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->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->page_type: 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	/*
34	* lock ordering:
35	* page_lock
36	* pool->lock
37	* zspage->lock
38	*/
39
40	#include <linux/module.h>
41	#include <linux/kernel.h>
42	#include <linux/sched.h>
43	#include <linux/bitops.h>
44	#include <linux/errno.h>
45	#include <linux/highmem.h>
46	#include <linux/string.h>
47	#include <linux/slab.h>
48	#include <linux/pgtable.h>
49	#include <asm/tlbflush.h>
50	#include <linux/cpumask.h>
51	#include <linux/cpu.h>
52	#include <linux/vmalloc.h>
53	#include <linux/preempt.h>
54	#include <linux/spinlock.h>
55	#include <linux/shrinker.h>
56	#include <linux/types.h>
57	#include <linux/debugfs.h>
58	#include <linux/zsmalloc.h>
59	#include <linux/zpool.h>
60	#include <linux/migrate.h>
61	#include <linux/wait.h>
62	#include <linux/pagemap.h>
63	#include <linux/fs.h>
64	#include <linux/local_lock.h>
65
66	#define ZSPAGE_MAGIC 0x58
67
68	/*
69	* This must be power of 2 and greater than or equal to sizeof(link_free).
70	* These two conditions ensure that any 'struct link_free' itself doesn't
71	* span more than 1 page which avoids complex case of mapping 2 pages simply
72	* to restore link_free pointer values.
73	*/
74	#define ZS_ALIGN 8
75
76	#define ZS_HANDLE_SIZE (sizeof(unsigned long))
77
78	/*
79	* Object location (<PFN>, <obj_idx>) is encoded as
80	* a single (unsigned long) handle value.
81	*
82	* Note that object index <obj_idx> starts from 0.
83	*
84	* This is made more complicated by various memory models and PAE.
85	*/
86
87	#ifndef MAX_POSSIBLE_PHYSMEM_BITS
88	#ifdef MAX_PHYSMEM_BITS
89	#define MAX_POSSIBLE_PHYSMEM_BITS MAX_PHYSMEM_BITS
90	#else
91	/*
92	* If this definition of MAX_PHYSMEM_BITS is used, OBJ_INDEX_BITS will just
93	* be PAGE_SHIFT
94	*/
95	#define MAX_POSSIBLE_PHYSMEM_BITS BITS_PER_LONG
96	#endif
97	#endif
98
99	#define _PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)
100
101	/*
102	* Head in allocated object should have OBJ_ALLOCATED_TAG
103	* to identify the object was allocated or not.
104	* It's okay to add the status bit in the least bit because
105	* header keeps handle which is 4byte-aligned address so we
106	* have room for two bit at least.
107	*/
108	#define OBJ_ALLOCATED_TAG 1
109
110	#define OBJ_TAG_BITS 1
111	#define OBJ_TAG_MASK OBJ_ALLOCATED_TAG
112
113	#define OBJ_INDEX_BITS (BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS)
114	#define OBJ_INDEX_MASK ((_AC(1, UL) << OBJ_INDEX_BITS) - 1)
115
116	#define HUGE_BITS 1
117	#define FULLNESS_BITS 4
118	#define CLASS_BITS 8
119	#define ISOLATED_BITS 5
120	#define MAGIC_VAL_BITS 8
121
122	#define MAX(a, b) ((a) >= (b) ? (a) : (b))
123
124	#define ZS_MAX_PAGES_PER_ZSPAGE (_AC(CONFIG_ZSMALLOC_CHAIN_SIZE, UL))
125
126	/* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
127	#define ZS_MIN_ALLOC_SIZE \
128	MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
129	/* each chunk includes extra space to keep handle */
130	#define ZS_MAX_ALLOC_SIZE PAGE_SIZE
131
132	/*
133	* On systems with 4K page size, this gives 255 size classes! There is a
134	* trader-off here:
135	* - Large number of size classes is potentially wasteful as free page are
136	* spread across these classes
137	* - Small number of size classes causes large internal fragmentation
138	* - Probably its better to use specific size classes (empirically
139	* determined). NOTE: all those class sizes must be set as multiple of
140	* ZS_ALIGN to make sure link_free itself never has to span 2 pages.
141	*
142	* ZS_MIN_ALLOC_SIZE and ZS_SIZE_CLASS_DELTA must be multiple of ZS_ALIGN
143	* (reason above)
144	*/
145	#define ZS_SIZE_CLASS_DELTA (PAGE_SIZE >> CLASS_BITS)
146	#define ZS_SIZE_CLASSES (DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \
147	ZS_SIZE_CLASS_DELTA) + 1)
148
149	/*
150	* Pages are distinguished by the ratio of used memory (that is the ratio
151	* of ->inuse objects to all objects that page can store). For example,
152	* INUSE_RATIO_10 means that the ratio of used objects is > 0% and <= 10%.
153	*
154	* The number of fullness groups is not random. It allows us to keep
155	* difference between the least busy page in the group (minimum permitted
156	* number of ->inuse objects) and the most busy page (maximum permitted
157	* number of ->inuse objects) at a reasonable value.
158	*/
159	enum fullness_group {
160	ZS_INUSE_RATIO_0,
161	ZS_INUSE_RATIO_10,
162	/* NOTE: 8 more fullness groups here */
163	ZS_INUSE_RATIO_99 = 10,
164	ZS_INUSE_RATIO_100,
165	NR_FULLNESS_GROUPS,
166	};
167
168	enum class_stat_type {
169	/* NOTE: stats for 12 fullness groups here: from inuse 0 to 100 */
170	ZS_OBJS_ALLOCATED = NR_FULLNESS_GROUPS,
171	ZS_OBJS_INUSE,
172	NR_CLASS_STAT_TYPES,
173	};
174
175	struct zs_size_stat {
176	unsigned long objs[NR_CLASS_STAT_TYPES];
177	};
178
179	#ifdef CONFIG_ZSMALLOC_STAT
180	static struct dentry *zs_stat_root;
181	#endif
182
183	static size_t huge_class_size;
184
185	struct size_class {
186	struct list_head fullness_list[NR_FULLNESS_GROUPS];
187	/*
188	* Size of objects stored in this class. Must be multiple
189	* of ZS_ALIGN.
190	*/
191	int size;
192	int objs_per_zspage;
193	/* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
194	int pages_per_zspage;
195
196	unsigned int index;
197	struct zs_size_stat stats;
198	};
199
200	/*
201	* Placed within free objects to form a singly linked list.
202	* For every zspage, zspage->freeobj gives head of this list.
203	*
204	* This must be power of 2 and less than or equal to ZS_ALIGN
205	*/
206	struct link_free {
207	union {
208	/*
209	* Free object index;
210	* It's valid for non-allocated object
211	*/
212	unsigned long next;
213	/*
214	* Handle of allocated object.
215	*/
216	unsigned long handle;
217	};
218	};
219
220	struct zs_pool {
221	const char *name;
222
223	struct size_class *size_class[ZS_SIZE_CLASSES];
224	struct kmem_cache *handle_cachep;
225	struct kmem_cache *zspage_cachep;
226
227	atomic_long_t pages_allocated;
228
229	struct zs_pool_stats stats;
230
231	/* Compact classes */
232	struct shrinker *shrinker;
233
234	#ifdef CONFIG_ZSMALLOC_STAT
235	struct dentry *stat_dentry;
236	#endif
237	#ifdef CONFIG_COMPACTION
238	struct work_struct free_work;
239	#endif
240	spinlock_t lock;
241	atomic_t compaction_in_progress;
242	};
243
244	struct zspage {
245	struct {
246	unsigned int huge:HUGE_BITS;
247	unsigned int fullness:FULLNESS_BITS;
248	unsigned int class:CLASS_BITS + 1;
249	unsigned int isolated:ISOLATED_BITS;
250	unsigned int magic:MAGIC_VAL_BITS;
251	};
252	unsigned int inuse;
253	unsigned int freeobj;
254	struct page *first_page;
255	struct list_head list; /* fullness list */
256	struct zs_pool *pool;
257	rwlock_t lock;
258	};
259
260	struct mapping_area {
261	local_lock_t lock;
262	char *vm_buf; /* copy buffer for objects that span pages */
263	char *vm_addr; /* address of kmap_atomic()'ed pages */
264	enum zs_mapmode vm_mm; /* mapping mode */
265	};
266
267	/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
268	static void SetZsHugePage(struct zspage *zspage)
269	{
270	zspage->huge = 1;
271	}
272
273	static bool ZsHugePage(struct zspage *zspage)
274	{
275	return zspage->huge;
276	}
277
278	static void migrate_lock_init(struct zspage *zspage);
279	static void migrate_read_lock(struct zspage *zspage);
280	static void migrate_read_unlock(struct zspage *zspage);
281
282	#ifdef CONFIG_COMPACTION
283	static void migrate_write_lock(struct zspage *zspage);
284	static void migrate_write_lock_nested(struct zspage *zspage);
285	static void migrate_write_unlock(struct zspage *zspage);
286	static void kick_deferred_free(struct zs_pool *pool);
287	static void init_deferred_free(struct zs_pool *pool);
288	static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage);
289	#else
290	static void migrate_write_lock(struct zspage *zspage) {}
291	static void migrate_write_lock_nested(struct zspage *zspage) {}
292	static void migrate_write_unlock(struct zspage *zspage) {}
293	static void kick_deferred_free(struct zs_pool *pool) {}
294	static void init_deferred_free(struct zs_pool *pool) {}
295	static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage) {}
296	#endif
297
298	static int create_cache(struct zs_pool *pool)
299	{
300	pool->handle_cachep = kmem_cache_create(name: "zs_handle", ZS_HANDLE_SIZE,
301	align: 0, flags: 0, NULL);
302	if (!pool->handle_cachep)
303	return 1;
304
305	pool->zspage_cachep = kmem_cache_create(name: "zspage", size: sizeof(struct zspage),
306	align: 0, flags: 0, NULL);
307	if (!pool->zspage_cachep) {
308	kmem_cache_destroy(s: pool->handle_cachep);
309	pool->handle_cachep = NULL;
310	return 1;
311	}
312
313	return 0;
314	}
315
316	static void destroy_cache(struct zs_pool *pool)
317	{
318	kmem_cache_destroy(s: pool->handle_cachep);
319	kmem_cache_destroy(s: pool->zspage_cachep);
320	}
321
322	static unsigned long cache_alloc_handle(struct zs_pool *pool, gfp_t gfp)
323	{
324	return (unsigned long)kmem_cache_alloc(cachep: pool->handle_cachep,
325	flags: gfp & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
326	}
327
328	static void cache_free_handle(struct zs_pool *pool, unsigned long handle)
329	{
330	kmem_cache_free(s: pool->handle_cachep, objp: (void *)handle);
331	}
332
333	static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags)
334	{
335	return kmem_cache_zalloc(k: pool->zspage_cachep,
336	flags: flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
337	}
338
339	static void cache_free_zspage(struct zs_pool *pool, struct zspage *zspage)
340	{
341	kmem_cache_free(s: pool->zspage_cachep, objp: zspage);
342	}
343
344	/* pool->lock(which owns the handle) synchronizes races */
345	static void record_obj(unsigned long handle, unsigned long obj)
346	{
347	*(unsigned long *)handle = obj;
348	}
349
350	/* zpool driver */
351
352	#ifdef CONFIG_ZPOOL
353
354	static void *zs_zpool_create(const char *name, gfp_t gfp)
355	{
356	/*
357	* Ignore global gfp flags: zs_malloc() may be invoked from
358	* different contexts and its caller must provide a valid
359	* gfp mask.
