xref: /openbmc/linux/mm/zsmalloc.c (revision c16c6655)
1 /*
2  * zsmalloc memory allocator
3  *
4  * Copyright (C) 2011  Nitin Gupta
5  * Copyright (C) 2012, 2013 Minchan Kim
6  *
7  * This code is released using a dual license strategy: BSD/GPL
8  * You can choose the license that better fits your requirements.
9  *
10  * Released under the terms of 3-clause BSD License
11  * Released under the terms of GNU General Public License Version 2.0
12  */
13 
14 /*
15  * Following is how we use various fields and flags of underlying
16  * struct page(s) to form a zspage.
17  *
18  * Usage of struct page fields:
19  *	page->private: points to zspage
20  *	page->freelist(index): links together all component pages of a zspage
21  *		For the huge page, this is always 0, so we use this field
22  *		to store handle.
23  *	page->units: first object offset in a subpage of zspage
24  *
25  * Usage of struct page flags:
26  *	PG_private: identifies the first component page
27  *	PG_owner_priv_1: identifies the huge component page
28  *
29  */
30 
31 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
32 
33 #include <linux/module.h>
34 #include <linux/kernel.h>
35 #include <linux/sched.h>
36 #include <linux/magic.h>
37 #include <linux/bitops.h>
38 #include <linux/errno.h>
39 #include <linux/highmem.h>
40 #include <linux/string.h>
41 #include <linux/slab.h>
42 #include <asm/tlbflush.h>
43 #include <asm/pgtable.h>
44 #include <linux/cpumask.h>
45 #include <linux/cpu.h>
46 #include <linux/vmalloc.h>
47 #include <linux/preempt.h>
48 #include <linux/spinlock.h>
49 #include <linux/shrinker.h>
50 #include <linux/types.h>
51 #include <linux/debugfs.h>
52 #include <linux/zsmalloc.h>
53 #include <linux/zpool.h>
54 #include <linux/mount.h>
55 #include <linux/pseudo_fs.h>
56 #include <linux/migrate.h>
57 #include <linux/wait.h>
58 #include <linux/pagemap.h>
59 #include <linux/fs.h>
60 
61 #define ZSPAGE_MAGIC	0x58
62 
63 /*
64  * This must be power of 2 and greater than of equal to sizeof(link_free).
65  * These two conditions ensure that any 'struct link_free' itself doesn't
66  * span more than 1 page which avoids complex case of mapping 2 pages simply
67  * to restore link_free pointer values.
68  */
69 #define ZS_ALIGN		8
70 
71 /*
72  * A single 'zspage' is composed of up to 2^N discontiguous 0-order (single)
73  * pages. ZS_MAX_ZSPAGE_ORDER defines upper limit on N.
74  */
75 #define ZS_MAX_ZSPAGE_ORDER 2
76 #define ZS_MAX_PAGES_PER_ZSPAGE (_AC(1, UL) << ZS_MAX_ZSPAGE_ORDER)
77 
78 #define ZS_HANDLE_SIZE (sizeof(unsigned long))
79 
80 /*
81  * Object location (<PFN>, <obj_idx>) is encoded as
82  * as single (unsigned long) handle value.
83  *
84  * Note that object index <obj_idx> starts from 0.
85  *
86  * This is made more complicated by various memory models and PAE.
87  */
88 
89 #ifndef MAX_POSSIBLE_PHYSMEM_BITS
90 #ifdef MAX_PHYSMEM_BITS
91 #define MAX_POSSIBLE_PHYSMEM_BITS MAX_PHYSMEM_BITS
92 #else
93 /*
94  * If this definition of MAX_PHYSMEM_BITS is used, OBJ_INDEX_BITS will just
95  * be PAGE_SHIFT
96  */
97 #define MAX_POSSIBLE_PHYSMEM_BITS BITS_PER_LONG
98 #endif
99 #endif
100 
101 #define _PFN_BITS		(MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)
102 
103 /*
104  * Memory for allocating for handle keeps object position by
105  * encoding <page, obj_idx> and the encoded value has a room
106  * in least bit(ie, look at obj_to_location).
107  * We use the bit to synchronize between object access by
108  * user and migration.
109  */
110 #define HANDLE_PIN_BIT	0
111 
112 /*
113  * Head in allocated object should have OBJ_ALLOCATED_TAG
114  * to identify the object was allocated or not.
115  * It's okay to add the status bit in the least bit because
116  * header keeps handle which is 4byte-aligned address so we
117  * have room for two bit at least.
118  */
119 #define OBJ_ALLOCATED_TAG 1
120 #define OBJ_TAG_BITS 1
121 #define OBJ_INDEX_BITS	(BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS)
122 #define OBJ_INDEX_MASK	((_AC(1, UL) << OBJ_INDEX_BITS) - 1)
123 
124 #define FULLNESS_BITS	2
125 #define CLASS_BITS	8
126 #define ISOLATED_BITS	3
127 #define MAGIC_VAL_BITS	8
128 
129 #define MAX(a, b) ((a) >= (b) ? (a) : (b))
130 /* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
131 #define ZS_MIN_ALLOC_SIZE \
132 	MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
133 /* each chunk includes extra space to keep handle */
134 #define ZS_MAX_ALLOC_SIZE	PAGE_SIZE
135 
136 /*
137  * On systems with 4K page size, this gives 255 size classes! There is a
138  * trader-off here:
139  *  - Large number of size classes is potentially wasteful as free page are
140  *    spread across these classes
141  *  - Small number of size classes causes large internal fragmentation
142  *  - Probably its better to use specific size classes (empirically
143  *    determined). NOTE: all those class sizes must be set as multiple of
144  *    ZS_ALIGN to make sure link_free itself never has to span 2 pages.
145  *
146  *  ZS_MIN_ALLOC_SIZE and ZS_SIZE_CLASS_DELTA must be multiple of ZS_ALIGN
147  *  (reason above)
148  */
149 #define ZS_SIZE_CLASS_DELTA	(PAGE_SIZE >> CLASS_BITS)
150 #define ZS_SIZE_CLASSES	(DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \
151 				      ZS_SIZE_CLASS_DELTA) + 1)
152 
153 enum fullness_group {
154 	ZS_EMPTY,
155 	ZS_ALMOST_EMPTY,
156 	ZS_ALMOST_FULL,
157 	ZS_FULL,
158 	NR_ZS_FULLNESS,
159 };
160 
161 enum zs_stat_type {
162 	CLASS_EMPTY,
163 	CLASS_ALMOST_EMPTY,
164 	CLASS_ALMOST_FULL,
165 	CLASS_FULL,
166 	OBJ_ALLOCATED,
167 	OBJ_USED,
168 	NR_ZS_STAT_TYPE,
169 };
170 
171 struct zs_size_stat {
172 	unsigned long objs[NR_ZS_STAT_TYPE];
173 };
174 
175 #ifdef CONFIG_ZSMALLOC_STAT
176 static struct dentry *zs_stat_root;
177 #endif
178 
179 #ifdef CONFIG_COMPACTION
180 static struct vfsmount *zsmalloc_mnt;
181 #endif
182 
183 /*
184  * We assign a page to ZS_ALMOST_EMPTY fullness group when:
185  *	n <= N / f, where
186  * n = number of allocated objects
187  * N = total number of objects zspage can store
188  * f = fullness_threshold_frac
189  *
190  * Similarly, we assign zspage to:
191  *	ZS_ALMOST_FULL	when n > N / f
192  *	ZS_EMPTY	when n == 0
193  *	ZS_FULL		when n == N
194  *
195  * (see: fix_fullness_group())
196  */
197 static const int fullness_threshold_frac = 4;
198 static size_t huge_class_size;
199 
200 struct size_class {
201 	spinlock_t lock;
202 	struct list_head fullness_list[NR_ZS_FULLNESS];
203 	/*
204 	 * Size of objects stored in this class. Must be multiple
205 	 * of ZS_ALIGN.
206 	 */
207 	int size;
208 	int objs_per_zspage;
209 	/* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
210 	int pages_per_zspage;
211 
212 	unsigned int index;
213 	struct zs_size_stat stats;
214 };
215 
216 /* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
217 static void SetPageHugeObject(struct page *page)
218 {
219 	SetPageOwnerPriv1(page);
220 }
221 
222 static void ClearPageHugeObject(struct page *page)
223 {
224 	ClearPageOwnerPriv1(page);
225 }
226 
227 static int PageHugeObject(struct page *page)
228 {
229 	return PageOwnerPriv1(page);
230 }
231 
232 /*
233  * Placed within free objects to form a singly linked list.
234  * For every zspage, zspage->freeobj gives head of this list.
235  *
236  * This must be power of 2 and less than or equal to ZS_ALIGN
237  */
238 struct link_free {
239 	union {
240 		/*
241 		 * Free object index;
242 		 * It's valid for non-allocated object
243 		 */
244 		unsigned long next;
245 		/*
246 		 * Handle of allocated object.
247 		 */
248 		unsigned long handle;
249 	};
250 };
251 
252 struct zs_pool {
253 	const char *name;
254 
255 	struct size_class *size_class[ZS_SIZE_CLASSES];
256 	struct kmem_cache *handle_cachep;
257 	struct kmem_cache *zspage_cachep;
258 
259 	atomic_long_t pages_allocated;
260 
261 	struct zs_pool_stats stats;
262 
263 	/* Compact classes */
264 	struct shrinker shrinker;
265 
266 #ifdef CONFIG_ZSMALLOC_STAT
267 	struct dentry *stat_dentry;
268 #endif
269 #ifdef CONFIG_COMPACTION
270 	struct inode *inode;
271 	struct work_struct free_work;
272 	/* A wait queue for when migration races with async_free_zspage() */
273 	struct wait_queue_head migration_wait;
274 	atomic_long_t isolated_pages;
275 	bool destroying;
276 #endif
277 };
278 
279 struct zspage {
280 	struct {
281 		unsigned int fullness:FULLNESS_BITS;
282 		unsigned int class:CLASS_BITS + 1;
283 		unsigned int isolated:ISOLATED_BITS;
284 		unsigned int magic:MAGIC_VAL_BITS;
285 	};
286 	unsigned int inuse;
287 	unsigned int freeobj;
288 	struct page *first_page;
289 	struct list_head list; /* fullness list */
290 #ifdef CONFIG_COMPACTION
291 	rwlock_t lock;
292 #endif
293 };
294 
295 struct mapping_area {
296 #ifdef CONFIG_PGTABLE_MAPPING
297 	struct vm_struct *vm; /* vm area for mapping object that span pages */
298 #else
299 	char *vm_buf; /* copy buffer for objects that span pages */
300 #endif
301 	char *vm_addr; /* address of kmap_atomic()'ed pages */
302 	enum zs_mapmode vm_mm; /* mapping mode */
303 };
304 
305 #ifdef CONFIG_COMPACTION
306 static int zs_register_migration(struct zs_pool *pool);
307 static void zs_unregister_migration(struct zs_pool *pool);
308 static void migrate_lock_init(struct zspage *zspage);
309 static void migrate_read_lock(struct zspage *zspage);
310 static void migrate_read_unlock(struct zspage *zspage);
311 static void kick_deferred_free(struct zs_pool *pool);
312 static void init_deferred_free(struct zs_pool *pool);
313 static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage);
314 #else
315 static int zsmalloc_mount(void) { return 0; }
316 static void zsmalloc_unmount(void) {}
317 static int zs_register_migration(struct zs_pool *pool) { return 0; }
318 static void zs_unregister_migration(struct zs_pool *pool) {}
319 static void migrate_lock_init(struct zspage *zspage) {}
320 static void migrate_read_lock(struct zspage *zspage) {}
321 static void migrate_read_unlock(struct zspage *zspage) {}
322 static void kick_deferred_free(struct zs_pool *pool) {}
323 static void init_deferred_free(struct zs_pool *pool) {}
324 static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage) {}
325 #endif
326 
327 static int create_cache(struct zs_pool *pool)
328 {
329 	pool->handle_cachep = kmem_cache_create("zs_handle", ZS_HANDLE_SIZE,
330 					0, 0, NULL);
331 	if (!pool->handle_cachep)
332 		return 1;
333 
334 	pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
335 					0, 0, NULL);
336 	if (!pool->zspage_cachep) {
337 		kmem_cache_destroy(pool->handle_cachep);
338 		pool->handle_cachep = NULL;
339 		return 1;
340 	}
341 
342 	return 0;
343 }
344 
345 static void destroy_cache(struct zs_pool *pool)
346 {
347 	kmem_cache_destroy(pool->handle_cachep);
348 	kmem_cache_destroy(pool->zspage_cachep);
349 }
350 
351 static unsigned long cache_alloc_handle(struct zs_pool *pool, gfp_t gfp)
352 {
353 	return (unsigned long)kmem_cache_alloc(pool->handle_cachep,
354 			gfp & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
355 }
356 
357 static void cache_free_handle(struct zs_pool *pool, unsigned long handle)
358 {
359 	kmem_cache_free(pool->handle_cachep, (void *)handle);
360 }
361 
362 static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags)
363 {
364 	return kmem_cache_alloc(pool->zspage_cachep,
365 			flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
366 }
367 
368 static void cache_free_zspage(struct zs_pool *pool, struct zspage *zspage)
369 {
370 	kmem_cache_free(pool->zspage_cachep, zspage);
371 }
372 
373 static void record_obj(unsigned long handle, unsigned long obj)
374 {
375 	/*
376 	 * lsb of @obj represents handle lock while other bits
377 	 * represent object value the handle is pointing so
378 	 * updating shouldn't do store tearing.
