linux-kernel - Re: [PATCH v4, part3 01/15] mm: fix build warnings caused by free_reserved

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Date:	Sat, 20 Apr 2013 23:34:34 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arch@...r.kernel.org,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	David Howells <dhowells@...hat.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Wen Congyang <wency@...fujitsu.com>, linux-mm@...ck.org,
	linux-arm-kernel@...ts.infradead.org,
	Mark Salter <msalter@...hat.com>, linux-kernel@...r.kernel.org,
	Michal Hocko <mhocko@...e.cz>,
	Minchan Kim <minchan@...nel.org>, Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Jianguo Wu <wujianguo@...wei.com>
Subject: Re: [PATCH v4, part3 01/15] mm: fix build warnings caused by free_reserved_area()

On 04/20/2013 12:52 AM, Russell King - ARM Linux wrote:
> On Sat, Apr 06, 2013 at 09:54:55PM +0800, Jiang Liu wrote:
>> Fix following build warnings cuased by free_reserved_area():
>>
>> arch/arm/mm/init.c: In function 'mem_init':
>> arch/arm/mm/init.c:603:2: warning: passing argument 1 of 'free_reserved_area' makes integer from pointer without a cast [enabled by default]
>>   free_reserved_area(__va(PHYS_PFN_OFFSET), swapper_pg_dir, 0, NULL);
>>   ^
>> In file included from include/linux/mman.h:4:0,
>>                  from arch/arm/mm/init.c:15:
>> include/linux/mm.h:1301:22: note: expected 'long unsigned int' but argument is of type 'void *'
>>  extern unsigned long free_reserved_area(unsigned long start, unsigned long end,
>>
>>    mm/page_alloc.c: In function 'free_reserved_area':
>>>> mm/page_alloc.c:5134:3: warning: passing argument 1 of 'virt_to_phys' makes pointer from integer without a cast [enabled by default]
>>    In file included from arch/mips/include/asm/page.h:49:0,
>>                     from include/linux/mmzone.h:20,
>>                     from include/linux/gfp.h:4,
>>                     from include/linux/mm.h:8,
>>                     from mm/page_alloc.c:18:
>>    arch/mips/include/asm/io.h:119:29: note: expected 'const volatile void *' but argument is of type 'long unsigned int'
>>    mm/page_alloc.c: In function 'free_area_init_nodes':
>>    mm/page_alloc.c:5030:34: warning: array subscript is below array bounds [-Warray-bounds]
>>
>> Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
>> Reported-by: Arnd Bergmann <arnd@...db.de>
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>> Cc: linux-mm@...ck.org
>> ---
>>  arch/arm/mm/init.c |    6 ++++--
>>  mm/page_alloc.c    |    2 +-
>>  2 files changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
>> index 9a5cdc0..7a82fcd 100644
>> --- a/arch/arm/mm/init.c
>> +++ b/arch/arm/mm/init.c
>> @@ -600,7 +600,8 @@ void __init mem_init(void)
>>  
>>  #ifdef CONFIG_SA1111
>>  	/* now that our DMA memory is actually so designated, we can free it */
>> -	free_reserved_area(__va(PHYS_PFN_OFFSET), swapper_pg_dir, 0, NULL);
>> +	free_reserved_area((unsigned long)__va(PHYS_PFN_OFFSET),
>> +			   (unsigned long)swapper_pg_dir, 0, NULL);
>>  #endif
>>  
>>  	free_highpages();
>> @@ -728,7 +729,8 @@ void free_initmem(void)
>>  	extern char __tcm_start, __tcm_end;
>>  
>>  	poison_init_mem(&__tcm_start, &__tcm_end - &__tcm_start);
>> -	free_reserved_area(&__tcm_start, &__tcm_end, 0, "TCM link");
>> +	free_reserved_area((unsigned long)&__tcm_start,
>> +			   (unsigned long)&__tcm_end, 0, "TCM link");
>>  #endif
>>  
>>  	poison_init_mem(__init_begin, __init_end - __init_begin);
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index e4923e9..8bf7956 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -5196,7 +5196,7 @@ unsigned long free_reserved_area(unsigned long start, unsigned long end,
>>  	for (pages = 0; pos < end; pos += PAGE_SIZE, pages++) {
>>  		if (poison)
>>  			memset((void *)pos, poison, PAGE_SIZE);
>> -		free_reserved_page(virt_to_page(pos));
>> +		free_reserved_page(virt_to_page((void *)pos));
> 
> Don't all these casts suggest to you that you may have the type wrong
> in the first place?
> 
Hi Russell,
	Good question! 
	Originally free_reserved_area() is designed to simplify free_initrd_mem(), and 
free_initrd_mem() is declared as:
	void free_initrd_mem(unsigned long start, unsigned long end)
	So I have chosen "unsigned long" for free_reserved_area()'s first and second
parameters, otherwise it will cause much more type casts in function free_initrd_mem().
For code purity, we should use "void *" instead. So should we change to "void *" here?
	Regards!
	Gerry
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