From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from BYAPR05CU005.outbound.protection.outlook.com (mail-westusazon11010066.outbound.protection.outlook.com [52.101.85.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E5429265CDD for ; Fri, 9 Jan 2026 19:44:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.85.66 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767987856; cv=fail; b=W+WPTMQ1UH/gRrO1A5qhA5iKm2tsUa4VS2D8FV4bsxjnEHleFxZ6C+tQRAgbF51uhFGfreKK8vFs96LdkcBUmxKqp4gZkF4SqVDtvHdW2uAiU2oyQBSs97+e7x4P6NTZb+J3tybJsk9g6kKtgPqqJ0B+H9s+C4wqZn2vO2oQ1Bs= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767987856; c=relaxed/simple; bh=HxULGJrwJzmx2ZB+LaZm8EamFiAnSK5l7zQuBhlIWPA=; h=Date:From:To:Cc:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:MIME-Version; b=IXflyhaBoQZ9y0FfrVuE5BrgggvvckRc95kXwbjcxweFBzMomaLBQGaScs6GhEeJzWdMuEqOfRy0z9i6E2ACshCYYdagLi1Q3w7T4rFXhMROjHai/AYsIHSb6dnz3IH/VFn6/tGOEhuHL8rFVZbWrZPrIGmAP0dG4rrhjHg9ZRQ= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=HhBXRhWv; arc=fail smtp.client-ip=52.101.85.66 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="HhBXRhWv" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=grKwP88dyoO6+Oi7141YLB9MTBSMHN48DiGFSA2AvfkrBVj4nVemYJu17ZXauahX3Ow1t+wK9y/ck7T3Ezo351qOfNOotzUgjeVdXAv6cs9CDcH+t4hch/nQPfINV+Ks0x9Ms7GirhbmlbWNl9JGCSgqolIV2JzO3fU3Gg7t36lT1Tfj5igyCr3FiKJSnIN4hkhpWh5yR5QGzN1T8ZS8AQ9sJYyLfGR3fhMmfyo5eSL4UoLzZFeiPSu9ufjnBODeFb/sE4Kr0k0E0eQX5UoW+yP1KTtkQdVRcl3C18ELrO/4AImgoLqv14ghSuTtCgDamDF0ZxfNh1Q77WXLYDdK2A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=xWhZUxDS1NP7O2/uxmSauhjGxcf09h7uNiWP39NKsBo=; b=fps36FoOopSwxG5jEQi1qPJmMZc15afoHJNCin/SkIdqpFfV2KU15JZ2K0E1udLFcqPFewbY3qAwXCD9fQNhs6pVp7KqngWXSjKfZ26+fdM+I4ZoAdpoPyUr10eaHRPopuk+hobmAVSnb47i+jxXm/jy5TMU6ddK3DmjC0jzBa7m5ItAlkmdjUDA0QKBpS4D6t/Q594fK1URsfQVFj9qbXBhsdmNcqONi4TkFOz2THZpHm6jNeFcj8bfS9E0GMAB0HNq1dcBqAod5O5UJpOXu6w/KdJEKmaUGTGEjwmusRPlfn3SDHkM0ly/MZZMpbCWDpGI9GtVQgl8BiaW0TZmcQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=xWhZUxDS1NP7O2/uxmSauhjGxcf09h7uNiWP39NKsBo=; b=HhBXRhWv3i5qYfhvEBkMggsYNMOaxOMQGFUhWpLnV0Mnlr3WzAGMJkLy92IF3NPb2IQwJUV5lWPeFwxPI9rHVG9NObJ2xbEU8CbMQEkVJgneoj86E2t+4qObfoXpCs/atlZjG6ZwBu5WJ/KmrJUzfP270c/XZJklpZkerjm4GQP5IUF3aLlN/aMQuEkL7IIHjci+8ftqvsg7CaBSlmj3n8JSwdlBCtRVc8HiAXEbpk4N/0ws9X9370SiTHrPbhmKpivKtODh4L3JNy5s9l8GMbQUg9KKB7jJhYoRcK6/CH8a6KZRcPCN1qpMJcSWxCTuGHP2AYf3cdFVxTDHoLkcTQ== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from PH0PR12MB8800.namprd12.prod.outlook.com (2603:10b6:510:26f::12) by DM6PR12MB4137.namprd12.prod.outlook.com (2603:10b6:5:218::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9499.5; Fri, 9 Jan 2026 19:44:10 +0000 Received: from PH0PR12MB8800.namprd12.prod.outlook.com ([fe80::bdb6:e12f:18b6:2b77]) by PH0PR12MB8800.namprd12.prod.outlook.com ([fe80::bdb6:e12f:18b6:2b77%5]) with mapi id 15.20.9499.003; Fri, 9 Jan 2026 19:44:10 +0000 Date: Fri, 9 Jan 2026 14:44:08 -0500 From: Yury Norov To: Petr Tesarik Cc: Yury Norov , Rasmus Villemoes , Richard Henderson , Matt Turner , Magnus Lindholm , Vineet Gupta , Geert Uytterhoeven , "Maciej W. Rozycki" , Thomas Bogendoerfer , Madhavan Srinivasan , Michael Ellerman , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Chris Zankel , Max Filippov , Patrik Jakobsson , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Robin Murphy , Joerg Roedel , Will Deacon , Jakub Kicinski , Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , Oliver Neukum , Arnd Bergmann , Kuan-Wei Chiu , Andrew Morton , Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz , Pablo Neira Ayuso , Florian Westphal , linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 1/2] bits: introduce ffs_val() Message-ID: References: <9767487fcab7dbe7a7282a48a492171629eb935b.1767975412.git.ptesarik@suse.com> <20260109184614.7b3b9bb3@mordecai> <20260109202711.5f356b3e@mordecai> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260109202711.5f356b3e@mordecai> X-ClientProxiedBy: BN9PR03CA0610.namprd03.prod.outlook.com (2603:10b6:408:106::15) To PH0PR12MB8800.namprd12.prod.outlook.com (2603:10b6:510:26f::12) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH0PR12MB8800:EE_|DM6PR12MB4137:EE_ X-MS-Office365-Filtering-Correlation-Id: ffb5e08b-c149-4d48-8133-08de4fb7755d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|10070799003|366016|1800799024|376014|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?epL6Qol3jUVIxcxOyTL7uEt3VUpiIEeFfLthe4GJ8bzvebpR1W8b+fAIE+xJ?= =?us-ascii?Q?XOFisPM2m4DtmEJGkYZn5W3zfv6VRP1X4mg2ZYJvqI0pkrTx2VNsQz2RZuic?= =?us-ascii?Q?jFiHMl0ajMj3HFEs1W2woS/Zxx1RE8RHZAmKyyN9oV04fan9M9peCAHnbocp?= =?us-ascii?Q?XdkcQpjJz/VSuhJ4YZJh0TZbllBd0BD19ZFYa7/LhVhuvO+0ustZ75JndeMp?= =?us-ascii?Q?pZOIP4kntqLDvF1SiZYeh/8G3wdcUTEfJU6La9IRE/RXe3q8bsKfZYNXhxs2?= =?us-ascii?Q?DfjzsEuDmCfFzSGBBHPfTFQCfXm9SfArs/MBKSx/CRSLsvjxPm6idT1BM87Z?= =?us-ascii?Q?VgWCTdZmoL8OeyMAW/XDLCqV1wwLe48B/3BtzDJbSMDS55h5HiSbC4rnG4F6?= =?us-ascii?Q?FNm8HAJAAv5hJDhHbl9j/4cGbcG2qoce7iR3yJ3AKJWm14Xg4Z4sJZRJycuD?= =?us-ascii?Q?n7YutwR24V2VkvdtbL7IqpdKuWxoDXNG8NOZZb0NMwi3HplATjhy5hpK80z7?= =?us-ascii?Q?NCBRk+WvbuxuEzL33EAHE0E0SMLgIeLUUnr/oRrnzw3LktIj5JHFi52BpM6E?