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Tue, 24 Mar 2020 18:58:15 +0000 Date: Tue, 24 Mar 2020 15:58:07 -0300 From: Jason Gunthorpe To: Christoph Hellwig Cc: Jerome Glisse , Ralph Campbell , Felix.Kuehling@amd.com, linux-mm@kvack.org, John Hubbard , dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Philip Yang Subject: Re: [PATCH v2 hmm 2/9] mm/hmm: return the fault type from hmm_pte_need_fault() Message-ID: <20200324185807.GN13183@mellanox.com> References: <20200324011457.2817-1-jgg@ziepe.ca> <20200324011457.2817-3-jgg@ziepe.ca> <20200324072712.GA23447@lst.de> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200324072712.GA23447@lst.de> User-Agent: Mutt/1.9.4 (2018-02-28) X-ClientProxiedBy: BL0PR05CA0025.namprd05.prod.outlook.com (2603:10b6:208:91::35) To VI1PR05MB4141.eurprd05.prod.outlook.com (2603:10a6:803:44::15) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from mlx.ziepe.ca (142.68.57.212) by BL0PR05CA0025.namprd05.prod.outlook.com (2603:10b6:208:91::35) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2856.12 via Frontend Transport; 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X-Microsoft-Antispam-Message-Info: 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 X-MS-Exchange-AntiSpam-MessageData: AD0IwTgRYuC/K6/KToIx9Zs1s2W6U2CCBhv0xO5fZ6p5jDUKD7RnXSS2WBZj3pHtereBSMP6GP442hVzoYbcHWTf3M4qW9QIqUxoBrWtAoh5fxX6sjCNGhdC8nMACq4HHt1PbWE53abo3LazK3SASQ== X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-Network-Message-Id: 2fddc5c4-9032-4b3b-5196-08d7d0254ec0 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Mar 2020 18:58:15.2237 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: a652971c-7d2e-4d9b-a6a4-d149256f461b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: JJdFZhD3aR4PxI4VUhlRkTgVCFtZ3voOMPkb6C+iYTx6WJ5WUUdeqsOA00BBYnU39BakpLTiKvaZBMi0+z8dxQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR05MB4734 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Mar 24, 2020 at 08:27:12AM +0100, Christoph Hellwig wrote: > On Mon, Mar 23, 2020 at 10:14:50PM -0300, Jason Gunthorpe wrote: > > +enum { > > + HMM_NEED_FAULT = 1 << 0, > > + HMM_NEED_WRITE_FAULT = HMM_NEED_FAULT | (1 << 1), > > + HMM_NEED_ALL_BITS = HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT, > > I have to say I find the compound version of HMM_NEED_WRITE_FAULT > way harder to understand than the logic in the previous version, > and would refer keeping separate bits here. > > Mostly beccause of statements like this: > > > + if ((required_fault & HMM_NEED_WRITE_FAULT) == HMM_NEED_WRITE_FAULT) { > > which seems rather weird. Okay, I checked it over, and there is one weird statement above but only one place that |'s them together, so it is overall simpler to split the enum. I'll keep the HMM_NEED_ALL_BITS, I think that purpose is clear enough. Thanks, Jason