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-rw-r--r--mm/swapfile.c3862
1 files changed, 3862 insertions, 0 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
new file mode 100644
index 000000000..86ade667a
--- /dev/null
+++ b/mm/swapfile.c
@@ -0,0 +1,3862 @@
+// 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/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/blkdev.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/frontswap.h>
+#include <linux/swapfile.h>
+#include <linux/export.h>
+#include <linux/swap_slots.h>
+#include <linux/sort.h>
+
+#include <asm/tlbflush.h>
+#include <linux/swapops.h>
+#include <linux/swap_cgroup.h>
+
+static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
+ unsigned char);
+static void free_swap_count_continuations(struct swap_info_struct *);
+static sector_t map_swap_entry(swp_entry_t, struct block_device**);
+
+DEFINE_SPINLOCK(swap_lock);
+static unsigned int nr_swapfiles;
+atomic_long_t nr_swap_pages;
+/*
+ * Some modules use swappable objects and may try to swap them out under
+ * memory pressure (via the shrinker). Before doing so, they may wish to
+ * check to see if any swap space is available.
+ */
+EXPORT_SYMBOL_GPL(nr_swap_pages);
+/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
+long total_swap_pages;
+static int least_priority = -1;
+
+static const char Bad_file[] = "Bad swap file entry ";
+static const char Unused_file[] = "Unused swap file entry ";
+static const char Bad_offset[] = "Bad swap offset entry ";
+static const char Unused_offset[] = "Unused swap offset entry ";
+
+/*
+ * all active swap_info_structs
+ * protected with swap_lock, and ordered by priority.
+ */
+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 get_swap_page() instead of swap_active_head
+ * because swap_active_head includes all swap_info_structs,
+ * but get_swap_page() doesn't need to look at full ones.
+ * This uses its own lock instead of swap_lock because when a
+ * swap_info_struct changes between not-full/full, it needs to
+ * add/remove itself to/from this list, but the swap_info_struct->lock
+ * is held and the locking order requires swap_lock to be taken
+ * before any swap_info_struct->lock.
+ */
+static struct plist_head *swap_avail_heads;
+static DEFINE_SPINLOCK(swap_avail_lock);
+
+struct swap_info_struct *swap_info[MAX_SWAPFILES];
+
+static DEFINE_MUTEX(swapon_mutex);
+
+static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
+/* Activity counter to indicate that a swapon or swapoff has occurred */
+static atomic_t proc_poll_event = ATOMIC_INIT(0);
+
+atomic_t nr_rotate_swap = ATOMIC_INIT(0);
+
+static struct swap_info_struct *swap_type_to_swap_info(int type)
+{
+ if (type >= READ_ONCE(nr_swapfiles))
+ return NULL;
+
+ smp_rmb(); /* Pairs with smp_wmb in alloc_swap_info. */
+ return READ_ONCE(swap_info[type]);
+}
+
+static inline unsigned char swap_count(unsigned char ent)
+{
+ return ent & ~SWAP_HAS_CACHE; /* may include COUNT_CONTINUED flag */
+}
+
+/* Reclaim the swap entry anyway if possible */
+#define TTRS_ANYWAY 0x1
+/*
+ * Reclaim the swap entry if there are no more mappings of the
+ * corresponding page
+ */
+#define TTRS_UNMAPPED 0x2
+/* Reclaim the swap entry if swap is getting full*/
+#define TTRS_FULL 0x4
+
+/* returns 1 if swap entry is freed */
+static int __try_to_reclaim_swap(struct swap_info_struct *si,
+ unsigned long offset, unsigned long flags)
+{
+ swp_entry_t entry = swp_entry(si->type, offset);
+ struct page *page;
+ int ret = 0;
+
+ page = find_get_page(swap_address_space(entry), offset);
+ if (!page)
+ return 0;
+ /*
+ * When this function is called from scan_swap_map_slots() and it's
+ * called by vmscan.c at reclaiming pages. So, we hold a lock on a page,
+ * here. We have to use trylock for avoiding deadlock. This is a special
+ * case and you should use try_to_free_swap() with explicit lock_page()
+ * in usual operations.
+ */
+ if (trylock_page(page)) {
+ if ((flags & TTRS_ANYWAY) ||
+ ((flags & TTRS_UNMAPPED) && !page_mapped(page)) ||
+ ((flags & TTRS_FULL) && mem_cgroup_swap_full(page)))
+ ret = try_to_free_swap(page);
+ unlock_page(page);
+ }
+ put_page(page);
+ 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, 0);
+ 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, 0);
+ if (err)
+ break;
+
+ cond_resched();
+ }
+ return err; /* That will often be -EOPNOTSUPP */
+}
+
+static struct swap_extent *
+offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset)
+{
+ struct swap_extent *se;
+ struct rb_node *rb;
+
+ rb = sis->swap_extent_root.rb_node;
+ while (rb) {
+ se = rb_entry(rb, struct swap_extent, rb_node);
+ if (offset < se->start_page)
+ rb = rb->rb_left;
+ else if (offset >= se->start_page + se->nr_pages)
+ rb = rb->rb_right;
+ else
+ return se;
+ }
+ /* It *must* be present */
+ BUG();
+}
+
+sector_t swap_page_sector(struct page *page)
+{
+ struct swap_info_struct *sis = page_swap_info(page);
+ struct swap_extent *se;
+ sector_t sector;
+ pgoff_t offset;
+
+ offset = __page_file_index(page);
+ se = offset_to_swap_extent(sis, offset);
+ sector = se->start_block + (offset - se->start_page);
+ return sector << (PAGE_SHIFT - 9);
+}
+
+/*
+ * swap allocation tell device that a cluster of swap can now be discarded,
+ * to allow the swap device to optimize its wear-levelling.
+ */
+static void discard_swap_cluster(struct swap_info_struct *si,
+ pgoff_t start_page, pgoff_t nr_pages)
+{
+ struct swap_extent *se = offset_to_swap_extent(si, start_page);
+
+ while (nr_pages) {
+ pgoff_t offset = start_page - se->start_page;
+ sector_t start_block = se->start_block + offset;
+ sector_t nr_blocks = se->nr_pages - offset;
+
+ if (nr_blocks > nr_pages)
+ nr_blocks = nr_pages;
+ start_page += nr_blocks;
+ nr_pages -= nr_blocks;
+
+ start_block <<= PAGE_SHIFT - 9;
+ nr_blocks <<= PAGE_SHIFT - 9;
+ if (blkdev_issue_discard(si->bdev, start_block,
+ nr_blocks, GFP_NOIO, 0))
+ break;
+
+ se = next_se(se);
+ }
+}
+
+#ifdef CONFIG_THP_SWAP
+#define SWAPFILE_CLUSTER HPAGE_PMD_NR
+
+#define swap_entry_size(size) (size)
+#else
+#define SWAPFILE_CLUSTER 256
+
+/*
+ * Define swap_entry_size() as constant to let compiler to optimize
+ * out some code if !CONFIG_THP_SWAP
+ */
+#define swap_entry_size(size) 1
+#endif
+#define LATENCY_LIMIT 256
+
+static inline void cluster_set_flag(struct swap_cluster_info *info,
+ unsigned int flag)
+{
+ info->flags = flag;
+}
+
+static inline unsigned int cluster_count(struct swap_cluster_info *info)
+{
+ return info->data;
+}
+
+static inline void cluster_set_count(struct swap_cluster_info *info,
+ unsigned int c)
+{
+ info->data = c;
+}
+
+static inline void cluster_set_count_flag(struct swap_cluster_info *info,
+ unsigned int c, unsigned int f)
+{
+ info->flags = f;
+ info->data = c;
+}
+
+static inline unsigned int cluster_next(struct swap_cluster_info *info)
+{
+ return info->data;
+}
+
+static inline void cluster_set_next(struct swap_cluster_info *info,
+ unsigned int n)
+{
+ info->data = n;
+}
+
+static inline void cluster_set_next_flag(struct swap_cluster_info *info,
+ unsigned int n, unsigned int f)
+{
+ info->flags = f;
+ info->data = n;
+}
+
+static inline bool cluster_is_free(struct swap_cluster_info *info)
+{
+ return info->flags & CLUSTER_FLAG_FREE;
+}
+
+static inline bool cluster_is_null(struct swap_cluster_info *info)
+{
+ return info->flags & CLUSTER_FLAG_NEXT_NULL;
+}
+
+static inline void cluster_set_null(struct swap_cluster_info *info)
+{
+ info->flags = CLUSTER_FLAG_NEXT_NULL;
+ info->data = 0;
+}
+
+static inline bool cluster_is_huge(struct swap_cluster_info *info)
+{
+ if (IS_ENABLED(CONFIG_THP_SWAP))
+ return info->flags & CLUSTER_FLAG_HUGE;
+ return false;
+}
+
+static inline void cluster_clear_huge(struct swap_cluster_info *info)
+{
+ info->flags &= ~CLUSTER_FLAG_HUGE;
+}
+
+static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
+ unsigned long offset)
+{
+ struct swap_cluster_info *ci;
+
+ ci = si->cluster_info;
+ if (ci) {
+ ci += offset / SWAPFILE_CLUSTER;
+ spin_lock(&ci->lock);
+ }
+ return ci;
+}
+
+static inline void unlock_cluster(struct swap_cluster_info *ci)
+{
+ if (ci)
+ spin_unlock(&ci->lock);
+}
+
+/*
+ * Determine the locking method in use for this device. Return
+ * swap_cluster_info if SSD-style cluster-based locking is in place.
+ */
+static inline struct swap_cluster_info *lock_cluster_or_swap_info(
+ struct swap_info_struct *si, unsigned long offset)
+{
+ struct swap_cluster_info *ci;
+
+ /* Try to use fine-grained SSD-style locking if available: */
+ ci = lock_cluster(si, offset);
+ /* Otherwise, fall back to traditional, coarse locking: */
+ if (!ci)
+ spin_lock(&si->lock);
+
+ return ci;
+}
+
+static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
+ struct swap_cluster_info *ci)
+{
+ if (ci)
+ unlock_cluster(ci);
+ else
+ spin_unlock(&si->lock);
+}
+
+static inline bool cluster_list_empty(struct swap_cluster_list *list)
+{
+ return cluster_is_null(&list->head);
+}
+
+static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
+{
+ return cluster_next(&list->head);
+}
+
+static void cluster_list_init(struct swap_cluster_list *list)
+{
+ cluster_set_null(&list->head);
+ cluster_set_null(&list->tail);
+}
+
+static void cluster_list_add_tail(struct swap_cluster_list *list,
+ struct swap_cluster_info *ci,
+ unsigned int idx)
+{
+ if (cluster_list_empty(list)) {
+ cluster_set_next_flag(&list->head, idx, 0);
+ cluster_set_next_flag(&list->tail, idx, 0);
+ } else {
+ struct swap_cluster_info *ci_tail;
+ unsigned int tail = cluster_next(&list->tail);
+
+ /*
+ * Nested cluster lock, but both cluster locks are
+ * only acquired when we held swap_info_struct->lock
+ */
+ ci_tail = ci + tail;
+ spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
+ cluster_set_next(ci_tail, idx);
+ spin_unlock(&ci_tail->lock);
+ cluster_set_next_flag(&list->tail, idx, 0);
+ }
+}
+
+static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
+ struct swap_cluster_info *ci)
+{
+ unsigned int idx;
+
+ idx = cluster_next(&list->head);
+ if (cluster_next(&list->tail) == idx) {
+ cluster_set_null(&list->head);
+ cluster_set_null(&list->tail);
+ } else
+ cluster_set_next_flag(&list->head,
+ cluster_next(&ci[idx]), 0);
+
+ return idx;
+}
+
+/* Add a cluster to discard list and schedule it to do discard */
+static void swap_cluster_schedule_discard(struct swap_info_struct *si,
+ unsigned int idx)
+{
+ /*
+ * If scan_swap_map() can't find a free cluster, it will check
+ * si->swap_map directly. To make sure the discarding cluster isn't
+ * taken by scan_swap_map(), mark the swap entries bad (occupied). It
+ * will be cleared after discard
+ */
+ memset(si->swap_map + idx * SWAPFILE_CLUSTER,
+ SWAP_MAP_BAD, SWAPFILE_CLUSTER);
+
+ cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
+
+ schedule_work(&si->discard_work);
+}
+
+static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
+{
+ struct swap_cluster_info *ci = si->cluster_info;
+
+ cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
+ cluster_list_add_tail(&si->free_clusters, ci, idx);
+}
+
+/*
+ * Doing discard actually. After a cluster discard is finished, the cluster
+ * will be added to free cluster list. caller should hold si->lock.
+*/
+static void swap_do_scheduled_discard(struct swap_info_struct *si)
+{
+ struct swap_cluster_info *info, *ci;
+ unsigned int idx;
+
+ info = si->cluster_info;
+
+ while (!cluster_list_empty(&si->discard_clusters)) {
+ idx = cluster_list_del_first(&si->discard_clusters, info);
+ spin_unlock(&si->lock);
+
+ discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
+ SWAPFILE_CLUSTER);
+
+ spin_lock(&si->lock);
+ ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
+ __free_cluster(si, idx);
+ memset(si->swap_map + idx * SWAPFILE_CLUSTER,
+ 0, SWAPFILE_CLUSTER);
+ unlock_cluster(ci);
+ }
+}
+
+static void swap_discard_work(struct work_struct *work)
+{
+ struct swap_info_struct *si;
+
+ si = container_of(work, struct swap_info_struct, discard_work);
+
+ spin_lock(&si->lock);
+ swap_do_scheduled_discard(si);
+ spin_unlock(&si->lock);
+}
+
+static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
+{
+ struct swap_cluster_info *ci = si->cluster_info;
+
+ VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
+ cluster_list_del_first(&si->free_clusters, ci);
+ cluster_set_count_flag(ci + idx, 0, 0);
+}
+
+static void free_cluster(struct swap_info_struct *si, unsigned long idx)
+{
+ struct swap_cluster_info *ci = si->cluster_info + idx;
+
+ VM_BUG_ON(cluster_count(ci) != 0);
+ /*
+ * If the swap is discardable, prepare discard the cluster
+ * instead of free it immediately. The cluster will be freed
+ * after discard.
