[PATCHv2 4/8] mm: Introduce PageUnaccepted() page type

[Kirill A. Shutemov]

The new page type allows physical memory scanners to detect unaccepted
memory and handle it accordingly.

The page type is serialized with zone lock.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
---
 include/linux/page-flags.h | 8 ++++++++
 mm/page_alloc.c            | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index a0a29bd092f8..17175a328e6b 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -939,6 +939,7 @@ enum pagetype {
 	PG_hugetlb	= 0x04000000,
 	PG_slab		= 0x02000000,
 	PG_zsmalloc	= 0x01000000,
+	PG_unaccepted	= 0x00800000,
 
 	PAGE_TYPE_BASE	= 0x80000000,
 
@@ -1072,6 +1073,13 @@ FOLIO_TEST_FLAG_FALSE(hugetlb)
 
 PAGE_TYPE_OPS(Zsmalloc, zsmalloc, zsmalloc)
 
+/*
+ * Mark pages that has to be accepted before touched for the first time.
+ *
+ * Serialized with zone lock.
+ */
+PAGE_TYPE_OPS(Unaccepted, unaccepted, unaccepted)
+
 /**
  * PageHuge - Determine if the page belongs to hugetlbfs
  * @page: The page to test.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ed62ecd6775f..f4368c2fa395 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7008,6 +7008,7 @@ static bool try_to_accept_memory_one(struct zone *zone)
 
 	account_freepages(zone, -MAX_ORDER_NR_PAGES, MIGRATE_MOVABLE);
 	__mod_zone_page_state(zone, NR_UNACCEPTED, -MAX_ORDER_NR_PAGES);
+	__ClearPageUnaccepted(page);
 	spin_unlock_irqrestore(&zone->lock, flags);
 
 	accept_page(page, MAX_PAGE_ORDER);
@@ -7066,6 +7067,7 @@ static bool __free_unaccepted(struct page *page)
 	list_add_tail(&page->lru, &zone->unaccepted_pages);
 	account_freepages(zone, MAX_ORDER_NR_PAGES, MIGRATE_MOVABLE);
 	__mod_zone_page_state(zone, NR_UNACCEPTED, MAX_ORDER_NR_PAGES);
+	__SetPageUnaccepted(page);
 	spin_unlock_irqrestore(&zone->lock, flags);
 
 	if (first)
-- 
2.43.0