* [PATCH net] net: fix __netdev_update_features return on ndo_set_features failure
@ 2015-11-13 14:20 Nikolay Aleksandrov
2015-11-16 19:56 ` David Miller
2015-11-17 13:54 ` Michał Mirosław
0 siblings, 2 replies; 6+ messages in thread
From: Nikolay Aleksandrov @ 2015-11-13 14:20 UTC (permalink / raw)
To: netdev; +Cc: davem, Nikolay Aleksandrov, Michał Mirosław
From: Nikolay Aleksandrov <nikolay@cumulusnetworks•com>
If ndo_set_features fails __netdev_update_features() will return -1 but
this is wrong because it is expected to return 0 if no features were
changed (see netdev_update_features()), which will cause a netdev
notifier to be called without any actual changes. Fix this by returning
0 if ndo_set_features fails.
Fixes: 6cb6a27c45ce ("net: Call netdev_features_change() from netdev_update_features()")
CC: Michał Mirosław <mirq-linux@rere•qmqm.pl>
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks•com>
---
net/core/dev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 4a1d198dbbff..1974aee005a6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6433,7 +6433,7 @@ int __netdev_update_features(struct net_device *dev)
netdev_err(dev,
"set_features() failed (%d); wanted %pNF, left %pNF\n",
err, &features, &dev->features);
- return -1;
+ return 0;
}
sync_lower:
--
2.4.3
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH net] net: fix __netdev_update_features return on ndo_set_features failure
2015-11-13 14:20 [PATCH net] net: fix __netdev_update_features return on ndo_set_features failure Nikolay Aleksandrov
@ 2015-11-16 19:56 ` David Miller
2015-11-17 13:54 ` Michał Mirosław
1 sibling, 0 replies; 6+ messages in thread
From: David Miller @ 2015-11-16 19:56 UTC (permalink / raw)
To: razor; +Cc: netdev, nikolay, mirq-linux
From: Nikolay Aleksandrov <razor@blackwall•org>
Date: Fri, 13 Nov 2015 15:20:24 +0100
> From: Nikolay Aleksandrov <nikolay@cumulusnetworks•com>
>
> If ndo_set_features fails __netdev_update_features() will return -1 but
> this is wrong because it is expected to return 0 if no features were
> changed (see netdev_update_features()), which will cause a netdev
> notifier to be called without any actual changes. Fix this by returning
> 0 if ndo_set_features fails.
>
> Fixes: 6cb6a27c45ce ("net: Call netdev_features_change() from netdev_update_features()")
> CC: Michał Mirosław <mirq-linux@rere•qmqm.pl>
> Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks•com>
Applied.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH net] net: fix __netdev_update_features return on ndo_set_features failure
2015-11-13 14:20 [PATCH net] net: fix __netdev_update_features return on ndo_set_features failure Nikolay Aleksandrov
2015-11-16 19:56 ` David Miller
@ 2015-11-17 13:54 ` Michał Mirosław
2015-11-17 14:31 ` Nikolay Aleksandrov
1 sibling, 1 reply; 6+ messages in thread
From: Michał Mirosław @ 2015-11-17 13:54 UTC (permalink / raw)
To: Nikolay Aleksandrov; +Cc: netdev, davem, Nikolay Aleksandrov
On Fri, Nov 13, 2015 at 03:20:24PM +0100, Nikolay Aleksandrov wrote:
> From: Nikolay Aleksandrov <nikolay@cumulusnetworks•com>
>
> If ndo_set_features fails __netdev_update_features() will return -1 but
> this is wrong because it is expected to return 0 if no features were
> changed (see netdev_update_features()), which will cause a netdev
> notifier to be called without any actual changes. Fix this by returning
> 0 if ndo_set_features fails.
Hmm. In case ndo_update_features() failed it might have changed the features.
The assumption I made was that we're better off initiating spurious notification
than miss one. This is an unlikely event - a bug in a driver or problem with the HW.
Best Regards,
Michał Mirosław
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH net] net: fix __netdev_update_features return on ndo_set_features failure
2015-11-17 13:54 ` Michał Mirosław
@ 2015-11-17 14:31 ` Nikolay Aleksandrov
2015-11-17 14:49 ` [PATCH net] net/core: revert "net: fix __netdev_update_features return.." and add comment Nikolay Aleksandrov
0 siblings, 1 reply; 6+ messages in thread
From: Nikolay Aleksandrov @ 2015-11-17 14:31 UTC (permalink / raw)
To: Michał Mirosław, Nikolay Aleksandrov; +Cc: netdev, davem
On 11/17/2015 02:54 PM, Michał Mirosław wrote:
> On Fri, Nov 13, 2015 at 03:20:24PM +0100, Nikolay Aleksandrov wrote:
>> From: Nikolay Aleksandrov <nikolay@cumulusnetworks•com>
>>
>> If ndo_set_features fails __netdev_update_features() will return -1 but
>> this is wrong because it is expected to return 0 if no features were
>> changed (see netdev_update_features()), which will cause a netdev
>> notifier to be called without any actual changes. Fix this by returning
>> 0 if ndo_set_features fails.