379 	 */
380 	WRITE_ONCE(*(unsigned long *)handle, obj);
381 }
382 
383 /* zpool driver */
384 
385 #ifdef CONFIG_ZPOOL
386 
387 static void *zs_zpool_create(const char *name, gfp_t gfp,
388 			     const struct zpool_ops *zpool_ops,
389 			     struct zpool *zpool)
390 {
391 	/*
392 	 * Ignore global gfp flags: zs_malloc() may be invoked from
393 	 * different contexts and its caller must provide a valid
394 	 * gfp mask.
395 	 */
396 	return zs_create_pool(name);
397 }
398 
399 static void zs_zpool_destroy(void *pool)
400 {
401 	zs_destroy_pool(pool);
402 }
403 
404 static int zs_zpool_malloc(void *pool, size_t size, gfp_t gfp,
405 			unsigned long *handle)
406 {
407 	*handle = zs_malloc(pool, size, gfp);
408 	return *handle ? 0 : -1;
409 }
410 static void zs_zpool_free(void *pool, unsigned long handle)
411 {
412 	zs_free(pool, handle);
413 }
414 
415 static void *zs_zpool_map(void *pool, unsigned long handle,
416 			enum zpool_mapmode mm)
417 {
418 	enum zs_mapmode zs_mm;
419 
420 	switch (mm) {
421 	case ZPOOL_MM_RO:
422 		zs_mm = ZS_MM_RO;
423 		break;
424 	case ZPOOL_MM_WO:
425 		zs_mm = ZS_MM_WO;
426 		break;
427 	case ZPOOL_MM_RW: /* fall through */
428 	default:
429 		zs_mm = ZS_MM_RW;
430 		break;
431 	}
432 
433 	return zs_map_object(pool, handle, zs_mm);
434 }
435 static void zs_zpool_unmap(void *pool, unsigned long handle)
436 {
437 	zs_unmap_object(pool, handle);
438 }
439 
440 static u64 zs_zpool_total_size(void *pool)
441 {
442 	return zs_get_total_pages(pool) << PAGE_SHIFT;
443 }
444 
445 static struct zpool_driver zs_zpool_driver = {
446 	.type =		"zsmalloc",
447 	.owner =	THIS_MODULE,
448 	.create =	zs_zpool_create,
449 	.destroy =	zs_zpool_destroy,
450 	.malloc =	zs_zpool_malloc,
451 	.free =		zs_zpool_free,
452 	.map =		zs_zpool_map,
453 	.unmap =	zs_zpool_unmap,
454 	.total_size =	zs_zpool_total_size,
455 };
456 
457 MODULE_ALIAS("zpool-zsmalloc");
458 #endif /* CONFIG_ZPOOL */
459 
460 /* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
461 static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
462 
463 static bool is_zspage_isolated(struct zspage *zspage)
464 {
465 	return zspage->isolated;
466 }
467 
468 static __maybe_unused int is_first_page(struct page *page)
469 {
470 	return PagePrivate(page);
471 }
472 
473 /* Protected by class->lock */
474 static inline int get_zspage_inuse(struct zspage *zspage)
475 {
476 	return zspage->inuse;
477 }
478 
479 static inline void set_zspage_inuse(struct zspage *zspage, int val)
480 {
481 	zspage->inuse = val;
482 }
483 
484 static inline void mod_zspage_inuse(struct zspage *zspage, int val)
485 {
486 	zspage->inuse += val;
487 }
488 
489 static inline struct page *get_first_page(struct zspage *zspage)
490 {
491 	struct page *first_page = zspage->first_page;
492 
493 	VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
494 	return first_page;
495 }
496 
497 static inline int get_first_obj_offset(struct page *page)
498 {
499 	return page->units;
500 }
501 
502 static inline void set_first_obj_offset(struct page *page, int offset)
503 {
504 	page->units = offset;
505 }
506 
507 static inline unsigned int get_freeobj(struct zspage *zspage)
508 {
509 	return zspage->freeobj;
510 }
511 
512 static inline void set_freeobj(struct zspage *zspage, unsigned int obj)
513 {
514 	zspage->freeobj = obj;
515 }
516 
517 static void get_zspage_mapping(struct zspage *zspage,
518 				unsigned int *class_idx,
519 				enum fullness_group *fullness)
520 {
521 	BUG_ON(zspage->magic != ZSPAGE_MAGIC);
522 
523 	*fullness = zspage->fullness;
524 	*class_idx = zspage->class;
525 }
526 
527 static void set_zspage_mapping(struct zspage *zspage,
528 				unsigned int class_idx,
529 				enum fullness_group fullness)
530 {
531 	zspage->class = class_idx;
532 	zspage->fullness = fullness;
533 }
534 
535 /*
536  * zsmalloc divides the pool into various size classes where each
537  * class maintains a list of zspages where each zspage is divided
538  * into equal sized chunks. Each allocation falls into one of these
539  * classes depending on its size. This function returns index of the
540  * size class which has chunk size big enough to hold the give size.
541  */
542 static int get_size_class_index(int size)
543 {
544 	int idx = 0;
545 
546 	if (likely(size > ZS_MIN_ALLOC_SIZE))
547 		idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
548 				ZS_SIZE_CLASS_DELTA);
549 
550 	return min_t(int, ZS_SIZE_CLASSES - 1, idx);
551 }
552 
553 /* type can be of enum type zs_stat_type or fullness_group */
554 static inline void zs_stat_inc(struct size_class *class,
555 				int type, unsigned long cnt)
556 {
557 	class->stats.objs[type] += cnt;
558 }
559 
560 /* type can be of enum type zs_stat_type or fullness_group */
561 static inline void zs_stat_dec(struct size_class *class,
562 				int type, unsigned long cnt)
563 {
564 	class->stats.objs[type] -= cnt;
565 }
566 
567 /* type can be of enum type zs_stat_type or fullness_group */
568 static inline unsigned long zs_stat_get(struct size_class *class,
569 				int type)
570 {
571 	return class->stats.objs[type];
572 }
573 
574 #ifdef CONFIG_ZSMALLOC_STAT
575 
576 static void __init zs_stat_init(void)
577 {
578 	if (!debugfs_initialized()) {
579 		pr_warn("debugfs not available, stat dir not created\n");
580 		return;
581 	}
582 
583 	zs_stat_root = debugfs_create_dir("zsmalloc", NULL);
584 }
585 
586 static void __exit zs_stat_exit(void)
587 {
588 	debugfs_remove_recursive(zs_stat_root);
589 }
590 
591 static unsigned long zs_can_compact(struct size_class *class);
592 
593 static int zs_stats_size_show(struct seq_file *s, void *v)
594 {
595 	int i;
596 	struct zs_pool *pool = s->private;
597 	struct size_class *class;
598 	int objs_per_zspage;
599 	unsigned long class_almost_full, class_almost_empty;
600 	unsigned long obj_allocated, obj_used, pages_used, freeable;
601 	unsigned long total_class_almost_full = 0, total_class_almost_empty = 0;
602 	unsigned long total_objs = 0, total_used_objs = 0, total_pages = 0;
603 	unsigned long total_freeable = 0;
604 
605 	seq_printf(s, " %5s %5s %11s %12s %13s %10s %10s %16s %8s\n",
606 			"class", "size", "almost_full", "almost_empty",
607 			"obj_allocated", "obj_used", "pages_used",
608 			"pages_per_zspage", "freeable");
609 
610 	for (i = 0; i < ZS_SIZE_CLASSES; i++) {
611 		class = pool->size_class[i];
612 
613 		if (class->index != i)
614 			continue;
615 
616 		spin_lock(&class->lock);
617 		class_almost_full = zs_stat_get(class, CLASS_ALMOST_FULL);
618 		class_almost_empty = zs_stat_get(class, CLASS_ALMOST_EMPTY);
619 		obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
620 		obj_used = zs_stat_get(class, OBJ_USED);
621 		freeable = zs_can_compact(class);
622 		spin_unlock(&class->lock);
623 
624 		objs_per_zspage = class->objs_per_zspage;
625 		pages_used = obj_allocated / objs_per_zspage *
626 				class->pages_per_zspage;
627 
628 		seq_printf(s, " %5u %5u %11lu %12lu %13lu"
629 				" %10lu %10lu %16d %8lu\n",
630 			i, class->size, class_almost_full, class_almost_empty,
631 			obj_allocated, obj_used, pages_used,
632 			class->pages_per_zspage, freeable);
633 
634 		total_class_almost_full += class_almost_full;
635 		total_class_almost_empty += class_almost_empty;
636 		total_objs += obj_allocated;
637 		total_used_objs += obj_used;
638 		total_pages += pages_used;
639 		total_freeable += freeable;
640 	}
641 
642 	seq_puts(s, "\n");
643 	seq_printf(s, " %5s %5s %11lu %12lu %13lu %10lu %10lu %16s %8lu\n",
644 			"Total", "", total_class_almost_full,
645 			total_class_almost_empty, total_objs,
646 			total_used_objs, total_pages, "", total_freeable);
647 
648 	return 0;
649 }
650 DEFINE_SHOW_ATTRIBUTE(zs_stats_size);
651 
652 static void zs_pool_stat_create(struct zs_pool *pool, const char *name)
653 {
654 	if (!zs_stat_root) {
655 		pr_warn("no root stat dir, not creating <%s> stat dir\n", name);
656 		return;
657 	}
658 
659 	pool->stat_dentry = debugfs_create_dir(name, zs_stat_root);
660 
661 	debugfs_create_file("classes", S_IFREG | 0444, pool->stat_dentry, pool,
662 			    &zs_stats_size_fops);
663 }
664 
665 static void zs_pool_stat_destroy(struct zs_pool *pool)
666 {
667 	debugfs_remove_recursive(pool->stat_dentry);
668 }
669 
670 #else /* CONFIG_ZSMALLOC_STAT */
671 static void __init zs_stat_init(void)
672 {
673 }
674 
675 static void __exit zs_stat_exit(void)
676 {
677 }
678 
679 static inline void zs_pool_stat_create(struct zs_pool *pool, const char *name)
680 {
681 }
682 
683 static inline void zs_pool_stat_destroy(struct zs_pool *pool)
684 {
685 }
686 #endif
687 
688 
689 /*
690  * For each size class, zspages are divided into different groups
691  * depending on how "full" they are. This was done so that we could
692  * easily find empty or nearly empty zspages when we try to shrink
693  * the pool (not yet implemented). This function returns fullness
694  * status of the given page.
