From: Hao Li Date: Mon, 30 Mar 2026 03:57:49 +0000 (+0800) Subject: mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2ecbe06abf9bfb2261cd6464a6bc3a3615625402;p=thirdparty%2Fkernel%2Flinux.git mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug 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. 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 Reviewed-by: Harry Yoo (Oracle) Acked-by: Vlastimil Babka (SUSE) Reviewed-by: Joshua Hahn Acked-by: David Hildenbrand (Arm) Cc: Oscar Salvador Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton --- diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index bc805029da51..05a47953ef21 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1209,6 +1209,13 @@ int online_pages(unsigned long pfn, unsigned long nr_pages, 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_pfn, unsigned long nr_pages, 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 @@ -2055,6 +2064,17 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages, /* reinitialise watermarks and update pcp limits */ 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.