blob: 7c76b396b74cfdb39b761124556ee4e428510fdf [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/preempt.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/zpool.h>
#include <linux/kmemleak.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 (TOTAL_CHUNKS - ZHDR_CHUNKS)
#define BUDDY_MASK (0x3)
#define BUDDY_SHIFT 2
#define SLOTS_ALIGN (0x40)
/*****************
* Structures
*****************/
struct z3fold_pool;
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 */
rwlock_t lock;
};
#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;
unsigned short foreign_handles:2;
};
/**
* struct z3fold_pool - stores metadata for each z3fold pool
* @name: pool name
* @lock: protects pool unbuddied 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.
* @stale: list of pages marked for freeing
* @pages_nr: number of z3fold pages in the pool.
* @c_handle: cache for z3fold_buddy_slots allocation
* @compact_wq: workqueue for page layout background optimization
* @release_wq: workqueue for safe page release
* @work: work_struct for safe page release
*
* 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 stale;
atomic64_t pages_nr;
struct kmem_cache *c_handle;
struct workqueue_struct *compact_wq;
struct workqueue_struct *release_wq;
struct work_struct work;
};
/*
* 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 */
PAGE_MIGRATED, /* page is migrated and soon to be released */
};
/*
* handle flags, go under HANDLE_FLAG_MASK
*/
enum z3fold_handle_flags {
HANDLES_NOFREE = 0,
};
/*
* Forward declarations
*/
static struct z3fold_header *__z3fold_alloc(struct z3fold_pool *, size_t, bool);
static void compact_page_work(struct work_struct *w);
/*****************
* 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 inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
gfp_t gfp)
{
struct z3fold_buddy_slots *slots = kmem_cache_zalloc(pool->c_handle,
gfp);
if (slots) {
/* It will be freed separately in free_handle(). */
kmemleak_not_leak(slots);
slots->pool = (unsigned long)pool;
rwlock_init(&slots->lock);
}
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));
}
/* 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);
}
/* return locked z3fold page if it's not headless */
static inline struct z3fold_header *get_z3fold_header(unsigned long handle)
{
struct z3fold_buddy_slots *slots;
struct z3fold_header *zhdr;
int locked = 0;
if (!(handle & (1 << PAGE_HEADLESS))) {
slots = handle_to_slots(handle);
do {
unsigned long addr;
read_lock(&slots->lock);
addr = *(unsigned long *)handle;
zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
locked = z3fold_page_trylock(zhdr);
read_unlock(&slots->lock);
if (locked) {
struct page *page = virt_to_page(zhdr);
if (!test_bit(PAGE_MIGRATED, &page->private))
break;
z3fold_page_unlock(zhdr);
}
cpu_relax();
} while (true);
} else {
zhdr = (struct z3fold_header *)(handle & PAGE_MASK);
}
return zhdr;
}
static inline void put_z3fold_header(struct z3fold_header *zhdr)
{
struct page *page = virt_to_page(zhdr);
if (!test_bit(PAGE_HEADLESS, &page->private))
z3fold_page_unlock(zhdr);
}
static inline void free_handle(unsigned long handle, struct z3fold_header *zhdr)
{
struct z3fold_buddy_slots *slots;
int i;
bool is_free;
if (WARN_ON(*(unsigned long *)handle == 0))
return;
slots = handle_to_slots(handle);
write_lock(&slots->lock);
*(unsigned long *)handle = 0;
if (test_bit(HANDLES_NOFREE, &slots->pool)) {
write_unlock(&slots->lock);
return; /* simple case, nothing else to do */
}
if (zhdr->slots != slots)
zhdr->foreign_handles--;
is_free = true;
for (i = 0; i <= BUDDY_MASK; i++) {
if (slots->slot[i]) {
is_free = false;
break;
}
}
write_unlock(&slots->lock);
if (is_free) {
