linux-kernel - Re: [announce] vfs-scale git tree update

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Message-ID: <1294883313.2757.5.camel@perseus>
Date:	Thu, 13 Jan 2011 09:48:33 +0800
From:	Ian Kent <raven@...maw.net>
To:	Nick Piggin <npiggin@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>, aelder@....com,
	Nick Piggin <npiggin@...nel.dk>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [announce] vfs-scale git tree update

On Thu, 2011-01-13 at 12:01 +1100, Nick Piggin wrote:
> On Wed, Jan 12, 2011 at 4:17 PM, Ian Kent <raven@...maw.net> wrote:
> > On Wed, 2011-01-12 at 12:41 +0800, Ian Kent wrote:
> >> On Tue, 2011-01-11 at 20:06 -0800, Linus Torvalds wrote:
> >> > On Tue, Jan 11, 2011 at 7:59 PM, Ian Kent <raven@...maw.net> wrote:
> 
> >> > > Yeah, a hangover from changes done over time.
> >> > > Not setting the dentry op in ->lookup() should fix this.
> >> >
> >> > Alex, care to test just removing the d_set_d_op() call from autofs4_lookup()?
> >> >
> >> > (That code is a bit scary, though - it explicitly makes it a negative
> >> > dentry with a d_instantiate(dentry, NULL), and then hides the inode
> >> > information away separately. Scary scary)
> >>
> >> Yeah, but the expire to mount races with autofs are difficult to handle
> >> and this approach has worked well under heavy stress testing. It's true
> >> that this would almost certainly be bad for a file system that supported
> >> a full range of functionality but that's not so for autofs.
> >
> > I think I have to partly take this back.
> > With Nick's recent vfs-scale patches this may not be OK any more since
> > the dcache_lock has gone away and, at first glance, it looks like the
> > added autofs4_lock spin lock doesn't provide the needed protection.
> 
> Hm, what are the concurrencies that you need protection from?

Ha, I think I'm wrong about this, after looking more closely at this I'm
struggling to see why autofs4_lock is needed at all.


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