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Fri, 3 Sep 2021 06:27:38 +0000 Subject: Re: [PATCH 1/1] debugfs: use IS_ERR to check for error To: "Das, Nirmoy" , Greg KH Cc: rafael@kernel.org, linux-kernel@vger.kernel.org, Nirmoy Das References: <20210902102917.2233-1-nirmoy.das@amd.com> <5ab7739d-15a4-2e84-0320-fee8d5df1e83@amd.com> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: Date: Fri, 3 Sep 2021 08:27:34 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; 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: AM8P251CA0009.EURP251.PROD.OUTLOOK.COM (2603:10a6:20b:21b::14) To MN2PR12MB3775.namprd12.prod.outlook.com (2603:10b6:208:159::19) MIME-Version: 1.0 Received: from [192.168.178.21] (91.14.161.181) by AM8P251CA0009.EURP251.PROD.OUTLOOK.COM (2603:10a6:20b:21b::14) 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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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?WHIvMTV2VVlac081LzRpNVVCNlRxZVZsYVhBSjVVUitPcDRQa2V4Wjl6S0ZB?= =?utf-8?B?NVJiQmhGWkg3a1ptbFZvbVJYYjlGdnowSWplN2QxRG5mM3h3T0t1LzQxNjJE?= =?utf-8?B?Ti9ObUJsUXJVcFlPTDd2a3NmZWFXWWd6MHJMcDQ3REpoSzBRVFJ2RmlIQUlp?= =?utf-8?B?QURmL3Y1SG9zNWp3OWYvR0pEc0s0eFIyMnlabkpsS25CTmgxMUx2SzZTQ0ov?= =?utf-8?B?ak42ZnpRRWVFYzBBdVN5Nk9mdUJQa2l1alB3cTJTTnkzUzJodlRlbkhQOWg4?= =?utf-8?B?WnRjZnVEb0J3VGh6UVVac2FRVEhBRUtWMDcvVnVlbjBCVE1XK3l0enpiK3Rr?= =?utf-8?B?RXQ3VEVQQ05kTlAvQnJHZlNubUY3SnVmM1RVbXVoWS9FM3ZHT3ZHK0VOakVE?= =?utf-8?B?N3dET3lLRHBnQ1RDN0JnNGJ5STNTZnBkNytBVExOZUVFcTczczFQdTZGNG9L?= =?utf-8?B?RFlvbmtXTVZkVERjcGZkcENnTzJ4WVJIRlNSaEVVVU1SMVZWaWpZZ3FUT3A2?= =?utf-8?B?anVDYmxSeExDQTl0Z3NycWlHTGVNOThnaVAzbHV6QmVmQVNqK05UU1N3c2la?= =?utf-8?B?RmdTRTlQazB5cS9zVWZhV2lKOGtKRkEwalU1cUpjV1VjZHZhRlMvVExzUFVO?= =?utf-8?B?ZVJBREJtTGpUSGxveVdOaFBnVXFwU2VEdGZOd3BjTTA3WHlWQkVGak1xdFZj?= =?utf-8?B?VmZYa2NSNFZnUC80T2kwT1BSTHN5QlpUNzZsOFoyVkk4eG4wODN3a1lDdHhk?= =?utf-8?B?djFiaTlHVDFwbW1MbWsrb2N0YUw0UWhNV0c1SmVWQTJYT29za3lwSVBJNmVj?= =?utf-8?B?eitkL1JRL0Z4cUJWaDI2MkhWR3lZQ1ZWYVRzT3pvOXFPTzdQbDdTRXV5d2J4?= =?utf-8?B?REpMY0ZUVW9kcCt0UDBOQUtwWTVQRWNZTWJubXI0UC96M243Q3dGNFk4cTlu?= =?utf-8?B?cWE2ZFpBNW82b0d3SFVrbk8wYW4vU1VORnVMaHRuVHU5eW55cTEzcDhrREdi?= =?utf-8?B?S25EZytDR0FyK2J6Z1IxM3VKeWc3R2FpajJwMEhGdkUvRVM4dFRabW5KQkN3?= =?utf-8?B?YXpxV0VObTljYmxaRHgxZXkyNXlrV0lmZ2tpQzI4djZsZXVqTk43VnRUU2lq?= =?utf-8?B?bWhoQXdpVHZRZkpXMmZlZkhWSm5OR2lVdlJYcW0wZjFML0dEUjZ6cjVlbVE1?= =?utf-8?B?SWFYMU81K0FqMHNzc1dRcExCSkpSKzBuMmxHZGVNMW9jUFVKdEJ5cHQrSFNs?