linux-kernel - Re: [PATCH 2/4] mm/memory_hotplug: Call register_mem_sect_under

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Date:   Wed, 20 Jun 2018 22:03:11 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     osalvador@...hadventures.net
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        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 2/4] mm/memory_hotplug: Call register_mem_sect_under_node

On Fri, Jun 1, 2018 at 8:54 AM <osalvador@...hadventures.net> wrote:
>
> From: Oscar Salvador <osalvador@...e.de>
>
> When hotpluging memory, it is possible that two calls are being made
> to register_mem_sect_under_node().
> One comes from __add_section()->hotplug_memory_register()
> and the other from add_memory_resource()->link_mem_sections() if
> we had to register a new node.
>
> In case we had to register a new node, hotplug_memory_register()
> will only handle/allocate the memory_block's since
> register_mem_sect_under_node() will return right away because the
> node it is not online yet.

Indeed.

>
> I think it is better if we leave hotplug_memory_register() to
> handle/allocate only memory_block's and make link_mem_sections()
> to call register_mem_sect_under_node().

Agree, this makes the code simpler.

Please remove:
> +register_fail:
> +       /*
> +        * If sysfs file of new node can't create, cpu on the node
> +        * can't be hot-added. There is no rollback way now.
> +        * So, check by BUG_ON() to catch it reluctantly..
> +        */
> +       BUG_ON(ret);

Merge the above comment with:
> +               /* we online node here. we can't roll back from here. */

And replace all:
> +       if (ret)
> +               goto register_fail;

With:
BUG_ON(ret);

With the above addressed:

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