Re: [next:master 7235/7555] mm/page_alloc.c:654:121: warning: comparison of distinct pointer types lacks a cast

[Andrew Morton <akpm@linux-foundation.org>]

On Sat, 30 May 2015 01:48:20 +0800 kbuild test robot <fengguang.wu@intel.com> wrote:

> tree:   git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> head:   7732a9817fb01002bde7615066e86c156fb5a31b
> commit: 0491d0d6aac97c5b8df17851db525f3758de26e6 [7235/7555] s390/mm: make hugepages_supported a boot time decision
> config: s390-defconfig (attached as .config)
> reproduce:
>   wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
>   chmod +x ~/bin/make.cross
>   git checkout 0491d0d6aac97c5b8df17851db525f3758de26e6
>   # save the attached .config to linux build tree
>   make.cross ARCH=s390 
> 
> All warnings:
> 
>    mm/page_alloc.c: In function '__free_one_page':
> >> mm/page_alloc.c:654:121: warning: comparison of distinct pointer types lacks a cast
>       max_order = min(MAX_ORDER, pageblock_order + 1);
>                                                                                                                             ^
> --
>    mm/cma.c: In function 'cma_init_reserved_mem':
> >> mm/cma.c:186:137: warning: comparison of distinct pointer types lacks a cast
>      alignment = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);

Dominik's patch has somehow managed to change the type of
pageblock_order.  Before the patch, pageblock_order expands to "(20 -
12)".  After the patch, pageblock_order expands to "(HPAGE_SHIFT -
12)".

And on s390, HPAGE_SHIFT is unsigned int.  On x86 HPAGE_SHIFT has type
int.  I suggest the fix here is to make s390's HPAGE_SHIFT have type
int as well.

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