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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id i65-20020a819144000000b0057072e7fa77sm637283ywg.95.2023.07.11.09.13.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Jul 2023 09:13:34 -0700 (PDT) Date: Tue, 11 Jul 2023 09:13:18 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Mark Brown cc: Hugh Dickins , Lorenzo Stoakes , Andrew Morton , Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Ryan Roberts , linux-kernel@vger.kernel.org, linux-mm@kvack.org, regressions@leemhuis.info, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 12/32] mm/vmalloc: vmalloc_to_page() use pte_offset_kernel() In-Reply-To: Message-ID: References: <696386a-84f8-b33c-82e5-f865ed6eb39@google.com> <42279f1f-7b82-40dc-8546-86171018729c@sirena.org.uk> <901ae88d-ad0c-4e9d-b199-f1566cc62a00@lucifer.local> <977ddee4-35f0-fcd1-2fd-1c3057e7ea2a@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 83B3D20009 X-Stat-Signature: afxaio3xhcmdowabgrshjrrb5k8igm4a X-Rspam-User: X-HE-Tag: 1689092015-927360 X-HE-Meta: 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 v2SZ1/dz FNeoqy3aEc2wLMHjP54rsjgOb6MJNlWqdJCb7yDY5Q1MVls7ULjxcWDXl1/VvIfyT3RaZ5s3mtVAcBbMnC/5LF6lfgqFvT2rh61dGLSC6IAF1cw7+1rNYOJjeyInwms/tIk31ZGo1+zmx8AEqmA2qw4kTfKpZQadG2Y09eejmpMW+T/owBRBlgxMmS34vFzMkWlRT/6DvYSLDSlINvWU9JUuc2FMY5VrpZGxGsMvebjEMCpQPzHiVSEtO1hqOKO1dTYuCedhCYAUcOaP9qJAKdA9O0JtwSiNzZM9mz9buyhfKQ0xWjdBHjjFJ9OnxPeiGBYMRIp+lnNcVYGb1swzmeHEfrVD7u7G7cf6orN1dfJHRbp9y/OZ5Csj5iLLT+Xbe+exQ4d9/epOHUtnEqqvKmAcNmKfccTW2blkZ 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 Tue, 11 Jul 2023, Mark Brown wrote: > On Mon, Jul 10, 2023 at 09:34:42PM -0700, Hugh Dickins wrote: > > > I suppose I should ask you to try reverting this 0d1c81edc61e alone > > from 6.5-rc1: the consistency of your bisection implies that it will > > "fix" the issues, and it is a commit which we could drop. It makes > > me a little nervous, applying userspace-pagetable validation to kernel > > pagetables, so I don't want to drop it; and it would really be cargo- > > culting to drop it without understanding. But we could drop it. > > I did look at that, it doesn't revert cleanly by itself. ... Right, that ptep_get() wrapper on the next line came in on top. The patch to revert just 0d1c81edc61e is this: --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -703,10 +703,11 @@ struct page *vmalloc_to_page(const void if (WARN_ON_ONCE(pmd_bad(*pmd))) return NULL; - ptep = pte_offset_kernel(pmd, addr); + ptep = pte_offset_map(pmd, addr); pte = ptep_get(ptep); if (pte_present(pte)) page = pte_page(pte); + pte_unmap(ptep); return page; }