linux-kernel - Re: [PATCH] mm: cma: fix accounting of CMA pages placed in high memory

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Message-ID: <20130205073428.GA11197@blaptop>
Date:	Tue, 5 Feb 2013 16:34:28 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Marek Szyprowski <m.szyprowski@...sung.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, mgorman@...e.de,
	kyungmin.park@...sung.com
Subject: Re: [PATCH] mm: cma: fix accounting of CMA pages placed in high
 memory

Hi Marek,

On Tue, Feb 05, 2013 at 08:10:19AM +0100, Marek Szyprowski wrote:
> Hello,
> 
> On 2/5/2013 12:34 AM, Minchan Kim wrote:
> >On Mon, Feb 04, 2013 at 11:27:05AM +0100, Marek Szyprowski wrote:
> >> The total number of low memory pages is determined as
> >> totalram_pages - totalhigh_pages, so without this patch all CMA
> >> pageblocks placed in highmem were accounted to low memory.
> >
> >So what's the end user effect? With the effect, we have to decide
> >routing it on stable.
> >
> >>
> >> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> >> ---
> >>  mm/page_alloc.c |    4 ++++
> >>  1 file changed, 4 insertions(+)
> >>
> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> >> index f5bab0a..6415d93 100644
> >> --- a/mm/page_alloc.c
> >> +++ b/mm/page_alloc.c
> >> @@ -773,6 +773,10 @@ void __init init_cma_reserved_pageblock(struct page *page)
> >>  	set_pageblock_migratetype(page, MIGRATE_CMA);
> >>  	__free_pages(page, pageblock_order);
> >>  	totalram_pages += pageblock_nr_pages;
> >> +#ifdef CONFIG_HIGHMEM
> >
> >We don't need #ifdef/#endif.
> 
> #ifdef is required to let this code compile when highmem is not enabled,
> becuase totalhigh_pages is defined as 0, see include/linux/highmem.h

Argh, Sorry for the noise.
I think it would be better to use accessor but it's a just nitpick. :)
Thanks!

> 
> >> +	if (PageHighMem(page))
> >> +		totalhigh_pages += pageblock_nr_pages;
> >> +#endif
> >>  }
> >>  #endif
> >>
> 
> Best regards
> -- 
> Marek Szyprowski
> Samsung Poland R&D Center
> 
> 
> --
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-- 
Kind regards,
Minchan Kim
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