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Date: Mon, 7 May 2012 23:17:06 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Oleg Nesterov <oleg@redhat.com>,
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        Mike Galbraith <efault@gmx.de>, Christoph Hellwig <hch@infradead.org>,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] vfs: Speed up deactivate_super for non-modular
 filesystems
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On Mon, May 07, 2012 at 02:51:08PM -0700, Eric W. Biederman wrote:

> /proc and similar non-modular filesystems do not need a rcu_barrier
> in deactivate_locked_super.  Being non-modular there is no danger
> of the rcu callback running after the module is unloaded.

There's more than just a module unload there, though - actual freeing
struct super_block also happens past that rcu_barrier()...