diff options
Diffstat (limited to 'mm/swapfile.c')
| -rw-r--r-- | mm/swapfile.c | 3958 |
1 files changed, 3958 insertions, 0 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c new file mode 100644 index 000000000..601979b97 --- /dev/null +++ b/mm/swapfile.c @@ -0,0 +1,3958 @@ +// 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/sort.h> +#include <linux/completion.h> +#include <linux/suspend.h> +#include <linux/zswap.h> +#include <linux/plist.h> + +#include <asm/tlbflush.h> +#include <linux/leafops.h> +#include "swap_table.h" +#include "internal.h" +#include "swap.h" + +static void swap_range_alloc(struct swap_info_struct *si, + unsigned int nr_entries); +static bool folio_swapcache_freeable(struct folio *folio); +static void move_cluster(struct swap_info_struct *si, + struct swap_cluster_info *ci, struct list_head *list, + enum swap_cluster_flags new_flags); + +/* + * Protects the swap_info array, and the SWP_USED flag. swap_info contains + * lazily allocated & freed swap device info struts, and SWP_USED indicates + * which device is used, ~SWP_USED devices and can be reused. + * + * Also protects swap_active_head total_swap_pages, and the SWP_WRITEOK flag. + */ +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; +#define DEF_SWAP_PRIO -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 Bad_offset[] = "Bad 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 PLIST_HEAD(swap_avail_head); +static DEFINE_SPINLOCK(swap_avail_lock); + +struct swap_info_struct *swap_info[MAX_SWAPFILES]; + +static struct kmem_cache *swap_table_cachep; + +/* Protects si->swap_file for /proc/swaps usage */ +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); + +struct percpu_swap_cluster { + struct swap_info_struct *si[SWAP_NR_ORDERS]; + unsigned long offset[SWAP_NR_ORDERS]; + local_lock_t lock; +}; + +static DEFINE_PER_CPU(struct percpu_swap_cluster, percpu_swap_cluster) = { + .si = { NULL }, + .offset = { SWAP_ENTRY_INVALID }, + .lock = INIT_LOCAL_LOCK(), +}; + +/* May return NULL on invalid type, caller must check for NULL return */ +static struct swap_info_struct *swap_type_to_info(int type) +{ + if (type < 0 || type >= MAX_SWAPFILES) + return NULL; + return READ_ONCE(swap_info[type]); /* rcu_dereference() */ +} + +/* May return NULL on invalid entry, caller must check for NULL return */ +static struct swap_info_struct *swap_entry_to_info(swp_entry_t entry) +{ + return swap_type_to_info(swp_type(entry)); +} + +/* + * Use the second highest bit of inuse_pages counter as the indicator + * if one swap device is on the available plist, so the atomic can + * still be updated arithmetically while having special data embedded. + * + * inuse_pages counter is the only thing indicating if a device should + * be on avail_lists or not (except swapon / swapoff). By embedding the + * off-list bit in the atomic counter, updates no longer need any lock + * to check the list status. + * + * This bit will be set if the device is not on the plist and not + * usable, will be cleared if the device is on the plist. + */ +#define SWAP_USAGE_OFFLIST_BIT (1UL << (BITS_PER_TYPE(atomic_long_t) - 2)) +#define SWAP_USAGE_COUNTER_MASK (~SWAP_USAGE_OFFLIST_BIT) +static long swap_usage_in_pages(struct swap_info_struct *si) +{ + return atomic_long_read(&si->inuse_pages) & SWAP_USAGE_COUNTER_MASK; +} + +/* 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 + +static bool swap_only_has_cache(struct swap_cluster_info *ci, + unsigned long offset, int nr_pages) +{ + unsigned int ci_off = offset % SWAPFILE_CLUSTER; + unsigned int ci_end = ci_off + nr_pages; + unsigned long swp_tb; + + do { + swp_tb = __swap_table_get(ci, ci_off); + VM_WARN_ON_ONCE(!swp_tb_is_folio(swp_tb)); + if (swp_tb_get_count(swp_tb)) + return false; + } while (++ci_off < ci_end); + + return true; +} + +/* + * returns number of pages in the folio that backs the swap entry. If positive, + * the folio was reclaimed. If negative, the folio was not reclaimed. If 0, no + * folio was associated with the swap entry. + */ +static int __try_to_reclaim_swap(struct swap_info_struct *si, + unsigned long offset, unsigned long flags) +{ + const swp_entry_t entry = swp_entry(si->type, offset); + struct swap_cluster_info *ci; + struct folio *folio; + int ret, nr_pages; + bool need_reclaim; + +again: + folio = swap_cache_get_folio(entry); + if (!folio) + return 0; + + nr_pages = folio_nr_pages(folio); + ret = -nr_pages; + + /* + * 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)) + goto out; + + /* + * Offset could point to the middle of a large folio, or folio + * may no longer point to the expected offset before it's locked. + */ + if (!folio_matches_swap_entry(folio, entry)) { + folio_unlock(folio); + folio_put(folio); + goto again; + } + offset = swp_offset(folio->swap); + + need_reclaim = ((flags & TTRS_ANYWAY) || + ((flags & TTRS_UNMAPPED) && !folio_mapped(folio)) || + ((flags & TTRS_FULL) && mem_cgroup_swap_full(folio))); + if (!need_reclaim || !folio_swapcache_freeable(folio)) + goto out_unlock; + + /* + * It's safe to delete the folio from swap cache only if the folio + * is in swap cache with swap count == 0. The slots have no page table + * reference or pending writeback, and can't be allocated to others. + */ + ci = swap_cluster_lock(si, offset); + need_reclaim = swap_only_has_cache(ci, offset, nr_pages); + swap_cluster_unlock(ci); + if (!need_reclaim) + goto out_unlock; + + swap_cache_del_folio(folio); + folio_set_dirty(folio); + ret = nr_pages; +out_unlock: + folio_unlock(folio); +out: + 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_folio_sector(struct folio *folio) +{ + struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); + struct swap_extent *se; + sector_t sector; + pgoff_t offset; + + offset = swp_offset(folio->swap); + 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); + } +} + +#define LATENCY_LIMIT 256 + +static inline bool cluster_is_empty(struct swap_cluster_info *info) +{ + return info->count == 0; +} + +static inline bool cluster_is_discard(struct swap_cluster_info *info) +{ + return info->flags == CLUSTER_FLAG_DISCARD; +} + +static inline bool cluster_table_is_alloced(struct swap_cluster_info *ci) +{ + return rcu_dereference_protected(ci->table, lockdep_is_held(&ci->lock)); +} + +static inline bool cluster_is_usable(struct swap_cluster_info *ci, int order) +{ + if (unlikely(ci->flags > CLUSTER_FLAG_USABLE)) + return false; + if (!cluster_table_is_alloced(ci)) + return false; + if (!order) + return true; + return cluster_is_empty(ci) || order == ci->order; +} + +static inline unsigned int cluster_index(struct swap_info_struct *si, + struct swap_cluster_info *ci) +{ + return ci - si->cluster_info; +} + +static inline unsigned int cluster_offset(struct swap_info_struct *si, + struct swap_cluster_info *ci) +{ + return cluster_index(si, ci) * SWAPFILE_CLUSTER; +} + +static void swap_cluster_free_table_folio_rcu_cb(struct rcu_head *head) +{ + struct folio *folio; + + folio = page_folio(container_of(head, struct page, rcu_head)); + folio_put(folio); +} + +static void swap_cluster_free_table(struct swap_cluster_info *ci) +{ + struct swap_table *table; + +#ifdef CONFIG_MEMCG + kfree(ci->memcg_table); + ci->memcg_table = NULL; +#endif + +#if !SWAP_TABLE_HAS_ZEROFLAG + kfree(ci->zero_bitmap); + ci->zero_bitmap = NULL; +#endif + + table = (struct swap_table *)rcu_access_pointer(ci->table); + if (!table) + return; + + rcu_assign_pointer(ci->table, NULL); + if (!SWP_TABLE_USE_PAGE) { + kmem_cache_free(swap_table_cachep, table); + return; + } + + call_rcu(&(folio_page(virt_to_folio(table), 0)->rcu_head), + swap_cluster_free_table_folio_rcu_cb); +} + +static int swap_cluster_alloc_table(struct swap_cluster_info *ci, gfp_t gfp) +{ + struct swap_table *table = NULL; + struct folio *folio; + + /* The cluster must be empty and not on any list during allocation. */ + VM_WARN_ON_ONCE(ci->flags || !cluster_is_empty(ci)); + if (rcu_access_pointer(ci->table)) + return 0; + + if (SWP_TABLE_USE_PAGE) { + folio = folio_alloc(gfp | __GFP_ZERO, 0); + if (folio) + table = folio_address(folio); + } else { + table = kmem_cache_zalloc(swap_table_cachep, gfp); + } + if (!table) + return -ENOMEM; + + rcu_assign_pointer(ci->table, table); + +#ifdef CONFIG_MEMCG + if (!mem_cgroup_disabled()) { + VM_WARN_ON_ONCE(ci->memcg_table); + ci->memcg_table = kzalloc_obj(*ci->memcg_table, gfp); + if (!ci->memcg_table) { + swap_cluster_free_table(ci); + return -ENOMEM; + } + } +#endif + +#if !SWAP_TABLE_HAS_ZEROFLAG + VM_WARN_ON_ONCE(ci->zero_bitmap); + ci->zero_bitmap = bitmap_zalloc(SWAPFILE_CLUSTER, gfp); + if (!ci->zero_bitmap) { + swap_cluster_free_table(ci); + return -ENOMEM; + } +#endif + return 0; +} + +/* + * Sanity check to ensure nothing leaked, and the specified range is empty. + * One special case is that bad slots can't be freed, so check the number of + * bad slots for swapoff, and non-swapoff path must never free bad slots. + */ +static void swap_cluster_assert_empty(struct swap_cluster_info *ci, + unsigned int ci_off, unsigned int nr, + bool swapoff) +{ + unsigned int ci_end = ci_off + nr; + unsigned long swp_tb; + int bad_slots = 0; + + if (!IS_ENABLED(CONFIG_DEBUG_VM) && !swapoff) + return; + + do { + swp_tb = __swap_table_get(ci, ci_off); + if (swp_tb_is_bad(swp_tb)) + bad_slots++; + else + WARN_ON_ONCE(!swp_tb_is_null(swp_tb)); + WARN_ON_ONCE(__swap_cgroup_get(ci, ci_off)); + } while (++ci_off < ci_end); + + WARN_ON_ONCE(bad_slots != (swapoff ? ci->count : 0)); + WARN_ON_ONCE(nr == SWAPFILE_CLUSTER && ci->extend_table); +} + +/* + * Allocate swap table for one cluster. Attempt an atomic allocation first, + * then fallback to sleeping allocation. + */ +static struct swap_cluster_info * +swap_cluster_populate(struct swap_info_struct *si, + struct swap_cluster_info *ci) +{ + int ret; + + /* + * Only cluster isolation from the allocator does table allocation. + * Swap allocator uses percpu clusters and holds the local lock. + */ + lockdep_assert_held(&this_cpu_ptr(&percpu_swap_cluster)->lock); + if (!