blob: e97143713021e02c5565ec4c40c9e3dae73b06bc [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-only
/*
* z3fold.c
*
* Author: Vitaly Wool <vitaly.wool@konsulko.com>
* Copyright (C) 2016, Sony Mobile Communications Inc.
*
* This implementation is based on zbud written by Seth Jennings.
*
* z3fold is an special purpose allocator for storing compressed pages. It
* can store up to three compressed pages per page which improves the
* compression ratio of zbud while retaining its main concepts (e. g. always
* storing an integral number of objects per page) and simplicity.
* It still has simple and deterministic reclaim properties that make it
* preferable to a higher density approach (with no requirement on integral
* number of object per page) when reclaim is used.
*
* As in zbud, pages are divided into "chunks". The size of the chunks is
* fixed at compile time and is determined by NCHUNKS_ORDER below.
*
* z3fold doesn't export any API and is meant to be used via zpool API.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/atomic.h>
#include <linux/sched.h>
#include <linux/cpumask.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/page-flags.h>
#include <linux/migrate.h>
#include <linux/node.h>
#include <linux/compaction.h>
#include <linux/percpu.h>
#include <linux/mount.h>
#include <linux/pseudo_fs.h>
#include <linux/fs.h>
#include <linux/preempt.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/zpool.h>
#include <linux/magic.h>
/*
* NCHUNKS_ORDER determines the internal allocation granularity, effectively
* adjusting internal fragmentation. It also determines the number of
* freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
* allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
* in the beginning of an allocated page are occupied by z3fold header, so
* NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
* which shows the max number of free chunks in z3fold page, also there will
* be 63, or 62, respectively, freelists per pool.
*/
#define NCHUNKS_ORDER 6
#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
#define CHUNK_SIZE (1 << CHUNK_SHIFT)
#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
#define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
#define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
#define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
#define BUDDY_MASK (0x3)
#define BUDDY_SHIFT 2
#define SLOTS_ALIGN (0x40)
/*****************
* Structures
*****************/
struct z3fold_pool;
struct z3fold_ops {
int (*evict)(struct z3fold_pool *pool, unsigned long handle);
};
enum buddy {
HEADLESS = 0,
FIRST,
MIDDLE,
LAST,
BUDDIES_MAX = LAST
};
struct z3fold_buddy_slots {
/*
* we are using BUDDY_MASK in handle_to_buddy etc. so there should
* be enough slots to hold all possible variants
*/
unsigned long slot[BUDDY_MASK + 1];
unsigned long pool; /* back link + flags */
};
#define HANDLE_FLAG_MASK (0x03)
/*
* struct z3fold_header - z3fold page metadata occupying first chunks of each
* z3fold page, except for HEADLESS pages
* @buddy: links the z3fold page into the relevant list in the
* pool
* @page_lock: per-page lock
* @refcount: reference count for the z3fold page
* @work: work_struct for page layout optimization
* @slots: pointer to the structure holding buddy slots
* @pool: pointer to the containing pool
* @cpu: CPU which this page "belongs" to
* @first_chunks: the size of the first buddy in chunks, 0 if free
* @middle_chunks: the size of the middle buddy in chunks, 0 if free
* @last_chunks: the size of the last buddy in chunks, 0 if free
* @first_num: the starting number (for the first handle)
* @mapped_count: the number of objects currently mapped
*/
struct z3fold_header {
struct list_head buddy;
spinlock_t page_lock;
struct kref refcount;
struct work_struct work;
struct z3fold_buddy_slots *slots;
struct z3fold_pool *pool;
short cpu;
unsigned short first_chunks;
unsigned short middle_chunks;
unsigned short last_chunks;
unsigned short start_middle;
unsigned short first_num:2;
unsigned short mapped_count:2;
};
/**
* struct z3fold_pool - stores metadata for each z3fold pool
* @name: pool name
* @lock: protects pool unbuddied/lru lists
* @stale_lock: protects pool stale page list
* @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2-
* buddies; the list each z3fold page is added to depends on
* the size of its free region.
* @lru: list tracking the z3fold pages in LRU order by most recently
* added buddy.
* @stale: list of pages marked for freeing
* @pages_nr: number of z3fold pages in the pool.
* @c_handle: cache for z3fold_buddy_slots allocation
* @ops: pointer to a structure of user defined operations specified at
* pool creation time.
* @compact_wq: workqueue for page layout background optimization
* @release_wq: workqueue for safe page release
* @work: work_struct for safe page release
* @inode: inode for z3fold pseudo filesystem
*
* This structure is allocated at pool creation time and maintains metadata
* pertaining to a particular z3fold pool.
