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

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Message-ID: <4A426825.80905@cs.helsinki.fi>
Date:	Wed, 24 Jun 2009 20:53:41 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Andrew Morton <akpm@...ux-foundation.org>
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

Hi Andrew,

Andrew Morton wrote:
> 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.

No, the fallback allocation would still use __GFP_NOFAIL so the 
semantics are preserved.

			Pekka
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