695  */
696 static enum fullness_group get_fullness_group(struct size_class *class,
697 						struct zspage *zspage)
698 {
699 	int inuse, objs_per_zspage;
700 	enum fullness_group fg;
701 
702 	inuse = get_zspage_inuse(zspage);
703 	objs_per_zspage = class->objs_per_zspage;
704 
705 	if (inuse == 0)
706 		fg = ZS_EMPTY;
707 	else if (inuse == objs_per_zspage)
708 		fg = ZS_FULL;
709 	else if (inuse <= 3 * objs_per_zspage / fullness_threshold_frac)
710 		fg = ZS_ALMOST_EMPTY;
711 	else
712 		fg = ZS_ALMOST_FULL;
713 
714 	return fg;
715 }
716 
717 /*
718  * Each size class maintains various freelists and zspages are assigned
719  * to one of these freelists based on the number of live objects they
720  * have. This functions inserts the given zspage into the freelist
721  * identified by <class, fullness_group>.
722  */
723 static void insert_zspage(struct size_class *class,
724 				struct zspage *zspage,
725 				enum fullness_group fullness)
726 {
727 	struct zspage *head;
728 
729 	zs_stat_inc(class, fullness, 1);
730 	head = list_first_entry_or_null(&class->fullness_list[fullness],
731 					struct zspage, list);
732 	/*
733 	 * We want to see more ZS_FULL pages and less almost empty/full.
734 	 * Put pages with higher ->inuse first.
735 	 */
736 	if (head) {
737 		if (get_zspage_inuse(zspage) < get_zspage_inuse(head)) {
738 			list_add(&zspage->list, &head->list);
739 			return;
740 		}
741 	}
742 	list_add(&zspage->list, &class->fullness_list[fullness]);
743 }
744 
745 /*
746  * This function removes the given zspage from the freelist identified
747  * by <class, fullness_group>.
748  */
749 static void remove_zspage(struct size_class *class,
750 				struct zspage *zspage,
751 				enum fullness_group fullness)
752 {
753 	VM_BUG_ON(list_empty(&class->fullness_list[fullness]));
754 	VM_BUG_ON(is_zspage_isolated(zspage));
755 
756 	list_del_init(&zspage->list);
757 	zs_stat_dec(class, fullness, 1);
758 }
759 
760 /*
761  * Each size class maintains zspages in different fullness groups depending
762  * on the number of live objects they contain. When allocating or freeing
763  * objects, the fullness status of the page can change, say, from ALMOST_FULL
764  * to ALMOST_EMPTY when freeing an object. This function checks if such
765  * a status change has occurred for the given page and accordingly moves the
766  * page from the freelist of the old fullness group to that of the new
767  * fullness group.
768  */
769 static enum fullness_group fix_fullness_group(struct size_class *class,
770 						struct zspage *zspage)
771 {
772 	int class_idx;
773 	enum fullness_group currfg, newfg;
774 
775 	get_zspage_mapping(zspage, &class_idx, &currfg);
776 	newfg = get_fullness_group(class, zspage);
777 	if (newfg == currfg)
778 		goto out;
779 
780 	if (!is_zspage_isolated(zspage)) {
781 		remove_zspage(class, zspage, currfg);
782 		insert_zspage(class, zspage, newfg);
783 	}
784 
785 	set_zspage_mapping(zspage, class_idx, newfg);
786 
787 out:
788 	return newfg;
789 }
790 
791 /*
792  * We have to decide on how many pages to link together
793  * to form a zspage for each size class. This is important
794  * to reduce wastage due to unusable space left at end of
795  * each zspage which is given as:
796  *     wastage = Zp % class_size
797  *     usage = Zp - wastage
798  * where Zp = zspage size = k * PAGE_SIZE where k = 1, 2, ...
799  *
800  * For example, for size class of 3/8 * PAGE_SIZE, we should
801  * link together 3 PAGE_SIZE sized pages to form a zspage
802  * since then we can perfectly fit in 8 such objects.
803  */
804 static int get_pages_per_zspage(int class_size)
805 {
806 	int i, max_usedpc = 0;
807 	/* zspage order which gives maximum used size per KB */
808 	int max_usedpc_order = 1;
809 
810 	for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) {
811 		int zspage_size;
812 		int waste, usedpc;
813 
814 		zspage_size = i * PAGE_SIZE;
815 		waste = zspage_size % class_size;
816 		usedpc = (zspage_size - waste) * 100 / zspage_size;
817 
818 		if (usedpc > max_usedpc) {
819 			max_usedpc = usedpc;
820 			max_usedpc_order = i;
821 		}
822 	}
823 
824 	return max_usedpc_order;
825 }
826 
827 static struct zspage *get_zspage(struct page *page)
828 {
829 	struct zspage *zspage = (struct zspage *)page->private;
830 
831 	BUG_ON(zspage->magic != ZSPAGE_MAGIC);
832 	return zspage;
833 }
834 
835 static struct page *get_next_page(struct page *page)
836 {
837 	if (unlikely(PageHugeObject(page)))
838 		return NULL;
839 
840 	return page->freelist;
841 }
842 
843 /**
844  * obj_to_location - get (<page>, <obj_idx>) from encoded object value
845  * @obj: the encoded object value
846  * @page: page object resides in zspage
847  * @obj_idx: object index
848  */
849 static void obj_to_location(unsigned long obj, struct page **page,
850 				unsigned int *obj_idx)
851 {
852 	obj >>= OBJ_TAG_BITS;
853 	*page = pfn_to_page(obj >> OBJ_INDEX_BITS);
854 	*obj_idx = (obj & OBJ_INDEX_MASK);
855 }
856 
857 /**
858  * location_to_obj - get obj value encoded from (<page>, <obj_idx>)
859  * @page: page object resides in zspage
860  * @obj_idx: object index
861  */
862 static unsigned long location_to_obj(struct page *page, unsigned int obj_idx)
863 {
864 	unsigned long obj;
865 
866 	obj = page_to_pfn(page) << OBJ_INDEX_BITS;
867 	obj |= obj_idx & OBJ_INDEX_MASK;
868 	obj <<= OBJ_TAG_BITS;
869 
870 	return obj;
871 }
872 
873 static unsigned long handle_to_obj(unsigned long handle)
874 {
875 	return *(unsigned long *)handle;
876 }
877 
878 static unsigned long obj_to_head(struct page *page, void *obj)
879 {
880 	if (unlikely(PageHugeObject(page))) {
881 		VM_BUG_ON_PAGE(!is_first_page(page), page);
882 		return page->index;
883 	} else
884 		return *(unsigned long *)obj;
885 }
886 
887 static inline int testpin_tag(unsigned long handle)
888 {
889 	return bit_spin_is_locked(HANDLE_PIN_BIT, (unsigned long *)handle);
890 }
891 
892 static inline int trypin_tag(unsigned long handle)
893 {
894 	return bit_spin_trylock(HANDLE_PIN_BIT, (unsigned long *)handle);
895 }
896 
897 static void pin_tag(unsigned long handle)
898 {
899 	bit_spin_lock(HANDLE_PIN_BIT, (unsigned long *)handle);
900 }
901 
902 static void unpin_tag(unsigned long handle)
903 {
904 	bit_spin_unlock(HANDLE_PIN_BIT, (unsigned long *)handle);
905 }
906 
907 static void reset_page(struct page *page)
908 {
909 	__ClearPageMovable(page);
910 	ClearPagePrivate(page);
911 	set_page_private(page, 0);
912 	page_mapcount_reset(page);
913 	ClearPageHugeObject(page);
914 	page->freelist = NULL;
915 }
916 
917 static int trylock_zspage(struct zspage *zspage)
918 {
919 	struct page *cursor, *fail;
920 
921 	for (cursor = get_first_page(zspage); cursor != NULL; cursor =
922 					get_next_page(cursor)) {
923 		if (!trylock_page(cursor)) {
924 			fail = cursor;
925 			goto unlock;
926 		}
927 	}
928 
929 	return 1;
930 unlock:
931 	for (cursor = get_first_page(zspage); cursor != fail; cursor =
932 					get_next_page(cursor))
933 		unlock_page(cursor);
934 
935 	return 0;
936 }
937 
938 static void __free_zspage(struct zs_pool *pool, struct size_class *class,
939 				struct zspage *zspage)
940 {
941 	struct page *page, *next;
942 	enum fullness_group fg;
943 	unsigned int class_idx;
944 
945 	get_zspage_mapping(zspage, &class_idx, &fg);
946 
947 	assert_spin_locked(&class->lock);
948 
949 	VM_BUG_ON(get_zspage_inuse(zspage));
950 	VM_BUG_ON(fg != ZS_EMPTY);
951 
952 	next = page = get_first_page(zspage);
953 	do {
954 		VM_BUG_ON_PAGE(!PageLocked(page), page);
955 		next = get_next_page(page);
956 		reset_page(page);
957 		unlock_page(page);
958 		dec_zone_page_state(page, NR_ZSPAGES);
959 		put_page(page);
960 		page = next;
961 	} while (page != NULL);
962 
963 	cache_free_zspage(pool, zspage);
964 
965 	zs_stat_dec(class, OBJ_ALLOCATED, class->objs_per_zspage);
966 	atomic_long_sub(class->pages_per_zspage,
967 					&pool->pages_allocated);
968 }
969 
970 static void free_zspage(struct zs_pool *pool, struct size_class *class,
971 				struct zspage *zspage)
972 {
973 	VM_BUG_ON(get_zspage_inuse(zspage));
974 	VM_BUG_ON(list_empty(&zspage->list));
975 
976 	if (!trylock_zspage(zspage)) {
977 		kick_deferred_free(pool);
978 		return;
979 	}
980 
981 	remove_zspage(class, zspage, ZS_EMPTY);
982 	__free_zspage(pool, class, zspage);
983 }
984 
985 /* Initialize a newly allocated zspage */
986 static void init_zspage(struct size_class *class, struct zspage *zspage)
987 {
988 	unsigned int freeobj = 1;
989 	unsigned long off = 0;
990 	struct page *page = get_first_page(zspage);
991 
992 	while (page) {
993 		struct page *next_page;
994 		struct link_free *link;
995 		void *vaddr;
996 
997 		set_first_obj_offset(page, off);
998 
999 		vaddr = kmap_atomic(page);
1000 		link = (struct link_free *)vaddr + off / sizeof(*link);
1001 
1002 		while ((off += class->size) < PAGE_SIZE) {
1003 			link->next = freeobj++ << OBJ_TAG_BITS;
1004 			link += class->size / sizeof(*link);
1005 		}
1006 
1007 		/*
1008 		 * We now come to the last (full or partial) object on this
1009 		 * page, which must point to the first object on the next
1010 		 * page (if present)
1011 		 */
1012 		next_page = get_next_page(page);
1013 		if (next_page) {
1014 			link->next = freeobj++ << OBJ_TAG_BITS;
1015 		} else {
1016 			/*
1017 			 * Reset OBJ_TAG_BITS bit to last link to tell
1018 			 * whether it's allocated object or not.
