linux/mm/zsmalloc.c
Markus Elfring c3491eca37 zsmalloc: Delete an unnecessary check before the function call "iput"
iput() tests whether its argument is NULL and then returns immediately.
Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

Link: http://lkml.kernel.org/r/559cf499-4a01-25f9-c87f-24d906626a57@users.sourceforge.net
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-07-28 16:07:41 -07:00

2575 lines
60 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->freelist(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->units: first object offset in a subpage of zspage
*
* Usage of struct page flags:
* PG_private: identifies the first component page
* PG_private2: identifies the last component page
* PG_owner_priv_1: indentifies the huge component page
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#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 <asm/tlbflush.h>
#include <asm/pgtable.h>
#include <linux/cpumask.h>
#include <linux/cpu.h>
#include <linux/vmalloc.h>
#include <linux/preempt.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/debugfs.h>
#include <linux/zsmalloc.h>
#include <linux/zpool.h>
#include <linux/mount.h>
#include <linux/migrate.h>
#include <linux/pagemap.h>
#define ZSPAGE_MAGIC 0x58
/*
* This must be power of 2 and greater than of 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
* as 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_PHYSMEM_BITS
#ifdef CONFIG_HIGHMEM64G
#define MAX_PHYSMEM_BITS 36
#else /* !CONFIG_HIGHMEM64G */
/*
* If this definition of MAX_PHYSMEM_BITS is used, OBJ_INDEX_BITS will just
* be PAGE_SHIFT
*/
#define MAX_PHYSMEM_BITS BITS_PER_LONG
#endif
#endif
#define _PFN_BITS (MAX_PHYSMEM_BITS - PAGE_SHIFT)
/*
* Memory for allocating for handle keeps object position by
* encoding <page, obj_idx> and the encoded value has a room
* in least bit(ie, look at obj_to_location).
* We use the bit to synchronize between object access by
* user and migration.
*/
#define HANDLE_PIN_BIT 0
/*
* 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 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)
enum fullness_group {
ZS_EMPTY,
ZS_ALMOST_EMPTY,
ZS_ALMOST_FULL,
ZS_FULL,
NR_ZS_FULLNESS,
};
enum zs_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
#ifdef CONFIG_COMPACTION
static struct vfsmount *zsmalloc_mnt;
#endif
/*
* number of size_classes
*/
static int zs_size_classes;
/*
* 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;
struct size_class {
spinlock_t lock;
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;
};
/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
static void SetPageHugeObject(struct page *page)
{
SetPageOwnerPriv1(page);
}
static void ClearPageHugeObject(struct page *page)
{
ClearPageOwnerPriv1(page);
}
static int PageHugeObject(struct page *page)
{
return PageOwnerPriv1(page);
}
/*
* 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;
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;
/*
* To signify that register_shrinker() was successful
* and unregister_shrinker() will not Oops.
*/
bool shrinker_enabled;
#ifdef CONFIG_ZSMALLOC_STAT
struct dentry *stat_dentry;
#endif
#ifdef CONFIG_COMPACTION
struct inode *inode;
struct work_struct free_work;
#endif
};
/*
* A zspage's class index and fullness group
* are encoded in its (first)page->mapping
*/
#define FULLNESS_BITS 2
#define CLASS_BITS 8
#define ISOLATED_BITS 3
#define MAGIC_VAL_BITS 8
struct zspage {
struct {
unsigned int fullness:FULLNESS_BITS;
unsigned int class:CLASS_BITS;
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_COMPACTION
rwlock_t lock;
#endif
};
struct mapping_area {
#ifdef CONFIG_PGTABLE_MAPPING
struct vm_struct *vm; /* vm area for mapping object that span pages */
#else
char *vm_buf; /* copy buffer for objects that span pages */
#endif
char *vm_addr; /* address of kmap_atomic()'ed pages */
enum zs_mapmode vm_mm; /* mapping mode */
};
#ifdef CONFIG_COMPACTION
static int zs_register_migration(struct zs_pool *pool);
static void zs_unregister_migration(struct zs_pool *pool);
static void migrate_lock_init(struct zspage *zspage);
static void migrate_read_lock(struct zspage *zspage);
static void migrate_read_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 int zsmalloc_mount(void) { return 0; }
static void zsmalloc_unmount(void) {}
static int zs_register_migration(struct zs_pool *pool) { return 0; }
static void zs_unregister_migration(struct zs_pool *pool) {}
static void migrate_lock_init(struct zspage *zspage) {}
static void migrate_read_lock(struct zspage *zspage) {}
static void migrate_read_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_alloc(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);
}
static void record_obj(unsigned long handle, unsigned long obj)
{
/*
* lsb of @obj represents handle lock while other bits
* represent object value the handle is pointing so
* updating shouldn't do store tearing.
