linux/mm/zsmalloc.c
Nhat Pham 9997bc0175 zsmalloc: implement writeback mechanism for zsmalloc
This commit adds the writeback mechanism for zsmalloc, analogous to the
zbud allocator.  Zsmalloc will attempt to determine the coldest zspage
(i.e least recently used) in the pool, and attempt to write back all the
stored compressed objects via the pool's evict handler.

Link: https://lkml.kernel.org/r/20221128191616.1261026-7-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-12-11 18:12:10 -08:00

2610 lines
63 KiB
C

/*
* zsmalloc memory allocator
*
* Copyright (C) 2011 Nitin Gupta
* Copyright (C) 2012, 2013 Minchan Kim
*
* This code is released using a dual license strategy: BSD/GPL
* You can choose the license that better fits your requirements.
*
* Released under the terms of 3-clause BSD License
* Released under the terms of GNU General Public License Version 2.0
*/
/*
* Following is how we use various fields and flags of underlying
* struct page(s) to form a zspage.
*
* Usage of struct page fields:
* page->private: points to zspage
* page->index: links together all component pages of a zspage
* For the huge page, this is always 0, so we use this field
* to store handle.
* page->page_type: first object offset in a subpage of zspage
*
* Usage of struct page flags:
* PG_private: identifies the first component page
* PG_owner_priv_1: identifies the huge component page
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
/*
* lock ordering:
* page_lock
* pool->lock
* zspage->lock
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/bitops.h>
#include <linux/errno.h>
#include <linux/highmem.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/pgtable.h>
#include <asm/tlbflush.h>
#include <linux/cpumask.h>
#include <linux/cpu.h>
#include <linux/vmalloc.h>
#include <linux/preempt.h>
#include <linux/spinlock.h>
#include <linux/shrinker.h>
#include <linux/types.h>
#include <linux/debugfs.h>
#include <linux/zsmalloc.h>
#include <linux/zpool.h>
#include <linux/migrate.h>
#include <linux/wait.h>
#include <linux/pagemap.h>
#include <linux/fs.h>
#include <linux/local_lock.h>
#define ZSPAGE_MAGIC 0x58
/*
* This must be power of 2 and greater than or equal to sizeof(link_free).
* These two conditions ensure that any 'struct link_free' itself doesn't
* span more than 1 page which avoids complex case of mapping 2 pages simply
* to restore link_free pointer values.
*/
#define ZS_ALIGN 8
/*
* A single 'zspage' is composed of up to 2^N discontiguous 0-order (single)
* pages. ZS_MAX_ZSPAGE_ORDER defines upper limit on N.
*/
#define ZS_MAX_ZSPAGE_ORDER 2
#define ZS_MAX_PAGES_PER_ZSPAGE (_AC(1, UL) << ZS_MAX_ZSPAGE_ORDER)
#define ZS_HANDLE_SIZE (sizeof(unsigned long))
/*
* Object location (<PFN>, <obj_idx>) is encoded as
* a single (unsigned long) handle value.
*
* Note that object index <obj_idx> starts from 0.
*
* This is made more complicated by various memory models and PAE.
*/
#ifndef MAX_POSSIBLE_PHYSMEM_BITS
#ifdef MAX_PHYSMEM_BITS
#define MAX_POSSIBLE_PHYSMEM_BITS MAX_PHYSMEM_BITS
#else
/*
* If this definition of MAX_PHYSMEM_BITS is used, OBJ_INDEX_BITS will just
* be PAGE_SHIFT
*/
#define MAX_POSSIBLE_PHYSMEM_BITS BITS_PER_LONG
#endif
#endif
#define _PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)
/*
* Head in allocated object should have OBJ_ALLOCATED_TAG
* to identify the object was allocated or not.
* It's okay to add the status bit in the least bit because
* header keeps handle which is 4byte-aligned address so we
* have room for two bit at least.
*/
#define OBJ_ALLOCATED_TAG 1
#define OBJ_TAG_BITS 1
#define OBJ_INDEX_BITS (BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS)
#define OBJ_INDEX_MASK ((_AC(1, UL) << OBJ_INDEX_BITS) - 1)
#define HUGE_BITS 1
#define FULLNESS_BITS 2
#define CLASS_BITS 8
#define ISOLATED_BITS 3
#define MAGIC_VAL_BITS 8
#define MAX(a, b) ((a) >= (b) ? (a) : (b))
/* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
#define ZS_MIN_ALLOC_SIZE \
MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
/* each chunk includes extra space to keep handle */
#define ZS_MAX_ALLOC_SIZE PAGE_SIZE
/*
* On systems with 4K page size, this gives 255 size classes! There is a
* trader-off here:
* - Large number of size classes is potentially wasteful as free page are
* spread across these classes
* - Small number of size classes causes large internal fragmentation
* - Probably its better to use specific size classes (empirically
* determined). NOTE: all those class sizes must be set as multiple of
* ZS_ALIGN to make sure link_free itself never has to span 2 pages.
*
* ZS_MIN_ALLOC_SIZE and ZS_SIZE_CLASS_DELTA must be multiple of ZS_ALIGN
* (reason above)
*/
#define ZS_SIZE_CLASS_DELTA (PAGE_SIZE >> CLASS_BITS)
#define ZS_SIZE_CLASSES (DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \
ZS_SIZE_CLASS_DELTA) + 1)
enum fullness_group {
ZS_EMPTY,
ZS_ALMOST_EMPTY,
ZS_ALMOST_FULL,
ZS_FULL,
NR_ZS_FULLNESS,
};
enum class_stat_type {
CLASS_EMPTY,
CLASS_ALMOST_EMPTY,
CLASS_ALMOST_FULL,
CLASS_FULL,
OBJ_ALLOCATED,
OBJ_USED,
NR_ZS_STAT_TYPE,
};
struct zs_size_stat {
unsigned long objs[NR_ZS_STAT_TYPE];
};
#ifdef CONFIG_ZSMALLOC_STAT
static struct dentry *zs_stat_root;
#endif
/*
* We assign a page to ZS_ALMOST_EMPTY fullness group when:
* n <= N / f, where
* n = number of allocated objects
* N = total number of objects zspage can store
* f = fullness_threshold_frac
*
* Similarly, we assign zspage to:
* ZS_ALMOST_FULL when n > N / f
* ZS_EMPTY when n == 0
* ZS_FULL when n == N
*
* (see: fix_fullness_group())
*/
static const int fullness_threshold_frac = 4;
static size_t huge_class_size;
struct size_class {
struct list_head fullness_list[NR_ZS_FULLNESS];
/*
* Size of objects stored in this class. Must be multiple
* of ZS_ALIGN.
*/
int size;
int objs_per_zspage;
/* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
int pages_per_zspage;
unsigned int index;
struct zs_size_stat stats;
};
/*
* Placed within free objects to form a singly linked list.
* For every zspage, zspage->freeobj gives head of this list.
*
* This must be power of 2 and less than or equal to ZS_ALIGN
*/
struct link_free {
union {
/*
* Free object index;
* It's valid for non-allocated object
*/
unsigned long next;
/*
* Handle of allocated object.
