diff options
| -rw-r--r-- | arch/arm/include/asm/pgtable.h | 30 |
1 files changed, 25 insertions, 5 deletions
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h index 1cd2d6416bd..c1d97938f3e 100644 --- a/arch/arm/include/asm/pgtable.h +++ b/arch/arm/include/asm/pgtable.h @@ -384,16 +384,36 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) extern pgd_t swapper_pg_dir[PTRS_PER_PGD]; -/* Encode and decode a swap entry. +/* + * Encode and decode a swap entry. Swap entries are stored in the Linux + * page tables as follows: + * + * 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 + * 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 + * <--------------- offset --------------------> <--- type --> 0 0 * - * We support up to 32GB of swap on 4k machines + * This gives us up to 127 swap files and 32GB per swap file. Note that + * the offset field is always non-zero. */ -#define __swp_type(x) (((x).val >> 2) & 0x7f) -#define __swp_offset(x) ((x).val >> 9) -#define __swp_entry(type,offset) ((swp_entry_t) { ((type) << 2) | ((offset) << 9) }) +#define __SWP_TYPE_SHIFT 2 +#define __SWP_TYPE_BITS 7 +#define __SWP_TYPE_MASK ((1 << __SWP_TYPE_BITS) - 1) +#define __SWP_OFFSET_SHIFT (__SWP_TYPE_BITS + __SWP_TYPE_SHIFT) + +#define __swp_type(x) (((x).val >> __SWP_TYPE_SHIFT) & __SWP_TYPE_MASK) +#define __swp_offset(x) ((x).val >> __SWP_OFFSET_SHIFT) +#define __swp_entry(type,offset) ((swp_entry_t) { ((type) << __SWP_TYPE_SHIFT) | ((offset) << __SWP_OFFSET_SHIFT) }) + #define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) }) #define __swp_entry_to_pte(swp) ((pte_t) { (swp).val }) +/* + * It is an error for the kernel to have more swap files than we can + * encode in the PTEs. This ensures that we know when MAX_SWAPFILES + * is increased beyond what we presently support. + */ +#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > __SWP_TYPE_BITS) + /* Needs to be defined here and not in linux/mm.h, as it is arch dependent */ /* FIXME: this is not correct */ #define kern_addr_valid(addr) (1) |