Hi Bernard,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.7-rc2 next-20200420]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Bernard-Zhao/kmalloc_index-optimization-code-size-runtime-stable/20200417-100445
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2fcd80144b93ff90836a44f2054b4d82133d3a85
config: s390-zfcpdump_defconfig (attached as .config)
compiler: s390-linux-gcc (GCC) 9.3.0
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
        COMPILER_INSTALL_PATH=$HOME/0day GCC_VERSION=9.3.0 make.cross ARCH=s390 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from include/linux/kvm_host.h:18,
                    from arch/s390/kernel/asm-offsets.c:11:
   include/linux/slab.h: In function 'kmalloc_index':
>> include/linux/slab.h:390:3: error: 'high_bit' undeclared (first use in this function); did you mean 'assign_bit'?
     390 |   high_bit = fls((int)size);
         |   ^~~~~~~~
         |   assign_bit
   include/linux/slab.h:390:3: note: each undeclared identifier is reported only once for each function it appears in
   make[2]: *** [scripts/Makefile.build:100: arch/s390/kernel/asm-offsets.s] Error 1
   make[2]: Target '__build' not remade because of errors.
   make[1]: *** [Makefile:1141: prepare0] Error 2
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [Makefile:180: sub-make] Error 2
   40 real  5 user  12 sys  44.33% cpu 	make prepare

vim +390 include/linux/slab.h

   356	
   357	/*
   358	 * Figure out which kmalloc slab an allocation of a certain size
   359	 * belongs to.
   360	 * 0 = zero alloc
   361	 * 1 =  65 .. 96 bytes
   362	 * 2 = 129 .. 192 bytes
   363	 * n = 2^(n-1)+1 .. 2^n
   364	 */
   365	static __always_inline unsigned int kmalloc_index(size_t size)
   366	{
   367		if (!size)
   368			return 0;
   369	
   370		if (size <= KMALLOC_MIN_SIZE)
   371			return KMALLOC_SHIFT_LOW;
   372	
   373		if (KMALLOC_MIN_SIZE <= 32 && size > 64 && size <= 96)
   374			return 1;
   375		if (KMALLOC_MIN_SIZE <= 64 && size > 128 && size <= 192)
   376			return 2;
   377	
   378		if (size <= 8)
   379			return 3;
   380	
   381		/* size over KMALLOC_MAX_SIZE should trigger BUG */
   382		if (size <= KMALLOC_MAX_SIZE) {
   383			/*
   384			 * kmalloc_info[index]
   385			 * size  8----16----32----64----128---256---512---1024---2048.
   386			 *       |  |  |  |  |  |  |  |  |  |  |  |  |  |   |  |   |
   387			 * index 3  4  4  5  5  6  6  7  7  8  8  9  9  10  10 11  11
   388			 */
   389	
 > 390			high_bit = fls((int)size);
   391	
   392			if (size == (2 << (high_bit - KMALLOC_SIZE_POW_2_SHIFT_BIT)))
   393				return (high_bit - KMALLOC_SIZE_POW_2_INDEX_BIT);
   394	
   395			return high_bit;
   396		}
   397	
   398		BUG();
   399	
   400		/* Will never be reached. Needed because the compiler may complain */
   401		return -1;
   402	}
   403	#endif /* !CONFIG_SLOB */
   404	

---
0-DAY CI Kernel Test Service, Intel Corporation
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