/*
* 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
*/
/*
* This allocator is designed for use with zram. Thus, the allocator is
* supposed to work well under low memory conditions. In particular, it
* never attempts higher order page allocation which is very likely to
* fail under memory pressure. On the other hand, if we just use single
* (0-order) pages, it would suffer from very high fragmentation --
* any object of size PAGE_SIZE/2 or larger would occupy an entire page.
* This was one of the major issues with its predecessor (xvmalloc).
*
* To overcome these issues, zsmalloc allocates a bunch of 0-order pages
* and links them together using various 'struct page' fields. These linked
* pages act as a single higher-order page i.e. an object can span 0-order
* page boundaries. The code refers to these linked pages as a single entity
* called zspage.
*
* For simplicity, zsmalloc can only allocate objects of size up to PAGE_SIZE
* since this satisfies the requirements of all its current users (in the
* worst case, page is incompressible and is thus stored "as-is" i.e. in
* uncompressed form). For allocation requests larger than this size, failure
* is returned (see zs_malloc).
*
* Additionally, zs_malloc() does not return a dereferenceable pointer.
* Instead, it returns an opaque handle (unsigned long) which encodes actual
* location of the allocated object. The reason for this indirection is that
* zsmalloc does not keep zspages permanently mapped since that would cause
* issues on 32-bit systems where the VA region for kernel space mappings
* is very small. So, before using the allocating memory, the object has to
* be mapped using zs_map_object() to get a usable pointer and subsequently
* unmapped using zs_unmap_object().
*
* Following is how we use various fields and flags of underlying
* struct page(s) to form a zspage.
*
* Usage of struct page fields:
* page->first_page: points to the first component (0-order) page
* page->index (union with page->freelist): offset of the first object
* starting in this page. For the first page, this is
* always 0, so we use this field (aka freelist) to point
* to the first free object in zspage.
* page->lru: links together all component pages (except the first page)
* of a zspage
*
* For _first_ page only:
*
* page->private (union with page->first_page): refers to the
* component page after the first page
* page->freelist: points to the first free object in zspage.
* Free objects are linked together using in-place
* metadata.
* page->objects: maximum number of objects we can store in this
* zspage (class->zspage_order * PAGE_SIZE / class->size)
* page->lru: links together first pages of various zspages.
* Basically forming list of zspages in a fullness group.
* page->mapping: class index and fullness group of the zspage
*
* Usage of struct page flags:
* PG_private: identifies the first component page
* PG_private2: identifies the last component page
*
*/
#ifdef CONFIG_ZSMALLOC_DEBUG
#define DEBUG
#endif
#include <linux/module.h>
#include <linux/kernel.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/hardirq.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/zsmalloc.h>
/*
* 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)
/*
* Object location (<PFN>, <obj_idx>) is encoded as
* as single (unsigned long) handle value.
*
* Note that object index <obj_idx> is relative to system
* page <PFN> it is stored in, so for each sub-page belonging
* to a zspage, obj_idx starts with 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)
#define OBJ_INDEX_BITS (BITS_PER_LONG - _PFN_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))
#define ZS_MAX_ALLOC_SIZE PAGE_SIZE
/*
* On systems with 4K page size, this gives 254 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 >> 8)
#define ZS_SIZE_CLASSES ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / \
ZS_SIZE_CLASS_DELTA + 1)
/*
* We do not maintain any list for completely empty or full pages
*/
enum fullness_group {
ZS_ALMOST_FULL,
ZS_ALMOST_EMPTY,
_ZS_NR_FULLNESS_GROUPS,
ZS_EMPTY,
ZS_FULL
};
/*
* 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 = 1/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 {
/*
* Size of objects stored in this class. Must be multiple
* of ZS_ALIGN.
*/
int size;
unsigned int index;
/* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
int pages_per_zspage;
spinlock_t lock;
/* stats */
u64 pages_allocated;
struct page *fullness_list[_ZS_NR_FULLNESS_GROUPS];
};
/*
* Placed within free objects to form a singly linked list.
