[PATCH 1/4] migrate: Allow migrate_misplaced_folio APIs without a VMA

Gregory Price
2024-11-27T16:28:47Z

To migrate unmapped pagecache folios, migrate_misplaced_folio and
migrate_misplaced_folio_prepare must handle folios without VMAs.

migrate_misplaced_folio_prepare checks VMA for exec bits, so allow
a NULL VMA when it does not have a mapping.

migrate_misplaced_folio must call migrate_pages with MIGRATE_SYNC
when in the pagecache path because it is a synchronous context.

Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Gregory Price <gourry@gourry.net>
---
mm/migrate.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index dfb5eba3c522..3b0bd3f21ac3 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2632,7 +2632,7 @@ int migrate_misplaced_folio_prepare(struct folio *folio,
* See folio_likely_mapped_shared() on possible imprecision
* when we cannot easily detect if a folio is shared.
*/
- if ((vma->vm_flags & VM_EXEC) &&
+ if (vma && (vma->vm_flags & VM_EXEC) &&
folio_likely_mapped_shared(folio))
return -EACCES;

--
2.43.0