[PATCH 4/9] swapfile: remove v0 SWAP-SPACE message

Hugh Dickins
2008-11-25T21:39:11Z

The kernel has not supported v0 SWAP-SPACE since 2.5.22: I think we can now
safely drop its "version 0 swap is no longer supported" message - just say
"Unable to find swap-space signature" as usual. This removes one level of
indentation from a stretch of sys_swapon().

I'd have liked to be specific, saying "Unable to find SWAPSPACE2 signature",
but it's just too confusing that the version 1 signature shows the number 2.

Irrelevant nearby cleanup: kmap(page) already gives page_address(page).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---
This reindentation clashes with memcg-swap-cgroup-for-remembering-usage.patch
See the [PATCH 0/9] message for two hunks to replace its final hunk.

mm/swapfile.c | 146 +++++++++++++++++++++---------------------------
1 file changed, 65 insertions(+), 81 deletions(-)

--- swapfile3/mm/swapfile.c 2008-11-25 12:41:24.000000000 +0000
+++ swapfile4/mm/swapfile.c 2008-11-25 12:41:26.000000000 +0000
@@ -1447,7 +1447,6 @@ asmlinkage long sys_swapon(const char __
int i, prev;
int error;
union swap_header *swap_header = NULL;
- int swap_header_version;
unsigned int nr_good_pages = 0;
int nr_extents = 0;
sector_t span;
@@ -1544,101 +1543,86 @@ asmlinkage long sys_swapon(const char __
error = PTR_ERR(page);
goto bad_swap;
}
- kmap(page);
- swap_header = page_address(page);
+ swap_header = kmap(page);

- if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
- swap_header_version = 1;
- else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
- swap_header_version = 2;
- else {
+ if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
printk(KERN_ERR "Unable to find swap-space signature\n");
error = -EINVAL;
goto bad_swap;
}

- switch (swap_header_version) {
- case 1:
- printk(KERN_ERR "version 0 swap is no longer supported. "
- "Use mkswap -v1 %s\n", name);
+ /* 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;
- case 2:
- /* 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 and the size of
- the swap file and bad block lists */
- 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->lowest_bit = 1;
+ p->cluster_next = 1;

- /*
- * 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;
- p->highest_bit = maxpages - 1;
+ /*
+ * 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;
+ p->highest_bit = maxpages - 1;

- error = -EINVAL;
- if (!maxpages)
- goto bad_swap;
- 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;
+ error = -EINVAL;
+ if (!maxpages)
+ goto bad_swap;
+ 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 = vmalloc(maxpages * sizeof(short));
- if (!swap_map) {
- error = -ENOMEM;
- goto bad_swap;
- }
+ /* OK, set up the swap map and apply the bad block list */
+ swap_map = vmalloc(maxpages * sizeof(short));
+ if (!swap_map) {
+ error = -ENOMEM;
+ goto bad_swap;
+ }

- error = 0;
- memset(swap_map, 0, maxpages * sizeof(short));
- for (i = 0; i < swap_header->info.nr_badpages; i++) {
- int page_nr = swap_header->info.badpages[i];
- if (page_nr <= 0 || page_nr >= swap_header->info.last_page)
- error = -EINVAL;
- else
- swap_map[page_nr] = SWAP_MAP_BAD;
- }
- nr_good_pages = swap_header->info.last_page -
- swap_header->info.nr_badpages -
- 1 /* header page */;
- if (error)
+ memset(swap_map, 0, maxpages * sizeof(short));
+ for (i = 0; i < swap_header->info.nr_badpages; i++) {
+ int page_nr = swap_header->info.badpages[i];
+ if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
+ error = -EINVAL;
goto bad_swap;
+ }
+ swap_map[page_nr] = SWAP_MAP_BAD;
}
+ nr_good_pages = swap_header->info.last_page -
+ swap_header->info.nr_badpages -
+ 1 /* header page */;

if (nr_good_pages) {
swap_map[0] = SWAP_MAP_BAD;