* For every zspage, first_page->freelist gives head of this list.
*
* This must be power of 2 and less than or equal to ZS_ALIGN
*/
struct link_free {
/* Handle of next free chunk (encodes <PFN, obj_idx>) */
void *next;
};
struct zs_pool {
struct size_class size_class[ZS_SIZE_CLASSES];
gfp_t flags; /* allocation flags used when growing pool */
};
/*
* A zspage's class index and fullness group
* are encoded in its (first)page->mapping
*/
#define CLASS_IDX_BITS 28
#define FULLNESS_BITS 4
#define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1)
#define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1)
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 */
};
/* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
static int is_first_page(struct page *page)
{
return PagePrivate(page);
}
static int is_last_page(struct page *page)
{
return PagePrivate2(page);
}
static void get_zspage_mapping(struct page *page, unsigned int *class_idx,
enum fullness_group *fullness)
{
unsigned long m;
BUG_ON(!is_first_page(page));
m = (unsigned long)page->mapping;
*fullness = m & FULLNESS_MASK;
*class_idx = (m >> FULLNESS_BITS) & CLASS_IDX_MASK;
}
static void set_zspage_mapping(struct page *page, unsigned int class_idx,
enum fullness_group fullness)
{
unsigned long m;
BUG_ON(!is_first_page(page));
m = ((class_idx & CLASS_IDX_MASK) << FULLNESS_BITS) |
(fullness & FULLNESS_MASK);
page->mapping = (struct address_space *)m;
}
/*
* 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 idx;
}
/*
* 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 page *page)
{
int inuse, max_objects;
enum fullness_group fg;
BUG_ON(!is_first_page(page));
inuse = page->inuse;
max_objects = page->objects;
if (inuse == 0)
fg = ZS_EMPTY;
else if (inuse == max_objects)
fg = ZS_FULL;
else if (inuse <= max_objects / 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 page *page, struct size_class *class,
enum fullness_group fullness)
{
struct page **head;
BUG_ON(!is_first_page(page));
if (fullness >= _ZS_NR_FULLNESS_GROUPS)
return;
head = &class->fullness_list[fullness];
if (*head)
list_add_tail(&page->lru, &(*head)->lru);
*head = page;
}
/*
* This function removes the given zspage from the freelist identified
* by <class, fullness_group>.
*/
static void remove_zspage(struct page *page, struct size_class *class,
enum fullness_group fullness)
{
struct page **head;
BUG_ON(!is_first_page(page));
if (fullness >= _ZS_NR_FULLNESS_GROUPS)
return;
head = &class->fullness_list[fullness];
BUG_ON(!*head);
if (list_empty(&(*head)->lru))
*head = NULL;
else if (*head == page)
*head = (struct page *)list_entry((*head)->lru.next,
struct page, lru);
list_del_init(&page->lru);
}
/*
* 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 zs_pool *pool,
struct page *page)
{
int class_idx;
struct size_class *class;
enum fullness_group currfg, newfg;
BUG_ON(!is_first_page(page));
get_zspage_mapping(page, &class_idx, &currfg);
newfg = get_fullness_group(page);
if (newfg == currfg)
goto out;
class = &pool->size_class[class_idx];
remove_zspage(page, class, currfg);
insert_zspage(page, class, newfg);
set_zspage_mapping(page, 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 - Zp % size_class
* 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;
}
/*
* A single 'zspage' is composed of many system pages which are
* linked together using fields in struct page. This function finds
* the first/head page, given any component page of a zspage.
*/
static struct page *get_first_page(struct page *page)
{
if (is_first_page(page))
return page;
else
return page->first_page;
}
static struct page *get_next_page(struct page *page)
{
struct page *next;
if (is_last_page(page))
next = NULL;
else if (is_first_page(page))
next = (struct page *)page_private(page);
else
next = list_entry(page->lru.next, struct page, lru);
return next;
}
/*
* Encode <page, obj_idx> as a single handle value.
