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Groups > linux.kernel > #1705862 > unrolled thread
| Started by | John Stultz <john.stultz@linaro.org> |
|---|---|
| First post | 2017-08-07 23:10 +0200 |
| Last post | 2017-08-14 01:10 +0200 |
| Articles | 8 on this page of 28 — 5 participants |
Back to article view | Back to linux.kernel
unregister_netdevice: waiting for eth0 to become free. Usage count = 1 John Stultz <john.stultz@linaro.org> - 2017-08-07 23:10 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 John Stultz <john.stultz@linaro.org> - 2017-08-07 23:20 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Cong Wang <xiyou.wangcong@gmail.com> - 2017-08-10 01:40 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 John Stultz <john.stultz@linaro.org> - 2017-08-10 01:50 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-10 02:40 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 John Stultz <john.stultz@linaro.org> - 2017-08-10 02:50 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 John Stultz <john.stultz@linaro.org> - 2017-08-10 03:30 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-10 03:40 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-10 07:50 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 John Stultz <john.stultz@linaro.org> - 2017-08-10 20:20 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-10 22:10 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Cong Wang <xiyou.wangcong@gmail.com> - 2017-08-11 18:50 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-11 19:30 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 David Ahern <dsahern@gmail.com> - 2017-08-12 02:20 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-12 02:30 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 David Ahern <dsahern@gmail.com> - 2017-08-12 05:40 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-12 21:40 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-12 02:20 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 John Stultz <john.stultz@linaro.org> - 2017-08-12 02:40 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-12 02:50 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 John Stultz <john.stultz@linaro.org> - 2017-08-12 05:10 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-12 21:30 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-12 21:30 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Ido Schimmel <idosch@idosch.org> - 2017-08-12 20:20 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-12 21:50 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 David Ahern <dsahern@gmail.com> - 2017-08-13 18:30 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 Wei Wang <weiwan@google.com> - 2017-08-13 23:00 +0200
Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 David Ahern <dsahern@gmail.com> - 2017-08-14 01:10 +0200
Page 2 of 2 — ← Prev page 1 [2]
| From | John Stultz <john.stultz@linaro.org> |
|---|---|
| Date | 2017-08-12 05:10 +0200 |
| Subject | Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 |
| Message-ID | <uduYh-3CJ-1@gated-at.bofh.it> |
| In reply to | #1710123 |
On Fri, Aug 11, 2017 at 5:31 PM, John Stultz <john.stultz@linaro.org> wrote: > On Fri, Aug 11, 2017 at 5:10 PM, Wei Wang <weiwan@google.com> wrote: >>> If after Cong's fix, the issue still happens, could you help try the >>> patch attached and collect all logs when you try the reproduce the >>> issue? It would be great to have logs for both success case and the >>> failure case. >>> >>> Thanks so much for your help. >>> >> >> I think we have a potential fix for this issue. >> Martin and I found that when addrconf_dst_alloc() creates a rt6, it is >> possible that rt6->dst.dev points to loopback device while >> rt6->rt6i_idev->dev points to a real device. >> When the real device goes down, the current fib6 clean up code only >> checks for rt6->dst.dev and assumes rt6->rt6i_idev->dev is the same. >> That leaves unreleased refcnt on the real device if rt6->dst.dev >> points to loopback dev. >> >> The attached potential fix is tested by Martin and made sure it fixes his issue. >> >> John, >> It will be great if you can also give it a try and see if it fixes the >> issue on your side before I submit an official patch. > > So yes, sorry I haven't been able to get back quicker on the other > patches sent, was mucking about in other work. > > So yea, this patch (potential fix for unregister_netdevice()) seems > to avoid the issue. > > I'm going to do some further testing, but its looking good so far. Looks good so far! I've not hit the issue yet. Thanks so much for sorting out a fix! If its useful: Tested-by: John Stultz <john.stultz@linaro.org> thanks again -john