+ */
+ if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
+ (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
+ swap_cluster_schedule_discard(si, idx);
+ return;
+ }
+
+ __free_cluster(si, idx);
+}
+
+/*
+ * The cluster corresponding to page_nr will be used. The cluster will be
+ * removed from free cluster list and its usage counter will be increased.
+ */
+static void inc_cluster_info_page(struct swap_info_struct *p,
+ struct swap_cluster_info *cluster_info, unsigned long page_nr)
+{
+ unsigned long idx = page_nr / SWAPFILE_CLUSTER;
+
+ if (!cluster_info)
+ return;
+ if (cluster_is_free(&cluster_info[idx]))
+ alloc_cluster(p, idx);
+
+ VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
+ cluster_set_count(&cluster_info[idx],
+ cluster_count(&cluster_info[idx]) + 1);
+}
+
+/*
+ * The cluster corresponding to page_nr decreases one usage. If the usage
+ * counter becomes 0, which means no page in the cluster is in using, we can
+ * optionally discard the cluster and add it to free cluster list.
+ */
+static void dec_cluster_info_page(struct swap_info_struct *p,
+ struct swap_cluster_info *cluster_info, unsigned long page_nr)
+{
+ unsigned long idx = page_nr / SWAPFILE_CLUSTER;
+
+ if (!cluster_info)
+ return;
+
+ VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
+ cluster_set_count(&cluster_info[idx],
+ cluster_count(&cluster_info[idx]) - 1);
+
+ if (cluster_count(&cluster_info[idx]) == 0)
+ free_cluster(p, idx);
+}
+
+/*
+ * It's possible scan_swap_map() uses a free cluster in the middle of free
+ * cluster list. Avoiding such abuse to avoid list corruption.
+ */
+static bool
+scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
+ unsigned long offset)
+{
+ struct percpu_cluster *percpu_cluster;
+ bool conflict;
+
+ offset /= SWAPFILE_CLUSTER;
+ conflict = !cluster_list_empty(&si->free_clusters) &&
+ offset != cluster_list_first(&si->free_clusters) &&
+ cluster_is_free(&si->cluster_info[offset]);
+
+ if (!conflict)
+ return false;
+
+ percpu_cluster = this_cpu_ptr(si->percpu_cluster);
+ cluster_set_null(&percpu_cluster->index);
+ return true;
+}
+
+/*
+ * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
+ * might involve allocating a new cluster for current CPU too.
+ */
+static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
+ unsigned long *offset, unsigned long *scan_base)
+{
+ struct percpu_cluster *cluster;
+ struct swap_cluster_info *ci;
+ unsigned long tmp, max;
+
+new_cluster:
+ cluster = this_cpu_ptr(si->percpu_cluster);
+ if (cluster_is_null(&cluster->index)) {
+ if (!cluster_list_empty(&si->free_clusters)) {
+ cluster->index = si->free_clusters.head;
+ cluster->next = cluster_next(&cluster->index) *
+ SWAPFILE_CLUSTER;
+ } else if (!cluster_list_empty(&si->discard_clusters)) {
+ /*
+ * we don't have free cluster but have some clusters in
+ * discarding, do discard now and reclaim them, then
+ * reread cluster_next_cpu since we dropped si->lock
+ */
+ swap_do_scheduled_discard(si);
+ *scan_base = this_cpu_read(*si->cluster_next_cpu);
+ *offset = *scan_base;
+ goto new_cluster;
+ } else
+ return false;
+ }
+
+ /*
+ * Other CPUs can use our cluster if they can't find a free cluster,
+ * check if there is still free entry in the cluster
+ */
+ tmp = cluster->next;
+ max = min_t(unsigned long, si->max,
+ (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
+ if (tmp < max) {
+ ci = lock_cluster(si, tmp);
+ while (tmp < max) {
+ if (!si->swap_map[tmp])
+ break;
+ tmp++;
+ }
+ unlock_cluster(ci);
+ }
+ if (tmp >= max) {
+ cluster_set_null(&cluster->index);
+ goto new_cluster;
+ }
+ cluster->next = tmp + 1;
+ *offset = tmp;
+ *scan_base = tmp;
+ return true;
+}
+
+static void __del_from_avail_list(struct swap_info_struct *p)
+{
+ int nid;
+
+ assert_spin_locked(&p->lock);
+ for_each_node(nid)
+ plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
+}
+
+static void del_from_avail_list(struct swap_info_struct *p)
+{
+ spin_lock(&swap_avail_lock);
+ __del_from_avail_list(p);
+ spin_unlock(&swap_avail_lock);
+}
+
+static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
+ unsigned int nr_entries)
+{
+ unsigned int end = offset + nr_entries - 1;
+
+ if (offset == si->lowest_bit)
+ si->lowest_bit += nr_entries;
+ if (end == si->highest_bit)
+ WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries);
+ si->inuse_pages += nr_entries;
+ if (si->inuse_pages == si->pages) {
+ si->lowest_bit = si->max;
+ si->highest_bit = 0;
+ del_from_avail_list(si);
+ }
+}
+
+static void add_to_avail_list(struct swap_info_struct *p)
+{
+ int nid;
+
+ spin_lock(&swap_avail_lock);
+ for_each_node(nid) {
+ WARN_ON(!plist_node_empty(&p->avail_lists[nid]));
+ plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]);
+ }
+ spin_unlock(&swap_avail_lock);
+}
+
+static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
+ unsigned int nr_entries)
+{
+ unsigned long begin = offset;
+ unsigned long end = offset + nr_entries - 1;
+ void (*swap_slot_free_notify)(struct block_device *, unsigned long);
+
+ if (offset < si->lowest_bit)
+ si->lowest_bit = offset;
+ if (end > si->highest_bit) {
+ bool was_full = !si->highest_bit;
+
+ WRITE_ONCE(si->highest_bit, end);
+ if (was_full && (si->flags & SWP_WRITEOK))
+ add_to_avail_list(si);
+ }
+ atomic_long_add(nr_entries, &nr_swap_pages);
+ si->inuse_pages -= nr_entries;
+ if (si->flags & SWP_BLKDEV)
+ swap_slot_free_notify =
+ si->bdev->bd_disk->fops->swap_slot_free_notify;
+ else
+ swap_slot_free_notify = NULL;
+ while (offset <= end) {
+ arch_swap_invalidate_page(si->type, offset);
+ frontswap_invalidate_page(si->type, offset);
+ if (swap_slot_free_notify)
+ swap_slot_free_notify(si->bdev, offset);
+ offset++;
+ }
+ clear_shadow_from_swap_cache(si->type, begin, end);
+}
+
+static void set_cluster_next(struct swap_info_struct *si, unsigned long next)
+{
+ unsigned long prev;
+
+ if (!(si->flags & SWP_SOLIDSTATE)) {
+ si->cluster_next = next;
+ return;
+ }
+
+ prev = this_cpu_read(*si->cluster_next_cpu);
+ /*
+ * Cross the swap address space size aligned trunk, choose
+ * another trunk randomly to avoid lock contention on swap
+ * address space if possible.
+ */
+ if ((prev >> SWAP_ADDRESS_SPACE_SHIFT) !=
+ (next >> SWAP_ADDRESS_SPACE_SHIFT)) {
+ /* No free swap slots available */
+ if (si->highest_bit <= si->lowest_bit)
+ return;
+ next = si->lowest_bit +
+ prandom_u32_max(si->highest_bit - si->lowest_bit + 1);
+ next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES);
+ next = max_t(unsigned int, next, si->lowest_bit);
+ }
+ this_cpu_write(*si->cluster_next_cpu, next);
+}
+
+static int scan_swap_map_slots(struct swap_info_struct *si,
+ unsigned char usage, int nr,
+ swp_entry_t slots[])
+{
+ struct swap_cluster_info *ci;
+ unsigned long offset;
+ unsigned long scan_base;
+ unsigned long last_in_cluster = 0;
+ int latency_ration = LATENCY_LIMIT;
+ int n_ret = 0;
+ bool scanned_many = false;
+
+ /*
+ * We try to cluster swap pages by allocating them sequentially
+ * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
+ * way, however, we resort to first-free allocation, starting
+ * a new cluster. This prevents us from scattering swap pages
+ * all over the entire swap partition, so that we reduce
+ * overall disk seek times between swap pages. -- sct
+ * But we do now try to find an empty cluster. -Andrea
+ * And we let swap pages go all over an SSD partition. Hugh
+ */
+
+ si->flags += SWP_SCANNING;
+ /*
+ * Use percpu scan base for SSD to reduce lock contention on
+ * cluster and swap cache. For HDD, sequential access is more
+ * important.
+ */
+ if (si->flags & SWP_SOLIDSTATE)
+ scan_base = this_cpu_read(*si->cluster_next_cpu);
+ else
+ scan_base = si->cluster_next;
+ offset = scan_base;
+
+ /* SSD algorithm */
+ if (si->cluster_info) {
+ if (!scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
+ goto scan;
+ } else if (unlikely(!si->cluster_nr--)) {
+ if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
+ si->cluster_nr = SWAPFILE_CLUSTER - 1;
+ goto checks;
+ }
+
+ spin_unlock(&si->lock);
+
+ /*
+ * If seek is expensive, start searching for new cluster from
+ * start of partition, to minimize the span of allocated swap.
+ * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info
+ * case, just handled by scan_swap_map_try_ssd_cluster() above.
+ */
+ scan_base = offset = si->lowest_bit;
+ last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
+
+ /* Locate the first empty (unaligned) cluster */
+ for (; last_in_cluster <= si->highest_bit; offset++) {
+ if (si->swap_map[offset])
+ last_in_cluster = offset + SWAPFILE_CLUSTER;
+ else if (offset == last_in_cluster) {
+ spin_lock(&si->lock);
+ offset -= SWAPFILE_CLUSTER - 1;
+ si->cluster_next = offset;
+ si->cluster_nr = SWAPFILE_CLUSTER - 1;
+ goto checks;
+ }
+ if (unlikely(--latency_ration < 0)) {
+ cond_resched();
+ latency_ration = LATENCY_LIMIT;
+ }
+ }
+
+ offset = scan_base;
+ spin_lock(&si->lock);
+ si->cluster_nr = SWAPFILE_CLUSTER - 1;
+ }
+
+checks:
+ if (si->cluster_info) {
+ while (scan_swap_map_ssd_cluster_conflict(si, offset)) {
+ /* take a break if we already got some slots */
+ if (n_ret)
+ goto done;
+ if (!scan_swap_map_try_ssd_cluster(si, &offset,
+ &scan_base))
+ goto scan;
+ }
+ }
+ if (!(si->flags & SWP_WRITEOK))
+ goto no_page;
+ if (!si->highest_bit)
+ goto no_page;
+ if (offset > si->highest_bit)
+ scan_base = offset = si->lowest_bit;
+
+ ci = lock_cluster(si, offset);
+ /* reuse swap entry of cache-only swap if not busy. */
+ if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
+ int swap_was_freed;
+ unlock_cluster(ci);
+ spin_unlock(&si->lock);
+ swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY);
+ spin_lock(&si->lock);
+ /* entry was freed successfully, try to use this again */
+ if (swap_was_freed)
+ goto checks;
+ goto scan; /* check next one */
+ }
+
+ if (si->swap_map[offset]) {
+ unlock_cluster(ci);
+ if (!n_ret)
+ goto scan;
+ else
+ goto done;
+ }
+ WRITE_ONCE(si->swap_map[offset], usage);
+ inc_cluster_info_page(si, si->cluster_info, offset);
+ unlock_cluster(ci);
+
+ swap_range_alloc(si, offset, 1);
+ slots[n_ret++] = swp_entry(si->type, offset);
+
+ /* got enough slots or reach max slots? */
+ if ((n_ret == nr) || (offset >= si->highest_bit))
+ goto done;
+
+ /* search for next available slot */
+
+ /* time to take a break? */
+ if (unlikely(--latency_ration < 0)) {
+ if (n_ret)
+ goto done;
+ spin_unlock(&si->lock);
+ cond_resched();
+ spin_lock(&si->lock);
+ latency_ration = LATENCY_LIMIT;
+ }
+
+ /* try to get more slots in cluster */
+ if (si->cluster_info) {
+ if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base))
+ goto checks;
+ } else if (si->cluster_nr && !si->swap_map[++offset]) {
+ /* non-ssd case, still more slots in cluster? */
+ --si->cluster_nr;
+ goto checks;
+ }
+
+ /*
+ * Even if there's no free clusters available (fragmented),
+ * try to scan a little more quickly with lock held unless we
+ * have scanned too many slots already.
+ */
+ if (!scanned_many) {
+ unsigned long scan_limit;
+
+ if (offset < scan_base)
+ scan_limit = scan_base;
+ else
+ scan_limit = si->highest_bit;
+ for (; offset <= scan_limit && --latency_ration > 0;
+ offset++) {
+ if (!si->swap_map[offset])
+ goto checks;
+ }
+ }
+
+done:
+ set_cluster_next(si, offset + 1);
+ si->flags -= SWP_SCANNING;
+ return n_ret;
+
+scan:
+ spin_unlock(&si->lock);
+ while (++offset <= READ_ONCE(si->highest_bit)) {
+ if (data_race(!si->swap_map[offset])) {
+ spin_lock(&si->lock);
+ goto checks;
+ }
+ if (vm_swap_full() &&
+ READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
+ spin_lock(&si->lock);
+ goto checks;
+ }
+ if (unlikely(--latency_ration < 0)) {
+ cond_resched();
+ latency_ration = LATENCY_LIMIT;
+ scanned_many = true;
+ }
+ }
+ offset = si->lowest_bit;
+ while (offset < scan_base) {
+ if (data_race(!si->swap_map[offset])) {
+ spin_lock(&si->lock);
+ goto checks;
+ }
+ if (vm_swap_full() &&
+ READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) {
+ spin_lock(&si->lock);
+ goto checks;
+ }
+ if (unlikely(--latency_ration < 0)) {
+ cond_resched();
+ latency_ration = LATENCY_LIMIT;
+ scanned_many = true;
+ }
+ offset++;
+ }
+ spin_lock(&si->lock);
+
+no_page:
+ si->flags -= SWP_SCANNING;
+ return n_ret;
+}
+
+static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
+{
+ unsigned long idx;
+ struct swap_cluster_info *ci;
+ unsigned long offset, i;
+ unsigned char *map;
+
+ /*
+ * Should not even be attempting cluster allocations when huge
+ * page swap is disabled. Warn and fail the allocation.