1019 			 */
1020 			link->next = -1UL << OBJ_TAG_BITS;
1021 		}
1022 		kunmap_atomic(vaddr);
1023 		page = next_page;
1024 		off %= PAGE_SIZE;
1025 	}
1026 
1027 	set_freeobj(zspage, 0);
1028 }
1029 
1030 static void create_page_chain(struct size_class *class, struct zspage *zspage,
1031 				struct page *pages[])
1032 {
1033 	int i;
1034 	struct page *page;
1035 	struct page *prev_page = NULL;
1036 	int nr_pages = class->pages_per_zspage;
1037 
1038 	/*
1039 	 * Allocate individual pages and link them together as:
1040 	 * 1. all pages are linked together using page->freelist
1041 	 * 2. each sub-page point to zspage using page->private
1042 	 *
1043 	 * we set PG_private to identify the first page (i.e. no other sub-page
1044 	 * has this flag set).
1045 	 */
1046 	for (i = 0; i < nr_pages; i++) {
1047 		page = pages[i];
1048 		set_page_private(page, (unsigned long)zspage);
1049 		page->freelist = NULL;
1050 		if (i == 0) {
1051 			zspage->first_page = page;
1052 			SetPagePrivate(page);
1053 			if (unlikely(class->objs_per_zspage == 1 &&
1054 					class->pages_per_zspage == 1))
1055 				SetPageHugeObject(page);
1056 		} else {
1057 			prev_page->freelist = page;
1058 		}
1059 		prev_page = page;
1060 	}
1061 }
1062 
1063 /*
1064  * Allocate a zspage for the given size class
1065  */
1066 static struct zspage *alloc_zspage(struct zs_pool *pool,
1067 					struct size_class *class,
1068 					gfp_t gfp)
1069 {
1070 	int i;
1071 	struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE];
1072 	struct zspage *zspage = cache_alloc_zspage(pool, gfp);
1073 
1074 	if (!zspage)
1075 		return NULL;
1076 
1077 	memset(zspage, 0, sizeof(struct zspage));
1078 	zspage->magic = ZSPAGE_MAGIC;
1079 	migrate_lock_init(zspage);
1080 
1081 	for (i = 0; i < class->pages_per_zspage; i++) {
1082 		struct page *page;
1083 
1084 		page = alloc_page(gfp);
1085 		if (!page) {
1086 			while (--i >= 0) {
1087 				dec_zone_page_state(pages[i], NR_ZSPAGES);
1088 				__free_page(pages[i]);
1089 			}
1090 			cache_free_zspage(pool, zspage);
1091 			return NULL;
1092 		}
1093 
1094 		inc_zone_page_state(page, NR_ZSPAGES);
1095 		pages[i] = page;
1096 	}
1097 
1098 	create_page_chain(class, zspage, pages);
1099 	init_zspage(class, zspage);
1100 
1101 	return zspage;
1102 }
1103 
1104 static struct zspage *find_get_zspage(struct size_class *class)
1105 {
1106 	int i;
1107 	struct zspage *zspage;
1108 
1109 	for (i = ZS_ALMOST_FULL; i >= ZS_EMPTY; i--) {
1110 		zspage = list_first_entry_or_null(&class->fullness_list[i],
1111 				struct zspage, list);
1112 		if (zspage)
1113 			break;
1114 	}
1115 
1116 	return zspage;
1117 }
1118 
1119 #ifdef CONFIG_PGTABLE_MAPPING
1120 static inline int __zs_cpu_up(struct mapping_area *area)
1121 {
1122 	/*
1123 	 * Make sure we don't leak memory if a cpu UP notification
1124 	 * and zs_init() race and both call zs_cpu_up() on the same cpu
1125 	 */
1126 	if (area->vm)
1127 		return 0;
1128 	area->vm = alloc_vm_area(PAGE_SIZE * 2, NULL);
1129 	if (!area->vm)
1130 		return -ENOMEM;
1131 	return 0;
1132 }
1133 
1134 static inline void __zs_cpu_down(struct mapping_area *area)
1135 {
1136 	if (area->vm)
1137 		free_vm_area(area->vm);
1138 	area->vm = NULL;
1139 }
1140 
1141 static inline void *__zs_map_object(struct mapping_area *area,
1142 				struct page *pages[2], int off, int size)
1143 {
1144 	BUG_ON(map_vm_area(area->vm, PAGE_KERNEL, pages));
1145 	area->vm_addr = area->vm->addr;
1146 	return area->vm_addr + off;
1147 }
1148 
1149 static inline void __zs_unmap_object(struct mapping_area *area,
1150 				struct page *pages[2], int off, int size)
1151 {
1152 	unsigned long addr = (unsigned long)area->vm_addr;
1153 
1154 	unmap_kernel_range(addr, PAGE_SIZE * 2);
1155 }
1156 
1157 #else /* CONFIG_PGTABLE_MAPPING */
1158 
1159 static inline int __zs_cpu_up(struct mapping_area *area)
1160 {
1161 	/*
1162 	 * Make sure we don't leak memory if a cpu UP notification
1163 	 * and zs_init() race and both call zs_cpu_up() on the same cpu
1164 	 */
1165 	if (area->vm_buf)
1166 		return 0;
1167 	area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);
1168 	if (!area->vm_buf)
1169 		return -ENOMEM;
1170 	return 0;
1171 }
1172 
1173 static inline void __zs_cpu_down(struct mapping_area *area)
1174 {
1175 	kfree(area->vm_buf);
1176 	area->vm_buf = NULL;
1177 }
1178 
1179 static void *__zs_map_object(struct mapping_area *area,
1180 			struct page *pages[2], int off, int size)
1181 {
1182 	int sizes[2];
1183 	void *addr;
1184 	char *buf = area->vm_buf;
1185 
1186 	/* disable page faults to match kmap_atomic() return conditions */
1187 	pagefault_disable();
1188 
1189 	/* no read fastpath */
1190 	if (area->vm_mm == ZS_MM_WO)
1191 		goto out;
1192 
1193 	sizes[0] = PAGE_SIZE - off;
1194 	sizes[1] = size - sizes[0];
1195 
1196 	/* copy object to per-cpu buffer */
1197 	addr = kmap_atomic(pages[0]);
1198 	memcpy(buf, addr + off, sizes[0]);
1199 	kunmap_atomic(addr);
1200 	addr = kmap_atomic(pages[1]);
1201 	memcpy(buf + sizes[0], addr, sizes[1]);
1202 	kunmap_atomic(addr);
1203 out:
1204 	return area->vm_buf;
1205 }
1206 
1207 static void __zs_unmap_object(struct mapping_area *area,
1208 			struct page *pages[2], int off, int size)
1209 {
1210 	int sizes[2];
1211 	void *addr;
1212 	char *buf;
1213 
1214 	/* no write fastpath */
1215 	if (area->vm_mm == ZS_MM_RO)
1216 		goto out;
1217 
1218 	buf = area->vm_buf;
1219 	buf = buf + ZS_HANDLE_SIZE;
1220 	size -= ZS_HANDLE_SIZE;
1221 	off += ZS_HANDLE_SIZE;
1222 
1223 	sizes[0] = PAGE_SIZE - off;
1224 	sizes[1] = size - sizes[0];
1225 
1226 	/* copy per-cpu buffer to object */
1227 	addr = kmap_atomic(pages[0]);
1228 	memcpy(addr + off, buf, sizes[0]);
1229 	kunmap_atomic(addr);
1230 	addr = kmap_atomic(pages[1]);
1231 	memcpy(addr, buf + sizes[0], sizes[1]);
1232 	kunmap_atomic(addr);
1233 
1234 out:
1235 	/* enable page faults to match kunmap_atomic() return conditions */
1236 	pagefault_enable();
1237 }
1238 
1239 #endif /* CONFIG_PGTABLE_MAPPING */
1240 
1241 static int zs_cpu_prepare(unsigned int cpu)
1242 {
1243 	struct mapping_area *area;
1244 
1245 	area = &per_cpu(zs_map_area, cpu);
1246 	return __zs_cpu_up(area);
1247 }
1248 
1249 static int zs_cpu_dead(unsigned int cpu)
1250 {
1251 	struct mapping_area *area;
1252 
1253 	area = &per_cpu(zs_map_area, cpu);
1254 	__zs_cpu_down(area);
1255 	return 0;
1256 }
1257 
1258 static bool can_merge(struct size_class *prev, int pages_per_zspage,
1259 					int objs_per_zspage)
1260 {
1261 	if (prev->pages_per_zspage == pages_per_zspage &&
1262 		prev->objs_per_zspage == objs_per_zspage)
1263 		return true;
1264 
1265 	return false;
1266 }
1267 
1268 static bool zspage_full(struct size_class *class, struct zspage *zspage)
1269 {
1270 	return get_zspage_inuse(zspage) == class->objs_per_zspage;
1271 }
1272 
1273 unsigned long zs_get_total_pages(struct zs_pool *pool)
1274 {
1275 	return atomic_long_read(&pool->pages_allocated);
1276 }
1277 EXPORT_SYMBOL_GPL(zs_get_total_pages);
1278 
1279 /**
1280  * zs_map_object - get address of allocated object from handle.
1281  * @pool: pool from which the object was allocated
1282  * @handle: handle returned from zs_malloc
1283  * @mm: maping mode to use
1284  *
1285  * Before using an object allocated from zs_malloc, it must be mapped using
1286  * this function. When done with the object, it must be unmapped using
1287  * zs_unmap_object.
1288  *
1289  * Only one object can be mapped per cpu at a time. There is no protection
1290  * against nested mappings.
1291  *
1292  * This function returns with preemption and page faults disabled.
1293  */
1294 void *zs_map_object(struct zs_pool *pool, unsigned long handle,
1295 			enum zs_mapmode mm)
1296 {
1297 	struct zspage *zspage;
1298 	struct page *page;
1299 	unsigned long obj, off;
1300 	unsigned int obj_idx;
1301 
1302 	unsigned int class_idx;
1303 	enum fullness_group fg;
1304 	struct size_class *class;
1305 	struct mapping_area *area;
1306 	struct page *pages[2];
1307 	void *ret;
1308 
1309 	/*
1310 	 * Because we use per-cpu mapping areas shared among the
1311 	 * pools/users, we can't allow mapping in interrupt context
1312 	 * because it can corrupt another users mappings.