*/
unsigned long handle;
};
};
struct zs_pool {
const char *name;
struct size_class *size_class[ZS_SIZE_CLASSES];
struct kmem_cache *handle_cachep;
struct kmem_cache *zspage_cachep;
atomic_long_t pages_allocated;
struct zs_pool_stats stats;
/* Compact classes */
struct shrinker shrinker;
#ifdef CONFIG_ZPOOL
/* List tracking the zspages in LRU order by most recently added object */
struct list_head lru;
struct zpool *zpool;
const struct zpool_ops *zpool_ops;
#endif
#ifdef CONFIG_ZSMALLOC_STAT
struct dentry *stat_dentry;
#endif
#ifdef CONFIG_COMPACTION
struct work_struct free_work;
#endif
spinlock_t lock;
};
struct zspage {
struct {
unsigned int huge:HUGE_BITS;
unsigned int fullness:FULLNESS_BITS;
unsigned int class:CLASS_BITS + 1;
unsigned int isolated:ISOLATED_BITS;
unsigned int magic:MAGIC_VAL_BITS;
};
unsigned int inuse;
unsigned int freeobj;
struct page *first_page;
struct list_head list; /* fullness list */
#ifdef CONFIG_ZPOOL
/* links the zspage to the lru list in the pool */
struct list_head lru;
bool under_reclaim;
/* list of unfreed handles whose objects have been reclaimed */
unsigned long *deferred_handles;
#endif
struct zs_pool *pool;
rwlock_t lock;
};
struct mapping_area {
local_lock_t lock;
char *vm_buf; /* copy buffer for objects that span pages */
char *vm_addr; /* address of kmap_atomic()'ed pages */
enum zs_mapmode vm_mm; /* mapping mode */
};
/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
static void SetZsHugePage(struct zspage *zspage)
{
zspage->huge = 1;
}
static bool ZsHugePage(struct zspage *zspage)
{
return zspage->huge;
}
static void migrate_lock_init(struct zspage *zspage);
static void migrate_read_lock(struct zspage *zspage);
static void migrate_read_unlock(struct zspage *zspage);
#ifdef CONFIG_COMPACTION
static void migrate_write_lock(struct zspage *zspage);
static void migrate_write_lock_nested(struct zspage *zspage);
static void migrate_write_unlock(struct zspage *zspage);
static void kick_deferred_free(struct zs_pool *pool);
static void init_deferred_free(struct zs_pool *pool);
static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage);
#else
static void migrate_write_lock(struct zspage *zspage) {}
static void migrate_write_lock_nested(struct zspage *zspage) {}
static void migrate_write_unlock(struct zspage *zspage) {}
static void kick_deferred_free(struct zs_pool *pool) {}
static void init_deferred_free(struct zs_pool *pool) {}
static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage) {}
#endif
static int create_cache(struct zs_pool *pool)
{
pool->handle_cachep = kmem_cache_create("zs_handle", ZS_HANDLE_SIZE,
0, 0, NULL);
if (!pool->handle_cachep)
return 1;
pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
0, 0, NULL);
if (!pool->zspage_cachep) {
kmem_cache_destroy(pool->handle_cachep);
pool->handle_cachep = NULL;
return 1;
}
return 0;
}
static void destroy_cache(struct zs_pool *pool)
{
kmem_cache_destroy(pool->handle_cachep);
kmem_cache_destroy(pool->zspage_cachep);
}
static unsigned long cache_alloc_handle(struct zs_pool *pool, gfp_t gfp)
{
return (unsigned long)kmem_cache_alloc(pool->handle_cachep,
gfp & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
}
static void cache_free_handle(struct zs_pool *pool, unsigned long handle)
{
kmem_cache_free(pool->handle_cachep, (void *)handle);
}
static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags)
{
return kmem_cache_zalloc(pool->zspage_cachep,
flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
}
static void cache_free_zspage(struct zs_pool *pool, struct zspage *zspage)
{
kmem_cache_free(pool->zspage_cachep, zspage);
}
/* pool->lock(which owns the handle) synchronizes races */
static void record_obj(unsigned long handle, unsigned long obj)
{
*(unsigned long *)handle = obj;
}
/* zpool driver */
#ifdef CONFIG_ZPOOL
static void *zs_zpool_create(const char *name, gfp_t gfp,
const struct zpool_ops *zpool_ops,
struct zpool *zpool)
{
/*
* Ignore global gfp flags: zs_malloc() may be invoked from
* different contexts and its caller must provide a valid
* gfp mask.
*/
struct zs_pool *pool = zs_create_pool(name);
if (pool) {
pool->zpool = zpool;
pool->zpool_ops = zpool_ops;
}
return pool;
}
static void zs_zpool_destroy(void *pool)
{
zs_destroy_pool(pool);
}
static int zs_zpool_malloc(void *pool, size_t size, gfp_t gfp,
unsigned long *handle)
{
*handle = zs_malloc(pool, size, gfp);
if (IS_ERR_VALUE(*handle))
return PTR_ERR((void *)*handle);
return 0;
}
static void zs_zpool_free(void *pool, unsigned long handle)
{
zs_free(pool, handle);
}
static int zs_reclaim_page(struct zs_pool *pool, unsigned int retries);
static int zs_zpool_shrink(void *pool, unsigned int pages,
unsigned int *reclaimed)
{
unsigned int total = 0;
int ret = -EINVAL;
while (total < pages) {
ret = zs_reclaim_page(pool, 8);
if (ret < 0)
break;
total++;
}
if (reclaimed)
*reclaimed = total;
return ret;
}
static void *zs_zpool_map(void *pool, unsigned long handle,
enum zpool_mapmode mm)
{
enum zs_mapmode zs_mm;
switch (mm) {
case ZPOOL_MM_RO:
zs_mm = ZS_MM_RO;
break;
case ZPOOL_MM_WO:
zs_mm = ZS_MM_WO;
break;
case ZPOOL_MM_RW:
default:
zs_mm = ZS_MM_RW;
break;
}
return zs_map_object(pool, handle, zs_mm);
}
static void zs_zpool_unmap(void *pool, unsigned long handle)
{
zs_unmap_object(pool, handle);
}
static u64 zs_zpool_total_size(void *pool)
{
return zs_get_total_pages(pool) << PAGE_SHIFT;
}
static struct zpool_driver zs_zpool_driver = {
.type = "zsmalloc",
.owner = THIS_MODULE,
.create = zs_zpool_create,
.destroy = zs_zpool_destroy,
.malloc_support_movable = true,
.malloc = zs_zpool_malloc,
.free = zs_zpool_free,
.shrink = zs_zpool_shrink,
.map = zs_zpool_map,
.unmap = zs_zpool_unmap,
.total_size = zs_zpool_total_size,
};
MODULE_ALIAS("zpool-zsmalloc");
#endif /* CONFIG_ZPOOL */
/* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
static DEFINE_PER_CPU(struct mapping_area, zs_map_area) = {
.lock = INIT_LOCAL_LOCK(lock),
};
static __maybe_unused int is_first_page(struct page *page)
{
return PagePrivate(page);
}
/* Protected by pool->lock */
static inline int get_zspage_inuse(struct zspage *zspage)
{
return zspage->inuse;
}
static inline void mod_zspage_inuse(struct zspage *zspage, int val)
{
zspage->inuse += val;
}
static inline struct page *get_first_page(struct zspage *zspage)
{
struct page *first_page = zspage->first_page;
VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
return first_page;
}
static inline unsigned int get_first_obj_offset(struct page *page)
{
return page->page_type;
}
static inline void set_first_obj_offset(struct page *page, unsigned int offset)
{
page->page_type = offset;
}
static inline unsigned int get_freeobj(struct zspage *zspage)
{
return zspage->freeobj;
}
static inline void set_freeobj(struct zspage *zspage, unsigned int obj)
{
zspage->freeobj = obj;
}
static void get_zspage_mapping(struct zspage *zspage,
unsigned int *class_idx,
enum fullness_group *fullness)
{
BUG_ON(zspage->magic != ZSPAGE_MAGIC);
*fullness = zspage->fullness;
*class_idx = zspage->class;
}
static struct size_class *zspage_class(struct zs_pool *pool,
struct zspage *zspage)
{
return pool->size_class[zspage->class];
}
static void set_zspage_mapping(struct zspage *zspage,
unsigned int class_idx,
enum fullness_group fullness)
{
zspage->class = class_idx;
zspage->fullness = fullness;
}
/*
* zsmalloc divides the pool into various size classes where each
* class maintains a list of zspages where each zspage is divided
* into equal sized chunks. Each allocation falls into one of these
* classes depending on its size. This function returns index of the
* size class which has chunk size big enough to hold the given size.
