Re: [PATCH] mm: Replace (20 - PAGE_SHIFT) with common macros for pages<->MB conversion

[kernel test robot <lkp@intel.com>]

Hi Ye,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Ye-Liu/mm-Replace-20-PAGE_SHIFT-with-common-macros-for-pages-MB-conversion/20250718-104347
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250718024134.1304745-1-ye.liu%40linux.dev
patch subject: [PATCH] mm: Replace (20 - PAGE_SHIFT) with common macros for pages<->MB conversion
config: arc-randconfig-001-20250719 (https://download.01.org/0day-ci/archive/20250719/202507190319.0rqhQw5l-lkp@intel.com/config)
compiler: arc-linux-gcc (GCC) 14.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250719/202507190319.0rqhQw5l-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202507190319.0rqhQw5l-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from arch/arc/kernel/asm-offsets.c:7:
>> include/linux/mm.h:78:9: warning: "PAGES_TO_MB" redefined
      78 | #define PAGES_TO_MB(pages) ((pages) >> (20 - PAGE_SHIFT))
         |         ^~~~~~~~~~~
   In file included from arch/arc/include/asm/irqflags-arcv2.h:9,
                    from arch/arc/include/asm/irqflags.h:13,
                    from include/linux/irqflags.h:18,
                    from include/linux/spinlock.h:59,
                    from include/linux/sched.h:2205,
                    from arch/arc/kernel/asm-offsets.c:6:
   arch/arc/include/asm/arcregs.h:155:9: note: this is the location of the previous definition
     155 | #define PAGES_TO_MB(n_pages)    (PAGES_TO_KB(n_pages) >> 10)
         |         ^~~~~~~~~~~
--
   In file included from arch/arc/include/asm/cacheflush.h:18,
                    from include/linux/cacheflush.h:5,
                    from include/linux/highmem.h:8,
                    from include/linux/bvec.h:10,
                    from include/linux/blk_types.h:10,
                    from include/linux/blkdev.h:9,
                    from fs/ufs/super.c:83:
>> include/linux/mm.h:78:9: warning: "PAGES_TO_MB" redefined
      78 | #define PAGES_TO_MB(pages) ((pages) >> (20 - PAGE_SHIFT))
         |         ^~~~~~~~~~~
   In file included from arch/arc/include/asm/irqflags-arcv2.h:9,
                    from arch/arc/include/asm/irqflags.h:13,
                    from include/linux/irqflags.h:18,
                    from include/linux/spinlock.h:59,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:7,
                    from include/linux/umh.h:4,
                    from include/linux/kmod.h:9,
                    from include/linux/module.h:17,
                    from fs/ufs/super.c:70:
   arch/arc/include/asm/arcregs.h:155:9: note: this is the location of the previous definition
     155 | #define PAGES_TO_MB(n_pages)    (PAGES_TO_KB(n_pages) >> 10)
         |         ^~~~~~~~~~~
   fs/ufs/super.c: In function 'ufs_reconfigure':
   fs/ufs/super.c:1246:22: warning: variable 'ufstype' set but not used [-Wunused-but-set-variable]
    1246 |         unsigned int ufstype;
         |                      ^~~~~~~
--
   In file included from arch/arc/kernel/asm-offsets.c:7:
>> include/linux/mm.h:78:9: warning: "PAGES_TO_MB" redefined
      78 | #define PAGES_TO_MB(pages) ((pages) >> (20 - PAGE_SHIFT))
         |         ^~~~~~~~~~~
   In file included from arch/arc/include/asm/irqflags-arcv2.h:9,
                    from arch/arc/include/asm/irqflags.h:13,
                    from include/linux/irqflags.h:18,
                    from include/linux/spinlock.h:59,
                    from include/linux/sched.h:2205,
                    from arch/arc/kernel/asm-offsets.c:6:
   arch/arc/include/asm/arcregs.h:155:9: note: this is the location of the previous definition
     155 | #define PAGES_TO_MB(n_pages)    (PAGES_TO_KB(n_pages) >> 10)
         |         ^~~~~~~~~~~


vim +/PAGES_TO_MB +78 include/linux/mm.h

    71	
    72	/*
    73	 * Convert between pages and MB
    74	 * 20 is the shift for 1MB (2^20 = 1MB)
    75	 * PAGE_SHIFT is the shift for page size (e.g., 12 for 4KB pages)
    76	 * So (20 - PAGE_SHIFT) converts between pages and MB
    77	 */
  > 78	#define PAGES_TO_MB(pages) ((pages) >> (20 - PAGE_SHIFT))
    79	#define MB_TO_PAGES(mb)    ((mb) << (20 - PAGE_SHIFT))
    80	

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