From: Nadav Amit <namit@xxxxxxxxxx> When using userfaultfd write-(un)protect ioctl, try to change the PTE to be writable. This would save a page-fault afterwards. Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Peter Xu <peterx@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Yu Zhao <yuzhao@xxxxxxxxxx> Cc: Nick Piggin <npiggin@xxxxxxxxx> Signed-off-by: Nadav Amit <namit@xxxxxxxxxx> --- mm/userfaultfd.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e0492f5f06a0..6013b217e9f3 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -799,6 +799,8 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, cp_flags = enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE; if (uffd_flags & (UFFD_FLAGS_ACCESS_LIKELY|UFFD_FLAGS_WRITE_LIKELY)) cp_flags |= MM_CP_WILL_NEED; + if (!enable_wp && (uffd_flags & UFFD_FLAGS_WRITE_LIKELY)) + cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; tlb_gather_mmu(&tlb, dst_mm); change_protection(&tlb, dst_vma, start, start + len, newprot, cp_flags); -- 2.25.1
