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 BtBg5NJw 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 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 29 Jan 2026, at 2:03, Muchun Song wrote: >> On Jan 29, 2026, at 11:29, Zi Yan wrote: >> >> On 28 Jan 2026, at 22:23, Muchun Song wrote: >> >>>> On Jan 29, 2026, at 11:10, Zi Yan wrote: >>>> >>>> On 28 Jan 2026, at 22:00, Muchun Song wrote: >>>> >>>>>> On Jan 28, 2026, at 21:54, Kiryl Shutsemau wrote: >>>>>> >>>>>> If page->compound_info encodes a mask, it is expected that vmemmap to be >>>>>> naturally aligned to the maximum folio size. >>>>>> >>>>>> Trigger a BUG() for CONFIG_DEBUG_VM=y or WARN() otherwise. >>>>>> >>>>>> Signed-off-by: Kiryl Shutsemau >>>>>> Acked-by: Zi Yan >>>>>> --- >>>>>> mm/sparse.c | 13 +++++++++++++ >>>>>> 1 file changed, 13 insertions(+) >>>>>> >>>>>> diff --git a/mm/sparse.c b/mm/sparse.c >>>>>> index b5b2b6f7041b..9c0f4015778c 100644 >>>>>> --- a/mm/sparse.c >>>>>> +++ b/mm/sparse.c >>>>>> @@ -600,6 +600,19 @@ 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; >>>>>> + bool aligned; >>>>>> + >>>>>> + alignment = MAX_FOLIO_NR_PAGES * sizeof(struct page); >>>>>> + aligned = IS_ALIGNED((unsigned long) pfn_to_page(0), alignment); >>>>>> + >>>>>> + if (IS_ENABLED(CONFIG_DEBUG_VM)) >>>>>> + BUG_ON(!aligned); >>>>>> + else >>>>>> + WARN_ON(!aligned); >>>>> >>>>> Since you’ve fixed all the problematic architectures, I don’t believe >>>>> we’ll ever hit the WARN or BUG here anymore. >>>>> >>>>> I think we can now simplify the code further and just use VM_BUG_ON: >>>>> if any architecture changes in the future, the misalignment will be >>>>> caught during testing, so we won’t need to worry about it at run-time. >>>>> >>>> >>>> VM_WARN_ON should be sufficient, since bots should report warnings >>>> from any patch/change. >>> >>> I’m not sure a WARN will get developers’ attention, since the message >>> is unlikely to have any visible consequences and only fires on >>> allocations with a special order. >> >> If a developer misses the WARN and the patch gets into linux-mm or linux-next, >> kernel test robot runs selftests on the kernel and reports any warnings >> to the mailing list. Do we have any related test in selftests/mm? That should >> help us catch anything if a developer does not catch it. > > I looked at the selftest and it doesn’t seem to have a test that > allocates at MAX_FOLIO_ORDER and checks that it works correctly. OK, we probably need a selftest for it. In terms of using VM_BUG_ON or VM_WARN_ON, I leave that decision to you and Kiryl. Thank you for the clarification. Best Regards, Yan, Zi