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.

If memory address has hole, memory address gets uncotinuous. Then memory
cannot be changed the zone by above the two conditions. So the conditions
shouold be removed.

Thanks,
Yasuaki Ishimatsu

> 
> Add zone_can_shift() to make this determination.
> 
> Signed-off-by: Reza Arbab <arbab@linux.vnet.ibm.com>
> ---
>  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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