[RFC PATCH 4/5] mm: add generic type support for device zone page migration

[Felix Kuehling]

From: Alex Sierra <alex.sierra at amd.com>

This support is only for generic type anonymous memory.
Generic type with zone device pages require to take an extra reference,
as it's done with device private type.
Also, support added to migrate pages meta-data for generic device type.

Signed-off-by: Alex Sierra <alex.sierra at amd.com>
---
 mm/migrate.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 20ca887ea769..33e573a992e5 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -380,7 +380,8 @@ static int expected_page_refs(struct address_space *mapping, struct page *page)
 	 * Device private pages have an extra refcount as they are
 	 * ZONE_DEVICE pages.
 	 */
-	expected_count += is_device_private_page(page);
+	expected_count +=
+			(is_device_private_page(page) || is_device_generic_page(page));
 	if (mapping)
 		expected_count += thp_nr_pages(page) + page_has_private(page);
 
@@ -2607,7 +2608,7 @@ static bool migrate_vma_check_page(struct page *page)
 		 * FIXME proper solution is to rework migration_entry_wait() so
 		 * it does not need to take a reference on page.
 		 */
-		return is_device_private_page(page);
+		return is_device_private_page(page) | is_device_generic_page(page);
 	}
 
 	/* For file back page */
@@ -3069,10 +3070,12 @@ void migrate_vma_pages(struct migrate_vma *migrate)
 		mapping = page_mapping(page);
 
 		if (is_zone_device_page(newpage)) {
-			if (is_device_private_page(newpage)) {
+			if (is_device_private_page(newpage) ||
+			    is_device_generic_page(newpage)) {
 				/*
-				 * For now only support private anonymous when
-				 * migrating to un-addressable device memory.
+				 * For now only support private and devdax/generic
+				 * anonymous when migrating to un-addressable
+				 * device memory.
 				 */
 				if (mapping) {
 					migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
-- 
2.31.1