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Subject[PATCH v6 04/12] mm/hotplug: Prepare shrink_{zone, pgdat}_span for sub-section removal
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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 <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
include/linux/mmzone.h | 2 ++
mm/memory_hotplug.c | 16 ++++++++--------
2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index cffde898e345..b13f0cddf75e 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1164,6 +1164,8 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)

#define SECTION_ACTIVE_SIZE ((1UL << SECTION_SIZE_BITS) / BITS_PER_LONG)
#define SECTION_ACTIVE_MASK (~(SECTION_ACTIVE_SIZE - 1))
+#define PAGES_PER_SUB_SECTION (SECTION_ACTIVE_SIZE / PAGE_SIZE)
+#define PAGE_SUB_SECTION_MASK (~(PAGES_PER_SUB_SECTION-1))

struct mem_section_usage {
/*
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 8b7415736d21..d5874f9d4043 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -327,10 +327,10 @@ static unsigned long find_smallest_section_pfn(int nid, struct zone *zone,
{
struct mem_section *ms;

- for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SECTION) {
+ for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SUB_SECTION) {
ms = __pfn_to_section(start_pfn);

- if (unlikely(!valid_section(ms)))
+ if (unlikely(!pfn_valid(start_pfn)))
continue;

if (unlikely(pfn_to_nid(start_pfn) != nid))
@@ -355,10 +355,10 @@ static unsigned long find_biggest_section_pfn(int nid, struct zone *zone,

/* pfn is the end pfn of a memory section. */
pfn = end_pfn - 1;
- for (; pfn >= start_pfn; pfn -= PAGES_PER_SECTION) {
+ for (; pfn >= start_pfn; pfn -= PAGES_PER_SUB_SECTION) {
ms = __pfn_to_section(pfn);

- if (unlikely(!valid_section(ms)))
+ if (unlikely(!pfn_valid(pfn)))
continue;

if (unlikely(pfn_to_nid(pfn) != nid))
@@ -417,10 +417,10 @@ 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) {
+ for (; pfn < zone_end_pfn; pfn += PAGES_PER_SUB_SECTION) {
ms = __pfn_to_section(pfn);

- if (unlikely(!valid_section(ms)))
+ if (unlikely(!pfn_valid(pfn)))
continue;

if (page_zone(pfn_to_page(pfn)) != zone)
@@ -485,10 +485,10 @@ 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) {
+ for (; pfn < pgdat_end_pfn; pfn += PAGES_PER_SUB_SECTION) {
ms = __pfn_to_section(pfn);

- if (unlikely(!valid_section(ms)))
+ if (unlikely(!pfn_valid(pfn)))
continue;

if (pfn_to_nid(pfn) != nid)
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