RE: [PATCH v2] mm/hugetlb: avoid hardcoding while checking if cma is enable

[Song Bao Hua (Barry Song)]

> -----Original Message-----
> From: Mike Rapoport [mailto:rppt@xxxxxxxxxx]
> Sent: Tuesday, July 7, 2020 7:38 PM
> To: Roman Gushchin <guro@xxxxxx>
> Cc: Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx>;
> akpm@xxxxxxxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; Linuxarm <linuxarm@xxxxxxxxxx>; Mike
> Kravetz <mike.kravetz@xxxxxxxxxx>; Jonathan Cameron
> <jonathan.cameron@xxxxxxxxxx>
> Subject: Re: [PATCH v2] mm/hugetlb: avoid hardcoding while checking if cma
> is enable
> 
> On Mon, Jul 06, 2020 at 08:36:31PM -0700, Roman Gushchin wrote:
> > On Tue, Jul 07, 2020 at 03:11:56PM +1200, Barry Song wrote:
> > > hugetlb_cma[0] can be NULL due to various reasons, for example, node0
> has
> > > no memory. so NULL hugetlb_cma[0] doesn't necessarily mean cma is not
> > > enabled. gigantic pages might have been reserved on other nodes.
> > >
> > > Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages
> using cma")
> > > Cc: Roman Gushchin <guro@xxxxxx>
> > > Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> > > Cc: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>
> > > Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
> > > ---
> > >  -v2: add hugetlb_cma_enabled() helper to improve readability according
> to Roman
> > >
> > >  mm/hugetlb.c | 16 +++++++++++++++-
> > >  1 file changed, 15 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > > index 57ece74e3aae..d5e98ed86bb9 100644
> > > --- a/mm/hugetlb.c
> > > +++ b/mm/hugetlb.c
> > > @@ -2546,6 +2546,20 @@ static void __init
> gather_bootmem_prealloc(void)
> > >  	}
> > >  }
> > >
> > > +bool __init hugetlb_cma_enabled(void)
> > > +{
> > > +	if (IS_ENABLED(CONFIG_CMA)) {
> > > +		int node;
> > > +
> > > +		for_each_online_node(node) {
> > > +			if (hugetlb_cma[node])
> > > +				return true;
> > > +		}
> > > +	}
> > > +
> > > +	return false;
> > > +}
> > > +
> >
> > Can you, please, change it to a more canonical
> >
> > #ifdef CONFIG_CMA
> > bool __init hugetlb_cma_enabled(void)
> > {
> > 	int node;
> >
> > 	for_each_online_node(node)
> > 		if (hugetlb_cma[node])
> > 			return true;
> >
> > 	return false;
> > }
> > #else
> > bool __init hugetlb_cma_enabled(void)
> > {
> > 	return false;
> > }
> > #endif
> >
> > or maybe just
> >
> > bool __init hugetlb_cma_enabled(void)
> > {
> > #ifdef CONFIG_CMA
> > 	int node;
> >
> > 	for_each_online_node(node)
> > 		if (hugetlb_cma[node])
> > 			return true;
> > #endif
> > 	return false;
> > }
> 
> This one please.

Yep. Patch v3 is just the one you prefer:
https://marc.info/?l=linux-mm&m=159409465228477&w=2

> 
> > ?
> >
> > Please, feel free to add
> > Acked-by: Roman Gushchin <guro@xxxxxx> after that.
> >
> > Thank you!
> >
> 
> --
> Sincerely yours,
> Mike.

Thanks
Barry