linux-kernel - Re: [PATCH v3] af_netlink: ensure that NLMSG

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Date:   Thu, 9 Nov 2017 11:57:27 +0900
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] af_netlink: ensure that NLMSG_DONE never fails in dumps

On Thu, Nov 9, 2017 at 11:02 AM, Johannes Berg
<johannes@...solutions.net> wrote:
> nit: I think your line got a little long here :)

Ack. For v4.

> and here

Ack. For v4.

>
>> +     nlk->dump_done_errno = INT_MAX;
>
> I guess positive values aren't really returned from dump?

When a positive value is returned, the API uses this to signify that
the dump is not done, and it should be called again. When 0 or
negative is returned, it means the dump is complete and the return
value should be returned in DONE. We therefore initialize
dump_done_errno to some positive value, so that we can make calling
->dump() conditional on it being positive. When it becomes zero or
negative, it's time to return. This mirrors the semantics of the
actual ->dump() function precisely.