netdev - Re: [PATCH net] xfrm: reuse uncached

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Date:   Thu, 15 Feb 2018 15:31:45 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     lucien.xin@...il.com
Cc:     netdev@...r.kernel.org, steffen.klassert@...unet.com, fw@...len.de,
        eyal.birger@...il.com, herbert@...dor.apana.org.au,
        weiwan@...gle.com, shannon.nelson@...cle.com,
        shmulik@...anetworks.com
Subject: Re: [PATCH net] xfrm: reuse uncached_list to track xdsts

From: Xin Long <lucien.xin@...il.com>
Date: Wed, 14 Feb 2018 19:06:02 +0800

> In early time, when freeing a xdst, it would be inserted into
> dst_garbage.list first. Then if it's refcnt was still held
> somewhere, later it would be put into dst_busy_list in
> dst_gc_task().
> 
> When one dev was being unregistered, the dev of these dsts in
> dst_busy_list would be set with loopback_dev and put this dev.
> So that this dev's removal wouldn't get blocked, and avoid the
> kmsg warning:
> 
>   kernel:unregister_netdevice: waiting for veth0 to become \
>   free. Usage count = 2
> 
> However after Commit 52df157f17e5 ("xfrm: take refcnt of dst
> when creating struct xfrm_dst bundle"), the xdst will not be
> freed with dst gc, and this warning happens.
> 
> To fix it, we need to find these xdsts that are still held by
> others when removing the dev, and free xdst's dev and set it
> with loopback_dev.
> 
> But unfortunately after flow_cache for xfrm was deleted, no
> list tracks them anymore. So we need to save these xdsts
> somewhere to release the xdst's dev later.
> 
> To make this easier, this patch is to reuse uncached_list to
> track xdsts, so that the dev refcnt can be released in the
> event NETDEV_UNREGISTER process of fib_netdev_notifier.
> 
> Thanks to Florian, we could move forward this fix quickly.
> 
> Fixes: 52df157f17e5 ("xfrm: take refcnt of dst when creating struct xfrm_dst bundle")
> Reported-by: Jianlin Shi <jishi@...hat.com>
> Reported-by: Hangbin Liu <liuhangbin@...il.com>
> Tested-by: Eyal Birger <eyal.birger@...il.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Steffen, I assume you will take this via your ipsec tree?

Thank you.