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AJvYcCXVTBASogvKJyowIp0DF4ietF/AII9CzwmI71ZcNgC+alIgmQiTVICseILMos1Rh/1LLiFmukGUjA==@kvack.org X-Gm-Message-State: AOJu0YykX3O4kwoatjNg64qQuCus8O3iXvOypUfNMt0Np9WhqANcedlQ U4tdiQdLh03puNirm/yRYHeVsquFilk83A4NKiZvqCRGVwgkY/URS9M6FjUHBQi08Y1/RrivVZR uhCkfwbJntuAsy48wSyRSlCsKiL5gUEQETNWOWP+30w== X-Gm-Gg: ASbGnctIAhtv3cumClIjZJ/hbICorw+Uy3nmj9h+PBWluJn3StagakqT7ko+fYZfWPF o6VMbxs7R/LvzpP6pvIPrZr/8+YCSS9m3WW10GBUY+d0oaMCIrNnBeKIawkdUQhtX1uATFaTiVh +wbBI7h5w0zaEi/Lpe9UPHJVtbVfK0f1SVNO4GfR7IVvbj/P/RJmdP9TjD+k5bkaYMfe52o+1IL lYOw/iOhqn5Sse9kI1YivWk38ntsCTTEXs+Wb15h2jPBw== X-Google-Smtp-Source: AGHT+IFqo0rWyO2Tzcdh9OXq9LZuz+iBrgY4hQc2106202QGZ76zZ9E9VZRcm0Gdr2Fju1hLpDpwI4qcelZS2+NEezM= X-Received: by 2002:a17:907:60d3:b0:afe:8d25:770f with SMTP id a640c23a62f3a-b01d8a26de5mr847287566b.3.1756738262736; Mon, 01 Sep 2025 07:51:02 -0700 (PDT) MIME-Version: 1.0 References: <20250901123028.3383461-1-max.kellermann@ionos.com> <20250901123028.3383461-3-max.kellermann@ionos.com> <26cb47bb-df98-4bda-a101-3c27298e4452@lucifer.local> In-Reply-To: <26cb47bb-df98-4bda-a101-3c27298e4452@lucifer.local> From: Max Kellermann Date: Mon, 1 Sep 2025 16:50:50 +0200 X-Gm-Features: Ac12FXzHZvMcadklQ3Hi-QaCR2-dPItzNryZ7uqKCm4rMw8McLpdl959UlJ37Wg Message-ID: Subject: Re: [PATCH v5 02/12] mm: constify pagemap related test functions for improved const-correctness To: Lorenzo Stoakes Cc: akpm@linux-foundation.org, david@redhat.com, axelrasmussen@google.com, yuanchu@google.com, willy@infradead.org, hughd@google.com, mhocko@suse.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, vishal.moola@gmail.com, linux@armlinux.org.uk, James.Bottomley@hansenpartnership.com, deller@gmx.de, agordeev@linux.ibm.com, gerald.schaefer@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, davem@davemloft.net, andreas@gaisler.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, chris@zankel.net, jcmvbkbc@gmail.com, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, weixugc@google.com, baolin.wang@linux.alibaba.com, rientjes@google.com, shakeel.butt@linux.dev, thuth@redhat.com, broonie@kernel.org, osalvador@suse.de, jfalempe@redhat.com, mpe@ellerman.id.au, nysal@linux.ibm.com, linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-fsdevel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 6D6C920004 X-Stat-Signature: 8hgdmbhmq39bijs6x6tmqyy9qttusdfu X-Rspam-User: X-HE-Tag: 1756738264-375301 X-HE-Meta: U2FsdGVkX19YWIXYqe/raOD1v5IglKRU72lRlwU53xnvvcC6K4My4DaQCI4kH38HLLp2TXcTYQq6btToEEhhR6herTiIiTZkXLa481C5Df8CoBN7YmnCERKlyW6TblXcD3TL9g97qZlwfcTFiPulsRq0dveS1+trFr6U+sfN5+Zcb/RfO4eMh7kqPYpbPf91IMMbgxl5483U/UJGPi/961UEIIM0tCYOfKDuKdGh9yTt4LjadL1jpNihRSWVLITfKGPQH8nbuKV0nJYon9uWzTbk9Qb9+uasgFc+ryA5AyZhXinOX5gFW3vH1Jp5lIkAUL6g9S3Lzzro5OougtuFagQ9y5EILyv0r+NWFhw8G8M6vG+MAWgrKdrRhMp9KR1r3PIOEPJnbS8sAz3wSOTtkg9n4Ocb7nQUw8mBC4lzLdCkuB24dtNTz6bRqrZxobqi948D0zV5Lsbs6Ut/WY37Rkq22H2yKnPLAIKoKt+QNLTc7djaz99hIXkGPZHDC1i6Sqn7K6FKSGgn5qv028ZCjfDGaqOphv4mq8rdz7NYMNIIHbwFnngEBhD+rQr7Q2sm1fUoECmPW7n1Gp666j3aL/tT1RCM3W3y6tIK9OceqfteU37icrhZep5HUsE0sKU6XKYZH5HqTie3WZiWOY0KBLlvzaceMB2wxGDYo1LQRvtPljIJ8dmDJAPJg6IHsmNeMy0hinu1BWtbGnvvmUNzfzn875kXoqpCvCMwX/XnHtYnx7NlvOpQcy6I49JGssT/sqI859+ExfLcG7pr7qYlLO6lDbzg4Y9KsEHMydSk3MXJVyOoT7/zpB5VRen4Dmv9APOn0Jgrc78i2HpPFGalpI35kzvADXe2K41gFtByBMRy5adZTXewl2EA6CeTouATiB2p/S4y4i1EOJ2UeFMcu8Y33C+XbZd1Cr+2THbGihWF09rUFc/bRxucXCAu8N7eWzZTvc5btULmDpJsegD rYaiKoQJ Ah8hjn//b3s2gF13nqCjYFte+/LOxi1mTKCbyIaK/9Zo+pL7MF7veyKdHrW7Oy3/PGoiNBYq1TR5ySNCX/NAol/tBH2lwnoBxhqbe+wMwnDxgo5K8lt2cswj8UQBWHnpciA6qKTaUUFrBSIRjpM4XXD+OWjw/XNKgFOaNTJ7f6M4DvtnKtA82gVXzTc38OpH+Ia+DhO9OZqUKgzGs1EvNvmy0ABuXpVYUfsrOtSO9+9tMOrboy/t4ur58Dfqq8rpqz4HIQtQ/RLXCNm3w9gfCnP+AMaavD88D4uEE 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 Mon, Sep 1, 2025 at 4:25=E2=80=AFPM Lorenzo Stoakes wrote: > 1. (most useful) Const pointer (const *) means that the der= effed > value is const, so * =3D or -> =3D ar= e prohibited. Only this was what my initial patch was about. > 2. (less useful) We can't modify the actual pointer value either, so > e.g. =3D is prohibited. This wasn't my idea, it was Andrew Morton's idea, supported by Yuanchu Xie: https://lore.kernel.org/lkml/CAJj2-QHVC0QW_4X95LLAnM=3D1g6apH=3D=3D-OXZu65= SVeBj0tSUcBg@mail.gmail.com/ You know that because you participated in the discussion. In that thread, nobody objected, so I took the time and adjusted all of my patches. There is some value, but of course it's very small. Note that I added the value-level "const" only to the implementation, never to prototypes, because it would have no effect there.