linux-kernel - [PATCH 2/2] mm/page_owner: simplify zone iteration logic in init_early_allocated

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Message-Id: <20250930092153.843109-2-husong@kylinos.cn>
Date: Tue, 30 Sep 2025 17:21:52 +0800
From: Hu Song <husong@...inos.cn>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>
Cc: Song Hu <husong@...inos.cn>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	Brendan Jackman <jackmanb@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Zi Yan <ziy@...dia.com>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] mm/page_owner: simplify zone iteration logic in init_early_allocated_pages()

From: Song Hu <husong@...inos.cn>

The current implementation uses nested loops: first iterating over all
online nodes, then over zones within each node. This can be simplified
by using the for_each_populated_zone() macro which directly iterates
through all populated zones.

This change:
1. Removes the intermediate init_zones_in_node() function
2. Simplifies init_early_allocated_pages() to use direct zone iteration
3. Updates init_pages_in_zone() to take only zone parameter and access
   node_id via zone->zone_pgdat

The functionality remains identical, but the code is cleaner and more
maintainable.

Signed-off-by: Song Hu <husong@...inos.cn>
---
 mm/page_owner.c | 23 +++++------------------
 1 file changed, 5 insertions(+), 18 deletions(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index bb88b72b6062..b170b27d87a1 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -757,7 +757,7 @@ static loff_t lseek_page_owner(struct file *file, loff_t offset, int orig)
 	return file->f_pos;
 }
 
-static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
+static void init_pages_in_zone(struct zone *zone)
 {
 	unsigned long pfn = zone->zone_start_pfn;
 	unsigned long end_pfn = zone_end_pfn(zone);
@@ -824,28 +824,15 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
 	}
 
 	pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
-		pgdat->node_id, zone->name, count);
-}
-
-static void init_zones_in_node(pg_data_t *pgdat)
-{
-	struct zone *zone;
-	struct zone *node_zones = pgdat->node_zones;
-
-	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
-		if (!populated_zone(zone))
-			continue;
-
-		init_pages_in_zone(pgdat, zone);
-	}
+		zone->zone_pgdat->node_id, zone->name, count);
 }
 
 static void init_early_allocated_pages(void)
 {
-	pg_data_t *pgdat;
+	struct zone *zone;
 
-	for_each_online_pgdat(pgdat)
-		init_zones_in_node(pgdat);
+	for_each_populated_zone(zone)
+		init_pages_in_zone(zone);
 }
 
 static const struct file_operations page_owner_fops = {
-- 
2.25.1