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Date: Thu, 28 Jun 2012 05:38:36 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        ". James Morris" <jmorris@namei.org>,
        linux-security-module@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>,
        David Howells <dhowells@redhat.com>
Subject: Re: [PATCH 0/4] Was: deferring __fput()
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On Wed, Jun 27, 2012 at 08:37:21PM +0200, Oleg Nesterov wrote:
> On 06/25, Oleg Nesterov wrote:
> >
> > And if it always takes ->pi_lock we do not need the new PF_ or something
> > else, exit_task_work() can set task->task_works = NO_MORE under ->pi_lock
> > (task_work_run() can check PF_EXITING), and task_work_add() ensures that
> > task_works != NO_MORE.
> >
> > What do you think?
> 
> It is not clear to me if you agree or not. So I am simply sending the
> patches I have.
> 
> Feel free to ignore or re-do.
> 
> Seriously, why should we add 2 pointers into task_struct? Sure, this
> is minor, but still... But perhaps task_work.c should not play tricks
> with the circular list, task_work_run() can reverse the list as you
> initially suggested.
> 
> Also, I am not sure about "define rcu_head callback_head", this series
> doesn't do this. But again, up to you.

Umm...  FWIW, my variant circa yesterday is in vfs.git#untested; it seems to survive
on uml/amd64 at least.  I'll look through your patches and see what can be nicked.
The list removal logics in mine looks really ugly ;-/