Re: [PATCH RFC 2/7] filemap: Change mapping_set_folio_min_order() -> mapping_set_folio_orders()

[John Garry <john.g.garry@xxxxxxxxxx>]

On 25/04/2024 15:47, Pankaj Raghav (Samsung) wrote:
> On Mon, Apr 22, 2024 at 02:39:18PM +0000, John Garry wrote:
> > Borrowed from:
> >
> > https://urldefense.com/v3/__https://lore.kernel.org/linux-fsdevel/20240213093713.1753368-2-kernel@xxxxxxxxxxxxxxxx/__;!!ACWV5N9M2RV99hQ!LvajFab0xQx8oBWDlDtVY8duiLDjOKX91G4YqadoCu6gqatA2H0FzBUvdSC69dqXNoe2QvStSwrxIZ142MXOKk8$
> > (credit given in due course)
> >
> > We will need to be able to only use a single folio order for buffered
> > atomic writes, so allow the mapping folio order min and max be set.
>
> > We still have the restriction of not being able to support order-1
> > folios - it will be required to lift this limit at some stage.
>
> This is already supported upstream for file-backed folios:
> commit: 8897277acfef7f70fdecc054073bea2542fc7a1b

ok

> > index fc8eb9c94e9c..c22455fa28a1 100644
> > --- a/include/linux/pagemap.h
> > +++ b/include/linux/pagemap.h
> > @@ -363,9 +363,10 @@ static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
> >   #endif
> >   
> >   /*
> > - * mapping_set_folio_min_order() - Set the minimum folio order
> > + * mapping_set_folio_orders() - Set the minimum and max folio order
>
> In the new series (sorry forgot to CC you),

no worries, I saw it

> I added a new helper called
> mapping_set_folio_order_range() which does something similar to avoid
> confusion based on willy's suggestion:
> https://urldefense.com/v3/__https://lore.kernel.org/linux-xfs/20240425113746.335530-3-kernel@xxxxxxxxxxxxxxxx/__;!!ACWV5N9M2RV99hQ!LvajFab0xQx8oBWDlDtVY8duiLDjOKX91G4YqadoCu6gqatA2H0FzBUvdSC69dqXNoe2QvStSwrxIZ14opzAoso$

Fine, I can include that

> mapping_set_folio_min_order() also sets max folio order to be
> MAX_PAGECACHE_ORDER order anyway. So no need of explicitly calling it
> here?

Here mapping_set_folio_min_order() is being replaced with 
mapping_set_folio_order_range(), so not sure why you mention that. 
Regardless, I'll use your mapping_set_folio_order_range().

> >   /**
> > @@ -400,7 +406,7 @@ static inline void mapping_set_folio_min_order(struct address_space *mapping,
> >    */
> >   static inline void mapping_set_large_folios(struct address_space *mapping)
> >   {
> > -	mapping_set_folio_min_order(mapping, 0);
> > +	mapping_set_folio_orders(mapping, 0, MAX_PAGECACHE_ORDER);
> >   }
> >   
> >   static inline unsigned int mapping_max_folio_order(struct address_space *mapping)
> > diff --git a/mm/filemap.c b/mm/filemap.c
> > index d81530b0aac0..d5effe50ddcb 100644
> > --- a/mm/filemap.c
> > +++ b/mm/filemap.c
> > @@ -1898,9 +1898,15 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
> >   no_page:
> >   	if (!folio && (fgp_flags & FGP_CREAT)) {
> >   		unsigned int min_order = mapping_min_folio_order(mapping);
> > -		unsigned int order = max(min_order, FGF_GET_ORDER(fgp_flags));
> > +		unsigned int max_order = mapping_max_folio_order(mapping);
> > +		unsigned int order = FGF_GET_ORDER(fgp_flags);
> >   		int err;
> >   
> > +		if (order > max_order)
> > +			order = max_order;
> > +		else if (order < min_order)
> > +			order = max_order;
>
> order = min_order; ?

right

Thanks,
John