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sys_swapon: separate parsing of swapfile header
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Move the code which parses and checks the swapfile header (except for
the bad block list) to a separate function. Only code movement, no
functional changes.

Signed-off-by: Cesar Eduardo Barros <[email protected]>
Tested-by: Eric B Munson <[email protected]>
Acked-by: Eric B Munson <[email protected]>
Reviewed-by: KAMEZAWA Hiroyuki <[email protected]>
Cc: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@cesarb @torvalds
cesarb authored and torvalds committed Mar 23, 2011
1 parent 5de771e commit ca8bd38
Showing 1 changed file with 78 additions and 62 deletions.
140 changes: 78 additions & 62 deletions mm/swapfile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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;
Expand Down Expand Up @@ -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) {
Expand Down

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