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