[PATCHv2 6/8] mm: Add a helper to accept page

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

Accept a given struct page and add it free list.

The help is useful for physical memory scanners that want to use free
unaccepted memory.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: David Hildenbrand <david@redhat.com>
---
 mm/internal.h   |  8 ++++++++
 mm/page_alloc.c | 53 +++++++++++++++++++++++++++++++++++--------------
 2 files changed, 46 insertions(+), 15 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 1159b04e76a3..ff47d57733ad 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1431,4 +1431,12 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
 	unsigned long new_addr, unsigned long len,
 	bool need_rmap_locks, bool for_stack);
 
+#ifdef CONFIG_UNACCEPTED_MEMORY
+void accept_page(struct page *page);
+#else /* CONFIG_UNACCEPTED_MEMORY */
+static inline void accept_page(struct page *page)
+{
+}
+#endif /* CONFIG_UNACCEPTED_MEMORY */
+
 #endif	/* __MM_INTERNAL_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e7e304d9e739..f0610c691ae5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6980,11 +6980,46 @@ static bool page_contains_unaccepted(struct page *page, unsigned int order)
 	return range_contains_unaccepted_memory(start, PAGE_SIZE << order);
 }
 
+static void __accept_page(struct zone *zone, unsigned long *flags,
+			  struct page *page)
+{
+	bool last;
+
+	list_del(&page->lru);
+	last = list_empty(&zone->unaccepted_pages);
+
+	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_memory(page_to_phys(page), PAGE_SIZE << MAX_PAGE_ORDER);
+
+	__free_pages_ok(page, MAX_PAGE_ORDER, FPI_TO_TAIL);
+
+	if (last)
+		static_branch_dec(&zones_with_unaccepted_pages);
+}
+
+void accept_page(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long flags;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	if (!PageUnaccepted(page)) {
+		spin_unlock_irqrestore(&zone->lock, flags);
+		return;
+	}
+
+	/* Unlocks zone->lock */
+	__accept_page(zone, &flags, page);
+}
+
 static bool try_to_accept_memory_one(struct zone *zone)
 {
 	unsigned long flags;
 	struct page *page;
-	bool last;
 
 	spin_lock_irqsave(&zone->lock, flags);
 	page = list_first_entry_or_null(&zone->unaccepted_pages,
@@ -6994,20 +7029,8 @@ static bool try_to_accept_memory_one(struct zone *zone)
 		return false;
 	}
 
-	list_del(&page->lru);
-	last = list_empty(&zone->unaccepted_pages);
-
-	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_memory(page_to_phys(page), PAGE_SIZE << MAX_PAGE_ORDER);
-
-	__free_pages_ok(page, MAX_PAGE_ORDER, FPI_TO_TAIL);
-
-	if (last)
-		static_branch_dec(&zones_with_unaccepted_pages);
+	/* Unlocks zone->lock */
+	__accept_page(zone, &flags, page);
 
 	return true;
 }
-- 
2.43.0