linux-kernel - Re: [PATCH v1 1/7] cxl/core: Use guard() to replace open-coded down

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Message-ID: <5ba7516c-2856-4bd1-9d5b-0e33ea91addc@zohomail.com>
Date: Wed, 12 Feb 2025 14:36:16 +0800
From: Li Ming <ming.li@...omail.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: dave@...olabs.net, dave.jiang@...el.com, alison.schofield@...el.com,
 vishal.l.verma@...el.com, ira.weiny@...el.com, dan.j.williams@...el.com,
 linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/7] cxl/core: Use guard() to replace open-coded
 down_read/write()

On 2/12/2025 1:26 AM, Jonathan Cameron wrote:
> On Tue, 11 Feb 2025 15:57:21 +0800
> Li Ming <ming.li@...omail.com> wrote:
>
>> Some down/up_read() and down/up_write() cases can be replaced by a
>> guard() simply to drop explicit unlock invoked. It helps to align coding
>> style with current CXL subsystem's.
>>
>> Signed-off-by: Li Ming <ming.li@...omail.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>
> I wondered if it was worth doing some early returns and dropping
> local variables, but on balance think it isn't worth doing.
>
>
>> @@ -364,10 +362,9 @@ resource_size_t cxl_dpa_size(struct cxl_endpoint_decoder *cxled)
>>  {
>>  	resource_size_t size = 0;
>>  
>> -	down_read(&cxl_dpa_rwsem);
>> +	guard(rwsem_read)(&cxl_dpa_rwsem);
>>  	if (cxled->dpa_res)
>>  		size = resource_size(cxled->dpa_res);
> Could return resource_size() here and return 0 below.
> I'm not sure it gains us much though. 

Right, I will do it in V2.


>> -	up_read(&cxl_dpa_rwsem);
>>  
>>  	return size;
>>  }
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index e8d11a988fd9..e3bb33109ced 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -3216,10 +3216,9 @@ static int match_region_by_range(struct device *dev, const void *data)
>>  	cxlr = to_cxl_region(dev);
>>  	p = &cxlr->params;
>>  
>> -	down_read(&cxl_region_rwsem);
>> +	guard(rwsem_read)(&cxl_region_rwsem);
>>  	if (p->res && p->res->start == r->start && p->res->end == r->end)
>>  		rc = 1;
> could do return 1 here and return 0 but it doesn't gain us much.

Will do it in V2. thanks for review.


Ming

>
>> -	up_read(&cxl_region_rwsem);
>>  
>>  	return rc;
>>  }
>