zsmalloc.c 28.7 KB
Newer Older
1 2 3 4
/*
 * zsmalloc memory allocator
 *
 * Copyright (C) 2011  Nitin Gupta
Minchan Kim's avatar
Minchan Kim committed
5
 * Copyright (C) 2012, 2013 Minchan Kim
6 7 8 9 10 11 12 13
 *
 * 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
 */

Nitin Gupta's avatar
Nitin Gupta committed
14
/*
Nitin Cupta's avatar
Nitin Cupta committed
15 16 17 18 19 20 21
 * 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).
Nitin Gupta's avatar
Nitin Gupta committed
22 23 24 25 26 27 28
 *
 * 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.
 *
Nitin Cupta's avatar
Nitin Cupta committed
29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
 * 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().
 *
Nitin Gupta's avatar
Nitin Gupta committed
44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74
 * 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
 *
 */

75 76 77 78 79 80 81 82 83 84 85 86 87 88 89
#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>
90
#include <linux/vmalloc.h>
91
#include <linux/hardirq.h>
92 93
#include <linux/spinlock.h>
#include <linux/types.h>
Minchan Kim's avatar
Minchan Kim committed
94
#include <linux/zsmalloc.h>
95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112

/*
 * 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
Nitin Cupta's avatar
Nitin Cupta committed
113
 * as single (unsigned long) handle value.
114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155
 *
 * 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)
 */
156
#define ZS_SIZE_CLASS_DELTA	(PAGE_SIZE >> 8)
157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222
#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 */
};
223 224 225 226 227 228 229 230 231 232

/*
 * 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)

233
struct mapping_area {
234
#ifdef CONFIG_PGTABLE_MAPPING
235 236 237 238 239 240 241 242 243
	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 */
};


244 245 246 247 248
/* 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)
{
249
	return PagePrivate(page);
250 251 252 253
}

static int is_last_page(struct page *page)
{
254
	return PagePrivate2(page);
255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278
}

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;
}

Nitin Cupta's avatar
Nitin Cupta committed
279 280 281 282 283 284 285
/*
 * 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.
 */
286 287 288 289 290 291 292 293 294 295 296
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;
}

Nitin Cupta's avatar
Nitin Cupta committed
297 298 299 300 301 302 303
/*
 * 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.
 */
304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324
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;
}

Nitin Cupta's avatar
Nitin Cupta committed
325 326 327 328 329 330
/*
 * 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>.
 */
331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347
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;
}

Nitin Cupta's avatar
Nitin Cupta committed
348 349 350 351
/*
 * This function removes the given zspage from the freelist identified
 * by <class, fullness_group>.
 */
352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372
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);
}

Nitin Cupta's avatar
Nitin Cupta committed
373 374 375 376 377 378 379 380 381
/*
 * 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.
 */
382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416
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.
 */
417
static int get_pages_per_zspage(int class_size)
418 419 420 421 422
{
	int i, max_usedpc = 0;
	/* zspage order which gives maximum used size per KB */
	int max_usedpc_order = 1;

423
	for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) {
424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459
		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))
460
		next = (struct page *)page_private(page);
461 462 463 464 465 466
	else
		next = list_entry(page->lru.next, struct page, lru);

	return next;
}

467 468 469 470 471 472
/*
 * 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.
 */
473 474 475 476 477 478 479 480 481 482
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;
483
	handle |= ((obj_idx + 1) & OBJ_INDEX_MASK);
484 485 486 487

	return (void *)handle;
}

488 489 490 491 492
/*
 * 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().
 */
493
static void obj_handle_to_location(unsigned long handle, struct page **page,
494 495
				unsigned long *obj_idx)
{
496
	*page = pfn_to_page(handle >> OBJ_INDEX_BITS);
497
	*obj_idx = (handle & OBJ_INDEX_MASK) - 1;
498 499 500 501 502 503 504 505 506 507 508 509 510
}

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;
}

511 512 513 514 515 516 517
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;
518
	page_mapcount_reset(page);
519 520
}

521 522
static void free_zspage(struct page *first_page)
{
523
	struct page *nextp, *tmp, *head_extra;
524 525 526 527

