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(p200300d82f0df000eec92b8d4913f32a.dip0.t-ipconnect.de. [2003:d8:2f0d:f000:eec9:2b8d:4913:f32a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-450d7f8ed32sm174020795e9.1.2025.06.03.15.02.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Jun 2025 15:02:53 -0700 (PDT) Message-ID: Date: Wed, 4 Jun 2025 00:02:51 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/2] mm/huge_memory: don't mark refcounted pages special in vmf_insert_folio_pud() To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, Andrew Morton , Alistair Popple , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Dan Williams References: <20250603211634.2925015-1-david@redhat.com> <20250603211634.2925015-3-david@redhat.com> 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/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: <20250603211634.2925015-3-david@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 03.06.25 23:16, David Hildenbrand wrote: > Marking PUDs that map a "normal" refcounted folios as special is > against our rules documented for vm_normal_page(). > > Fortunately, there are not that many pud_special() check that can be > mislead and are right now rather harmless: e.g., none so far > bases decisions whether to grab a folio reference on that decision. > > Well, and GUP-fast will fallback to GUP-slow. All in all, so far no big > implications as it seems. > > Getting this right will get more important as we introduce > folio_normal_page_pud() and start using it in more place where we > currently special-case based on other VMA flags. > > Fix it by just inlining the relevant code, making the whole > pud_none() handling cleaner. > > Add folio_mk_pud() to mimic what we do with folio_mk_pmd(). > > While at it, make sure that the pud that is non-none is actually present > before comparing PFNs. > > Fixes: dbe54153296d ("mm/huge_memory: add vmf_insert_folio_pud()") > Signed-off-by: David Hildenbrand > --- > include/linux/mm.h | 15 +++++++++++++++ > mm/huge_memory.c | 33 +++++++++++++++++++++++---------- > 2 files changed, 38 insertions(+), 10 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 0ef2ba0c667af..047c8261d4002 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1816,6 +1816,21 @@ static inline pmd_t folio_mk_pmd(struct folio *folio, pgprot_t pgprot) > { > return pmd_mkhuge(pfn_pmd(folio_pfn(folio), pgprot)); > } > + > +/** > + * folio_mk_pud - Create a PUD for this folio > + * @folio: The folio to create a PUD for > + * @pgprot: The page protection bits to use > + * > + * Create a page table entry for the first page of this folio. > + * This is suitable for passing to set_pud_at(). > + * > + * Return: A page table entry suitable for mapping this folio. > + */ > +static inline pud_t folio_mk_pud(struct folio *folio, pgprot_t pgprot) > +{ > + return pud_mkhuge(pfn_pud(folio_pfn(folio), pgprot)); > +} > #endif > #endif /* CONFIG_MMU */ The following on top should make cross-compiles happy (git diff output because it's late here, probably whitespace messed up): diff --git a/include/linux/mm.h b/include/linux/mm.h index 047c8261d4002..b7e2abd8ce0df 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1817,6 +1817,7 @@ static inline pmd_t folio_mk_pmd(struct folio *folio, pgprot_t pgprot) return pmd_mkhuge(pfn_pmd(folio_pfn(folio), pgprot)); } +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD /** * folio_mk_pud - Create a PUD for this folio * @folio: The folio to create a PUD for @@ -1831,7 +1832,8 @@ static inline pud_t folio_mk_pud(struct folio *folio, pgprot_t pgprot) { return pud_mkhuge(pfn_pud(folio_pfn(folio), pgprot)); } -#endif +#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif /* CONFIG_MMU */ static inline bool folio_has_pincount(const struct folio *folio -- Cheers, David / dhildenb