linux-kernel - Re: [PATCH followup] mm: get rid of CONFIG_STACK_GROWSUP || CONFIG

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Message-ID: <20110420065943.GA18799@tiehlicka.suse.cz>
Date:	Wed, 20 Apr 2011 08:59:43 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH followup] mm: get rid of CONFIG_STACK_GROWSUP ||
 CONFIG_IA64

Hi Kosaki,

On Wed 20-04-11 09:33:26, KOSAKI Motohiro wrote:
> > While I am in the cleanup mode. We should use VM_GROWSUP rather than
> > tricky CONFIG_STACK_GROWSUP||CONFIG_IA64.
> > 
> > What do you think?
> 
> Now, VM_GROWSUP share the same value with VM_NOHUGEPAGE.
> (this trick use the fact that thp don't support any stack growup architecture)

I am not sure I understand you. AFAICS, VM_GROWSUP is defined to non 0
only if CONFIG_STACK_GROWSUP||CONFIG_IA64 (include/linux/mm.h).
And we use it to determine whether expand_stack_growsup[*] should be
defined (in include/linux/mm.h).

The patch basically unifies the way how we export expand_stack_growsup
function and how define it (in mm/mmap.c).

So either we should use CONFIG_STACK_GROWSUP||CONFIG_IA64 at both places
or we should use VM_GROWSUP trick. I am for the later one.

Am I missing something?

--- 
[*] the previous patch renamed expand_growsup to expand_stack_growsup.
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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