*/
struct z3fold_pool {
const char *name;
spinlock_t lock;
spinlock_t stale_lock;
struct list_head *unbuddied;
struct list_head lru;
struct list_head stale;
atomic64_t pages_nr;
struct kmem_cache *c_handle;
const struct z3fold_ops *ops;
struct zpool *zpool;
const struct zpool_ops *zpool_ops;
struct workqueue_struct *compact_wq;
struct workqueue_struct *release_wq;
struct work_struct work;
struct inode *inode;
};
/*
* Internal z3fold page flags
*/
enum z3fold_page_flags {
PAGE_HEADLESS = 0,
MIDDLE_CHUNK_MAPPED,
NEEDS_COMPACTING,
PAGE_STALE,
PAGE_CLAIMED, /* by either reclaim or free */
};
/*****************
* Helpers
*****************/
/* Converts an allocation size in bytes to size in z3fold chunks */
static int size_to_chunks(size_t size)
{
return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
}
#define for_each_unbuddied_list(_iter, _begin) \
for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
static void compact_page_work(struct work_struct *w);
static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
gfp_t gfp)
{
struct z3fold_buddy_slots *slots;
slots = kmem_cache_alloc(pool->c_handle,
(gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
if (slots) {
memset(slots->slot, 0, sizeof(slots->slot));
slots->pool = (unsigned long)pool;
}
return slots;
}
static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
{
return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
}
static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
{
return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
}
static inline void free_handle(unsigned long handle)
{
struct z3fold_buddy_slots *slots;
int i;
bool is_free;
if (handle & (1 << PAGE_HEADLESS))
return;
WARN_ON(*(unsigned long *)handle == 0);
*(unsigned long *)handle = 0;
slots = handle_to_slots(handle);
is_free = true;
for (i = 0; i <= BUDDY_MASK; i++) {
if (slots->slot[i]) {
is_free = false;
break;
}
}
if (is_free) {
struct z3fold_pool *pool = slots_to_pool(slots);
kmem_cache_free(pool->c_handle, slots);
}
}
static int z3fold_init_fs_context(struct fs_context *fc)
{
return init_pseudo(fc, Z3FOLD_MAGIC) ? 0 : -ENOMEM;
}
static struct file_system_type z3fold_fs = {
.name = "z3fold",
.init_fs_context = z3fold_init_fs_context,
.kill_sb = kill_anon_super,
};
static struct vfsmount *z3fold_mnt;
static int z3fold_mount(void)
{
int ret = 0;
z3fold_mnt = kern_mount(&z3fold_fs);
if (IS_ERR(z3fold_mnt))
ret = PTR_ERR(z3fold_mnt);
return ret;
}
static void z3fold_unmount(void)
{
kern_unmount(z3fold_mnt);
}
static const struct address_space_operations z3fold_aops;
static int z3fold_register_migration(struct z3fold_pool *pool)
{
pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
if (IS_ERR(pool->inode)) {
pool->inode = NULL;
return 1;
}
pool->inode->i_mapping->private_data = pool;
pool->inode->i_mapping->a_ops = &z3fold_aops;
return 0;
}
static void z3fold_unregister_migration(struct z3fold_pool *pool)
{
if (pool->inode)
iput(pool->inode);
}
/* Initializes the z3fold header of a newly allocated z3fold page */
static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
struct z3fold_pool *pool, gfp_t gfp)
{
struct z3fold_header *zhdr = page_address(page);
struct z3fold_buddy_slots *slots;
INIT_LIST_HEAD(&page->lru);
clear_bit(PAGE_HEADLESS, &page->private);
clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
clear_bit(NEEDS_COMPACTING, &page->private);
clear_bit(PAGE_STALE, &page->private);
clear_bit(PAGE_CLAIMED, &page->private);
if (headless)
return zhdr;
slots = alloc_slots(pool, gfp);
if (!slots)
return NULL;
spin_lock_init(&zhdr->page_lock);
kref_init(&zhdr->refcount);
zhdr->first_chunks = 0;
zhdr->middle_chunks = 0;
zhdr->last_chunks = 0;
zhdr->first_num = 0;
zhdr->start_middle = 0;
zhdr->cpu = -1;
zhdr->slots = slots;
zhdr->pool = pool;
INIT_LIST_HEAD(&zhdr->buddy);
INIT_WORK(&zhdr->work, compact_page_work);
return zhdr;
}
/* Resets the struct page fields and frees the page */
static void free_z3fold_page(struct page *page, bool headless)
{
if (!headless) {
lock_page(page);
__ClearPageMovable(page);
unlock_page(page);
}
ClearPagePrivate(page);
__free_page(page);
}
/* Lock a z3fold page */
static inline void z3fold_page_lock(struct z3fold_header *zhdr)
{
spin_lock(&zhdr->page_lock);
}
/* Try to lock a z3fold page */
static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
{
return spin_trylock(&zhdr->page_lock);
}
/* Unlock a z3fold page */
static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
{
spin_unlock(&zhdr->page_lock);
}
/* Helper function to build the index */
static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
{
return (bud + zhdr->first_num) & BUDDY_MASK;
}
/*
* Encodes the handle of a particular buddy within a z3fold page
* Pool lock should be held as this function accesses first_num
*/
static unsigned long __encode_handle(struct z3fold_header *zhdr,
struct z3fold_buddy_slots *slots,
enum buddy bud)
{
unsigned long h = (unsigned long)zhdr;
int idx = 0;
/*
* For a headless page, its handle is its pointer with the extra
* PAGE_HEADLESS bit set
*/
if (bud == HEADLESS)
return h | (1 << PAGE_HEADLESS);
/* otherwise, return pointer to encoded handle */
idx = __idx(zhdr, bud);
h += idx;
if (bud == LAST)
h |= (zhdr->last_chunks << BUDDY_SHIFT);
slots->slot[idx] = h;
return (unsigned long)&slots->slot[idx];
}
static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
{
return __encode_handle(zhdr, zhdr->slots, bud);
}
/* Returns the z3fold page where a given handle is stored */
static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
{
unsigned long addr = h;
if (!(addr & (1 << PAGE_HEADLESS)))
addr = *(unsigned long *)h;
return (struct z3fold_header *)(addr & PAGE_MASK);
}
/* only for LAST bud, returns zero otherwise */
static unsigned short handle_to_chunks(unsigned long handle)
{
unsigned long addr = *(unsigned long *)handle;
return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
}
/*
* (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
* but that doesn't matter. because the masking will result in the
* correct buddy number.
