thp: do not mark zero-page pmd write-protected explicitly

Zero pages can be used only in anonymous mappings, which never have
writable vma->vm_page_prot: see protection_map in mm/mmap.c and __PX1X
definitions.

Let's drop redundant pmd_wrprotect() in set_huge_zero_page().

Signed-off-by: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index de98415..5b2c687 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -784,7 +784,6 @@ static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
        if (!pmd_none(*pmd))
                return false;
        entry = mk_pmd(zero_page, vma->vm_page_prot);
-       entry = pmd_wrprotect(entry);
        entry = pmd_mkhuge(entry);
        pgtable_trans_huge_deposit(mm, pmd, pgtable);
        set_pmd_at(mm, haddr, pmd, entry);