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swap_info: swap_map of chars not shorts

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Halve the vmalloc'ed swap_map array from unsigned shorts to unsigned
chars: it's still very unusual to reach a swap count of 126, and the
next patch allows it to be extended indefinitely.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2009-12-14 17:58:45 -08:00 committed by Linus Torvalds
parent 253d553ba7
commit 8d69aaee80
2 changed files with 27 additions and 21 deletions
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8
include/linux/swap.h
View file

@ -151,9 +151,9 @@ enum {
#define SWAP_CLUSTER_MAX 32 #define SWAP_CLUSTER_MAX 32
#define SWAP_MAP_MAX 0x7ffe #define SWAP_MAP_MAX 0x7e
#define SWAP_MAP_BAD 0x7fff #define SWAP_MAP_BAD 0x7f
#define SWAP_HAS_CACHE 0x8000 /* There is a swap cache of entry. */ #define SWAP_HAS_CACHE 0x80 /* There is a swap cache of entry. */
/* /*
* The in-memory structure used to track swap areas. * The in-memory structure used to track swap areas.
@ -167,7 +167,7 @@ struct swap_info_struct {
struct block_device *bdev; struct block_device *bdev;
struct swap_extent first_swap_extent; struct swap_extent first_swap_extent;
struct swap_extent *curr_swap_extent; struct swap_extent *curr_swap_extent;
unsigned short *swap_map; unsigned char *swap_map;
unsigned int lowest_bit; unsigned int lowest_bit;
unsigned int highest_bit; unsigned int highest_bit;
unsigned int lowest_alloc; /* while preparing discard cluster */ unsigned int lowest_alloc; /* while preparing discard cluster */

