[PATCH 1/3] migrate: Allow migrate_misplaced_folio APIs without a VMA

[Gregory Price <gourry@xxxxxxxxxx>]

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
does not require a VMA, remove it from the argument list.

Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Gregory Price <gourry@xxxxxxxxxx>
---
 include/linux/migrate.h | 6 ++----
 mm/huge_memory.c        | 2 +-
 mm/memory.c             | 2 +-
 mm/migrate.c            | 7 +++----
 4 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 644be30b69c8..553bdb4a65db 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -141,16 +141,14 @@ const struct movable_operations *page_movable_ops(struct page *page)
 #ifdef CONFIG_NUMA_BALANCING
 int migrate_misplaced_folio_prepare(struct folio *folio,
 		struct vm_area_struct *vma, int node);
-int migrate_misplaced_folio(struct folio *folio, struct vm_area_struct *vma,
-			   int node);
+int migrate_misplaced_folio(struct folio *folio, int node);
 #else
 static inline int migrate_misplaced_folio_prepare(struct folio *folio,
 		struct vm_area_struct *vma, int node)
 {
 	return -EAGAIN; /* can't migrate now */
 }
-static inline int migrate_misplaced_folio(struct folio *folio,
-					 struct vm_area_struct *vma, int node)
+static inline int migrate_misplaced_folio(struct folio *folio, int node)
 {
 	return -EAGAIN; /* can't migrate now */
 }
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f4be468e06a4..f79c42e36d37 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1725,7 +1725,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 	spin_unlock(vmf->ptl);
 	writable = false;
 
-	if (!migrate_misplaced_folio(folio, vma, target_nid)) {
+	if (!migrate_misplaced_folio(folio, target_nid)) {
 		flags |= TNF_MIGRATED;
 		nid = target_nid;
 	} else {
diff --git a/mm/memory.c b/mm/memory.c
index 34f8402d2046..1d97bdfd0ed6 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5355,7 +5355,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 	ignore_writable = true;
 
 	/* Migrate to the requested node */
-	if (!migrate_misplaced_folio(folio, vma, target_nid)) {
+	if (!migrate_misplaced_folio(folio, target_nid)) {
 		nid = target_nid;
 		flags |= TNF_MIGRATED;
 	} else {
diff --git a/mm/migrate.c b/mm/migrate.c
index e7296c0fb5d5..c648dc08758b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2546,7 +2546,7 @@ 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. If VMA is not NULL, Must be called with the PTL still held.
  */
 int migrate_misplaced_folio_prepare(struct folio *folio,
 		struct vm_area_struct *vma, int node)
@@ -2563,7 +2563,7 @@ 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;
 
@@ -2614,8 +2614,7 @@ int migrate_misplaced_folio_prepare(struct folio *folio,
  * elevated reference count on the folio. This function will un-isolate the
  * folio, dereferencing the folio before returning.
  */
-int migrate_misplaced_folio(struct folio *folio, struct vm_area_struct *vma,
-			    int node)
+int migrate_misplaced_folio(struct folio *folio, int node)
 {
 	pg_data_t *pgdat = NODE_DATA(node);
 	int nr_remaining;
-- 
2.43.0