linux-kernel - Re: [RFC PATCH] asynchronous page fault.

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Message-ID: <27db4d47e5a95e7a85942c0278892467.squirrel@webmail-b.css.fujitsu.com>
Date:	Mon, 28 Dec 2009 18:58:43 +0900 (JST)
From:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
To:	"Peter Zijlstra" <peterz@...radead.org>
Cc:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"minchan.kim@...il.com" <minchan.kim@...il.com>,
	cl@...ux-foundation.org
Subject: Re: [RFC PATCH] asynchronous page fault.

Peter Zijlstra さんは書きました：
> On Mon, 2009-12-28 at 09:36 +0900, KAMEZAWA Hiroyuki wrote:
>>
>> > The idea is to let the RCU lock span whatever length you need the vma
>> > for, the easy way is to simply use PREEMPT_RCU=y for now,
>>
>> I tried to remove his kind of reference count trick but I can't do that
>> without synchronize_rcu() somewhere in unmap code. I don't like that and
>> use this refcnt.
>
> Why, because otherwise we can access page tables for an already unmapped
> vma? Yeah that is the interesting bit ;-)
>
Without that
  vma->a_ops->fault()
and
  vma->a_ops->unmap()
can be called at the same time. and vma->vm_file can be dropped while
vma->a_ops->fault() is called. etc...
Ah, I may miss something. I'll consider in the next year.

Thanks,
-Kame

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