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/* SPDX-License-Identifier: GPL-2.0 */
#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 <linux/fs.h>
#include <linux/atomic.h>
#include <linux/page-flags.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_DISCARD 0x10000 /* enable discard for swap */
#define SWAP_FLAG_DISCARD_ONCE 0x20000 /* discard swap area at swapon-time */
#define SWAP_FLAG_DISCARD_PAGES 0x40000 /* discard page-clusters after use */
#define SWAP_BATCH 64
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.
* Use some of the swap files numbers for other purposes. This
* is a convenient way to hook into the VM to trigger special
* actions on faults.
* Unaddressable device memory support. See include/linux/hmm.h and
* Documentation/vm/hmm.rst. Short description is we need struct pages for
* device memory that is unaddressable (inaccessible) by CPU, so that we can
* migrate part of a process memory to device memory.
* When a page is migrated from CPU to device, we set the CPU page table entry
* to a special SWP_DEVICE_* entry.
#define SWP_DEVICE_NUM 2
#define SWP_DEVICE_NUM 0
* NUMA node memory migration support
* Handling of hardware poisoned pages with memory corruption.
* 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;
* 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)
((__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? */
SWP_DISCARDABLE = (1 << 2), /* blkdev support discard */
SWP_DISCARDING = (1 << 3), /* now discarding a free cluster */
SWP_SOLIDSTATE = (1 << 4), /* blkdev seeks are cheap */
SWP_CONTINUED = (1 << 5), /* swap_map has count continuation */
SWP_BLKDEV = (1 << 6), /* its a block device */
SWP_FILE = (1 << 7), /* set after swap_activate success */
SWP_AREA_DISCARD = (1 << 8), /* single-time swap area discards */
SWP_PAGE_DISCARD = (1 << 9), /* freed swap page-cluster discards */
SWP_STABLE_WRITES = (1 << 10), /* no overwrite PG_writeback pages */
SWP_SYNCHRONOUS_IO = (1 << 11), /* synchronous IO is efficient */
/* add others here before... */
SWP_SCANNING = (1 << 12), /* refcount in scan_swap_map */
#define SWAP_MAP_MAX 0x3e /* Max duplication count, in first swap_map */
#define SWAP_MAP_BAD 0x3f /* Note pageblock is bad, in first swap_map */
#define SWAP_HAS_CACHE 0x40 /* Flag page is cached, in first swap_map */
#define SWAP_CONT_MAX 0x7f /* Max count, in each swap_map continuation */
#define COUNT_CONTINUED 0x80 /* See swap_map continuation for full count */
#define SWAP_MAP_SHMEM 0xbf /* Owned by shmem/tmpfs, in first swap_map */
* We use this to track usage of a cluster. A cluster is a block of swap disk
* space with SWAPFILE_CLUSTER pages long and naturally aligns in disk. All
* free clusters are organized into a list. We fetch an entry from the list to
* get a free cluster.
* The data field stores next cluster if the cluster is free or cluster usage
* counter otherwise. The flags field determines if a cluster is free. This is
* protected by swap_info_struct.lock.
struct swap_cluster_info {
spinlock_t lock; /*
* Protect swap_cluster_info fields
* and swap_info_struct->swap_map
* elements correspond to the swap
* cluster
unsigned int data:24;
unsigned int flags:8;
#define CLUSTER_FLAG_FREE 1 /* This cluster is free */
#define CLUSTER_FLAG_NEXT_NULL 2 /* This cluster has no next cluster */
#define CLUSTER_FLAG_HUGE 4 /* This cluster is backing a transparent huge page */
* We assign a cluster to each CPU, so each CPU can allocate swap entry from
* its own cluster and swapout sequentially. The purpose is to optimize swapout
* throughput.
struct percpu_cluster {
struct swap_cluster_info index; /* Current cluster index */
unsigned int next; /* Likely next allocation offset */
struct swap_cluster_list {
struct swap_cluster_info head;
struct swap_cluster_info tail;
* The in-memory structure used to track swap areas.
