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Date: Tue, 3 Jun 2014 11:12:08 +0200
Message-ID: <CAJfpegsUDcFZ+9jPDU6mMXuAOwvzNFV3Q2WRE6QdoPYSqKeRqQ@mail.gmail.com>
Subject: Re: Unionmount and overlayfs testsuite
From: Miklos Szeredi <miklos@szeredi.hu>
To: David Howells <dhowells@redhat.com>
Cc: Sedat Dilek <sedat.dilek@gmail.com>,
        "J. R. Okajima" <hooanon05g@gmail.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Robo Bot <apw@canonical.com>, Felix Fietkau <nbd@openwrt.org>,
        Neil Brown <neilb@suse.de>, Jordi Pujol <jordipujolp@gmail.com>,
        ezk@fsl.cs.sunysb.edu, "mszeredi@suse.cz" <mszeredi@suse.cz>
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On Tue, Jun 3, 2014 at 11:00 AM, David Howells <dhowells@redhat.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