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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a892e598d2sm15404861f8f.76.2025.07.02.02.09.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Jul 2025 02:09:43 -0700 (PDT) Message-ID: <09c356c3-5874-43ac-93e5-4374a386df98@redhat.com> Date: Wed, 2 Jul 2025 11:09:41 +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 4/4] mm: remove boolean output parameters from folio_pte_batch_ext() From: David Hildenbrand To: Zi Yan Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Pedro Falcato , Rik van Riel , Harry Yoo References: <20250627115510.3273675-1-david@redhat.com> <20250627115510.3273675-5-david@redhat.com> 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 02.07.25 11:08, David Hildenbrand wrote: > On 30.06.25 19:59, Zi Yan wrote: >> On 27 Jun 2025, at 7:55, David Hildenbrand wrote: >> >>> Instead, let's just allow for specifying through flags whether we want >>> to have bits merged into the original PTE. >>> >>> For the madvise() case, simplify by having only a single parameter for >>> merging young+dirty. For madvise_cold_or_pageout_pte_range() merging the >>> dirty bit is not required, but also not harmful. This code is not that >>> performance critical after all to really force all micro-optimizations. >>> >>> As we now have two pte_t * parameters, use PageTable() to make sure we >>> are actually given a pointer at a copy of the PTE, not a pointer into >>> an actual page table. >>> >>> Signed-off-by: David Hildenbrand >>> --- >>> mm/internal.h | 58 +++++++++++++++++++++++++++++++-------------------- >>> mm/madvise.c | 26 +++++------------------ >>> mm/memory.c | 8 ++----- >>> mm/util.c | 2 +- >>> 4 files changed, 43 insertions(+), 51 deletions(-) >>> >>> diff --git a/mm/internal.h b/mm/internal.h >>> index 6000b683f68ee..fe69e21b34a24 100644 >>> --- a/mm/internal.h >>> +++ b/mm/internal.h >>> @@ -208,6 +208,18 @@ typedef int __bitwise fpb_t; >>> /* Compare PTEs honoring the soft-dirty bit. */ >>> #define FPB_HONOR_SOFT_DIRTY ((__force fpb_t)BIT(1)) >>> >>> +/* >>> + * Merge PTE write bits: if any PTE in the batch is writable, modify the >>> + * PTE at @ptentp to be writable. >>> + */ >>> +#define FPB_MERGE_WRITE ((__force fpb_t)BIT(2)) >>> + >>> +/* >>> + * Merge PTE young and dirty bits: if any PTE in the batch is young or dirty, >>> + * modify the PTE at @ptentp to be young or dirty, respectively. >>> + */ >>> +#define FPB_MERGE_YOUNG_DIRTY ((__force fpb_t)BIT(3)) >>> + >>> static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags) >>> { >>> if (!(flags & FPB_HONOR_DIRTY)) >>> @@ -220,16 +232,11 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags) >>> /** >>> * folio_pte_batch_ext - detect a PTE batch for a large folio >>> * @folio: The large folio to detect a PTE batch for. >>> + * @vma: The VMA. Only relevant with FPB_MERGE_WRITE, otherwise can be NULL. >>> * @ptep: Page table pointer for the first entry. >>> - * @pte: Page table entry for the first page. >>> + * @ptentp: Pointer at a copy of the first page table entry. >>> * @max_nr: The maximum number of table entries to consider. >>> * @flags: Flags to modify the PTE batch semantics. >>> - * @any_writable: Optional pointer to indicate whether any entry except the >>> - * first one is writable. >>> - * @any_young: Optional pointer to indicate whether any entry except the >>> - * first one is young. >>> - * @any_dirty: Optional pointer to indicate whether any entry except the >>> - * first one is dirty. >>> * >>> * Detect a PTE batch: consecutive (present) PTEs that map consecutive >>> * pages of the same large folio in a single VMA and a single page table. >>> @@ -242,28 +249,26 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags) >>> * must be limited by the caller so scanning cannot exceed a single VMA and >>> * a single page table. >>> * >>> + * Depending on the FPB_MERGE_* flags, the pte stored at @ptentp will >>> + * be modified. >>> + * >>> * This function will be inlined to optimize based on the input parameters; >>> * consider using folio_pte_batch() instead if applicable. >>> * >>> * Return: the number of table entries in the batch. >>> */ >>> static inline unsigned int folio_pte_batch_ext(struct folio *folio, >>> - pte_t *ptep, pte_t pte, unsigned int max_nr, fpb_t flags, >>> - bool *any_writable, bool *any_young, bool *any_dirty) >>> + struct vm_area_struct *vma, pte_t *ptep, pte_t *ptentp, >>> + unsigned int max_nr, fpb_t flags) >>> { >>> + bool any_writable = false, any_young = false, any_dirty = false; >>> + pte_t expected_pte, pte = *ptentp; >>> unsigned int nr, cur_nr; >>> - pte_t expected_pte; >>> - >>> - if (any_writable) >>> - *any_writable = false; >>> - if (any_young) >>> - *any_young = false; >>> - if (any_dirty) >>> - *any_dirty = false; >>> >>> VM_WARN_ON_FOLIO(!pte_present(pte), folio); >>> VM_WARN_ON_FOLIO(!folio_test_large(folio) || max_nr < 1, folio); >>> VM_WARN_ON_FOLIO(page_folio(pfn_to_page(pte_pfn(pte))) != folio, folio); >>> + VM_WARN_ON(virt_addr_valid(ptentp) && PageTable(virt_to_page(ptentp))); >> >> Why not just VM_WARN_ON(!pte_same(*ptep, *ptentp)) ? >> >> ptep points to the first page table entry and ptentp points to the copy of it. >> I assume ptep should point to a valid page table entry to begin with. > > That would also work, only miss the case where someone would by accident > flip both pointers :) ... or pass the same pointer twice. -- Cheers, David / dhildenb