Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma
[linux-2.6-microblaze.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 <asm/tlbflush.h>
43 #include <asm/pgtable.h>
44 #include <linux/cpumask.h>
45 #include <linux/cpu.h>
46 #include <linux/vmalloc.h>
47 #include <linux/preempt.h>
48 #include <linux/spinlock.h>
49 #include <linux/types.h>
50 #include <linux/debugfs.h>
51 #include <linux/zsmalloc.h>
52 #include <linux/zpool.h>
53 #include <linux/mount.h>
54 #include <linux/migrate.h>
55 #include <linux/pagemap.h>
56
57 #define ZSPAGE_MAGIC    0x58
58
59 /*
60  * This must be power of 2 and greater than of equal to sizeof(link_free).
61  * These two conditions ensure that any 'struct link_free' itself doesn't
62  * span more than 1 page which avoids complex case of mapping 2 pages simply
63  * to restore link_free pointer values.
64  */
65 #define ZS_ALIGN                8
66
67 /*
68  * A single 'zspage' is composed of up to 2^N discontiguous 0-order (single)
69  * pages. ZS_MAX_ZSPAGE_ORDER defines upper limit on N.
70  */
71 #define ZS_MAX_ZSPAGE_ORDER 2
72 #define ZS_MAX_PAGES_PER_ZSPAGE (_AC(1, UL) << ZS_MAX_ZSPAGE_ORDER)
73
74 #define ZS_HANDLE_SIZE (sizeof(unsigned long))
75
76 /*
77  * Object location (<PFN>, <obj_idx>) is encoded as
78  * as single (unsigned long) handle value.
79  *
80  * Note that object index <obj_idx> starts from 0.
81  *
82  * This is made more complicated by various memory models and PAE.
83  */
84
85 #ifndef MAX_PHYSMEM_BITS
86 #ifdef CONFIG_HIGHMEM64G
87 #define MAX_PHYSMEM_BITS 36
88 #else /* !CONFIG_HIGHMEM64G */
89 /*
90  * If this definition of MAX_PHYSMEM_BITS is used, OBJ_INDEX_BITS will just
91  * be PAGE_SHIFT
92  */
93 #define MAX_PHYSMEM_BITS BITS_PER_LONG
94 #endif
95 #endif
96 #define _PFN_BITS               (MAX_PHYSMEM_BITS - PAGE_SHIFT)
97
98 /*
99  * Memory for allocating for handle keeps object position by
100  * encoding <page, obj_idx> and the encoded value has a room
101  * in least bit(ie, look at obj_to_location).
102  * We use the bit to synchronize between object access by
103  * user and migration.
104  */
105 #define HANDLE_PIN_BIT  0
106
107 /*
108  * Head in allocated object should have OBJ_ALLOCATED_TAG
109  * to identify the object was allocated or not.
110  * It's okay to add the status bit in the least bit because
111  * header keeps handle which is 4byte-aligned address so we
112  * have room for two bit at least.
113  */
114 #define OBJ_ALLOCATED_TAG 1
115 #define OBJ_TAG_BITS 1
116 #define OBJ_INDEX_BITS  (BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS)
117 #define OBJ_INDEX_MASK  ((_AC(1, UL) << OBJ_INDEX_BITS) - 1)
118
119 #define FULLNESS_BITS   2
120 #define CLASS_BITS      8
121 #define ISOLATED_BITS   3
122 #define MAGIC_VAL_BITS  8
123
124 #define MAX(a, b) ((a) >= (b) ? (a) : (b))
125 /* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
126 #define ZS_MIN_ALLOC_SIZE \
127         MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
128 /* each chunk includes extra space to keep handle */
129 #define ZS_MAX_ALLOC_SIZE       PAGE_SIZE
130
131 /*
132  * On systems with 4K page size, this gives 255 size classes! There is a
133  * trader-off here:
134  *  - Large number of size classes is potentially wasteful as free page are
135  *    spread across these classes
136  *  - Small number of size classes causes large internal fragmentation
137  *  - Probably its better to use specific size classes (empirically
138  *    determined). NOTE: all those class sizes must be set as multiple of
139  *    ZS_ALIGN to make sure link_free itself never has to span 2 pages.
