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Date:   Mon, 22 Jul 2019 11:33:55 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     john.hubbard@gmail.com
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= <bjorn.topel@intel.com>,
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        Christoph Hellwig <hch@lst.de>,
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        Dan Williams <dan.j.williams@intel.com>,
        Dave Chinner <david@fromorbit.com>,
        David Airlie <airlied@linux.ie>,
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        Jason Gunthorpe <jgg@ziepe.ca>, Jens Axboe <axboe@kernel.dk>,
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        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>,
        Santosh Shilimkar <santosh.shilimkar@oracle.com>,
        Yan Zheng <zyan@redhat.com>, netdev@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linux-mm@kvack.org,
        linux-rdma@vger.kernel.org, bpf@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH 1/3] drivers/gpu/drm/via: convert put_page() to
 put_user_page*()
Message-ID: <20190722093355.GB29538@lst.de>
References: <20190722043012.22945-1-jhubbard@nvidia.com> <20190722043012.22945-2-jhubbard@nvidia.com>
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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.