+ */
+ if (!IS_ENABLED(CONFIG_THP_SWAP)) {
+ VM_WARN_ON_ONCE(1);
+ return 0;
+ }
+
+ if (cluster_list_empty(&si->free_clusters))
+ return 0;
+
+ idx = cluster_list_first(&si->free_clusters);
+ offset = idx * SWAPFILE_CLUSTER;
+ ci = lock_cluster(si, offset);
+ alloc_cluster(si, idx);
+ cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
+
+ map = si->swap_map + offset;
+ for (i = 0; i < SWAPFILE_CLUSTER; i++)
+ map[i] = SWAP_HAS_CACHE;
+ unlock_cluster(ci);
+ swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
+ *slot = swp_entry(si->type, offset);
+
+ return 1;
+}
+
+static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
+{
+ unsigned long offset = idx * SWAPFILE_CLUSTER;
+ struct swap_cluster_info *ci;
+
+ ci = lock_cluster(si, offset);
+ memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
+ cluster_set_count_flag(ci, 0, 0);
+ free_cluster(si, idx);
+ unlock_cluster(ci);
+ swap_range_free(si, offset, SWAPFILE_CLUSTER);
+}
+
+static unsigned long scan_swap_map(struct swap_info_struct *si,
+ unsigned char usage)
+{
+ swp_entry_t entry;
+ int n_ret;
+
+ n_ret = scan_swap_map_slots(si, usage, 1, &entry);
+
+ if (n_ret)
+ return swp_offset(entry);
+ else
+ return 0;
+
+}
+
+int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
+{
+ unsigned long size = swap_entry_size(entry_size);
+ struct swap_info_struct *si, *next;
+ long avail_pgs;
+ int n_ret = 0;
+ int node;
+
+ /* Only single cluster request supported */
+ WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
+
+ spin_lock(&swap_avail_lock);
+
+ avail_pgs = atomic_long_read(&nr_swap_pages) / size;
+ if (avail_pgs <= 0) {
+ spin_unlock(&swap_avail_lock);
+ goto noswap;
+ }
+
+ n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs);
+
+ atomic_long_sub(n_goal * size, &nr_swap_pages);
+
+start_over:
+ node = numa_node_id();
+ plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) {
+ /* requeue si to after same-priority siblings */
+ plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
+ spin_unlock(&swap_avail_lock);
+ spin_lock(&si->lock);
+ if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
+ spin_lock(&swap_avail_lock);
+ if (plist_node_empty(&si->avail_lists[node])) {
+ spin_unlock(&si->lock);
+ goto nextsi;
+ }
+ WARN(!si->highest_bit,
+ "swap_info %d in list but !highest_bit\n",
+ si->type);
+ WARN(!(si->flags & SWP_WRITEOK),
+ "swap_info %d in list but !SWP_WRITEOK\n",
+ si->type);
+ __del_from_avail_list(si);
+ spin_unlock(&si->lock);
+ goto nextsi;
+ }
+ if (size == SWAPFILE_CLUSTER) {
+ if (si->flags & SWP_BLKDEV)
+ n_ret = swap_alloc_cluster(si, swp_entries);
+ } else
+ n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
+ n_goal, swp_entries);
+ spin_unlock(&si->lock);
+ if (n_ret || size == SWAPFILE_CLUSTER)
+ goto check_out;
+ pr_debug("scan_swap_map of si %d failed to find offset\n",
+ si->type);
+ cond_resched();
+
+ spin_lock(&swap_avail_lock);
+nextsi:
+ /*
+ * if we got here, it's likely that si was almost full before,
+ * and since scan_swap_map() can drop the si->lock, multiple
+ * callers probably all tried to get a page from the same si
+ * and it filled up before we could get one; or, the si filled
+ * up between us dropping swap_avail_lock and taking si->lock.
+ * Since we dropped the swap_avail_lock, the swap_avail_head
+ * list may have been modified; so if next is still in the
+ * swap_avail_head list then try it, otherwise start over
+ * if we have not gotten any slots.
+ */
+ if (plist_node_empty(&next->avail_lists[node]))
+ goto start_over;
+ }
+
+ spin_unlock(&swap_avail_lock);
+
+check_out:
+ if (n_ret < n_goal)
+ atomic_long_add((long)(n_goal - n_ret) * size,
+ &nr_swap_pages);
+noswap:
+ return n_ret;
+}
+
+/* The only caller of this function is now suspend routine */
+swp_entry_t get_swap_page_of_type(int type)
+{
+ struct swap_info_struct *si = swap_type_to_swap_info(type);
+ pgoff_t offset;
+
+ if (!si)
+ goto fail;
+
+ spin_lock(&si->lock);
+ if (si->flags & SWP_WRITEOK) {
+ /* This is called for allocating swap entry, not cache */
+ offset = scan_swap_map(si, 1);
+ if (offset) {
+ atomic_long_dec(&nr_swap_pages);
+ spin_unlock(&si->lock);
+ return swp_entry(type, offset);
+ }
+ }
+ spin_unlock(&si->lock);
+fail:
+ return (swp_entry_t) {0};
+}
+
+static struct swap_info_struct *__swap_info_get(swp_entry_t entry)
+{
+ struct swap_info_struct *p;
+ unsigned long offset;
+
+ if (!entry.val)
+ goto out;
+ p = swp_swap_info(entry);
+ if (!p)
+ goto bad_nofile;
+ if (data_race(!(p->flags & SWP_USED)))
+ goto bad_device;
+ offset = swp_offset(entry);
+ if (offset >= p->max)
+ goto bad_offset;
+ return p;
+
+bad_offset:
+ pr_err("swap_info_get: %s%08lx\n", Bad_offset, entry.val);
+ goto out;
+bad_device:
+ pr_err("swap_info_get: %s%08lx\n", Unused_file, entry.val);
+ goto out;
+bad_nofile:
+ pr_err("swap_info_get: %s%08lx\n", Bad_file, entry.val);
+out:
+ return NULL;
+}
+
+static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
+{
+ struct swap_info_struct *p;
+
+ p = __swap_info_get(entry);
+ if (!p)
+ goto out;
+ if (data_race(!p->swap_map[swp_offset(entry)]))
+ goto bad_free;
+ return p;
+
+bad_free:
+ pr_err("swap_info_get: %s%08lx\n", Unused_offset, entry.val);
+out:
+ return NULL;
+}
+
+static struct swap_info_struct *swap_info_get(swp_entry_t entry)
+{
+ struct swap_info_struct *p;
+
+ p = _swap_info_get(entry);
+ if (p)
+ spin_lock(&p->lock);
+ return p;
+}
+
+static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,
+ struct swap_info_struct *q)
+{
+ struct swap_info_struct *p;
+
+ p = _swap_info_get(entry);
+
+ if (p != q) {
+ if (q != NULL)
+ spin_unlock(&q->lock);
+ if (p != NULL)
+ spin_lock(&p->lock);
+ }
+ return p;
+}
+
+static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
+ unsigned long offset,
+ unsigned char usage)
+{
+ unsigned char count;
+ unsigned char has_cache;
+
+ count = p->swap_map[offset];
+
+ has_cache = count & SWAP_HAS_CACHE;
+ count &= ~SWAP_HAS_CACHE;
+
+ if (usage == SWAP_HAS_CACHE) {
+ VM_BUG_ON(!has_cache);
+ has_cache = 0;
+ } else if (count == SWAP_MAP_SHMEM) {
+ /*
+ * Or we could insist on shmem.c using a special
+ * swap_shmem_free() and free_shmem_swap_and_cache()...
+ */
+ count = 0;
+ } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) {
+ if (count == COUNT_CONTINUED) {
+ if (swap_count_continued(p, offset, count))
+ count = SWAP_MAP_MAX | COUNT_CONTINUED;
+ else
+ count = SWAP_MAP_MAX;
+ } else
+ count--;
+ }
+
+ usage = count | has_cache;
+ if (usage)
+ WRITE_ONCE(p->swap_map[offset], usage);
+ else
+ WRITE_ONCE(p->swap_map[offset], SWAP_HAS_CACHE);
+
+ return usage;
+}
+
+/*
+ * 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.
+ *
+ * The entirety of the RCU read critical section must come before the
+ * return from or after the call to synchronize_rcu() in
+ * enable_swap_info() or swapoff(). So if "si->flags & SWP_VALID" is
+ * true, the si->map, si->cluster_info, etc. must be valid in the
+ * critical section.
+ *
+ * Notice that swapoff or swapoff+swapon can still happen before the
+ * rcu_read_lock() in get_swap_device() or after the rcu_read_unlock()
+ * in put_swap_device() if there isn't any other way to prevent
+ * swapoff, such as page lock, page table lock, etc. The caller must
+ * be prepared for that. For example, the following situation is
+ * possible.
+ *
+ * CPU1 CPU2
+ * do_swap_page()
+ * ... swapoff+swapon
+ * __read_swap_cache_async()
+ * swapcache_prepare()
+ * __swap_duplicate()
+ * // check swap_map
+ * // verify PTE not changed
+ *
+ * In __swap_duplicate(), the swap_map need to be checked before
+ * changing partly because the specified swap entry may be for another
+ * swap device which has been swapoff. And in do_swap_page(), after
+ * the page is read from the swap device, the PTE is verified not
+ * changed with the page table locked to check whether the swap device
+ * has been swapoff or swapoff+swapon.
+ */
+struct swap_info_struct *get_swap_device(swp_entry_t entry)
+{
+ struct swap_info_struct *si;
+ unsigned long offset;
+
+ if (!entry.val)
+ goto out;
+ si = swp_swap_info(entry);
+ if (!si)
+ goto bad_nofile;
+
+ rcu_read_lock();
+ if (data_race(!(si->flags & SWP_VALID)))
+ goto unlock_out;
+ offset = swp_offset(entry);
+ if (offset >= si->max)
+ goto unlock_out;
+
+ return si;
+bad_nofile:
+ pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
+out:
+ return NULL;
+unlock_out:
+ rcu_read_unlock();
+ return NULL;
+}
+
+static unsigned char __swap_entry_free(struct swap_info_struct *p,
+ swp_entry_t entry)
+{
+ struct swap_cluster_info *ci;
+ unsigned long offset = swp_offset(entry);
+ unsigned char usage;
+
+ ci = lock_cluster_or_swap_info(p, offset);
+ usage = __swap_entry_free_locked(p, offset, 1);
+ unlock_cluster_or_swap_info(p, ci);
+ if (!usage)
+ free_swap_slot(entry);
+
+ return usage;
+}
+
+static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
+{
+ struct swap_cluster_info *ci;
+ unsigned long offset = swp_offset(entry);
+ unsigned char count;
+
+ ci = lock_cluster(p, offset);
+ count = p->swap_map[offset];
+ VM_BUG_ON(count != SWAP_HAS_CACHE);
+ p->swap_map[offset] = 0;
+ dec_cluster_info_page(p, p->cluster_info, offset);
+ unlock_cluster(ci);
+
+ mem_cgroup_uncharge_swap(entry, 1);
+ swap_range_free(p, offset, 1);
+}
+
+/*
+ * Caller has made sure that the swap device corresponding to entry
+ * is still around or has not been recycled.
+ */
+void swap_free(swp_entry_t entry)
+{
+ struct swap_info_struct *p;
+
+ p = _swap_info_get(entry);
+ if (p)
+ __swap_entry_free(p, entry);
+}
+
+/*
+ * Called after dropping swapcache to decrease refcnt to swap entries.
+ */
+void put_swap_page(struct page *page, swp_entry_t entry)
+{
+ unsigned long offset = swp_offset(entry);
+ unsigned long idx = offset / SWAPFILE_CLUSTER;
+ struct swap_cluster_info *ci;
+ struct swap_info_struct *si;
+ unsigned char *map;
+ unsigned int i, free_entries = 0;
+ unsigned char val;
+ int size = swap_entry_size(thp_nr_pages(page));
+
+ si = _swap_info_get(entry);
+ if (!si)
+ return;
+
+ ci = lock_cluster_or_swap_info(si, offset);
+ if (size == SWAPFILE_CLUSTER) {
+ VM_BUG_ON(!cluster_is_huge(ci));
+ map = si->swap_map + offset;
+ for (i = 0; i < SWAPFILE_CLUSTER; i++) {
+ val = map[i];
+ VM_BUG_ON(!(val & SWAP_HAS_CACHE));
+ if (val == SWAP_HAS_CACHE)
+ free_entries++;
+ }
+ cluster_clear_huge(ci);
+ if (free_entries == SWAPFILE_CLUSTER) {
+ unlock_cluster_or_swap_info(si, ci);
+ spin_lock(&si->lock);
+ mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER);
+ swap_free_cluster(si, idx);
+ spin_unlock(&si->lock);
+ return;
+ }
+ }
+ for (i = 0; i < size; i++, entry.val++) {
+ if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) {
+ unlock_cluster_or_swap_info(si, ci);
+ free_swap_slot(entry);
+ if (i == size - 1)
+ return;
+ lock_cluster_or_swap_info(si, offset);
+ }
+ }
+ unlock_cluster_or_swap_info(si, ci);
+}
+
+#ifdef CONFIG_THP_SWAP
+int split_swap_cluster(swp_entry_t entry)
+{
+ struct swap_info_struct *si;
+ struct swap_cluster_info *ci;
+ unsigned long offset = swp_offset(entry);
+
+ si = _swap_info_get(entry);
+ if (!si)
+ return -EBUSY;
+ ci = lock_cluster(si, offset);
+ cluster_clear_huge(ci);
+ unlock_cluster(ci);
+ return 0;
+}
+#endif
+
+static int swp_entry_cmp(const void *ent1, const void *ent2)
+{
+ const swp_entry_t *e1 = ent1, *e2 = ent2;
+
+ return (int)swp_type(*e1) - (int)swp_type(*e2);
+}
+
+void swapcache_free_entries(swp_entry_t *entries, int n)
+{
+ struct swap_info_struct *p, *prev;
+ int i;
+
+ if (n <= 0)
+ return;
+
+ prev = NULL;
+ p = NULL;
+
+ /*
+ * Sort swap entries by swap device, so each lock is only taken once.
+ * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
+ * so low that it isn't necessary to optimize further.
+ */
+ if (nr_swapfiles > 1)
+ sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
+ for (i = 0; i < n; ++i) {
+ p = swap_info_get_cont(entries[i], prev);
+ if (p)
+ swap_entry_free(p, entries[i]);
+ prev = p;
+ }
+ if (p)
+ spin_unlock(&p->lock);
+}
+
+/*
+ * How many references to page are currently swapped out?
+ * This does not give an exact answer when swap count is continued,
+ * but does include the high COUNT_CONTINUED flag to allow for that.
+ */
+int page_swapcount(struct page *page)
+{
+ int count = 0;
+ struct swap_info_struct *p;
+ struct swap_cluster_info *ci;
+ swp_entry_t entry;
+ unsigned long offset;
+
+ entry.val = page_private(page);
+ p = _swap_info_get(entry);
+ if (p) {
+ offset = swp_offset(entry);
+ ci = lock_cluster_or_swap_info(p, offset);
+ count = swap_count(p->swap_map[offset]);
+ unlock_cluster_or_swap_info(p, ci);
+ }
+ return count;
+}
+
+int __swap_count(swp_entry_t entry)
+{
+ struct swap_info_struct *si;
+ pgoff_t offset = swp_offset(entry);
+ int count = 0;
+
+ si = get_swap_device(entry);
+ if (si) {
+ count = swap_count(si->swap_map[offset]);
+ put_swap_device(si);
+ }
+ return count;
+}
+
+static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
+{
+ int count = 0;
+ pgoff_t offset = swp_offset(entry);
+ struct swap_cluster_info *ci;
+
+ ci = lock_cluster_or_swap_info(si, offset);
+ count = swap_count(si->swap_map[offset]);
+ unlock_cluster_or_swap_info(si, ci);
+ return count;
+}
+
+/*
+ * How many references to @entry are currently swapped out?
+ * This does not give an exact answer when swap count is continued,
+ * but does include the high COUNT_CONTINUED flag to allow for that.
+ */
+int __swp_swapcount(swp_entry_t entry)
+{
+ int count = 0;
+ struct swap_info_struct *si;
+
+ si = get_swap_device(entry);
+ if (si) {
+ count = swap_swapcount(si, entry);
+ put_swap_device(si);
+ }
+ return count;
+}
+
+/*
+ * How many references to @entry are currently swapped out?
+ * This considers COUNT_CONTINUED so it returns exact answer.
+ */
+int swp_swapcount(swp_entry_t entry)
+{
+ int count, tmp_count, n;
+ struct swap_info_struct *p;
+ struct swap_cluster_info *ci;
+ struct page *page;
+ pgoff_t offset;
+ unsigned char *map;
+
+ p = _swap_info_get(entry);
+ if (!p)
+ return 0;
+
+ offset = swp_offset(entry);
+
+ ci = lock_cluster_or_swap_info(p, offset);
+
+ count = swap_count(p->swap_map[offset]);
+ if (!(count & COUNT_CONTINUED))
+ goto out;
+
+ count &= ~COUNT_CONTINUED;
+ n = SWAP_MAP_MAX + 1;
+
+ page = vmalloc_to_page(p->swap_map + offset);
+ offset &= ~PAGE_MASK;
+ VM_BUG_ON(page_private(page) != SWP_CONTINUED);
+
+ do {
+ page = list_next_entry(page, lru);
+ map = kmap_atomic(page);
+ tmp_count = map[offset];
+ kunmap_atomic(map);
+
+ count += (tmp_count & ~COUNT_CONTINUED) * n;
+ n *= (SWAP_CONT_MAX + 1);
+ } while (tmp_count & COUNT_CONTINUED);
+out:
+ unlock_cluster_or_swap_info(p, ci);
+ return count;
+}
+
+static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
+ swp_entry_t entry)
+{
+ struct swap_cluster_info *ci;
+ unsigned char *map = si->swap_map;
+ unsigned long roffset = swp_offset(entry);
+ unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER);
+ int i;
+ bool ret = false;
+
+ ci = lock_cluster_or_swap_info(si, offset);
+ if (!ci || !cluster_is_huge(ci)) {
+ if (swap_count(map[roffset]))
+ ret = true;
+ goto unlock_out;
+ }
+ for (i = 0; i < SWAPFILE_CLUSTER; i++) {
+ if (swap_count(map[offset + i])) {
+ ret = true;
+ break;
+ }
+ }
+unlock_out:
+ unlock_cluster_or_swap_info(si, ci);
+ return ret;
+}
+
+static bool page_swapped(struct page *page)
+{
+ swp_entry_t entry;
+ struct swap_info_struct *si;
+
+ if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page)))
+ return page_swapcount(page) != 0;
+
+ page = compound_head(page);
+ entry.val = page_private(page);
+ si = _swap_info_get(entry);
+ if (si)
+ return swap_page_trans_huge_swapped(si, entry);
+ return false;
+}
+
+static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
+ int *total_swapcount)
+{
+ int i, map_swapcount, _total_mapcount, _total_swapcount;
+ unsigned long offset = 0;
+ struct swap_info_struct *si;
+ struct swap_cluster_info *ci = NULL;
+ unsigned char *map = NULL;
+ int mapcount, swapcount = 0;
+
+ /* hugetlbfs shouldn't call it */
+ VM_BUG_ON_PAGE(PageHuge(page), page);
+
+ if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page))) {
+ mapcount = page_trans_huge_mapcount(page, total_mapcount);
+ if (PageSwapCache(page))
+ swapcount = page_swapcount(page);
+ if (total_swapcount)
+ *total_swapcount = swapcount;
+ return mapcount + swapcount;
+ }
+
+ page = compound_head(page);
+
+ _total_mapcount = _total_swapcount = map_swapcount = 0;
+ if (PageSwapCache(page)) {
+ swp_entry_t entry;
+
+ entry.val = page_private(page);
+ si = _swap_info_get(entry);
+ if (si) {
+ map = si->swap_map;
+ offset = swp_offset(entry);
+ }
+ }
+ if (map)
+ ci = lock_cluster(si, offset);
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ mapcount = atomic_read(&page[i]._mapcount) + 1;
+ _total_mapcount += mapcount;
+ if (map) {
+ swapcount = swap_count(map[offset + i]);
+ _total_swapcount += swapcount;
+ }
+ map_swapcount = max(map_swapcount, mapcount + swapcount);
+ }
+ unlock_cluster(ci);
+ if (PageDoubleMap(page)) {
+ map_swapcount -= 1;
+ _total_mapcount -= HPAGE_PMD_NR;
+ }
+ mapcount = compound_mapcount(page);
+ map_swapcount += mapcount;
+ _total_mapcount += mapcount;
+ if (total_mapcount)
+ *total_mapcount = _total_mapcount;
+ if (total_swapcount)
+ *total_swapcount = _total_swapcount;
+
+ return map_swapcount;
+}
+
+/*
+ * We can write to an anon page without COW if there are no other references
+ * to it. And as a side-effect, free up its swap: because the old content
+ * on disk will never be read, and seeking back there to write new content
+ * later would only waste time away from clustering.
+ *
+ * NOTE: total_map_swapcount should not be relied upon by the caller if
+ * reuse_swap_page() returns false, but it may be always overwritten
+ * (see the other implementation for CONFIG_SWAP=n).
+ */
+bool reuse_swap_page(struct page *page, int *total_map_swapcount)
+{
+ int count, total_mapcount, total_swapcount;
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ if (unlikely(PageKsm(page)))
+ return false;
+ count = page_trans_huge_map_swapcount(page, &total_mapcount,
+ &total_swapcount);
+ if (total_map_swapcount)
+ *total_map_swapcount = total_mapcount + total_swapcount;
+ if (count == 1 && PageSwapCache(page) &&
+ (likely(!PageTransCompound(page)) ||
+ /* The remaining swap count will be freed soon */
+ total_swapcount == page_swapcount(page))) {
+ if (!PageWriteback(page)) {
+ page = compound_head(page);
+ delete_from_swap_cache(page);
+ SetPageDirty(page);
+ } else {
+ swp_entry_t entry;
+ struct swap_info_struct *p;
+
+ entry.val = page_private(page);
+ p = swap_info_get(entry);
+ if (p->flags & SWP_STABLE_WRITES) {
+ spin_unlock(&p->lock);
+ return false;
+ }
+ spin_unlock(&p->lock);
+ }
+ }
+
+ return count <= 1;
+}
+
+/*
+ * If swap is getting full, or if there are no more mappings of this page,
+ * then try_to_free_swap is called to free its swap space.
+ */
+int try_to_free_swap(struct page *page)
+{
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+
+ if (!PageSwapCache(page))
+ return 0;
+ if (PageWriteback(page))
+ return 0;
+ if (page_swapped(page))
+ return 0;
+
+ /*
+ * Once hibernation has begun to create its image of memory,
+ * there's a danger that one of the calls to try_to_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 page which has already been recorded in the
+ * image as a clean swapcache page, and then reuse its swap for
+ * another page of the image. On waking from hibernation, the
+ * original page 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 0;
+
+ page = compound_head(page);
+ delete_from_swap_cache(page);
+ SetPageDirty(page);
+ return 1;
+}
+
+/*
+ * Free the swap entry like above, but also try to
+ * free the page cache entry if it is the last user.
+ */
+int free_swap_and_cache(swp_entry_t entry)
+{
+ struct swap_info_struct *p;
+ unsigned char count;
+
+ if (non_swap_entry(entry))
+ return 1;
+
+ p = _swap_info_get(entry);
+ if (p) {
+ count = __swap_entry_free(p, entry);
+ if (count == SWAP_HAS_CACHE &&
+ !swap_page_trans_huge_swapped(p, entry))
+ __try_to_reclaim_swap(p, swp_offset(entry),
+ TTRS_UNMAPPED | TTRS_FULL);
+ }
+ return p != NULL;
+}
+
+#ifdef CONFIG_HIBERNATION
+/*
+ * Find the swap type that corresponds to given device (if any).
+ *
+ * @offset - number of the PAGE_SIZE-sized block of the device, starting
+ * from 0, in which the swap header is expected to be located.
+ *
+ * This is needed for the suspend to disk (aka swsusp).
+ */
+int swap_type_of(dev_t device, sector_t offset)
+{
+ int type;
+
+ if (!device)
+ return -1;
+
+ spin_lock(&swap_lock);
+ for (type = 0; type < nr_swapfiles; type++) {
+ struct swap_info_struct *sis = swap_info[type];
+
+ if (!(sis->flags & SWP_WRITEOK))
+ continue;
+
+ if (device == sis->bdev->bd_dev) {
+ struct swap_extent *se = first_se(sis);
+
+ if (se->start_block == offset) {
+ spin_unlock(&swap_lock);
+ return type;
+ }
+ }
+ }
+ spin_unlock(&swap_lock);
+ return -ENODEV;
+}
+
+int find_first_swap(dev_t *device)
+{
+ int type;
+
+ spin_lock(&swap_lock);
+ for (type = 0; type < nr_swapfiles; type++) {
+ struct swap_info_struct *sis = swap_info[type];
+
+ if (!(sis->flags & SWP_WRITEOK))
+ continue;
+ *device = sis->bdev->bd_dev;
+ spin_unlock(&swap_lock);
+ return type;
+ }
+ spin_unlock(&swap_lock);
+ return -ENODEV;
+}
+
+/*
+ * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
+ * corresponding to given index in swap_info (swap type).
+ */
+sector_t swapdev_block(int type, pgoff_t offset)
+{
+ struct block_device *bdev;
+ struct swap_info_struct *si = swap_type_to_swap_info(type);
+
+ if (!si || !(si->flags & SWP_WRITEOK))
+ return 0;
+ return map_swap_entry(swp_entry(type, offset), &bdev);
+}
+
+/*
+ * Return either the total number of swap pages of given type, or the number
+ * of free pages of that type (depending on @free)
+ *
+ * This is needed for software suspend
+ */
+unsigned int count_swap_pages(int type, int free)
+{
+ unsigned int n = 0;
+
+ spin_lock(&swap_lock);
+ if ((unsigned int)type < nr_swapfiles) {
+ struct swap_info_struct *sis = swap_info[type];
+
+ spin_lock(&sis->lock);
+ if (sis->flags & SWP_WRITEOK) {
+ n = sis->pages;
+ if (free)
+ n -= sis->inuse_pages;
+ }
+ spin_unlock(&sis->lock);
+ }
+ spin_unlock(&swap_lock);
+ return n;
+}
+#endif /* CONFIG_HIBERNATION */
+
+static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
+{
+ return pte_same(pte_swp_clear_flags(pte), swp_pte);
+}
+
+/*
+ * No need to decide whether this PTE shares the swap entry with others,
+ * just let do_wp_page work it out if a write is requested later - to
+ * force COW, vm_page_prot omits write permission from any private vma.
