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Date:   Tue, 3 Jul 2018 18:03:16 +0300
From:   Mike Rapoport <rppt@linux.vnet.ibm.com>
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Greg Ungerer <gerg@linux-m68k.org>,
        Sam Creasey <sammy@sammy.net>, linux-m68k@lists.linux-m68k.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] m68k/page_no.h: force __va argument to be unsigned
 long
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 <20180703142054.GL16767@dhcp22.suse.cz>
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On Tue, Jul 03, 2018 at 04:20:54PM +0200, Michal Hocko wrote:
> On Tue 03-07-18 13:29:54, Mike Rapoport wrote:
> > Add explicit casting to unsigned long to the __va() parameter
> 
> Why is this needed?

To make it consitent with other architecures and asm-generic :)

But more importantly, __memblock_free_late() passes u64 to page_to_pfn().
On m68k-nommu this results in:

  CC      mm/nobootmem.o
In file included from
arch/m68k/include/asm/page.h:49,
                 from
arch/m68k/include/asm/thread_info.h:6,
                 from
include/linux/thread_info.h:38,
                 from
include/asm-generic/preempt.h:5,
                 from ./arch/m68k/include/generated/asm/preempt.h:1,
                 from include/linux/preempt.h:81,
                 from include/linux/spinlock.h:51,
                 from include/linux/mmzone.h:8,
                 from include/linux/gfp.h:6,
                 from include/linux/slab.h:15,
                 from mm/memblock.c:14:
mm/memblock.c: In function '__memblock_free_late':
arch/m68k/include/asm/page_no.h:21:23: warning:
cast to pointer from integer of different size [-Wint-to-pointer-cast]
 #define __va(paddr)  ((void *)(paddr))
                       ^
arch/m68k/include/asm/page_no.h:26:57: note: in
definition of macro 'virt_to_page'
 #define virt_to_page(addr) (mem_map + (((unsigned long)(addr)-PAGE_OFFSET)
>> PAGE_SHIFT))
                                                         ^~~~
arch/m68k/include/asm/page_no.h:24:26: note: in
expansion of macro '__va'
 #define pfn_to_virt(pfn) __va((pfn) << PAGE_SHIFT)
                          ^~~~
arch/m68k/include/asm/page_no.h:29:39: note: in
expansion of macro 'pfn_to_virt'
 #define pfn_to_page(pfn) virt_to_page(pfn_to_virt(pfn))
                                       ^~~~~~~~~~~
mm/memblock.c:1473:24: note: in expansion of macro
'pfn_to_page'
   __free_pages_bootmem(pfn_to_page(cursor), cursor, 0);
                        ^~~~~~~~~~~

 
> > Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
> > ---
> >  arch/m68k/include/asm/page_no.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/m68k/include/asm/page_no.h b/arch/m68k/include/asm/page_no.h
> > index e644c4d..6bbe520 100644
> > --- a/arch/m68k/include/asm/page_no.h
> > +++ b/arch/m68k/include/asm/page_no.h
> > @@ -18,7 +18,7 @@ extern unsigned long memory_end;
> >  #define __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE
> >  
> >  #define __pa(vaddr)		((unsigned long)(vaddr))
> > -#define __va(paddr)		((void *)(paddr))
> > +#define __va(paddr)		((void *)((unsigned long)(paddr)))
> >  
> >  #define virt_to_pfn(kaddr)	(__pa(kaddr) >> PAGE_SHIFT)
> >  #define pfn_to_virt(pfn)	__va((pfn) << PAGE_SHIFT)
> > -- 
> > 2.7.4
> 
> -- 
> Michal Hocko
> SUSE Labs
> 

-- 
Sincerely yours,
Mike.