[toc] | [prev] | [next] | [standalone]
| From | Wei Wang <weiwan@google.com> |
|---|---|
| Date | 2017-08-12 21:30 +0200 |
| Subject | Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 |
| Message-ID | <udKgF-51N-7@gated-at.bofh.it> |
| In reply to | #1710147 |
> Looks good so far! I've not hit the issue yet. > Great. I will prepare an official patch then. > Thanks so much for sorting out a fix! > > If its useful: > Tested-by: John Stultz <john.stultz@linaro.org> Sure will do. Thanks. Wei On Fri, Aug 11, 2017 at 8:07 PM, John Stultz <john.stultz@linaro.org> wrote: > On Fri, Aug 11, 2017 at 5:31 PM, John Stultz <john.stultz@linaro.org> wrote: >> On Fri, Aug 11, 2017 at 5:10 PM, Wei Wang <weiwan@google.com> wrote: >>>> If after Cong's fix, the issue still happens, could you help try the >>>> patch attached and collect all logs when you try the reproduce the >>>> issue? It would be great to have logs for both success case and the >>>> failure case. >>>> >>>> Thanks so much for your help. >>>> >>> >>> I think we have a potential fix for this issue. >>> Martin and I found that when addrconf_dst_alloc() creates a rt6, it is >>> possible that rt6->dst.dev points to loopback device while >>> rt6->rt6i_idev->dev points to a real device. >>> When the real device goes down, the current fib6 clean up code only >>> checks for rt6->dst.dev and assumes rt6->rt6i_idev->dev is the same. >>> That leaves unreleased refcnt on the real device if rt6->dst.dev >>> points to loopback dev. >>> >>> The attached potential fix is tested by Martin and made sure it fixes his issue. >>> >>> John, >>> It will be great if you can also give it a try and see if it fixes the >>> issue on your side before I submit an official patch. >> >> So yes, sorry I haven't been able to get back quicker on the other >> patches sent, was mucking about in other work. >> >> So yea, this patch (potential fix for unregister_netdevice()) seems >> to avoid the issue. >> >> I'm going to do some further testing, but its looking good so far. > > Looks good so far! I've not hit the issue yet. > > Thanks so much for sorting out a fix! > > If its useful: > Tested-by: John Stultz <john.stultz@linaro.org> > > thanks again > -john
[toc] | [prev] | [next] | [standalone]
| From | Wei Wang <weiwan@google.com> |
|---|---|
| Date | 2017-08-12 21:30 +0200 |
| Subject | Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 |
| Message-ID | <udKgG-51N-11@gated-at.bofh.it> |
| In reply to | #1710147 |
On Fri, Aug 11, 2017 at 8:07 PM, John Stultz <john.stultz@linaro.org> wrote: > On Fri, Aug 11, 2017 at 5:31 PM, John Stultz <john.stultz@linaro.org> wrote: >> On Fri, Aug 11, 2017 at 5:10 PM, Wei Wang <weiwan@google.com> wrote: >>>> If after Cong's fix, the issue still happens, could you help try the >>>> patch attached and collect all logs when you try the reproduce the >>>> issue? It would be great to have logs for both success case and the >>>> failure case. >>>> >>>> Thanks so much for your help. >>>> >>> >>> I think we have a potential fix for this issue. >>> Martin and I found that when addrconf_dst_alloc() creates a rt6, it is >>> possible that rt6->dst.dev points to loopback device while >>> rt6->rt6i_idev->dev points to a real device. >>> When the real device goes down, the current fib6 clean up code only >>> checks for rt6->dst.dev and assumes rt6->rt6i_idev->dev is the same. >>> That leaves unreleased refcnt on the real device if rt6->dst.dev >>> points to loopback dev. >>> >>> The attached potential fix is tested by Martin and made sure it fixes his issue. >>> >>> John, >>> It will be great if you can also give it a try and see if it fixes the >>> issue on your side before I submit an official patch. >> >> So yes, sorry I haven't been able to get back quicker on the other >> patches sent, was mucking about in other work. >> >> So yea, this patch (potential fix for unregister_netdevice()) seems >> to avoid the issue. >> >> I'm going to do some further testing, but its looking good so far. > > Looks good so far! I've not hit the issue yet. > > Thanks so much for sorting out a fix! > > If its useful: > Tested-by: John Stultz <john.stultz@linaro.org> > > thanks again > -john
[toc] | [prev] | [next] | [standalone]
| From | Ido Schimmel <idosch@idosch.org> |
|---|---|
| Date | 2017-08-12 20:20 +0200 |
| Subject | Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 |
| Message-ID | <udJaV-4mD-1@gated-at.bofh.it> |
| In reply to | #1710119 |
Hi Wei,
On Fri, Aug 11, 2017 at 05:10:02PM -0700, Wei Wang wrote:
> I think we have a potential fix for this issue.
