[PATCH v2 1/9] mm: track present early pages per zone

[David Hildenbrand <david@redhat.com>]

For implementing a new memory onlining policy, which determines when to
online memory blocks to ZONE_MOVABLE semi-automatically, we need the number
of present early (boot) pages -- present pages excluding hotplugged pages.
Let's track these pages per zone.

Pass a page instead of the zone to adjust_present_page_count(), similar
as adjust_managed_page_count() and derive the zone from the page.

It's worth noting that a memory block to be offlined/onlined is either
completely "early" or "not early". add_memory() and friends can only add
complete memory blocks and we only online/offline complete (individual)
memory blocks.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 drivers/base/memory.c          | 14 +++++++-------
 include/linux/memory_hotplug.h |  2 +-
 include/linux/mmzone.h         |  7 +++++++
 mm/memory_hotplug.c            | 14 +++++++++++---
 mm/page_alloc.c                |  3 +++
 5 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index aa31a21f33d7..86ec2dc82fc2 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -205,7 +205,8 @@ static int memory_block_online(struct memory_block *mem)
 	 * now already properly populated.
 	 */
 	if (nr_vmemmap_pages)
-		adjust_present_page_count(zone, nr_vmemmap_pages);
+		adjust_present_page_count(pfn_to_page(start_pfn),
+					  nr_vmemmap_pages);
 
 	return ret;
 }
@@ -215,24 +216,23 @@ static int memory_block_offline(struct memory_block *mem)
 	unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
 	unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
 	unsigned long nr_vmemmap_pages = mem->nr_vmemmap_pages;
-	struct zone *zone;
 	int ret;
 
 	/*
 	 * Unaccount before offlining, such that unpopulated zone and kthreads
 	 * can properly be torn down in offline_pages().
 	 */
-	if (nr_vmemmap_pages) {
-		zone = page_zone(pfn_to_page(start_pfn));
-		adjust_present_page_count(zone, -nr_vmemmap_pages);
-	}
+	if (nr_vmemmap_pages)
+		adjust_present_page_count(pfn_to_page(start_pfn),
+					  -nr_vmemmap_pages);
 
 	ret = offline_pages(start_pfn + nr_vmemmap_pages,
 			    nr_pages - nr_vmemmap_pages);
 	if (ret) {
 		/* offline_pages() failed. Account back. */
 		if (nr_vmemmap_pages)
-			adjust_present_page_count(zone, nr_vmemmap_pages);
+			adjust_present_page_count(pfn_to_page(start_pfn),
+						  nr_vmemmap_pages);
 		return ret;
 	}
 
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 068e3dcf4690..39b04e99a30e 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -95,7 +95,7 @@ static inline void zone_seqlock_init(struct zone *zone)
 extern int zone_grow_free_lists(struct zone *zone, unsigned long new_nr_pages);
 extern int zone_grow_waitqueues(struct zone *zone, unsigned long nr_pages);
 extern int add_one_highpage(struct page *page, int pfn, int bad_ppro);
-extern void adjust_present_page_count(struct zone *zone, long nr_pages);
+extern void adjust_present_page_count(struct page *page, long nr_pages);
 /* VM interface that may be used by firmware interface */
 extern int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages,
 				     struct zone *zone);
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index fcb535560028..6fbe59702bf2 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -540,6 +540,10 @@ struct zone {
 	 * is calculated as:
 	 *	present_pages = spanned_pages - absent_pages(pages in holes);
 	 *
+	 * present_early_pages is present pages existing within the zone
+	 * located on memory available since early boot, excluding hotplugged
+	 * memory.
+	 *
 	 * managed_pages is present pages managed by the buddy system, which
 	 * is calculated as (reserved_pages includes pages allocated by the
 	 * bootmem allocator):
@@ -572,6 +576,9 @@ struct zone {
 	atomic_long_t		managed_pages;
 	unsigned long		spanned_pages;
 	unsigned long		present_pages;
+#if defined(CONFIG_MEMORY_HOTPLUG)
+	unsigned long		present_early_pages;
+#endif
 #ifdef CONFIG_CMA
 	unsigned long		cma_pages;
 #endif
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 388c8627f17f..65dbb30f81c2 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -724,8 +724,16 @@ struct zone *zone_for_pfn_range(int online_type, int nid,
  * This function should only be called by memory_block_{online,offline},
  * and {online,offline}_pages.
  */
-void adjust_present_page_count(struct zone *zone, long nr_pages)
+void adjust_present_page_count(struct page *page, long nr_pages)
 {
+	struct zone *zone = page_zone(page);
+
+	/*
+	 * We only support onlining/offlining/adding/removing of complete
+	 * memory blocks; therefore, either all is either early or hotplugged.
+	 */
+	if (early_section(__pfn_to_section(page_to_pfn(page))))
+		zone->present_early_pages += nr_pages;
 	zone->present_pages += nr_pages;
 	zone->zone_pgdat->node_present_pages += nr_pages;
 }
@@ -826,7 +834,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, struct zone *z
 	}
 
 	online_pages_range(pfn, nr_pages);
-	adjust_present_page_count(zone, nr_pages);
+	adjust_present_page_count(pfn_to_page(pfn), nr_pages);
 
 	node_states_set_node(nid, &arg);
 	if (need_zonelists_rebuild)
@@ -1704,7 +1712,7 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
 
 	/* removal success */
 	adjust_managed_page_count(pfn_to_page(start_pfn), -nr_pages);
-	adjust_present_page_count(zone, -nr_pages);
+	adjust_present_page_count(pfn_to_page(start_pfn), -nr_pages);
 
 	/* reinitialise watermarks and update pcp limits */
 	init_per_zone_wmark_min();
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3e97e68aef7a..213728db3c01 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7255,6 +7255,9 @@ static void __init calculate_node_totalpages(struct pglist_data *pgdat,
 			zone->zone_start_pfn = 0;
 		zone->spanned_pages = size;
 		zone->present_pages = real_size;
+#if defined(CONFIG_MEMORY_HOTPLUG)
+		zone->present_early_pages = real_size;
+#endif
 
 		totalpages += size;
 		realtotalpages += real_size;
-- 
2.31.1