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Thu, 2 Sep 2021 16:48:39 +0000 Subject: Re: [PATCH 1/1] debugfs: use IS_ERR to check for error To: Greg KH , =?UTF-8?Q?Christian_K=c3=b6nig?= Cc: rafael@kernel.org, linux-kernel@vger.kernel.org References: <20210902102917.2233-1-nirmoy.das@amd.com> <5ab7739d-15a4-2e84-0320-fee8d5df1e83@amd.com> From: "Das, Nirmoy" Message-ID: <8f9ad7f8-d4fb-1737-6728-3278af1b3504@amd.com> Date: Thu, 2 Sep 2021 18:48:34 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-ClientProxiedBy: AM0PR05CA0076.eurprd05.prod.outlook.com (2603:10a6:208:136::16) To DM4PR12MB5136.namprd12.prod.outlook.com (2603:10b6:5:393::23) MIME-Version: 1.0 Received: from [IPv6:2003:c5:8f1d:d000:ad20:9749:da12:5f0e] (2003:c5:8f1d:d000:ad20:9749:da12:5f0e) by AM0PR05CA0076.eurprd05.prod.outlook.com (2603:10a6:208:136::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4478.19 via Frontend Transport; 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>>>>>> - 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. > Ah, yes, sorry, you are right. This function can not return an error > value, if something went wrong, the result will always be NULL. [I pressed send too early in my previous email :/ ] The issue occurs when CONFIG_DEBUG_FS=y and CONFIG_DEBUG_FS_ALLOW_NONE=y config options are set, so a call to debugfs_create_file() will return ERR_PTR(-EPERM) instead of NULL. So I think it still makes sense to keep the check with IS_ERR_OR_NULL() Regards, Nirmoy > >> Nirmoys other patch is for a driver and there the function can indeed return >> both error code and NULL. > You should never be checking this stuff in a caller anyway, so no, don't > do it there either. > > thanks, > > greg k-h