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[2003:d8:2f1f:3600:dc8:26ee:9aa9:fdc7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4562e89c87esm48000855e9.33.2025.07.17.04.43.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Jul 2025 04:43:47 -0700 (PDT) Message-ID: Date: Thu, 17 Jul 2025 13:43:45 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] selftests/mm: reuse FORCE_READ to replace "asm volatile("" : "+r" (XXX));" To: wang lian , akpm@linux-foundation.org Cc: Liam.Howlett@oracle.com, brauner@kernel.org, broonie@kernel.org, gkwang@linx-info.com, jannh@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, ludovico.zy.wu@gmail.com, p1ucky0923@gmail.com, ryncsn@gmail.com, shuah@kernel.org, sj@kernel.org, vbabka@suse.cz, zijing.zhang@proton.me, ziy@nvidia.com References: <20250716151543.998b121a58064011e9ce68cb@linux-foundation.org> <20250717104811.3773-1-lianux.mm@gmail.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/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz 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+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: <20250717104811.3773-1-lianux.mm@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: TNbYP_yrVAnIGp-vJuda7ULD7ZAXwtWOcdiV4Wket9w_1752752628 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: 4D1BFA0006 X-Stat-Signature: y5ouo43z5f1mo3q5om7qbdqp3ggo81uj X-Rspam-User: X-HE-Tag: 1752752631-700593 X-HE-Meta: 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 nKtVeuG5 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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 17.07.25 12:48, wang lian wrote: >> On Wed, 16 Jul 2025 20:31:26 +0800 wang lian wrote: > >>> Several mm selftests use the `asm volatile("" : "+r" (variable));` >>> construct to force a read of a variable, preventing the compiler from >>> optimizing away the memory access. This idiom is cryptic and duplicated >>> across multiple test files. >>> >>> Following a suggestion from David[1], this patch refactors this >>> common pattern into a FORCE_READ() macro >>> >>> tools/testing/selftests/mm/cow.c | 30 +++++++++---------- >>> tools/testing/selftests/mm/hugetlb-madvise.c | 5 +--- >>> tools/testing/selftests/mm/migration.c | 13 ++++---- >>> tools/testing/selftests/mm/pagemap_ioctl.c | 4 +-- >>> .../selftests/mm/split_huge_page_test.c | 4 +-- >>> 5 files changed, 24 insertions(+), 32 deletions(-) > >> The patch forgot to move the FORCE_READ definition into a header? > > Hi Andrew, > You are absolutely right. My apologies for the inconvenience. > This patch was sent standalone based on a suggestion from David during > the discussion of a previous, larger patch series. In that original series, > I had already moved the FORCE_READ() macro definition into vm_util.h. > > You can find the original patch series and discussion at this link: > https://lore.kernel.org/lkml/20250714130009.14581-1-lianux.mm@gmail.com/ > It should also be in your mailing list archive. > > To make this easier to review and apply, I can send a new, small patch series > that first introduces the FORCE_READ() macro in vm_util.h and then applies this refactoring. Please simply perform the move of FORCE_READ() in this very patch where you also use it elswehere. I missed that when skimming over this patch. -- Cheers, David / dhildenb