1313 	 */
1314 	BUG_ON(in_interrupt());
1315 
1316 	/* From now on, migration cannot move the object */
1317 	pin_tag(handle);
1318 
1319 	obj = handle_to_obj(handle);
1320 	obj_to_location(obj, &page, &obj_idx);
1321 	zspage = get_zspage(page);
1322 
1323 	/* migration cannot move any subpage in this zspage */
1324 	migrate_read_lock(zspage);
1325 
1326 	get_zspage_mapping(zspage, &class_idx, &fg);
1327 	class = pool->size_class[class_idx];
1328 	off = (class->size * obj_idx) & ~PAGE_MASK;
1329 
1330 	area = &get_cpu_var(zs_map_area);
1331 	area->vm_mm = mm;
1332 	if (off + class->size <= PAGE_SIZE) {
1333 		/* this object is contained entirely within a page */
1334 		area->vm_addr = kmap_atomic(page);
1335 		ret = area->vm_addr + off;
1336 		goto out;
1337 	}
1338 
1339 	/* this object spans two pages */
1340 	pages[0] = page;
1341 	pages[1] = get_next_page(page);
1342 	BUG_ON(!pages[1]);
1343 
1344 	ret = __zs_map_object(area, pages, off, class->size);
1345 out:
1346 	if (likely(!PageHugeObject(page)))
1347 		ret += ZS_HANDLE_SIZE;
1348 
1349 	return ret;
1350 }
1351 EXPORT_SYMBOL_GPL(zs_map_object);
1352 
1353 void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
1354 {
1355 	struct zspage *zspage;
1356 	struct page *page;
1357 	unsigned long obj, off;
1358 	unsigned int obj_idx;
1359 
1360 	unsigned int class_idx;
1361 	enum fullness_group fg;
1362 	struct size_class *class;
1363 	struct mapping_area *area;
1364 
1365 	obj = handle_to_obj(handle);
1366 	obj_to_location(obj, &page, &obj_idx);
1367 	zspage = get_zspage(page);
1368 	get_zspage_mapping(zspage, &class_idx, &fg);
1369 	class = pool->size_class[class_idx];
1370 	off = (class->size * obj_idx) & ~PAGE_MASK;
1371 
1372 	area = this_cpu_ptr(&zs_map_area);
1373 	if (off + class->size <= PAGE_SIZE)
1374 		kunmap_atomic(area->vm_addr);
1375 	else {
1376 		struct page *pages[2];
1377 
1378 		pages[0] = page;
1379 		pages[1] = get_next_page(page);
1380 		BUG_ON(!pages[1]);
1381 
1382 		__zs_unmap_object(area, pages, off, class->size);
1383 	}
1384 	put_cpu_var(zs_map_area);
1385 
1386 	migrate_read_unlock(zspage);
1387 	unpin_tag(handle);
1388 }
1389 EXPORT_SYMBOL_GPL(zs_unmap_object);
1390 
1391 /**
1392  * zs_huge_class_size() - Returns the size (in bytes) of the first huge
1393  *                        zsmalloc &size_class.
1394  * @pool: zsmalloc pool to use
1395  *
1396  * The function returns the size of the first huge class - any object of equal
1397  * or bigger size will be stored in zspage consisting of a single physical
1398  * page.
1399  *
1400  * Context: Any context.
1401  *
1402  * Return: the size (in bytes) of the first huge zsmalloc &size_class.
1403  */
1404 size_t zs_huge_class_size(struct zs_pool *pool)
1405 {
1406 	return huge_class_size;
1407 }
1408 EXPORT_SYMBOL_GPL(zs_huge_class_size);
1409 
1410 static unsigned long obj_malloc(struct size_class *class,
1411 				struct zspage *zspage, unsigned long handle)
1412 {
1413 	int i, nr_page, offset;
1414 	unsigned long obj;
1415 	struct link_free *link;
1416 
1417 	struct page *m_page;
1418 	unsigned long m_offset;
1419 	void *vaddr;
1420 
1421 	handle |= OBJ_ALLOCATED_TAG;
1422 	obj = get_freeobj(zspage);
1423 
1424 	offset = obj * class->size;
1425 	nr_page = offset >> PAGE_SHIFT;
1426 	m_offset = offset & ~PAGE_MASK;
1427 	m_page = get_first_page(zspage);
1428 
1429 	for (i = 0; i < nr_page; i++)
1430 		m_page = get_next_page(m_page);
1431 
1432 	vaddr = kmap_atomic(m_page);
1433 	link = (struct link_free *)vaddr + m_offset / sizeof(*link);
1434 	set_freeobj(zspage, link->next >> OBJ_TAG_BITS);
1435 	if (likely(!PageHugeObject(m_page)))
1436 		/* record handle in the header of allocated chunk */
1437 		link->handle = handle;
1438 	else
1439 		/* record handle to page->index */
1440 		zspage->first_page->index = handle;
1441 
1442 	kunmap_atomic(vaddr);
1443 	mod_zspage_inuse(zspage, 1);
1444 	zs_stat_inc(class, OBJ_USED, 1);
1445 
1446 	obj = location_to_obj(m_page, obj);
1447 
1448 	return obj;
1449 }
1450 
1451 
1452 /**
1453  * zs_malloc - Allocate block of given size from pool.
1454  * @pool: pool to allocate from
1455  * @size: size of block to allocate
1456  * @gfp: gfp flags when allocating object
1457  *
1458  * On success, handle to the allocated object is returned,
1459  * otherwise 0.
1460  * Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail.
1461  */
1462 unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
1463 {
1464 	unsigned long handle, obj;
1465 	struct size_class *class;
1466 	enum fullness_group newfg;
1467 	struct zspage *zspage;
1468 
1469 	if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
1470 		return 0;
1471 
1472 	handle = cache_alloc_handle(pool, gfp);
1473 	if (!handle)
1474 		return 0;
1475 
1476 	/* extra space in chunk to keep the handle */
1477 	size += ZS_HANDLE_SIZE;
1478 	class = pool->size_class[get_size_class_index(size)];
1479 
1480 	spin_lock(&class->lock);
1481 	zspage = find_get_zspage(class);
1482 	if (likely(zspage)) {
1483 		obj = obj_malloc(class, zspage, handle);
1484 		/* Now move the zspage to another fullness group, if required */
1485 		fix_fullness_group(class, zspage);
1486 		record_obj(handle, obj);
1487 		spin_unlock(&class->lock);
1488 
1489 		return handle;
1490 	}
1491 
1492 	spin_unlock(&class->lock);
1493 
1494 	zspage = alloc_zspage(pool, class, gfp);
1495 	if (!zspage) {
1496 		cache_free_handle(pool, handle);
1497 		return 0;
1498 	}
1499 
1500 	spin_lock(&class->lock);
1501 	obj = obj_malloc(class, zspage, handle);
1502 	newfg = get_fullness_group(class, zspage);
1503 	insert_zspage(class, zspage, newfg);
1504 	set_zspage_mapping(zspage, class->index, newfg);
1505 	record_obj(handle, obj);
1506 	atomic_long_add(class->pages_per_zspage,
1507 				&pool->pages_allocated);
1508 	zs_stat_inc(class, OBJ_ALLOCATED, class->objs_per_zspage);
1509 
1510 	/* We completely set up zspage so mark them as movable */
1511 	SetZsPageMovable(pool, zspage);
1512 	spin_unlock(&class->lock);
1513 
1514 	return handle;
1515 }
1516 EXPORT_SYMBOL_GPL(zs_malloc);
1517 
1518 static void obj_free(struct size_class *class, unsigned long obj)
1519 {
1520 	struct link_free *link;
1521 	struct zspage *zspage;
1522 	struct page *f_page;
1523 	unsigned long f_offset;
1524 	unsigned int f_objidx;
1525 	void *vaddr;
1526 
1527 	obj &= ~OBJ_ALLOCATED_TAG;
1528 	obj_to_location(obj, &f_page, &f_objidx);
1529 	f_offset = (class->size * f_objidx) & ~PAGE_MASK;
1530 	zspage = get_zspage(f_page);
1531 
1532 	vaddr = kmap_atomic(f_page);
1533 
1534 	/* Insert this object in containing zspage's freelist */
1535 	link = (struct link_free *)(vaddr + f_offset);
1536 	link->next = get_freeobj(zspage) << OBJ_TAG_BITS;
1537 	kunmap_atomic(vaddr);
1538 	set_freeobj(zspage, f_objidx);
1539 	mod_zspage_inuse(zspage, -1);
1540 	zs_stat_dec(class, OBJ_USED, 1);
1541 }
1542 
1543 void zs_free(struct zs_pool *pool, unsigned long handle)
1544 {
1545 	struct zspage *zspage;
1546 	struct page *f_page;
1547 	unsigned long obj;
1548 	unsigned int f_objidx;
1549 	int class_idx;
1550 	struct size_class *class;
1551 	enum fullness_group fullness;
1552 	bool isolated;
1553 
1554 	if (unlikely(!handle))
1555 		return;
1556 
1557 	pin_tag(handle);
1558 	obj = handle_to_obj(handle);
1559 	obj_to_location(obj, &f_page, &f_objidx);
1560 	zspage = get_zspage(f_page);
1561 
1562 	migrate_read_lock(zspage);
1563 
1564 	get_zspage_mapping(zspage, &class_idx, &fullness);
1565 	class = pool->size_class[class_idx];
1566 
1567 	spin_lock(&class->lock);
1568 	obj_free(class, obj);
1569 	fullness = fix_fullness_group(class, zspage);
1570 	if (fullness != ZS_EMPTY) {
1571 		migrate_read_unlock(zspage);
1572 		goto out;
1573 	}
1574 
1575 	isolated = is_zspage_isolated(zspage);
1576 	migrate_read_unlock(zspage);
1577 	/* If zspage is isolated, zs_page_putback will free the zspage */
1578 	if (likely(!isolated))
1579 		free_zspage(pool, class, zspage);
1580 out:
1581 
1582 	spin_unlock(&class->lock);
1583 	unpin_tag(handle);
1584 	cache_free_handle(pool, handle);
1585 }
1586 EXPORT_SYMBOL_GPL(zs_free);
1587 
1588 static void zs_object_copy(struct size_class *class, unsigned long dst,
1589 				unsigned long src)
1590 {
1591 	struct page *s_page, *d_page;
1592 	unsigned int s_objidx, d_objidx;
1593 	unsigned long s_off, d_off;
1594 	void *s_addr, *d_addr;
1595 	int s_size, d_size, size;
1596 	int written = 0;
1597 
1598 	s_size = d_size = class->size;
1599 
1600 	obj_to_location(src, &s_page, &s_objidx);
1601 	obj_to_location(dst, &d_page, &d_objidx);
1602 
1603 	s_off = (class->size * s_objidx) & ~PAGE_MASK;
1604 	d_off = (class->size * d_objidx) & ~PAGE_MASK;
1605 
1606 	if (s_off + class->size > PAGE_SIZE)
1607 		s_size = PAGE_SIZE - s_off;
1608 
1609 	if (d_off + class->size > PAGE_SIZE)
1610 		d_size = PAGE_SIZE - d_off;
1611 
1612 	s_addr = kmap_atomic(s_page);
1613 	d_addr = kmap_atomic(d_page);
1614 
1615 	while (1) {
1616 		size = min(s_size, d_size);
1617 		memcpy(d_addr + d_off, s_addr + s_off, size);
1618 		written += size;
1619 
1620 		if (written == class->size)
1621 			break;
1622 
1623 		s_off += size;
1624 		s_size -= size;
1625 		d_off += size;
1626 		d_size -= size;
1627 
1628 		if (s_off >= PAGE_SIZE) {
1629 			kunmap_atomic(d_addr);
1630 			kunmap_atomic(s_addr);
1631 			s_page = get_next_page(s_page);
1632 			s_addr = kmap_atomic(s_page);
1633 			d_addr = kmap_atomic(d_page);
1634 			s_size = class->size - written;
1635 			s_off = 0;
1636 		}
1637 
1638 		if (d_off >= PAGE_SIZE) {
1639 			kunmap_atomic(d_addr);
1640 			d_page = get_next_page(d_page);
1641 			d_addr = kmap_atomic(d_page);
1642 			d_size = class->size - written;
1643 			d_off = 0;
1644 		}
1645 	}
1646 
1647 	kunmap_atomic(d_addr);
1648 	kunmap_atomic(s_addr);
1649 }
1650 
1651 /*
1652  * Find alloced object in zspage from index object and
1653  * return handle.