*/
WRITE_ONCE(*(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.
*/
return zs_create_pool(name);
}
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);
return *handle ? 0 : -1;
}
static void zs_zpool_free(void *pool, unsigned long handle)
{
zs_free(pool, handle);
}
static int zs_zpool_shrink(void *pool, unsigned int pages,
unsigned int *reclaimed)
{
return -EINVAL;
}
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: /* fallthru */
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 = 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);
static bool is_zspage_isolated(struct zspage *zspage)
{
return zspage->isolated;
}
static int is_first_page(struct page *page)
{
return PagePrivate(page);
}
/* Protected by class->lock */
static inline int get_zspage_inuse(struct zspage *zspage)
{
return zspage->inuse;
}
static inline void set_zspage_inuse(struct zspage *zspage, int val)
{
zspage->inuse = val;
}
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 int get_first_obj_offset(struct page *page)
{
return page->units;
}
static inline void set_first_obj_offset(struct page *page, int offset)
{
page->units = 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 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 give 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(zs_size_classes - 1, idx);
}
static inline void zs_stat_inc(struct size_class *class,
enum zs_stat_type type, unsigned long cnt)
{
class->stats.objs[type] += cnt;
}
static inline void zs_stat_dec(struct size_class *class,
enum zs_stat_type type, unsigned long cnt)
{
class->stats.objs[type] -= cnt;
}
static inline unsigned long zs_stat_get(struct size_class *class,
enum zs_stat_type 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);
if (!zs_stat_root)
pr_warn("debugfs 'zsmalloc' stat dir creation failed\n");
}
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(&class->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(&class->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;
}
static int zs_stats_size_open(struct inode *inode, struct file *file)
{
return single_open(file, zs_stats_size_show, inode->i_private);
}
static const struct file_operations zs_stat_size_ops = {
.open = zs_stats_size_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static void zs_pool_stat_create(struct zs_pool *pool, const char *name)
{
struct dentry *entry;
if (!zs_stat_root) {
pr_warn("no root stat dir, not creating <%s> stat dir\n", name);
return;
}
entry = debugfs_create_dir(name, zs_stat_root);
if (!entry) {
pr_warn("debugfs dir <%s> creation failed\n", name);
return;
}
pool->stat_dentry = entry;
entry = debugfs_create_file("classes", S_IFREG | S_IRUGO,
pool->stat_dentry, pool, &zs_stat_size_ops);
if (!entry) {
pr_warn("%s: debugfs file entry <%s> creation failed\n",
name, "classes");
debugfs_remove_recursive(pool->stat_dentry);
pool->stat_dentry = NULL;
}
}
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;
zs_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) {
if (get_zspage_inuse(zspage) < get_zspage_inuse(head)) {
list_add(&zspage->list, &head->list);
return;
}
}
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]));
VM_BUG_ON(is_zspage_isolated(zspage));
list_del_init(&zspage->list);
zs_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;
if (!is_zspage_isolated(zspage)) {
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;
BUG_ON(zspage->magic != ZSPAGE_MAGIC);
return zspage;
}
static struct page *get_next_page(struct page *page)
{
if (unlikely(PageHugeObject(page)))
return NULL;
return page->freelist;
}
/**
* obj_to_location - get (<page>, <obj_idx>) from 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);
}
/**
* 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 unsigned long obj_to_head(struct page *page, void *obj)
{
if (unlikely(PageHugeObject(page))) {
VM_BUG_ON_PAGE(!is_first_page(page), page);
return page->index;
} else
return *(unsigned long *)obj;
}
static inline int testpin_tag(unsigned long handle)
{
return bit_spin_is_locked(HANDLE_PIN_BIT, (unsigned long *)handle);
}
static inline int trypin_tag(unsigned long handle)
{
return bit_spin_trylock(HANDLE_PIN_BIT, (unsigned long *)handle);
}
static void pin_tag(unsigned long handle)
{
bit_spin_lock(HANDLE_PIN_BIT, (unsigned long *)handle);
}
static void unpin_tag(unsigned long handle)
{
bit_spin_unlock(HANDLE_PIN_BIT, (unsigned long *)handle);
}
static void reset_page(struct page *page)
{
__ClearPageMovable(page);
ClearPagePrivate(page);
ClearPagePrivate2(page);
set_page_private(page, 0);
page_mapcount_reset(page);
ClearPageHugeObject(page);
page->freelist = NULL;
}
/*
* To prevent zspage destroy during migration, zspage freeing should
* hold locks of all pages in the zspage.