(si->flags & SWP_SOLIDSTATE)) + lockdep_assert_held(&si->global_cluster_lock); + lockdep_assert_held(&ci->lock); + + if (!swap_cluster_alloc_table(ci, __GFP_HIGH | __GFP_NOMEMALLOC | + __GFP_NOWARN)) + return ci; + + /* + * Try a sleep allocation. Each isolated free cluster may cause + * a sleep allocation, but there is a limited number of them, so + * the potential recursive allocation is limited. + */ + spin_unlock(&ci->lock); + if (!(si->flags & SWP_SOLIDSTATE)) + spin_unlock(&si->global_cluster_lock); + local_unlock(&percpu_swap_cluster.lock); + + ret = swap_cluster_alloc_table(ci, __GFP_HIGH | __GFP_NOMEMALLOC | + GFP_KERNEL); + + /* + * Back to atomic context. We might have migrated to a new CPU with a + * usable percpu cluster. But just keep using the isolated cluster to + * make things easier. Migration indicates a slight change of workload + * so using a new free cluster might not be a bad idea, and the worst + * could happen with ignoring the percpu cluster is fragmentation, + * which is acceptable since this fallback and race is rare. + */ + local_lock(&percpu_swap_cluster.lock); + if (!(si->flags & SWP_SOLIDSTATE)) + spin_lock(&si->global_cluster_lock); + spin_lock(&ci->lock); + + if (ret) { + move_cluster(si, ci, &si->free_clusters, CLUSTER_FLAG_FREE); + spin_unlock(&ci->lock); + return NULL; + } + return ci; +} + +static void move_cluster(struct swap_info_struct *si, + struct swap_cluster_info *ci, struct list_head *list, + enum swap_cluster_flags new_flags) +{ + VM_WARN_ON(ci->flags == new_flags); + + BUILD_BUG_ON(1 << sizeof(ci->flags) * BITS_PER_BYTE < CLUSTER_FLAG_MAX); + lockdep_assert_held(&ci->lock); + + spin_lock(&si->lock); + if (ci->flags == CLUSTER_FLAG_NONE) + list_add_tail(&ci->list, list); + else + list_move_tail(&ci->list, list); + spin_unlock(&si->lock); + ci->flags = new_flags; +} + +/* Add a cluster to discard list and schedule it to do discard */ +static void swap_cluster_schedule_discard(struct swap_info_struct *si, + struct swap_cluster_info *ci) +{ + VM_BUG_ON(ci->flags == CLUSTER_FLAG_FREE); + move_cluster(si, ci, &si->discard_clusters, CLUSTER_FLAG_DISCARD); + schedule_work(&si->discard_work); +} + +static void __free_cluster(struct swap_info_struct *si, struct swap_cluster_info *ci) +{ + swap_cluster_assert_empty(ci, 0, SWAPFILE_CLUSTER, false); + swap_cluster_free_table(ci); + move_cluster(si, ci, &si->free_clusters, CLUSTER_FLAG_FREE); + ci->order = 0; +} + +/* + * Isolate and lock the first cluster that is not contented on a list, + * clean its flag before taken off-list. Cluster flag must be in sync + * with list status, so cluster updaters can always know the cluster + * list status without touching si lock. + * + * Note it's possible that all clusters on a list are contented so + * this returns NULL for an non-empty list. + */ +static struct swap_cluster_info *isolate_lock_cluster( + struct swap_info_struct *si, struct list_head *list) +{ + struct swap_cluster_info *ci, *found = NULL; + u8 flags = CLUSTER_FLAG_NONE; + + spin_lock(&si->lock); + list_for_each_entry(ci, list, list) { + if (!spin_trylock(&ci->lock)) + continue; + + /* We may only isolate and clear flags of following lists */ + VM_BUG_ON(!ci->flags); + VM_BUG_ON(ci->flags > CLUSTER_FLAG_USABLE && + ci->flags != CLUSTER_FLAG_FULL); + + list_del(&ci->list); + flags = ci->flags; + ci->flags = CLUSTER_FLAG_NONE; + found = ci; + break; + } + spin_unlock(&si->lock); + + /* Cluster's table is freed when and only when it's on the free list. */ + if (found && flags == CLUSTER_FLAG_FREE) { + VM_WARN_ON_ONCE(list != &si->free_clusters); + VM_WARN_ON_ONCE(cluster_table_is_alloced(found)); + return swap_cluster_populate(si, found); + } + + return found; +} + +/* + * Doing discard actually. After a cluster discard is finished, the cluster + * will be added to free cluster list. Discard cluster is a bit special as + * they don't participate in allocation or reclaim, so clusters marked as + * CLUSTER_FLAG_DISCARD must remain off-list or on discard list. + */ +static bool swap_do_scheduled_discard(struct swap_info_struct *si) +{ + struct swap_cluster_info *ci; + bool ret = false; + unsigned int idx; + + spin_lock(&si->lock); + while (!list_empty(&si->discard_clusters)) { + ci = list_first_entry(&si->discard_clusters, struct swap_cluster_info, list); + /* + * Delete the cluster from list to prepare for discard, but keep + * the CLUSTER_FLAG_DISCARD flag, percpu_swap_cluster could be + * pointing to it, or ran into by relocate_cluster. + */ + list_del(&ci->list); + idx = cluster_index(si, ci); + spin_unlock(&si->lock); + discard_swap_cluster(si, idx * SWAPFILE_CLUSTER, + SWAPFILE_CLUSTER); + + spin_lock(&ci->lock); + /* + * Discard is done, clear its flags as it's off-list, then + * return the cluster to allocation list. + */ + ci->flags = CLUSTER_FLAG_NONE; + __free_cluster(si, ci); + spin_unlock(&ci->lock); + ret = true; + spin_lock(&si->lock); + } + spin_unlock(&si->lock); + return ret; +} + +static void swap_discard_work(struct work_struct *work) +{ + struct swap_info_struct *si; + + si = container_of(work, struct swap_info_struct, discard_work); + + swap_do_scheduled_discard(si); +} + +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); +} + +/* + * Must be called after freeing if ci->count == 0, moves the cluster to free + * or discard list. + */ +static void free_cluster(struct swap_info_struct *si, struct swap_cluster_info *ci) +{ + VM_BUG_ON(ci->count != 0); + VM_BUG_ON(ci->flags == CLUSTER_FLAG_FREE); + lockdep_assert_held(&ci->lock); + + /* + * 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, ci); + return; + } + + __free_cluster(si, ci); +} + +/* + * Must be called after freeing if ci->count != 0, moves the cluster to + * nonfull list. + */ +static void partial_free_cluster(struct swap_info_struct *si, + struct swap_cluster_info *ci) +{ + VM_BUG_ON(!ci->count || ci->count == SWAPFILE_CLUSTER); + lockdep_assert_held(&ci->lock); + + if (ci->flags != CLUSTER_FLAG_NONFULL) + move_cluster(si, ci, &si->nonfull_clusters[ci->order], + CLUSTER_FLAG_NONFULL); +} + +/* + * Must be called after allocation, moves the cluster to full or frag list. + * Note: allocation doesn't acquire si lock, and may drop the ci lock for + * reclaim, so the cluster could be any where when called. + */ +static void relocate_cluster(struct swap_info_struct *si, + struct swap_cluster_info *ci) +{ + lockdep_assert_held(&ci->lock); + + /* Discard cluster must remain off-list or on discard list */ + if (cluster_is_discard(ci)) + return; + + if (!ci->count) { + if (ci->flags != CLUSTER_FLAG_FREE) + free_cluster(si, ci); + } else if (ci->count != SWAPFILE_CLUSTER) { + if (ci->flags != CLUSTER_FLAG_FRAG) + move_cluster(si, ci, &si->frag_clusters[ci->order], + CLUSTER_FLAG_FRAG); + } else { + if (ci->flags != CLUSTER_FLAG_FULL) + move_cluster(si, ci, &si->full_clusters, + CLUSTER_FLAG_FULL); + } +} + +/* + * The cluster corresponding to @offset will be accounted as having one bad + * slot. The cluster will not be added to the free cluster list, and its + * usage counter will be increased by 1. Only used for initialization. + */ +static int swap_cluster_setup_bad_slot(struct swap_info_struct *si, + struct swap_cluster_info *cluster_info, + unsigned int offset, bool mask) +{ + unsigned int ci_off = offset % SWAPFILE_CLUSTER; + unsigned long idx = offset / SWAPFILE_CLUSTER; + struct swap_cluster_info *ci; + int ret = 0; + + /* si->max may got shrunk by swap swap_activate() */ + if (offset >= si->max && !mask) { + pr_debug("Ignoring bad slot %u (max: %u)\n", offset, si->max); + return 0; + } + /* + * Account it, skip header slot: si->pages is initiated as + * si->max - 1. Also skip the masking of last cluster, + * si->pages doesn't include that part. + */ + if (offset && !mask) + si->pages -= 1; + if (!si->pages) { + pr_warn("Empty swap-file\n"); + return -EINVAL; + } + + ci = cluster_info + idx; + /* Need to allocate swap table first for initial bad slot marking. */ + if (!ci->count && swap_cluster_alloc_table(ci, GFP_KERNEL)) + return -ENOMEM; + spin_lock(&ci->lock); + /* Check for duplicated bad swap slots. */ + if (__swap_table_xchg(ci, ci_off, SWP_TB_BAD) != SWP_TB_NULL) { + pr_warn("Duplicated bad slot offset %d\n", offset); + ret = -EINVAL; + } else { + ci->count++; + } + spin_unlock(&ci->lock); + + WARN_ON(ci->count > SWAPFILE_CLUSTER); + WARN_ON(ci->flags); + + return ret; +} + +/* + * Reclaim drops the ci lock, so the cluster may become unusable (freed or + * stolen by a lower order). @usable will be set to false if that happens. + */ +static bool cluster_reclaim_range(struct swap_info_struct *si, + struct swap_cluster_info *ci, + unsigned long start, unsigned int order, + bool *usable) +{ + unsigned int nr_pages = 1 << order; + unsigned long offset = start, end = start + nr_pages; + unsigned long swp_tb; + + spin_unlock(&ci->lock); + do { + swp_tb = swap_table_get(ci, offset % SWAPFILE_CLUSTER); + if (swp_tb_get_count(swp_tb)) + break; + if (swp_tb_is_folio(swp_tb)) + if (__try_to_reclaim_swap(si, offset, TTRS_ANYWAY) < 0) + break; + } while (++offset < end); + spin_lock(&ci->lock); + + /* + * We just dropped ci->lock so cluster could be used by another + * order or got freed, check if it's still usable or empty. + */ + if (!cluster_is_usable(ci, order)) { + *usable = false; + return false; + } + *usable = true; + + /* Fast path, no need to scan if the whole cluster is empty */ + if (cluster_is_empty(ci)) + return true; + + /* + * Recheck the range no matter reclaim succeeded or not, the slot + * could have been be freed while we are not holding the lock. + */ + for (offset = start; offset < end; offset++) { + swp_tb = __swap_table_get(ci, offset % SWAPFILE_CLUSTER); + if (!swp_tb_is_null(swp_tb)) + return false; + } + + return true; +} + +static bool cluster_scan_range(struct swap_info_struct *si, + struct swap_cluster_info *ci, + unsigned long offset, unsigned int nr_pages, + bool *need_reclaim) +{ + unsigned int ci_off = offset % SWAPFILE_CLUSTER; + unsigned int ci_end = ci_off + nr_pages; + unsigned long swp_tb; + + do { + swp_tb = __swap_table_get(ci, ci_off); + if (swp_tb_is_null(swp_tb)) + continue; + if (swp_tb_is_folio(swp_tb) && !