Re: [PATCH 2/3] memory-hotplug: more general validation of zone during online

[Yasuaki Ishimatsu <yasu.isimatu@gmail.com>]

On Mon,  9 May 2016 12:53:38 -0500
Reza Arbab <arbab@linux.vnet.ibm.com> wrote:

> When memory is onlined, we are only able to rezone from ZONE_MOVABLE to
> ZONE_KERNEL, or from (ZONE_MOVABLE - 1) to ZONE_MOVABLE.
> 
> To be more flexible, use the following criteria instead; to online memory
> from zone X into zone Y,
> 
> * Any zones between X and Y must be unused.
> * If X is lower than Y, the onlined memory must lie at the end of X.
> * If X is higher than Y, the onlined memory must lie at the start of X.
> 
> Add zone_can_shift() to make this determination.
> 
> Signed-off-by: Reza Arbab <arbab@linux.vnet.ibm.com>
> ---

Looks good to me.

Reviewd-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>

Thanks,
Yasuaki Ishimatsu

>  include/linux/memory_hotplug.h |  2 ++
>  mm/memory_hotplug.c            | 42 +++++++++++++++++++++++++++++++++++-------
>  2 files changed, 37 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index adbef58..7bff0f9 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -284,5 +284,7 @@ extern void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
>  		unsigned long map_offset);
>  extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map,
>  					  unsigned long pnum);
> +extern int zone_can_shift(unsigned long pfn, unsigned long nr_pages,
> +			  enum zone_type target);
>  
>  #endif /* __LINUX_MEMORY_HOTPLUG_H */
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 6b4b005..b63cc28 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1032,6 +1032,37 @@ static void node_states_set_node(int node, struct memory_notify *arg)
>  	node_set_state(node, N_MEMORY);
>  }
>  
> +int zone_can_shift(unsigned long pfn, unsigned long nr_pages,
> +		   enum zone_type target)
> +{
> +	struct zone *zone = page_zone(pfn_to_page(pfn));
> +	enum zone_type idx = zone_idx(zone);
> +	int i;
> +
> +	if (idx < target) {
> +		/* pages must be at end of current zone */
> +		if (pfn + nr_pages != zone_end_pfn(zone))
> +			return 0;
> +
> +		/* no zones in use between current zone and target */
> +		for (i = idx + 1; i < target; i++)
> +			if (zone_is_initialized(zone - idx + i))
> +				return 0;
> +	}
> +
> +	if (target < idx) {
> +		/* pages must be at beginning of current zone */
> +		if (pfn != zone->zone_start_pfn)
> +			return 0;
> +
> +		/* no zones in use between current zone and target */
> +		for (i = target + 1; i < idx; i++)
> +			if (zone_is_initialized(zone - idx + i))
> +				return 0;
> +	}
> +
> +	return target - idx;
> +}
>  
>  /* Must be protected by mem_hotplug_begin() */
>  int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_type)
> @@ -1057,13 +1088,10 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>  	    !can_online_high_movable(zone))
>  		return -EINVAL;
>  
> -	if (online_type == MMOP_ONLINE_KERNEL &&
> -	    zone_idx(zone) == ZONE_MOVABLE)
> -		zone_shift = -1;
> -
> -	if (online_type == MMOP_ONLINE_MOVABLE &&
> -	    zone_idx(zone) == ZONE_MOVABLE - 1)
> -		zone_shift = 1;
> +	if (online_type == MMOP_ONLINE_KERNEL)
> +		zone_shift = zone_can_shift(pfn, nr_pages, ZONE_NORMAL);
> +	else if (online_type == MMOP_ONLINE_MOVABLE)
> +		zone_shift = zone_can_shift(pfn, nr_pages, ZONE_MOVABLE);
>  
>  	zone = move_pfn_range(zone_shift, pfn, pfn + nr_pages);
>  	if (!zone)
> -- 
> 1.8.3.1
> 
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