*/
static enum buddy handle_to_buddy(unsigned long handle)
{
struct z3fold_header *zhdr;
unsigned long addr;
WARN_ON(handle & (1 << PAGE_HEADLESS));
addr = *(unsigned long *)handle;
zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
return (addr - zhdr->first_num) & BUDDY_MASK;
}
static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
{
return zhdr->pool;
}
static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
{
struct page *page = virt_to_page(zhdr);
struct z3fold_pool *pool = zhdr_to_pool(zhdr);
WARN_ON(!list_empty(&zhdr->buddy));
set_bit(PAGE_STALE, &page->private);
clear_bit(NEEDS_COMPACTING, &page->private);
spin_lock(&pool->lock);
if (!list_empty(&page->lru))
list_del_init(&page->lru);
spin_unlock(&pool->lock);
if (locked)
z3fold_page_unlock(zhdr);
spin_lock(&pool->stale_lock);
list_add(&zhdr->buddy, &pool->stale);
queue_work(pool->release_wq, &pool->work);
spin_unlock(&pool->stale_lock);
}
static void __attribute__((__unused__))
release_z3fold_page(struct kref *ref)
{
struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
refcount);
__release_z3fold_page(zhdr, false);
}
static void release_z3fold_page_locked(struct kref *ref)
{
struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
refcount);
WARN_ON(z3fold_page_trylock(zhdr));
__release_z3fold_page(zhdr, true);
}
static void release_z3fold_page_locked_list(struct kref *ref)
{
struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
refcount);
struct z3fold_pool *pool = zhdr_to_pool(zhdr);
spin_lock(&pool->lock);
list_del_init(&zhdr->buddy);
spin_unlock(&pool->lock);
WARN_ON(z3fold_page_trylock(zhdr));
__release_z3fold_page(zhdr, true);
}
static void free_pages_work(struct work_struct *w)
{
struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
spin_lock(&pool->stale_lock);
while (!list_empty(&pool->stale)) {
struct z3fold_header *zhdr = list_first_entry(&pool->stale,
struct z3fold_header, buddy);
struct page *page = virt_to_page(zhdr);
list_del(&zhdr->buddy);
if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
continue;
spin_unlock(&pool->stale_lock);
cancel_work_sync(&zhdr->work);
free_z3fold_page(page, false);
cond_resched();
spin_lock(&pool->stale_lock);
}
spin_unlock(&pool->stale_lock);
}
/*
* Returns the number of free chunks in a z3fold page.
* NB: can't be used with HEADLESS pages.
*/
static int num_free_chunks(struct z3fold_header *zhdr)
{
int nfree;
/*
* If there is a middle object, pick up the bigger free space
* either before or after it. Otherwise just subtract the number
* of chunks occupied by the first and the last objects.
*/
if (zhdr->middle_chunks != 0) {
int nfree_before = zhdr->first_chunks ?
0 : zhdr->start_middle - ZHDR_CHUNKS;
int nfree_after = zhdr->last_chunks ?
0 : TOTAL_CHUNKS -
(zhdr->start_middle + zhdr->middle_chunks);
nfree = max(nfree_before, nfree_after);
} else
nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
return nfree;
}
/* Add to the appropriate unbuddied list */
static inline void add_to_unbuddied(struct z3fold_pool *pool,
struct z3fold_header *zhdr)
{
if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
zhdr->middle_chunks == 0) {
struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
int freechunks = num_free_chunks(zhdr);
spin_lock(&pool->lock);
list_add(&zhdr->buddy, &unbuddied[freechunks]);
spin_unlock(&pool->lock);
zhdr->cpu = smp_processor_id();
put_cpu_ptr(pool->unbuddied);
}
}
static inline void *mchunk_memmove(struct z3fold_header *zhdr,
unsigned short dst_chunk)
{
void *beg = zhdr;
return memmove(beg + (dst_chunk << CHUNK_SHIFT),
beg + (zhdr->start_middle << CHUNK_SHIFT),
zhdr->middle_chunks << CHUNK_SHIFT);
}
#define BIG_CHUNK_GAP 3
/* Has to be called with lock held */
static int z3fold_compact_page(struct z3fold_header *zhdr)
{
struct page *page = virt_to_page(zhdr);
if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
return 0; /* can't move middle chunk, it's used */
if (unlikely(PageIsolated(page)))
return 0;
if (zhdr->middle_chunks == 0)
return 0; /* nothing to compact */
if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
/* move to the beginning */
mchunk_memmove(zhdr, ZHDR_CHUNKS);
zhdr->first_chunks = zhdr->middle_chunks;
zhdr->middle_chunks = 0;
zhdr->start_middle = 0;
zhdr->first_num++;
return 1;
}
/*
* moving data is expensive, so let's only do that if
* there's substantial gain (at least BIG_CHUNK_GAP chunks)
*/
if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
BIG_CHUNK_GAP) {
mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
return 1;
} else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
+ zhdr->middle_chunks) >=
BIG_CHUNK_GAP) {
unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
zhdr->middle_chunks;
mchunk_memmove(zhdr, new_start);
zhdr->start_middle = new_start;
return 1;
}
