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(p200300d82f4efd008e13e3b590c81159.dip0.t-ipconnect.de. [2003:d8:2f4e:fd00:8e13:e3b5:90c8:1159]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a6d0f1d902sm9900905f8f.43.2025.06.23.12.22.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Jun 2025 12:22:05 -0700 (PDT) Message-ID: <4d35795f-df24-40eb-a1e8-2914b0f5d697@redhat.com> Date: Mon, 23 Jun 2025 21:22:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 03/14] mm: compare pfns only if the entry is present when inserting pfns/pages To: Oscar Salvador Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, nvdimm@lists.linux.dev, Andrew Morton , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dan Williams , Alistair Popple , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , Zi Yan , Baolin Wang , Lorenzo Stoakes , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato References: <20250617154345.2494405-1-david@redhat.com> <20250617154345.2494405-4-david@redhat.com> From: David Hildenbrand 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/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz 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+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 4OKLfkqsYOUCMqI_FeZXZ5Hi2GpOiSYpA9YSJsus6OE_1750706526 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A49908000A X-Stat-Signature: 6r1bmp46rfnmirhgdzjq5chauopunp5i X-Rspam-User: X-HE-Tag: 1750706531-403572 X-HE-Meta: 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 YJLhDA8Y Pz+QFYFv/88aaIbQmW5VxUQ4sKAhj38/ZOd4BKHXrdLtyQcGBItvj9dwe4fyS+c6hlAnSnXJ55bJsXqz9RqZUsKE/f6/9d4IW5DjIWwsgse0e/21JsHHtYDH3OfgydlNeQpKtcMKJsUv59uZHWQ0jg2ND9HARytfa2Qg81LFwYZsjgmTtAOMlLB4KaUy3qbd+di4AZF0jMC0MviZDM3enb/W3AxGzyv9xRg5+Y+96E1IXm1ywK/hAzHIUOVN8p1T+gDdVnQtHmTPevdqMvJACf2piAMBvVHTzMjp5Yoj3kzlY79oGygic5N5RoyIYYFCJv0xm/CEB3NhLv9tymqE4/rI+xp00vUnf4xkEOS4DnQA7gj2C4u2Z8g9LA31GB2qL0qlW93OR8PgMfluXj3juH4N4O8RwUxLtLEivghc/ffz+Ht4= 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: List-Subscribe: List-Unsubscribe: On 20.06.25 15:27, Oscar Salvador wrote: > On Tue, Jun 17, 2025 at 05:43:34PM +0200, David Hildenbrand wrote: >> Doing a pte_pfn() etc. of something that is not a present page table >> entry is wrong. Let's check in all relevant cases where we want to >> upgrade write permissions when inserting pfns/pages whether the entry >> is actually present. > > Maybe I would add that's because the pte can have other info like > marker, swp_entry etc. > >> It's not expected to have caused real harm in practice, so this is more a >> cleanup than a fix for something that would likely trigger in some >> weird circumstances. >> >> At some point, we should likely unify the two pte handling paths, >> similar to how we did it for pmds/puds. >> >> Signed-off-by: David Hildenbrand > > Reviewed-by: Oscar Salvador > > Should we scream if someone passes us a non-present entry? > Probably? Good point, let me think about that. > >> --- >> mm/huge_memory.c | 4 ++-- >> mm/memory.c | 4 ++-- >> 2 files changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 8e0e3cfd9f223..e52360df87d15 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -1392,7 +1392,7 @@ static int insert_pmd(struct vm_area_struct *vma, unsigned long addr, >> const unsigned long pfn = fop.is_folio ? folio_pfn(fop.folio) : >> fop.pfn; >> >> - if (write) { >> + if (write && pmd_present(*pmd)) { >> if (pmd_pfn(*pmd) != pfn) { >> WARN_ON_ONCE(!is_huge_zero_pmd(*pmd)); >> return -EEXIST; >> @@ -1541,7 +1541,7 @@ static void insert_pud(struct vm_area_struct *vma, unsigned long addr, >> const unsigned long pfn = fop.is_folio ? folio_pfn(fop.folio) : >> fop.pfn; >> >> - if (write) { >> + if (write && pud_present(*pud)) { >> if (WARN_ON_ONCE(pud_pfn(*pud) != pfn)) >> return; >> entry = pud_mkyoung(*pud); >> diff --git a/mm/memory.c b/mm/memory.c >> index a1b5575db52ac..9a1acd057ce59 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -2137,7 +2137,7 @@ static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte, >> pte_t pteval = ptep_get(pte); >> >> if (!pte_none(pteval)) { >> - if (!mkwrite) >> + if (!mkwrite || !pte_present(pteval)) >> return -EBUSY; > > Why EBUSY? because it might transitory? I was confused myself about error handling, and why it differs for all cases ... adding to me todo list to investigate that (clean it up ...) :) -- Cheers, David / dhildenb