[PATCH RFC] mm: do not start node_reclaim for page order > MAX_ORDER

[Konstantin Khlebnikov]

Page allocator has check in __alloc_pages_slowpath() but nowdays
there is earlier entry point into reclimer without such check:
get_page_from_freelist() -> node_reclaim().

Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
 mm/vmscan.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 62ac0c488624..52f672420f0b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4117,6 +4117,12 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
 {
 	int ret;
 
+	/*
+	 * Do not scan if allocation will never succeed.
+	 */
+	if (order >= MAX_ORDER)
+		return NODE_RECLAIM_NOSCAN;
+
 	/*
 	 * Node reclaim reclaims unmapped file backed pages and
 	 * slab pages if we are over the defined limits.