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[2003:d8:2f27:6d00:7b96:afc9:83d0:5bd]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4613eb27f25sm38795825e9.23.2025.09.17.06.29.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Sep 2025 06:29:52 -0700 (PDT) Message-ID: Date: Wed, 17 Sep 2025 15:29:51 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] mm/memblock: Correct totalram_pages accounting with KMSAN To: Alexander Potapenko Cc: akpm@linux-foundation.org, vbabka@suse.cz, rppt@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, elver@google.com, dvyukov@google.com, kasan-dev@googlegroups.com, Aleksandr Nogikh References: <20250917123250.3597556-1-glider@google.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 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: <20250917123250.3597556-1-glider@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: l9vgYte2Go4UZ04xf9fVGYyHxOTVuZzaJ9aREoFvxKY_1758115793 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: DA992160002 X-Stat-Signature: ii44736ggdk1gpqf35bsuqekgpwzz3qm X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1758115796-290904 X-HE-Meta: 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 fTiHZGas ASZnyWNVHiUJZVi7+0v0rQvQprSS8+RH1pM4GjrBO45zgCZxAttfE7ClgWFKF4C4IcTJkOWNrviei3QItKgunamUkvGMJNATRoI+BwJiBwU+wDWN5GPmH4d8qKhlG8o7wu8PdKTMPHlN4QbvlhmDTTeP6LZ813SAYL0+eu/c4pb+2CBAvubSA5KFdmWgIx1GRNkdMBP/RoynQjJ+lDlFCBQ21uwDu93Prg9kDKJi/eSFrd28J0VX8DTrv9TU4+4cqDcDxnqudDdH3jTsspoN7vkFj5yvhPH2Bwvxv8BQ9x6U/6puziphslwP+18N0ZjCbMNy0m8xXjVVnI5kU905kjYUgutNUxfMtM5TpX7+9ZGQG5wHBgNwUq3bJl/x7LXR1tlPjcABUGQ2E5yq5GKfz7UFHgTFJG2nO0JVFmI2ZSGLENo1ma3L8MB1W8KKRCj+NT12hBAq3N1ic3Z3D39uFhjy5dN02p3c+iItBk8pW0eXYOsk= 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 17.09.25 14:32, Alexander Potapenko wrote: > When KMSAN is enabled, `kmsan_memblock_free_pages()` can hold back pages > for metadata instead of returning them to the early allocator. The callers, > however, would unconditionally increment `totalram_pages`, assuming the > pages were always freed. This resulted in an incorrect calculation of the > total available RAM, causing the kernel to believe it had more memory than > it actually did. > > This patch refactors `memblock_free_pages()` to return the number of pages > it successfully frees. If KMSAN stashes the pages, the function now > returns 0; otherwise, it returns the number of pages in the block. > > The callers in `memblock.c` have been updated to use this return value, > ensuring that `totalram_pages` is incremented only by the number of pages > actually returned to the allocator. This corrects the total RAM accounting > when KMSAN is active. > > Cc: Aleksandr Nogikh > Fixes: 3c2065098260 ("init: kmsan: call KMSAN initialization routines") > Signed-off-by: Alexander Potapenko > --- > mm/internal.h | 4 ++-- > mm/memblock.c | 18 +++++++++--------- > mm/mm_init.c | 9 +++++---- > 3 files changed, 16 insertions(+), 15 deletions(-) > > diff --git a/mm/internal.h b/mm/internal.h > index 45b725c3dc030..ae1ee6e02eff9 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -742,8 +742,8 @@ static inline void clear_zone_contiguous(struct zone *zone) > extern int __isolate_free_page(struct page *page, unsigned int order); > extern void __putback_isolated_page(struct page *page, unsigned int order, > int mt); > -extern void memblock_free_pages(struct page *page, unsigned long pfn, > - unsigned int order); > +extern unsigned long memblock_free_pages(struct page *page, unsigned long pfn, > + unsigned int order); > extern void __free_pages_core(struct page *page, unsigned int order, > enum meminit_context context); > > diff --git a/mm/memblock.c b/mm/memblock.c > index 117d963e677c9..de7ff644d8f4f 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -1834,10 +1834,9 @@ void __init memblock_free_late(phys_addr_t base, phys_addr_t size) > cursor = PFN_UP(base); > end = PFN_DOWN(base + size); > > - for (; cursor < end; cursor++) { > - memblock_free_pages(pfn_to_page(cursor), cursor, 0); > - totalram_pages_inc(); > - } > + for (; cursor < end; cursor++) > + totalram_pages_add( > + memblock_free_pages(pfn_to_page(cursor), cursor, 0)); > } That part is clear. But for readability we should probably just do if (memblock_free_pages(pfn_to_page(cursor), cursor, 0)) totalram_pages_inc(); Or use a temp variable as an alternative. LGTM Reviewed-by: David Hildenbrand -- Cheers David / dhildenb