*/
static int get_size_class_index(int size)
{
int idx = 0;
if (likely(size > ZS_MIN_ALLOC_SIZE))
idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
ZS_SIZE_CLASS_DELTA);
return min_t(int, ZS_SIZE_CLASSES - 1, idx);
}
/* type can be of enum type class_stat_type or fullness_group */
static inline void class_stat_inc(struct size_class *class,
int type, unsigned long cnt)
{
class->stats.objs[type] += cnt;
}
/* type can be of enum type class_stat_type or fullness_group */
static inline void class_stat_dec(struct size_class *class,
int type, unsigned long cnt)
{
class->stats.objs[type] -= cnt;
}
/* type can be of enum type class_stat_type or fullness_group */
static inline unsigned long zs_stat_get(struct size_class *class,
int type)
{
return class->stats.objs[type];
}
#ifdef CONFIG_ZSMALLOC_STAT
static void __init zs_stat_init(void)
{
if (!debugfs_initialized()) {
pr_warn("debugfs not available, stat dir not created\n");
return;
}
zs_stat_root = debugfs_create_dir("zsmalloc", NULL);
}
static void __exit zs_stat_exit(void)
{
debugfs_remove_recursive(zs_stat_root);
}
static unsigned long zs_can_compact(struct size_class *class);
static int zs_stats_size_show(struct seq_file *s, void *v)
{
int i;
struct zs_pool *pool = s->private;
struct size_class *class;
int objs_per_zspage;
unsigned long class_almost_full, class_almost_empty;
unsigned long obj_allocated, obj_used, pages_used, freeable;
unsigned long total_class_almost_full = 0, total_class_almost_empty = 0;
unsigned long total_objs = 0, total_used_objs = 0, total_pages = 0;
unsigned long total_freeable = 0;
seq_printf(s, " %5s %5s %11s %12s %13s %10s %10s %16s %8s\n",
"class", "size", "almost_full", "almost_empty",
"obj_allocated", "obj_used", "pages_used",
"pages_per_zspage", "freeable");
for (i = 0; i < ZS_SIZE_CLASSES; i++) {
class = pool->size_class[i];
if (class->index != i)
continue;
spin_lock(&pool->lock);
class_almost_full = zs_stat_get(class, CLASS_ALMOST_FULL);
class_almost_empty = zs_stat_get(class, CLASS_ALMOST_EMPTY);
obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
obj_used = zs_stat_get(class, OBJ_USED);
freeable = zs_can_compact(class);
spin_unlock(&pool->lock);
objs_per_zspage = class->objs_per_zspage;
pages_used = obj_allocated / objs_per_zspage *
class->pages_per_zspage;
seq_printf(s, " %5u %5u %11lu %12lu %13lu"
" %10lu %10lu %16d %8lu\n",
i, class->size, class_almost_full, class_almost_empty,
obj_allocated, obj_used, pages_used,
class->pages_per_zspage, freeable);
total_class_almost_full += class_almost_full;
total_class_almost_empty += class_almost_empty;
total_objs += obj_allocated;
total_used_objs += obj_used;
total_pages += pages_used;
total_freeable += freeable;
}
seq_puts(s, "\n");
seq_printf(s, " %5s %5s %11lu %12lu %13lu %10lu %10lu %16s %8lu\n",
"Total", "", total_class_almost_full,
total_class_almost_empty, total_objs,
total_used_objs, total_pages, "", total_freeable);
return 0;
}
DEFINE_SHOW_ATTRIBUTE(zs_stats_size);
static void zs_pool_stat_create(struct zs_pool *pool, const char *name)
{
if (!zs_stat_root) {
pr_warn("no root stat dir, not creating <%s> stat dir\n", name);
return;
}
pool->stat_dentry = debugfs_create_dir(name, zs_stat_root);
debugfs_create_file("classes", S_IFREG | 0444, pool->stat_dentry, pool,
&zs_stats_size_fops);
}
static void zs_pool_stat_destroy(struct zs_pool *pool)
{
debugfs_remove_recursive(pool->stat_dentry);
}
#else /* CONFIG_ZSMALLOC_STAT */
static void __init zs_stat_init(void)
{
}
static void __exit zs_stat_exit(void)
{
}
static inline void zs_pool_stat_create(struct zs_pool *pool, const char *name)
{
}
static inline void zs_pool_stat_destroy(struct zs_pool *pool)
{
}
#endif
/*
* For each size class, zspages are divided into different groups
* depending on how "full" they are. This was done so that we could
* easily find empty or nearly empty zspages when we try to shrink
* the pool (not yet implemented). This function returns fullness
* status of the given page.
*/
static enum fullness_group get_fullness_group(struct size_class *class,
struct zspage *zspage)
{
int inuse, objs_per_zspage;
enum fullness_group fg;
inuse = get_zspage_inuse(zspage);
objs_per_zspage = class->objs_per_zspage;
if (inuse == 0)
fg = ZS_EMPTY;
else if (inuse == objs_per_zspage)
fg = ZS_FULL;
else if (inuse <= 3 * objs_per_zspage / fullness_threshold_frac)
fg = ZS_ALMOST_EMPTY;
else
fg = ZS_ALMOST_FULL;
return fg;
}
/*
* Each size class maintains various freelists and zspages are assigned
* to one of these freelists based on the number of live objects they
* have. This functions inserts the given zspage into the freelist
* identified by <class, fullness_group>.
*/
static void insert_zspage(struct size_class *class,
struct zspage *zspage,
enum fullness_group fullness)
{
struct zspage *head;
class_stat_inc(class, fullness, 1);
head = list_first_entry_or_null(&class->fullness_list[fullness],
struct zspage, list);
/*
* We want to see more ZS_FULL pages and less almost empty/full.
* Put pages with higher ->inuse first.
*/
if (head && get_zspage_inuse(zspage) < get_zspage_inuse(head))
list_add(&zspage->list, &head->list);
else
list_add(&zspage->list, &class->fullness_list[fullness]);
}
/*
* This function removes the given zspage from the freelist identified
* by <class, fullness_group>.
*/
static void remove_zspage(struct size_class *class,
struct zspage *zspage,
enum fullness_group fullness)
{
VM_BUG_ON(list_empty(&class->fullness_list[fullness]));
list_del_init(&zspage->list);
class_stat_dec(class, fullness, 1);
}
/*
* Each size class maintains zspages in different fullness groups depending
* on the number of live objects they contain. When allocating or freeing
* objects, the fullness status of the page can change, say, from ALMOST_FULL
* to ALMOST_EMPTY when freeing an object. This function checks if such
* a status change has occurred for the given page and accordingly moves the
* page from the freelist of the old fullness group to that of the new
* fullness group.
*/
static enum fullness_group fix_fullness_group(struct size_class *class,
struct zspage *zspage)
{
int class_idx;
enum fullness_group currfg, newfg;
get_zspage_mapping(zspage, &class_idx, &currfg);
newfg = get_fullness_group(class, zspage);
if (newfg == currfg)
goto out;
remove_zspage(class, zspage, currfg);
insert_zspage(class, zspage, newfg);
set_zspage_mapping(zspage, class_idx, newfg);
out:
return newfg;
}
/*
* We have to decide on how many pages to link together
* to form a zspage for each size class. This is important
* to reduce wastage due to unusable space left at end of
* each zspage which is given as:
* wastage = Zp % class_size
* usage = Zp - wastage
* where Zp = zspage size = k * PAGE_SIZE where k = 1, 2, ...
*
* For example, for size class of 3/8 * PAGE_SIZE, we should
* link together 3 PAGE_SIZE sized pages to form a zspage
* since then we can perfectly fit in 8 such objects.
*/
static int get_pages_per_zspage(int class_size)
{
int i, max_usedpc = 0;
/* zspage order which gives maximum used size per KB */
int max_usedpc_order = 1;
for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) {
int zspage_size;
int waste, usedpc;
zspage_size = i * PAGE_SIZE;
waste = zspage_size % class_size;
usedpc = (zspage_size - waste) * 100 / zspage_size;
if (usedpc > max_usedpc) {
max_usedpc = usedpc;
max_usedpc_order = i;
}
}
return max_usedpc_order;
}
static struct zspage *get_zspage(struct page *page)
{
struct zspage *zspage = (struct zspage *)page_private(page);
BUG_ON(zspage->magic != ZSPAGE_MAGIC);
return zspage;
}
static struct page *get_next_page(struct page *page)
{
struct zspage *zspage = get_zspage(page);
if (unlikely(ZsHugePage(zspage)))
return NULL;
return (struct page *)page->index;
}
/**
* obj_to_location - get (<page>, <obj_idx>) from encoded object value
* @obj: the encoded object value
* @page: page object resides in zspage
* @obj_idx: object index
*/
static void obj_to_location(unsigned long obj, struct page **page,
unsigned int *obj_idx)
{
obj >>= OBJ_TAG_BITS;
*page = pfn_to_page(obj >> OBJ_INDEX_BITS);
*obj_idx = (obj & OBJ_INDEX_MASK);
}
static void obj_to_page(unsigned long obj, struct page **page)
{
obj >>= OBJ_TAG_BITS;
*page = pfn_to_page(obj >> OBJ_INDEX_BITS);
}
/**
* location_to_obj - get obj value encoded from (<page>, <obj_idx>)
* @page: page object resides in zspage
* @obj_idx: object index
*/
static unsigned long location_to_obj(struct page *page, unsigned int obj_idx)
{
unsigned long obj;
obj = page_to_pfn(page) << OBJ_INDEX_BITS;
obj |= obj_idx & OBJ_INDEX_MASK;
obj <<= OBJ_TAG_BITS;
return obj;
}
static unsigned long handle_to_obj(unsigned long handle)
{
return *(unsigned long *)handle;
}
static bool obj_allocated(struct page *page, void *obj, unsigned long *phandle)
{
unsigned long handle;
struct zspage *zspage = get_zspage(page);
if (unlikely(ZsHugePage(zspage))) {
VM_BUG_ON_PAGE(!is_first_page(page), page);
handle = page->index;
} else
handle = *(unsigned long *)obj;
if (!(handle & OBJ_ALLOCATED_TAG))
return false;
*phandle = handle & ~OBJ_ALLOCATED_TAG;
return true;
}
static void reset_page(struct page *page)
{
__ClearPageMovable(page);
ClearPagePrivate(page);
set_page_private(page, 0);
page_mapcount_reset(page);
page->index = 0;
}
static int trylock_zspage(struct zspage *zspage)
{
struct page *cursor, *fail;
for (cursor = get_first_page(zspage); cursor != NULL; cursor =
get_next_page(cursor)) {
if (!trylock_page(cursor)) {
fail = cursor;
goto unlock;
}
}
return 1;
unlock:
for (cursor = get_first_page(zspage); cursor != fail; cursor =
get_next_page(cursor))
unlock_page(cursor);
return 0;
}
#ifdef CONFIG_ZPOOL
/*
* Free all the deferred handles whose objects are freed in zs_free.
