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From:   Christoph Hellwig <hch@lst.de>
To:     john.hubbard@gmail.com
Cc:     Andrew Morton <akpm@linux-foundation.org>,
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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.