netdev - Re: [PATCH v2 09/15] cxl: define a driver interface for HPA free space enumaration

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Message-ID: <3e8b9c3e-f533-8eab-d560-0afe68108e10@amd.com>
Date: Thu, 25 Jul 2024 12:59:07 +0100
From: Alejandro Lucero Palau <alucerop@....com>
To: "Li, Ming4" <ming4.li@...el.com>, alejandro.lucero-palau@....com,
 linux-cxl@...r.kernel.org, netdev@...r.kernel.org, dan.j.williams@...el.com,
 martin.habets@...inx.com, edward.cree@....com, davem@...emloft.net,
 kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com,
 richard.hughes@....com
Subject: Re: [PATCH v2 09/15] cxl: define a driver interface for HPA free
 space enumaration


On 7/25/24 06:51, Li, Ming4 wrote:
> On 7/24/2024 4:24 PM, Alejandro Lucero Palau wrote:
>> On 7/16/24 07:06, Li, Ming4 wrote:
>>> On 7/16/2024 1:28 AM, alejandro.lucero-palau@....com wrote:
>>>> From: Alejandro Lucero <alucerop@....com>
>>>>
>>>>
>>> Could use scope-based resource management  __free() here to drop below put_device(&root_port->dev);
>>>
>>> e.g. struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(endpoint);
>>>
>> I need to admit not familiar yet with scope-based macros, but I think these are different things. The scope of the pointer is inside this function, but the data referenced is likely to persist.
>>
>>
>>   get_device, inside find_cxl_root, is needed to avoid the device-related data disappearing while referenced by the code inside this function, and at the time of put_device, the data will be freed if ref counter reaches 0. Am I missing something?
>>
> Yes, get_device() is to avoid the device-related data disappearing, __free(put_cxl_root) will help to release the reference of cxl_root->port.dev when cxl_get_hpa_freespace() finished, so that you don't need a put_device(&root_port->dev) in the function.
>
> I think that your case is similar to this patch
>
> https://lore.kernel.org/all/170449247353.3779673.5963704495491343135.stgit@djiang5-mobl3/
>

OK. It makes sense. I was blinded assuming it was just about freeing 
memory, but the function to call for cleaning up can do other things as 
well.

I will use it in next version.

Thanks