return 0;
}
static void do_compact_page(struct z3fold_header *zhdr, bool locked)
{
struct z3fold_pool *pool = zhdr_to_pool(zhdr);
struct page *page;
page = virt_to_page(zhdr);
if (locked)
WARN_ON(z3fold_page_trylock(zhdr));
else
z3fold_page_lock(zhdr);
if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
z3fold_page_unlock(zhdr);
return;
}
spin_lock(&pool->lock);
list_del_init(&zhdr->buddy);
spin_unlock(&pool->lock);
if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
atomic64_dec(&pool->pages_nr);
return;
}
if (unlikely(PageIsolated(page) ||
test_bit(PAGE_CLAIMED, &page->private) ||
test_bit(PAGE_STALE, &page->private))) {
z3fold_page_unlock(zhdr);
return;
}
z3fold_compact_page(zhdr);
add_to_unbuddied(pool, zhdr);
z3fold_page_unlock(zhdr);
}
static void compact_page_work(struct work_struct *w)
{
struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
work);
do_compact_page(zhdr, false);
}
/* returns _locked_ z3fold page header or NULL */
static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
size_t size, bool can_sleep)
{
struct z3fold_header *zhdr = NULL;
struct page *page;
struct list_head *unbuddied;
int chunks = size_to_chunks(size), i;
lookup:
/* First, try to find an unbuddied z3fold page. */
unbuddied = get_cpu_ptr(pool->unbuddied);
for_each_unbuddied_list(i, chunks) {
struct list_head *l = &unbuddied[i];
zhdr = list_first_entry_or_null(READ_ONCE(l),
struct z3fold_header, buddy);
if (!zhdr)
continue;
/* Re-check under lock. */
spin_lock(&pool->lock);
l = &unbuddied[i];
if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
struct z3fold_header, buddy)) ||
!z3fold_page_trylock(zhdr)) {
spin_unlock(&pool->lock);
zhdr = NULL;
put_cpu_ptr(pool->unbuddied);
if (can_sleep)
cond_resched();
goto lookup;
}
list_del_init(&zhdr->buddy);
zhdr->cpu = -1;
spin_unlock(&pool->lock);
page = virt_to_page(zhdr);
if (test_bit(NEEDS_COMPACTING, &page->private)) {
z3fold_page_unlock(zhdr);
zhdr = NULL;
put_cpu_ptr(pool->unbuddied);
if (can_sleep)
cond_resched();
goto lookup;
}
/*
* this page could not be removed from its unbuddied
* list while pool lock was held, and then we've taken
* page lock so kref_put could not be called before
* we got here, so it's safe to just call kref_get()
*/
kref_get(&zhdr->refcount);
break;
}
put_cpu_ptr(pool->unbuddied);
if (!zhdr) {
int cpu;
/* look for _exact_ match on other cpus' lists */
for_each_online_cpu(cpu) {
struct list_head *l;
unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
spin_lock(&pool->lock);
l = &unbuddied[chunks];
zhdr = list_first_entry_or_null(READ_ONCE(l),
struct z3fold_header, buddy);
if (!zhdr || !z3fold_page_trylock(zhdr)) {
spin_unlock(&pool->lock);
zhdr = NULL;
continue;
}
list_del_init(&zhdr->buddy);
zhdr->cpu = -1;
spin_unlock(&pool->lock);
page = virt_to_page(zhdr);
if (test_bit(NEEDS_COMPACTING, &page->private)) {
z3fold_page_unlock(zhdr);
zhdr = NULL;
if (can_sleep)
cond_resched();
continue;
}
kref_get(&zhdr->refcount);
break;
}
}
return zhdr;
}
/*
* API Functions
*/
/**
* z3fold_create_pool() - create a new z3fold pool
* @name: pool name
* @gfp: gfp flags when allocating the z3fold pool structure
* @ops: user-defined operations for the z3fold pool
*
* Return: pointer to the new z3fold pool or NULL if the metadata allocation
* failed.
*/
static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
const struct z3fold_ops *ops)
{
struct z3fold_pool *pool = NULL;
int i, cpu;
pool = kzalloc(sizeof(struct z3fold_pool), gfp);
if (!pool)
goto out;
pool->c_handle = kmem_cache_create("z3fold_handle",
sizeof(struct z3fold_buddy_slots),
SLOTS_ALIGN, 0, NULL);
if (!pool->c_handle)
goto out_c;
spin_lock_init(&pool->lock);
spin_lock_init(&pool->stale_lock);
pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
if (!pool->unbuddied)
goto out_pool;
for_each_possible_cpu(cpu) {
struct list_head *unbuddied =
per_cpu_ptr(pool->unbuddied, cpu);
for_each_unbuddied_list(i, 0)
INIT_LIST_HEAD(&unbuddied[i]);
}
INIT_LIST_HEAD(&pool->lru);
INIT_LIST_HEAD(&pool->stale);
atomic64_set(&pool->pages_nr, 0);
pool->name = name;
pool->compact_wq = create_singlethread_workqueue(pool->name);
if (!pool->compact_wq)
goto out_unbuddied;
pool->release_wq = create_singlethread_workqueue(pool->name);
if (!pool->release_wq)
goto out_wq;
if (z3fold_register_migration(pool))
goto out_rwq;
INIT_WORK(&pool->work, free_pages_work);
pool->ops = ops;
return pool;
out_rwq:
destroy_workqueue(pool->release_wq);
out_wq:
destroy_workqueue(pool->compact_wq);
out_unbuddied:
free_percpu(pool->unbuddied);
out_pool:
kmem_cache_destroy(pool->c_handle);
out_c:
kfree(pool);
out:
return NULL;
}
/**
* z3fold_destroy_pool() - destroys an existing z3fold pool
* @pool: the z3fold pool to be destroyed
*
* The pool should be emptied before this function is called.
