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

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Date:	Mon, 12 May 2014 08:57:20 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Jianyu Zhan <nasa4836@...il.com>
cc:	akpm@...ux-foundation.org, mhocko@...e.cz, hannes@...xchg.org,
	riel@...hat.com, minchan@...nel.org, zhangyanfei@...fujitsu.com,
	hanpt@...ux.vnet.ibm.com, sasha.levin@...cle.com, oleg@...hat.com,
	fabf@...net.be, mgorman@...e.de, aarcange@...hat.com,
	cldu@...vell.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 Sat, 10 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 need not
> use an irq-safe mod_zone_page_state() here, using a light-weight version
> __mod_zone_page_state() would be OK.

This has nothing to do with the safety of statistics operations that work
on different data structures. Which leads to the conclusion that
__mod_page_state cannot be used here.


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