__swp_tb_get_count(swp_tb)) { + if (!vm_swap_full()) + return false; + *need_reclaim = true; + continue; + } + /* Slot with zero count can only be NULL or folio */ + VM_WARN_ON(!swp_tb_get_count(swp_tb)); + return false; + } while (++ci_off < ci_end); + + return true; +} + +static bool __swap_cluster_alloc_entries(struct swap_info_struct *si, + struct swap_cluster_info *ci, + struct folio *folio, + unsigned int ci_off) +{ + unsigned int order; + unsigned long nr_pages; + + lockdep_assert_held(&ci->lock); + + if (!(si->flags & SWP_WRITEOK)) + return false; + + /* + * All mm swap allocation starts with a folio (folio_alloc_swap), + * it's also the only allocation path for large orders allocation. + * Such swap slots starts with count == 0 and will be increased + * upon folio unmap. + * + * Else, it's a exclusive order 0 allocation for hibernation. + * The slot starts with count == 1 and never increases. + */ + if (likely(folio)) { + order = folio_order(folio); + nr_pages = 1 << order; + swap_cluster_assert_empty(ci, ci_off, nr_pages, false); + __swap_cache_add_folio(ci, folio, swp_entry(si->type, + ci_off + cluster_offset(si, ci))); + } else if (IS_ENABLED(CONFIG_HIBERNATION)) { + order = 0; + nr_pages = 1; + swap_cluster_assert_empty(ci, ci_off, 1, false); + /* Fake shadow placeholder with no flag, hibernation does not use the zeromap */ + __swap_table_set(ci, ci_off, __swp_tb_mk_count(shadow_to_swp_tb(NULL, 0), 1)); + } else { + /* Allocation without folio is only possible with hibernation */ + WARN_ON_ONCE(1); + return false; + } + + /* + * The first allocation in a cluster makes the + * cluster exclusive to this order + */ + if (cluster_is_empty(ci)) + ci->order = order; + ci->count += nr_pages; + swap_range_alloc(si, nr_pages); + + return true; +} + +/* Try use a new cluster for current CPU and allocate from it. */ +static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si, + struct swap_cluster_info *ci, + struct folio *folio, unsigned long offset) +{ + unsigned int next = SWAP_ENTRY_INVALID, found = SWAP_ENTRY_INVALID; + unsigned long start = ALIGN_DOWN(offset, SWAPFILE_CLUSTER); + unsigned int order = likely(folio) ? folio_order(folio) : 0; + unsigned long end = start + SWAPFILE_CLUSTER; + unsigned int nr_pages = 1 << order; + bool need_reclaim, ret, usable; + + lockdep_assert_held(&ci->lock); + VM_WARN_ON(!cluster_is_usable(ci, order)); + + if (end < nr_pages || ci->count + nr_pages > SWAPFILE_CLUSTER) + goto out; + + for (end -= nr_pages; offset <= end; offset += nr_pages) { + need_reclaim = false; + if (!cluster_scan_range(si, ci, offset, nr_pages, &need_reclaim)) + continue; + if (need_reclaim) { + ret = cluster_reclaim_range(si, ci, offset, order, &usable); + if (!usable) + goto out; + if (cluster_is_empty(ci)) + offset = start; + /* Reclaim failed but cluster is usable, try next */ + if (!ret) + continue; + } + if (!__swap_cluster_alloc_entries(si, ci, folio, offset % SWAPFILE_CLUSTER)) + break; + found = offset; + offset += nr_pages; + if (ci->count < SWAPFILE_CLUSTER && offset <= end) + next = offset; + break; + } +out: + relocate_cluster(si, ci); + swap_cluster_unlock(ci); + if (si->flags & SWP_SOLIDSTATE) { + this_cpu_write(percpu_swap_cluster.offset[order], next); + this_cpu_write(percpu_swap_cluster.si[order], si); + } else { + si->global_cluster->next[order] = next; + } + return found; +} + +static unsigned int alloc_swap_scan_list(struct swap_info_struct *si, + struct list_head *list, + struct folio *folio, + bool scan_all) +{ + unsigned int found = SWAP_ENTRY_INVALID; + + do { + struct swap_cluster_info *ci = isolate_lock_cluster(si, list); + unsigned long offset; + + if (!ci) + break; + offset = cluster_offset(si, ci); + found = alloc_swap_scan_cluster(si, ci, folio, offset); + if (found) + break; + } while (scan_all); + + return found; +} + +static void swap_reclaim_full_clusters(struct swap_info_struct *si, bool force) +{ + long to_scan = 1; + unsigned long offset, end; + struct swap_cluster_info *ci; + unsigned long swp_tb; + int nr_reclaim; + + if (force) + to_scan = swap_usage_in_pages(si) / SWAPFILE_CLUSTER; + + while ((ci = isolate_lock_cluster(si, &si->full_clusters))) { + offset = cluster_offset(si, ci); + end = min(si->max, offset + SWAPFILE_CLUSTER); + to_scan--; + + while (offset < end) { + swp_tb = swap_table_get(ci, offset % SWAPFILE_CLUSTER); + if (swp_tb_is_folio(swp_tb) && !__swp_tb_get_count(swp_tb)) { + spin_unlock(&ci->lock); + nr_reclaim = __try_to_reclaim_swap(si, offset, + TTRS_ANYWAY); + spin_lock(&ci->lock); + if (nr_reclaim) { + offset += abs(nr_reclaim); + continue; + } + } + offset++; + } + + /* in case no swap cache is reclaimed */ + if (ci->flags == CLUSTER_FLAG_NONE) + relocate_cluster(si, ci); + + swap_cluster_unlock(ci); + if (to_scan <= 0) + break; + + /* + * When 'force' is false, 'to_scan' is initialized to 1. + * The loop breaks above, making this cond_resched() unreachable + * in atomic contexts. + */ + cond_resched(); + } +} + +static void swap_reclaim_work(struct work_struct *work) +{ + struct swap_info_struct *si; + + si = container_of(work, struct swap_info_struct, reclaim_work); + + swap_reclaim_full_clusters(si, true); +} + +/* + * Try to allocate swap entries with specified order and try set a new + * cluster for current CPU too. + */ +static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, + struct folio *folio) +{ + struct swap_cluster_info *ci; + unsigned int order = likely(folio) ? folio_order(folio) : 0; + unsigned int offset = SWAP_ENTRY_INVALID, found = SWAP_ENTRY_INVALID; + + /* + * Swapfile is not block device so unable + * to allocate large entries. + */ + if (order && !(si->flags & SWP_BLKDEV)) + return 0; + + if (!(si->flags & SWP_SOLIDSTATE)) { + /* Serialize HDD SWAP allocation for each device. */ + spin_lock(&si->global_cluster_lock); + offset = si->global_cluster->next[order]; + if (offset == SWAP_ENTRY_INVALID) + goto new_cluster; + + ci = swap_cluster_lock(si, offset); + /* Cluster could have been used by another order */ + if (cluster_is_usable(ci, order)) { + if (cluster_is_empty(ci)) + offset = cluster_offset(si, ci); + found = alloc_swap_scan_cluster(si, ci, folio, offset); + } else { + swap_cluster_unlock(ci); + } + if (found) + goto done; + } + +new_cluster: + /* + * If the device need discard, prefer new cluster over nonfull + * to spread out the writes. + */ + if (si->flags & SWP_PAGE_DISCARD) { + found = alloc_swap_scan_list(si, &si->free_clusters, folio, false); + if (found) + goto done; + } + + if (order < PMD_ORDER) { + found = alloc_swap_scan_list(si, &si->nonfull_clusters[order], folio, true); + if (found) + goto done; + } + + if (!(si->flags & SWP_PAGE_DISCARD)) { + found = alloc_swap_scan_list(si, &si->free_clusters, folio, false); + if (found) + goto done; + } + + /* Try reclaim full clusters if free and nonfull lists are drained */ + if (vm_swap_full()) + swap_reclaim_full_clusters(si, false); + + if (order < PMD_ORDER) { + /* + * Scan only one fragment cluster is good enough. Order 0 + * allocation will surely success, and large allocation + * failure is not critical. Scanning one cluster still + * keeps the list rotated and reclaimed (for clean swap cache). + */ + found = alloc_swap_scan_list(si, &si->frag_clusters[order], folio, false); + if (found) + goto done; + } + + if (order) + goto done; + + /* Order 0 stealing from higher order */ + for (int o = 1; o < SWAP_NR_ORDERS; o++) { + /* + * Clusters here have at least one usable slots and can't fail order 0 + * allocation, but reclaim may drop si->lock and race with another user. + */ + found = alloc_swap_scan_list(si, &si->frag_clusters[o], folio, true); + if (found) + goto done; + + found = alloc_swap_scan_list(si, &si->nonfull_clusters[o], folio, true); + if (found) + goto done; + } +done: + if (!(si->flags & SWP_SOLIDSTATE)) + spin_unlock(&si->global_cluster_lock); + + return found; +} + +/* SWAP_USAGE_OFFLIST_BIT can only be set by this helper. */ +static void del_from_avail_list(struct swap_info_struct *si, bool swapoff) +{ + unsigned long pages; + + spin_lock(&swap_avail_lock); + + if (swapoff) { + /* + * Forcefully remove it. Clear the SWP_WRITEOK flags for + * swapoff here so it's synchronized by both si->lock and + * swap_avail_lock, to ensure the result can be seen by + * add_to_avail_list. + */ + lockdep_assert_held(&si->lock); + si->flags &= ~SWP_WRITEOK; + atomic_long_or(SWAP_USAGE_OFFLIST_BIT, &si->inuse_pages); + } else { + /* + * If not called by swapoff, take it off-list only if it's + * full and SWAP_USAGE_OFFLIST_BIT is not set (strictly + * si->inuse_pages == pages), any concurrent slot freeing, + * or device already removed from plist by someone else + * will make this return false. + */ + pages = si->pages; + if (!atomic_long_try_cmpxchg(&si->inuse_pages, &pages, + pages | SWAP_USAGE_OFFLIST_BIT)) + goto skip; + } + + plist_del(&si->avail_list, &swap_avail_head); + +skip: + spin_unlock(&swap_avail_lock); +} + +/* SWAP_USAGE_OFFLIST_BIT can only be cleared by this helper. */ +static void add_to_avail_list(struct swap_info_struct *si, bool swapon) +{ + long val; + unsigned long pages; + + spin_lock(&swap_avail_lock); + + /* Corresponding to SWP_WRITEOK clearing in del_from_avail_list */ + if (swapon) { + lockdep_assert_held(&si->lock); + si->flags |= SWP_WRITEOK; + } else { + if (!(READ_ONCE(si->flags) & SWP_WRITEOK)) + goto skip; + } + + if (!