From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Howells <dhowells@redhat.com>
Subject: Re: [PATCH] fix race in mark_mounts_for_expiry()
Date: Wed, 18 May 2005 11:32:34 +0100
Message-ID: <6865.1116412354@redhat.com>
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In-Reply-To: <E1DYLCv-0000W7-00@dorka.pomaz.szeredi.hu> 
To: Miklos Szeredi <miklos@szeredi.hu>
Sender: linux-fsdevel-owner@vger.kernel.org
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Miklos Szeredi <miklos@szeredi.hu> wrote:

> 
> How about this patch?  It tries to solve this race without additional
> locking.  If refcount is already zero, it will increment and decrement
> it.  So be careful to only call grab_namespace() with vfsmount_lock
> held, otherwise it could race with itself.  (vfsmount_lock is also
> needed in this case so that mnt->mnt_namespace, doesn't change, while
> grabbing the namespace)

How about using cmpxchg?

David