= =?us-ascii?Q?lu2Dc71c9t1ld668C1uxq9yVS09ngYCbbfWMaPWDs1uAEZKkCrt5iMAv6CLW?= =?us-ascii?Q?oN0wKxQgq1mC7eVbETTRqby6VZUNG4vfugkwR+80fxmZT19D+XTGytSVH5lz?= =?us-ascii?Q?1Q80W9Nb5iFREi5mskHS6BNTcV26nFcTlnQaXvUmREtCF4322hZEP0XhZfoG?= =?us-ascii?Q?yNGOVCva6SEDSI7uSUfA9YbrXQx8NVYjgB8bMIQx9CdOycGTUtwtrJZOdheW?= =?us-ascii?Q?XtHiPypuF9CM5UPpG3SkNujAK2lQqNsweU9S0JcUi0b3TpACX71FntROAeQ6?= =?us-ascii?Q?SeD/mJbBxxPJIc9EhK5vQnUv8Sakt9XZuuhJiiWuOpMXHiQoFcUCcI5O7MMJ?= =?us-ascii?Q?E3T0RnxYJq3WAplozWZdCOKFysAmr/bOq1Jfo4dpC3A76H4Esc25yI2iHQy5?= =?us-ascii?Q?5tHN8Ov/3aoVelXtHd8lPvulW0hCUXqFVoEQ1UVPaPsvYdxBol2rKKeB/2Sx?= =?us-ascii?Q?tTn9//e/UU6pqKTiIZFeJ7pg5E5qVWniOfADnk5oeuzZ9vjr6T6jowS/3ohR?= =?us-ascii?Q?vf4aeWPz6i1uqX/SrRVWxrzLPU3JhDXa4h90HVYSFAw2TH/bIspfszfwTBOT?= =?us-ascii?Q?lM0q0sTG71iuL9nZhyC89qWHdsPTXyl/XOShzGCAGGkDGeO69PlBHS3CIoTg?= =?us-ascii?Q?hnBfG+ObQk52riXNBYTSXkZ5zvusB6mHhLYx3DTbdFAeRmBRodr+8f9z2XtR?= =?us-ascii?Q?skK9FmFO5Dc42Rkfm4yvaW5QZJI6aYOQ3Jd6hFwZTW6bIXevD+rxhJSaea3X?= =?us-ascii?Q?ljq6uNCLba1/xsDzE5Yw/vaGqWsF2OsVp4mNTnlQdP0yESygV5eBlr0Ij6tp?= =?us-ascii?Q?d7uTrJSS9/gV7ozMWxu0n/xr2pj1Fgso?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:PH0PR12MB8800.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(10070799003)(366016)(1800799024)(376014)(7416014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?zBgAU9bsx0qj7ZrUmK29vg9j6TnUlYUSxBlH1b3BWBD8vUthhee6TJLBKh39?= =?us-ascii?Q?qLzLj2wmMxdA5rRRtvWWKnLyuN8mQjxSsADf4g1Uad5hztEbs3TsQXSmp7Ug?= =?us-ascii?Q?aFs8I6QsRub/BZO6gCsHQqu1AUPftZ+baviWBBcQwsThcaGHTSQcBVFYPvwt?= =?us-ascii?Q?KYshttt2p8YNYH9LVQiqCW/FZw8vFXtGmnHeQbt+sv6p/y0W+x7A1gTnFkkU?= =?us-ascii?Q?UiF8yBKaano/Jq2FxJdUCYihiTqqvy8osyQZ36w9diDI/jJuY0p8qeVlF8l5?= =?us-ascii?Q?+IZYszGD9TIFR2Ln5FYKp4hi3lSDmtYCllopfanh37p2RcW4eAncxI68GMrk?= =?us-ascii?Q?W7OKHz95CSQGmR1l/TNWICKWURD9VB8vX7BeJhAmkov6uDSnicrmeh1lnsTc?= =?us-ascii?Q?dopaYoCxed7nXLEgKKqIOFafysl2ZI/AdzLX0ET3DPQpwOI1YW75W+wugxwS?= =?us-ascii?Q?upA9nxat3bxLpCADUOhSjEbiMEiGTBzSLPd1+66PYdOt86wEmx8lKctGgLT7?= =?us-ascii?Q?5lPAGdsgrVZevtd43QNrKpp8m0ioOtE0cROrilCCtUgJuwxr5oDDS1GkT6ie?= =?us-ascii?Q?xHOZvjd3LSDVk0+x0rp8BU9C444mgdrjROfb/Zg+COCkUmWEdiWsyAasSoxQ?= =?us-ascii?Q?rz0C4QkLsLOIYVrKSHyav7T8+JAJ/K01AiplHTNA8Uo/VSreiEb/zlnHuDJr?= =?us-ascii?Q?RDoQsKQAIlToomekFxdVHBLHu7HxWJztZgercLhvyY2iLiDF33raYXsUF5TR?= =?us-ascii?Q?FBWCK5P5J+h2G9JMF3aAlnTcvTZHcHo42h4TPZOzTaZbDF65M1Qzw9I22nYg?= =?us-ascii?Q?9rlvxACxXsrTRFiJU2pRNvPB+RZoKbWA4GuZ0FLZaUTO9qU1B8WcJA9cEW/s?= =?us-ascii?Q?VvDalv5F+dUD6LnBaHy9NKpLGj+YcV9XF8JvZW6qugUeqCK5rPjxrenQDKoW?= =?us-ascii?Q?bum+lTpaciZnxk6eExfW09IoXq8IHI9xYs+JcNrFgcQrMMJ6kwZLu1ActWPc?