Re: [PATCH v2 10/26] userfaultfd: wp: add UFFDIO_COPY_MODE_WP

Jerome Glisse
2019-02-21T17:29:26Z

On Tue, Feb 12, 2019 at 10:56:16AM +0800, Peter Xu wrote:
> From: Andrea Arcangeli <aarcange@redhat.com>
>
> This allows UFFDIO_COPY to map pages wrprotected.
>
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>

Minor nitpick down below, but in any case:

Reviewed-by: Jérôme Glisse <jglisse@redhat.com>

> ---
> fs/userfaultfd.c | 5 +++--
> include/linux/userfaultfd_k.h | 2 +-
> include/uapi/linux/userfaultfd.h | 11 +++++-----
> mm/userfaultfd.c | 36 ++++++++++++++++++++++----------
> 4 files changed, 35 insertions(+), 19 deletions(-)
>

[...]

> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> index d59b5a73dfb3..73a208c5c1e7 100644
> --- a/mm/userfaultfd.c
> +++ b/mm/userfaultfd.c
> @@ -25,7 +25,8 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr,
> unsigned long src_addr,
> - struct page **pagep)
> + struct page **pagep,
> + bool wp_copy)
> {
> struct mem_cgroup *memcg;
> pte_t _dst_pte, *dst_pte;
> @@ -71,9 +72,9 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
> if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg, false))
> goto out_release;
>
> - _dst_pte = mk_pte(page, dst_vma->vm_page_prot);
> - if (dst_vma->vm_flags & VM_WRITE)
> - _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
> + _dst_pte = pte_mkdirty(mk_pte(page, dst_vma->vm_page_prot));
> + if (dst_vma->vm_flags & VM_WRITE && !wp_copy)
> + _dst_pte = pte_mkwrite(_dst_pte);

I like parenthesis around around and :) ie:
(dst_vma->vm_flags & VM_WRITE) && !wp_copy

I feel it is easier to read.

[...]

> @@ -416,11 +418,13 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
> if (!(dst_vma->vm_flags & VM_SHARED)) {
> if (!zeropage)
> err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
> - dst_addr, src_addr, page);
> + dst_addr, src_addr, page,
> + wp_copy);
> else
> err = mfill_zeropage_pte(dst_mm, dst_pmd,
> dst_vma, dst_addr);
> } else {
> + VM_WARN_ON(wp_copy); /* WP only available for anon */

Don't you want to return with error here ?

> if (!zeropage)
> err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd,
> dst_vma, dst_addr, …