Re: [PATCH v2 5/7] cxl/core: Use guard() to drop goto pattern of cxl_dpa_alloc()

[Dave Jiang]

On 2/17/25 7:48 AM, Li Ming wrote:
> In cxl_dpa_alloc(), some checking and operations need to be protected by
> a rwsem called cxl_dpa_rwsem, so there is a goto pattern in
> cxl_dpa_alloc() to release the rwsem. The goto pattern can be optimized
> by using guard() to hold the rwsem.
> 
> Creating a new function called __cxl_dpa_alloc() to include all checking
> and operations needed to be procted by cxl_dpa_rwsem. Using
s/procted/protected/

> guard(rwsem_write()) to hold cxl_dpa_rwsem at the beginning of the new
> function.
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> Signed-off-by: Li Ming <ming.li@xxxxxxxxxxxx>

Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> ---
>  drivers/cxl/core/hdm.c | 29 ++++++++++++++---------------
>  1 file changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 874a791f8292..1edbf7873471 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -442,29 +442,25 @@ int cxl_dpa_set_mode(struct cxl_endpoint_decoder *cxled,
>  	return 0;
>  }
>  
> -int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
> +static int __cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
>  {
>  	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
>  	resource_size_t free_ram_start, free_pmem_start;
> -	struct cxl_port *port = cxled_to_port(cxled);
>  	struct cxl_dev_state *cxlds = cxlmd->cxlds;
>  	struct device *dev = &cxled->cxld.dev;
>  	resource_size_t start, avail, skip;
>  	struct resource *p, *last;
> -	int rc;
>  
> -	down_write(&cxl_dpa_rwsem);
> +	guard(rwsem_write)(&cxl_dpa_rwsem);
>  	if (cxled->cxld.region) {
>  		dev_dbg(dev, "decoder attached to %s\n",
>  			dev_name(&cxled->cxld.region->dev));
> -		rc = -EBUSY;
> -		goto out;
> +		return -EBUSY;
>  	}
>  
>  	if (cxled->cxld.flags & CXL_DECODER_F_ENABLE) {
>  		dev_dbg(dev, "decoder enabled\n");
> -		rc = -EBUSY;
> -		goto out;
> +		return -EBUSY;
>  	}
>  
>  	for (p = cxlds->ram_res.child, last = NULL; p; p = p->sibling)
> @@ -504,21 +500,24 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
>  		skip = skip_end - skip_start + 1;
>  	} else {
>  		dev_dbg(dev, "mode not set\n");
> -		rc = -EINVAL;
> -		goto out;
> +		return -EINVAL;
>  	}
>  
>  	if (size > avail) {
>  		dev_dbg(dev, "%pa exceeds available %s capacity: %pa\n", &size,
>  			cxl_decoder_mode_name(cxled->mode), &avail);
> -		rc = -ENOSPC;
> -		goto out;
> +		return -ENOSPC;
>  	}
>  
> -	rc = __cxl_dpa_reserve(cxled, start, size, skip);
> -out:
> -	up_write(&cxl_dpa_rwsem);
> +	return __cxl_dpa_reserve(cxled, start, size, skip);
> +}
> +
> +int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
> +{
> +	struct cxl_port *port = cxled_to_port(cxled);
> +	int rc;
>  
> +	rc = __cxl_dpa_alloc(cxled, size);
>  	if (rc)
>  		return rc;
>