linux-kernel - Re: [PATCH 1/2] mm: Introduce GFP_PANIC for early-boot allocations

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Message-ID: <4A054156.60501@cs.helsinki.fi>
Date:	Sat, 09 May 2009 11:39:50 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	gorcunov@...nvz.org, kosaki.motohiro@...fujitsu.com, mel@....ul.ie,
	cl@...ux-foundation.org, riel@...hat.com,
	linux-kernel@...r.kernel.org, mingo@...e.hu, rientjes@...gle.com
Subject: Re: [PATCH 1/2] mm: Introduce GFP_PANIC for early-boot allocations

Hi Andrew,

Andrew Morton wrote:
> On Fri, 08 May 2009 18:10:28 +0300
> Pekka Enberg <penberg@...helsinki.fi> wrote:
> 
>> +#define GFP_PANIC	(__GFP_NOFAIL | __GFP_NORETRY)
> 
> urgh, you have to be kidding me.  This significantly worsens complexity
> and risk in core MM and it's just yuk.
> 
> I think we can justify pulling such dopey party tricks to save
> pageframe space, or bits in page.flags and such.  But just to save a
> scrap of memory which would have been released during boot anwyay? 
> Don't think so.

No, I wasn't kidding and I don't agree that it "significantly worsens 
complexity". The point is not to save memory but to clearly annotate 
those special call-sites that really don't need to check for out-of-memory.

But anyway, if you don't want it, then I guess it stays out of the kernel.

Andrew Morton wrote:
> I'd suggest panic_if_null().  Or just leave everything alone - it's
> hardly a pressing problem.

It has no advantage over the current BUG_ON() pattern.

			Pekka
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