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b=SyJuGFWiUcPeBxCdaRixnSKJwxzYOwBlgf8r6DSBiIskHODytyCt/a24weLhedxUXjYfOsA1u6DVO7QyDQHgL2NBoiiUtaoUagkEtn6kny3Hi0qiyyrt60wbUleHC3IJU3ZFF2QW2EkWQwltFjDCM/neLd/NM/NCgbNA66LAToc= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=prevas.dk; Received: from AS5PR10MB8243.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:20b:681::18) by PA2PR10MB8649.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:102:420::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9228.16; Sun, 19 Oct 2025 21:53:36 +0000 Received: from AS5PR10MB8243.EURPRD10.PROD.OUTLOOK.COM ([fe80::c2c9:6363:c7c2:fad5]) by AS5PR10MB8243.EURPRD10.PROD.OUTLOOK.COM ([fe80::c2c9:6363:c7c2:fad5%6]) with mapi id 15.20.9228.015; Sun, 19 Oct 2025 21:53:36 +0000 From: Rasmus Villemoes To: Linus Torvalds Cc: David Sterba , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [GIT PULL] Btrfs fixes for 6.18-rc2 In-Reply-To: (Linus Torvalds's message of "Thu, 16 Oct 2025 10:58:16 -0700") References: Date: Sun, 19 Oct 2025 23:53:33 +0200 Message-ID: <87plaieexu.fsf@prevas.dk> User-Agent: Gnus/5.13 (Gnus v5.13) Content-Type: text/plain X-ClientProxiedBy: FR4P281CA0410.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:d0::15) To AS5PR10MB8243.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:20b:681::18) Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: AS5PR10MB8243:EE_|PA2PR10MB8649:EE_ X-MS-Office365-Filtering-Correlation-Id: 814d3a6a-ddb5-44f7-0944-08de0f59f47e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|52116014|7053199007|38350700014; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?7gM1DpU9ounvl2WELS3zMCUnQtuxccyxiQPilEc8v1h0Xo+HaZRB6YoTZsGl?= =?us-ascii?Q?frQeX5qDISM9f3QiNDXhGlaXpyL97OwVCaLlkVUrQ4hdaMq+nH6mOghynX0K?= =?us-ascii?Q?yk1BIF22d/qkzVTJV9Dtj9zg9oSEAh8Bn9oqr3SAcYfKAKdmiN33oCBr/3gi?= =?us-ascii?Q?8IaewBNP4KpYMlPUyrsfd9DL/PS631m6miLRUdxnEnFn/mS94d30wb9Fjgkb?= =?us-ascii?Q?0SqitpDWen5Jh0Gk1oW6pSt47jle8ghIO04ImDnZkG6hdhWXTaHgrD0kx32D?= =?us-ascii?Q?AoBhP/c7QzTvruYSpVAI/w5gYHw9wJxil12vEJF1OCv9cdkQBv7+b8w3aJEF?= =?us-ascii?Q?kf/fK6k34Ew3QasyMvpeqiUKfq+VZg4v+A+sUQvllZCP4lhhvx2Ld/l3wP61?= =?us-ascii?Q?J/h0DPd1dfiXfxWAk9rxMqNjTS8+o754JRsFV9c6vKfmg9tozOwZBSfGlITF?= =?us-ascii?Q?s21InQnr6N/tFURRMIry42qMJkUwzLBRD9d5/A6Lu432o7heW3t6AVdMytjb?= =?us-ascii?Q?Pr6YJiQ/dXgpYJdBJdQlMg7t7yzQHH86dNN8MWGWtRP6FqSIhsrU6wegR3cV?= =?us-ascii?Q?n1jFmkTVWHp4t1Olk5RFJVhq69BhDVFU2uDKrO4B+1IRCP3T89obVFkN3j3W?= =?us-ascii?Q?aDgkHIW/w99tWwPlpSkbmRITCQ4pWGbZ8Rl1HQTxOHRCN4df8zVySjwXyTql?= =?us-ascii?Q?zb1plj96vqUB/HhoIL4+eGVtbv1BpEOQKKKQBdf/SCGtM8qzXmb8fPB1FUW7?= =?us-ascii?Q?82d6BoBTVoFy6WlyblHsiBDr+kexizifu2JwGGT81/YRNdAWCaKkV6Qkx/PE?= =?us-ascii?Q?cJndKSO4GRWtqRhjJGGYkjvd9BBqhjriXZOpI9XX9YBGNySvQu8NskcPXv2Y?= =?us-ascii?Q?2DlqFuCwb1kCMUQ4hI3h0MN6rQKJQPvcBIYT0rfXXFANjY0tnx0J+Cw/gfLx?