[PATCH v3 5/6] migrate: implement migrate_misplaced_folio_batch

Gregory Price
2025-01-07T00:04:01Z

A common operation in tiering is to migrate multiple pages at once.
The migrate_misplaced_folio function requires one call for each
individual folio. Expose a batch-variant of the same call for use
when doing batch migrations.

Signed-off-by: Gregory Price <gourry@gourry.net>
---
include/linux/migrate.h | 5 +++++
mm/migrate.c | 31 +++++++++++++++++++++++++++++++
2 files changed, 36 insertions(+)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 29919faea2f1..3dfbe7c1cc83 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -145,6 +145,7 @@ const struct movable_operations *page_movable_ops(struct page *page)
int migrate_misplaced_folio_prepare(struct folio *folio,
struct vm_area_struct *vma, int node);
int migrate_misplaced_folio(struct folio *folio, int node);
+int migrate_misplaced_folio_batch(struct list_head *foliolist, int node);
#else
static inline int migrate_misplaced_folio_prepare(struct folio *folio,
struct vm_area_struct *vma, int node)
@@ -155,6 +156,10 @@ static inline int migrate_misplaced_folio(struct folio *folio, int node)
{
return -EAGAIN; /* can't migrate now */
}
+int migrate_misplaced_folio_batch(struct list_head *foliolist, int node)
+{
+ return -EAGAIN; /* can't migrate now */
+}
#endif /* CONFIG_NUMA_BALANCING */

#ifdef CONFIG_MIGRATION
diff --git a/mm/migrate.c b/mm/migrate.c
index ea20d9bc4f40..a751a995f2d9 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2705,5 +2705,36 @@ int migrate_misplaced_folio(struct folio *folio, int node)
BUG_ON(!list_empty(&migratepages));
return nr_remaining ? -EAGAIN : 0;
}
+
+/*
+ * Batch variant of migrate_misplaced_folio. Attempts to migrate
+ * a folio list to the specified destination.
+ *
+ * Caller is expected to have isolated the folios by calling
+ * migrate_misplaced_folio_prepare(), which will result in an
+ * elevated reference count on the folio.
+ *
+ * This function will un-isolate the folios, dereference them, and
+ * remove them from the list before returning.
+ */
+int migrate_misplaced_folio_batch(struct list_head *folio_list, int node)
+{
+ pg_data_t *pgdat = NODE_DATA(node);
+ unsigned int nr_succeeded;
+ int nr_remaining;
+
+ nr_remaining = migrate_pages(folio_list, alloc_misplaced_dst_folio,
+ NULL, node, MIGRATE_ASYNC,
+ MR_NUMA_MISPLACED, &nr_succeeded);
+ if (nr_remaining)
+ putback_movable_pages(folio_list);
+
+ if (nr_succeeded) {
+ count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
+ mod_node_page_state(pgdat, PGPROMOTE_SUCCESS, nr_succeeded);
+ }
+ BUG_ON(!list_empty(folio_list));
+ return nr_remaining ? -EAGAIN : 0;
+}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_NUMA */
--
2.47.1