netdev - Re: [PATCH 1/3] drivers/gpu/drm/via: convert put_page() to put_user

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Date:   Mon, 22 Jul 2019 12:07:22 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Christoph Hellwig <hch@....de>, john.hubbard@...il.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Björn Töpel <bjorn.topel@...el.com>,
        Boaz Harrosh <boaz@...xistor.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        David Airlie <airlied@...ux.ie>,
        "David S . Miller" <davem@...emloft.net>,
        Ilya Dryomov <idryomov@...il.com>, Jan Kara <jack@...e.cz>,
        Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>,
        Jérôme Glisse <jglisse@...hat.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Ming Lei <ming.lei@...hat.com>, Sage Weil <sage@...hat.com>,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        Yan Zheng <zyan@...hat.com>, netdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-mm@...ck.org,
        linux-rdma@...r.kernel.org, bpf@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] drivers/gpu/drm/via: convert put_page() to
 put_user_page*()

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@...il.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 };
?