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pppoe: drop sock reference counting on fast path

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Now that PPPoE sockets are freed via RCU (SOCK_RCU_FREE), it is no longer
necessary to take a reference count when looking up sockets on the receive
path. Readers are protected by RCU, so the socket memory remains valid
until after a grace period.

Convert fast-path lookups to avoid refcounting:
 - Replace get_item() and sk_receive_skb() in pppoe_rcv() with
   __get_item() and __sk_receive_skb().
 - Rework get_item_by_addr() into __get_item_by_addr() (no refcount and
   move RCU lock into pppoe_ioctl)
 - Remove unnecessary sock_put() calls.

This avoids cacheline bouncing from atomic reference counting and improves
performance on the receive fast path.

Signed-off-by: Qingfang Deng <dqfext@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250828012018.15922-2-dqfext@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Qingfang Deng
2025-08-28 09:20:17 +08:00
committed by Jakub Kicinski
parent 72cdc67e7f
commit 4f54dff818
1 changed files with 13 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

35
drivers/net/ppp/pppoe.c
View File

@@ -237,8 +237,8 @@ static inline struct pppox_sock *get_item(struct pppoe_net *pn, __be16 sid,
return po;
}
static inline struct pppox_sock *get_item_by_addr(struct net *net,
struct sockaddr_pppox *sp)
static inline struct pppox_sock *__get_item_by_addr(struct net *net,
struct sockaddr_pppox *sp)
{
struct net_device *dev;
struct pppoe_net *pn;
@@ -246,15 +246,13 @@ static inline struct pppox_sock *get_item_by_addr(struct net *net,
int ifindex;
rcu_read_lock();
dev = dev_get_by_name_rcu(net, sp->sa_addr.pppoe.dev);
if (dev) {
ifindex = dev->ifindex;
pn = pppoe_pernet(net);
pppox_sock = get_item(pn, sp->sa_addr.pppoe.sid,
sp->sa_addr.pppoe.remote, ifindex);
pppox_sock = __get_item(pn, sp->sa_addr.pppoe.sid,
sp->sa_addr.pppoe.remote, ifindex);
}
rcu_read_unlock();
return pppox_sock;
}
@@ -381,18 +379,16 @@ static int pppoe_rcv_core(struct sock *sk, struct sk_buff *skb)
if (sk->sk_state & PPPOX_BOUND) {
ppp_input(&po->chan, skb);
} else if (sk->sk_state & PPPOX_RELAY) {
relay_po = get_item_by_addr(sock_net(sk),
&po->pppoe_relay);
relay_po = __get_item_by_addr(sock_net(sk),
&po->pppoe_relay);
if (relay_po == NULL)
goto abort_kfree;
if ((sk_pppox(relay_po)->sk_state & PPPOX_CONNECTED) == 0)
goto abort_put;
goto abort_kfree;
if (!__pppoe_xmit(sk_pppox(relay_po), skb))
goto abort_put;
sock_put(sk_pppox(relay_po));
goto abort_kfree;
} else {
if (sock_queue_rcv_skb(sk, skb))
goto abort_kfree;
@@ -400,9 +396,6 @@ static int pppoe_rcv_core(struct sock *sk, struct sk_buff *skb)
return NET_RX_SUCCESS;
abort_put:
sock_put(sk_pppox(relay_po));
abort_kfree:
kfree_skb(skb);
return NET_RX_DROP;
@@ -447,14 +440,11 @@ static int pppoe_rcv(struct sk_buff *skb, struct net_device *dev,
ph = pppoe_hdr(skb);
pn = pppoe_pernet(dev_net(dev));
/* Note that get_item does a sock_hold(), so sk_pppox(po)
* is known to be safe.
*/
po = get_item(pn, ph->sid, eth_hdr(skb)->h_source, dev->ifindex);
po = __get_item(pn, ph->sid, eth_hdr(skb)->h_source, dev->ifindex);
if (!po)
goto drop;
return sk_receive_skb(sk_pppox(po), skb, 0);
return __sk_receive_skb(sk_pppox(po), skb, 0, 1, false);
drop:
kfree_skb(skb);
@@ -820,11 +810,12 @@ static int pppoe_ioctl(struct socket *sock, unsigned int cmd,
/* Check that the socket referenced by the address
actually exists. */
relay_po = get_item_by_addr(sock_net(sk), &po->pppoe_relay);
rcu_read_lock();
relay_po = __get_item_by_addr(sock_net(sk), &po->pppoe_relay);
rcu_read_unlock();
if (!relay_po)
break;
sock_put(sk_pppox(relay_po));
sk->sk_state |= PPPOX_RELAY;
err = 0;
break;