360	*/
361	return zs_create_pool(name);
362	}
363
364	static void zs_zpool_destroy(void *pool)
365	{
366	zs_destroy_pool(pool);
367	}
368
369	static int zs_zpool_malloc(void *pool, size_t size, gfp_t gfp,
370	unsigned long *handle)
371	{
372	*handle = zs_malloc(pool, size, flags: gfp);
373
374	if (IS_ERR_VALUE(*handle))
375	return PTR_ERR(ptr: (void *)*handle);
376	return 0;
377	}
378	static void zs_zpool_free(void *pool, unsigned long handle)
379	{
380	zs_free(pool, obj: handle);
381	}
382
383	static void *zs_zpool_map(void *pool, unsigned long handle,
384	enum zpool_mapmode mm)
385	{
386	enum zs_mapmode zs_mm;
387
388	switch (mm) {
389	case ZPOOL_MM_RO:
390	zs_mm = ZS_MM_RO;
391	break;
392	case ZPOOL_MM_WO:
393	zs_mm = ZS_MM_WO;
394	break;
395	case ZPOOL_MM_RW:
396	default:
397	zs_mm = ZS_MM_RW;
398	break;
399	}
400
401	return zs_map_object(pool, handle, mm: zs_mm);
402	}
403	static void zs_zpool_unmap(void *pool, unsigned long handle)
404	{
405	zs_unmap_object(pool, handle);
406	}
407
408	static u64 zs_zpool_total_size(void *pool)
409	{
410	return zs_get_total_pages(pool) << PAGE_SHIFT;
411	}
412
413	static struct zpool_driver zs_zpool_driver = {
414	.type = "zsmalloc",
415	.owner = THIS_MODULE,
416	.create = zs_zpool_create,
417	.destroy = zs_zpool_destroy,
418	.malloc_support_movable = true,
419	.malloc = zs_zpool_malloc,
420	.free = zs_zpool_free,
421	.map = zs_zpool_map,
422	.unmap = zs_zpool_unmap,
423	.total_size = zs_zpool_total_size,
424	};
425
426	MODULE_ALIAS("zpool-zsmalloc");
427	#endif /* CONFIG_ZPOOL */
428
429	/* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
430	static DEFINE_PER_CPU(struct mapping_area, zs_map_area) = {
431	.lock = INIT_LOCAL_LOCK(lock),
432	};
433
434	static __maybe_unused int is_first_page(struct page *page)
435	{
436	return PagePrivate(page);
437	}
438
439	/* Protected by pool->lock */
440	static inline int get_zspage_inuse(struct zspage *zspage)
441	{
442	return zspage->inuse;
443	}
444
445
446	static inline void mod_zspage_inuse(struct zspage *zspage, int val)
447	{
448	zspage->inuse += val;
449	}
450
451	static inline struct page *get_first_page(struct zspage *zspage)
452	{
453	struct page *first_page = zspage->first_page;
454
455	VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
456	return first_page;
457	}
458
459	static inline unsigned int get_first_obj_offset(struct page *page)
460	{
461	return page->page_type;
462	}
463
464	static inline void set_first_obj_offset(struct page *page, unsigned int offset)
465	{
466	page->page_type = offset;
467	}
468
469	static inline unsigned int get_freeobj(struct zspage *zspage)
470	{
471	return zspage->freeobj;
472	}
473
474	static inline void set_freeobj(struct zspage *zspage, unsigned int obj)
475	{
476	zspage->freeobj = obj;
477	}
478
479	static void get_zspage_mapping(struct zspage *zspage,
480	unsigned int *class_idx,
481	int *fullness)
482	{
483	BUG_ON(zspage->magic != ZSPAGE_MAGIC);
484
485	*fullness = zspage->fullness;
486	*class_idx = zspage->class;
487	}
488
489	static struct size_class *zspage_class(struct zs_pool *pool,
490	struct zspage *zspage)
491	{
492	return pool->size_class[zspage->class];
493	}
494
495	static void set_zspage_mapping(struct zspage *zspage,
496	unsigned int class_idx,
497	int fullness)
498	{
499	zspage->class = class_idx;
500	zspage->fullness = fullness;
501	}
502
503	/*
504	* zsmalloc divides the pool into various size classes where each
505	* class maintains a list of zspages where each zspage is divided
506	* into equal sized chunks. Each allocation falls into one of these
507	* classes depending on its size. This function returns index of the
508	* size class which has chunk size big enough to hold the given size.
509	*/
510	static int get_size_class_index(int size)
511	{
512	int idx = 0;
513
514	if (likely(size > ZS_MIN_ALLOC_SIZE))
515	idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
516	ZS_SIZE_CLASS_DELTA);
517
518	return min_t(int, ZS_SIZE_CLASSES - 1, idx);
519	}
520
521	static inline void class_stat_inc(struct size_class *class,
522	int type, unsigned long cnt)
523	{
524	class->stats.objs[type] += cnt;
525	}
526
527	static inline void class_stat_dec(struct size_class *class,
528	int type, unsigned long cnt)
529	{
530	class->stats.objs[type] -= cnt;
531	}
532
533	static inline unsigned long zs_stat_get(struct size_class *class, int type)
534	{
535	return class->stats.objs[type];
536	}
537
538	#ifdef CONFIG_ZSMALLOC_STAT
539
540	static void __init zs_stat_init(void)
541	{
542	if (!debugfs_initialized()) {
543	pr_warn("debugfs not available, stat dir not created\n");
544	return;
545	}
546
547	zs_stat_root = debugfs_create_dir(name: "zsmalloc", NULL);
548	}
549
550	static void __exit zs_stat_exit(void)
551	{
552	debugfs_remove_recursive(dentry: zs_stat_root);
553	}
554
555	static unsigned long zs_can_compact(struct size_class *class);
556
557	static int zs_stats_size_show(struct seq_file *s, void *v)
558	{
559	int i, fg;
560	struct zs_pool *pool = s->private;
561	struct size_class *class;
562	int objs_per_zspage;
563	unsigned long obj_allocated, obj_used, pages_used, freeable;
564	unsigned long total_objs = 0, total_used_objs = 0, total_pages = 0;
565	unsigned long total_freeable = 0;
566	unsigned long inuse_totals[NR_FULLNESS_GROUPS] = {0, };
567
568	seq_printf(m: s, fmt: " %5s %5s %9s %9s %9s %9s %9s %9s %9s %9s %9s %9s %9s %13s %10s %10s %16s %8s\n",
569	"class", "size", "10%", "20%", "30%", "40%",
570	"50%", "60%", "70%", "80%", "90%", "99%", "100%",
571	"obj_allocated", "obj_used", "pages_used",
572	"pages_per_zspage", "freeable");
573
574	for (i = 0; i < ZS_SIZE_CLASSES; i++) {
575
576	class = pool->size_class[i];
577
578	if (class->index != i)
579	continue;
580
581	spin_lock(lock: &pool->lock);
582
583	seq_printf(m: s, fmt: " %5u %5u ", i, class->size);
584	for (fg = ZS_INUSE_RATIO_10; fg < NR_FULLNESS_GROUPS; fg++) {
585	inuse_totals[fg] += zs_stat_get(class, type: fg);
586	seq_printf(m: s, fmt: "%9lu ", zs_stat_get(class, type: fg));
587	}
588
589	obj_allocated = zs_stat_get(class, type: ZS_OBJS_ALLOCATED);
590	obj_used = zs_stat_get(class, type: ZS_OBJS_INUSE);
591	freeable = zs_can_compact(class);
592	spin_unlock(lock: &pool->lock);
593
594	objs_per_zspage = class->objs_per_zspage;
595	pages_used = obj_allocated / objs_per_zspage *
596	class->pages_per_zspage;
597
598	seq_printf(m: s, fmt: "%13lu %10lu %10lu %16d %8lu\n",
599	obj_allocated, obj_used, pages_used,
600	class->pages_per_zspage, freeable);
601
602	total_objs += obj_allocated;
603	total_used_objs += obj_used;
604	total_pages += pages_used;
605	total_freeable += freeable;
606	}
607
608	seq_puts(m: s, s: "\n");
609	seq_printf(m: s, fmt: " %5s %5s ", "Total", "");
610
611	for (fg = ZS_INUSE_RATIO_10; fg < NR_FULLNESS_GROUPS; fg++)
612	seq_printf(m: s, fmt: "%9lu ", inuse_totals[fg]);
613
614	seq_printf(m: s, fmt: "%13lu %10lu %10lu %16s %8lu\n",
615	total_objs, total_used_objs, total_pages, "",
616	total_freeable);
617
618	return 0;
619	}
620	DEFINE_SHOW_ATTRIBUTE(zs_stats_size);
621
622	static void zs_pool_stat_create(struct zs_pool *pool, const char *name)
623	{
624	if (!zs_stat_root) {
625	pr_warn("no root stat dir, not creating <%s> stat dir\n", name);
626	return;
627	}
628
629	pool->stat_dentry = debugfs_create_dir(name, parent: zs_stat_root);
630
631	debugfs_create_file(name: "classes", S_IFREG | 0444, parent: pool->stat_dentry, data: pool,
632	fops: &zs_stats_size_fops);
633	}
634
635	static void zs_pool_stat_destroy(struct zs_pool *pool)
636	{
637	debugfs_remove_recursive(dentry: pool->stat_dentry);
638	}
639
640	#else /* CONFIG_ZSMALLOC_STAT */
641	static void __init zs_stat_init(void)
642	{
643	}
644
645	static void __exit zs_stat_exit(void)
646	{
647	}
648
649	static inline void zs_pool_stat_create(struct zs_pool *pool, const char *name)
650	{
651	}
652
653	static inline void zs_pool_stat_destroy(struct zs_pool *pool)
654	{
655	}
656	#endif
657
658
659	/*
660	* For each size class, zspages are divided into different groups
661	* depending on their usage ratio. This function returns fullness
662	* status of the given page.