1654  */
1655 static unsigned long find_alloced_obj(struct size_class *class,
1656 					struct page *page, int *obj_idx)
1657 {
1658 	unsigned long head;
1659 	int offset = 0;
1660 	int index = *obj_idx;
1661 	unsigned long handle = 0;
1662 	void *addr = kmap_atomic(page);
1663 
1664 	offset = get_first_obj_offset(page);
1665 	offset += class->size * index;
1666 
1667 	while (offset < PAGE_SIZE) {
1668 		head = obj_to_head(page, addr + offset);
1669 		if (head & OBJ_ALLOCATED_TAG) {
1670 			handle = head & ~OBJ_ALLOCATED_TAG;
1671 			if (trypin_tag(handle))
1672 				break;
1673 			handle = 0;
1674 		}
1675 
1676 		offset += class->size;
1677 		index++;
1678 	}
1679 
1680 	kunmap_atomic(addr);
1681 
1682 	*obj_idx = index;
1683 
1684 	return handle;
1685 }
1686 
1687 struct zs_compact_control {
1688 	/* Source spage for migration which could be a subpage of zspage */
1689 	struct page *s_page;
1690 	/* Destination page for migration which should be a first page
1691 	 * of zspage. */
1692 	struct page *d_page;
1693 	 /* Starting object index within @s_page which used for live object
1694 	  * in the subpage. */
1695 	int obj_idx;
1696 };
1697 
1698 static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
1699 				struct zs_compact_control *cc)
1700 {
1701 	unsigned long used_obj, free_obj;
1702 	unsigned long handle;
1703 	struct page *s_page = cc->s_page;
1704 	struct page *d_page = cc->d_page;
1705 	int obj_idx = cc->obj_idx;
1706 	int ret = 0;
1707 
1708 	while (1) {
1709 		handle = find_alloced_obj(class, s_page, &obj_idx);
1710 		if (!handle) {
1711 			s_page = get_next_page(s_page);
1712 			if (!s_page)
1713 				break;
1714 			obj_idx = 0;
1715 			continue;
1716 		}
1717 
1718 		/* Stop if there is no more space */
1719 		if (zspage_full(class, get_zspage(d_page))) {
1720 			unpin_tag(handle);
1721 			ret = -ENOMEM;
1722 			break;
1723 		}
1724 
1725 		used_obj = handle_to_obj(handle);
1726 		free_obj = obj_malloc(class, get_zspage(d_page), handle);
1727 		zs_object_copy(class, free_obj, used_obj);
1728 		obj_idx++;
1729 		/*
1730 		 * record_obj updates handle's value to free_obj and it will
1731 		 * invalidate lock bit(ie, HANDLE_PIN_BIT) of handle, which
1732 		 * breaks synchronization using pin_tag(e,g, zs_free) so
1733 		 * let's keep the lock bit.
1734 		 */
1735 		free_obj |= BIT(HANDLE_PIN_BIT);
1736 		record_obj(handle, free_obj);
1737 		unpin_tag(handle);
1738 		obj_free(class, used_obj);
1739 	}
1740 
1741 	/* Remember last position in this iteration */
1742 	cc->s_page = s_page;
1743 	cc->obj_idx = obj_idx;
1744 
1745 	return ret;
1746 }
1747 
1748 static struct zspage *isolate_zspage(struct size_class *class, bool source)
1749 {
1750 	int i;
1751 	struct zspage *zspage;
1752 	enum fullness_group fg[2] = {ZS_ALMOST_EMPTY, ZS_ALMOST_FULL};
1753 
1754 	if (!source) {
1755 		fg[0] = ZS_ALMOST_FULL;
1756 		fg[1] = ZS_ALMOST_EMPTY;
1757 	}
1758 
1759 	for (i = 0; i < 2; i++) {
1760 		zspage = list_first_entry_or_null(&class->fullness_list[fg[i]],
1761 							struct zspage, list);
1762 		if (zspage) {
1763 			VM_BUG_ON(is_zspage_isolated(zspage));
1764 			remove_zspage(class, zspage, fg[i]);
1765 			return zspage;
1766 		}
1767 	}
1768 
1769 	return zspage;
1770 }
1771 
1772 /*
1773  * putback_zspage - add @zspage into right class's fullness list
1774  * @class: destination class
1775  * @zspage: target page
1776  *
1777  * Return @zspage's fullness_group
1778  */
1779 static enum fullness_group putback_zspage(struct size_class *class,
1780 			struct zspage *zspage)
1781 {
1782 	enum fullness_group fullness;
1783 
1784 	VM_BUG_ON(is_zspage_isolated(zspage));
1785 
1786 	fullness = get_fullness_group(class, zspage);
1787 	insert_zspage(class, zspage, fullness);
1788 	set_zspage_mapping(zspage, class->index, fullness);
1789 
1790 	return fullness;
1791 }
1792 
1793 #ifdef CONFIG_COMPACTION
1794 /*
1795  * To prevent zspage destroy during migration, zspage freeing should
1796  * hold locks of all pages in the zspage.
1797  */
1798 static void lock_zspage(struct zspage *zspage)
1799 {
1800 	struct page *page = get_first_page(zspage);
1801 
1802 	do {
1803 		lock_page(page);
1804 	} while ((page = get_next_page(page)) != NULL);
1805 }
1806 
1807 static int zs_init_fs_context(struct fs_context *fc)
1808 {
1809 	return init_pseudo(fc, ZSMALLOC_MAGIC) ? 0 : -ENOMEM;
1810 }
1811 
1812 static struct file_system_type zsmalloc_fs = {
1813 	.name		= "zsmalloc",
1814 	.init_fs_context = zs_init_fs_context,
1815 	.kill_sb	= kill_anon_super,
1816 };
1817 
1818 static int zsmalloc_mount(void)
1819 {
1820 	int ret = 0;
1821 
1822 	zsmalloc_mnt = kern_mount(&zsmalloc_fs);
1823 	if (IS_ERR(zsmalloc_mnt))
1824 		ret = PTR_ERR(zsmalloc_mnt);
1825 
1826 	return ret;
1827 }
1828 
1829 static void zsmalloc_unmount(void)
1830 {
1831 	kern_unmount(zsmalloc_mnt);
1832 }
1833 
1834 static void migrate_lock_init(struct zspage *zspage)
1835 {
1836 	rwlock_init(&zspage->lock);
1837 }
1838 
1839 static void migrate_read_lock(struct zspage *zspage)
1840 {
1841 	read_lock(&zspage->lock);
1842 }
1843 
1844 static void migrate_read_unlock(struct zspage *zspage)
1845 {
1846 	read_unlock(&zspage->lock);
1847 }
1848 
1849 static void migrate_write_lock(struct zspage *zspage)
1850 {
1851 	write_lock(&zspage->lock);
1852 }
1853 
1854 static void migrate_write_unlock(struct zspage *zspage)
1855 {
1856 	write_unlock(&zspage->lock);
1857 }
1858 
1859 /* Number of isolated subpage for *page migration* in this zspage */
1860 static void inc_zspage_isolation(struct zspage *zspage)
1861 {
1862 	zspage->isolated++;
1863 }
1864 
1865 static void dec_zspage_isolation(struct zspage *zspage)
1866 {
1867 	zspage->isolated--;
1868 }
1869 
1870 static void putback_zspage_deferred(struct zs_pool *pool,
1871 				    struct size_class *class,
1872 				    struct zspage *zspage)
1873 {
1874 	enum fullness_group fg;
1875 
1876 	fg = putback_zspage(class, zspage);
1877 	if (fg == ZS_EMPTY)
1878 		schedule_work(&pool->free_work);
1879 
1880 }
1881 
1882 static inline void zs_pool_dec_isolated(struct zs_pool *pool)
1883 {
1884 	VM_BUG_ON(atomic_long_read(&pool->isolated_pages) <= 0);
1885 	atomic_long_dec(&pool->isolated_pages);
1886 	/*
1887 	 * There's no possibility of racing, since wait_for_isolated_drain()
1888 	 * checks the isolated count under &class->lock after enqueuing
1889 	 * on migration_wait.
1890 	 */
1891 	if (atomic_long_read(&pool->isolated_pages) == 0 && pool->destroying)
1892 		wake_up_all(&pool->migration_wait);
1893 }
1894 
1895 static void replace_sub_page(struct size_class *class, struct zspage *zspage,
1896 				struct page *newpage, struct page *oldpage)
1897 {
1898 	struct page *page;
1899 	struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE] = {NULL, };
1900 	int idx = 0;
1901 
1902 	page = get_first_page(zspage);
1903 	do {
1904 		if (page == oldpage)
1905 			pages[idx] = newpage;
1906 		else
1907 			pages[idx] = page;
1908 		idx++;
1909 	} while ((page = get_next_page(page)) != NULL);
1910 
1911 	create_page_chain(class, zspage, pages);
1912 	set_first_obj_offset(newpage, get_first_obj_offset(oldpage));
1913 	if (unlikely(PageHugeObject(oldpage)))
1914 		newpage->index = oldpage->index;
1915 	__SetPageMovable(newpage, page_mapping(oldpage));
1916 }
1917 
1918 static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
1919 {
1920 	struct zs_pool *pool;
1921 	struct size_class *class;
1922 	int class_idx;
1923 	enum fullness_group fullness;
1924 	struct zspage *zspage;
1925 	struct address_space *mapping;
1926 
1927 	/*
1928 	 * Page is locked so zspage couldn't be destroyed. For detail, look at
1929 	 * lock_zspage in free_zspage.
1930 	 */
1931 	VM_BUG_ON_PAGE(!PageMovable(page), page);
1932 	VM_BUG_ON_PAGE(PageIsolated(page), page);
1933 
1934 	zspage = get_zspage(page);
1935 
1936 	/*
1937 	 * Without class lock, fullness could be stale while class_idx is okay
1938 	 * because class_idx is constant unless page is freed so we should get
1939 	 * fullness again under class lock.
1940 	 */
1941 	get_zspage_mapping(zspage, &class_idx, &fullness);
1942 	mapping = page_mapping(page);
1943 	pool = mapping->private_data;
1944 	class = pool->size_class[class_idx];
1945 
1946 	spin_lock(&class->lock);
1947 	if (get_zspage_inuse(zspage) == 0) {
1948 		spin_unlock(&class->lock);
1949 		return false;
1950 	}
1951 
1952 	/* zspage is isolated for object migration */
1953 	if (list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
1954 		spin_unlock(&class->lock);
1955 		return false;
1956 	}
1957 
1958 	/*
1959 	 * If this is first time isolation for the zspage, isolate zspage from
1960 	 * size_class to prevent further object allocation from the zspage.
