netdevice: convert private flags > BIT(31) to bitfields

Make dev->priv_flags `u32` back and define bits higher than 31 as
bitfield booleans as per Jakub's suggestion. This simplifies code
which accesses these bits with no optimization loss (testb both
before/after), allows to not extend &netdev_priv_flags each time,
but also scales better as bits > 63 in the future would only add
a new u64 to the structure with no complications, comparing to
that extending ::priv_flags would require converting it to a bitmap.
Note that I picked `unsigned long :1` to not lose any potential
optimizations comparing to `bool :1` etc.

Suggested-by: Jakub Kicinski <[e-mail]>
Signed-off-by: Alexander Lobakin <[e-mail]>
Signed-off-by: Paolo Abeni <[e-mail]>

Documentation/networking/net_cachelines/net_device.rst

···
 
 Type                                Name                    fastpath_tx_access  fastpath_rx_access  Comments
 ..struct                            ..net_device                                                    
+unsigned_long:32                    priv_flags              read_mostly         -                   __dev_queue_xmit(tx)
 char                                name[16]                -                   -                   
 struct_netdev_name_node*            name_node                                                       
 struct_dev_ifalias*                 ifalias                                                         
···
 struct                              adj_list                                                        
 unsigned_int                        flags                   read_mostly         read_mostly         __dev_queue_xmit,__dev_xmit_skb,ip6_output,__ip6_finish_output(tx);ip6_rcv_core(rx)
 xdp_features_t                      xdp_features                                                    
-unsigned_long_long                  priv_flags              read_mostly         -                   __dev_queue_xmit(tx)
 struct_net_device_ops*              netdev_ops              read_mostly         -                   netdev_core_pick_tx,netdev_start_xmit(tx)
 struct_xdp_metadata_ops*            xdp_metadata_ops                                                
 int                                 ifindex                 -                   read_mostly         ip6_rcv_core
···
 bool                                proto_down                                                      
 unsigned:1                          wol_enabled                                                     
 unsigned:1                          threaded                -                   -                   napi_poll(napi_enable,dev_set_threaded)
+unsigned_long:1                     see_all_hwtstamp_requests                                       
+unsigned_long:1                     change_proto_down                                               
 struct_list_head                    net_notifier_list                                               
 struct_macsec_ops*                  macsec_ops                                                      
 struct_udp_tunnel_nic_info*         udp_tunnel_nic_info                                             

drivers/net/ethernet/microchip/lan966x/lan966x_main.c

···
 			 NETIF_F_HW_VLAN_STAG_TX |
 			 NETIF_F_HW_TC;
 	dev->hw_features |= NETIF_F_HW_TC;
-	dev->priv_flags |= IFF_SEE_ALL_HWTSTAMP_REQUESTS;
+	dev->see_all_hwtstamp_requests = true;
 	dev->needed_headroom = IFH_LEN_BYTES;
 
 	eth_hw_addr_gen(dev, lan966x->base_mac, p + 1);

drivers/net/macvlan.c

···
 	dev->max_mtu		= ETH_MAX_MTU;
 	dev->priv_flags	       &= ~IFF_TX_SKB_SHARING;
 	netif_keep_dst(dev);
-	dev->priv_flags	       |= IFF_UNICAST_FLT | IFF_CHANGE_PROTO_DOWN;
+	dev->priv_flags	       |= IFF_UNICAST_FLT;
+	dev->change_proto_down	= true;
 	dev->netdev_ops		= &macvlan_netdev_ops;
 	dev->needs_free_netdev	= true;
 	dev->priv_destructor	= macvlan_dev_free;

drivers/net/vxlan/vxlan_core.c

···
 	dev->hw_features |= NETIF_F_RXCSUM;
 	dev->hw_features |= NETIF_F_GSO_SOFTWARE;
 	netif_keep_dst(dev);
-	dev->priv_flags |= IFF_NO_QUEUE | IFF_CHANGE_PROTO_DOWN;
+	dev->priv_flags |= IFF_NO_QUEUE;
+	dev->change_proto_down = true;
 
 	/* MTU range: 68 - 65535 */
 	dev->min_mtu = ETH_MIN_MTU;

include/linux/netdevice.h

···
  * userspace; this means that the order of these flags can change
  * during any kernel release.
  *
- * You should have a pretty good reason to be extending these flags.
+ * You should add bitfield booleans after either net_device::priv_flags
+ * (hotpath) or ::threaded (slowpath) instead of extending these flags.
  *
  * @IFF_802_1Q_VLAN: 802.1Q VLAN device
  * @IFF_EBRIDGE: Ethernet bridging device
···
  * @IFF_NO_ADDRCONF: prevent ipv6 addrconf
  * @IFF_TX_SKB_NO_LINEAR: device/driver is capable of xmitting frames with
  *	skb_headlen(skb) == 0 (data starts from frag0)
- * @IFF_CHANGE_PROTO_DOWN: device supports setting carrier via IFLA_PROTO_DOWN
- * @IFF_SEE_ALL_HWTSTAMP_REQUESTS: device wants to see calls to
- *	ndo_hwtstamp_set() for all timestamp requests regardless of source,
- *	even if those aren't HWTSTAMP_SOURCE_NETDEV.
  */
 enum netdev_priv_flags {
 	IFF_802_1Q_VLAN			= 1<<0,
···
 	IFF_L3MDEV_RX_HANDLER		= 1<<29,
 	IFF_NO_ADDRCONF			= BIT_ULL(30),
 	IFF_TX_SKB_NO_LINEAR		= BIT_ULL(31),
-	IFF_CHANGE_PROTO_DOWN		= BIT_ULL(32),
-	IFF_SEE_ALL_HWTSTAMP_REQUESTS	= BIT_ULL(33),
 };
 