> Martin and I found that when addrconf_dst_alloc() creates a rt6, it is
> possible that rt6->dst.dev points to loopback device while
> rt6->rt6i_idev->dev points to a real device.
> When the real device goes down, the current fib6 clean up code only
> checks for rt6->dst.dev and assumes rt6->rt6i_idev->dev is the same.
> That leaves unreleased refcnt on the real device if rt6->dst.dev
> points to loopback dev.
[...]
> From 2d8861808c2029013f6b6e86120ba6902329145b Mon Sep 17 00:00:00 2001
> From: Wei Wang <weiwan@google.com>
> Date: Fri, 11 Aug 2017 16:36:04 -0700
> Subject: [PATCH 1/2] potential fix for unregister_netdevice()
>
> Change-Id: I5d5f6f7a7ad0f5dd769f33487db17ff2570d52ea
> ---
> net/ipv6/route.c | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 4d30c96a819d..105922903932 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -417,14 +417,12 @@ static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
> struct net_device *loopback_dev =
> dev_net(dev)->loopback_dev;
>
> - if (dev != loopback_dev) {
> - if (idev && idev->dev == dev) {
> - struct inet6_dev *loopback_idev =
> - in6_dev_get(loopback_dev);
> - if (loopback_idev) {
> - rt->rt6i_idev = loopback_idev;
> - in6_dev_put(idev);
> - }
> + if (idev && idev->dev != loopback_dev) {
> + struct inet6_dev *loopback_idev =
> + in6_dev_get(loopback_dev);
> + if (loopback_idev) {
> + rt->rt6i_idev = loopback_idev;
> + in6_dev_put(idev);
> }
> }
> }
> @@ -2789,7 +2787,8 @@ static int fib6_ifdown(struct rt6_info *rt, void *arg)
> const struct arg_dev_net *adn = arg;
> const struct net_device *dev = adn->dev;
>
> - if ((rt->dst.dev == dev || !dev) &&
> + if ((rt->dst.dev == dev || !dev ||
> + rt->rt6i_idev->dev == dev) &&
Can you please explain why this line is needed? While host routes aren't
removed from the FIB by rt6_ifdown() (when dst.dev goes down), they are
removed later on in addrconf_ifdown().
With your patch, if I check the return value of ip6_del_rt() in
__ipv6_ifa_notify() I see that -ENONET is returned. Because the host
route was already removed by rt6_ifdown(). When the line in question is
removed from the patch I don't get the error anymore.
Is it possible that in John's case the host route was correctly removed
from the FIB and that the unreleased reference was due to a wrong check
in ip6_dst_ifdown() (which you patched correctly AFAICT)?
Thanks
> rt != adn->net->ipv6.ip6_null_entry &&
> (rt->rt6i_nsiblings == 0 ||
> (dev && netdev_unregistering(dev)) ||
> --
> 2.14.0.434.g98096fd7a8-goog
>
[toc] | [prev] | [next] | [standalone]
| From | Wei Wang <weiwan@google.com> |
|---|---|
| Date | 2017-08-12 21:50 +0200 |
| Subject | Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 |
| Message-ID | <udKA2-5bj-19@gated-at.bofh.it> |
| In reply to | #1710347 |
Hi Ido,
>> - if ((rt->dst.dev == dev || !dev) &&
>> + if ((rt->dst.dev == dev || !dev ||
>> + rt->rt6i_idev->dev == dev) &&
>
> Can you please explain why this line is needed? While host routes aren't
> removed from the FIB by rt6_ifdown() (when dst.dev goes down), they are
> removed later on in addrconf_ifdown().
>
Yes.. Agree. But one difference is that if the route is removed from
addrconf_ifdown(), dst_dev_put() won't be called to release the
devices before doing dst_release(). It is OK if dst_release() sees the
refcnt on dst already drops to 0 and directly destroys the dst. But I
think it will cause problem if at the time, the dst is still held by
some other users because then the refcnt on the device going down will
not get released.
