From 838691a1c0ec44739db558834e6954d62577d6b8 Mon Sep 17 00:00:00 2001 From: Muchun Song Date: Tue, 28 Jun 2022 17:22:34 +0800 Subject: mm: hugetlb_vmemmap: move code comments to vmemmap_dedup.rst All the comments which explains how HVO works are moved to vmemmap_dedup.rst since commit 4917f55b4ef9 ("mm/sparse-vmemmap: improve memory savings for compound devmaps") except some comments above page_fixed_fake_head(). This commit moves those comments to vmemmap_dedup.rst and improve vmemmap_dedup.rst as well. Link: https://lkml.kernel.org/r/20220628092235.91270-8-songmuchun@bytedance.com Signed-off-by: Muchun Song Cc: Anshuman Khandual Cc: Catalin Marinas Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Mike Kravetz Cc: Oscar Salvador Cc: Will Deacon Cc: Xiongchun Duan Signed-off-by: Andrew Morton --- include/linux/page-flags.h | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) (limited to 'include/linux') diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 78ed46ae6ee5..465ff35a8c00 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -208,19 +208,8 @@ enum pageflags { DECLARE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key); /* - * If HVO is enabled, the head vmemmap page frame is reused and all of the tail - * vmemmap addresses map to the head vmemmap page frame (furture details can - * refer to the figure at the head of the mm/hugetlb_vmemmap.c). In other - * words, there are more than one page struct with PG_head associated with each - * HugeTLB page. We __know__ that there is only one head page struct, the tail - * page structs with PG_head are fake head page structs. We need an approach - * to distinguish between those two different types of page structs so that - * compound_head() can return the real head page struct when the parameter is - * the tail page struct but with PG_head. - * - * The page_fixed_fake_head() returns the real head page struct if the @page is - * fake page head, otherwise, returns @page which can either be a true page - * head or tail. + * Return the real head page struct iff the @page is a fake head page, otherwise + * return the @page itself. See Documentation/mm/vmemmap_dedup.rst. */ static __always_inline const struct page *page_fixed_fake_head(const struct page *page) { -- cgit v1.2.3