linux-kernel - Re: [PATCH v2 7/7] cxl/region: Drop goto pattern of construct

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Message-ID: <4e30257f-5535-4333-abf5-d424436ee853@intel.com>
Date: Wed, 19 Feb 2025 10:24:33 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Li Ming <ming.li@...omail.com>, dave@...olabs.net,
 jonathan.cameron@...wei.com, alison.schofield@...el.com,
 vishal.l.verma@...el.com, ira.weiny@...el.com, dan.j.williams@...el.com
Cc: linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 7/7] cxl/region: Drop goto pattern of
 construct_region()



On 2/17/25 7:48 AM, Li Ming wrote:
> Some operations need to be protected by the cxl_region_rwsem in
> construct_region(). Currently, construct_region() uses down_write() and
> up_write() for the cxl_region_rwsem locking, so there is a goto pattern
> after down_write() invoked to release cxl_region_rwsem.
> 
> construct region() can be optimized to remove the goto pattern. The
> changes are creating a new function called construct_auto_region() which
> will include all checking and operations protected by the
> cxl_region_rwsem, and using guard(rwsem_write) to replace down_write()
> and up_write() in construct_auto_region().
> 
> Signed-off-by: Li Ming <ming.li@...omail.com>
Reviewed-by: Dave Jiang <dave.jiang@...el.com>

> ---
> v2:
> - Rename __construct_region() to construct_auto_region(). (Jonathan and Dave)
> ---
>  drivers/cxl/core/region.c | 71 +++++++++++++++++++++------------------
>  1 file changed, 39 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 320a3f218131..7a9e51aba9f4 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3216,49 +3216,31 @@ static int match_region_by_range(struct device *dev, const void *data)
>  	return 0;
>  }
>  
> -/* Establish an empty region covering the given HPA range */
> -static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> -					   struct cxl_endpoint_decoder *cxled)
> +static int construct_auto_region(struct cxl_region *cxlr,
> +				 struct cxl_root_decoder *cxlrd,
> +				 struct cxl_endpoint_decoder *cxled)
>  {
>  	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> -	struct cxl_port *port = cxlrd_to_port(cxlrd);
>  	struct range *hpa = &cxled->cxld.hpa_range;
>  	struct cxl_region_params *p;
> -	struct cxl_region *cxlr;
>  	struct resource *res;
>  	int rc;
>  
> -	do {
> -		cxlr = __create_region(cxlrd, cxled->mode,
> -				       atomic_read(&cxlrd->region_id));
> -	} while (IS_ERR(cxlr) && PTR_ERR(cxlr) == -EBUSY);
> -
> -	if (IS_ERR(cxlr)) {
> -		dev_err(cxlmd->dev.parent,
> -			"%s:%s: %s failed assign region: %ld\n",
> -			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev),
> -			__func__, PTR_ERR(cxlr));
> -		return cxlr;
> -	}
> -
> -	down_write(&cxl_region_rwsem);
> +	guard(rwsem_write)(&cxl_region_rwsem);
>  	p = &cxlr->params;
>  	if (p->state >= CXL_CONFIG_INTERLEAVE_ACTIVE) {
>  		dev_err(cxlmd->dev.parent,
>  			"%s:%s: %s autodiscovery interrupted\n",
>  			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev),
>  			__func__);
> -		rc = -EBUSY;
> -		goto err;
> +		return -EBUSY;
>  	}
>  
>  	set_bit(CXL_REGION_F_AUTO, &cxlr->flags);
>  
>  	res = kmalloc(sizeof(*res), GFP_KERNEL);
> -	if (!res) {
> -		rc = -ENOMEM;
> -		goto err;
> -	}
> +	if (!res)
> +		return -ENOMEM;
>  
>  	*res = DEFINE_RES_MEM_NAMED(hpa->start, range_len(hpa),
>  				    dev_name(&cxlr->dev));
> @@ -3281,7 +3263,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>  
>  	rc = sysfs_update_group(&cxlr->dev.kobj, get_cxl_region_target_group());
>  	if (rc)
> -		goto err;
> +		return rc;
>  
>  	dev_dbg(cxlmd->dev.parent, "%s:%s: %s %s res: %pr iw: %d ig: %d\n",
>  		dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev), __func__,
> @@ -3290,14 +3272,39 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>  
>  	/* ...to match put_device() in cxl_add_to_region() */
>  	get_device(&cxlr->dev);
> -	up_write(&cxl_region_rwsem);
>  
> -	return cxlr;
> +	return 0;
> +}
>  
> -err:
> -	up_write(&cxl_region_rwsem);
> -	devm_release_action(port->uport_dev, unregister_region, cxlr);
> -	return ERR_PTR(rc);
> +/* Establish an empty region covering the given HPA range */
> +static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
> +					   struct cxl_endpoint_decoder *cxled)
> +{
> +	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> +	struct cxl_port *port = cxlrd_to_port(cxlrd);
> +	struct cxl_region *cxlr;
> +	int rc;
> +
> +	do {
> +		cxlr = __create_region(cxlrd, cxled->mode,
> +				       atomic_read(&cxlrd->region_id));
> +	} while (IS_ERR(cxlr) && PTR_ERR(cxlr) == -EBUSY);
> +
> +	if (IS_ERR(cxlr)) {
> +		dev_err(cxlmd->dev.parent,
> +			"%s:%s: %s failed assign region: %ld\n",
> +			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev),
> +			__func__, PTR_ERR(cxlr));
> +		return cxlr;
> +	}
> +
> +	rc = construct_auto_region(cxlr, cxlrd, cxled);
> +	if (rc) {
> +		devm_release_action(port->uport_dev, unregister_region, cxlr);
> +		return ERR_PTR(rc);
> +	}
> +
> +	return cxlr;
>  }
>  
>  int cxl_add_to_region(struct cxl_port *root, struct cxl_endpoint_decoder *cxled)