*/
static void free_handles(struct zs_pool *pool, struct zspage *zspage)
{
unsigned long handle = (unsigned long)zspage->deferred_handles;
while (handle) {
unsigned long nxt_handle = handle_to_obj(handle);
cache_free_handle(pool, handle);
handle = nxt_handle;
}
}
#else
static inline void free_handles(struct zs_pool *pool, struct zspage *zspage) {}
#endif
static void __free_zspage(struct zs_pool *pool, struct size_class *class,
struct zspage *zspage)
{
struct page *page, *next;
enum fullness_group fg;
unsigned int class_idx;
get_zspage_mapping(zspage, &class_idx, &fg);
assert_spin_locked(&pool->lock);
VM_BUG_ON(get_zspage_inuse(zspage));
VM_BUG_ON(fg != ZS_EMPTY);
/* Free all deferred handles from zs_free */
free_handles(pool, zspage);
next = page = get_first_page(zspage);
do {
VM_BUG_ON_PAGE(!PageLocked(page), page);
next = get_next_page(page);
reset_page(page);
unlock_page(page);
dec_zone_page_state(page, NR_ZSPAGES);
put_page(page);
page = next;
} while (page != NULL);
cache_free_zspage(pool, zspage);
class_stat_dec(class, OBJ_ALLOCATED, class->objs_per_zspage);
atomic_long_sub(class->pages_per_zspage,
&pool->pages_allocated);
}
static void free_zspage(struct zs_pool *pool, struct size_class *class,
struct zspage *zspage)
{
VM_BUG_ON(get_zspage_inuse(zspage));
VM_BUG_ON(list_empty(&zspage->list));
/*
* Since zs_free couldn't be sleepable, this function cannot call
* lock_page. The page locks trylock_zspage got will be released
* by __free_zspage.
*/
if (!trylock_zspage(zspage)) {
kick_deferred_free(pool);
return;
}
remove_zspage(class, zspage, ZS_EMPTY);
#ifdef CONFIG_ZPOOL
list_del(&zspage->lru);
#endif
__free_zspage(pool, class, zspage);
}
/* Initialize a newly allocated zspage */
static void init_zspage(struct size_class *class, struct zspage *zspage)
{
unsigned int freeobj = 1;
unsigned long off = 0;
struct page *page = get_first_page(zspage);
while (page) {
struct page *next_page;
struct link_free *link;
void *vaddr;
set_first_obj_offset(page, off);
vaddr = kmap_atomic(page);
link = (struct link_free *)vaddr + off / sizeof(*link);
while ((off += class->size) < PAGE_SIZE) {
link->next = freeobj++ << OBJ_TAG_BITS;
link += class->size / sizeof(*link);
}
/*
* We now come to the last (full or partial) object on this
* page, which must point to the first object on the next
* page (if present)
*/
next_page = get_next_page(page);
if (next_page) {
link->next = freeobj++ << OBJ_TAG_BITS;
} else {
/*
* Reset OBJ_TAG_BITS bit to last link to tell
* whether it's allocated object or not.
*/
link->next = -1UL << OBJ_TAG_BITS;
}
kunmap_atomic(vaddr);
page = next_page;
off %= PAGE_SIZE;
}
#ifdef CONFIG_ZPOOL
INIT_LIST_HEAD(&zspage->lru);
zspage->under_reclaim = false;
zspage->deferred_handles = NULL;
#endif
set_freeobj(zspage, 0);
}
static void create_page_chain(struct size_class *class, struct zspage *zspage,
struct page *pages[])
{
int i;
struct page *page;
struct page *prev_page = NULL;
int nr_pages = class->pages_per_zspage;
/*
* Allocate individual pages and link them together as:
* 1. all pages are linked together using page->index
* 2. each sub-page point to zspage using page->private
*
* we set PG_private to identify the first page (i.e. no other sub-page
* has this flag set).
*/
for (i = 0; i < nr_pages; i++) {
page = pages[i];
set_page_private(page, (unsigned long)zspage);
page->index = 0;
if (i == 0) {
zspage->first_page = page;
SetPagePrivate(page);
if (unlikely(class->objs_per_zspage == 1 &&
class->pages_per_zspage == 1))
SetZsHugePage(zspage);
} else {
prev_page->index = (unsigned long)page;
}
prev_page = page;
}
}
/*
* Allocate a zspage for the given size class
*/
static struct zspage *alloc_zspage(struct zs_pool *pool,
struct size_class *class,
gfp_t gfp)
{
int i;
struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE];
struct zspage *zspage = cache_alloc_zspage(pool, gfp);
if (!zspage)
return NULL;
zspage->magic = ZSPAGE_MAGIC;
migrate_lock_init(zspage);
for (i = 0; i < class->pages_per_zspage; i++) {
struct page *page;
page = alloc_page(gfp);
if (!page) {
while (--i >= 0) {
dec_zone_page_state(pages[i], NR_ZSPAGES);
__free_page(pages[i]);
}
cache_free_zspage(pool, zspage);
return NULL;
}
inc_zone_page_state(page, NR_ZSPAGES);
pages[i] = page;
}
create_page_chain(class, zspage, pages);
init_zspage(class, zspage);
zspage->pool = pool;
return zspage;
}
static struct zspage *find_get_zspage(struct size_class *class)
{
int i;
struct zspage *zspage;
for (i = ZS_ALMOST_FULL; i >= ZS_EMPTY; i--) {
zspage = list_first_entry_or_null(&class->fullness_list[i],
struct zspage, list);
if (zspage)
break;
}
return zspage;
}
static inline int __zs_cpu_up(struct mapping_area *area)
{
/*
* Make sure we don't leak memory if a cpu UP notification
* and zs_init() race and both call zs_cpu_up() on the same cpu
*/
if (area->vm_buf)
return 0;
area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);
if (!area->vm_buf)
return -ENOMEM;
return 0;
}
static inline void __zs_cpu_down(struct mapping_area *area)
{
kfree(area->vm_buf);
area->vm_buf = NULL;
}
static void *__zs_map_object(struct mapping_area *area,
struct page *pages[2], int off, int size)
{
int sizes[2];
void *addr;
char *buf = area->vm_buf;
/* disable page faults to match kmap_atomic() return conditions */
pagefault_disable();
/* no read fastpath */
if (area->vm_mm == ZS_MM_WO)
goto out;
sizes[0] = PAGE_SIZE - off;
sizes[1] = size - sizes[0];
/* copy object to per-cpu buffer */
addr = kmap_atomic(pages[0]);
memcpy(buf, addr + off, sizes[0]);
kunmap_atomic(addr);
addr = kmap_atomic(pages[1]);
memcpy(buf + sizes[0], addr, sizes[1]);
kunmap_atomic(addr);
out:
return area->vm_buf;
}
static void __zs_unmap_object(struct mapping_area *area,
struct page *pages[2], int off, int size)
{
int sizes[2];
void *addr;
char *buf;
/* no write fastpath */
if (area->vm_mm == ZS_MM_RO)
goto out;
buf = area->vm_buf;
buf = buf + ZS_HANDLE_SIZE;
size -= ZS_HANDLE_SIZE;
off += ZS_HANDLE_SIZE;
sizes[0] = PAGE_SIZE - off;
sizes[1] = size - sizes[0];
/* copy per-cpu buffer to object */
addr = kmap_atomic(pages[0]);
memcpy(addr + off, buf, sizes[0]);
kunmap_atomic(addr);
addr = kmap_atomic(pages[1]);
memcpy(addr, buf + sizes[0], sizes[1]);
kunmap_atomic(addr);
out:
/* enable page faults to match kunmap_atomic() return conditions */
pagefault_enable();
}
static int zs_cpu_prepare(unsigned int cpu)
{
struct mapping_area *area;
area = &per_cpu(zs_map_area, cpu);
return __zs_cpu_up(area);
}
static int zs_cpu_dead(unsigned int cpu)
{
struct mapping_area *area;
area = &per_cpu(zs_map_area, cpu);
__zs_cpu_down(area);
return 0;
}
static bool can_merge(struct size_class *prev, int pages_per_zspage,
int objs_per_zspage)
{
if (prev->pages_per_zspage == pages_per_zspage &&
prev->objs_per_zspage == objs_per_zspage)
return true;
return false;
}
static bool zspage_full(struct size_class *class, struct zspage *zspage)
{
return get_zspage_inuse(zspage) == class->objs_per_zspage;
}
/**
* zs_lookup_class_index() - Returns index of the zsmalloc &size_class
* that hold objects of the provided size.
* @pool: zsmalloc pool to use
* @size: object size
*
* Context: Any context.