* On hardware platforms with physical memory starting at 0x0 the pfn
* could be 0 so we ensure that the handle will never be 0 by adjusting the
* encoded obj_idx value before encoding.
*/
static void *obj_location_to_handle(struct page *page, unsigned long obj_idx)
{
unsigned long handle;
if (!page) {
BUG_ON(obj_idx);
return NULL;
}
handle = page_to_pfn(page) << OBJ_INDEX_BITS;
handle |= ((obj_idx + 1) & OBJ_INDEX_MASK);
return (void *)handle;
}
/*
* Decode <page, obj_idx> pair from the given object handle. We adjust the
* decoded obj_idx back to its original value since it was adjusted in
* obj_location_to_handle().
*/
static void obj_handle_to_location(unsigned long handle, struct page **page,
unsigned long *obj_idx)
{
*page = pfn_to_page(handle >> OBJ_INDEX_BITS);
*obj_idx = (handle & OBJ_INDEX_MASK) - 1;
}
static unsigned long obj_idx_to_offset(struct page *page,
unsigned long obj_idx, int class_size)
{
unsigned long off = 0;
if (!is_first_page(page))
off = page->index;
return off + obj_idx * class_size;
}
static void reset_page(struct page *page)
{
clear_bit(PG_private, &page->flags);
clear_bit(PG_private_2, &page->flags);
set_page_private(page, 0);
page->mapping = NULL;
page->freelist = NULL;
page_mapcount_reset(page);
}
static void free_zspage(struct page *first_page)
{
struct page *nextp, *tmp, *head_extra;
BUG_ON(!is_first_page(first_page));
BUG_ON(first_page->inuse);
head_extra = (struct page *)page_private(first_page);
reset_page(first_page);
__free_page(first_page);
/* zspage with only 1 system page */
if (!head_extra)
return;
list_for_each_entry_safe(nextp, tmp, &head_extra->lru, lru) {
list_del(&nextp->lru);
reset_page(nextp);
__free_page(nextp);
}
reset_page(head_extra);
__free_page(head_extra);
}
/* Initialize a newly allocated zspage */
static void init_zspage(struct page *first_page, struct size_class *class)
{
unsigned long off = 0;
struct page *page = first_page;
BUG_ON(!is_first_page(first_page));
while (page) {
struct page *next_page;
struct link_free *link;
unsigned int i, objs_on_page;
/*
* page->index stores offset of first object starting
* in the page. For the first page, this is always 0,
* so we use first_page->index (aka ->freelist) to store
* head of corresponding zspage's freelist.
*/
if (page != first_page)
page->index = off;
link = (struct link_free *)kmap_atomic(page) +
off / sizeof(*link);
objs_on_page = (PAGE_SIZE - off) / class->size;
for (i = 1; i <= objs_on_page; i++) {
off += class->size;
if (off < PAGE_SIZE) {
link->next = obj_location_to_handle(page, i);
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);
link->next = obj_location_to_handle(next_page, 0);
kunmap_atomic(link);
page = next_page;
off = (off + class->size) % PAGE_SIZE;
}
}
/*
* Allocate a zspage for the given size class
*/
static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
{
int i, error;
struct page *first_page = NULL, *uninitialized_var(prev_page);
/*
* Allocate individual pages and link them together as:
* 1. first page->private = first sub-page
* 2. all sub-pages are linked together using page->lru
* 3. each sub-page is linked to the first page using page->first_page
*
* For each size class, First/Head pages are linked together using
* page->lru. Also, 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.
