+ mm-memory_hotplug-maintain-n_normal_memory-during-hotplug.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-memory_hotplug-maintain-n_normal_memory-during-hotplug.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory_hotplug-maintain-n_normal_memory-during-hotplug.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Hao Li <hao.li@linux.dev>
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.

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.

Link: https://lkml.kernel.org/r/20260330035941.518186-1-hao.li@linux.dev
Fixes: 8d2882a8edb8 ("mm,memory_hotplug: remove status_change_nid_normal and update documentation")
Signed-off-by: Hao Li <hao.li@linux.dev>
Reviewed-by: Harry Yoo (Oracle) <harry@kernel.org>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

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

--- a/mm/memory_hotplug.c~mm-memory_hotplug-maintain-n_normal_memory-during-hotplug
+++ a/mm/memory_hotplug.c
@@ -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 hao.li@linux.dev are

mm-memory_hotplug-maintain-n_normal_memory-during-hotplug.patch