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. Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> --- mm/huge_memory.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 0611b2fd145a..e8e78d1bac5f 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2005,7 +2005,7 @@ 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; @@ -2098,6 +2098,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, SetPageDirty(page); write = pmd_write(old_pmd); young = pmd_young(old_pmd); + dirty = pmd_dirty(old_pmd); soft_dirty = pmd_soft_dirty(old_pmd); uffd_wp = pmd_uffd_wp(old_pmd); @@ -2161,6 +2162,9 @@ 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) -- 2.32.0
