linux-kernel - Re: [PATCH 2/2] PCI: endpoint: Use scoped

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Message-ID: <20250502094313.000055d1@huawei.com>
Date: Fri, 2 May 2025 09:43:13 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Erick Karanja <karanja99erick@...il.com>
CC: <manivannan.sadhasivam@...aro.org>, <kw@...ux.com>, <kishon@...nel.org>,
	<bhelgaas@...gle.com>, <linux-pci@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <julia.lawall@...ia.fr>
Subject: Re: [PATCH 2/2] PCI: endpoint: Use scoped_guard for manual mutex
 lock/unlock

On Thu,  1 May 2025 18:56:12 +0300
Erick Karanja <karanja99erick@...il.com> wrote:

> This refactor replaces manual mutex lock/unlock with scoped_guard()
> in places where early exits use goto. Using scoped_guard()
> avoids error-prone unlock paths and simplifies control flow.
> 
> Signed-off-by: Erick Karanja <karanja99erick@...il.com>
> ---
>  drivers/pci/endpoint/pci-epc-core.c | 53 +++++++++++++----------------
>  1 file changed, 24 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index beabea00af91..3f3ff36fa8ab 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -709,7 +709,6 @@ int pci_epc_add_epf(struct pci_epc *epc, struct pci_epf *epf,
>  {
>  	struct list_head *list;
>  	u32 func_no;
> -	int ret = 0;
>  
>  	if (IS_ERR_OR_NULL(epc) || epf->is_vf)
>  		return -EINVAL;
> @@ -720,36 +719,32 @@ int pci_epc_add_epf(struct pci_epc *epc, struct pci_epf *epf,
>  	if (type == SECONDARY_INTERFACE && epf->sec_epc)
>  		return -EBUSY;
>  
> -	mutex_lock(&epc->list_lock);
> -	func_no = find_first_zero_bit(&epc->function_num_map,
> -				      BITS_PER_LONG);
> -	if (func_no >= BITS_PER_LONG) {
> -		ret = -EINVAL;
> -		goto ret;
> -	}
> -
> -	if (func_no > epc->max_functions - 1) {
> -		dev_err(&epc->dev, "Exceeding max supported Function Number\n");
> -		ret = -EINVAL;
> -		goto ret;
> +	scoped_guard(mutex, &epc->list_lock) {
This one is better, but using
	guard(mutex)(&epc->list_lock);
Is going to make for an easier to read patch and lower indent etc.

Unless there is some subsystem related reason that scoped_guard() is
preferred then I'd go that way.

> +		func_no = find_first_zero_bit(&epc->function_num_map,
> +					      BITS_PER_LONG);
> +		if (func_no >= BITS_PER_LONG)
> +			return -EINVAL;
> +
> +		if (func_no > epc->max_functions - 1) {
> +			dev_err(&epc->dev, "Exceeding max supported Function Number\n");
> +			return -EINVAL;
> +		}
> +
> +		set_bit(func_no, &epc->function_num_map);
> +		if (type == PRIMARY_INTERFACE) {
> +			epf->func_no = func_no;
> +			epf->epc = epc;
> +			list = &epf->list;
> +		} else {
> +			epf->sec_epc_func_no = func_no;
> +			epf->sec_epc = epc;
> +			list = &epf->sec_epc_list;
> +		}
> +
> +		list_add_tail(list, &epc->pci_epf);
>  	}
>  
> -	set_bit(func_no, &epc->function_num_map);
> -	if (type == PRIMARY_INTERFACE) {
> -		epf->func_no = func_no;
> -		epf->epc = epc;
> -		list = &epf->list;
> -	} else {
> -		epf->sec_epc_func_no = func_no;
> -		epf->sec_epc = epc;
> -		list = &epf->sec_epc_list;
> -	}
> -
> -	list_add_tail(list, &epc->pci_epf);
> -ret:
> -	mutex_unlock(&epc->list_lock);
> -
> -	return ret;
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(pci_epc_add_epf);
>