663	*/
664	static int get_fullness_group(struct size_class *class, struct zspage *zspage)
665	{
666	int inuse, objs_per_zspage, ratio;
667
668	inuse = get_zspage_inuse(zspage);
669	objs_per_zspage = class->objs_per_zspage;
670
671	if (inuse == 0)
672	return ZS_INUSE_RATIO_0;
673	if (inuse == objs_per_zspage)
674	return ZS_INUSE_RATIO_100;
675
676	ratio = 100 * inuse / objs_per_zspage;
677	/*
678	* Take integer division into consideration: a page with one inuse
679	* object out of 127 possible, will end up having 0 usage ratio,
680	* which is wrong as it belongs in ZS_INUSE_RATIO_10 fullness group.
681	*/
682	return ratio / 10 + 1;
683	}
684
685	/*
686	* Each size class maintains various freelists and zspages are assigned
687	* to one of these freelists based on the number of live objects they
688	* have. This functions inserts the given zspage into the freelist
689	* identified by <class, fullness_group>.
690	*/
691	static void insert_zspage(struct size_class *class,
692	struct zspage *zspage,
693	int fullness)
694	{
695	class_stat_inc(class, type: fullness, cnt: 1);
696	list_add(new: &zspage->list, head: &class->fullness_list[fullness]);
697	}
698
699	/*
700	* This function removes the given zspage from the freelist identified
701	* by <class, fullness_group>.
702	*/
703	static void remove_zspage(struct size_class *class,
704	struct zspage *zspage,
705	int fullness)
706	{
707	VM_BUG_ON(list_empty(&class->fullness_list[fullness]));
708
709	list_del_init(entry: &zspage->list);
710	class_stat_dec(class, type: fullness, cnt: 1);
711	}
712
713	/*
714	* Each size class maintains zspages in different fullness groups depending
715	* on the number of live objects they contain. When allocating or freeing
716	* objects, the fullness status of the page can change, for instance, from
717	* INUSE_RATIO_80 to INUSE_RATIO_70 when freeing an object. This function
718	* checks if such a status change has occurred for the given page and
719	* accordingly moves the page from the list of the old fullness group to that
720	* of the new fullness group.
721	*/
722	static int fix_fullness_group(struct size_class *class, struct zspage *zspage)
723	{
724	int class_idx;
725	int currfg, newfg;
726
727	get_zspage_mapping(zspage, class_idx: &class_idx, fullness: &currfg);
728	newfg = get_fullness_group(class, zspage);
729	if (newfg == currfg)
730	goto out;
731
732	remove_zspage(class, zspage, fullness: currfg);
733	insert_zspage(class, zspage, fullness: newfg);
734	set_zspage_mapping(zspage, class_idx, fullness: newfg);
735	out:
736	return newfg;
737	}
738
739	static struct zspage *get_zspage(struct page *page)
740	{
741	struct zspage *zspage = (struct zspage *)page_private(page);
742
743	BUG_ON(zspage->magic != ZSPAGE_MAGIC);
744	return zspage;
745	}
746
747	static struct page *get_next_page(struct page *page)
748	{
749	struct zspage *zspage = get_zspage(page);
750
751	if (unlikely(ZsHugePage(zspage)))
752	return NULL;
753
754	return (struct page *)page->index;
755	}
756
757	/**
758	* obj_to_location - get (<page>, <obj_idx>) from encoded object value
759	* @obj: the encoded object value
760	* @page: page object resides in zspage
761	* @obj_idx: object index
762	*/
763	static void obj_to_location(unsigned long obj, struct page **page,
764	unsigned int *obj_idx)
765	{
766	obj >>= OBJ_TAG_BITS;
767	*page = pfn_to_page(obj >> OBJ_INDEX_BITS);
768	*obj_idx = (obj & OBJ_INDEX_MASK);
769	}
770
771	static void obj_to_page(unsigned long obj, struct page **page)
772	{
773	obj >>= OBJ_TAG_BITS;
774	*page = pfn_to_page(obj >> OBJ_INDEX_BITS);
775	}
776
777	/**
778	* location_to_obj - get obj value encoded from (<page>, <obj_idx>)
779	* @page: page object resides in zspage
780	* @obj_idx: object index
781	*/
782	static unsigned long location_to_obj(struct page *page, unsigned int obj_idx)
783	{
784	unsigned long obj;
785
786	obj = page_to_pfn(page) << OBJ_INDEX_BITS;
787	obj |= obj_idx & OBJ_INDEX_MASK;
788	obj <<= OBJ_TAG_BITS;
789
790	return obj;
791	}
792
793	static unsigned long handle_to_obj(unsigned long handle)
794	{
795	return *(unsigned long *)handle;
796	}
797
798	static inline bool obj_allocated(struct page *page, void *obj,
799	unsigned long *phandle)
800	{
801	unsigned long handle;
802	struct zspage *zspage = get_zspage(page);
803
804	if (unlikely(ZsHugePage(zspage))) {
805	VM_BUG_ON_PAGE(!is_first_page(page), page);
806	handle = page->index;
807	} else
808	handle = *(unsigned long *)obj;
809
810	if (!(handle & OBJ_ALLOCATED_TAG))
811	return false;
812
813	/* Clear all tags before returning the handle */
814	*phandle = handle & ~OBJ_TAG_MASK;
815	return true;
816	}
817
818	static void reset_page(struct page *page)
819	{
820	__ClearPageMovable(page);
821	ClearPagePrivate(page);
822	set_page_private(page, private: 0);
823	page_mapcount_reset(page);
824	page->index = 0;
825	}
826
827	static int trylock_zspage(struct zspage *zspage)
828	{
829	struct page *cursor, *fail;
830
831	for (cursor = get_first_page(zspage); cursor != NULL; cursor =
832	get_next_page(page: cursor)) {
833	if (!trylock_page(page: cursor)) {
834	fail = cursor;
835	goto unlock;
836	}
837	}
838
839	return 1;
840	unlock:
841	for (cursor = get_first_page(zspage); cursor != fail; cursor =
842	get_next_page(page: cursor))
843	unlock_page(page: cursor);
844
845	return 0;
846	}
847
848	static void __free_zspage(struct zs_pool *pool, struct size_class *class,
849	struct zspage *zspage)
850	{
851	struct page *page, *next;
852	int fg;
853	unsigned int class_idx;
854
855	get_zspage_mapping(zspage, class_idx: &class_idx, fullness: &fg);
856
857	assert_spin_locked(&pool->lock);
858
859	VM_BUG_ON(get_zspage_inuse(zspage));
860	VM_BUG_ON(fg != ZS_INUSE_RATIO_0);
861
862	next = page = get_first_page(zspage);
863	do {
864	VM_BUG_ON_PAGE(!PageLocked(page), page);
865	next = get_next_page(page);
866	reset_page(page);
867	unlock_page(page);
868	dec_zone_page_state(page, NR_ZSPAGES);
869	put_page(page);
870	page = next;
871	} while (page != NULL);
872
873	cache_free_zspage(pool, zspage);
874
875	class_stat_dec(class, type: ZS_OBJS_ALLOCATED, cnt: class->objs_per_zspage);
876	atomic_long_sub(i: class->pages_per_zspage, v: &pool->pages_allocated);
877	}
878
879	static void free_zspage(struct zs_pool *pool, struct size_class *class,
880	struct zspage *zspage)
881	{
882	VM_BUG_ON(get_zspage_inuse(zspage));
883	VM_BUG_ON(list_empty(&zspage->list));
884
885	/*
886	* Since zs_free couldn't be sleepable, this function cannot call
887	* lock_page. The page locks trylock_zspage got will be released
888	* by __free_zspage.
