[mirror_ubuntu-bionic-kernel.git] / include / linux / swap.h

#ifndef _LINUX_SWAP_H
#define _LINUX_SWAP_H

#include <linux/spinlock.h>
#include <linux/linkage.h>
#include <linux/mmzone.h>
#include <linux/list.h>
#include <linux/memcontrol.h>
#include <linux/sched.h>
#include <linux/node.h>

#include <asm/atomic.h>
#include <asm/page.h>

struct notifier_block;

struct bio;

#define SWAP_FLAG_PREFER	0x8000	/* set if swap priority specified */
#define SWAP_FLAG_PRIO_MASK	0x7fff
#define SWAP_FLAG_PRIO_SHIFT	0

static inline int current_is_kswapd(void)
{
	return current->flags & PF_KSWAPD;
}

/*
 * MAX_SWAPFILES defines the maximum number of swaptypes: things which can
 * be swapped to.  The swap type and the offset into that swap type are
 * encoded into pte's and into pgoff_t's in the swapcache.  Using five bits
 * for the type means that the maximum number of swapcache pages is 27 bits
 * on 32-bit-pgoff_t architectures.  And that assumes that the architecture packs
 * the type/offset into the pte as 5/27 as well.
 */
#define MAX_SWAPFILES_SHIFT	5
#ifndef CONFIG_MIGRATION
#define MAX_SWAPFILES		(1 << MAX_SWAPFILES_SHIFT)
#else
/* Use last two entries for page migration swap entries */
#define MAX_SWAPFILES		((1 << MAX_SWAPFILES_SHIFT)-2)
#define SWP_MIGRATION_READ	MAX_SWAPFILES
#define SWP_MIGRATION_WRITE	(MAX_SWAPFILES + 1)
#endif

/*
 * Magic header for a swap area. The first part of the union is
 * what the swap magic looks like for the old (limited to 128MB)
 * swap area format, the second part of the union adds - in the
 * old reserved area - some extra information. Note that the first
 * kilobyte is reserved for boot loader or disk label stuff...
 *
 * Having the magic at the end of the PAGE_SIZE makes detecting swap
 * areas somewhat tricky on machines that support multiple page sizes.
 * For 2.5 we'll probably want to move the magic to just beyond the
 * bootbits...
 */
union swap_header {
	struct {
		char reserved[PAGE_SIZE - 10];
		char magic[10];			/* SWAP-SPACE or SWAPSPACE2 */
	} magic;
	struct {
		char		bootbits[1024];	/* Space for disklabel etc. */
		__u32		version;
		__u32		last_page;
		__u32		nr_badpages;
		unsigned char	sws_uuid[16];
		unsigned char	sws_volume[16];
		__u32		padding[117];
		__u32		badpages[1];
	} info;
};

 /* A swap entry has to fit into a "unsigned long", as
  * the entry is hidden in the "index" field of the
  * swapper address space.
  */
typedef struct {
	unsigned long val;
} swp_entry_t;

/*
 * current->reclaim_state points to one of these when a task is running
 * memory reclaim
 */
struct reclaim_state {
	unsigned long reclaimed_slab;
};

#ifdef __KERNEL__

struct address_space;
struct sysinfo;
struct writeback_control;
struct zone;

/*
 * A swap extent maps a range of a swapfile's PAGE_SIZE pages onto a range of
 * disk blocks.  A list of swap extents maps the entire swapfile.  (Where the
 * term `swapfile' refers to either a blockdevice or an IS_REG file.  Apart
 * from setup, they're handled identically.
 *
 * We always assume that blocks are of size PAGE_SIZE.
 */
struct swap_extent {
	struct list_head list;
	pgoff_t start_page;
	pgoff_t nr_pages;
	sector_t start_block;
};

/*
 * Max bad pages in the new format..
 */
#define __swapoffset(x) ((unsigned long)&((union swap_header *)0)->x)
#define MAX_SWAP_BADPAGES \
	((__swapoffset(magic.magic) - __swapoffset(info.badpages)) / sizeof(int))

enum {
	SWP_USED	= (1 << 0),	/* is slot in swap_info[] used? */
	SWP_WRITEOK	= (1 << 1),	/* ok to write to this swap?	*/
					/* add others here before... */
	SWP_SCANNING	= (1 << 8),	/* refcount in scan_swap_map */
};

