linux-kernel - Re: [PATCH] fs/proc/vmcore: a few cleanups for vmcore_add_device

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Message-ID: <33a9a2a5-a725-4ab0-865c-1d26e941e054@suswa.mountain>
Date: Mon, 23 Jun 2025 18:06:40 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Su Hui <suhui@...china.com>
Cc: akpm@...ux-foundation.org, bhe@...hat.com, vgoyal@...hat.com,
	dyoung@...hat.com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] fs/proc/vmcore: a few cleanups for vmcore_add_device_dump

On Mon, Jun 23, 2025 at 06:47:05PM +0800, Su Hui wrote:
> There are three cleanups for vmcore_add_device_dump(). Adjust data_size's
> type from 'size_t' to 'unsigned int' for the consistency of data->size.
> Return -ENOMEM directly rather than goto the label to simplify the code.
> Using scoped_guard() to simplify the lock/unlock code.
> 
> Signed-off-by: Su Hui <suhui@...china.com>
> ---
>  fs/proc/vmcore.c | 33 ++++++++++++++-------------------
>  1 file changed, 14 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index 10d01eb09c43..9ac2863c68d8 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -1477,7 +1477,7 @@ int vmcore_add_device_dump(struct vmcoredd_data *data)
>  {
>  	struct vmcoredd_node *dump;
>  	void *buf = NULL;
> -	size_t data_size;
> +	unsigned int data_size;
>  	int ret;

This was in reverse Christmas tree order before.  Move the data_size
declaration up a line.

	long long_variable_name;
	medium variable_name;
	short name;

>  
>  	if (vmcoredd_disabled) {
> @@ -1490,10 +1490,8 @@ int vmcore_add_device_dump(struct vmcoredd_data *data)
>  		return -EINVAL;
>  
>  	dump = vzalloc(sizeof(*dump));
> -	if (!dump) {
> -		ret = -ENOMEM;
> -		goto out_err;
> -	}
> +	if (!dump)
> +		return -ENOMEM;
>  
>  	/* Keep size of the buffer page aligned so that it can be mmaped */
>  	data_size = roundup(sizeof(struct vmcoredd_header) + data->size,
> @@ -1519,21 +1517,18 @@ int vmcore_add_device_dump(struct vmcoredd_data *data)
>  	dump->size = data_size;
>  
>  	/* Add the dump to driver sysfs list and update the elfcore hdr */
> -	mutex_lock(&vmcore_mutex);
> -	if (vmcore_opened)
> -		pr_warn_once("Unexpected adding of device dump\n");
> -	if (vmcore_open) {
> -		ret = -EBUSY;
> -		goto unlock;
> -	}
> -
> -	list_add_tail(&dump->list, &vmcoredd_list);
> -	vmcoredd_update_size(data_size);
> -	mutex_unlock(&vmcore_mutex);
> -	return 0;
> +	scoped_guard(mutex, &vmcore_mutex) {
> +		if (vmcore_opened)
> +			pr_warn_once("Unexpected adding of device dump\n");
> +		if (vmcore_open) {
> +			ret = -EBUSY;
> +			goto out_err;
> +		}
>  
> -unlock:
> -	mutex_unlock(&vmcore_mutex);
> +		list_add_tail(&dump->list, &vmcoredd_list);
> +		vmcoredd_update_size(data_size);
> +		return 0;

Please, move this "return 0;" out of the scoped_guard().  Otherwise
it's not obvious that we return zero on the success path.

regards,
dan carpenter

> +	}
>  
>  out_err:
>  	vfree(buf);
> -- 
> 2.30.2
>