Re: [PATCH net-next v5 6/7] tap: Keep hdr_len in tap_get_user()

[Willem de Bruijn]

Akihiko Odaki wrote:
> hdr_len is repeatedly used so keep it in a local variable.
> 
> Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com>

> @@ -682,11 +683,8 @@ static ssize_t tap_get_user(struct tap_queue *q, void 
> *msg_control,
>       if (msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
>               struct iov_iter i;
>  
> -             copylen = vnet_hdr.hdr_len ?
> -                     tap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;
> -             if (copylen > good_linear)
> -                     copylen = good_linear;
> -             else if (copylen < ETH_HLEN)
> +             copylen = min(hdr_len ? hdr_len : GOODCOPY_LEN, good_linear);
> +             if (copylen < ETH_HLEN)
>                       copylen = ETH_HLEN;

I forgot earlier: this can also use single line statement

    copylen = max(copylen, ETH_HLEN);

And perhaps easiest to follow is

    copylen = hdr_len ?: GOODCOPY_LEN;
    copylen = min(copylen, good_linear);
    copylen = max(copylen, ETH_HLEN);

>               linear = copylen;
>               i = *from;
> @@ -697,11 +695,9 @@ static ssize_t tap_get_user(struct tap_queue *q, void 
> *msg_control,
>  
>       if (!zerocopy) {
>               copylen = len;
> -             linear = tap16_to_cpu(q, vnet_hdr.hdr_len);
> -             if (linear > good_linear)
> -                     linear = good_linear;
> -             else if (linear < ETH_HLEN)
> -                     linear = ETH_HLEN;
> +             linear = min(hdr_len, good_linear);
> +             if (copylen < ETH_HLEN)
> +                     copylen = ETH_HLEN;

Same