#define SWAP_CLUSTER_MAX 32

#define SWAP_MAP_MAX	0x7fff
#define SWAP_MAP_BAD	0x8000

/*
 * The in-memory structure used to track swap areas.
 */
struct swap_info_struct {
	unsigned long flags;
	int prio;			/* swap priority */
	int next;			/* next entry on swap list */
	struct file *swap_file;
	struct block_device *bdev;
	struct list_head extent_list;
	struct swap_extent *curr_swap_extent;
	unsigned short *swap_map;
	unsigned int lowest_bit;
	unsigned int highest_bit;
	unsigned int cluster_next;
	unsigned int cluster_nr;
	unsigned int pages;
	unsigned int max;
	unsigned int inuse_pages;
	unsigned int old_block_size;
};

struct swap_list_t {
	int head;	/* head of priority-ordered swapfile list */
	int next;	/* swapfile to be used next */
};

/* Swap 50% full? Release swapcache more aggressively.. */
#define vm_swap_full() (nr_swap_pages*2 < total_swap_pages)

/* linux/mm/page_alloc.c */
extern unsigned long totalram_pages;
extern unsigned long totalreserve_pages;
extern unsigned int nr_free_buffer_pages(void);
extern unsigned int nr_free_pagecache_pages(void);

/* Definition of global_page_state not available yet */
#define nr_free_pages() global_page_state(NR_FREE_PAGES)


/* linux/mm/swap.c */
extern void __lru_cache_add(struct page *, enum lru_list lru);
extern void lru_cache_add_lru(struct page *, enum lru_list lru);
extern void activate_page(struct page *);
extern void mark_page_accessed(struct page *);
extern void lru_add_drain(void);
extern int lru_add_drain_all(void);
extern void rotate_reclaimable_page(struct page *page);
extern void swap_setup(void);

extern void add_page_to_unevictable_list(struct page *page);

/**
 * lru_cache_add: add a page to the page lists
 * @page: the page to add
 */
static inline void lru_cache_add_anon(struct page *page)
{
	__lru_cache_add(page, LRU_INACTIVE_ANON);
}

static inline void lru_cache_add_active_anon(struct page *page)
{
	__lru_cache_add(page, LRU_ACTIVE_ANON);
}

static inline void lru_cache_add_file(struct page *page)
{
	__lru_cache_add(page, LRU_INACTIVE_FILE);
}

static inline void lru_cache_add_active_file(struct page *page)
{
	__lru_cache_add(page, LRU_ACTIVE_FILE);
}

/* linux/mm/vmscan.c */
extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
					gfp_t gfp_mask);
extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
							gfp_t gfp_mask);
extern int __isolate_lru_page(struct page *page, int mode, int file);
extern unsigned long shrink_all_memory(unsigned long nr_pages);
extern int vm_swappiness;
extern int remove_mapping(struct address_space *mapping, struct page *page);
extern long vm_total_pages;

#ifdef CONFIG_NUMA
extern int zone_reclaim_mode;
extern int sysctl_min_unmapped_ratio;
extern int sysctl_min_slab_ratio;
extern int zone_reclaim(struct zone *, gfp_t, unsigned int);
#else
#define zone_reclaim_mode 0
static inline int zone_reclaim(struct zone *z, gfp_t mask, unsigned int order)
{
	return 0;
}
#endif

#ifdef CONFIG_UNEVICTABLE_LRU
extern int page_evictable(struct page *page, struct vm_area_struct *vma);
extern void scan_mapping_unevictable_pages(struct address_space *);

extern unsigned long scan_unevictable_pages;
extern int scan_unevictable_handler(struct ctl_table *, int, struct file *,
					void __user *, size_t *, loff_t *);
extern int scan_unevictable_register_node(struct node *node);
extern void scan_unevictable_unregister_node(struct node *node);
#else
static inline int page_evictable(struct page *page,
						struct vm_area_struct *vma)
{
	return 1;
}

static inline void scan_mapping_unevictable_pages(struct address_space *mapping)
{
}

static inline int scan_unevictable_register_node(struct node *node)
{
	return 0;
}

static inline void scan_unevictable_unregister_node(struct node *node) { }
#endif

extern int kswapd_run(int nid);