*/
static void z3fold_destroy_pool(struct z3fold_pool *pool)
{
kmem_cache_destroy(pool->c_handle);
/*
* We need to destroy pool->compact_wq before pool->release_wq,
* as any pending work on pool->compact_wq will call
* queue_work(pool->release_wq, &pool->work).
*
* There are still outstanding pages until both workqueues are drained,
* so we cannot unregister migration until then.
*/
destroy_workqueue(pool->compact_wq);
destroy_workqueue(pool->release_wq);
z3fold_unregister_migration(pool);
free_percpu(pool->unbuddied);
kfree(pool);
}
/**
* z3fold_alloc() - allocates a region of a given size
* @pool: z3fold pool from which to allocate
* @size: size in bytes of the desired allocation
* @gfp: gfp flags used if the pool needs to grow
* @handle: handle of the new allocation
*
* This function will attempt to find a free region in the pool large enough to
* satisfy the allocation request. A search of the unbuddied lists is
* performed first. If no suitable free region is found, then a new page is
* allocated and added to the pool to satisfy the request.
*
* gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
* as z3fold pool pages.
*
* Return: 0 if success and handle is set, otherwise -EINVAL if the size or
* gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
* a new page.
*/
static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
unsigned long *handle)
{
int chunks = size_to_chunks(size);
struct z3fold_header *zhdr = NULL;
struct page *page = NULL;
enum buddy bud;
bool can_sleep = gfpflags_allow_blocking(gfp);
if (!size)
return -EINVAL;
if (size > PAGE_SIZE)
return -ENOSPC;
if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
bud = HEADLESS;
else {
retry:
zhdr = __z3fold_alloc(pool, size, can_sleep);
if (zhdr) {
if (zhdr->first_chunks == 0) {
if (zhdr->middle_chunks != 0 &&
chunks >= zhdr->start_middle)
bud = LAST;
else
bud = FIRST;
} else if (zhdr->last_chunks == 0)
bud = LAST;
else if (zhdr->middle_chunks == 0)
bud = MIDDLE;
else {
if (kref_put(&zhdr->refcount,
release_z3fold_page_locked))
atomic64_dec(&pool->pages_nr);
else
z3fold_page_unlock(zhdr);
pr_err("No free chunks in unbuddied\n");
WARN_ON(1);
goto retry;
}
page = virt_to_page(zhdr);
goto found;
}
bud = FIRST;
}
page = NULL;
if (can_sleep) {
spin_lock(&pool->stale_lock);
zhdr = list_first_entry_or_null(&pool->stale,
struct z3fold_header, buddy);
/*
* Before allocating a page, let's see if we can take one from
* the stale pages list. cancel_work_sync() can sleep so we
* limit this case to the contexts where we can sleep
*/
if (zhdr) {
list_del(&zhdr->buddy);
spin_unlock(&pool->stale_lock);
cancel_work_sync(&zhdr->work);
page = virt_to_page(zhdr);
} else {
spin_unlock(&pool->stale_lock);
}
}
if (!page)
page = alloc_page(gfp);
if (!page)
return -ENOMEM;
zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
if (!zhdr) {
__free_page(page);
return -ENOMEM;
}
atomic64_inc(&pool->pages_nr);
if (bud == HEADLESS) {
set_bit(PAGE_HEADLESS, &page->private);
goto headless;
}
if (can_sleep) {
lock_page(page);
__SetPageMovable(page, pool->inode->i_mapping);
unlock_page(page);
} else {
if (trylock_page(page)) {
__SetPageMovable(page, pool->inode->i_mapping);
unlock_page(page);
}
}
z3fold_page_lock(zhdr);
found:
if (bud == FIRST)
zhdr->first_chunks = chunks;
else if (bud == LAST)
zhdr->last_chunks = chunks;
else {
zhdr->middle_chunks = chunks;
zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
}
add_to_unbuddied(pool, zhdr);
headless:
spin_lock(&pool->lock);
/* Add/move z3fold page to beginning of LRU */
if (!list_empty(&page->lru))
list_del(&page->lru);
list_add(&page->lru, &pool->lru);
*handle = encode_handle(zhdr, bud);
spin_unlock(&pool->lock);
if (bud != HEADLESS)
z3fold_page_unlock(zhdr);
return 0;
}
/**
* z3fold_free() - frees the allocation associated with the given handle
* @pool: pool in which the allocation resided
* @handle: handle associated with the allocation returned by z3fold_alloc()
*
* In the case that the z3fold page in which the allocation resides is under
* reclaim, as indicated by the PG_reclaim flag being set, this function
* only sets the first|last_chunks to 0. The page is actually freed
* once both buddies are evicted (see z3fold_reclaim_page() below).
