Re: [PATCH 0/4] Was: deferring __fput()

From: Al Viro
Date: Thu Jun 28 2012 - 00:38:39 EST


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 ;-/
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