From: Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH UPDATED] xen: add xenfs to allow usermode
	<-> Xen interaction
Date: Thu, 18 Dec 2008 14:18:12 +0100
Message-ID: <20081218131812.GD32135@elte.hu>
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	<20081216125425.30524946.akpm@linux-foundation.org>
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	<20081217133429.b64e6421.akpm@linux-foundation.org>
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To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>, alex.zeffertt@eu.citrix.com, Ian.Campbell@citrix.com, linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, viro@ftp.linux.org.uk
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* Andrew Morton <akpm@linux-foundation.org> wrote:

> On Wed, 17 Dec 2008 13:24:39 -0800
> Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> 
> > The xenfs filesystem exports various interfaces to usermode.  Initially
> > this exports a file to allow usermode to interact with xenbus/xenstore.
> > 
> > Traditionally this appeared in /proc/xen.  Rather than extending procfs,
> > this patch adds a backward-compat mountpoint on /proc/xen, and provides
> > a xenfs filesystem which can be mounted there.
> > 
> > [ 
> >   I did quite a lot of work to this code as a result of review, which is
> >   why this is a repost rather than a delta.  The changes are:
> > 
> >    - Moved the XENFS_SUPER_MAGIC to linux/magic.h
> >    - Added comments to answer the "what's this for?" questions (I hope)
> >    - Split things out into smaller functions
> >    - Cleaned up type of queue_reply(), removed casts
> >    - Added a mutex to protect struct xenbus_file_priv.  This protects
> >       the list heads, and the partial message buffer.  There were
> >       several ways in which usermode could overwrite the kernel's
> >       memory via races without this locking.
> >    - Fixed a bug in which usermode could start sending a message
> >       which can never be sent, leaving the file descriptor in a
> >       useless state.
> 
> I'm bored of your filesystem, so I think I'll just merge it, unless
> someone else wants to ;)

please do - there should be no big overlap with existing other Xen bits in 
tip/*.

	Ingo