mm: refactor the ZONE_DEVICE handling in migrate_vma_insert_page

Make the flow a little more clear and prepare for adding a new
ZONE_DEVICE memory type.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Alistair Popple <[email protected]>
Tested-by: "Sierra Guiza, Alejandro (Alex)" <[email protected]>

Cc: Alex Deucher <[email protected]>
Cc: Ben Skeggs <[email protected]>
Cc: Chaitanya Kulkarni <[email protected]>
Cc: Christian Knig <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Felix Kuehling <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Karol Herbst <[email protected]>
Cc: Logan Gunthorpe <[email protected]>
Cc: Lyude Paul <[email protected]>
Cc: Miaohe Lin <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: "Pan, Xinhui" <[email protected]>
Cc: Ralph Campbell <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>

1 files changed, 15 insertions, 16 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index af0534de618a..4246dca6c469 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2674,26 +2674,25 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
 	 */
 	__SetPageUptodate(page);
 
-	if (is_zone_device_page(page)) {
-		if (is_device_private_page(page)) {
-			swp_entry_t swp_entry;
+	if (is_device_private_page(page)) {
+		swp_entry_t swp_entry;
 
-			if (vma->vm_flags & VM_WRITE)
-				swp_entry = make_writable_device_private_entry(
-							page_to_pfn(page));
-			else
-				swp_entry = make_readable_device_private_entry(
-							page_to_pfn(page));
-			entry = swp_entry_to_pte(swp_entry);
-		} else {
-			/*
-			 * For now we only support migrating to un-addressable
-			 * device memory.
-			 */
+		if (vma->vm_flags & VM_WRITE)
+			swp_entry = make_writable_device_private_entry(
+						page_to_pfn(page));
+		else
+			swp_entry = make_readable_device_private_entry(
+						page_to_pfn(page));
+		entry = swp_entry_to_pte(swp_entry);
+	} else {
+		/*
+		 * For now we only support migrating to un-addressable device
+		 * memory.
+		 */
+		if (is_zone_device_page(page)) {
 			pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
 			goto abort;
 		}
-	} else {
 		entry = mk_pte(page, vma->vm_page_prot);
 		if (vma->vm_flags & VM_WRITE)
 			entry = pte_mkwrite(pte_mkdirty(entry));