On Thu, 2018-08-30 at 13:06 -0700, Dave Jiang wrote:
> It looks like I missed the PUD path when doing VM_MIXEDMAP removal.
> This can be triggered by:
> 1. Boot with memmap=4G!8G
> 2. build ndctl with destructive flag on
> 3. make TESTS=device-dax check
> 
> [  +0.000675] kernel BUG at mm/huge_memory.c:824!
> 
> Applying the same change that was applied to vmf_insert_pfn_pmd() in
> the
> original patch.
> 
> Fixes: e1fb4a08649 ("dax: remove VM_MIXEDMAP for fsdax and device
> dax")
> 
> Reported-by: Vishal Verma <[email protected]>
> Signed-off-by: Dave Jiang <[email protected]>
> ---
>  mm/huge_memory.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

This fixes the unit test failure, feel free to add:
Tested-by: Vishal Verma <[email protected]>

> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index c3bc7e9c9a2a..533f9b00147d 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -821,11 +821,11 @@ vm_fault_t vmf_insert_pfn_pud(struct
> vm_area_struct *vma, unsigned long addr,
>        * but we need to be consistent with PTEs and architectures
> that
>        * can't support a 'special' bit.
>        */
> -     BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
> +     BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
> +                     !pfn_t_devmap(pfn));
>       BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
>                                               (VM_PFNMAP|VM_MIXEDM
> AP));
>       BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma-
> >vm_flags));
> -     BUG_ON(!pfn_t_devmap(pfn));
>  
>       if (addr < vma->vm_start || addr >= vma->vm_end)
>               return VM_FAULT_SIGBUS;
> 
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