*/
error = -ENOMEM;
for (i = 0; i < class->pages_per_zspage; i++) {
struct page *page;
page = alloc_page(flags);
if (!page)
goto cleanup;
INIT_LIST_HEAD(&page->lru);
if (i == 0) { /* first page */
SetPagePrivate(page);
set_page_private(page, 0);
first_page = page;
first_page->inuse = 0;
}
if (i == 1)
set_page_private(first_page, (unsigned long)page);
if (i >= 1)
page->first_page = first_page;
if (i >= 2)
list_add(&page->lru, &prev_page->lru);
if (i == class->pages_per_zspage - 1) /* last page */
SetPagePrivate2(page);
prev_page = page;
}
init_zspage(first_page, class);
first_page->freelist = obj_location_to_handle(first_page, 0);
/* Maximum number of objects we can store in this zspage */
first_page->objects = class->pages_per_zspage * PAGE_SIZE / class->size;
error = 0; /* Success */
cleanup:
if (unlikely(error) && first_page) {
free_zspage(first_page);
first_page = NULL;
}
return first_page;
}
static struct page *find_get_zspage(struct size_class *class)
{
int i;
struct page *page;
for (i = 0; i < _ZS_NR_FULLNESS_GROUPS; i++) {
page = class->fullness_list[i];
if (page)
break;
}
return page;
}
#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 = (char *)__get_free_page(GFP_KERNEL);
if (!area->vm_buf)
return -ENOMEM;
return 0;
}
static inline void __zs_cpu_down(struct mapping_area *area)
{
if (area->vm_buf)
free_page((unsigned long)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 = area->vm_buf;
/* no write fastpath */
if (area->vm_mm == ZS_MM_RO)
goto out;
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 void zs_exit(void)
{
int cpu;
for_each_online_cpu(cpu)
zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu);
unregister_cpu_notifier(&zs_cpu_nb);
}
static int zs_init(void)
{
int cpu, ret;
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))
goto fail;
}
return 0;
fail:
zs_exit();
return notifier_to_errno(ret);
}
/**
* zs_create_pool - Creates an allocation pool to work from.
* @flags: allocation flags used to allocate pool metadata
*
* 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(gfp_t flags)
{
int i, ovhd_size;
struct zs_pool *pool;
ovhd_size = roundup(sizeof(*pool), PAGE_SIZE);
pool = kzalloc(ovhd_size, GFP_KERNEL);
if (!pool)
return NULL;
for (i = 0; i < ZS_SIZE_CLASSES; i++) {
int size;
struct size_class *class;
size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
if (size > ZS_MAX_ALLOC_SIZE)
size = ZS_MAX_ALLOC_SIZE;
class = &pool->size_class[i];
class->size = size;
class->index = i;
spin_lock_init(&class->lock);
class->pages_per_zspage = get_pages_per_zspage(size);
}
pool->flags = flags;
return pool;
}
EXPORT_SYMBOL_GPL(zs_create_pool);
void zs_destroy_pool(struct zs_pool *pool)
{
int i;
for (i = 0; i < ZS_SIZE_CLASSES; i++) {
int fg;
struct size_class *class = &pool->size_class[i];
for (fg = 0; fg < _ZS_NR_FULLNESS_GROUPS; fg++) {
if (class->fullness_list[fg]) {
pr_info("Freeing non-empty class with size %db, fullness group %d\n",
class->size, fg);
}
}
}
kfree(pool);
}
EXPORT_SYMBOL_GPL(zs_destroy_pool);
/**
* zs_malloc - Allocate block of given size from pool.
