linux-kernel - Re: Locking problem in overlayfs

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Message-ID: <6032.1414420761@warthog.procyon.org.uk>
Date:	Mon, 27 Oct 2014 14:39:21 +0000
From:	David Howells <dhowells@...hat.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	dhowells@...hat.com, Al Viro <viro@...IV.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-unionfs@...r.kernel.org
Subject: Re: Locking problem in overlayfs

Miklos Szeredi <miklos@...redi.hu> wrote:

> Uh-oh.  We changed nesting late in the cycle and I didn't retest with lockdep.
> 
> And it's actually harmless, but AFAICS needs another level of nesting between
> I_MUTEX_CHILD and I_MUTEX_NORMAL.

In an overlay directory that shadows an empty lower directory, say
/mnt/a/empty102, do:

	touch /mnt/a/empty102/x
	unlink /mnt/a/empty102/x
	rmdir /mnt/a/empty102

David
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