[PATCH net-next 0/2] geneve: make geneve_fill_info() RTNL-less

[Eric Dumazet <edumazet@google.com>]

This series makes geneve_fill_info() independent of the RTNL lock by
converting the device configuration to an RCU-protected pointer.

Historically, geneve_changelink() updated the device configuration by
copying the new configuration over the old one using memcpy() under RTNL.

To prevent the transmit/receive data paths from reading torn values during
the copy, geneve_quiesce() was used to pause the data path and wait for
a synchronize_net(), causing packet loss and latency.

By converting the configuration to an RCU-protected pointer, we can
perform atomic updates via RCU swap. This allows data path readers to
safely access the configuration locklessly under RCU read lock, and
removes the need to stop the data path during changelink.

With the RCU infrastructure in place, geneve_fill_info() is then updated
to read the configuration under RCU read lock, removing its dependency
on RTNL.

Eric Dumazet (2):
  geneve: convert config to RCU-protected pointer
  geneve: make geneve_fill_info() RTNL independent

 drivers/net/geneve.c | 390 +++++++++++++++++++++++++------------------
 1 file changed, 229 insertions(+), 161 deletions(-)

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2.55.0.rc0.799.gd6f94ed593-goog