linux-kernel - Re: [PATCH 2/9] mm: alloc_contig_freed

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Date:	Tue, 18 Oct 2011 10:48:46 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Michal Nazarewicz <mina86@...a86.com>
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	Mel Gorman <mel@....ul.ie>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
	linux-mm@...ck.org, linaro-mm-sig@...ts.linaro.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Ankita Garg <ankita@...ibm.com>,
	Daniel Walker <dwalker@...eaurora.org>,
	Arnd Bergmann <arnd@...db.de>,
	Jesse Barker <jesse.barker@...aro.org>,
	Jonathan Corbet <corbet@....net>,
	Shariq Hasnain <shariq.hasnain@...aro.org>,
	Chunsang Jeong <chunsang.jeong@...aro.org>
Subject: Re: [PATCH 2/9] mm: alloc_contig_freed_pages() added

On Tue, 2011-10-18 at 10:26 -0700, Michal Nazarewicz wrote:
> > You can do this in a more general fashion by checking the
> > zone boundaries and resolving the pfn->page every MAX_ORDER_NR_PAGES.
> > That will not be SPARSEMEM specific.
> 
> I've tried doing stuff that way but it ended up with much more code.

I guess instead of:

>> +static inline bool zone_pfn_same_memmap(unsigned long pfn1, unsigned long pfn2)
>> +{
>> +    return pfn_to_section_nr(pfn1) == pfn_to_section_nr(pfn2);
>> +}

You could do:

static inline bool zone_pfn_same_maxorder(unsigned long pfn1, unsigned long pfn2)
{
	unsigned long mask = MAX_ORDER_NR_PAGES-1;
	return (pfn1 & mask) == (pfn2 & mask);
}

I think that works.  Should be the same code you have now, basically.

-- Dave

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