Subject: Re: [PATCH v3 02/26] MIPS: sgi-ip27: make NODE_DATA() the same as on all other architectures

From: Jonathan Cameron <[email-masked]>
Date: Thu, 1 Aug 2024 18:44:08 +0100

On Thu,  1 Aug 2024 09:08:02 +0300
Mike Rapoport <[email-masked]> wrote:

> From: "Mike Rapoport (Microsoft)" <[email-masked]>
> 
> sgi-ip27 is the only system that defines NODE_DATA() differently than
> the rest of NUMA machines.
> 
> Add node_data array of struct pglist pointers that will point to
> __node_data[node]->pglist and redefine NODE_DATA() to use node_data
> array.
> 
> This will allow pulling declaration of node_data to the generic mm code
> in the next commit.
> 
> Signed-off-by: Mike Rapoport (Microsoft) <[email-masked]>
After staring for a while at the use made of the other part
of the __node_data I think what you have in this an the next
two patches is fine.

I'm far from convinced it was correct before though as
arch_refresh_node_data() called on offline nodes in free_area_init()
would have replaced __node_data with an allocation of
size pg_data_t but the hub_data(), visible below, is after that.
Maybe hub_data() as never called for offline nodes, but
I couldn't establish that.

After these patches the arch_refresh_node_data() generic
version will only be replacing the pointer in node_data
leaving the hub_data where it was in the first place and
thus is fine.

So with that in mind (and it could be completely wrong ;)

Reviewed-by: Jonathan Cameron <[email-masked]>

> ---
>  arch/mips/include/asm/mach-ip27/mmzone.h | 5 ++++-
>  arch/mips/sgi-ip27/ip27-memory.c         | 5 ++++-
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/include/asm/mach-ip27/mmzone.h b/arch/mips/include/asm/mach-ip27/mmzone.h
> index 08c36e50a860..629c3f290203 100644
> --- a/arch/mips/include/asm/mach-ip27/mmzone.h
> +++ b/arch/mips/include/asm/mach-ip27/mmzone.h
> @@ -22,7 +22,10 @@ struct node_data {
>  
>  extern struct node_data *__node_data[];
>  
> -#define NODE_DATA(n)		(&__node_data[(n)]->pglist)
>  #define hub_data(n)		(&__node_data[(n)]->hub)
>  
> +extern struct pglist_data *node_data[];
> +
> +#define NODE_DATA(nid)		(node_data[nid])
> +
>  #endif /* _ASM_MACH_MMZONE_H */
> diff --git a/arch/mips/sgi-ip27/ip27-memory.c b/arch/mips/sgi-ip27/ip27-memory.c
> index b8ca94cfb4fe..c30ef6958b97 100644
> --- a/arch/mips/sgi-ip27/ip27-memory.c
> +++ b/arch/mips/sgi-ip27/ip27-memory.c
> @@ -34,8 +34,10 @@
>  #define SLOT_PFNSHIFT		(SLOT_SHIFT - PAGE_SHIFT)
>  #define PFN_NASIDSHFT		(NASID_SHFT - PAGE_SHIFT)
>  
> -struct node_data *__node_data[MAX_NUMNODES];
> +struct pglist_data *node_data[MAX_NUMNODES];
> +EXPORT_SYMBOL(node_data);
>  
> +struct node_data *__node_data[MAX_NUMNODES];
>  EXPORT_SYMBOL(__node_data);
>  
>  static u64 gen_region_mask(void)
> @@ -361,6 +363,7 @@ static void __init node_mem_init(nasid_t node)
>  	 */
>  	__node_data[node] = __va(slot_freepfn << PAGE_SHIFT);
>  	memset(__node_data[node], 0, PAGE_SIZE);
> +	node_data[node] = &__node_data[node]->pglist;
>  
>  	NODE_DATA(node)->node_start_pfn = start_pfn;
>  	NODE_DATA(node)->node_spanned_pages = end_pfn - start_pfn;