889	*/
890	if (!trylock_zspage(zspage)) {
891	kick_deferred_free(pool);
892	return;
893	}
894
895	remove_zspage(class, zspage, fullness: ZS_INUSE_RATIO_0);
896	__free_zspage(pool, class, zspage);
897	}
898
899	/* Initialize a newly allocated zspage */
900	static void init_zspage(struct size_class *class, struct zspage *zspage)
901	{
902	unsigned int freeobj = 1;
903	unsigned long off = 0;
904	struct page *page = get_first_page(zspage);
905
906	while (page) {
907	struct page *next_page;
908	struct link_free *link;
909	void *vaddr;
910
911	set_first_obj_offset(page, offset: off);
912
913	vaddr = kmap_atomic(page);
914	link = (struct link_free *)vaddr + off / sizeof(*link);
915
916	while ((off += class->size) < PAGE_SIZE) {
917	link->next = freeobj++ << OBJ_TAG_BITS;
918	link += class->size / sizeof(*link);
919	}
920
921	/*
922	* We now come to the last (full or partial) object on this
923	* page, which must point to the first object on the next
924	* page (if present)
925	*/
926	next_page = get_next_page(page);
927	if (next_page) {
928	link->next = freeobj++ << OBJ_TAG_BITS;
929	} else {
930	/*
931	* Reset OBJ_TAG_BITS bit to last link to tell
932	* whether it's allocated object or not.
933	*/
934	link->next = -1UL << OBJ_TAG_BITS;
935	}
936	kunmap_atomic(vaddr);
937	page = next_page;
938	off %= PAGE_SIZE;
939	}
940
941	set_freeobj(zspage, obj: 0);
942	}
943
944	static void create_page_chain(struct size_class *class, struct zspage *zspage,
945	struct page *pages[])
946	{
947	int i;
948	struct page *page;
949	struct page *prev_page = NULL;
950	int nr_pages = class->pages_per_zspage;
951
952	/*
953	* Allocate individual pages and link them together as:
954	* 1. all pages are linked together using page->index
955	* 2. each sub-page point to zspage using page->private
956	*
957	* we set PG_private to identify the first page (i.e. no other sub-page
958	* has this flag set).
959	*/
960	for (i = 0; i < nr_pages; i++) {
961	page = pages[i];
962	set_page_private(page, private: (unsigned long)zspage);
963	page->index = 0;
964	if (i == 0) {
965	zspage->first_page = page;
966	SetPagePrivate(page);
967	if (unlikely(class->objs_per_zspage == 1 &&
968	class->pages_per_zspage == 1))
969	SetZsHugePage(zspage);
970	} else {
971	prev_page->index = (unsigned long)page;
972	}
973	prev_page = page;
974	}
975	}
976
977	/*
978	* Allocate a zspage for the given size class
979	*/
980	static struct zspage *alloc_zspage(struct zs_pool *pool,
981	struct size_class *class,
982	gfp_t gfp)
983	{
984	int i;
985	struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE];
986	struct zspage *zspage = cache_alloc_zspage(pool, flags: gfp);
987
988	if (!zspage)
989	return NULL;
990
991	zspage->magic = ZSPAGE_MAGIC;
992	migrate_lock_init(zspage);
993
994	for (i = 0; i < class->pages_per_zspage; i++) {
995	struct page *page;
996
997	page = alloc_page(gfp);
998	if (!page) {
999	while (--i >= 0) {
1000	dec_zone_page_state(pages[i], NR_ZSPAGES);
1001	__free_page(pages[i]);
1002	}
1003	cache_free_zspage(pool, zspage);
1004	return NULL;
1005	}
1006
1007	inc_zone_page_state(page, NR_ZSPAGES);
1008	pages[i] = page;
1009	}
1010
1011	create_page_chain(class, zspage, pages);
1012	init_zspage(class, zspage);
1013	zspage->pool = pool;
1014
1015	return zspage;
1016	}
1017
1018	static struct zspage *find_get_zspage(struct size_class *class)
1019	{
1020	int i;
1021	struct zspage *zspage;
1022
1023	for (i = ZS_INUSE_RATIO_99; i >= ZS_INUSE_RATIO_0; i--) {
1024	zspage = list_first_entry_or_null(&class->fullness_list[i],
1025	struct zspage, list);
1026	if (zspage)
1027	break;
1028	}
1029
1030	return zspage;
1031	}
1032
1033	static inline int __zs_cpu_up(struct mapping_area *area)
1034	{
1035	/*
1036	* Make sure we don't leak memory if a cpu UP notification
1037	* and zs_init() race and both call zs_cpu_up() on the same cpu
1038	*/
1039	if (area->vm_buf)
1040	return 0;
1041	area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);
1042	if (!area->vm_buf)
1043	return -ENOMEM;
1044	return 0;
1045	}
1046
1047	static inline void __zs_cpu_down(struct mapping_area *area)
1048	{
1049	kfree(objp: area->vm_buf);
1050	area->vm_buf = NULL;
1051	}
1052
1053	static void *__zs_map_object(struct mapping_area *area,
1054	struct page *pages[2], int off, int size)
1055	{
1056	int sizes[2];
1057	void *addr;
1058	char *buf = area->vm_buf;
1059
1060	/* disable page faults to match kmap_atomic() return conditions */
1061	pagefault_disable();
1062
1063	/* no read fastpath */
1064	if (area->vm_mm == ZS_MM_WO)
1065	goto out;
1066
1067	sizes[0] = PAGE_SIZE - off;
1068	sizes[1] = size - sizes[0];
1069
1070	/* copy object to per-cpu buffer */
1071	addr = kmap_atomic(page: pages[0]);
1072	memcpy(buf, addr + off, sizes[0]);
1073	kunmap_atomic(addr);
1074	addr = kmap_atomic(page: pages[1]);
1075	memcpy(buf + sizes[0], addr, sizes[1]);
1076	kunmap_atomic(addr);
1077	out:
1078	return area->vm_buf;
1079	}
1080
1081	static void __zs_unmap_object(struct mapping_area *area,
1082	struct page *pages[2], int off, int size)
1083	{
1084	int sizes[2];
1085	void *addr;
1086	char *buf;
1087
1088	/* no write fastpath */
1089	if (area->vm_mm == ZS_MM_RO)
1090	goto out;
1091
1092	buf = area->vm_buf;
1093	buf = buf + ZS_HANDLE_SIZE;
1094	size -= ZS_HANDLE_SIZE;
1095	off += ZS_HANDLE_SIZE;
1096
1097	sizes[0] = PAGE_SIZE - off;
1098	sizes[1] = size - sizes[0];
1099
1100	/* copy per-cpu buffer to object */
1101	addr = kmap_atomic(page: pages[0]);
1102	memcpy(addr + off, buf, sizes[0]);
1103	kunmap_atomic(addr);
1104	addr = kmap_atomic(page: pages[1]);
1105	memcpy(addr, buf + sizes[0], sizes[1]);
1106	kunmap_atomic(addr);
1107
1108	out:
1109	/* enable page faults to match kunmap_atomic() return conditions */
1110	pagefault_enable();
1111	}
1112
1113	static int zs_cpu_prepare(unsigned int cpu)
1114	{
1115	struct mapping_area *area;
1116
1117	area = &per_cpu(zs_map_area, cpu);
1118	return __zs_cpu_up(area);
1119	}
1120
1121	static int zs_cpu_dead(unsigned int cpu)
1122	{
1123	struct mapping_area *area;
1124
1125	area = &per_cpu(zs_map_area, cpu);
1126	__zs_cpu_down(area);
1127	return 0;
1128	}
1129
1130	static bool can_merge(struct size_class *prev, int pages_per_zspage,
1131	int objs_per_zspage)
1132	{
1133	if (prev->pages_per_zspage == pages_per_zspage &&
1134	prev->objs_per_zspage == objs_per_zspage)
1135	return true;
1136
1137	return false;
1138	}
1139
1140	static bool zspage_full(struct size_class *class, struct zspage *zspage)
1141	{
1142	return get_zspage_inuse(zspage) == class->objs_per_zspage;
1143	}
1144
1145	static bool zspage_empty(struct zspage *zspage)
1146	{
1147	return get_zspage_inuse(zspage) == 0;
1148	}
1149
1150	/**
1151	* zs_lookup_class_index() - Returns index of the zsmalloc &size_class
1152	* that hold objects of the provided size.
1153	* @pool: zsmalloc pool to use
1154	* @size: object size
1155	*
1156	* Context: Any context.
1157	*
1158	* Return: the index of the zsmalloc &size_class that hold objects of the
1159	* provided size.
1160	*/
1161	unsigned int zs_lookup_class_index(struct zs_pool *pool, unsigned int size)
1162	{
1163	struct size_class *class;
1164
1165	class = pool->size_class[get_size_class_index(size)];
1166
1167	return class->index;
1168	}
1169	EXPORT_SYMBOL_GPL(zs_lookup_class_index);
1170
1171	unsigned long zs_get_total_pages(struct zs_pool *pool)
1172	{
1173	return atomic_long_read(v: &pool->pages_allocated);
1174	}
1175	EXPORT_SYMBOL_GPL(zs_get_total_pages);
1176
1177	/**
1178	* zs_map_object - get address of allocated object from handle.
1179	* @pool: pool from which the object was allocated
1180	* @handle: handle returned from zs_malloc
1181	* @mm: mapping mode to use
1182	*
1183	* Before using an object allocated from zs_malloc, it must be mapped using
1184	* this function. When done with the object, it must be unmapped using
1185	* zs_unmap_object.
1186	*
1187	* Only one object can be mapped per cpu at a time. There is no protection
1188	* against nested mappings.
1189	*
1190	* This function returns with preemption and page faults disabled.
1191	*/
1192	void *zs_map_object(struct zs_pool *pool, unsigned long handle,
1193	enum zs_mapmode mm)
1194	{
1195	struct zspage *zspage;
1196	struct page *page;
1197	unsigned long obj, off;
1198	unsigned int obj_idx;
1199
1200	struct size_class *class;
1201	struct mapping_area *area;
1202	struct page *pages[2];
1203	void *ret;
1204
1205	/*
1206	* Because we use per-cpu mapping areas shared among the
1207	* pools/users, we can't allow mapping in interrupt context
1208	* because it can corrupt another users mappings.
