arch/x86/lib/copy_mc.c:30:1: warning: no previous prototype for 'copy_mc_fragile_handle_tail'

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   1e43c377a79f9189fea8f2711b399d4e8b4e609b
commit: ec6347bb43395cb92126788a1a5b25302543f815 x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}()
date:   6 months ago
config: x86_64-randconfig-r002-20210330 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ec6347bb43395cb92126788a1a5b25302543f815
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout ec6347bb43395cb92126788a1a5b25302543f815
        # save the attached .config to linux build tree
        make W=1 ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

>> arch/x86/lib/copy_mc.c:30:1: warning: no previous prototype for 'copy_mc_fragile_handle_tail' [-Wmissing-prototypes]
      30 | copy_mc_fragile_handle_tail(char *to, char *from, unsigned len)
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~~


vim +/copy_mc_fragile_handle_tail +30 arch/x86/lib/copy_mc.c

    24	
    25	/*
    26	 * Similar to copy_user_handle_tail, probe for the write fault point, or
    27	 * source exception point.
    28	 */
    29	__visible notrace unsigned long
  > 30	copy_mc_fragile_handle_tail(char *to, char *from, unsigned len)
    31	{
    32		for (; len; --len, to++, from++)
    33			if (copy_mc_fragile(to, from, 1))
    34				break;
    35		return len;
    36	}
    37	#else
    38	/*
    39	 * No point in doing careful copying, or consulting a static key when
    40	 * there is no #MC handler in the CONFIG_X86_MCE=n case.
    41	 */
    42	void enable_copy_mc_fragile(void)
    43	{
    44	}
    45	#define copy_mc_fragile_enabled (0)
    46	#endif
    47	

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Attachment: .config.gz
Description: application/gzip