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
guard(rwsem_write()) to hold cxl_dpa_rwsem at the beginning of the new
function.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Li Ming <ming.li@zohomail.com>
---
 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;
 
-- 
2.34.1

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
> guard(rwsem_write()) to hold cxl_dpa_rwsem at the beginning of the new
> function.
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Li Ming <ming.li@zohomail.com>
> ---
>  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
[..]
> @@ -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);

Am I missing something? This @port variable is unused?

> +	int rc;
>  
> +	rc = __cxl_dpa_alloc(cxled, size);
>  	if (rc)
>  		return rc;
>  

So I think you can drop this new cxl_dpa_alloc + __cxl_dpa_alloc scheme?

After that you can add:

Reviewed-by: Dan Williams <dan.j.williams@intel.com>

On 2/20/2025 9:01 AM, Dan Williams wrote:
> 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
>> guard(rwsem_write()) to hold cxl_dpa_rwsem at the beginning of the new
>> function.
>>
>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>> Signed-off-by: Li Ming <ming.li@zohomail.com>
>> ---
>>  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
> [..]
>> @@ -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);
> Am I missing something? This @port variable is unused?
@port will be used after below __cxl_dpa_alloc().
>
>> +	int rc;
>>  
>> +	rc = __cxl_dpa_alloc(cxled, size);
>>  	if (rc)
>>  		return rc;
>>  
> So I think you can drop this new cxl_dpa_alloc + __cxl_dpa_alloc scheme?

After __cxl_dpa_alloc(), a 'devm_add_action_or_reset(&port->dev, cxl_dpa_release, cxled)' will be invoked, cxl_dpa_rwsem is possible to be held in cxl_dpa_release() in devm_add_action_or_reset() failure case.

So I create __cxl_dpa_alloc() to hold cxl_dpa_rwsem for the operations needed cxl_dpa_resem protection, make sure that the cxl_dpa_rwsem is released before devm_add_action_or_reset() invoking.

>
> After that you can add:
>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>

Li Ming wrote:
[..]
> After __cxl_dpa_alloc(), a 'devm_add_action_or_reset(&port->dev,
> cxl_dpa_release, cxled)' will be invoked, cxl_dpa_rwsem is possible to
> be held in cxl_dpa_release() in devm_add_action_or_reset() failure
> case.
> 
> So I create __cxl_dpa_alloc() to hold cxl_dpa_rwsem for the operations
> needed cxl_dpa_resem protection, make sure that the cxl_dpa_rwsem is
> released before devm_add_action_or_reset() invoking.

Ah, got it, missing context, makes sense.

On Mon, Feb 17, 2025 at 10:48:26PM +0800, 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
> guard(rwsem_write()) to hold cxl_dpa_rwsem at the beginning of the new
> function.
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Li Ming <ming.li@zohomail.com>

Reviewed-by: Alison Schofield <alison.schofield@intel.com>

snip

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@huawei.com>
> Signed-off-by: Li Ming <ming.li@zohomail.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  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;
>