+ */
+static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
+ unsigned long addr, swp_entry_t entry, struct page *page)
+{
+ struct page *swapcache;
+ spinlock_t *ptl;
+ pte_t *pte;
+ int ret = 1;
+
+ swapcache = page;
+ page = ksm_might_need_to_copy(page, vma, addr);
+ if (unlikely(!page))
+ return -ENOMEM;
+
+ pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+ if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
+ ret = 0;
+ goto out;
+ }
+
+ dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
+ inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
+ get_page(page);
+ set_pte_at(vma->vm_mm, addr, pte,
+ pte_mkold(mk_pte(page, vma->vm_page_prot)));
+ if (page == swapcache) {
+ page_add_anon_rmap(page, vma, addr, false);
+ } else { /* ksm created a completely new copy */
+ page_add_new_anon_rmap(page, vma, addr, false);
+ lru_cache_add_inactive_or_unevictable(page, vma);
+ }
+ swap_free(entry);
+out:
+ pte_unmap_unlock(pte, ptl);
+ if (page != swapcache) {
+ unlock_page(page);
+ put_page(page);
+ }
+ return ret;
+}
+
+static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
+ unsigned long addr, unsigned long end,
+ unsigned int type, bool frontswap,
+ unsigned long *fs_pages_to_unuse)
+{
+ struct page *page;
+ swp_entry_t entry;
+ pte_t *pte;
+ struct swap_info_struct *si;
+ unsigned long offset;
+ int ret = 0;
+ volatile unsigned char *swap_map;
+
+ si = swap_info[type];
+ pte = pte_offset_map(pmd, addr);
+ do {
+ struct vm_fault vmf;
+
+ if (!is_swap_pte(*pte))
+ continue;
+
+ entry = pte_to_swp_entry(*pte);
+ if (swp_type(entry) != type)
+ continue;
+
+ offset = swp_offset(entry);
+ if (frontswap && !frontswap_test(si, offset))
+ continue;
+
+ pte_unmap(pte);
+ swap_map = &si->swap_map[offset];
+ page = lookup_swap_cache(entry, vma, addr);
+ if (!page) {
+ vmf.vma = vma;
+ vmf.address = addr;
+ vmf.pmd = pmd;
+ page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
+ &vmf);
+ }
+ if (!page) {
+ if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
+ goto try_next;
+ return -ENOMEM;
+ }
+
+ lock_page(page);
+ wait_on_page_writeback(page);
+ ret = unuse_pte(vma, pmd, addr, entry, page);
+ if (ret < 0) {
+ unlock_page(page);
+ put_page(page);
+ goto out;
+ }
+
+ try_to_free_swap(page);
+ unlock_page(page);
+ put_page(page);
+
+ if (*fs_pages_to_unuse && !--(*fs_pages_to_unuse)) {
+ ret = FRONTSWAP_PAGES_UNUSED;
+ goto out;
+ }
+try_next:
+ pte = pte_offset_map(pmd, addr);
+ } while (pte++, addr += PAGE_SIZE, addr != end);
+ pte_unmap(pte - 1);
+
+ ret = 0;
+out:
+ return ret;
+}
+
+static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
+ unsigned long addr, unsigned long end,
+ unsigned int type, bool frontswap,
+ unsigned long *fs_pages_to_unuse)
+{
+ pmd_t *pmd;
+ unsigned long next;
+ int ret;
+
+ pmd = pmd_offset(pud, addr);
+ do {
+ cond_resched();
+ next = pmd_addr_end(addr, end);
+ if (pmd_none_or_trans_huge_or_clear_bad(pmd))
+ continue;
+ ret = unuse_pte_range(vma, pmd, addr, next, type,
+ frontswap, fs_pages_to_unuse);
+ 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, bool frontswap,
+ unsigned long *fs_pages_to_unuse)
+{
+ 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,
+ frontswap, fs_pages_to_unuse);
+ 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, bool frontswap,
+ unsigned long *fs_pages_to_unuse)
+{
+ 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,
+ frontswap, fs_pages_to_unuse);
+ if (ret)
+ return ret;
+ } while (p4d++, addr = next, addr != end);
+ return 0;
+}
+
+static int unuse_vma(struct vm_area_struct *vma, unsigned int type,
+ bool frontswap, unsigned long *fs_pages_to_unuse)
+{
+ 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,
+ frontswap, fs_pages_to_unuse);
+ if (ret)
+ return ret;
+ } while (pgd++, addr = next, addr != end);
+ return 0;
+}
+
+static int unuse_mm(struct mm_struct *mm, unsigned int type,
+ bool frontswap, unsigned long *fs_pages_to_unuse)
+{
+ struct vm_area_struct *vma;
+ int ret = 0;
+
+ mmap_read_lock(mm);
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ if (vma->anon_vma) {
+ ret = unuse_vma(vma, type, frontswap,
+ fs_pages_to_unuse);
+ if (ret)
+ break;
+ }
+ cond_resched();
+ }
+ mmap_read_unlock(mm);
+ return ret;
+}
+
+/*
+ * Scan swap_map (or frontswap_map if frontswap parameter is true)
+ * 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, bool frontswap)
+{
+ unsigned int i;
+ unsigned char count;
+
+ /*
+ * No need for swap_lock here: we're just looking
+ * for whether an entry is in use, not modifying it; false
+ * hits are okay, and sys_swapoff() has already prevented new
+ * allocations from this area (while holding swap_lock).
+ */
+ for (i = prev + 1; i < si->max; i++) {
+ count = READ_ONCE(si->swap_map[i]);
+ if (count && swap_count(count) != SWAP_MAP_BAD)
+ if (!frontswap || frontswap_test(si, i))
+ break;
+ if ((i % LATENCY_LIMIT) == 0)
+ cond_resched();
+ }
+
+ if (i == si->max)
+ i = 0;
+
+ return i;
+}
+
+/*
+ * If the boolean frontswap is true, only unuse pages_to_unuse pages;
+ * pages_to_unuse==0 means all pages; ignored if frontswap is false
+ */
+int try_to_unuse(unsigned int type, bool frontswap,
+ unsigned long pages_to_unuse)
+{
+ 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 page *page;
+ swp_entry_t entry;
+ unsigned int i;
+
+ if (!READ_ONCE(si->inuse_pages))
+ return 0;
+
+ if (!frontswap)
+ pages_to_unuse = 0;
+
+retry:
+ retval = shmem_unuse(type, frontswap, &pages_to_unuse);
+ if (retval)
+ goto out;
+
+ prev_mm = &init_mm;
+ mmget(prev_mm);
+
+ spin_lock(&mmlist_lock);
+ p = &init_mm.mmlist;
+ while (READ_ONCE(si->inuse_pages) &&
+ !signal_pending(current) &&
+ (p = p->next) != &init_mm.mmlist) {
+
+ mm = list_entry(p, struct mm_struct, mmlist);
+ if (!mmget_not_zero(mm))
+ continue;
+ spin_unlock(&mmlist_lock);
+ mmput(prev_mm);
+ prev_mm = mm;
+ retval = unuse_mm(mm, type, frontswap, &pages_to_unuse);
+
+ if (retval) {
+ mmput(prev_mm);
+ goto out;
+ }
+
+ /*
+ * Make sure that we aren't completely killing
+ * interactive performance.
+ */
+ cond_resched();
+ spin_lock(&mmlist_lock);
+ }
+ spin_unlock(&mmlist_lock);
+
+ mmput(prev_mm);
+
+ i = 0;
+ while (READ_ONCE(si->inuse_pages) &&
+ !signal_pending(current) &&
+ (i = find_next_to_unuse(si, i, frontswap)) != 0) {
+
+ entry = swp_entry(type, i);
+ page = find_get_page(swap_address_space(entry), i);
+ if (!page)
+ continue;
+
+ /*
+ * It is conceivable that a racing task removed this page from
+ * swap cache just before we acquired the page lock. The page
+ * might even be back in swap cache on another swap area. But
+ * that is okay, try_to_free_swap() only removes stale pages.
+ */
+ lock_page(page);
+ wait_on_page_writeback(page);
+ try_to_free_swap(page);
+ unlock_page(page);
+ put_page(page);
+
+ /*
+ * For frontswap, we just need to unuse pages_to_unuse, if
+ * it was specified. Need not check frontswap again here as
+ * we already zeroed out pages_to_unuse if not frontswap.
+ */
+ if (pages_to_unuse && --pages_to_unuse == 0)
+ goto out;
+ }
+
+ /*
+ * Lets check again to see if there are still swap entries in the map.
+ * If yes, we would need to do retry the unuse logic again.
+ * Under global memory pressure, swap entries can be reinserted back
+ * into process space after the mmlist loop above passes over them.
+ *
+ * Limit the number of retries? No: when mmget_not_zero() above fails,
+ * that mm is likely to be freeing swap from exit_mmap(), which proceeds
+ * at its own independent pace; and even shmem_writepage() could have
+ * been preempted after get_swap_page(), temporarily hiding that swap.
+ * It's easy and robust (though cpu-intensive) just to keep retrying.
+ */
+ if (READ_ONCE(si->inuse_pages)) {
+ if (!signal_pending(current))
+ goto retry;
+ retval = -EINTR;
+ }
+out:
+ return (retval == FRONTSWAP_PAGES_UNUSED) ? 0 : retval;
+}
+
+/*
+ * After a successful try_to_unuse, if no swap is now in use, we know
+ * we can empty the mmlist. swap_lock must be held on entry and exit.
+ * Note that mmlist_lock nests inside swap_lock, and an mm must be
+ * added to the mmlist just after page_duplicate - before would be racy.
+ */
+static void drain_mmlist(void)
+{
+ struct list_head *p, *next;
+ unsigned int type;
+
+ for (type = 0; type < nr_swapfiles; type++)
+ if (swap_info[type]->inuse_pages)
+ return;
+ spin_lock(&mmlist_lock);
+ list_for_each_safe(p, next, &init_mm.mmlist)
+ list_del_init(p);
+ spin_unlock(&mmlist_lock);
+}
+
+/*
+ * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
+ * corresponds to page offset for the specified swap entry.
+ * Note that the type of this function is sector_t, but it returns page offset
+ * into the bdev, not sector offset.
+ */
+static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
+{
+ struct swap_info_struct *sis;
+ struct swap_extent *se;
+ pgoff_t offset;
+
+ sis = swp_swap_info(entry);
+ *bdev = sis->bdev;
+
+ offset = swp_offset(entry);
+ se = offset_to_swap_extent(sis, offset);
+ return se->start_block + (offset - se->start_page);
+}
+
+/*
+ * Returns the page offset into bdev for the specified page's swap entry.
+ */
+sector_t map_swap_page(struct page *page, struct block_device **bdev)
+{
+ swp_entry_t entry;
+ entry.val = page_private(page);
+ return map_swap_entry(entry, bdev);
+}
+
+/*
+ * Free all of a swapdev's extent information
+ */
+static void destroy_swap_extents(struct swap_info_struct *sis)
+{
+ while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
+ struct rb_node *rb = sis->swap_extent_root.rb_node;
+ struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
+
+ rb_erase(rb, &sis->swap_extent_root);
+ kfree(se);
+ }
+
+ if (sis->flags & SWP_ACTIVATED) {
+ struct file *swap_file = sis->swap_file;
+ struct address_space *mapping = swap_file->f_mapping;
+
+ sis->flags &= ~SWP_ACTIVATED;
+ if (mapping->a_ops->swap_deactivate)
+ mapping->a_ops->swap_deactivate(swap_file);
+ }
+}
+
+/*
+ * Add a block range (and the corresponding page range) into this swapdev's
+ * extent tree.
+ *
+ * This function rather assumes that it is called in ascending page order.
+ */
+int
+add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
+ unsigned long nr_pages, sector_t start_block)
+{
+ struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
+ struct swap_extent *se;
+ struct swap_extent *new_se;
+
+ /*
+ * place the new node at the right most since the
+ * function is called in ascending page order.
+ */
+ while (*link) {
+ parent = *link;
+ link = &parent->rb_right;
+ }
+
+ if (parent) {
+ se = rb_entry(parent, struct swap_extent, rb_node);
+ BUG_ON(se->start_page + se->nr_pages != start_page);
+ if (se->start_block + se->nr_pages == start_block) {
+ /* Merge it */
+ se->nr_pages += nr_pages;
+ return 0;
+ }
+ }
+
+ /* No merge, insert a new extent. */
+ new_se = kmalloc(sizeof(*se), GFP_KERNEL);
+ if (new_se == NULL)
+ return -ENOMEM;
+ new_se->start_page = start_page;
+ new_se->nr_pages = nr_pages;
+ new_se->start_block = start_block;
+
+ rb_link_node(&new_se->rb_node, parent, link);
+ rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
+ return 1;
+}
+EXPORT_SYMBOL_GPL(add_swap_extent);
+
+/*
+ * A `swap extent' is a simple thing which maps a contiguous range of pages
+ * onto a contiguous range of disk blocks. An ordered list of swap extents
+ * is built at swapon time and is then used at swap_writepage/swap_readpage
+ * time for locating where on disk a page belongs.
+ *
+ * If the swapfile is an S_ISBLK block device, a single extent is installed.
+ * This is done so that the main operating code can treat S_ISBLK and S_ISREG
+ * swap files identically.
+ *
+ * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
+ * extent list 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 an ordered extent list, 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 list. To avoid much list walking, we cache the previous
+ * search location in `curr_swap_extent', and start new searches from there.
+ * This is extremely effective. The average number of iterations in
+ * map_swap_page() has been measured at about 0.3 per page. - akpm.
