linux-kernel - Re: [PATCH 5/9] mm, memory_hotplug: split up register_one

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Date:   Thu, 13 Apr 2017 16:05:17 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Michal Hocko <mhocko@...nel.org>, linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
        slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 5/9] mm, memory_hotplug: split up register_one_node

On 04/10/2017 01:03 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> Memory hotplug (add_memory_resource) has to reinitialize node
> infrastructure if the node is offline (one which went through the
> complete add_memory(); remove_memory() cycle). That involves node
> registration to the kobj infrastructure (register_node), the proper
> association with cpus (register_cpu_under_node) and finally creation of
> node<->memblock symlinks (link_mem_sections).
> 
> The last part requires to know node_start_pfn and node_spanned_pages
> which we currently have but a leter patch will postpone this
> initialization to the onlining phase which happens later. In fact we do
> not need to rely on the early pgdat initialization even now because the
> currently hot added pfn range is currently known.
> 
> Split register_one_node into core which does all the common work for
> the boot time NUMA initialization and the hotplug (__register_one_node).
> register_one_node keeps the full initialization while hotplug calls
> __register_one_node and manually calls link_mem_sections for the proper
> range.
> 
> This shouldn't introduce any functional change.
> 
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

nit:
> @@ -1387,7 +1387,22 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online)
>  	node_set_online(nid);
>  
>  	if (new_node) {
> -		ret = register_one_node(nid);
> +		unsigned long start_pfn = start >> PAGE_SHIFT;
> +		unsigned long nr_pages = size >> PAGE_SHIFT;
> +
> +		ret = __register_one_node(nid);
> +		if (ret)
> +			goto register_fail;
> +
> +		/*
> +		 * link memory sections under this node. This is already
> +		 * done when creatig memory section in register_new_memory
> +		 * but that depends to have the node registered so offline
> +		 * nodes have to go through register_node.
> +		 * TODO clean up this mess.

Is this a work-in-progress or final TODO? :)

> +		 */
> +		ret = link_mem_sections(nid, start_pfn, nr_pages);
> +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.
>