struct z3fold_pool *pool = slots_to_pool(slots);
if (zhdr->slots == slots)
zhdr->slots = NULL;
kmem_cache_free(pool->c_handle, slots);
}
}
/* 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;
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);
clear_bit(PAGE_MIGRATED, &page->private);
if (headless)
return zhdr;
slots = alloc_slots(pool, gfp);
if (!slots)
return NULL;
memset(zhdr, 0, sizeof(*zhdr));
spin_lock_init(&zhdr->page_lock);
kref_init(&zhdr->refcount);
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);
}
__free_page(page);
}
/* 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);
write_lock(&slots->lock);
slots->slot[idx] = h;
write_unlock(&slots->lock);
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);
}
/* only for LAST bud, returns zero otherwise */
static unsigned short handle_to_chunks(unsigned long handle)
{
struct z3fold_buddy_slots *slots = handle_to_slots(handle);
unsigned long addr;
read_lock(&slots->lock);
addr = *(unsigned long *)handle;
read_unlock(&slots->lock);
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;
struct z3fold_buddy_slots *slots = handle_to_slots(handle);
unsigned long addr;
read_lock(&slots->lock);
WARN_ON(handle & (1 << PAGE_HEADLESS));
addr = *(unsigned long *)handle;
read_unlock(&slots->lock);
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);
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);
atomic64_dec(&pool->pages_nr);
}
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 inline int put_z3fold_locked(struct z3fold_header *zhdr)
{
return kref_put(&zhdr->refcount, release_z3fold_page_locked);
}
static inline int put_z3fold_locked_list(struct z3fold_header *zhdr)
{
return kref_put(&zhdr->refcount, release_z3fold_page_locked_list);
}
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;
int freechunks = num_free_chunks(zhdr);
migrate_disable();
unbuddied = this_cpu_ptr(pool->unbuddied);
spin_lock(&pool->lock);
list_add(&zhdr->buddy, &unbuddied[freechunks]);
spin_unlock(&pool->lock);
zhdr->cpu = smp_processor_id();
migrate_enable();
}
}
static inline enum buddy get_free_buddy(struct z3fold_header *zhdr, int chunks)
{
enum buddy bud = HEADLESS;
if (zhdr->middle_chunks) {
if (!zhdr->first_chunks &&
chunks <= zhdr->start_middle - ZHDR_CHUNKS)
bud = FIRST;
else if (!zhdr->last_chunks)
bud = LAST;
} else {
if (!zhdr->first_chunks)
bud = FIRST;
else if (!zhdr->last_chunks)
bud = LAST;
else
bud = MIDDLE;
}
return bud;
}
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);
}
static inline bool buddy_single(struct z3fold_header *zhdr)
{
return !((zhdr->first_chunks && zhdr->middle_chunks) ||
(zhdr->first_chunks && zhdr->last_chunks) ||
(zhdr->middle_chunks && zhdr->last_chunks));
}
static struct z3fold_header *compact_single_buddy(struct z3fold_header *zhdr)
{
struct z3fold_pool *pool = zhdr_to_pool(zhdr);
void *p = zhdr;
unsigned long old_handle = 0;
size_t sz = 0;
struct z3fold_header *new_zhdr = NULL;
int first_idx = __idx(zhdr, FIRST);
int middle_idx = __idx(zhdr, MIDDLE);
int last_idx = __idx(zhdr, LAST);
unsigned short *moved_chunks = NULL;
/*
* No need to protect slots here -- all the slots are "local" and
* the page lock is already taken
*/
if (zhdr->first_chunks && zhdr->slots->slot[first_idx]) {
p += ZHDR_SIZE_ALIGNED;
sz = zhdr->first_chunks << CHUNK_SHIFT;
old_handle = (unsigned long)&zhdr->slots->slot[first_idx];
moved_chunks = &zhdr->first_chunks;
} else if (zhdr->middle_chunks && zhdr->slots->slot[middle_idx]) {
p += zhdr->start_middle << CHUNK_SHIFT;
sz = zhdr->middle_chunks << CHUNK_SHIFT;
old_handle = (unsigned long)&zhdr->slots->slot[middle_idx];
moved_chunks = &zhdr->middle_chunks;
} else if (zhdr->last_chunks && zhdr->slots->slot[last_idx]) {
p += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
sz = zhdr->last_chunks << CHUNK_SHIFT;
old_handle = (unsigned long)&zhdr->slots->slot[last_idx];
moved_chunks = &zhdr->last_chunks;
}
if (sz > 0) {
enum buddy new_bud = HEADLESS;
short chunks = size_to_chunks(sz);
void *q;
new_zhdr = __z3fold_alloc(pool, sz, false);
if (!new_zhdr)
return NULL;
if (WARN_ON(new_zhdr == zhdr))
goto out_fail;
new_bud = get_free_buddy(new_zhdr, chunks);
q = new_zhdr;
switch (new_bud) {
case FIRST:
new_zhdr->first_chunks = chunks;
q += ZHDR_SIZE_ALIGNED;
break;
case MIDDLE:
new_zhdr->middle_chunks = chunks;
new_zhdr->start_middle =
new_zhdr->first_chunks + ZHDR_CHUNKS;
q += new_zhdr->start_middle << CHUNK_SHIFT;
break;
case LAST:
new_zhdr->last_chunks = chunks;
q += PAGE_SIZE - (new_zhdr->last_chunks << CHUNK_SHIFT);
break;
default:
goto out_fail;
}
new_zhdr->foreign_handles++;
memcpy(q, p, sz);
write_lock(&zhdr->slots->lock);
*(unsigned long *)old_handle = (unsigned long)new_zhdr +
__idx(new_zhdr, new_bud);
if (new_bud == LAST)
*(unsigned long *)old_handle |=
(new_zhdr->last_chunks << BUDDY_SHIFT);
write_unlock(&zhdr->slots->lock);
add_to_unbuddied(pool, new_zhdr);
z3fold_page_unlock(new_zhdr);
*moved_chunks = 0;
}
return new_zhdr;
out_fail:
if (new_zhdr && !put_z3fold_locked(new_zhdr)) {
add_to_unbuddied(pool, new_zhdr);
z3fold_page_unlock(new_zhdr);
}
return NULL;
}
#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 (put_z3fold_locked(zhdr))
return;
if (test_bit(PAGE_STALE, &page->private) ||
test_and_set_bit(PAGE_CLAIMED, &page->private)) {
z3fold_page_unlock(zhdr);
return;
}
if (!zhdr->foreign_handles && buddy_single(zhdr) &&
zhdr->mapped_count == 0 && compact_single_buddy(zhdr)) {
if (!put_z3fold_locked(zhdr)) {
clear_bit(PAGE_CLAIMED, &page->private);
z3fold_page_unlock(zhdr);
}
return;
}
z3fold_compact_page(zhdr);
add_to_unbuddied(pool, zhdr);
clear_bit(PAGE_CLAIMED, &page->private);
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:
migrate_disable();
/* First, try to find an unbuddied z3fold page. */
unbuddied = this_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);
if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
struct z3fold_header, buddy)) ||
!z3fold_page_trylock(zhdr)) {
spin_unlock(&pool->lock);
zhdr = NULL;
migrate_enable();
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) ||
test_bit(PAGE_CLAIMED, &page->private)) {
z3fold_page_unlock(zhdr);
zhdr = NULL;
migrate_enable();
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;
}
migrate_enable();
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) ||
test_bit(PAGE_CLAIMED, &page->private)) {
z3fold_page_unlock(zhdr);
zhdr = NULL;
if (can_sleep)
cond_resched();
continue;
}
kref_get(&zhdr->refcount);
break;
}
}
if (zhdr && !zhdr->slots) {
zhdr->slots = alloc_slots(pool, GFP_ATOMIC);
if (!zhdr->slots)
goto out_fail;
}
return zhdr;
out_fail:
if (!put_z3fold_locked(zhdr)) {
add_to_unbuddied(pool, zhdr);
z3fold_page_unlock(zhdr);
}
return NULL;
}
/*
* API Functions
*/
/**
* z3fold_create_pool() - create a new z3fold pool
* @name: pool name
* @gfp: gfp flags when allocating the z3fold pool structure
*
* 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)
{
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,
__alignof__(struct list_head));
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->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;
INIT_WORK(&pool->work, free_pages_work);
return pool;
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);
free_percpu(pool->unbuddied);
kfree(pool);
}
static const struct movable_operations z3fold_mops;
/**
* 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.