#ifdef CONFIG_MMU
/* linux/mm/shmem.c */
extern int shmem_unuse(swp_entry_t entry, struct page *page);
#endif /* CONFIG_MMU */

extern void swap_unplug_io_fn(struct backing_dev_info *, struct page *);

#ifdef CONFIG_SWAP
/* linux/mm/page_io.c */
extern int swap_readpage(struct file *, struct page *);
extern int swap_writepage(struct page *page, struct writeback_control *wbc);
extern void end_swap_bio_read(struct bio *bio, int err);

/* linux/mm/swap_state.c */
extern struct address_space swapper_space;
#define total_swapcache_pages  swapper_space.nrpages
extern void show_swap_cache_info(void);
extern int add_to_swap(struct page *);
extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
extern void __delete_from_swap_cache(struct page *);
extern void delete_from_swap_cache(struct page *);
extern void free_page_and_swap_cache(struct page *);
extern void free_pages_and_swap_cache(struct page **, int);
extern struct page *lookup_swap_cache(swp_entry_t);
extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,
			struct vm_area_struct *vma, unsigned long addr);
extern struct page *swapin_readahead(swp_entry_t, gfp_t,
			struct vm_area_struct *vma, unsigned long addr);

/* linux/mm/swapfile.c */
extern long nr_swap_pages;
extern long total_swap_pages;
extern void si_swapinfo(struct sysinfo *);
extern swp_entry_t get_swap_page(void);
extern swp_entry_t get_swap_page_of_type(int);
extern int swap_duplicate(swp_entry_t);
extern int valid_swaphandles(swp_entry_t, unsigned long *);
extern void swap_free(swp_entry_t);
extern void free_swap_and_cache(swp_entry_t);
extern int swap_type_of(dev_t, sector_t, struct block_device **);
extern unsigned int count_swap_pages(int, int);
extern sector_t map_swap_page(struct swap_info_struct *, pgoff_t);
extern sector_t swapdev_block(int, pgoff_t);
extern struct swap_info_struct *get_swap_info_struct(unsigned);
extern int reuse_swap_page(struct page *);
extern int try_to_free_swap(struct page *);
struct backing_dev_info;

/* linux/mm/thrash.c */
extern struct mm_struct * swap_token_mm;
extern void grab_swap_token(void);
extern void __put_swap_token(struct mm_struct *);

static inline int has_swap_token(struct mm_struct *mm)
{
	return (mm == swap_token_mm);
}

static inline void put_swap_token(struct mm_struct *mm)
{
	if (has_swap_token(mm))
		__put_swap_token(mm);
}

static inline void disable_swap_token(void)
{
	put_swap_token(swap_token_mm);
}

#else /* CONFIG_SWAP */

#define nr_swap_pages				0L
#define total_swap_pages			0L
#define total_swapcache_pages			0UL

#define si_swapinfo(val) \
	do { (val)->freeswap = (val)->totalswap = 0; } while (0)
/* only sparc can not include linux/pagemap.h in this file
 * so leave page_cache_release and release_pages undeclared... */
#define free_page_and_swap_cache(page) \
	page_cache_release(page)
#define free_pages_and_swap_cache(pages, nr) \
	release_pages((pages), (nr), 0);

static inline void show_swap_cache_info(void)
{
}

static inline void free_swap_and_cache(swp_entry_t swp)
{
}

static inline int swap_duplicate(swp_entry_t swp)
{
	return 0;
}

static inline void swap_free(swp_entry_t swp)
{
}

static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
			struct vm_area_struct *vma, unsigned long addr)
{
	return NULL;
}

static inline struct page *lookup_swap_cache(swp_entry_t swp)
{
	return NULL;
}

static inline int add_to_swap(struct page *page)
{
	return 0;
}

static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
							gfp_t gfp_mask)
{
	return -1;
}

static inline void __delete_from_swap_cache(struct page *page)
{
}

static inline void delete_from_swap_cache(struct page *page)
{
}

#define reuse_swap_page(page)	(page_mapcount(page) == 1)

static inline int try_to_free_swap(struct page *page)
{
	return 0;
}

static inline swp_entry_t get_swap_page(void)
{
	swp_entry_t entry;
	entry.val = 0;
	return entry;
}

