Re: [PATCH for-next] RDMA/rxe: Cleanup rxe_init_packet()

[Bob Pearson <rpearsonhpe@gmail.com>]

On 7/27/22 05:23, Haris Iqbal wrote:
> On Tue, Jul 26, 2022 at 9:56 PM Bob Pearson <rpearsonhpe@gmail.com> wrote:
>>
>> Currently rxe_init_packet() recomputes ndev from the address
>> vector but struct rxe_dev already holds a reference to ndev.
>>
>> Cleanup rxe_init_packet to use the value of ndev in rxe and drop
>> an unneeded parameter paylen since it is already carried in the
>> packet info struct.
>>
>> Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
>> ---
>>  drivers/infiniband/sw/rxe/rxe_loc.h  |  2 +-
>>  drivers/infiniband/sw/rxe/rxe_net.c  | 49 +++++++++++-----------------
>>  drivers/infiniband/sw/rxe/rxe_req.c  |  2 +-
>>  drivers/infiniband/sw/rxe/rxe_resp.c |  3 +-
>>  4 files changed, 23 insertions(+), 33 deletions(-)
>>
>> diff --git a/drivers/infiniband/sw/rxe/rxe_loc.h b/drivers/infiniband/sw/rxe/rxe_loc.h
>> index f9af30f582c6..7f98d296bc0d 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_loc.h
>> +++ b/drivers/infiniband/sw/rxe/rxe_loc.h
>> @@ -93,7 +93,7 @@ void rxe_mw_cleanup(struct rxe_pool_elem *elem);
>>
>>  /* rxe_net.c */
>>  struct sk_buff *rxe_init_packet(struct rxe_dev *rxe, struct rxe_av *av,
>> -                               int paylen, struct rxe_pkt_info *pkt);
>> +                               struct rxe_pkt_info *pkt);
>>  int rxe_prepare(struct rxe_av *av, struct rxe_pkt_info *pkt,
>>                 struct sk_buff *skb);
>>  int rxe_xmit_packet(struct rxe_qp *qp, struct rxe_pkt_info *pkt,
>> diff --git a/drivers/infiniband/sw/rxe/rxe_net.c b/drivers/infiniband/sw/rxe/rxe_net.c
>> index c53f4529f098..4a091f236dde 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_net.c
>> +++ b/drivers/infiniband/sw/rxe/rxe_net.c
>> @@ -443,18 +443,22 @@ int rxe_xmit_packet(struct rxe_qp *qp, struct rxe_pkt_info *pkt,
>>         return err;
>>  }
>>
>> +/**
>> + * rxe_init_packet - allocate and initialize a new skb
>> + * @rxe: rxe device
>> + * @av: remote address vector
>> + * @pkt: packet info
>> + *
>> + * Returns: an skb on success else NULL
>> + */
>>  struct sk_buff *rxe_init_packet(struct rxe_dev *rxe, struct rxe_av *av,
>> -                               int paylen, struct rxe_pkt_info *pkt)
>> +                               struct rxe_pkt_info *pkt)
>>  {
>>         unsigned int hdr_len;
>>         struct sk_buff *skb = NULL;
>> -       struct net_device *ndev;
>> -       const struct ib_gid_attr *attr;
>> +       struct net_device *ndev = rxe->ndev;
>>         const int port_num = 1;
>> -
>> -       attr = rdma_get_gid_attr(&rxe->ib_dev, port_num, av->grh.sgid_index);
>> -       if (IS_ERR(attr))
>> -               return NULL;
>> +       int skb_size;
>>
>>         if (av->network_type == RXE_NETWORK_TYPE_IPV4)
>>                 hdr_len = ETH_HLEN + sizeof(struct udphdr) +
>> @@ -463,26 +467,13 @@ struct sk_buff *rxe_init_packet(struct rxe_dev *rxe, struct rxe_av *av,
>>                 hdr_len = ETH_HLEN + sizeof(struct udphdr) +
>>                         sizeof(struct ipv6hdr);
>>
>> -       rcu_read_lock();
> 
> Was removing this rcu lock intentional? If so, do we need a mention of
