linux-kernel - Re: [PATCH v2] cxl/region: Remove lock from memory notifier callback

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Message-ID: <87frqgb1wv.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Wed, 04 Sep 2024 10:14:40 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Ira Weiny <ira.weiny@...el.com>
Cc: Davidlohr Bueso <dave@...olabs.net>,  Jonathan Cameron
 <jonathan.cameron@...wei.com>,  Dave Jiang <dave.jiang@...el.com>,  Alison
 Schofield <alison.schofield@...el.com>,  Vishal Verma
 <vishal.l.verma@...el.com>,  Dan Williams <dan.j.williams@...el.com>,
  linux-cxl@...r.kernel.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] cxl/region: Remove lock from memory notifier callback

Hi, Ira,

Ira Weiny <ira.weiny@...el.com> writes:

[snip]

> @@ -2391,18 +2389,6 @@ static bool cxl_region_update_coordinates(struct cxl_region *cxlr, int nid)
>  	return true;
>  }
>  
> -static int cxl_region_nid(struct cxl_region *cxlr)
> -{
> -	struct cxl_region_params *p = &cxlr->params;
> -	struct resource *res;
> -
> -	guard(rwsem_read)(&cxl_region_rwsem);
> -	res = p->res;
> -	if (!res)
> -		return NUMA_NO_NODE;
> -	return phys_to_target_node(res->start);
> -}
> -
>  static int cxl_region_perf_attrs_callback(struct notifier_block *nb,
>  					  unsigned long action, void *arg)
>  {
> @@ -2415,7 +2401,7 @@ static int cxl_region_perf_attrs_callback(struct notifier_block *nb,
>  	if (nid == NUMA_NO_NODE || action != MEM_ONLINE)
>  		return NOTIFY_DONE;
>  
> -	region_nid = cxl_region_nid(cxlr);
> +	region_nid = phys_to_target_node(cxlr->params.res->start);

Better to add some comments about why we don't need to hold
cxl_region_rwsem to access cxlr->params.res here?

Otherwise, LGTM, Thanks!  Feel free to add

Reviewed-by: "Huang, Ying" <ying.huang@...el.com>

in the future versions.

>  	if (nid != region_nid)
>  		return NOTIFY_DONE;
>  
> @@ -2434,7 +2420,7 @@ static int cxl_region_calculate_adistance(struct notifier_block *nb,
>  	int *adist = data;
>  	int region_nid;
>  
> -	region_nid = cxl_region_nid(cxlr);
> +	region_nid = phys_to_target_node(cxlr->params.res->start);
>  	if (nid != region_nid)
>  		return NOTIFY_OK;
>  

[snip]

--
Best Regards,
Huang, Ying