140  *
141  *  ZS_MIN_ALLOC_SIZE and ZS_SIZE_CLASS_DELTA must be multiple of ZS_ALIGN
142  *  (reason above)
143  */
144 #define ZS_SIZE_CLASS_DELTA     (PAGE_SIZE >> CLASS_BITS)
145 #define ZS_SIZE_CLASSES (DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \
146                                       ZS_SIZE_CLASS_DELTA) + 1)
147
148 enum fullness_group {
149         ZS_EMPTY,
150         ZS_ALMOST_EMPTY,
151         ZS_ALMOST_FULL,
152         ZS_FULL,
153         NR_ZS_FULLNESS,
154 };
155
156 enum zs_stat_type {
157         CLASS_EMPTY,
158         CLASS_ALMOST_EMPTY,
159         CLASS_ALMOST_FULL,
160         CLASS_FULL,
161         OBJ_ALLOCATED,
162         OBJ_USED,
163         NR_ZS_STAT_TYPE,
164 };
165
166 struct zs_size_stat {
167         unsigned long objs[NR_ZS_STAT_TYPE];
168 };
169
170 #ifdef CONFIG_ZSMALLOC_STAT
171 static struct dentry *zs_stat_root;
172 #endif
173
174 #ifdef CONFIG_COMPACTION
175 static struct vfsmount *zsmalloc_mnt;
176 #endif
177
178 /*
179  * We assign a page to ZS_ALMOST_EMPTY fullness group when:
180  *      n <= N / f, where
181  * n = number of allocated objects
182  * N = total number of objects zspage can store
183  * f = fullness_threshold_frac
184  *
185  * Similarly, we assign zspage to:
186  *      ZS_ALMOST_FULL  when n > N / f
187  *      ZS_EMPTY        when n == 0
188  *      ZS_FULL         when n == N
189  *
190  * (see: fix_fullness_group())
191  */
192 static const int fullness_threshold_frac = 4;
193
194 struct size_class {
195         spinlock_t lock;
196         struct list_head fullness_list[NR_ZS_FULLNESS];
197         /*
198          * Size of objects stored in this class. Must be multiple
199          * of ZS_ALIGN.
200          */
201         int size;
202         int objs_per_zspage;
203         /* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
204         int pages_per_zspage;
205
206         unsigned int index;
207         struct zs_size_stat stats;
208 };
209
210 /* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
211 static void SetPageHugeObject(struct page *page)
212 {
213         SetPageOwnerPriv1(page);
214 }
215
216 static void ClearPageHugeObject(struct page *page)
217 {
218         ClearPageOwnerPriv1(page);
219 }
220
221 static int PageHugeObject(struct page *page)
222 {
223         return PageOwnerPriv1(page);
224 }
225
226 /*
227  * Placed within free objects to form a singly linked list.
228  * For every zspage, zspage->freeobj gives head of this list.
229  *
230  * This must be power of 2 and less than or equal to ZS_ALIGN
231  */
232 struct link_free {
233         union {
234                 /*
235                  * Free object index;
236                  * It's valid for non-allocated object
237                  */
238                 unsigned long next;
239                 /*
240                  * Handle of allocated object.
241                  */
242                 unsigned long handle;
243         };
244 };
245
246 struct zs_pool {
247         const char *name;
248
249         struct size_class *size_class[ZS_SIZE_CLASSES];
250         struct kmem_cache *handle_cachep;
251         struct kmem_cache *zspage_cachep;
252
253         atomic_long_t pages_allocated;
254
255         struct zs_pool_stats stats;
256
257         /* Compact classes */
258         struct shrinker shrinker;
259         /*
260          * To signify that register_shrinker() was successful
261          * and unregister_shrinker() will not Oops.
262          */
263         bool shrinker_enabled;
264 #ifdef CONFIG_ZSMALLOC_STAT
265         struct dentry *stat_dentry;
266 #endif
267 #ifdef CONFIG_COMPACTION
268         struct inode *inode;
269         struct work_struct free_work;
270 #endif
271 };
272
273 struct zspage {
274         struct {
275                 unsigned int fullness:FULLNESS_BITS;
276                 unsigned int class:CLASS_BITS + 1;
277                 unsigned int isolated:ISOLATED_BITS;
278                 unsigned int magic:MAGIC_VAL_BITS;
279         };
280         unsigned int inuse;
281         unsigned int freeobj;
282         struct page *first_page;
283         struct list_head list; /* fullness list */
284 #ifdef CONFIG_COMPACTION
285         rwlock_t lock;
286 #endif
287 };
288
289 struct mapping_area {
290 #ifdef CONFIG_PGTABLE_MAPPING
291         struct vm_struct *vm; /* vm area for mapping object that span pages */
292 #else
293         char *vm_buf; /* copy buffer for objects that span pages */
294 #endif
295         char *vm_addr; /* address of kmap_atomic()'ed pages */
296         enum zs_mapmode vm_mm; /* mapping mode */
297 };
298
299 #ifdef CONFIG_COMPACTION
300 static int zs_register_migration(struct zs_pool *pool);
301 static void zs_unregister_migration(struct zs_pool *pool);
302 static void migrate_lock_init(struct zspage *zspage);