*
* Return: the index of the zsmalloc &size_class that hold objects of the
* provided size.
*/
unsigned int zs_lookup_class_index(struct zs_pool *pool, unsigned int size)
{
struct size_class *class;
class = pool->size_class[get_size_class_index(size)];
return class->index;
}
EXPORT_SYMBOL_GPL(zs_lookup_class_index);
unsigned long zs_get_total_pages(struct zs_pool *pool)
{
return atomic_long_read(&pool->pages_allocated);
}
EXPORT_SYMBOL_GPL(zs_get_total_pages);
/**
* zs_map_object - get address of allocated object from handle.
* @pool: pool from which the object was allocated
* @handle: handle returned from zs_malloc
* @mm: mapping mode to use
*
* Before using an object allocated from zs_malloc, it must be mapped using
* this function. When done with the object, it must be unmapped using
* zs_unmap_object.
*
* Only one object can be mapped per cpu at a time. There is no protection
* against nested mappings.
*
* This function returns with preemption and page faults disabled.
*/
void *zs_map_object(struct zs_pool *pool, unsigned long handle,
enum zs_mapmode mm)
{
struct zspage *zspage;
struct page *page;
unsigned long obj, off;
unsigned int obj_idx;
struct size_class *class;
struct mapping_area *area;
struct page *pages[2];
void *ret;
/*
* Because we use per-cpu mapping areas shared among the
* pools/users, we can't allow mapping in interrupt context
* because it can corrupt another users mappings.
*/
BUG_ON(in_interrupt());
/* It guarantees it can get zspage from handle safely */
spin_lock(&pool->lock);
obj = handle_to_obj(handle);
obj_to_location(obj, &page, &obj_idx);
zspage = get_zspage(page);
#ifdef CONFIG_ZPOOL
/*
* Move the zspage to front of pool's LRU.
*
* Note that this is swap-specific, so by definition there are no ongoing
* accesses to the memory while the page is swapped out that would make
* it "hot". A new entry is hot, then ages to the tail until it gets either
* written back or swaps back in.
*
* Furthermore, map is also called during writeback. We must not put an
* isolated page on the LRU mid-reclaim.
*
* As a result, only update the LRU when the page is mapped for write
* when it's first instantiated.
*
* This is a deviation from the other backends, which perform this update
* in the allocation function (zbud_alloc, z3fold_alloc).
*/
if (mm == ZS_MM_WO) {
if (!list_empty(&zspage->lru))
list_del(&zspage->lru);
list_add(&zspage->lru, &pool->lru);
}
#endif
/*
* migration cannot move any zpages in this zspage. Here, pool->lock
* is too heavy since callers would take some time until they calls
* zs_unmap_object API so delegate the locking from class to zspage
* which is smaller granularity.
*/
migrate_read_lock(zspage);
spin_unlock(&pool->lock);
class = zspage_class(pool, zspage);
off = (class->size * obj_idx) & ~PAGE_MASK;
local_lock(&zs_map_area.lock);
area = this_cpu_ptr(&zs_map_area);
area->vm_mm = mm;
if (off + class->size <= PAGE_SIZE) {
/* this object is contained entirely within a page */
area->vm_addr = kmap_atomic(page);
ret = area->vm_addr + off;
goto out;
}
/* this object spans two pages */
pages[0] = page;
pages[1] = get_next_page(page);
BUG_ON(!pages[1]);
ret = __zs_map_object(area, pages, off, class->size);
out:
if (likely(!ZsHugePage(zspage)))
ret += ZS_HANDLE_SIZE;
return ret;
}
EXPORT_SYMBOL_GPL(zs_map_object);
void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
{
struct zspage *zspage;
struct page *page;
unsigned long obj, off;
unsigned int obj_idx;
struct size_class *class;
struct mapping_area *area;
obj = handle_to_obj(handle);
obj_to_location(obj, &page, &obj_idx);
zspage = get_zspage(page);
class = zspage_class(pool, zspage);
off = (class->size * obj_idx) & ~PAGE_MASK;
area = this_cpu_ptr(&zs_map_area);
if (off + class->size <= PAGE_SIZE)
kunmap_atomic(area->vm_addr);
else {
struct page *pages[2];
pages[0] = page;
pages[1] = get_next_page(page);
BUG_ON(!pages[1]);
__zs_unmap_object(area, pages, off, class->size);
}
local_unlock(&zs_map_area.lock);
migrate_read_unlock(zspage);
}
EXPORT_SYMBOL_GPL(zs_unmap_object);
/**
* zs_huge_class_size() - Returns the size (in bytes) of the first huge
* zsmalloc &size_class.
* @pool: zsmalloc pool to use
*
* The function returns the size of the first huge class - any object of equal
* or bigger size will be stored in zspage consisting of a single physical
* page.
*
* Context: Any context.
*
* Return: the size (in bytes) of the first huge zsmalloc &size_class.
*/
size_t zs_huge_class_size(struct zs_pool *pool)
{
return huge_class_size;
}
EXPORT_SYMBOL_GPL(zs_huge_class_size);
static unsigned long obj_malloc(struct zs_pool *pool,
struct zspage *zspage, unsigned long handle)
{
int i, nr_page, offset;
unsigned long obj;
struct link_free *link;
struct size_class *class;
struct page *m_page;
unsigned long m_offset;
void *vaddr;
class = pool->size_class[zspage->class];
handle |= OBJ_ALLOCATED_TAG;
obj = get_freeobj(zspage);
offset = obj * class->size;
nr_page = offset >> PAGE_SHIFT;
m_offset = offset & ~PAGE_MASK;
m_page = get_first_page(zspage);
for (i = 0; i < nr_page; i++)
m_page = get_next_page(m_page);
vaddr = kmap_atomic(m_page);
link = (struct link_free *)vaddr + m_offset / sizeof(*link);
set_freeobj(zspage, link->next >> OBJ_TAG_BITS);
if (likely(!ZsHugePage(zspage)))
/* record handle in the header of allocated chunk */
link->handle = handle;
else
/* record handle to page->index */
zspage->first_page->index = handle;
kunmap_atomic(vaddr);
mod_zspage_inuse(zspage, 1);
obj = location_to_obj(m_page, obj);
return obj;
}
/**
* zs_malloc - Allocate block of given size from pool.
* @pool: pool to allocate from
* @size: size of block to allocate
* @gfp: gfp flags when allocating object
*
* On success, handle to the allocated object is returned,
* otherwise an ERR_PTR().
* Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail.
*/
unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
{
unsigned long handle, obj;
struct size_class *class;
enum fullness_group newfg;
struct zspage *zspage;
if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
return (unsigned long)ERR_PTR(-EINVAL);
handle = cache_alloc_handle(pool, gfp);
if (!handle)
return (unsigned long)ERR_PTR(-ENOMEM);
/* extra space in chunk to keep the handle */
size += ZS_HANDLE_SIZE;
class = pool->size_class[get_size_class_index(size)];
/* pool->lock effectively protects the zpage migration */
spin_lock(&pool->lock);
zspage = find_get_zspage(class);
if (likely(zspage)) {
obj = obj_malloc(pool, zspage, handle);
/* Now move the zspage to another fullness group, if required */
fix_fullness_group(class, zspage);
record_obj(handle, obj);
class_stat_inc(class, OBJ_USED, 1);
spin_unlock(&pool->lock);
return handle;
}
spin_unlock(&pool->lock);
zspage = alloc_zspage(pool, class, gfp);
if (!zspage) {
cache_free_handle(pool, handle);
return (unsigned long)ERR_PTR(-ENOMEM);
}
spin_lock(&pool->lock);
obj = obj_malloc(pool, zspage, handle);
newfg = get_fullness_group(class, zspage);
insert_zspage(class, zspage, newfg);
set_zspage_mapping(zspage, class->index, newfg);
record_obj(handle, obj);
atomic_long_add(class->pages_per_zspage,
&pool->pages_allocated);
class_stat_inc(class, OBJ_ALLOCATED, class->objs_per_zspage);
class_stat_inc(class, OBJ_USED, 1);
/* We completely set up zspage so mark them as movable */
SetZsPageMovable(pool, zspage);
spin_unlock(&pool->lock);
return handle;
}
EXPORT_SYMBOL_GPL(zs_malloc);
static void obj_free(int class_size, unsigned long obj)
{
struct link_free *link;
struct zspage *zspage;
struct page *f_page;
unsigned long f_offset;
unsigned int f_objidx;
void *vaddr;
obj_to_location(obj, &f_page, &f_objidx);
f_offset = (class_size * f_objidx) & ~PAGE_MASK;
zspage = get_zspage(f_page);
vaddr = kmap_atomic(f_page);
/* Insert this object in containing zspage's freelist */
link = (struct link_free *)(vaddr + f_offset);
if (likely(!ZsHugePage(zspage)))
link->next = get_freeobj(zspage) << OBJ_TAG_BITS;
else
f_page->index = 0;
kunmap_atomic(vaddr);
set_freeobj(zspage, f_objidx);
mod_zspage_inuse(zspage, -1);
}
void zs_free(struct zs_pool *pool, unsigned long handle)
{
struct zspage *zspage;
struct page *f_page;
unsigned long obj;
struct size_class *class;
enum fullness_group fullness;
if (IS_ERR_OR_NULL((void *)handle))
return;
/*
* The pool->lock protects the race with zpage's migration
* so it's safe to get the page from handle.
