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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6158b7504f3sm993939a12.27.2025.07.30.05.54.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 30 Jul 2025 05:54:47 -0700 (PDT) Message-ID: Date: Wed, 30 Jul 2025 14:54:46 +0200 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 7/9] mm/memory: factor out common code from vm_normal_page_*() To: Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, xen-devel@lists.xenproject.org, linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev, Andrew Morton , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dan Williams , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Jann Horn , Pedro Falcato , Hugh Dickins , Oscar Salvador , Lance Yang References: <20250717115212.1825089-1-david@redhat.com> <20250717115212.1825089-8-david@redhat.com> <1aef6483-18e6-463b-a197-34dd32dd6fbd@lucifer.local> <50190a14-78fb-4a4a-82fa-d7b887aa4754@lucifer.local> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 18.07.25 14:43, Lorenzo Stoakes wrote: > On Thu, Jul 17, 2025 at 10:03:44PM +0200, David Hildenbrand wrote: >> On 17.07.25 21:55, Lorenzo Stoakes wrote: >>> On Thu, Jul 17, 2025 at 08:51:51PM +0100, Lorenzo Stoakes wrote: >>>>> @@ -721,37 +772,21 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr, >>>>> print_bad_page_map(vma, addr, pmd_val(pmd), NULL); >>>>> return NULL; >>>>> } >>>>> - >>>>> - if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) { >>>>> - if (vma->vm_flags & VM_MIXEDMAP) { >>>>> - if (!pfn_valid(pfn)) >>>>> - return NULL; >>>>> - goto out; >>>>> - } else { >>>>> - unsigned long off; >>>>> - off = (addr - vma->vm_start) >> PAGE_SHIFT; >>>>> - if (pfn == vma->vm_pgoff + off) >>>>> - return NULL; >>>>> - if (!is_cow_mapping(vma->vm_flags)) >>>>> - return NULL; >>>>> - } >>>>> - } >>>>> - >>>>> - if (is_huge_zero_pfn(pfn)) >>>>> - return NULL; >>>>> - if (unlikely(pfn > highest_memmap_pfn)) { >>>>> - print_bad_page_map(vma, addr, pmd_val(pmd), NULL); >>>>> - return NULL; >>>>> - } >>>>> - >>>>> - /* >>>>> - * NOTE! We still have PageReserved() pages in the page tables. >>>>> - * eg. VDSO mappings can cause them to exist. >>>>> - */ >>>>> -out: >>>>> - return pfn_to_page(pfn); >>>>> + return vm_normal_page_pfn(vma, addr, pfn, pmd_val(pmd)); >>>> >>>> Hmm this seems broken, because you're now making these special on arches with >>>> pte_special() right? But then you're invoking the not-special function? >>>> >>>> Also for non-pte_special() arches you're kind of implying they _maybe_ could be >>>> special. >>> >>> OK sorry the diff caught me out here, you explicitly handle the pmd_special() >>> case here, duplicatively (yuck). >>> >>> Maybe you fix this up in a later patch :) >> >> I had that, but the conditions depend on the level, meaning: unnecessary >> checks for pte/pmd/pud level. >> >> I had a variant where I would pass "bool special" into vm_normal_page_pfn(), >> but I didn't like it. >> >> To optimize out, I would have to provide a "level" argument, and did not >> convince myself yet that that is a good idea at this point. > > Yeah fair enough. That probably isn't worth it or might end up making things > even more ugly. So, I decided to add the level arguments, but not use them to optimize the checks, only to forward it to the new print_bad_pte(). So the new helper will be /** * __vm_normal_page() - Get the "struct page" associated with a page table entry. * @vma: The VMA mapping the page table entry. * @addr: The address where the page table entry is mapped. * @pfn: The PFN stored in the page table entry. * @special: Whether the page table entry is marked "special". * @level: The page table level for error reporting purposes only. * @entry: The page table entry value for error reporting purposes only. ... */ static inline struct page *__vm_normal_page(struct vm_area_struct *vma, unsigned long addr, unsigned long pfn, bool special, unsigned long long entry, enum pgtable_level level) ... And vm_nomal_page() will for example be /** * vm_normal_page() - Get the "struct page" associated with a PTE * @vma: The VMA mapping the @pte. * @addr: The address where the @pte is mapped. * @pte: The PTE. * * Get the "struct page" associated with a PTE. See __vm_normal_page() * for details on "normal" and "special" mappings. * * Return: Returns the "struct page" if this is a "normal" mapping. Returns * NULL if this is a "special" mapping. */ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, pte_t pte) { return __vm_normal_page(vma, addr, pte_pfn(pte), pte_special(pte), pte_val(pte), PGTABLE_LEVEL_PTE); } -- Cheers, David / dhildenb