= =?utf-8?B?bzIvYlp2S3BDZ2VMbG1rSUVmQ2NZNjhRbXYrSlRzaUpzaWZhWDY3cFRkRzd0?= =?utf-8?B?ZXptNVI2bDRDY2UxMjVneVpoVzZlTGtuaGsxY3VXaUlnd0I0cHV3cEt0ekFZ?= =?utf-8?B?ckhTSDd4OU1vSDhHU1VGb2F0UkVvUkIxQ1VNd0NiMS9rMkpwSlBnczBLM1cr?= =?utf-8?B?cmtOOUVYU1U2MTJBU0MyWnNnUWRxWHFMS0NMSDRCbS9EQkFLTThLU0ZsbEZF?= =?utf-8?B?UGlHYnlRZFQzMUR6eWZSdmhlMEpxZ3JHNEZpRzJrcE1ocG40cTcyRzl0aGt5?= =?utf-8?B?dS9jdkVkMS9ibjhwdG1TTHp6dXEwS1FSQXgrVGRjVmpDU0xRdlBndGwvUE5R?= =?utf-8?B?MytVQytJc1FVWnJvYUcxWXFXOWRxUjdTazBaSW80UEVYWlVHSk1XTGV3dFNW?= =?utf-8?B?YVUzM3pMTmhBVy9IZFkvOWk2U2J3S2NwQmtsUk45ejJKakJ4UjR1UC8zc3dX?= =?utf-8?Q?hrDLRmwPEmc4Fve5kI9CVUf1Qliq3+S6uVCGVQ9?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9906b685-8b00-4e7a-e344-08d96ea3ed1a X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB3775.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Sep 2021 06:27:38.7931 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: mwJqWj04ZPkP4mH0NsD7+tEEmTbCbrzfuWhPTRkmMwVBl+2gYVpNkvB+cVaF11Wh X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB4550 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 02.09.21 um 19:01 schrieb Das, Nirmoy: > > On 9/2/2021 6:34 PM, Greg KH wrote: >> On Thu, Sep 02, 2021 at 05:10:24PM +0200, Christian König wrote: >>> 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&data=04%7C01%7Cnirmoy.das%40amd.com%7C7a1f1095c0d64416576c08d96e2f7b38%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637661973378236086%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=g9BQRJG8gvjGFq6oj5vk9PCemQ39U19CLmkMNHVUafg%3D&reserved=0 >>>>>>> Signed-off-by: Nirmoy Das >>>>>>> --- >>>>>>>     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. >> 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 just realized that we don't return NULL on error anymore: > > commit ff9fb72bc07705c00795ca48631f7fffe24d2c6b > Author: Greg Kroah-Hartman > Date:   Wed Jan 23 11:28:14 2019 +0100 > >     debugfs: return error values, not NULL > > > and the current doc also says "If an error occurs, ERR_PTR(-ERROR) > will be returned." > > If I am not missing anything, this patch should be fine. Ah! Yes, now that makes sense. Looks like that my memory and the documentation under https://www.kernel.org/doc/htmldocs/filesystems/API-debugfs-create-file.html is outdated. I can update my memory, but I have no idea where this documentation comes from and how to fix it. Regards, Christian. > > > 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