40
mm/swapfile.c
View file

@ -53,7 +53,7 @@ static struct swap_info_struct *swap_info[MAX_SWAPFILES];
static DEFINE_MUTEX(swapon_mutex); static DEFINE_MUTEX(swapon_mutex);
static inline int swap_count(unsigned short ent) static inline unsigned char swap_count(unsigned char ent)
{ {
return ent & ~SWAP_HAS_CACHE; return ent & ~SWAP_HAS_CACHE;
} }
@ -203,7 +203,7 @@ static int wait_for_discard(void *word)
#define LATENCY_LIMIT 256 #define LATENCY_LIMIT 256
static inline unsigned long scan_swap_map(struct swap_info_struct *si, static inline unsigned long scan_swap_map(struct swap_info_struct *si,
unsigned short usage) unsigned char usage)
{ {
unsigned long offset; unsigned long offset;
unsigned long scan_base; unsigned long scan_base;
@ -531,12 +531,12 @@ static struct swap_info_struct *swap_info_get(swp_entry_t entry)
return NULL; return NULL;
} }
static unsigned short swap_entry_free(struct swap_info_struct *p, static unsigned char swap_entry_free(struct swap_info_struct *p,
swp_entry_t entry, unsigned short usage) swp_entry_t entry, unsigned char usage)
{ {
unsigned long offset = swp_offset(entry); unsigned long offset = swp_offset(entry);
unsigned short count; unsigned char count;
unsigned short has_cache; unsigned char has_cache;
count = p->swap_map[offset]; count = p->swap_map[offset];
has_cache = count & SWAP_HAS_CACHE; has_cache = count & SWAP_HAS_CACHE;
@ -591,7 +591,7 @@ void swap_free(swp_entry_t entry)
void swapcache_free(swp_entry_t entry, struct page *page) void swapcache_free(swp_entry_t entry, struct page *page)
{ {
struct swap_info_struct *p; struct swap_info_struct *p;
unsigned short count; unsigned char count;
p = swap_info_get(entry); p = swap_info_get(entry);
if (p) { if (p) {
@ -975,7 +975,7 @@ static unsigned int find_next_to_unuse(struct swap_info_struct *si,
{ {
unsigned int max = si->max; unsigned int max = si->max;
unsigned int i = prev; unsigned int i = prev;
int count; unsigned char count;
/* /*
* No need for swap_lock here: we're just looking * No need for swap_lock here: we're just looking
@ -1013,8 +1013,8 @@ static int try_to_unuse(unsigned int type)
{ {
struct swap_info_struct *si = swap_info[type]; struct swap_info_struct *si = swap_info[type];
struct mm_struct *start_mm; struct mm_struct *start_mm;
unsigned short *swap_map; unsigned char *swap_map;
unsigned short swcount; unsigned char swcount;
struct page *page; struct page *page;
swp_entry_t entry; swp_entry_t entry;
unsigned int i = 0; unsigned int i = 0;
@ -1174,6 +1174,12 @@ static int try_to_unuse(unsigned int type)
* If that's wrong, then we should worry more about * If that's wrong, then we should worry more about
* exit_mmap() and do_munmap() cases described above: * exit_mmap() and do_munmap() cases described above:
* we might be resetting SWAP_MAP_MAX too early here. * we might be resetting SWAP_MAP_MAX too early here.
*
* Yes, that's wrong: though very unlikely, swap count 0x7ffe
* could surely occur if pid_max raised from PID_MAX_DEFAULT;
* and we are now lowering SWAP_MAP_MAX to 0x7e, making it
* much easier to reach. But the next patch will fix that.
*
* We know "Undead"s can happen, they're okay, so don't * We know "Undead"s can happen, they're okay, so don't
* report them; but do report if we reset SWAP_MAP_MAX. * report them; but do report if we reset SWAP_MAP_MAX.
*/ */
@ -1492,7 +1498,7 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
{ {
struct swap_info_struct *p = NULL; struct swap_info_struct *p = NULL;
unsigned short *swap_map; unsigned char *swap_map;
struct file *swap_file, *victim; struct file *swap_file, *victim;
struct address_space *mapping; struct address_space *mapping;
struct inode *inode; struct inode *inode;
@ -1762,7 +1768,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
sector_t span; sector_t span;
unsigned long maxpages = 1; unsigned long maxpages = 1;
unsigned long swapfilepages; unsigned long swapfilepages;
unsigned short *swap_map = NULL; unsigned char *swap_map = NULL;
struct page *page = NULL; struct page *page = NULL;
struct inode *inode = NULL; struct inode *inode = NULL;
int did_down = 0; int did_down = 0;
@ -1938,13 +1944,13 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
goto bad_swap; goto bad_swap;
/* OK, set up the swap map and apply the bad block list */ /* OK, set up the swap map and apply the bad block list */
swap_map = vmalloc(maxpages * sizeof(short)); swap_map = vmalloc(maxpages);
if (!swap_map) { if (!swap_map) {
error = -ENOMEM; error = -ENOMEM;
goto bad_swap; goto bad_swap;
} }
memset(swap_map, 0, maxpages * sizeof(short)); memset(swap_map, 0, maxpages);
for (i = 0; i < swap_header->info.nr_badpages; i++) { for (i = 0; i < swap_header->info.nr_badpages; i++) {
int page_nr = swap_header->info.badpages[i]; int page_nr = swap_header->info.badpages[i];
if (page_nr <= 0 || page_nr >= swap_header->info.last_page) { if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
@ -2082,12 +2088,12 @@ void si_swapinfo(struct sysinfo *val)
* - swap-cache reference is requested but there is already one. -> EEXIST * - swap-cache reference is requested but there is already one. -> EEXIST
* - swap-cache reference is requested but the entry is not used. -> ENOENT * - swap-cache reference is requested but the entry is not used. -> ENOENT
*/ */
static int __swap_duplicate(swp_entry_t entry, unsigned short usage) static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
{ {
struct swap_info_struct *p; struct swap_info_struct *p;
unsigned long offset, type; unsigned long offset, type;
unsigned short count; unsigned char count;
unsigned short has_cache; unsigned char has_cache;
int err = -EINVAL; int err = -EINVAL;
if (non_swap_entry(entry)) if (non_swap_entry(entry))