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Date:   Fri, 4 Aug 2023 23:05:02 +0200
From:   Simon Horman <horms@kernel.org>
To:     "huangjie.albert" <huangjie.albert@bytedance.com>
Cc:     davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
        pabeni@redhat.com, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>,
        Magnus Karlsson <magnus.karlsson@intel.com>,
        Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
        Pavel Begunkov <asml.silence@gmail.com>,
        Yunsheng Lin <linyunsheng@huawei.com>,
        Kees Cook <keescook@chromium.org>,
        Richard Gobert <richardbgobert@gmail.com>,
        "open list:NETWORKING DRIVERS" <netdev@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:XDP (eXpress Data Path)" <bpf@vger.kernel.org>
Subject: Re: [RFC Optimizing veth xsk performance 09/10] veth: support zero
 copy for af xdp
Message-ID: <ZM1n/kAXoL3oeprb@vergenet.net>
References: <20230803140441.53596-1-huangjie.albert@bytedance.com>
 <20230803140441.53596-10-huangjie.albert@bytedance.com>
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In-Reply-To: <20230803140441.53596-10-huangjie.albert@bytedance.com>
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On Thu, Aug 03, 2023 at 10:04:35PM +0800, huangjie.albert wrote:

...

> +static struct sk_buff *veth_build_skb_zerocopy(struct net_device *dev, struct xsk_buff_pool *pool,
> +					      struct xdp_desc *desc)
> +{
> +	struct veth_seg_info *seg_info;
> +	struct sk_buff *skb;
> +	struct page *page;
> +	void *hard_start;
> +	u32 len, ts;
> +	void *buffer;
> +	int headroom;
> +	u64 addr;
> +	u32 index;
> +
> +	addr = desc->addr;
> +	len = desc->len;
> +	buffer = xsk_buff_raw_get_data(pool, addr);
> +	ts = pool->unaligned ? len : pool->chunk_size;
> +
> +	headroom = offset_in_page(buffer);
> +
> +	/* offset in umem pool buffer */
> +	addr = buffer - pool->addrs;
> +
> +	/* get the page of the desc */
> +	page = pool->umem->pgs[addr >> PAGE_SHIFT];
> +
> +	/* in order to avoid to get freed by kfree_skb */
> +	get_page(page);
> +
> +	hard_start = page_to_virt(page);
> +
> +	skb = veth_build_skb(hard_start, headroom, len, ts);
> +	seg_info = (struct veth_seg_info *)kmalloc(struct_size(seg_info, desc, MAX_SKB_FRAGS), GFP_KERNEL);

There is no need to explicitly case the return value of kmalloc,
as it returns void *.

	seg_info = kmalloc(struct_size(seg_info, desc, MAX_SKB_FRAGS),
			   GFP_KERNEL);

...