Akihiko Odaki wrote:
> On 2025/01/20 20:24, Willem de Bruijn wrote:
> > Akihiko Odaki wrote:
> >> hdr_len is repeatedly used so keep it in a local variable.
> >>
> >> Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com>
> >> ---
> >> drivers/net/tap.c | 17 +++++++----------
> >> 1 file changed, 7 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> >> index
> >> 061c2f27dfc83f5e6d0bea4da0e845cc429b1fd8..7ee2e9ee2a89fd539b087496b92d2f6198266f44
> >> 100644
> >> --- a/drivers/net/tap.c
> >> +++ b/drivers/net/tap.c
> >> @@ -645,6 +645,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void
> >> *msg_control,
> >> int err;
> >> struct virtio_net_hdr vnet_hdr = { 0 };
> >> int vnet_hdr_len = 0;
> >> + int hdr_len = 0;
> >> int copylen = 0;
> >> int depth;
> >> bool zerocopy = false;
> >> @@ -672,6 +673,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void
> >> *msg_control,
> >> err = -EINVAL;
> >> if (tap16_to_cpu(q, vnet_hdr.hdr_len) > iov_iter_count(from))
> >> goto err;
> >> + hdr_len = tap16_to_cpu(q, vnet_hdr.hdr_len);
> >> }
> >>
> >> len = iov_iter_count(from);
> >> @@ -683,11 +685,8 @@ 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;
> >> linear = copylen;
> >> i = *from;
> >> @@ -698,11 +697,9 @@ 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;
> >
> > Similar to previous patch, I don't think this patch is significant
> > enough to warrant the code churn.
>
> The following patch will require replacing
> tap16_to_cpu(q, vnet_hdr.hdr_len)
> with
> tap16_to_cpu(q->flags, vnet_hdr.hdr_len)
>
> It will make some lines a bit too long. Calling tap16_to_cpu() at
> multiple places is also not good to keep the vnet implementation unified
> as the function inspects vnet_hdr.
>
> This patch is independently too trivial, but I think it is a worthwhile
> cleanup combined with the following patch.
Ok. I see what you mean.
