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Commit 8d69aaee authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

swap_info: swap_map of chars not shorts 



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: default avatarHugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 253d553b

include/linux/swap.h

+4 −4
Original line number Diff line number Diff line
@@ -151,9 +151,9 @@ enum { 


#define SWAP_CLUSTER_MAX 32



#define SWAP_MAP_MAX	0x7ffe

#define SWAP_MAP_BAD	0x7fff

#define SWAP_HAS_CACHE  0x8000		/* There is a swap cache of entry. */

#define SWAP_MAP_MAX	0x7e

#define SWAP_MAP_BAD	0x7f

#define SWAP_HAS_CACHE	0x80		/* There is a swap cache of entry. */



/*

 * The in-memory structure used to track swap areas.
@@ -167,7 +167,7 @@ struct swap_info_struct { 
	struct block_device *bdev;

	struct swap_extent first_swap_extent;

	struct swap_extent *curr_swap_extent;

	unsigned short *swap_map;

	unsigned char *swap_map;

	unsigned int lowest_bit;

	unsigned int highest_bit;

	unsigned int lowest_alloc;	/* while preparing discard cluster */

mm/swapfile.c

+23 −17
Original line number Diff line number Diff line
@@ -53,7 +53,7 @@ static struct swap_info_struct *swap_info[MAX_SWAPFILES]; 


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;

}
@@ -203,7 +203,7 @@ static int wait_for_discard(void *word) 
#define LATENCY_LIMIT		256



static inline unsigned long scan_swap_map(struct swap_info_struct *si,

					  unsigned short usage)

					  unsigned char usage)

{

	unsigned long offset;

	unsigned long scan_base;
@@ -531,12 +531,12 @@ static struct swap_info_struct *swap_info_get(swp_entry_t entry) 
	return NULL;

}



static unsigned short swap_entry_free(struct swap_info_struct *p,

			   swp_entry_t entry, unsigned short usage)

static unsigned char swap_entry_free(struct swap_info_struct *p,

				     swp_entry_t entry, unsigned char usage)

{

	unsigned long offset = swp_offset(entry);

	unsigned short count;

	unsigned short has_cache;

	unsigned char count;

	unsigned char has_cache;



	count = p->swap_map[offset];

	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)

{

	struct swap_info_struct *p;

	unsigned short count;

	unsigned char count;



	p = swap_info_get(entry);

	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 i = prev;

	int count;

	unsigned char count;



	/*

	 * 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 mm_struct *start_mm;

	unsigned short *swap_map;

	unsigned short swcount;

	unsigned char *swap_map;

	unsigned char swcount;

	struct page *page;

	swp_entry_t entry;

	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

		 * exit_mmap() and do_munmap() cases described above:

		 * 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

		 * 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)

{

	struct swap_info_struct *p = NULL;

	unsigned short *swap_map;

	unsigned char *swap_map;

	struct file *swap_file, *victim;

	struct address_space *mapping;

	struct inode *inode;
@@ -1762,7 +1768,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 
	sector_t span;

	unsigned long maxpages = 1;

	unsigned long swapfilepages;

	unsigned short *swap_map = NULL;

	unsigned char *swap_map = NULL;

	struct page *page = NULL;

	struct inode *inode = NULL;

	int did_down = 0;
@@ -1938,13 +1944,13 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 
		goto bad_swap;



	/* 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) {

		error = -ENOMEM;

		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++) {

		int page_nr = swap_header->info.badpages[i];

		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 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;

	unsigned long offset, type;

	unsigned short count;

	unsigned short has_cache;

	unsigned char count;

	unsigned char has_cache;

	int err = -EINVAL;



	if (non_swap_entry(entry))