From 50625744220c101705a989d7c57a6c16e945f3b1 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Fri, 7 Jun 2024 11:09:38 +0200 Subject: mm/memory_hotplug: skip adjust_managed_page_count() for PageOffline() pages when offlining MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We currently have a hack for virtio-mem in place to handle memory offlining with PageOffline pages for which we already adjusted the managed page count. Let's enlighten memory offlining code so we can get rid of that hack, and document the situation. Link: https://lkml.kernel.org/r/20240607090939.89524-4-david@redhat.com Signed-off-by: David Hildenbrand Acked-by: Oscar Salvador Cc: Alexander Potapenko Cc: Dexuan Cui Cc: Dmitry Vyukov Cc: Eugenio Pérez Cc: Haiyang Zhang Cc: Jason Wang Cc: Juergen Gross Cc: "K. Y. Srinivasan" Cc: Marco Elver Cc: Michael S. Tsirkin Cc: Mike Rapoport (IBM) Cc: Oleksandr Tyshchenko Cc: Stefano Stabellini Cc: Wei Liu Cc: Xuan Zhuo Signed-off-by: Andrew Morton --- include/linux/memory_hotplug.h | 4 ++-- include/linux/page-flags.h | 8 ++++++-- 2 files changed, 8 insertions(+), 4 deletions(-) (limited to 'include/linux') diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index 7a9ff464608d..ebe876930e78 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -175,8 +175,8 @@ extern int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages, extern void mhp_deinit_memmap_on_memory(unsigned long pfn, unsigned long nr_pages); extern int online_pages(unsigned long pfn, unsigned long nr_pages, struct zone *zone, struct memory_group *group); -extern void __offline_isolated_pages(unsigned long start_pfn, - unsigned long end_pfn); +extern unsigned long __offline_isolated_pages(unsigned long start_pfn, + unsigned long end_pfn); typedef void (*online_page_callback_t)(struct page *page, unsigned int order); diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index b23772b08cc1..1d441908b726 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -1023,11 +1023,15 @@ PAGE_TYPE_OPS(Buddy, buddy, buddy) * putting them back to the buddy, it can do so via the memory notifier by * decrementing the reference count in MEM_GOING_OFFLINE and incrementing the * reference count in MEM_CANCEL_OFFLINE. When offlining, the PageOffline() - * pages (now with a reference count of zero) are treated like free pages, - * allowing the containing memory block to get offlined. A driver that + * pages (now with a reference count of zero) are treated like free (unmanaged) + * pages, allowing the containing memory block to get offlined. A driver that * relies on this feature is aware that re-onlining the memory block will * require not giving them to the buddy via generic_online_page(). * + * Memory offlining code will not adjust the managed page count for any + * PageOffline() pages, treating them like they were never exposed to the + * buddy using generic_online_page(). + * * There are drivers that mark a page PageOffline() and expect there won't be * any further access to page content. PFN walkers that read content of random * pages should check PageOffline() and synchronize with such drivers using -- cgit v1.2.3