	BUG_ON(!is_first_page(first_page));
	BUG_ON(first_page->inuse);

528
	head_extra = (struct page *)page_private(first_page);
529

530
	reset_page(first_page);
531 532 533
	__free_page(first_page);

	/* zspage with only 1 system page */
534
	if (!head_extra)
535 536
		return;

537
	list_for_each_entry_safe(nextp, tmp, &head_extra->lru, lru) {
538
		list_del(&nextp->lru);
539
		reset_page(nextp);
540 541
		__free_page(nextp);
	}
542 543
	reset_page(head_extra);
	__free_page(head_extra);
544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597
}

/* 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;
598
	struct page *first_page = NULL, *uninitialized_var(prev_page);
599 600 601 602 603 604 605 606 607 608 609 610 611

	/*
	 * 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;
612
	for (i = 0; i < class->pages_per_zspage; i++) {
613
		struct page *page;
614 615 616 617 618 619 620

		page = alloc_page(flags);
		if (!page)
			goto cleanup;

		INIT_LIST_HEAD(&page->lru);
		if (i == 0) {	/* first page */
621
			SetPagePrivate(page);
622 623 624 625 626
			set_page_private(page, 0);
			first_page = page;
			first_page->inuse = 0;
		}
		if (i == 1)
627
			set_page_private(first_page, (unsigned long)page);
628 629 630 631
		if (i >= 1)
			page->first_page = first_page;
		if (i >= 2)
			list_add(&page->lru, &prev_page->lru);
632
		if (i == class->pages_per_zspage - 1)	/* last page */
633
			SetPagePrivate2(page);
634 635 636 637 638 639 640
		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 */
641
	first_page->objects = class->pages_per_zspage * PAGE_SIZE / class->size;
642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667

	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;
}

668
#ifdef CONFIG_PGTABLE_MAPPING
669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702
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;

703
	unmap_kernel_range(addr, PAGE_SIZE * 2);
704 705
}

706
#else /* CONFIG_PGTABLE_MAPPING */
707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730

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)
731 732 733
{
	int sizes[2];
	void *addr;
734
	char *buf = area->vm_buf;
735

736 737 738 739 740 741
	/* disable page faults to match kmap_atomic() return conditions */
	pagefault_disable();

	/* no read fastpath */
	if (area->vm_mm == ZS_MM_WO)
		goto out;
742 743 744 745 746 747 748 749 750 751 752

	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);
753 754
out:
	return area->vm_buf;
755 756
}

757 758
static void __zs_unmap_object(struct mapping_area *area,
			struct page *pages[2], int off, int size)
759 760 761
{
	int sizes[2];
	void *addr;
762
	char *buf = area->vm_buf;
763

764 765 766
	/* no write fastpath */
	if (area->vm_mm == ZS_MM_RO)
		goto out;
767 768 769 770 771 772 773 774 775 776 777

	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);
778 779 780 781

out:
	/* enable page faults to match kunmap_atomic() return conditions */
	pagefault_enable();
782
}
783

784
#endif /* CONFIG_PGTABLE_MAPPING */
785

786 787 788
static int zs_cpu_notifier(struct notifier_block *nb, unsigned long action,
				void *pcpu)
{
789
	int ret, cpu = (long)pcpu;
790 791 792 793 794
	struct mapping_area *area;

	switch (action) {
	case CPU_UP_PREPARE:
		area = &per_cpu(zs_map_area, cpu);
795 796 797
		ret = __zs_cpu_up(area);
		if (ret)
			return notifier_from_errno(ret);
798 799 800 801
		break;
	case CPU_DEAD:
	case CPU_UP_CANCELED:
		area = &per_cpu(zs_map_area, cpu);
802
		__zs_cpu_down(area);
803 804 805 806 807 808 809 810 811 812 813 814 815 816
		break;
	}

	return NOTIFY_OK;
}

static struct notifier_block zs_cpu_nb = {
	.notifier_call = zs_cpu_notifier
};

static void zs_exit(void)
{
	int cpu;

817 818
	cpu_notifier_register_begin();

819 820
	for_each_online_cpu(cpu)
		zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu);
821 822 823
	__unregister_cpu_notifier(&zs_cpu_nb);

	cpu_notifier_register_done();
824 825 826 827 828 829
}

static int zs_init(void)
{
	int cpu, ret;

