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linux-mm@kvack.org, david@fromorbit.com, dan.j.williams@intel.com, jhubbard@nvidia.com, rcampbell@nvidia.com, willy@infradead.org, linux-fsdevel@vger.kernel.org, jack@suse.cz, djwong@kernel.org, hch@lst.de, david@redhat.com, ruansy.fnst@fujitsu.com, nvdimm@lists.linux.dev, linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org, jglisse@redhat.com Subject: Re: [RFC 02/10] mm/hmm: Remove dead check for HugeTLB and FS DAX Date: Fri, 12 Apr 2024 11:28:47 +1000 In-reply-to: Message-ID: <87wmp35pq6.fsf@nvdebian.thelocal> Content-Type: text/plain X-ClientProxiedBy: SY5P300CA0035.AUSP300.PROD.OUTLOOK.COM (2603:10c6:10:1fd::10) To CY8PR12MB7705.namprd12.prod.outlook.com (2603:10b6:930:84::9) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY8PR12MB7705:EE_|MW4PR12MB7440:EE_ X-MS-Office365-Filtering-Correlation-Id: 741decff-aab6-417a-4234-08dc5a909fb1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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6PIdSFIiiCJAhGRRqnQP5pkHD839qe6wKzowq7gjZYW6hBYCklaAdEW7DRi85mp60GZGQndVdojCxqLocF3XhGRaSTH2E70sDsYDVq0KQ6od6568Pz6gVLJcRVenNwI4dorJL0zegD/LBjo3mX5bg/g881R7QFb6L5Ci+mAlnJnyB0bcBeF95/hiRk1jSTcKaWIAmYyz4v38wLZY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Peter Xu writes: > On Thu, Apr 11, 2024 at 09:25:30AM -0300, Jason Gunthorpe wrote: >> On Thu, Apr 11, 2024 at 10:57:23AM +1000, Alistair Popple wrote: >> > pud_huge() returns true only for a HugeTLB page. pud_devmap() is only >> > used by FS DAX pages. These two things are mutually exclusive so this >> > code is dead code and can be removed. >> >> I'm not sure this is true.. pud_huge() is mostly a misspelling of pud_leaf().. >> >> > - if (pud_huge(pud) && pud_devmap(pud)) { >> >> I suspect this should be written as: >> >> if (pud_leaf(pud) && pud_devmap(pud)) { Oh that makes a lot more sense. I'd taken the comment for pud_huge() at face value (ie. that it's a hugetlbfs page) without digging further. >> In line with Peter's work here: >> >> https://lore.kernel.org/linux-mm/20240321220802.679544-1-peterx@redhat.com/ > > Just to provide more information for Alistair, this patch already switched > that over to a _leaf(): Got it, thanks (and apologies for missing my Cc on that). > https://lore.kernel.org/r/20240318200404.448346-12-peterx@redhat.com > > That's in mm-unstable now, so should see that in a rebase. > > And btw it's great to see that pxx_devmap() can go away. Yep, AFAICT pxx_devmap only exists to do this special FS DAX refcounting. Once that is fixed it can go away. > Thanks,