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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 05/10] vmscan: Synchrounous lumpy reclaim use lock_page() instead trylock_page()
In-Reply-To: <20100909182649.C94F.A69D9226@jp.fujitsu.com>
References: <20100909092203.GL29263@csn.ul.ie> <20100909182649.C94F.A69D9226@jp.fujitsu.com>
Message-Id: <20100910193307.C97B.A69D9226@jp.fujitsu.com>
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Date: Fri, 10 Sep 2010 19:33:32 +0900 (JST)
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To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Linux Kernel List <linux-kernel@vger.kernel.org>, Rik van Riel <riel@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>, Minchan Kim <minchan.kim@gmail.com>, Wu Fengguang <fengguang.wu@intel.com>, Andrea Arcangeli <aarcange@redhat.com>, Dave Chinner <david@fromorbit.com>, Chris Mason <chris.mason@oracle.com>, Christoph Hellwig <hch@lst.de>, Andrew Morton <akpm@linux-foundation.org>
List-ID: <linux-mm.kvack.org>

> Afaik, detailed rule is,
> 
> o kswapd can call lock_page() because they never take page lock outside vmscan

s/lock_page()/lock_page_nosync()/



> o if try_lock() is successed, we can call lock_page_nosync() against its page after unlock.
>   because the task have gurantee of no lock taken.
> o otherwise, direct reclaimer can't call lock_page(). the task may have a lock already.
> 
> I think.
> 
> 
> >  I did not
> > think of an obvious example of when this would happen. Similarly,
> > deadlock situations with mmap_sem shouldn't happen unless multiple page
> > locks are being taken.
> > 
> > (prepares to feel foolish)
> > 
> > What did I miss?
> 
> 
> 
> 
> 



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