diff options
| -rw-r--r-- | include/linux/swapops.h | 8 | ||||
| -rw-r--r-- | mm/swapfile.c | 12 |
2 files changed, 9 insertions, 11 deletions
diff --git a/include/linux/swapops.h b/include/linux/swapops.h index 792d16d9cbc7..47ead515c811 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -9,13 +9,15 @@ * get good packing density in that tree, so the index should be dense in * the low-order bits. * - * We arrange the `type' and `offset' fields so that `type' is at the five + * We arrange the `type' and `offset' fields so that `type' is at the seven * high-order bits of the swp_entry_t and `offset' is right-aligned in the - * remaining bits. + * remaining bits. Although `type' itself needs only five bits, we allow for + * shmem/tmpfs to shift it all up a further two bits: see swp_to_radix_entry(). * * swp_entry_t's are *never* stored anywhere in their arch-dependent format. */ -#define SWP_TYPE_SHIFT(e) (sizeof(e.val) * 8 - MAX_SWAPFILES_SHIFT) +#define SWP_TYPE_SHIFT(e) ((sizeof(e.val) * 8) - \ + (MAX_SWAPFILES_SHIFT + RADIX_TREE_EXCEPTIONAL_SHIFT)) #define SWP_OFFSET_MASK(e) ((1UL << SWP_TYPE_SHIFT(e)) - 1) /* diff --git a/mm/swapfile.c b/mm/swapfile.c index fafc26d1b1dc..38186d96a72b 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1924,24 +1924,20 @@ static unsigned long read_swap_header(struct swap_info_struct *p, /* * Find out how many pages are allowed for a single swap - * device. There are three limiting factors: 1) the number + * device. There are two limiting factors: 1) the number * of bits for the swap offset in the swp_entry_t type, and * 2) the number of bits in the swap pte as defined by the - * the different architectures, and 3) the number of free bits - * in an exceptional radix_tree entry. In order to find the + * different architectures. In order to find the * largest possible bit mask, a swap entry with swap type 0 * and swap offset ~0UL is created, encoded to a swap pte, * decoded to a swp_entry_t again, and finally the swap * offset is extracted. This will mask all the bits from * the initial ~0UL mask that can't be encoded in either * the swp_entry_t or the architecture definition of a - * swap pte. Then the same is done for a radix_tree entry. + * swap pte. */ maxpages = swp_offset(pte_to_swp_entry( - swp_entry_to_pte(swp_entry(0, ~0UL)))); - maxpages = swp_offset(radix_to_swp_entry( - swp_to_radix_entry(swp_entry(0, maxpages)))) + 1; - + swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1; if (maxpages > swap_header->info.last_page) { maxpages = swap_header->info.last_page + 1; /* p->max is an unsigned int: don't overflow it */ |