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