linux-kernel - Re: [PATCH] Section mismatch contig_page_data and bootmem_node

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Message-ID: <20080822130503.GA10776@joi>
Date:	Fri, 22 Aug 2008 15:05:08 +0200
From:	Marcin Slusarz <marcin.slusarz@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Johannes Weiner <hannes@...urebad.de>,
	Sean MacLennan <smaclennan@...atech.com>,
	linux-kernel@...r.kernel.org, Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH] Section mismatch contig_page_data and bootmem_node_data

On Thu, Aug 21, 2008 at 11:15:51PM -0700, Andrew Morton wrote:
> On Thu, 21 Aug 2008 22:10:23 +0200 Marcin Slusarz <marcin.slusarz@...il.com> wrote:
> 
> > From: Marcin Slusarz <marcin.slusarz@...il.com>
> > Subject: [PATCH] bootmem: don't embed bootmem_data in pglist_data
> > 
> > Replace direct pointer from struct pglist_data to struct bootmem_data
> > with index into bootmem_node_data.
> > 
> > As bootmem_node_data are discarded after bootup this change allows
> > more fine-grained analysis of access to bootmem data - every access
> > to bootmem_node_data from non-__init function will now emit section
> > mismatch warning.
> > 
> > This patch fixes following section mismatch warning:
> > WARNING: vmlinux.o(.data+0x1f5c0): Section mismatch in reference from the variable contig_page_data to the variable .init.data:bootmem_node_data
> > The variable contig_page_data references
> > the variable __initdata bootmem_node_data
> > If the reference is valid then annotate the
> > variable with __init* (see linux/init.h) or name the variable:
> > *driver, *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console,
> > 
> > Signed-off-by: Marcin Slusarz <marcin.slusarz@...il.com>
> > Cc: Johannes Weiner <hannes@...urebad.de>
> > ---
> >  arch/alpha/mm/numa.c             |    5 +++--
> >  arch/arm/mm/discontig.c          |   32 ++++++++++++++++----------------
> >  arch/arm/plat-omap/fb.c          |    2 +-
> >  arch/avr32/mm/init.c             |    5 +++--
> >  arch/ia64/mm/discontig.c         |    5 ++---
> >  arch/ia64/mm/init.c              |    2 +-
> >  arch/m32r/mm/discontig.c         |    6 +++---
> >  arch/m32r/mm/init.c              |    4 ++--
> >  arch/m68k/mm/init.c              |    2 +-
> >  arch/mips/sgi-ip27/ip27-memory.c |    2 +-
> >  arch/mn10300/mm/init.c           |    9 ++++-----
> >  arch/parisc/mm/init.c            |    2 +-
> >  arch/powerpc/mm/numa.c           |    2 +-
> >  arch/sh/mm/init.c                |    5 +++--
> >  arch/sh/mm/numa.c                |    4 ++--
> >  arch/sparc64/mm/init.c           |    2 +-
> >  arch/x86/mm/discontig_32.c       |    2 +-
> >  arch/x86/mm/numa_64.c            |    2 +-
> >  include/linux/mmzone.h           |    4 +++-
> >  mm/bootmem.c                     |   30 +++++++++++++++++++-----------
> >  mm/page_alloc.c                  |    2 +-
> >  21 files changed, 70 insertions(+), 59 deletions(-)
> 
> erp.  Can we go with Sean's obviously-safe one-liner for now, fix this
> up properly in 2.6.28?

I think my one-liner (below) is better. :)
 
> Plus...  replacing a direct pointer with an index which requires a
> subscripting operation each time it is used just to fix a section
> warning is a bit sad.

If we could mark only one field in structure as __initdata as an
inidication of valid use only from __init section...

---
From: Marcin Slusarz <marcin.slusarz@...il.com>
Subject: [PATCH] mm/bootmem: silence section mismatch warning - contig_page_data/bootmem_node_data

WARNING: vmlinux.o(.data+0x1f5c0): Section mismatch in reference from the variable contig_page_data to the variable .init.data:bootmem_node_data
The variable contig_page_data references
the variable __initdata bootmem_node_data
If the reference is valid then annotate the
variable with __init* (see linux/init.h) or name the variable:
*driver, *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console,

Signed-off-by: Marcin Slusarz <marcin.slusarz@...il.com>
Cc: Johannes Weiner <hannes@...urebad.de>
---
 mm/page_alloc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index af982f7..969433a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4064,7 +4064,7 @@ void __init set_dma_reserve(unsigned long new_dma_reserve)
 }
 
 #ifndef CONFIG_NEED_MULTIPLE_NODES
-struct pglist_data contig_page_data = { .bdata = &bootmem_node_data[0] };
+struct pglist_data __refdata contig_page_data = { .bdata = &bootmem_node_data[0] };
 EXPORT_SYMBOL(contig_page_data);
 #endif
 
-- 
1.5.4.5

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