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[2003:d8:2f1f:3f00:731a:f5e5:774e:d40c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45b98c95c77sm10525715e9.7.2025.09.02.01.11.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Sep 2025 01:11:07 -0700 (PDT) Message-ID: <12bb3414-2ca8-4384-80e5-81889f2bd35f@redhat.com> Date: Tue, 2 Sep 2025 10:11:04 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 12/12] mm: constify highmem related functions for improved const-correctness To: Max Kellermann , akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, willy@infradead.org, hughd@google.com, mhocko@suse.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, 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 References: <20250901205021.3573313-1-max.kellermann@ionos.com> <20250901205021.3573313-13-max.kellermann@ionos.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 01.09.25 22:50, Max Kellermann wrote: > Lots of functions in mm/highmem.c do not write to the given pointers > and do not call functions that take non-const pointers and can > therefore be constified. > > This includes functions like kunmap() which might be implemented in a > way that writes to the pointer (e.g. to update reference counters or > mapping fields), but currently are not. > > kmap() on the other hand cannot be made const because it calls > set_page_address() which is non-const in some > architectures/configurations. Right, we store the address in page->virtual. It's interesting that kumap() won't set that field to NULL. That seems to happen in flush_all_zero_pkmaps(). And we seem to flush during kmap() in case we have to empty slots. Acked-by: David Hildenbrand -- Cheers David / dhildenb