Hi Jia,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on mmotm/master]
[cannot apply to v4.16-rc6]
[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/Jia-He/optimize-memblock_next_valid_pfn-and-early_pfn_valid/20180325-175026
base:   git://git.cmpxchg.org/linux-mmotm.git master
config: arm64-defconfig (attached as .config)
compiler: aarch64-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
        make.cross ARCH=arm64 

All warnings (new ones prefixed by >>):

   arch/arm64/mm/init.c: In function 'pfn_valid_region':
>> arch/arm64/mm/init.c:304:35: warning: self-comparison always evaluates to false [-Wtautological-compare]
      if (pfn >= start_pfn && end_pfn < end_pfn)
                                      ^

vim +304 arch/arm64/mm/init.c

   293	
   294	int pfn_valid_region(unsigned long pfn, int *last_idx)
   295	{
   296		unsigned long start_pfn, end_pfn;
   297		struct memblock_type *type = &memblock.memory;
   298	
   299		if (*last_idx != -1) {
   300			start_pfn = PFN_DOWN(type->regions[*last_idx].base);
   301			end_pfn= PFN_DOWN(type->regions[*last_idx].base +
   302						type->regions[*last_idx].size);
   303	
 > 304			if (pfn >= start_pfn && end_pfn < end_pfn)
   305				return !memblock_is_nomap(
   306					&memblock.memory.regions[*last_idx]);
   307		}
   308	
   309		*last_idx = memblock_search_pfn_regions(pfn);
   310		if (*last_idx == -1)
   311			return false;
   312	
   313		return !memblock_is_nomap(&memblock.memory.regions[*last_idx]);
   314	}
   315	EXPORT_SYMBOL(pfn_valid_region);
   316	#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
   317	

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