linux-kernel - Re: [PATCH 2/3] m68k/page_no.h: force _

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Date:   Tue, 3 Jul 2018 17:55:05 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Mike Rapoport <rppt@...ux.vnet.ibm.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Sam Creasey <sammy@...my.net>, linux-m68k@...ts.linux-m68k.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] m68k/page_no.h: force __va argument to be unsigned
 long

On Tue 03-07-18 18:47:51, Mike Rapoport wrote:
> On Tue, Jul 03, 2018 at 05:14:01PM +0200, Michal Hocko wrote:
> > On Tue 03-07-18 08:05:35, Matthew Wilcox wrote:
> > > On Tue, Jul 03, 2018 at 06:03:16PM +0300, Mike Rapoport wrote:
> > > > 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().
> > > 
> > > Why does memblock work in terms of u64 instead of phys_addr_t?
> > 
> > Yes, phys_addr_t was exactly that came to my mind as well. Casting
> > physical address to unsigned long just screams for potential problems.
> 
> Not sure if for m68k-nommu the physical address can really go beyond 32
> bits, but in general this is something that should be taken care of.
> 
> I think adding the cast in m68k-nommu case is a viable band aid to allow
> sorting out the bootmem vs nobootmem.
> 
> In any case care should be taken of all those
> 
> 	#define __va(x)	((void *)((unsigned long)(x))) 

Yeah, sounds like a good idea to me.

> all around.
> 
> Regardless, I can s/u64/phys_addr_t/ in memblock.c.

Yeah, sounds like a good thing to me.

-- 
Michal Hocko
SUSE Labs