*/
void lock_zspage(struct zspage *zspage)
{
struct page *page = get_first_page(zspage);
do {
lock_page(page);
} while ((page = get_next_page(page)) != NULL);
}
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;
}
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(&class->lock);
VM_BUG_ON(get_zspage_inuse(zspage));
VM_BUG_ON(fg != ZS_EMPTY);
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);
zs_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));
if (!trylock_zspage(zspage)) {
kick_deferred_free(pool);
return;
}
remove_zspage(class, zspage, ZS_EMPTY);
__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 = -1 << OBJ_TAG_BITS;
}
kunmap_atomic(vaddr);
page = next_page;
off %= PAGE_SIZE;
}
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->freelist
* 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) and PG_private_2 to identify the last page.
*/
for (i = 0; i < nr_pages; i++) {
page = pages[i];
set_page_private(page, (unsigned long)zspage);
page->freelist = NULL;
if (i == 0) {
zspage->first_page = page;
SetPagePrivate(page);
if (unlikely(class->objs_per_zspage == 1 &&
class->pages_per_zspage == 1))
SetPageHugeObject(page);
} else {
prev_page->freelist = page;
}
if (i == nr_pages - 1)
SetPagePrivate2(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;
memset(zspage, 0, sizeof(struct zspage));
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);
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;
}
#ifdef CONFIG_PGTABLE_MAPPING
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)
return 0;
area->vm = alloc_vm_area(PAGE_SIZE * 2, NULL);
if (!area->vm)
return -ENOMEM;
return 0;
}
static inline void __zs_cpu_down(struct mapping_area *area)
{
if (area->vm)
free_vm_area(area->vm);
area->vm = NULL;
}
static inline void *__zs_map_object(struct mapping_area *area,
struct page *pages[2], int off, int size)
{
BUG_ON(map_vm_area(area->vm, PAGE_KERNEL, pages));
area->vm_addr = area->vm->addr;
return area->vm_addr + off;
}
static inline void __zs_unmap_object(struct mapping_area *area,
struct page *pages[2], int off, int size)
{
unsigned long addr = (unsigned long)area->vm_addr;
unmap_kernel_range(addr, PAGE_SIZE * 2);
}
#else /* CONFIG_PGTABLE_MAPPING */
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();
}
#endif /* CONFIG_PGTABLE_MAPPING */
static int zs_cpu_notifier(struct notifier_block *nb, unsigned long action,
void *pcpu)
{
int ret, cpu = (long)pcpu;
struct mapping_area *area;
switch (action) {
case CPU_UP_PREPARE:
area = &per_cpu(zs_map_area, cpu);
ret = __zs_cpu_up(area);
if (ret)
return notifier_from_errno(ret);
break;
case CPU_DEAD:
case CPU_UP_CANCELED:
area = &per_cpu(zs_map_area, cpu);
__zs_cpu_down(area);
break;
}
return NOTIFY_OK;
}
static struct notifier_block zs_cpu_nb = {
.notifier_call = zs_cpu_notifier
};
static int zs_register_cpu_notifier(void)
{
int cpu, uninitialized_var(ret);
cpu_notifier_register_begin();
__register_cpu_notifier(&zs_cpu_nb);
for_each_online_cpu(cpu) {
ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
if (notifier_to_errno(ret))
break;
}
cpu_notifier_register_done();
return notifier_to_errno(ret);
}
static void zs_unregister_cpu_notifier(void)
{
int cpu;
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu);
__unregister_cpu_notifier(&zs_cpu_nb);
cpu_notifier_register_done();
}
static void __init init_zs_size_classes(void)
{
int nr;
nr = (ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1;
if ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) % ZS_SIZE_CLASS_DELTA)
nr += 1;
zs_size_classes = nr;
}
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;
}
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
*
* 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;
unsigned int class_idx;
enum fullness_group fg;
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.
