linux-kernel - Re: [PATCH v3 07/18] cxl/region: Avoid duplicate call of cxl_find_decoder

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Message-ID: <20250214160725.0000662f@huawei.com>
Date: Fri, 14 Feb 2025 16:07:25 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Robert Richter <rrichter@....com>
CC: Alison Schofield <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Dan Williams
	<dan.j.williams@...el.com>, Dave Jiang <dave.jiang@...el.com>, "Davidlohr
 Bueso" <dave@...olabs.net>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Gregory Price <gourry@...rry.net>, "Fabio M.
 De Francesco" <fabio.m.de.francesco@...ux.intel.com>, Terry Bowman
	<terry.bowman@....com>
Subject: Re: [PATCH v3 07/18] cxl/region: Avoid duplicate call of
 cxl_find_decoder_early()

On Tue, 11 Feb 2025 10:53:37 +0100
Robert Richter <rrichter@....com> wrote:

> Function cxl_find_decoder_early() is called twice, in
> alloc_region_ref() and cxl_rr_alloc_decoder(). Move it out there and

out where?  I'd make it clear that both these calls are in
cxl_port_attach_region()

> instead pass the decoder as function argument to both.
> 
> Signed-off-by: Robert Richter <rrichter@....com>
> Reviewed-by: Gregory Price <gourry@...rry.net>
> Tested-by: Gregory Price <gourry@...rry.net>

I think this is fine but it's not immediately obvious so a request
inline for some more details in this description.

> ---
>  drivers/cxl/core/region.c | 31 +++++++++++++++----------------
>  1 file changed, 15 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 13e3ba984a53..b8201c2faa87 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -908,7 +908,8 @@ static bool auto_order_ok(struct cxl_port *port, struct cxl_region *cxlr_iter,
>  
>  static struct cxl_region_ref *
>  alloc_region_ref(struct cxl_port *port, struct cxl_region *cxlr,
> -		 struct cxl_endpoint_decoder *cxled)
> +		 struct cxl_endpoint_decoder *cxled,
> +		 struct cxl_decoder *cxld)
>  {
>  	struct cxl_region_params *p = &cxlr->params;
>  	struct cxl_region_ref *cxl_rr, *iter;
> @@ -922,9 +923,6 @@ alloc_region_ref(struct cxl_port *port, struct cxl_region *cxlr,
>  			continue;
>  
>  		if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
> -			struct cxl_decoder *cxld;
> -
> -			cxld = cxl_find_decoder_early(port, cxled, cxlr);


This is buried a little deep to be obviously fine to lift out.
Seems like it should always have been done outside the xa_for_each()
loop in here.  So I think this is fine but maybe some more in the
patch description is needed to make that point.

>  			if (auto_order_ok(port, iter->region, cxld))
>  				continue;
>  		}
> @@ -1008,17 +1006,9 @@ static int cxl_rr_ep_add(struct cxl_region_ref *cxl_rr,
>  
>  static int cxl_rr_alloc_decoder(struct cxl_port *port, struct cxl_region *cxlr,
>  				struct cxl_endpoint_decoder *cxled,
> -				struct cxl_region_ref *cxl_rr)
> +				struct cxl_region_ref *cxl_rr,
> +				struct cxl_decoder *cxld)
>  {
> -	struct cxl_decoder *cxld;
> -
> -	cxld = cxl_find_decoder_early(port, cxled, cxlr);
> -	if (!cxld) {
> -		dev_dbg(&cxlr->dev, "%s: no decoder available\n",
> -			dev_name(&port->dev));
> -		return -EBUSY;
> -	}
> -
>  	if (cxld->region) {
>  		dev_dbg(&cxlr->dev, "%s: %s already attached to %s\n",
>  			dev_name(&port->dev), dev_name(&cxld->dev),
> @@ -1109,7 +1099,16 @@ static int cxl_port_attach_region(struct cxl_port *port,
>  			nr_targets_inc = true;
>  		}
>  	} else {
> -		cxl_rr = alloc_region_ref(port, cxlr, cxled);
> +		struct cxl_decoder *cxld;
> +
> +		cxld = cxl_find_decoder_early(port, cxled, cxlr);
> +		if (!cxld) {
> +			dev_dbg(&cxlr->dev, "%s: no decoder available\n",
> +				dev_name(&port->dev));
> +			return -EBUSY;
> +		}
> +
> +		cxl_rr = alloc_region_ref(port, cxlr, cxled, cxld);
>  		if (IS_ERR(cxl_rr)) {
>  			dev_dbg(&cxlr->dev,
>  				"%s: failed to allocate region reference\n",
> @@ -1118,7 +1117,7 @@ static int cxl_port_attach_region(struct cxl_port *port,
>  		}
>  		nr_targets_inc = true;
>  
> -		rc = cxl_rr_alloc_decoder(port, cxlr, cxled, cxl_rr);
> +		rc = cxl_rr_alloc_decoder(port, cxlr, cxled, cxl_rr, cxld);
>  		if (rc)
>  			goto out_erase;
>  	}