \
--cc=xfs@oss.sgi.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).