linux-kernel - Re: [RFC] CMA page migration failure due to buffers on bh

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Message-ID: <53B216C5.8020503@codeaurora.org>
Date:	Mon, 30 Jun 2014 19:02:45 -0700
From:	Laura Abbott <lauraa@...eaurora.org>
To:	Gioh Kim <gioh.kim@....com>, Michal Nazarewicz <mina86@...a86.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
CC:	Joonsoo Kim <iamjoonsoo.kim@....com>, Mel Gorman <mgorman@...e.de>,
	이건호 <gunho.lee@....com>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [RFC] CMA page migration failure due to buffers on bh_lru

On 6/30/2014 6:07 PM, Gioh Kim wrote:
> Hi,Laura.
> 
> I have a question.
> 
> Does the __evict_bh_lru() not need bh_lru_lock()?
> The get_cpu_var() has already preenpt_disable() and can prevent other thread.
> But get_cpu_var cannot prevent IRQ context such like page-fault.
> I think if a page-fault occured and a file is read in IRQ context it can change cpu-lru.
> 
> Is my concern correct?
> 
> 

__evict_bh_lru is called via on_each_cpu_cond which I believe will disable irqs.
I based the code on the existing invalidate_bh_lru which did not take the bh_lru_lock
either. It's possible I missed something though.

Thanks,
Laura

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