[PATCH v6 05/11] mm: Add fast_only bool to test_young and clear_young MMU notifiers

[Jason Gunthorpe]

On Thu, Aug 01, 2024 at 04:13:40PM -0700, James Houghton wrote:
> --- a/include/linux/mmu_notifier.h
> +++ b/include/linux/mmu_notifier.h
> @@ -106,6 +106,18 @@ struct mmu_notifier_ops {
>          * clear_young is a lightweight version of clear_flush_young. Like the
>          * latter, it is supposed to test-and-clear the young/accessed bitflag
>          * in the secondary pte, but it may omit flushing the secondary tlb.
> +        *
> +        * The fast_only parameter indicates that this call should not block,
> +        * and this function should not cause other MMU notifier calls to
> +        * block. Usually this means that the implementation should be
> +        * lockless.
> +        *
> +        * When called with fast_only, this notifier will be a no-op unless
> +        * has_fast_aging is set on the struct mmu_notifier.

If you add a has_fast_aging I wonder if it is better to introduce new
ops instead? The semantics are a bit easier to explain that way

Jason