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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH v2 06/10] mm/hugetlb: Make hugetlb_follow_page_mask() safe to pmd unshare 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> <20221207203034.650899-7-peterx@redhat.com> From: John Hubbard In-Reply-To: <20221207203034.650899-7-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: rnnvmail203.nvidia.com (10.129.68.9) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY4PEPF0000C96F:EE_|LV2PR12MB5751:EE_ X-MS-Office365-Filtering-Correlation-Id: 8f6a7a9d-e774-4c76-ad35-08dad8a9da7d 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 23:22:05.1682 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 8f6a7a9d-e774-4c76-ad35-08dad8a9da7d 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: CY4PEPF0000C96F.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV2PR12MB5751 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/7/22 12:30, Peter Xu wrote: > Since hugetlb_follow_page_mask() walks the pgtable, it needs the vma lock > to make sure the pgtable page will not be freed concurrently. > > Acked-by: David Hildenbrand > Reviewed-by: Mike Kravetz > Signed-off-by: Peter Xu > --- > mm/hugetlb.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 49f73677a418..3fbbd599d015 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6226,9 +6226,10 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, > if (WARN_ON_ONCE(flags & FOLL_PIN)) > return NULL; > > + hugetlb_vma_lock_read(vma); > pte = huge_pte_offset(mm, haddr, huge_page_size(h)); > if (!pte) > - return NULL; > + goto out_unlock; > > ptl = huge_pte_lock(h, mm, pte); > entry = huge_ptep_get(pte); > @@ -6251,6 +6252,8 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, > } > out: > spin_unlock(ptl); > +out_unlock: > + hugetlb_vma_unlock_read(vma); > return page; > } >