*
* 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 || (gfp & __GFP_HIGHMEM))
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) {
bud = get_free_buddy(zhdr, chunks);
if (bud == HEADLESS) {
if (!put_z3fold_locked(zhdr))
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 = 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, &z3fold_mops);
unlock_page(page);
} else {
WARN_ON(!trylock_page(page));
__SetPageMovable(page, &z3fold_mops);
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);
*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 PAGE_CLAIMED flag being set, this function
* only sets the first|middle|last_chunks to 0. The page is actually freed
* once all 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 = get_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) {
put_z3fold_header(zhdr);
free_z3fold_page(page, true);
atomic64_dec(&pool->pages_nr);
}
return;
}
/* Non-headless case */
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);
put_z3fold_header(zhdr);
return;
}
if (!page_claimed)
free_handle(handle, zhdr);
if (put_z3fold_locked_list(zhdr))
return;
if (page_claimed) {
/* the page has not been claimed by us */
put_z3fold_header(zhdr);
return;
}
if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
clear_bit(PAGE_CLAIMED, &page->private);
put_z3fold_header(zhdr);
return;
}
if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
zhdr->cpu = -1;
kref_get(&zhdr->refcount);
clear_bit(PAGE_CLAIMED, &page->private);
do_compact_page(zhdr, true);
return;
}
kref_get(&zhdr->refcount);
clear_bit(PAGE_CLAIMED, &page->private);
queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
put_z3fold_header(zhdr);
}
/**
* 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 = get_z3fold_header(handle);
addr = zhdr;
page = virt_to_page(zhdr);
if (test_bit(PAGE_HEADLESS, &page->private))
goto out;
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++;
out:
put_z3fold_header(zhdr);
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 = get_z3fold_header(handle);
page = virt_to_page(zhdr);
if (test_bit(PAGE_HEADLESS, &page->private))
return;
buddy = handle_to_buddy(handle);
if (buddy == MIDDLE)
clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
zhdr->mapped_count--;
put_z3fold_header(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(PageIsolated(page), page);
if (test_bit(PAGE_HEADLESS, &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;
if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
goto out;
if (test_and_set_bit(PAGE_CLAIMED, &page->private))
goto out;
pool = zhdr_to_pool(zhdr);
spin_lock(&pool->lock);
if (!list_empty(&zhdr->buddy))
list_del_init(&zhdr->buddy);
spin_unlock(&pool->lock);
kref_get(&zhdr->refcount);
z3fold_page_unlock(zhdr);
return true;
out:
z3fold_page_unlock(zhdr);
return false;
}
static int z3fold_page_migrate(struct page *newpage, struct page *page,
enum migrate_mode mode)
{
struct z3fold_header *zhdr, *new_zhdr;
struct z3fold_pool *pool;
VM_BUG_ON_PAGE(!PageIsolated(page), page);
VM_BUG_ON_PAGE(!test_bit(PAGE_CLAIMED, &page->private), 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 || zhdr->foreign_handles != 0) {
clear_bit(PAGE_CLAIMED, &page->private);
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;
set_bit(PAGE_MIGRATED, &page->private);
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);
__ClearPageMovable(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();
__SetPageMovable(newpage, &z3fold_mops);
z3fold_page_unlock(new_zhdr);
queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
/* PAGE_CLAIMED and PAGE_MIGRATED are cleared now. */
page->private = 0;
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 (put_z3fold_locked(zhdr))
return;
if (list_empty(&zhdr->buddy))
add_to_unbuddied(pool, zhdr);
clear_bit(PAGE_CLAIMED, &page->private);
z3fold_page_unlock(zhdr);
}
static const struct movable_operations z3fold_mops = {
.isolate_page = z3fold_page_isolate,
.migrate_page = z3fold_page_migrate,
.putback_page = z3fold_page_putback,
};
/*****************
* zpool
****************/
static void *z3fold_zpool_create(const char *name, gfp_t gfp)
{
return z3fold_create_pool(name, gfp);
}
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 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",
.sleep_mapped = true,
.owner = THIS_MODULE,
.create = z3fold_zpool_create,
.destroy = z3fold_zpool_destroy,
.malloc = z3fold_zpool_malloc,
.free = z3fold_zpool_free,
.map = z3fold_zpool_map,
.unmap = z3fold_zpool_unmap,
.total_size = z3fold_zpool_total_size,
};
MODULE_ALIAS("zpool-z3fold");
static int __init init_z3fold(void)
{
/*
* Make sure the z3fold header is not larger than the page size and
* there has remaining spaces for its buddy.
*/
BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE - CHUNK_SIZE);
zpool_register_driver(&z3fold_zpool_driver);
return 0;
}
static void __exit exit_z3fold(void)
{
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");