struct swap_info_struct {
unsigned long flags; /* SWP_USED etc: see above */
signed short prio; /* swap priority of this type */
struct plist_node list; /* entry in swap_active_head */
struct plist_node avail_lists[MAX_NUMNODES];/* entry in swap_avail_heads */
signed char type; /* strange name for an index */
unsigned int max; /* extent of the swap_map */
unsigned char *swap_map; /* vmalloc'ed array of usage counts */
struct swap_cluster_info *cluster_info; /* cluster info. Only for SSD */
struct swap_cluster_list free_clusters; /* free clusters list */
unsigned int lowest_bit; /* index of first free in swap_map */
unsigned int highest_bit; /* index of last free in swap_map */
unsigned int pages; /* total of usable pages of swap */
unsigned int inuse_pages; /* number of those currently in use */
unsigned int cluster_next; /* likely index for next allocation */
unsigned int cluster_nr; /* countdown to next cluster search */
struct percpu_cluster __percpu *percpu_cluster; /* per cpu's swap location */
struct swap_extent *curr_swap_extent;
struct swap_extent first_swap_extent;
struct block_device *bdev; /* swap device or bdev of swap file */
struct file *swap_file; /* seldom referenced */
unsigned int old_block_size; /* seldom referenced */
unsigned long *frontswap_map; /* frontswap in-use, one bit per page */
atomic_t frontswap_pages; /* frontswap pages in-use counter */
spinlock_t lock; /*
* protect map scan related fields like
* swap_map, lowest_bit, highest_bit,
* inuse_pages, cluster_next,
* cluster_nr, lowest_alloc,
* highest_alloc, free/discard cluster
* list. other fields are only changed
* at swapon/swapoff, so are protected
* by swap_lock. changing flags need
* hold this lock and swap_lock. If
* both locks need hold, hold swap_lock
* first.
spinlock_t cont_lock; /*
* protect swap count continuation page
* list.
struct work_struct discard_work; /* discard worker */
struct swap_cluster_list discard_clusters; /* discard clusters list */
#ifdef CONFIG_64BIT
/* Avoid stack overflow, because we need to save part of page table */
struct vma_swap_readahead {
unsigned short win;
unsigned short offset;
unsigned short nr_pte;
#ifdef CONFIG_64BIT
pte_t *ptes;
/* linux/mm/workingset.c */
void *workingset_eviction(struct address_space *mapping, struct page *page);
bool workingset_refault(void *shadow);
void workingset_activation(struct page *page);
/* Do not use directly, use workingset_lookup_update */
void workingset_update_node(struct radix_tree_node *node);
/* Returns workingset_update_node() if the mapping has shadow entries. */
#define workingset_lookup_update(mapping) \
({ \
radix_tree_update_node_t __helper = workingset_update_node; \
if (dax_mapping(mapping) || shmem_mapping(mapping)) \
__helper = NULL; \
__helper; \
/* linux/mm/page_alloc.c */
extern unsigned long totalram_pages;
extern unsigned long totalreserve_pages;
extern unsigned long nr_free_buffer_pages(void);
extern unsigned long nr_free_pagecache_pages(void);
/* Definition of global_zone_page_state not available yet */
#define nr_free_pages() global_zone_page_state(NR_FREE_PAGES)
/* linux/mm/swap.c */
extern void lru_cache_add(struct page *);
extern void lru_cache_add_anon(struct page *page);
extern void lru_cache_add_file(struct page *page);
extern void lru_add_page_tail(struct page *page, struct page *page_tail,
struct lruvec *lruvec, struct list_head *head);
extern void activate_page(struct page *);
extern void mark_page_accessed(struct page *);
extern void lru_add_drain(void);
extern void lru_add_drain_cpu(int cpu);
extern void lru_add_drain_all(void);
extern void rotate_reclaimable_page(struct page *page);
extern void deactivate_file_page(struct page *page);
extern void mark_page_lazyfree(struct page *page);
extern void swap_setup(void);
extern void lru_cache_add_active_or_unevictable(struct page *page,
struct vm_area_struct *vma);
/* linux/mm/vmscan.c */
