linux-kernel - Re: [PATCH] nbd: Fix return value check for debugfs_create

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Date:	Fri, 12 Feb 2016 15:57:23 +0100
From:	Markus Pargmann <mpa@...gutronix.de>
To:	weiyj_lk@....com
Cc:	Jens Axboe <axboe@...com>,
	Wei Yongjun <yongjun_wei@...ndmicro.com.cn>,
	nbd-general@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nbd: Fix return value check for debugfs_create_*()

Hi,

On Friday, February 05, 2016 09:48:21 PM weiyj_lk@....com wrote:
> From: Wei Yongjun <yongjun_wei@...ndmicro.com.cn>
> 
> In case of error, the function debugfs_create_*() returns NULL
> pointer not ERR_PTR() if debugfs is enabled. The IS_ERR() test
> in the return value check should be replaced with NULL test.

I tried to fix this already but it didn't reach 4.5. It is queued for
4.6. Please have a look at
	http://git.pengutronix.de/?p=mpa/linux-nbd.git;a=commitdiff;h=27ea43fe2a32f63bb6f442dafc2133232b8af4a6;hp=92e963f50fc74041b5e9e744c330dca48e04f08d
whether this works for you as well. The difference is that I removed all
error checks for the debugfs files. The code looks nicer but of course
there are no error messages if it went wrong.

Thanks,

Markus

> 
> Signed-off-by: Wei Yongjun <yongjun_wei@...ndmicro.com.cn>
> ---
>  drivers/block/nbd.c | 50 ++++++++++++++++++++++++--------------------------
>  1 file changed, 24 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index e4c5cc1..02bc697 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -895,49 +895,47 @@ static int nbd_dev_dbg_init(struct nbd_device *nbd)
>  	struct dentry *f;
>  
>  	dir = debugfs_create_dir(nbd_name(nbd), nbd_dbg_dir);
> -	if (IS_ERR_OR_NULL(dir)) {
> -		dev_err(nbd_to_dev(nbd), "Failed to create debugfs dir for '%s' (%ld)\n",
> -			nbd_name(nbd), PTR_ERR(dir));
> -		return PTR_ERR(dir);
> +	if (!dir) {
> +		dev_err(nbd_to_dev(nbd), "Failed to create debugfs dir for '%s'\n",
> +			nbd_name(nbd));
> +		return -ENOMEM;
>  	}
>  	nbd->dbg_dir = dir;
>  
>  	f = debugfs_create_file("tasks", 0444, dir, nbd, &nbd_dbg_tasks_ops);
> -	if (IS_ERR_OR_NULL(f)) {
> -		dev_err(nbd_to_dev(nbd), "Failed to create debugfs file 'tasks', %ld\n",
> -			PTR_ERR(f));
> -		return PTR_ERR(f);
> +	if (!f) {
> +		dev_err(nbd_to_dev(nbd), "Failed to create debugfs file 'tasks'\n");
> +		goto fail;
>  	}
>  
>  	f = debugfs_create_u64("size_bytes", 0444, dir, &nbd->bytesize);
> -	if (IS_ERR_OR_NULL(f)) {
> -		dev_err(nbd_to_dev(nbd), "Failed to create debugfs file 'size_bytes', %ld\n",
> -			PTR_ERR(f));
> -		return PTR_ERR(f);
> +	if (!f) {
> +		dev_err(nbd_to_dev(nbd), "Failed to create debugfs file 'size_bytes'\n");
> +		goto fail;
>  	}
>  
>  	f = debugfs_create_u32("timeout", 0444, dir, &nbd->xmit_timeout);
> -	if (IS_ERR_OR_NULL(f)) {
> -		dev_err(nbd_to_dev(nbd), "Failed to create debugfs file 'timeout', %ld\n",
> -			PTR_ERR(f));
> -		return PTR_ERR(f);
> +	if (!f) {
> +		dev_err(nbd_to_dev(nbd), "Failed to create debugfs file 'timeout'\n");
> +		goto fail;
>  	}
>  
>  	f = debugfs_create_u32("blocksize", 0444, dir, &nbd->blksize);
> -	if (IS_ERR_OR_NULL(f)) {
> -		dev_err(nbd_to_dev(nbd), "Failed to create debugfs file 'blocksize', %ld\n",
> -			PTR_ERR(f));
> -		return PTR_ERR(f);
> +	if (!f) {
> +		dev_err(nbd_to_dev(nbd), "Failed to create debugfs file 'blocksize'\n");
> +		goto fail;
>  	}
>  
>  	f = debugfs_create_file("flags", 0444, dir, &nbd, &nbd_dbg_flags_ops);
> -	if (IS_ERR_OR_NULL(f)) {
> -		dev_err(nbd_to_dev(nbd), "Failed to create debugfs file 'flags', %ld\n",
> -			PTR_ERR(f));
> -		return PTR_ERR(f);
> +	if (!f) {
> +		dev_err(nbd_to_dev(nbd), "Failed to create debugfs file 'flags'\n");
> +		goto fail;
>  	}
>  
>  	return 0;
> +fail:
> +	debugfs_remove_recursive(nbd->dbg_dir);
> +	return -ENOMEM;
>  }
>  
>  static void nbd_dev_dbg_close(struct nbd_device *nbd)
> @@ -950,8 +948,8 @@ static int nbd_dbg_init(void)
>  	struct dentry *dbg_dir;
>  
>  	dbg_dir = debugfs_create_dir("nbd", NULL);
> -	if (IS_ERR(dbg_dir))
> -		return PTR_ERR(dbg_dir);
> +	if (!dbg_dir)
> +		return -ENOMEM;
>  
>  	nbd_dbg_dir = dbg_dir;
>  
> 
> 

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