[RFC v1 07/19] mm, vmscan: use first_node in throttle_direct_reclaim()

[Pengfei Li <fly@kernel.page>]

In throttle_direct_reclaim(), we want to access first node instead of
first zone, so use first_node_nlist instead of first_zone_zonelist.

Signed-off-by: Pengfei Li <fly@kernel.page>
---
 mm/vmscan.c | 41 +++++++++++++++++++----------------------
 1 file changed, 19 insertions(+), 22 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 159a2aaa8db1..7554c8ba0841 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3166,9 +3166,9 @@ static bool allow_direct_reclaim(pg_data_t *pgdat)
 static bool throttle_direct_reclaim(gfp_t gfp_mask, struct nodelist *nodelist,
 					nodemask_t *nodemask)
 {
-	struct nlist_traverser t;
-	struct zone *zone;
-	pg_data_t *pgdat = NULL;
+	pg_data_t *pgdat;
+	enum zone_type high_idx;
+	int node;
 
 	/*
 	 * Kernel threads should not be throttled as they may be indirectly
@@ -3178,21 +3178,24 @@ static bool throttle_direct_reclaim(gfp_t gfp_mask, struct nodelist *nodelist,
 	 * processes to block on log_wait_commit().
 	 */
 	if (current->flags & PF_KTHREAD)
-		goto out;
+		return false;
 
 	/*
 	 * If a fatal signal is pending, this process should not throttle.
 	 * It should return quickly so it can exit and free its memory
 	 */
 	if (fatal_signal_pending(current))
-		goto out;
+		return false;
 
 	/*
 	 * Check if the pfmemalloc reserves are ok by finding the first node
 	 * with a usable ZONE_NORMAL or lower zone. The expectation is that
 	 * GFP_KERNEL will be required for allocating network buffers when
 	 * swapping over the network so ZONE_HIGHMEM is unusable.
-	 *
+	 */
+	high_idx = min_t(enum zone_type, ZONE_NORMAL, gfp_zone(gfp_mask));
+
+	/*
 	 * Throttling is based on the first usable node and throttled processes
 	 * wait on a queue until kswapd makes progress and wakes them. There
 	 * is an affinity then between processes waking up and where reclaim
@@ -3201,21 +3204,16 @@ static bool throttle_direct_reclaim(gfp_t gfp_mask, struct nodelist *nodelist,
 	 * for remote pfmemalloc reserves and processes on different nodes
 	 * should make reasonable progress.
 	 */
-	for_each_zone_nlist_nodemask(zone, &t, nodelist,
-					gfp_zone(gfp_mask), nodemask) {
-		if (zone_idx(zone) > ZONE_NORMAL)
-			continue;
-
-		/* Throttle based on the first usable node */
-		pgdat = zone->zone_pgdat;
-		if (allow_direct_reclaim(pgdat))
-			goto out;
-		break;
-	}
+	node = first_node_nlist_nodemask(nodelist, high_idx, nodemask);
 
 	/* If no zone was usable by the allocation flags then do not throttle */
-	if (!pgdat)
-		goto out;
+	if (node == NUMA_NO_NODE)
+		return false;
+
+	pgdat = NODE_DATA(node);
+	/* Throttle based on the first usable node */
+	if (allow_direct_reclaim(pgdat))
+		return false;
 
 	/* Account for the throttling */
 	count_vm_event(PGSCAN_DIRECT_THROTTLE);
@@ -3236,14 +3234,13 @@ static bool throttle_direct_reclaim(gfp_t gfp_mask, struct nodelist *nodelist,
 	}
 
 	/* Throttle until kswapd wakes the process */
-	wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
-		allow_direct_reclaim(pgdat));
+	wait_event_killable(pgdat->pfmemalloc_wait,
+				allow_direct_reclaim(pgdat));
 
 check_pending:
 	if (fatal_signal_pending(current))
 		return true;
 
-out:
 	return false;
 }
 
-- 
2.23.0