From: Hugh Dickins <hughd@xxxxxxxxxx> Subject: mm/thp: remap_page() is only needed on anonymous THP THP splitting's unmap_page() only sets TTU_SPLIT_FREEZE when PageAnon, and migration entries are only inserted when TTU_MIGRATION (unused here) or TTU_SPLIT_FREEZE is set: so it's just a waste of time for remap_page() to search for migration entries to remove when !PageAnon. Link: https://lkml.kernel.org/r/f987bc44-f28e-688d-2424-b4722153ed8@xxxxxxxxxx Fixes: baa355fd3314 ("thp: file pages support for split_huge_page()") Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> Reviewed-by: Yang Shi <shy828301@xxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Alistair Popple <apopple@xxxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Jue Wang <juew@xxxxxxxxxx> Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxx> Cc: Peter Xu <peterx@xxxxxxxxxx> Cc: Ralph Campbell <rcampbell@xxxxxxxxxx> Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> Cc: Wang Yugui <wangyugui@xxxxxxxxxxxx> Cc: Zi Yan <ziy@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/huge_memory.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/mm/huge_memory.c~mm-thp-remap_page-is-only-needed-on-anonymous-thp +++ a/mm/huge_memory.c @@ -2307,6 +2307,7 @@ static void unmap_page(struct page *page VM_BUG_ON_PAGE(!PageHead(page), page); + /* If TTU_SPLIT_FREEZE is ever extended to file, update remap_page() */ if (PageAnon(page)) ttu_flags |= TTU_SPLIT_FREEZE; @@ -2318,6 +2319,10 @@ static void unmap_page(struct page *page static void remap_page(struct page *page, unsigned int nr) { int i; + + /* If TTU_SPLIT_FREEZE is ever extended to file, remove this check */ + if (!PageAnon(page)) + return; if (PageTransHuge(page)) { remove_migration_ptes(page, page, true); } else { _