*/
WARN_ON_ONCE(in_interrupt());
/* From now on, migration cannot move the object */
pin_tag(handle);
obj = handle_to_obj(handle);
obj_to_location(obj, &page, &obj_idx);
zspage = get_zspage(page);
/* migration cannot move any subpage in this zspage */
migrate_read_lock(zspage);
get_zspage_mapping(zspage, &class_idx, &fg);
class = pool->size_class[class_idx];
off = (class->size * obj_idx) & ~PAGE_MASK;
area = &get_cpu_var(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(!PageHugeObject(page)))
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;
unsigned int class_idx;
enum fullness_group fg;
struct size_class *class;
struct mapping_area *area;
obj = handle_to_obj(handle);
obj_to_location(obj, &page, &obj_idx);
zspage = get_zspage(page);
get_zspage_mapping(zspage, &class_idx, &fg);
class = pool->size_class[class_idx];
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);
}
put_cpu_var(zs_map_area);
migrate_read_unlock(zspage);
unpin_tag(handle);
}
EXPORT_SYMBOL_GPL(zs_unmap_object);
static unsigned long obj_malloc(struct size_class *class,
struct zspage *zspage, unsigned long handle)
{
int i, nr_page, offset;
unsigned long obj;
struct link_free *link;
struct page *m_page;
unsigned long m_offset;
void *vaddr;
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(!PageHugeObject(m_page)))
/* 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);
zs_stat_inc(class, OBJ_USED, 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 0.
* 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 0;
handle = cache_alloc_handle(pool, gfp);
if (!handle)
return 0;
/* extra space in chunk to keep the handle */
size += ZS_HANDLE_SIZE;
class = pool->size_class[get_size_class_index(size)];
spin_lock(&class->lock);
zspage = find_get_zspage(class);
if (likely(zspage)) {
obj = obj_malloc(class, zspage, handle);
/* Now move the zspage to another fullness group, if required */
fix_fullness_group(class, zspage);
record_obj(handle, obj);
spin_unlock(&class->lock);
return handle;
}
spin_unlock(&class->lock);
zspage = alloc_zspage(pool, class, gfp);
if (!zspage) {
cache_free_handle(pool, handle);
return 0;
}
spin_lock(&class->lock);
obj = obj_malloc(class, 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);
zs_stat_inc(class, OBJ_ALLOCATED, class->objs_per_zspage);
/* We completely set up zspage so mark them as movable */
SetZsPageMovable(pool, zspage);
spin_unlock(&class->lock);
return handle;
}
EXPORT_SYMBOL_GPL(zs_malloc);
static void obj_free(struct size_class *class, 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 &= ~OBJ_ALLOCATED_TAG;
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);
link->next = get_freeobj(zspage) << OBJ_TAG_BITS;
kunmap_atomic(vaddr);
set_freeobj(zspage, f_objidx);
mod_zspage_inuse(zspage, -1);
zs_stat_dec(class, OBJ_USED, 1);
}
void zs_free(struct zs_pool *pool, unsigned long handle)
{
struct zspage *zspage;
struct page *f_page;
unsigned long obj;
unsigned int f_objidx;
int class_idx;
struct size_class *class;
enum fullness_group fullness;
bool isolated;
if (unlikely(!handle))
return;
pin_tag(handle);
obj = handle_to_obj(handle);
obj_to_location(obj, &f_page, &f_objidx);
zspage = get_zspage(f_page);
migrate_read_lock(zspage);
get_zspage_mapping(zspage, &class_idx, &fullness);
class = pool->size_class[class_idx];
spin_lock(&class->lock);
obj_free(class, obj);
fullness = fix_fullness_group(class, zspage);
if (fullness != ZS_EMPTY) {
migrate_read_unlock(zspage);
goto out;
}
isolated = is_zspage_isolated(zspage);
migrate_read_unlock(zspage);
