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[2003:cb:c73a:3a00:a025:9b06:549e:c16b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4214beb5c9asm10928485e9.7.2024.06.04.01.19.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Jun 2024 01:19:40 -0700 (PDT) Message-ID: <8a4d048c-0764-442a-aa70-48518068f163@redhat.com> Date: Tue, 4 Jun 2024 10:19:39 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 03/10] mm/ksm: use folio in try_to_merge_one_page To: alexs@kernel.org, Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, izik.eidus@ravellosystems.com, willy@infradead.org, aarcange@redhat.com, chrisw@sous-sol.org, hughd@google.com References: <20240604042454.2012091-1-alexs@kernel.org> <20240604042454.2012091-4-alexs@kernel.org> 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: <20240604042454.2012091-4-alexs@kernel.org> 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-Stat-Signature: 6fcfdyaggojrby95huept1n4nwemf41j X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7BB98C000D X-HE-Tag: 1717489184-471489 X-HE-Meta: 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 zrnVfIxm 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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 04.06.24 06:24, alexs@kernel.org wrote: > From: "Alex Shi (tencent)" > > scan_get_next_rmap_item() return folio actually now. So in the calling > path to try_to_merge_one_page() parameter pages are actually folios. > So let's use folio instead of of page in the function to save few > compound checking in callee functions. > > The 'page' left here since flush functions still not support folios yet. > > Signed-off-by: Alex Shi (tencent) > --- > mm/ksm.c | 61 ++++++++++++++++++++++++++++++++------------------------ > 1 file changed, 35 insertions(+), 26 deletions(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index e2fdb9dd98e2..21bfa9bfb210 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -1462,24 +1462,29 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, > } > > /* > - * try_to_merge_one_page - take two pages and merge them into one > - * @vma: the vma that holds the pte pointing to page > - * @page: the PageAnon page that we want to replace with kpage > - * @kpage: the PageKsm page that we want to map instead of page, > - * or NULL the first time when we want to use page as kpage. > + * try_to_merge_one_page - take two folios and merge them into one > + * @vma: the vma that holds the pte pointing to folio > + * @folio: the PageAnon page that we want to replace with kfolio > + * @kfolio: the PageKsm page that we want to map instead of folio, > + * or NULL the first time when we want to use folio as kfolio. > * > - * This function returns 0 if the pages were merged, -EFAULT otherwise. > + * This function returns 0 if the folios were merged, -EFAULT otherwise. > */ > -static int try_to_merge_one_page(struct vm_area_struct *vma, struct page *page, > - struct ksm_rmap_item *rmap_item, struct page *kpage) > +static int try_to_merge_one_page(struct vm_area_struct *vma, struct folio *folio, > + struct ksm_rmap_item *rmap_item, struct folio *kfolio) > { > pte_t orig_pte = __pte(0); > int err = -EFAULT; > + struct page *page = folio_page(folio, 0); > + struct page *kpage; > > - if (page == kpage) /* ksm page forked */ > + if (kfolio) > + kpage = folio_page(kfolio, 0); > + > + if (folio == kfolio) /* ksm page forked */ > return 0; > > - if (!PageAnon(page)) > + if (!folio_test_anon(folio)) > goto out; > > /* > @@ -1489,11 +1494,11 @@ static int try_to_merge_one_page(struct vm_area_struct *vma, struct page *page, > * prefer to continue scanning and merging different pages, > * then come back to this page when it is unlocked. > */ > - if (!trylock_page(page)) > + if (!folio_trylock(folio)) > goto out; > > - if (PageTransCompound(page)) { > - if (split_huge_page(page)) > + if (folio_test_large(folio)) { > + if (split_folio(folio)) > goto out_unlock; > } Careful: there is a subtle change: In the old code, after split_huge_page() succeeded, you would have a ref on *page* that you have to drop. Now, you would have a ref on *folio* -- IOW the head page that calling code has to drop. Is that handled accordingly? IOW, is there no code that would assume it would drop the reference on the *page* instead of on the *folio* (that, after split succeeds, would be an order-0 folio) If so, worth spelling out in the description (you say "So in the calling path to try_to_merge_one_page() parameter pages are actually folios", but I am not sure if that means that all page refcounting code was changed to folio refcounting code). -- Cheers, David / dhildenb