linux-kernel - Re: [PATCH 04/12] mm: alloc_contig_freed

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Date:	Thu, 31 Mar 2011 23:09:42 +0200
From:	"Michal Nazarewicz" <mina86@...a86.com>
To:	"Marek Szyprowski" <m.szyprowski@...sung.com>,
	"Dave Hansen" <dave@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-media@...r.kernel.org,
	linux-mm@...ck.org, "Kyungmin Park" <kyungmin.park@...sung.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	"Ankita Garg" <ankita@...ibm.com>,
	"Daniel Walker" <dwalker@...eaurora.org>,
	"Johan MOSSBERG" <johan.xx.mossberg@...ricsson.com>,
	"Mel Gorman" <mel@....ul.ie>, "Pawel Osciak" <pawel@...iak.com>
Subject: Re: [PATCH 04/12] mm: alloc_contig_freed_pages() added

On Thu, 31 Mar 2011 17:58:03 +0200, Dave Hansen <dave@...ux.vnet.ibm.com>  
wrote:

> On Thu, 2011-03-31 at 15:16 +0200, Marek Szyprowski wrote:
>>
>> +unsigned long alloc_contig_freed_pages(unsigned long start, unsigned  
>> long end,
>> +                                      gfp_t flag)
>> +{
>> +       unsigned long pfn = start, count;
>> +       struct page *page;
>> +       struct zone *zone;
>> +       int order;
>> +
>> +       VM_BUG_ON(!pfn_valid(start));
>
> This seems kinda mean.  Could we return an error?  I understand that
> this is largely going to be an early-boot thing, but surely trying to
> punt on crappy input beats a full-on BUG().

Actually, I would have to check but I think that the usage of this function
(in this patchset) is that the caller expects the function to succeed.  It  
is
quite a low-level function so before running it a lot of preparation is  
needed
and the caller must make sure that several conditions are met.  I don't  
really
see advantage of returning a value rather then BUG()ing.

Also, CMA does not call this function at boot time.

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michal "mina86" Nazarewicz    (o o)
ooo +-----<email/xmpp: mnazarewicz@...gle.com>-----ooO--(_)--Ooo--
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