On Thu, Jun 16, 2011 at 05:28:19PM +0900, KAMEZAWA Hiroyuki wrote:

On Wed, 15 Jun 2011 21:49:17 -0700
Randy Dunlap [off-list ref] wrote:

quoted

On Wed, 15 Jun 2011 16:56:49 -0700 akpm@linux-foundation.org wrote:

quoted

The mm-of-the-moment snapshot 2011-06-15-16-56 has been uploaded to

   http://userweb.kernel.org/~akpm/mmotm/

and will soon be available at
   git://zen-kernel.org/kernel/mmotm.git
or
   git://git.cmpxchg.org/linux-mmotm.git

It contains the following patches against 3.0-rc3:

(x86_64 build:)

mm/page_cgroup.c: In function 'page_cgroup_init':
mm/page_cgroup.c:308: error: implicit declaration of function 'node_start_pfn'
mm/page_cgroup.c:309: error: implicit declaration of function 'node_end_pfn'

Bug fix is here. Added CC to Mel to get review.
==
From add3b670119f1c1f762194b432d3997d595bc213 Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <redacted>
Date: Thu, 16 Jun 2011 17:28:07 +0900
Subject: [PATCH] Fix node_start/end_pfn() definition for mm/page_cgroup.c

commit 21a3c96 uses node_start/end_pfn(nid) for detection start/end
of nodes. But, it's not defined in linux/mmzone.h but defined in
/arch/???/include/mmzone.h which is included only under
CONFIG_NEED_MULTIPLE_NODES=y.

Then, we see
mm/page_cgroup.c: In function 'page_cgroup_init':
mm/page_cgroup.c:308: error: implicit declaration of function 'node_start_pfn'
mm/page_cgroup.c:309: error: implicit declaration of function 'node_end_pfn'

So, fixing page_cgroup.c is an idea...

But node_start_pfn()/node_end_pfn() is a very generic macro and
should be implemented in the same manner for all archs.
(m32r has different implementation...)

I would expect node_start_pfn to always be the equivalent of
NODE_DATA(nid)->node_start_pfn and that does appear to be case even
though it is not universally defined;

alpha/include/asm/mmzone.h:#define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)
m32r/include/asm/mmzone.h:#define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)
parisc/include/asm/mmzone.h:#define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)
powerpc/include/asm/mmzone.h:#define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)
sh/include/asm/mmzone.h:#define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)
sparc/include/asm/mmzone.h:#define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)
tile/include/asm/mmzone.h:#define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)
x86/include/asm/mmzone_32.h:#define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)
x86/include/asm/mmzone_64.h:#define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)

Similarly I would always expect node_end_pfn to be related to
node_spanned_pages which is true of x86, tile, sh and parisc. sparc
and powerpc uses node_end_pfn which is a good trick because that
is not a member of pglist_data (suspect they do not build on
!CONFIG_NEED_MULTIPLE_NODES?).

m32r does differ from everyone else in that it's
__pgdat->node_start_pfn + __pgdat->node_spanned_pages - 1 and this was
the case when it was introduced in 2004. It's not explained why it is
like this but I suspect it's a mistake and I think your cleanup is
appropriate.

This patch removes definitions of node_start/end_pfn() in each archs
and defines a unified one in linux/mmzone.h. It's not under
CONFIG_NEED_MULTIPLE_NODES, now.

Does anyone remember *why* this did not happen in the first place? I
can't think of a good reason so I've cc'd Dave Hansen as he might
remember.

Would it also be worth cleaning up users of node_spanned_pages to
use node_end_pfn in mm/ where appropriate rather than having a mix
of spanned_pages and node_end_pfn?

Signed-off-by: KAMEZAWA Hiroyuki <redacted>

For the most part, it looks good! I haven't compile-tested this but
I did spot one one problem unfortunately;

A caller that does node_end_pfn(nid++) will get a nasty surprise
due to side-effects. I know architectures currently get this wrong
including x86_64 but we might as well fix it up now. The definition
in arch/x86/include/asm/mmzone_32.h is immune to side-effects and
might be a better choice despite the use of a temporary variable.

 #include <linux/memory_hotplug.h>
 
 extern struct mutex zonelists_mutex;
-- 
1.7.4.1

-- 
Mel Gorman
SUSE Labs

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