* @pool: pool to allocate from
* @size: size of block to allocate
*
* 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)
{
unsigned long obj;
struct link_free *link;
int class_idx;
struct size_class *class;
struct page *first_page, *m_page;
unsigned long m_objidx, m_offset;
if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
return 0;
class_idx = get_size_class_index(size);
class = &pool->size_class[class_idx];
BUG_ON(class_idx != class->index);
spin_lock(&class->lock);
first_page = find_get_zspage(class);
if (!first_page) {
spin_unlock(&class->lock);
first_page = alloc_zspage(class, pool->flags);
if (unlikely(!first_page))
return 0;
set_zspage_mapping(first_page, class->index, ZS_EMPTY);
spin_lock(&class->lock);
class->pages_allocated += class->pages_per_zspage;
}
obj = (unsigned long)first_page->freelist;
obj_handle_to_location(obj, &m_page, &m_objidx);
m_offset = obj_idx_to_offset(m_page, m_objidx, class->size);
link = (struct link_free *)kmap_atomic(m_page) +
m_offset / sizeof(*link);
first_page->freelist = link->next;
memset(link, POISON_INUSE, sizeof(*link));
kunmap_atomic(link);
first_page->inuse++;
/* Now move the zspage to another fullness group, if required */
fix_fullness_group(pool, first_page);
spin_unlock(&class->lock);
return obj;
}
EXPORT_SYMBOL_GPL(zs_malloc);
void zs_free(struct zs_pool *pool, unsigned long obj)
{
struct link_free *link;
struct page *first_page, *f_page;
unsigned long f_objidx, f_offset;
int class_idx;
struct size_class *class;
enum fullness_group fullness;
if (unlikely(!obj))
return;
obj_handle_to_location(obj, &f_page, &f_objidx);
first_page = get_first_page(f_page);
get_zspage_mapping(first_page, &class_idx, &fullness);
class = &pool->size_class[class_idx];
f_offset = obj_idx_to_offset(f_page, f_objidx, class->size);
spin_lock(&class->lock);
/* Insert this object in containing zspage's freelist */
link = (struct link_free *)((unsigned char *)kmap_atomic(f_page)
+ f_offset);
link->next = first_page->freelist;
kunmap_atomic(link);
first_page->freelist = (void *)obj;
first_page->inuse--;
fullness = fix_fullness_group(pool, first_page);
if (fullness == ZS_EMPTY)
class->pages_allocated -= class->pages_per_zspage;
spin_unlock(&class->lock);
if (fullness == ZS_EMPTY)
free_zspage(first_page);
}
EXPORT_SYMBOL_GPL(zs_free);
/**
* 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 page *page;
unsigned long obj_idx, off;
unsigned int class_idx;
enum fullness_group fg;
struct size_class *class;
struct mapping_area *area;
struct page *pages[2];
BUG_ON(!handle);
/*
* 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());
obj_handle_to_location(handle, &page, &obj_idx);
get_zspage_mapping(get_first_page(page), &class_idx, &fg);
class = &pool->size_class[class_idx];
off = obj_idx_to_offset(page, obj_idx, class->size);
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);
return area->vm_addr + off;
}
/* this object spans two pages */
pages[0] = page;
pages[1] = get_next_page(page);
BUG_ON(!pages[1]);
return __zs_map_object(area, pages, off, class->size);
}
EXPORT_SYMBOL_GPL(zs_map_object);
void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
{
struct page *page;
unsigned long obj_idx, off;
unsigned int class_idx;
enum fullness_group fg;
struct size_class *class;
struct mapping_area *area;
BUG_ON(!handle);
obj_handle_to_location(handle, &page, &obj_idx);
get_zspage_mapping(get_first_page(page), &class_idx, &fg);
class = &pool->size_class[class_idx];
off = obj_idx_to_offset(page, obj_idx, class->size);
area = &__get_cpu_var(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);
}
EXPORT_SYMBOL_GPL(zs_unmap_object);
u64 zs_get_total_size_bytes(struct zs_pool *pool)
{
int i;
u64 npages = 0;
for (i = 0; i < ZS_SIZE_CLASSES; i++)
npages += pool->size_class[i].pages_allocated;
return npages << PAGE_SHIFT;
}
EXPORT_SYMBOL_GPL(zs_get_total_size_bytes);
module_init(zs_init);
module_exit(zs_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
