linux-kernel - Re: upcoming kerneloops.org item: get_page_from

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Message-Id: <20090624105517.904f93da.akpm@linux-foundation.org>
Date:	Wed, 24 Jun 2009 10:55:17 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: upcoming kerneloops.org item: get_page_from_freelist

On Wed, 24 Jun 2009 19:55:24 +0300 Pekka Enberg <penberg@...helsinki.fi> wrote:

> On Wed, Jun 24, 2009 at 7:46 PM, Andrew Morton<akpm@...ux-foundation.org> wrote:
> > Well yes. __Using GFP_NOFAIL on a higher-order allocation is bad. __This
> > patch is there to find, name, shame, blame and hopefully fix callers.
> >
> > A fix for cxgb3 is in the works. __slub's design is a big problem.
> >
> > But we'll probably have to revert it for 2.6.31 :(
> 
> How is SLUB's design a problem here? Can't we just clear GFP_NOFAIL
> from the higher order allocation and thus force GFP_NOFAIL allocations
> to use the minimum required order?

That could then lead to the __GFP_NOFAIL allocation attempt returning
NULL.  But the callers cannot handle that and probably don't even test
for it - this is why they used __GFP_NOFAIL.

I dunno.  Mabe we should just remove __GFP_NOFAIL and convert callers back
to open-coded infinite retry loops.  Hardly an improvement, but it at
least would stop people naively using __GFP_NOFAIL.

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