1209	*/
1210	BUG_ON(in_interrupt());
1211
1212	/* It guarantees it can get zspage from handle safely */
1213	spin_lock(lock: &pool->lock);
1214	obj = handle_to_obj(handle);
1215	obj_to_location(obj, page: &page, obj_idx: &obj_idx);
1216	zspage = get_zspage(page);
1217
1218	/*
1219	* migration cannot move any zpages in this zspage. Here, pool->lock
1220	* is too heavy since callers would take some time until they calls
1221	* zs_unmap_object API so delegate the locking from class to zspage
1222	* which is smaller granularity.
1223	*/
1224	migrate_read_lock(zspage);
1225	spin_unlock(lock: &pool->lock);
1226
1227	class = zspage_class(pool, zspage);
1228	off = offset_in_page(class->size * obj_idx);
1229
1230	local_lock(&zs_map_area.lock);
1231	area = this_cpu_ptr(&zs_map_area);
1232	area->vm_mm = mm;
1233	if (off + class->size <= PAGE_SIZE) {
1234	/* this object is contained entirely within a page */
1235	area->vm_addr = kmap_atomic(page);
1236	ret = area->vm_addr + off;
1237	goto out;
1238	}
1239
1240	/* this object spans two pages */
1241	pages[0] = page;
1242	pages[1] = get_next_page(page);
1243	BUG_ON(!pages[1]);
1244
1245	ret = __zs_map_object(area, pages, off, size: class->size);
1246	out:
1247	if (likely(!ZsHugePage(zspage)))
1248	ret += ZS_HANDLE_SIZE;
1249
1250	return ret;
1251	}
1252	EXPORT_SYMBOL_GPL(zs_map_object);
1253
1254	void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
1255	{
1256	struct zspage *zspage;
1257	struct page *page;
1258	unsigned long obj, off;
1259	unsigned int obj_idx;
1260
1261	struct size_class *class;
1262	struct mapping_area *area;
1263
1264	obj = handle_to_obj(handle);
1265	obj_to_location(obj, page: &page, obj_idx: &obj_idx);
1266	zspage = get_zspage(page);
1267	class = zspage_class(pool, zspage);
1268	off = offset_in_page(class->size * obj_idx);
1269
1270	area = this_cpu_ptr(&zs_map_area);
1271	if (off + class->size <= PAGE_SIZE)
1272	kunmap_atomic(area->vm_addr);
1273	else {
1274	struct page *pages[2];
1275
1276	pages[0] = page;
1277	pages[1] = get_next_page(page);
1278	BUG_ON(!pages[1]);
1279
1280	__zs_unmap_object(area, pages, off, size: class->size);
1281	}
1282	local_unlock(&zs_map_area.lock);
1283
1284	migrate_read_unlock(zspage);
1285	}
1286	EXPORT_SYMBOL_GPL(zs_unmap_object);
1287
1288	/**
1289	* zs_huge_class_size() - Returns the size (in bytes) of the first huge
1290	* zsmalloc &size_class.
1291	* @pool: zsmalloc pool to use
1292	*
1293	* The function returns the size of the first huge class - any object of equal
1294	* or bigger size will be stored in zspage consisting of a single physical
1295	* page.
1296	*
1297	* Context: Any context.
1298	*
1299	* Return: the size (in bytes) of the first huge zsmalloc &size_class.
1300	*/
1301	size_t zs_huge_class_size(struct zs_pool *pool)
1302	{
1303	return huge_class_size;
1304	}
1305	EXPORT_SYMBOL_GPL(zs_huge_class_size);
1306
1307	static unsigned long obj_malloc(struct zs_pool *pool,
1308	struct zspage *zspage, unsigned long handle)
1309	{
1310	int i, nr_page, offset;
1311	unsigned long obj;
1312	struct link_free *link;
1313	struct size_class *class;
1314
1315	struct page *m_page;
1316	unsigned long m_offset;
1317	void *vaddr;
1318
1319	class = pool->size_class[zspage->class];
1320	handle |= OBJ_ALLOCATED_TAG;
1321	obj = get_freeobj(zspage);
1322
1323	offset = obj * class->size;
1324	nr_page = offset >> PAGE_SHIFT;
1325	m_offset = offset_in_page(offset);
1326	m_page = get_first_page(zspage);
1327
1328	for (i = 0; i < nr_page; i++)
1329	m_page = get_next_page(page: m_page);
1330
1331	vaddr = kmap_atomic(page: m_page);
1332	link = (struct link_free *)vaddr + m_offset / sizeof(*link);
1333	set_freeobj(zspage, obj: link->next >> OBJ_TAG_BITS);
1334	if (likely(!ZsHugePage(zspage)))
1335	/* record handle in the header of allocated chunk */
1336	link->handle = handle;
1337	else
1338	/* record handle to page->index */
1339	zspage->first_page->index = handle;
1340
1341	kunmap_atomic(vaddr);
1342	mod_zspage_inuse(zspage, val: 1);
1343
1344	obj = location_to_obj(page: m_page, obj_idx: obj);
1345
1346	return obj;
1347	}
1348
1349
1350	/**
1351	* zs_malloc - Allocate block of given size from pool.
1352	* @pool: pool to allocate from
1353	* @size: size of block to allocate
1354	* @gfp: gfp flags when allocating object
1355	*
1356	* On success, handle to the allocated object is returned,
1357	* otherwise an ERR_PTR().
1358	* Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail.
1359	*/
1360	unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
1361	{
1362	unsigned long handle, obj;
1363	struct size_class *class;
1364	int newfg;
1365	struct zspage *zspage;
1366
1367	if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
1368	return (unsigned long)ERR_PTR(error: -EINVAL);
1369
1370	handle = cache_alloc_handle(pool, gfp);
1371	if (!handle)
1372	return (unsigned long)ERR_PTR(error: -ENOMEM);
1373
1374	/* extra space in chunk to keep the handle */
1375	size += ZS_HANDLE_SIZE;
1376	class = pool->size_class[get_size_class_index(size)];
1377
1378	/* pool->lock effectively protects the zpage migration */
1379	spin_lock(lock: &pool->lock);
1380	zspage = find_get_zspage(class);
1381	if (likely(zspage)) {
1382	obj = obj_malloc(pool, zspage, handle);
1383	/* Now move the zspage to another fullness group, if required */
1384	fix_fullness_group(class, zspage);
1385	record_obj(handle, obj);
1386	class_stat_inc(class, type: ZS_OBJS_INUSE, cnt: 1);
1387
1388	goto out;
1389	}
1390
1391	spin_unlock(lock: &pool->lock);
1392
1393	zspage = alloc_zspage(pool, class, gfp);
1394	if (!zspage) {
1395	cache_free_handle(pool, handle);
1396	return (unsigned long)ERR_PTR(error: -ENOMEM);
1397	}
1398
1399	spin_lock(lock: &pool->lock);
1400	obj = obj_malloc(pool, zspage, handle);
1401	newfg = get_fullness_group(class, zspage);
1402	insert_zspage(class, zspage, fullness: newfg);
1403	set_zspage_mapping(zspage, class_idx: class->index, fullness: newfg);
1404	record_obj(handle, obj);
1405	atomic_long_add(i: class->pages_per_zspage, v: &pool->pages_allocated);
1406	class_stat_inc(class, type: ZS_OBJS_ALLOCATED, cnt: class->objs_per_zspage);
1407	class_stat_inc(class, type: ZS_OBJS_INUSE, cnt: 1);
1408
1409	/* We completely set up zspage so mark them as movable */
1410	SetZsPageMovable(pool, zspage);
1411	out:
1412	spin_unlock(lock: &pool->lock);
1413
1414	return handle;
1415	}
1416	EXPORT_SYMBOL_GPL(zs_malloc);
1417
1418	static void obj_free(int class_size, unsigned long obj)
1419	{
1420	struct link_free *link;
1421	struct zspage *zspage;
1422	struct page *f_page;
1423	unsigned long f_offset;
1424	unsigned int f_objidx;
1425	void *vaddr;
1426
1427	obj_to_location(obj, page: &f_page, obj_idx: &f_objidx);
1428	f_offset = offset_in_page(class_size * f_objidx);
1429	zspage = get_zspage(page: f_page);
1430
1431	vaddr = kmap_atomic(page: f_page);
1432	link = (struct link_free *)(vaddr + f_offset);
1433
1434	/* Insert this object in containing zspage's freelist */
1435	if (likely(!ZsHugePage(zspage)))
1436	link->next = get_freeobj(zspage) << OBJ_TAG_BITS;
1437	else
1438	f_page->index = 0;
1439	set_freeobj(zspage, obj: f_objidx);
1440
1441	kunmap_atomic(vaddr);
1442	mod_zspage_inuse(zspage, val: -1);
1443	}
1444
1445	void zs_free(struct zs_pool *pool, unsigned long handle)
1446	{
1447	struct zspage *zspage;
1448	struct page *f_page;
1449	unsigned long obj;
1450	struct size_class *class;
1451	int fullness;
1452
1453	if (IS_ERR_OR_NULL(ptr: (void *)handle))
1454	return;
1455
1456	/*
1457	* The pool->lock protects the race with zpage's migration
1458	* so it's safe to get the page from handle.
1459	*/
1460	spin_lock(lock: &pool->lock);
1461	obj = handle_to_obj(handle);
1462	obj_to_page(obj, page: &f_page);
1463	zspage = get_zspage(page: f_page);
1464	class = zspage_class(pool, zspage);
1465
1466	class_stat_dec(class, type: ZS_OBJS_INUSE, cnt: 1);
1467	obj_free(class_size: class->size, obj);
1468
1469	fullness = fix_fullness_group(class, zspage);
1470	if (fullness == ZS_INUSE_RATIO_0)
1471	free_zspage(pool, class, zspage);
1472
1473	spin_unlock(lock: &pool->lock);
1474	cache_free_handle(pool, handle);
1475	}
1476	EXPORT_SYMBOL_GPL(zs_free);
1477
1478	static void zs_object_copy(struct size_class *class, unsigned long dst,
1479	unsigned long src)
1480	{
1481	struct page *s_page, *d_page;
1482	unsigned int s_objidx, d_objidx;
1483	unsigned long s_off, d_off;
1484	void *s_addr, *d_addr;
1485	int s_size, d_size, size;
1486	int written = 0;
1487
1488	s_size = d_size = class->size;
1489
1490	obj_to_location(obj: src, page: &s_page, obj_idx: &s_objidx);
1491	obj_to_location(obj: dst, page: &d_page, obj_idx: &d_objidx);
1492
1493	s_off = offset_in_page(class->size * s_objidx);
1494	d_off = offset_in_page(class->size * d_objidx);
1495
1496	if (s_off + class->size > PAGE_SIZE)
1497	s_size = PAGE_SIZE - s_off;
1498
1499	if (d_off + class->size > PAGE_SIZE)
1500	d_size = PAGE_SIZE - d_off;
1501
1502	s_addr = kmap_atomic(page: s_page);
1503	d_addr = kmap_atomic(page: d_page);
1504
1505	while (1) {
1506	size = min(s_size, d_size);
1507	memcpy(d_addr + d_off, s_addr + s_off, size);
1508	written += size;
1509
1510	if (written == class->size)
1511	break;
1512
1513	s_off += size;
1514	s_size -= size;
1515	d_off += size;
1516	d_size -= size;
1517
1518	/*
1519	* Calling kunmap_atomic(d_addr) is necessary. kunmap_atomic()
1520	* calls must occurs in reverse order of calls to kmap_atomic().
1521	* So, to call kunmap_atomic(s_addr) we should first call
1522	* kunmap_atomic(d_addr). For more details see
1523	* Documentation/mm/highmem.rst.
1524	*/
1525	if (s_off >= PAGE_SIZE) {
1526	kunmap_atomic(d_addr);
1527	kunmap_atomic(s_addr);
1528	s_page = get_next_page(page: s_page);
1529	s_addr = kmap_atomic(page: s_page);
1530	d_addr = kmap_atomic(page: d_page);
1531	s_size = class->size - written;
1532	s_off = 0;
1533	}
1534
1535	if (d_off >= PAGE_SIZE) {
1536	kunmap_atomic(d_addr);
1537	d_page = get_next_page(page: d_page);
1538	d_addr = kmap_atomic(page: d_page);
1539	d_size = class->size - written;
1540	d_off = 0;
1541	}
1542	}
1543
1544	kunmap_atomic(d_addr);
1545	kunmap_atomic(s_addr);
1546	}
1547
1548	/*
1549	* Find alloced object in zspage from index object and
1550	* return handle.
1551	*/
1552	static unsigned long find_alloced_obj(struct size_class *class,
1553	struct page *page, int *obj_idx)
1554	{
1555	unsigned int offset;
1556	int index = *obj_idx;
1557	unsigned long handle = 0;
1558	void *addr = kmap_atomic(page);
1559
1560	offset = get_first_obj_offset(page);
1561	offset += class->size * index;
1562
1563	while (offset < PAGE_SIZE) {
1564	if (obj_allocated(page, obj: addr + offset, phandle: &handle))
1565	break;
1566
1567	offset += class->size;
1568	index++;
1569	}
1570
1571	kunmap_atomic(addr);
1572
1573	*obj_idx = index;
1574
1575	return handle;
1576	}
1577
1578	static void migrate_zspage(struct zs_pool *pool, struct zspage *src_zspage,
1579	struct zspage *dst_zspage)
1580	{
1581	unsigned long used_obj, free_obj;
1582	unsigned long handle;
1583	int obj_idx = 0;
1584	struct page *s_page = get_first_page(zspage: src_zspage);
1585	struct size_class *class = pool->size_class[src_zspage->class];
1586
1587	while (1) {
1588	handle = find_alloced_obj(class, page: s_page, obj_idx: &obj_idx);
1589	if (!handle) {
1590	s_page = get_next_page(page: s_page);
1591	if (!s_page)
1592	break;
1593	obj_idx = 0;
1594	continue;
1595	}
1596
1597	used_obj = handle_to_obj(handle);
1598	free_obj = obj_malloc(pool, zspage: dst_zspage, handle);
1599	zs_object_copy(class, dst: free_obj, src: used_obj);
1600	obj_idx++;
1601	record_obj(handle, obj: free_obj);
1602	obj_free(class_size: class->size, obj: used_obj);
1603
1604	/* Stop if there is no more space */
1605	if (zspage_full(class, zspage: dst_zspage))
1606	break;
1607
1608	/* Stop if there are no more objects to migrate */
1609	if (zspage_empty(zspage: src_zspage))
1610	break;
1611	}
1612	}
1613
1614	static struct zspage *isolate_src_zspage(struct size_class *class)
1615	{
1616	struct zspage *zspage;
1617	int fg;
1618
1619	for (fg = ZS_INUSE_RATIO_10; fg <= ZS_INUSE_RATIO_99; fg++) {
1620	zspage = list_first_entry_or_null(&class->fullness_list[fg],
1621	struct zspage, list);
1622	if (zspage) {
1623	remove_zspage(class, zspage, fullness: fg);
1624	return zspage;
1625	}
1626	}
1627
1628	return zspage;
1629	}
1630
1631	static struct zspage *isolate_dst_zspage(struct size_class *class)
1632	{
1633	struct zspage *zspage;
1634	int fg;
1635
1636	for (fg = ZS_INUSE_RATIO_99; fg >= ZS_INUSE_RATIO_10; fg--) {
1637	zspage = list_first_entry_or_null(&class->fullness_list[fg],
1638	struct zspage, list);
1639	if (zspage) {
1640	remove_zspage(class, zspage, fullness: fg);
1641	return zspage;
1642	}
1643	}
1644
1645	return zspage;
1646	}
1647
1648	/*
1649	* putback_zspage - add @zspage into right class's fullness list
1650	* @class: destination class
1651	* @zspage: target page
1652	*
1653	* Return @zspage's fullness status
1654	*/
1655	static int putback_zspage(struct size_class *class, struct zspage *zspage)
1656	{
1657	int fullness;
1658
1659	fullness = get_fullness_group(class, zspage);
1660	insert_zspage(class, zspage, fullness);
1661	set_zspage_mapping(zspage, class_idx: class->index, fullness);
1662
1663	return fullness;
1664	}
1665
1666	#ifdef CONFIG_COMPACTION
1667	/*
1668	* To prevent zspage destroy during migration, zspage freeing should
1669	* hold locks of all pages in the zspage.
1670	*/
1671	static void lock_zspage(struct zspage *zspage)
1672	{
1673	struct page *curr_page, *page;
1674
1675	/*
1676	* Pages we haven't locked yet can be migrated off the list while we're
1677	* trying to lock them, so we need to be careful and only attempt to
1678	* lock each page under migrate_read_lock(). Otherwise, the page we lock
1679	* may no longer belong to the zspage. This means that we may wait for
1680	* the wrong page to unlock, so we must take a reference to the page
1681	* prior to waiting for it to unlock outside migrate_read_lock().
1682	*/
1683	while (1) {
1684	migrate_read_lock(zspage);
1685	page = get_first_page(zspage);
1686	if (trylock_page(page))
1687	break;
1688	get_page(page);
1689	migrate_read_unlock(zspage);
1690	wait_on_page_locked(page);
1691	put_page(page);
1692	}
1693
1694	curr_page = page;
1695	while ((page = get_next_page(page: curr_page))) {
1696	if (trylock_page(page)) {
1697	curr_page = page;
1698	} else {
1699	get_page(page);
1700	migrate_read_unlock(zspage);
1701	wait_on_page_locked(page);
1702	put_page(page);
1703	migrate_read_lock(zspage);
1704	}
1705	}
1706	migrate_read_unlock(zspage);
1707	}
1708	#endif /* CONFIG_COMPACTION */
1709
1710	static void migrate_lock_init(struct zspage *zspage)
1711	{
1712	rwlock_init(&zspage->lock);
1713	}
1714
1715	static void migrate_read_lock(struct zspage *zspage) __acquires(&zspage->lock)
1716	{
1717	read_lock(&zspage->lock);
1718	}
1719
1720	static void migrate_read_unlock(struct zspage *zspage) __releases(&zspage->lock)
1721	{
1722	read_unlock(&zspage->lock);
1723	}
1724
1725	#ifdef CONFIG_COMPACTION
1726	static void migrate_write_lock(struct zspage *zspage)
1727	{
1728	write_lock(&zspage->lock);
1729	}
1730
1731	static void migrate_write_lock_nested(struct zspage *zspage)
1732	{
1733	write_lock_nested(&zspage->lock, SINGLE_DEPTH_NESTING);
1734	}
1735
1736	static void migrate_write_unlock(struct zspage *zspage)
1737	{
1738	write_unlock(&zspage->lock);
1739	}
1740
1741	/* Number of isolated subpage for *page migration* in this zspage */
1742	static void inc_zspage_isolation(struct zspage *zspage)
1743	{
1744	zspage->isolated++;
1745	}
1746
1747	static void dec_zspage_isolation(struct zspage *zspage)
1748	{
1749	VM_BUG_ON(zspage->isolated == 0);
1750	zspage->isolated--;
1751	}
1752
1753	static const struct movable_operations zsmalloc_mops;
1754
1755	static void replace_sub_page(struct size_class *class, struct zspage *zspage,
1756	struct page *newpage, struct page *oldpage)
1757	{
1758	struct page *page;
1759	struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE] = {NULL, };
1760	int idx = 0;
1761
1762	page = get_first_page(zspage);
1763	do {
1764	if (page == oldpage)
1765	pages[idx] = newpage;
1766	else
1767	pages[idx] = page;
1768	idx++;
1769	} while ((page = get_next_page(page)) != NULL);
1770
1771	create_page_chain(class, zspage, pages);
1772	set_first_obj_offset(page: newpage, offset: get_first_obj_offset(page: oldpage));
1773	if (unlikely(ZsHugePage(zspage)))
1774	newpage->index = oldpage->index;
1775	__SetPageMovable(page: newpage, ops: &zsmalloc_mops);
1776	}
1777
1778	static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
1779	{
1780	struct zs_pool *pool;
1781	struct zspage *zspage;
1782
1783	/*
1784	* Page is locked so zspage couldn't be destroyed. For detail, look at
1785	* lock_zspage in free_zspage.
1786	*/
1787	VM_BUG_ON_PAGE(PageIsolated(page), page);
1788
1789	zspage = get_zspage(page);
1790	pool = zspage->pool;
1791	spin_lock(lock: &pool->lock);
1792	inc_zspage_isolation(zspage);
1793	spin_unlock(lock: &pool->lock);
1794
1795	return true;
1796	}
1797
1798	static int zs_page_migrate(struct page *newpage, struct page *page,
1799	enum migrate_mode mode)
1800	{
1801	struct zs_pool *pool;
1802	struct size_class *class;
1803	struct zspage *zspage;
1804	struct page *dummy;
1805	void *s_addr, *d_addr, *addr;
1806	unsigned int offset;
1807	unsigned long handle;
1808	unsigned long old_obj, new_obj;
1809	unsigned int obj_idx;
1810
1811	/*
1812	* We cannot support the _NO_COPY case here, because copy needs to
1813	* happen under the zs lock, which does not work with
1814	* MIGRATE_SYNC_NO_COPY workflow.
1815	*/
1816	if (mode == MIGRATE_SYNC_NO_COPY)
1817	return -EINVAL;
1818
1819	VM_BUG_ON_PAGE(!PageIsolated(page), page);
1820
1821	/* The page is locked, so this pointer must remain valid */
1822	zspage = get_zspage(page);
1823	pool = zspage->pool;
1824
1825	/*
1826	* The pool's lock protects the race between zpage migration
1827	* and zs_free.
1828	*/
1829	spin_lock(lock: &pool->lock);
1830	class = zspage_class(pool, zspage);
1831
1832	/* the migrate_write_lock protects zpage access via zs_map_object */
1833	migrate_write_lock(zspage);
1834
1835	offset = get_first_obj_offset(page);
1836	s_addr = kmap_atomic(page);
1837
1838	/*
1839	* Here, any user cannot access all objects in the zspage so let's move.
1840	*/
1841	d_addr = kmap_atomic(page: newpage);
1842	copy_page(to: d_addr, from: s_addr);
1843	kunmap_atomic(d_addr);
1844
1845	for (addr = s_addr + offset; addr < s_addr + PAGE_SIZE;
1846	addr += class->size) {
1847	if (obj_allocated(page, obj: addr, phandle: &handle)) {
1848
1849	old_obj = handle_to_obj(handle);
1850	obj_to_location(obj: old_obj, page: &dummy, obj_idx: &obj_idx);
1851	new_obj = (unsigned long)location_to_obj(page: newpage,
1852	obj_idx);
1853	record_obj(handle, obj: new_obj);
1854	}
1855	}
1856	kunmap_atomic(s_addr);
1857
1858	replace_sub_page(class, zspage, newpage, oldpage: page);
1859	dec_zspage_isolation(zspage);
1860	/*
1861	* Since we complete the data copy and set up new zspage structure,
1862	* it's okay to release the pool's lock.
1863	*/
1864	spin_unlock(lock: &pool->lock);
1865	migrate_write_unlock(zspage);
1866
1867	get_page(page: newpage);
1868	if (page_zone(page: newpage) != page_zone(page)) {
1869	dec_zone_page_state(page, NR_ZSPAGES);
1870	inc_zone_page_state(newpage, NR_ZSPAGES);
1871	}
1872
1873	reset_page(page);
1874	put_page(page);
1875
1876	return MIGRATEPAGE_SUCCESS;
1877	}
1878
1879	static void zs_page_putback(struct page *page)
1880	{
1881	struct zs_pool *pool;
1882	struct zspage *zspage;
1883
1884	VM_BUG_ON_PAGE(!PageIsolated(page), page);
1885
1886	zspage = get_zspage(page);
1887	pool = zspage->pool;
1888	spin_lock(lock: &pool->lock);
1889	dec_zspage_isolation(zspage);
1890	spin_unlock(lock: &pool->lock);
1891	}
1892
1893	static const struct movable_operations zsmalloc_mops = {
1894	.isolate_page = zs_page_isolate,
1895	.migrate_page = zs_page_migrate,
1896	.putback_page = zs_page_putback,
1897	};
1898
1899	/*
1900	* Caller should hold page_lock of all pages in the zspage
1901	* In here, we cannot use zspage meta data.
1902	*/
1903	static void async_free_zspage(struct work_struct *work)
1904	{
1905	int i;
1906	struct size_class *class;
1907	unsigned int class_idx;
1908	int fullness;
1909	struct zspage *zspage, *tmp;
1910	LIST_HEAD(free_pages);
1911	struct zs_pool *pool = container_of(work, struct zs_pool,
1912	free_work);
1913
1914	for (i = 0; i < ZS_SIZE_CLASSES; i++) {
1915	class = pool->size_class[i];
1916	if (class->index != i)
1917	continue;
1918
1919	spin_lock(lock: &pool->lock);
1920	list_splice_init(list: &class->fullness_list[ZS_INUSE_RATIO_0],
1921	head: &free_pages);
1922	spin_unlock(lock: &pool->lock);
1923	}
1924
1925	list_for_each_entry_safe(zspage, tmp, &free_pages, list) {
1926	list_del(entry: &zspage->list);
1927	lock_zspage(zspage);
1928
1929	get_zspage_mapping(zspage, class_idx: &class_idx, fullness: &fullness);
1930	VM_BUG_ON(fullness != ZS_INUSE_RATIO_0);
1931	class = pool->size_class[class_idx];
1932	spin_lock(lock: &pool->lock);
1933	__free_zspage(pool, class, zspage);
1934	spin_unlock(lock: &pool->lock);
1935	}
1936	};
1937
1938	static void kick_deferred_free(struct zs_pool *pool)
1939	{
1940	schedule_work(work: &pool->free_work);
1941	}
1942
1943	static void zs_flush_migration(struct zs_pool *pool)
1944	{
1945	flush_work(work: &pool->free_work);
1946	}
1947
1948	static void init_deferred_free(struct zs_pool *pool)
1949	{
1950	INIT_WORK(&pool->free_work, async_free_zspage);
1951	}
1952
1953	static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage)
1954	{
1955	struct page *page = get_first_page(zspage);
1956
1957	do {
1958	WARN_ON(!trylock_page(page));
1959	__SetPageMovable(page, ops: &zsmalloc_mops);
1960	unlock_page(page);
1961	} while ((page = get_next_page(page)) != NULL);
1962	}
1963	#else
1964	static inline void zs_flush_migration(struct zs_pool *pool) { }
1965	#endif
1966
1967	/*
1968	*
1969	* Based on the number of unused allocated objects calculate
1970	* and return the number of pages that we can free.
1971	*/
1972	static unsigned long zs_can_compact(struct size_class *class)
1973	{
1974	unsigned long obj_wasted;
1975	unsigned long obj_allocated = zs_stat_get(class, type: ZS_OBJS_ALLOCATED);
1976	unsigned long obj_used = zs_stat_get(class, type: ZS_OBJS_INUSE);
1977
1978	if (obj_allocated <= obj_used)
1979	return 0;
1980
1981	obj_wasted = obj_allocated - obj_used;
1982	obj_wasted /= class->objs_per_zspage;
1983
1984	return obj_wasted * class->pages_per_zspage;
1985	}
1986
1987	static unsigned long __zs_compact(struct zs_pool *pool,
1988	struct size_class *class)
1989	{
1990	struct zspage *src_zspage = NULL;
1991	struct zspage *dst_zspage = NULL;
1992	unsigned long pages_freed = 0;
1993
1994	/*
1995	* protect the race between zpage migration and zs_free
1996	* as well as zpage allocation/free
1997	*/
1998	spin_lock(lock: &pool->lock);
1999	while (zs_can_compact(class)) {
2000	int fg;
2001
2002	if (!dst_zspage) {
2003	dst_zspage = isolate_dst_zspage(class);
2004	if (!dst_zspage)
2005	break;
2006	migrate_write_lock(zspage: dst_zspage);
2007	}
2008
2009	src_zspage = isolate_src_zspage(class);
2010	if (!src_zspage)
2011	break;
2012
2013	migrate_write_lock_nested(zspage: src_zspage);
2014
2015	migrate_zspage(pool, src_zspage, dst_zspage);
2016	fg = putback_zspage(class, zspage: src_zspage);
2017	migrate_write_unlock(zspage: src_zspage);
2018
2019	if (fg == ZS_INUSE_RATIO_0) {
2020	free_zspage(pool, class, zspage: src_zspage);
2021	pages_freed += class->pages_per_zspage;
2022	}
2023	src_zspage = NULL;
2024
2025	if (get_fullness_group(class, zspage: dst_zspage) == ZS_INUSE_RATIO_100
2026	|| spin_is_contended(lock: &pool->lock)) {
2027	putback_zspage(class, zspage: dst_zspage);
2028	migrate_write_unlock(zspage: dst_zspage);
2029	dst_zspage = NULL;
2030
2031	spin_unlock(lock: &pool->lock);
2032	cond_resched();
2033	spin_lock(lock: &pool->lock);
2034	}
2035	}
2036
2037	if (src_zspage) {
2038	putback_zspage(class, zspage: src_zspage);
2039	migrate_write_unlock(zspage: src_zspage);
2040	}
2041
2042	if (dst_zspage) {
2043	putback_zspage(class, zspage: dst_zspage);
2044	migrate_write_unlock(zspage: dst_zspage);
2045	}
2046	spin_unlock(lock: &pool->lock);
2047
2048	return pages_freed;
2049	}
2050
2051	unsigned long zs_compact(struct zs_pool *pool)
2052	{
2053	int i;
2054	struct size_class *class;
2055	unsigned long pages_freed = 0;
2056
2057	/*
2058	* Pool compaction is performed under pool->lock so it is basically
2059	* single-threaded. Having more than one thread in __zs_compact()
2060	* will increase pool->lock contention, which will impact other
2061	* zsmalloc operations that need pool->lock.
2062	*/
2063	if (atomic_xchg(v: &pool->compaction_in_progress, new: 1))
2064	return 0;
2065
2066	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2067	class = pool->size_class[i];
2068	if (class->index != i)
2069	continue;
2070	pages_freed += __zs_compact(pool, class);
2071	}
2072	atomic_long_add(i: pages_freed, v: &pool->stats.pages_compacted);
2073	atomic_set(v: &pool->compaction_in_progress, i: 0);
2074
2075	return pages_freed;
2076	}
2077	EXPORT_SYMBOL_GPL(zs_compact);
2078
2079	void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats)
2080	{
2081	memcpy(stats, &pool->stats, sizeof(struct zs_pool_stats));
2082	}
2083	EXPORT_SYMBOL_GPL(zs_pool_stats);
2084
2085	static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
2086	struct shrink_control *sc)
2087	{
2088	unsigned long pages_freed;
2089	struct zs_pool *pool = shrinker->private_data;
2090
2091	/*
2092	* Compact classes and calculate compaction delta.
2093	* Can run concurrently with a manually triggered
2094	* (by user) compaction.
2095	*/
2096	pages_freed = zs_compact(pool);
2097
2098	return pages_freed ? pages_freed : SHRINK_STOP;
2099	}
2100
2101	static unsigned long zs_shrinker_count(struct shrinker *shrinker,
2102	struct shrink_control *sc)
2103	{
2104	int i;
2105	struct size_class *class;
2106	unsigned long pages_to_free = 0;
2107	struct zs_pool *pool = shrinker->private_data;
2108
2109	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2110	class = pool->size_class[i];
2111	if (class->index != i)
2112	continue;
2113
2114	pages_to_free += zs_can_compact(class);
2115	}
2116
2117	return pages_to_free;
2118	}
2119
2120	static void zs_unregister_shrinker(struct zs_pool *pool)
2121	{
2122	shrinker_free(shrinker: pool->shrinker);
2123	}
2124
2125	static int zs_register_shrinker(struct zs_pool *pool)
2126	{
2127	pool->shrinker = shrinker_alloc(flags: 0, fmt: "mm-zspool:%s", pool->name);
2128	if (!pool->shrinker)
2129	return -ENOMEM;
2130
2131	pool->shrinker->scan_objects = zs_shrinker_scan;
2132	pool->shrinker->count_objects = zs_shrinker_count;
2133	pool->shrinker->batch = 0;
2134	pool->shrinker->private_data = pool;
2135
2136	shrinker_register(shrinker: pool->shrinker);
2137
2138	return 0;
2139	}
2140
2141	static int calculate_zspage_chain_size(int class_size)
2142	{
2143	int i, min_waste = INT_MAX;
2144	int chain_size = 1;
2145
2146	if (is_power_of_2(n: class_size))
2147	return chain_size;
2148
2149	for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) {
2150	int waste;
2151
2152	waste = (i * PAGE_SIZE) % class_size;
2153	if (waste < min_waste) {
2154	min_waste = waste;
2155	chain_size = i;
2156	}
2157	}
2158
2159	return chain_size;
2160	}
2161
2162	/**
2163	* zs_create_pool - Creates an allocation pool to work from.
2164	* @name: pool name to be created
2165	*
2166	* This function must be called before anything when using
2167	* the zsmalloc allocator.
2168	*
2169	* On success, a pointer to the newly created pool is returned,
2170	* otherwise NULL.
2171	*/
2172	struct zs_pool *zs_create_pool(const char *name)
2173	{
2174	int i;
2175	struct zs_pool *pool;
2176	struct size_class *prev_class = NULL;
2177
2178	pool = kzalloc(size: sizeof(*pool), GFP_KERNEL);
2179	if (!pool)
2180	return NULL;
2181
2182	init_deferred_free(pool);
2183	spin_lock_init(&pool->lock);
2184	atomic_set(v: &pool->compaction_in_progress, i: 0);
2185
2186	pool->name = kstrdup(s: name, GFP_KERNEL);
2187	if (!pool->name)
2188	goto err;
2189
2190	if (create_cache(pool))
2191	goto err;
2192
2193	/*
2194	* Iterate reversely, because, size of size_class that we want to use
2195	* for merging should be larger or equal to current size.
2196	*/
2197	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2198	int size;
2199	int pages_per_zspage;
2200	int objs_per_zspage;
2201	struct size_class *class;
2202	int fullness;
2203
2204	size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
2205	if (size > ZS_MAX_ALLOC_SIZE)
2206	size = ZS_MAX_ALLOC_SIZE;
2207	pages_per_zspage = calculate_zspage_chain_size(class_size: size);
2208	objs_per_zspage = pages_per_zspage * PAGE_SIZE / size;
2209
2210	/*
2211	* We iterate from biggest down to smallest classes,
2212	* so huge_class_size holds the size of the first huge
2213	* class. Any object bigger than or equal to that will
2214	* endup in the huge class.
2215	*/
2216	if (pages_per_zspage != 1 && objs_per_zspage != 1 &&
2217	!huge_class_size) {
2218	huge_class_size = size;
2219	/*
2220	* The object uses ZS_HANDLE_SIZE bytes to store the
2221	* handle. We need to subtract it, because zs_malloc()
2222	* unconditionally adds handle size before it performs
2223	* size class search - so object may be smaller than
2224	* huge class size, yet it still can end up in the huge
2225	* class because it grows by ZS_HANDLE_SIZE extra bytes
2226	* right before class lookup.
2227	*/
2228	huge_class_size -= (ZS_HANDLE_SIZE - 1);
2229	}
2230
2231	/*
2232	* size_class is used for normal zsmalloc operation such
2233	* as alloc/free for that size. Although it is natural that we
2234	* have one size_class for each size, there is a chance that we
2235	* can get more memory utilization if we use one size_class for
2236	* many different sizes whose size_class have same
2237	* characteristics. So, we makes size_class point to
2238	* previous size_class if possible.
2239	*/
2240	if (prev_class) {
2241	if (can_merge(prev: prev_class, pages_per_zspage, objs_per_zspage)) {
2242	pool->size_class[i] = prev_class;
2243	continue;
2244	}
2245	}
2246
2247	class = kzalloc(size: sizeof(struct size_class), GFP_KERNEL);
2248	if (!class)
2249	goto err;
2250
2251	class->size = size;
2252	class->index = i;
2253	class->pages_per_zspage = pages_per_zspage;
2254	class->objs_per_zspage = objs_per_zspage;
2255	pool->size_class[i] = class;
2256
2257	fullness = ZS_INUSE_RATIO_0;
2258	while (fullness < NR_FULLNESS_GROUPS) {
2259	INIT_LIST_HEAD(list: &class->fullness_list[fullness]);
2260	fullness++;
2261	}
2262
2263	prev_class = class;
2264	}
2265
2266	/* debug only, don't abort if it fails */
2267	zs_pool_stat_create(pool, name);
2268
2269	/*
2270	* Not critical since shrinker is only used to trigger internal
2271	* defragmentation of the pool which is pretty optional thing. If
2272	* registration fails we still can use the pool normally and user can
2273	* trigger compaction manually. Thus, ignore return code.
2274	*/
2275	zs_register_shrinker(pool);
2276
2277	return pool;
2278
2279	err:
2280	zs_destroy_pool(pool);
2281	return NULL;
2282	}
2283	EXPORT_SYMBOL_GPL(zs_create_pool);
2284
2285	void zs_destroy_pool(struct zs_pool *pool)
2286	{
2287	int i;
2288
2289	zs_unregister_shrinker(pool);
2290	zs_flush_migration(pool);
2291	zs_pool_stat_destroy(pool);
2292
2293	for (i = 0; i < ZS_SIZE_CLASSES; i++) {
2294	int fg;
2295	struct size_class *class = pool->size_class[i];
2296
2297	if (!class)
2298	continue;
2299
2300	if (class->index != i)
2301	continue;
2302
2303	for (fg = ZS_INUSE_RATIO_0; fg < NR_FULLNESS_GROUPS; fg++) {
2304	if (list_empty(head: &class->fullness_list[fg]))
2305	continue;
2306
2307	pr_err("Class-%d fullness group %d is not empty\n",
2308	class->size, fg);
2309	}
2310	kfree(objp: class);
2311	}
2312
2313	destroy_cache(pool);
2314	kfree(objp: pool->name);
2315	kfree(objp: pool);
2316	}
2317	EXPORT_SYMBOL_GPL(zs_destroy_pool);
2318
2319	static int __init zs_init(void)
2320	{
2321	int ret;
2322
2323	ret = cpuhp_setup_state(state: CPUHP_MM_ZS_PREPARE, name: "mm/zsmalloc:prepare",
2324	startup: zs_cpu_prepare, teardown: zs_cpu_dead);
2325	if (ret)
2326	goto out;
2327
2328	#ifdef CONFIG_ZPOOL
2329	zpool_register_driver(driver: &zs_zpool_driver);
2330	#endif
2331
2332	zs_stat_init();
2333
2334	return 0;
2335
2336	out:
2337	return ret;
2338	}
2339
2340	static void __exit zs_exit(void)
2341	{
2342	#ifdef CONFIG_ZPOOL
2343	zpool_unregister_driver(driver: &zs_zpool_driver);
2344	#endif
2345	cpuhp_remove_state(state: CPUHP_MM_ZS_PREPARE);
2346
2347	zs_stat_exit();
2348	}
2349
2350	module_init(zs_init);
2351	module_exit(zs_exit);
2352
2353	MODULE_LICENSE("Dual BSD/GPL");
2354	MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
2355