extern unsigned long zone_reclaimable_pages(struct zone *zone);
extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
gfp_t gfp_mask, nodemask_t *mask);
extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
unsigned long nr_pages,
gfp_t gfp_mask,
bool may_swap);
extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem,
gfp_t gfp_mask, bool noswap,
pg_data_t *pgdat,
unsigned long *nr_scanned);
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 unsigned long vm_total_pages;
extern int node_reclaim_mode;
extern int sysctl_min_unmapped_ratio;
extern int sysctl_min_slab_ratio;
extern int node_reclaim(struct pglist_data *, gfp_t, unsigned int);
#define node_reclaim_mode 0
static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask,
unsigned int order)
return 0;
extern int page_evictable(struct page *page);
extern void check_move_unevictable_pages(struct page **, int nr_pages);
extern int kswapd_run(int nid);
extern void kswapd_stop(int nid);
#include <linux/blk_types.h> /* for bio_end_io_t */
/* linux/mm/page_io.c */
extern int swap_readpage(struct page *page, bool do_poll);
extern int swap_writepage(struct page *page, struct writeback_control *wbc);
extern void end_swap_bio_write(struct bio *bio);
extern int __swap_writepage(struct page *page, struct writeback_control *wbc,
bio_end_io_t end_write_func);
extern int swap_set_page_dirty(struct page *page);
int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
unsigned long nr_pages, sector_t start_block);
int generic_swapfile_activate(struct swap_info_struct *, struct file *,
sector_t *);
/* linux/mm/swap_state.c */
/* One swap address space for each 64M swap space */
extern struct address_space *swapper_spaces[];
#define swap_address_space(entry) \
(&swapper_spaces[swp_type(entry)][swp_offset(entry) \
extern unsigned long total_swapcache_pages(void);
extern void show_swap_cache_info(void);
extern int add_to_swap(struct page *page);
extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
extern int __add_to_swap_cache(struct page *page, swp_entry_t entry);
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 entry,
struct vm_area_struct *vma,
unsigned long addr);
extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,
struct vm_area_struct *vma, unsigned long addr,
bool do_poll);
extern struct page *__read_swap_cache_async(swp_entry_t, gfp_t,
struct vm_area_struct *vma, unsigned long addr,
bool *new_page_allocated);
extern struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
struct vm_fault *vmf);
extern struct page *swapin_readahead(swp_entry_t entry, gfp_t flag,
struct vm_fault *vmf);
/* linux/mm/swapfile.c */
extern atomic_long_t nr_swap_pages;
extern long total_swap_pages;
extern atomic_t nr_rotate_swap;
extern bool has_usable_swap(void);
/* Swap 50% full? Release swapcache more aggressively.. */
static inline bool vm_swap_full(void)
return atomic_long_read(&nr_swap_pages) * 2 < total_swap_pages;
static inline long get_nr_swap_pages(void)
return atomic_long_read(&nr_swap_pages);
extern void si_swapinfo(struct sysinfo *);
extern swp_entry_t get_swap_page(struct page *page);
extern void put_swap_page(struct page *page, swp_entry_t entry);
extern swp_entry_t get_swap_page_of_type(int);
extern int get_swap_pages(int n, swp_entry_t swp_entries[], int entry_size);
extern int add_swap_count_continuation(swp_entry_t, gfp_t);
extern void swap_shmem_alloc(swp_entry_t);
extern int swap_duplicate(swp_entry_t);
extern int swapcache_prepare(swp_entry_t);
extern void swap_free(swp_entry_t);
extern void swapcache_free_entries(swp_entry_t *entries, int n);
extern int 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 page *, struct block_device **);
extern sector_t swapdev_block(int, pgoff_t);
extern int page_swapcount(struct page *);
extern int __swap_count(struct swap_info_struct *si, swp_entry_t entry);
extern int __swp_swapcount(swp_entry_t entry);
