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[91.12.107.195]) by smtp.gmail.com with ESMTPSA id o10-20020a5d47ca000000b0034d9e5411ebsm14666395wrc.45.2024.05.08.00.15.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 May 2024 00:15:30 -0700 (PDT) Message-ID: <5564e708-4a9f-4010-806e-4c5a7a5d2ebe@redhat.com> Date: Wed, 8 May 2024 09:15:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/8] mm: memory: extend finish_fault() to support large folio To: Baolin Wang , Ryan Roberts , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, ioworker0@gmail.com, wangkefeng.wang@huawei.com, ying.huang@intel.com, 21cnbao@gmail.com, shy828301@gmail.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <13939ade-a99a-4075-8a26-9be7576b7e03@arm.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-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 5E97CA0008 X-Stat-Signature: wa3pxiuny51mj3jhzma6pdfaj361ep1i X-Rspam-User: X-HE-Tag: 1715152534-334523 X-HE-Meta: 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 fDfJOMYW 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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 08.05.24 05:44, Baolin Wang wrote: > > > On 2024/5/7 18:37, Ryan Roberts wrote: >> On 06/05/2024 09:46, Baolin Wang wrote: >>> Add large folio mapping establishment support for finish_fault() as a preparation, >>> to support multi-size THP allocation of anonymous shmem pages in the following >>> patches. >>> >>> Signed-off-by: Baolin Wang >>> --- >>> mm/memory.c | 43 +++++++++++++++++++++++++++++++++---------- >>> 1 file changed, 33 insertions(+), 10 deletions(-) >>> >>> diff --git a/mm/memory.c b/mm/memory.c >>> index eea6e4984eae..936377220b77 100644 >>> --- a/mm/memory.c >>> +++ b/mm/memory.c >>> @@ -4747,9 +4747,12 @@ vm_fault_t finish_fault(struct vm_fault *vmf) >>> { >>> struct vm_area_struct *vma = vmf->vma; >>> struct page *page; >>> + struct folio *folio; >>> vm_fault_t ret; >>> bool is_cow = (vmf->flags & FAULT_FLAG_WRITE) && >>> !(vma->vm_flags & VM_SHARED); >>> + int type, nr_pages, i; >>> + unsigned long addr = vmf->address; >>> >>> /* Did we COW the page? */ >>> if (is_cow) >>> @@ -4780,24 +4783,44 @@ vm_fault_t finish_fault(struct vm_fault *vmf) >>> return VM_FAULT_OOM; >>> } >>> >>> + folio = page_folio(page); >>> + nr_pages = folio_nr_pages(folio); >>> + >>> + if (unlikely(userfaultfd_armed(vma))) { >>> + nr_pages = 1; >>> + } else if (nr_pages > 1) { >>> + unsigned long start = ALIGN_DOWN(vmf->address, nr_pages * PAGE_SIZE); >>> + unsigned long end = start + nr_pages * PAGE_SIZE; >>> + >>> + /* In case the folio size in page cache beyond the VMA limits. */ >>> + addr = max(start, vma->vm_start); >>> + nr_pages = (min(end, vma->vm_end) - addr) >> PAGE_SHIFT; >>> + >>> + page = folio_page(folio, (addr - start) >> PAGE_SHIFT); >> >> I still don't really follow the logic in this else if block. Isn't it possible >> that finish_fault() gets called with a page from a folio that isn't aligned with >> vmf->address? >> >> For example, let's say we have a file who's size is 64K and which is cached in a >> single large folio in the page cache. But the file is mapped into a process at >> VA 16K to 80K. Let's say we fault on the first page (VA=16K). You will calculate > > For shmem, this doesn't happen because the VA is aligned with the > hugepage size in the shmem_get_unmapped_area() function. See patch 7. Does that cover mremap() and MAP_FIXED as well. We should try doing this as cleanly as possible, to prepare for the future / corner cases. -- Cheers, David / dhildenb