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

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

Hi

Thank you for good commenting!


> I don't like use oom_killer_disabled directly.
> That's because we have wrapper inline functions to handle the
> variable(ex, oom_killer_[disable/enable]).
> It means we are reluctant to use the global variable directly.
> So should we make new function as is_oom_killer_disable?
> 
> I think NO.
> 
> As I read your description, this problem is related to only hibernation.
> Since hibernation freezes all processes(include kswapd), this problem
> happens. Of course, now oom_killer_disabled is used by only
> hibernation. But it can be used others in future(Off-topic : I don't
> want it). Others can use it without freezing processes. Then kswapd
> can set zone->all_unreclaimable and the problem can't happen.
> 
> So I want to use sc->hibernation_mode which is already used
> do_try_to_free_pages instead of oom_killer_disabled.

Unfortunatelly, It's impossible. shrink_all_memory() turn on
sc->hibernation_mode. but other hibernation caller merely call
alloc_pages(). so we don't have any hint.