netdev - Re: [PATCH net] ipv4: disable BH in set_ping_group

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Date:   Thu, 20 Oct 2016 14:00:20 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>, Eric Salo <salo@...gle.com>
Subject: Re: [PATCH net] ipv4: disable BH in set_ping_group_range()

On Thu, Oct 20, 2016 at 1:43 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2016-10-20 at 12:44 -0700, Cong Wang wrote:
>> On Thu, Oct 20, 2016 at 12:40 PM, Cong Wang <xiyou.wangcong@...il.com> wrote:
>> > On Thu, Oct 20, 2016 at 12:32 PM, Cong Wang <xiyou.wangcong@...il.com> wrote:
>> >> On Thu, Oct 20, 2016 at 10:26 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> >>> From: Eric Dumazet <edumazet@...gle.com>
>> >>>
>> >>> In commit 4ee3bd4a8c746 ("ipv4: disable BH when changing ip local port
>> >>> range") Cong added BH protection in set_local_port_range() but missed
>> >>> that same fix was needed in set_ping_group_range()
>> >>
>> >> Don't know why ping_group_range shares the same lock with local_port_range...
>> >> Perhaps just for saving a few bytes, but that is why I missed this place.
>> >
>> > Hold on... We clearly have typos there... Your fix is not correct.
>>
>> We need the attached patch, your patch should be reverted, because
>> unlike local_port_range we never read it in BH context, no need to bother _bh.
>
> Well, we do not change this sysctl very often, so I am not sure why we
> need different seqlocks to protect these ranges.
>
> Seems a waste of space really (per netns)

Error prone vs. space saving, it's up to you...

But clearly current code is still broken even after your patch. I will send
a revert + previous typo fix.