Re: [PATCH v1 02/10] mm: pass gfp flags and order to vma_alloc_zeroed_movable_folio()

Ryan Roberts
2023-06-27T07:28:13Z

On 27/06/2023 03:27, Yu Zhao wrote:
> On Mon, Jun 26, 2023 at 11:14 AM Ryan Roberts <ryan.roberts@arm.com> wrote:
>>
>> Allow allocation of large folios with vma_alloc_zeroed_movable_folio().
>> This prepares the ground for large anonymous folios. The generic
>> implementation of vma_alloc_zeroed_movable_folio() now uses
>> clear_huge_page() to zero the allocated folio since it may now be a
>> non-0 order.
>>
>> Currently the function is always called with order 0 and no extra gfp
>> flags, so no functional change intended. But a subsequent commit will
>> take advantage of the new parameters to allocate large folios. The extra
>> gfp flags will be used to control the reclaim policy.
>>
>> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
>> ---
>> arch/alpha/include/asm/page.h | 5 +++--
>> arch/arm64/include/asm/page.h | 3 ++-
>> arch/arm64/mm/fault.c | 7 ++++---
>> arch/ia64/include/asm/page.h | 5 +++--
>> arch/m68k/include/asm/page_no.h | 7 ++++---
>> arch/s390/include/asm/page.h | 5 +++--
>> arch/x86/include/asm/page.h | 5 +++--
>> include/linux/highmem.h | 23 +++++++++++++----------
>> mm/memory.c | 5 +++--
>> 9 files changed, 38 insertions(+), 27 deletions(-)
>>
>> diff --git a/arch/alpha/include/asm/page.h b/arch/alpha/include/asm/page.h
>> index 4db1ebc0ed99..6fc7fe91b6cb 100644
>> --- a/arch/alpha/include/asm/page.h
>> +++ b/arch/alpha/include/asm/page.h
>> @@ -17,8 +17,9 @@
>> extern void clear_page(void *page);
>> #define clear_user_page(page, vaddr, pg) clear_page(page)
>>
>> -#define vma_alloc_zeroed_movable_folio(vma, vaddr) \
>> - vma_alloc_folio(GFP_HIGHUSER_MOVABLE | __GFP_ZERO, 0, vma, vaddr, false)
>> +#define vma_alloc_zeroed_movable_folio(vma, vaddr, gfp, order) \
>> + vma_alloc_folio(GFP_HIGHUSER_MOVABLE | __GFP_ZERO | (gfp), \
>> + order, vma, vaddr, false)
>
> I don't think we need to worry about gfp if we want to make a minimum
> series. There would be many discussion points around it, e.g., I
> already disagree with what you chose: GFP_TRANSHUGE_LIGHT would be
> more suitable than __GFP_NORETRY, and there are even better options
> than GFP_TRANSHUGE_LIGHT.

OK, but disagreeing about what the GFP flags should be is different from
disagreeing about whether we need a mechanism for specifying them. Given I need
to do the changes to add `order` I thought it was sensible to add the gfp flags
at the same time.

I'll follow your advice and remove the gfp flag addition for now.