From: Jay Vosburgh <jay.vosburgh@canonical.com>
To: Jarod Wilson <jarod@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Ivan Vecera <ivecera@redhat.com>,
Veaceslav Falico <vfalico@gmail.com>,
Andy Gospodarek <andy@greyhouse.net>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Thomas Davis <tadavis@lbl.gov>,
Netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH net v2] bonding: fix feature flag setting at init time
Date: Wed, 02 Dec 2020 12:17:26 -0800 [thread overview]
Message-ID: <21153.1606940246@famine> (raw)
In-Reply-To: <CAKfmpSez1UYLG5nGYbMsRALGpEyXnwJcoFJV_7vALgpG3Xotcw@mail.gmail.com>
Jarod Wilson <jarod@redhat.com> wrote:
>On Wed, Dec 2, 2020 at 12:55 PM Jay Vosburgh <jay.vosburgh@canonical.com> wrote:
>>
>> Jarod Wilson <jarod@redhat.com> wrote:
>>
>> >Don't try to adjust XFRM support flags if the bond device isn't yet
>> >registered. Bad things can currently happen when netdev_change_features()
>> >is called without having wanted_features fully filled in yet. Basically,
>> >this code was racing against register_netdevice() filling in
>> >wanted_features, and when it got there first, the empty wanted_features
>> >led to features also getting emptied out, which was definitely not the
>> >intended behavior, so prevent that from happening.
>>
>> Is this an actual race? Reading Ivan's prior message, it sounds
>> like it's an ordering problem (in that bond_newlink calls
>> register_netdevice after bond_changelink).
>
>Sorry, yeah, this is not actually a race condition, just an ordering
>issue, bond_check_params() gets called at init time, which leads to
>bond_option_mode_set() being called, and does so prior to
>bond_create() running, which is where we actually call
>register_netdevice().
So this only happens if there's a "mode" module parameter? That
doesn't sound like the call path that Ivan described (coming in via
bond_newlink).
-J
>> The change to bond_option_mode_set tests against reg_state, so
>> presumably it wants to skip the first(?) time through, before the
>> register_netdevice call; is that right?
>
>Correct. Later on, when the bonding driver is already loaded, and
>parameter changes are made, bond_option_mode_set() gets called and if
>the mode changes to or from active-backup, we do need/want this code
>to run to update wanted and features flags properly.
>
>
>--
>Jarod Wilson
>jarod@redhat.com
---
-Jay Vosburgh, jay.vosburgh@canonical.com
next prev parent reply other threads:[~2020-12-02 20:18 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-23 3:17 [PATCH net] bonding: fix feature flag setting at init time Jarod Wilson
2020-11-23 8:19 ` Ivan Vecera
2020-11-23 15:32 ` kernel test robot
2020-12-02 17:30 ` [PATCH net v2] " Jarod Wilson
2020-12-02 17:41 ` Ivan Vecera
2020-12-02 17:53 ` Jakub Kicinski
2020-12-02 19:03 ` Jarod Wilson
2020-12-02 19:22 ` Jakub Kicinski
2020-12-02 19:39 ` Jarod Wilson
2020-12-02 17:55 ` Jay Vosburgh
2020-12-02 19:23 ` Jarod Wilson
2020-12-02 20:17 ` Jay Vosburgh [this message]
2020-12-02 20:54 ` Jarod Wilson
2020-12-03 0:43 ` [PATCH net v3] " Jarod Wilson
2020-12-03 16:45 ` Jakub Kicinski
2020-12-05 16:13 ` Jarod Wilson
2020-12-03 16:50 ` Jakub Kicinski
2020-12-04 3:14 ` Jarod Wilson
2020-12-04 15:45 ` Jakub Kicinski
2020-12-05 17:22 ` [PATCH net v4] " Jarod Wilson
2020-12-08 19:27 ` Jakub Kicinski
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