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 Mr1Fl+y+ 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79a61cc3fc04 ("mm: avoid leaving partial pfn mappings around in > > > error case") from Sep 11, 2024 (linux-next), leads to the following > > > Smatch static checker warning: > > > > > > mm/memory.c:2709 remap_pfn_range_notrack() > > > warn: sleeping in atomic context > > > > > > mm/memory.c > > > 2696 int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr, > > > 2697 unsigned long pfn, unsigned long size, pgprot_t prot) > > > 2698 { > > > 2699 int error = remap_pfn_range_internal(vma, addr, pfn, size, prot); > > > 2700 > > > 2701 if (!error) > > > 2702 return 0; > > > 2703 > > > 2704 /* > > > 2705 * A partial pfn range mapping is dangerous: it does not > > > 2706 * maintain page reference counts, and callers may free > > > 2707 * pages due to the error. So zap it early. > > > 2708 */ > > > --> 2709 zap_page_range_single(vma, addr, size, NULL); > > > > > > The lru_add_drain() function at the start of zap_page_range_single() takes a > > > mutext. > > > > Hm does it? I see a local lock, and some folio batch locking which are > > local locks too? > > Ah... No it doesn't. It's the mmu_notifier_invalidate_range_start() which is > a might_sleep() function. Sorry for the confusion. OK so in conclusion it seems to be that Linus's commit introducing zap_page_range_single() accidentally had smatch hit a might_sleep() via mmu_notifier_invalidate_range_start(), but it should, in theory, have fired due to page table allocations invoking the page allocator that might sleep, but didn't, because smatch misses the below might_alloc() path... -> prepare_alloc_pages() -> might_alloc() -> might_sleep_if(gfpflags_allow_blocking(gfp_mask)) ...as a result of get_zeroed_page() tripping it up *breathes*. :) (please correct me if I am wrong here). The preempt_disable() is introduced in commit fe5bb6b00c3a9 ("sgi-gru: misc GRU cleanup") from... 2009, but it fixed it from the far far more broken 'disable preemption before taking a mutex' situation that existed before. So fix seems to me to not invoke remap_pfn_range() with preemption disabled and a mutex held? gru_fault() maintainers added for input... > > regards, > dan carpenter > >