diff options
Diffstat (limited to 'mm/swapfile.c')
| -rw-r--r-- | mm/swapfile.c | 3670 |
1 files changed, 3670 insertions, 0 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c new file mode 100644 index 000000000..e52f48683 --- /dev/null +++ b/mm/swapfile.c @@ -0,0 +1,3670 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/mm/swapfile.c + * + * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds + * Swap reorganised 29.12.95, Stephen Tweedie + */ + +#include <linux/blkdev.h> +#include <linux/mm.h> +#include <linux/sched/mm.h> +#include <linux/sched/task.h> +#include <linux/hugetlb.h> +#include <linux/mman.h> +#include <linux/slab.h> +#include <linux/kernel_stat.h> +#include <linux/swap.h> +#include <linux/vmalloc.h> +#include <linux/pagemap.h> +#include <linux/namei.h> +#include <linux/shmem_fs.h> +#include <linux/blk-cgroup.h> +#include <linux/random.h> +#include <linux/writeback.h> +#include <linux/proc_fs.h> +#include <linux/seq_file.h> +#include <linux/init.h> +#include <linux/ksm.h> +#include <linux/rmap.h> +#include <linux/security.h> +#include <linux/backing-dev.h> +#include <linux/mutex.h> +#include <linux/capability.h> +#include <linux/syscalls.h> +#include <linux/memcontrol.h> +#include <linux/poll.h> +#include <linux/oom.h> +#include <linux/swapfile.h> +#include <linux/export.h> +#include <linux/swap_slots.h> +#include <linux/sort.h> +#include <linux/completion.h> +#include <linux/suspend.h> +#include <linux/zswap.h> + +#include <asm/tlbflush.h> +#include <linux/swapops.h> +#include <linux/swap_cgroup.h> +#include "internal.h" +#include "swap.h" + +static bool swap_count_continued(struct swap_info_struct *, pgoff_t, + unsigned char); +static void free_swap_count_continuations(struct swap_info_struct *); + +static DEFINE_SPINLOCK(swap_lock); +static unsigned int nr_swapfiles; +atomic_long_t nr_swap_pages; +/* + * Some modules use swappable objects and may try to swap them out under + * memory pressure (via the shrinker). Before doing so, they may wish to + * check to see if any swap space is available. + */ +EXPORT_SYMBOL_GPL(nr_swap_pages); +/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */ +long total_swap_pages; +static int least_priority = -1; +unsigned long swapfile_maximum_size; +#ifdef CONFIG_MIGRATION +bool swap_migration_ad_supported; +#endif /* CONFIG_MIGRATION */ + +static const char Bad_file[] = "Bad swap file entry "; +static const char Unused_file[] = "Unused swap file entry "; +static const char Bad_offset[] = "Bad swap offset entry "; +static const char Unused_offset[] = "Unused swap offset entry "; + +/* + * all active swap_info_structs + * protected with swap_lock, and ordered by priority. + */ +static PLIST_HEAD(swap_active_head); + +/* + * all available (active, not full) swap_info_structs + * protected with swap_avail_lock, ordered by priority. + * This is used by folio_alloc_swap() instead of swap_active_head + * because swap_active_head includes all swap_info_structs, + * but folio_alloc_swap() doesn't need to look at full ones. + * This uses its own lock instead of swap_lock because when a + * swap_info_struct changes between not-full/full, it needs to + * add/remove itself to/from this list, but the swap_info_struct->lock + * is held and the locking order requires swap_lock to be taken + * before any swap_info_struct->lock. + */ +static struct plist_head *swap_avail_heads; +static DEFINE_SPINLOCK(swap_avail_lock); + +static struct swap_info_struct *swap_info[MAX_SWAPFILES]; + +static DEFINE_MUTEX(swapon_mutex); + +static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait); +/* Activity counter to indicate that a swapon or swapoff has occurred */ +static atomic_t proc_poll_event = ATOMIC_INIT(0); + +atomic_t nr_rotate_swap = ATOMIC_INIT(0); + +static struct swap_info_struct *swap_type_to_swap_info(int type) +{ + if (type >= MAX_SWAPFILES) + return NULL; + + return READ_ONCE(swap_info[type]); /* rcu_dereference() */ +} + +static inline unsigned char swap_count(unsigned char ent) +{ + return ent & ~SWAP_HAS_CACHE; /* may include COUNT_CONTINUED flag */ +} + +/* Reclaim the swap entry anyway if possible */ +#define TTRS_ANYWAY 0x1 +/* + * Reclaim the swap entry if there are no more mappings of the + * corresponding page + */ +#define TTRS_UNMAPPED 0x2 +/* Reclaim the swap entry if swap is getting full*/ +#define TTRS_FULL 0x4 + +/* returns 1 if swap entry is freed */ +static int __try_to_reclaim_swap(struct swap_info_struct *si, + unsigned long offset, unsigned long flags) +{ + swp_entry_t entry = swp_entry(si->type, offset); + struct folio *folio; + int ret = 0; + + folio = filemap_get_folio(swap_address_space(entry), offset); + if (IS_ERR(folio)) + return 0; + /* + * When this function is called from scan_swap_map_slots() and it's + * called by vmscan.c at reclaiming folios. So we hold a folio lock + * here. We have to use trylock for avoiding deadlock. This is a special + * case and you should use folio_free_swap() with explicit folio_lock() + * in usual operations. + */ + if (folio_trylock(folio)) { + if ((flags & TTRS_ANYWAY) || + ((flags & TTRS_UNMAPPED) && !folio_mapped(folio)) || + ((flags & TTRS_FULL) && mem_cgroup_swap_full(folio))) + ret = folio_free_swap(folio); + folio_unlock(folio); + } + folio_put(folio); + return ret; +} + +static inline struct swap_extent *first_se(struct swap_info_struct *sis) +{ + struct rb_node *rb = rb_first(&sis->swap_extent_root); + return rb_entry(rb, struct swap_extent, rb_node); +} + +static inline struct swap_extent *next_se(struct swap_extent *se) +{ + struct rb_node *rb = rb_next(&se->rb_node); + return rb ? rb_entry(rb, struct swap_extent, rb_node) : NULL; +} + +/* + * swapon tell device that all the old swap contents can be discarded, + * to allow the swap device to optimize its wear-levelling. + */ +static int discard_swap(struct swap_info_struct *si) +{ + struct swap_extent *se; + sector_t start_block; + sector_t nr_blocks; + int err = 0; + + /* Do not discard the swap header page! */ + se = first_se(si); + start_block = (se->start_block + 1) << (PAGE_SHIFT - 9); + nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9); + if (nr_blocks) { + err = blkdev_issue_discard(si->bdev, start_block, + nr_blocks, GFP_KERNEL); + if (err) + return err; + cond_resched(); + } + + for (se = next_se(se); se; se = next_se(se)) { + start_block = se->start_block << (PAGE_SHIFT - 9); + nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9); + + err = blkdev_issue_discard(si->bdev, start_block, + nr_blocks, GFP_KERNEL); + if (err) + break; + + cond_resched(); + } + return err; /* That will often be -EOPNOTSUPP */ +} + +static struct swap_extent * +offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset) +{ + struct swap_extent *se; + struct rb_node *rb; + + rb = sis->swap_extent_root.rb_node; + while (rb) { + se = rb_entry(rb, struct swap_extent, rb_node); + if (offset < se->start_page) + rb = rb->rb_left; + else if (offset >= se->start_page + se->nr_pages) + rb = rb->rb_right; + else + return se; + } + /* It *must* be present */ + BUG(); +} + +sector_t swap_page_sector(struct page *page) +{ + struct swap_info_struct *sis = page_swap_info(page); + struct swap_extent *se; + sector_t sector; + pgoff_t offset; + + offset = __page_file_index(page); + se = offset_to_swap_extent(sis, offset); + sector = se->start_block + (offset - se->start_page); + return sector << (PAGE_SHIFT - 9); +} + +/* + * swap allocation tell device that a cluster of swap can now be discarded, + * to allow the swap device to optimize its wear-levelling. + */ +static void discard_swap_cluster(struct swap_info_struct *si, + pgoff_t start_page, pgoff_t nr_pages) +{ + struct swap_extent *se = offset_to_swap_extent(si, start_page); + + while (nr_pages) { + pgoff_t offset = start_page - se->start_page; + sector_t start_block = se->start_block + offset; + sector_t nr_blocks = se->nr_pages - offset; + + if (nr_blocks > nr_pages) + nr_blocks = nr_pages; + start_page += nr_blocks; + nr_pages -= nr_blocks; + + start_block <<= PAGE_SHIFT - 9; + nr_blocks <<= PAGE_SHIFT - 9; + if (blkdev_issue_discard(si->bdev, start_block, + nr_blocks, GFP_NOIO)) + break; + + se = next_se(se); + } +} + +#ifdef CONFIG_THP_SWAP +#define SWAPFILE_CLUSTER HPAGE_PMD_NR + +#define swap_entry_size(size) (size) +#else +#define SWAPFILE_CLUSTER 256 + +/* + * Define swap_entry_size() as constant to let compiler to optimize + * out some code if !CONFIG_THP_SWAP + */ +#define swap_entry_size(size) 1 +#endif +#define LATENCY_LIMIT 256 + +static inline void cluster_set_flag(struct swap_cluster_info *info, + unsigned int flag) +{ + info->flags = flag; +} + +static inline unsigned int cluster_count(struct swap_cluster_info *info) +{ + return info->data; +} + +static inline void cluster_set_count(struct swap_cluster_info *info, + unsigned int c) +{ + info->data = c; +} + +static inline void cluster_set_count_flag(struct swap_cluster_info *info, + unsigned int c, unsigned int f) +{ + info->flags = f; + info->data = c; +} + +static inline unsigned int cluster_next(struct swap_cluster_info *info) +{ + return info->data; +} + +static inline void cluster_set_next(struct swap_cluster_info *info, + unsigned int n) +{ + info->data = n; +} + +static inline void cluster_set_next_flag(struct swap_cluster_info *info, + unsigned int n, unsigned int f) +{ + info->flags = f; + info->data = n; +} + +static inline bool cluster_is_free(struct swap_cluster_info *info) +{ + return info->flags & CLUSTER_FLAG_FREE; +} + +static inline bool cluster_is_null(struct swap_cluster_info *info) +{ + return info->flags & CLUSTER_FLAG_NEXT_NULL; +} + +static inline void cluster_set_null(struct swap_cluster_info *info) +{ + info->flags = CLUSTER_FLAG_NEXT_NULL; + info->data = 0; +} + +static inline bool cluster_is_huge(struct swap_cluster_info *info) +{ + if (IS_ENABLED(CONFIG_THP_SWAP)) + return info->flags & CLUSTER_FLAG_HUGE; + return false; +} + +static inline void cluster_clear_huge(struct swap_cluster_info *info) +{ + info->flags &= ~CLUSTER_FLAG_HUGE; +} + +static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si, + unsigned long offset) +{ + struct swap_cluster_info *ci; + + ci = si->cluster_info; + if (ci) { + ci += offset / SWAPFILE_CLUSTER; + spin_lock(&ci->lock); + } + return ci; +} + +static inline void unlock_cluster(struct swap_cluster_info *ci) +{ + if (ci) + spin_unlock(&ci->lock); +} + +/* + * Determine the locking method in use for this device. Return + * swap_cluster_info if SSD-style cluster-based locking is in place. + */ +static inline struct swap_cluster_info *lock_cluster_or_swap_info( + struct swap_info_struct *si, unsigned long offset) +{ + struct swap_cluster_info *ci; + + /* Try to use fine-grained SSD-style locking if available: */ + ci = lock_cluster(si, offset); + /* Otherwise, fall back to traditional, coarse locking: */ + if (!ci) + spin_lock(&si->lock); + + return ci; +} + +static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si, + struct swap_cluster_info *ci) +{ + if (ci) + unlock_cluster(ci); + else + spin_unlock(&si->lock); +} + +static inline bool cluster_list_empty(struct swap_cluster_list *list) +{ + return cluster_is_null(&list->head); +} + +static inline unsigned int cluster_list_first(struct swap_cluster_list *list) +{ + return cluster_next(&list->head); +} + +static void cluster_list_init(struct swap_cluster_list *list) +{ + cluster_set_null(&list->head); + cluster_set_null(&list->tail); +} + +static void cluster_list_add_tail(struct swap_cluster_list *list, + struct swap_cluster_info *ci, + unsigned int idx) +{ + if (cluster_list_empty(list)) { + cluster_set_next_flag(&list->head, idx, 0); + cluster_set_next_flag(&list->tail, idx, 0); + } else { + struct swap_cluster_info *ci_tail; + unsigned int tail = cluster_next(&list->tail); + + /* + * Nested cluster lock, but