[PATCH v2 0/3] Implement numa node notifier

[Oscar Salvador <osalvador@suse.de>]

v1 -> v2:
  - Remove status_change_nid_normal and the code that
    deals with it (David & Vlastimil)
  - Remove slab_mem_offline_callback (David & Vlastimil)
  - Change the order of canceling the notifiers
    in {online,offline}_pages (Vlastimil)
  - Fix up a couple of whitespaces (Jonathan Cameron)
  - Add RBs-by

Memory notifier is a tool that allow consumers to get notified whenever
memory gets onlined or offlined in the system.
Currently, there are 10 consumers of that, but 5 out of those 10 consumers
are only interested in getting notifications when a numa node changes its
memory state.
That means going from memoryless to memory-aware of vice versa.

Which means that for every {online,offline}_pages operation they get
notified even though the numa node might not have changed its state.

While we are doing this, remove status_change_nid_normal, as the only
current user (slub) does not really need it.
This allows us to further simplify and clean up the code.

The first patch gets rid of status_change_nid_normal in slub.
The second patch implements a numa node notifier that does just that, and have
those consumers register in there, so they get notified only when they are
interested.

The third patch replaces 'status_change_nid{_normal}' fields within
memory_notify with a 'nid', as that is only what we need for memory
notifer and update the only user of it (page_ext).

Consumers that are only interested in numa node states change are:

 - memory-tier
 - slub
 - cpuset
 - hmat
 - cxl

Oscar Salvador (3):
  mm,slub: Do not special case N_NORMAL nodes for slab_nodes
  mm,memory_hotplug: Implement numa node notifier
  mm,memory_hotplug: Rename status_change_nid parameter in memory_notify

 drivers/acpi/numa/hmat.c  |   6 +-
 drivers/base/node.c       |  19 +++++++
 drivers/cxl/core/region.c |  14 ++---
 drivers/cxl/cxl.h         |   4 +-
 include/linux/memory.h    |  38 ++++++++++++-
 kernel/cgroup/cpuset.c    |   2 +-
 mm/memory-tiers.c         |   8 +--
 mm/memory_hotplug.c       | 117 +++++++++++++++++++++-----------------
 mm/page_ext.c             |  12 +---
 mm/slub.c                 |  41 ++-----------
 10 files changed, 145 insertions(+), 116 deletions(-)

-- 
2.49.0