linux-kernel - Re: [PATCH] vmscan: don't use return value trick when oom_killer

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Message-Id: <201009022204.14661.rjw@sisk.pl>
Date:	Thu, 2 Sep 2010 22:04:14 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>,
	"M. Vefa Bicakci" <bicave@...eronline.com>, stable@...nel.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [PATCH] vmscan: don't use return value trick when oom_killer_disabled

On Thursday, September 02, 2010, Minchan Kim wrote:
> M. Vefa Bicakci reported 2.6.35 kernel hang up when hibernation on his
> 32bit 3GB mem machine. (https://bugzilla.kernel.org/show_bug.cgi?id=16771)
> Also he was bisected first bad commit is below
> 
>   commit bb21c7ce18eff8e6e7877ca1d06c6db719376e3c
>   Author: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>   Date:   Fri Jun 4 14:15:05 2010 -0700
> 
>      vmscan: fix do_try_to_free_pages() return value when priority==0 reclaim failure
> 
> At first impression, this seemed very strange because the above commit only
> chenged function return value and hibernate_preallocate_memory() ignore
> return value of shrink_all_memory(). But it's related.
> 
> Now, page allocation from hibernation code may enter infinite loop if
> the system has highmem.
> 
> The reasons are two. 1) hibernate_preallocate_memory() call
> alloc_pages() wrong order

This isn't the case, as explained here: http://lkml.org/lkml/2010/9/1/316 .

The ordering of calls is correct, but it's better to check if there are any
non-highmem pages to allocate from before the last call (for performance
reasons, but that also would eliminate the failure in question).

Thanks,
Rafael
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