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[2003:cb:c738:3100:8133:26cf:7877:94aa]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-436e9d8fc51sm180089645e9.7.2025.01.14.07.03.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Jan 2025 07:03:31 -0800 (PST) Message-ID: Date: Tue, 14 Jan 2025 16:03:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 12/26] mm/memory: Enhance insert_page_into_pte_locked() to create writable mappings To: Alistair Popple , akpm@linux-foundation.org, dan.j.williams@intel.com, linux-mm@kvack.org Cc: alison.schofield@intel.com, lina@asahilina.net, zhang.lyra@gmail.com, gerald.schaefer@linux.ibm.com, vishal.l.verma@intel.com, dave.jiang@intel.com, logang@deltatee.com, bhelgaas@google.com, jack@suse.cz, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, mpe@ellerman.id.au, npiggin@gmail.com, dave.hansen@linux.intel.com, ira.weiny@intel.com, willy@infradead.org, djwong@kernel.org, tytso@mit.edu, linmiaohe@huawei.com, peterx@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, jhubbard@nvidia.com, hch@lst.de, david@fromorbit.com, chenhuacai@kernel.org, kernel@xen0n.name, loongarch@lists.linux.dev References: <68974d46091eea460f404f8ced3c6de5964c9ec4.1736488799.git-series.apopple@nvidia.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250114_070336_429146_1AF4A812 X-CRM114-Status: GOOD ( 21.95 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 10.01.25 07:00, Alistair Popple wrote: > In preparation for using insert_page() for DAX, enhance > insert_page_into_pte_locked() to handle establishing writable > mappings. Recall that DAX returns VM_FAULT_NOPAGE after installing a > PTE which bypasses the typical set_pte_range() in finish_fault. > > Signed-off-by: Alistair Popple > Suggested-by: Dan Williams > > --- > > Changes for v5: > - Minor comment/formatting fixes suggested by David Hildenbrand > > Changes since v2: > > - New patch split out from "mm/memory: Add dax_insert_pfn" > --- > mm/memory.c | 37 +++++++++++++++++++++++++++++-------- > 1 file changed, 29 insertions(+), 8 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 06bb29e..8531acb 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2126,19 +2126,40 @@ static int validate_page_before_insert(struct vm_area_struct *vma, > } > > static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte, > - unsigned long addr, struct page *page, pgprot_t prot) > + unsigned long addr, struct page *page, > + pgprot_t prot, bool mkwrite) > { > struct folio *folio = page_folio(page); > + pte_t entry = ptep_get(pte); > pte_t pteval; > Just drop "entry" and reuse "pteval"; even saves you from one bug below :) pte_t pteval = ptep_get(pte); > - if (!pte_none(ptep_get(pte))) > - return -EBUSY; > + if (!pte_none(entry)) { > + if (!mkwrite) > + return -EBUSY; > + > + /* see insert_pfn(). */ > + if (pte_pfn(entry) != page_to_pfn(page)) { > + WARN_ON_ONCE(!is_zero_pfn(pte_pfn(entry))); > + return -EFAULT; > + } > + entry = maybe_mkwrite(entry, vma); > + entry = pte_mkyoung(entry); > + if (ptep_set_access_flags(vma, addr, pte, entry, 1)) > + update_mmu_cache(vma, addr, pte); > + return 0; > + } > + > /* Ok, finally just insert the thing.. */ > pteval = mk_pte(page, prot); > if (unlikely(is_zero_folio(folio))) { > pteval = pte_mkspecial(pteval); > } else { > folio_get(folio); > + entry = mk_pte(page, prot); we already do "pteval = mk_pte(page, prot);" above? And I think your change here does not do what you want, because you modify the new "entry" but we do set_pte_at(vma->vm_mm, addr, pte, pteval); below ... > + if (mkwrite) { > + entry = pte_mkyoung(entry); > + entry = maybe_mkwrite(pte_mkdirty(entry), vma); > + } So again, better just reuse pteval :) -- Cheers, David / dhildenb