Dan Williams <dan.j.williams@xxxxxxxxx> writes:
[...]
> +/**
> + * pgmap_request_folios - activate an contiguous span of folios in @pgmap
> + * @pgmap: host page map for the folio array
> + * @folio: start of the folio list, all subsequent folios have same folio_size()
> + *
> + * Caller is responsible for @pgmap remaining live for the duration of
> + * this call. Caller is also responsible for not racing requests for the
> + * same folios.
> + */
> +bool pgmap_request_folios(struct dev_pagemap *pgmap, struct folio *folio,
> + int nr_folios)
All callers of pgmap_request_folios() I could see call this with
nr_folios == 1 and pgmap == folio_pgmap(folio). Could we remove the
redundant arguments and simplify it to
pgmap_request_folios(struct folio *folio)?
> +{
> + struct folio *iter;
> + int i;
> +
> + /*
> + * All of the WARNs below are for catching bugs in future
> + * development that changes the assumptions of:
> + * 1/ uniform folios in @pgmap
> + * 2/ @pgmap death does not race this routine.
> + */
> + VM_WARN_ON_ONCE(!folio_span_valid(pgmap, folio, nr_folios));
> +
> + if (WARN_ON_ONCE(percpu_ref_is_dying(&pgmap->ref)))
> + return false;
> +
> + for (iter = folio_next(folio), i = 1; i < nr_folios;
> + iter = folio_next(folio), i++)
> + if (WARN_ON_ONCE(folio_order(iter) != folio_order(folio)))
> + return false;
> +
> + for (iter = folio, i = 0; i < nr_folios; iter = folio_next(iter), i++) {
> + folio_ref_inc(iter);
> + if (folio_ref_count(iter) == 1)
> + percpu_ref_tryget(&pgmap->ref);
> + }
> +
> + return true;
> +}
> +
> +void pgmap_release_folios(struct dev_pagemap *pgmap, struct folio *folio, int nr_folios)
> +{
> + struct folio *iter;
> + int i;
> +
> + for (iter = folio, i = 0; i < nr_folios; iter = folio_next(iter), i++) {
> + if (!put_devmap_managed_page(&iter->page))
> + folio_put(iter);
> + if (!folio_ref_count(iter))
> + put_dev_pagemap(pgmap);
> + }
> +}
> +
> #ifdef CONFIG_FS_DAX
> bool __put_devmap_managed_page_refs(struct page *page, int refs)
> {
