mm/migrate_device: try to handle swapcache pages

Migrating file pages and swapcache pages into device memory is not
supported.  Try to get rid of the swap cache, and if successful, go ahead
as with other anonymous pages.

Link: https://lkml.kernel.org/r/20230607172944.11713-1-mpenttil@redhat.com
Signed-off-by: Mika Penttilä <mpenttil@redhat.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index 8365158..e29626e 100644 (file)
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -727,13 +727,22 @@ static void __migrate_device_pages(unsigned long *src_pfns,
 
                if (is_device_private_page(newpage) ||
                    is_device_coherent_page(newpage)) {
-                       /*
-                        * For now only support anonymous memory migrating to
-                        * device private or coherent memory.
-                        */
                        if (mapping) {
-                               src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
-                               continue;
+                               struct folio *folio;
+
+                               folio = page_folio(page);
+
+                               /*
+                                * For now only support anonymous memory migrating to
+                                * device private or coherent memory.
+                                *
+                                * Try to get rid of swap cache if possible.
+                                */
+                               if (!folio_test_anon(folio) ||
+                                   !folio_free_swap(folio)) {
+                                       src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
+                                       continue;
+                               }
                        }
                } else if (is_zone_device_page(newpage)) {
                        /*