303 static void migrate_read_lock(struct zspage *zspage);
304 static void migrate_read_unlock(struct zspage *zspage);
305 static void kick_deferred_free(struct zs_pool *pool);
306 static void init_deferred_free(struct zs_pool *pool);
307 static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage);
308 #else
309 static int zsmalloc_mount(void) { return 0; }
310 static void zsmalloc_unmount(void) {}
311 static int zs_register_migration(struct zs_pool *pool) { return 0; }
312 static void zs_unregister_migration(struct zs_pool *pool) {}
313 static void migrate_lock_init(struct zspage *zspage) {}
314 static void migrate_read_lock(struct zspage *zspage) {}
315 static void migrate_read_unlock(struct zspage *zspage) {}
316 static void kick_deferred_free(struct zs_pool *pool) {}
317 static void init_deferred_free(struct zs_pool *pool) {}
318 static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage) {}
319 #endif
320
321 static int create_cache(struct zs_pool *pool)
322 {
323         pool->handle_cachep = kmem_cache_create("zs_handle", ZS_HANDLE_SIZE,
324                                         0, 0, NULL);
325         if (!pool->handle_cachep)
326                 return 1;
327
328         pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
329                                         0, 0, NULL);
330         if (!pool->zspage_cachep) {
331                 kmem_cache_destroy(pool->handle_cachep);
332                 pool->handle_cachep = NULL;
333                 return 1;
334         }
335
336         return 0;
337 }
338
339 static void destroy_cache(struct zs_pool *pool)
340 {
341         kmem_cache_destroy(pool->handle_cachep);
342         kmem_cache_destroy(pool->zspage_cachep);
343 }
344
345 static unsigned long cache_alloc_handle(struct zs_pool *pool, gfp_t gfp)
346 {
347         return (unsigned long)kmem_cache_alloc(pool->handle_cachep,
348                         gfp & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
349 }
350
351 static void cache_free_handle(struct zs_pool *pool, unsigned long handle)
352 {
353         kmem_cache_free(pool->handle_cachep, (void *)handle);
354 }
355
356 static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags)
357 {
358         return kmem_cache_alloc(pool->zspage_cachep,
359                         flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
360 }
361
362 static void cache_free_zspage(struct zs_pool *pool, struct zspage *zspage)
363 {
364         kmem_cache_free(pool->zspage_cachep, zspage);
365 }
366
367 static void record_obj(unsigned long handle, unsigned long obj)
368 {
369         /*
370          * lsb of @obj represents handle lock while other bits
371          * represent object value the handle is pointing so
372          * updating shouldn't do store tearing.
373          */
374         WRITE_ONCE(*(unsigned long *)handle, obj);
375 }
376
377 /* zpool driver */
378
379 #ifdef CONFIG_ZPOOL
380
381 static void *zs_zpool_create(const char *name, gfp_t gfp,
382                              const struct zpool_ops *zpool_ops,
383                              struct zpool *zpool)
384 {
385         /*
386          * Ignore global gfp flags: zs_malloc() may be invoked from
387          * different contexts and its caller must provide a valid
388          * gfp mask.
389          */
390         return zs_create_pool(name);
391 }
392
393 static void zs_zpool_destroy(void *pool)
394 {
395         zs_destroy_pool(pool);
396 }
397
398 static int zs_zpool_malloc(void *pool, size_t size, gfp_t gfp,
399                         unsigned long *handle)
400 {
401         *handle = zs_malloc(pool, size, gfp);
402         return *handle ? 0 : -1;
403 }
404 static void zs_zpool_free(void *pool, unsigned long handle)
405 {
406         zs_free(pool, handle);
407 }
408
409 static int zs_zpool_shrink(void *pool, unsigned int pages,
410                         unsigned int *reclaimed)
411 {
412         return -EINVAL;
413 }
414
415 static void *zs_zpool_map(void *pool, unsigned long handle,
416                         enum zpool_mapmode mm)
417 {
418         enum zs_mapmode zs_mm;
419
420         switch (mm) {
421         case ZPOOL_MM_RO:
422                 zs_mm = ZS_MM_RO;
423                 break;
424         case ZPOOL_MM_WO:
425                 zs_mm = ZS_MM_WO;
426                 break;
427         case ZPOOL_MM_RW: /* fallthru */
428         default:
429                 zs_mm = ZS_MM_RW;
430                 break;
431         }
432
433         return zs_map_object(pool, handle, zs_mm);
434 }
435 static void zs_zpool_unmap(void *pool, unsigned long handle)
436 {
437         zs_unmap_object(pool, handle);
438 }
439
440 static u64 zs_zpool_total_size(void *pool)
441 {
442         return zs_get_total_pages(pool) << PAGE_SHIFT;
443 }
444
