Re: [Patch v4 10/12] memory-hotplug: memory_hotplug: clear zone when removing the memory

[Tang Chen <tangchen@cn.fujitsu.com>]

On 11/27/2012 06:00 PM, Wen Congyang wrote:
> From: Yasuaki Ishimatsu<isimatu.yasuaki@jp.fujitsu.com>
>
> When a memory is added, we update zone's and pgdat's start_pfn and
> spanned_pages in the function __add_zone(). So we should revert them
> when the memory is removed.
>
> The patch adds a new function __remove_zone() to do this.
>
> CC: David Rientjes<rientjes@google.com>
> CC: Jiang Liu<liuj97@gmail.com>
> CC: Len Brown<len.brown@intel.com>
> CC: Christoph Lameter<cl@linux.com>
> Cc: Minchan Kim<minchan.kim@gmail.com>
> CC: Andrew Morton<akpm@linux-foundation.org>
> CC: KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Yasuaki Ishimatsu<isimatu.yasuaki@jp.fujitsu.com>
> Signed-off-by: Wen Congyang<wency@cn.fujitsu.com>

Reviewed-by: Tang Chen <tangchen@cn.fujitsu.com>

> ---
>   mm/memory_hotplug.c | 207 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 207 insertions(+)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 7797e91..aa97d56 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -301,10 +301,213 @@ static int __meminit __add_section(int nid, struct zone *zone,
>   	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
>   }
>
> +/* find the smallest valid pfn in the range [start_pfn, end_pfn) */
> +static int find_smallest_section_pfn(int nid, struct zone *zone,
> +				     unsigned long start_pfn,
> +				     unsigned long end_pfn)
> +{
> +	struct mem_section *ms;
> +
> +	for (; start_pfn<  end_pfn; start_pfn += PAGES_PER_SECTION) {
> +		ms = __pfn_to_section(start_pfn);
> +
> +		if (unlikely(!valid_section(ms)))
> +			continue;
> +
> +		if (unlikely(pfn_to_nid(start_pfn) != nid))
> +			continue;
> +
> +		if (zone&&  zone != page_zone(pfn_to_page(start_pfn)))
> +			continue;
> +
> +		return start_pfn;
> +	}
> +
> +	return 0;
> +}
> +
> +/* find the biggest valid pfn in the range [start_pfn, end_pfn). */
> +static int find_biggest_section_pfn(int nid, struct zone *zone,
> +				    unsigned long start_pfn,
> +				    unsigned long end_pfn)
> +{
> +	struct mem_section *ms;
> +	unsigned long pfn;
> +
> +	/* pfn is the end pfn of a memory section. */
> +	pfn = end_pfn - 1;
> +	for (; pfn>= start_pfn; pfn -= PAGES_PER_SECTION) {
> +		ms = __pfn_to_section(pfn);
> +
> +		if (unlikely(!valid_section(ms)))
> +			continue;
> +
> +		if (unlikely(pfn_to_nid(pfn) != nid))
> +			continue;
> +
> +		if (zone&&  zone != page_zone(pfn_to_page(pfn)))
> +			continue;
> +
> +		return pfn;
> +	}
> +
> +	return 0;
> +}
> +
> +static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
> +			     unsigned long end_pfn)
> +{
> +	unsigned long zone_start_pfn =  zone->zone_start_pfn;
> +	unsigned long zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
> +	unsigned long pfn;
> +	struct mem_section *ms;
> +	int nid = zone_to_nid(zone);
> +
> +	zone_span_writelock(zone);
> +	if (zone_start_pfn == start_pfn) {
> +		/*
> +		 * If the section is smallest section in the zone, it need
> +		 * shrink zone->zone_start_pfn and zone->zone_spanned_pages.
> +		 * In this case, we find second smallest valid mem_section
> +		 * for shrinking zone.
> +		 */
> +		pfn = find_smallest_section_pfn(nid, zone, end_pfn,
> +						zone_end_pfn);
> +		if (pfn) {
> +			zone->zone_start_pfn = pfn;
> +			zone->spanned_pages = zone_end_pfn - pfn;
> +		}
> +	} else if (zone_end_pfn == end_pfn) {
> +		/*
> +		 * If the section is biggest section in the zone, it need
> +		 * shrink zone->spanned_pages.
> +		 * In this case, we find second biggest valid mem_section for
> +		 * shrinking zone.
> +		 */
> +		pfn = find_biggest_section_pfn(nid, zone, zone_start_pfn,
> +					       start_pfn);
> +		if (pfn)
> +			zone->spanned_pages = pfn - zone_start_pfn + 1;
> +	}
> +
> +	/*
> +	 * The section is not biggest or smallest mem_section in the zone, it
> +	 * only creates a hole in the zone. So in this case, we need not
