linux-kernel - Re: [PATCH 1/1] debugfs: use IS

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Message-ID: <c918f1a5-7c88-bf47-14b6-b6e892695951@amd.com>
Date:   Thu, 2 Sep 2021 17:10:24 +0200
From:   Christian König <christian.koenig@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Nirmoy Das <nirmoy.das@....com>, rafael@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] debugfs: use IS_ERR to check for error

Am 02.09.21 um 14:20 schrieb Greg KH:
> On Thu, Sep 02, 2021 at 02:03:12PM +0200, Christian König wrote:
>>
>> Am 02.09.21 um 12:38 schrieb Greg KH:
>>> On Thu, Sep 02, 2021 at 12:29:17PM +0200, Nirmoy Das wrote:
>>>> debugfs_create_file() returns encoded error so
>>>> use IS_ERR for checking return value.
>>>>
>>>> References: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Fdrm%2Famd%2F-%2Fissues%2F1686&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7Cffc1109aeb744082181b08d96e0c06db%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637661820207117289%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=6NDHX9sEhGF2jakVfUJ7Qurql6UAdNpFQZ6XvCjwz0E%3D&amp;reserved=0
>>>> Signed-off-by: Nirmoy Das <nirmoy.das@....com>
>>>> ---
>>>>    fs/debugfs/inode.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
>>>> index 8129a430d789..2f117c57160d 100644
>>>> --- a/fs/debugfs/inode.c
>>>> +++ b/fs/debugfs/inode.c
>>>> @@ -528,7 +528,7 @@ void debugfs_create_file_size(const char *name, umode_t mode,
>>>>    {
>>>>    	struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
>>>> -	if (de)
>>>> +	if (!IS_ERR(de))
>>>>    		d_inode(de)->i_size = file_size;
>>>>    }
>>>>    EXPORT_SYMBOL_GPL(debugfs_create_file_size);
>>>> -- 
>>>> 2.32.0
>>>>
>>> Ah, good catch, I'll queue this up after 5.15-rc1 is out, thanks!
>> Thinking more about this if I'm not completely mistaken
>> debugfs_create_file() returns -ENODEV when debugfs is disabled and NULL on
>> any other error.
> How can this function be called if debugfs is not enabled in the system
> configuration?  This _is_ the debugfs core code.

Well, that's what I meant. The original code is correct and Nirmoy's 
patch here is breaking it.

Nirmoys other patch is for a driver and there the function can indeed 
return both error code and NULL.

Thanks,
Christian.

>
> thanks,
>
> greg k-h