/* If zspage is isolated, zs_page_putback will free the zspage */
if (likely(!isolated))
free_zspage(pool, class, zspage);
out:
spin_unlock(&class->lock);
unpin_tag(handle);
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;
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 long head;
int offset = 0;
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) {
head = obj_to_head(page, addr + offset);
if (head & OBJ_ALLOCATED_TAG) {
handle = head & ~OBJ_ALLOCATED_TAG;
if (trypin_tag(handle))
break;
handle = 0;
}
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))) {
unpin_tag(handle);
ret = -ENOMEM;
break;
}
used_obj = handle_to_obj(handle);
free_obj = obj_malloc(class, get_zspage(d_page), handle);
zs_object_copy(class, free_obj, used_obj);
obj_idx++;
/*
* record_obj updates handle's value to free_obj and it will
* invalidate lock bit(ie, HANDLE_PIN_BIT) of handle, which
* breaks synchronization using pin_tag(e,g, zs_free) so
* let's keep the lock bit.
*/
free_obj |= BIT(HANDLE_PIN_BIT);
record_obj(handle, free_obj);
unpin_tag(handle);
obj_free(class, 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) {
VM_BUG_ON(is_zspage_isolated(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;
VM_BUG_ON(is_zspage_isolated(zspage));
fullness = get_fullness_group(class, zspage);
insert_zspage(class, zspage, fullness);
set_zspage_mapping(zspage, class->index, fullness);
return fullness;
}
#ifdef CONFIG_COMPACTION
static struct dentry *zs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
static const struct dentry_operations ops = {
.d_dname = simple_dname,
};
return mount_pseudo(fs_type, "zsmalloc:", NULL, &ops, ZSMALLOC_MAGIC);
}
static struct file_system_type zsmalloc_fs = {
.name = "zsmalloc",
.mount = zs_mount,
.kill_sb = kill_anon_super,
};
static int zsmalloc_mount(void)
{
int ret = 0;
zsmalloc_mnt = kern_mount(&zsmalloc_fs);
if (IS_ERR(zsmalloc_mnt))
ret = PTR_ERR(zsmalloc_mnt);
return ret;
}
static void zsmalloc_unmount(void)
{
kern_unmount(zsmalloc_mnt);
}
static void migrate_lock_init(struct zspage *zspage)
{
rwlock_init(&zspage->lock);
}
static void migrate_read_lock(struct zspage *zspage)
{
read_lock(&zspage->lock);
}
static void migrate_read_unlock(struct zspage *zspage)
{
read_unlock(&zspage->lock);
}
static void migrate_write_lock(struct zspage *zspage)
{
write_lock(&zspage->lock);
}
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)
{
zspage->isolated--;
}
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(PageHugeObject(oldpage)))
newpage->index = oldpage->index;
__SetPageMovable(newpage, page_mapping(oldpage));
}
bool zs_page_isolate(struct page *page, isolate_mode_t mode)
{
struct zs_pool *pool;
struct size_class *class;
int class_idx;
enum fullness_group fullness;
struct zspage *zspage;
struct address_space *mapping;
/*
* 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);
/*
* Without class lock, fullness could be stale while class_idx is okay
* because class_idx is constant unless page is freed so we should get
* fullness again under class lock.
*/
get_zspage_mapping(zspage, &class_idx, &fullness);
mapping = page_mapping(page);
pool = mapping->private_data;
class = pool->size_class[class_idx];
spin_lock(&class->lock);
if (get_zspage_inuse(zspage) == 0) {
spin_unlock(&class->lock);
return false;
}
/* zspage is isolated for object migration */
if (list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
spin_unlock(&class->lock);
return false;
}
/*
* If this is first time isolation for the zspage, isolate zspage from
* size_class to prevent further object allocation from the zspage.
