Re: [PATCH net-next 1/3] tuntap: reorganize tun_msg_ctl usage

[Prashant Bhole <prashantbhole.linux@xxxxxxxxx>]

Hi Jason,
Thanks for reviewing.

On 10/12/19 4:44 PM, Jason Wang wrote:
> On 2019/10/12 上午9:53, prashantbhole.linux@xxxxxxxxx wrote:
> > From: Prashant Bhole <prashantbhole.linux@xxxxxxxxx>
> >
> > In order to extend the usage of tun_msg_ctl structure, this patch
> > changes the member name from type to cmd. Also following definitions
> > are changed:
> > TUN_MSG_PTR : TUN_CMD_BATCH
> > TUN_MSG_UBUF: TUN_CMD_PACKET
>
>
> Not a native English speaker, but the conversion here looks not as 
> straightforward as it did.
>
> For TUN_MSG_PTR, it means recvmsg() can do receiving from a pointer to 
> either XDP or skb instead of ptr_ring. TUN_CMD_BATCH sounds not related.
>
> For TUN_MSG_UBUF, it means the packet is a zercopy (buffer pointers to 
> userspace). TUN_CMD_PACKET may bring confusion in this case.

Understood. Next time I will come up with better command names,
performance numbers and other changes suggested by you.

Thanks.

> Thanks
>
>
> > Signed-off-by: Prashant Bhole <prashantbhole.linux@xxxxxxxxx>
> > ---
> >   drivers/net/tap.c      | 9 ++++++---
> >   drivers/net/tun.c      | 8 ++++++--
> >   drivers/vhost/net.c    | 4 ++--
> >   include/linux/if_tun.h | 6 +++---
> >   4 files changed, 17 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> > index 3ae70c7e6860..01bd260ce60c 100644
> > --- a/drivers/net/tap.c
> > +++ b/drivers/net/tap.c
> > @@ -1213,9 +1213,10 @@ static int tap_sendmsg(struct socket *sock, 
> > struct msghdr *m,
> >       struct tap_queue *q = container_of(sock, struct tap_queue, sock);
> >       struct tun_msg_ctl *ctl = m->msg_control;
> >       struct xdp_buff *xdp;
> > +    void *ptr = NULL;
> >       int i;
> > -    if (ctl && (ctl->type == TUN_MSG_PTR)) {
> > +    if (ctl && ctl->cmd == TUN_CMD_BATCH) {
> >           for (i = 0; i < ctl->num; i++) {
> >               xdp = &((struct xdp_buff *)ctl->ptr)[i];
> >               tap_get_user_xdp(q, xdp);
> > @@ -1223,8 +1224,10 @@ static int tap_sendmsg(struct socket *sock, 
> > struct msghdr *m,
> >           return 0;
> >       }
> > -    return tap_get_user(q, ctl ? ctl->ptr : NULL, &m->msg_iter,
> > -                m->msg_flags & MSG_DONTWAIT);
> > +    if (ctl && ctl->cmd == TUN_CMD_PACKET)
> > +        ptr = ctl->ptr;
> > +
> > +    return tap_get_user(q, ptr, &m->msg_iter, m->msg_flags & 
> > MSG_DONTWAIT);
> >   }
> >   static int tap_recvmsg(struct socket *sock, struct msghdr *m,
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > index 0413d182d782..29711671959b 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -2529,11 +2529,12 @@ static int tun_sendmsg(struct socket *sock, 
> > struct msghdr *m, size_t total_len)
> >       struct tun_struct *tun = tun_get(tfile);
> >       struct tun_msg_ctl *ctl = m->msg_control;
> >       struct xdp_buff *xdp;
> > +    void *ptr = NULL;
> >       if (!tun)
> >           return -EBADFD;
> > -    if (ctl && (ctl->type == TUN_MSG_PTR)) {
> > +    if (ctl && ctl->cmd == TUN_CMD_BATCH) {
> >           struct tun_page tpage;
> >           int n = ctl->num;
> >           int flush = 0;
> > @@ -2560,7 +2561,10 @@ static int tun_sendmsg(struct socket *sock, 
> > struct msghdr *m, size_t total_len)
> >           goto out;
> >       }
> > -    ret = tun_get_user(tun, tfile, ctl ? ctl->ptr : NULL, &m->msg_iter,
> > +    if (ctl && ctl->cmd == TUN_CMD_PACKET)
> > +        ptr = ctl->ptr;
> > +
> > +    ret = tun_get_user(tun, tfile, ptr, &m->msg_iter,
> >                  m->msg_flags & MSG_DONTWAIT,
> >                  m->msg_flags & MSG_MORE);
> >   out:
> > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > index 1a2dd53caade..5946d2775bd0 100644
> > --- a/drivers/vhost/net.c
> > +++ b/drivers/vhost/net.c
> > @@ -462,7 +462,7 @@ static void vhost_tx_batch(struct vhost_net *net,
> >                  struct msghdr *msghdr)
> >   {
> >       struct tun_msg_ctl ctl = {
> > -        .type = TUN_MSG_PTR,
> > +        .cmd = TUN_CMD_BATCH,
> >           .num = nvq->batched_xdp,
> >           .ptr = nvq->xdp,
> >       };
> > @@ -902,7 +902,7 @@ static void handle_tx_zerocopy(struct vhost_net 
> > *net, struct socket *sock)
> >               ubuf->desc = nvq->upend_idx;
> >               refcount_set(&ubuf->refcnt, 1);
> >               msg.msg_control = &ctl;
> > -            ctl.type = TUN_MSG_UBUF;
> > +            ctl.cmd = TUN_CMD_PACKET;
> >               ctl.ptr = ubuf;
> >               msg.msg_controllen = sizeof(ctl);
> >               ubufs = nvq->ubufs;
> > diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h
> > index 5bda8cf457b6..bdfa671612db 100644
> > --- a/include/linux/if_tun.h
> > +++ b/include/linux/if_tun.h
> > @@ -11,10 +11,10 @@
> >   #define TUN_XDP_FLAG 0x1UL
> > -#define TUN_MSG_UBUF 1
> > -#define TUN_MSG_PTR  2
> > +#define TUN_CMD_PACKET 1
> > +#define TUN_CMD_BATCH  2
> >   struct tun_msg_ctl {
> > -    unsigned short type;
> > +    unsigned short cmd;
> >       unsigned short num;
> >       void *ptr;
> >   };