830 831 832
	cpu_notifier_register_begin();

	__register_cpu_notifier(&zs_cpu_nb);
833 834
	for_each_online_cpu(cpu) {
		ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
835 836
		if (notifier_to_errno(ret)) {
			cpu_notifier_register_done();
837
			goto fail;
838
		}
839
	}
840 841 842

	cpu_notifier_register_done();

843 844 845 846 847 848
	return 0;
fail:
	zs_exit();
	return notifier_to_errno(ret);
}

849 850
/**
 * zs_create_pool - Creates an allocation pool to work from.
851
 * @flags: allocation flags used to allocate pool metadata
852 853 854 855 856 857 858
 *
 * 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.
 */
859
struct zs_pool *zs_create_pool(gfp_t flags)
860
{
861
	int i, ovhd_size;
862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880
	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);
881
		class->pages_per_zspage = get_pages_per_zspage(size);
882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900

	}

	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]) {
901
				pr_info("Freeing non-empty class with size %db, fullness group %d\n",
902 903 904 905 906 907 908 909 910 911 912 913 914
					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
 *
915
 * On success, handle to the allocated object is returned,
916
 * otherwise 0.
917 918
 * Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail.
 */
919
unsigned long zs_malloc(struct zs_pool *pool, size_t size)
920
{
921
	unsigned long obj;
922 923 924 925 926 927 928 929
	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))
930
		return 0;
931 932 933 934 935 936 937 938 939 940 941 942

	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))
943
			return 0;
944 945 946

		set_zspage_mapping(first_page, class->index, ZS_EMPTY);
		spin_lock(&class->lock);
947
		class->pages_allocated += class->pages_per_zspage;
948 949
	}

950
	obj = (unsigned long)first_page->freelist;
951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968
	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);

969
void zs_free(struct zs_pool *pool, unsigned long obj)
970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995
{
	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);
996
	first_page->freelist = (void *)obj;
997 998 999 1000 1001

	first_page->inuse--;
	fullness = fix_fullness_group(pool, first_page);

	if (fullness == ZS_EMPTY)
1002
		class->pages_allocated -= class->pages_per_zspage;
1003 1004 1005 1006 1007 1008 1009 1010

	spin_unlock(&class->lock);

	if (fullness == ZS_EMPTY)
		free_zspage(first_page);
}
EXPORT_SYMBOL_GPL(zs_free);

1011 1012 1013 1014 1015 1016 1017
/**
 * 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
1018 1019 1020 1021 1022 1023
 * 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.
1024
 */
1025 1026
void *zs_map_object(struct zs_pool *pool, unsigned long handle,
			enum zs_mapmode mm)
1027 1028 1029 1030 1031 1032 1033 1034
{
	struct page *page;
	unsigned long obj_idx, off;

	unsigned int class_idx;
	enum fullness_group fg;
	struct size_class *class;
	struct mapping_area *area;
1035
	struct page *pages[2];
1036 1037 1038

	BUG_ON(!handle);

1039 1040 1041 1042 1043 1044 1045
	/*
	 * 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());

1046 1047 1048 1049 1050 1051
	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);
1052
	area->vm_mm = mm;
1053 1054 1055
	if (off + class->size <= PAGE_SIZE) {
		/* this object is contained entirely within a page */
		area->vm_addr = kmap_atomic(page);
1056
		return area->vm_addr + off;
1057 1058
	}

1059 1060 1061 1062
	/* this object spans two pages */
	pages[0] = page;
	pages[1] = get_next_page(page);
	BUG_ON(!pages[1]);
1063

1064
	return __zs_map_object(area, pages, off, class->size);
1065 1066 1067
}
EXPORT_SYMBOL_GPL(zs_map_object);

1068
void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084
{
	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);

1085
	area = this_cpu_ptr(&zs_map_area);
1086 1087 1088 1089 1090 1091 1092 1093
	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]);
1094

1095 1096
		__zs_unmap_object(area, pages, off, class->size);
	}
1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111
	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);
1112 1113 1114 1115 1116 1117

module_init(zs_init);
module_exit(zs_exit);

MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");