linux-kernel - Re: [PATCH v6 2/4] dax/bus: Use guard(device) in sysfs attribute helpers

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Date: Tue, 19 Dec 2023 15:27:26 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Vishal Verma <vishal.l.verma@...el.com>
CC: Dan Williams <dan.j.williams@...el.com>, Dave Jiang
	<dave.jiang@...el.com>, Andrew Morton <akpm@...ux-foundation.org>, "Oscar
 Salvador" <osalvador@...e.de>, <linux-kernel@...r.kernel.org>,
	<nvdimm@...ts.linux.dev>, <linux-cxl@...r.kernel.org>, David Hildenbrand
	<david@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>, Huang Ying
	<ying.huang@...el.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-mm@...ck.org>, Joao Martins <joao.m.martins@...cle.com>
Subject: Re: [PATCH v6 2/4] dax/bus: Use guard(device) in sysfs attribute
 helpers

On Thu, 14 Dec 2023 22:25:27 -0700
Vishal Verma <vishal.l.verma@...el.com> wrote:

> Use the guard(device) macro to lock a 'struct device', and unlock it
> automatically when going out of scope using Scope Based Resource
> Management semantics. A lot of the sysfs attribute writes in
> drivers/dax/bus.c benefit from a cleanup using these, so change these
> where applicable.
> 
> Cc: Joao Martins <joao.m.martins@...cle.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@...el.com>
Hi Vishal,

A few really minor suggestions inline if you happen to be doing a v7.
Either way
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

>  
> @@ -481,12 +466,9 @@ static int __free_dev_dax_id(struct dev_dax *dev_dax)
>  static int free_dev_dax_id(struct dev_dax *dev_dax)
>  {
>  	struct device *dev = &dev_dax->dev;
> -	int rc;
>  
> -	device_lock(dev);
> -	rc = __free_dev_dax_id(dev_dax);
> -	device_unlock(dev);
> -	return rc;
> +	guard(device)(dev);

	guard(device)(&dev_dax->dev); /* Only one user now */
	
> +	return __free_dev_dax_id(dev_dax);
>  }
>  
>  static int alloc_dev_dax_id(struct dev_dax *dev_dax)
> @@ -908,9 +890,8 @@ static ssize_t size_show(struct device *dev,
>  	struct dev_dax *dev_dax = to_dev_dax(dev);
>  	unsigned long long size;
>  
> -	device_lock(dev);
> +	guard(device)(dev);
>  	size = dev_dax_size(dev_dax);
> -	device_unlock(dev);
>  
>  	return sprintf(buf, "%llu\n", size);
Might as well make this

	guard(device)(dev);
	return sprintf(buf, "%llu\n", dev_dax_size(to_dev_dax(dev));

>  }