linux-kernel - Re: [PATCH 6/7] mm/gfp: make gfp_zonelist return directly and bool

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Message-ID: <20151117015950.GA5867@yaowei-K42JY>
Date:	Tue, 17 Nov 2015 09:59:50 +0800
From:	Yaowei Bai <baiyaowei@...s.chinamobile.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	akpm@...ux-foundation.org, bhe@...hat.com,
	dan.j.williams@...el.com, dave.hansen@...ux.intel.com,
	dave@...olabs.net, dhowells@...hat.com, dingel@...ux.vnet.ibm.com,
	hannes@...xchg.org, hillf.zj@...baba-inc.com, holt@....com,
	iamjoonsoo.kim@....com, joe@...ches.com, kuleshovmail@...il.com,
	mgorman@...e.de, mhocko@...e.cz, mike.kravetz@...cle.com,
	n-horiguchi@...jp.nec.com, penberg@...nel.org,
	sasha.levin@...cle.com, tj@...nel.org, tony.luck@...el.com,
	vbabka@...e.cz, vdavydov@...allels.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/7] mm/gfp: make gfp_zonelist return directly and bool

On Mon, Nov 16, 2015 at 02:05:46AM -0800, David Rientjes wrote:
> On Mon, 16 Nov 2015, Yaowei Bai wrote:
> 
> > diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> > index 6523109..1da03f5 100644
> > --- a/include/linux/gfp.h
> > +++ b/include/linux/gfp.h
> > @@ -375,12 +375,9 @@ static inline enum zone_type gfp_zone(gfp_t flags)
> >   * virtual kernel addresses to the allocated page(s).
> >   */
> >  
> > -static inline int gfp_zonelist(gfp_t flags)
> > +static inline bool gfp_zonelist(gfp_t flags)
> >  {
> > -	if (IS_ENABLED(CONFIG_NUMA) && unlikely(flags & __GFP_THISNODE))
> > -		return 1;
> > -
> > -	return 0;
> > +	return IS_ENABLED(CONFIG_NUMA) && unlikely(flags & __GFP_THISNODE);
> >  }
> >  
> >  /*
> 
> This function is used to index into a pgdat's node_zonelists[] array, bool 
> makes no sense.

Yes, you'r right, but i think hardcoding the index here is not a good idea.
How about this:

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 6523109..14a6249 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -378,9 +378,9 @@ static inline enum zone_type gfp_zone(gfp_t flags)
 static inline int gfp_zonelist(gfp_t flags)
 {
        if (IS_ENABLED(CONFIG_NUMA) && unlikely(flags & __GFP_THISNODE))
-               return 1;
+               return ZONELIST_NOFALLBACK;
 
-       return 0;
+       return ZONELIST_FALLBACK;
 }
 
 /*
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index e23a9e7..9664d6c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -576,8 +576,6 @@ static inline bool zone_is_empty(struct zone *zone)
 /* Maximum number of zones on a zonelist */
 #define MAX_ZONES_PER_ZONELIST (MAX_NUMNODES * MAX_NR_ZONES)
 
-#ifdef CONFIG_NUMA
-
 /*
  * The NUMA zonelists are doubled because we need zonelists that restrict the
  * allocations to a single node for __GFP_THISNODE.
@@ -585,10 +583,13 @@ static inline bool zone_is_empty(struct zone *zone)
  * [0] : Zonelist with fallback
  * [1] : No fallback (__GFP_THISNODE)
  */
-#define MAX_ZONELISTS 2
-#else
-#define MAX_ZONELISTS 1
+enum {
+       ZONELIST_FALLBACK,
+#ifdef CONFIG_NUMA
+       ZONELIST_NOFALLBACK,
 #endif
+       MAX_ZONELISTS
+};
 
 /*
  * This struct contains information about a zone in a zonelist. It is stored


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