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

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Message-ID: <da9907a9-3150-15c3-fb4e-460d63fc5a1f@nvidia.com>
Date:   Wed, 14 Nov 2018 16:45:57 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Keith Busch <keith.busch@...el.com>
CC:     John Hubbard <john.hubbard@...il.com>,
        Linux MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH v2 1/6] mm/gup: finish consolidating error handling

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