*/
static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
{
struct z3fold_header *zhdr;
struct page *page;
enum buddy bud;
bool page_claimed;
zhdr = handle_to_z3fold_header(handle);
page = virt_to_page(zhdr);
page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
if (test_bit(PAGE_HEADLESS, &page->private)) {
/* if a headless page is under reclaim, just leave.
* NB: we use test_and_set_bit for a reason: if the bit
* has not been set before, we release this page
* immediately so we don't care about its value any more.
*/
if (!page_claimed) {
spin_lock(&pool->lock);
list_del(&page->lru);
spin_unlock(&pool->lock);
free_z3fold_page(page, true);
atomic64_dec(&pool->pages_nr);
}
return;
}
/* Non-headless case */
z3fold_page_lock(zhdr);
bud = handle_to_buddy(handle);
switch (bud) {
case FIRST:
zhdr->first_chunks = 0;
break;
case MIDDLE:
zhdr->middle_chunks = 0;
break;
case LAST:
zhdr->last_chunks = 0;
break;
default:
pr_err("%s: unknown bud %d\n", __func__, bud);
WARN_ON(1);
z3fold_page_unlock(zhdr);
return;
}
free_handle(handle);
if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
atomic64_dec(&pool->pages_nr);
return;
}
if (page_claimed) {
/* the page has not been claimed by us */
z3fold_page_unlock(zhdr);
return;
}
if (unlikely(PageIsolated(page)) ||
test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
z3fold_page_unlock(zhdr);
clear_bit(PAGE_CLAIMED, &page->private);
return;
}
if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
spin_lock(&pool->lock);
list_del_init(&zhdr->buddy);
spin_unlock(&pool->lock);
zhdr->cpu = -1;
kref_get(&zhdr->refcount);
do_compact_page(zhdr, true);
clear_bit(PAGE_CLAIMED, &page->private);
return;
}
kref_get(&zhdr->refcount);
queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
clear_bit(PAGE_CLAIMED, &page->private);
z3fold_page_unlock(zhdr);
}
/**
* z3fold_reclaim_page() - evicts allocations from a pool page and frees it
* @pool: pool from which a page will attempt to be evicted
* @retries: number of pages on the LRU list for which eviction will
* be attempted before failing
*
* z3fold reclaim is different from normal system reclaim in that it is done
* from the bottom, up. This is because only the bottom layer, z3fold, has
* information on how the allocations are organized within each z3fold page.
* This has the potential to create interesting locking situations between
* z3fold and the user, however.
*
* To avoid these, this is how z3fold_reclaim_page() should be called:
*
* The user detects a page should be reclaimed and calls z3fold_reclaim_page().
* z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
* call the user-defined eviction handler with the pool and handle as
* arguments.
*
* If the handle can not be evicted, the eviction handler should return
* non-zero. z3fold_reclaim_page() will add the z3fold page back to the
* appropriate list and try the next z3fold page on the LRU up to
* a user defined number of retries.
*
* If the handle is successfully evicted, the eviction handler should
* return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
* contains logic to delay freeing the page if the page is under reclaim,
* as indicated by the setting of the PG_reclaim flag on the underlying page.
*
* If all buddies in the z3fold page are successfully evicted, then the
* z3fold page can be freed.
*
* Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
* no pages to evict or an eviction handler is not registered, -EAGAIN if
* the retry limit was hit.
*/
static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
{
int i, ret = 0;
struct z3fold_header *zhdr = NULL;
struct page *page = NULL;
struct list_head *pos;
struct z3fold_buddy_slots slots;
unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
spin_lock(&pool->lock);
if (!pool->ops || !pool->ops->evict || retries == 0) {
spin_unlock(&pool->lock);
return -EINVAL;
}
for (i = 0; i < retries; i++) {
if (list_empty(&pool->lru)) {
spin_unlock(&pool->lock);
return -EINVAL;
}
list_for_each_prev(pos, &pool->lru) {
page = list_entry(pos, struct page, lru);
/* this bit could have been set by free, in which case
* we pass over to the next page in the pool.
