[PATCH for-next v2 12/18] RDMA/rxe: Extend rxe_init_packet() to support frags

Bob Pearson
2022-10-31T20:28:51Z

Add a subroutine rxe_can_use_sg() to determine if a packet is
a candidate for a fragmented skb. Add a global variable rxe_use_sg
to control whether to support nonlinear skbs. Modify rxe_init_packet()
to test if the packet should use a fragmented skb. Fixup calls to
rxe_init_packet() to use the new API but disable creating nonlinear
skbs for now.

This is in preparation for using fragmented skbs.

Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
---
drivers/infiniband/sw/rxe/rxe.c | 3 ++
drivers/infiniband/sw/rxe/rxe.h | 3 ++
drivers/infiniband/sw/rxe/rxe_loc.h | 2 +-
drivers/infiniband/sw/rxe/rxe_mr.c | 12 +++--
drivers/infiniband/sw/rxe/rxe_net.c | 79 +++++++++++++++++++++++++---
drivers/infiniband/sw/rxe/rxe_req.c | 2 +-
drivers/infiniband/sw/rxe/rxe_resp.c | 7 ++-
7 files changed, 92 insertions(+), 16 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe.c b/drivers/infiniband/sw/rxe/rxe.c
index 51daac5c4feb..388d8103ec20 100644
--- a/drivers/infiniband/sw/rxe/rxe.c
+++ b/drivers/infiniband/sw/rxe/rxe.c
@@ -13,6 +13,9 @@ MODULE_AUTHOR("Bob Pearson, Frank Zago, John Groves, Kamal Heib");
MODULE_DESCRIPTION("Soft RDMA transport");
MODULE_LICENSE("Dual BSD/GPL");

+/* if true allow using fragmented skbs */
+bool rxe_use_sg;
+
/* free resources for a rxe device all objects created for this device must
* have been destroyed
*/
diff --git a/drivers/infiniband/sw/rxe/rxe.h b/drivers/infiniband/sw/rxe/rxe.h
index 30fbdf3bc76a..c78fb497d9c3 100644
--- a/drivers/infiniband/sw/rxe/rxe.h
+++ b/drivers/infiniband/sw/rxe/rxe.h
@@ -30,6 +30,9 @@
#include "rxe_verbs.h"
#include "rxe_loc.h"

+/* if true allow using fragmented skbs */
+extern bool rxe_use_sg;
+
/*
* Version 1 and Version 2 are identical on 64 bit machines, but on 32 bit
* machines Version 2 has a different struct layout.
diff --git a/drivers/infiniband/sw/rxe/rxe_loc.h b/drivers/infiniband/sw/rxe/rxe_loc.h
index 4e5fbc33277d..12fd5811cd79 100644
--- a/drivers/infiniband/sw/rxe/rxe_loc.h
+++ b/drivers/infiniband/sw/rxe/rxe_loc.h
@@ -101,7 +101,7 @@ void rxe_mw_cleanup(struct rxe_pool_elem *elem);

/* rxe_net.c */
struct sk_buff *rxe_init_packet(struct rxe_qp *qp, struct rxe_av *av,
- struct rxe_pkt_info *pkt);
+ struct rxe_pkt_info *pkt, bool *is_frag);
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_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
index 6fe5bbe43a60..cf538d97c7a5 100644
--- a/drivers/infiniband/sw/rxe/rxe_mr.c
+++ b/drivers/infiniband/sw/rxe/rxe_mr.c
@@ -541,7 +541,7 @@ int rxe_num_dma_frags(const struct rxe_pd *pd, const struct rxe_dma_info *dma,
struct rxe_mr *mr = NULL;
int bytes;
u64 iova;
- int ret;
+ int nf;
int num_frags = 0;

if (length == 0)
@@ -572,18 +572,22 @@ int rxe_num_dma_frags(const struct rxe_pd *pd, const struct rxe_dma_info *dma,
bytes = min_t(int, length, sge->length - buf_offset);
if (bytes > 0) {
iova = sge->addr + buf_offset;
- ret = rxe_num_mr_frags(mr, iova, length);
- if (ret < 0) {
+ nf = rxe_num_mr_frags(mr, iova, length);
+ if (nf < 0) {
rxe_put(mr);
- return ret;
+ return nf;
}

+ num_frags += nf;
buf_offset += bytes;
resid -= bytes;
length -= bytes;
}
}

+ if (mr)
+ rxe_put(mr);
+
return num_frags;
}

diff --git a/drivers/infiniband/sw/rxe/rxe_net.c b/drivers/infiniband/sw/rxe/rxe_net.c
index faabc444d546..c6d8f5c80562 100644
--- a/drivers/infiniband/sw/rxe/rxe_net.c
+++ b/drivers/infiniband/sw/rxe/rxe_net.c
@@ -442,8 +442,60 @@ int rxe_xmit_packet(struct rxe_qp *qp, struct rxe_pkt_info *pkt,
return err;
}