> this in the commit message why its not needed anymore?
> 
The rcu lock was required to use the rdma_read_gid_attr_ndev_rcu() API.
For the rxe driver there is no way that the ndev is changing once the rxe device
is set up and ndev was passed in to rxe_newlink() and saved in the rxe_dev struct.
Not any good reason to do all this work to get ndev when we already know it.
>> -       ndev = rdma_read_gid_attr_ndev_rcu(attr);
>> -       if (IS_ERR(ndev)) {
>> -               rcu_read_unlock();
>> -               goto out;
>> -       }
>> -       skb = alloc_skb(paylen + hdr_len + LL_RESERVED_SPACE(ndev),
>> -                       GFP_ATOMIC);
>> -
>> -       if (unlikely(!skb)) {
>> -               rcu_read_unlock();
>> -               goto out;
>> -       }
>> -
>> -       skb_reserve(skb, hdr_len + LL_RESERVED_SPACE(ndev));
>> -
>> -       /* FIXME: hold reference to this netdev until life of this skb. */
>> -       skb->dev        = ndev;
>> -       rcu_read_unlock();
>> +       skb_size = LL_RESERVED_SPACE(ndev) + hdr_len + pkt->paylen;
>> +       skb = alloc_skb(skb_size, GFP_ATOMIC);
>> +       if (unlikely(!skb))
>> +               return NULL;
>>
>> +       skb_reserve(skb, LL_RESERVED_SPACE(ndev) + hdr_len);
>> +       skb->dev = ndev;
>>         if (av->network_type == RXE_NETWORK_TYPE_IPV4)
>>                 skb->protocol = htons(ETH_P_IP);
>>         else
>> @@ -490,11 +481,9 @@ struct sk_buff *rxe_init_packet(struct rxe_dev *rxe, struct rxe_av *av,
>>
>>         pkt->rxe        = rxe;
>>         pkt->port_num   = port_num;
>> -       pkt->hdr        = skb_put(skb, paylen);
>> -       pkt->mask       |= RXE_GRH_MASK;
>> +       pkt->hdr        = skb_put(skb, pkt->paylen);
>> +       pkt->mask      |= RXE_GRH_MASK;
>>
>> -out:
>> -       rdma_put_gid_attr(attr);
>>         return skb;
>>  }
>>
>> diff --git a/drivers/infiniband/sw/rxe/rxe_req.c b/drivers/infiniband/sw/rxe/rxe_req.c
>> index 49e8f54db6f5..e72db960d7ea 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_req.c
>> +++ b/drivers/infiniband/sw/rxe/rxe_req.c
>> @@ -397,7 +397,7 @@ static struct sk_buff *init_req_packet(struct rxe_qp *qp,
>>         pkt->paylen = paylen;
>>
>>         /* init skb */
>> -       skb = rxe_init_packet(rxe, av, paylen, pkt);
>> +       skb = rxe_init_packet(rxe, av, pkt);
>>         if (unlikely(!skb))
>>                 return NULL;
>>
>> diff --git a/drivers/infiniband/sw/rxe/rxe_resp.c b/drivers/infiniband/sw/rxe/rxe_resp.c
>> index b36ec5c4d5e0..02a5d4ebb45e 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_resp.c
>> +++ b/drivers/infiniband/sw/rxe/rxe_resp.c
>> @@ -670,8 +670,9 @@ static struct sk_buff *prepare_ack_packet(struct rxe_qp *qp,
>>          */
>>         pad = (-payload) & 0x3;
>>         paylen = rxe_opcode[opcode].length + payload + pad + RXE_ICRC_SIZE;
>> +       ack->paylen = paylen;
> 
> Maybe remove the old ack->paylen assignment which is done later in
> this function?
> 
Agreed. Will send a v2 with this change.
>>
>> -       skb = rxe_init_packet(rxe, &qp->pri_av, paylen, ack);
>> +       skb = rxe_init_packet(rxe, &qp->pri_av, ack);
>>         if (!skb)
>>                 return NULL;
>>
>> --
>> 2.34.1
>>

Bob