linux-kernel - Re: [PATCH v6 6/6] mm/mempolicy: unify the create() func for bind/interleave/prefer-many policies

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Message-ID: <20210728135000.GB43486@shbuild999.sh.intel.com>
Date:   Wed, 28 Jul 2021 21:50:00 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Ben Widawsky <ben.widawsky@...el.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andi Kleen <ak@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>, ying.huang@...el.com
Subject: Re: [PATCH v6 6/6] mm/mempolicy: unify the create() func for
 bind/interleave/prefer-many policies

On Wed, Jul 28, 2021 at 02:51:42PM +0200, Michal Hocko wrote:
> On Mon 12-07-21 16:09:34, Feng Tang wrote:
> > As they all do the same thing: sanity check and save nodemask info, create
> > one mpol_new_nodemask() to reduce redundancy.
> 
> Do we really need a create() callback these days?

I think it tries to provide a per-policy sanity check (though
it's the same for all existing ones), and a per-policy
nodemask setting (current 'prefer' policy is different from
others).

> > Signed-off-by: Feng Tang <feng.tang@...el.com>
> 
> Other than that LGTM
> Acked-by: Michal Hocko <mhocko@...e.com>

Thanks!

- Feng

> > ---
> >  mm/mempolicy.c | 24 ++++--------------------
> >  1 file changed, 4 insertions(+), 20 deletions(-)
> > 
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index d90247d6a71b..e5ce5a7e8d92 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -192,7 +192,7 @@ static void mpol_relative_nodemask(nodemask_t *ret, const nodemask_t *orig,
> >  	nodes_onto(*ret, tmp, *rel);
> >  }
> >  
> > -static int mpol_new_interleave(struct mempolicy *pol, const nodemask_t *nodes)
> > +static int mpol_new_nodemask(struct mempolicy *pol, const nodemask_t *nodes)
> >  {
> >  	if (nodes_empty(*nodes))
> >  		return -EINVAL;
> > @@ -210,22 +210,6 @@ static int mpol_new_preferred(struct mempolicy *pol, const nodemask_t *nodes)
> >  	return 0;
> >  }
> >  
> > -static int mpol_new_preferred_many(struct mempolicy *pol, const nodemask_t *nodes)
> > -{
> > -	if (nodes_empty(*nodes))
> > -		return -EINVAL;
> > -	pol->nodes = *nodes;
> > -	return 0;
> > -}
> > -
> > -static int mpol_new_bind(struct mempolicy *pol, const nodemask_t *nodes)
> > -{
> > -	if (nodes_empty(*nodes))
> > -		return -EINVAL;
> > -	pol->nodes = *nodes;
> > -	return 0;
> > -}
> > -
> >  /*
> >   * mpol_set_nodemask is called after mpol_new() to set up the nodemask, if
> >   * any, for the new policy.  mpol_new() has already validated the nodes
> > @@ -405,7 +389,7 @@ static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
> >  		.rebind = mpol_rebind_default,
> >  	},
> >  	[MPOL_INTERLEAVE] = {
> > -		.create = mpol_new_interleave,
> > +		.create = mpol_new_nodemask,
> >  		.rebind = mpol_rebind_nodemask,
> >  	},
> >  	[MPOL_PREFERRED] = {
> > @@ -413,14 +397,14 @@ static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
> >  		.rebind = mpol_rebind_preferred,
> >  	},
> >  	[MPOL_BIND] = {
> > -		.create = mpol_new_bind,
> > +		.create = mpol_new_nodemask,
> >  		.rebind = mpol_rebind_nodemask,
> >  	},
> >  	[MPOL_LOCAL] = {
> >  		.rebind = mpol_rebind_default,
> >  	},
> >  	[MPOL_PREFERRED_MANY] = {
> > -		.create = mpol_new_preferred_many,
> > +		.create = mpol_new_nodemask,
> >  		.rebind = mpol_rebind_preferred,
> >  	},
> >  };
> > -- 
> > 2.7.4
> 
> -- 
> Michal Hocko
> SUSE Labs