linux-kernel - Re: [PATCH] iommu: use iommu_group_ref

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Message-ID: <5f47c5b7-534d-5714-1f91-04005ada8b8f@arm.com>
Date:   Tue, 30 Aug 2022 10:32:24 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Yuan Can <yuancan@...wei.com>, joro@...tes.org, will@...nel.org,
        iommu@...ts.linux.dev
Cc:     linux-kernel@...r.kernel.org, baolu.lu@...ux.intel.com,
        haifeng.zhao@...ux.intel.com
Subject: Re: [PATCH] iommu: use iommu_group_ref_get to hold group reference

On 2022-08-26 03:40, Yuan Can wrote:
> Replace kobject_get with iommu_group_ref_get for better
> readability.

I disagree, sorry. iommu_group_ref_get() is meant as a helper for 
drivers, and the core code uses the raw kobject internally everywhere 
else, including several other times within this function. Especially the 
raw kobject_put() in the cleanup path - in terms of readability I'd say 
it's actively harmful to obfuscate what that pairs with.

Thanks,
Robin.

> Signed-off-by: Yuan Can <yuancan@...wei.com>
> ---
>   drivers/iommu/iommu.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 780fb7071577..8e7f30f7188c 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -903,7 +903,7 @@ int iommu_group_add_device(struct iommu_group *group, struct device *dev)
>   		goto err_free_name;
>   	}
>   
> -	kobject_get(group->devices_kobj);
> +	iommu_group_ref_get(group);
>   
>   	dev->iommu_group = group;
>