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Date:   Mon, 22 Jul 2019 11:34:28 +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>,
        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>,
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        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,
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        John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH 2/3] net/xdp: convert put_page() to put_user_page*()
Message-ID: <20190722093428.GC29538@lst.de>
References: <20190722043012.22945-1-jhubbard@nvidia.com> <20190722043012.22945-3-jhubbard@nvidia.com>
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> diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
> index 83de74ca729a..9cbbb96c2a32 100644
> --- a/net/xdp/xdp_umem.c
> +++ b/net/xdp/xdp_umem.c
> @@ -171,8 +171,7 @@ static void xdp_umem_unpin_pages(struct xdp_umem *umem)
>  	for (i = 0; i < umem->npgs; i++) {
>  		struct page *page = umem->pgs[i];
>  
> -		set_page_dirty_lock(page);
> -		put_page(page);
> +		put_user_pages_dirty_lock(&page, 1);

Same here, we really should avoid the need for the loop here and
do the looping inside the helper.