On Wed, Aug 18, 2021 at 12:28:30PM -0700, Ralph Campbell wrote: > Did you test on a system without CONFIG_ARCH_HAS_PTE_SPECIAL defined? > In that case, mmap() of a DAX device will call insert_page() which calls > get_page() which would trigger VM_BUG_ON_PAGE(). __vm_insert_mixed still ends up calling insert_pfn for the !CASE_ARCH_HAS_PTE_SPECIAL if pfn_t_devmap() is true, which it should be for DAX. (and as said in my other mail, I suspect we should disallow that case anyway, as no one can test it in practice).
