On Thu, Jun 13, 2019 at 09:44:40PM -0300, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
>
> Ralph observes that hmm_range_register() can only be called by a driver
> while a mirror is registered. Make this clear in the API by passing in the
> mirror structure as a parameter.
>
> This also simplifies understanding the lifetime model for struct hmm, as
> the hmm pointer must be valid as part of a registered mirror so all we
> need in hmm_register_range() is a simple kref_get.
Looks good, at least an an intermediate step:
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> index f6956d78e3cb25..22a97ada108b4e 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -914,13 +914,13 @@ static void hmm_pfns_clear(struct hmm_range *range,
> * Track updates to the CPU page table see include/linux/hmm.h
> */
> int hmm_range_register(struct hmm_range *range,
> - struct mm_struct *mm,
> + struct hmm_mirror *mirror,
> unsigned long start,
> unsigned long end,
> unsigned page_shift)
> {
> unsigned long mask = ((1UL << page_shift) - 1UL);
> - struct hmm *hmm;
> + struct hmm *hmm = mirror->hmm;
>
> range->valid = false;
> range->hmm = NULL;
> @@ -934,20 +934,15 @@ int hmm_range_register(struct hmm_range *range,
> range->start = start;
> range->end = end;
But while you're at it: the calling conventions of hmm_range_register
are still rather odd, as the staet, end and page_shift arguments are
only used to fill out fields in the range structure passed in. Might
be worth cleaning up as well if we change the calling convention.
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