[RFC PATCH 1/4] mm: migrate: Allow misplaced migration without VMA too

Bharata B Rao
2025-03-06T05:47:25Z

migrate_misplaced_folio_prepare() can be called from a
context where VMA isn't available. Allow the migration
to work from such contexts too.

Signed-off-by: Bharata B Rao <bharata@amd.com>
---
mm/migrate.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index fb19a18892c8..5b21856a0dd0 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2639,7 +2639,8 @@ static struct folio *alloc_misplaced_dst_folio(struct folio *src,

/*
* Prepare for calling migrate_misplaced_folio() by isolating the folio if
- * permitted. Must be called with the PTL still held.
+ * permitted. Must be called with the PTL still held if called with a non-NULL
+ * vma.
*/
int migrate_misplaced_folio_prepare(struct folio *folio,
struct vm_area_struct *vma, int node)
@@ -2656,7 +2657,7 @@ 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;

--
2.34.1