linux-kernel - Re: [PATCH v4 03/25] mm/vmstat: Add functions to account folio statistics

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Date:   Sun, 14 Mar 2021 04:11:55 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v4 03/25] mm/vmstat: Add functions to account folio
 statistics

On Sat, Mar 13, 2021 at 12:37:07PM -0800, Andrew Morton wrote:
> On Fri,  5 Mar 2021 04:18:39 +0000 "Matthew Wilcox (Oracle)" <willy@...radead.org> wrote:
> 
> > Allow page counters to be more readily modified by callers which have
> > a folio.  Name these wrappers with 'stat' instead of 'state' as requested
> > by Linus here:
> > https://lore.kernel.org/linux-mm/CAHk-=wj847SudR-kt+46fT3+xFFgiwpgThvm7DJWGdi4cVrbnQ@mail.gmail.com/
> > 
> > --- a/include/linux/vmstat.h
> > +++ b/include/linux/vmstat.h
> > @@ -402,6 +402,54 @@ static inline void drain_zonestat(struct zone *zone,
> >  			struct per_cpu_pageset *pset) { }
> >  #endif		/* CONFIG_SMP */
> >  
> > +static inline
> > +void __inc_zone_folio_stat(struct folio *folio, enum zone_stat_item item)
> > +{
> > +	__mod_zone_page_state(folio_zone(folio), item, folio_nr_pages(folio));
> > +}
> 
> The naming is unfortunate.  We expect
> 
> inc: add one to
> dec: subtract one from
> mod: modify by signed quantity
> 
> So these are inconsistent.  Perhaps use "add" and "sub" instead.  At
> least to alert people to the fact that these are different.
> 
> And, again, it's nice to see the subsystem's name leading the
> identifiers, so "zone_folio_stat_add()".

I thought this was a 'zone stat', so __zone_stat_add_folio()?
I'm not necessarily signing up to change the existing
__inc_node_page_state(), but I might.  If so, __node_stat_add_page()?