mm-memory_hotplug-maintain-n_normal_memory-during-hotplug.patch removed from -mm tree

The quilt patch titled
Subject: mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
has been removed from the -mm tree. Its filename was
mm-memory_hotplug-maintain-n_normal_memory-during-hotplug.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Hao Li <[email protected]>
Subject: mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
Date: Mon, 30 Mar 2026 11:57:49 +0800

N_NORMAL_MEMORY is initialized from zone population at boot, but memory hotplug currently only updates N_MEMORY. As a result, a node that gains normal memory via hotplug can remain invisible to users iterating over N_NORMAL_MEMORY, while a node that loses its last normal memory can stay incorrectly marked as such.

The most visible effect is that /sys/devices/system/node/has_normal_memory does not report a node even after that node has gained normal memory via hotplug.

Also, list_lru-based shrinkers can undercount objects on such a node and may skip reclaim on that node entirely, which can lead to a higher memory footprint than expected.

Restore N_NORMAL_MEMORY maintenance directly in online_pages() and offline_pages(). Set the bit when a node that currently lacks normal memory onlines pages into a zone <= ZONE_NORMAL, and clear it when offlining removes the last present pages from zones <= ZONE_NORMAL.

This restores the intended semantics without bringing back the old status_change_nid_normal notifier plumbing which was removed in 8d2882a8edb8.

Current users that benefit include list_lru, zswap, nfsd filecache, hugetlb_cgroup, and has_normal_memory sysfs reporting.

---

 mm/memory_hotplug.c |   20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

@@ -1209,6 +1209,13 @@ int online_pages(unsigned long pfn, unsi
 
 	if (node_arg.nid >= 0)
 		node_set_state(nid, N_MEMORY);
+	/*
+	 * Check whether we are adding normal memory to the node for the first
+	 * time.
+	 */
+	if (!node_state(nid, N_NORMAL_MEMORY) && zone_idx(zone) <= ZONE_NORMAL)
+		node_set_state(nid, N_NORMAL_MEMORY);
+
 	if (need_zonelists_rebuild)
 		build_all_zonelists(NULL);
 

@@ -1908,6 +1915,8 @@ int offline_pages(unsigned long start_pf
 	unsigned long flags;
 	char *reason;
 	int ret;
+	unsigned long normal_pages = 0;
+	enum zone_type zt;
 
 	/*
 	 * {on,off}lining is constrained to full memory sections (or more

@@ -2056,6 +2065,17 @@ int offline_pages(unsigned long start_pf
 	init_per_zone_wmark_min();
 
 	/*
+	 * Check whether this operation removes the last normal memory from
+	 * the node. We do this before clearing N_MEMORY to avoid the possible
+	 * transient "!N_MEMORY && N_NORMAL_MEMORY" state.
+	 */
+	if (zone_idx(zone) <= ZONE_NORMAL) {
+		for (zt = 0; zt <= ZONE_NORMAL; zt++)
+			normal_pages += pgdat->node_zones[zt].present_pages;
+		if (!normal_pages)
+			node_clear_state(node, N_NORMAL_MEMORY);
+	}
+	/*
 	 * Make sure to mark the node as memory-less before rebuilding the zone
 	 * list. Otherwise this node would still appear in the fallback lists.
 	 */

_

Patches currently in -mm which might be from [email protected] are