Re: [RFC v2 03/14] filemap: use mapping_min_order while allocating folios

Pankaj Raghav (Samsung)
2024-02-14T10:13:41Z

> > +++ b/mm/filemap.c
> > @@ -127,6 +127,7 @@
> > static void page_cache_delete(struct address_space *mapping,
> > struct folio *folio, void *shadow)
> > {
> > + unsigned int min_order = mapping_min_folio_order(mapping);
> > XA_STATE(xas, &mapping->i_pages, folio->index);
> > long nr = 1;
> >
> > @@ -135,6 +136,7 @@ static void page_cache_delete(struct address_space *mapping,
> > xas_set_order(&xas, folio->index, folio_order(folio));
> > nr = folio_nr_pages(folio);
> >
> > + VM_BUG_ON_FOLIO(folio_order(folio) < min_order, folio);
> > VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
>
> If you are only using min_order in the VM_BUG_ON_FOLIO() macro, then
> please just do:
>
> VM_BUG_ON_FOLIO(folio_order(folio) < mapping_min_folio_order(mapping),
> folio);
>
> There is no need to clutter up the function with variables that are
> only used in one debug-only check.
>
Got it. I will fold it in.

> > @@ -1847,6 +1853,10 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
> > fgf_t fgp_flags, gfp_t gfp)
> > {
> > struct folio *folio;
> > + unsigned int min_order = mapping_min_folio_order(mapping);
> > + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping);
> > +
> > + index = round_down(index, min_nrpages);
>
> index = mapping_align_start_index(mapping, index);

I will add this helper. Makes the intent more clear. Thanks.

>
> The rest of the function only cares about min_order, not
> min_nrpages....
>
> -Dave.
> --
> Dave Chinner
> david@fromorbit.com