Re: [PATCH v5 03/10] mm,memory_hotplug: Implement numa node notifier

[Oscar Salvador <osalvador@suse.de>]

On Thu, Jun 05, 2025 at 04:22:54PM +0200, Oscar Salvador wrote:
> There are at least six consumers of hotplug_memory_notifier that what they
> really are interested in is whether any numa node changed its state, e.g: going
> from having memory to not having memory and vice versa.
> 
> Implement a specific notifier for numa nodes when their state gets changed,
> which will later be used by those consumers that are only interested
> in numa node state changes.
> 
> Add documentation as well.
> 
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
...
> diff --git a/include/linux/node.h b/include/linux/node.h
> index 2b7517892230..8c783269011d 100644
> --- a/include/linux/node.h
> +++ b/include/linux/node.h
> @@ -123,6 +123,48 @@ static inline void register_memory_blocks_under_node(int nid, unsigned long star
>  #endif
>  
>  extern void unregister_node(struct node *node);
> +
> +#ifdef CONFIG_MEMORY_HOTPLUG
> +struct node_notify {
> +	int nid;
> +};
> +
> +#define NODE_ADDING_FIRST_MEMORY                (1<<0)
> +#define NODE_ADDED_FIRST_MEMORY                 (1<<1)
> +#define NODE_CANCEL_ADDING_FIRST_MEMORY         (1<<2)
> +#define NODE_REMOVING_LAST_MEMORY               (1<<3)
> +#define NODE_REMOVED_LAST_MEMORY                (1<<4)
> +#define NODE_CANCEL_REMOVING_LAST_MEMORY        (1<<5)
> +
> +#if defined(CONFIG_MEMORY_HOTPLUG) && defined(CONFIG_NUMA)
> +extern int register_node_notifier(struct notifier_block *nb);
> +extern void unregister_node_notifier(struct notifier_block *nb);
> +extern int node_notify(unsigned long val, void *v);
> +
> +#define hotplug_node_notifier(fn, pri) ({		\
> +	static __meminitdata struct notifier_block fn##_node_nb =\
> +		{ .notifier_call = fn, .priority = pri };\
> +	register_node_notifier(&fn##_node_nb);			\
> +})
> +#else
> +static inline int register_node_notifier(struct notifier_block *nb)
> +{
> +	return 0;
> +}
> +static inline void unregister_node_notifier(struct notifier_block *nb)
> +{
> +}
> +static inline int node_notify(unsigned long val, void *v)
> +{
> +	return 0;
> +}
> +static inline int hotplug_node_notifier(notifier_fn_t fn, int pri)
> +{
> +	return 0;
> +}
> +#endif
> +#endif


I got carried away, sorry.
We need this fixup on top:

 diff --git a/include/linux/node.h b/include/linux/node.h
 index 8c783269011d..d7aa2636d948 100644
 --- a/include/linux/node.h
 +++ b/include/linux/node.h
 @@ -124,7 +124,6 @@ static inline void register_memory_blocks_under_node(int nid, unsigned long star
 
  extern void unregister_node(struct node *node);
 
 -#ifdef CONFIG_MEMORY_HOTPLUG
  struct node_notify {
  	int nid;
  };
 @@ -163,7 +162,6 @@ static inline int hotplug_node_notifier(notifier_fn_t fn, int pri)
  	return 0;
  }
  #endif
 -#endif
 
  #ifdef CONFIG_NUMA
  extern void node_dev_init(void);
 

-- 
Oscar Salvador
SUSE Labs