Merge branch 'net-sysfs-remove-the-rtnl_trylock-restart_syscall-construction'

Antoine Tenart says:

====================
net-sysfs: remove the rtnl_trylock/restart_syscall construction

The series initially aimed at improving spins (and thus delays) while
accessing net sysfs under rtnl lock contention[1]. The culprit was the
trylock/restart_syscall constructions. There wasn't much interest at the
time but it got traction recently for other reasons (lowering the rtnl
lock pressure).

Since v1[2]:

- Do not export rtnl_lock_interruptible [Stephen].
- Add netdev_warn_once messages in rx_queue_add_kobject [Jakub].

Since the RFC[1]:

- Limit the breaking of the sysfs protection to sysfs_rtnl_lock() only
  as this is not needed in the whole rtnl locking section thanks to the
  additional check on dev_isalive(). This simplifies error handling as
  well as the unlocking path.
- Used an interruptible version of rtnl_lock, as done by Jakub in
  his experiments.
- Removed a WARN_ONCE_ONCE [Greg].
- Removed explicit inline markers [Stephen].

Most of the reasoning is explained in comments added in patch 1. This
was tested by stress-testing net sysfs attributes (read/write ops) while
adding/removing queues and adding/removing veths, all in parallel. I
also used an OCP single node cluster, spawning lots of pods.

[1] https://lore.kernel.org/all/20231018154804.420823-1-atenart@kernel.org/T/
[2] https://lore.kernel.org/all/20250117102612.132644-1-atenart@kernel.org/T/
====================

Link: https://patch.msgid.link/20250204170314.146022-1-atenart@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 2a59034a5fa2..1dcc76af7520 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -658,6 +658,7 @@ struct netdev_queue {
 	struct Qdisc __rcu	*qdisc_sleeping;
 #ifdef CONFIG_SYSFS
 	struct kobject		kobj;
+	const struct attribute_group	**groups;
 #endif
 	unsigned long		tx_maxrate;
 	/*
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 4bc2ee0b10b0..ccaaf4c7d5f6 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -43,6 +43,7 @@ extern void rtnl_lock(void);
 extern void rtnl_unlock(void);
 extern int rtnl_trylock(void);
 extern int rtnl_is_locked(void);
+extern int rtnl_lock_interruptible(void);
 extern int rtnl_lock_killable(void);
 extern bool refcount_dec_and_rtnl_lock(refcount_t *r);
 
diff --git a/include/net/netdev_rx_queue.h b/include/net/netdev_rx_queue.h
index 596836abf7bf..af40842f229d 100644
--- a/include/net/netdev_rx_queue.h
+++ b/include/net/netdev_rx_queue.h
@@ -16,6 +16,7 @@ struct netdev_rx_queue {
 	struct rps_dev_flow_table __rcu	*rps_flow_table;
 #endif
 	struct kobject			kobj;
+	const struct attribute_group	**groups;
 	struct net_device		*dev;
 	netdevice_tracker		dev_tracker;