/* linux/mm/thrash.c */
#define put_swap_token(x) do { } while(0)
#define grab_swap_token()  do { } while(0)
#define has_swap_token(x) 0
#define disable_swap_token() do { } while(0)

#endif /* CONFIG_SWAP */
#endif /* __KERNEL__*/
#endif /* _LINUX_SWAP_H */
Commit	Line	Data
	1	#ifndef _LINUX_SWAP_H
	2	#define _LINUX_SWAP_H
	3
	4	#include <linux/spinlock.h>
	5	#include <linux/linkage.h>
	6	#include <linux/mmzone.h>
	7	#include <linux/list.h>
	8	#include <linux/memcontrol.h>
	9	#include <linux/sched.h>
	10	#include <linux/node.h>
	11
	12	#include <asm/atomic.h>
	13	#include <asm/page.h>
	14
	15	struct notifier_block;
	16
	17	struct bio;
	18
	19	#define SWAP_FLAG_PREFER 0x8000 /* set if swap priority specified */
	20	#define SWAP_FLAG_PRIO_MASK 0x7fff
	21	#define SWAP_FLAG_PRIO_SHIFT 0
	22
	23	static inline int current_is_kswapd(void)
	24	{
	25	return current->flags & PF_KSWAPD;
	26	}
	27
	28	/*
	29	* MAX_SWAPFILES defines the maximum number of swaptypes: things which can
	30	* be swapped to. The swap type and the offset into that swap type are
	31	* encoded into pte's and into pgoff_t's in the swapcache. Using five bits
	32	* for the type means that the maximum number of swapcache pages is 27 bits
	33	* on 32-bit-pgoff_t architectures. And that assumes that the architecture packs
	34	* the type/offset into the pte as 5/27 as well.
	35	*/
	36	#define MAX_SWAPFILES_SHIFT 5
	37	#ifndef CONFIG_MIGRATION
	38	#define MAX_SWAPFILES (1 << MAX_SWAPFILES_SHIFT)
	39	#else
	40	/* Use last two entries for page migration swap entries */
	41	#define MAX_SWAPFILES ((1 << MAX_SWAPFILES_SHIFT)-2)
	42	#define SWP_MIGRATION_READ MAX_SWAPFILES
	43	#define SWP_MIGRATION_WRITE (MAX_SWAPFILES + 1)
	44	#endif
	45
	46	/*
	47	* Magic header for a swap area. The first part of the union is
	48	* what the swap magic looks like for the old (limited to 128MB)
	49	* swap area format, the second part of the union adds - in the
	50	* old reserved area - some extra information. Note that the first
	51	* kilobyte is reserved for boot loader or disk label stuff...
	52	*
	53	* Having the magic at the end of the PAGE_SIZE makes detecting swap
	54	* areas somewhat tricky on machines that support multiple page sizes.
	55	* For 2.5 we'll probably want to move the magic to just beyond the
	56	* bootbits...
	57	*/
	58	union swap_header {
	59	struct {
	60	char reserved[PAGE_SIZE - 10];
	61	char magic[10]; /* SWAP-SPACE or SWAPSPACE2 */
	62	} magic;
	63	struct {
	64	char bootbits[1024]; /* Space for disklabel etc. */
	65	__u32 version;
	66	__u32 last_page;
	67	__u32 nr_badpages;
	68	unsigned char sws_uuid[16];
	69	unsigned char sws_volume[16];
	70	__u32 padding[117];
	71	__u32 badpages[1];
	72	} info;
	73	};
	74
	75	/* A swap entry has to fit into a "unsigned long", as
	76	* the entry is hidden in the "index" field of the
	77	* swapper address space.
	78	*/
	79	typedef struct {
	80	unsigned long val;
	81	} swp_entry_t;
	82
	83	/*
	84	* current->reclaim_state points to one of these when a task is running
	85	* memory reclaim
	86	*/
	87	struct reclaim_state {
	88	unsigned long reclaimed_slab;
	89	};
	90
	91	#ifdef __KERNEL__
	92
	93	struct address_space;
	94	struct sysinfo;
	95	struct writeback_control;
	96	struct zone;
	97
	98	/*
	99	* A swap extent maps a range of a swapfile's PAGE_SIZE pages onto a range of