(atomic_long_read(&si->inuse_pages) & SWAP_USAGE_OFFLIST_BIT)) + goto skip; + + val = atomic_long_fetch_and_relaxed(~SWAP_USAGE_OFFLIST_BIT, &si->inuse_pages); + + /* + * When device is full and device is on the plist, only one updater will + * see (inuse_pages == si->pages) and will call del_from_avail_list. If + * that updater happen to be here, just skip adding. + */ + pages = si->pages; + if (val == pages) { + /* Just like the cmpxchg in del_from_avail_list */ + if (atomic_long_try_cmpxchg(&si->inuse_pages, &pages, + pages | SWAP_USAGE_OFFLIST_BIT)) + goto skip; + } + + plist_add(&si->avail_list, &swap_avail_head); + +skip: + spin_unlock(&swap_avail_lock); +} + +/* + * swap_usage_add / swap_usage_sub of each slot are serialized by ci->lock + * within each cluster, so the total contribution to the global counter should + * always be positive and cannot exceed the total number of usable slots. + */ +static bool swap_usage_add(struct swap_info_struct *si, unsigned int nr_entries) +{ + long val = atomic_long_add_return_relaxed(nr_entries, &si->inuse_pages); + + /* + * If device is full, and SWAP_USAGE_OFFLIST_BIT is not set, + * remove it from the plist. + */ + if (unlikely(val == si->pages)) { + del_from_avail_list(si, false); + return true; + } + + return false; +} + +static void swap_usage_sub(struct swap_info_struct *si, unsigned int nr_entries) +{ + long val = atomic_long_sub_return_relaxed(nr_entries, &si->inuse_pages); + + /* + * If device is not full, and SWAP_USAGE_OFFLIST_BIT is set, + * add it to the plist. + */ + if (unlikely(val & SWAP_USAGE_OFFLIST_BIT)) + add_to_avail_list(si, false); +} + +static void swap_range_alloc(struct swap_info_struct *si, + unsigned int nr_entries) +{ + if (swap_usage_add(si, nr_entries)) { + if (vm_swap_full()) + schedule_work(&si->reclaim_work); + } + atomic_long_sub(nr_entries, &nr_swap_pages); +} + +static void swap_range_free(struct swap_info_struct *si, unsigned long offset, + unsigned int nr_entries) +{ + unsigned long end = offset + nr_entries - 1; + void (*swap_slot_free_notify)(struct block_device *, unsigned long); + unsigned int i; + + for (i = 0; i < nr_entries; i++) + zswap_invalidate(swp_entry(si->type, offset + i)); + + 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); + if (swap_slot_free_notify) + swap_slot_free_notify(si->bdev, offset); + offset++; + } + + /* + * Make sure that try_to_unuse() observes si->inuse_pages reaching 0 + * only after the above cleanups are done. + */ + smp_wmb(); + atomic_long_add(nr_entries, &nr_swap_pages); + swap_usage_sub(si, nr_entries); +} + +static bool get_swap_device_info(struct swap_info_struct *si) +{ + if (!percpu_ref_tryget_live(&si->users)) + return false; + /* + * Guarantee the si->users are checked before accessing other + * fields of swap_info_struct, and si->flags (SWP_WRITEOK) is + * up to dated. + * + * Paired with the spin_unlock() after setup_swap_info() in + * enable_swap_info(), and smp_wmb() in swapoff. + */ + smp_rmb(); + return true; +} + +/* + * Fast path try to get swap entries with specified order from current + * CPU's swap entry pool (a cluster). + */ +static bool swap_alloc_fast(struct folio *folio) +{ + unsigned int order = folio_order(folio); + struct swap_cluster_info *ci; + struct swap_info_struct *si; + unsigned int offset; + + /* + * Once allocated, swap_info_struct will never be completely freed, + * so checking it's liveness by get_swap_device_info is enough. + */ + si = this_cpu_read(percpu_swap_cluster.si[order]); + offset = this_cpu_read(percpu_swap_cluster.offset[order]); + if (!si || !offset || !get_swap_device_info(si)) + return false; + + ci = swap_cluster_lock(si, offset); + if (cluster_is_usable(ci, order)) { + if (cluster_is_empty(ci)) + offset = cluster_offset(si, ci); + alloc_swap_scan_cluster(si, ci, folio, offset); + } else { + swap_cluster_unlock(ci); + } + + put_swap_device(si); + return folio_test_swapcache(folio); +} + +/* Rotate the device and switch to a new cluster */ +static void swap_alloc_slow(struct folio *folio) +{ + struct swap_info_struct *si, *next; + + spin_lock(&swap_avail_lock); +start_over: + plist_for_each_entry_safe(si, next, &swap_avail_head, avail_list) { + /* Rotate the device and switch to a new cluster */ + plist_requeue(&si->avail_list, &swap_avail_head); + spin_unlock(&swap_avail_lock); + if (get_swap_device_info(si)) { + cluster_alloc_swap_entry(si, folio); + put_swap_device(si); + if (folio_test_swapcache(folio)) + return; + if (folio_test_large(folio)) + return; + } + + spin_lock(&swap_avail_lock); + /* + * if we got here, it's likely that si was almost full before, + * 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. + * Since we dropped the swap_avail_lock, the swap_avail_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_list)) + goto start_over; + } + spin_unlock(&swap_avail_lock); +} + +/* + * Discard pending clusters in a synchronized way when under high pressure. + * Return: true if any cluster is discarded. + */ +static bool swap_sync_discard(void) +{ + bool ret = false; + struct swap_info_struct *si, *next; + + spin_lock(&swap_lock); +start_over: + plist_for_each_entry_safe(si, next, &swap_active_head, list) { + spin_unlock(&swap_lock); + if (get_swap_device_info(si)) { + if (si->flags & SWP_PAGE_DISCARD) + ret = swap_do_scheduled_discard(si); + put_swap_device(si); + } + if (ret) + return true; + + spin_lock(&swap_lock); + if (plist_node_empty(&next->list)) + goto start_over; + } + spin_unlock(&swap_lock); + + return false; +} + +static int swap_extend_table_alloc(struct swap_info_struct *si, + struct swap_cluster_info *ci, + unsigned int ci_off, gfp_t gfp) +{ + int count; + void *table; + + table = kzalloc(sizeof(ci->extend_table[0]) * SWAPFILE_CLUSTER, gfp); + if (!table) + return -ENOMEM; + + spin_lock(&ci->lock); + /* + * Extend table allocation requires releasing ci lock first so it's + * possible that the slot has been freed, no longer overflowed, or + * a concurrent extend table allocation has already succeeded, so + * the allocation is no longer needed. + */ + if (!cluster_table_is_alloced(ci)) + goto out_free; + count = swp_tb_get_count(__swap_table_get(ci, ci_off)); + if (count < (SWP_TB_COUNT_MAX - 1)) + goto out_free; + if (ci->extend_table) + goto out_free; + + ci->extend_table = table; + spin_unlock(&ci->lock); + return 0; + +out_free: + spin_unlock(&ci->lock); + kfree(table); + return 0; +} + +int swap_retry_table_alloc(swp_entry_t entry, gfp_t gfp) +{ + int ret; + struct swap_info_struct *si; + struct swap_cluster_info *ci; + unsigned long offset = swp_offset(entry); + + si = get_swap_device(entry); + if (!si) + return 0; + + ci = __swap_offset_to_cluster(si, offset); + ret = swap_extend_table_alloc(si, ci, swp_cluster_offset(entry), gfp); + + put_swap_device(si); + return ret; +} + +static void swap_extend_table_try_free(struct swap_cluster_info *ci) +{ + unsigned long i; + bool can_free = true; + + if (!ci->extend_table) + return; + + for (i = 0; i < SWAPFILE_CLUSTER; i++) { + if (ci->extend_table[i]) + can_free = false; + } + + if (can_free) { + kfree(ci->extend_table); + ci->extend_table = NULL; + } +} + +/* Decrease the swap count of one slot, without freeing it */ +static void __swap_cluster_put_entry(struct swap_cluster_info *ci, + unsigned int ci_off) +{ + int count; + unsigned long swp_tb; + + lockdep_assert_held(&ci->lock); + swp_tb = __swap_table_get(ci, ci_off); + count = __swp_tb_get_count(swp_tb); + + VM_WARN_ON_ONCE(count <= 0); + VM_WARN_ON_ONCE(count > SWP_TB_COUNT_MAX); + + if (count == SWP_TB_COUNT_MAX) { + count = ci->extend_table[ci_off]; + /* Overflow starts with SWP_TB_COUNT_MAX */ + VM_WARN_ON_ONCE(count < SWP_TB_COUNT_MAX); + count--; + if (count == (SWP_TB_COUNT_MAX - 1)) { + ci->extend_table[ci_off] = 0; + __swap_table_set(ci, ci_off, __swp_tb_mk_count(swp_tb, count)); + } else { + ci->extend_table[ci_off] = count; + } + } else { + __swap_table_set(ci, ci_off, __swp_tb_mk_count(swp_tb, --count)); + } + + /* + * `SWP_TB_COUNT_MAX - 1` triggers extend table allocation. If the + * count was above that, then the extend table is no longer needed, + * so free it. And if we just put the count value from MAX - 1, it's + * also possible that a pending dup just attached an extend table. + */ + if (unlikely(count == SWP_TB_COUNT_MAX - 2 || count == SWP_TB_COUNT_MAX - 1)) + swap_extend_table_try_free(ci); +} + +/** + * swap_put_entries_cluster - Decrease the swap count of slots within one cluster + * @si: The swap device. + * @offset: start offset of slots. + * @nr: number of slots. + * @reclaim_cache: if true, also reclaim the swap cache if slots are freed. + * + * This helper decreases the swap count of a set of slots and tries to + * batch free them. Also reclaims the swap cache if @reclaim_cache is true. + * + * Context: The specified slots must be pinned by existing swap count or swap + * cache reference, so they won't be released until this helper returns. + */ +static void swap_put_entries_cluster(struct swap_info_struct *si, + pgoff_t offset, int nr, + bool reclaim_cache) +{ + struct swap_cluster_info *ci; + unsigned int ci_off, ci_end; + pgoff_t end = offset + nr; + bool need_reclaim = false; + unsigned int nr_reclaimed; + unsigned long swp_tb; + int ci_batch = -1; + + ci = swap_cluster_lock(si, offset); + ci_off = offset % SWAPFILE_CLUSTER; + ci_end = ci_off + nr; + do { + swp_tb = __swap_table_get(ci, ci_off); + if (swp_tb_get_count(swp_tb) == 1) { + /* count == 1 and non-cached slots will be batch freed. */ + if (!swp_tb_is_folio(swp_tb)) { + if (ci_batch == -1) + ci_batch = ci_off; + continue; + } + /* count will be 0 after put, slot can be reclaimed */ + need_reclaim = true; + } + /* + * A count != 1 or cached slot can't be freed. Put its swap + * count and then free the interrupted pending batch. Cached + * slots will be freed when folio is removed from swap cache + * (__swap_cache_del_folio). + */ + __swap_cluster_put_entry(ci, ci_off); + if (ci_batch != -1) { + __swap_cluster_free_entries(si, ci, ci_batch, ci_off - ci_batch); + ci_batch = -1; + } + } while (++ci_off < ci_end); + + if (ci_batch != -1) + __swap_cluster_free_entries(si, ci, ci_batch, ci_off - ci_batch); + swap_cluster_unlock(ci); + + if (!need_reclaim || !reclaim_cache) + return; + + do { + nr_reclaimed = __try_to_reclaim_swap(si, offset, + TTRS_UNMAPPED | TTRS_FULL); + offset++; + if (nr_reclaimed) + offset = round_up(offset, abs(nr_reclaimed)); + } while (offset < end); +} + +/* Increase the swap count of one slot. */ +static int __swap_cluster_dup_entry(struct swap_cluster_info *ci, + unsigned int ci_off) +{ + int count; + unsigned long swp_tb; + + lockdep_assert_held(&ci->lock); + swp_tb = __swap_table_get(ci, ci_off); + /* Bad or special slots can't be handled */ + if (WARN_ON_ONCE(swp_tb_is_bad(swp_tb))) + return -EINVAL; + count = __swp_tb_get_count(swp_tb); + /* Must be either cached or have a count already */ + if (WARN_ON_ONCE(!count && !swp_tb_is_folio(swp_tb))) + return -ENOENT; + + if (likely(count < (SWP_TB_COUNT_MAX - 1))) { + __swap_table_set(ci, ci_off, __swp_tb_mk_count(swp_tb, count + 1)); + VM_WARN_ON_ONCE(ci->extend_table && ci->extend_table[ci_off]); + } else if (count == (SWP_TB_COUNT_MAX - 1)) { + if (ci->extend_table) { + VM_WARN_ON_ONCE(ci->extend_table[ci_off]); + ci->extend_table[ci_off] = SWP_TB_COUNT_MAX; + __swap_table_set(ci, ci_off, __swp_tb_mk_count(swp_tb, SWP_TB_COUNT_MAX)); + } else { + return -ENOMEM; + } + } else if (count == SWP_TB_COUNT_MAX) { + VM_WARN_ON_ONCE(ci->extend_table[ci_off] >= + type_max(typeof(ci->extend_table[0]))); + ++ci->extend_table[ci_off]; + } else { + /* Never happens unless counting went wrong */ + WARN_ON_ONCE(1); + } + + return 0; +} + +/** + * swap_dup_entries_cluster: Increase the swap count of slots within one cluster. + * @si: The swap device. + * @offset: start offset of slots. + * @nr: number of slots. + * + * Context: The specified slots must be pinned by existing swap count or swap + * cache reference, so they won't be released until this helper returns. + * Return: 0 on success. -ENOMEM if the swap count maxed out (SWP_TB_COUNT_MAX) + * and failed to allocate an extended table, -EINVAL if any entry is bad entry. + */ +static int swap_dup_entries_cluster(struct swap_info_struct *si, + pgoff_t offset, int nr) +{ + int err; + struct swap_cluster_info *ci; + unsigned int ci_start, ci_off, ci_end; + + ci_start = offset % SWAPFILE_CLUSTER; + ci_end = ci_start + nr; + ci_off = ci_start; + ci = swap_cluster_lock(si, offset); +restart: + do { + err = __swap_cluster_dup_entry(ci, ci_off); + if (unlikely(err)) { + if (err == -ENOMEM) { + spin_unlock(&ci->lock); + err = swap_extend_table_alloc(si, ci, ci_off, GFP_ATOMIC); + spin_lock(&ci->lock); + if (!err) + goto restart; + } + goto failed; + } + } while (++ci_off < ci_end); + swap_cluster_unlock(ci); + return 0; +failed: + while (ci_off-- > ci_start) + __swap_cluster_put_entry(ci, ci_off); + swap_extend_table_try_free(ci); + swap_cluster_unlock(ci); + return err; +} + +/** + * folio_alloc_swap - allocate swap space for a folio + * @folio: folio we want to move to swap + * + * Allocate swap space for the folio and add the folio to the + * swap cache. + * + * Context: Caller needs to hold the folio lock. + * Return: Whether the folio was added to the swap cache. + */ +int folio_alloc_swap(struct folio *folio) +{ + unsigned int order = folio_order(folio); + unsigned int size = 1 << order; + + VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); + VM_BUG_ON_FOLIO(!folio_test_uptodate(folio), folio); + + if (order) { + /* + * Reject large allocation when THP_SWAP is disabled, + * the caller should split the folio and try again. + */ + if (!IS_ENABLED(CONFIG_THP_SWAP)) + return -EAGAIN; + + /* + * Allocation size should never exceed cluster size + * (HPAGE_PMD_SIZE). + */ + if (size > SWAPFILE_CLUSTER) { + VM_WARN_ON_ONCE(1); + return -EINVAL; + } + } + +again: + local_lock(&percpu_swap_cluster.lock); + if (!swap_alloc_fast(folio)) + swap_alloc_slow(folio); + local_unlock(&percpu_swap_cluster.lock); + + if (!order && unlikely(!folio_test_swapcache(folio))) { + if (swap_sync_discard()) + goto again; + } + + /* Need to call this even if allocation failed, for MEMCG_SWAP_FAIL. */ + if (unlikely(mem_cgroup_try_charge_swap(folio))) + swap_cache_del_folio(folio); + + if (unlikely(!folio_test_swapcache(folio))) + return -ENOMEM; + + return 0; +} + +/** + * folio_dup_swap() - Increase swap count of swap entries of a folio. + * @folio: folio with swap entries bounded. + * @page: if not NULL, only increase the swap count of this page. + * + * Typically called when the folio is unmapped and have its swap entry to + * take its place: Swap entries allocated to a folio has count == 0 and pinned + * by swap cache. The swap cache pin doesn't increase the swap count. This + * helper sets the initial count == 1 and increases the count as the folio is + * unmapped and swap entries referencing the slots are generated to replace + * the folio. + * + * Context: Caller must ensure the folio is locked and in the swap cache. + * NOTE: The caller also has to ensure there is no raced call to + * swap_put_entries_direct on its swap entry before this helper returns, or + * the swap count may underflow. + */ +int folio_dup_swap(struct folio *folio, struct page *page) +{ + swp_entry_t entry = folio->swap; + unsigned long nr_pages = folio_nr_pages(folio); + + VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio); + VM_WARN_ON_FOLIO(!folio_test_swapcache(folio), folio); + + if (page) { + entry.val += folio_page_idx(folio, page); + nr_pages = 1; + } + + return swap_dup_entries_cluster(swap_entry_to_info(entry), + swp_offset(entry), nr_pages); +} + +/** + * folio_put_swap() - Decrease swap count of swap entries of a folio. + * @folio: folio with swap entries bounded, must be in swap cache and locked. + * @page: if not NULL, only decrease the swap count of this page. + * + * This won't free the swap slots even if swap count drops to zero, they are + * still pinned by the swap cache. User may call folio_free_swap to free them. + * Context: Caller must ensure the folio is locked and in the swap cache. + */ +void folio_put_swap(struct folio *folio, struct page *page) +{ + swp_entry_t entry = folio->swap; + unsigned long nr_pages = folio_nr_pages(folio); + struct swap_info_struct *si = __swap_entry_to_info(entry); + + VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio); + VM_WARN_ON_FOLIO(!folio_test_swapcache(folio), folio); + + if (page) { + entry.val += folio_page_idx(folio, page); + nr_pages = 1; + } + + swap_put_entries_cluster(si, swp_offset(entry), nr_pages, false); +} + +/* + * 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, RCU + * reader side is locked, 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. + * + * RCU reader side lock (including any spinlock) is sufficient to + * prevent swapoff, because synchronize_rcu() is called in swapoff() + * before freeing data structures. + * + * 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 + * swap_cache_alloc_folio() + * // 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 = swap_entry_to_info(entry); + if (!si) + goto bad_nofile; + if (!get_swap_device_info(si)) + goto out; + offset = swp_offset(entry); + if (offset >= si->max) + goto put_out; + + return si; +bad_nofile: + pr_err_ratelimited("%s: %s%08lx\n", __func__, Bad_file, entry.val); +out: + return NULL; +put_out: + pr_err_ratelimited("%s: %s%08lx\n", __func__, Bad_offset, entry.val); + percpu_ref_put(&si->users); + return NULL; +} + +/* + * Free a set of swap slots after their swap count dropped to zero, or will be + * zero after putting the last ref (saves one __swap_cluster_put_entry call). + */ +void __swap_cluster_free_entries(struct swap_info_struct *si, + struct swap_cluster_info *ci, + unsigned int ci_start, unsigned int nr_pages) +{ + unsigned long old_tb; + unsigned short batch_id = 0, id_cur; + unsigned int ci_off = ci_start, ci_end = ci_start + nr_pages; + unsigned long ci_head = cluster_offset(si, ci); + unsigned int batch_off = ci_off; + + VM_WARN_ON(ci->count < nr_pages); + + ci->count -= nr_pages; + do { + old_tb = __swap_table_get(ci, ci_off); + /* + * Freeing is done after release of the last swap count + * ref, or after swap cache is dropped + */ + VM_WARN_ON(!swp_tb_is_shadow(old_tb) || __swp_tb_get_count(old_tb) > 1); + + /* Resetting the slot to NULL also clears the inline flags. */ + __swap_table_set(ci, ci_off, null_to_swp_tb()); + if (!SWAP_TABLE_HAS_ZEROFLAG) + __swap_table_clear_zero(ci, ci_off); + + /* + * Uncharge swap slots by memcg in batches. Consecutive + * slots with the same cgroup id are uncharged together. + */ + id_cur = __swap_cgroup_clear(ci, ci_off, 1); + if (batch_id != id_cur) { + if (batch_id) + mem_cgroup_uncharge_swap(batch_id, ci_off - batch_off); + batch_id = id_cur; + batch_off = ci_off; + } + } while (++ci_off < ci_end); + + if (batch_id) + mem_cgroup_uncharge_swap(batch_id, ci_off - batch_off); + + swap_range_free(si, ci_head + ci_start, nr_pages); + swap_cluster_assert_empty(ci, ci_start, nr_pages, false); + + if (!ci->count) + free_cluster(si, ci); + else + partial_free_cluster(si, ci); +} + +int __swap_count(swp_entry_t entry) +{ + struct swap_cluster_info *ci = __swap_entry_to_cluster(entry); + unsigned int ci_off = swp_cluster_offset(entry); + + return swp_tb_get_count(__swap_table_get(ci, ci_off)); +} + +/** + * swap_entry_swapped - Check if the swap entry is swapped. + * @si: the swap device. + * @entry: the swap entry. + */ +bool swap_entry_swapped(struct swap_info_struct *si, swp_entry_t entry) +{ + pgoff_t offset = swp_offset(entry); + struct swap_cluster_info *ci; + unsigned long swp_tb; + + ci = swap_cluster_lock(si, offset); + swp_tb = swap_table_get(ci, offset % SWAPFILE_CLUSTER); + swap_cluster_unlock(ci); + + return swp_tb_get_count(swp_tb) > 0; +} + +/* + * How many references to @entry are currently swapped out? + * This returns exact answer. + */ +int swp_swapcount(swp_entry_t entry) +{ + struct swap_info_struct *si; + struct swap_cluster_info *ci; + unsigned long swp_tb; + int count; + + si = get_swap_device(entry); + if (!si) + return 0; + + ci = swap_cluster_lock(si, swp_offset(entry)); + swp_tb = __swap_table_get(ci, swp_cluster_offset(entry)); + count = swp_tb_get_count(swp_tb); + if (count == SWP_TB_COUNT_MAX) + count = ci->extend_table[swp_cluster_offset(entry)]; + swap_cluster_unlock(ci); + put_swap_device(si); + + return count < 0 ? 