Re: [PATCH v2 1/6] mm/gup: finish consolidating error handling

[John Hubbard]

On 11/12/18 8:14 AM, Dan Williams wrote:
> On Mon, Nov 12, 2018 at 7:45 AM Keith Busch <keith.busch@xxxxxxxxx> wrote:
> > On Sat, Nov 10, 2018 at 12:50:36AM -0800, john.hubbard@xxxxxxxxx wrote:
> > > From: John Hubbard <jhubbard@xxxxxxxxxx>
> > >
> > > An upcoming patch wants to be able to operate on each page that
> > > get_user_pages has retrieved. In order to do that, it's best to
> > > have a common exit point from the routine. Most of this has been
> > > taken care of by commit df06b37ffe5a4 ("mm/gup: cache dev_pagemap while
> > > pinning pages"), but there was one case remaining.
> > >
> > > Also, there was still an unnecessary shadow declaration (with a
> > > different type) of the "ret" variable, which this commit removes.
> > >
> > > Cc: Keith Busch <keith.busch@xxxxxxxxx>
> > > Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> > > Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > > Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
> > > Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
> > > ---
> > >   mm/gup.c | 3 +--
> > >   1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/mm/gup.c b/mm/gup.c
> > > index f76e77a2d34b..55a41dee0340 100644
> > > --- a/mm/gup.c
> > > +++ b/mm/gup.c
> > > @@ -696,12 +696,11 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> > >                if (!vma || start >= vma->vm_end) {
> > >                        vma = find_extend_vma(mm, start);
> > >                        if (!vma && in_gate_area(mm, start)) {
> > > -                             int ret;
> > >                                ret = get_gate_page(mm, start & PAGE_MASK,
> > >                                                gup_flags, &vma,
> > >                                                pages ? &pages[i] : NULL);
> > >                                if (ret)
> > > -                                     return i ? : ret;
> > > +                                     goto out;
> > >                                ctx.page_mask = 0;
> > >                                goto next_page;
> > >                        }
> >
> > This also fixes a potentially leaked dev_pagemap reference count if a
> > failure occurs when an iteration crosses a vma boundary. I don't think
> > it's normal to have different vma's on a users mapped zone device memory,
> > but good to fix anyway.
>
> Does not sound abnormal to me, we should promote this as a fix for the
> current cycle with an updated changelog.

Andrew, should I send this patch separately, or do you have what you 
need already?

thanks,
--
John Hubbard
NVIDIA