Re: [PATCH 01/19] mm/swap: rename __read_swap_cache_async to swap_cache_alloc_folio

[Barry Song <baohua@kernel.org>]

> > +/**
> > + * swap_cache_alloc_folio - Allocate folio for swapped out slot in swap cache.
> > + * @entry: the swapped out swap entry to be binded to the folio.
> > + * @gfp_mask: memory allocation flags
> > + * @mpol: NUMA memory allocation policy to be applied
> > + * @ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE
> > + * @new_page_allocated: sets true if allocation happened, false otherwise
> > + * @skip_if_exists: if the slot is a partially cached state, return NULL.
> > + *                  This is a workaround that would be removed shortly.
> > + *
> > + * Allocate a folio in the swap cache for one swap slot, typically before
> > + * doing IO (swap in or swap out). The swap slot indicated by @entry must
> > + * have a non-zero swap count (swapped out). Currently only supports order 0.
>
> Is it used for swap in? That's confusing because the next sentence
> mention that it needs to be already swapped out.
>
> I suspect you're referring to the zswap writeback use case, but in this
> case we're still "swapping-in" the folio from zswap to swap it out to
> disk. I'd avoid mentioning swap in here because it's confusing.

I assume you mean avoiding any mention of swap-out? As for swap-out, we’re
swapping a folio out from the LRU — we’re not allocating a new folio.

BTW, this sentence also feels a bit odd to me. I’d prefer removing
“swap out” from
“doing IO (swap in or swap out)”.

Thanks
Barry