netdev - Re: [PATCH net-next v2] ibmvnic: Bail from ibmvnic

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Date:   Mon, 12 Mar 2018 21:10:02 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     John Allen <jallen@...ux.vnet.ibm.com>
Cc:     netdev@...r.kernel.org,
        Thomas Falcon <tlfalcon@...ux.vnet.ibm.com>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>
Subject: Re: [PATCH net-next v2] ibmvnic: Bail from ibmvnic_open if driver is
 already open

> The problem here is that our routine to change the mtu does a full reset on
> the driver meaning that in the process we go from effectively "open" to
> "closed" to "open" again.
> 
> Consider the scenario where we change the mtu by running "ifdown <interface>",
> editing the ifcfg file with the new mtu, and finally running "ifup <interface".
> In this case, we call ibmvnic_close from the ifdown and as a result of the ifup,
> we do the reset for the mtu change (which puts us back in the "open" state) and
> call ibmvnic_open. After the reset, we are already in the "open" state and the
> following call to open is redundant.

Hi John

So you are saying "ip link set mtu 4242 eth1" on a down interface will
put it up. That i would say is broken. You should be fixing this,
rather than papering over the cracks.

      Andrew