Hi Mike,

I love your patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v4.18 next-20180821]
[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/Mike-Kravetz/huge_pmd_unshare-migration-and-flushing/20180822-050255
config: sparc64-allyesconfig (attached as .config)
compiler: sparc64-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.2.0 make.cross ARCH=sparc64 

All errors (new ones prefixed by >>):

   mm/rmap.o: In function `try_to_unmap_one':
   rmap.c:(.text+0x2708): undefined reference to `huge_pmd_sharing_possible'
   mm/hugetlb.o: In function `__unmap_hugepage_range':
>> hugetlb.c:(.text+0x5530): undefined reference to `huge_pmd_sharing_possible'
   mm/hugetlb.o: In function `unmap_hugepage_range':
   hugetlb.c:(.text+0x57bc): undefined reference to `huge_pmd_sharing_possible'
   mm/hugetlb.o: In function `hugetlb_change_protection':
   hugetlb.c:(.text+0x7714): undefined reference to `huge_pmd_sharing_possible'
   `.exit.data' referenced in section `.exit.text' of drivers/tty/n_hdlc.o: defined in discarded section `.exit.data' of drivers/tty/n_hdlc.o
   `.exit.data' referenced in section `.exit.text' of drivers/tty/n_hdlc.o: defined in discarded section `.exit.data' of drivers/tty/n_hdlc.o
   `.exit.data' referenced in section `.exit.text' of drivers/tty/n_hdlc.o: defined in discarded section `.exit.data' of drivers/tty/n_hdlc.o
   `.exit.data' referenced in section `.exit.text' of drivers/tty/n_hdlc.o: defined in discarded section `.exit.data' of drivers/tty/n_hdlc.o

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