extern int swp_swapcount(swp_entry_t entry);
extern struct swap_info_struct *page_swap_info(struct page *);
extern struct swap_info_struct *swp_swap_info(swp_entry_t entry);
extern bool reuse_swap_page(struct page *, int *);
extern int try_to_free_swap(struct page *);
struct backing_dev_info;
extern int init_swap_address_space(unsigned int type, unsigned long nr_pages);
extern void exit_swap_address_space(unsigned int type);
#else /* CONFIG_SWAP */
static inline int swap_readpage(struct page *page, bool do_poll)
return 0;
static inline struct swap_info_struct *swp_swap_info(swp_entry_t entry)
return NULL;
#define swap_address_space(entry) (NULL)
#define get_nr_swap_pages() 0L
#define total_swap_pages 0L
#define total_swapcache_pages() 0UL
#define vm_swap_full() 0
#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 put_page and release_pages undeclared... */
#define free_page_and_swap_cache(page) \
#define free_pages_and_swap_cache(pages, nr) \
release_pages((pages), (nr));
static inline void show_swap_cache_info(void)
#define free_swap_and_cache(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
#define swapcache_prepare(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
return 0;
static inline void swap_shmem_alloc(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 void put_swap_page(struct page *page, swp_entry_t swp)
static inline struct page *swap_cluster_readahead(swp_entry_t entry,
gfp_t gfp_mask, struct vm_fault *vmf)
return NULL;
static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
struct vm_fault *vmf)
return NULL;
static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
return 0;
static inline struct page *lookup_swap_cache(swp_entry_t swp,
struct vm_area_struct *vma,
unsigned long addr)
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)
static inline int page_swapcount(struct page *page)
return 0;
static inline int __swap_count(struct swap_info_struct *si, swp_entry_t entry)
return 0;
static inline int __swp_swapcount(swp_entry_t entry)
return 0;
static inline int swp_swapcount(swp_entry_t entry)
return 0;
#define reuse_swap_page(page, total_map_swapcount) \
(page_trans_huge_mapcount(page, total_map_swapcount) == 1)
static inline int try_to_free_swap(struct page *page)
return 0;
static inline swp_entry_t get_swap_page(struct page *page)
swp_entry_t entry;
entry.val = 0;
return entry;
#endif /* CONFIG_SWAP */
extern int split_swap_cluster(swp_entry_t entry);
static inline int split_swap_cluster(swp_entry_t entry)
return 0;
static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
/* Cgroup2 doesn't have per-cgroup swappiness */
if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
return vm_swappiness;
/* root ? */
if (mem_cgroup_disabled() || !memcg->css.parent)
return vm_swappiness;
return memcg->swappiness;
static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
return vm_swappiness;
#if defined(CONFIG_SWAP) && defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
extern void mem_cgroup_throttle_swaprate(struct mem_cgroup *memcg, int node,
gfp_t gfp_mask);
static inline void mem_cgroup_throttle_swaprate(struct mem_cgroup *memcg,
int node, gfp_t gfp_mask)
extern void mem_cgroup_swapout(struct page *page, swp_entry_t entry);
extern int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry);
extern void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
extern bool mem_cgroup_swap_full(struct page *page);
static inline void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
static inline int mem_cgroup_try_charge_swap(struct page *page,
swp_entry_t entry)
return 0;
static inline void mem_cgroup_uncharge_swap(swp_entry_t entry,
unsigned int nr_pages)
static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
return get_nr_swap_pages();
static inline bool mem_cgroup_swap_full(struct page *page)
return vm_swap_full();
#endif /* __KERNEL__*/
#endif /* _LINUX_SWAP_H */