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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH v2 07/10] mm/hugetlb: Make follow_hugetlb_page() 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> <20221207203034.650899-8-peterx@redhat.com> From: John Hubbard In-Reply-To: <20221207203034.650899-8-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: BN8NAM11FT009:EE_|MN0PR12MB6004:EE_ X-MS-Office365-Filtering-Correlation-Id: b1e112c3-3a36-4b9d-14fb-08dad8aa7450 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 23:26:23.1760 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b1e112c3-3a36-4b9d-14fb-08dad8aa7450 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT009.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB6004 X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 823D3C000D X-Stat-Signature: wsn8wp8yzddtu1r69mfrz5kr85bzywrz X-HE-Tag: 1670455585-131451 X-HE-Meta: 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 KyK+nAuQ i/1FSusooN0yJdo653KFL/Ir/N90PrEdpz/02LwCXnTcRy3Yhp6u3Yx16laJLff7FYw4dNvOICdsCT7BxB6IXLOBpKXfhgtDOdh13 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: > Since follow_hugetlb_page() 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 | 7 +++++++ > 1 file changed, 7 insertions(+) Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 3fbbd599d015..f42399522805 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6284,6 +6284,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, > break; > } > > + hugetlb_vma_lock_read(vma); > /* > * Some archs (sparc64, sh*) have multiple pte_ts to > * each hugepage. We have to make sure we get the > @@ -6308,6 +6309,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, > !hugetlbfs_pagecache_present(h, vma, vaddr)) { > if (pte) > spin_unlock(ptl); > + hugetlb_vma_unlock_read(vma); > remainder = 0; > break; > } > @@ -6329,6 +6331,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, > > if (pte) > spin_unlock(ptl); > + hugetlb_vma_unlock_read(vma); > + > if (flags & FOLL_WRITE) > fault_flags |= FAULT_FLAG_WRITE; > else if (unshare) > @@ -6388,6 +6392,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, > remainder -= pages_per_huge_page(h); > i += pages_per_huge_page(h); > spin_unlock(ptl); > + hugetlb_vma_unlock_read(vma); > continue; > } > > @@ -6415,6 +6420,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, > if (WARN_ON_ONCE(!try_grab_folio(pages[i], refs, > flags))) { > spin_unlock(ptl); > + hugetlb_vma_unlock_read(vma); > remainder = 0; > err = -ENOMEM; > break; > @@ -6426,6 +6432,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, > i += refs; > > spin_unlock(ptl); > + hugetlb_vma_unlock_read(vma); > } > *nr_pages = remainder; > /*