both cluster locks are + * only acquired when we held swap_info_struct->lock + */ + ci_tail = ci + tail; + spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING); + cluster_set_next(ci_tail, idx); + spin_unlock(&ci_tail->lock); + cluster_set_next_flag(&list->tail, idx, 0); + } +} + +static unsigned int cluster_list_del_first(struct swap_cluster_list *list, + struct swap_cluster_info *ci) +{ + unsigned int idx; + + idx = cluster_next(&list->head); + if (cluster_next(&list->tail) == idx) { + cluster_set_null(&list->head); + cluster_set_null(&list->tail); + } else + cluster_set_next_flag(&list->head, + cluster_next(&ci[idx]), 0); + + return idx; +} + +/* Add a cluster to discard list and schedule it to do discard */ +static void swap_cluster_schedule_discard(struct swap_info_struct *si, + unsigned int idx) +{ + /* + * If scan_swap_map_slots() can't find a free cluster, it will check + * si->swap_map directly. To make sure the discarding cluster isn't + * taken by scan_swap_map_slots(), mark the swap entries bad (occupied). + * It will be cleared after discard + */ + memset(si->swap_map + idx * SWAPFILE_CLUSTER, + SWAP_MAP_BAD, SWAPFILE_CLUSTER); + + cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx); + + schedule_work(&si->discard_work); +} + +static void __free_cluster(struct swap_info_struct *si, unsigned long idx) +{ + struct swap_cluster_info *ci = si->cluster_info; + + cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE); + cluster_list_add_tail(&si->free_clusters, ci, idx); +} + +/* + * Doing discard actually. After a cluster discard is finished, the cluster + * will be added to free cluster list. caller should hold si->lock. +*/ +static void swap_do_scheduled_discard(struct swap_info_struct *si) +{ + struct swap_cluster_info *info, *ci; + unsigned int idx; + + info = si->cluster_info; + + while (!cluster_list_empty(&si->discard_clusters)) { + idx = cluster_list_del_first(&si->discard_clusters, info); + spin_unlock(&si->lock); + + discard_swap_cluster(si, idx * SWAPFILE_CLUSTER, + SWAPFILE_CLUSTER); + + spin_lock(&si->lock); + ci = lock_cluster(si, idx * SWAPFILE_CLUSTER); + __free_cluster(si, idx); + memset(si->swap_map + idx * SWAPFILE_CLUSTER, + 0, SWAPFILE_CLUSTER); + unlock_cluster(ci); + } +} + +static void swap_discard_work(struct work_struct *work) +{ + struct swap_info_struct *si; + + si = container_of(work, struct swap_info_struct, discard_work); + + spin_lock(&si->lock); + swap_do_scheduled_discard(si); + spin_unlock(&si->lock); +} + +static void swap_users_ref_free(struct percpu_ref *ref) +{ + struct swap_info_struct *si; + + si = container_of(ref, struct swap_info_struct, users); + complete(&si->comp); +} + +static void alloc_cluster(struct swap_info_struct *si, unsigned long idx) +{ + struct swap_cluster_info *ci = si->cluster_info; + + VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx); + cluster_list_del_first(&si->free_clusters, ci); + cluster_set_count_flag(ci + idx, 0, 0); +} + +static void free_cluster(struct swap_info_struct *si, unsigned long idx) +{ + struct swap_cluster_info *ci = si->cluster_info + idx; + + VM_BUG_ON(cluster_count(ci) != 0); + /* + * If the swap is discardable, prepare discard the cluster + * instead of free it immediately. The cluster will be freed + * after discard. + */ + if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) == + (SWP_WRITEOK | SWP_PAGE_DISCARD)) { + swap_cluster_schedule_discard(si, idx); + return; + } + + __free_cluster(si, idx); +} + +/* + * The cluster corresponding to page_nr will be used. The cluster will be + * removed from free cluster list and its usage counter will be increased. + */ +static void inc_cluster_info_page(struct swap_info_struct *p, + struct swap_cluster_info *cluster_info, unsigned long page_nr) +{ + unsigned long idx = page_nr / SWAPFILE_CLUSTER; + + if (!cluster_info) + return; + if (cluster_is_free(&cluster_info[idx])) + alloc_cluster(p, idx); + + VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER); + cluster_set_count(&cluster_info[idx], + cluster_count(&cluster_info[idx]) + 1); +} + +/* + * The cluster corresponding to page_nr decreases one usage. If the usage + * counter becomes 0, which means no page in the cluster is in using, we can + * optionally discard the cluster and add it to free cluster list. + */ +static void dec_cluster_info_page(struct swap_info_struct *p, + struct swap_cluster_info *cluster_info, unsigned long page_nr) +{ + unsigned long idx = page_nr / SWAPFILE_CLUSTER; + + if (!cluster_info) + return; + + VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0); + cluster_set_count(&cluster_info[idx], + cluster_count(&cluster_info[idx]) - 1); + + if (cluster_count(&cluster_info[idx]) == 0) + free_cluster(p, idx); +} + +/* + * It's possible scan_swap_map_slots() uses a free cluster in the middle of free + * cluster list. Avoiding such abuse to avoid list corruption. + */ +static bool +scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si, + unsigned long offset) +{ + struct percpu_cluster *percpu_cluster; + bool conflict; + + offset /= SWAPFILE_CLUSTER; + conflict = !cluster_list_empty(&si->free_clusters) && + offset != cluster_list_first(&si->free_clusters) && + cluster_is_free(&si->cluster_info[offset]); + + if (!conflict) + return false; + + percpu_cluster = this_cpu_ptr(si->percpu_cluster); + cluster_set_null(&percpu_cluster->index); + return true; +} + +/* + * Try to get a swap entry from current cpu's swap entry pool (a cluster). This + * might involve allocating a new cluster for current CPU too. + */ +static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si, + unsigned long *offset, unsigned long *scan_base) +{ + struct percpu_cluster *cluster; + struct swap_cluster_info *ci; + unsigned long tmp, max; + +new_cluster: + cluster = this_cpu_ptr(si->percpu_cluster); + if (cluster_is_null(&cluster->index)) { + if (!cluster_list_empty(&si->free_clusters)) { + cluster->index = si->free_clusters.head; + cluster->next = cluster_next(&cluster->index) * + SWAPFILE_CLUSTER; + } else if (!cluster_list_empty(&si->discard_clusters)) { + /* + * we don't have free cluster but have some clusters in + * discarding, do discard now and reclaim them, then + * reread cluster_next_cpu since we dropped si->lock + */ + swap_do_scheduled_discard(si); + *scan_base = this_cpu_read(*si->cluster_next_cpu); + *offset = *scan_base; + goto new_cluster; + } else + return false; + } + + /* + * Other CPUs can use our cluster if they can't find a free cluster, + * check if there is still free entry in the cluster + */ + tmp = cluster->next; + max = min_t(unsigned long, si->max, + (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER); + if (tmp < max) { + ci = lock_cluster(si, tmp); + while (tmp < max) { + if (!si->swap_map[tmp]) + break; + tmp++; + } + unlock_cluster(ci); + } + if (tmp >= max) { + cluster_set_null(&cluster->index); + goto new_cluster; + } + cluster->next = tmp + 1; + *offset = tmp; + *scan_base = tmp; + return true; +} + +static void __del_from_avail_list(struct swap_info_struct *p) +{ + int nid; + + assert_spin_locked(&p->lock); + for_each_node(nid) + plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]); +} + +static void del_from_avail_list(struct swap_info_struct *p) +{ + spin_lock(&swap_avail_lock); + __del_from_avail_list(p); + spin_unlock(&swap_avail_lock); +} + +static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset, + unsigned int nr_entries) +{ + unsigned int end = offset + nr_entries - 1; + + if (offset == si->lowest_bit) + si->lowest_bit += nr_entries; + if (end == si->highest_bit) + WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries); + WRITE_ONCE(si->inuse_pages, si->inuse_pages + nr_entries); + if (si->inuse_pages == si->pages) { + si->lowest_bit = si->max; + si->highest_bit = 0; + del_from_avail_list(si); + } +} + +static void add_to_avail_list(struct swap_info_struct *p) +{ + int nid; + + spin_lock(&swap_avail_lock); + for_each_node(nid) + plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]); + spin_unlock(&swap_avail_lock); +} + +static void swap_range_free(struct swap_info_struct *si, unsigned long offset, + unsigned int nr_entries) +{ + unsigned long begin = offset; + unsigned long end = offset + nr_entries - 1; + void (*swap_slot_free_notify)(struct block_device *, unsigned long); + + if (offset < si->lowest_bit) + si->lowest_bit = offset; + if (end > si->highest_bit) { + bool was_full = !si->highest_bit; + + WRITE_ONCE(si->highest_bit, end); + if (was_full && (si->flags & SWP_WRITEOK)) + add_to_avail_list(si); + } + atomic_long_add(nr_entries, &nr_swap_pages); + WRITE_ONCE(si->inuse_pages, si->inuse_pages - nr_entries); + if (si->flags & SWP_BLKDEV) + swap_slot_free_notify = + si->bdev->bd_disk->fops->swap_slot_free_notify; + else + swap_slot_free_notify = NULL; + while (offset <= end) { + arch_swap_invalidate_page(si->type, offset); + zswap_invalidate(si->type, offset); + if (swap_slot_free_notify) + swap_slot_free_notify(si->bdev, offset); + offset++; + } + clear_shadow_from_swap_cache(si->type, begin, end); +} + +static void set_cluster_next(struct swap_info_struct *si, unsigned long next) +{ + unsigned long prev; + + if (!(si->flags & SWP_SOLIDSTATE)) { + si->cluster_next = next; + return; + } + + prev = this_cpu_read(*si->cluster_next_cpu); + /* + * Cross the swap address space size aligned trunk, choose + * another trunk randomly to avoid lock contention on swap + * address space if possible. + */ + if ((prev >> SWAP_ADDRESS_SPACE_SHIFT) != + (next >> SWAP_ADDRESS_SPACE_SHIFT)) { + /* No free swap slots available */ + if (si->highest_bit <= si->lowest_bit) + return; + next = get_random_u32_inclusive(si->lowest_bit, si->highest_bit); + next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES); + next = max_t(unsigned int, next, si->lowest_bit); + } + this_cpu_write(*si->cluster_next_cpu, next); +} + +static bool swap_offset_available_and_locked(struct swap_info_struct *si, + unsigned long offset) +{ + if (data_race(!si->swap_map[offset])) { + spin_lock(&si->lock); + return true; + } + + if (vm_swap_full() && READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) { + spin_lock(&si->lock); + return true; + } + + return false; +} + +static int scan_swap_map_slots(struct swap_info_struct *si, + unsigned char usage, int nr, + swp_entry_t slots[]) +{ + struct swap_cluster_info *ci; + unsigned long offset; + unsigned long scan_base; + unsigned long last_in_cluster = 0; + int latency_ration = LATENCY_LIMIT; + int n_ret = 0; + bool scanned_many = false; + + /* + * We try to cluster swap pages by allocating them sequentially + * in swap. Once we've allocated SWAPFILE_CLUSTER pages this + * way, however, we resort to first-free allocation, starting + * a new cluster. This prevents us from scattering swap pages + * all over the entire swap partition, so that we reduce + * overall disk seek times between swap pages. -- sct + * But we do now try to find an empty cluster. -Andrea + * And we let swap pages go all over an SSD partition. Hugh + */ + + si->flags += SWP_SCANNING; + /* + * Use percpu scan base for SSD to reduce lock contention on + * cluster and swap cache. For HDD, sequential access is more + * important. + */ + if (si->flags & SWP_SOLIDSTATE) + scan_base = this_cpu_read(*si->cluster_next_cpu); + else + scan_base = si->cluster_next; + offset = scan_base; + + /* SSD algorithm */ + if (si->cluster_info) { + if (!scan_swap_map_try_ssd_cluster(si, &offset, &scan_base)) + goto scan; + } else if (unlikely(!si->cluster_nr--)) { + if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) { + si->cluster_nr = SWAPFILE_CLUSTER - 1; + goto checks; + } + + spin_unlock(&si->lock); + + /* + * If seek is expensive, start searching for new cluster from + * start of partition, to minimize the span of allocated swap. + * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info + * case, just handled by scan_swap_map_try_ssd_cluster() above. + */ + scan_base = offset = si->lowest_bit; + last_in_cluster = offset + SWAPFILE_CLUSTER - 1; + + /* Locate the first empty (unaligned) cluster */ + for (; last_in_cluster <= si->highest_bit; offset++) { + if (si->swap_map[offset]) + last_in_cluster = offset + SWAPFILE_CLUSTER; + else if (offset == last_in_cluster) { + spin_lock(&si->lock); + offset -= SWAPFILE_CLUSTER - 1; + si->cluster_next = offset; + si->cluster_nr = SWAPFILE_CLUSTER - 1; + goto checks; + } + if (unlikely(--latency_ration < 0)) { + cond_resched(); + latency_ration = LATENCY_LIMIT; + } + } + + offset = scan_base; + spin_lock(&si->lock); + si->cluster_nr = SWAPFILE_CLUSTER - 1; + } + +checks: + if (si->cluster_info) { + while (scan_swap_map_ssd_cluster_conflict(si, offset)) { + /* take a break if we already got some slots */ + if (n_ret) + goto done; + if (!scan_swap_map_try_ssd_cluster(si, &offset, + &scan_base)) + goto scan; + } + } + if (!