linux-kernel - Re: [PATCH 05/10] vmscan: Synchrounous lumpy reclaim use lock_page() instead trylock

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Date:	Fri, 10 Sep 2010 19:33:32 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	kosaki.motohiro@...fujitsu.com, Mel Gorman <mel@....ul.ie>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	Linux Kernel List <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Christoph Hellwig <hch@....de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 05/10] vmscan: Synchrounous lumpy reclaim use lock_page() instead trylock_page()

> 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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