netdev - Re: [PATCH net] mld: fix panic in mld

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Date:   Sun, 27 Dec 2020 11:24:28 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Taehee Yoo <ap420073@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net] mld: fix panic in mld_newpack()

On Sun, Dec 27, 2020 at 6:40 AM Taehee Yoo <ap420073@...il.com> wrote:
> But I'm so sorry I didn't understand some points.
>
> 1. you said "both side" and I understand these as follows:
> a) failure of allocation because of a high order and it is fixed
> by 72e09ad107e7
> b) kernel panic because of 72e09ad107e7
> Are these two issues right?

Yes, we can't fix one by reverting the fix for the other.

>
> 2. So, as far as I understand your mention, these timers are
> good to be changed to the delayed works And these timers are mca_timer,
> mc_gq_timer, mc_ifc_timer, mc_dad_timer.
> Do I understand your mention correctly?
> If so, what is the benefit of it?
> I, unfortunately, couldn't understand the relationship between changing
> timers to the delayed works and these issues.

Because a work has process context so we can use GFP_KERNEL
allocation rather than GFP_ATOMIC, which is what commit 72e09ad107e7
addresses.

Thanks.