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Wed, 18 Mar 2026 20:12:56 +0000 Message-ID: <06df6bde-6790-4320-bcf1-cad2ab3d473e@intel.com> Date: Wed, 18 Mar 2026 13:12:20 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 00/11] x86,fs/resctrl: Improve resctrl quality and consistency To: Ben Horgan , , , , , , , CC: , , , , , , References: <8be6feef-b7a5-4fd7-9bc0-9aeed7ef0fda@arm.com> <38e5c384-4d08-425e-a4fb-a63913be35ac@arm.com> <55a9461e-32f8-4665-905e-bc18b7201c7e@intel.com> From: Reinette Chatre Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MW3PR06CA0018.namprd06.prod.outlook.com (2603:10b6:303:2a::23) To SJ2PR11MB7573.namprd11.prod.outlook.com (2603:10b6:a03:4d2::10) Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ2PR11MB7573:EE_|CH0PR11MB5217:EE_ X-MS-Office365-Filtering-Correlation-Id: e574463c-0cef-4398-ef89-08de852abe21 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|366016|1800799024|56012099003|18002099003|22082099003; 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Consider, for example: >> >> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c >> index 5da305bd36c9..ea77fa6a38f7 100644 >> --- a/fs/resctrl/rdtgroup.c >> +++ b/fs/resctrl/rdtgroup.c >> @@ -973,10 +973,13 @@ static int rdt_last_cmd_status_show(struct kernfs_open_file *of, >> >> mutex_lock(&rdtgroup_mutex); >> len = seq_buf_used(&last_cmd_status); >> - if (len) >> + if (len) { >> seq_printf(seq, "%.*s", len, last_cmd_status_buf); >> - else >> + if (seq_buf_has_overflowed(&last_cmd_status)) >> + seq_puts(seq, "[truncated]\n"); >> + } else { >> seq_puts(seq, "ok\n"); >> + } >> mutex_unlock(&rdtgroup_mutex); >> return 0; >> } > > Adding a truncation indication makes sense to me. Would it be good to reserve space in the > last_cmd_status_buf[] to ensure this can always be displayed? It looks like space could be > made by interacting with seq->size directly but I'm not sure if there is a cleaner way > to do it. > Please note the distinction between the struct seq_file instance pointed to by seq and the struct seq_buf instance last_cmd_status. The last_cmd_status seq_buf instance is backed by last_cmd_status_buf of 512 bytes which is printed to the seq_file instance seq that is backed by another buffer that starts out with size PAGE_SIZE. So, it looks to me like printing last_cmd_status_buf to the seq seq_file instance followed by "[truncated]\n" should fit by default? This should keep working even if last_cmd_status_buf size is increased since seq_read_iter() that calls this show() would just keep increasing the buffer backing the seq_file (up to a very large limit of MAX_RW_COUNT which is INT_MAX & PAGE_MASK) until it does fit. Reinette