+/**
+ * rxe_can_use_sg() - determine if packet is a candidate for fragmenting
+ * @rxe: the rxe device
+ * @pkt: packet info
+ *
+ * Limit to packets with:
+ * rxe_use_sg set
+ * qp is RC
+ * ndev supports SG
+ * #sges less than #frags for sends
+ *
+ * Returns: true if conditions are met else 0
+ */
+static bool rxe_can_use_sg(struct rxe_qp *qp, struct rxe_pkt_info *pkt)
+{
+ struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
+ int length = pkt->paylen - rxe_opcode[pkt->opcode].length
+ - RXE_ICRC_SIZE;
+ int nf;
+
+ if (!rxe_use_sg)
+ return false;
+ if (qp_type(pkt->qp) != IB_QPT_RC)
+ return false;
+ if (!(rxe->ndev->features & NETIF_F_SG))
+ return false;
+
+ /* check we don't have a pathological sge list with lots of
+ * short segments. Recall we need one extra frag for icrc.
+ */
+ if (pkt->mask & RXE_SEND_MASK) {
+ nf = rxe_num_dma_frags(qp->pd, &pkt->wqe->dma, length);
+ return (nf >= 0 && nf <= MAX_SKB_FRAGS - 1) ? true : false;
+ }
+
+ return true;
+}
+
+#define RXE_MIN_SKB_SIZE (256)
+
+/**
+ * rxe_init_packet - allocate and initialize a new skb
+ * @qp: the queue pair
+ * @av: remote address vector
+ * @pkt: packet info
+ * @frag: optional return value for fragmented skb
+ * on call if frag == NULL do not use fragmented skb
+ * on return if not NULL set *frag to 1
+ * if packet will be fragmented else 0
+ *
+ * Returns: an skb on success else NULL
+ */
struct sk_buff *rxe_init_packet(struct rxe_qp *qp, struct rxe_av *av,
- struct rxe_pkt_info *pkt)
+ struct rxe_pkt_info *pkt, bool *frag)
{
struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
unsigned int hdr_len;
@@ -451,6 +503,7 @@ struct sk_buff *rxe_init_packet(struct rxe_qp *qp, struct rxe_av *av,
struct net_device *ndev;
const struct ib_gid_attr *attr;
const int port_num = 1;
+ int skb_size;

attr = rdma_get_gid_attr(&rxe->ib_dev, port_num, av->grh.sgid_index);
if (IS_ERR(attr))
@@ -469,9 +522,19 @@ struct sk_buff *rxe_init_packet(struct rxe_qp *qp, struct rxe_av *av,
rcu_read_unlock();
goto out;
}
- skb = alloc_skb(pkt->paylen + hdr_len + LL_RESERVED_SPACE(ndev),
- GFP_ATOMIC);

+ skb_size = LL_RESERVED_SPACE(ndev) + hdr_len + pkt->paylen;
+ if (frag) {
+ if (rxe_use_sg && (skb_size > RXE_MIN_SKB_SIZE) &&
+ rxe_can_use_sg(qp, pkt)) {
+ skb_size = RXE_MIN_SKB_SIZE;
+ *frag = true;
+ } else {
+ *frag = false;
+ }
+ }
+
+ skb = alloc_skb(skb_size, GFP_ATOMIC);
if (unlikely(!skb)) {
rcu_read_unlock();
goto out;
@@ -480,7 +543,7 @@ struct sk_buff *rxe_init_packet(struct rxe_qp *qp, struct rxe_av *av,
skb_reserve(skb, hdr_len + LL_RESERVED_SPACE(ndev));

/* FIXME: hold reference to this netdev until life of this skb. */
- skb->dev = ndev;
+ skb->dev = ndev;
rcu_read_unlock();

if (av->network_type == RXE_NETWORK_TYPE_IPV4)
@@ -488,10 +551,10 @@ struct sk_buff *rxe_init_packet(struct rxe_qp *qp, struct rxe_av *av,
else
skb->protocol = htons(ETH_P_IPV6);

- pkt->rxe = rxe;
- pkt->port_num = port_num;
- pkt->hdr = skb_put(skb, pkt->paylen);
- pkt->mask |= RXE_GRH_MASK;
+ if (frag && *frag)
+ pkt->hdr = skb_put(skb, rxe_opcode[pkt->opcode].length);
+ else
+ pkt->hdr = skb_put(skb, pkt->paylen);

out:
rdma_put_gid_attr(attr);
diff --git a/drivers/infiniband/sw/rxe/rxe_req.c b/drivers/infiniband/sw/rxe/rxe_req.c
index 0a4b8825bd55..71a65f2a5d6d 100644
--- a/drivers/infiniband/sw/rxe/rxe_req.c
+++ b/drivers/infiniband/sw/rxe/rxe_req.c
@@ -491,7 +491,7 @@ static struct sk_buff *rxe_init_req_packet(struct rxe_qp *qp,
pad + RXE_ICRC_SIZE;

/* init skb */
- skb = rxe_init_packet(qp, av, pkt);
+ skb = rxe_init_packet(qp, av, pkt, NULL);
if (unlikely(!skb))
goto err_out;

diff --git a/drivers/infiniband/sw/rxe/rxe_resp.c b/drivers/infiniband/sw/rxe/rxe_resp.c
index 8503d22f9114..8868415b71b6 100644
--- a/drivers/infiniband/sw/rxe/rxe_resp.c
+++ b/drivers/infiniband/sw/rxe/rxe_resp.c
@@ -665,6 +665,7 @@ static struct sk_buff *prepare_ack_packet(struct rxe_qp *qp,
u32 psn,
u8 syndrome)
{
+ struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
struct sk_buff *skb;
int paylen;
int pad;
@@ -672,14 +673,16 @@ 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;

+ ack->rxe = rxe;
ack->qp = qp;
ack->opcode = opcode;
ack->mask = rxe_opcode[opcode].mask;
+ ack->paylen = paylen;
ack->psn = psn;
+ ack->port_num = 1;

- skb = rxe_init_packet(qp, &qp->pri_av, ack);
+ skb = rxe_init_packet(qp, &qp->pri_av, ack, NULL);
if (!skb)
return NULL;

--
2.34.1