net: add NETDEV_PRECHANGEMTU to notify before mtu change happens

Currently, if a device changes its mtu, first the change happens (invloving
all the side effects), and after that the NETDEV_CHANGEMTU is sent so that
other devices can catch up with the new mtu. However, if they return
NOTIFY_BAD, then the change is reverted and error returned.

This is a really long and costy operation (sometimes). To fix this, add
NETDEV_PRECHANGEMTU notification which is called prior to any change
actually happening, and if any callee returns NOTIFY_BAD - the change is
aborted. This way we're skipping all the playing with apply/revert the mtu.

CC: "David S. Miller" <[email protected]>
CC: Jiri Pirko <[email protected]>
CC: Eric Dumazet <[email protected]>
CC: Nicolas Dichtel <[email protected]>
CC: Cong Wang <[email protected]>
Signed-off-by: Veaceslav Falico <[email protected]>
Acked-by: Jiri Pirko <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

0 files changed, 0 insertions, 0 deletions