 /* Specifies the type of the struct net_device::ml_priv pointer */
···
  *	Actually, this whole structure is a big mistake.  It mixes I/O
  *	data with strictly "high-level" data, and it has to know about
  *	almost every data structure used in the INET module.
+ *
+ *	@priv_flags:	flags invisible to userspace defined as bits, see
+ *			enum netdev_priv_flags for the definitions
  *
  *	@name:	This is the first field of the "visible" part of this structure
  *		(i.e. as seen by users in the "Space.c" file).  It is the name
···
  *
  *	@flags:		Interface flags (a la BSD)
  *	@xdp_features:	XDP capability supported by the device
- *	@priv_flags:	Like 'flags' but invisible to userspace,
- *			see if.h for the definitions
  *	@gflags:	Global flags ( kept as legacy )
  *	@priv_len:	Size of the ->priv flexible array
  *	@priv:		Flexible array containing private data
···
  *
  *	@threaded:	napi threaded mode is enabled
  *
+ *	@see_all_hwtstamp_requests: device wants to see calls to
+ *			ndo_hwtstamp_set() for all timestamp requests
+ *			regardless of source, even if those aren't
+ *			HWTSTAMP_SOURCE_NETDEV
+ *	@change_proto_down: device supports setting carrier via IFLA_PROTO_DOWN
+ *
  *	@net_notifier_list:	List of per-net netdev notifier block
  *				that follow this device when it is moved
  *				to another network namespace.
···
 
 	/* TX read-mostly hotpath */
 	__cacheline_group_begin(net_device_read_tx);
-	unsigned long long	priv_flags;
+	struct_group(priv_flags_fast,
+		unsigned long		priv_flags:32;
+	);
 	const struct net_device_ops *netdev_ops;
 	const struct header_ops *header_ops;
 	struct netdev_queue	*_tx;
···
 	struct lock_class_key	*qdisc_tx_busylock;
 	bool			proto_down;
 	bool			threaded;
+
+	/* priv_flags_slow, ungrouped to save space */
+	unsigned long		see_all_hwtstamp_requests:1;
+	unsigned long		change_proto_down:1;
 
 	struct list_head	net_notifier_list;
 

net/8021q/vlanproc.c

···
 
 	stats = dev_get_stats(vlandev, &temp);
 	seq_printf(seq,
-		   "%s  VID: %d	 REORDER_HDR: %i  dev->priv_flags: %llx\n",
+		   "%s  VID: %d	 REORDER_HDR: %i  dev->priv_flags: %x\n",
 		   vlandev->name, vlan->vlan_id,
-		   (int)(vlan->flags & 1), vlandev->priv_flags);
+		   (int)(vlan->flags & 1), (u32)vlandev->priv_flags);
 
 	seq_printf(seq, fmt64, "total frames received", stats->rx_packets);
 	seq_printf(seq, fmt64, "total bytes received", stats->rx_bytes);

net/core/dev.c

···
  */
 int dev_change_proto_down(struct net_device *dev, bool proto_down)
 {
-	if (!(dev->priv_flags & IFF_CHANGE_PROTO_DOWN))
+	if (!dev->change_proto_down)
 		return -EOPNOTSUPP;
 	if (!netif_device_present(dev))
 		return -ENODEV;
···
 static void __init net_dev_struct_check(void)
 {
 	/* TX read-mostly hotpath */
-	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_tx, priv_flags);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_tx, priv_flags_fast);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_tx, netdev_ops);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_tx, header_ops);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_tx, _tx);

net/core/dev_ioctl.c

···
  * should take precedence in front of hardware timestamping provided by the
  * netdev. If the netdev driver needs to perform specific actions even for PHY
  * timestamping to work properly (a switch port must trap the timestamped
- * frames and not forward them), it must set IFF_SEE_ALL_HWTSTAMP_REQUESTS in
- * dev->priv_flags.
+ * frames and not forward them), it must set dev->see_all_hwtstamp_requests.
  */
 int dev_set_hwtstamp_phylib(struct net_device *dev,
 			    struct kernel_hwtstamp_config *cfg,
···
 
 	cfg->source = phy_ts ? HWTSTAMP_SOURCE_PHYLIB : HWTSTAMP_SOURCE_NETDEV;
 
-	if (phy_ts && (dev->priv_flags & IFF_SEE_ALL_HWTSTAMP_REQUESTS)) {
+	if (phy_ts && dev->see_all_hwtstamp_requests) {
 		err = ops->ndo_hwtstamp_get(dev, &old_cfg);
 		if (err)
 			return err;
 	}
 
-	if (!phy_ts || (dev->priv_flags & IFF_SEE_ALL_HWTSTAMP_REQUESTS)) {
+	if (!phy_ts || dev->see_all_hwtstamp_requests) {
 		err = ops->ndo_hwtstamp_set(dev, cfg, extack);
 		if (err) {
 			if (extack->_msg)
···
 		}
 	}
 
-	if (phy_ts && (dev->priv_flags & IFF_SEE_ALL_HWTSTAMP_REQUESTS))
+	if (phy_ts && dev->see_all_hwtstamp_requests)
 		changed = kernel_hwtstamp_config_changed(&old_cfg, cfg);
 
 	if (phy_ts) {

net/core/rtnetlink.c

···
 	bool proto_down;
 	int err;
 
-	if (!(dev->priv_flags & IFF_CHANGE_PROTO_DOWN)) {
+	if (!dev->change_proto_down) {
 		NL_SET_ERR_MSG(extack,  "Protodown not supported by device");
 		return -EOPNOTSUPP;
 	}