>
> Hmm. In case ndo_update_features() failed it might have changed the features.
> The assumption I made was that we're better off initiating spurious notification
> than miss one. This is an unlikely event - a bug in a driver or problem with the HW.
>
> Best Regards,
> Michał Mirosław
>
Hmm, good point. I went over a dozen drivers and I can see that some might
actually do that (e.g. bnx2x in bnx2x_set_features()). It's rare but possible,
most of them return only 0.
Okay then, I'll revert this change and add a comment with this so it's clear
in the future.
Thanks for the feedback,
Nik
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH net] net/core: revert "net: fix __netdev_update_features return.." and add comment
2015-11-17 14:31 ` Nikolay Aleksandrov
@ 2015-11-17 14:49 ` Nikolay Aleksandrov
2015-11-17 20:27 ` David Miller
0 siblings, 1 reply; 6+ messages in thread
From: Nikolay Aleksandrov @ 2015-11-17 14:49 UTC (permalink / raw)
To: netdev; +Cc: davem, Nikolay Aleksandrov, Michał Mirosław
From: Nikolay Aleksandrov <nikolay@cumulusnetworks•com>
This reverts commit 00ee59271777 ("net: fix __netdev_update_features return
on ndo_set_features failure")
and adds a comment explaining why it's okay to return a value other than
0 upon error. Some drivers might actually change flags and return an
error so it's better to fire a spurious notification rather than miss
these.
CC: Michał Mirosław <mirq-linux@rere•qmqm.pl>
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks•com>
---
Thanks to Michal for the explanation on why it was made to act like that.
Also sorry for the noise, unfortunately I missed this. IMO this should've
been an all or nothing op from the beginning.
net/core/dev.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 5dbc86ea6b58..ae00b894e675 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6436,7 +6436,10 @@ int __netdev_update_features(struct net_device *dev)
netdev_err(dev,
"set_features() failed (%d); wanted %pNF, left %pNF\n",
err, &features, &dev->features);
- return 0;
+ /* return non-0 since some features might have changed and
+ * it's better to fire a spurious notification than miss it
+ */
+ return -1;
}
sync_lower:
--
2.4.3
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH net] net/core: revert "net: fix __netdev_update_features return.." and add comment
2015-11-17 14:49 ` [PATCH net] net/core: revert "net: fix __netdev_update_features return.." and add comment Nikolay Aleksandrov
@ 2015-11-17 20:27 ` David Miller
0 siblings, 0 replies; 6+ messages in thread
From: David Miller @ 2015-11-17 20:27 UTC (permalink / raw)
To: razor; +Cc: netdev, nikolay, mirq-linux
From: Nikolay Aleksandrov <razor@blackwall•org>
Date: Tue, 17 Nov 2015 15:49:06 +0100
> From: Nikolay Aleksandrov <nikolay@cumulusnetworks•com>
>
> This reverts commit 00ee59271777 ("net: fix __netdev_update_features return
> on ndo_set_features failure")
> and adds a comment explaining why it's okay to return a value other than
> 0 upon error. Some drivers might actually change flags and return an
> error so it's better to fire a spurious notification rather than miss
> these.
>
> CC: Michał Mirosław <mirq-linux@rere•qmqm.pl>
> Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks•com>
> ---
> Thanks to Michal for the explanation on why it was made to act like that.
> Also sorry for the noise, unfortunately I missed this. IMO this should've
> been an all or nothing op from the beginning.
Applied.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2015-11-17 20:27 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2015-11-13 14:20 [PATCH net] net: fix __netdev_update_features return on ndo_set_features failure Nikolay Aleksandrov
2015-11-16 19:56 ` David Miller
2015-11-17 13:54 ` Michał Mirosław
2015-11-17 14:31 ` Nikolay Aleksandrov
2015-11-17 14:49 ` [PATCH net] net/core: revert "net: fix __netdev_update_features return.." and add comment Nikolay Aleksandrov
2015-11-17 20:27 ` David Miller
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