[PATCH v2 net-next 0/5] Make SWITCHDEV_FDB_{ADD,DEL}_TO_DEVICE blocking

Vladimir Oltean
2021-08-19T16:07:53Z

Problem statement:

Any time a driver needs to create a private association between a bridge
upper interface and use that association within its
SWITCHDEV_FDB_{ADD,DEL}_TO_DEVICE handler, we have an issue with FDB
entries deleted by the bridge when the port leaves. The issue is that
all switchdev drivers schedule a work item to have sleepable context,
and that work item can be actually scheduled after the port has left the
bridge, which means the association might have already been broken by
the time the scheduled FDB work item attempts to use it.

The solution is to modify switchdev to use its embedded SWITCHDEV_F_DEFER
mechanism to make the FDB notifiers emitted from the fastpath be
scheduled in sleepable context. All drivers are converted to handle
SWITCHDEV_FDB_{ADD,DEL}_TO_DEVICE from their blocking notifier block
handler (or register a blocking switchdev notifier handler if they
didn't have one). This solves the aforementioned problem because the
bridge waits for the switchdev deferred work items to finish before a
port leaves (del_nbp calls switchdev_deferred_process), whereas a work
item privately scheduled by the driver will obviously not be waited upon
by the bridge, leading to the possibility of having the race.

This is a dependency for the "DSA FDB isolation" posted here. It was
split out of that series hence the numbering starts directly at v2.

https://patchwork.kernel.org/project/netdevbpf/cover/20210818120150.892647-1-vladimir.oltean@nxp.com/

Vladimir Oltean (5):
net: switchdev: move SWITCHDEV_FDB_{ADD,DEL}_TO_DEVICE to the blocking
notifier chain
net: bridge: switchdev: make br_fdb_replay offer sleepable context to
consumers
net: switchdev: drop the atomic notifier block from
switchdev_bridge_port_{,un}offload
net: switchdev: don't assume RCU context in
switchdev_handle_fdb_{add,del}_to_device
net: dsa: handle SWITCHDEV_FDB_{ADD,DEL}_TO_DEVICE synchronously

.../ethernet/freescale/dpaa2/dpaa2-switch.c | 86 +++++------
.../marvell/prestera/prestera_switchdev.c | 110 +++++++-------
.../mellanox/mlx5/core/en/rep/bridge.c | 59 +++++++-
.../mellanox/mlxsw/spectrum_switchdev.c | 61 +++++++-
.../microchip/sparx5/sparx5_switchdev.c | 78 +++++-----
drivers/net/ethernet/mscc/ocelot_net.c | 3 -
drivers/net/ethernet/rocker/rocker_main.c | 73 ++++-----
drivers/net/ethernet/rocker/rocker_ofdpa.c | 4 +-
drivers/net/ethernet/ti/am65-cpsw-nuss.c | 4 +-
drivers/net/ethernet/ti/am65-cpsw-switchdev.c | 57 ++++----
drivers/net/ethernet/ti/cpsw_new.c | 4 +-
drivers/net/ethernet/ti/cpsw_switchdev.c | 60 ++++----
drivers/s390/net/qeth_l2_main.c | 10 +-
include/net/switchdev.h | 30 +++-
net/bridge/br.c | 5 +-
net/bridge/br_fdb.c | 40 ++++-
net/bridge/br_private.h | 4 -
net/bridge/br_switchdev.c | 18 +--
net/dsa/dsa.c | 15 --
net/dsa/dsa_priv.h | 15 --
net/dsa/port.c | 3 -
net/dsa/slave.c | 138 ++++++------------
net/switchdev/switchdev.c | 61 +++++++-
23 files changed, 529 insertions(+), 409 deletions(-)

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2.25.1