[PATCH v2 hmm 2/9] mm/hmm: return the fault type from hmm_pte_need_fault()

[Christoph Hellwig]

On Mon, Mar 23, 2020 at 10:14:50PM -0300, Jason Gunthorpe wrote:
> +enum {
> +	HMM_NEED_FAULT = 1 << 0,
> +	HMM_NEED_WRITE_FAULT = HMM_NEED_FAULT | (1 << 1),
> +	HMM_NEED_ALL_BITS = HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT,

I have to say I find the compound version of HMM_NEED_WRITE_FAULT
way harder to understand than the logic in the previous version,
and would refer keeping separate bits here.

Mostly beccause of statements like this:

> +	if ((required_fault & HMM_NEED_WRITE_FAULT) == HMM_NEED_WRITE_FAULT) {

which seems rather weird.