[PATCH 5.15 72/76] can: use skb hash instead of private variable in headroom

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oliver Hartkopp <socketcan@hartkopp.net>

commit d4fb6514ff8ed6912a71294e6b66a5d59ee88007 upstream.

The can_skb_priv::skbcnt variable is used to identify CAN skbs in the RX
path analogue to the skb->hash.

As the skb hash is not filled in CAN skbs move the private skbcnt value to
skb->hash and set skb->sw_hash accordingly. The skb->hash is a value used
for RPS to identify skbs. Use it as intended.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20260201-can_skb_ext-v8-1-3635d790fe8b@hartkopp.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/can/dev/skb.c |    2 --
 drivers/net/can/slcan.c   |    1 -
 include/linux/can/core.h  |    1 +
 include/linux/can/skb.h   |    3 ---
 net/can/af_can.c          |   14 +++++++++++---
 net/can/bcm.c             |    2 --
 net/can/isotp.c           |    3 ---
 net/can/j1939/socket.c    |    1 -
 net/can/j1939/transport.c |    2 --
 net/can/raw.c             |    7 +++----
 10 files changed, 15 insertions(+), 21 deletions(-)

--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -203,7 +203,6 @@ struct sk_buff *alloc_can_skb(struct net
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	*cf = skb_put_zero(skb, sizeof(struct can_frame));
 
@@ -234,7 +233,6 @@ struct sk_buff *alloc_canfd_skb(struct n
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	*cfd = skb_put_zero(skb, sizeof(struct canfd_frame));
 
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -213,7 +213,6 @@ static void slc_bump(struct slcan *sl)
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = sl->dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	skb_put_data(skb, &cf, sizeof(struct can_frame));
 
--- a/include/linux/can/core.h
+++ b/include/linux/can/core.h
@@ -58,6 +58,7 @@ extern void can_rx_unregister(struct net
 			      void *data);
 
 extern int can_send(struct sk_buff *skb, int loop);
+void can_set_skb_uid(struct sk_buff *skb);
 void can_sock_destruct(struct sock *sk);
 
 #endif /* !_CAN_CORE_H */
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -43,13 +43,11 @@ struct sk_buff *alloc_can_err_skb(struct
 /**
  * struct can_skb_priv - private additional data inside CAN sk_buffs
  * @ifindex:	ifindex of the first interface the CAN frame appeared on
- * @skbcnt:	atomic counter to have an unique id together with skb pointer
  * @frame_len:	length of CAN frame in data link layer
  * @cf:		align to the following CAN frame at skb->data
  */
 struct can_skb_priv {
 	int ifindex;
-	int skbcnt;
 	unsigned int frame_len;
 	struct can_frame cf[];
 };
@@ -107,7 +105,6 @@ static inline bool can_skb_headroom_vali
 	if (skb->ip_summed == CHECKSUM_NONE) {
 		/* init headroom */
 		can_skb_prv(skb)->ifindex = dev->ifindex;
-		can_skb_prv(skb)->skbcnt = 0;
 
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -641,6 +641,16 @@ static int can_rcv_filter(struct can_dev
 	return matches;
 }
 
+void can_set_skb_uid(struct sk_buff *skb)
+{
+	/* create non-zero unique skb identifier together with *skb */
+	while (!(skb->hash))
+		skb->hash = atomic_inc_return(&skbcounter);
+
+	skb->sw_hash = 1;
+}
+EXPORT_SYMBOL(can_set_skb_uid);
+
 static void can_receive(struct sk_buff *skb, struct net_device *dev)
 {
 	struct can_dev_rcv_lists *dev_rcv_lists;
@@ -652,9 +662,7 @@ static void can_receive(struct sk_buff *
 	atomic_long_inc(&pkg_stats->rx_frames);
 	atomic_long_inc(&pkg_stats->rx_frames_delta);
 
-	/* create non-zero unique skb identifier together with *skb */
-	while (!(can_skb_prv(skb)->skbcnt))
-		can_skb_prv(skb)->skbcnt = atomic_inc_return(&skbcounter);
+	can_set_skb_uid(skb);
 
 	rcu_read_lock();
 
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -338,7 +338,6 @@ static void bcm_can_tx(struct bcm_op *op
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	skb_put_data(skb, cf, op->cfsiz);
 
@@ -1577,7 +1576,6 @@ static int bcm_tx_send(struct msghdr *ms
 	}
 
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 	skb->dev = dev;
 	can_skb_set_owner(skb, sk);
 	err = can_send(skb, 1); /* send with loopback */
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -218,7 +218,6 @@ static int isotp_send_fc(struct sock *sk
 
 	can_skb_reserve(nskb);
 	can_skb_prv(nskb)->ifindex = dev->ifindex;
-	can_skb_prv(nskb)->skbcnt = 0;
 
 	nskb->dev = dev;
 	can_skb_set_owner(nskb, sk);
@@ -773,7 +772,6 @@ static void isotp_send_cframe(struct iso
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	cf = (struct canfd_frame *)skb->data;
 	skb_put_zero(skb, so->ll.mtu);
@@ -1069,7 +1067,6 @@ static int isotp_sendmsg(struct socket *
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	so->tx.len = size;
 	so->tx.idx = 0;
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -889,7 +889,6 @@ static struct sk_buff *j1939_sk_alloc_sk
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = ndev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 	skb_reserve(skb, offsetof(struct can_frame, data));
 
 	ret = memcpy_from_msg(skb_put(skb, size), msg, size);
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -612,7 +612,6 @@ sk_buff *j1939_tp_tx_dat_new(struct j193
 	skb->dev = priv->ndev;
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 	/* reserve CAN header */
 	skb_reserve(skb, offsetof(struct can_frame, data));
 
@@ -1551,7 +1550,6 @@ j1939_session *j1939_session_fresh_new(s
 	skb->dev = priv->ndev;
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 	skcb = j1939_skb_to_cb(skb);
 	memcpy(skcb, rel_skcb, sizeof(*skcb));
 
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -74,8 +74,8 @@ MODULE_ALIAS("can-proto-1");
  */
 
 struct uniqframe {
-	int skbcnt;
 	const struct sk_buff *skb;
+	u32 hash;
 	unsigned int join_rx_count;
 };
 
@@ -136,7 +136,7 @@ static void raw_rcv(struct sk_buff *oskb
 
 	/* eliminate multiple filter matches for the same skb */
 	if (this_cpu_ptr(ro->uniq)->skb == oskb &&
-	    this_cpu_ptr(ro->uniq)->skbcnt == can_skb_prv(oskb)->skbcnt) {
+	    this_cpu_ptr(ro->uniq)->hash == oskb->hash) {
 		if (ro->join_filters) {
 			this_cpu_inc(ro->uniq->join_rx_count);
 			/* drop frame until all enabled filters matched */
@@ -147,7 +147,7 @@ static void raw_rcv(struct sk_buff *oskb
 		}
 	} else {
 		this_cpu_ptr(ro->uniq)->skb = oskb;
-		this_cpu_ptr(ro->uniq)->skbcnt = can_skb_prv(oskb)->skbcnt;
+		this_cpu_ptr(ro->uniq)->hash = oskb->hash;
 		this_cpu_ptr(ro->uniq)->join_rx_count = 1;
 		/* drop first frame to check all enabled filters? */
 		if (ro->join_filters && ro->count > 1)
@@ -829,7 +829,6 @@ static int raw_sendmsg(struct socket *so
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	err = memcpy_from_msg(skb_put(skb, size), msg, size);
 	if (err < 0)