linux-kernel - [PATCH v7 10/11] mm,page_ext: Derive the node from the pfn

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Message-ID: <20250616135158.450136-11-osalvador@suse.de>
Date: Mon, 16 Jun 2025 15:51:53 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Harry Yoo <harry.yoo@...cle.com>,
	Rakie Kim <rakie.kim@...com>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v7 10/11] mm,page_ext: Derive the node from the pfn

page_ext is the only user of 'status_change_nid', which is set in
online/offline operations, to know to which node we are
adding/removing memory.

Prior to call any notifiers, the memmap is initialized via, which among
other things, sets the node the pages belong to, to all corresponging pages.
This means that there is no need to keep using 'status_change_nid' since
we can derive the node from the pfn.
This will allow us to finally drop 'status_change_nid' from the memory_notify
struct.

Suggested-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Oscar Salvador <osalvador@...e.de>
Reviewed-by: Harry Yoo <harry.yoo@...cle.com>
Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
Acked-by: David Hildenbrand <david@...hat.com>
---
 mm/page_ext.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/mm/page_ext.c b/mm/page_ext.c
index c351fdfe9e9a..d7396a8970e5 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -369,25 +369,15 @@ static void __invalidate_page_ext(unsigned long pfn)
 }
 
 static int __meminit online_page_ext(unsigned long start_pfn,
-				unsigned long nr_pages,
-				int nid)
+				unsigned long nr_pages)
 {
+	int nid = pfn_to_nid(start_pfn);
 	unsigned long start, end, pfn;
 	int fail = 0;
 
 	start = SECTION_ALIGN_DOWN(start_pfn);
 	end = SECTION_ALIGN_UP(start_pfn + nr_pages);
 
-	if (nid == NUMA_NO_NODE) {
-		/*
-		 * In this case, "nid" already exists and contains valid memory.
-		 * "start_pfn" passed to us is a pfn which is an arg for
-		 * online__pages(), and start_pfn should exist.
-		 */
-		nid = pfn_to_nid(start_pfn);
-		VM_BUG_ON(!node_online(nid));
-	}
-
 	for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION)
 		fail = init_section_page_ext(pfn, nid);
 	if (!fail)
@@ -435,8 +425,7 @@ static int __meminit page_ext_callback(struct notifier_block *self,
 
 	switch (action) {
 	case MEM_GOING_ONLINE:
-		ret = online_page_ext(mn->start_pfn,
-				   mn->nr_pages, mn->status_change_nid);
+		ret = online_page_ext(mn->start_pfn, mn->nr_pages);
 		break;
 	case MEM_OFFLINE:
 		offline_page_ext(mn->start_pfn,
-- 
2.49.0