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Tue, 24 Mar 2020 19:31:20 +0000 Date: Tue, 24 Mar 2020 16:31:16 -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 4/9] mm/hmm: remove HMM_FAULT_SNAPSHOT Message-ID: <20200324193116.GO13183@mellanox.com> References: <20200324011457.2817-1-jgg@ziepe.ca> <20200324011457.2817-5-jgg@ziepe.ca> <20200324073339.GC23447@lst.de> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200324073339.GC23447@lst.de> User-Agent: Mutt/1.9.4 (2018-02-28) X-ClientProxiedBy: MN2PR11CA0010.namprd11.prod.outlook.com (2603:10b6:208:23b::15) 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 MN2PR11CA0010.namprd11.prod.outlook.com (2603:10b6:208:23b::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2835.19 via Frontend Transport; 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> > +} > > So my idea behind the helper was to turn this into something readable :) Well, it does help to give the expression a name :) > E.g. > > /* > * We only need to fault if either the default mask requires to fault all > * pages, or at least the mask allows for individual pages to be faulted. > */ > static bool hmm_can_fault(struct hmm_range *range) > { > return ((range->default_flags | range->pfn_flags_mask) & > range->flags[HMM_PFN_VALID]); > } Okay, I find this as understandable and it is less cluttered. I think the comment is good enough now. Can we concur on this then: static unsigned int hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk, const uint64_t *pfns, unsigned long npages, uint64_t cpu_flags) { + struct hmm_range *range = hmm_vma_walk->range; unsigned int required_fault = 0; unsigned long i; - if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT) + /* + * If the default flags do not request to fault pages, and the mask does + * not allow for individual pages to be faulted, then + * hmm_pte_need_fault() will always return 0. + */ + if (!((range->default_flags | range->pfn_flags_mask) & + range->flags[HMM_PFN_VALID])) return 0; I think everything else is sorted now, so if yes I'll send this as v3. Thanks, Jason