That's why I think we should remove the dst with either dst->dev ==
going down dev or rt6->rt6i_idev->dev == going down dev from the fib6
tree always because there, we always call dst_dev_put() to release the
device.
> With your patch, if I check the return value of ip6_del_rt() in
> __ipv6_ifa_notify() I see that -ENONET is returned. Because the host
> route was already removed by rt6_ifdown(). When the line in question is
> removed from the patch I don't get the error anymore.
>
Right. That is expected as the route is already removed from the tree.
> Is it possible that in John's case the host route was correctly removed
> from the FIB and that the unreleased reference was due to a wrong check
> in ip6_dst_ifdown() (which you patched correctly AFAICT)?
>
Yes. possible. But as I explained earlier, I still think we should
also remove routes with rt6->rt6i_idev->dev == going down dev from the
tree.
Thanks.
Wei
On Sat, Aug 12, 2017 at 11:01 AM, Ido Schimmel <idosch@idosch.org> wrote:
> Hi Wei,
>
> On Fri, Aug 11, 2017 at 05:10:02PM -0700, Wei Wang wrote:
>> I think we have a potential fix for this issue.
>> Martin and I found that when addrconf_dst_alloc() creates a rt6, it is
>> possible that rt6->dst.dev points to loopback device while
>> rt6->rt6i_idev->dev points to a real device.
>> When the real device goes down, the current fib6 clean up code only
>> checks for rt6->dst.dev and assumes rt6->rt6i_idev->dev is the same.
>> That leaves unreleased refcnt on the real device if rt6->dst.dev
>> points to loopback dev.
>
> [...]
>
>> From 2d8861808c2029013f6b6e86120ba6902329145b Mon Sep 17 00:00:00 2001
>> From: Wei Wang <weiwan@google.com>
>> Date: Fri, 11 Aug 2017 16:36:04 -0700
>> Subject: [PATCH 1/2] potential fix for unregister_netdevice()
>>
>> Change-Id: I5d5f6f7a7ad0f5dd769f33487db17ff2570d52ea
>> ---
>> net/ipv6/route.c | 17 ++++++++---------
>> 1 file changed, 8 insertions(+), 9 deletions(-)
>>
>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
>> index 4d30c96a819d..105922903932 100644
>> --- a/net/ipv6/route.c
>> +++ b/net/ipv6/route.c
>> @@ -417,14 +417,12 @@ static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
>> struct net_device *loopback_dev =
>> dev_net(dev)->loopback_dev;
>>
>> - if (dev != loopback_dev) {
>> - if (idev && idev->dev == dev) {
>> - struct inet6_dev *loopback_idev =
>> - in6_dev_get(loopback_dev);
>> - if (loopback_idev) {
>> - rt->rt6i_idev = loopback_idev;
>> - in6_dev_put(idev);
>> - }
>> + if (idev && idev->dev != loopback_dev) {
>> + struct inet6_dev *loopback_idev =
>> + in6_dev_get(loopback_dev);
>> + if (loopback_idev) {
>> + rt->rt6i_idev = loopback_idev;
>> + in6_dev_put(idev);
>> }
>> }
>> }
>> @@ -2789,7 +2787,8 @@ static int fib6_ifdown(struct rt6_info *rt, void *arg)
>> const struct arg_dev_net *adn = arg;
>> const struct net_device *dev = adn->dev;
>>
>> - if ((rt->dst.dev == dev || !dev) &&
>> + if ((rt->dst.dev == dev || !dev ||
>> + rt->rt6i_idev->dev == dev) &&
>
> Can you please explain why this line is needed? While host routes aren't
> removed from the FIB by rt6_ifdown() (when dst.dev goes down), they are
> removed later on in addrconf_ifdown().
>
> With your patch, if I check the return value of ip6_del_rt() in
> __ipv6_ifa_notify() I see that -ENONET is returned. Because the host
> route was already removed by rt6_ifdown(). When the line in question is
> removed from the patch I don't get the error anymore.
>
> Is it possible that in John's case the host route was correctly removed
> from the FIB and that the unreleased reference was due to a wrong check
> in ip6_dst_ifdown() (which you patched correctly AFAICT)?