*/
if (!list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
get_zspage_mapping(zspage, &class_idx, &fullness);
remove_zspage(class, zspage, fullness);
}
inc_zspage_isolation(zspage);
spin_unlock(&class->lock);
return true;
}
int zs_page_migrate(struct address_space *mapping, struct page *newpage,
struct page *page, enum migrate_mode mode)
{
struct zs_pool *pool;
struct size_class *class;
int class_idx;
enum fullness_group fullness;
struct zspage *zspage;
struct page *dummy;
void *s_addr, *d_addr, *addr;
int offset, pos;
unsigned long handle, head;
unsigned long old_obj, new_obj;
unsigned int obj_idx;
int ret = -EAGAIN;
VM_BUG_ON_PAGE(!PageMovable(page), page);
VM_BUG_ON_PAGE(!PageIsolated(page), page);
zspage = get_zspage(page);
/* Concurrent compactor cannot migrate any subpage in zspage */
migrate_write_lock(zspage);
get_zspage_mapping(zspage, &class_idx, &fullness);
pool = mapping->private_data;
class = pool->size_class[class_idx];
offset = get_first_obj_offset(page);
spin_lock(&class->lock);
if (!get_zspage_inuse(zspage)) {
ret = -EBUSY;
goto unlock_class;
}
pos = offset;
s_addr = kmap_atomic(page);
while (pos < PAGE_SIZE) {
head = obj_to_head(page, s_addr + pos);
if (head & OBJ_ALLOCATED_TAG) {
handle = head & ~OBJ_ALLOCATED_TAG;
if (!trypin_tag(handle))
goto unpin_objects;
}
pos += class->size;
}
/*
* 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 + pos;
addr += class->size) {
head = obj_to_head(page, addr);
if (head & OBJ_ALLOCATED_TAG) {
handle = head & ~OBJ_ALLOCATED_TAG;
if (!testpin_tag(handle))
BUG();
old_obj = handle_to_obj(handle);
obj_to_location(old_obj, &dummy, &obj_idx);
new_obj = (unsigned long)location_to_obj(newpage,
obj_idx);
new_obj |= BIT(HANDLE_PIN_BIT);
record_obj(handle, new_obj);
}
}
replace_sub_page(class, zspage, newpage, page);
get_page(newpage);
dec_zspage_isolation(zspage);
/*
* Page migration is done so let's putback isolated zspage to
* the list if @page is final isolated subpage in the zspage.
*/
if (!is_zspage_isolated(zspage))
putback_zspage(class, zspage);
reset_page(page);
put_page(page);
page = newpage;
ret = MIGRATEPAGE_SUCCESS;
unpin_objects:
for (addr = s_addr + offset; addr < s_addr + pos;
addr += class->size) {
head = obj_to_head(page, addr);
if (head & OBJ_ALLOCATED_TAG) {
handle = head & ~OBJ_ALLOCATED_TAG;
if (!testpin_tag(handle))
BUG();
unpin_tag(handle);
}
}
kunmap_atomic(s_addr);
unlock_class:
spin_unlock(&class->lock);
migrate_write_unlock(zspage);
return ret;
}
void zs_page_putback(struct page *page)
{
struct zs_pool *pool;
struct size_class *class;
int class_idx;
enum fullness_group fg;
struct address_space *mapping;
struct zspage *zspage;
VM_BUG_ON_PAGE(!PageMovable(page), page);
VM_BUG_ON_PAGE(!PageIsolated(page), page);
zspage = get_zspage(page);
get_zspage_mapping(zspage, &class_idx, &fg);
mapping = page_mapping(page);
pool = mapping->private_data;
class = pool->size_class[class_idx];
spin_lock(&class->lock);
dec_zspage_isolation(zspage);
if (!is_zspage_isolated(zspage)) {
fg = putback_zspage(class, zspage);
/*
* Due to page_lock, we cannot free zspage immediately
* so let's defer.
