[106/114] mm/huge_memory: remove stale page_trans_huge_mapcount()

Commit Message

Andrew Morton March 25, 2022, 1:13 a.m. UTC

From: David Hildenbrand <[e-mail]>
Subject: mm/huge_memory: remove stale page_trans_huge_mapcount()

All users are gone, let's remove it.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: David Hildenbrand <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>
Cc: Andrea Arcangeli <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Don Dutile <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Jan Kara <[e-mail]>
Cc: Jann Horn <[e-mail]>
Cc: Jason Gunthorpe <[e-mail]>
Cc: John Hubbard <[e-mail]>
Cc: Kirill A. Shutemov <[e-mail]>
Cc: Liang Zhang <[e-mail]>
Cc: Matthew Wilcox (Oracle) <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Nadav Amit <[e-mail]>
Cc: Oleg Nesterov <[e-mail]>
Cc: Peter Xu <[e-mail]>
Cc: Rik van Riel <[e-mail]>
Cc: Roman Gushchin <[e-mail]>
Cc: Shakeel Butt <[e-mail]>
Cc: Yang Shi <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 include/linux/mm.h |    5 ----
 mm/huge_memory.c   |   48 -------------------------------------------
 2 files changed, 53 deletions(-)

Patch

--- a/include/linux/mm.h~mm-huge_memory-remove-stale-page_trans_huge_mapcount
+++ a/include/linux/mm.h
@@ -834,16 +834,11 @@  static inline int total_mapcount(struct
 	return folio_mapcount(page_folio(page));
 }
 
-int page_trans_huge_mapcount(struct page *page);
 #else
 static inline int total_mapcount(struct page *page)
 {
 	return page_mapcount(page);
 }
-static inline int page_trans_huge_mapcount(struct page *page)
-{
-	return page_mapcount(page);
-}
 #endif
 
 static inline struct page *virt_to_head_page(const void *x)
--- a/mm/huge_memory.c~mm-huge_memory-remove-stale-page_trans_huge_mapcount
+++ a/mm/huge_memory.c
@@ -2483,54 +2483,6 @@  static void __split_huge_page(struct pag
 	}
 }
 
-/*
- * This calculates accurately how many mappings a transparent hugepage
- * has (unlike page_mapcount() which isn't fully accurate). This full
- * accuracy is primarily needed to know if copy-on-write faults can
- * reuse the page and change the mapping to read-write instead of
- * copying them. At the same time this returns the total_mapcount too.
- *
- * The function returns the highest mapcount any one of the subpages
- * has. If the return value is one, even if different processes are
- * mapping different subpages of the transparent hugepage, they can
- * all reuse it, because each process is reusing a different subpage.
- *
- * The total_mapcount is instead counting all virtual mappings of the
- * subpages. If the total_mapcount is equal to "one", it tells the
- * caller all mappings belong to the same "mm" and in turn the
- * anon_vma of the transparent hugepage can become the vma->anon_vma
- * local one as no other process may be mapping any of the subpages.
- *
- * It would be more accurate to replace page_mapcount() with
- * page_trans_huge_mapcount(), however we only use
- * page_trans_huge_mapcount() in the copy-on-write faults where we
- * need full accuracy to avoid breaking page pinning, because
- * page_trans_huge_mapcount() is slower than page_mapcount().
- */
-int page_trans_huge_mapcount(struct page *page)
-{
-	int i, ret;
-
-	/* hugetlbfs shouldn't call it */
-	VM_BUG_ON_PAGE(PageHuge(page), page);
-
-	if (likely(!PageTransCompound(page)))
-		return atomic_read(&page->_mapcount) + 1;
-
-	page = compound_head(page);
-
-	ret = 0;
-	for (i = 0; i < thp_nr_pages(page); i++) {
-		int mapcount = atomic_read(&page[i]._mapcount) + 1;
-		ret = max(ret, mapcount);
-	}
-
-	if (PageDoubleMap(page))
-		ret -= 1;
-
-	return ret + compound_mapcount(page);
-}
-
 /* Racy check whether the huge page can be split */
 bool can_split_folio(struct folio *folio, int *pextra_pins)
 {