linux-kernel - Re: [PATCH] drm/via: use get_user_pages

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Date:   Fri, 6 Jan 2017 07:09:36 +0000
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     linux-mm <linux-mm@...ck.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] drm/via: use get_user_pages_unlocked()

On 3 January 2017 at 20:23, Lorenzo Stoakes <lstoakes@...il.com> wrote:
> Hi All,
>
> Just a gentle ping on this one :)
>
> Cheers, Lorenzo
>
> On 1 November 2016 at 19:43, Lorenzo Stoakes <lstoakes@...il.com> wrote:
>> Moving from get_user_pages() to get_user_pages_unlocked() simplifies the code
>> and takes advantage of VM_FAULT_RETRY functionality when faulting in pages.
>>
>> Signed-off-by: Lorenzo Stoakes <lstoakes@...il.com>
>> ---
>>  drivers/gpu/drm/via/via_dmablit.c | 10 +++-------
>>  1 file changed, 3 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/via/via_dmablit.c b/drivers/gpu/drm/via/via_dmablit.c
>> index 1a3ad76..98aae98 100644
>> --- a/drivers/gpu/drm/via/via_dmablit.c
>> +++ b/drivers/gpu/drm/via/via_dmablit.c
>> @@ -238,13 +238,9 @@ via_lock_all_dma_pages(drm_via_sg_info_t *vsg,  drm_via_dmablit_t *xfer)
>>         vsg->pages = vzalloc(sizeof(struct page *) * vsg->num_pages);
>>         if (NULL == vsg->pages)
>>                 return -ENOMEM;
>> -       down_read(&current->mm->mmap_sem);
>> -       ret = get_user_pages((unsigned long)xfer->mem_addr,
>> -                            vsg->num_pages,
>> -                            (vsg->direction == DMA_FROM_DEVICE) ? FOLL_WRITE : 0,
>> -                            vsg->pages, NULL);
>> -
>> -       up_read(&current->mm->mmap_sem);
>> +       ret = get_user_pages_unlocked((unsigned long)xfer->mem_addr,
>> +                       vsg->num_pages, vsg->pages,
>> +                       (vsg->direction == DMA_FROM_DEVICE) ? FOLL_WRITE : 0);
>>         if (ret != vsg->num_pages) {
>>                 if (ret < 0)
>>                         return ret;
>> --
>> 2.10.2
>>

Adding Andrew, as this may be another less active corner of the corner, thanks!

-- 
Lorenzo Stoakes
https://ljs.io