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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH v2 02/10] mm/hugetlb: Don't wait for migration entry during follow page Content-Language: en-US To: Peter Xu , , CC: Muchun Song , Andrea Arcangeli , James Houghton , Jann Horn , Rik van Riel , Miaohe Lin , Andrew Morton , "Mike Kravetz" , David Hildenbrand , Nadav Amit References: <20221207203034.650899-1-peterx@redhat.com> <20221207203034.650899-3-peterx@redhat.com> From: John Hubbard In-Reply-To: <20221207203034.650899-3-peterx@redhat.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.126.231.37] X-ClientProxiedBy: rnnvmail202.nvidia.com (10.129.68.7) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL02EPF0000EE3E:EE_|MN0PR12MB6199:EE_ X-MS-Office365-Filtering-Correlation-Id: f8055373-9723-444b-9b44-08dad89ef9e8 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Dec 2022 22:04:13.3518 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f8055373-9723-444b-9b44-08dad89ef9e8 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BL02EPF0000EE3E.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB6199 X-Rspamd-Queue-Id: 3845640022 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: 9f96sb38phb87h985sesmcffnd6nzyzf X-HE-Tag: 1670450655-536197 X-HE-Meta: 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 bjWQIDDt +t2+SRHi5YokHT4Gnee0ey5JdlkPsgKfwGMROmY8S8Kt3iZQ= 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 12/7/22 12:30, Peter Xu wrote: > That's what the code does with !hugetlb pages, so we should logically do > the same for hugetlb, so migration entry will also be treated as no page. This reasoning make good sense to me. I looked again at the follow_page*() paths and just double-checked that this is accurate, and it is. > > This is probably also the last piece in follow_page code that may sleep, > the last one should be removed in cf994dd8af27 ("mm/gup: remove > FOLL_MIGRATION", 2022-11-16). > > Reviewed-by: Mike Kravetz > Reviewed-by: David Hildenbrand > Signed-off-by: Peter Xu > --- > mm/hugetlb.c | 11 ----------- > 1 file changed, 11 deletions(-) Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 1088f2f41c88..c8a6673fe5b4 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6232,7 +6232,6 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, > if (WARN_ON_ONCE(flags & FOLL_PIN)) > return NULL; > > -retry: > pte = huge_pte_offset(mm, haddr, huge_page_size(h)); > if (!pte) > return NULL; > @@ -6255,16 +6254,6 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, > page = NULL; > goto out; > } > - } else { > - if (is_hugetlb_entry_migration(entry)) { > - spin_unlock(ptl); > - __migration_entry_wait_huge(pte, ptl); > - goto retry; > - } > - /* > - * hwpoisoned entry is treated as no_page_table in > - * follow_page_mask(). > - */ > } > out: > spin_unlock(ptl);