	100	* disk blocks. A list of swap extents maps the entire swapfile. (Where the
	101	* term `swapfile' refers to either a blockdevice or an IS_REG file. Apart
	102	* from setup, they're handled identically.
	103	*
	104	* We always assume that blocks are of size PAGE_SIZE.
	105	*/
	106	struct swap_extent {
	107	struct list_head list;
	108	pgoff_t start_page;
	109	pgoff_t nr_pages;
	110	sector_t start_block;
	111	};
	112
	113	/*
	114	* Max bad pages in the new format..
	115	*/
	116	#define __swapoffset(x) ((unsigned long)&((union swap_header *)0)->x)
	117	#define MAX_SWAP_BADPAGES \
	118	((__swapoffset(magic.magic) - __swapoffset(info.badpages)) / sizeof(int))
	119
	120	enum {
	121	SWP_USED = (1 << 0), /* is slot in swap_info[] used? */
	122	SWP_WRITEOK = (1 << 1), /* ok to write to this swap? */
	123	/* add others here before... */
	124	SWP_SCANNING = (1 << 8), /* refcount in scan_swap_map */
	125	};
	126
	127	#define SWAP_CLUSTER_MAX 32
	128
	129	#define SWAP_MAP_MAX 0x7fff
	130	#define SWAP_MAP_BAD 0x8000
	131
	132	/*
	133	* The in-memory structure used to track swap areas.
	134	*/
	135	struct swap_info_struct {
	136	unsigned long flags;
	137	int prio; /* swap priority */
	138	int next; /* next entry on swap list */
	139	struct file *swap_file;
	140	struct block_device *bdev;
	141	struct list_head extent_list;
	142	struct swap_extent *curr_swap_extent;
	143	unsigned short *swap_map;
	144	unsigned int lowest_bit;
	145	unsigned int highest_bit;
	146	unsigned int cluster_next;
	147	unsigned int cluster_nr;
	148	unsigned int pages;
	149	unsigned int max;
	150	unsigned int inuse_pages;
	151	unsigned int old_block_size;
	152	};
	153
	154	struct swap_list_t {
	155	int head; /* head of priority-ordered swapfile list */
	156	int next; /* swapfile to be used next */
	157	};
	158
	159	/* Swap 50% full? Release swapcache more aggressively.. */
	160	#define vm_swap_full() (nr_swap_pages*2 < total_swap_pages)
	161
	162	/* linux/mm/page_alloc.c */
	163	extern unsigned long totalram_pages;
	164	extern unsigned long totalreserve_pages;
	165	extern unsigned int nr_free_buffer_pages(void);
	166	extern unsigned int nr_free_pagecache_pages(void);
	167
	168	/* Definition of global_page_state not available yet */
	169	#define nr_free_pages() global_page_state(NR_FREE_PAGES)
	170
	171
	172	/* linux/mm/swap.c */
	173	extern void __lru_cache_add(struct page *, enum lru_list lru);
	174	extern void lru_cache_add_lru(struct page *, enum lru_list lru);
	175	extern void activate_page(struct page *);
	176	extern void mark_page_accessed(struct page *);
	177	extern void lru_add_drain(void);
	178	extern int lru_add_drain_all(void);
	179	extern void rotate_reclaimable_page(struct page *page);
	180	extern void swap_setup(void);
	181
	182	extern void add_page_to_unevictable_list(struct page *page);
	183
	184	/**
	185	* lru_cache_add: add a page to the page lists
	186	* @page: the page to add
	187	*/
	188	static inline void lru_cache_add_anon(struct page *page)
	189	{
	190	__lru_cache_add(page, LRU_INACTIVE_ANON);
	191	}
	192
	193	static inline void lru_cache_add_active_anon(struct page *page)
	194	{
	195	__lru_cache_add(page, LRU_ACTIVE_ANON);
	196	}
	197
	198	static inline void lru_cache_add_file(struct page *page)
	199	{
	200	__lru_cache_add(page, LRU_INACTIVE_FILE);
	201	}
	202
	203	static inline void lru_cache_add_active_file(struct page *page)
	204	{
