Re: [PATCH v2 10/12] memory-hotplug: memory_hotplug: clear zone when removing the memory

[Wen Congyang <wency@cn.fujitsu.com>]

At 10/29/2012 11:34 PM, Jianguo Wu Wrote:
> On 2012/10/23 18:30, wency@cn.fujitsu.com 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>
>> ---
>>  mm/memory_hotplug.c |  207 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 files changed, 207 insertions(+), 0 deletions(-)
>>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 03153cf..55a228d 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -312,10 +312,213 @@ 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)
> 
> if (unlikely(pfn_to_nid(start_pfn) != nid))

Thanks for pointing it out. I will fix it soon.

Wen Congyang

> 
>> +			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)
> 
> 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))
>> @@ -325,6 +528,10 @@ 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);
>>
> 
> 

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