Sub-section hotplug support reduces the unit of operation of hotplug
from section-sized-units (PAGES_PER_SECTION) to sub-section-sized units
(PAGES_PER_SUBSECTION). Teach shrink_{zone,pgdat}_span() to consider
PAGES_PER_SUBSECTION boundaries as the points where pfn_valid(), not
valid_section(), can toggle.

Cc: Michal Hocko <mho...@suse.com>
Cc: Vlastimil Babka <vba...@suse.cz>
Cc: Logan Gunthorpe <log...@deltatee.com>
Reviewed-by: Pavel Tatashin <pasha.tatas...@soleen.com>
Reviewed-by: Oscar Salvador <osalva...@suse.de>
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 mm/memory_hotplug.c |   29 ++++++++---------------------
 1 file changed, 8 insertions(+), 21 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a76fc6a6e9fe..393ab2b9c3f7 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -325,12 +325,8 @@ static unsigned long 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)))
+       for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SUBSECTION) {
+               if (unlikely(!pfn_valid(start_pfn)))
                        continue;
 
                if (unlikely(pfn_to_nid(start_pfn) != nid))
@@ -350,15 +346,12 @@ static unsigned long 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)))
+       for (; pfn >= start_pfn; pfn -= PAGES_PER_SUBSECTION) {
+               if (unlikely(!pfn_valid(pfn)))
                        continue;
 
                if (unlikely(pfn_to_nid(pfn) != nid))
@@ -380,7 +373,6 @@ static void shrink_zone_span(struct zone *zone, unsigned 
long start_pfn,
        unsigned long z = zone_end_pfn(zone); /* zone_end_pfn namespace clash */
        unsigned long zone_end_pfn = z;
        unsigned long pfn;
-       struct mem_section *ms;
        int nid = zone_to_nid(zone);
 
        zone_span_writelock(zone);
@@ -417,10 +409,8 @@ static void shrink_zone_span(struct zone *zone, unsigned 
long start_pfn,
         * 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)))
+       for (; pfn < zone_end_pfn; pfn += PAGES_PER_SUBSECTION) {
+               if (unlikely(!pfn_valid(pfn)))
                        continue;
 
                if (page_zone(pfn_to_page(pfn)) != zone)
@@ -448,7 +438,6 @@ static void shrink_pgdat_span(struct pglist_data *pgdat,
        unsigned long p = pgdat_end_pfn(pgdat); /* pgdat_end_pfn namespace 
clash */
        unsigned long pgdat_end_pfn = p;
        unsigned long pfn;
-       struct mem_section *ms;
        int nid = pgdat->node_id;
 
        if (pgdat_start_pfn == start_pfn) {
@@ -485,10 +474,8 @@ static void shrink_pgdat_span(struct pglist_data *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)))
+       for (; pfn < pgdat_end_pfn; pfn += PAGES_PER_SUBSECTION) {
+               if (unlikely(!pfn_valid(pfn)))
                        continue;
 
                if (pfn_to_nid(pfn) != nid)

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