445 static struct zpool_driver zs_zpool_driver = {
446         .type =         "zsmalloc",
447         .owner =        THIS_MODULE,
448         .create =       zs_zpool_create,
449         .destroy =      zs_zpool_destroy,
450         .malloc =       zs_zpool_malloc,
451         .free =         zs_zpool_free,
452         .shrink =       zs_zpool_shrink,
453         .map =          zs_zpool_map,
454         .unmap =        zs_zpool_unmap,
455         .total_size =   zs_zpool_total_size,
456 };
457
458 MODULE_ALIAS("zpool-zsmalloc");
459 #endif /* CONFIG_ZPOOL */
460
461 /* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
462 static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
463
464 static bool is_zspage_isolated(struct zspage *zspage)
465 {
466         return zspage->isolated;
467 }
468
469 static __maybe_unused int is_first_page(struct page *page)
470 {
471         return PagePrivate(page);
472 }
473
474 /* Protected by class->lock */
475 static inline int get_zspage_inuse(struct zspage *zspage)
476 {
477         return zspage->inuse;
478 }
479
480 static inline void set_zspage_inuse(struct zspage *zspage, int val)
481 {
482         zspage->inuse = val;
483 }
484
485 static inline void mod_zspage_inuse(struct zspage *zspage, int val)
486 {
487         zspage->inuse += val;
488 }
489
490 static inline struct page *get_first_page(struct zspage *zspage)
491 {
492         struct page *first_page = zspage->first_page;
493
494         VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
495         return first_page;
496 }
497
498 static inline int get_first_obj_offset(struct page *page)
499 {
500         return page->units;
501 }
502
503 static inline void set_first_obj_offset(struct page *page, int offset)
504 {
505         page->units = offset;
506 }
507
508 static inline unsigned int get_freeobj(struct zspage *zspage)
509 {
510         return zspage->freeobj;
511 }
512
513 static inline void set_freeobj(struct zspage *zspage, unsigned int obj)
514 {
515         zspage->freeobj = obj;
516 }
517
518 static void get_zspage_mapping(struct zspage *zspage,
519                                 unsigned int *class_idx,
520                                 enum fullness_group *fullness)
521 {
522         BUG_ON(zspage->magic != ZSPAGE_MAGIC);
523
524         *fullness = zspage->fullness;
525         *class_idx = zspage->class;
526 }
527
528 static void set_zspage_mapping(struct zspage *zspage,
529                                 unsigned int class_idx,
530                                 enum fullness_group fullness)
531 {
532         zspage->class = class_idx;
533         zspage->fullness = fullness;
534 }
535
536 /*
537  * zsmalloc divides the pool into various size classes where each
538  * class maintains a list of zspages where each zspage is divided
539  * into equal sized chunks. Each allocation falls into one of these
540  * classes depending on its size. This function returns index of the
541  * size class which has chunk size big enough to hold the give size.
542  */
543 static int get_size_class_index(int size)
544 {
545         int idx = 0;
546
547         if (likely(size > ZS_MIN_ALLOC_SIZE))
548                 idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
549                                 ZS_SIZE_CLASS_DELTA);
550
551         return min_t(int, ZS_SIZE_CLASSES - 1, idx);
552 }
553
554 /* type can be of enum type zs_stat_type or fullness_group */
555 static inline void zs_stat_inc(struct size_class *class,
556                                 int type, unsigned long cnt)
557 {
558         class->stats.objs[type] += cnt;
559 }
560
561 /* type can be of enum type zs_stat_type or fullness_group */
562 static inline void zs_stat_dec(struct size_class *class,
563                                 int type, unsigned long cnt)
564 {
565         class->stats.objs[type] -= cnt;
566 }
567
568 /* type can be of enum type zs_stat_type or fullness_group */
569 static inline unsigned long zs_stat_get(struct size_class *class,
570                                 int type)
571 {
572         return class->stats.objs[type];
573 }
574
575 #ifdef CONFIG_ZSMALLOC_STAT
576
577 static void __init zs_stat_init(void)
578 {
579         if (!debugfs_initialized()) {
580                 pr_warn("debugfs not available, stat dir not created\n");
581                 return;
582         }
583
584         zs_stat_root = debugfs_create_dir("zsmalloc", NULL);
585         if (!zs_stat_root)
586                 pr_warn("debugfs 'zsmalloc' stat dir creation failed\n");
587 }
588
589 static void __exit zs_stat_exit(void)
590 {
591         debugfs_remove_recursive(zs_stat_root);
592 }
593
594 static unsigned long zs_can_compact(struct size_class *class);
595
596 static int zs_stats_size_show(struct seq_file *s, void *v)
597 {
598         int i;