(si->flags & SWP_WRITEOK)) + goto no_page; + if (!si->highest_bit) + goto no_page; + if (offset > si->highest_bit) + scan_base = offset = si->lowest_bit; + + ci = lock_cluster(si, offset); + /* reuse swap entry of cache-only swap if not busy. */ + if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { + int swap_was_freed; + unlock_cluster(ci); + spin_unlock(&si->lock); + swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY); + spin_lock(&si->lock); + /* entry was freed successfully, try to use this again */ + if (swap_was_freed) + goto checks; + goto scan; /* check next one */ + } + + if (si->swap_map[offset]) { + unlock_cluster(ci); + if (!n_ret) + goto scan; + else + goto done; + } + WRITE_ONCE(si->swap_map[offset], usage); + inc_cluster_info_page(si, si->cluster_info, offset); + unlock_cluster(ci); + + swap_range_alloc(si, offset, 1); + slots[n_ret++] = swp_entry(si->type, offset); + + /* got enough slots or reach max slots? */ + if ((n_ret == nr) || (offset >= si->highest_bit)) + goto done; + + /* search for next available slot */ + + /* time to take a break? */ + if (unlikely(--latency_ration < 0)) { + if (n_ret) + goto done; + spin_unlock(&si->lock); + cond_resched(); + spin_lock(&si->lock); + latency_ration = LATENCY_LIMIT; + } + + /* try to get more slots in cluster */ + if (si->cluster_info) { + if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base)) + goto checks; + } else if (si->cluster_nr && !si->swap_map[++offset]) { + /* non-ssd case, still more slots in cluster? */ + --si->cluster_nr; + goto checks; + } + + /* + * Even if there's no free clusters available (fragmented), + * try to scan a little more quickly with lock held unless we + * have scanned too many slots already. + */ + if (!scanned_many) { + unsigned long scan_limit; + + if (offset < scan_base) + scan_limit = scan_base; + else + scan_limit = si->highest_bit; + for (; offset <= scan_limit && --latency_ration > 0; + offset++) { + if (!si->swap_map[offset]) + goto checks; + } + } + +done: + set_cluster_next(si, offset + 1); + si->flags -= SWP_SCANNING; + return n_ret; + +scan: + spin_unlock(&si->lock); + while (++offset <= READ_ONCE(si->highest_bit)) { + if (unlikely(--latency_ration < 0)) { + cond_resched(); + latency_ration = LATENCY_LIMIT; + scanned_many = true; + } + if (swap_offset_available_and_locked(si, offset)) + goto checks; + } + offset = si->lowest_bit; + while (offset < scan_base) { + if (unlikely(--latency_ration < 0)) { + cond_resched(); + latency_ration = LATENCY_LIMIT; + scanned_many = true; + } + if (swap_offset_available_and_locked(si, offset)) + goto checks; + offset++; + } + spin_lock(&si->lock); + +no_page: + si->flags -= SWP_SCANNING; + return n_ret; +} + +static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot) +{ + unsigned long idx; + struct swap_cluster_info *ci; + unsigned long offset; + + /* + * Should not even be attempting cluster allocations when huge + * page swap is disabled. Warn and fail the allocation. + */ + if (!IS_ENABLED(CONFIG_THP_SWAP)) { + VM_WARN_ON_ONCE(1); + return 0; + } + + if (cluster_list_empty(&si->free_clusters)) + return 0; + + idx = cluster_list_first(&si->free_clusters); + offset = idx * SWAPFILE_CLUSTER; + ci = lock_cluster(si, offset); + alloc_cluster(si, idx); + cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE); + + memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER); + unlock_cluster(ci); + swap_range_alloc(si, offset, SWAPFILE_CLUSTER); + *slot = swp_entry(si->type, offset); + + return 1; +} + +static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx) +{ + unsigned long offset = idx * SWAPFILE_CLUSTER; + struct swap_cluster_info *ci; + + ci = lock_cluster(si, offset); + memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER); + cluster_set_count_flag(ci, 0, 0); + free_cluster(si, idx); + unlock_cluster(ci); + swap_range_free(si, offset, SWAPFILE_CLUSTER); +} + +int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size) +{ + unsigned long size = swap_entry_size(entry_size); + struct swap_info_struct *si, *next; + long avail_pgs; + int n_ret = 0; + int node; + + /* Only single cluster request supported */ + WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER); + + spin_lock(&swap_avail_lock); + + avail_pgs = atomic_long_read(&nr_swap_pages) / size; + if (avail_pgs <= 0) { + spin_unlock(&swap_avail_lock); + goto noswap; + } + + n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs); + + atomic_long_sub(n_goal * size, &nr_swap_pages); + +start_over: + node = numa_node_id(); + plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) { + /* requeue si to after same-priority siblings */ + plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]); + spin_unlock(&swap_avail_lock); + spin_lock(&si->lock); + if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) { + spin_lock(&swap_avail_lock); + if (plist_node_empty(&si->avail_lists[node])) { + spin_unlock(&si->lock); + goto nextsi; + } + WARN(!si->highest_bit, + "swap_info %d in list but !highest_bit\n", + si->type); + WARN(!(si->flags & SWP_WRITEOK), + "swap_info %d in list but !SWP_WRITEOK\n", + si->type); + __del_from_avail_list(si); + spin_unlock(&si->lock); + goto nextsi; + } + if (size == SWAPFILE_CLUSTER) { + if (si->flags & SWP_BLKDEV) + n_ret = swap_alloc_cluster(si, swp_entries); + } else + n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE, + n_goal, swp_entries); + spin_unlock(&si->lock); + if (n_ret || size == SWAPFILE_CLUSTER) + goto check_out; + cond_resched(); + + spin_lock(&swap_avail_lock); +nextsi: + /* + * if we got here, it's likely that si was almost full before, + * and since scan_swap_map_slots() can drop the si->lock, + * multiple callers probably all tried to get a page from the + * same si and it filled up before we could get one; or, the si + * filled up between us dropping swap_avail_lock and taking + * si->lock. Since we dropped the swap_avail_lock, the + * swap_avail_head list may have been modified; so if next is + * still in the swap_avail_head list then try it, otherwise + * start over if we have not gotten any slots. + */ + if (plist_node_empty(&next->avail_lists[node])) + goto start_over; + } + + spin_unlock(&swap_avail_lock); + +check_out: + if (n_ret < n_goal) + atomic_long_add((long)(n_goal - n_ret) * size, + &nr_swap_pages); +noswap: + return n_ret; +} + +static struct swap_info_struct *_swap_info_get(swp_entry_t entry) +{ + struct swap_info_struct *p; + unsigned long offset; + + if (!entry.val) + goto out; + p = swp_swap_info(entry); + if (!p) + goto bad_nofile; + if (data_race(!(p->flags & SWP_USED))) + goto bad_device; + offset = swp_offset(entry); + if (offset >= p->max) + goto bad_offset; + if (data_race(!p->swap_map[swp_offset(entry)])) + goto bad_free; + return p; + +bad_free: + pr_err("%s: %s%08lx\n", __func__, Unused_offset, entry.val); + goto out; +bad_offset: + pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val); + goto out; +bad_device: + pr_err("%s: %s%08lx\n", __func__, Unused_file, entry.val); + goto out; +bad_nofile: + pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val); +out: + return NULL; +} + +static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry, + struct swap_info_struct *q) +{ + struct swap_info_struct *p; + + p = _swap_info_get(entry); + + if (p != q) { + if (q != NULL) + spin_unlock(&q->lock); + if (p != NULL) + spin_lock(&p->lock); + } + return p; +} + +static unsigned char __swap_entry_free_locked(struct swap_info_struct *p, + unsigned long offset, + unsigned char usage) +{ + unsigned char count; + unsigned char has_cache; + + count = p->swap_map[offset]; + + has_cache = count & SWAP_HAS_CACHE; + count &= ~SWAP_HAS_CACHE; + + if (usage == SWAP_HAS_CACHE) { + VM_BUG_ON(!has_cache); + has_cache = 0; + } else if (count == SWAP_MAP_SHMEM) { + /* + * Or we could insist on shmem.c using a special + * swap_shmem_free() and free_shmem_swap_and_cache()... + */ + count = 0; + } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { + if (count == COUNT_CONTINUED) { + if (swap_count_continued(p, offset, count)) + count = SWAP_MAP_MAX | COUNT_CONTINUED; + else + count = SWAP_MAP_MAX; + } else + count--; + } + + usage = count | has_cache; + if (usage) + WRITE_ONCE(p->swap_map[offset], usage); + else + WRITE_ONCE(p->swap_map[offset], SWAP_HAS_CACHE); + + return usage; +} + +/* + * When we get a swap entry, if there aren't some other ways to + * prevent swapoff, such as the folio in swap cache is locked, page + * table lock is held, etc., the swap entry may become invalid because + * of swapoff. Then, we need to enclose all swap related functions + * with get_swap_device() and put_swap_device(), unless the swap + * functions call get/put_swap_device() by themselves. + * + * Check whether swap entry is valid in the swap device. If so, + * return pointer to swap_info_struct, and keep the swap entry valid + * via preventing the swap device from being swapoff, until + * put_swap_device() is called. Otherwise return NULL. + * + * Notice that swapoff or swapoff+swapon can still happen before the + * percpu_ref_tryget_live() in get_swap_device() or after the + * percpu_ref_put() in put_swap_device() if there isn't any other way + * to prevent swapoff. The caller must be prepared for that. For + * example, the following situation is possible. + * + * CPU1 CPU2 + * do_swap_page() + * ... swapoff+swapon + * __read_swap_cache_async() + * swapcache_prepare() + * __swap_duplicate() + * // check swap_map + * // verify PTE not changed + * + * In __swap_duplicate(), the swap_map need to be checked before + * changing partly because the specified swap entry may be for another + * swap device which has been swapoff. And in do_swap_page(), after + * the page is read from the swap device, the PTE is verified not + * changed with the page table locked to check whether the swap device + * has been swapoff or swapoff+swapon. + */ +struct swap_info_struct *get_swap_device(swp_entry_t entry) +{ + struct swap_info_struct *si; + unsigned long offset; + + if (!entry.val) + goto out; + si = swp_swap_info(entry); + if (!si) + goto bad_nofile; + if (!percpu_ref_tryget_live(&si->users)) + goto out; + /* + * Guarantee the si->users are checked before accessing other + * fields of swap_info_struct. + * + * Paired with the spin_unlock() after setup_swap_info() in + * enable_swap_info(). + */ + smp_rmb(); + offset = swp_offset(entry); + if (offset >= si->max) + goto put_out; + + return si; +bad_nofile: + pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val); +out: + return NULL; +put_out: + pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val); + percpu_ref_put(&si->users); + return NULL; +} + +static unsigned char __swap_entry_free(struct swap_info_struct *p, + swp_entry_t entry) +{ + struct swap_cluster_info *ci; + unsigned long offset = swp_offset(entry); + unsigned char usage; + + ci = lock_cluster_or_swap_info(p, offset); + usage = __swap_entry_free_locked(p, offset, 1); + unlock_cluster_or_swap_info(p, ci); + if (!usage) + free_swap_slot(entry); + + return usage; +} + +static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry) +{ + struct swap_cluster_info *ci; + unsigned long offset = swp_offset(entry); + unsigned char count; + + ci = lock_cluster(p, offset); + count = p->swap_map[offset]; + VM_BUG_ON(count != SWAP_HAS_CACHE); + p->swap_map[offset] = 0; + dec_cluster_info_page(p, p->cluster_info, offset); + unlock_cluster(ci); + + mem_cgroup_uncharge_swap(entry, 1); + swap_range_free(p, offset, 1); +} + +/* + * Caller has made sure that the swap device corresponding to entry + * is still around or has not been recycled. + */ +void swap_free(swp_entry_t entry) +{ + struct swap_info_struct *p; + + p = _swap_info_get(entry); + if (p) + __swap_entry_free(p, entry); +} + +/* + * Called after dropping swapcache to decrease refcnt to swap entries. + */ +void put_swap_folio(struct folio *folio, swp_entry_t entry) +{ + unsigned long offset = swp_offset(entry); + unsigned long idx = offset / SWAPFILE_CLUSTER; + struct swap_cluster_info *ci; + struct swap_info_struct *si; + unsigned char *map; + unsigned int i, free_entries = 0; + unsigned char val; + int size = swap_entry_size(folio_nr_pages(folio)); + + si = _swap_info_get(entry); + if (!si) + return; + + ci = lock_cluster_or_swap_info(si, offset); + if (size == SWAPFILE_CLUSTER) { + VM_BUG_ON(!cluster_is_huge(ci)); + map = si->swap_map + offset; + for (i = 0; i < SWAPFILE_CLUSTER; i++) { + val = map[i]; + VM_BUG_ON(!