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

John Hubbard
2018-11-15T00:46:02Z

On 11/12/18 8:14 AM, Dan Williams wrote:
> On Mon, Nov 12, 2018 at 7:45 AM Keith Busch <keith.busch@intel.com> wrote:
>>
>> On Sat, Nov 10, 2018 at 12:50:36AM -0800, john.hubbard@gmail.com wrote:
>>> From: John Hubbard <jhubbard@nvidia.com>
>>>
>>> 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@intel.com>
>>> Cc: Dan Williams <dan.j.williams@intel.com>
>>> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>>> Cc: Dave Hansen <dave.hansen@intel.com>
>>> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
>>> ---
>>> 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