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b=UDgEXs2326E6nluf1TRc8JSNvhmzOon3wFQO4IGhep2GcsTFGb51oZnfVZiY1GAaR AP8fzqcnv7eYrYj9lL4FNmIylIXtktJO6S/8lPEsr9/blHUuTeaYrMQZrCri1qieYO cq0gkqvEXFYLEhEOZv7vi4RklL+UFVEE6ysMw5CnfQHGwPi5Qp1XZ6xxWiFW46pN2N kiqi1m6pj9kSW9RPBUIsDiBzSO344zesdF59KRQwvqScPSbSq4fhaJHCL1XMX/KL6Z AGh6cTxV+hX4OwAQ5pwgwcuIpE1fW7fngurZgxukYKy1X9RCDc7bsKDUrmmVxEI6CF RZ/PweRaGfL5Q== Message-ID: Date: Thu, 5 Feb 2026 14:58:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv6 09/17] mm/sparse: Check memmap alignment for compound_info_has_mask() From: "David Hildenbrand (Arm)" To: Kiryl Shutsemau , Andrew Morton , Muchun Song , Matthew Wilcox , Usama Arif , Frank van der Linden Cc: Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , Huacai Chen , WANG Xuerui , Palmer Dabbelt , Paul Walmsley , Albert Ou , Alexandre Ghiti , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org References: <20260202155634.650837-1-kas@kernel.org> <20260202155634.650837-10-kas@kernel.org> Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 770BA100008 X-Stat-Signature: cy7rxxjikywrnb3jfan4f9w715bb5grq X-Rspam-User: X-HE-Tag: 1770299947-30444 X-HE-Meta: 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 HjSd8nRu P4VTWtsIYqb3zDsW/RWxtOV0cytAeGd0N8WpOwn+9KA/a4fhuN3boF+ZI+B4h+1SBp3zniMrNmPLoB5cG+Y2rWe0hZlmLyDrmT6Rpj3LH6gfX5mmUOGl8MVMLPDw9YxG+YLJKZ9hTWolb5mijqYnYupB7FfIaDIA5ngR9gHxLcN2WNdEZI8mSzErJ96MpP7l7V33pT1VFDoVlQAHFj4+TodynuTvkF/O1F5T3TFJFUidocta9I4woK8oIpUELM+DIJ+wiKODlhHTiqzawV7gu42HaHhVkixgyKlURQNXTKqqt3w3DFfl3vZfd+brHWHkL0Hr06MUmtfBrSLg0uUGZA/7fkIGoAHET4dAj1FG0XdxhsZkt6wL20zXaUwm5X3JCrGrx 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 2/5/26 14:31, David Hildenbrand (Arm) wrote: > On 2/2/26 16:56, Kiryl Shutsemau wrote: >> If page->compound_info encodes a mask, it is expected that vmemmap to be >> naturally aligned to the maximum folio size. >> >> Add a VM_BUG_ON() to check the alignment. >> >> Signed-off-by: Kiryl Shutsemau >> Acked-by: Zi Yan >> --- >>   mm/sparse.c | 7 +++++++ >>   1 file changed, 7 insertions(+) >> >> diff --git a/mm/sparse.c b/mm/sparse.c >> index b5b2b6f7041b..6c9b62607f3f 100644 >> --- a/mm/sparse.c >> +++ b/mm/sparse.c >> @@ -600,6 +600,13 @@ void __init sparse_init(void) >>       BUILD_BUG_ON(!is_power_of_2(sizeof(struct mem_section))); >>       memblocks_present(); >> +    if (compound_info_has_mask()) { >> +        unsigned long alignment; >> + >> +        alignment = MAX_FOLIO_NR_PAGES * sizeof(struct page); >> +        VM_BUG_ON(!IS_ALIGNED((unsigned long) pfn_to_page(0), >> alignment)); > > No VM_BUG_ON. VM_WARN_ON_ONCE() should be good enough, no? > > As discussed in the other thread, is checking for MAX_FOLIO_NR_PAGES > alignment sufficient? And after further discussions, we could use MAX_FOLIO_VMEMMAP_ALIGN macro once we have that. -- Cheers, David