Re: [PATCH 5/6] mm, memory_hotplug: do not associate hotadded memory to zones until online

[Michal Hocko]

On Thu 30-03-17 13:54:53, Michal Hocko wrote:
[...]
> -static int __meminit __add_section(int nid, struct zone *zone,
> -					unsigned long phys_start_pfn)
> +static int __meminit __add_section(int nid, unsigned long phys_start_pfn)
>  {
>  	int ret;
> +	int i;
>  
>  	if (pfn_valid(phys_start_pfn))
>  		return -EEXIST;
>  
> -	ret = sparse_add_one_section(zone, phys_start_pfn);
> -
> +	ret = sparse_add_one_section(NODE_DATA(nid), phys_start_pfn);
>  	if (ret < 0)
>  		return ret;
>  
> -	ret = __add_zone(zone, phys_start_pfn);
> +	/*
> +	 * Make all the pages reserved so that nobody will stumble over half
> +	 * initialized state.
> +	 */
> +	for (i = 0; i < PAGES_PER_SECTION; i++) {
> +		unsigned long pfn = phys_start_pfn + i;
> +		if (!pfn_valid(pfn))
> +			continue;
>  
> -	if (ret < 0)
> -		return ret;
> +		SetPageReserved(pfn_to_page(phys_start_pfn + i));
> +	}
>  
>  	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));

I have just realized one more dependency on the zone initialization.
register_new_memory relies on is_zone_device_section to rule out
memblock specific operations including sysfs infrastructure. I have come
up with the following to handle this.
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