Re: [PATCH 1/1] mm: thp: fix SMP race condition between THP page fault

[kbuild test robot <lkp@xxxxxxxxx>]

Hi Andrea,

[auto build test ERROR on v4.5-rc5]
[also build test ERROR on next-20160223]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Andrea-Arcangeli/mm-thp-fix-SMP-race-condition-between-THP-page-fault/20160224-020835
config: i386-tinyconfig (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   In file included from include/uapi/linux/stddef.h:1:0,
                    from include/linux/stddef.h:4,
                    from include/uapi/linux/posix_types.h:4,
                    from include/uapi/linux/types.h:13,
                    from include/linux/types.h:5,
                    from include/linux/smp.h:10,
                    from include/linux/kernel_stat.h:4,
                    from mm/memory.c:41:
   mm/memory.c: In function '__handle_mm_fault':
>> mm/memory.c:3419:34: error: incompatible type for argument 1 of 'pmd_trans_unstable'
     if (unlikely(pmd_trans_unstable(*pmd) || pmd_devmap(*pmd)))
                                     ^
   include/linux/compiler.h:166:42: note: in definition of macro 'unlikely'
    # define unlikely(x) __builtin_expect(!!(x), 0)
                                             ^
   In file included from arch/x86/include/asm/pgtable.h:914:0,
                    from include/linux/mm.h:67,
                    from mm/memory.c:42:
   include/asm-generic/pgtable.h:731:19: note: expected 'pmd_t * {aka struct <anonymous> *}' but argument is of type 'pmd_t {aka struct <anonymous>}'
    static inline int pmd_trans_unstable(pmd_t *pmd)
                      ^

vim +/pmd_trans_unstable +3419 mm/memory.c

  3413		 * a different thread of this mm, in turn leading to a false
  3414		 * negative pmd_trans_huge() retval. All we have to ensure is
  3415		 * that it is a regular pmd that we can walk with
  3416		 * pte_offset_map() and we can do that through an atomic read
  3417		 * in C, which is what pmd_trans_unstable() is provided for.
  3418		 */
> 3419		if (unlikely(pmd_trans_unstable(*pmd) || pmd_devmap(*pmd)))
  3420			return 0;
  3421		/*
  3422		 * A regular pmd is established and it can't morph into a huge pmd

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