From: Hannes Hering <hannes.hering@linux.vnet.ibm.com>
Organization: IBM
To: Nathan Lynch <ntl@pobox.com>
Subject: Re: [PATCH 2/3] [2.6.26] ehea: Add dependency to Kconfig
Date: Tue, 3 Jun 2008 10:07:39 +0200
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Hi Nathan,

I agree that the ehea cannot be built without MEMORY_HOTPLUG. The problem is
the fact that the ppc walk_memory_resource declaration is in the scope of
MEMORY_HOTPLUG. At the moment I don't have complete overview if the move of the
code as you propose in your patch has any side effects. We probably need to
talk to Badari who provided the walk_memory_resource code. We can also just
throw it onto one of our boxes to see what happens. ;)

Regards

Hannes

On Wednesday 28 May 2008 18:44:05 Nathan Lynch wrote:
> Hello,
> 
> Hannes Hering wrote:
> > The new ehea memory hot plug implementation depends on MEMORY_HOTPLUG.
> > 
> > Signed-off-by: Hannes Hering <hering2@de.ibm.com>
> > ---
> > 
> > diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
> > index f90a86b..181cd86 100644
> > --- a/drivers/net/Kconfig
> > +++ b/drivers/net/Kconfig
> > @@ -2440,7 +2440,7 @@ config CHELSIO_T3
> >  
> >  config EHEA
> >  	tristate "eHEA Ethernet support"
> > -	depends on IBMEBUS && INET && SPARSEMEM
> > +	depends on IBMEBUS && INET && SPARSEMEM && MEMORY_HOTPLUG
> >  	select INET_LRO
> >  	---help---
> >  	  This driver supports the IBM pSeries eHEA ethernet adapter.
> 
> I disagree with this change.
> 
> It makes it impossible to build the ehea driver without memory hotplug
> enabled.  Presumably, this commit was intended to work around a build
> break of this sort (with EHEA=m and MEMORY_HOTPLUG=n):
> 
> drivers/net/ehea/ehea_qmr.c: In function 'ehea_create_busmap':
> drivers/net/ehea/ehea_qmr.c:635: error: implicit declaration of function 'walk_memory_resource'
> 
> (some indication of this should have been in the commit message, btw)
> 
> I think this was the wrong way to fix the issue.  EHEA=m and
> MEMORY_HOTPLUG=n is a valid configuration for machines I test.
> 
> Any thoughts on the following, which makes walk_memory_resource()
> available regardless of MEMORY_HOTPLUG's setting?  I've tested it on a
> JS22 (Power6 blade).
> 
> ---
> 
>  arch/powerpc/mm/mem.c          |    3 +--
>  drivers/net/Kconfig            |    2 +-
>  include/linux/memory_hotplug.h |   16 ++++++++--------
>  3 files changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index f67e118..51f82d8 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -151,6 +151,7 @@ out:
>  	return ret;
>  }
>  #endif /* CONFIG_MEMORY_HOTREMOVE */
> +#endif /* CONFIG_MEMORY_HOTPLUG */
> 
>  /*
>   * walk_memory_resource() needs to make sure there is no holes in a given
> @@ -184,8 +185,6 @@ walk_memory_resource(unsigned long start_pfn, unsigned long nr_pages, void *arg,
>  }
>  EXPORT_SYMBOL_GPL(walk_memory_resource);
> 
> -#endif /* CONFIG_MEMORY_HOTPLUG */
> -
>  void show_mem(void)
>  {
>  	unsigned long total = 0, reserved = 0;
> diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
> index dd0ec9e..f4182cf 100644
> --- a/drivers/net/Kconfig
> +++ b/drivers/net/Kconfig
> @@ -2426,7 +2426,7 @@ config CHELSIO_T3
> 
>  config EHEA
>  	tristate "eHEA Ethernet support"
> -	depends on IBMEBUS && INET && SPARSEMEM && MEMORY_HOTPLUG
> +	depends on IBMEBUS && INET && SPARSEMEM
>  	select INET_LRO
>  	---help---
>  	  This driver supports the IBM pSeries eHEA ethernet adapter.
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 73e3586..ea9f5ad 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -77,14 +77,6 @@ extern int __add_pages(struct zone *zone, unsigned long start_pfn,
>  extern int __remove_pages(struct zone *zone, unsigned long start_pfn,
>  	unsigned long nr_pages);
> 
> -/*
> - * Walk through all memory which is registered as resource.
> - * arg is (start_pfn, nr_pages, private_arg_pointer)
> - */
> -extern int walk_memory_resource(unsigned long start_pfn,
> -			unsigned long nr_pages, void *arg,
> -			int (*func)(unsigned long, unsigned long, void *));
> -
>  #ifdef CONFIG_NUMA
>  extern int memory_add_physaddr_to_nid(u64 start);
>  #else
> @@ -199,6 +191,14 @@ static inline void register_page_bootmem_info_node(struct pglist_data *pgdat)
> 
>  #endif /* ! CONFIG_MEMORY_HOTPLUG */
> 
> +/*
> + * Walk through all memory which is registered as resource.
> + * arg is (start_pfn, nr_pages, private_arg_pointer)
> + */
> +extern int walk_memory_resource(unsigned long start_pfn,
> +			unsigned long nr_pages, void *arg,
> +			int (*func)(unsigned long, unsigned long, void *));
> +
>  extern int add_memory(int nid, u64 start, u64 size);
>  extern int arch_add_memory(int nid, u64 start, u64 size);
>  extern int remove_memory(u64 start, u64 size);
> 


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