From mboxrd@z Thu Jan  1 00:00:00 1970
From: John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH 1/3] drivers/gpu/drm/via: convert put_page() to
 put_user_page*()
Date: Mon, 22 Jul 2019 11:53:54 -0700
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 <20190722043012.22945-2-jhubbard@nvidia.com> <20190722093355.GB29538@lst.de>
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To: Christoph Hellwig <hch@lst.de>, john.hubbard@gmail.com
Cc: Andrew Morton <akpm@linux-foundation.org>, Alexander Viro <viro@zeniv.linux.org.uk>, =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@intel.com>, Boaz Harrosh <boaz@plexistor.com>, Daniel Vetter <daniel@ffwll.ch>, Dan Williams <dan.j.williams@intel.com>, Dave Chinner <david@fromorbit.com>, David Airlie <airlied@linux.ie>, "David S . Miller" <davem@davemloft.net>, Ilya Dryomov <idryomov@gmail.com>, Jan Kara <jack@suse.cz>, Jason Gunthorpe <jgg@ziepe.ca>, Jens Axboe <axboe@kernel.dk>, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= <jglisse@redhat.com>, Johannes Thumshirn <jthumshirn@suse.de>, Magnus Karlsson <magnus.karlsson@intel.com>, Matthew Wilcox <willy@infradead.org>, Miklos Szeredi <miklos@szeredi.hu>, Ming Lei <ming.lei@redhat.com>, Sage Weil <sage@redhat.com>
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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,
-- 
John Hubbard
NVIDIA