(val & SWAP_HAS_CACHE)); + if (val == SWAP_HAS_CACHE) + free_entries++; + } + cluster_clear_huge(ci); + if (free_entries == SWAPFILE_CLUSTER) { + unlock_cluster_or_swap_info(si, ci); + spin_lock(&si->lock); + mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER); + swap_free_cluster(si, idx); + spin_unlock(&si->lock); + return; + } + } + for (i = 0; i < size; i++, entry.val++) { + if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) { + unlock_cluster_or_swap_info(si, ci); + free_swap_slot(entry); + if (i == size - 1) + return; + lock_cluster_or_swap_info(si, offset); + } + } + unlock_cluster_or_swap_info(si, ci); +} + +#ifdef CONFIG_THP_SWAP +int split_swap_cluster(swp_entry_t entry) +{ + struct swap_info_struct *si; + struct swap_cluster_info *ci; + unsigned long offset = swp_offset(entry); + + si = _swap_info_get(entry); + if (!si) + return -EBUSY; + ci = lock_cluster(si, offset); + cluster_clear_huge(ci); + unlock_cluster(ci); + return 0; +} +#endif + +static int swp_entry_cmp(const void *ent1, const void *ent2) +{ + const swp_entry_t *e1 = ent1, *e2 = ent2; + + return (int)swp_type(*e1) - (int)swp_type(*e2); +} + +void swapcache_free_entries(swp_entry_t *entries, int n) +{ + struct swap_info_struct *p, *prev; + int i; + + if (n <= 0) + return; + + prev = NULL; + p = NULL; + + /* + * Sort swap entries by swap device, so each lock is only taken once. + * nr_swapfiles isn't absolutely correct, but the overhead of sort() is + * so low that it isn't necessary to optimize further. + */ + if (nr_swapfiles > 1) + sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL); + for (i = 0; i < n; ++i) { + p = swap_info_get_cont(entries[i], prev); + if (p) + swap_entry_free(p, entries[i]); + prev = p; + } + if (p) + spin_unlock(&p->lock); +} + +int __swap_count(swp_entry_t entry) +{ + struct swap_info_struct *si = swp_swap_info(entry); + pgoff_t offset = swp_offset(entry); + + return swap_count(si->swap_map[offset]); +} + +/* + * How many references to @entry are currently swapped out? + * This does not give an exact answer when swap count is continued, + * but does include the high COUNT_CONTINUED flag to allow for that. + */ +int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry) +{ + pgoff_t offset = swp_offset(entry); + struct swap_cluster_info *ci; + int count; + + ci = lock_cluster_or_swap_info(si, offset); + count = swap_count(si->swap_map[offset]); + unlock_cluster_or_swap_info(si, ci); + return count; +} + +/* + * How many references to @entry are currently swapped out? + * This considers COUNT_CONTINUED so it returns exact answer. + */ +int swp_swapcount(swp_entry_t entry) +{ + int count, tmp_count, n; + struct swap_info_struct *p; + struct swap_cluster_info *ci; + struct page *page; + pgoff_t offset; + unsigned char *map; + + p = _swap_info_get(entry); + if (!p) + return 0; + + offset = swp_offset(entry); + + ci = lock_cluster_or_swap_info(p, offset); + + count = swap_count(p->swap_map[offset]); + if (!(count & COUNT_CONTINUED)) + goto out; + + count &= ~COUNT_CONTINUED; + n = SWAP_MAP_MAX + 1; + + page = vmalloc_to_page(p->swap_map + offset); + offset &= ~PAGE_MASK; + VM_BUG_ON(page_private(page) != SWP_CONTINUED); + + do { + page = list_next_entry(page, lru); + map = kmap_atomic(page); + tmp_count = map[offset]; + kunmap_atomic(map); + + count += (tmp_count & ~COUNT_CONTINUED) * n; + n *= (SWAP_CONT_MAX + 1); + } while (tmp_count & COUNT_CONTINUED); +out: + unlock_cluster_or_swap_info(p, ci); + return count; +} + +static bool swap_page_trans_huge_swapped(struct swap_info_struct *si, + swp_entry_t entry) +{ + struct swap_cluster_info *ci; + unsigned char *map = si->swap_map; + unsigned long roffset = swp_offset(entry); + unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER); + int i; + bool ret = false; + + ci = lock_cluster_or_swap_info(si, offset); + if (!ci || !cluster_is_huge(ci)) { + if (swap_count(map[roffset])) + ret = true; + goto unlock_out; + } + for (i = 0; i < SWAPFILE_CLUSTER; i++) { + if (swap_count(map[offset + i])) { + ret = true; + break; + } + } +unlock_out: + unlock_cluster_or_swap_info(si, ci); + return ret; +} + +static bool folio_swapped(struct folio *folio) +{ + swp_entry_t entry = folio->swap; + struct swap_info_struct *si = _swap_info_get(entry); + + if (!si) + return false; + + if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!folio_test_large(folio))) + return swap_swapcount(si, entry) != 0; + + return swap_page_trans_huge_swapped(si, entry); +} + +/** + * folio_free_swap() - Free the swap space used for this folio. + * @folio: The folio to remove. + * + * If swap is getting full, or if there are no more mappings of this folio, + * then call folio_free_swap to free its swap space. + * + * Return: true if we were able to release the swap space. + */ +bool folio_free_swap(struct folio *folio) +{ + VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); + + if (!folio_test_swapcache(folio)) + return false; + if (folio_test_writeback(folio)) + return false; + if (folio_swapped(folio)) + return false; + + /* + * Once hibernation has begun to create its image of memory, + * there's a danger that one of the calls to folio_free_swap() + * - most probably a call from __try_to_reclaim_swap() while + * hibernation is allocating its own swap pages for the image, + * but conceivably even a call from memory reclaim - will free + * the swap from a folio which has already been recorded in the + * image as a clean swapcache folio, and then reuse its swap for + * another page of the image. On waking from hibernation, the + * original folio might be freed under memory pressure, then + * later read back in from swap, now with the wrong data. + * + * Hibernation suspends storage while it is writing the image + * to disk so check that here. + */ + if (pm_suspended_storage()) + return false; + + delete_from_swap_cache(folio); + folio_set_dirty(folio); + return true; +} + +/* + * Free the swap entry like above, but also try to + * free the page cache entry if it is the last user. + */ +int free_swap_and_cache(swp_entry_t entry) +{ + struct swap_info_struct *p; + unsigned char count; + + if (non_swap_entry(entry)) + return 1; + + p = _swap_info_get(entry); + if (p) { + count = __swap_entry_free(p, entry); + if (count == SWAP_HAS_CACHE && + !swap_page_trans_huge_swapped(p, entry)) + __try_to_reclaim_swap(p, swp_offset(entry), + TTRS_UNMAPPED | TTRS_FULL); + } + return p != NULL; +} + +#ifdef CONFIG_HIBERNATION + +swp_entry_t get_swap_page_of_type(int type) +{ + struct swap_info_struct *si = swap_type_to_swap_info(type); + swp_entry_t entry = {0}; + + if (!si) + goto fail; + + /* This is called for allocating swap entry, not cache */ + spin_lock(&si->lock); + if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry)) + atomic_long_dec(&nr_swap_pages); + spin_unlock(&si->lock); +fail: + return entry; +} + +/* + * Find the swap type that corresponds to given device (if any). + * + * @offset - number of the PAGE_SIZE-sized block of the device, starting + * from 0, in which the swap header is expected to be located. + * + * This is needed for the suspend to disk (aka swsusp). + */ +int swap_type_of(dev_t device, sector_t offset) +{ + int type; + + if (!device) + return -1; + + spin_lock(&swap_lock); + for (type = 0; type < nr_swapfiles; type++) { + struct swap_info_struct *sis = swap_info[type]; + + if (!(sis->flags & SWP_WRITEOK)) + continue; + + if (device == sis->bdev->bd_dev) { + struct swap_extent *se = first_se(sis); + + if (se->start_block == offset) { + spin_unlock(&swap_lock); + return type; + } + } + } + spin_unlock(&swap_lock); + return -ENODEV; +} + +int find_first_swap(dev_t *device) +{ + int type; + + spin_lock(&swap_lock); + for (type = 0; type < nr_swapfiles; type++) { + struct swap_info_struct *sis = swap_info[type]; + + if (!(sis->flags & SWP_WRITEOK)) + continue; + *device = sis->bdev->bd_dev; + spin_unlock(&swap_lock); + return type; + } + spin_unlock(&swap_lock); + return -ENODEV; +} + +/* + * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev + * corresponding to given index in swap_info (swap type). + */ +sector_t swapdev_block(int type, pgoff_t offset) +{ + struct swap_info_struct *si = swap_type_to_swap_info(type); + struct swap_extent *se; + + if (!si || !(si->flags & SWP_WRITEOK)) + return 0; + se = offset_to_swap_extent(si, offset); + return se->start_block + (offset - se->start_page); +} + +/* + * Return either the total number of swap pages of given type, or the number + * of free pages of that type (depending on @free) + * + * This is needed for software suspend + */ +unsigned int count_swap_pages(int type, int free) +{ + unsigned int n = 0; + + spin_lock(&swap_lock); + if ((unsigned int)type < nr_swapfiles) { + struct swap_info_struct *sis = swap_info[type]; + + spin_lock(&sis->lock); + if (sis->flags & SWP_WRITEOK) { + n = sis->pages; + if (free) + n -= sis->inuse_pages; + } + spin_unlock(&sis->lock); + } + spin_unlock(&swap_lock); + return n; +} +#endif /* CONFIG_HIBERNATION */ + +static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte) +{ + return pte_same(pte_swp_clear_flags(pte), swp_pte); +} + +/* + * No need to decide whether this PTE shares the swap entry with others, + * just let do_wp_page work it out if a write is requested later - to + * force COW, vm_page_prot omits write permission from any private vma. + */ +static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, + unsigned long addr, swp_entry_t entry, struct folio *folio) +{ + struct page *page = folio_file_page(folio, swp_offset(entry)); + struct page *swapcache; + spinlock_t *ptl; + pte_t *pte, new_pte, old_pte; + bool hwpoisoned = PageHWPoison(page); + int ret = 1; + + swapcache = page; + page = ksm_might_need_to_copy(page, vma, addr); + if (unlikely(!page)) + return -ENOMEM; + else if (unlikely(PTR_ERR(page) == -EHWPOISON)) + hwpoisoned = true; + + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + if (unlikely(!pte || !pte_same_as_swp(ptep_get(pte), + swp_entry_to_pte(entry)))) { + ret = 0; + goto out; + } + + old_pte = ptep_get(pte); + + if (unlikely(hwpoisoned || !PageUptodate(page))) { + swp_entry_t swp_entry; + + dec_mm_counter(vma->vm_mm, MM_SWAPENTS); + if (hwpoisoned) { + swp_entry = make_hwpoison_entry(swapcache); + page = swapcache; + } else { + swp_entry = make_poisoned_swp_entry(); + } + new_pte = swp_entry_to_pte(swp_entry); + ret = 0; + goto setpte; + } + + /* + * Some architectures may have to restore extra metadata to the page + * when reading from swap. This metadata may be indexed by swap entry + * so this must be called before swap_free(). + */ + arch_swap_restore(entry, page_folio(page)); + + /* See do_swap_page() */ + BUG_ON(!PageAnon(page) && PageMappedToDisk(page)); + BUG_ON(PageAnon(page) && PageAnonExclusive(page)); + + dec_mm_counter(vma->vm_mm, MM_SWAPENTS); + inc_mm_counter(vma->vm_mm, MM_ANONPAGES); + get_page(page); + if (page == swapcache) { + rmap_t rmap_flags = RMAP_NONE; + + /* + * See do_swap_page(): PageWriteback() would be problematic. + * However, we do a wait_on_page_writeback() just before this + * call and have the page locked. + */ + VM_BUG_ON_PAGE(PageWriteback(page), page); + if (pte_swp_exclusive(old_pte)) + rmap_flags |= RMAP_EXCLUSIVE; + + page_add_anon_rmap(page, vma, addr, rmap_flags); + } else { /* ksm created a completely new copy */ + page_add_new_anon_rmap(page, vma, addr); + lru_cache_add_inactive_or_unevictable(page, vma); + } + new_pte = pte_mkold(mk_pte(page, vma->vm_page_prot)); + if (pte_swp_soft_dirty(old_pte)) + new_pte = pte_mksoft_dirty(new_pte); + if (pte_swp_uffd_wp(old_pte)) + new_pte = pte_mkuffd_wp(new_pte); +setpte: + set_pte_at(vma->vm_mm, addr, pte, new_pte); + swap_free(entry); +out: + if (pte) + pte_unmap_unlock(pte, ptl); + if (page != swapcache) { + unlock_page(page); + put_page(page); + } + return ret; +} + +static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, + unsigned long addr, unsigned long end, + unsigned int type) +{ + pte_t *pte = NULL; + struct swap_info_struct *si; + + si = swap_info[type]; + do { + struct folio *folio; + unsigned long offset; + unsigned char swp_count; + swp_entry_t entry; + int ret; + pte_t ptent; + + if (!pte++) { + pte = pte_offset_map(pmd, addr); + if (!pte) + break; + } + + ptent = ptep_get_lockless(pte); + + if (!is_swap_pte(ptent)) + continue; + + entry = pte_to_swp_entry(ptent); + if (swp_type(entry) != type) + continue; + + offset = swp_offset(entry); + pte_unmap(pte); + pte = NULL; + + folio = swap_cache_get_folio(entry, vma, addr); + if (!folio) { + struct page *page; + struct vm_fault vmf = { + .vma = vma, + .address = addr, + .real_address = addr, + .pmd = pmd, + }; + + page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, + &vmf); + if (page) + folio = page_folio(page); + } + if (!folio) { + swp_count = READ_ONCE(si->swap_map[offset]); + if (swp_count == 0 || swp_count == SWAP_MAP_BAD) + continue; + return -ENOMEM; + } + + folio_lock(folio); + folio_wait_writeback(folio); + ret = unuse_pte(vma, pmd, addr, entry, folio); + if (ret < 0) { + folio_unlock(folio); + folio_put(folio); + return ret; + } + + folio_free_swap(folio); + folio_unlock(folio); + folio_put(folio); + } while (addr += PAGE_SIZE, addr != end); + + if (pte) + pte_unmap(pte); + return 0; +} + +static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, + unsigned long addr, unsigned long end, + unsigned int type) +{ + pmd_t *pmd; + unsigned long next; + int ret; + + pmd = pmd_offset(pud, addr); + do { + cond_resched(); + next = pmd_addr_end(addr, end); + ret = unuse_pte_range(vma, pmd, addr, next, type); + if (ret) + return ret; + } while (pmd++, addr = next, addr != end); + return 0; +} + +static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d, + unsigned long addr, unsigned long end, + unsigned int type) +{ + pud_t *pud; + unsigned long next; + int ret; + + pud = pud_offset(p4d, addr); + do { + next = pud_addr_end(addr, end); + if (pud_none_or_clear_bad(pud)) + continue; + ret = unuse_pmd_range(vma, pud, addr, next, type); + if (ret) + return ret; + } while (pud++, addr = next, addr != end); + return 0; +} + +static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd, + unsigned long addr, unsigned long end, + unsigned int type) +{ + p4d_t *p4d; + unsigned long next; + int ret; + + p4d = p4d_offset(pgd, addr); + do { + next = p4d_addr_end(addr, end); + if (p4d_none_or_clear_bad(p4d)) + continue; + ret = unuse_pud_range(vma, p4d, addr, next, type); + if (ret) + return ret; + } while (p4d++, addr = next, addr != end); + return 0; +} + +static int unuse_vma(struct vm_area_struct *vma, unsigned int type) +{ + pgd_t *pgd; + unsigned long addr, end, next; + int ret; + + addr = vma->vm_start; + end = vma->vm_end; + + pgd = pgd_offset(vma->vm_mm, addr); + do { + next = pgd_addr_end(addr, end); + if (pgd_none_or_clear_bad(pgd)) + continue; + ret = unuse_p4d_range(vma, pgd, addr, next, type); + if (ret) + return ret; + } while (pgd++, addr = next, addr != end); + return 0; +} + +static int unuse_mm(struct mm_struct *mm, unsigned int type) +{ + struct vm_area_struct *vma; + int ret = 0; + VMA_ITERATOR(vmi, mm, 0); + + mmap_read_lock(mm); + for_each_vma(vmi, vma) { + if (vma->anon_vma) { + ret = unuse_vma(vma, type); + if (ret) + break; + } + + cond_resched(); + } + mmap_read_unlock(mm); + return ret; +} + +/* + * Scan swap_map from current position to next entry still in use. + * Return 0 if there are no inuse entries after prev till end of + * the map. + */ +static unsigned int find_next_to_unuse(struct swap_info_struct *si, + unsigned int prev) +{ + unsigned int i; + unsigned char count; + + /* + * No need for swap_lock here: we're just looking + * for whether an entry is in use, not modifying it; false + * hits are okay, and sys_swapoff() has already prevented new + * allocations from this area (while holding swap_lock). + */ + for (i = prev + 1; i < si->max; i++) { + count = READ_ONCE(si->swap_map[i]); + if (count && swap_count(count) != SWAP_MAP_BAD) + break; + if ((i % LATENCY_LIMIT) == 0) + cond_resched(); + } + + if (i == si->max) + i = 0; + + return i; +} + +static int try_to_unuse(unsigned int type) +{ + struct mm_struct *prev_mm; + struct mm_struct *mm; + struct list_head *p; + int retval = 0; + struct swap_info_struct *si = swap_info[type]; + struct folio *folio; + swp_entry_t entry; + unsigned int i; + + if (!READ_ONCE(si->inuse_pages)) + return 0; + +retry: + retval = shmem_unuse(type); + if (retval) + return retval; + + prev_mm = &init_mm; + mmget(prev_mm); + + spin_lock(&mmlist_lock); + p = &init_mm.mmlist; + while (READ_ONCE(si->inuse_pages) && + !signal_pending(current) && + (p = p->next) != &init_mm.mmlist) { + + mm = list_entry(p, struct mm_struct, mmlist); + if (!mmget_not_zero(mm)) + continue; + spin_unlock(&mmlist_lock); + mmput(prev_mm); + prev_mm = mm; + retval = unuse_mm(mm, type); + if (retval) { + mmput(prev_mm); + return retval; + } + + /* + * Make sure that we aren't completely killing + * interactive performance. + */ + cond_resched(); + spin_lock(&mmlist_lock); + } + spin_unlock(&mmlist_lock); + + mmput(prev_mm); + + i = 0; + while (READ_ONCE(si->inuse_pages) && + !signal_pending(current) && + (i = find_next_to_unuse(si, i)) != 0) { + + entry = swp_entry(type, i); + folio = filemap_get_folio(swap_address_space(entry), i); + if (IS_ERR(folio)) + continue; + + /* + * It is conceivable that a racing task removed this folio from + * swap cache just before we acquired the page lock. The folio + * might even be back in swap cache on another swap area. But + * that is okay, folio_free_swap() only removes stale folios. + */ + folio_lock(folio); + folio_wait_writeback(folio); + folio_free_swap(folio); + folio_unlock(folio); + folio_put(folio); + } + + /* + * Lets check again to see if there are still swap entries in the map. + * If yes, we would need to do retry the unuse logic again. + * Under global memory pressure, swap entries can be reinserted back + * into process space after the mmlist loop above passes over them. + * + * Limit the number of retries? No: when mmget_not_zero() + * above fails, that mm is likely to be freeing swap from + * exit_mmap(), which proceeds at its own independent pace; + * and even shmem_writepage() could have been preempted after + * folio_alloc_swap(), temporarily hiding that swap. It's easy + * and robust (though cpu-intensive) just to keep retrying. + */ + if (READ_ONCE(si->inuse_pages)) { + if (!signal_pending(current)) + goto retry; + return -EINTR; + } + + return 0; +} + +/* + * After a successful try_to_unuse, if no swap is now in use, we know + * we can empty the mmlist. swap_lock must be held on entry and exit. + * Note that mmlist_lock nests inside swap_lock, and an mm must be + * added to the mmlist just after page_duplicate - before would be racy. + */ +static void drain_mmlist(void) +{ + struct list_head *p, *next; + unsigned int type; + + for (type = 0; type < nr_swapfiles; type++) + if (swap_info[type]->inuse_pages) + return; + spin_lock(&mmlist_lock); + list_for_each_safe(p, next, &init_mm.mmlist) + list_del_init(p); + spin_unlock(&mmlist_lock); +} + +/* + * Free all of a swapdev's extent information + */ +static void destroy_swap_extents(struct swap_info_struct *sis) +{ + while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) { + struct rb_node *rb = sis->swap_extent_root.rb_node; + struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node); + + rb_erase(rb, &sis->swap_extent_root); + kfree(se); + } + + if (sis->flags & SWP_ACTIVATED) { + struct file *swap_file = sis->swap_file; + struct address_space *mapping = swap_file->f_mapping; + + sis->flags &= ~SWP_ACTIVATED; + if (mapping->a_ops->swap_deactivate) + mapping->a_ops->swap_deactivate(swap_file); + } +} + +/* + * Add a block range (and the corresponding page range) into this swapdev's + * extent tree. + * + * This function rather assumes that it is called in ascending page order. + */ +int +add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, + unsigned long nr_pages, sector_t start_block) +{ + struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL; + struct swap_extent *se; + struct swap_extent *new_se; + + /* + * place the new node at the right most since the + * function is called in ascending page order. + */ + while (*link) { + parent = *link; + link = &parent->rb_right; + } + + if (parent) { + se = rb_entry(parent, struct swap_extent, rb_node); + BUG_ON(se->start_page + se->nr_pages != start_page); + if (se->start_block + se->nr_pages == start_block) { + /* Merge it */ + se->nr_pages += nr_pages; + return 0; + } + } + + /* No merge, insert a new extent. */ + new_se = kmalloc(sizeof(*se), GFP_KERNEL); + if (new_se == NULL) + return -ENOMEM; + new_se->start_page = start_page; + new_se->nr_pages = nr_pages; + new_se->start_block = start_block; + + rb_link_node(&new_se->rb_node, parent, link); + rb_insert_color(&new_se->rb_node, &sis->swap_extent_root); + return 1; +} +EXPORT_SYMBOL_GPL(add_swap_extent); + +/* + * A `swap extent' is a simple thing which maps a contiguous range of pages + * onto a contiguous range of disk blocks. A rbtree of swap extents is + * built at swapon time and is then used at swap_writepage/swap_readpage + * time for locating where on disk a page belongs. + * + * If the swapfile is an S_ISBLK block device, a single extent is installed. + * This is done so that the main operating code can treat S_ISBLK and S_ISREG + * swap files identically. + * + * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap + * extent rbtree operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK + * swapfiles are handled *identically* after swapon time. + * + * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks + * and will parse them into a rbtree, in PAGE_SIZE chunks. If some stray + * blocks are found which do not fall within the PAGE_SIZE alignment + * requirements, they are simply tossed out - we will never use those