[1/3] drivers/gpu/drm/via: convert put_page() to put_user_page*()

From: John Hubbard <jhubbard@nvidia.com>

For pages that were retained via get_user_pages*(), release those pages
via the new put_user_page*() routines, instead of via put_page() or
release_pages().

This is part a tree-wide conversion, as described in commit fc1d8e7cca2d
("mm: introduce put_user_page*(), placeholder versions").

Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/drm/via/via_dmablit.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

On Sun, Jul 21, 2019 at 09:30:10PM -0700, john.hubbard@gmail.com wrote:
>  		for (i = 0; i < vsg->num_pages; ++i) {
>  			if (NULL != (page = vsg->pages[i])) {
>  				if (!PageReserved(page) && (DMA_FROM_DEVICE == vsg->direction))
> -					SetPageDirty(page);
> -				put_page(page);
> +					put_user_pages_dirty(&page, 1);
> +				else
> +					put_user_page(page);
>  			}

Can't just pass a dirty argument to put_user_pages?  Also do we really
need a separate put_user_page for the single page case?
put_user_pages_dirty?

Also the PageReserved check looks bogus, as I can't see how a reserved
page can end up here.  So IMHO the above snippled should really look
something like this:

	put_user_pages(vsg->pages[i], vsg->num_pages,
			vsg->direction == DMA_FROM_DEVICE);

in the end.

On 7/22/19 2:33 AM, Christoph Hellwig wrote:
> On Sun, Jul 21, 2019 at 09:30:10PM -0700, john.hubbard@gmail.com wrote:
>>  		for (i = 0; i < vsg->num_pages; ++i) {
>>  			if (NULL != (page = vsg->pages[i])) {
>>  				if (!PageReserved(page) && (DMA_FROM_DEVICE == vsg->direction))
>> -					SetPageDirty(page);
>> -				put_page(page);
>> +					put_user_pages_dirty(&page, 1);
>> +				else
>> +					put_user_page(page);
>>  			}
> 
> Can't just pass a dirty argument to put_user_pages?  Also do we really

Yes, and in fact that would help a lot more than the single page case,
which is really just cosmetic after all.

> need a separate put_user_page for the single page case?
> put_user_pages_dirty?

Not really. I'm still zeroing in on the ideal API for all these call sites,
and I agree that the approach below is cleaner.

> 
> Also the PageReserved check looks bogus, as I can't see how a reserved
> page can end up here.  So IMHO the above snippled should really look
> something like this:
> 
> 	put_user_pages(vsg->pages[i], vsg->num_pages,
> 			vsg->direction == DMA_FROM_DEVICE);
> 
> in the end.
> 

Agreed.

thanks,

On Mon, Jul 22, 2019 at 11:53:54AM -0700, John Hubbard wrote:
> On 7/22/19 2:33 AM, Christoph Hellwig wrote:
> > On Sun, Jul 21, 2019 at 09:30:10PM -0700, john.hubbard@gmail.com wrote:
> >>  		for (i = 0; i < vsg->num_pages; ++i) {
> >>  			if (NULL != (page = vsg->pages[i])) {
> >>  				if (!PageReserved(page) && (DMA_FROM_DEVICE == vsg->direction))
> >> -					SetPageDirty(page);
> >> -				put_page(page);
> >> +					put_user_pages_dirty(&page, 1);
> >> +				else
> >> +					put_user_page(page);
> >>  			}
> > 
> > Can't just pass a dirty argument to put_user_pages?  Also do we really
> 
> Yes, and in fact that would help a lot more than the single page case,
> which is really just cosmetic after all.
> 
> > need a separate put_user_page for the single page case?
> > put_user_pages_dirty?
> 
> Not really. I'm still zeroing in on the ideal API for all these call sites,
> and I agree that the approach below is cleaner.

so enum { CLEAN = 0, DIRTY = 1, LOCK = 2, DIRTY_LOCK = 3 };
?

On 7/22/19 12:07 PM, Matthew Wilcox wrote:
> On Mon, Jul 22, 2019 at 11:53:54AM -0700, John Hubbard wrote:
>> On 7/22/19 2:33 AM, Christoph Hellwig wrote:
>>> On Sun, Jul 21, 2019 at 09:30:10PM -0700, john.hubbard@gmail.com wrote:
>>>>  		for (i = 0; i < vsg->num_pages; ++i) {
>>>>  			if (NULL != (page = vsg->pages[i])) {
>>>>  				if (!PageReserved(page) && (DMA_FROM_DEVICE == vsg->direction))
>>>> -					SetPageDirty(page);
>>>> -				put_page(page);
>>>> +					put_user_pages_dirty(&page, 1);
>>>> +				else
>>>> +					put_user_page(page);
>>>>  			}
>>>
>>> Can't just pass a dirty argument to put_user_pages?  Also do we really
>>
>> Yes, and in fact that would help a lot more than the single page case,
>> which is really just cosmetic after all.
>>
>>> need a separate put_user_page for the single page case?
>>> put_user_pages_dirty?
>>
>> Not really. I'm still zeroing in on the ideal API for all these call sites,
>> and I agree that the approach below is cleaner.
> 
> so enum { CLEAN = 0, DIRTY = 1, LOCK = 2, DIRTY_LOCK = 3 };
> ?
> 

Sure. In fact, I just applied something similar to bio_release_pages()
locally, in order to reconcile Christoph's and Jerome's approaches 
(they each needed to add a bool arg), so I'm all about the enums in the
arg lists. :)

I'm going to post that one shortly, let's see how it goes over. heh.

thanks,