0 : count; +} + +/* + * folio_maybe_swapped - Test if a folio covers any swap slot with count > 0. + * + * Check if a folio is swapped. Holding the folio lock ensures the folio won't + * go from not-swapped to swapped because the initial swap count increment can + * only be done by folio_dup_swap, which also locks the folio. But a concurrent + * decrease of swap count is possible through swap_put_entries_direct, so this + * may return a false positive. + * + * Context: Caller must ensure the folio is locked and in the swap cache. + */ +static bool folio_maybe_swapped(struct folio *folio) +{ + swp_entry_t entry = folio->swap; + struct swap_cluster_info *ci; + unsigned int ci_off, ci_end; + bool ret = false; + + VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio); + VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio); + + ci = __swap_entry_to_cluster(entry); + ci_off = swp_cluster_offset(entry); + ci_end = ci_off + folio_nr_pages(folio); + /* + * Extra locking not needed, folio lock ensures its swap entries + * won't be released, the backing data won't be gone either. + */ + rcu_read_lock(); + do { + if (__swp_tb_get_count(__swap_table_get(ci, ci_off))) { + ret = true; + break; + } + } while (++ci_off < ci_end); + rcu_read_unlock(); + + return ret; +} + +static bool folio_swapcache_freeable(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; + + /* + * 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; + + return true; +} + +/** + * 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) +{ + if (!folio_swapcache_freeable(folio)) + return false; + if (folio_maybe_swapped(folio)) + return false; + + swap_cache_del_folio(folio); + folio_set_dirty(folio); + return true; +} + +/** + * swap_put_entries_direct() - Release reference on range of swap entries and + * reclaim their cache if no more references remain. + * @entry: First entry of range. + * @nr: Number of entries in range. + * + * For each swap entry in the contiguous range, release a reference. If any swap + * entries become free, try to reclaim their underlying folios, if present. The + * offset range is defined by [entry.offset, entry.offset + nr). + * + * Context: Caller must ensure there is no race condition on the reference + * owner. e.g., locking the PTL of a PTE containing the entry being released. + */ +void swap_put_entries_direct(swp_entry_t entry, int nr) +{ + const unsigned long start_offset = swp_offset(entry); + const unsigned long end_offset = start_offset + nr; + unsigned long offset, cluster_end; + struct swap_info_struct *si; + + si = get_swap_device(entry); + if (WARN_ON_ONCE(!si)) + return; + if (WARN_ON_ONCE(end_offset > si->max)) + goto out; + + /* Put entries and reclaim cache in each cluster */ + offset = start_offset; + do { + cluster_end = min(round_up(offset + 1, SWAPFILE_CLUSTER), end_offset); + swap_put_entries_cluster(si, offset, cluster_end - offset, true); + offset = cluster_end; + } while (offset < end_offset); +out: + put_swap_device(si); +} + +#ifdef CONFIG_HIBERNATION +/** + * swap_alloc_hibernation_slot() - Allocate a swap slot for hibernation. + * @type: swap device type index to allocate from. + * + * The caller must ensure the swap device is stable, either by pinning + * it (SWP_HIBERNATION) or by freezing user-space. + * + * Return: a valid swp_entry_t on success, or an empty entry (val == 0) + * on failure. + */ +swp_entry_t swap_alloc_hibernation_slot(int type) +{ + struct swap_info_struct *pcp_si, *si = swap_type_to_info(type); + unsigned long pcp_offset, offset = SWAP_ENTRY_INVALID; + struct swap_cluster_info *ci; + swp_entry_t entry = {0}; + + if (!si) + goto fail; + + /* + * Try the local cluster first if it matches the device. If + * not, try grab a new cluster and override local cluster. + */ + local_lock(&percpu_swap_cluster.lock); + pcp_si = this_cpu_read(percpu_swap_cluster.si[0]); + pcp_offset = this_cpu_read(percpu_swap_cluster.offset[0]); + if (pcp_si == si && pcp_offset) { + ci = swap_cluster_lock(si, pcp_offset); + if (cluster_is_usable(ci, 0)) + offset = alloc_swap_scan_cluster(si, ci, NULL, pcp_offset); + else + swap_cluster_unlock(ci); + } + if (!offset) + offset = cluster_alloc_swap_entry(si, NULL); + local_unlock(&percpu_swap_cluster.lock); + if (offset) + entry = swp_entry(si->type, offset); + +fail: + return entry; +} + +/** + * swap_free_hibernation_slot() - Free a swap slot allocated for hibernation. + * @entry: swap entry to free. + * + * The caller must ensure the swap device is stable. + */ +void swap_free_hibernation_slot(swp_entry_t entry) +{ + struct swap_info_struct *si = __swap_entry_to_info(entry); + struct swap_cluster_info *ci; + pgoff_t offset = swp_offset(entry); + + ci = swap_cluster_lock(si, offset); + __swap_cluster_put_entry(ci, offset % SWAPFILE_CLUSTER); + /* + * A slot with a folio in the swap cache is freed when the folio + * leaves the cache, the same rule swap_put_entries_cluster() follows. + * Readahead can put a folio here, and freeing the slot now would + * leave that folio with no entry behind it. + */ + if (!swp_tb_is_folio(__swap_table_get(ci, offset % SWAPFILE_CLUSTER))) + __swap_cluster_free_entries(si, ci, offset % SWAPFILE_CLUSTER, 1); + swap_cluster_unlock(ci); + + /* In theory readahead might add it to the swap cache by accident */ + __try_to_reclaim_swap(si, offset, TTRS_ANYWAY); +} + +static int __find_hibernation_swap_type(dev_t device, sector_t offset) +{ + int type; + + lockdep_assert_held(&swap_lock); + + if (!device) + return -EINVAL; + + 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) + return type; + } + } + return -ENODEV; +} + +/** + * pin_hibernation_swap_type - Pin the swap device for hibernation + * @device: Block device containing the resume image + * @offset: Offset identifying the swap area + * + * Locate the swap device for @device/@offset and mark it as pinned + * for hibernation. While pinned, swapoff() is prevented. + * + * Only one uswsusp context may pin a swap device at a time. + * If already pinned, this function returns -EBUSY. + * + * Return: + * >= 0 on success (swap type). + * -EINVAL if @device is invalid. + * -ENODEV if the swap device is not found. + * -EBUSY if the device is already pinned for hibernation. + */ +int pin_hibernation_swap_type(dev_t device, sector_t offset) +{ + int type; + struct swap_info_struct *si; + + spin_lock(&swap_lock); + + type = __find_hibernation_swap_type(device, offset); + if (type < 0) { + spin_unlock(&swap_lock); + return type; + } + + si = swap_type_to_info(type); + if (WARN_ON_ONCE(!si)) { + spin_unlock(&swap_lock); + return -ENODEV; + } + + /* + * hibernate_acquire() prevents concurrent hibernation sessions. + * This check additionally guards against double-pinning within + * the same session. + */ + if (WARN_ON_ONCE(si->flags & SWP_HIBERNATION)) { + spin_unlock(&swap_lock); + return -EBUSY; + } + + si->flags |= SWP_HIBERNATION; + + spin_unlock(&swap_lock); + return type; +} + +/** + * unpin_hibernation_swap_type - Unpin the swap device for hibernation + * @type: Swap type previously returned by pin_hibernation_swap_type() + * + * Clear the hibernation pin on the given swap device, allowing + * swapoff() to proceed normally. + * + * If @type does not refer to a valid swap device, this function + * does nothing. + */ +void unpin_hibernation_swap_type(int type) +{ + struct swap_info_struct *si; + + spin_lock(&swap_lock); + si = swap_type_to_info(type); + if (!si) { + spin_unlock(&swap_lock); + return; + } + si->flags &= ~SWP_HIBERNATION; + spin_unlock(&swap_lock); +} + +/** + * find_hibernation_swap_type - Find swap type for hibernation + * @device: Block device containing the resume image + * @offset: Offset within the device identifying the swap area + * + * Locate the swap device corresponding to @device and @offset. + * + * Unlike pin_hibernation_swap_type(), this function only performs a + * lookup and does not mark the swap device as pinned for hibernation. + * + * This is safe in the sysfs-based hibernation path where user space + * is already frozen and swapoff() cannot run concurrently. + * + * Return: + * A non-negative swap type on success. + * -EINVAL if @device is invalid. + * -ENODEV if no matching swap device is found. + */ +int find_hibernation_swap_type(dev_t device, sector_t offset) +{ + int type; + + spin_lock(&swap_lock); + type = __find_hibernation_swap_type(device, offset); + spin_unlock(&swap_lock); + + return type; +} + +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_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 -= swap_usage_in_pages(sis); + } + 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; + struct folio *swapcache; + spinlock_t *ptl; + pte_t *pte, new_pte, old_pte; + bool hwpoisoned = false; + int ret = 1; + + /* + * If the folio is removed from swap cache by others, continue to + * unuse other PTEs. try_to_unuse may try again if we missed this one. + */ + if (!folio_matches_swap_entry(folio, entry)) + return 0; + + swapcache = folio; + folio = ksm_might_need_to_copy(folio, vma, addr); + if (unlikely(!folio)) + return -ENOMEM; + else if (unlikely(folio == ERR_PTR(-EHWPOISON))) { + hwpoisoned = true; + folio = swapcache; + } + + page = folio_file_page(folio, swp_offset(entry)); + if (PageHWPoison(page)) + 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 || !folio_test_uptodate(folio))) { + swp_entry_t swp_entry; + + dec_mm_counter(vma->vm_mm, MM_SWAPENTS); + if (hwpoisoned) { + swp_entry = make_hwpoison_entry(page); + } 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 folio_put_swap(). + */ + arch_swap_restore(folio_swap(entry, folio), folio); + + dec_mm_counter(vma->vm_mm, MM_SWAPENTS); + inc_mm_counter(vma->vm_mm, MM_ANONPAGES); + folio_get(folio); + if (folio == swapcache) { + rmap_t rmap_flags = RMAP_NONE; + + /* + * See do_swap_page(): writeback would be problematic. + * However, we do a folio_wait_writeback() just before this + * call and have the folio locked. + */ + VM_BUG_ON_FOLIO(folio_test_writeback(folio), folio); + if (pte_swp_exclusive(old_pte)) + rmap_flags |= RMAP_EXCLUSIVE; + /* + * We currently only expect small !anon folios, which are either + * fully exclusive or fully shared. If we ever get large folios + * here, we have to be careful. + */ + if (!folio_test_anon(folio)) { + VM_WARN_ON_ONCE(folio_test_large(folio)); + VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio); + folio_add_new_anon_rmap(folio, vma, addr, rmap_flags); + } else { + folio_add_anon_rmap_pte(folio, page, vma, addr, rmap_flags); + } + } else { /* ksm created a completely new copy */ + folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE); + folio_add_lru_vma(folio, 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(old_pte)) + new_pte = pte_mkuffd(new_pte); + + /* See do_swap_page(): restore PAGE_NONE for RWP */ + if (pte_swp_uffd(old_pte) && userfaultfd_rwp(vma)) + new_pte = pte_modify(new_pte, PAGE_NONE); + +setpte: + set_pte_at(vma->vm_mm, addr, pte, new_pte); + folio_put_swap(swapcache, folio_file_page(swapcache, swp_offset(entry))); +out: + if (pte) + pte_unmap_unlock(pte, ptl); + if (folio != swapcache) { + folio_unlock(folio); + folio_put(folio); + } + 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; + + do { + struct folio *folio; + unsigned long swp_tb; + softleaf_t entry; + int ret; + pte_t ptent; + + if (!pte++) { + pte = pte_offset_map(pmd, addr); + if (!pte) + break; + } + + ptent = ptep_get_lockless(pte); + entry = softleaf_from_pte(ptent); + + if (!softleaf_is_swap(entry)) + continue; + if (swp_type(entry) != type) + continue; + + pte_unmap(pte); + pte = NULL; + + folio = swap_cache_get_folio(entry); + if (!folio) { + struct vm_fault vmf = { + .vma = vma, + .address = addr, + .real_address = addr, + .pmd = pmd, + }; + + folio = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, + &vmf); + } + if (!folio) { + swp_tb = swap_table_get(__swap_entry_to_cluster(entry), + swp_cluster_offset(entry)); + if (swp_tb_get_count(swp_tb) <= 0) + 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); + if (check_stable_address_space(mm)) + goto unlock; + for_each_vma(vmi, vma) { + if (vma->anon_vma && !is_vm_hugetlb_page(vma)) { + ret = unuse_vma(vma, type); + if (ret) + break; + } + + cond_resched(); + } +unlock: + mmap_read_unlock(mm); + return ret; +} + +/* + * Scan swap table 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 long swp_tb; + + /* + * 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++) { + swp_tb = swap_table_get(__swap_offset_to_cluster(si, i), + i % SWAPFILE_CLUSTER); + if (!swp_tb_is_null(swp_tb) && !swp_tb_is_bad(swp_tb)) + 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 (!swap_usage_in_pages(si)) + goto success; + +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 (swap_usage_in_pages(si) && + !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 (swap_usage_in_pages(si) && + !signal_pending(current) && + (i = find_next_to_unuse(si, i)) != 0) { + + entry = swp_entry(type, i); + folio = swap_cache_get_folio(entry); + if (!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_writeout() 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 (swap_usage_in_pages(si)) { + if (!signal_pending(current)) + goto retry; + return -EINTR; + } + +success: + /* + * Make sure that further cleanups after try_to_unuse() returns happen + * after swap_range_free() reduces si->inuse_pages to 0. + */ + smp_mb(); + 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_usage_in_pages(swap_info[type])) + 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, + struct file *swap_file) +{ + 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 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_obj(*se); + 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_read_folio + * 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, + struct file *swap_file, sector_t *span) +{ + struct address_space *mapping = swap_file->f_mapping; + struct inode *inode = mapping->host; + int ret; + + ret = sio_pool_init(); + if (ret) + return ret; + + sis->ops = &swap_bdev_ops; + + 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; + return ret; + } + + return generic_swapfile_activate(sis, swap_file, span); +} + +static void _enable_swap_info(struct swap_info_struct *si) +{ + atomic_long_add(si->pages, &nr_swap_pages); + total_swap_pages += si->pages; + + assert_spin_locked(&swap_lock); + + plist_add(&si->list, &swap_active_head); + + /* Add back to available list */ + add_to_avail_list(si, true); +} + +/* + * Called after the swap device is ready, resurrect its percpu ref, it's now + * safe to reference it. Add it to the list to expose it to the allocator. + */ +static void enable_swap_info(struct swap_info_struct *si) +{ + percpu_ref_resurrect(&si->users); + spin_lock(&swap_lock); + spin_lock(&si->lock); + _enable_swap_info(si); + spin_unlock(&si->lock); + spin_unlock(&swap_lock); +} + +static void reinsert_swap_info(struct swap_info_struct *si) +{ + spin_lock(&swap_lock); + spin_lock(&si->lock); + _enable_swap_info(si); + spin_unlock(&si->lock); + spin_unlock(&swap_lock); +} + +/* + * Called after clearing SWP_WRITEOK, ensures cluster_alloc_range + * see the updated flags, so there will be no more allocations. + */ +static void wait_for_allocation(struct swap_info_struct *si) +{ + unsigned long offset; + unsigned long end = ALIGN(si->max, SWAPFILE_CLUSTER); + struct swap_cluster_info *ci; + + BUG_ON(si->flags & SWP_WRITEOK); + + for (offset = 0; offset < end; offset += SWAPFILE_CLUSTER) { + ci = swap_cluster_lock(si, offset); + swap_cluster_unlock(ci); + } +} + +static void free_swap_cluster_info(struct swap_cluster_info *cluster_info, + unsigned long maxpages) +{ + struct swap_cluster_info *ci; + int i, nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER); + + if (!cluster_info) + return; + for (i = 0; i < nr_clusters; i++) { + ci = cluster_info + i; + /* Cluster with bad marks count will have a remaining table */ + spin_lock(&ci->lock); + if (cluster_table_is_alloced(ci)) { + swap_cluster_assert_empty(ci, 0, SWAPFILE_CLUSTER, true); + swap_cluster_free_table(ci); + } + spin_unlock(&ci->lock); + } + kvfree(cluster_info); +} + +/* + * Called after swap device's reference count is dead, so + * neither scan nor allocation will use it. + */ +static void flush_percpu_swap_cluster(struct swap_info_struct *si) +{ + int cpu, i; + struct swap_info_struct **pcp_si; + + for_each_possible_cpu(cpu) { + pcp_si = per_cpu_ptr(percpu_swap_cluster.si, cpu); + /* + * Invalidate the percpu swap cluster cache, si->users + * is dead, so no new user will point to it, just flush + * any existing user. + */ + for (i = 0; i < SWAP_NR_ORDERS; i++) + cmpxchg(&pcp_si[i], si, NULL); + } +} + + +SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) +{ + struct swap_info_struct *p = NULL; + struct swap_cluster_info *cluster_info; + struct file *swap_file, *victim; + struct address_space *mapping; + struct inode *inode; + unsigned int maxpages; + int err, found = 0; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + BUG_ON(!current->mm); + + CLASS(filename, pathname)(specialfile); + victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0); + if (IS_ERR(victim)) + return PTR_ERR(victim); + + 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; + } + + /* Refuse swapoff while the device is pinned for hibernation */ + if (p->flags & SWP_HIBERNATION) { + err = -EBUSY; + 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, true); + plist_del(&p->list, &swap_active_head); + atomic_long_sub(p->pages, &nr_swap_pages); + total_swap_pages -= p->pages; + spin_unlock(&p->lock); + spin_unlock(&swap_lock); + + wait_for_allocation(p); + + 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); + goto out_dput; + } + + /* + * Wait for swap operations protected by get/put_swap_device() + * to complete. Because of synchronize_rcu() here, all swap + * operations protected by RCU reader side lock (including any + * spinlock) will be waited too. This makes it easy to + * prevent folio_test_swapcache() and the following swap cache + * operations from racing with swapoff. + */ + percpu_ref_kill(&p->users); + synchronize_rcu(); + wait_for_completion(&p->comp); + + flush_work(&p->discard_work); + flush_work(&p->reclaim_work); + flush_percpu_swap_cluster(p); + + destroy_swap_extents(p, p->swap_file); + + if (!(p->flags & SWP_SOLIDSTATE)) + atomic_dec(&nr_rotate_swap); + + mutex_lock(&swapon_mutex); + spin_lock(&swap_lock); + spin_lock(&p->lock); + drain_mmlist(); + + swap_file = p->swap_file; + p->swap_file = NULL; + maxpages = p->max; + cluster_info = p->cluster_info; + p->max = 0; + 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); + kfree(p->global_cluster); + p->global_cluster = NULL; + free_swap_cluster_info(cluster_info, maxpages); + + inode = mapping->host; + + 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); + 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_info(type)); type++) { + if (!(si->swap_file)) + 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_info(type)); type++) { + if (!