netdev - Re: [Patch net v3 2/3] net_sched: fix reference counting of tc filter chain

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Message-ID: <20170912104312.GF2036@nanopsycho>
Date:   Tue, 12 Sep 2017 12:43:12 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev@...r.kernel.org, jiri@...lanox.com,
        jakub.kicinski@...ronome.com, jhs@...atatu.com
Subject: Re: [Patch net v3 2/3] net_sched: fix reference counting of tc
 filter chain

Tue, Sep 12, 2017 at 01:33:31AM CEST, xiyou.wangcong@...il.com wrote:
>This patch fixes the following ugliness of tc filter chain refcnt:
>
>a) tp proto should hold a refcnt to the chain too. This significantly
>   simplifies the logic.
>
>b) Chain 0 is no longer special, it is created with refcnt=1 like any
>   other chains. All the ugliness in tcf_chain_put() can be gone!
>
>c) No need to handle the flushing oddly, because block still holds
>   chain 0, it can not be released, this guarantees block is the last
>   user.
>
>d) The race condition with RCU callbacks is easier to handle with just
>   a rcu_barrier(). Much easier to understand, nothing to hide. Thanks
>   to the previous patch. Please see also the comments in code.
>
>e) Make the code understandable by humans, much less error-prone.
>
>Fixes: 744a4cf63e52 ("net: sched: fix use after free when tcf_chain_destroy is called multiple times")
>Fixes: 5bc1701881e3 ("net: sched: introduce multichain support for filters")
>Cc: Jiri Pirko <jiri@...lanox.com>
>Cc: Jamal Hadi Salim <jhs@...atatu.com>
>Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>

Looking good to me. Thanks!

Acked-by: Jiri Pirko <jiri@...lanox.com>