linux-kernel - Re: [PATCH 1/2] mm,memory_hotplug: Implement numa node notifier

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Message-ID: <20250403134410.000006c7@huawei.com>
Date: Thu, 3 Apr 2025 13:44:10 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Oscar Salvador <osalvador@...e.de>
CC: Andrew Morton <akpm@...ux-foundation.org>, David Hildenbrand
	<david@...hat.com>, <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
	Vlastimil Babka <vbabka@...e.cz>, Hyeonggon Yoo <42.hyeyoo@...il.com>,
	<mkoutny@...e.com>, Dan Williams <dan.j.williams@...el.com>,
	<linux-cxl@...r.kernel.org>
Subject: Re: [PATCH 1/2] mm,memory_hotplug: Implement numa node notifier

On Tue,  1 Apr 2025 11:27:15 +0200
Oscar Salvador <osalvador@...e.de> wrote:

> There are at least four consumers of hotplug_memory_notifier that what they
> really are interested in is whether any numa node changed its state, e.g: going
> from being memory aware to becoming memoryless.

Cover letter says 5.  Whilst that's at least 4, maybe update this if you do
a v2 to say at least 5 :)

> 
> Implement a specific notifier for numa nodes when their state gets changed,
> and have those consumers that only care about numa node state changes use it.
> 
> Signed-off-by: Oscar Salvador <osalvador@...e.de>

A couple of trivial things below.  To me this looks fine otherwise.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> +#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);			\
> +})

Trivial but spacing before \ seems rather random. Maybe I'm missing
how it is consistent.

> +
>  #ifdef CONFIG_NUMA
>  void memory_block_add_nid(struct memory_block *mem, int nid,
>  			  enum meminit_context context);

> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 75401866fb76..4bb9ff282ec9 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c


> @@ -2106,27 +2143,32 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages,
>  	 * Make sure to mark the node as memory-less before rebuilding the zone
>  	 * list. Otherwise this node would still appear in the fallback lists.
>  	 */
> -	node_states_clear_node(node, &arg);
> +	node_states_clear_node(node, &node_arg);
>  	if (!populated_zone(zone)) {
>  		zone_pcp_reset(zone);
>  		build_all_zonelists(NULL);
>  	}
>  
> -	if (arg.status_change_nid >= 0) {
> +	if (node_arg.status_change_nid >= 0) {
>  		kcompactd_stop(node);
>  		kswapd_stop(node);
> +		/*Node went memoryless. Notifiy interested consumers */

Trivial: missing space after *

> +		node_notify(NODE_BECAME_MEMORYLESS, &node_arg);
>  	}
>  
>  	writeback_set_ratelimit();
>  
> -	memory_notify(MEM_OFFLINE, &arg);
> +	memory_notify(MEM_OFFLINE, &mem_arg);
>  	remove_pfn_range_from_zone(zone, start_pfn, nr_pages);
>  	return 0;
>  
>  failed_removal_isolated:
>  	/* pushback to free area */
>  	undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
> -	memory_notify(MEM_CANCEL_OFFLINE, &arg);
> +	if (cancel_node_notifier_on_err)
> +		node_notify(NODE_CANCEL_MEMORYLESS, &node_arg);
> +	if (cancel_mem_notifier_on_err)
> +		memory_notify(MEM_CANCEL_OFFLINE, &mem_arg);
>  failed_removal_pcplists_disabled:
>  	lru_cache_enable();
>  	zone_pcp_enable(zone);