(si->swap_file)) + 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(swap_usage_in_pages(si)); + + 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; + + p = kvzalloc_obj(struct swap_info_struct); + 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); + plist_node_init(&p->avail_list, 0); + p->flags = SWP_USED; + spin_unlock(&swap_lock); + if (defer) { + percpu_ref_exit(&defer->users); + kvfree(defer); + } + spin_lock_init(&p->lock); + atomic_long_set(&p->inuse_pages, SWAP_USAGE_OFFLIST_BIT); + init_completion(&p->comp); + + return p; +} + +static int claim_swapfile(struct swap_info_struct *si, struct inode *inode) +{ + if (S_ISBLK(inode->i_mode)) { + si->bdev = I_BDEV(inode); + /* + * 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(si->bdev)) + return -EINVAL; + si->flags |= SWP_BLKDEV; + } else if (S_ISREG(inode->i_mode)) { + si->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) +{ + swp_entry_t entry = swp_entry(0, ~0UL); + const pte_t pte = softleaf_to_pte(entry); + + /* + * Since the PTE can be an invalid softleaf entry (e.g. the none PTE), + * we need to do this manually. + */ + entry = __pte_to_swp_entry(pte); + entry = swp_entry(__swp_type(entry), __swp_offset(entry)); + + return swp_offset(entry) + 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 *si, + 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; + } + + 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; + } + + 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; +} + +static int setup_swap_clusters_info(struct swap_info_struct *si, + union swap_header *swap_header, + unsigned long maxpages) +{ + unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER); + struct swap_cluster_info *cluster_info; + int err = -ENOMEM; + unsigned long i; + + cluster_info = kvzalloc_objs(*cluster_info, nr_clusters); + if (!cluster_info) + goto err; + + for (i = 0; i < nr_clusters; i++) + spin_lock_init(&cluster_info[i].lock); + + if (!(si->flags & SWP_SOLIDSTATE)) { + si->global_cluster = kmalloc_obj(*si->global_cluster); + if (!si->global_cluster) + goto err; + for (i = 0; i < SWAP_NR_ORDERS; i++) + si->global_cluster->next[i] = SWAP_ENTRY_INVALID; + spin_lock_init(&si->global_cluster_lock); + } + + /* + * Mark unusable pages (header page, bad pages, and the EOF part of + * the last cluster) as unavailable. The clusters aren't marked free + * yet, so no list operations are involved yet. + */ + err = swap_cluster_setup_bad_slot(si, cluster_info, 0, false); + if (err) + goto err; + for (i = 0; i < swap_header->info.nr_badpages; i++) { + unsigned int page_nr = swap_header->info.badpages[i]; + + if (!page_nr || page_nr > swap_header->info.last_page) { + pr_warn("Bad slot offset is out of border: %d (last_page: %d)\n", + page_nr, swap_header->info.last_page); + err = -EINVAL; + goto err; + } + err = swap_cluster_setup_bad_slot(si, cluster_info, page_nr, false); + if (err) + goto err; + } + for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++) { + err = swap_cluster_setup_bad_slot(si, cluster_info, i, true); + if (err) + goto err; + } + + INIT_LIST_HEAD(&si->free_clusters); + INIT_LIST_HEAD(&si->full_clusters); + INIT_LIST_HEAD(&si->discard_clusters); + + for (i = 0; i < SWAP_NR_ORDERS; i++) { + INIT_LIST_HEAD(&si->nonfull_clusters[i]); + INIT_LIST_HEAD(&si->frag_clusters[i]); + } + + for (i = 0; i < nr_clusters; i++) { + struct swap_cluster_info *ci = &cluster_info[i]; + + if (ci->count) { + ci->flags = CLUSTER_FLAG_NONFULL; + list_add_tail(&ci->list, &si->nonfull_clusters[0]); + } else { + ci->flags = CLUSTER_FLAG_FREE; + list_add_tail(&ci->list, &si->free_clusters); + } + } + + si->cluster_info = cluster_info; + return 0; +err: + free_swap_cluster_info(cluster_info, maxpages); + return err; +} + +SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) +{ + struct swap_info_struct *si; + 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; + struct folio *folio = 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; + + /* + * Allocate or reuse existing !SWP_USED swap_info. The returned + * si will stay in a dying status, so nothing will access its content + * until enable_swap_info resurrects its percpu ref and expose it. + */ + si = alloc_swap_info(); + if (IS_ERR(si)) + return PTR_ERR(si); + + INIT_WORK(&si->discard_work, swap_discard_work); + INIT_WORK(&si->reclaim_work, swap_reclaim_work); + + CLASS(filename, name)(specialfile); + swap_file = file_open_name(name, O_RDWR | O_LARGEFILE | O_EXCL, 0); + if (IS_ERR(swap_file)) { + error = PTR_ERR(swap_file); + swap_file = NULL; + goto bad_swap; + } + + mapping = swap_file->f_mapping; + dentry = swap_file->f_path.dentry; + inode = mapping->host; + + error = claim_swapfile(si, 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; + } + if (IS_ENCRYPTED(inode)) { + pr_warn_once( + "Filesystem-level encrypted swapfile '%s' is unsupported. Create a loop device over it, or use dm-crypt\n", + name->name); + error = -EINVAL; + goto bad_swap_unlock_inode; + } + + /* + * The swap subsystem needs a major overhaul to support this. + * It doesn't work yet so just disable it for now. + */ + if (mapping_min_folio_order(mapping) > 0) { + error = -EINVAL; + goto bad_swap_unlock_inode; + } + + /* + * Read the swap header. + */ + if (!mapping->a_ops->read_folio) { + error = -EINVAL; + goto bad_swap_unlock_inode; + } + folio = read_mapping_folio(mapping, 0, swap_file); + if (IS_ERR(folio)) { + error = PTR_ERR(folio); + goto bad_swap_unlock_inode; + } + swap_header = kmap_local_folio(folio, 0); + + maxpages = read_swap_header(si, swap_header, inode); + if (unlikely(!maxpages)) { + error = -EINVAL; + goto bad_swap_unlock_inode; + } + + si->max = maxpages; + si->pages = maxpages - 1; + nr_extents = setup_swap_extents(si, swap_file, &span); + if (nr_extents < 0) { + error = nr_extents; + goto bad_swap_unlock_inode; + } + if (si->pages != si->max - 1) { + pr_err("swap:%u != (max:%u - 1)\n", si->pages, si->max); + error = -EINVAL; + goto bad_swap_unlock_inode; + } + + maxpages = si->max; + + /* Set up the swap cluster info */ + error = setup_swap_clusters_info(si, swap_header, maxpages); + if (error) + goto bad_swap_unlock_inode; + + if (si->bdev && bdev_stable_writes(si->bdev)) + si->flags |= SWP_STABLE_WRITES; + + if (si->bdev && bdev_synchronous(si->bdev)) + si->flags |= SWP_SYNCHRONOUS_IO; + + if (si->bdev && !bdev_rot(si->bdev)) { + si->flags |= SWP_SOLIDSTATE; + } else { + atomic_inc(&nr_rotate_swap); + inced_nr_rotate_swap = true; + } + + if ((swap_flags & SWAP_FLAG_DISCARD) && + si->bdev && bdev_max_discard_sectors(si->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. + */ + si->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) + si->flags &= ~SWP_PAGE_DISCARD; + else if (swap_flags & SWAP_FLAG_DISCARD_PAGES) + si->flags &= ~SWP_AREA_DISCARD; + + /* issue a swapon-time discard if it's still required */ + if (si->flags & SWP_AREA_DISCARD) { + int err = discard_swap(si); + if (unlikely(err)) + pr_err("swapon: discard_swap(%p): %d\n", + si, err); + } + } + + error = zswap_swapon(si->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_zswap; + } + + mutex_lock(&swapon_mutex); + prio = DEF_SWAP_PRIO; + if (swap_flags & SWAP_FLAG_PREFER) + prio = swap_flags & SWAP_FLAG_PRIO_MASK; + + /* + * The plist prio is negated because plist ordering is + * low-to-high, while swap ordering is high-to-low + */ + si->prio = prio; + si->list.prio = -si->prio; + si->avail_list.prio = -si->prio; + si->swap_file = swap_file; + + /* Sets SWP_WRITEOK, resurrect the percpu ref, expose the swap device */ + enable_swap_info(si); + + pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s\n", + K(si->pages), name->name, si->prio, nr_extents, + K((unsigned long long)span), + (si->flags & SWP_SOLIDSTATE) ? "SS" : "", + (si->flags & SWP_DISCARDABLE) ? "D" : "", + (si->flags & SWP_AREA_DISCARD) ? "s" : "", + (si->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_zswap: + zswap_swapoff(si->type); +bad_swap_unlock_inode: + inode_unlock(inode); +bad_swap: + kfree(si->global_cluster); + si->global_cluster = NULL; + inode = NULL; + destroy_swap_extents(si, swap_file); + free_swap_cluster_info(si->cluster_info, si->max); + si->cluster_info = NULL; + /* + * Clear the SWP_USED flag after all resources are freed so + * alloc_swap_info can reuse this si safely. + */ + spin_lock(&swap_lock); + si->flags = 0; + spin_unlock(&swap_lock); + if (inced_nr_rotate_swap) + atomic_dec(&nr_rotate_swap); + if (swap_file) + filp_close(swap_file, NULL); +out: + if (!IS_ERR_OR_NULL(folio)) + folio_release_kmap(folio, swap_header); + if (inode) + inode_unlock(inode); + 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 += swap_usage_in_pages(si); + } + 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); +} + +/* + * swap_dup_entry_direct() - Increase reference count of a swap entry by one. + * @entry: first swap entry from which we want to increase the refcount. + * + * Returns 0 for success, or -ENOMEM if the extend table is required + * but could not be atomically allocated. Returns -EINVAL if the swap + * entry is invalid, which might occur if a page table entry has got + * corrupted. + * + * Context: Caller must ensure there is no race condition on the reference + * owner. e.g., locking the PTL of a PTE containing the entry being increased. + * Also the swap entry must have a count >= 1. Otherwise folio_dup_swap should + * be used. + */ +int swap_dup_entry_direct(swp_entry_t entry) +{ + struct swap_info_struct *si; + + si = swap_entry_to_info(entry); + if (WARN_ON_ONCE(!si)) { + pr_err_ratelimited("%s%08lx\n", Bad_file, entry.val); + return -EINVAL; + } + + /* + * The caller must be increasing the swap count from a direct + * reference of the swap slot (e.g. a swap entry in page table). + * So the swap count must be >= 1. + */ + VM_WARN_ON_ONCE(!swap_entry_swapped(si, entry)); + + return swap_dup_entries_cluster(si, swp_offset(entry), 1); +} + +#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) +static bool __has_usable_swap(void) +{ + return !plist_head_empty(&swap_active_head); +} + +void __folio_throttle_swaprate(struct folio *folio, gfp_t gfp) +{ + struct swap_info_struct *si; + + if (!(gfp & __GFP_IO)) + return; + + if (!__has_usable_swap()) + 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(si, &swap_avail_head, avail_list) { + if (si->bdev) { + blkcg_schedule_throttle(si->bdev->bd_disk, true); + break; + } + } + spin_unlock(&swap_avail_lock); +} +#endif + +static int __init swapfile_init(void) +{ + swapfile_maximum_size = arch_max_swapfile_size(); + + /* + * Once a cluster is freed, it's swap table content is read + * only, and all swap cache readers (swap_cache_*) verifies + * the content before use. So it's safe to use RCU slab here. + */ + if (!SWP_TABLE_USE_PAGE) + swap_table_cachep = kmem_cache_create("swap_table", + sizeof(struct swap_table), + 0, SLAB_PANIC | SLAB_TYPESAFE_BY_RCU, NULL); + +#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); |