> +	 * change the zone. But perhaps, the zone has only hole data. Thus
> +	 * it check the zone has only hole or not.
> +	 */
> +	pfn = zone_start_pfn;
> +	for (; pfn<  zone_end_pfn; pfn += PAGES_PER_SECTION) {
> +		ms = __pfn_to_section(pfn);
> +
> +		if (unlikely(!valid_section(ms)))
> +			continue;
> +
> +		if (page_zone(pfn_to_page(pfn)) != zone)
> +			continue;
> +
> +		 /* If the section is current section, it continues the loop */
> +		if (start_pfn == pfn)
> +			continue;
> +
> +		/* If we find valid section, we have nothing to do */
> +		zone_span_writeunlock(zone);
> +		return;
> +	}
> +
> +	/* The zone has no valid section */
> +	zone->zone_start_pfn = 0;
> +	zone->spanned_pages = 0;
> +	zone_span_writeunlock(zone);
> +}
> +
> +static void shrink_pgdat_span(struct pglist_data *pgdat,
> +			      unsigned long start_pfn, unsigned long end_pfn)
> +{
> +	unsigned long pgdat_start_pfn =  pgdat->node_start_pfn;
> +	unsigned long pgdat_end_pfn =
> +		pgdat->node_start_pfn + pgdat->node_spanned_pages;
> +	unsigned long pfn;
> +	struct mem_section *ms;
> +	int nid = pgdat->node_id;
> +
> +	if (pgdat_start_pfn == start_pfn) {
> +		/*
> +		 * If the section is smallest section in the pgdat, it need
> +		 * shrink pgdat->node_start_pfn and pgdat->node_spanned_pages.
> +		 * In this case, we find second smallest valid mem_section
> +		 * for shrinking zone.
> +		 */
> +		pfn = find_smallest_section_pfn(nid, NULL, end_pfn,
> +						pgdat_end_pfn);
> +		if (pfn) {
> +			pgdat->node_start_pfn = pfn;
> +			pgdat->node_spanned_pages = pgdat_end_pfn - pfn;
> +		}
> +	} else if (pgdat_end_pfn == end_pfn) {
> +		/*
> +		 * If the section is biggest section in the pgdat, it need
> +		 * shrink pgdat->node_spanned_pages.
> +		 * In this case, we find second biggest valid mem_section for
> +		 * shrinking zone.
> +		 */
> +		pfn = find_biggest_section_pfn(nid, NULL, pgdat_start_pfn,
> +					       start_pfn);
> +		if (pfn)
> +			pgdat->node_spanned_pages = pfn - pgdat_start_pfn + 1;
> +	}
> +
> +	/*
> +	 * If the section is not biggest or smallest mem_section in the pgdat,
> +	 * it only creates a hole in the pgdat. So in this case, we need not
> +	 * change the pgdat.
> +	 * But perhaps, the pgdat has only hole data. Thus it check the pgdat
> +	 * has only hole or not.
> +	 */
> +	pfn = pgdat_start_pfn;
> +	for (; pfn<  pgdat_end_pfn; pfn += PAGES_PER_SECTION) {
> +		ms = __pfn_to_section(pfn);
> +
> +		if (unlikely(!valid_section(ms)))
> +			continue;
> +
> +		if (pfn_to_nid(pfn) != nid)
> +			continue;
> +
> +		 /* If the section is current section, it continues the loop */
> +		if (start_pfn == pfn)
> +			continue;
> +
> +		/* If we find valid section, we have nothing to do */
> +		return;
> +	}
> +
> +	/* The pgdat has no valid section */
> +	pgdat->node_start_pfn = 0;
> +	pgdat->node_spanned_pages = 0;
> +}
> +
> +static void __remove_zone(struct zone *zone, unsigned long start_pfn)
> +{
> +	struct pglist_data *pgdat = zone->zone_pgdat;
> +	int nr_pages = PAGES_PER_SECTION;
> +	int zone_type;
> +	unsigned long flags;
> +
> +	zone_type = zone - pgdat->node_zones;
> +
> +	pgdat_resize_lock(zone->zone_pgdat,&flags);
> +	shrink_zone_span(zone, start_pfn, start_pfn + nr_pages);
> +	shrink_pgdat_span(pgdat, start_pfn, start_pfn + nr_pages);
> +	pgdat_resize_unlock(zone->zone_pgdat,&flags);
> +}
> +
>   static int __remove_section(struct zone *zone, struct mem_section *ms)
>   {
>   	unsigned long flags;
>   	struct pglist_data *pgdat = zone->zone_pgdat;
> +	unsigned long start_pfn;
> +	int scn_nr;
>   	int ret = -EINVAL;
>
>   	if (!valid_section(ms))
> @@ -314,6 +517,10 @@ static int __remove_section(struct zone *zone, struct mem_section *ms)
>   	if (ret)
>   		return ret;
>
> +	scn_nr = __section_nr(ms);
> +	start_pfn = section_nr_to_pfn(scn_nr);
> +	__remove_zone(zone, start_pfn);
> +
>   	pgdat_resize_lock(pgdat,&flags);
>   	sparse_remove_one_section(zone, ms);
>   	pgdat_resize_unlock(pgdat,&flags);