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[2003:d8:2f25:1e00:ce4c:be3:97b3:6587]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45b81a9e971sm279217845e9.18.2025.09.03.23.33.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Sep 2025 23:33:27 -0700 (PDT) Message-ID: Date: Thu, 4 Sep 2025 08:33:26 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: linux-next: build warning after merge of the mm-unstable tree To: Andrew Morton , Stephen Rothwell Cc: Max Kellermann , Linux Kernel Mailing List , Linux Next Mailing List , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Matthew Wilcox References: <20250904121438.3d2daab2@canb.auug.org.au> <20250903195947.97af912dc103f8a055e73537@linux-foundation.org> From: David Hildenbrand Content-Language: en-US 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20250903195947.97af912dc103f8a055e73537@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 04.09.25 04:59, Andrew Morton wrote: > On Thu, 4 Sep 2025 12:14:38 +1000 Stephen Rothwell wrote: > >> After merging the mm-unstable tree, today's linux-next build (arm >> multi_v7_defconfig) produced this warning: >> >> In file included from include/linux/highmem.h:14, >> from include/linux/bvec.h:10, >> from include/linux/blk_types.h:10, >> from include/linux/writeback.h:13, >> from include/linux/memcontrol.h:23, >> from include/linux/swap.h:9, >> from include/linux/suspend.h:5, >> from arch/arm/mach-highbank/pm.c:9: >> include/linux/highmem-internal.h: In function 'kmap_local_folio': >> include/linux/highmem-internal.h:86:46: warning: passing argument 1 of 'folio_page' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] >> 86 | const struct page *page = folio_page(folio, offset / PAGE_SIZE); >> | ^~~~~ >> In file included from include/linux/mmzone.h:23, >> from include/linux/swap.h:7: >> include/linux/page-flags.h:319:53: note: expected 'struct folio *' but argument is of type 'const struct folio *' >> 319 | static inline struct page *folio_page(struct folio *folio, unsigned long n) > Hm, why did we not detect that in mm-new? > > Yeah, thanks, folio_page() is a problem. I'll do the below nasty for > now, but nasty. > > --- a/include/linux/page-flags.h~mm-constify-highmem-related-functions-for-improved-const-correctness-fix > +++ a/include/linux/page-flags.h > @@ -316,9 +316,9 @@ static __always_inline unsigned long _co > * check that the page number lies within @folio; the caller is presumed > * to have a reference to the page. > */ > -static inline struct page *folio_page(struct folio *folio, unsigned long n) > +static inline struct page *folio_page(const struct folio *folio, unsigned long n) > { > - return &folio->page + n; > + return (struct page *)(&folio->page + n); > } > > static __always_inline int PageTail(const struct page *page) > _ I think the problem appears when nth_page() removal is paired with const-correctness. Not a fan of going back to a plain macro either. Likely we can handle it similar to page_folio() and perform the cast cleanly: diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index faf17ca211b4f..dc67fe08e77c8 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -307,6 +307,12 @@ static __always_inline unsigned long _compound_head(const struct page *page) const struct page *: (const struct folio *)_compound_head(p), \ struct page *: (struct folio *)_compound_head(p))) +static inline const struct page *_folio_page(const struct folio *folio, + unsigned long n) +{ + return &folio->page + n; +} + /** * folio_page - Return a page from a folio. * @folio: The folio. @@ -316,10 +322,9 @@ static __always_inline unsigned long _compound_head(const struct page *page) * check that the page number lies within @folio; the caller is presumed * to have a reference to the page. */ -static inline struct page *folio_page(struct folio *folio, unsigned long n) -{ - return &folio->page + n; -} +#define folio_page(f, p) (_Generic((f), \ + const struct folio *: (const struct page *)_folio_page(f, p), \ + struct folio *: (struct page *)_folio_page(f, p))) static __always_inline int PageTail(const struct page *page) { -- Cheers David / dhildenb