netdev - Re: [PATCH net-next 1/4] soreuseport: define reuseport groups

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Message-ID: <CAEfhGiyG8Y_amDZ2C8dQoQqjZJMHjTY76b=KBkTKcBtA=dhdGQ@mail.gmail.com>
Date:	Tue, 22 Dec 2015 16:58:11 -0500
From:	Craig Gallek <kraigatgoog@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/4] soreuseport: define reuseport groups

On Tue, Dec 22, 2015 at 4:40 PM, David Miller <davem@...emloft.net> wrote:
> From: Craig Gallek <kraigatgoog@...il.com>
> Date: Tue, 22 Dec 2015 15:05:07 -0500
>
>> +     for (i = 0; i < reuse->num_socks; i++) {
>> +             if (reuse->socks[i] == sk) {
>> +                     reuse->socks[i] = reuse->socks[reuse->num_socks - 1];
>> +                     reuse->num_socks--;
>> +                     if (reuse->num_socks == 0)
>> +                             kfree_rcu(reuse, rcu);
>> +                     break;
>> +             }
>> +     }
>
> Don't you need to memmove() the entire rest of the array down one slot
> when you hit the matching 'sk' in there?  I can't see how it can work
> to only move one entry down.
It moves the last element in the list into the slot that was just
emptied.  You could argue that this may cause unexpected changes in
the index -> socket mapping observed by the user, but I'm not sure
making many socket indexes change (by sliding everything down one)
when one is removed is a desirable behavior either.  I don't have a
strong opinion either way though...
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