netdev - Re: [PATCH net v2] net: nsid cannot be allocated for a dead netns

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Date:   Wed, 16 Nov 2016 22:32:18 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        Andrey Wagin <avagin@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net v2] net: nsid cannot be allocated for a dead netns

On Wed, Nov 16, 2016 at 8:17 PM, David Miller <davem@...emloft.net> wrote:
> From: Cong Wang <xiyou.wangcong@...il.com>
> Date: Wed, 16 Nov 2016 09:29:29 -0800
>
>> On Wed, Nov 16, 2016 at 1:49 AM, Nicolas Dichtel
>> <nicolas.dichtel@...nd.com> wrote:
>>> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
>>> index f61c0e02a413..63f65387f4e1 100644
>>> --- a/net/core/net_namespace.c
>>> +++ b/net/core/net_namespace.c
>>> @@ -159,6 +159,9 @@ static int alloc_netid(struct net *net, struct net *peer, int reqid)
>>>                 max = reqid + 1;
>>>         }
>>>
>>> +       if (!atomic_read(&net->count) || !atomic_read(&peer->count))
>>> +               return -EINVAL;
>>> +
>>>         return idr_alloc(&net->netns_ids, peer, min, max, GFP_ATOMIC);
>>>  }
>>
>>
>> There is already a check in peernet2id_alloc(), so why not just the following?
>>
>> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
>> index f61c0e0..7001da9 100644
>> --- a/net/core/net_namespace.c
>> +++ b/net/core/net_namespace.c
>> @@ -219,6 +219,8 @@ int peernet2id_alloc(struct net *net, struct net *peer)
>>         bool alloc;
>>         int id;
>>
>> +       if (atomic_read(&net->count) == 0)
>> +               return NETNSA_NSID_NOT_ASSIGNED;
>>         spin_lock_irqsave(&net->nsid_lock, flags);
>>         alloc = atomic_read(&peer->count) == 0 ? false : true;
>>         id = __peernet2id_alloc(net, peer, &alloc);
>
> Indeed, this looks cleaner, Nicolas?

Yeah, I already sent a formal patch:
https://patchwork.ozlabs.org/patch/695747/

since Nicolas' patch doesn't even compile...