netdev - Re: [PATCH net-next 1/3] tuntap: reorganize tun_msg

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Message-ID: <18ab09ed-55b9-babb-6d78-04a920918562@gmail.com>
Date:   Tue, 15 Oct 2019 09:33:42 +0900
From:   Prashant Bhole <prashantbhole.linux@...il.com>
To:     Jason Wang <jasowang@...hat.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     David Ahern <dsahern@...il.com>, kvm@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] tuntap: reorganize tun_msg_ctl usage

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@...il.com wrote:
>> From: Prashant Bhole <prashantbhole.linux@...il.com>
>>
>> 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@...il.com>
>> ---
>>   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;
>>   };