[PATCH v1 0/3] mm/memory_hotplug: use PageOffline() instead of PageReserved() for !ZONE_DEVICE

[David Hildenbrand <david@redhat.com>]

This can be a considered a long-overdue follow-up to some parts of [1].
The patches are based on [2], but they are not strictly required -- just
makes it clearer why we can use adjust_managed_page_count() for memory
hotplug without going into details about highmem.

We stop initializing pages with PageReserved() in memory hotplug code --
except when dealing with ZONE_DEVICE for now. Instead, we use
PageOffline(): all pages are initialized to PageOffline() when onlining a
memory section, and only the ones actually getting exposed to the
system/page allocator will get PageOffline cleared.

This way, we enlighten memory hotplug more about PageOffline() pages and
can cleanup some hacks we have in virtio-mem code.

What about ZONE_DEVICE? PageOffline() is wrong, but we might just stop
using PageReserved() for them later by simply checking for
is_zone_device_page() at suitable places. That will be a separate patch
set / proposal.

This primarily affects virtio-mem, HV-balloon and XEN balloon. I only
briefly tested with virtio-mem, which benefits most from these cleanups.

[1] https://lore.kernel.org/all/20191024120938.11237-1-david@redhat.com/
[2] https://lkml.kernel.org/r/20240607083711.62833-1-david@redhat.com

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: "Eugenio Pérez" <eperezma@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>

David Hildenbrand (3):
  mm: pass meminit_context to __free_pages_core()
  mm/memory_hotplug: initialize memmap of !ZONE_DEVICE with
    PageOffline() instead of PageReserved()
  mm/memory_hotplug: skip adjust_managed_page_count() for PageOffline()
    pages when offlining

 drivers/hv/hv_balloon.c        |  5 ++--
 drivers/virtio/virtio_mem.c    | 29 +++++++++---------
 drivers/xen/balloon.c          |  9 ++++--
 include/linux/memory_hotplug.h |  4 +--
 include/linux/page-flags.h     | 20 +++++++------
 mm/internal.h                  |  3 +-
 mm/kmsan/init.c                |  2 +-
 mm/memory_hotplug.c            | 31 +++++++++----------
 mm/mm_init.c                   | 14 ++++++---
 mm/page_alloc.c                | 55 +++++++++++++++++++++++++++-------
 10 files changed, 108 insertions(+), 64 deletions(-)


base-commit: 19b8422c5bd56fb5e7085995801c6543a98bda1f
prerequisite-patch-id: ca280eafd2732d7912e0c5249dc0df9ecbef19ca
prerequisite-patch-id: 8f43ebc81fdf7b9b665b57614e9e569535094758
-- 
2.45.1