Re: [PATCH] mm: fix build warnings in <linux/compaction.h>

From: Minchan Kim <minchan@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>,
	Linux MM <linux-mm@kvack.org>,
	"linux-next@vger.kernel.org" <linux-next@vger.kernel.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Gioh Kim <gi-oh.kim@profitbricks.com>,
	Konstantin Khlebnikov <koct9i@gmail.com>,
	Rafael Aquini <aquini@redhat.com>,
	Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH] mm: fix build warnings in <linux/compaction.h>
Date: Fri, 10 Jun 2016 09:33:04 +0900	[thread overview]
Message-ID: <20160610003304.GE29779@bbox> (raw)
In-Reply-To: <20160609235141.GD29779@bbox>

On Fri, Jun 10, 2016 at 08:51:41AM +0900, Minchan Kim wrote:
> On Thu, Jun 09, 2016 at 04:37:19PM -0700, Andrew Morton wrote:
> > On Fri, 10 Jun 2016 08:31:43 +0900 Minchan Kim <minchan@kernel.org> wrote:
> > 
> > > Hi Andrew,
> > > 
> > > On Thu, Jun 09, 2016 at 03:27:16PM -0700, Andrew Morton wrote:
> > > > On Thu, 9 Jun 2016 10:06:01 -0700 Randy Dunlap <rdunlap@infradead.org> wrote:
> > > > 
> > > > > From: Randy Dunlap <rdunlap@infradead.org>
> > > > > 
> > > > > Fix build warnings when struct node is not defined:
> > > > > 
> > > > > In file included from ../include/linux/balloon_compaction.h:48:0,
> > > > >                  from ../mm/balloon_compaction.c:11:
> > > > > ../include/linux/compaction.h:237:51: warning: 'struct node' declared inside parameter list [enabled by default]
> > > > >  static inline int compaction_register_node(struct node *node)
> > > > > ../include/linux/compaction.h:237:51: warning: its scope is only this definition or declaration, which is probably not what you want [enabled by default]
> > > > > ../include/linux/compaction.h:242:54: warning: 'struct node' declared inside parameter list [enabled by default]
> > > > >  static inline void compaction_unregister_node(struct node *node)
> > > > > 
> > > > > ...
> > > > >
> > > > > --- linux-next-20160609.orig/include/linux/compaction.h
> > > > > +++ linux-next-20160609/include/linux/compaction.h
> > > > > @@ -233,6 +233,7 @@ extern int compaction_register_node(stru
> > > > >  extern void compaction_unregister_node(struct node *node);
> > > > >  
> > > > >  #else
> > > > > +struct node;
> > > > >  
> > > > >  static inline int compaction_register_node(struct node *node)
> > > > >  {
> > > > 
> > > > Well compaction.h has no #includes at all and obviously depends on its
> > > > including file(s) to bring in the definitions which it needs.
> > > > 
> > > > So if we want to keep that (odd) model then we should fix
> > > > mm-balloon-use-general-non-lru-movable-page-feature.patch thusly:
> > > 
> > > How about fixing such odd model in this chance?
> > > Otherwise, every non-lru page migration driver should include
> > > both compaction.h and node.h which is weired to me. :(
> > > 
> > > I think there are two ways.
> > > 
> > > 1. compaction.h include node.h directly so user of compaction.h don't
> > > need to take care about node.h
> > > 
> > > 2. Randy's fix
> > > 
> > > I looked up who use compaction_[un]register_node and found it's used
> > > only drivers/base/node.c which already include node.h so no problem.
> > > 
> > > 1) I believe it's rare those functions to be needed by other files.
> > > 2) Those functions works if CONFIG_NUMA as well as CONFIG_COMPACTION
> > > which is rare configuration for many not-server system.
> > 
> > If we're going to convert compaction.h to be standalone then it will
> > need to include a whole bunch of things - what's special about node.h?
> 
> Fair enough.
> I realize it would be better to relocate non-lru page migration functions to
> new separate header but I don't have an good idea to name that file. :(
> Anyway, I will work for it.
> 

Andrew, it's quick fix. How about this?