From 0ccf7f168e17bb7eb5a322397ba5a841f4fbaccb Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Thu, 11 Aug 2022 12:13:28 -0400 Subject: mm/thp: carry over dirty bit when thp splits on pmd Carry over the dirty bit from pmd to pte when a huge pmd splits. It shouldn't be a correctness issue since when pmd_dirty() we'll have the page marked dirty anyway, however having dirty bit carried over helps the next initial writes of split ptes on some archs like x86. Link: https://lkml.kernel.org/r/20220811161331.37055-5-peterx@redhat.com Signed-off-by: Peter Xu Reviewed-by: Huang Ying Cc: Alistair Popple Cc: Andi Kleen Cc: Andrea Arcangeli Cc: David Hildenbrand Cc: Hugh Dickins Cc: "Kirill A . Shutemov" Cc: Minchan Kim Cc: Nadav Amit Cc: Vlastimil Babka Cc: Dave Hansen Signed-off-by: Andrew Morton --- mm/huge_memory.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 7bf2299cb24b..b4666774abf0 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2037,7 +2037,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, pgtable_t pgtable; pmd_t old_pmd, _pmd; bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; - bool anon_exclusive = false; + bool anon_exclusive = false, dirty = false; unsigned long addr; int i; @@ -2126,8 +2126,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, uffd_wp = pmd_swp_uffd_wp(old_pmd); } else { page = pmd_page(old_pmd); - if (pmd_dirty(old_pmd)) + if (pmd_dirty(old_pmd)) { + dirty = true; SetPageDirty(page); + } write = pmd_write(old_pmd); young = pmd_young(old_pmd); soft_dirty = pmd_soft_dirty(old_pmd); @@ -2195,6 +2197,9 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, entry = pte_wrprotect(entry); if (!young) entry = pte_mkold(entry); + /* NOTE: this may set soft-dirty too on some archs */ + if (dirty) + entry = pte_mkdirty(entry); if (soft_dirty) entry = pte_mksoft_dirty(entry); if (uffd_wp) -- cgit v1.2.3