[mmotm:master 61/139] include/asm-generic/memory_model.h:54:52: warning: 'page' is used uninitialized in this function

[mmotm:master 61/139] include/asm-generic/memory_model.h:54:52: warning: 'page' is used uninitialized in this function

[kbuild test robot]

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tree:   git://git.cmpxchg.org/linux-mmotm.git master
head:   ecfddce33be51ebedf97f1e03d954c14e575afb6
commit: d9f7aec054d6fdbf8f9c4f37c269bf7fff4c04bd [61/139] mm, vmstat: skip reporting offline pages in pagetypeinfo
config: x86_64-kexec (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        git checkout d9f7aec054d6fdbf8f9c4f37c269bf7fff4c04bd
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from arch/x86/include/asm/page.h:75:0,
                    from arch/x86/include/asm/thread_info.h:11,
                    from include/linux/thread_info.h:37,
                    from arch/x86/include/asm/preempt.h:6,
                    from include/linux/preempt.h:80,
                    from include/linux/spinlock.h:50,
                    from include/linux/wait.h:8,
                    from include/linux/fs.h:5,
                    from mm/vmstat.c:12:
   mm/vmstat.c: In function 'pagetypeinfo_showblockcount_print':
>> include/asm-generic/memory_model.h:54:52: warning: 'page' is used uninitialized in this function [-Wuninitialized]
    #define __page_to_pfn(page) (unsigned long)((page) - vmemmap)
                                                       ^
   mm/vmstat.c:1224:16: note: 'page' was declared here
      struct page *page;
                   ^~~~

vim +/page +54 include/asm-generic/memory_model.h

a117e66e KAMEZAWA Hiroyuki  2006-03-27  38  ({	unsigned long __pfn = (pfn);		\
c5d71243 Rafael J. Wysocki  2008-11-08  39  	unsigned long __nid = arch_pfn_to_nid(__pfn);  \
a117e66e KAMEZAWA Hiroyuki  2006-03-27  40  	NODE_DATA(__nid)->node_mem_map + arch_local_page_offset(__pfn, __nid);\
a117e66e KAMEZAWA Hiroyuki  2006-03-27  41  })
a117e66e KAMEZAWA Hiroyuki  2006-03-27  42  
67de6482 Andy Whitcroft     2006-06-23  43  #define __page_to_pfn(pg)						\
aa462abe Ian Campbell       2011-08-17  44  ({	const struct page *__pg = (pg);					\
a0140c1d KAMEZAWA Hiroyuki  2006-03-27  45  	struct pglist_data *__pgdat = NODE_DATA(page_to_nid(__pg));	\
a0140c1d KAMEZAWA Hiroyuki  2006-03-27  46  	(unsigned long)(__pg - __pgdat->node_mem_map) +			\
a0140c1d KAMEZAWA Hiroyuki  2006-03-27  47  	 __pgdat->node_start_pfn;					\
a117e66e KAMEZAWA Hiroyuki  2006-03-27  48  })
a117e66e KAMEZAWA Hiroyuki  2006-03-27  49  
8f6aac41 Christoph Lameter  2007-10-16  50  #elif defined(CONFIG_SPARSEMEM_VMEMMAP)
8f6aac41 Christoph Lameter  2007-10-16  51  
af901ca1 Andre Goddard Rosa 2009-11-14  52  /* memmap is virtually contiguous.  */
8f6aac41 Christoph Lameter  2007-10-16  53  #define __pfn_to_page(pfn)	(vmemmap + (pfn))
32272a26 Martin Schwidefsky 2008-12-25 @54  #define __page_to_pfn(page)	(unsigned long)((page) - vmemmap)
8f6aac41 Christoph Lameter  2007-10-16  55  
a117e66e KAMEZAWA Hiroyuki  2006-03-27  56  #elif defined(CONFIG_SPARSEMEM)
a117e66e KAMEZAWA Hiroyuki  2006-03-27  57  /*
1a49123b Zhang Yanfei       2013-10-03  58   * Note: section's mem_map is encoded to reflect its start_pfn.
a117e66e KAMEZAWA Hiroyuki  2006-03-27  59   * section[i].section_mem_map == mem_map's address - start_pfn;
a117e66e KAMEZAWA Hiroyuki  2006-03-27  60   */
67de6482 Andy Whitcroft     2006-06-23  61  #define __page_to_pfn(pg)					\
aa462abe Ian Campbell       2011-08-17  62  ({	const struct page *__pg = (pg);				\

:::::: The code at line 54 was first introduced by commit
:::::: 32272a26974d2027384fd4010cd1780fca425d94 [S390] __page_to_pfn warnings

:::::: TO: Martin Schwidefsky <schwidefsky@de.ibm.com>
:::::: CC: Martin Schwidefsky <schwidefsky@de.ibm.com>

---
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Re: [mmotm:master 61/139] include/asm-generic/memory_model.h:54:52: warning: 'page' is used uninitialized in this function

[Michal Hocko]

Ups, sorry about that. Andrew could you fold the following into
mm-vmstat-skip-reporting-offline-pages-in-pagetypeinfo.patch
---