+ */
+static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
+{
+ struct file *swap_file = sis->swap_file;
+ struct address_space *mapping = swap_file->f_mapping;
+ struct inode *inode = mapping->host;
+ int ret;
+
+ if (S_ISBLK(inode->i_mode)) {
+ ret = add_swap_extent(sis, 0, sis->max, 0);
+ *span = sis->pages;
+ return ret;
+ }
+
+ if (mapping->a_ops->swap_activate) {
+ ret = mapping->a_ops->swap_activate(sis, swap_file, span);
+ if (ret >= 0)
+ sis->flags |= SWP_ACTIVATED;
+ if (!ret) {
+ sis->flags |= SWP_FS_OPS;
+ ret = add_swap_extent(sis, 0, sis->max, 0);
+ *span = sis->pages;
+ }
+ return ret;
+ }
+
+ return generic_swapfile_activate(sis, swap_file, span);
+}
+
+static int swap_node(struct swap_info_struct *p)
+{
+ struct block_device *bdev;
+
+ if (p->bdev)
+ bdev = p->bdev;
+ else
+ bdev = p->swap_file->f_inode->i_sb->s_bdev;
+
+ return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
+}
+
+static void setup_swap_info(struct swap_info_struct *p, int prio,
+ unsigned char *swap_map,
+ struct swap_cluster_info *cluster_info)
+{
+ int i;
+
+ if (prio >= 0)
+ p->prio = prio;
+ else
+ p->prio = --least_priority;
+ /*
+ * the plist prio is negated because plist ordering is
+ * low-to-high, while swap ordering is high-to-low
+ */
+ p->list.prio = -p->prio;
+ for_each_node(i) {
+ if (p->prio >= 0)
+ p->avail_lists[i].prio = -p->prio;
+ else {
+ if (swap_node(p) == i)
+ p->avail_lists[i].prio = 1;
+ else
+ p->avail_lists[i].prio = -p->prio;
+ }
+ }
+ p->swap_map = swap_map;
+ p->cluster_info = cluster_info;
+}
+
+static void _enable_swap_info(struct swap_info_struct *p)
+{
+ p->flags |= SWP_WRITEOK | SWP_VALID;
+ atomic_long_add(p->pages, &nr_swap_pages);
+ total_swap_pages += p->pages;
+
+ assert_spin_locked(&swap_lock);
+ /*
+ * both lists are plists, and thus priority ordered.
+ * swap_active_head needs to be priority ordered for swapoff(),
+ * which on removal of any swap_info_struct with an auto-assigned
+ * (i.e. negative) priority increments the auto-assigned priority
+ * of any lower-priority swap_info_structs.
+ * swap_avail_head needs to be priority ordered for get_swap_page(),
+ * which allocates swap pages from the highest available priority
+ * swap_info_struct.
+ */
+ plist_add(&p->list, &swap_active_head);
+ add_to_avail_list(p);
+}
+
+static void enable_swap_info(struct swap_info_struct *p, int prio,
+ unsigned char *swap_map,
+ struct swap_cluster_info *cluster_info,
+ unsigned long *frontswap_map)
+{
+ frontswap_init(p->type, frontswap_map);
+ spin_lock(&swap_lock);
+ spin_lock(&p->lock);
+ setup_swap_info(p, prio, swap_map, cluster_info);
+ spin_unlock(&p->lock);
+ spin_unlock(&swap_lock);
+ /*
+ * Guarantee swap_map, cluster_info, etc. fields are valid
+ * between get/put_swap_device() if SWP_VALID bit is set
+ */
+ synchronize_rcu();
+ spin_lock(&swap_lock);
+ spin_lock(&p->lock);
+ _enable_swap_info(p);
+ spin_unlock(&p->lock);
+ spin_unlock(&swap_lock);
+}
+
+static void reinsert_swap_info(struct swap_info_struct *p)
+{
+ spin_lock(&swap_lock);
+ spin_lock(&p->lock);
+ setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
+ _enable_swap_info(p);
+ spin_unlock(&p->lock);
+ spin_unlock(&swap_lock);
+}
+
+bool has_usable_swap(void)
+{
+ bool ret = true;
+
+ spin_lock(&swap_lock);
+ if (plist_head_empty(&swap_active_head))
+ ret = false;
+ spin_unlock(&swap_lock);
+ return ret;
+}
+
+SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
+{
+ struct swap_info_struct *p = NULL;
+ unsigned char *swap_map;
+ struct swap_cluster_info *cluster_info;
+ unsigned long *frontswap_map;
+ struct file *swap_file, *victim;
+ struct address_space *mapping;
+ struct inode *inode;
+ struct filename *pathname;
+ int err, found = 0;
+ unsigned int old_block_size;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ BUG_ON(!current->mm);
+
+ pathname = getname(specialfile);
+ if (IS_ERR(pathname))
+ return PTR_ERR(pathname);
+
+ victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
+ err = PTR_ERR(victim);
+ if (IS_ERR(victim))
+ goto out;
+
+ mapping = victim->f_mapping;
+ spin_lock(&swap_lock);
+ plist_for_each_entry(p, &swap_active_head, list) {
+ if (p->flags & SWP_WRITEOK) {
+ if (p->swap_file->f_mapping == mapping) {
+ found = 1;
+ break;
+ }
+ }
+ }
+ if (!found) {
+ err = -EINVAL;
+ spin_unlock(&swap_lock);
+ goto out_dput;
+ }
+ if (!security_vm_enough_memory_mm(current->mm, p->pages))
+ vm_unacct_memory(p->pages);
+ else {
+ err = -ENOMEM;
+ spin_unlock(&swap_lock);
+ goto out_dput;
+ }
+ spin_lock(&p->lock);
+ del_from_avail_list(p);
+ if (p->prio < 0) {
+ struct swap_info_struct *si = p;
+ int nid;
+
+ plist_for_each_entry_continue(si, &swap_active_head, list) {
+ si->prio++;
+ si->list.prio--;
+ for_each_node(nid) {
+ if (si->avail_lists[nid].prio != 1)
+ si->avail_lists[nid].prio--;
+ }
+ }
+ least_priority++;
+ }
+ plist_del(&p->list, &swap_active_head);
+ atomic_long_sub(p->pages, &nr_swap_pages);
+ total_swap_pages -= p->pages;
+ p->flags &= ~SWP_WRITEOK;
+ spin_unlock(&p->lock);
+ spin_unlock(&swap_lock);
+
+ disable_swap_slots_cache_lock();
+
+ set_current_oom_origin();
+ err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
+ clear_current_oom_origin();
+
+ if (err) {
+ /* re-insert swap space back into swap_list */
+ reinsert_swap_info(p);
+ reenable_swap_slots_cache_unlock();
+ goto out_dput;
+ }
+
+ reenable_swap_slots_cache_unlock();
+
+ spin_lock(&swap_lock);
+ spin_lock(&p->lock);
+ p->flags &= ~SWP_VALID; /* mark swap device as invalid */
+ spin_unlock(&p->lock);
+ spin_unlock(&swap_lock);
+ /*
+ * wait for swap operations protected by get/put_swap_device()
+ * to complete
+ */
+ synchronize_rcu();
+
+ flush_work(&p->discard_work);
+
+ destroy_swap_extents(p);
+ if (p->flags & SWP_CONTINUED)
+ free_swap_count_continuations(p);
+
+ if (!p->bdev || !blk_queue_nonrot(bdev_get_queue(p->bdev)))
+ atomic_dec(&nr_rotate_swap);
+
+ mutex_lock(&swapon_mutex);
+ spin_lock(&swap_lock);
+ spin_lock(&p->lock);
+ drain_mmlist();
+
+ /* wait for anyone still in scan_swap_map */
+ p->highest_bit = 0; /* cuts scans short */
+ while (p->flags >= SWP_SCANNING) {
+ spin_unlock(&p->lock);
+ spin_unlock(&swap_lock);
+ schedule_timeout_uninterruptible(1);
+ spin_lock(&swap_lock);
+ spin_lock(&p->lock);
+ }
+
+ swap_file = p->swap_file;
+ old_block_size = p->old_block_size;
+ p->swap_file = NULL;
+ p->max = 0;
+ swap_map = p->swap_map;
+ p->swap_map = NULL;
+ cluster_info = p->cluster_info;
+ p->cluster_info = NULL;
+ frontswap_map = frontswap_map_get(p);
+ spin_unlock(&p->lock);
+ spin_unlock(&swap_lock);
+ arch_swap_invalidate_area(p->type);
+ frontswap_invalidate_area(p->type);
+ frontswap_map_set(p, NULL);
+ mutex_unlock(&swapon_mutex);
+ free_percpu(p->percpu_cluster);
+ p->percpu_cluster = NULL;
+ free_percpu(p->cluster_next_cpu);
+ p->cluster_next_cpu = NULL;
+ vfree(swap_map);
+ kvfree(cluster_info);
+ kvfree(frontswap_map);
+ /* Destroy swap account information */
+ swap_cgroup_swapoff(p->type);
+ exit_swap_address_space(p->type);
+
+ inode = mapping->host;
+ if (S_ISBLK(inode->i_mode)) {
+ struct block_device *bdev = I_BDEV(inode);
+
+ set_blocksize(bdev, old_block_size);
+ blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+ }
+
+ inode_lock(inode);
+ inode->i_flags &= ~S_SWAPFILE;
+ inode_unlock(inode);
+ filp_close(swap_file, NULL);
+
+ /*
+ * Clear the SWP_USED flag after all resources are freed so that swapon
+ * can reuse this swap_info in alloc_swap_info() safely. It is ok to
+ * not hold p->lock after we cleared its SWP_WRITEOK.
+ */
+ spin_lock(&swap_lock);
+ p->flags = 0;
+ spin_unlock(&swap_lock);
+
+ err = 0;
+ atomic_inc(&proc_poll_event);
+ wake_up_interruptible(&proc_poll_wait);
+
+out_dput:
+ filp_close(victim, NULL);
+out:
+ putname(pathname);
+ return err;
+}
+
+#ifdef CONFIG_PROC_FS
+static __poll_t swaps_poll(struct file *file, poll_table *wait)
+{
+ struct seq_file *seq = file->private_data;
+
+ poll_wait(file, &proc_poll_wait, wait);
+
+ if (seq->poll_event != atomic_read(&proc_poll_event)) {
+ seq->poll_event = atomic_read(&proc_poll_event);
+ return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
+ }
+
+ return EPOLLIN | EPOLLRDNORM;
+}
+
+/* iterator */
+static void *swap_start(struct seq_file *swap, loff_t *pos)
+{
+ struct swap_info_struct *si;
+ int type;
+ loff_t l = *pos;
+
+ mutex_lock(&swapon_mutex);
+
+ if (!l)
+ return SEQ_START_TOKEN;
+
+ for (type = 0; (si = swap_type_to_swap_info(type)); type++) {
+ if (!(si->flags & SWP_USED) || !si->swap_map)
+ continue;
+ if (!--l)
+ return si;
+ }
+
+ return NULL;
+}
+
+static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
+{
+ struct swap_info_struct *si = v;
+ int type;
+
+ if (v == SEQ_START_TOKEN)
+ type = 0;
+ else
+ type = si->type + 1;
+
+ ++(*pos);
+ for (; (si = swap_type_to_swap_info(type)); type++) {
+ if (!(si->flags & SWP_USED) || !si->swap_map)
+ continue;
+ return si;
+ }
+
+ return NULL;
+}
+
+static void swap_stop(struct seq_file *swap, void *v)
+{
+ mutex_unlock(&swapon_mutex);
+}
+
+static int swap_show(struct seq_file *swap, void *v)
+{
+ struct swap_info_struct *si = v;
+ struct file *file;
+ int len;
+ unsigned int 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 = si->pages << (PAGE_SHIFT - 10);
+ inuse = si->inuse_pages << (PAGE_SHIFT - 10);
+
+ file = si->swap_file;
+ len = seq_file_path(swap, file, " \t\n\\");
+ seq_printf(swap, "%*s%s\t%u\t%s%u\t%s%d\n",
+ len < 40 ? 40 - len : 1, " ",
+ S_ISBLK(file_inode(file)->i_mode) ?
+ "partition" : "file\t",
+ bytes, bytes < 10000000 ? "\t" : "",
+ inuse, inuse < 10000000 ? "\t" : "",
+ si->prio);
+ return 0;
+}
+
+static const struct seq_operations swaps_op = {
+ .start = swap_start,
+ .next = swap_next,
+ .stop = swap_stop,
+ .show = swap_show
+};
+
+static int swaps_open(struct inode *inode, struct file *file)
+{
+ struct seq_file *seq;
+ int ret;
+
+ ret = seq_open(file, &swaps_op);
+ if (ret)
+ return ret;
+
+ seq = file->private_data;
+ seq->poll_event = atomic_read(&proc_poll_event);
+ return 0;
+}
+
+static const struct proc_ops swaps_proc_ops = {
+ .proc_flags = PROC_ENTRY_PERMANENT,
+ .proc_open = swaps_open,
+ .proc_read = seq_read,
+ .proc_lseek = seq_lseek,
+ .proc_release = seq_release,
+ .proc_poll = swaps_poll,
+};
+
+static int __init procswaps_init(void)
+{
+ proc_create("swaps", 0, NULL, &swaps_proc_ops);
+ return 0;
+}
+__initcall(procswaps_init);
+#endif /* CONFIG_PROC_FS */
+
+#ifdef MAX_SWAPFILES_CHECK
+static int __init max_swapfiles_check(void)
+{
+ MAX_SWAPFILES_CHECK();
+ return 0;
+}
+late_initcall(max_swapfiles_check);
+#endif
+
+static struct swap_info_struct *alloc_swap_info(void)
+{
+ struct swap_info_struct *p;
+ struct swap_info_struct *defer = NULL;
+ unsigned int type;
+ int i;
+
+ p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
+ if (!p)
+ return ERR_PTR(-ENOMEM);
+
+ 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);
+ kvfree(p);
+ return ERR_PTR(-EPERM);
+ }
+ if (type >= nr_swapfiles) {
+ p->type = type;
+ WRITE_ONCE(swap_info[type], p);
+ /*
+ * Write swap_info[type] before nr_swapfiles, in case a
+ * racing procfs swap_start() or swap_next() is reading them.
+ * (We never shrink nr_swapfiles, we never free this entry.)
+ */
+ smp_wmb();
+ WRITE_ONCE(nr_swapfiles, nr_swapfiles + 1);
+ } else {
+ defer = p;
+ p = swap_info[type];
+ /*
+ * Do not memset this entry: a racing procfs swap_next()
+ * would be relying on p->type to remain valid.
