linux-kernel - Re: [PATCH 1/4] mm/memory_hotplug: Make add_memory_resource use __try_online

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Date:   Wed, 20 Jun 2018 21:41:35 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     osalvador@...hadventures.net, Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, osalvador@...e.de
Subject: Re: [PATCH 1/4] mm/memory_hotplug: Make add_memory_resource use __try_online_node

> I don't think __try_online_node() will ever return a value greater than
> zero.  I assume what was meant was

Hi Andrew and Oscar,

Actually, the new __try_online_node()  returns:
1 -> a new node was allocated
0 -> node is already online
-error -> an error encountered.

The function simply missing the return comment at the beginning.

Oscar, please check it via ./scripts/checkpatch.pl

Add comment explaining the return values.

And change:
        ret = __try_online_node (nid, start, false);
        new_node = !!(ret > 0);
        if (ret < 0)
                goto error;
To:
        ret = __try_online_node (nid, start, false);
        if (ret < 0)
                goto error;
        new_node = ret;

Other than that the patch looks good to me, it simplifies the code.
So, if the above is addressed:

Reviewed-by: Pavel Tatashin <pasha.tatashin@...cle.com>

Thank you,
Pavel

>
>         new_node = !!(ret >= 0);
>
> which may as well be
>
>         new_node = (ret >= 0);
>
> since both sides have bool type.
>
> The fact that testing didn't detect this is worrisome....
>
> > +     if (ret < 0)
> > +             goto error;
> > +
> >
> >       /* call arch's memory hotadd */
> >       ret = arch_add_memory(nid, start, size, NULL, true);
> > -
> >       if (ret < 0)
> >               goto error;
> >
> >
> > ...
> >
>