*/
spin_lock(&pool->lock);
obj = handle_to_obj(handle);
obj_to_page(obj, &f_page);
zspage = get_zspage(f_page);
class = zspage_class(pool, zspage);
obj_free(class->size, obj);
class_stat_dec(class, OBJ_USED, 1);
#ifdef CONFIG_ZPOOL
if (zspage->under_reclaim) {
/*
* Reclaim needs the handles during writeback. It'll free
* them along with the zspage when it's done with them.
*
* Record current deferred handle at the memory location
* whose address is given by handle.
*/
record_obj(handle, (unsigned long)zspage->deferred_handles);
zspage->deferred_handles = (unsigned long *)handle;
spin_unlock(&pool->lock);
return;
}
#endif
fullness = fix_fullness_group(class, zspage);
if (fullness == ZS_EMPTY)
free_zspage(pool, class, zspage);
spin_unlock(&pool->lock);
cache_free_handle(pool, handle);
}
EXPORT_SYMBOL_GPL(zs_free);
static void zs_object_copy(struct size_class *class, unsigned long dst,
unsigned long src)
{
struct page *s_page, *d_page;
unsigned int s_objidx, d_objidx;
unsigned long s_off, d_off;
void *s_addr, *d_addr;
int s_size, d_size, size;
int written = 0;
s_size = d_size = class->size;
obj_to_location(src, &s_page, &s_objidx);
obj_to_location(dst, &d_page, &d_objidx);
s_off = (class->size * s_objidx) & ~PAGE_MASK;
d_off = (class->size * d_objidx) & ~PAGE_MASK;
if (s_off + class->size > PAGE_SIZE)
s_size = PAGE_SIZE - s_off;
if (d_off + class->size > PAGE_SIZE)
d_size = PAGE_SIZE - d_off;
s_addr = kmap_atomic(s_page);
d_addr = kmap_atomic(d_page);
while (1) {
size = min(s_size, d_size);
memcpy(d_addr + d_off, s_addr + s_off, size);
written += size;
if (written == class->size)
break;
s_off += size;
s_size -= size;
d_off += size;
d_size -= size;
/*
* Calling kunmap_atomic(d_addr) is necessary. kunmap_atomic()
* calls must occurs in reverse order of calls to kmap_atomic().
* So, to call kunmap_atomic(s_addr) we should first call
* kunmap_atomic(d_addr). For more details see
* Documentation/mm/highmem.rst.
*/
if (s_off >= PAGE_SIZE) {
kunmap_atomic(d_addr);
kunmap_atomic(s_addr);
s_page = get_next_page(s_page);
s_addr = kmap_atomic(s_page);
d_addr = kmap_atomic(d_page);
s_size = class->size - written;
s_off = 0;
}
if (d_off >= PAGE_SIZE) {
kunmap_atomic(d_addr);
d_page = get_next_page(d_page);
d_addr = kmap_atomic(d_page);
d_size = class->size - written;
d_off = 0;
}
}
kunmap_atomic(d_addr);
kunmap_atomic(s_addr);
}
/*
* Find alloced object in zspage from index object and
* return handle.
*/
static unsigned long find_alloced_obj(struct size_class *class,
struct page *page, int *obj_idx)
{
unsigned int offset;
int index = *obj_idx;
unsigned long handle = 0;
void *addr = kmap_atomic(page);
offset = get_first_obj_offset(page);
offset += class->size * index;
while (offset < PAGE_SIZE) {
if (obj_allocated(page, addr + offset, &handle))
break;
offset += class->size;
index++;
}
kunmap_atomic(addr);
*obj_idx = index;
return handle;
}
struct zs_compact_control {
/* Source spage for migration which could be a subpage of zspage */
struct page *s_page;
/* Destination page for migration which should be a first page
* of zspage. */
struct page *d_page;
/* Starting object index within @s_page which used for live object
* in the subpage. */
int obj_idx;
};
static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
struct zs_compact_control *cc)
{
unsigned long used_obj, free_obj;
unsigned long handle;
struct page *s_page = cc->s_page;
struct page *d_page = cc->d_page;
int obj_idx = cc->obj_idx;
int ret = 0;
while (1) {
handle = find_alloced_obj(class, s_page, &obj_idx);
if (!handle) {
s_page = get_next_page(s_page);
if (!s_page)
break;
obj_idx = 0;
continue;
}
/* Stop if there is no more space */
if (zspage_full(class, get_zspage(d_page))) {
ret = -ENOMEM;
break;
}
used_obj = handle_to_obj(handle);
free_obj = obj_malloc(pool, get_zspage(d_page), handle);
zs_object_copy(class, free_obj, used_obj);
obj_idx++;
record_obj(handle, free_obj);
obj_free(class->size, used_obj);
}
/* Remember last position in this iteration */
cc->s_page = s_page;
cc->obj_idx = obj_idx;
return ret;
}
static struct zspage *isolate_zspage(struct size_class *class, bool source)
{
int i;
struct zspage *zspage;
enum fullness_group fg[2] = {ZS_ALMOST_EMPTY, ZS_ALMOST_FULL};
if (!source) {
fg[0] = ZS_ALMOST_FULL;
fg[1] = ZS_ALMOST_EMPTY;
}
for (i = 0; i < 2; i++) {
zspage = list_first_entry_or_null(&class->fullness_list[fg[i]],
struct zspage, list);
if (zspage) {
remove_zspage(class, zspage, fg[i]);
return zspage;
}
}
return zspage;
}
/*
* putback_zspage - add @zspage into right class's fullness list
* @class: destination class
* @zspage: target page
*
* Return @zspage's fullness_group
*/
static enum fullness_group putback_zspage(struct size_class *class,
struct zspage *zspage)
{
enum fullness_group fullness;
fullness = get_fullness_group(class, zspage);
insert_zspage(class, zspage, fullness);
set_zspage_mapping(zspage, class->index, fullness);
return fullness;
}
#if defined(CONFIG_ZPOOL) || defined(CONFIG_COMPACTION)
/*
* To prevent zspage destroy during migration, zspage freeing should
* hold locks of all pages in the zspage.
*/
static void lock_zspage(struct zspage *zspage)
{
struct page *curr_page, *page;
/*
* Pages we haven't locked yet can be migrated off the list while we're
* trying to lock them, so we need to be careful and only attempt to
* lock each page under migrate_read_lock(). Otherwise, the page we lock
* may no longer belong to the zspage. This means that we may wait for
* the wrong page to unlock, so we must take a reference to the page
* prior to waiting for it to unlock outside migrate_read_lock().
*/
while (1) {
migrate_read_lock(zspage);
page = get_first_page(zspage);
if (trylock_page(page))
break;
get_page(page);
migrate_read_unlock(zspage);
wait_on_page_locked(page);
put_page(page);
}
curr_page = page;
while ((page = get_next_page(curr_page))) {
if (trylock_page(page)) {
curr_page = page;
} else {
get_page(page);
migrate_read_unlock(zspage);
wait_on_page_locked(page);
put_page(page);
migrate_read_lock(zspage);
}
}
migrate_read_unlock(zspage);
}
#endif /* defined(CONFIG_ZPOOL) || defined(CONFIG_COMPACTION) */
#ifdef CONFIG_ZPOOL
/*
* Unlocks all the pages of the zspage.
*
* pool->lock must be held before this function is called
* to prevent the underlying pages from migrating.
