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[2003:d8:2f38:ca00:ca3a:83da:653e:234]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-454dd439051sm135912815e9.8.2025.07.14.07.26.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Jul 2025 07:26:42 -0700 (PDT) Message-ID: <5e65d43c-787c-4e42-9aa6-6f84018c6f33@redhat.com> Date: Mon, 14 Jul 2025 16:26:42 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/4] mm/memory: introduce is_huge_zero_pfn() and use it in vm_normal_page_pmd() To: Luiz Capitulino , willy@infradead.org, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, shivankg@amd.com, sj@kernel.org, harry.yoo@oracle.com References: <4940826e99f0c709a7cf7beb94f53288320aea5a.1752499009.git.luizcap@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: <4940826e99f0c709a7cf7beb94f53288320aea5a.1752499009.git.luizcap@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: tg_6QWI0pP_hSkd2QFvqOIDLEd9Np0fexKa5PLuTM08_1752503204 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: rspam03 X-Rspamd-Queue-Id: 3D10A140006 X-Stat-Signature: req59ainmxag77g4ckfimkrwspgd16hg X-Rspam-User: X-HE-Tag: 1752503207-873276 X-HE-Meta: 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 +NswGDV+ G5LOr+RQlaputFybU0AbDGY9WmHJ+d5bwLYSes9bYg9GvrsM0HPaGuqLEJ7RIIxfKGrwsX37JOXNShnhRQt+XFlvxVP0NH5SDu3lzhRTZEcCJ3B+8JKRplLzSPZZk4J7rBW5N0gB18M3J4hSDfxfx0exvrdeczG5vbKnf 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 14.07.25 15:16, Luiz Capitulino wrote: > From: David Hildenbrand > > Let's avoid working with the PMD when not required. If > vm_normal_page_pmd() would be called on something that is not a present > pmd, it would already be a bug (pfn possibly garbage). > > While at it, let's support passing in any pfn covered by the huge zero > folio by masking off PFN bits -- which should be rather cheap. > > Signed-off-by: David Hildenbrand > Reviewed-by: Oscar Salvador > Signed-off-by: Luiz Capitulino > --- > include/linux/huge_mm.h | 12 +++++++++++- > mm/memory.c | 2 +- > 2 files changed, 12 insertions(+), 2 deletions(-) > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index 2f190c90192d..59e93fba15f4 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -486,9 +486,14 @@ static inline bool is_huge_zero_folio(const struct folio *folio) > return READ_ONCE(huge_zero_folio) == folio; > } > > +static inline bool is_huge_zero_pfn(unsigned long pfn) > +{ > + return READ_ONCE(huge_zero_pfn) == (pfn & ~(HPAGE_PMD_NR - 1)); > +} > + > static inline bool is_huge_zero_pmd(pmd_t pmd) > { > - return pmd_present(pmd) && READ_ONCE(huge_zero_pfn) == pmd_pfn(pmd); > + return pmd_present(pmd) && is_huge_zero_pfn(pmd_pfn(pmd)); > } > > struct folio *mm_get_huge_zero_folio(struct mm_struct *mm); > @@ -636,6 +641,11 @@ static inline bool is_huge_zero_folio(const struct folio *folio) > return false; > } > > +static inline bool is_huge_zero_pfn(unsigned long pfn) > +{ > + return false; > +} > + > static inline bool is_huge_zero_pmd(pmd_t pmd) > { > return false; > diff --git a/mm/memory.c b/mm/memory.c > index b0cda5aab398..3a765553bacb 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -687,7 +687,7 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr, > > if (pmd_devmap(pmd)) > return NULL; This likely doesn't apply as-is on top of mm-unstable / mm-new (and likely also not mm-stable). Should be trivial to fixup, though. -- Cheers, David / dhildenb