[PATCH net-next 3/5] net/af_iucv: count packets in the xmit path

Julian Wiedmann
2021-01-28T11:41:59Z

The TX code keeps track of all skbs that are in-flight but haven't
actually been sent out yet. For native IUCV sockets that's not a huge
deal, but with TRANS_HIPER sockets it would be much better if we
didn't need to maintain a list of skb clones.

Note that we actually only care about the _count_ of skbs in this stage
of the TX pipeline. So as prep work for removing the skb tracking on
TRANS_HIPER sockets, keep track of the skb count in a separate variable
and pair any list {enqueue, unlink} with a count {increment, decrement}.

Then replace all occurences where we currently look at the skb list's
fill level.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
---
include/net/iucv/af_iucv.h | 1 +
net/iucv/af_iucv.c | 30 ++++++++++++++++++++++++------
2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/include/net/iucv/af_iucv.h b/include/net/iucv/af_iucv.h
index 9259ce2b22f3..0816bcd44dd1 100644
--- a/include/net/iucv/af_iucv.h
+++ b/include/net/iucv/af_iucv.h
@@ -128,6 +128,7 @@ struct iucv_sock {
u8 flags;
u16 msglimit;
u16 msglimit_peer;
+ atomic_t skbs_in_xmit;
atomic_t msg_sent;
atomic_t msg_recv;
atomic_t pendings;
diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index 8683b6939f45..e487f472027a 100644
--- a/net/iucv/af_iucv.c
+++ b/net/iucv/af_iucv.c
@@ -182,7 +182,7 @@ static inline int iucv_below_msglim(struct sock *sk)
if (sk->sk_state != IUCV_CONNECTED)
return 1;
if (iucv->transport == AF_IUCV_TRANS_IUCV)
- return (skb_queue_len(&iucv->send_skb_q) < iucv->path->msglim);
+ return (atomic_read(&iucv->skbs_in_xmit) < iucv->path->msglim);
else
return ((atomic_read(&iucv->msg_sent) < iucv->msglimit_peer) &&
(atomic_read(&iucv->pendings) <= 0));
@@ -269,8 +269,10 @@ static int afiucv_hs_send(struct iucv_message *imsg, struct sock *sock,
}

skb_queue_tail(&iucv->send_skb_q, nskb);
+ atomic_inc(&iucv->skbs_in_xmit);
err = dev_queue_xmit(skb);
if (net_xmit_eval(err)) {
+ atomic_dec(&iucv->skbs_in_xmit);
skb_unlink(nskb, &iucv->send_skb_q);
kfree_skb(nskb);
} else {
@@ -424,7 +426,7 @@ static void iucv_sock_close(struct sock *sk)
sk->sk_state = IUCV_CLOSING;
sk->sk_state_change(sk);

- if (!err && !skb_queue_empty(&iucv->send_skb_q)) {
+ if (!err && atomic_read(&iucv->skbs_in_xmit) > 0) {
if (sock_flag(sk, SOCK_LINGER) && sk->sk_lingertime)
timeo = sk->sk_lingertime;
else
@@ -491,6 +493,7 @@ static struct sock *iucv_sock_alloc(struct socket *sock, int proto, gfp_t prio,
atomic_set(&iucv->pendings, 0);
iucv->flags = 0;
iucv->msglimit = 0;
+ atomic_set(&iucv->skbs_in_xmit, 0);
atomic_set(&iucv->msg_sent, 0);
atomic_set(&iucv->msg_recv, 0);
iucv->path = NULL;
@@ -1055,6 +1058,7 @@ static int iucv_sock_sendmsg(struct socket *sock, struct msghdr *msg,
}
} else { /* Classic VM IUCV transport */
skb_queue_tail(&iucv->send_skb_q, skb);
+ atomic_inc(&iucv->skbs_in_xmit);

