linux-kernel - Re: [PATCH 4/8] vmscan: Do not writeback filesystem pages in direct reclaim

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Message-ID: <20100721143955.GB10480@cmpxchg.org>
Date:	Wed, 21 Jul 2010 16:39:56 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mel@....ul.ie>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Nick Piggin <npiggin@...e.de>, Rik van Riel <riel@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH 4/8] vmscan: Do not writeback filesystem pages in direct
 reclaim

On Wed, Jul 21, 2010 at 03:31:19PM +0100, Mel Gorman wrote:
> On Wed, Jul 21, 2010 at 04:28:44PM +0200, Johannes Weiner wrote:
> > On Wed, Jul 21, 2010 at 02:38:57PM +0100, Mel Gorman wrote:
> > > @@ -858,7 +872,7 @@ keep:
> > >  
> > >  	free_page_list(&free_pages);
> > >  
> > > -	list_splice(&ret_pages, page_list);
> > 
> > This will lose all retry pages forever, I think.
> > 
> 
> Above this is
> 
> while (!list_empty(page_list)) {
> 	...
> }
> 
> page_list should be empty and keep_locked is putting the pages on ret_pages
> already so I think it's ok.

But ret_pages is function-local.  Putting them back on the then-empty
page_list is to give them back to the caller, otherwise they are lost
in a dead stack slot.
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