>
> Thanks
>
>> rt != adn->net->ipv6.ip6_null_entry &&
>> (rt->rt6i_nsiblings == 0 ||
>> (dev && netdev_unregistering(dev)) ||
>> --
>> 2.14.0.434.g98096fd7a8-goog
>>
[toc] | [prev] | [next] | [standalone]
| From | David Ahern <dsahern@gmail.com> |
|---|---|
| Date | 2017-08-13 18:30 +0200 |
| Subject | Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 |
| Message-ID | <ue3W1-YX-1@gated-at.bofh.it> |
| In reply to | #1710360 |
On 8/12/17 1:42 PM, Wei Wang wrote:
> Hi Ido,
>
>>> - if ((rt->dst.dev == dev || !dev) &&
>>> + if ((rt->dst.dev == dev || !dev ||
>>> + rt->rt6i_idev->dev == dev) &&
>>
>> Can you please explain why this line is needed? While host routes aren't
>> removed from the FIB by rt6_ifdown() (when dst.dev goes down), they are
>> removed later on in addrconf_ifdown().
>>
>
> Yes.. Agree. But one difference is that if the route is removed from
> addrconf_ifdown(), dst_dev_put() won't be called to release the
> devices before doing dst_release(). It is OK if dst_release() sees the
> refcnt on dst already drops to 0 and directly destroys the dst. But I
> think it will cause problem if at the time, the dst is still held by
> some other users because then the refcnt on the device going down will
> not get released.
> That's why I think we should remove the dst with either dst->dev ==
> going down dev or rt6->rt6i_idev->dev == going down dev from the fib6
> tree always because there, we always call dst_dev_put() to release the
> device.
>
>> With your patch, if I check the return value of ip6_del_rt() in
>> __ipv6_ifa_notify() I see that -ENONET is returned. Because the host
>> route was already removed by rt6_ifdown(). When the line in question is
>> removed from the patch I don't get the error anymore.
>>
>
> Right. That is expected as the route is already removed from the tree.
>
>> Is it possible that in John's case the host route was correctly removed
>> from the FIB and that the unreleased reference was due to a wrong check
>> in ip6_dst_ifdown() (which you patched correctly AFAICT)?
>>
>
> Yes. possible. But as I explained earlier, I still think we should
> also remove routes with rt6->rt6i_idev->dev == going down dev from the
> tree.
Looking at my patch to move host routes from loopback to device with the
address, I have this:
@@ -2789,7 +2808,8 @@ static int fib6_ifdown(struct rt6_info *rt, void *arg)
const struct arg_dev_net *adn = arg;
const struct net_device *dev = adn->dev;
- if ((rt->dst.dev == dev || !dev) &&
+ if ((rt->dst.dev == dev || !dev ||
+ (netdev_unregistering(dev) && rt->rt6i_idev->dev == dev)) &&
rt != adn->net->ipv6.ip6_null_entry &&
(rt->rt6i_nsiblings == 0 ||
(dev && netdev_unregistering(dev)) ||
[toc] | [prev] | [next] | [standalone]
| From | Wei Wang <weiwan@google.com> |
|---|---|
| Date | 2017-08-13 23:00 +0200 |
| Subject | Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 |
| Message-ID | <ue89k-3tL-27@gated-at.bofh.it> |
| In reply to | #1710569 |
> Looking at my patch to move host routes from loopback to device with the > address, I have this: > > @@ -2789,7 +2808,8 @@ static int fib6_ifdown(struct rt6_info *rt, void *arg) > const struct arg_dev_net *adn = arg; > const struct net_device *dev = adn->dev; > > - if ((rt->dst.dev == dev || !dev) && > + if ((rt->dst.dev == dev || !dev || > + (netdev_unregistering(dev) && rt->rt6i_idev->dev == dev)) && > rt != adn->net->ipv6.ip6_null_entry && > (rt->rt6i_nsiblings == 0 || > (dev && netdev_unregistering(dev)) || As you explained earlier, after your patch, all entries in the fib6 tree will have rt->dst.dev be the same as rt->rt6i_idev->dev except those ones created by p6_rt_cache_alloc() and ip6_rt_pcpu_alloc(). Then the above newly added check is mainly to catch those cached dst entries (created by ip6_rt_cached_alloc()). right? And it is required because __ipv6_ifa_notify() -> ip6_del_rt() won't take care of those cached dst entries. Then I think I should wait for your patches to get merged before