Re: deferring __fput()

From: Al Viro
Date: Sat Jun 23 2012 - 17:12:23 EST


On Sat, Jun 23, 2012 at 10:01:41PM +0100, Al Viro wrote:
> On Sat, Jun 23, 2012 at 10:38:00PM +0200, Oleg Nesterov wrote:
>
> > > Matter of fact, it would become identical to struct rcu_head
> > > after that...
> >
> > This is not clear to me... Why this is good?
>
> Occam's Razor.
>
> > I understand that sizeof(task_work) == sizeof(rcu_head) would be
> > nice, probably you meant just this?
>
> More than that - the callback type is also the same (pointer to such
> struct -> void). IOW, they both look like two instances of the
> same thing ("list of callbacks"), differing only in what and
> when does calling.

BTW, scratch that "task_work + cred" - cred has rcu_head in it.
So we can put a union in there and slap the trimmed task_work into
it. Voila - there goes separate allocation and *any* need for ->data.
It's just container_of(), in that case as well.
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