linux-kernel - Re: [PATCH] memory-hotplug: don't BUG() in register_memory

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Date:	Tue, 22 Dec 2015 13:56:54 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>
cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tang Chen <tangchen@...fujitsu.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Xishi Qiu <qiuxishi@...wei.com>,
	Sheng Yong <shengyong1@...wei.com>,
	Zhu Guihua <zhugh.fnst@...fujitsu.com>,
	Dan Williams <dan.j.williams@...el.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Igor Mammedov <imammedo@...hat.com>
Subject: Re: [PATCH] memory-hotplug: don't BUG() in
 register_memory_resource()

On Fri, 18 Dec 2015, Vitaly Kuznetsov wrote:

> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 67d488a..9392f01 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -127,11 +127,13 @@ void mem_hotplug_done(void)
>  }
>  
>  /* add this memory to iomem resource */
> -static struct resource *register_memory_resource(u64 start, u64 size)
> +static int register_memory_resource(u64 start, u64 size,
> +				    struct resource **resource)
>  {
>  	struct resource *res;
>  	res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> -	BUG_ON(!res);
> +	if (!res)
> +		return -ENOMEM;
>  
>  	res->name = "System RAM";
>  	res->start = start;
> @@ -140,9 +142,10 @@ static struct resource *register_memory_resource(u64 start, u64 size)
>  	if (request_resource(&iomem_resource, res) < 0) {
>  		pr_debug("System RAM resource %pR cannot be added\n", res);
>  		kfree(res);
> -		res = NULL;
> +		return -EEXIST;
>  	}
> -	return res;
> +	*resource = res;
> +	return 0;
>  }
>  
>  static void release_memory_resource(struct resource *res)
> @@ -1311,9 +1314,9 @@ int __ref add_memory(int nid, u64 start, u64 size)
>  	struct resource *res;
>  	int ret;
>  
> -	res = register_memory_resource(start, size);
> -	if (!res)
> -		return -EEXIST;
> +	ret = register_memory_resource(start, size, &res);
> +	if (ret)
> +		return ret;
>  
>  	ret = add_memory_resource(nid, res);
>  	if (ret < 0)

Wouldn't it be simpler and cleaner to keep the return type of 
register_memory_resource() the same and return ERR_PTR(-ENOMEM) or 
ERR_PTR(-EEXIST) on error?  add_memory() can check IS_ERR(res) and return 
PTR_ERR(res).
--
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