*/
if (test_and_set_bit(PAGE_CLAIMED, &page->private)) {
page = NULL;
continue;
}
if (unlikely(PageIsolated(page))) {
clear_bit(PAGE_CLAIMED, &page->private);
page = NULL;
continue;
}
zhdr = page_address(page);
if (test_bit(PAGE_HEADLESS, &page->private))
break;
if (!z3fold_page_trylock(zhdr)) {
clear_bit(PAGE_CLAIMED, &page->private);
zhdr = NULL;
continue; /* can't evict at this point */
}
kref_get(&zhdr->refcount);
list_del_init(&zhdr->buddy);
zhdr->cpu = -1;
break;
}
if (!zhdr)
break;
list_del_init(&page->lru);
spin_unlock(&pool->lock);
if (!test_bit(PAGE_HEADLESS, &page->private)) {
/*
* We need encode the handles before unlocking, and
* use our local slots structure because z3fold_free
* can zero out zhdr->slots and we can't do much
* about that
*/
first_handle = 0;
last_handle = 0;
middle_handle = 0;
if (zhdr->first_chunks)
first_handle = __encode_handle(zhdr, &slots,
FIRST);
if (zhdr->middle_chunks)
middle_handle = __encode_handle(zhdr, &slots,
MIDDLE);
if (zhdr->last_chunks)
last_handle = __encode_handle(zhdr, &slots,
LAST);
/*
* it's safe to unlock here because we hold a
* reference to this page
*/
z3fold_page_unlock(zhdr);
} else {
first_handle = __encode_handle(zhdr, &slots, HEADLESS);
last_handle = middle_handle = 0;
}
/* Issue the eviction callback(s) */
if (middle_handle) {
ret = pool->ops->evict(pool, middle_handle);
if (ret)
goto next;
}
if (first_handle) {
ret = pool->ops->evict(pool, first_handle);
if (ret)
goto next;
}
if (last_handle) {
ret = pool->ops->evict(pool, last_handle);
if (ret)
goto next;
}
next:
if (test_bit(PAGE_HEADLESS, &page->private)) {
if (ret == 0) {
free_z3fold_page(page, true);
atomic64_dec(&pool->pages_nr);
return 0;
}
spin_lock(&pool->lock);
list_add(&page->lru, &pool->lru);
spin_unlock(&pool->lock);
clear_bit(PAGE_CLAIMED, &page->private);
} else {
z3fold_page_lock(zhdr);
if (kref_put(&zhdr->refcount,
release_z3fold_page_locked)) {
atomic64_dec(&pool->pages_nr);
return 0;
}
/*
* if we are here, the page is still not completely
* free. Take the global pool lock then to be able
* to add it back to the lru list
*/
spin_lock(&pool->lock);
list_add(&page->lru, &pool->lru);
spin_unlock(&pool->lock);
z3fold_page_unlock(zhdr);
clear_bit(PAGE_CLAIMED, &page->private);
}
/* We started off locked to we need to lock the pool back */
spin_lock(&pool->lock);
}
spin_unlock(&pool->lock);
return -EAGAIN;
}
/**
* z3fold_map() - maps the allocation associated with the given handle
* @pool: pool in which the allocation resides
* @handle: handle associated with the allocation to be mapped
*
* Extracts the buddy number from handle and constructs the pointer to the
* correct starting chunk within the page.
*
* Returns: a pointer to the mapped allocation
*/
static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
{
struct z3fold_header *zhdr;
struct page *page;
void *addr;
enum buddy buddy;
zhdr = handle_to_z3fold_header(handle);
addr = zhdr;
page = virt_to_page(zhdr);
if (test_bit(PAGE_HEADLESS, &page->private))
goto out;
z3fold_page_lock(zhdr);
buddy = handle_to_buddy(handle);
switch (buddy) {
case FIRST:
addr += ZHDR_SIZE_ALIGNED;
break;
case MIDDLE:
addr += zhdr->start_middle << CHUNK_SHIFT;
set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
break;
case LAST:
addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
break;
default:
pr_err("unknown buddy id %d\n", buddy);
WARN_ON(1);
addr = NULL;
break;
}
if (addr)
zhdr->mapped_count++;
z3fold_page_unlock(zhdr);
out:
return addr;
}
/**
* z3fold_unmap() - unmaps the allocation associated with the given handle
* @pool: pool in which the allocation resides
* @handle: handle associated with the allocation to be unmapped
*/
static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
{
struct z3fold_header *zhdr;
struct page *page;
enum buddy buddy;
zhdr = handle_to_z3fold_header(handle);
page = virt_to_page(zhdr);
if (test_bit(PAGE_HEADLESS, &page->private))
return;
z3fold_page_lock(zhdr);
buddy = handle_to_buddy(handle);
if (buddy == MIDDLE)
clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
zhdr->mapped_count--;
z3fold_page_unlock(zhdr);
}
/**
* z3fold_get_pool_size() - gets the z3fold pool size in pages
* @pool: pool whose size is being queried
*
* Returns: size in pages of the given pool.
*/
static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
{
return atomic64_read(&pool->pages_nr);
}
static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
{
struct z3fold_header *zhdr;
struct z3fold_pool *pool;
VM_BUG_ON_PAGE(!PageMovable(page), page);
VM_BUG_ON_PAGE(PageIsolated(page), page);
if (test_bit(PAGE_HEADLESS, &page->private) ||
test_bit(PAGE_CLAIMED, &page->private))
return false;
zhdr = page_address(page);
z3fold_page_lock(zhdr);
if (test_bit(NEEDS_COMPACTING, &page->private) ||
test_bit(PAGE_STALE, &page->private))
goto out;
pool = zhdr_to_pool(zhdr);
if (zhdr->mapped_count == 0) {
kref_get(&zhdr->refcount);
if (!list_empty(&zhdr->buddy))
list_del_init(&zhdr->buddy);
spin_lock(&pool->lock);
if (!list_empty(&page->lru))
list_del(&page->lru);
spin_unlock(&pool->lock);
z3fold_page_unlock(zhdr);
return true;
}
out:
z3fold_page_unlock(zhdr);
return false;
}
static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
struct page *page, enum migrate_mode mode)
{
struct z3fold_header *zhdr, *new_zhdr;
struct z3fold_pool *pool;
struct address_space *new_mapping;
VM_BUG_ON_PAGE(!PageMovable(page), page);
VM_BUG_ON_PAGE(!PageIsolated(page), page);
VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
zhdr = page_address(page);
pool = zhdr_to_pool(zhdr);
if (!z3fold_page_trylock(zhdr)) {
return -EAGAIN;
}
if (zhdr->mapped_count != 0) {
z3fold_page_unlock(zhdr);
return -EBUSY;
}
if (work_pending(&zhdr->work)) {
z3fold_page_unlock(zhdr);
return -EAGAIN;
}
new_zhdr = page_address(newpage);
memcpy(new_zhdr, zhdr, PAGE_SIZE);
newpage->private = page->private;
page->private = 0;
z3fold_page_unlock(zhdr);
spin_lock_init(&new_zhdr->page_lock);
INIT_WORK(&new_zhdr->work, compact_page_work);
/*
* z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
* so we only have to reinitialize it.
