Date: Fri, 20 May 2005 10:11:29 +0100
From: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: akpm@osdl.org, linuxram@us.ibm.com, dhowells@redhat.com,
       linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] namespace.c: fix race in mark_mounts_for_expiry()
Message-ID: <20050520091129.GL29811@parcelfarce.linux.theplanet.co.uk>
References: <E1DZ34O-0003RL-00@dorka.pomaz.szeredi.hu>
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On Fri, May 20, 2005 at 10:41:24AM +0200, Miklos Szeredi wrote:
> This patch fixes a race found by Ram in mark_mounts_for_expiry() in
> The solution is to make the atomic_read() and the get_namespace() into
> a single atomic operation.  The patch does this in a fairly ugly way
> (see comment above fix), which should be safe regardless.

That it certainly is.  What's more, there is a trivial way to deal with
that crap - have put_namespace() do atomic_dec_and_lock() instead of
atomic_dec_and_test().  And use the same spinlock (vfsmount_lock would be
an obvious choice) to protect the atomicity here.  End of story.
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