linux-kernel - Re: [PATCH v3 05/23] ata: libahci_platform: Explicitly set rc on devres

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Date:   Thu, 12 May 2022 08:27:53 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Rob Herring <robh+dt@...nel.org>, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 05/23] ata: libahci_platform: Explicitly set rc on
 devres_alloc failure

On 5/12/22 01:17, Serge Semin wrote:
> It's better for readability and maintainability to explicitly assign an
> error number to the variable used then as a return value from the method
> on the cleanup-on-error path. So adding new code in the method we won't
> have to think whether the overridden rc-variable is set afterward in case
> of an error. Saving one line of code doesn't worth it especially seeing
> the rest of the ahci_platform_get_resources() function errors handling
> blocks do explicitly write errno to rc.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> 
> ---
> 
> Changelog v2:
> - Drop rc variable initialization (@Damien)
> ---
>   drivers/ata/libahci_platform.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
> index 32495ae96567..f7f9bfcfc164 100644
> --- a/drivers/ata/libahci_platform.c
> +++ b/drivers/ata/libahci_platform.c
> @@ -389,7 +389,7 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
>   	struct ahci_host_priv *hpriv;
>   	struct clk *clk;
>   	struct device_node *child;
> -	int i, enabled_ports = 0, rc = -ENOMEM, child_nodes;
> +	int i, enabled_ports = 0, rc, child_nodes;
>   	u32 mask_port_map = 0;
>   
>   	if (!devres_open_group(dev, NULL, GFP_KERNEL))
> @@ -397,8 +397,10 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
>   
>   	hpriv = devres_alloc(ahci_platform_put_resources, sizeof(*hpriv),
>   			     GFP_KERNEL);
> -	if (!hpriv)
> +	if (!hpriv) {
> +		rc = -ENOMEM;
>   		goto err_out;
> +	}
>   
>   	devres_add(dev, hpriv);
>   
I disagree.
As 'rc' is now only initialized within a conditional we're risking 'rc' 
will be left uninitialized.
And in the end, it's a matter of style; this patch doesn't change the 
flow of events and the benefits are hard to see.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@...e.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer