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-da...@redhat.com/ [2] https://lkml.kernel.org/r/20240607083711.62833-1-da...@redhat.com Cc: Andrew Morton <a...@linux-foundation.org> Cc: Mike Rapoport <r...@kernel.org> Cc: Oscar Salvador <osalva...@suse.de> Cc: "K. Y. Srinivasan" <k...@microsoft.com> Cc: Haiyang Zhang <haiya...@microsoft.com> Cc: Wei Liu <wei....@kernel.org> Cc: Dexuan Cui <de...@microsoft.com> Cc: "Michael S. Tsirkin" <m...@redhat.com> Cc: Jason Wang <jasow...@redhat.com> Cc: Xuan Zhuo <xuanz...@linux.alibaba.com> Cc: "Eugenio Pérez" <epere...@redhat.com> Cc: Juergen Gross <jgr...@suse.com> Cc: Stefano Stabellini <sstabell...@kernel.org> Cc: Oleksandr Tyshchenko <oleksandr_tyshche...@epam.com> Cc: Alexander Potapenko <gli...@google.com> Cc: Marco Elver <el...@google.com> Cc: Dmitry Vyukov <dvyu...@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
