Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751530AbaBGX1v (ORCPT ); Fri, 7 Feb 2014 18:27:51 -0500 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:54321 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751438AbaBGX1X (ORCPT ); Fri, 7 Feb 2014 18:27:23 -0500 X-Originating-IP: 50.43.14.201 Date: Fri, 7 Feb 2014 15:27:12 -0800 From: Josh Triplett To: David Rientjes Cc: Andrew Morton , Rashika Kheria , linux-kernel@vger.kernel.org, Rik van Riel , "Kirill A. Shutemov" , Jiang Liu , Michel Lespinasse , linux-mm@kvack.org Subject: Re: [PATCH 9/9] mm: Remove ifdef condition in include/linux/mm.h Message-ID: <20140207232711.GA16836@jtriplet-mobl1> References: <63adb3b97f2869d4c7e76d17ef4aa76b8cf599f3.1391167128.git.rashika.kheria@gmail.com> <20140207210705.GB13604@jtriplet-mobl1> <20140207143050.6bd35ed5c670a3ca143ba59a@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 07, 2014 at 03:09:09PM -0800, David Rientjes wrote: > On Fri, 7 Feb 2014, Andrew Morton wrote: > > > > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > > > > > index 1cedd00..5f8348f 100644 > > > > > > --- a/include/linux/mm.h > > > > > > +++ b/include/linux/mm.h > > > > > > @@ -1589,10 +1589,8 @@ static inline int __early_pfn_to_nid(unsigned long pfn) > > > > > > #else > > > > > > /* please see mm/page_alloc.c */ > > > > > > extern int __meminit early_pfn_to_nid(unsigned long pfn); > > > > > > -#ifdef CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID > > > > > > /* there is a per-arch backend function. */ > > > > > > extern int __meminit __early_pfn_to_nid(unsigned long pfn); > > > > > > -#endif /* CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID */ > > > > > > #endif > > > > > > > > > > > > extern void set_dma_reserve(unsigned long new_dma_reserve); > > > > > > > > > > Wouldn't it be better to just declare the __early_pfn_to_nid() in > > > > > mm/page_alloc.c to be static? > > > > > > > > Won't that break the ability to override that function in > > > > architecture-specific code (as arch/ia64/mm/numa.c does)? > > > > > > > > > > Why? CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID should define where this function > > > is defined so ia64 should have it set and the definition which I'm > > > suggesting be static is only compiled when this is undefined in > > > mm/page_alloc.c. I'm not sure why we'd want to be messing with the > > > declaration? > > > > __early_pfn_to_nid() must be global if it is implemented in arch/. > > > > Why?? If CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID then, yes, we need it to be > global. Otherwise it's perfectly fine just being static in file scope. > This causes the compilation unit to break when you compile it, not wait > until vmlinux and find undefined references. > > I see no reason it can't be done like this in mm/page_alloc.c: > > #ifdef CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID > extern int __meminit __early_pfn_to_nid(unsigned long pfn); No, a .c file should not have an extern declaration in it. This should live in an appropriate header file, to be included in both page_alloc.c and any arch file that defines an overriding function. > Both of these options look much better than > > include/linux/mm.h: > > #if !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) && \ > !defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) > static inline int __early_pfn_to_nid(unsigned long pfn) > { > return 0; > } > #else > /* please see mm/page_alloc.c */ > extern int __meminit early_pfn_to_nid(unsigned long pfn); > #ifdef CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID > /* there is a per-arch backend function. */ > extern int __meminit __early_pfn_to_nid(unsigned long pfn); > #endif /* CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID */ > #endif > > where all this confusion is originating from. The proposal is to first simplify those ifdefs by eliminating the inner one in the #else; I agree with Andrew that we ought to go ahead and take that step given the patch at hand, and then figure out if there's an additional simplification possible. - Josh Triplett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/