netdev - Re: [Patch net] netns: correct gfp flags for alloc

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Date:	Thu, 26 Feb 2015 19:29:57 -0800
From:	Cong Wang <cwang@...pensource.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Cong Wang <xiyou.wangcong@...il.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>
Subject: Re: [Patch net] netns: correct gfp flags for alloc_netid()

On Thu, Feb 26, 2015 at 6:34 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2015-02-26 at 18:19 -0800, Cong Wang wrote:
>
>>
>> LOL, it has been changed back and forth.
>>
>> I thought rcu read lock was introduced to optimize dumping
>> performance, if it were really important, we should solve the
>> deadlock you mentioned in commit 2907c35ff647080?
>>
>> Otherwise, as you said, completely revert to using rtnl lock.
>
> Dumping is so fat nowadays, it makes sense to remove rcu_read_lock() to
> allow cond_resched() eventually.
>
> rcu_read_lock() made sense _if_ RTNL mutex could be avoided, but
> unfortunately this could not be done easily.

Thinking a bit more, in this specific case, we don't have to allocate
memory in dumping. I am testing the attached patch.

>
> Please try this patch instead :
>

It should fix the warning, I can test it tomorrow.

Thanks.

View attachment "netns.patch" of type "text/x-patch" (3093 bytes)