submitting my patch? Thanks. Wei On Sun, Aug 13, 2017 at 9:24 AM, David Ahern <dsahern@gmail.com> wrote: > On 8/12/17 1:42 PM, Wei Wang wrote: >> Hi Ido, >> >>>> - if ((rt->dst.dev == dev || !dev) && >>>> + if ((rt->dst.dev == dev || !dev || >>>> + rt->rt6i_idev->dev == dev) && >>> >>> Can you please explain why this line is needed? While host routes aren't >>> removed from the FIB by rt6_ifdown() (when dst.dev goes down), they are >>> removed later on in addrconf_ifdown(). >>> >> >> Yes.. Agree. But one difference is that if the route is removed from >> addrconf_ifdown(), dst_dev_put() won't be called to release the >> devices before doing dst_release(). It is OK if dst_release() sees the >> refcnt on dst already drops to 0 and directly destroys the dst. But I >> think it will cause problem if at the time, the dst is still held by >> some other users because then the refcnt on the device going down will >> not get released. >> That's why I think we should remove the dst with either dst->dev == >> going down dev or rt6->rt6i_idev->dev == going down dev from the fib6 >> tree always because there, we always call dst_dev_put() to release the >> device. >> >>> With your patch, if I check the return value of ip6_del_rt() in >>> __ipv6_ifa_notify() I see that -ENONET is returned. Because the host >>> route was already removed by rt6_ifdown(). When the line in question is >>> removed from the patch I don't get the error anymore. >>> >> >> Right. That is expected as the route is already removed from the tree. >> >>> Is it possible that in John's case the host route was correctly removed >>> from the FIB and that the unreleased reference was due to a wrong check >>> in ip6_dst_ifdown() (which you patched correctly AFAICT)? >>> >> >> Yes. possible. But as I explained earlier, I still think we should >> also remove routes with rt6->rt6i_idev->dev == going down dev from the >> tree. > > Looking at my patch to move host routes from loopback to device with the > address, I have this: > > @@ -2789,7 +2808,8 @@ static int fib6_ifdown(struct rt6_info *rt, void *arg) > const struct arg_dev_net *adn = arg; > const struct net_device *dev = adn->dev; > > - if ((rt->dst.dev == dev || !dev) && > + if ((rt->dst.dev == dev || !dev || > + (netdev_unregistering(dev) && rt->rt6i_idev->dev == dev)) && > rt != adn->net->ipv6.ip6_null_entry && > (rt->rt6i_nsiblings == 0 || > (dev && netdev_unregistering(dev)) || > >
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| From | David Ahern <dsahern@gmail.com> |
|---|---|
| Date | 2017-08-14 01:10 +0200 |
| Subject | Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 |
| Message-ID | <ueab7-4ST-7@gated-at.bofh.it> |
| In reply to | #1710581 |
On 8/13/17 2:56 PM, Wei Wang wrote: >> Looking at my patch to move host routes from loopback to device with the >> address, I have this: >> >> @@ -2789,7 +2808,8 @@ static int fib6_ifdown(struct rt6_info *rt, void *arg) >> const struct arg_dev_net *adn = arg; >> const struct net_device *dev = adn->dev; >> >> - if ((rt->dst.dev == dev || !dev) && >> + if ((rt->dst.dev == dev || !dev || >> + (netdev_unregistering(dev) && rt->rt6i_idev->dev == dev)) && >> rt != adn->net->ipv6.ip6_null_entry && >> (rt->rt6i_nsiblings == 0 || >> (dev && netdev_unregistering(dev)) || > > As you explained earlier, after your patch, all entries in the fib6 > tree will have rt->dst.dev be the same as rt->rt6i_idev->dev except > those ones created by p6_rt_cache_alloc() and ip6_rt_pcpu_alloc(). > Then the above newly added check is mainly to catch those cached dst > entries (created by ip6_rt_cached_alloc()). right? > And it is required because __ipv6_ifa_notify() -> ip6_del_rt() won't > take care of those cached dst entries. > > Then I think I should wait for your patches to get merged before > submitting my patch? no. your patch will need to go back to 4.12; my changes will not be appropriate for that.
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