	205	__lru_cache_add(page, LRU_ACTIVE_FILE);
	206	}
	207
	208	/* linux/mm/vmscan.c */
	209	extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
	210	gfp_t gfp_mask);
	211	extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
	212	gfp_t gfp_mask);
	213	extern int __isolate_lru_page(struct page *page, int mode, int file);
	214	extern unsigned long shrink_all_memory(unsigned long nr_pages);
	215	extern int vm_swappiness;
	216	extern int remove_mapping(struct address_space mapping, struct page page);
	217	extern long vm_total_pages;
	218
	219	#ifdef CONFIG_NUMA
	220	extern int zone_reclaim_mode;
	221	extern int sysctl_min_unmapped_ratio;
	222	extern int sysctl_min_slab_ratio;
	223	extern int zone_reclaim(struct zone *, gfp_t, unsigned int);
	224	#else
	225	#define zone_reclaim_mode 0
	226	static inline int zone_reclaim(struct zone *z, gfp_t mask, unsigned int order)
	227	{
	228	return 0;
	229	}
	230	#endif
	231
	232	#ifdef CONFIG_UNEVICTABLE_LRU
	233	extern int page_evictable(struct page page, struct vm_area_struct vma);
	234	extern void scan_mapping_unevictable_pages(struct address_space *);
	235
	236	extern unsigned long scan_unevictable_pages;
	237	extern int scan_unevictable_handler(struct ctl_table , int, struct file ,
	238	void __user , size_t , loff_t *);
	239	extern int scan_unevictable_register_node(struct node *node);
	240	extern void scan_unevictable_unregister_node(struct node *node);
	241	#else
	242	static inline int page_evictable(struct page *page,
	243	struct vm_area_struct *vma)
	244	{
	245	return 1;
	246	}
	247
	248	static inline void scan_mapping_unevictable_pages(struct address_space *mapping)
	249	{
	250	}
	251
	252	static inline int scan_unevictable_register_node(struct node *node)
	253	{
	254	return 0;
	255	}
	256
	257	static inline void scan_unevictable_unregister_node(struct node *node) { }
	258	#endif
	259
	260	extern int kswapd_run(int nid);
	261
	262	#ifdef CONFIG_MMU
	263	/* linux/mm/shmem.c */
	264	extern int shmem_unuse(swp_entry_t entry, struct page *page);
	265	#endif /* CONFIG_MMU */
	266
	267	extern void swap_unplug_io_fn(struct backing_dev_info , struct page );
	268
	269	#ifdef CONFIG_SWAP
	270	/* linux/mm/page_io.c */
	271	extern int swap_readpage(struct file , struct page );
	272	extern int swap_writepage(struct page page, struct writeback_control wbc);
	273	extern void end_swap_bio_read(struct bio *bio, int err);
	274
	275	/* linux/mm/swap_state.c */
	276	extern struct address_space swapper_space;
	277	#define total_swapcache_pages swapper_space.nrpages
	278	extern void show_swap_cache_info(void);
	279	extern int add_to_swap(struct page *);
	280	extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
	281	extern void __delete_from_swap_cache(struct page *);
	282	extern void delete_from_swap_cache(struct page *);
	283	extern void free_page_and_swap_cache(struct page *);
	284	extern void free_pages_and_swap_cache(struct page **, int);
	285	extern struct page *lookup_swap_cache(swp_entry_t);
	286	extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,
	287	struct vm_area_struct *vma, unsigned long addr);
	288	extern struct page *swapin_readahead(swp_entry_t, gfp_t,
	289	struct vm_area_struct *vma, unsigned long addr);
	290
	291	/* linux/mm/swapfile.c */
	292	extern long nr_swap_pages;
	293	extern long total_swap_pages;
	294	extern void si_swapinfo(struct sysinfo *);
