linux-kernel - Re: [PATCH] mm: use a irq-safe __mod_zone_page_state in mlocked_vma

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Message-ID: <alpine.DEB.2.10.1405091050520.11318@gentwo.org>
Date:	Fri, 9 May 2014 10:56:19 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Jianyu Zhan <nasa4836@...il.com>
cc:	akpm@...ux-foundation.org, hannes@...xchg.org, riel@...hat.com,
	mhocko@...e.cz, aarcange@...hat.com, hanpt@...ux.vnet.ibm.com,
	mgorman@...e.de, oleg@...hat.com, cldu@...vell.com, fabf@...net.be,
	sasha.levin@...cle.com, zhangyanfei@...fujitsu.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: use a irq-safe __mod_zone_page_state in
 mlocked_vma_newpage()


On Fri, 9 May 2014, Jianyu Zhan wrote:

> mlocked_vma_newpage() is only called in fault path by
> page_add_new_anon_rmap(), which is called on a *new* page.
> And such page is initially only visible via the pagetables, and the
> pte is locked while calling page_add_new_anon_rmap(), so we could use
> a irq-safe version of __mod_zone_page_state() here.

You are changing from the irq safe variant to __mod_zone_page_state which
is *not* irq safe. Its legit to do so since presumably irqs are disabled
anyways so you do not have to worry about irq safeness of
__mod_zone_page_state.

Please update the description. Its a bit confusing right now.
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