+ */
+ }
+ p->swap_extent_root = RB_ROOT;
+ plist_node_init(&p->list, 0);
+ for_each_node(i)
+ plist_node_init(&p->avail_lists[i], 0);
+ p->flags = SWP_USED;
+ spin_unlock(&swap_lock);
+ kvfree(defer);
+ spin_lock_init(&p->lock);
+ spin_lock_init(&p->cont_lock);
+
+ return p;
+}
+
+static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
+{
+ int error;
+
+ if (S_ISBLK(inode->i_mode)) {
+ p->bdev = blkdev_get_by_dev(inode->i_rdev,
+ FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
+ if (IS_ERR(p->bdev)) {
+ error = PTR_ERR(p->bdev);
+ p->bdev = NULL;
+ return error;
+ }
+ p->old_block_size = block_size(p->bdev);
+ error = set_blocksize(p->bdev, PAGE_SIZE);
+ if (error < 0)
+ return error;
+ /*
+ * Zoned block devices contain zones that have a sequential
+ * write only restriction. Hence zoned block devices are not
+ * suitable for swapping. Disallow them here.
+ */
+ if (blk_queue_is_zoned(p->bdev->bd_disk->queue))
+ return -EINVAL;
+ p->flags |= SWP_BLKDEV;
+ } else if (S_ISREG(inode->i_mode)) {
+ p->bdev = inode->i_sb->s_bdev;
+ }
+
+ return 0;
+}
+
+
+/*
+ * Find out how many pages are allowed for a single swap device. There
+ * are two limiting factors:
+ * 1) the number of bits for the swap offset in the swp_entry_t type, and
+ * 2) the number of bits in the swap pte, as defined by the different
+ * architectures.
+ *
+ * In order to find the largest possible bit mask, a swap entry with
+ * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
+ * decoded to a swp_entry_t again, and finally the swap offset is
+ * extracted.
+ *
+ * This will mask all the bits from the initial ~0UL mask that can't
+ * be encoded in either the swp_entry_t or the architecture definition
+ * of a swap pte.
+ */
+unsigned long generic_max_swapfile_size(void)
+{
+ return swp_offset(pte_to_swp_entry(
+ swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
+}
+
+/* Can be overridden by an architecture for additional checks. */
+__weak unsigned long max_swapfile_size(void)
+{
+ return generic_max_swapfile_size();
+}
+
+static unsigned long read_swap_header(struct swap_info_struct *p,
+ union swap_header *swap_header,
+ struct inode *inode)
+{
+ int i;
+ unsigned long maxpages;
+ unsigned long swapfilepages;
+ unsigned long last_page;
+
+ if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
+ pr_err("Unable to find swap-space signature\n");
+ return 0;
+ }
+
+ /* swap partition endianess hack... */
+ if (swab32(swap_header->info.version) == 1) {
+ swab32s(&swap_header->info.version);
+ swab32s(&swap_header->info.last_page);
+ swab32s(&swap_header->info.nr_badpages);
+ if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
+ return 0;
+ for (i = 0; i < swap_header->info.nr_badpages; i++)
+ swab32s(&swap_header->info.badpages[i]);
+ }
+ /* Check the swap header's sub-version */
+ if (swap_header->info.version != 1) {
+ pr_warn("Unable to handle swap header version %d\n",
+ swap_header->info.version);
+ return 0;
+ }
+
+ p->lowest_bit = 1;
+ p->cluster_next = 1;
+ p->cluster_nr = 0;
+
+ maxpages = max_swapfile_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",
+ maxpages << (PAGE_SHIFT - 10),
+ last_page << (PAGE_SHIFT - 10));
+ }
+ if (maxpages > last_page) {
+ maxpages = last_page + 1;
+ /* p->max is an unsigned int: don't overflow it */
+ if ((unsigned int)maxpages == 0)
+ maxpages = UINT_MAX;
+ }
+ p->highest_bit = maxpages - 1;
+
+ if (!maxpages)
+ return 0;
+ swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
+ if (swapfilepages && maxpages > swapfilepages) {
+ pr_warn("Swap area shorter than signature indicates\n");
+ return 0;
+ }
+ if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
+ return 0;
+ if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
+ return 0;
+
+ return maxpages;
+}
+
+#define SWAP_CLUSTER_INFO_COLS \
+ DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
+#define SWAP_CLUSTER_SPACE_COLS \
+ DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER)
+#define SWAP_CLUSTER_COLS \
+ max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS)
+
+static int setup_swap_map_and_extents(struct swap_info_struct *p,
+ union swap_header *swap_header,
+ unsigned char *swap_map,
+ struct swap_cluster_info *cluster_info,
+ unsigned long maxpages,
+ sector_t *span)
+{
+ unsigned int j, k;
+ unsigned int nr_good_pages;
+ int nr_extents;
+ unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
+ unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
+ unsigned long i, idx;
+
+ nr_good_pages = maxpages - 1; /* omit header page */
+
+ cluster_list_init(&p->free_clusters);
+ cluster_list_init(&p->discard_clusters);
+
+ for (i = 0; i < swap_header->info.nr_badpages; i++) {
+ unsigned int page_nr = swap_header->info.badpages[i];
+ if (page_nr == 0 || page_nr > swap_header->info.last_page)
+ return -EINVAL;
+ if (page_nr < maxpages) {
+ swap_map[page_nr] = SWAP_MAP_BAD;
+ nr_good_pages--;
+ /*
+ * Haven't marked the cluster free yet, no list
+ * operation involved
+ */
+ inc_cluster_info_page(p, cluster_info, page_nr);
+ }
+ }
+
+ /* Haven't marked the cluster free yet, no list operation involved */
+ for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++)
+ inc_cluster_info_page(p, cluster_info, i);
+
+ if (nr_good_pages) {
+ swap_map[0] = SWAP_MAP_BAD;
+ /*
+ * Not mark the cluster free yet, no list
+ * operation involved
+ */
+ inc_cluster_info_page(p, cluster_info, 0);
+ p->max = maxpages;
+ p->pages = nr_good_pages;
+ nr_extents = setup_swap_extents(p, span);
+ if (nr_extents < 0)
+ return nr_extents;
+ nr_good_pages = p->pages;
+ }
+ if (!nr_good_pages) {
+ pr_warn("Empty swap-file\n");
+ return -EINVAL;
+ }
+
+ if (!cluster_info)
+ return nr_extents;
+
+
+ /*
+ * Reduce false cache line sharing between cluster_info and
+ * sharing same address space.
+ */
+ for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
+ j = (k + col) % SWAP_CLUSTER_COLS;
+ for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
+ idx = i * SWAP_CLUSTER_COLS + j;
+ if (idx >= nr_clusters)
+ continue;
+ if (cluster_count(&cluster_info[idx]))
+ continue;
+ cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
+ cluster_list_add_tail(&p->free_clusters, cluster_info,
+ idx);
+ }
+ }
+ return nr_extents;
+}
+
+/*
+ * Helper to sys_swapon determining if a given swap
+ * backing device queue supports DISCARD operations.
+ */
+static bool swap_discardable(struct swap_info_struct *si)
+{
+ struct request_queue *q = bdev_get_queue(si->bdev);
+
+ if (!q || !blk_queue_discard(q))
+ return false;
+
+ return true;
+}
+
+SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
+{
+ struct swap_info_struct *p;
+ struct filename *name;
+ struct file *swap_file = NULL;
+ struct address_space *mapping;
+ int prio;
+ int error;
+ union swap_header *swap_header;
+ int nr_extents;
+ sector_t span;
+ unsigned long maxpages;
+ unsigned char *swap_map = NULL;
+ struct swap_cluster_info *cluster_info = NULL;
+ unsigned long *frontswap_map = NULL;
+ struct page *page = NULL;
+ struct inode *inode = NULL;
+ bool inced_nr_rotate_swap = false;
+
+ if (swap_flags & ~SWAP_FLAGS_VALID)
+ return -EINVAL;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ if (!swap_avail_heads)
+ return -ENOMEM;
+
+ p = alloc_swap_info();
+ if (IS_ERR(p))
+ return PTR_ERR(p);
+
+ INIT_WORK(&p->discard_work, swap_discard_work);
+
+ name = getname(specialfile);
+ if (IS_ERR(name)) {
+ error = PTR_ERR(name);
+ name = NULL;
+ goto bad_swap;
+ }
+ swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
+ if (IS_ERR(swap_file)) {
+ error = PTR_ERR(swap_file);
+ swap_file = NULL;
+ goto bad_swap;
+ }
+
+ p->swap_file = swap_file;
+ mapping = swap_file->f_mapping;
+ inode = mapping->host;
+
+ error = claim_swapfile(p, inode);
+ if (unlikely(error))
+ goto bad_swap;
+
+ inode_lock(inode);
+ if (IS_SWAPFILE(inode)) {
+ error = -EBUSY;
+ goto bad_swap_unlock_inode;
+ }
+
+ /*
+ * Read the swap header.
+ */
+ if (!mapping->a_ops->readpage) {
+ error = -EINVAL;
+ goto bad_swap_unlock_inode;
+ }
+ page = read_mapping_page(mapping, 0, swap_file);
+ if (IS_ERR(page)) {
+ error = PTR_ERR(page);
+ goto bad_swap_unlock_inode;
+ }
+ swap_header = kmap(page);
+
+ maxpages = read_swap_header(p, swap_header, inode);
+ if (unlikely(!maxpages)) {
+ error = -EINVAL;
+ goto bad_swap_unlock_inode;
+ }
+
+ /* OK, set up the swap map and apply the bad block list */
+ swap_map = vzalloc(maxpages);
+ if (!swap_map) {
+ error = -ENOMEM;
+ goto bad_swap_unlock_inode;
+ }
+
+ if (p->bdev && blk_queue_stable_writes(p->bdev->bd_disk->queue))
+ p->flags |= SWP_STABLE_WRITES;
+
+ if (p->bdev && p->bdev->bd_disk->fops->rw_page)
+ p->flags |= SWP_SYNCHRONOUS_IO;
+
+ if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
+ int cpu;
+ unsigned long ci, nr_cluster;
+
+ p->flags |= SWP_SOLIDSTATE;
+ p->cluster_next_cpu = alloc_percpu(unsigned int);
+ if (!p->cluster_next_cpu) {
+ error = -ENOMEM;
+ goto bad_swap_unlock_inode;
+ }
+ /*
+ * select a random position to start with to help wear leveling
+ * SSD
+ */
+ for_each_possible_cpu(cpu) {
+ per_cpu(*p->cluster_next_cpu, cpu) =
+ 1 + prandom_u32_max(p->highest_bit);
+ }
+ nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
+
+ cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info),
+ GFP_KERNEL);
+ if (!cluster_info) {
+ error = -ENOMEM;
+ goto bad_swap_unlock_inode;
+ }
+
+ for (ci = 0; ci < nr_cluster; ci++)
+ spin_lock_init(&((cluster_info + ci)->lock));
+
+ p->percpu_cluster = alloc_percpu(struct percpu_cluster);
+ if (!p->percpu_cluster) {
+ error = -ENOMEM;
+ goto bad_swap_unlock_inode;
+ }
+ for_each_possible_cpu(cpu) {
+ struct percpu_cluster *cluster;
+ cluster = per_cpu_ptr(p->percpu_cluster, cpu);
+ cluster_set_null(&cluster->index);
+ }
+ } else {
+ atomic_inc(&nr_rotate_swap);
+ inced_nr_rotate_swap = true;
+ }
+
+ error = swap_cgroup_swapon(p->type, maxpages);
+ if (error)
+ goto bad_swap_unlock_inode;
+
+ nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
+ cluster_info, maxpages, &span);
+ if (unlikely(nr_extents < 0)) {
+ error = nr_extents;
+ goto bad_swap_unlock_inode;
+ }
+ /* frontswap enabled? set up bit-per-page map for frontswap */
+ if (IS_ENABLED(CONFIG_FRONTSWAP))
+ frontswap_map = kvcalloc(BITS_TO_LONGS(maxpages),
+ sizeof(long),
+ GFP_KERNEL);
+
+ if (p->bdev &&(swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
+ /*
+ * When discard is enabled for swap with no particular
+ * policy flagged, we set all swap discard flags here in
+ * order to sustain backward compatibility with older
+ * swapon(8) releases.
+ */
+ p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD |
+ SWP_PAGE_DISCARD);
+
+ /*
+ * By flagging sys_swapon, a sysadmin can tell us to
+ * either do single-time area discards only, or to just
+ * perform discards for released swap page-clusters.
+ * Now it's time to adjust the p->flags accordingly.
+ */
+ if (swap_flags & SWAP_FLAG_DISCARD_ONCE)
+ p->flags &= ~SWP_PAGE_DISCARD;
+ else if (swap_flags & SWAP_FLAG_DISCARD_PAGES)
+ p->flags &= ~SWP_AREA_DISCARD;
+
+ /* issue a swapon-time discard if it's still required */
+ if (p->flags & SWP_AREA_DISCARD) {
+ int err = discard_swap(p);
+ if (unlikely(err))
+ pr_err("swapon: discard_swap(%p): %d\n",
+ p, err);
+ }
+ }
+
+ error = init_swap_address_space(p->type, maxpages);
+ if (error)
+ goto bad_swap_unlock_inode;
+
+ /*
+ * Flush any pending IO and dirty mappings before we start using this
+ * swap device.
+ */
+ inode->i_flags |= S_SWAPFILE;
+ error = inode_drain_writes(inode);
+ if (error) {
+ inode->i_flags &= ~S_SWAPFILE;
+ goto free_swap_address_space;
+ }
+
+ mutex_lock(&swapon_mutex);
+ prio = -1;
+ if (swap_flags & SWAP_FLAG_PREFER)
+ prio =
+ (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
+ enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
+
+ pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
+ p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
+ nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
+ (p->flags & SWP_SOLIDSTATE) ? "SS" : "",
+ (p->flags & SWP_DISCARDABLE) ? "D" : "",
+ (p->flags & SWP_AREA_DISCARD) ? "s" : "",
+ (p->flags & SWP_PAGE_DISCARD) ? "c" : "",
+ (frontswap_map) ? "FS" : "");
+
+ mutex_unlock(&swapon_mutex);
+ atomic_inc(&proc_poll_event);
+ wake_up_interruptible(&proc_poll_wait);
+
+ error = 0;
+ goto out;
+free_swap_address_space:
+ exit_swap_address_space(p->type);
+bad_swap_unlock_inode:
+ inode_unlock(inode);
+bad_swap:
+ free_percpu(p->percpu_cluster);
+ p->percpu_cluster = NULL;
+ free_percpu(p->cluster_next_cpu);
+ p->cluster_next_cpu = NULL;
+ if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
+ set_blocksize(p->bdev, p->old_block_size);
+ blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+ }
+ inode = NULL;
+ destroy_swap_extents(p);
+ swap_cgroup_swapoff(p->type);
+ spin_lock(&swap_lock);
+ p->swap_file = NULL;
+ p->flags = 0;
+ spin_unlock(&swap_lock);
+ vfree(swap_map);
+ kvfree(cluster_info);
+ kvfree(frontswap_map);
+ if (inced_nr_rotate_swap)
+ atomic_dec(&nr_rotate_swap);
+ if (swap_file)
+ filp_close(swap_file, NULL);
+out:
+ if (page && !IS_ERR(page)) {
+ kunmap(page);
+ put_page(page);
+ }
+ if (name)
+ putname(name);
+ if (inode)
+ inode_unlock(inode);
+ if (!error)
+ enable_swap_slots_cache();
+ return error;
+}
+
+void si_swapinfo(struct sysinfo *val)
+{
+ unsigned int type;
+ unsigned long nr_to_be_unused = 0;
+
+ spin_lock(&swap_lock);
+ for (type = 0; type < nr_swapfiles; type++) {
+ struct swap_info_struct *si = swap_info[type];
+
+ if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
+ nr_to_be_unused += si->inuse_pages;
+ }
+ val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
+ val->totalswap = total_swap_pages + nr_to_be_unused;
+ spin_unlock(&swap_lock);
+}
+
+/*
+ * Verify that a swap entry is valid and increment its swap map count.
+ *
+ * Returns error code in following case.
+ * - success -> 0
+ * - swp_entry is invalid -> EINVAL
+ * - swp_entry is migration entry -> EINVAL
+ * - swap-cache reference is requested but there is already one. -> EEXIST
+ * - swap-cache reference is requested but the entry is not used. -> ENOENT
+ * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
+ */
+static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
+{
+ struct swap_info_struct *p;
+ struct swap_cluster_info *ci;
+ unsigned long offset;
+ unsigned char count;
+ unsigned char has_cache;
+ int err = -EINVAL;
+
+ p = get_swap_device(entry);
+ if (!p)
+ goto out;
+
+ offset = swp_offset(entry);
+ ci = lock_cluster_or_swap_info(p, offset);
+
+ count = p->swap_map[offset];
+
+ /*
+ * swapin_readahead() doesn't check if a swap entry is valid, so the
+ * swap entry could be SWAP_MAP_BAD. Check here with lock held.
+ */
+ if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
+ err = -ENOENT;
+ goto unlock_out;
+ }
+
+ has_cache = count & SWAP_HAS_CACHE;
+ count &= ~SWAP_HAS_CACHE;
+ err = 0;
+
+ if (usage == SWAP_HAS_CACHE) {
+
+ /* set SWAP_HAS_CACHE if there is no cache and entry is used */
+ if (!has_cache && count)
+ has_cache = SWAP_HAS_CACHE;
+ else if (has_cache) /* someone else added cache */
+ err = -EEXIST;
+ else /* no users remaining */
+ err = -ENOENT;
+
+ } else if (count || has_cache) {
+
+ if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
+ count += usage;
+ else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
+ err = -EINVAL;
+ else if (swap_count_continued(p, offset, count))
+ count = COUNT_CONTINUED;
+ else
+ err = -ENOMEM;
+ } else
+ err = -ENOENT; /* unused swap entry */
+
+ WRITE_ONCE(p->swap_map[offset], count | has_cache);
+
+unlock_out:
+ unlock_cluster_or_swap_info(p, ci);
+out:
+ if (p)
+ put_swap_device(p);
+ return err;
+}
+
+/*
+ * Help swapoff by noting that swap entry belongs to shmem/tmpfs
+ * (in which case its reference count is never incremented).
+ */
+void swap_shmem_alloc(swp_entry_t entry)
+{
+ __swap_duplicate(entry, SWAP_MAP_SHMEM);
+}
+
+/*
+ * Increase reference count of swap entry by 1.
+ * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
+ * but could not be atomically allocated. Returns 0, just as if it succeeded,
+ * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
+ * might occur if a page table entry has got corrupted.
+ */
+int swap_duplicate(swp_entry_t entry)
+{
+ int err = 0;
+
+ while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
+ err = add_swap_count_continuation(entry, GFP_ATOMIC);
+ return err;
+}
+
+/*
+ * @entry: swap entry for which we allocate swap cache.
+ *
+ * Called when allocating swap cache for existing swap entry,
+ * This can return error codes. Returns 0 at success.
+ * -EEXIST means there is a swap cache.
+ * Note: return code is different from swap_duplicate().
+ */
+int swapcache_prepare(swp_entry_t entry)
+{
+ return __swap_duplicate(entry, SWAP_HAS_CACHE);
+}
+
+struct swap_info_struct *swp_swap_info(swp_entry_t entry)
+{
+ return swap_type_to_swap_info(swp_type(entry));
+}
+
+struct swap_info_struct *page_swap_info(struct page *page)
+{
+ swp_entry_t entry = { .val = page_private(page) };
+ return swp_swap_info(entry);
+}
+
+/*
+ * out-of-line __page_file_ methods to avoid include hell.
+ */
+struct address_space *__page_file_mapping(struct page *page)
+{
+ return page_swap_info(page)->swap_file->f_mapping;
+}
+EXPORT_SYMBOL_GPL(__page_file_mapping);
+
+pgoff_t __page_file_index(struct page *page)
+{
+ swp_entry_t swap = { .val = page_private(page) };
+ return swp_offset(swap);
+}
+EXPORT_SYMBOL_GPL(__page_file_index);
+
+/*
+ * add_swap_count_continuation - called when a swap count is duplicated
+ * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
+ * page of the original vmalloc'ed swap_map, to hold the continuation count
+ * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called
+ * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc.
+ *
+ * These continuation pages are seldom referenced: the common paths all work
+ * on the original swap_map, only referring to a continuation page when the
+ * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX.
+ *
+ * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding
+ * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL)
+ * can be called after dropping locks.
+ */
+int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
+{
+ struct swap_info_struct *si;
+ struct swap_cluster_info *ci;
+ struct page *head;
+ struct page *page;
+ struct page *list_page;
+ pgoff_t offset;
+ unsigned char count;
+ int ret = 0;
+
+ /*
+ * When debugging, it's easier to use __GFP_ZERO here; but it's better
+ * for latency not to zero a page while GFP_ATOMIC and holding locks.
+ */
+ page = alloc_page(gfp_mask | __GFP_HIGHMEM);
+
+ si = get_swap_device(entry);
+ if (!si) {
+ /*
+ * An acceptable race has occurred since the failing
+ * __swap_duplicate(): the swap device may be swapoff
+ */
+ goto outer;
+ }
+ spin_lock(&si->lock);
+
+ offset = swp_offset(entry);
+
+ ci = lock_cluster(si, offset);
+
+ count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
+
+ if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
+ /*
+ * The higher the swap count, the more likely it is that tasks
+ * will race to add swap count continuation: we need to avoid
+ * over-provisioning.
+ */
+ goto out;
+ }
+
+ if (!page) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ /*
+ * We are fortunate that although vmalloc_to_page uses pte_offset_map,
+ * no architecture is using highmem pages for kernel page tables: so it
+ * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps.
+ */
+ head = vmalloc_to_page(si->swap_map + offset);
+ offset &= ~PAGE_MASK;
+
+ spin_lock(&si->cont_lock);
+ /*
+ * Page allocation does not initialize the page's lru field,
+ * but it does always reset its private field.
+ */
+ if (!page_private(head)) {
+ BUG_ON(count & COUNT_CONTINUED);
+ INIT_LIST_HEAD(&head->lru);
+ set_page_private(head, SWP_CONTINUED);
+ si->flags |= SWP_CONTINUED;
+ }
+
+ list_for_each_entry(list_page, &head->lru, lru) {
+ unsigned char *map;
+
+ /*
+ * If the previous map said no continuation, but we've found
+ * a continuation page, free our allocation and use this one.
+ */
+ if (!(count & COUNT_CONTINUED))
+ goto out_unlock_cont;
+
+ map = kmap_atomic(list_page) + offset;
+ count = *map;
+ kunmap_atomic(map);
+
+ /*
+ * If this continuation count now has some space in it,
+ * free our allocation and use this one.
+ */
+ if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX)
+ goto out_unlock_cont;
+ }
+
+ list_add_tail(&page->lru, &head->lru);
+ page = NULL; /* now it's attached, don't free it */
+out_unlock_cont:
+ spin_unlock(&si->cont_lock);
+out:
+ unlock_cluster(ci);
+ spin_unlock(&si->lock);
+ put_swap_device(si);
+outer:
+ if (page)
+ __free_page(page);
+ return ret;
+}
+
+/*
+ * swap_count_continued - when the original swap_map count is incremented
+ * from SWAP_MAP_MAX, check if there is already a continuation page to carry
+ * into, carry if so, or else fail until a new continuation page is allocated;
+ * when the original swap_map count is decremented from 0 with continuation,
+ * borrow from the continuation and report whether it still holds more.
+ * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
+ * lock.
+ */
+static bool swap_count_continued(struct swap_info_struct *si,
+ pgoff_t offset, unsigned char count)
+{
+ struct page *head;
+ struct page *page;
+ unsigned char *map;
+ bool ret;
+
+ head = vmalloc_to_page(si->swap_map + offset);
+ if (page_private(head) != SWP_CONTINUED) {
+ BUG_ON(count & COUNT_CONTINUED);
+ return false; /* need to add count continuation */
+ }
+
+ spin_lock(&si->cont_lock);
+ offset &= ~PAGE_MASK;
+ page = list_next_entry(head, lru);
+ map = kmap_atomic(page) + offset;
+
+ if (count == SWAP_MAP_MAX) /* initial increment from swap_map */
+ goto init_map; /* jump over SWAP_CONT_MAX checks */
+
+ if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */
+ /*
+ * Think of how you add 1 to 999
+ */
+ while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
+ kunmap_atomic(map);
+ page = list_next_entry(page, lru);
+ BUG_ON(page == head);
+ map = kmap_atomic(page) + offset;
+ }
+ if (*map == SWAP_CONT_MAX) {
+ kunmap_atomic(map);
+ page = list_next_entry(page, lru);
+ if (page == head) {
+ ret = false; /* add count continuation */
+ goto out;
+ }
+ map = kmap_atomic(page) + offset;
+init_map: *map = 0; /* we didn't zero the page */
+ }
+ *map += 1;
+ kunmap_atomic(map);
+ while ((page = list_prev_entry(page, lru)) != head) {
+ map = kmap_atomic(page) + offset;
+ *map = COUNT_CONTINUED;
+ kunmap_atomic(map);
+ }
+ ret = true; /* incremented */
+
+ } else { /* decrementing */
+ /*
+ * Think of how you subtract 1 from 1000
+ */
+ BUG_ON(count != COUNT_CONTINUED);
+ while (*map == COUNT_CONTINUED) {
+ kunmap_atomic(map);
+ page = list_next_entry(page, lru);
+ BUG_ON(page == head);
+ map = kmap_atomic(page) + offset;
+ }
+ BUG_ON(*map == 0);
+ *map -= 1;
+ if (*map == 0)
+ count = 0;
+ kunmap_atomic(map);
+ while ((page = list_prev_entry(page, lru)) != head) {
+ map = kmap_atomic(page) + offset;
+ *map = SWAP_CONT_MAX | count;
+ count = COUNT_CONTINUED;
+ kunmap_atomic(map);
+ }
+ ret = count == COUNT_CONTINUED;
+ }
+out:
+ spin_unlock(&si->cont_lock);
+ return ret;
+}
+
+/*
+ * free_swap_count_continuations - swapoff free all the continuation pages
+ * appended to the swap_map, after swap_map is quiesced, before vfree'ing it.
+ */
+static void free_swap_count_continuations(struct swap_info_struct *si)
+{
+ pgoff_t offset;
+
+ for (offset = 0; offset < si->max; offset += PAGE_SIZE) {
+ struct page *head;
+ head = vmalloc_to_page(si->swap_map + offset);
+ if (page_private(head)) {
+ struct page *page, *next;
+
+ list_for_each_entry_safe(page, next, &head->lru, lru) {
+ list_del(&page->lru);
+ __free_page(page);
+ }
+ }
+ }
+}
+
+#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
+void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
+{
+ struct swap_info_struct *si, *next;
+ int nid = page_to_nid(page);
+
+ if (!(gfp_mask & __GFP_IO))
+ return;
+
+ if (!blk_cgroup_congested())
+ return;
+
+ /*
+ * We've already scheduled a throttle, avoid taking the global swap
+ * lock.
+ */
+ if (current->throttle_queue)
+ return;
+
+ spin_lock(&swap_avail_lock);
+ plist_for_each_entry_safe(si, next, &swap_avail_heads[nid],
+ avail_lists[nid]) {
+ if (si->bdev) {
+ blkcg_schedule_throttle(bdev_get_queue(si->bdev), true);
+ break;
+ }
+ }
+ spin_unlock(&swap_avail_lock);
+}
+#endif
+
+static int __init swapfile_init(void)
+{
+ int nid;
+
+ swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head),
+ GFP_KERNEL);
+ if (!swap_avail_heads) {
+ pr_emerg("Not enough memory for swap heads, swap is disabled\n");
+ return -ENOMEM;
+ }
+
+ for_each_node(nid)
+ plist_head_init(&swap_avail_heads[nid]);
+
+ return 0;
+}
+subsys_initcall(swapfile_init);