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[2003:d8:2f2d:2400:4052:3b5:fff9:4ed0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a568a547d2sm16662553f8f.19.2025.06.18.01.54.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Jun 2025 01:54:39 -0700 (PDT) Message-ID: <58f9d004-918d-4f66-85e7-d090db0af5de@redhat.com> Date: Wed, 18 Jun 2025 10:54:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 3/3] vfio/type1: optimize vfio_unpin_pages_remote() for large folio To: lizhe.67@bytedance.com Cc: akpm@linux-foundation.org, alex.williamson@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, peterx@redhat.com References: <20250618061143.6470-1-lizhe.67@bytedance.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: <20250618061143.6470-1-lizhe.67@bytedance.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 7exvibDYOsHuxsCzuNUdnx5QfQbnbZNCoJA_VnsvBPI_1750236880 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: rspam05 X-Rspamd-Queue-Id: 3E139180009 X-Stat-Signature: b4gg71gtgi14s93yxm6bam5315pkxg1k X-Rspam-User: X-HE-Tag: 1750236883-921506 X-HE-Meta: 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 syuDwbgK 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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 18.06.25 08:11, lizhe.67@bytedance.com wrote: > On Tue, 17 Jun 2025 15:47:09 +0200, david@redhat.com wrote: > >>> How do you think of this implementation? >>> >>> diff --git a/include/linux/mm.h b/include/linux/mm.h >>> index 242b05671502..eb91f99ea973 100644 >>> --- a/include/linux/mm.h >>> +++ b/include/linux/mm.h >>> @@ -2165,6 +2165,23 @@ static inline long folio_nr_pages(const struct folio *folio) >>> return folio_large_nr_pages(folio); >>> } >>> >>> +/* >>> + * folio_remaining_pages - Counts the number of pages from a given >>> + * start page to the end of the folio. >>> + * >>> + * @folio: Pointer to folio >>> + * @start_page: The starting page from which to begin counting. >>> + * >>> + * Returned number includes the provided start page. >>> + * >>> + * The caller must ensure that @start_page belongs to @folio. >>> + */ >>> +static inline unsigned long folio_remaining_pages(struct folio *folio, >>> + struct page *start_page) >>> +{ >>> + return folio_nr_pages(folio) - folio_page_idx(folio, start_page); >>> +} >>> + >>> /* Only hugetlbfs can allocate folios larger than MAX_ORDER */ >>> #ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE >>> #define MAX_FOLIO_NR_PAGES (1UL << PUD_ORDER) >>> diff --git a/mm/gup.c b/mm/gup.c >>> index 15debead5f5b..14ae2e3088b4 100644 >>> --- a/mm/gup.c >>> +++ b/mm/gup.c >>> @@ -242,7 +242,7 @@ static inline struct folio *gup_folio_range_next(struct page *start, >>> >>> if (folio_test_large(folio)) >>> nr = min_t(unsigned int, npages - i, >>> - folio_nr_pages(folio) - folio_page_idx(folio, next)); >>> + folio_remaining_pages(folio, next)); >>> >>> *ntails = nr; >>> return folio; >>> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >>> index b2fc5266e3d2..34e85258060c 100644 >>> --- a/mm/page_isolation.c >>> +++ b/mm/page_isolation.c >>> @@ -96,7 +96,7 @@ static struct page *has_unmovable_pages(unsigned long start_pfn, unsigned long e >>> return page; >>> } >>> >>> - skip_pages = folio_nr_pages(folio) - folio_page_idx(folio, page); >>> + skip_pages = folio_remaining_pages(folio, page); >>> pfn += skip_pages - 1; >>> continue; >>> } >>> --- >> >> Guess I would have pulled the "min" in there, but passing something like >> ULONG_MAX for the page_isolation case also looks rather ugly. > > Yes, the page_isolation case does not require the 'min' logic. Since > there are already places in the current kernel code where > folio_remaining_pages() is used without needing min, we could simply > create a custom wrapper function based on folio_remaining_pages() only > in those specific scenarios where min is necessary. I would just do something like that, removing gup_folio_range_next() completely. diff --git a/include/linux/mm.h b/include/linux/mm.h index 98a606908307b..6c224b1c6c169 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1995,6 +1995,32 @@ static inline long folio_nr_pages(const struct folio *folio) return folio_large_nr_pages(folio); } +/** + * folio_remaining_pages - The remaining number of pages in the folio. + * @folio: The folio. + * @page: The folio page to start the counting. + * @max_npages: Limit how far to count. + * + * The returned number will include the provided page. + * + * The caller must ensure that @page belongs to @folio. When setting + * @max_npages to ULONG_MAX, the parameter is effectively ignored. + * + * Return: The remaining number of pages, limited by @max_npages. + */ +static inline unsigned long folio_remaining_pages(struct folio *folio, + struct page *page, unsigned long max_npages) +{ + unsigned long nr; + + if (!folio_test_large(folio)) + return 1; + nr = folio_large_nr_pages(folio) - folio_page_idx(folio, page); + if (__builtin_constant_p(max_npages) && max_npages == ULONG_MAX) + return nr; + return min_t(unsigned long, nr, max_npages); +} + /* Only hugetlbfs can allocate folios larger than MAX_ORDER */ #ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE #define MAX_FOLIO_NR_PAGES (1UL << PUD_ORDER) diff --git a/mm/gup.c b/mm/gup.c index 6888e871a74a9..3385428d028f6 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -234,21 +234,6 @@ void folio_add_pin(struct folio *folio) } } -static inline struct folio *gup_folio_range_next(struct page *start, - unsigned long npages, unsigned long i, unsigned int *ntails) -{ - struct page *next = nth_page(start, i); - struct folio *folio = page_folio(next); - unsigned int nr = 1; - - if (folio_test_large(folio)) - nr = min_t(unsigned int, npages - i, - folio_nr_pages(folio) - folio_page_idx(folio, next)); - - *ntails = nr; - return folio; -} - static inline struct folio *gup_folio_next(struct page **list, unsigned long npages, unsigned long i, unsigned int *ntails) { @@ -356,11 +341,13 @@ void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages, bool make_dirty) { unsigned long i; - struct folio *folio; unsigned int nr; for (i = 0; i < npages; i += nr) { - folio = gup_folio_range_next(page, npages, i, &nr); + struct page *next = nth_page(page, i); + struct folio *folio = page_folio(next); + + nr = folio_remaining_pages(folio, next, npages - i); if (make_dirty && !folio_test_dirty(folio)) { folio_lock(folio); folio_mark_dirty(folio); diff --git a/mm/page_isolation.c b/mm/page_isolation.c index ece3bfc56bcd5..6f75defb38d73 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -96,7 +96,7 @@ static struct page *has_unmovable_pages(unsigned long start_pfn, unsigned long e return page; } - skip_pages = folio_nr_pages(folio) - folio_page_idx(folio, page); + skip_pages = folio_remaining_pages(folio, page, ULONG_MAX); pfn += skip_pages - 1; continue; } -- But up to you, anything with such a helper function makes the code easier to digest. -- Cheers, David / dhildenb