[PATCH] mm/migrate: skip unsupported ZONE_DEVICE page in migrate_vma_collect_pmd()

[Miaohe Lin]

For now we only support migrating to un-addressable device memory. Other
types of ZONE_DEVICE pages are not supported yet. So skip those pages in
MIGRATE_VMA_SELECT_SYSTEM case to save useless effort.

Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
 mm/migrate_device.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index 5052093d0262..a0452c1d69dd 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -157,6 +157,11 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 				goto next;
 			}
 			page = vm_normal_page(migrate->vma, addr, pte);
+			/*
+			 * Other types of ZONE_DEVICE page are not supported.
+			 */
+			if (page && is_zone_device_page(page))
+				goto next;
 			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
 			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
 		}
-- 
2.23.0