*/
INIT_LIST_HEAD(&new_zhdr->buddy);
new_mapping = page_mapping(page);
__ClearPageMovable(page);
ClearPagePrivate(page);
get_page(newpage);
z3fold_page_lock(new_zhdr);
if (new_zhdr->first_chunks)
encode_handle(new_zhdr, FIRST);
if (new_zhdr->last_chunks)
encode_handle(new_zhdr, LAST);
if (new_zhdr->middle_chunks)
encode_handle(new_zhdr, MIDDLE);
set_bit(NEEDS_COMPACTING, &newpage->private);
new_zhdr->cpu = smp_processor_id();
spin_lock(&pool->lock);
list_add(&newpage->lru, &pool->lru);
spin_unlock(&pool->lock);
__SetPageMovable(newpage, new_mapping);
z3fold_page_unlock(new_zhdr);
queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
page_mapcount_reset(page);
put_page(page);
return 0;
}
static void z3fold_page_putback(struct page *page)
{
struct z3fold_header *zhdr;
struct z3fold_pool *pool;
zhdr = page_address(page);
pool = zhdr_to_pool(zhdr);
z3fold_page_lock(zhdr);
if (!list_empty(&zhdr->buddy))
list_del_init(&zhdr->buddy);
INIT_LIST_HEAD(&page->lru);
if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
atomic64_dec(&pool->pages_nr);
return;
}
spin_lock(&pool->lock);
list_add(&page->lru, &pool->lru);
spin_unlock(&pool->lock);
z3fold_page_unlock(zhdr);
}
static const struct address_space_operations z3fold_aops = {
.isolate_page = z3fold_page_isolate,
.migratepage = z3fold_page_migrate,
.putback_page = z3fold_page_putback,
};
/*****************
* zpool
****************/
static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
{
if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
return pool->zpool_ops->evict(pool->zpool, handle);
else
return -ENOENT;
}
static const struct z3fold_ops z3fold_zpool_ops = {
.evict = z3fold_zpool_evict
};
static void *z3fold_zpool_create(const char *name, gfp_t gfp,
const struct zpool_ops *zpool_ops,
struct zpool *zpool)
{
struct z3fold_pool *pool;
pool = z3fold_create_pool(name, gfp,
zpool_ops ? &z3fold_zpool_ops : NULL);
if (pool) {
pool->zpool = zpool;
pool->zpool_ops = zpool_ops;
}
return pool;
}
static void z3fold_zpool_destroy(void *pool)
{
z3fold_destroy_pool(pool);
}
static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
unsigned long *handle)
{
return z3fold_alloc(pool, size, gfp, handle);
}
static void z3fold_zpool_free(void *pool, unsigned long handle)
{
z3fold_free(pool, handle);
}
static int z3fold_zpool_shrink(void *pool, unsigned int pages,
unsigned int *reclaimed)
{
unsigned int total = 0;
int ret = -EINVAL;
while (total < pages) {
ret = z3fold_reclaim_page(pool, 8);
if (ret < 0)
break;
total++;
}
if (reclaimed)
*reclaimed = total;
return ret;
}
static void *z3fold_zpool_map(void *pool, unsigned long handle,
enum zpool_mapmode mm)
{
return z3fold_map(pool, handle);
}
static void z3fold_zpool_unmap(void *pool, unsigned long handle)
{
z3fold_unmap(pool, handle);
}
static u64 z3fold_zpool_total_size(void *pool)
{
return z3fold_get_pool_size(pool) * PAGE_SIZE;
}
static struct zpool_driver z3fold_zpool_driver = {
.type = "z3fold",
.owner = THIS_MODULE,
.create = z3fold_zpool_create,
.destroy = z3fold_zpool_destroy,
.malloc = z3fold_zpool_malloc,
.free = z3fold_zpool_free,
.shrink = z3fold_zpool_shrink,
.map = z3fold_zpool_map,
.unmap = z3fold_zpool_unmap,
.total_size = z3fold_zpool_total_size,
};
MODULE_ALIAS("zpool-z3fold");
static int __init init_z3fold(void)
{
int ret;
/* Make sure the z3fold header is not larger than the page size */
BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
ret = z3fold_mount();
if (ret)
return ret;
zpool_register_driver(&z3fold_zpool_driver);
return 0;
}
static void __exit exit_z3fold(void)
{
z3fold_unmount();
zpool_unregister_driver(&z3fold_zpool_driver);
}
module_init(init_z3fold);
module_exit(exit_z3fold);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");