linux-kernel - Re: 2.6.18-rc6-mm2: fix for error compiling ppc/mm/init.c

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Date:	Tue, 03 Oct 2006 14:24:51 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Judith Lebzelter <judith@...l.org>, linux-kernel@...r.kernel.org,
	akpm@...l.org, Paul Mackerras <paulus@...ba.org>
Subject: Re: 2.6.18-rc6-mm2: fix for error compiling ppc/mm/init.c

On Thu, 2006-09-14 at 19:11 +0100, Mel Gorman wrote:
> On Thu, 14 Sep 2006, Judith Lebzelter wrote:
> 
> > For ppc in our cross-compile build farm (PLM), there is an error
> > compiling file ppc/mm/init.c:
> >
> >  CC      arch/ppc/mm/init.o
> >  CC      arch/powerpc/kernel/init_task.o
> > arch/ppc/mm/init.c: In function 'paging_init':
> > arch/ppc/mm/init.c:381: error: subscripted value is neither array nor pointer
> > arch/ppc/mm/init.c:383: warning: passing argument 1 of '/' makes pointer from integer without a cast
> > make[1]: [arch/ppc/mm/init.o] Error 1 (ignored)
> >
> >
> > This is caused by an error/oversight in file
> > 'have-power-use-add_active_range-and-free_area_init_nodes.patch'
> >
> > Here is a patch to fix that patch.
> >
> 
> Looks good. Thanks
> 
> Acked-by: Mel Gorman <mel@....ul.ie>

Note that the whole ppc patch here seems broken. Sorry for not jumping
earlier, I've been swamped with other things.

First, why the heck do you use indices 0 and 1 explicitely rather than
the symbolic constants ? ppc doesn't have a ZONE_NORMAL, so we should be
filling ZONE_DMA and ZONE_HIGHMEM but you end up filling ZONE_DMA and
ZONE_NORMAL and leave ZONE_HIGHMEM alone. Also, you leave other entries
filled with crap (the array isn't initialized) which cause some strange
display of the PFN list, if not worse problems later, I don't know for
sure at this stage.

I've about to run some tests with this patch. Looks like we need give a
closer look at those patches, in case that breakage appears on other
archs as well (or similar).
---

New zone initialisation on powerpc is broken, especially with
CONFIG_HIGHMEM, this fixes it by initializing the array to 0 and filling
up the right entries.

Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>

Index: linux-work/arch/powerpc/mm/mem.c
===================================================================
--- linux-work.orig/arch/powerpc/mm/mem.c	2006-10-03 12:41:03.000000000 +1000
+++ linux-work/arch/powerpc/mm/mem.c	2006-10-03 14:08:30.000000000 +1000
@@ -307,11 +307,12 @@ void __init paging_init(void)
 	       top_of_ram, total_ram);
 	printk(KERN_DEBUG "Memory hole size: %ldMB\n",
 	       (top_of_ram - total_ram) >> 20);
+	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
 #ifdef CONFIG_HIGHMEM
-	max_zone_pfns[0] = total_lowmem >> PAGE_SHIFT;
-	max_zone_pfns[1] = top_of_ram >> PAGE_SHIFT;
+	max_zone_pfns[ZONE_DMA] = total_lowmem >> PAGE_SHIFT;
+	max_zone_pfns[ZONE_HIGHMEM] = top_of_ram >> PAGE_SHIFT;
 #else
-	max_zone_pfns[0] = top_of_ram >> PAGE_SHIFT;
+	max_zone_pfns[ZONE_DMA] = top_of_ram >> PAGE_SHIFT;
 #endif
 	free_area_init_nodes(max_zone_pfns);
 }



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