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[2003:cb:c72f:300:1ec7:2962:8889:ef6]) by smtp.gmail.com with ESMTPSA id jg23-20020a05600ca01700b0040b30be6244sm18663406wmb.24.2023.12.05.05.17.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Dec 2023 05:17:39 -0800 (PST) Message-ID: <88a341bf-0b6a-454a-aeb1-0699233eb37c@redhat.com> Date: Tue, 5 Dec 2023 14:17:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 34/39] mm/rmap: introduce folio_try_dup_anon_rmap_[pte|ptes|pmd]() To: Ryan Roberts , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , "Matthew Wilcox (Oracle)" , Hugh Dickins , Yin Fengwei , Mike Kravetz , Muchun Song , Peter Xu References: <20231204142146.91437-1-david@redhat.com> <20231204142146.91437-35-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-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: AE08B80007 X-Stat-Signature: xkueeogriaiubn87obpmfm4ihbddj7y3 X-HE-Tag: 1701782263-154587 X-HE-Meta: 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 DEgKugpd 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 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 05.12.23 14:12, Ryan Roberts wrote: > On 04/12/2023 14:21, David Hildenbrand wrote: >> The last user of page_needs_cow_for_dma() and __page_dup_rmap() are gone, >> remove them. >> >> Add folio_try_dup_anon_rmap_ptes() right away, we want to perform rmap >> baching during fork() soon. >> >> Signed-off-by: David Hildenbrand >> --- >> include/linux/mm.h | 6 -- >> include/linux/rmap.h | 145 +++++++++++++++++++++++++++++-------------- >> 2 files changed, 100 insertions(+), 51 deletions(-) >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index 24c1c7c5a99c0..f7565b35ae931 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -1964,12 +1964,6 @@ static inline bool folio_needs_cow_for_dma(struct vm_area_struct *vma, >> return folio_maybe_dma_pinned(folio); >> } >> >> -static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma, >> - struct page *page) >> -{ >> - return folio_needs_cow_for_dma(vma, page_folio(page)); >> -} >> - >> /** >> * is_zero_page - Query if a page is a zero page >> * @page: The page to query >> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >> index 21d72cc602adc..84439f7720c62 100644 >> --- a/include/linux/rmap.h >> +++ b/include/linux/rmap.h >> @@ -354,68 +354,123 @@ static inline void folio_dup_file_rmap_pmd(struct folio *folio, >> #endif >> } >> >> -static inline void __page_dup_rmap(struct page *page, bool compound) >> +static inline int __folio_try_dup_anon_rmap(struct folio *folio, > > __always_inline? Yes. > >> + struct page *page, unsigned int nr_pages, >> + struct vm_area_struct *src_vma, enum rmap_mode mode) >> { >> - VM_WARN_ON(folio_test_hugetlb(page_folio(page))); >> + int i; >> >> - if (compound) { >> - struct folio *folio = (struct folio *)page; >> + VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); >> >> - VM_BUG_ON_PAGE(compound && !PageHead(page), page); >> - atomic_inc(&folio->_entire_mapcount); >> - } else { >> - atomic_inc(&page->_mapcount); >> + /* >> + * No need to check+clear for already shared PTEs/PMDs of the folio. >> + * This includes PTE mappings of (order-0) KSM folios. >> + */ >> + if (likely(mode == RMAP_MODE_PTE)) { > > Presumbly if __always_inline then the compiler will remove this if/else and just > keep the part indicated by mode? In which case "likely" is pretty useless? Same > for all similar sites in the other patches. Yes, also had this in mind. As long as we use __always_inline it shouldn't ever matter. > >> + for (i = 0; i < nr_pages; i++) { >> + if (PageAnonExclusive(page + i)) >> + goto clear; >> + } >> + } else if (mode == RMAP_MODE_PMD) { >> + if (PageAnonExclusive(page)) >> + goto clear; >> } >> + goto dup; >> + >> +clear: >> + /* >> + * If this folio may have been pinned by the parent process, >> + * don't allow to duplicate the mappings but instead require to e.g., >> + * copy the subpage immediately for the child so that we'll always >> + * guarantee the pinned folio won't be randomly replaced in the >> + * future on write faults. >> + */ >> + if (likely(!folio_is_device_private(folio) && >> + unlikely(folio_needs_cow_for_dma(src_vma, folio)))) >> + return -EBUSY; >> + >> + if (likely(mode == RMAP_MODE_PTE)) { >> + for (i = 0; i < nr_pages; i++) > > Do you really need to reset i=0 here? You have already checked that lower pages > are shared in the above loop, so can't you just start from the first exclusive > page here? It's best to check the updated patch I sent. -- Cheers, David / dhildenb