if (((iucv->path->flags & IUCV_IPRMDATA) & iucv->flags) &&
skb->len <= 7) {
@@ -1063,6 +1067,7 @@ static int iucv_sock_sendmsg(struct socket *sock, struct msghdr *msg,
/* on success: there is no message_complete callback */
/* for an IPRMDATA msg; remove skb from send queue */
if (err == 0) {
+ atomic_dec(&iucv->skbs_in_xmit);
skb_unlink(skb, &iucv->send_skb_q);
kfree_skb(skb);
}
@@ -1071,6 +1076,7 @@ static int iucv_sock_sendmsg(struct socket *sock, struct msghdr *msg,
/* IUCV_IPRMDATA path flag is set... sever path */
if (err == 0x15) {
pr_iucv->path_sever(iucv->path, NULL);
+ atomic_dec(&iucv->skbs_in_xmit);
skb_unlink(skb, &iucv->send_skb_q);
err = -EPIPE;
goto fail;
@@ -1109,6 +1115,8 @@ static int iucv_sock_sendmsg(struct socket *sock, struct msghdr *msg,
} else {
err = -EPIPE;
}
+
+ atomic_dec(&iucv->skbs_in_xmit);
skb_unlink(skb, &iucv->send_skb_q);
goto fail;
}
@@ -1748,10 +1756,14 @@ static void iucv_callback_txdone(struct iucv_path *path,
{
struct sock *sk = path->private;
struct sk_buff *this = NULL;
- struct sk_buff_head *list = &iucv_sk(sk)->send_skb_q;
+ struct sk_buff_head *list;
struct sk_buff *list_skb;
+ struct iucv_sock *iucv;
unsigned long flags;

+ iucv = iucv_sk(sk);
+ list = &iucv->send_skb_q;
+
bh_lock_sock(sk);

spin_lock_irqsave(&list->lock, flags);
@@ -1761,8 +1773,11 @@ static void iucv_callback_txdone(struct iucv_path *path,
break;
}
}
- if (this)
+ if (this) {
+ atomic_dec(&iucv->skbs_in_xmit);
__skb_unlink(this, list);
+ }
+
spin_unlock_irqrestore(&list->lock, flags);

if (this) {
@@ -1772,7 +1787,7 @@ static void iucv_callback_txdone(struct iucv_path *path,
}

if (sk->sk_state == IUCV_CLOSING) {
- if (skb_queue_empty(&iucv_sk(sk)->send_skb_q)) {
+ if (atomic_read(&iucv->skbs_in_xmit) == 0) {
sk->sk_state = IUCV_CLOSED;
sk->sk_state_change(sk);
}
@@ -2150,6 +2165,7 @@ static void afiucv_hs_callback_txnotify(struct sk_buff *skb,
if (skb_shinfo(list_skb) == skb_shinfo(skb)) {
switch (n) {
case TX_NOTIFY_OK:
+ atomic_dec(&iucv->skbs_in_xmit);
__skb_unlink(list_skb, list);
kfree_skb(list_skb);
iucv_sock_wake_msglim(sk);
@@ -2158,6 +2174,7 @@ static void afiucv_hs_callback_txnotify(struct sk_buff *skb,
atomic_inc(&iucv->pendings);
break;
case TX_NOTIFY_DELAYED_OK:
+ atomic_dec(&iucv->skbs_in_xmit);
__skb_unlink(list_skb, list);
atomic_dec(&iucv->pendings);
if (atomic_read(&iucv->pendings) <= 0)
@@ -2169,6 +2186,7 @@ static void afiucv_hs_callback_txnotify(struct sk_buff *skb,
case TX_NOTIFY_TPQFULL: /* not yet used */
case TX_NOTIFY_GENERALERROR:
case TX_NOTIFY_DELAYED_GENERALERROR:
+ atomic_dec(&iucv->skbs_in_xmit);
__skb_unlink(list_skb, list);
kfree_skb(list_skb);
if (sk->sk_state == IUCV_CONNECTED) {
@@ -2183,7 +2201,7 @@ static void afiucv_hs_callback_txnotify(struct sk_buff *skb,
spin_unlock_irqrestore(&list->lock, flags);

if (sk->sk_state == IUCV_CLOSING) {
- if (skb_queue_empty(&iucv_sk(sk)->send_skb_q)) {
+ if (atomic_read(&iucv->skbs_in_xmit) == 0) {
sk->sk_state = IUCV_CLOSED;
sk->sk_state_change(sk);
}
--
2.17.1