diff options
Diffstat (limited to 'mm/swapfile.c')
| -rw-r--r-- | mm/swapfile.c | 140 |
1 files changed, 78 insertions, 62 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c index 4dade515b08..5e13bff1764 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1918,6 +1918,82 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) return 0; } +static unsigned long read_swap_header(struct swap_info_struct *p, + union swap_header *swap_header, + struct inode *inode) +{ + int i; + unsigned long maxpages; + unsigned long swapfilepages; + + if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { + printk(KERN_ERR "Unable to find swap-space signature\n"); + goto bad_swap; + } + + /* swap partition endianess hack... */ + if (swab32(swap_header->info.version) == 1) { + swab32s(&swap_header->info.version); + swab32s(&swap_header->info.last_page); + swab32s(&swap_header->info.nr_badpages); + for (i = 0; i < swap_header->info.nr_badpages; i++) + swab32s(&swap_header->info.badpages[i]); + } + /* Check the swap header's sub-version */ + if (swap_header->info.version != 1) { + printk(KERN_WARNING + "Unable to handle swap header version %d\n", + swap_header->info.version); + goto bad_swap; + } + + p->lowest_bit = 1; + p->cluster_next = 1; + p->cluster_nr = 0; + + /* + * Find out how many pages are allowed for a single swap + * 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 a swap pte as defined by + * 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. + */ + maxpages = swp_offset(pte_to_swp_entry( + 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 */ + if ((unsigned int)maxpages == 0) + maxpages = UINT_MAX; + } + p->highest_bit = maxpages - 1; + + if (!maxpages) + goto bad_swap; + swapfilepages = i_size_read(inode) >> PAGE_SHIFT; + if (swapfilepages && maxpages > swapfilepages) { + printk(KERN_WARNING + "Swap area shorter than signature indicates\n"); + goto bad_swap; + } + if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) + goto bad_swap; + if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) + goto bad_swap; + + return maxpages; + +bad_swap: + return 0; +} + SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) { struct swap_info_struct *p; @@ -1931,7 +2007,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) int nr_extents = 0; sector_t span; unsigned long maxpages; - unsigned long swapfilepages; unsigned char *swap_map = NULL; struct page *page = NULL; struct inode *inode = NULL; @@ -1989,71 +2064,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) } swap_header = kmap(page); - if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { - printk(KERN_ERR "Unable to find swap-space signature\n"); + maxpages = read_swap_header(p, swap_header, inode); + if (unlikely(!maxpages)) { error = -EINVAL; goto bad_swap; } - /* swap partition endianess hack... */ - if (swab32(swap_header->info.version) == 1) { - swab32s(&swap_header->info.version); - swab32s(&swap_header->info.last_page); - swab32s(&swap_header->info.nr_badpages); - for (i = 0; i < swap_header->info.nr_badpages; i++) - swab32s(&swap_header->info.badpages[i]); - } - /* Check the swap header's sub-version */ - if (swap_header->info.version != 1) { - printk(KERN_WARNING - "Unable to handle swap header version %d\n", - swap_header->info.version); - error = -EINVAL; - goto bad_swap; - } - - p->lowest_bit = 1; - p->cluster_next = 1; - p->cluster_nr = 0; - - /* - * Find out how many pages are allowed for a single swap - * 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 a swap pte as defined by - * 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. - */ - maxpages = swp_offset(pte_to_swp_entry( - 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 */ - if ((unsigned int)maxpages == 0) - maxpages = UINT_MAX; - } - p->highest_bit = maxpages - 1; - - error = -EINVAL; - if (!maxpages) - goto bad_swap; - swapfilepages = i_size_read(inode) >> PAGE_SHIFT; - if (swapfilepages && maxpages > swapfilepages) { - printk(KERN_WARNING - "Swap area shorter than signature indicates\n"); - goto bad_swap; - } - if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) - goto bad_swap; - if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) - goto bad_swap; - /* OK, set up the swap map and apply the bad block list */ swap_map = vzalloc(maxpages); if (!swap_map) { |