On Wed, Jul 27, 2022 at 6:01 PM Bob Pearson <rpearsonhpe@xxxxxxxxx> wrote:
>
> On 7/27/22 05:23, Haris Iqbal wrote:
> > On Tue, Jul 26, 2022 at 9:56 PM Bob Pearson <rpearsonhpe@xxxxxxxxx> 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@xxxxxxxxx>
> >> ---
> >> 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.
I see. Thanks for the explanation.
One more question for my understanding.
There was a FIXME line (removed with this commit) mentioning that we
should hold a reference to the netdev. I assume it was talking about
dev_hold.
Now, while initing the rxe we call ib_device_set_netdev, which does
dev_hold. But I could not find rxe doing dev_hold anywhere directly. I
am assuming this is enough, or should rxe be also holding a reference
for this net device since technically it does use it directly at some
places?
> >> - 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