1961 	 */
1962 	if (!list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
1963 		get_zspage_mapping(zspage, &class_idx, &fullness);
1964 		atomic_long_inc(&pool->isolated_pages);
1965 		remove_zspage(class, zspage, fullness);
1966 	}
1967 
1968 	inc_zspage_isolation(zspage);
1969 	spin_unlock(&class->lock);
1970 
1971 	return true;
1972 }
1973 
1974 static int zs_page_migrate(struct address_space *mapping, struct page *newpage,
1975 		struct page *page, enum migrate_mode mode)
1976 {
1977 	struct zs_pool *pool;
1978 	struct size_class *class;
1979 	int class_idx;
1980 	enum fullness_group fullness;
1981 	struct zspage *zspage;
1982 	struct page *dummy;
1983 	void *s_addr, *d_addr, *addr;
1984 	int offset, pos;
1985 	unsigned long handle, head;
1986 	unsigned long old_obj, new_obj;
1987 	unsigned int obj_idx;
1988 	int ret = -EAGAIN;
1989 
1990 	/*
1991 	 * We cannot support the _NO_COPY case here, because copy needs to
1992 	 * happen under the zs lock, which does not work with
1993 	 * MIGRATE_SYNC_NO_COPY workflow.
1994 	 */
1995 	if (mode == MIGRATE_SYNC_NO_COPY)
1996 		return -EINVAL;
1997 
1998 	VM_BUG_ON_PAGE(!PageMovable(page), page);
1999 	VM_BUG_ON_PAGE(!PageIsolated(page), page);
2000 
2001 	zspage = get_zspage(page);
2002 
2003 	/* Concurrent compactor cannot migrate any subpage in zspage */
2004 	migrate_write_lock(zspage);
2005 	get_zspage_mapping(zspage, &class_idx, &fullness);
2006 	pool = mapping->private_data;
2007 	class = pool->size_class[class_idx];
2008 	offset = get_first_obj_offset(page);
2009 
2010 	spin_lock(&class->lock);
2011 	if (!get_zspage_inuse(zspage)) {
2012 		/*
2013 		 * Set "offset" to end of the page so that every loops
2014 		 * skips unnecessary object scanning.
2015 		 */
2016 		offset = PAGE_SIZE;
2017 	}
2018 
2019 	pos = offset;
2020 	s_addr = kmap_atomic(page);
2021 	while (pos < PAGE_SIZE) {
2022 		head = obj_to_head(page, s_addr + pos);
2023 		if (head & OBJ_ALLOCATED_TAG) {
2024 			handle = head & ~OBJ_ALLOCATED_TAG;
2025 			if (!trypin_tag(handle))
2026 				goto unpin_objects;
2027 		}
2028 		pos += class->size;
2029 	}
2030 
2031 	/*
2032 	 * Here, any user cannot access all objects in the zspage so let's move.
2033 	 */
2034 	d_addr = kmap_atomic(newpage);
2035 	memcpy(d_addr, s_addr, PAGE_SIZE);
2036 	kunmap_atomic(d_addr);
2037 
2038 	for (addr = s_addr + offset; addr < s_addr + pos;
2039 					addr += class->size) {
2040 		head = obj_to_head(page, addr);
2041 		if (head & OBJ_ALLOCATED_TAG) {
2042 			handle = head & ~OBJ_ALLOCATED_TAG;
2043 			if (!testpin_tag(handle))
2044 				BUG();
2045 
2046 			old_obj = handle_to_obj(handle);
2047 			obj_to_location(old_obj, &dummy, &obj_idx);
2048 			new_obj = (unsigned long)location_to_obj(newpage,
2049 								obj_idx);
2050 			new_obj |= BIT(HANDLE_PIN_BIT);
2051 			record_obj(handle, new_obj);
2052 		}
2053 	}
2054 
2055 	replace_sub_page(class, zspage, newpage, page);
2056 	get_page(newpage);
2057 
2058 	dec_zspage_isolation(zspage);
2059 
2060 	/*
2061 	 * Page migration is done so let's putback isolated zspage to
2062 	 * the list if @page is final isolated subpage in the zspage.
2063 	 */
2064 	if (!is_zspage_isolated(zspage)) {
2065 		/*
2066 		 * We cannot race with zs_destroy_pool() here because we wait
2067 		 * for isolation to hit zero before we start destroying.
2068 		 * Also, we ensure that everyone can see pool->destroying before
2069 		 * we start waiting.
2070 		 */
2071 		putback_zspage_deferred(pool, class, zspage);
2072 		zs_pool_dec_isolated(pool);
2073 	}
2074 
2075 	reset_page(page);
2076 	put_page(page);
2077 	page = newpage;
2078 
2079 	ret = MIGRATEPAGE_SUCCESS;
2080 unpin_objects:
2081 	for (addr = s_addr + offset; addr < s_addr + pos;
2082 						addr += class->size) {
2083 		head = obj_to_head(page, addr);
2084 		if (head & OBJ_ALLOCATED_TAG) {
2085 			handle = head & ~OBJ_ALLOCATED_TAG;
2086 			if (!testpin_tag(handle))
2087 				BUG();
2088 			unpin_tag(handle);
2089 		}
2090 	}
2091 	kunmap_atomic(s_addr);
2092 	spin_unlock(&class->lock);
2093 	migrate_write_unlock(zspage);
2094 
2095 	return ret;
2096 }
2097 
2098 static void zs_page_putback(struct page *page)
2099 {
2100 	struct zs_pool *pool;
2101 	struct size_class *class;
2102 	int class_idx;
2103 	enum fullness_group fg;
2104 	struct address_space *mapping;
2105 	struct zspage *zspage;
2106 
2107 	VM_BUG_ON_PAGE(!PageMovable(page), page);
2108 	VM_BUG_ON_PAGE(!PageIsolated(page), page);
2109 
2110 	zspage = get_zspage(page);
2111 	get_zspage_mapping(zspage, &class_idx, &fg);
2112 	mapping = page_mapping(page);
2113 	pool = mapping->private_data;
2114 	class = pool->size_class[class_idx];
2115 
2116 	spin_lock(&class->lock);
2117 	dec_zspage_isolation(zspage);
2118 	if (!is_zspage_isolated(zspage)) {
2119 		/*
2120 		 * Due to page_lock, we cannot free zspage immediately
2121 		 * so let's defer.
2122 		 */
2123 		putback_zspage_deferred(pool, class, zspage);
2124 		zs_pool_dec_isolated(pool);
2125 	}
2126 	spin_unlock(&class->lock);
2127 }
2128 
2129 static const struct address_space_operations zsmalloc_aops = {
2130 	.isolate_page = zs_page_isolate,
2131 	.migratepage = zs_page_migrate,
2132 	.putback_page = zs_page_putback,
2133 };
2134 
2135 static int zs_register_migration(struct zs_pool *pool)
2136 {
2137 	pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb);
2138 	if (IS_ERR(pool->inode)) {
2139 		pool->inode = NULL;
2140 		return 1;
2141 	}
2142 
2143 	pool->inode->i_mapping->private_data = pool;
2144 	pool->inode->i_mapping->a_ops = &zsmalloc_aops;
2145 	return 0;
2146 }
2147 
2148 static bool pool_isolated_are_drained(struct zs_pool *pool)
2149 {
2150 	return atomic_long_read(&pool->isolated_pages) == 0;
2151 }
2152 
2153 /* Function for resolving migration */
2154 static void wait_for_isolated_drain(struct zs_pool *pool)
2155 {
2156 
2157 	/*
2158 	 * We're in the process of destroying the pool, so there are no
2159 	 * active allocations. zs_page_isolate() fails for completely free
2160 	 * zspages, so we need only wait for the zs_pool's isolated
2161 	 * count to hit zero.
2162 	 */
2163 	wait_event(pool->migration_wait,
2164 		   pool_isolated_are_drained(pool));
2165 }
2166 
2167 static void zs_unregister_migration(struct zs_pool *pool)
2168 {
2169 	pool->destroying = true;
2170 	/*
2171 	 * We need a memory barrier here to ensure global visibility of
2172 	 * pool->destroying. Thus pool->isolated pages will either be 0 in which
2173 	 * case we don't care, or it will be > 0 and pool->destroying will
2174 	 * ensure that we wake up once isolation hits 0.
2175 	 */
2176 	smp_mb();
2177 	wait_for_isolated_drain(pool); /* This can block */
2178 	flush_work(&pool->free_work);
2179 	iput(pool->inode);
2180 }
2181 
2182 /*
2183  * Caller should hold page_lock of all pages in the zspage
2184  * In here, we cannot use zspage meta data.
2185  */
2186 static void async_free_zspage(struct work_struct *work)
2187 {
2188 	int i;
2189 	struct size_class *class;
2190 	unsigned int class_idx;
2191 	enum fullness_group fullness;
2192 	struct zspage *zspage, *tmp;
2193 	LIST_HEAD(free_pages);
2194 	struct zs_pool *pool = container_of(work, struct zs_pool,
2195 					free_work);
2196 
2197 	for (i = 0; i < ZS_SIZE_CLASSES; i++) {
2198 		class = pool->size_class[i];
2199 		if (class->index != i)
2200 			continue;
2201 
2202 		spin_lock(&class->lock);
2203 		list_splice_init(&class->fullness_list[ZS_EMPTY], &free_pages);
2204 		spin_unlock(&class->lock);
2205 	}
2206 
2207 
2208 	list_for_each_entry_safe(zspage, tmp, &free_pages, list) {
2209 		list_del(&zspage->list);
2210 		lock_zspage(zspage);
2211 
2212 		get_zspage_mapping(zspage, &class_idx, &fullness);
2213 		VM_BUG_ON(fullness != ZS_EMPTY);
2214 		class = pool->size_class[class_idx];
2215 		spin_lock(&class->lock);
2216 		__free_zspage(pool, pool->size_class[class_idx], zspage);
2217 		spin_unlock(&class->lock);
2218 	}
2219 };
2220 
2221 static void kick_deferred_free(struct zs_pool *pool)
2222 {
2223 	schedule_work(&pool->free_work);
2224 }
2225 
2226 static void init_deferred_free(struct zs_pool *pool)
2227 {
2228 	INIT_WORK(&pool->free_work, async_free_zspage);
2229 }
2230 
2231 static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage)
2232 {
2233 	struct page *page = get_first_page(zspage);
2234 
2235 	do {
2236 		WARN_ON(!trylock_page(page));
2237 		__SetPageMovable(page, pool->inode->i_mapping);
2238 		unlock_page(page);
2239 	} while ((page = get_next_page(page)) != NULL);
2240 }
2241 #endif
2242 
2243 /*
2244  *
2245  * Based on the number of unused allocated objects calculate
2246  * and return the number of pages that we can free.
2247  */
2248 static unsigned long zs_can_compact(struct size_class *class)
2249 {
2250 	unsigned long obj_wasted;
2251 	unsigned long obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
2252 	unsigned long obj_used = zs_stat_get(class, OBJ_USED);
2253 
2254 	if (obj_allocated <= obj_used)
2255 		return 0;
2256 
2257 	obj_wasted = obj_allocated - obj_used;
2258 	obj_wasted /= class->objs_per_zspage;
2259 
2260 	return obj_wasted * class->pages_per_zspage;
2261 }
2262 
2263 static void __zs_compact(struct zs_pool *pool, struct size_class *class)
2264 {
2265 	struct zs_compact_control cc;
2266 	struct zspage *src_zspage;
2267 	struct zspage *dst_zspage = NULL;
2268 
2269 	spin_lock(&class->lock);
2270 	while ((src_zspage = isolate_zspage(class, true))) {
2271 
2272 		if (!zs_can_compact(class))
2273 			break;
2274 
2275 		cc.obj_idx = 0;
2276 		cc.s_page = get_first_page(src_zspage);
2277 
2278 		while ((dst_zspage = isolate_zspage(class, false))) {
2279 			cc.d_page = get_first_page(dst_zspage);
2280 			/*
2281 			 * If there is no more space in dst_page, resched
2282 			 * and see if anyone had allocated another zspage.
2283 			 */
2284 			if (!migrate_zspage(pool, class, &cc))
2285 				break;
2286 
2287 			putback_zspage(class, dst_zspage);
2288 		}
2289 
2290 		/* Stop if we couldn't find slot */
2291 		if (dst_zspage == NULL)
2292 			break;
2293 
2294 		putback_zspage(class, dst_zspage);
2295 		if (putback_zspage(class, src_zspage) == ZS_EMPTY) {
2296 			free_zspage(pool, class, src_zspage);
2297 			pool->stats.pages_compacted += class->pages_per_zspage;
2298 		}
2299 		spin_unlock(&class->lock);
2300 		cond_resched();
2301 		spin_lock(&class->lock);
2302 	}
2303 
2304 	if (src_zspage)
2305 		putback_zspage(class, src_zspage);
2306 
2307 	spin_unlock(&class->lock);
2308 }
2309 
2310 unsigned long zs_compact(struct zs_pool *pool)
2311 {
2312 	int i;
2313 	struct size_class *class;
2314 
2315 	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2316 		class = pool->size_class[i];
2317 		if (!class)
2318 			continue;
2319 		if (class->index != i)
2320 			continue;
2321 		__zs_compact(pool, class);
2322 	}
2323 
2324 	return pool->stats.pages_compacted;
2325 }
2326 EXPORT_SYMBOL_GPL(zs_compact);
2327 
2328 void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats)
2329 {
2330 	memcpy(stats, &pool->stats, sizeof(struct zs_pool_stats));
2331 }
2332 EXPORT_SYMBOL_GPL(zs_pool_stats);
2333 
2334 static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
2335 		struct shrink_control *sc)
2336 {
2337 	unsigned long pages_freed;
2338 	struct zs_pool *pool = container_of(shrinker, struct zs_pool,
2339 			shrinker);
2340 
2341 	pages_freed = pool->stats.pages_compacted;
2342 	/*
2343 	 * Compact classes and calculate compaction delta.
2344 	 * Can run concurrently with a manually triggered
2345 	 * (by user) compaction.
2346 	 */
2347 	pages_freed = zs_compact(pool) - pages_freed;
2348 
2349 	return pages_freed ? pages_freed : SHRINK_STOP;
2350 }
2351 
2352 static unsigned long zs_shrinker_count(struct shrinker *shrinker,
2353 		struct shrink_control *sc)
2354 {
2355 	int i;
2356 	struct size_class *class;
2357 	unsigned long pages_to_free = 0;
2358 	struct zs_pool *pool = container_of(shrinker, struct zs_pool,
2359 			shrinker);
2360 
2361 	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2362 		class = pool->size_class[i];
2363 		if (!class)
2364 			continue;
2365 		if (class->index != i)
2366 			continue;
2367 
2368 		pages_to_free += zs_can_compact(class);
2369 	}
2370 
2371 	return pages_to_free;
2372 }
2373 
2374 static void zs_unregister_shrinker(struct zs_pool *pool)
2375 {
2376 	unregister_shrinker(&pool->shrinker);
2377 }
2378 
2379 static int zs_register_shrinker(struct zs_pool *pool)
2380 {
2381 	pool->shrinker.scan_objects = zs_shrinker_scan;
2382 	pool->shrinker.count_objects = zs_shrinker_count;
2383 	pool->shrinker.batch = 0;
2384 	pool->shrinker.seeks = DEFAULT_SEEKS;
2385 
2386 	return register_shrinker(&pool->shrinker);
2387 }
2388 
2389 /**
2390  * zs_create_pool - Creates an allocation pool to work from.
2391  * @name: pool name to be created
2392  *
2393  * This function must be called before anything when using
2394  * the zsmalloc allocator.
2395  *
2396  * On success, a pointer to the newly created pool is returned,
2397  * otherwise NULL.
2398  */
2399 struct zs_pool *zs_create_pool(const char *name)
2400 {
2401 	int i;
2402 	struct zs_pool *pool;
2403 	struct size_class *prev_class = NULL;
2404 
2405 	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
2406 	if (!pool)
2407 		return NULL;
2408 
2409 	init_deferred_free(pool);
2410 
2411 	pool->name = kstrdup(name, GFP_KERNEL);
2412 	if (!pool->name)
2413 		goto err;
2414 
2415 #ifdef CONFIG_COMPACTION
2416 	init_waitqueue_head(&pool->migration_wait);
2417 #endif
2418 
2419 	if (create_cache(pool))
2420 		goto err;
2421 
2422 	/*
2423 	 * Iterate reversely, because, size of size_class that we want to use
2424 	 * for merging should be larger or equal to current size.
2425 	 */
2426 	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2427 		int size;
2428 		int pages_per_zspage;
2429 		int objs_per_zspage;
2430 		struct size_class *class;
2431 		int fullness = 0;
2432 
2433 		size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
2434 		if (size > ZS_MAX_ALLOC_SIZE)
2435 			size = ZS_MAX_ALLOC_SIZE;
2436 		pages_per_zspage = get_pages_per_zspage(size);
2437 		objs_per_zspage = pages_per_zspage * PAGE_SIZE / size;
2438 
2439 		/*
2440 		 * We iterate from biggest down to smallest classes,
2441 		 * so huge_class_size holds the size of the first huge
2442 		 * class. Any object bigger than or equal to that will
2443 		 * endup in the huge class.
2444 		 */
2445 		if (pages_per_zspage != 1 && objs_per_zspage != 1 &&
2446 				!huge_class_size) {
2447 			huge_class_size = size;
2448 			/*
2449 			 * The object uses ZS_HANDLE_SIZE bytes to store the
2450 			 * handle. We need to subtract it, because zs_malloc()
2451 			 * unconditionally adds handle size before it performs
2452 			 * size class search - so object may be smaller than
2453 			 * huge class size, yet it still can end up in the huge
2454 			 * class because it grows by ZS_HANDLE_SIZE extra bytes
2455 			 * right before class lookup.
2456 			 */
2457 			huge_class_size -= (ZS_HANDLE_SIZE - 1);
2458 		}
2459 
2460 		/*
2461 		 * size_class is used for normal zsmalloc operation such
2462 		 * as alloc/free for that size. Although it is natural that we
2463 		 * have one size_class for each size, there is a chance that we
2464 		 * can get more memory utilization if we use one size_class for
2465 		 * many different sizes whose size_class have same
2466 		 * characteristics. So, we makes size_class point to
2467 		 * previous size_class if possible.
2468 		 */
2469 		if (prev_class) {
2470 			if (can_merge(prev_class, pages_per_zspage, objs_per_zspage)) {
2471 				pool->size_class[i] = prev_class;
2472 				continue;
2473 			}
2474 		}
2475 
2476 		class = kzalloc(sizeof(struct size_class), GFP_KERNEL);
2477 		if (!class)
2478 			goto err;
2479 
2480 		class->size = size;
2481 		class->index = i;
2482 		class->pages_per_zspage = pages_per_zspage;
2483 		class->objs_per_zspage = objs_per_zspage;
2484 		spin_lock_init(&class->lock);
2485 		pool->size_class[i] = class;
2486 		for (fullness = ZS_EMPTY; fullness < NR_ZS_FULLNESS;
2487 							fullness++)
2488 			INIT_LIST_HEAD(&class->fullness_list[fullness]);
2489 
2490 		prev_class = class;
2491 	}
2492 
2493 	/* debug only, don't abort if it fails */
2494 	zs_pool_stat_create(pool, name);
2495 
2496 	if (zs_register_migration(pool))
2497 		goto err;
2498 
2499 	/*
2500 	 * Not critical since shrinker is only used to trigger internal
2501 	 * defragmentation of the pool which is pretty optional thing.  If
2502 	 * registration fails we still can use the pool normally and user can
2503 	 * trigger compaction manually. Thus, ignore return code.
2504 	 */
2505 	zs_register_shrinker(pool);
2506 
2507 	return pool;
2508 
2509 err:
2510 	zs_destroy_pool(pool);
2511 	return NULL;
2512 }
2513 EXPORT_SYMBOL_GPL(zs_create_pool);
2514 
2515 void zs_destroy_pool(struct zs_pool *pool)
2516 {
2517 	int i;
2518 
2519 	zs_unregister_shrinker(pool);
2520 	zs_unregister_migration(pool);
2521 	zs_pool_stat_destroy(pool);
2522 
2523 	for (i = 0; i < ZS_SIZE_CLASSES; i++) {
2524 		int fg;
2525 		struct size_class *class = pool->size_class[i];
2526 
2527 		if (!class)
2528 			continue;
2529 
2530 		if (class->index != i)
2531 			continue;
2532 
2533 		for (fg = ZS_EMPTY; fg < NR_ZS_FULLNESS; fg++) {
2534 			if (!list_empty(&class->fullness_list[fg])) {
2535 				pr_info("Freeing non-empty class with size %db, fullness group %d\n",
2536 					class->size, fg);
2537 			}
2538 		}
2539 		kfree(class);
2540 	}
2541 
2542 	destroy_cache(pool);
2543 	kfree(pool->name);
2544 	kfree(pool);
2545 }
2546 EXPORT_SYMBOL_GPL(zs_destroy_pool);
2547 
2548 static int __init zs_init(void)
2549 {
2550 	int ret;
2551 
2552 	ret = zsmalloc_mount();
2553 	if (ret)
2554 		goto out;
2555 
2556 	ret = cpuhp_setup_state(CPUHP_MM_ZS_PREPARE, "mm/zsmalloc:prepare",
2557 				zs_cpu_prepare, zs_cpu_dead);
2558 	if (ret)
2559 		goto hp_setup_fail;
2560 
2561 #ifdef CONFIG_ZPOOL
2562 	zpool_register_driver(&zs_zpool_driver);
2563 #endif
2564 
2565 	zs_stat_init();
2566 
2567 	return 0;
2568 
2569 hp_setup_fail:
2570 	zsmalloc_unmount();
2571 out:
2572 	return ret;
2573 }
2574 
2575 static void __exit zs_exit(void)
2576 {
2577 #ifdef CONFIG_ZPOOL
2578 	zpool_unregister_driver(&zs_zpool_driver);
2579 #endif
2580 	zsmalloc_unmount();
2581 	cpuhp_remove_state(CPUHP_MM_ZS_PREPARE);
2582 
2583 	zs_stat_exit();
2584 }
2585 
2586 module_init(zs_init);
2587 module_exit(zs_exit);
2588 
2589 MODULE_LICENSE("Dual BSD/GPL");
2590 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
2591