linux-kernel - Re: Unionmount and overlayfs testsuite

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Message-ID: <CAJfpegsUDcFZ+9jPDU6mMXuAOwvzNFV3Q2WRE6QdoPYSqKeRqQ@mail.gmail.com>
Date:	Tue, 3 Jun 2014 11:12:08 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	David Howells <dhowells@...hat.com>
Cc:	Sedat Dilek <sedat.dilek@...il.com>,
	"J. R. Okajima" <hooanon05g@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Robo Bot <apw@...onical.com>, Felix Fietkau <nbd@...nwrt.org>,
	Neil Brown <neilb@...e.de>,
	Jordi Pujol <jordipujolp@...il.com>, ezk@....cs.sunysb.edu,
	"mszeredi@...e.cz" <mszeredi@...e.cz>
Subject: Re: Unionmount and overlayfs testsuite

On Tue, Jun 3, 2014 at 11:00 AM, David Howells <dhowells@...hat.com> wrote:
> My suspicion is that overlayfs is doing stuff to the lower layer whilst
> holding a lock on the upper layer or vice versa.

No.  It's holding the overlayfs i_mutex and then getting either the
upper *or* the lower i_mutex, but never both.  So it's a simple and
unproblematic ordering.

Thanks,
Miklos
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