599         struct zs_pool *pool = s->private;
600         struct size_class *class;
601         int objs_per_zspage;
602         unsigned long class_almost_full, class_almost_empty;
603         unsigned long obj_allocated, obj_used, pages_used, freeable;
604         unsigned long total_class_almost_full = 0, total_class_almost_empty = 0;
605         unsigned long total_objs = 0, total_used_objs = 0, total_pages = 0;
606         unsigned long total_freeable = 0;
607
608         seq_printf(s, " %5s %5s %11s %12s %13s %10s %10s %16s %8s\n",
609                         "class", "size", "almost_full", "almost_empty",
610                         "obj_allocated", "obj_used", "pages_used",
611                         "pages_per_zspage", "freeable");
612
613         for (i = 0; i < ZS_SIZE_CLASSES; i++) {
614                 class = pool->size_class[i];
615
616                 if (class->index != i)
617                         continue;
618
619                 spin_lock(&class->lock);
620                 class_almost_full = zs_stat_get(class, CLASS_ALMOST_FULL);
621                 class_almost_empty = zs_stat_get(class, CLASS_ALMOST_EMPTY);
622                 obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
623                 obj_used = zs_stat_get(class, OBJ_USED);
624                 freeable = zs_can_compact(class);
625                 spin_unlock(&class->lock);
626
627                 objs_per_zspage = class->objs_per_zspage;
628                 pages_used = obj_allocated / objs_per_zspage *
629                                 class->pages_per_zspage;
630
631                 seq_printf(s, " %5u %5u %11lu %12lu %13lu"
632                                 " %10lu %10lu %16d %8lu\n",
633                         i, class->size, class_almost_full, class_almost_empty,
634                         obj_allocated, obj_used, pages_used,
635                         class->pages_per_zspage, freeable);
636
637                 total_class_almost_full += class_almost_full;
638                 total_class_almost_empty += class_almost_empty;
639                 total_objs += obj_allocated;
640                 total_used_objs += obj_used;
641                 total_pages += pages_used;
642                 total_freeable += freeable;
643         }
644
645         seq_puts(s, "\n");
646         seq_printf(s, " %5s %5s %11lu %12lu %13lu %10lu %10lu %16s %8lu\n",
647                         "Total", "", total_class_almost_full,
648                         total_class_almost_empty, total_objs,
649                         total_used_objs, total_pages, "", total_freeable);
650
651         return 0;
652 }
653
654 static int zs_stats_size_open(struct inode *inode, struct file *file)
655 {
656         return single_open(file, zs_stats_size_show, inode->i_private);
657 }
658
659 static const struct file_operations zs_stat_size_ops = {
660         .open           = zs_stats_size_open,
661         .read           = seq_read,
662         .llseek         = seq_lseek,
663         .release        = single_release,
664 };
665
666 static void zs_pool_stat_create(struct zs_pool *pool, const char *name)
667 {
668         struct dentry *entry;
669
670         if (!zs_stat_root) {
671                 pr_warn("no root stat dir, not creating <%s> stat dir\n", name);
672                 return;
673         }
674
675         entry = debugfs_create_dir(name, zs_stat_root);
676         if (!entry) {
677                 pr_warn("debugfs dir <%s> creation failed\n", name);
678                 return;
679         }
680         pool->stat_dentry = entry;
681
682         entry = debugfs_create_file("classes", S_IFREG | S_IRUGO,
683                         pool->stat_dentry, pool, &zs_stat_size_ops);
684         if (!entry) {
685                 pr_warn("%s: debugfs file entry <%s> creation failed\n",
686                                 name, "classes");
687                 debugfs_remove_recursive(pool->stat_dentry);
688                 pool->stat_dentry = NULL;
689         }
690 }
691
692 static void zs_pool_stat_destroy(struct zs_pool *pool)
693 {
694         debugfs_remove_recursive(pool->stat_dentry);
695 }
696
697 #else /* CONFIG_ZSMALLOC_STAT */
698 static void __init zs_stat_init(void)
699 {
700 }
701
702 static void __exit zs_stat_exit(void)
703 {
704 }
705
706 static inline void zs_pool_stat_create(struct zs_pool *pool, const char *name)
707 {
708 }
709
710 static inline void zs_pool_stat_destroy(struct zs_pool *pool)
711 {
712 }
713 #endif
714
715
716 /*
717  * For each size class, zspages are divided into different groups
718  * depending on how "full" they are. This was done so that we could
719  * easily find empty or nearly empty zspages when we try to shrink
720  * the pool (not yet implemented). This function returns fullness
721  * status of the given page.
