Couple cleanup patches to recently posted series[0] from Bjorn to cleanup and optimize the devmap usage. Patches have commit ids the cleanup applies to. Toshiaki, noted that virtio_net depends on rcu_lock being held when calling xdp flush routines. This is specific to virtio_net dereferencing xdp program to determine if xdp is enabled or not. More typical pattern is to look at a flag set by the driver, at least in the case of real hardware drivers. veth has a similar requirement where it derferences the peer netdev priv structure requiring the rcu_read_lock. I believe its better to put the rcu_read_lock()/unlock() pair where its actually used in the driver. FWIW in other xdp paths we expect driver writers to place rcu_read_lock/unlock pairs where they are needed as well so this keeps that expectation. Also it improves readability making it obvious why the rcu_read_lock and unlock pair is needed. In the virtio case we can probably do some further cleanup and remove it altogether if we want. For more details see patch 2/2. [0] https://www.spinics.net/lists/netdev/msg620639.html v2: Place rcu_read_{un}lock pair in virtio_net and veth drivers so we don't break this requirement when removing rcu read lock from devmap. --- John Fastabend (2): bpf: xdp, update devmap comments to reflect napi/rcu usage bpf: xdp, remove no longer required rcu_read_{un}lock() drivers/net/veth.c | 6 +++++- drivers/net/virtio_net.c | 8 ++++++-- kernel/bpf/devmap.c | 26 ++++++++++++++------------ 3 files changed, 25 insertions(+), 15 deletions(-) -- Signature
