include/linux/mm_inline.h:131:19: warning: overflow in conversion from 'long unsigned int' to 'int' changes value from '18446744073709551615' to '-1'

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

tree:   https://github.com/intel-lab-lkp/linux/commits/Kairui-Song-via-B4-Relay/mm-memcontrol-allow-update-of-LRU-statistic-without-holding-LRU-lock/20261003-205512
head:   fb7e985a90aa08774d1149de30384a36bb55bafb
commit: a24ab9c3982c5dca7d02d319bddb26221bbe433c mm/mglru: make folio lru referenced times count a generic API
config: alpha-allnoconfig (https://download.01.org/0day-ci/archive/20261004/202610041009.rRGnlvdY-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 16.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261004/202610041009.rRGnlvdY-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/r/202610041009.rRGnlvdY-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from kernel/fork.c:47:
   include/linux/mm_inline.h: In function 'lru_get_gen_flags':
>> include/linux/mm_inline.h:131:19: warning: overflow in conversion from 'long unsigned int' to 'int' changes value from '18446744073709551615' to '-1' [-Woverflow]
     131 |         int gen = ((flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
         |                   ^


vim +131 include/linux/mm_inline.h

49ccf47e2e054a Kairui Song 2026-09-06  121  
49ccf47e2e054a Kairui Song 2026-09-06  122  /**
49ccf47e2e054a Kairui Song 2026-09-06  123   * lru_get_gen_flags - Return the LRU generation number from folio flags.
49ccf47e2e054a Kairui Song 2026-09-06  124   * @flags: folio flags
49ccf47e2e054a Kairui Song 2026-09-06  125   *
49ccf47e2e054a Kairui Song 2026-09-06  126   * Returns: A number between 0 and (MAX_NR_GENS - 1), inclusive. Returns
49ccf47e2e054a Kairui Song 2026-09-06  127   * -1 if the flags indicate the folio is off the list (e.g., isolated).
49ccf47e2e054a Kairui Song 2026-09-06  128   */
49ccf47e2e054a Kairui Song 2026-09-06  129  static inline int lru_get_gen_flags(unsigned long flags)
ac35a490237446 Yu Zhao     2022-09-18  130  {
49ccf47e2e054a Kairui Song 2026-09-06 @131  	int gen = ((flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
ac35a490237446 Yu Zhao     2022-09-18  132  
49ccf47e2e054a Kairui Song 2026-09-06  133  	/* Exclude the legal -1 from the unsigned MAX_NR_GENS comparison */
49ccf47e2e054a Kairui Song 2026-09-06  134  	VM_WARN_ON_ONCE(gen != -1 && gen >= MAX_NR_GENS);
49ccf47e2e054a Kairui Song 2026-09-06  135  	return gen;
49ccf47e2e054a Kairui Song 2026-09-06  136  }
49ccf47e2e054a Kairui Song 2026-09-06  137  

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