	295	extern swp_entry_t get_swap_page(void);
	296	extern swp_entry_t get_swap_page_of_type(int);
	297	extern int swap_duplicate(swp_entry_t);
	298	extern int valid_swaphandles(swp_entry_t, unsigned long *);
	299	extern void swap_free(swp_entry_t);
	300	extern void free_swap_and_cache(swp_entry_t);
	301	extern int swap_type_of(dev_t, sector_t, struct block_device **);
	302	extern unsigned int count_swap_pages(int, int);
	303	extern sector_t map_swap_page(struct swap_info_struct *, pgoff_t);
	304	extern sector_t swapdev_block(int, pgoff_t);
	305	extern struct swap_info_struct *get_swap_info_struct(unsigned);
	306	extern int reuse_swap_page(struct page *);
	307	extern int try_to_free_swap(struct page *);
	308	struct backing_dev_info;
	309
	310	/* linux/mm/thrash.c */
	311	extern struct mm_struct * swap_token_mm;
	312	extern void grab_swap_token(void);
	313	extern void __put_swap_token(struct mm_struct *);
	314
	315	static inline int has_swap_token(struct mm_struct *mm)
	316	{
	317	return (mm == swap_token_mm);
	318	}
	319
	320	static inline void put_swap_token(struct mm_struct *mm)
	321	{
	322	if (has_swap_token(mm))
	323	__put_swap_token(mm);
	324	}
	325
	326	static inline void disable_swap_token(void)
	327	{
	328	put_swap_token(swap_token_mm);
	329	}
	330
	331	#else /* CONFIG_SWAP */
	332
	333	#define nr_swap_pages 0L
	334	#define total_swap_pages 0L
	335	#define total_swapcache_pages 0UL
	336
	337	#define si_swapinfo(val) \
	338	do { (val)->freeswap = (val)->totalswap = 0; } while (0)
	339	/* only sparc can not include linux/pagemap.h in this file
	340	* so leave page_cache_release and release_pages undeclared... */
	341	#define free_page_and_swap_cache(page) \
	342	page_cache_release(page)
	343	#define free_pages_and_swap_cache(pages, nr) \
	344	release_pages((pages), (nr), 0);
	345
	346	static inline void show_swap_cache_info(void)
	347	{
	348	}
	349
	350	static inline void free_swap_and_cache(swp_entry_t swp)
	351	{
	352	}
	353
	354	static inline int swap_duplicate(swp_entry_t swp)
	355	{
	356	return 0;
	357	}
	358
	359	static inline void swap_free(swp_entry_t swp)
	360	{
	361	}
	362
	363	static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
	364	struct vm_area_struct *vma, unsigned long addr)
	365	{
	366	return NULL;
	367	}
	368
	369	static inline struct page *lookup_swap_cache(swp_entry_t swp)
	370	{
	371	return NULL;
	372	}
	373
	374	static inline int add_to_swap(struct page *page)
	375	{
	376	return 0;
	377	}
	378
	379	static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
	380	gfp_t gfp_mask)
	381	{
	382	return -1;
	383	}
	384
	385	static inline void __delete_from_swap_cache(struct page *page)
	386	{
	387	}
	388
	389	static inline void delete_from_swap_cache(struct page *page)
	390	{
	391	}
	392
	393	#define reuse_swap_page(page) (page_mapcount(page) == 1)
	394
	395	static inline int try_to_free_swap(struct page *page)
	396	{
	397	return 0;
	398	}
	399
	400	static inline swp_entry_t get_swap_page(void)
	401	{
	402	swp_entry_t entry;
	403	entry.val = 0;
	404	return entry;
	405	}
	406
	407	/* linux/mm/thrash.c */
	408	#define put_swap_token(x) do { } while(0)
	409	#define grab_swap_token() do { } while(0)
	410	#define has_swap_token(x) 0
	411	#define disable_swap_token() do { } while(0)
	412
	413	#endif /* CONFIG_SWAP */
	414	#endif /* __KERNEL__*/
	415	#endif /* _LINUX_SWAP_H */