722  */
723 static enum fullness_group get_fullness_group(struct size_class *class,
724                                                 struct zspage *zspage)
725 {
726         int inuse, objs_per_zspage;
727         enum fullness_group fg;
728
729         inuse = get_zspage_inuse(zspage);
730         objs_per_zspage = class->objs_per_zspage;
731
732         if (inuse == 0)
733                 fg = ZS_EMPTY;
734         else if (inuse == objs_per_zspage)
735                 fg = ZS_FULL;
736         else if (inuse <= 3 * objs_per_zspage / fullness_threshold_frac)
737                 fg = ZS_ALMOST_EMPTY;
738         else
739                 fg = ZS_ALMOST_FULL;
740
741         return fg;
742 }
743
744 /*
745  * Each size class maintains various freelists and zspages are assigned
746  * to one of these freelists based on the number of live objects they
747  * have. This functions inserts the given zspage into the freelist
748  * identified by <class, fullness_group>.
749  */
750 static void insert_zspage(struct size_class *class,
751                                 struct zspage *zspage,
752                                 enum fullness_group fullness)
753 {
754         struct zspage *head;
755
756         zs_stat_inc(class, fullness, 1);
757         head = list_first_entry_or_null(&class->fullness_list[fullness],
758                                         struct zspage, list);
759         /*
760          * We want to see more ZS_FULL pages and less almost empty/full.
761          * Put pages with higher ->inuse first.
762          */
763         if (head) {
764                 if (get_zspage_inuse(zspage) < get_zspage_inuse(head)) {
765                         list_add(&zspage->list, &head->list);
766                         return;
767                 }
768         }
769         list_add(&zspage->list, &class->fullness_list[fullness]);
770 }
771
772 /*
773  * This function removes the given zspage from the freelist identified
774  * by <class, fullness_group>.
775  */
776 static void remove_zspage(struct size_class *class,
777                                 struct zspage *zspage,
778                                 enum fullness_group fullness)
779 {
780         VM_BUG_ON(list_empty(&class->fullness_list[fullness]));
781         VM_BUG_ON(is_zspage_isolated(zspage));
782
783         list_del_init(&zspage->list);
784         zs_stat_dec(class, fullness, 1);
785 }
786
787 /*
788  * Each size class maintains zspages in different fullness groups depending
789  * on the number of live objects they contain. When allocating or freeing
790  * objects, the fullness status of the page can change, say, from ALMOST_FULL
791  * to ALMOST_EMPTY when freeing an object. This function checks if such
792  * a status change has occurred for the given page and accordingly moves the
793  * page from the freelist of the old fullness group to that of the new
794  * fullness group.
795  */
796 static enum fullness_group fix_fullness_group(struct size_class *class,
797                                                 struct zspage *zspage)
798 {
799         int class_idx;
800         enum fullness_group currfg, newfg;
801
802         get_zspage_mapping(zspage, &class_idx, &currfg);
803         newfg = get_fullness_group(class, zspage);
804         if (newfg == currfg)
805                 goto out;
806
807         if (!is_zspage_isolated(zspage)) {
808                 remove_zspage(class, zspage, currfg);
809                 insert_zspage(class, zspage, newfg);
810         }
811
812         set_zspage_mapping(zspage, class_idx, newfg);
813
814 out:
815         return newfg;
816 }
817
818 /*
819  * We have to decide on how many pages to link together
820  * to form a zspage for each size class. This is important
821  * to reduce wastage due to unusable space left at end of
822  * each zspage which is given as:
823  *     wastage = Zp % class_size
824  *     usage = Zp - wastage
825  * where Zp = zspage size = k * PAGE_SIZE where k = 1, 2, ...
826  *
827  * For example, for size class of 3/8 * PAGE_SIZE, we should
828  * link together 3 PAGE_SIZE sized pages to form a zspage
829  * since then we can perfectly fit in 8 such objects.