= =?us-ascii?Q?DXSdbEl3CSLVC4v528xieNIhgsq0nGwJPn84Cg09wU8Oy3hCxjUZd6K35Uh/?= =?us-ascii?Q?CccxL6+1LbS2q35wCKnFjwRs/dY978ZrAww+i4ho/dpvf9ekrVwxCCCGPWp9?= =?us-ascii?Q?gEHsOU/As+13uv5Qrk6wh13VI5jBo+ECRidTENX3ky5GvD5Zcs1qsqmuBD7w?= =?us-ascii?Q?kzic+SYbYICdkpM/d1GjhvPOlquMt2axLhBamRTvphewANfEVFIOLXbvO/Jq?= =?us-ascii?Q?/m0TyyBcJ3NQQBrHDwsqQV7Ru+BHVHIT4U7j9JCrtmC6otC7mNr/+A2awmQO?= =?us-ascii?Q?uxi5AwvDxs/Pn0ZSEad2sjZ93qv5vvQI64m1Hu9YKCNyA5Js6e9uCtA9BdWp?= =?us-ascii?Q?OpjQ9lOK02T08mYbsrt4iu8elRT+4Fm3rF7saBvH7jMeGO/FuKwE/Dx+YBxP?= =?us-ascii?Q?fWGflPoOIm+V0/9n3exsvF9r2WJWk+qjJN/V3XYg87sAvtQA3e52e0ZyaWta?= =?us-ascii?Q?Krtie02oIFUJAd3E39kFJ82rZYahBm7AqDxPIDnV7Y+F0/9glIUaEqbyw4mP?= =?us-ascii?Q?Rb9jedlay0EHQNzKKv70mNoZLmP328ZUow44N8OLhecx4y036BJnvH0dkQXS?= =?us-ascii?Q?MuvNQtCE16bqbahEkvMbT04EU6JsHYalBkWMVjX3+3MImNFsO1NbBqlvqFxz?= =?us-ascii?Q?uBioj2xeUzXcyoo7GOE0v1RtpGRtNcZ58WS2zTntd32SNF9E1Z2c8zsCJiDs?= =?us-ascii?Q?05TH0p7AwsivdgUZyBiEd1aXpEsspXrxT0dQcCH6Q0TwosvDuZUF?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: ffb5e08b-c149-4d48-8133-08de4fb7755d X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB8800.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Jan 2026 19:44:10.1024 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: F9by2l+Kh8C2s2h5Ods2sH3mvac1Sk/TMjqEkQ3yrnmKc8b4oAx6tndQ41CkqQFr0a6+g3AIe2OVDWoCg5Q/pA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4137 On Fri, Jan 09, 2026 at 08:27:11PM +0100, Petr Tesarik wrote: > On Fri, 9 Jan 2026 13:26:30 -0500 > Yury Norov wrote: ... > > In bitops world, something_mask() has a very clear meaning. Consider > > GENMASK(), BITMAP_FIRST_BYTE_MASK(), __BF_FIELD_CHECK_MASK(), and so > > on. > > > > lsb_mask(), or LSB_MASK() if you prefer, is just right. > > I assume you mean BITMAP_FIRST_WORD_MASK(), not btrfs-specific > BITMAP_FIRST_BYTE_MASK(), defined in fs/btrfs/extent_io.h. > > But then it nicely illustrate exactly what I mean: They all have a consistent meaning: > BIT_MASK(4) = 0x0000000000000010 A mask constructed from bit #4. > GENMASK(4, 0) = 0x000000000000001f A mask constructed from bits #0..4. > BITMAP_FIRST_WORD_MASK(4) == 0xfffffffffffffff0 A mask constructed from all bits starting #4. Don't see any misalignment here. > > > The only issue is that LSB may also refer to least-significant BYTE. :-( > > > > It will never mean byte because it hosts in bitops.h, not byteops.h > > I'm afraid that identifiers from various sources end up next to each > other and they do not carry tags where each of them came from... You can name it lsb_bitmask() if you want, either way works. But to me shorter is better.