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[2003:d8:2f09:3f00:d228:bd67:7baa:d604]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-429ceb6d8a5sm49353455e9.1.2024.08.12.02.10.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Aug 2024 02:10:03 -0700 (PDT) Message-ID: <8e987e3f-6899-41d1-9ba4-c49cb91f7815@redhat.com> Date: Mon, 12 Aug 2024 11:10:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/swap: take folio refcount after testing the LRU flag To: yangge1116@126.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, 21cnbao@gmail.com, baolin.wang@linux.alibaba.com, liuzixing@hygon.cn References: <1723270558-31674-1-git-send-email-yangge1116@126.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: <1723270558-31674-1-git-send-email-yangge1116@126.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: rspam12 X-Rspamd-Queue-Id: A948F40003 X-Stat-Signature: csau63cockx4ejikna6ftu3cbzfru1fe X-Rspam-User: X-HE-Tag: 1723453807-863820 X-HE-Meta: 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 74CXky/6 CPBLhUoHhUSRbWg9Z91pAo7aApYNt+gHANWKEJHzHhslNRJOUkyzwKcW2tUiVQlfugyJAse/yJkqt0WYCp6QXpGkK501dmF8f2eJb4NRsveNj4ISHO6b2ekiuf7NgKpSaPA+nNw6GWzu96s3eUPd/KZHddx1u+aOCEZPzDWegXQVqDAmm+KpvoNFu7dWH97v6czPRGgjnCSe0ZlqaQEhGcFnqhEcZAlLpG6fO5twt/ep47gUJ3f072uVRE7v9vebWUnhJeMLIvqjJVSEGlOqcw5Nqvoig3ow76u9vNjk+C7QGGJBL87m5D1m9i3Gm3FK0PlhrdpVlMff6jbNRT4FWH/SNrz8BWZ4qvl2nHaLmNcohNnKT7nuhRKSA3d0uUH+NLt2ptzQvgInIsRGHI9P4Msn3sDLFdOr7s6+Z8Copz4KuUc6i30aJRl87dnZh0EyajfLvrDzEwhXnlVQXDqT7D5i2cZonugRTif3b 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 10.08.24 08:15, yangge1116@126.com wrote: > From: yangge > > Whoever passes a folio to __folio_batch_add_and_move() must hold > a reference, otherwise something else would already be messed up. > If the folio is referenced, it will not be freed elsewhere, so we > can safely clear the folio's lru flag. As discussed with David > in [1], we should take the reference after testing the LRU flag, > not before. > > Link: https://lore.kernel.org/lkml/d41865b4-d6fa-49ba-890a-921eefad27dd@redhat.com/ [1] > Signed-off-by: yangge > --- > mm/swap.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/mm/swap.c b/mm/swap.c > index 67a2467..6b83898 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -226,12 +226,10 @@ static void __folio_batch_add_and_move(struct folio_batch __percpu *fbatch, > { > unsigned long flags; > > - folio_get(folio); > - > - if (on_lru && !folio_test_clear_lru(folio)) { > - folio_put(folio); > + if (on_lru && !folio_test_clear_lru(folio)) > return; > - } > + > + folio_get(folio); > > if (disable_irq) > local_lock_irqsave(&cpu_fbatches.lock_irq, flags); Ah, "mm/swap: remove boilerplate" reduced them to a single instance, good. You can throw in a VM_WARN_ON_ONCE(!folio_ref_count(folio)); before the folio_get(folio) so we would realize when something very unexpected happens. Acked-by: David Hildenbrand -- Cheers, David / dhildenb