linux-kernel - Re: [RFC PATCH 04/11] drivers/base/devcoredump: convert devcd_count to counter

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Message-ID: <20200923103149.GH3154647@kroah.com>
Date:   Wed, 23 Sep 2020 12:31:49 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     johannes@...solutions.net, rafael@...nel.org,
        keescook@...omium.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 04/11] drivers/base/devcoredump: convert devcd_count
 to counter_atomic

On Tue, Sep 22, 2020 at 07:43:33PM -0600, Shuah Khan wrote:
> counter_atomic is introduced to be used when a variable is used as
> a simple counter and doesn't guard object lifetimes. This clearly
> differentiates atomic_t usages that guard object lifetimes.
> 
> counter_atomic variables will wrap around to 0 when it overflows and
> should not be used to guard resource lifetimes, device usage and
> open counts that control state changes, and pm states.
> 
> devcd_count is used to track dev_coredumpm device count and used in
> device name string. It doesn't guard object lifetimes, device usage
> counts, device open counts, and pm states. There is very little chance
> of this counter overflowing. Convert it to use counter_atomic.
> 
> This conversion doesn't change the oveflow wrap around behavior.
> 
> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
> ---
>  drivers/base/devcoredump.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c
> index e42d0b514384..d719424d1e0b 100644
> --- a/drivers/base/devcoredump.c
> +++ b/drivers/base/devcoredump.c
> @@ -16,6 +16,7 @@
>  #include <linux/slab.h>
>  #include <linux/fs.h>
>  #include <linux/workqueue.h>
> +#include <linux/counters.h>
>  
>  static struct class devcd_class;
>  
> @@ -255,7 +256,7 @@ void dev_coredumpm(struct device *dev, struct module *owner,
>  				   void *data, size_t datalen),
>  		   void (*free)(void *data))
>  {
> -	static atomic_t devcd_count = ATOMIC_INIT(0);
> +	static struct counter_atomic devcd_count = COUNTER_ATOMIC_INIT(0);
>  	struct devcd_entry *devcd;
>  	struct device *existing;
>  
> @@ -286,7 +287,7 @@ void dev_coredumpm(struct device *dev, struct module *owner,
>  	device_initialize(&devcd->devcd_dev);
>  
>  	dev_set_name(&devcd->devcd_dev, "devcd%d",
> -		     atomic_inc_return(&devcd_count));
> +		     counter_atomic_inc_return(&devcd_count));
>  	devcd->devcd_dev.class = &devcd_class;
>  
>  	if (device_add(&devcd->devcd_dev))
> -- 
> 2.25.1
> 

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>