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SubjectRe: [RFC PATCH 2/3] mm: Introduce a new Vmemmap page-type
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On 22.10.20 14:58, Oscar Salvador wrote:
> This patch introduces a new Vmemmap page-type so we can better
> picture and handle those kind of pages.
>
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> ---
> include/linux/mm.h | 6 ++++++
> include/linux/mm_types.h | 5 +++++
> include/linux/page-flags.h | 6 ++++++
> 3 files changed, 17 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ef360fe70aaf..48845f054136 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3126,6 +3126,12 @@ static inline bool debug_guardpage_enabled(void) { return false; }
> static inline bool page_is_guard(struct page *page) { return false; }
> #endif /* CONFIG_DEBUG_PAGEALLOC */
>
> +static __always_inline unsigned long vmemmap_nr_pages(struct page *page)
> +{
> + struct page *head = (struct page *)page->vmemmap_head;
> + return head->vmemmap_pages - (page - head);
> +}
> +
> #if MAX_NUMNODES > 1
> void __init setup_nr_node_ids(void);
> #else
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index ae891c0c55fc..0bb8de4262c3 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -171,6 +171,11 @@ struct page {
> * pmem backed DAX files are mapped.
> */
> };
> + struct { /* Vmemmap pages */
> + unsigned long vmemmap_head;
> + unsigned long vmemmap_sections; /* Number of sections */
> + unsigned long vmemmap_pages; /* Number of pages */
> + };
>
> /** @rcu_head: You can use this to free a page by RCU. */
> struct rcu_head rcu_head;
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 4f6ba9379112..2bad207515fa 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -718,6 +718,7 @@ PAGEFLAG_FALSE(DoubleMap)
> #define PG_kmemcg 0x00000200
> #define PG_table 0x00000400
> #define PG_guard 0x00000800
> +#define PG_vmemmap 0x00001000
>
> #define PageType(page, flag) \
> ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
> @@ -784,6 +785,11 @@ PAGE_TYPE_OPS(Table, table)
> */
> PAGE_TYPE_OPS(Guard, guard)
>
> +/*
> + * Vmemmap pages (see include/linux/memory_hotplug.h).
> + */
> +PAGE_TYPE_OPS(Vmemmap, vmemmap)
> +
> extern bool is_free_buddy_page(struct page *page);
>
> __PAGEFLAG(Isolated, isolated, PF_ANY);
>

I guess this will no longer be strictly necessary to get it flying :)

--
Thanks,

David / dhildenb

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