netdev - Re: [patch v2 04/11] nf_conntrack_netlink: pass nf_conntrack_netlink module to netlink_dump

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Message-ID: <5062F6A9.7020309@cn.fujitsu.com>
Date:	Wed, 26 Sep 2012 20:35:53 +0800
From:	Gao feng <gaofeng@...fujitsu.com>
To:	Pablo Neira Ayuso <pablo@...filter.org>
CC:	davem@...emloft.net, eric.dumazet@...il.com,
	steffen.klassert@...unet.com, netfilter-devel@...r.kernel.org,
	linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
	linux-crypto@...r.kernel.org, stephen.hemminger@...tta.com,
	jengelh@...i.de
Subject: Re: [patch v2 04/11] nf_conntrack_netlink: pass nf_conntrack_netlink
 module to netlink_dump_start

于 2012年09月26日 17:58, Pablo Neira Ayuso 写道:
> On Wed, Sep 26, 2012 at 05:42:31PM +0800, Gao feng wrote:
>> Hi Pablo:
>>
>> 于 2012年09月26日 17:26, Pablo Neira Ayuso 写道:
>>> On Wed, Sep 26, 2012 at 04:41:21PM +0800, Gao feng wrote:
>>>> use proper netlink_dump_control.done and .module to avoid panic.
>>>>
>>>> Signed-off-by: Gao feng <gaofeng@...fujitsu.com>
>>>> ---
>>>>  net/netfilter/nf_conntrack_netlink.c |    8 ++++++++
>>>>  1 files changed, 8 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
>>>> index 9807f32..509a257 100644
>>>> --- a/net/netfilter/nf_conntrack_netlink.c
>>>> +++ b/net/netfilter/nf_conntrack_netlink.c
>>>> @@ -706,6 +706,7 @@ static int ctnetlink_done(struct netlink_callback *cb)
>>>>  		nf_ct_put((struct nf_conn *)cb->args[1]);
>>>>  	if (cb->data)
>>>>  		kfree(cb->data);
>>>> +	netlink_dump_done(cb);
>>>
>>> I think you can call netlink_dump_done from af_netlink.c:
>>>
>>> static int netlink_dump(struct sock *sk) 
>>>         ...
>>>         if (cb->done) {
>>>                 cb->done(cb);
>>>                 netlink_dump_done(...);
>>>         }
>>>
>>> Thus, you don't need to change netlink_dump_control in every netlink
>>> subsystem.
>>
>> because cb->done is called by netlink_sock_destruct too,it's very usefully
>> when userspace program only send dump request to kernel without reading
>> data from kernel.
> 
> Then add that to netlink_sock_destruct as well. If possible, I prefer
> if this remains in the netlink core to avoid leaking module refcount
> if you forget to call netlink_dump_done.

make sense,I will update it in next version.
Thanks!

> 
>>>
>>>>  	return 0;
>>>>  }
>>>>  
>>>> @@ -1022,6 +1023,7 @@ ctnetlink_get_conntrack(struct sock *ctnl, struct sk_buff *skb,
>>>>  		struct netlink_dump_control c = {
>>>>  			.dump = ctnetlink_dump_table,
>>>>  			.done = ctnetlink_done,
>>>> +			.module = THIS_MODULE,
>>>
>>> You can do something similar to:
>>>
>>> 9f00d97 netlink: hide struct module parameter in netlink_kernel_create
>>>
>>> by definiting netlink_dump_start as static inline and using
>>> THIS_MODULE from there.
>>>
>>> If I'm not missing anything, with those two changes, you will not need
>>> to modify any caller and it will result one single patch.
>>>
>>
>> You can see the patch [11/11], THIS_MODULE in infiniband/core/cma.c
>> means module rdma_cm,but we call netlink_dump_start in infiniband/core/netlink.c
> 
> You can still use __netlink_dump_start for that case, which allows you
> to specify a custom struct module * parameter. But for most cases,
> netlink_dump_start (which hides THIS_MODULE) should be fine.
> 

I don't know how to deal with module_put in this way.
and I think my  way is simple enough.

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