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[213.175.37.12]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7acde6259e8sm73066485a.132.2024.09.24.07.39.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 24 Sep 2024 07:39:19 -0700 (PDT) Message-ID: <090c6ebc-c5cd-4d72-989d-40ee03ec1297@redhat.com> Date: Tue, 24 Sep 2024 16:39:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 12/13] mm: multi-gen LRU: walk_pte_range() use pte_offset_map_rw_nolock() To: Qi Zheng , hughd@google.com, willy@infradead.org, muchun.song@linux.dev, vbabka@kernel.org, akpm@linux-foundation.org, rppt@kernel.org, vishal.moola@gmail.com, peterx@redhat.com, ryan.roberts@arm.com, christophe.leroy2@cs-soprasteria.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org References: <6efef5316d7468d13ed5f344452a0b872481972b.1727148662.git.zhengqi.arch@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: <6efef5316d7468d13ed5f344452a0b872481972b.1727148662.git.zhengqi.arch@bytedance.com> 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: rspam06 X-Rspamd-Queue-Id: CA597A0004 X-Stat-Signature: fcf75ddf9gs9scjbd1cyuayz1twmndj3 X-Rspam-User: X-HE-Tag: 1727188762-802643 X-HE-Meta: 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 8HRpEPSR 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, 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 24.09.24 08:10, Qi Zheng wrote: > In walk_pte_range(), we may modify the pte entry after holding the ptl, so > convert it to using pte_offset_map_rw_nolock(). At this time, the > pte_same() check is not performed after the ptl held, so we should get > pmdval and do pmd_same() check to ensure the stability of pmd entry. > > Signed-off-by: Qi Zheng > Reviewed-by: Muchun Song > --- > mm/vmscan.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 749cdc110c745..bdca94e663bc5 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3375,8 +3375,10 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, > struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); > DEFINE_MAX_SEQ(walk->lruvec); > int old_gen, new_gen = lru_gen_from_seq(max_seq); > + pmd_t pmdval; > > - pte = pte_offset_map_nolock(args->mm, pmd, start & PMD_MASK, &ptl); > + pte = pte_offset_map_rw_nolock(args->mm, pmd, start & PMD_MASK, &pmdval, > + &ptl); > if (!pte) > return false; > if (!spin_trylock(ptl)) { > @@ -3384,6 +3386,11 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, > return false; > } > > + if (unlikely(!pmd_same(pmdval, pmdp_get_lockless(pmd)))) { > + pte_unmap_unlock(pte, ptl); > + return false; > + } Acked-by: David Hildenbrand -- Cheers, David / dhildenb