linux-kernel - Re: [PATCH v2] x86/mm/64: Rename the register_page_bootmem_memmap() 'size' parameter to 'nr

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Message-ID: <20171026064301.GA2275@x1>
Date:   Thu, 26 Oct 2017 14:43:01 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, akpm@...ux-foundation.org
Subject: Re: [PATCH v2] x86/mm/64: Rename the register_page_bootmem_memmap()
 'size' parameter to 'nr_pages'

On 10/26/17 at 08:25am, Ingo Molnar wrote:
> 
> * Baoquan He <bhe@...hat.com> wrote:
> 
> > register_page_bootmem_memmap()'s 3rd 'size' parameter is named
> > in a somewhat misleading fashion - rename it to 'nr_pages' which
> > makes the units of it much clearer.
> > 
> > And also rename the existing local variable 'nr_pages' to 'pages'.
> > Otherwise building error will be reported since these two variables
> > are different type though both represent number of pages. Take
> > 'nr_pages' as register_page_bootmem_memmap()'s parameter name since
> > it has more specific meaning, can make better function interface.
> > 
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: akpm@...ux-foundation.org
> > Link: http://lkml.kernel.org/r/1508849249-18035-1-git-send-email-bhe@redhat.com
> > Signed-off-by: Ingo Molnar <mingo@...nel.org>
> > ---
> > v1->v2:
> >   Code change in v1 is incomplete, caused build failure. Change
> >   it after Ingo pointed it out.
> > 
> >   And Ingo helped rewrite the change log of v1. I also add description
> >   about the local variable change. 
> > 
> >  arch/x86/mm/init_64.c | 10 +++++-----
> >  include/linux/mm.h    |  2 +-
> >  2 files changed, 6 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> > index 048fbe8fc274..18b9d2c7f5ef 100644
> > --- a/arch/x86/mm/init_64.c
> > +++ b/arch/x86/mm/init_64.c
> > @@ -1426,16 +1426,16 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
> >  
> >  #if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_HAVE_BOOTMEM_INFO_NODE)
> >  void register_page_bootmem_memmap(unsigned long section_nr,
> > -				  struct page *start_page, unsigned long size)
> > +				  struct page *start_page, unsigned long nr_pages)
> >  {
> >  	unsigned long addr = (unsigned long)start_page;
> > -	unsigned long end = (unsigned long)(start_page + size);
> > +	unsigned long end = (unsigned long)(start_page + nr_pages);
> >  	unsigned long next;
> >  	pgd_t *pgd;
> >  	p4d_t *p4d;
> >  	pud_t *pud;
> >  	pmd_t *pmd;
> > -	unsigned int nr_pages;
> > +	unsigned int pages;
> >  	struct page *page;
> >  
> >  	for (; addr < end; addr = next) {
> > @@ -1482,9 +1482,9 @@ void register_page_bootmem_memmap(unsigned long section_nr,
> >  			if (pmd_none(*pmd))
> >  				continue;
> >  
> > -			nr_pages = 1 << (get_order(PMD_SIZE));
> > +			pages = 1 << (get_order(PMD_SIZE));
> 
> Why is the get_order() call in extra parentheses?

Yeah, the extra parentheses makes no sense,  will clean it up.

> 
> Also, the 'pages' name sucks in a similar way 'size' sucks - in this context where 
> we _already_ have a nr_pages variable it should be something more expressive like 
> 'nr_pmd_pages' or so.

nr_pmd_pages looks better, will use it instead.

Thanks for reviewing and great suggestion!

Thanks
Baoquan