830  */
831 static int get_pages_per_zspage(int class_size)
832 {
833         int i, max_usedpc = 0;
834         /* zspage order which gives maximum used size per KB */
835         int max_usedpc_order = 1;
836
837         for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) {
838                 int zspage_size;
839                 int waste, usedpc;
840
841                 zspage_size = i * PAGE_SIZE;
842                 waste = zspage_size % class_size;
843                 usedpc = (zspage_size - waste) * 100 / zspage_size;
844
845                 if (usedpc > max_usedpc) {
846                         max_usedpc = usedpc;
847                         max_usedpc_order = i;
848                 }
849         }
850
851         return max_usedpc_order;
852 }
853
854 static struct zspage *get_zspage(struct page *page)
855 {
856         struct zspage *zspage = (struct zspage *)page->private;
857
858         BUG_ON(zspage->magic != ZSPAGE_MAGIC);
859         return zspage;
860 }
861
862 static struct page *get_next_page(struct page *page)
863 {
864         if (unlikely(PageHugeObject(page)))
865                 return NULL;
866
867         return page->freelist;
868 }
869
870 /**
871  * obj_to_location - get (<page>, <obj_idx>) from encoded object value
872  * @page: page object resides in zspage
873  * @obj_idx: object index
874  */
875 static void obj_to_location(unsigned long obj, struct page **page,
876                                 unsigned int *obj_idx)
877 {
878         obj >>= OBJ_TAG_BITS;
879         *page = pfn_to_page(obj >> OBJ_INDEX_BITS);
880         *obj_idx = (obj & OBJ_INDEX_MASK);
881 }
882
883 /**
884  * location_to_obj - get obj value encoded from (<page>, <obj_idx>)
885  * @page: page object resides in zspage
886  * @obj_idx: object index
887  */
888 static unsigned long location_to_obj(struct page *page, unsigned int obj_idx)
889 {
890         unsigned long obj;
891
892         obj = page_to_pfn(page) << OBJ_INDEX_BITS;
893         obj |= obj_idx & OBJ_INDEX_MASK;
894         obj <<= OBJ_TAG_BITS;
895
896         return obj;
897 }
898
899 static unsigned long handle_to_obj(unsigned long handle)
900 {
901         return *(unsigned long *)handle;
902 }
903
904 static unsigned long obj_to_head(struct page *page, void *obj)
905 {
906         if (unlikely(PageHugeObject(page))) {
907                 VM_BUG_ON_PAGE(!is_first_page(page), page);
908                 return page->index;
909         } else
910                 return *(unsigned long *)obj;
911 }
912
913 static inline int testpin_tag(unsigned long handle)
914 {
915         return bit_spin_is_locked(HANDLE_PIN_BIT, (unsigned long *)handle);
916 }
917
918 static inline int trypin_tag(unsigned long handle)
919 {
920         return bit_spin_trylock(HANDLE_PIN_BIT, (unsigned long *)handle);
921 }
922
923 static void pin_tag(unsigned long handle)
924 {
925         bit_spin_lock(HANDLE_PIN_BIT, (unsigned long *)handle);
926 }
927
928 static void unpin_tag(unsigned long handle)
929 {
930         bit_spin_unlock(HANDLE_PIN_BIT, (unsigned long *)handle);
931 }
932
933 static void reset_page(struct page *page)
934 {
935         __ClearPageMovable(page);
936         ClearPagePrivate(page);
937         set_page_private(page, 0);
938         page_mapcount_reset(page);
939         ClearPageHugeObject(page);
940         page->freelist = NULL;
941 }
942
943 /*
944  * To prevent zspage destroy during migration, zspage freeing should
945  * hold locks of all pages in the zspage.
946  */
947 void lock_zspage(struct zspage *zspage)
948 {
949         struct page *page = get_first_page(zspage);
950
951         do {
952                 lock_page(page);
953         } while ((page = get_next_page(page)) != NULL);
954 }
955
956 int trylock_zspage(struct zspage *zspage)
957 {
958         struct page *cursor, *fail;
959
960         for (cursor = get_first_page(zspage); cursor != NULL; cursor =
961                                         get_next_page(cursor)) {
962                 if (!trylock_page(cursor)) {
963                         fail = cursor;
964                         goto unlock;
965                 }
966         }
967
968         return 1;
969 unlock:
970         for (cursor = get_first_page(zspage); cursor != fail; cursor =
971                                         get_next_page(cursor))
972                 unlock_page(cursor);
973
974         return 0;
975 }
976
977 static void __free_zspage(struct zs_pool *pool, struct size_class *class,
978                                 struct zspage *zspage)
979 {
980         struct page *page, *next;
981         enum fullness_group fg;
982         unsigned int class_idx;
983
984         get_zspage_mapping(zspage, &class_idx, &fg);
985
986         assert_spin_locked(&class->lock);
987
988         VM_BUG_ON(get_zspage_inuse(zspage));
989         VM_BUG_ON(fg != ZS_EMPTY);
990
991         next = page = get_first_page(zspage);
992         do {
993                 VM_BUG_ON_PAGE(!PageLocked(page), page);
994                 next = get_next_page(page);
995                 reset_page(page);
996                 unlock_page(page);
997                 dec_zone_page_state(page, NR_ZSPAGES);
998                 put_page(page);
999                 page = next;
1000         } while (page != NULL);
1001
1002         cache_free_zspage(pool, zspage);
1003
