[PATCH v2 hmm 4/9] mm/hmm: remove HMM_FAULT_SNAPSHOT

[Christoph Hellwig]

>  
> +/*
> + * If the valid flag is masked off, and default_flags doesn't set valid, then
> + * hmm_pte_need_fault() always returns 0.
> + */
> +static bool hmm_can_fault(struct hmm_range *range)
> +{
> +	return ((range->flags[HMM_PFN_VALID] & range->pfn_flags_mask) |
> +		range->default_flags) &
> +	       range->flags[HMM_PFN_VALID];
> +}

So my idea behind the helper was to turn this into something readable :)

E.g.

/*
 * We only need to fault if either the default mask requires to fault all
 * pages, or at least the mask allows for individual pages to be faulted.
 */
static bool hmm_can_fault(struct hmm_range *range)
{
	return ((range->default_flags | range->pfn_flags_mask) &
		range->flags[HMM_PFN_VALID]);
}

In fact now that I managed to destill it down to this I'm not even
sure we really even need the helper, although the comment really helps.