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 <kuba@kernel.org>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 18 insertions, 10 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index fce70990b209..d6f35c9d8580 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1613,7 +1613,8 @@ struct net_device_ops {
  * 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
@@ -1652,10 +1653,6 @@ struct net_device_ops {
  * @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,
@@ -1690,8 +1687,6 @@ enum netdev_priv_flags {
 	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 */
@@ -1723,6 +1718,9 @@ enum netdev_reg_state {
  *	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
  *		of the interface.
@@ -1789,8 +1787,6 @@ enum netdev_reg_state {
  *
  *	@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
@@ -1964,6 +1960,12 @@ enum netdev_reg_state {
  *
  *	@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.
@@ -2014,7 +2016,9 @@ struct net_device {
 
 	/* 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;
@@ -2350,6 +2354,10 @@ struct net_device {
 	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;
 
 #if IS_ENABLED(CONFIG_MACSEC)