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| author | Hao Li <hao.li@linux.dev> | 2026-03-30 11:57:49 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-04-06 11:13:43 -0700 |
| commit | 2ecbe06abf9bfb2261cd6464a6bc3a3615625402 (patch) | |
| tree | 78e8c3d8480d86be77074563578e8c1586ffbd73 /mm | |
| parent | 0199390a6b92fc21860e1b858abf525c7e73b956 (diff) | |
| download | lwn-2ecbe06abf9bfb2261cd6464a6bc3a3615625402.tar.gz lwn-2ecbe06abf9bfb2261cd6464a6bc3a3615625402.zip | |
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 <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>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/memory_hotplug.c | 20 |
1 files changed, 20 insertions, 0 deletions
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 @@ -2056,6 +2065,17 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages, 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. */ |