*/
if (fg == ZS_EMPTY)
schedule_work(&pool->free_work);
}
spin_unlock(&class->lock);
}
const struct address_space_operations zsmalloc_aops = {
.isolate_page = zs_page_isolate,
.migratepage = zs_page_migrate,
.putback_page = zs_page_putback,
};
static int zs_register_migration(struct zs_pool *pool)
{
pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb);
if (IS_ERR(pool->inode)) {
pool->inode = NULL;
return 1;
}
pool->inode->i_mapping->private_data = pool;
pool->inode->i_mapping->a_ops = &zsmalloc_aops;
return 0;
}
static void zs_unregister_migration(struct zs_pool *pool)
{
flush_work(&pool->free_work);
iput(pool->inode);
}
/*
* 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(&class->lock);
list_splice_init(&class->fullness_list[ZS_EMPTY], &free_pages);
spin_unlock(&class->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(&class->lock);
__free_zspage(pool, pool->size_class[class_idx], zspage);
spin_unlock(&class->lock);
}
};
static void kick_deferred_free(struct zs_pool *pool)
{
schedule_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, pool->inode->i_mapping);
unlock_page(page);
} while ((page = get_next_page(page)) != NULL);
}
#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 void __zs_compact(struct zs_pool *pool, struct size_class *class)
{
struct zs_compact_control cc;
struct zspage *src_zspage;
struct zspage *dst_zspage = NULL;
spin_lock(&class->lock);
while ((src_zspage = isolate_zspage(class, true))) {
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))) {
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);
}
/* Stop if we couldn't find slot */
if (dst_zspage == NULL)
break;
putback_zspage(class, dst_zspage);
if (putback_zspage(class, src_zspage) == ZS_EMPTY) {
free_zspage(pool, class, src_zspage);
pool->stats.pages_compacted += class->pages_per_zspage;
}
spin_unlock(&class->lock);
cond_resched();
spin_lock(&class->lock);
}
if (src_zspage)
putback_zspage(class, src_zspage);
spin_unlock(&class->lock);
}
unsigned long zs_compact(struct zs_pool *pool)
{
int i;
struct size_class *class;
for (i = zs_size_classes - 1; i >= 0; i--) {
class = pool->size_class[i];
if (!class)
continue;
if (class->index != i)
continue;
__zs_compact(pool, class);
}
return pool->stats.pages_compacted;
}
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);
pages_freed = pool->stats.pages_compacted;
/*
* Compact classes and calculate compaction delta.
* Can run concurrently with a manually triggered
* (by user) compaction.
*/
pages_freed = zs_compact(pool) - pages_freed;
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)
continue;
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)
{
if (pool->shrinker_enabled) {
unregister_shrinker(&pool->shrinker);
pool->shrinker_enabled = false;
}
}
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);
}
/**
* 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);
pool->size_class = kcalloc(zs_size_classes, sizeof(struct size_class *),
GFP_KERNEL);
if (!pool->size_class) {
kfree(pool);
return NULL;
}
pool->name = kstrdup(name, GFP_KERNEL);
if (!pool->name)
goto err;
if (create_cache(pool))
goto err;
/*
* Iterate reversly, 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;
/*
* 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;
spin_lock_init(&class->lock);
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);
if (zs_register_migration(pool))
goto err;
/*
* Not critical, we still can use the pool
* and user can trigger compaction manually.
*/
if (zs_register_shrinker(pool) == 0)
pool->shrinker_enabled = true;
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_unregister_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->size_class);
kfree(pool->name);
kfree(pool);
}
EXPORT_SYMBOL_GPL(zs_destroy_pool);
static int __init zs_init(void)
{
int ret;
ret = zsmalloc_mount();
if (ret)
goto out;
ret = zs_register_cpu_notifier();
if (ret)
goto notifier_fail;
init_zs_size_classes();
#ifdef CONFIG_ZPOOL
zpool_register_driver(&zs_zpool_driver);
#endif
zs_stat_init();
return 0;
notifier_fail:
zs_unregister_cpu_notifier();
zsmalloc_unmount();
out:
return ret;
}
static void __exit zs_exit(void)
{
#ifdef CONFIG_ZPOOL
zpool_unregister_driver(&zs_zpool_driver);
#endif
zsmalloc_unmount();
zs_unregister_cpu_notifier();
zs_stat_exit();
}
module_init(zs_init);
module_exit(zs_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");