[PATCH 2/2] arm64: mm: run pgtable_page_ctor() on non-swapper translation table pages

[Suzuki K Poulose]

On 25/07/16 17:46, Catalin Marinas wrote:
> On Mon, Jul 25, 2016 at 03:43:21PM +0100, Suzuki K. Poulose wrote:
>> On 25/07/16 15:31, Suzuki K Poulose wrote:
>>> On 22/07/16 18:32, Ard Biesheuvel wrote:
>>>> The kernel page table creation routines are accessible to other subsystems
>>>> (e.g., EFI) via the create_pgd_mapping() entry point, which allows mappings
>>>> to be created that are not covered by init_mm.
>>>>
>>>> Since generic code such as apply_to_page_range() may expect translation
>>>> table pages that are not associated with init_mm to be covered by fully
>>>> constructed struct pages, add a call to pgtable_page_ctor() in the alloc
>>>> function used by create_pgd_mapping. Since it is no longer used by
>>>> create_mapping_late(), also update the name of this function to better
>>>> reflect its purpose.
>>>>
>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>>>> ---
>>>> arch/arm64/mm/mmu.c | 9 ++++++---
>>>> 1 file changed, 6 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>>>> index 33f36cede02d..51a558195bb9 100644
>>>> --- a/arch/arm64/mm/mmu.c
>>>> +++ b/arch/arm64/mm/mmu.c
>>>> @@ -268,10 +268,11 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
>>>>     } while (pgd++, addr = next, addr != end);
>>>> }
>>>>
>>>> -static phys_addr_t late_pgtable_alloc(void)
>>>> +static phys_addr_t pgd_pgtable_alloc(void)
>>>> {
>>>>     void *ptr = (void *)__get_free_page(PGALLOC_GFP);
>>>> -    BUG_ON(!ptr);
>>>> +    if (!ptr || !pgtable_page_ctor(virt_to_page(ptr)))
>>>
>>> Should we free the page and return NULL when we encounter an error
>>> in pgtable_page_ctor(), like the rest of the callers ?
>>>
>>>
>>>> +        BUG();
>>
>> Just to clarify, of course with the BUG() retained.
>
> But then, if we return, we no longer trigger BUG(). The callers of this
> function assume that it always succeeds or does not return.

Bah, my bad. I somehow confused myself it with WARN behavior and thought
that we could still continue after BUG(). Please ignore the noise.

Suzuki