On Wed, 17 Jul 2024 16:32:59 +0200
David Hildenbrand [off-list ref] wrote:

On 16.07.24 13:13, Mike Rapoport wrote:

quoted

From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

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) <rppt@kernel.org>
---
  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;  

I was assuming we could get rid of __node_data->pglist.

But now I am confused where that is actually set.

It looks nasty... Cast in arch_refresh_nodedata() takes
incoming pg_data_t * and casts it to the local version of
struct node_data * which I think is this one

struct node_data {
	struct pglist_data pglist; (which is pg_data_t pglist)
	struct hub_data hub;
};

https://elixir.bootlin.com/linux/v6.10/source/arch/mips/sgi-ip27/ip27-memory.c#L432

Now that pg_data_t is allocated by 
arch_alloc_nodedata() which might be fine (though types could be handled in a more
readable fashion via some container_of() magic.
https://elixir.bootlin.com/linux/v6.10/source/arch/mips/sgi-ip27/ip27-memory.c#L427

However that call is:
pg_data_t * __init arch_alloc_nodedata(int nid)
{
	return memblock_alloc(sizeof(pg_data_t), SMP_CACHE_BYTES);
}

So doesn't seem to allocate enough space to me as should be sizeof(struct node_data)

Worth cleaning up whilst here?  Proper handling of types would definitely
help.

Jonathan

Anyhow

Reviewed-by: David Hildenbrand <redacted>