Subject: Re: [RFC v1 08/14] bus1: implement peer management context
To: Tom Gundersen <teg@jklm.no>
References: <20161026191810.12275-1-dh.herrmann@gmail.com>
 <20161026191810.12275-9-dh.herrmann@gmail.com>
 <CAFLxGvzAQQdKMEDyO-9cWV3EydppCmVNQzikQ0K5jyhBMbRM8Q@mail.gmail.com>
 <CAG-2HqVw64ewD3Tj68g+2M-+SZbRdO_GfkVKHEadutKyerv2vA@mail.gmail.com>
Cc: David Herrmann <dh.herrmann@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Andy Lutomirski <luto@amacapital.net>, Jiri Kosina <jikos@kernel.org>,
        Greg KH <greg@kroah.com>, Hannes Reinecke <hare@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>, Arnd Bergmann <arnd@arndb.de>,
        Josh Triplett <josh@joshtriplett.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>
From: Richard Weinberger <richard@nod.at>
Message-ID: <d2ad100a-f1ed-c9d7-1285-fd8b0d3dd9aa@nod.at>
Date: Fri, 28 Oct 2016 15:21:44 +0200
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On 28.10.2016 15:18, Tom Gundersen wrote:
> On Fri, Oct 28, 2016 at 2:06 PM, Richard Weinberger
> <richard.weinberger@gmail.com> wrote:
>> David, Tom,
>>
>> On Wed, Oct 26, 2016 at 9:18 PM, David Herrmann <dh.herrmann@gmail.com> wrote:
>>> +struct bus1_peer *bus1_peer_new(void)
>>> +{
>>> +       static atomic64_t peer_ids = ATOMIC64_INIT(0);
>>> +       const struct cred *cred = current_cred();
>>> +       struct bus1_peer *peer;
>>> +       struct bus1_user *user;
>>> +
>>> +       user = bus1_user_ref_by_uid(cred->uid);
>>> +       if (IS_ERR(user))
>>> +               return ERR_CAST(user);
>>> +
>>> +       peer = kmalloc(sizeof(*peer), GFP_KERNEL);
>>> +       if (!peer) {
>>> +               bus1_user_unref(user);
>>> +               return ERR_PTR(-ENOMEM);
>>> +       }
>>> +
>>> +       /* initialize constant fields */
>>> +       peer->id = atomic64_inc_return(&peer_ids);
>>
>> What is the purpose of this id? Do other components depend on it
>> and are they aware of possible overflows?
> 
> The id is used purely to give a name to the peer in debugfs.

Okay.

>> Since it is an 64bit integer overflowing it is hard but not impossible.
> 
> Hm, what scenario do you have in mind? I cannot see how this could
> happen (short of creating peers in a loop for hundreds of years).

When it is purely for naming creating peers is slow enough it is no problem
at all. That's why I was asking.

Thanks,
//richard