Re: [BUGFIX][PATCH] vmscan: don't use return value trick when oom_killer_disabled

[Minchan Kim <minchan.kim@gmail.com>]

Hi KOSAKI,

On Wed, Sep 1, 2010 at 9:31 AM, KOSAKI Motohiro
<kosaki.motohiro@jp.fujitsu.com> 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@jp.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 2) vmscan don't care enough OOM case when
> oom_killer_disabled.
>
> This patch only fix (2). Why is oom_killer_disabled so special?
> because when hibernation case, zone->all_unreclaimable never be turned on