linux-kernel - Re: [PATCH 0/6 v7] overlay filesystem

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Message-Id: <E1Q26mX-0001Tt-Jq@pomaz-ex.szeredi.hu>
Date:	Tue, 22 Mar 2011 19:58:17 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	viro@...iv.linux.org.uk, miklos@...redi.hu,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, apw@...onical.com, nbd@...nwrt.org,
	neilb@...e.de
Subject: Re: [PATCH 0/6 v7] overlay filesystem - request for inclusion

On Tue, 22 Mar 2011, Linus Torvalds wrote:
> On Tue, Mar 22, 2011 at 11:39 AM, Al Viro <viro@...iv.linux.org.uk> wrote:
> >
> > Locking analysis would be really nice; AFAICS, it violates locking order
> > when called from e.g. ->setattr()

Locking order is always:

-> overlayfs locks
   -> upper fs locks
   -> lower fs locks

So it's really pretty simple and easy to validate.

> >  and its protection against renames is
> > nowhere near enough.  I might be missing something subtle, but...

Protection is exactly as for userspace callers.  AFAICT.

> Miklos - have you tried using this with lockdep (together with the
> same filesystems mounted natively too)? I'd expect that that should
> show any bad lock usage..

Ah, lockdep.  I have tried, but there seems to be always something
that triggers it at boot time on my laptop, which makes it useless.  I
could find some other machine to test this on, though.

Thanks,
Miklos
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