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

[Simon Jeons]

On 02/05/2013 03:10 PM, 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@xxxxxxxxxxx>
> > > ---
> > >  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

Hi Marek,

1) Why can support CMA regions placed in highmem? CMA is for dma buffer, 
correct? Then how can old dma device access highmem?
2) Why there is no totalhigh_pages variable define in the case of config 
highmem?

> > > +    if (PageHighMem(page))
> > > +        totalhigh_pages += pageblock_nr_pages;
> > > +#endif
> > >  }
> > >  #endif
> > >
>
> Best regards

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