= =?us-ascii?Q?yhwRVymxpGLvZ8mEENJS7s5GkvHkYllcR9vbb6woJZKSOaSAs5NyzvIyqnk2?= =?us-ascii?Q?kkdTNyVhM8b/YCiPBo61DBFYxdOJ9+LHwJP8n18RzMF0wXRjBVNvO2zaAjJF?= =?us-ascii?Q?oDc/ThCMlEFvuNNJe+Q5bKhKv9FMatQOsgV9LQF16Tcg5A3AsMzEqAta5ft/?= =?us-ascii?Q?ISM1gz2jSSpa9Seap7gF7yteTy6Ql5XLlb2a1lG2txMoCH2YfG9h6z42EsYH?= =?us-ascii?Q?xlJvXUEH6XoSn1mucLPKsVFLO5neEbU9jkNY4PCq0fZhmwuoxqKBZ3VjOc5w?= =?us-ascii?Q?zIcB+cetAJgwJzgHpZq2Yu6oIQ5J/QPdZgeOpb5IZdTPxeXrc9h2v/3aHN+D?= =?us-ascii?Q?J/MDMGSMKybqfIpph5XExJh64vL5bR/9H58sJ18l+Gc4m2+/GeaxoXiTLMH1?= =?us-ascii?Q?MNBsv7UU4qwMrHHOzgycPcSUuzRQrRQTocoG/zFeXDU7tUz0dvAm0NkVVSLT?= =?us-ascii?Q?URt17kbTgQmfv6aMNAAnJZ5E6T7kftk9qSgA31jjrixSNerpQmXQNdDcolm9?= =?us-ascii?Q?oejwBUdmuaj59S6YJMUf/+DGvM2EzFHMAUWFUKhQIC2iN8byZ7hePwK9Dr1K?= =?us-ascii?Q?c1Vrf0l4JVLjWPfqzrX+7ZNdObMmtqjOI78Am3VRcJJivkkVSMiJ8PVPgjBu?= =?us-ascii?Q?Pg=3D=3D?= X-OriginatorOrg: prevas.dk X-MS-Exchange-CrossTenant-Network-Message-Id: 814d3a6a-ddb5-44f7-0944-08de0f59f47e X-MS-Exchange-CrossTenant-AuthSource: AS5PR10MB8243.EURPRD10.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Oct 2025 21:53:36.4636 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: d350cf71-778d-4780-88f5-071a4cb1ed61 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: GkjmIEtvL49sIuerxT249ywSjDnGCaybBdyca3faicmnGHejLhoo/oigMa+CiHCj+iH4lmQS4oX27/DCaVJYNJIKS6Ioz5qoOofqYGGF+kY= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PA2PR10MB8649 On Thu, Oct 16 2025, Linus Torvalds wrote: > On Thu, 16 Oct 2025 at 10:00, David Sterba wrote: >> >> - reorder send context structure to avoid -Wflex-array-member-not-at-end >> warning > > Ok, I took a look because this sounded like a bad bug, but that flex > array member really isn't a flex array at all. > > It's clearly intended to be a fixed-size inline array, just using a > flex array for syntacting reasons. > [...] > > Sadly, I can't think of a way to have the compiler just calculate the > right size at structure definition time without just having to repeat > the whole structure definition twice. > > So that flex array may be the best approach even if it has these downsides. > > Does anybody know of some C language trick to get the remaining > padding size without repeating the struct definition? > > "offsetof()" sadly does not work until the structure has been fully > defined, so you can't use the "obvious" trick > > char buffer[256 - offsetof(struct .., buffer)]; > I think this has come up before [*]. Doesn't -fms-extensions allow one to do struct __fs_path { char *start; char *end; ... }; static_assert(sizeof(struct __fs_path) < 256); struct fs_path { struct __fs_path; char inline_buf[256 - sizeof(struct __fs_path)]; }; and access every member of fs_path as one used to? With the bonus that it's a real array with known size. Rasmus [*] https://lore.kernel.org/lkml/CAHk-=wh6Ra8=dBUTo1vKT5Wao1hFq3+2x1mDwmBcVx2Ahp_rag@mail.gmail.com/