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Date: Tue, 20 Jan 2015 15:01:50 -0800
From: josh@joshtriplett.org
To: Kim Phillips <kim.phillips@freescale.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>, Minchan Kim <minchan@kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>, Rik van Riel <riel@redhat.com>,
        Sasha Levin <sasha.levin@oracle.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Konstantin Khlebnikov <k.khlebnikov@samsung.com>,
        Jens Axboe <axboe@fb.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 2/2] mm: fix undefined reference to `.kernel_map_pages'
 on PPC builds
Message-ID: <20150120230150.GA14475@cloud>
References: <20150120140200.aa7ba0eb28d95e456972e178@freescale.com>
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On Tue, Jan 20, 2015 at 02:02:00PM -0600, Kim Phillips wrote:
> It's possible to configure DEBUG_PAGEALLOC without PAGE_POISONING on
> ppc.  Fix building the generic kernel_map_pages() implementation in
> this case:
> 
>   LD      init/built-in.o
> mm/built-in.o: In function `free_pages_prepare':
> mm/page_alloc.c:770: undefined reference to `.kernel_map_pages'
> mm/built-in.o: In function `prep_new_page':
> mm/page_alloc.c:933: undefined reference to `.kernel_map_pages'
> mm/built-in.o: In function `map_pages':
> mm/compaction.c:61: undefined reference to `.kernel_map_pages'
> make: *** [vmlinux] Error 1
> 
> Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
> ---
>  mm/Makefile | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/Makefile b/mm/Makefile
> index 4bf586e..2956467 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -46,6 +46,7 @@ obj-$(CONFIG_SLOB) += slob.o
>  obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o
>  obj-$(CONFIG_KSM) += ksm.o
>  obj-$(CONFIG_PAGE_POISONING) += debug-pagealloc.o
> +obj-$(CONFIG_DEBUG_PAGEALLOC) += debug-pagealloc.o

Does it work correctly to list the same object file twice?  Doesn't seem
like it would.  Shouldn't this do something like the following instead:

ifneq ($(CONFIG_DEBUG_PAGEALLOC)$(CONFIG_PAGE_POISONING),)
obj-y += debug-pagealloc.o
endif

?

>  obj-$(CONFIG_SLAB) += slab.o
>  obj-$(CONFIG_SLUB) += slub.o
>  obj-$(CONFIG_KMEMCHECK) += kmemcheck.o
> -- 
> 2.2.2
>