*/
static void unlock_zspage(struct zspage *zspage)
{
struct page *page = get_first_page(zspage);
do {
unlock_page(page);
} while ((page = get_next_page(page)) != NULL);
}
#endif /* CONFIG_ZPOOL */
static void migrate_lock_init(struct zspage *zspage)
{
rwlock_init(&zspage->lock);
}
static void migrate_read_lock(struct zspage *zspage) __acquires(&zspage->lock)
{
read_lock(&zspage->lock);
}
static void migrate_read_unlock(struct zspage *zspage) __releases(&zspage->lock)
{
read_unlock(&zspage->lock);
}
#ifdef CONFIG_COMPACTION
static void migrate_write_lock(struct zspage *zspage)
{
write_lock(&zspage->lock);
}
static void migrate_write_lock_nested(struct zspage *zspage)
{
write_lock_nested(&zspage->lock, SINGLE_DEPTH_NESTING);
}
static void migrate_write_unlock(struct zspage *zspage)
{
write_unlock(&zspage->lock);
}
/* Number of isolated subpage for *page migration* in this zspage */
static void inc_zspage_isolation(struct zspage *zspage)
{
zspage->isolated++;
}
static void dec_zspage_isolation(struct zspage *zspage)
{
VM_BUG_ON(zspage->isolated == 0);
zspage->isolated--;
}
static const struct movable_operations zsmalloc_mops;
static void replace_sub_page(struct size_class *class, struct zspage *zspage,
struct page *newpage, struct page *oldpage)
{
struct page *page;
struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE] = {NULL, };
int idx = 0;
page = get_first_page(zspage);
do {
if (page == oldpage)
pages[idx] = newpage;
else
pages[idx] = page;
idx++;
} while ((page = get_next_page(page)) != NULL);
create_page_chain(class, zspage, pages);
set_first_obj_offset(newpage, get_first_obj_offset(oldpage));
if (unlikely(ZsHugePage(zspage)))
newpage->index = oldpage->index;
__SetPageMovable(newpage, &zsmalloc_mops);
}
static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
{
struct zspage *zspage;
/*
* Page is locked so zspage couldn't be destroyed. For detail, look at
* lock_zspage in free_zspage.
*/
VM_BUG_ON_PAGE(!PageMovable(page), page);
VM_BUG_ON_PAGE(PageIsolated(page), page);
zspage = get_zspage(page);
migrate_write_lock(zspage);
inc_zspage_isolation(zspage);
migrate_write_unlock(zspage);
return true;
}
static int zs_page_migrate(struct page *newpage, struct page *page,
enum migrate_mode mode)
{
struct zs_pool *pool;
struct size_class *class;
struct zspage *zspage;
struct page *dummy;
void *s_addr, *d_addr, *addr;
unsigned int offset;
unsigned long handle;
unsigned long old_obj, new_obj;
unsigned int obj_idx;
/*
* We cannot support the _NO_COPY case here, because copy needs to
* happen under the zs lock, which does not work with
* MIGRATE_SYNC_NO_COPY workflow.
*/
if (mode == MIGRATE_SYNC_NO_COPY)
return -EINVAL;
VM_BUG_ON_PAGE(!PageMovable(page), page);
VM_BUG_ON_PAGE(!PageIsolated(page), page);
/* The page is locked, so this pointer must remain valid */
zspage = get_zspage(page);
pool = zspage->pool;
/*
* The pool's lock protects the race between zpage migration
* and zs_free.
*/
spin_lock(&pool->lock);
class = zspage_class(pool, zspage);
/* the migrate_write_lock protects zpage access via zs_map_object */
migrate_write_lock(zspage);
offset = get_first_obj_offset(page);
s_addr = kmap_atomic(page);
/*
* Here, any user cannot access all objects in the zspage so let's move.
*/
d_addr = kmap_atomic(newpage);
memcpy(d_addr, s_addr, PAGE_SIZE);
kunmap_atomic(d_addr);
for (addr = s_addr + offset; addr < s_addr + PAGE_SIZE;
addr += class->size) {
if (obj_allocated(page, addr, &handle)) {
old_obj = handle_to_obj(handle);
obj_to_location(old_obj, &dummy, &obj_idx);
new_obj = (unsigned long)location_to_obj(newpage,
obj_idx);
record_obj(handle, new_obj);
}
}
kunmap_atomic(s_addr);
replace_sub_page(class, zspage, newpage, page);
/*
* Since we complete the data copy and set up new zspage structure,
* it's okay to release the pool's lock.
*/
spin_unlock(&pool->lock);
dec_zspage_isolation(zspage);
migrate_write_unlock(zspage);
get_page(newpage);
if (page_zone(newpage) != page_zone(page)) {
dec_zone_page_state(page, NR_ZSPAGES);
inc_zone_page_state(newpage, NR_ZSPAGES);
}
reset_page(page);
put_page(page);
return MIGRATEPAGE_SUCCESS;
}
static void zs_page_putback(struct page *page)
{
struct zspage *zspage;
VM_BUG_ON_PAGE(!PageMovable(page), page);
VM_BUG_ON_PAGE(!PageIsolated(page), page);
zspage = get_zspage(page);
migrate_write_lock(zspage);
dec_zspage_isolation(zspage);
migrate_write_unlock(zspage);
}
static const struct movable_operations zsmalloc_mops = {
.isolate_page = zs_page_isolate,
.migrate_page = zs_page_migrate,
.putback_page = zs_page_putback,
};
/*
* Caller should hold page_lock of all pages in the zspage
* In here, we cannot use zspage meta data.
*/
static void async_free_zspage(struct work_struct *work)
{
int i;
struct size_class *class;
unsigned int class_idx;
enum fullness_group fullness;
struct zspage *zspage, *tmp;
LIST_HEAD(free_pages);
struct zs_pool *pool = container_of(work, struct zs_pool,
free_work);
for (i = 0; i < ZS_SIZE_CLASSES; i++) {
class = pool->size_class[i];
if (class->index != i)
continue;
spin_lock(&pool->lock);
list_splice_init(&class->fullness_list[ZS_EMPTY], &free_pages);
spin_unlock(&pool->lock);
}
list_for_each_entry_safe(zspage, tmp, &free_pages, list) {
list_del(&zspage->list);
lock_zspage(zspage);
get_zspage_mapping(zspage, &class_idx, &fullness);
VM_BUG_ON(fullness != ZS_EMPTY);
class = pool->size_class[class_idx];
spin_lock(&pool->lock);
#ifdef CONFIG_ZPOOL
list_del(&zspage->lru);
#endif
__free_zspage(pool, class, zspage);
spin_unlock(&pool->lock);
}
};
static void kick_deferred_free(struct zs_pool *pool)
{
schedule_work(&pool->free_work);
}
static void zs_flush_migration(struct zs_pool *pool)
{
flush_work(&pool->free_work);
}
static void init_deferred_free(struct zs_pool *pool)
{
INIT_WORK(&pool->free_work, async_free_zspage);
}
static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage)
{
struct page *page = get_first_page(zspage);
do {
WARN_ON(!trylock_page(page));
__SetPageMovable(page, &zsmalloc_mops);
unlock_page(page);
} while ((page = get_next_page(page)) != NULL);
}
#else
static inline void zs_flush_migration(struct zs_pool *pool) { }
#endif
/*
*
* Based on the number of unused allocated objects calculate
* and return the number of pages that we can free.
*/
static unsigned long zs_can_compact(struct size_class *class)
{
unsigned long obj_wasted;
unsigned long obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
unsigned long obj_used = zs_stat_get(class, OBJ_USED);
if (obj_allocated <= obj_used)
return 0;
obj_wasted = obj_allocated - obj_used;
obj_wasted /= class->objs_per_zspage;
return obj_wasted * class->pages_per_zspage;
}
static unsigned long __zs_compact(struct zs_pool *pool,
struct size_class *class)
{
struct zs_compact_control cc;
struct zspage *src_zspage;
struct zspage *dst_zspage = NULL;
unsigned long pages_freed = 0;
/*
* protect the race between zpage migration and zs_free
* as well as zpage allocation/free
*/
spin_lock(&pool->lock);
while ((src_zspage = isolate_zspage(class, true))) {
/* protect someone accessing the zspage(i.e., zs_map_object) */
migrate_write_lock(src_zspage);
if (!zs_can_compact(class))
break;
cc.obj_idx = 0;
cc.s_page = get_first_page(src_zspage);
while ((dst_zspage = isolate_zspage(class, false))) {
migrate_write_lock_nested(dst_zspage);
cc.d_page = get_first_page(dst_zspage);
/*
* If there is no more space in dst_page, resched
* and see if anyone had allocated another zspage.
*/
if (!migrate_zspage(pool, class, &cc))
break;
putback_zspage(class, dst_zspage);
migrate_write_unlock(dst_zspage);
dst_zspage = NULL;
if (spin_is_contended(&pool->lock))
break;
}
/* Stop if we couldn't find slot */
if (dst_zspage == NULL)
break;
putback_zspage(class, dst_zspage);
migrate_write_unlock(dst_zspage);
if (putback_zspage(class, src_zspage) == ZS_EMPTY) {
migrate_write_unlock(src_zspage);
free_zspage(pool, class, src_zspage);
pages_freed += class->pages_per_zspage;
} else
migrate_write_unlock(src_zspage);
spin_unlock(&pool->lock);
cond_resched();
spin_lock(&pool->lock);
}
if (src_zspage) {
putback_zspage(class, src_zspage);
migrate_write_unlock(src_zspage);
}
spin_unlock(&pool->lock);
return pages_freed;
}
unsigned long zs_compact(struct zs_pool *pool)
{
int i;
struct size_class *class;
unsigned long pages_freed = 0;
for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
class = pool->size_class[i];
if (class->index != i)
continue;
pages_freed += __zs_compact(pool, class);
}
atomic_long_add(pages_freed, &pool->stats.pages_compacted);
return pages_freed;
}
EXPORT_SYMBOL_GPL(zs_compact);
void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats)
{
memcpy(stats, &pool->stats, sizeof(struct zs_pool_stats));
}
EXPORT_SYMBOL_GPL(zs_pool_stats);
static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
struct shrink_control *sc)
{
unsigned long pages_freed;
struct zs_pool *pool = container_of(shrinker, struct zs_pool,
shrinker);
/*
* Compact classes and calculate compaction delta.