blocks + * for swapping. + * + * For all swap devices we set S_SWAPFILE across the life of the swapon. This + * prevents users from writing to the swap device, which will corrupt memory. + * + * The amount of disk space which a single swap extent represents varies. + * Typically it is in the 1-4 megabyte range. So we can have hundreds of + * extents in the rbtree. - akpm. + */ +static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) +{ + struct file *swap_file = sis->swap_file; + struct address_space *mapping = swap_file->f_mapping; + struct inode *inode = mapping->host; + int ret; + + if (S_ISBLK(inode->i_mode)) { + ret = add_swap_extent(sis, 0, sis->max, 0); + *span = sis->pages; + return ret; + } + + if (mapping->a_ops->swap_activate) { + ret = mapping->a_ops->swap_activate(sis, swap_file, span); + if (ret < 0) + return ret; + sis->flags |= SWP_ACTIVATED; + if ((sis->flags & SWP_FS_OPS) && + sio_pool_init() != 0) { + destroy_swap_extents(sis); + return -ENOMEM; + } + return ret; + } + + return generic_swapfile_activate(sis, swap_file, span); +} + +static int swap_node(struct swap_info_struct *p) +{ + struct block_device *bdev; + + if (p->bdev) + bdev = p->bdev; + else + bdev = p->swap_file->f_inode->i_sb->s_bdev; + + return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE; +} + +static void setup_swap_info(struct swap_info_struct *p, int prio, + unsigned char *swap_map, + struct swap_cluster_info *cluster_info) +{ + int i; + + if (prio >= 0) + p->prio = prio; + else + p->prio = --least_priority; + /* + * the plist prio is negated because plist ordering is + * low-to-high, while swap ordering is high-to-low + */ + p->list.prio = -p->prio; + for_each_node(i) { + if (p->prio >= 0) + p->avail_lists[i].prio = -p->prio; + else { + if (swap_node(p) == i) + p->avail_lists[i].prio = 1; + else + p->avail_lists[i].prio = -p->prio; + } + } + p->swap_map = swap_map; + p->cluster_info = cluster_info; +} + +static void _enable_swap_info(struct swap_info_struct *p) +{ + p->flags |= SWP_WRITEOK; + atomic_long_add(p->pages, &nr_swap_pages); + total_swap_pages += p->pages; + + assert_spin_locked(&swap_lock); + /* + * both lists are plists, and thus priority ordered. + * swap_active_head needs to be priority ordered for swapoff(), + * which on removal of any swap_info_struct with an auto-assigned + * (i.e. negative) priority increments the auto-assigned priority + * of any lower-priority swap_info_structs. + * swap_avail_head needs to be priority ordered for folio_alloc_swap(), + * which allocates swap pages from the highest available priority + * swap_info_struct. + */ + plist_add(&p->list, &swap_active_head); + + /* add to available list iff swap device is not full */ + if (p->highest_bit) + add_to_avail_list(p); +} + +static void enable_swap_info(struct swap_info_struct *p, int prio, + unsigned char *swap_map, + struct swap_cluster_info *cluster_info) +{ + zswap_swapon(p->type); + + spin_lock(&swap_lock); + spin_lock(&p->lock); + setup_swap_info(p, prio, swap_map, cluster_info); + spin_unlock(&p->lock); + spin_unlock(&swap_lock); + /* + * Finished initializing swap device, now it's safe to reference it. + */ + percpu_ref_resurrect(&p->users); + spin_lock(&swap_lock); + spin_lock(&p->lock); + _enable_swap_info(p); + spin_unlock(&p->lock); + spin_unlock(&swap_lock); +} + +static void reinsert_swap_info(struct swap_info_struct *p) +{ + spin_lock(&swap_lock); + spin_lock(&p->lock); + setup_swap_info(p, p->prio, p->swap_map, p->cluster_info); + _enable_swap_info(p); + spin_unlock(&p->lock); + spin_unlock(&swap_lock); +} + +bool has_usable_swap(void) +{ + bool ret = true; + + spin_lock(&swap_lock); + if (plist_head_empty(&swap_active_head)) + ret = false; + spin_unlock(&swap_lock); + return ret; +} + +SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) +{ + struct swap_info_struct *p = NULL; + unsigned char *swap_map; + struct swap_cluster_info *cluster_info; + struct file *swap_file, *victim; + struct address_space *mapping; + struct inode *inode; + struct filename *pathname; + int err, found = 0; + unsigned int old_block_size; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + BUG_ON(!current->mm); + + pathname = getname(specialfile); + if (IS_ERR(pathname)) + return PTR_ERR(pathname); + + victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0); + err = PTR_ERR(victim); + if (IS_ERR(victim)) + goto out; + + mapping = victim->f_mapping; + spin_lock(&swap_lock); + plist_for_each_entry(p, &swap_active_head, list) { + if (p->flags & SWP_WRITEOK) { + if (p->swap_file->f_mapping == mapping) { + found = 1; + break; + } + } + } + if (!found) { + err = -EINVAL; + spin_unlock(&swap_lock); + goto out_dput; + } + if (!security_vm_enough_memory_mm(current->mm, p->pages)) + vm_unacct_memory(p->pages); + else { + err = -ENOMEM; + spin_unlock(&swap_lock); + goto out_dput; + } + spin_lock(&p->lock); + del_from_avail_list(p); + if (p->prio < 0) { + struct swap_info_struct *si = p; + int nid; + + plist_for_each_entry_continue(si, &swap_active_head, list) { + si->prio++; + si->list.prio--; + for_each_node(nid) { + if (si->avail_lists[nid].prio != 1) + si->avail_lists[nid].prio--; + } + } + least_priority++; + } + plist_del(&p->list, &swap_active_head); + atomic_long_sub(p->pages, &nr_swap_pages); + total_swap_pages -= p->pages; + p->flags &= ~SWP_WRITEOK; + spin_unlock(&p->lock); + spin_unlock(&swap_lock); + + disable_swap_slots_cache_lock(); + + set_current_oom_origin(); + err = try_to_unuse(p->type); + clear_current_oom_origin(); + + if (err) { + /* re-insert swap space back into swap_list */ + reinsert_swap_info(p); + reenable_swap_slots_cache_unlock(); + goto out_dput; + } + + reenable_swap_slots_cache_unlock(); + + /* + * Wait for swap operations protected by get/put_swap_device() + * to complete. + * + * We need synchronize_rcu() here to protect the accessing to + * the swap cache data structure. + */ + percpu_ref_kill(&p->users); + synchronize_rcu(); + wait_for_completion(&p->comp); + + flush_work(&p->discard_work); + + destroy_swap_extents(p); + if (p->flags & SWP_CONTINUED) + free_swap_count_continuations(p); + + if (!p->bdev || !bdev_nonrot(p->bdev)) + atomic_dec(&nr_rotate_swap); + + mutex_lock(&swapon_mutex); + spin_lock(&swap_lock); + spin_lock(&p->lock); + drain_mmlist(); + + /* wait for anyone still in scan_swap_map_slots */ + p->highest_bit = 0; /* cuts scans short */ + while (p->flags >= SWP_SCANNING) { + spin_unlock(&p->lock); + spin_unlock(&swap_lock); + schedule_timeout_uninterruptible(1); + spin_lock(&swap_lock); + spin_lock(&p->lock); + } + + swap_file = p->swap_file; + old_block_size = p->old_block_size; + p->swap_file = NULL; + p->max = 0; + swap_map = p->swap_map; + p->swap_map = NULL; + cluster_info = p->cluster_info; + p->cluster_info = NULL; + spin_unlock(&p->lock); + spin_unlock(&swap_lock); + arch_swap_invalidate_area(p->type); + zswap_swapoff(p->type); + mutex_unlock(&swapon_mutex); + free_percpu(p->percpu_cluster); + p->percpu_cluster = NULL; + free_percpu(p->cluster_next_cpu); + p->cluster_next_cpu = NULL; + vfree(swap_map); + kvfree(cluster_info); + /* Destroy swap account information */ + swap_cgroup_swapoff(p->type); + exit_swap_address_space(p->type); + + inode = mapping->host; + if (S_ISBLK(inode->i_mode)) { + struct block_device *bdev = I_BDEV(inode); + + set_blocksize(bdev, old_block_size); + blkdev_put(bdev, p); + } + + inode_lock(inode); + inode->i_flags &= ~S_SWAPFILE; + inode_unlock(inode); + filp_close(swap_file, NULL); + + /* + * Clear the SWP_USED flag after all resources are freed so that swapon + * can reuse this swap_info in alloc_swap_info() safely. It is ok to + * not hold p->lock after we cleared its SWP_WRITEOK. + */ + spin_lock(&swap_lock); + p->flags = 0; + spin_unlock(&swap_lock); + + err = 0; + atomic_inc(&proc_poll_event); + wake_up_interruptible(&proc_poll_wait); + +out_dput: + filp_close(victim, NULL); +out: + putname(pathname); + return err; +} + +#ifdef CONFIG_PROC_FS +static __poll_t swaps_poll(struct file *file, poll_table *wait) +{ + struct seq_file *seq = file->private_data; + + poll_wait(file, &proc_poll_wait, wait); + + if (seq->poll_event != atomic_read(&proc_poll_event)) { + seq->poll_event = atomic_read(&proc_poll_event); + return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI; + } + + return EPOLLIN | EPOLLRDNORM; +} + +/* iterator */ +static void *swap_start(struct seq_file *swap, loff_t *pos) +{ + struct swap_info_struct *si; + int type; + loff_t l = *pos; + + mutex_lock(&swapon_mutex); + + if (!l) + return SEQ_START_TOKEN; + + for (type = 0; (si = swap_type_to_swap_info(type)); type++) { + if (!(si->flags & SWP_USED) || !si->swap_map) + continue; + if (!--l) + return si; + } + + return NULL; +} + +static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) +{ + struct swap_info_struct *si = v; + int type; + + if (v == SEQ_START_TOKEN) + type = 0; + else + type = si->type + 1; + + ++(*pos); + for (; (si = swap_type_to_swap_info(type)); type++) { + if (!(si->flags & SWP_USED) || !si->swap_map) + continue; + return si; + } + + return NULL; +} + +static void swap_stop(struct seq_file *swap, void *v) +{ + mutex_unlock(&swapon_mutex); +} + +static int swap_show(struct seq_file *swap, void *v) +{ + struct swap_info_struct *si = v; + struct file *file; + int len; + unsigned long bytes, inuse; + + if (si == SEQ_START_TOKEN) { + seq_puts(swap, "Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n"); + return 0; + } + + bytes = K(si->pages); + inuse = K(READ_ONCE(si->inuse_pages)); + + file = si->swap_file; + len = seq_file_path(swap, file, " \t\n\\"); + seq_printf(swap, "%*s%s\t%lu\t%s%lu\t%s%d\n", + len < 40 ? 40 - len : 1, " ", + S_ISBLK(file_inode(file)->i_mode) ? + "partition" : "file\t", + bytes, bytes < 10000000 ? "\t" : "", + inuse, inuse < 10000000 ? "\t" : "", + si->prio); + return 0; +} + +static const struct seq_operations swaps_op = { + .start = swap_start, + .next = swap_next, + .stop = swap_stop, + .show = swap_show +}; + +static int swaps_open(struct inode *inode, struct file *file) +{ + struct seq_file *seq; + int ret; + + ret = seq_open(file, &swaps_op); + if (ret) + return ret; + + seq = file->private_data; + seq->poll_event = atomic_read(&proc_poll_event); + return 0; +} + +static const struct proc_ops swaps_proc_ops = { + .proc_flags = PROC_ENTRY_PERMANENT, + .proc_open = swaps_open, + .proc_read = seq_read, + .proc_lseek = seq_lseek, + .proc_release = seq_release, + .proc_poll = swaps_poll, +}; + +static int __init procswaps_init(void) +{ + proc_create("swaps", 0, NULL, &swaps_proc_ops); + return 0; +} +__initcall(procswaps_init); +#endif /* CONFIG_PROC_FS */ + +#ifdef MAX_SWAPFILES_CHECK +static int __init max_swapfiles_check(void) +{ + MAX_SWAPFILES_CHECK(); + return 0; +} +late_initcall(max_swapfiles_check); +#endif + +static struct swap_info_struct *alloc_swap_info(void) +{ + struct swap_info_struct *p; + struct swap_info_struct *defer = NULL; + unsigned int type; + int i; + + p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL); + if (!p) + return ERR_PTR(-ENOMEM); + + if (percpu_ref_init(&p->users, swap_users_ref_free, + PERCPU_REF_INIT_DEAD, GFP_KERNEL)) { + kvfree(p); + return ERR_PTR(-ENOMEM); + } + + spin_lock(&swap_lock); + for (type = 0; type < nr_swapfiles; type++) { + if (!