Re: [PATCH 12/17] md: raid1: avoid direct access to bvec table in process_checks()

Hi Ming,

[auto build test WARNING on linus/master]
[also build test WARNING on v4.10-rc8]
[cannot apply to next-20170216]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Ming-Lei/md-cleanup-on-direct-access-to-bvec-table/20170216-210357
config: powerpc-cell_defconfig (attached as .config)
compiler: powerpc64-linux-gnu-gcc (Debian 6.1.1-9) 6.1.1 20160705
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
        # save the attached .config to linux build tree
        make.cross ARCH=powerpc 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   In file included from arch/powerpc/include/asm/page.h:331:0,
                    from arch/powerpc/include/asm/thread_info.h:34,
                    from include/linux/thread_info.h:25,
                    from include/asm-generic/preempt.h:4,
                    from ./arch/powerpc/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:59,
                    from include/linux/spinlock.h:50,
                    from include/linux/mmzone.h:7,
                    from include/linux/gfp.h:5,
                    from include/linux/slab.h:14,
                    from drivers/md/raid1.c:34:
   drivers/md/raid1.c: In function 'raid1d':

quoted

include/asm-generic/memory_model.h:54:52: warning: 'sbio_pages$' may be used uninitialized in this function [-Wmaybe-uninitialized]

    #define __page_to_pfn(page) (unsigned long)((page) - vmemmap)
                                                       ^
   drivers/md/raid1.c:2008:42: note: 'sbio_pages$' was declared here
     struct page *pbio_pages[RESYNC_PAGES], *sbio_pages[RESYNC_PAGES];
                                             ^~~~~~~~~~
   drivers/md/raid1.c:2075:9: warning: 'page_len$' may be used uninitialized in this function [-Wmaybe-uninitialized]
        if (memcmp(page_address(p),
            ^~~~~~~~~~~~~~~~~~~~~~~
            page_address(s),
            ~~~~~~~~~~~~~~~~
            page_len[j]))
            ~~~~~~~~~~~~
   drivers/md/raid1.c:2007:6: note: 'page_len$' was declared here
     int page_len[RESYNC_PAGES];
         ^~~~~~~~
   In file included from arch/powerpc/include/asm/page.h:331:0,
                    from arch/powerpc/include/asm/thread_info.h:34,
                    from include/linux/thread_info.h:25,
                    from include/asm-generic/preempt.h:4,
                    from ./arch/powerpc/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:59,
                    from include/linux/spinlock.h:50,
                    from include/linux/mmzone.h:7,
                    from include/linux/gfp.h:5,
                    from include/linux/slab.h:14,
                    from drivers/md/raid1.c:34:

quoted

include/asm-generic/memory_model.h:54:52: warning: 'pbio_pages$' may be used uninitialized in this function [-Wmaybe-uninitialized]

    #define __page_to_pfn(page) (unsigned long)((page) - vmemmap)
                                                       ^
   drivers/md/raid1.c:2008:15: note: 'pbio_pages$' was declared here
     struct page *pbio_pages[RESYNC_PAGES], *sbio_pages[RESYNC_PAGES];
                  ^~~~~~~~~~
   drivers/md/raid1.c:1978:8: warning: 'pages$' may be used uninitialized in this function [-Wmaybe-uninitialized]
       if (r1_sync_page_io(rdev, sect, s,
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             pages[idx],
             ~~~~~~~~~~~
             READ) != 0)
             ~~~~~
   drivers/md/raid1.c:1872:15: note: 'pages$' was declared here
     struct page *pages[RESYNC_PAGES];
                  ^~~~~

vim +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 André 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 [off-list ref]
:::::: CC: Martin Schwidefsky [off-list ref]

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