* Can run concurrently with a manually triggered
* (by user) compaction.
*/
pages_freed = zs_compact(pool);
return pages_freed ? pages_freed : SHRINK_STOP;
}
static unsigned long zs_shrinker_count(struct shrinker *shrinker,
struct shrink_control *sc)
{
int i;
struct size_class *class;
unsigned long pages_to_free = 0;
struct zs_pool *pool = container_of(shrinker, struct zs_pool,
shrinker);
for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
class = pool->size_class[i];
if (class->index != i)
continue;
pages_to_free += zs_can_compact(class);
}
return pages_to_free;
}
static void zs_unregister_shrinker(struct zs_pool *pool)
{
unregister_shrinker(&pool->shrinker);
}
static int zs_register_shrinker(struct zs_pool *pool)
{
pool->shrinker.scan_objects = zs_shrinker_scan;
pool->shrinker.count_objects = zs_shrinker_count;
pool->shrinker.batch = 0;
pool->shrinker.seeks = DEFAULT_SEEKS;
return register_shrinker(&pool->shrinker, "mm-zspool:%s",
pool->name);
}
/**
* zs_create_pool - Creates an allocation pool to work from.
* @name: pool name to be created
*
* This function must be called before anything when using
* the zsmalloc allocator.
*
* On success, a pointer to the newly created pool is returned,
* otherwise NULL.
*/
struct zs_pool *zs_create_pool(const char *name)
{
int i;
struct zs_pool *pool;
struct size_class *prev_class = NULL;
pool = kzalloc(sizeof(*pool), GFP_KERNEL);
if (!pool)
return NULL;
init_deferred_free(pool);
spin_lock_init(&pool->lock);
pool->name = kstrdup(name, GFP_KERNEL);
if (!pool->name)
goto err;
if (create_cache(pool))
goto err;
/*
* Iterate reversely, because, size of size_class that we want to use
* for merging should be larger or equal to current size.
*/
for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
int size;
int pages_per_zspage;
int objs_per_zspage;
struct size_class *class;
int fullness = 0;
size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
if (size > ZS_MAX_ALLOC_SIZE)
size = ZS_MAX_ALLOC_SIZE;
pages_per_zspage = get_pages_per_zspage(size);
objs_per_zspage = pages_per_zspage * PAGE_SIZE / size;
/*
* We iterate from biggest down to smallest classes,
* so huge_class_size holds the size of the first huge
* class. Any object bigger than or equal to that will
* endup in the huge class.
*/
if (pages_per_zspage != 1 && objs_per_zspage != 1 &&
!huge_class_size) {
huge_class_size = size;
/*
* The object uses ZS_HANDLE_SIZE bytes to store the
* handle. We need to subtract it, because zs_malloc()
* unconditionally adds handle size before it performs
* size class search - so object may be smaller than
* huge class size, yet it still can end up in the huge
* class because it grows by ZS_HANDLE_SIZE extra bytes
* right before class lookup.
*/
huge_class_size -= (ZS_HANDLE_SIZE - 1);
}
/*
* size_class is used for normal zsmalloc operation such
* as alloc/free for that size. Although it is natural that we
* have one size_class for each size, there is a chance that we
* can get more memory utilization if we use one size_class for
* many different sizes whose size_class have same
* characteristics. So, we makes size_class point to
* previous size_class if possible.
*/
if (prev_class) {
if (can_merge(prev_class, pages_per_zspage, objs_per_zspage)) {
pool->size_class[i] = prev_class;
continue;
}
}
class = kzalloc(sizeof(struct size_class), GFP_KERNEL);
if (!class)
goto err;
class->size = size;
class->index = i;
class->pages_per_zspage = pages_per_zspage;
class->objs_per_zspage = objs_per_zspage;
pool->size_class[i] = class;
for (fullness = ZS_EMPTY; fullness < NR_ZS_FULLNESS;
fullness++)
INIT_LIST_HEAD(&class->fullness_list[fullness]);
prev_class = class;
}
/* debug only, don't abort if it fails */
zs_pool_stat_create(pool, name);
/*
* Not critical since shrinker is only used to trigger internal
* defragmentation of the pool which is pretty optional thing. If
* registration fails we still can use the pool normally and user can
* trigger compaction manually. Thus, ignore return code.
*/
zs_register_shrinker(pool);
#ifdef CONFIG_ZPOOL
INIT_LIST_HEAD(&pool->lru);
#endif
return pool;
err:
zs_destroy_pool(pool);
return NULL;
}
EXPORT_SYMBOL_GPL(zs_create_pool);
void zs_destroy_pool(struct zs_pool *pool)
{
int i;
zs_unregister_shrinker(pool);
zs_flush_migration(pool);
zs_pool_stat_destroy(pool);
for (i = 0; i < ZS_SIZE_CLASSES; i++) {
int fg;
struct size_class *class = pool->size_class[i];
if (!class)
continue;
if (class->index != i)
continue;
for (fg = ZS_EMPTY; fg < NR_ZS_FULLNESS; fg++) {
if (!list_empty(&class->fullness_list[fg])) {
pr_info("Freeing non-empty class with size %db, fullness group %d\n",
class->size, fg);
}
}
kfree(class);
}
destroy_cache(pool);
kfree(pool->name);
kfree(pool);
}
EXPORT_SYMBOL_GPL(zs_destroy_pool);
#ifdef CONFIG_ZPOOL
static int zs_reclaim_page(struct zs_pool *pool, unsigned int retries)
{
int i, obj_idx, ret = 0;
unsigned long handle;
struct zspage *zspage;
struct page *page;
enum fullness_group fullness;
/* Lock LRU and fullness list */
spin_lock(&pool->lock);
if (list_empty(&pool->lru)) {
spin_unlock(&pool->lock);
return -EINVAL;
}
for (i = 0; i < retries; i++) {
struct size_class *class;
zspage = list_last_entry(&pool->lru, struct zspage, lru);
list_del(&zspage->lru);
/* zs_free may free objects, but not the zspage and handles */
zspage->under_reclaim = true;
class = zspage_class(pool, zspage);
fullness = get_fullness_group(class, zspage);
/* Lock out object allocations and object compaction */
remove_zspage(class, zspage, fullness);
spin_unlock(&pool->lock);
cond_resched();
/* Lock backing pages into place */
lock_zspage(zspage);
obj_idx = 0;
page = get_first_page(zspage);
while (1) {
handle = find_alloced_obj(class, page, &obj_idx);
if (!handle) {
page = get_next_page(page);
if (!page)
break;
obj_idx = 0;
continue;
}
/*
* This will write the object and call zs_free.
*
* zs_free will free the object, but the
* under_reclaim flag prevents it from freeing
* the zspage altogether. This is necessary so
* that we can continue working with the
* zspage potentially after the last object
* has been freed.
*/
ret = pool->zpool_ops->evict(pool->zpool, handle);
if (ret)
goto next;
obj_idx++;
}
next:
/* For freeing the zspage, or putting it back in the pool and LRU list. */
spin_lock(&pool->lock);
zspage->under_reclaim = false;
if (!get_zspage_inuse(zspage)) {
/*
* Fullness went stale as zs_free() won't touch it
* while the page is removed from the pool. Fix it
* up for the check in __free_zspage().
*/
zspage->fullness = ZS_EMPTY;
__free_zspage(pool, class, zspage);
spin_unlock(&pool->lock);
return 0;
}
putback_zspage(class, zspage);
list_add(&zspage->lru, &pool->lru);
unlock_zspage(zspage);
}
spin_unlock(&pool->lock);
return -EAGAIN;
}
#endif /* CONFIG_ZPOOL */
static int __init zs_init(void)
{
int ret;
ret = cpuhp_setup_state(CPUHP_MM_ZS_PREPARE, "mm/zsmalloc:prepare",
zs_cpu_prepare, zs_cpu_dead);
if (ret)
goto out;
#ifdef CONFIG_ZPOOL
zpool_register_driver(&zs_zpool_driver);
#endif
zs_stat_init();
return 0;
out:
return ret;
}
static void __exit zs_exit(void)
{
#ifdef CONFIG_ZPOOL
zpool_unregister_driver(&zs_zpool_driver);
#endif
cpuhp_remove_state(CPUHP_MM_ZS_PREPARE);
zs_stat_exit();
}
module_init(zs_init);
module_exit(zs_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");