linux-kernel - async_pf.c && use_mm() (Was: mm,vmacache: also flush cache for VM

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Date:	Thu, 13 Mar 2014 19:27:02 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Gleb Natapov <gleb@...hat.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Davidlohr Bueso <davi@...hat.com>,
	Davidlohr Bueso <davidlohr@...com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michel Lespinasse <walken@...gle.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: async_pf.c && use_mm() (Was: mm,vmacache: also flush cache for
	VM_CLONE)

On 03/13, Oleg Nesterov wrote:
>
> Hmm, but at first glance async_pf_execute() doesn't need use_mm() at all.

Seriously, why it nees use_mm? get_user_pages(mm => apf->mm) should work.
Perhaps there is some kvm magic ?

But actually I am writing this email because mmdrop() doesn't look right
or I missed something. I think that kvm_setup_async_pf() should increment
->mm_users and async_pf_execute() needs mmput() ?

Oleg.

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