[PATCH v2] mm/swap: Fix release_pages() when releasing devmap pages

[ira . weiny]

From: Ira Weiny <ira.weiny@xxxxxxxxx>

Device pages can be more than type MEMORY_DEVICE_PUBLIC.

Handle all device pages within release_pages()

This was found via code inspection while determining if release_pages()
and the new put_user_pages() could be interchangeable.

Cc: JÃrÃme Glisse <jglisse@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>

---
Changes from V1:
	Add comment clarifying that put_devmap_managed_page() can still
	fail.
	Add Reviewed-by tags.

 mm/swap.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/mm/swap.c b/mm/swap.c
index 9d0432baddb0..f03b7b4bfb4f 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -740,15 +740,18 @@ void release_pages(struct page **pages, int nr)
 		if (is_huge_zero_page(page))
 			continue;
 
-		/* Device public page can not be huge page */
-		if (is_device_public_page(page)) {
+		if (is_zone_device_page(page)) {
 			if (locked_pgdat) {
 				spin_unlock_irqrestore(&locked_pgdat->lru_lock,
 						       flags);
 				locked_pgdat = NULL;
 			}
-			put_devmap_managed_page(page);
-			continue;
+			/*
+			 * zone-device-pages can still fail here and will
+			 * therefore need put_page_testzero()
+			 */
+			if (put_devmap_managed_page(page))
+				continue;
 		}
 
 		page = compound_head(page);
-- 
2.20.1