6.1-stable review patch. If anyone has any objections, please let me know.
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From: Jamal Hadi Salim jhs@mojatatu.com
[ Upstream commit c5e2a973448d958feb7881e4d875eac59fdeff3d ]
As of today, rtnl code creates a new skb and unconditionally fills and broadcasts it to the relevant group. For most operations this is okay and doesn't waste resources in general.
When operations are done without the rtnl_lock, as in tc-flower, such skb allocation, message fill and no-op broadcasting can happen in all cores of the system, which contributes to system pressure and wastes precious cpu cycles when no one will receive the built message.
Introduce this helper so rtnetlink operations can simply check if someone is listening and then proceed if necessary.
Reviewed-by: Jiri Pirko jiri@nvidia.com Reviewed-by: Simon Horman horms@kernel.org Signed-off-by: Jamal Hadi Salim jhs@mojatatu.com Signed-off-by: Victor Nogueira victor@mojatatu.com Signed-off-by: Pedro Tammela pctammela@mojatatu.com Link: https://lore.kernel.org/r/20231208192847.714940-2-pctammela@mojatatu.com Signed-off-by: Jakub Kicinski kuba@kernel.org Stable-dep-of: 369609fc6272 ("tc: Ensure we have enough buffer space when sending filter netlink notifications") Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/rtnetlink.h | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h index ae2c6a3cec5db..ad5f15d369235 100644 --- a/include/linux/rtnetlink.h +++ b/include/linux/rtnetlink.h @@ -138,4 +138,11 @@ extern int ndo_dflt_bridge_getlink(struct sk_buff *skb, u32 pid, u32 seq,
extern void rtnl_offload_xstats_notify(struct net_device *dev);
+static inline int rtnl_has_listeners(const struct net *net, u32 group) +{ + struct sock *rtnl = net->rtnl; + + return netlink_has_listeners(rtnl, group); +} + #endif /* __LINUX_RTNETLINK_H */