linux-kernel - [PATCH v1 0/3] mm/memory_hotplug: use PageOffline() instead of PageReserved() for !ZONE

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Date: Fri,  7 Jun 2024 11:09:35 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	linux-hyperv@...r.kernel.org,
	virtualization@...ts.linux.dev,
	xen-devel@...ts.xenproject.org,
	kasan-dev@...glegroups.com,
	David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Rapoport <rppt@...nel.org>,
	Oscar Salvador <osalvador@...e.de>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	Juergen Gross <jgross@...e.com>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
	Alexander Potapenko <glider@...gle.com>,
	Marco Elver <elver@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: [PATCH v1 0/3] mm/memory_hotplug: use PageOffline() instead of PageReserved() for !ZONE_DEVICE

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@...ux-foundation.org>
Cc: Mike Rapoport <rppt@...nel.org>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>
Cc: Haiyang Zhang <haiyangz@...rosoft.com>
Cc: Wei Liu <wei.liu@...nel.org>
Cc: Dexuan Cui <decui@...rosoft.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Jason Wang <jasowang@...hat.com>
Cc: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: "Eugenio Pérez" <eperezma@...hat.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Cc: Alexander Potapenko <glider@...gle.com>
Cc: Marco Elver <elver@...gle.com>
Cc: Dmitry Vyukov <dvyukov@...gle.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