linux-kernel - [PATCH v6 10/10] mm,memory_hotplug: Drop status_change_nid parameter from memory

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Message-ID: <20250609092149.312114-11-osalvador@suse.de>
Date: Mon,  9 Jun 2025 11:21:47 +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>,
	Joshua Hahn <joshua.hahnjy@...il.com>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v6 10/10] mm,memory_hotplug: Drop status_change_nid parameter from memory_notify

The 'status_change_nid' field was used to track changes in the memory
state of a numa node, but that funcionality has been decoupled from
memory_notify and moved to node_notify.
Current consumers of memory_notify are only interested in which node the
memory we are adding belongs to, but we can derive the nid from the pfn
because we call move_pfn_range_to_zone(), which sets the node in the page
via __init_single_page(), before calling in any memory notifier.

Drop the 'status_change_nid' parameter from 'memory_notify' struct and update documentation
accordingly.

Suggested-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Harry Yoo <harry.yoo@...cle.com>
Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Oscar Salvador <osalvador@...e.de>
---
 Documentation/core-api/memory-hotplug.rst |  7 -------
 include/linux/memory.h                    |  1 -
 mm/memory_hotplug.c                       |  2 --
 mm/page_ext.c                             | 16 +++-------------
 4 files changed, 3 insertions(+), 23 deletions(-)

diff --git a/Documentation/core-api/memory-hotplug.rst b/Documentation/core-api/memory-hotplug.rst
index b19c3be7437d..74897713c4f8 100644
--- a/Documentation/core-api/memory-hotplug.rst
+++ b/Documentation/core-api/memory-hotplug.rst
@@ -59,17 +59,10 @@ The third argument (arg) passes a pointer of struct memory_notify::
 	struct memory_notify {
 		unsigned long start_pfn;
 		unsigned long nr_pages;
-		int status_change_nid;
 	}
 
 - start_pfn is start_pfn of online/offline memory.
 - nr_pages is # of pages of online/offline memory.
-- status_change_nid is set node id when N_MEMORY of nodemask is (will be)
-  set/clear. It means a new(memoryless) node gets new memory by online and a
-  node loses all memory. If this is -1, then nodemask status is not changed.
-
-  If status_changed_nid* >= 0, callback should create/discard structures for the
-  node if necessary.
 
 The callback routine shall return one of the values
 NOTIFY_DONE, NOTIFY_OK, NOTIFY_BAD, NOTIFY_STOP
diff --git a/include/linux/memory.h b/include/linux/memory.h
index a9ccd6579422..de8b898ada3f 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -109,7 +109,6 @@ struct memory_notify {
 	unsigned long altmap_nr_pages;
 	unsigned long start_pfn;
 	unsigned long nr_pages;
-	int status_change_nid;
 };
 
 struct notifier_block;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 0550f3061fc4..07d7bdb65761 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1186,7 +1186,6 @@ int online_pages(unsigned long pfn, unsigned long nr_pages,
 
 	mem_arg.start_pfn = pfn;
 	mem_arg.nr_pages = nr_pages;
-	mem_arg.status_change_nid = node_arg.nid;
 	cancel_mem_notifier_on_err = true;
 	ret = memory_notify(MEM_GOING_ONLINE, &mem_arg);
 	ret = notifier_to_errno(ret);
@@ -1987,7 +1986,6 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages,
 
 	mem_arg.start_pfn = start_pfn;
 	mem_arg.nr_pages = nr_pages;
-	mem_arg.status_change_nid = node_arg.nid;
 	cancel_mem_notifier_on_err = true;
 	ret = memory_notify(MEM_GOING_OFFLINE, &mem_arg);
 	ret = notifier_to_errno(ret);
diff --git a/mm/page_ext.c b/mm/page_ext.c
index c351fdfe9e9a..f08353802fa6 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)
 {
 	unsigned long start, end, pfn;
 	int fail = 0;
+	int nid = pfn_to_nid(start_pfn);
 
 	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)
@@ -436,7 +426,7 @@ 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);
+				   mn->nr_pages);
 		break;
 	case MEM_OFFLINE:
 		offline_page_ext(mn->start_pfn,
-- 
2.49.0