(swap_info[type]->flags & SWP_USED)) + break; + } + if (type >= MAX_SWAPFILES) { + spin_unlock(&swap_lock); + percpu_ref_exit(&p->users); + kvfree(p); + return ERR_PTR(-EPERM); + } + if (type >= nr_swapfiles) { + p->type = type; + /* + * Publish the swap_info_struct after initializing it. + * Note that kvzalloc() above zeroes all its fields. + */ + smp_store_release(&swap_info[type], p); /* rcu_assign_pointer() */ + nr_swapfiles++; + } else { + defer = p; + p = swap_info[type]; + /* + * Do not memset this entry: a racing procfs swap_next() + * would be relying on p->type to remain valid. + */ + } + p->swap_extent_root = RB_ROOT; + plist_node_init(&p->list, 0); + for_each_node(i) + plist_node_init(&p->avail_lists[i], 0); + p->flags = SWP_USED; + spin_unlock(&swap_lock); + if (defer) { + percpu_ref_exit(&defer->users); + kvfree(defer); + } + spin_lock_init(&p->lock); + spin_lock_init(&p->cont_lock); + init_completion(&p->comp); + + return p; +} + +static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) +{ + int error; + + if (S_ISBLK(inode->i_mode)) { + p->bdev = blkdev_get_by_dev(inode->i_rdev, + BLK_OPEN_READ | BLK_OPEN_WRITE, p, NULL); + if (IS_ERR(p->bdev)) { + error = PTR_ERR(p->bdev); + p->bdev = NULL; + return error; + } + p->old_block_size = block_size(p->bdev); + error = set_blocksize(p->bdev, PAGE_SIZE); + if (error < 0) + return error; + /* + * Zoned block devices contain zones that have a sequential + * write only restriction. Hence zoned block devices are not + * suitable for swapping. Disallow them here. + */ + if (bdev_is_zoned(p->bdev)) + return -EINVAL; + p->flags |= SWP_BLKDEV; + } else if (S_ISREG(inode->i_mode)) { + p->bdev = inode->i_sb->s_bdev; + } + + return 0; +} + + +/* + * 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 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. + */ +unsigned long generic_max_swapfile_size(void) +{ + return swp_offset(pte_to_swp_entry( + swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1; +} + +/* Can be overridden by an architecture for additional checks. */ +__weak unsigned long arch_max_swapfile_size(void) +{ + return generic_max_swapfile_size(); +} + +static unsigned long read_swap_header(struct swap_info_struct *p, + union swap_header *swap_header, + struct inode *inode) +{ + int i; + unsigned long maxpages; + unsigned long swapfilepages; + unsigned long last_page; + + if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { + pr_err("Unable to find swap-space signature\n"); + return 0; + } + + /* swap partition endianness 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); + if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) + return 0; + 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) { + pr_warn("Unable to handle swap header version %d\n", + swap_header->info.version); + return 0; + } + + p->lowest_bit = 1; + p->cluster_next = 1; + p->cluster_nr = 0; + + maxpages = swapfile_maximum_size; + last_page = swap_header->info.last_page; + if (!last_page) { + pr_warn("Empty swap-file\n"); + return 0; + } + if (last_page > maxpages) { + pr_warn("Truncating oversized swap area, only using %luk out of %luk\n", + K(maxpages), K(last_page)); + } + if (maxpages > last_page) { + maxpages = last_page + 1; + /* p->max is an unsigned int: don't overflow it */ + if ((unsigned int)maxpages == 0) + maxpages = UINT_MAX; + } + p->highest_bit = maxpages - 1; + + if (!maxpages) + return 0; + swapfilepages = i_size_read(inode) >> PAGE_SHIFT; + if (swapfilepages && maxpages > swapfilepages) { + pr_warn("Swap area shorter than signature indicates\n"); + return 0; + } + if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) + return 0; + if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) + return 0; + + return maxpages; +} + +#define SWAP_CLUSTER_INFO_COLS \ + DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info)) +#define SWAP_CLUSTER_SPACE_COLS \ + DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER) +#define SWAP_CLUSTER_COLS \ + max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS) + +static int setup_swap_map_and_extents(struct swap_info_struct *p, + union swap_header *swap_header, + unsigned char *swap_map, + struct swap_cluster_info *cluster_info, + unsigned long maxpages, + sector_t *span) +{ + unsigned int j, k; + unsigned int nr_good_pages; + int nr_extents; + unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER); + unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS; + unsigned long i, idx; + + nr_good_pages = maxpages - 1; /* omit header page */ + + cluster_list_init(&p->free_clusters); + cluster_list_init(&p->discard_clusters); + + for (i = 0; i < swap_header->info.nr_badpages; i++) { + unsigned int page_nr = swap_header->info.badpages[i]; + if (page_nr == 0 || page_nr > swap_header->info.last_page) + return -EINVAL; + if (page_nr < maxpages) { + swap_map[page_nr] = SWAP_MAP_BAD; + nr_good_pages--; + /* + * Haven't marked the cluster free yet, no list + * operation involved + */ + inc_cluster_info_page(p, cluster_info, page_nr); + } + } + + /* Haven't marked the cluster free yet, no list operation involved */ + for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++) + inc_cluster_info_page(p, cluster_info, i); + + if (nr_good_pages) { + swap_map[0] = SWAP_MAP_BAD; + /* + * Not mark the cluster free yet, no list + * operation involved + */ + inc_cluster_info_page(p, cluster_info, 0); + p->max = maxpages; + p->pages = nr_good_pages; + nr_extents = setup_swap_extents(p, span); + if (nr_extents < 0) + return nr_extents; + nr_good_pages = p->pages; + } + if (!nr_good_pages) { + pr_warn("Empty swap-file\n"); + return -EINVAL; + } + + if (!cluster_info) + return nr_extents; + + + /* + * Reduce false cache line sharing between cluster_info and + * sharing same address space. + */ + for (k = 0; k < SWAP_CLUSTER_COLS; k++) { + j = (k + col) % SWAP_CLUSTER_COLS; + for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) { + idx = i * SWAP_CLUSTER_COLS + j; + if (idx >= nr_clusters) + continue; + if (cluster_count(&cluster_info[idx])) + continue; + cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE); + cluster_list_add_tail(&p->free_clusters, cluster_info, + idx); + } + } + return nr_extents; +} + +SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) +{ + struct swap_info_struct *p; + struct filename *name; + struct file *swap_file = NULL; + struct address_space *mapping; + struct dentry *dentry; + int prio; + int error; + union swap_header *swap_header; + int nr_extents; + sector_t span; + unsigned long maxpages; + unsigned char *swap_map = NULL; + struct swap_cluster_info *cluster_info = NULL; + struct page *page = NULL; + struct inode *inode = NULL; + bool inced_nr_rotate_swap = false; + + if (swap_flags & ~SWAP_FLAGS_VALID) + return -EINVAL; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (!swap_avail_heads) + return -ENOMEM; + + p = alloc_swap_info(); + if (IS_ERR(p)) + return PTR_ERR(p); + + INIT_WORK(&p->discard_work, swap_discard_work); + + name = getname(specialfile); + if (IS_ERR(name)) { + error = PTR_ERR(name); + name = NULL; + goto bad_swap; + } + swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0); + if (IS_ERR(swap_file)) { + error = PTR_ERR(swap_file); + swap_file = NULL; + goto bad_swap; + } + + p->swap_file = swap_file; + mapping = swap_file->f_mapping; + dentry = swap_file->f_path.dentry; + inode = mapping->host; + + error = claim_swapfile(p, inode); + if (unlikely(error)) + goto bad_swap; + + inode_lock(inode); + if (d_unlinked(dentry) || cant_mount(dentry)) { + error = -ENOENT; + goto bad_swap_unlock_inode; + } + if (IS_SWAPFILE(inode)) { + error = -EBUSY; + goto bad_swap_unlock_inode; + } + + /* + * Read the swap header. + */ + if (!mapping->a_ops->read_folio) { + error = -EINVAL; + goto bad_swap_unlock_inode; + } + page = read_mapping_page(mapping, 0, swap_file); + if (IS_ERR(page)) { + error = PTR_ERR(page); + goto bad_swap_unlock_inode; + } + swap_header = kmap(page); + + maxpages = read_swap_header(p, swap_header, inode); + if (unlikely(!maxpages)) { + error = -EINVAL; + goto bad_swap_unlock_inode; + } + + /* OK, set up the swap map and apply the bad block list */ + swap_map = vzalloc(maxpages); + if (!swap_map) { + error = -ENOMEM; + goto bad_swap_unlock_inode; + } + + if (p->bdev && bdev_stable_writes(p->bdev)) + p->flags |= SWP_STABLE_WRITES; + + if (p->bdev && bdev_synchronous(p->bdev)) + p->flags |= SWP_SYNCHRONOUS_IO; + + if (p->bdev && bdev_nonrot(p->bdev)) { + int cpu; + unsigned long ci, nr_cluster; + + p->flags |= SWP_SOLIDSTATE; + p->cluster_next_cpu = alloc_percpu(unsigned int); + if (!p->cluster_next_cpu) { + error = -ENOMEM; + goto bad_swap_unlock_inode; + } + /* + * select a random position to start with to help wear leveling + * SSD + */ + for_each_possible_cpu(cpu) { + per_cpu(*p->cluster_next_cpu, cpu) = + get_random_u32_inclusive(1, p->highest_bit); + } + nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER); + + cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info), + GFP_KERNEL); + if (!cluster_info) { + error = -ENOMEM; + goto bad_swap_unlock_inode; + } + + for (ci = 0; ci < nr_cluster; ci++) + spin_lock_init(&((cluster_info + ci)->lock)); + + p->percpu_cluster = alloc_percpu(struct percpu_cluster); + if (!p->percpu_cluster) { + error = -ENOMEM; + goto bad_swap_unlock_inode; + } + for_each_possible_cpu(cpu) { + struct percpu_cluster *cluster; + cluster = per_cpu_ptr(p->percpu_cluster, cpu); + cluster_set_null(&cluster->index); + } + } else { + atomic_inc(&nr_rotate_swap); + inced_nr_rotate_swap = true; + } + + error = swap_cgroup_swapon(p->type, maxpages); + if (error) + goto bad_swap_unlock_inode; + + nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map, + cluster_info, maxpages, &span); + if (unlikely(nr_extents < 0)) { + error = nr_extents; + goto bad_swap_unlock_inode; + } + + if ((swap_flags & SWAP_FLAG_DISCARD) && + p->bdev && bdev_max_discard_sectors(p->bdev)) { + /* + * When discard is enabled for swap with no particular + * policy flagged, we set all swap discard flags here in + * order to sustain backward compatibility with older + * swapon(8) releases. + */ + p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD | + SWP_PAGE_DISCARD); + + /* + * By flagging sys_swapon, a sysadmin can tell us to + * either do single-time area discards only, or to just + * perform discards for released swap page-clusters. + * Now it's time to adjust the p->flags accordingly. + */ + if (swap_flags & SWAP_FLAG_DISCARD_ONCE) + p->flags &= ~SWP_PAGE_DISCARD; + else if (swap_flags & SWAP_FLAG_DISCARD_PAGES) + p->flags &= ~SWP_AREA_DISCARD; + + /* issue a swapon-time discard if it's still required */ + if (p->flags & SWP_AREA_DISCARD) { + int err = discard_swap(p); + if (unlikely(err)) + pr_err("swapon: discard_swap(%p): %d\n", + p, err); + } + } + + error = init_swap_address_space(p->type, maxpages); + if (error) + goto bad_swap_unlock_inode; + + /* + * Flush any pending IO and dirty mappings before we start using this + * swap device. + */ + inode->i_flags |= S_SWAPFILE; + error = inode_drain_writes(inode); + if (error) { + inode->i_flags &= ~S_SWAPFILE; + goto free_swap_address_space; + } + + mutex_lock(&swapon_mutex); + prio = -1; + if (swap_flags & SWAP_FLAG_PREFER) + prio = + (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; + enable_swap_info(p, prio, swap_map, cluster_info); + + pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s\n", + K(p->pages), name->name, p->prio, nr_extents, + K((unsigned long long)span), + (p->flags & SWP_SOLIDSTATE) ? "SS" : "", + (p->flags & SWP_DISCARDABLE) ? "D" : "", + (p->flags & SWP_AREA_DISCARD) ? "s" : "", + (p->flags & SWP_PAGE_DISCARD) ? "c" : ""); + + mutex_unlock(&swapon_mutex); + atomic_inc(&proc_poll_event); + wake_up_interruptible(&proc_poll_wait); + + error = 0; + goto out; +free_swap_address_space: + exit_swap_address_space(p->type); +bad_swap_unlock_inode: + inode_unlock(inode); +bad_swap: + free_percpu(p->percpu_cluster); + p->percpu_cluster = NULL; + free_percpu(p->cluster_next_cpu); + p->cluster_next_cpu = NULL; + if (inode && S_ISBLK(inode->i_mode) && p->bdev) { + set_blocksize(p->bdev, p->old_block_size); + blkdev_put(p->bdev, p); + } + inode = NULL; + destroy_swap_extents(p); + swap_cgroup_swapoff(p->type); + spin_lock(&swap_lock); + p->swap_file = NULL; + p->flags = 