linux-kernel - Re: [v4 5/6] mm/memory_hotplug: don't read nid from struct page during hotplug

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Date:   Fri, 16 Feb 2018 10:19:18 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>
Cc:     steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        akpm@...ux-foundation.org, mgorman@...hsingularity.net,
        mhocko@...e.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, vbabka@...e.cz,
        bharata@...ux.vnet.ibm.com, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org, dan.j.williams@...el.com,
        kirill.shutemov@...ux.intel.com, bhe@...hat.com
Subject: Re: [v4 5/6] mm/memory_hotplug: don't read nid from struct page
 during hotplug


* Pavel Tatashin <pasha.tatashin@...cle.com> wrote:

> During memory hotplugging the probe routine will leave struct pages
> uninitialized, the same as it is currently done during boot. Therefore, we
> do not want to access the inside of struct pages before
> __init_single_page() is called during onlining.
> 
> Because during hotplug we know that pages in one memory block belong to
> the same numa node, we can skip the checking. We should keep checking for
> the boot case.
> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
> ---
>  drivers/base/memory.c |  2 +-
>  drivers/base/node.c   | 22 +++++++++++++++-------
>  include/linux/node.h  |  4 ++--
>  3 files changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index deb3f029b451..a14fb0cd424a 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -731,7 +731,7 @@ int register_new_memory(int nid, struct mem_section *section)
>  	}
>  
>  	if (mem->section_count == sections_per_block)
> -		ret = register_mem_sect_under_node(mem, nid);
> +		ret = register_mem_sect_under_node(mem, nid, false);
>  out:

The namespace of all these memory range handling functions is horribly random,
and I think now it got worse: we add an assumption that register_new_memory() is 
implicitly called as part of hotplugged memory (where things are pre-cleared) - 
but nothing in its naming suggests so.

How about renaming it to hotplug_memory_register() or so?

With that change you can add:

  Reviewed-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo