[PATCH] mm/damon: prevent migration fallback to non-target nodes

[zjh]

DAMOS_MIGRATE_{HOT,COLD} passes a target NUMA node to migrate_pages().
But alloc_migration_target() treats mtc->nid as a preferred node unless
__GFP_THISNODE is set.  Hence target allocation can fall back to another
node, and migrate_pages() can report success without placing the folio on
the requested target node.

Make DAMON migration target allocation strict by setting __GFP_THISNODE.
This is consistent with alloc_misplaced_dst_folio() and
alloc_demote_folio(), which also use __GFP_THISNODE for migrations to an
explicit destination node.

Signed-off-by: zjh <jiahuitry@xxxxxxxxxxx>
---
 mm/damon/ops-common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
index 6bdd1cfd3863..d21b106b81ca 100644
--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -311,7 +311,7 @@ static unsigned int __damon_migrate_folio_list(
 		 * instead of migrated.
 		 */
 		.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) |
-			__GFP_NOMEMALLOC | GFP_NOWAIT,
+			__GFP_NOMEMALLOC | GFP_NOWAIT | __GFP_THISNODE,
 		.nid = target_nid,
 	};
 

base-commit: 42db70db0bf4f1aa4eac4ddbe121143131b793df
-- 
2.53.0