0; + spin_unlock(&swap_lock); + vfree(swap_map); + kvfree(cluster_info); + if (inced_nr_rotate_swap) + atomic_dec(&nr_rotate_swap); + if (swap_file) + filp_close(swap_file, NULL); +out: + if (page && !IS_ERR(page)) { + kunmap(page); + put_page(page); + } + if (name) + putname(name); + if (inode) + inode_unlock(inode); + if (!error) + enable_swap_slots_cache(); + return error; +} + +void si_swapinfo(struct sysinfo *val) +{ + unsigned int type; + unsigned long nr_to_be_unused = 0; + + spin_lock(&swap_lock); + for (type = 0; type < nr_swapfiles; type++) { + struct swap_info_struct *si = swap_info[type]; + + if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK)) + nr_to_be_unused += READ_ONCE(si->inuse_pages); + } + val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused; + val->totalswap = total_swap_pages + nr_to_be_unused; + spin_unlock(&swap_lock); +} + +/* + * Verify that a swap entry is valid and increment its swap map count. + * + * Returns error code in following case. + * - success -> 0 + * - swp_entry is invalid -> EINVAL + * - swp_entry is migration entry -> EINVAL + * - swap-cache reference is requested but there is already one. -> EEXIST + * - swap-cache reference is requested but the entry is not used. -> ENOENT + * - swap-mapped reference requested but needs continued swap count. -> ENOMEM + */ +static int __swap_duplicate(swp_entry_t entry, unsigned char usage) +{ + struct swap_info_struct *p; + struct swap_cluster_info *ci; + unsigned long offset; + unsigned char count; + unsigned char has_cache; + int err; + + p = swp_swap_info(entry); + + offset = swp_offset(entry); + ci = lock_cluster_or_swap_info(p, offset); + + count = p->swap_map[offset]; + + /* + * swapin_readahead() doesn't check if a swap entry is valid, so the + * swap entry could be SWAP_MAP_BAD. Check here with lock held. + */ + if (unlikely(swap_count(count) == SWAP_MAP_BAD)) { + err = -ENOENT; + goto unlock_out; + } + + has_cache = count & SWAP_HAS_CACHE; + count &= ~SWAP_HAS_CACHE; + err = 0; + + if (usage == SWAP_HAS_CACHE) { + + /* set SWAP_HAS_CACHE if there is no cache and entry is used */ + if (!has_cache && count) + has_cache = SWAP_HAS_CACHE; + else if (has_cache) /* someone else added cache */ + err = -EEXIST; + else /* no users remaining */ + err = -ENOENT; + + } else if (count || has_cache) { + + if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX) + count += usage; + else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) + err = -EINVAL; + else if (swap_count_continued(p, offset, count)) + count = COUNT_CONTINUED; + else + err = -ENOMEM; + } else + err = -ENOENT; /* unused swap entry */ + + WRITE_ONCE(p->swap_map[offset], count | has_cache); + +unlock_out: + unlock_cluster_or_swap_info(p, ci); + return err; +} + +/* + * Help swapoff by noting that swap entry belongs to shmem/tmpfs + * (in which case its reference count is never incremented). + */ +void swap_shmem_alloc(swp_entry_t entry) +{ + __swap_duplicate(entry, SWAP_MAP_SHMEM); +} + +/* + * Increase reference count of swap entry by 1. + * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required + * but could not be atomically allocated. Returns 0, just as if it succeeded, + * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which + * might occur if a page table entry has got corrupted. + */ +int swap_duplicate(swp_entry_t entry) +{ + int err = 0; + + while (!err && __swap_duplicate(entry, 1) == -ENOMEM) + err = add_swap_count_continuation(entry, GFP_ATOMIC); + return err; +} + +/* + * @entry: swap entry for which we allocate swap cache. + * + * Called when allocating swap cache for existing swap entry, + * This can return error codes. Returns 0 at success. + * -EEXIST means there is a swap cache. + * Note: return code is different from swap_duplicate(). + */ +int swapcache_prepare(swp_entry_t entry) +{ + return __swap_duplicate(entry, SWAP_HAS_CACHE); +} + +struct swap_info_struct *swp_swap_info(swp_entry_t entry) +{ + return swap_type_to_swap_info(swp_type(entry)); +} + +struct swap_info_struct *page_swap_info(struct page *page) +{ + swp_entry_t entry = page_swap_entry(page); + return swp_swap_info(entry); +} + +/* + * out-of-line methods to avoid include hell. + */ +struct address_space *swapcache_mapping(struct folio *folio) +{ + return page_swap_info(&folio->page)->swap_file->f_mapping; +} +EXPORT_SYMBOL_GPL(swapcache_mapping); + +pgoff_t __page_file_index(struct page *page) +{ + swp_entry_t swap = page_swap_entry(page); + return swp_offset(swap); +} +EXPORT_SYMBOL_GPL(__page_file_index); + +/* + * add_swap_count_continuation - called when a swap count is duplicated + * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's + * page of the original vmalloc'ed swap_map, to hold the continuation count + * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called + * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc. + * + * These continuation pages are seldom referenced: the common paths all work + * on the original swap_map, only referring to a continuation page when the + * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX. + * + * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding + * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL) + * can be called after dropping locks. + */ +int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask) +{ + struct swap_info_struct *si; + struct swap_cluster_info *ci; + struct page *head; + struct page *page; + struct page *list_page; + pgoff_t offset; + unsigned char count; + int ret = 0; + + /* + * When debugging, it's easier to use __GFP_ZERO here; but it's better + * for latency not to zero a page while GFP_ATOMIC and holding locks. + */ + page = alloc_page(gfp_mask | __GFP_HIGHMEM); + + si = get_swap_device(entry); + if (!si) { + /* + * An acceptable race has occurred since the failing + * __swap_duplicate(): the swap device may be swapoff + */ + goto outer; + } + spin_lock(&si->lock); + + offset = swp_offset(entry); + + ci = lock_cluster(si, offset); + + count = swap_count(si->swap_map[offset]); + + if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) { + /* + * The higher the swap count, the more likely it is that tasks + * will race to add swap count continuation: we need to avoid + * over-provisioning. + */ + goto out; + } + + if (!page) { + ret = -ENOMEM; + goto out; + } + + head = vmalloc_to_page(si->swap_map + offset); + offset &= ~PAGE_MASK; + + spin_lock(&si->cont_lock); + /* + * Page allocation does not initialize the page's lru field, + * but it does always reset its private field. + */ + if (!page_private(head)) { + BUG_ON(count & COUNT_CONTINUED); + INIT_LIST_HEAD(&head->lru); + set_page_private(head, SWP_CONTINUED); + si->flags |= SWP_CONTINUED; + } + + list_for_each_entry(list_page, &head->lru, lru) { + unsigned char *map; + + /* + * If the previous map said no continuation, but we've found + * a continuation page, free our allocation and use this one. + */ + if (!(count & COUNT_CONTINUED)) + goto out_unlock_cont; + + map = kmap_atomic(list_page) + offset; + count = *map; + kunmap_atomic(map); + + /* + * If this continuation count now has some space in it, + * free our allocation and use this one. + */ + if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX) + goto out_unlock_cont; + } + + list_add_tail(&page->lru, &head->lru); + page = NULL; /* now it's attached, don't free it */ +out_unlock_cont: + spin_unlock(&si->cont_lock); +out: + unlock_cluster(ci); + spin_unlock(&si->lock); + put_swap_device(si); +outer: + if (page) + __free_page(page); + return ret; +} + +/* + * swap_count_continued - when the original swap_map count is incremented + * from SWAP_MAP_MAX, check if there is already a continuation page to carry + * into, carry if so, or else fail until a new continuation page is allocated; + * when the original swap_map count is decremented from 0 with continuation, + * borrow from the continuation and report whether it still holds more. + * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster + * lock. + */ +static bool swap_count_continued(struct swap_info_struct *si, + pgoff_t offset, unsigned char count) +{ + struct page *head; + struct page *page; + unsigned char *map; + bool ret; + + head = vmalloc_to_page(si->swap_map + offset); + if (page_private(head) != SWP_CONTINUED) { + BUG_ON(count & COUNT_CONTINUED); + return false; /* need to add count continuation */ + } + + spin_lock(&si->cont_lock); + offset &= ~PAGE_MASK; + page = list_next_entry(head, lru); + map = kmap_atomic(page) + offset; + + if (count == SWAP_MAP_MAX) /* initial increment from swap_map */ + goto init_map; /* jump over SWAP_CONT_MAX checks */ + + if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */ + /* + * Think of how you add 1 to 999 + */ + while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) { + kunmap_atomic(map); + page = list_next_entry(page, lru); + BUG_ON(page == head); + map = kmap_atomic(page) + offset; + } + if (*map == SWAP_CONT_MAX) { + kunmap_atomic(map); + page = list_next_entry(page, lru); + if (page == head) { + ret = false; /* add count continuation */ + goto out; + } + map = kmap_atomic(page) + offset; +init_map: *map = 0; /* we didn't zero the page */ + } + *map += 1; + kunmap_atomic(map); + while ((page = list_prev_entry(page, lru)) != head) { + map = kmap_atomic(page) + offset; + *map = COUNT_CONTINUED; + kunmap_atomic(map); + } + ret = true; /* incremented */ + + } else { /* decrementing */ + /* + * Think of how you subtract 1 from 1000 + */ + BUG_ON(count != COUNT_CONTINUED); + while (*map == COUNT_CONTINUED) { + kunmap_atomic(map); + page = list_next_entry(page, lru); + BUG_ON(page == head); + map = kmap_atomic(page) + offset; + } + BUG_ON(*map == 0); + *map -= 1; + if (*map == 0) + count = 0; + kunmap_atomic(map); + while ((page = list_prev_entry(page, lru)) != head) { + map = kmap_atomic(page) + offset; + *map = SWAP_CONT_MAX | count; + count = COUNT_CONTINUED; + kunmap_atomic(map); + } + ret = count == COUNT_CONTINUED; + } +out: + spin_unlock(&si->cont_lock); + return ret; +} + +/* + * free_swap_count_continuations - swapoff free all the continuation pages + * appended to the swap_map, after swap_map is quiesced, before vfree'ing it. + */ +static void free_swap_count_continuations(struct swap_info_struct *si) +{ + pgoff_t offset; + + for (offset = 0; offset < si->max; offset += PAGE_SIZE) { + struct page *head; + head = vmalloc_to_page(si->swap_map + offset); + if (page_private(head)) { + struct page *page, *next; + + list_for_each_entry_safe(page, next, &head->lru, lru) { + list_del(&page->lru); + __free_page(page); + } + } + } +} + +#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) +void __folio_throttle_swaprate(struct folio *folio, gfp_t gfp) +{ + struct swap_info_struct *si, *next; + int nid = folio_nid(folio); + + if (!(gfp & __GFP_IO)) + return; + + if (!blk_cgroup_congested()) + return; + + /* + * We've already scheduled a throttle, avoid taking the global swap + * lock. + */ + if (current->throttle_disk) + return; + + spin_lock(&swap_avail_lock); + plist_for_each_entry_safe(si, next, &swap_avail_heads[nid], + avail_lists[nid]) { + if (si->bdev) { + blkcg_schedule_throttle(si->bdev->bd_disk, true); + break; + } + } + spin_unlock(&swap_avail_lock); +} +#endif + +static int __init swapfile_init(void) +{ + int nid; + + swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head), + GFP_KERNEL); + if (!swap_avail_heads) { + pr_emerg("Not enough memory for swap heads, swap is disabled\n"); + return -ENOMEM; + } + + for_each_node(nid) + plist_head_init(&swap_avail_heads[nid]); + + swapfile_maximum_size = arch_max_swapfile_size(); + +#ifdef CONFIG_MIGRATION + if (swapfile_maximum_size >= (1UL << SWP_MIG_TOTAL_BITS)) + swap_migration_ad_supported = true; +#endif /* CONFIG_MIGRATION */ + + return 0; +} +subsys_initcall(swapfile_init); |