linux-kernel - Re: [PATCH v2] mm/hugetlb: avoid hardcoding while checking if cma is enable

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Message-ID: <20200707073735.GB9449@kernel.org>
Date:   Tue, 7 Jul 2020 10:37:35 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Roman Gushchin <guro@...com>
Cc:     Barry Song <song.bao.hua@...ilicon.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linuxarm@...wei.com, Mike Kravetz <mike.kravetz@...cle.com>,
        Jonathan Cameron <jonathan.cameron@...wei.com>
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@...com>
> > Cc: Mike Kravetz <mike.kravetz@...cle.com>
> > Cc: Jonathan Cameron <jonathan.cameron@...wei.com>
> > Signed-off-by: Barry Song <song.bao.hua@...ilicon.com>
> > ---
> >  -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.

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

-- 
Sincerely yours,
Mike.