Re: [Qemu-devel] Breaking out virtfs as a standalone server?

[Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>]

On 04/11/2011 10:52 PM, Rob Landley wrote:
> On 04/11/2011 03:28 PM, Venkateswararao Jujjuri wrote:
>> On 04/11/2011 06:42 AM, Rob Landley wrote:
>>> Right now, there's no decent userspace server for the 9p filesystem that
>>> I can find.  (In part because the 9P2000.L spec is an undocumented work
>>> in progress.)
>> This statement is true for 9P2000.L protocol;
> According to my research on the topic, anyway:
>
>    http://landley.livejournal.com/48698.html

You wrote " And at the moment write support seems to be broken for me. 
But I was able to mount a directory from the host system and cat a file, 
which is progress."

Can you please explain where it is broken. IT should be working good.

- JV

>> But for older protocols we have standalone servers like spfs/npfs.
>> http://sourceforge.net/projects/npfs/
> This would be the one that has no documentation or web page, builds
> without ./configure, and has no way to specify which directory to export
> but apparently can ONLY export / on the host?
>
>> http://9p.cat-v.org/implementations
> I looked at those.  Several are unfinished libraries, some also only
> export / and treat the whole "restrict what you're exporting to a
> subdir" problem as inherently unsolvable (readlink -f), the main one
> everybody seems to test with is the Inferno equivalent of usermode
> Linux, there's a python server that refuses to run without some third
> party encryption/authentication library that it never OCCURRED to their
> developers you might want t disable...
>
> I also tracked down more like http://code.google.com/p/diod/ (and
> emailed its author for a while: that project is stalled due to his
> desire to rewrite large chunks of it, and a lack of time).
>
> I also subscribed to v9fs-users, which is not the world's highest
> traffic list:
>
>    http://sourceforge.net/mailarchive/forum.php?forum_name=v9fs-users
>
>>> The only up-to-date server seems to be virtfs in qemu, which has no TCP
>>> transport layer.
>>>
>>> Are there any plans to:
>>>
>>> A) Add a TCP transport layer so we can test with something we can
>>> intercept/examine/log/redirect with netcat and such?
>> No plans as of now; I know folks in the Latchesar Ionkov attempted char
>> dev transport.
> NFS works over TCP.  Samba works over TCP.  But not p9.  Is there some
> reason to go out of the way to avoid it?
>
>> Not sure the latest though.
>>
>> http://sourceforge.net/mailarchive/forum.php?thread_name=AANLkTim4eZttAmaNQfOuM1h7cmLvO-osckHNunMvG7o%2B%40mail.gmail.com&forum_name=v9fs-developer
> Ah, if I want information about userspace servers I should subscribe to
> v9fs-developer instead of v9fs-user, because it has no users yet.  Got it.
>
>>> B) Break the 9p server out so it could be built as a standalone
>>> userspace program?
>> No plans yet..and I think this is a bigger discussion.
> If this filesystem is to become more than an academic exercise, it needs
> a server that can export a specific directory.
>
>> Being part of QEMU brings few implicit advantages like simplicity in
>> sharing, security
>> and performance advantage. I think taking it out can have its own merits.
> I wasn't suggesting removing it from QEMU.  Having it in QEMU is great,
> the code is written and works, it's useful as-is, and half the _idea_ of
> this is that it's simpler than samba or NFS (which is damning with faint
> praise, I know).
>
> In theory, all the actual protocol encoding and decoding (and doing the
> read/write/stat stuff on the host) is a single C file, correct?  Right
> now there isn't any reference implementation of that server-side code,
> but there is a working example of it.  Virtfs is a working example, just
> not hooked up to a particularly useful transport.  (If it had a TCP
> transport I could route it back out through a tap interface or -redir
> port and use qemu as a test server... but it doesn't.  As far as I can
> tell, virtio is intentionally the _least_ flexible mechanism for that
> sort of thing.  Although maybe there's docs on this and I've just missed
> them...)
>
> Rob
>