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

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Date:   Thu, 7 Jun 2018 11:48:51 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     <osalvador@...hadventures.net>
CC:     <akpm@...ux-foundation.org>, <mhocko@...e.com>, <vbabka@...e.cz>,
        <pasha.tatashin@...cle.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH 1/4] mm/memory_hotplug: Make add_memory_resource use
 __try_online_node

On Fri, 1 Jun 2018 14:53:18 +0200
<osalvador@...hadventures.net> wrote:

> From: Oscar Salvador <osalvador@...e.de>
> 
> add_memory_resource() contains code to allocate a new node in case
> it is necessary.
> Since try_online_node() also hast some code for this purpose,
> let us make use of that and remove duplicate code.
> 
> This introduces __try_online_node(), which is called by add_memory_resource()
> and try_online_node().
> __try_online_node() has two new parameters, start_addr of the node,
> and if the node should be onlined and registered right away.
> This is always wanted if we are calling from do_cpu_up(), but not
> when we are calling from memhotplug code.
> Nothing changes from the point of view of the users of try_online_node(),
> since try_online_node passes start_addr=0 and online_node=true to
> __try_online_node().
> 

Trivial whitespace issue inline...

> Signed-off-by: Oscar Salvador <osalvador@...e.de>
> ---
>  mm/memory_hotplug.c | 61 +++++++++++++++++++++++++++++------------------------
>  1 file changed, 34 insertions(+), 27 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 7deb49f69e27..29a5fc89bdb1 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1034,8 +1034,10 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>  	return pgdat;
>  }
>  
> -static void rollback_node_hotadd(int nid, pg_data_t *pgdat)
> +static void rollback_node_hotadd(int nid)
>  {
> +	pg_data_t *pgdat = NODE_DATA(nid);
> +
>  	arch_refresh_nodedata(nid, NULL);
>  	free_percpu(pgdat->per_cpu_nodestats);
>  	arch_free_nodedata(pgdat);
> @@ -1046,28 +1048,43 @@ static void rollback_node_hotadd(int nid, pg_data_t *pgdat)
>  /**
>   * try_online_node - online a node if offlined
>   * @nid: the node ID
> - *
> + * @start: start addr of the node
> + * @set_node_online: Whether we want to online the node
>   * called by cpu_up() to online a node without onlined memory.
>   */
> -int try_online_node(int nid)
> +static int __try_online_node(int nid, u64 start, bool set_node_online)
>  {
> -	pg_data_t	*pgdat;
> -	int	ret;
> +	pg_data_t *pgdat;
> +	int ret = 1;
>  
>  	if (node_online(nid))
>  		return 0;
>  
> -	mem_hotplug_begin();
> -	pgdat = hotadd_new_pgdat(nid, 0);
> +	pgdat = hotadd_new_pgdat(nid, start);
>  	if (!pgdat) {
>  		pr_err("Cannot online node %d due to NULL pgdat\n", nid);
>  		ret = -ENOMEM;
>  		goto out;
>  	}
> -	node_set_online(nid);
> -	ret = register_one_node(nid);
> -	BUG_ON(ret);
> +
> +	if (set_node_online) {
> +		node_set_online(nid);
> +		ret = register_one_node(nid);
> +		BUG_ON(ret);
> +	}
>  out:
> +	return ret;
> +}
> +
> +/*
> + * Users of this function always want to online/register the node
> + */
> +int try_online_node(int nid)
> +{
> +	int ret;
> +
> +	mem_hotplug_begin();
> +	ret =  __try_online_node (nid, 0, true);
>  	mem_hotplug_done();
>  	return ret;
>  }
> @@ -1099,8 +1116,6 @@ static int online_memory_block(struct memory_block *mem, void *arg)
>  int __ref add_memory_resource(int nid, struct resource *res, bool online)
>  {
>  	u64 start, size;
> -	pg_data_t *pgdat = NULL;
> -	bool new_pgdat;
>  	bool new_node;
>  	int ret;
>  
> @@ -1111,11 +1126,6 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online)
>  	if (ret)
>  		return ret;
>  
> -	{	/* Stupid hack to suppress address-never-null warning */
> -		void *p = NODE_DATA(nid);
> -		new_pgdat = !p;
> -	}
> -
>  	mem_hotplug_begin();
>  
>  	/*
> @@ -1126,17 +1136,14 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online)
>  	 */
>  	memblock_add_node(start, size, nid);
>  
> -	new_node = !node_online(nid);
> -	if (new_node) {
> -		pgdat = hotadd_new_pgdat(nid, start);
> -		ret = -ENOMEM;
> -		if (!pgdat)
> -			goto error;
> -	}
> +	ret = __try_online_node (nid, start, false);

space before (


> +	new_node = !!(ret > 0);
> +	if (ret < 0)
> +		goto error;
> +
>  
>  	/* call arch's memory hotadd */
>  	ret = arch_add_memory(nid, start, size, NULL, true);
> -
>  	if (ret < 0)
>  		goto error;
>  
> @@ -1180,8 +1187,8 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online)
>  
>  error:
>  	/* rollback pgdat allocation and others */
> -	if (new_pgdat && pgdat)
> -		rollback_node_hotadd(nid, pgdat);
> +	if (new_node)
> +		rollback_node_hotadd(nid);
>  	memblock_remove(start, size);
>  
>  out: