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linux-stable/mm/swapfile.c
Christoph Hellwig 633423a09c mm: mark swap_lock and swap_active_head static 
swap_lock and swap_active_head are only used in swapfile.c, so mark them
static.

Link: https://lkml.kernel.org/r/20211224062246.1258487-12-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Konrad Rzeszutek Wilk <Konrad.wilk@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-22 08:33:38 +02:00

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// 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/blk-cgroup.h>
#include <linux/random.h>
#include <linux/writeback.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/ksm.h>
#include <linux/rmap.h>
#include <linux/security.h>
#include <linux/backing-dev.h>
#include <linux/mutex.h>
#include <linux/capability.h>
#include <linux/syscalls.h>
#include <linux/memcontrol.h>
#include <linux/poll.h>
#include <linux/oom.h>
#include <linux/frontswap.h>
#include <linux/swapfile.h>
#include <linux/export.h>
#include <linux/swap_slots.h>
#include <linux/sort.h>
#include <linux/completion.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 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.
*/
static PLIST_HEAD(swap_active_head);
/*
* all available (active, not full) swap_info_structs
* protected with swap_avail_lock, ordered by priority.
* This is used by 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 >= MAX_SWAPFILES)
return NULL;
return READ_ONCE(swap_info[type]); /* rcu_dereference() */
}
static inline unsigned char swap_count(unsigned char ent)
{
return ent & ~SWAP_HAS_CACHE; /* may include COUNT_CONTINUED flag */
}
/* Reclaim the swap entry anyway if possible */
#define TTRS_ANYWAY 0x1
/*
* Reclaim the swap entry if there are no more mappings of the
* corresponding page
*/
#define TTRS_UNMAPPED 0x2
/* Reclaim the swap entry if swap is getting full*/
#define TTRS_FULL 0x4
/* returns 1 if swap entry is freed */
static int __try_to_reclaim_swap(struct swap_info_struct *si,
unsigned long offset, unsigned long flags)
{
swp_entry_t entry = swp_entry(si->type, offset);
struct 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_slots() can't find a free cluster, it will check
* si->swap_map directly. To make sure the discarding cluster isn't
* taken by scan_swap_map_slots(), mark the swap entries bad (occupied).
* It will be cleared after discard
*/
memset(si->swap_map + idx * SWAPFILE_CLUSTER,
SWAP_MAP_BAD, SWAPFILE_CLUSTER);
cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
schedule_work(&si->discard_work);
}
static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
{
struct swap_cluster_info *ci = si->cluster_info;
cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
cluster_list_add_tail(&si->free_clusters, ci, idx);
}
/*
* Doing discard actually. After a cluster discard is finished, the cluster
* will be added to free cluster list. caller should hold si->lock.
*/
static void swap_do_scheduled_discard(struct swap_info_struct *si)
{
struct swap_cluster_info *info, *ci;
unsigned int idx;
info = si->cluster_info;
while (!cluster_list_empty(&si->discard_clusters)) {
idx = cluster_list_del_first(&si->discard_clusters, info);
spin_unlock(&si->lock);
discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
SWAPFILE_CLUSTER);
spin_lock(&si->lock);
ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
__free_cluster(si, idx);
memset(si->swap_map + idx * SWAPFILE_CLUSTER,
0, SWAPFILE_CLUSTER);
unlock_cluster(ci);
}
}
static void swap_discard_work(struct work_struct *work)
{
struct swap_info_struct *si;
si = container_of(work, struct swap_info_struct, discard_work);
spin_lock(&si->lock);
swap_do_scheduled_discard(si);
spin_unlock(&si->lock);
}
static void swap_users_ref_free(struct percpu_ref *ref)
{
struct swap_info_struct *si;
si = container_of(ref, struct swap_info_struct, users);
complete(&si->comp);
}
static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
{
struct swap_cluster_info *ci = si->cluster_info;
VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
cluster_list_del_first(&si->free_clusters, ci);
cluster_set_count_flag(ci + idx, 0, 0);
}
static void free_cluster(struct swap_info_struct *si, unsigned long idx)
{
struct swap_cluster_info *ci = si->cluster_info + idx;
VM_BUG_ON(cluster_count(ci) != 0);
/*
* If the swap is discardable, prepare discard the cluster
* instead of free it immediately. The cluster will be freed
* after discard.
*/
if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
(SWP_WRITEOK | SWP_PAGE_DISCARD)) {
swap_cluster_schedule_discard(si, idx);
return;
}
__free_cluster(si, idx);
}
/*
* The cluster corresponding to page_nr will be used. The cluster will be
* removed from free cluster list and its usage counter will be increased.
*/
static void inc_cluster_info_page(struct swap_info_struct *p,
struct swap_cluster_info *cluster_info, unsigned long page_nr)
{
unsigned long idx = page_nr / SWAPFILE_CLUSTER;
if (!cluster_info)
return;
if (cluster_is_free(&cluster_info[idx]))
alloc_cluster(p, idx);
VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
cluster_set_count(&cluster_info[idx],
cluster_count(&cluster_info[idx]) + 1);
}
/*
* The cluster corresponding to page_nr decreases one usage. If the usage
* counter becomes 0, which means no page in the cluster is in using, we can
* optionally discard the cluster and add it to free cluster list.
*/
static void dec_cluster_info_page(struct swap_info_struct *p,
struct swap_cluster_info *cluster_info, unsigned long page_nr)
{
unsigned long idx = page_nr / SWAPFILE_CLUSTER;
if (!cluster_info)
return;
VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
cluster_set_count(&cluster_info[idx],
cluster_count(&cluster_info[idx]) - 1);
if (cluster_count(&cluster_info[idx]) == 0)
free_cluster(p, idx);
}
/*
* It's possible scan_swap_map_slots() uses a free cluster in the middle of free
* cluster list. Avoiding such abuse to avoid list corruption.
*/
static bool
scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
unsigned long offset)
{
struct percpu_cluster *percpu_cluster;
bool conflict;
offset /= SWAPFILE_CLUSTER;
conflict = !cluster_list_empty(&si->free_clusters) &&
offset != cluster_list_first(&si->free_clusters) &&
cluster_is_free(&si->cluster_info[offset]);
if (!conflict)
return false;
percpu_cluster = this_cpu_ptr(si->percpu_cluster);
cluster_set_null(&percpu_cluster->index);
return true;
}
/*
* Try to get a swap entry from current cpu's swap entry pool (a cluster). This
* might involve allocating a new cluster for current CPU too.
*/
static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
unsigned long *offset, unsigned long *scan_base)
{
struct percpu_cluster *cluster;
struct swap_cluster_info *ci;
unsigned long tmp, max;
new_cluster:
cluster = this_cpu_ptr(si->percpu_cluster);
if (cluster_is_null(&cluster->index)) {
if (!cluster_list_empty(&si->free_clusters)) {
cluster->index = si->free_clusters.head;
cluster->next = cluster_next(&cluster->index) *
SWAPFILE_CLUSTER;
} else if (!cluster_list_empty(&si->discard_clusters)) {
/*
* we don't have free cluster but have some clusters in
* discarding, do discard now and reclaim them, then
* reread cluster_next_cpu since we dropped si->lock
*/
swap_do_scheduled_discard(si);
*scan_base = this_cpu_read(*si->cluster_next_cpu);
*offset = *scan_base;
goto new_cluster;
} else
return false;
}
/*
* Other CPUs can use our cluster if they can't find a free cluster,
* check if there is still free entry in the cluster
*/
tmp = cluster->next;
max = min_t(unsigned long, si->max,
(cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
if (tmp < max) {
ci = lock_cluster(si, tmp);
while (tmp < max) {
if (!si->swap_map[tmp])
break;
tmp++;
}
unlock_cluster(ci);
}
if (tmp >= max) {
cluster_set_null(&cluster->index);
goto new_cluster;
}
cluster->next = tmp + 1;
*offset = tmp;
*scan_base = tmp;
return true;
}
static void __del_from_avail_list(struct swap_info_struct *p)
{
int nid;
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;
/*
* Should not even be attempting cluster allocations when huge
* page swap is disabled. Warn and fail the allocation.
*/
if (!IS_ENABLED(CONFIG_THP_SWAP)) {
VM_WARN_ON_ONCE(1);
return 0;
}
if (cluster_list_empty(&si->free_clusters))
return 0;
idx = cluster_list_first(&si->free_clusters);
offset = idx * SWAPFILE_CLUSTER;
ci = lock_cluster(si, offset);
alloc_cluster(si, idx);
cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER);
unlock_cluster(ci);
swap_range_alloc(si, offset, SWAPFILE_CLUSTER);
*slot = swp_entry(si->type, offset);
return 1;
}
static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
{
unsigned long offset = idx * SWAPFILE_CLUSTER;
struct swap_cluster_info *ci;
ci = lock_cluster(si, offset);
memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
cluster_set_count_flag(ci, 0, 0);
free_cluster(si, idx);
unlock_cluster(ci);
swap_range_free(si, offset, SWAPFILE_CLUSTER);
}
int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
{
unsigned long size = swap_entry_size(entry_size);
struct swap_info_struct *si, *next;
long avail_pgs;
int n_ret = 0;
int node;
/* Only single cluster request supported */
WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER);
spin_lock(&swap_avail_lock);
avail_pgs = atomic_long_read(&nr_swap_pages) / size;
if (avail_pgs <= 0) {
spin_unlock(&swap_avail_lock);
goto noswap;
}
n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs);
atomic_long_sub(n_goal * size, &nr_swap_pages);
start_over:
node = numa_node_id();
plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) {
/* requeue si to after same-priority siblings */
plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
spin_unlock(&swap_avail_lock);
spin_lock(&si->lock);
if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
spin_lock(&swap_avail_lock);
if (plist_node_empty(&si->avail_lists[node])) {
spin_unlock(&si->lock);
goto nextsi;
}
WARN(!si->highest_bit,
"swap_info %d in list but !highest_bit\n",
si->type);
WARN(!(si->flags & SWP_WRITEOK),
"swap_info %d in list but !SWP_WRITEOK\n",
si->type);
__del_from_avail_list(si);
spin_unlock(&si->lock);
goto nextsi;
}
if (size == SWAPFILE_CLUSTER) {
if (si->flags & SWP_BLKDEV)
n_ret = swap_alloc_cluster(si, swp_entries);
} else
n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
n_goal, swp_entries);
spin_unlock(&si->lock);
if (n_ret || size == SWAPFILE_CLUSTER)
goto check_out;
pr_debug("scan_swap_map of si %d failed to find offset\n",
si->type);
spin_lock(&swap_avail_lock);
nextsi:
/*
* if we got here, it's likely that si was almost full before,
* and since scan_swap_map_slots() can drop the si->lock,
* multiple callers probably all tried to get a page from the
* same si and it filled up before we could get one; or, the si
* filled up between us dropping swap_avail_lock and taking
* si->lock. Since we dropped the swap_avail_lock, the
* swap_avail_head list may have been modified; so if next is
* still in the swap_avail_head list then try it, otherwise
* start over if we have not gotten any slots.
*/
if (plist_node_empty(&next->avail_lists[node]))
goto start_over;
}
spin_unlock(&swap_avail_lock);
check_out:
if (n_ret < n_goal)
atomic_long_add((long)(n_goal - n_ret) * size,
&nr_swap_pages);
noswap:
return n_ret;
}
static struct swap_info_struct *__swap_info_get(swp_entry_t entry)
{
struct swap_info_struct *p;
unsigned long offset;
if (!entry.val)
goto out;
p = swp_swap_info(entry);
if (!p)
goto bad_nofile;
if (data_race(!(p->flags & SWP_USED)))
goto bad_device;
offset = swp_offset(entry);
if (offset >= p->max)
goto bad_offset;
return p;
bad_offset:
pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
goto out;
bad_device:
pr_err("%s: %s%08lx\n", __func__, Unused_file, entry.val);
goto out;
bad_nofile:
pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
out:
return NULL;
}
static struct swap_info_struct *_swap_info_get(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("%s: %s%08lx\n", __func__, 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.
*
* Notice that swapoff or swapoff+swapon can still happen before the
* percpu_ref_tryget_live() in get_swap_device() or after the
* percpu_ref_put() in put_swap_device() if there isn't any other way
* to prevent swapoff, 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;
if (!percpu_ref_tryget_live(&si->users))
goto out;
/*
* Guarantee the si->users are checked before accessing other
* fields of swap_info_struct.
*
* Paired with the spin_unlock() after setup_swap_info() in
* enable_swap_info().
*/
smp_rmb();
offset = swp_offset(entry);
if (offset >= si->max)
goto put_out;
return si;
bad_nofile:
pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
out:
return NULL;
put_out:
percpu_ref_put(&si->users);
return NULL;
}
static unsigned char __swap_entry_free(struct swap_info_struct *p,
swp_entry_t entry)
{
struct swap_cluster_info *ci;
unsigned long offset = swp_offset(entry);
unsigned char usage;
ci = lock_cluster_or_swap_info(p, offset);
usage = __swap_entry_free_locked(p, offset, 1);
unlock_cluster_or_swap_info(p, ci);
if (!usage)
free_swap_slot(entry);
return usage;
}
static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
{
struct swap_cluster_info *ci;
unsigned long offset = swp_offset(entry);
unsigned char count;
ci = lock_cluster(p, offset);
count = p->swap_map[offset];
VM_BUG_ON(count != SWAP_HAS_CACHE);
p->swap_map[offset] = 0;
dec_cluster_info_page(p, p->cluster_info, offset);
unlock_cluster(ci);
mem_cgroup_uncharge_swap(entry, 1);
swap_range_free(p, offset, 1);
}
/*
* Caller has made sure that the swap device corresponding to entry
* is still around or has not been recycled.
*/
void swap_free(swp_entry_t entry)
{
struct swap_info_struct *p;
p = _swap_info_get(entry);
if (p)
__swap_entry_free(p, entry);
}
/*
* Called after dropping swapcache to decrease refcnt to swap entries.
*/
void put_swap_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_swapcount)
{
int i, map_swapcount, _total_swapcount;
unsigned long offset = 0;
struct swap_info_struct *si;
struct swap_cluster_info *ci = NULL;
unsigned char *map = NULL;
int swapcount = 0;
/* hugetlbfs shouldn't call it */
VM_BUG_ON_PAGE(PageHuge(page), page);
if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!PageTransCompound(page))) {
if (PageSwapCache(page))
swapcount = page_swapcount(page);
if (total_swapcount)
*total_swapcount = swapcount;
return swapcount + page_trans_huge_mapcount(page);
}
page = compound_head(page);
_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++) {
int mapcount = atomic_read(&page[i]._mapcount) + 1;
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;
if (total_swapcount)
*total_swapcount = _total_swapcount;
return map_swapcount + compound_mapcount(page);
}
/*
* 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.
*/
bool reuse_swap_page(struct page *page)
{
int count, total_swapcount;
VM_BUG_ON_PAGE(!PageLocked(page), page);
if (unlikely(PageKsm(page)))
return false;
count = page_trans_huge_map_swapcount(page, &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
swp_entry_t get_swap_page_of_type(int type)
{
struct swap_info_struct *si = swap_type_to_swap_info(type);
swp_entry_t entry = {0};
if (!si)
goto fail;
/* This is called for allocating swap entry, not cache */
spin_lock(&si->lock);
if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry))
atomic_long_dec(&nr_swap_pages);
spin_unlock(&si->lock);
fail:
return entry;
}
/*
* Find the swap type that corresponds to given device (if any).
*
* @offset - number of the PAGE_SIZE-sized block of the device, starting
* from 0, in which the swap header is expected to be located.
*
* This is needed for the suspend to disk (aka swsusp).
*/
int swap_type_of(dev_t device, sector_t offset)
{
int type;
if (!device)
return -1;
spin_lock(&swap_lock);
for (type = 0; type < nr_swapfiles; type++) {
struct swap_info_struct *sis = swap_info[type];
if (!(sis->flags & SWP_WRITEOK))
continue;
if (device == sis->bdev->bd_dev) {
struct swap_extent *se = first_se(sis);
if (se->start_block == offset) {
spin_unlock(&swap_lock);
return type;
}
}
}
spin_unlock(&swap_lock);
return -ENODEV;
}
int find_first_swap(dev_t *device)
{
int type;
spin_lock(&swap_lock);
for (type = 0; type < nr_swapfiles; type++) {
struct swap_info_struct *sis = swap_info[type];
if (!(sis->flags & SWP_WRITEOK))
continue;
*device = sis->bdev->bd_dev;
spin_unlock(&swap_lock);
return type;
}
spin_unlock(&swap_lock);
return -ENODEV;
}
/*
* Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
* corresponding to given index in swap_info (swap type).
*/
sector_t swapdev_block(int type, pgoff_t offset)
{
struct swap_info_struct *si = swap_type_to_swap_info(type);
struct swap_extent *se;
if (!si || !(si->flags & SWP_WRITEOK))
return 0;
se = offset_to_swap_extent(si, offset);
return se->start_block + (offset - se->start_page);
}
/*
* Return either the total number of swap pages of given type, or the number
* of free pages of that type (depending on @free)
*
* This is needed for software suspend
*/
unsigned int count_swap_pages(int type, int free)
{
unsigned int n = 0;
spin_lock(&swap_lock);
if ((unsigned int)type < nr_swapfiles) {
struct swap_info_struct *sis = swap_info[type];
spin_lock(&sis->lock);
if (sis->flags & SWP_WRITEOK) {
n = sis->pages;
if (free)
n -= sis->inuse_pages;
}
spin_unlock(&sis->lock);
}
spin_unlock(&swap_lock);
return n;
}
#endif /* CONFIG_HIBERNATION */
static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
{
return pte_same(pte_swp_clear_flags(pte), swp_pte);
}
/*
* No need to decide whether this PTE shares the swap entry with others,
* just let do_wp_page work it out if a write is requested later - to
* force COW, vm_page_prot omits write permission from any private vma.
*/
static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, swp_entry_t entry, struct 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);
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);
}
set_pte_at(vma->vm_mm, addr, pte,
pte_mkold(mk_pte(page, vma->vm_page_prot)));
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)
{
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 {
if (!is_swap_pte(*pte))
continue;
entry = pte_to_swp_entry(*pte);
if (swp_type(entry) != type)
continue;
offset = swp_offset(entry);
pte_unmap(pte);
swap_map = &si->swap_map[offset];
page = lookup_swap_cache(entry, vma, addr);
if (!page) {
struct vm_fault vmf = {
.vma = vma,
.address = addr,
.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);
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)
{
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);
if (ret)
return ret;
} while (pmd++, addr = next, addr != end);
return 0;
}
static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
unsigned long addr, unsigned long end,
unsigned int type)
{
pud_t *pud;
unsigned long next;
int ret;
pud = pud_offset(p4d, addr);
do {
next = pud_addr_end(addr, end);
if (pud_none_or_clear_bad(pud))
continue;
ret = unuse_pmd_range(vma, pud, addr, next, type);
if (ret)
return ret;
} while (pud++, addr = next, addr != end);
return 0;
}
static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
unsigned long addr, unsigned long end,
unsigned int type)
{
p4d_t *p4d;
unsigned long next;
int ret;
p4d = p4d_offset(pgd, addr);
do {
next = p4d_addr_end(addr, end);
if (p4d_none_or_clear_bad(p4d))
continue;
ret = unuse_pud_range(vma, p4d, addr, next, type);
if (ret)
return ret;
} while (p4d++, addr = next, addr != end);
return 0;
}
static int unuse_vma(struct vm_area_struct *vma, unsigned int type)
{
pgd_t *pgd;
unsigned long addr, end, next;
int ret;
addr = vma->vm_start;
end = vma->vm_end;
pgd = pgd_offset(vma->vm_mm, addr);
do {
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd))
continue;
ret = unuse_p4d_range(vma, pgd, addr, next, type);
if (ret)
return ret;
} while (pgd++, addr = next, addr != end);
return 0;
}
static int unuse_mm(struct mm_struct *mm, unsigned int type)
{
struct vm_area_struct *vma;
int ret = 0;
mmap_read_lock(mm);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
if (vma->anon_vma) {
ret = unuse_vma(vma, type);
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)
{
unsigned int i;
unsigned char count;
/*
* No need for swap_lock here: we're just looking
* for whether an entry is in use, not modifying it; false
* hits are okay, and sys_swapoff() has already prevented new
* allocations from this area (while holding swap_lock).
*/
for (i = prev + 1; i < si->max; i++) {
count = READ_ONCE(si->swap_map[i]);
if (count && swap_count(count) != SWAP_MAP_BAD)
break;
if ((i % LATENCY_LIMIT) == 0)
cond_resched();
}
if (i == si->max)
i = 0;
return i;
}
static int try_to_unuse(unsigned int type)
{
struct mm_struct *prev_mm;
struct mm_struct *mm;
struct list_head *p;
int retval = 0;
struct swap_info_struct *si = swap_info[type];
struct page *page;
swp_entry_t entry;
unsigned int i;
if (!READ_ONCE(si->inuse_pages))
return 0;
retry:
retval = shmem_unuse(type);
if (retval)
return retval;
prev_mm = &init_mm;
mmget(prev_mm);
spin_lock(&mmlist_lock);
p = &init_mm.mmlist;
while (READ_ONCE(si->inuse_pages) &&
!signal_pending(current) &&
(p = p->next) != &init_mm.mmlist) {
mm = list_entry(p, struct mm_struct, mmlist);
if (!mmget_not_zero(mm))
continue;
spin_unlock(&mmlist_lock);
mmput(prev_mm);
prev_mm = mm;
retval = unuse_mm(mm, type);
if (retval) {
mmput(prev_mm);
return retval;
}
/*
* Make sure that we aren't completely killing
* interactive performance.
*/
cond_resched();
spin_lock(&mmlist_lock);
}
spin_unlock(&mmlist_lock);
mmput(prev_mm);
i = 0;
while (READ_ONCE(si->inuse_pages) &&
!signal_pending(current) &&
(i = find_next_to_unuse(si, i)) != 0) {
entry = swp_entry(type, i);
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);
}
/*
* 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;
return -EINTR;
}
return 0;
}
/*
* After a successful try_to_unuse, if no swap is now in use, we know
* we can empty the mmlist. swap_lock must be held on entry and exit.
* Note that mmlist_lock nests inside swap_lock, and an mm must be
* added to the mmlist just after page_duplicate - before would be racy.
*/
static void drain_mmlist(void)
{
struct list_head *p, *next;
unsigned int type;
for (type = 0; type < nr_swapfiles; type++)
if (swap_info[type]->inuse_pages)
return;
spin_lock(&mmlist_lock);
list_for_each_safe(p, next, &init_mm.mmlist)
list_del_init(p);
spin_unlock(&mmlist_lock);
}
/*
* Free all of a swapdev's extent information
*/
static void destroy_swap_extents(struct swap_info_struct *sis)
{
while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
struct rb_node *rb = sis->swap_extent_root.rb_node;
struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
rb_erase(rb, &sis->swap_extent_root);
kfree(se);
}
if (sis->flags & SWP_ACTIVATED) {
struct file *swap_file = sis->swap_file;
struct address_space *mapping = swap_file->f_mapping;
sis->flags &= ~SWP_ACTIVATED;
if (mapping->a_ops->swap_deactivate)
mapping->a_ops->swap_deactivate(swap_file);
}
}
/*
* Add a block range (and the corresponding page range) into this swapdev's
* extent tree.
*
* This function rather assumes that it is called in ascending page order.
*/
int
add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
unsigned long nr_pages, sector_t start_block)
{
struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
struct swap_extent *se;
struct swap_extent *new_se;
/*
* place the new node at the right most since the
* function is called in ascending page order.
*/
while (*link) {
parent = *link;
link = &parent->rb_right;
}
if (parent) {
se = rb_entry(parent, struct swap_extent, rb_node);
BUG_ON(se->start_page + se->nr_pages != start_page);
if (se->start_block + se->nr_pages == start_block) {
/* Merge it */
se->nr_pages += nr_pages;
return 0;
}
}
/* No merge, insert a new extent. */
new_se = kmalloc(sizeof(*se), GFP_KERNEL);
if (new_se == NULL)
return -ENOMEM;
new_se->start_page = start_page;
new_se->nr_pages = nr_pages;
new_se->start_block = start_block;
rb_link_node(&new_se->rb_node, parent, link);
rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
return 1;
}
EXPORT_SYMBOL_GPL(add_swap_extent);
/*
* A `swap extent' is a simple thing which maps a contiguous range of pages
* onto a contiguous range of disk blocks. 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;
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)
{
if (IS_ENABLED(CONFIG_FRONTSWAP))
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);
/*
* Finished initializing swap device, now it's safe to reference it.
*/
percpu_ref_resurrect(&p->users);
spin_lock(&swap_lock);
spin_lock(&p->lock);
_enable_swap_info(p);
spin_unlock(&p->lock);
spin_unlock(&swap_lock);
}
static void reinsert_swap_info(struct swap_info_struct *p)
{
spin_lock(&swap_lock);
spin_lock(&p->lock);
setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
_enable_swap_info(p);
spin_unlock(&p->lock);
spin_unlock(&swap_lock);
}
bool has_usable_swap(void)
{
bool ret = true;
spin_lock(&swap_lock);
if (plist_head_empty(&swap_active_head))
ret = false;
spin_unlock(&swap_lock);
return ret;
}
SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
{
struct swap_info_struct *p = NULL;
unsigned char *swap_map;
struct swap_cluster_info *cluster_info;
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;
}
del_from_avail_list(p);
spin_lock(&p->lock);
if (p->prio < 0) {
struct swap_info_struct *si = p;
int nid;
plist_for_each_entry_continue(si, &swap_active_head, list) {
si->prio++;
si->list.prio--;
for_each_node(nid) {
if (si->avail_lists[nid].prio != 1)
si->avail_lists[nid].prio--;
}
}
least_priority++;
}
plist_del(&p->list, &swap_active_head);
atomic_long_sub(p->pages, &nr_swap_pages);
total_swap_pages -= p->pages;
p->flags &= ~SWP_WRITEOK;
spin_unlock(&p->lock);
spin_unlock(&swap_lock);
disable_swap_slots_cache_lock();
set_current_oom_origin();
err = try_to_unuse(p->type);
clear_current_oom_origin();
if (err) {
/* re-insert swap space back into swap_list */
reinsert_swap_info(p);
reenable_swap_slots_cache_unlock();
goto out_dput;
}
reenable_swap_slots_cache_unlock();
/*
* Wait for swap operations protected by get/put_swap_device()
* to complete.
*
* We need synchronize_rcu() here to protect the accessing to
* the swap cache data structure.
*/
percpu_ref_kill(&p->users);
synchronize_rcu();
wait_for_completion(&p->comp);
flush_work(&p->discard_work);
destroy_swap_extents(p);
if (p->flags & SWP_CONTINUED)
free_swap_count_continuations(p);
if (!p->bdev || !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_slots */
p->highest_bit = 0; /* cuts scans short */
while (p->flags >= SWP_SCANNING) {
spin_unlock(&p->lock);
spin_unlock(&swap_lock);
schedule_timeout_uninterruptible(1);
spin_lock(&swap_lock);
spin_lock(&p->lock);
}
swap_file = p->swap_file;
old_block_size = p->old_block_size;
p->swap_file = NULL;
p->max = 0;
swap_map = p->swap_map;
p->swap_map = NULL;
cluster_info = p->cluster_info;
p->cluster_info = NULL;
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 long bytes, inuse;
if (si == SEQ_START_TOKEN) {
seq_puts(swap, "Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n");
return 0;
}
bytes = 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%lu\t%s%lu\t%s%d\n",
len < 40 ? 40 - len : 1, " ",
S_ISBLK(file_inode(file)->i_mode) ?
"partition" : "file\t",
bytes, bytes < 10000000 ? "\t" : "",
inuse, inuse < 10000000 ? "\t" : "",
si->prio);
return 0;
}
static const struct seq_operations swaps_op = {
.start = swap_start,
.next = swap_next,
.stop = swap_stop,
.show = swap_show
};
static int swaps_open(struct inode *inode, struct file *file)
{
struct seq_file *seq;
int ret;
ret = seq_open(file, &swaps_op);
if (ret)
return ret;
seq = file->private_data;
seq->poll_event = atomic_read(&proc_poll_event);
return 0;
}
static const struct proc_ops swaps_proc_ops = {
.proc_flags = PROC_ENTRY_PERMANENT,
.proc_open = swaps_open,
.proc_read = seq_read,
.proc_lseek = seq_lseek,
.proc_release = seq_release,
.proc_poll = swaps_poll,
};
static int __init procswaps_init(void)
{
proc_create("swaps", 0, NULL, &swaps_proc_ops);
return 0;
}
__initcall(procswaps_init);
#endif /* CONFIG_PROC_FS */
#ifdef MAX_SWAPFILES_CHECK
static int __init max_swapfiles_check(void)
{
MAX_SWAPFILES_CHECK();
return 0;
}
late_initcall(max_swapfiles_check);
#endif
static struct swap_info_struct *alloc_swap_info(void)
{
struct swap_info_struct *p;
struct swap_info_struct *defer = NULL;
unsigned int type;
int i;
p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL);
if (!p)
return ERR_PTR(-ENOMEM);
if (percpu_ref_init(&p->users, swap_users_ref_free,
PERCPU_REF_INIT_DEAD, GFP_KERNEL)) {
kvfree(p);
return ERR_PTR(-ENOMEM);
}
spin_lock(&swap_lock);
for (type = 0; type < nr_swapfiles; type++) {
if (!(swap_info[type]->flags & SWP_USED))
break;
}
if (type >= MAX_SWAPFILES) {
spin_unlock(&swap_lock);
percpu_ref_exit(&p->users);
kvfree(p);
return ERR_PTR(-EPERM);
}
if (type >= nr_swapfiles) {
p->type = type;
/*
* Publish the swap_info_struct after initializing it.
* Note that kvzalloc() above zeroes all its fields.
*/
smp_store_release(&swap_info[type], p); /* rcu_assign_pointer() */
nr_swapfiles++;
} else {
defer = p;
p = swap_info[type];
/*
* Do not memset this entry: a racing procfs swap_next()
* would be relying on p->type to remain valid.
*/
}
p->swap_extent_root = RB_ROOT;
plist_node_init(&p->list, 0);
for_each_node(i)
plist_node_init(&p->avail_lists[i], 0);
p->flags = SWP_USED;
spin_unlock(&swap_lock);
if (defer) {
percpu_ref_exit(&defer->users);
kvfree(defer);
}
spin_lock_init(&p->lock);
spin_lock_init(&p->cont_lock);
init_completion(&p->comp);
return p;
}
static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
{
int error;
if (S_ISBLK(inode->i_mode)) {
p->bdev = blkdev_get_by_dev(inode->i_rdev,
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 endianness hack... */
if (swab32(swap_header->info.version) == 1) {
swab32s(&swap_header->info.version);
swab32s(&swap_header->info.last_page);
swab32s(&swap_header->info.nr_badpages);
if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
return 0;
for (i = 0; i < swap_header->info.nr_badpages; i++)
swab32s(&swap_header->info.badpages[i]);
}
/* Check the swap header's sub-version */
if (swap_header->info.version != 1) {
pr_warn("Unable to handle swap header version %d\n",
swap_header->info.version);
return 0;
}
p->lowest_bit = 1;
p->cluster_next = 1;
p->cluster_nr = 0;
maxpages = 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 (!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;
struct dentry *dentry;
int prio;
int error;
union swap_header *swap_header;
int nr_extents;
sector_t span;
unsigned long maxpages;
unsigned char *swap_map = NULL;
struct swap_cluster_info *cluster_info = NULL;
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;
dentry = swap_file->f_path.dentry;
inode = mapping->host;
error = claim_swapfile(p, inode);
if (unlikely(error))
goto bad_swap;
inode_lock(inode);
if (d_unlinked(dentry) || cant_mount(dentry)) {
error = -ENOENT;
goto bad_swap_unlock_inode;
}
if (IS_SWAPFILE(inode)) {
error = -EBUSY;
goto bad_swap_unlock_inode;
}
/*
* Read the swap header.
*/
if (!mapping->a_ops->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;
p = get_swap_device(entry);
if (!p)
return -EINVAL;
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);
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 methods to avoid include hell.
*/
struct address_space *swapcache_mapping(struct folio *folio)
{
return page_swap_info(&folio->page)->swap_file->f_mapping;
}
EXPORT_SYMBOL_GPL(swapcache_mapping);
pgoff_t __page_file_index(struct page *page)
{
swp_entry_t swap = { .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 = swap_count(si->swap_map[offset]);
if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
/*
* The higher the swap count, the more likely it is that tasks
* will race to add swap count continuation: we need to avoid
* over-provisioning.
*/
goto out;
}
if (!page) {
ret = -ENOMEM;
goto out;
}
/*
* 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);
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