SWP_HWPOISON_NUM 57 include/linux/swap.h #define SWP_MIGRATION_READ (MAX_SWAPFILES + SWP_HWPOISON_NUM) SWP_HWPOISON_NUM 58 include/linux/swap.h #define SWP_MIGRATION_WRITE (MAX_SWAPFILES + SWP_HWPOISON_NUM + 1) SWP_HWPOISON_NUM 74 include/linux/swap.h ((1 << MAX_SWAPFILES_SHIFT) - SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)