在 2016/1/2 6:27, Arnd Bergmann 写道:
> gcc fails to see that the use of the 'last_offset' variable
> in hns_nic_reuse_page() is used correctly and issues a bogus
> warning:
>
> drivers/net/ethernet/hisilicon/hns/hns_enet.c: In function
> 'hns_nic_reuse_page':
> drivers/net/ethernet/hisilicon/hns/hns_enet.c:541:6: warning: 'last_offset'
> may be used uninitialized in this function [-Wmaybe-uninitialized]
>
> This simplifies the function to make it more obvious what is
> going on to both readers and compilers, which makes the warning
> go away.
>
Hi Arnd,
This patch is fine to me.
Many thanks,
Yisen
> Signed-off-by: Arnd Bergmann <a...@arndb.de>
> ---
> Compile-tested only, and complex enough that this requires a proper
> review and testing before it gets apply. Please have a look at this.
>
> diff --git a/drivers/net/ethernet/hisilicon/hns/hns_enet.c
> b/drivers/net/ethernet/hisilicon/hns/hns_enet.c
> index 5a81dafd725e..0e30846a24f8 100644
> --- a/drivers/net/ethernet/hisilicon/hns/hns_enet.c
> +++ b/drivers/net/ethernet/hisilicon/hns/hns_enet.c
> @@ -499,50 +499,47 @@ static void hns_nic_reuse_page(struct sk_buff *skb, int
> i,
> struct hnae_desc *desc;
> int truesize, size;
> int last_offset;
> + bool twobufs;
> +
> + twobufs = ((PAGE_SIZE < 8192) && hnae_buf_size(ring) ==
> HNS_BUFFER_SIZE_2048);
>
> desc = &ring->desc[ring->next_to_clean];
> size = le16_to_cpu(desc->rx.size);
>
> -#if (PAGE_SIZE < 8192)
> - if (hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048) {
> + if (twobufs) {
> truesize = hnae_buf_size(ring);
> } else {
> truesize = ALIGN(size, L1_CACHE_BYTES);
> last_offset = hnae_page_size(ring) - hnae_buf_size(ring);
> }
>
> -#else
> - truesize = ALIGN(size, L1_CACHE_BYTES);
> - last_offset = hnae_page_size(ring) - hnae_buf_size(ring);
> -#endif
> -
> skb_add_rx_frag(skb, i, desc_cb->priv, desc_cb->page_offset + pull_len,
> size - pull_len, truesize - pull_len);
>
> /* avoid re-using remote pages,flag default unreuse */
> - if (likely(page_to_nid(desc_cb->priv) == numa_node_id())) {
> -#if (PAGE_SIZE < 8192)
> - if (hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048) {
> - /* if we are only owner of page we can reuse it */
> - if (likely(page_count(desc_cb->priv) == 1)) {
> - /* flip page offset to other buffer */
> - desc_cb->page_offset ^= truesize;
> -
> - desc_cb->reuse_flag = 1;
> - /* bump ref count on page before it is given*/
> - get_page(desc_cb->priv);
> - }
> - return;
> - }
> -#endif
> - /* move offset up to the next cache line */
> - desc_cb->page_offset += truesize;
> + if (unlikely(page_to_nid(desc_cb->priv) != numa_node_id()))
> + return;
> +
> + if (twobufs) {
> + /* if we are only owner of page we can reuse it */
> + if (likely(page_count(desc_cb->priv) == 1)) {
> + /* flip page offset to other buffer */
> + desc_cb->page_offset ^= truesize;
>
> - if (desc_cb->page_offset <= last_offset) {
> desc_cb->reuse_flag = 1;
> /* bump ref count on page before it is given*/
> get_page(desc_cb->priv);
> }
> + return;
> + }
> +
> + /* move offset up to the next cache line */
> + desc_cb->page_offset += truesize;
> +
> + if (desc_cb->page_offset <= last_offset) {
> + desc_cb->reuse_flag = 1;
> + /* bump ref count on page before it is given*/
> + get_page(desc_cb->priv);
> }
> }
>
>
>
> .
>
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