1004         zs_stat_dec(class, OBJ_ALLOCATED, class->objs_per_zspage);
1005         atomic_long_sub(class->pages_per_zspage,
1006                                         &pool->pages_allocated);
1007 }
1008
1009 static void free_zspage(struct zs_pool *pool, struct size_class *class,
1010                                 struct zspage *zspage)
1011 {
1012         VM_BUG_ON(get_zspage_inuse(zspage));
1013         VM_BUG_ON(list_empty(&zspage->list));
1014
1015         if (!trylock_zspage(zspage)) {
1016                 kick_deferred_free(pool);
1017                 return;
1018         }
1019
1020         remove_zspage(class, zspage, ZS_EMPTY);
1021         __free_zspage(pool, class, zspage);
1022 }
1023
1024 /* Initialize a newly allocated zspage */
1025 static void init_zspage(struct size_class *class, struct zspage *zspage)
1026 {
1027         unsigned int freeobj = 1;
1028         unsigned long off = 0;
1029         struct page *page = get_first_page(zspage);
1030
1031         while (page) {
1032                 struct page *next_page;
1033                 struct link_free *link;
1034                 void *vaddr;
1035
1036                 set_first_obj_offset(page, off);
1037
1038                 vaddr = kmap_atomic(page);
1039                 link = (struct link_free *)vaddr + off / sizeof(*link);
1040
1041                 while ((off += class->size) < PAGE_SIZE) {
1042                         link->next = freeobj++ << OBJ_TAG_BITS;
1043                         link += class->size / sizeof(*link);
1044                 }
1045
1046                 /*
1047                  * We now come to the last (full or partial) object on this
1048                  * page, which must point to the first object on the next
1049                  * page (if present)
1050                  */
1051                 next_page = get_next_page(page);
1052                 if (next_page) {
1053                         link->next = freeobj++ << OBJ_TAG_BITS;
1054                 } else {
1055                         /*
1056                          * Reset OBJ_TAG_BITS bit to last link to tell
1057                          * whether it's allocated object or not.
1058                          */
1059                         link->next = -1 << OBJ_TAG_BITS;
1060                 }
1061                 kunmap_atomic(vaddr);
1062                 page = next_page;
1063                 off %= PAGE_SIZE;
1064         }
1065
1066         set_freeobj(zspage, 0);
1067 }
1068
1069 static void create_page_chain(struct size_class *class, struct zspage *zspage,
1070                                 struct page *pages[])
1071 {
1072         int i;
1073         struct page *page;
1074         struct page *prev_page = NULL;
1075         int nr_pages = class->pages_per_zspage;
1076
1077         /*
1078          * Allocate individual pages and link them together as:
1079          * 1. all pages are linked together using page->freelist
1080          * 2. each sub-page point to zspage using page->private
1081          *
1082          * we set PG_private to identify the first page (i.e. no other sub-page
1083          * has this flag set).
1084          */
1085         for (i = 0; i < nr_pages; i++) {
1086                 page = pages[i];
1087                 set_page_private(page, (unsigned long)zspage);
1088                 page->freelist = NULL;
1089                 if (i == 0) {
1090                         zspage->first_page = page;
1091                         SetPagePrivate(page);
1092                         if (unlikely(class->objs_per_zspage == 1 &&
1093                                         class->pages_per_zspage == 1))
1094                                 SetPageHugeObject(page);
1095                 } else {
1096                         prev_page->freelist = page;
1097                 }
1098                 prev_page = page;
1099         }
1100 }
1101
1102 /*
1103  * Allocate a zspage for the given size class
1104  */
1105 static struct zspage *alloc_zspage(struct zs_pool *pool,
1106                                         struct size_class *class,
1107                                         gfp_t gfp)
1108 {
1109         int i;
1110         struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE];
1111         struct zspage *zspage = cache_alloc_zspage(pool, gfp);
1112
1113         if (!zspage)
1114                 return NULL;
1115
1116         memset(zspage, 0, sizeof(struct zspage));
1117         zspage->magic = ZSPAGE_MAGIC;
1118         migrate_lock_init(zspage);
1119
1120         for (i = 0; i < class->pages_per_zspage; i++) {
1121                 struct page *page;
1122
1123                 page = alloc_page(gfp);
1124                 if (!page) {
1125                         while (--i >= 0) {
1126                                 dec_zone_page_state(pages[i], NR_ZSPAGES);
1127                                 __free_page(pages[i]);
1128                         }
1129                         cache_free_zspage(pool, zspage);
1130                         return NULL;
1131                 }
1132
1133                 inc_zone_page_state(page, NR_ZSPAGES);
1134                 pages[i] = page;
1135         }
1136
1137         create_page_chain(class, zspage, pages);
1138         init_zspage(class, zspage);
1139
1140         return zspage;
1141 }
1142
1143 static struct zspage *find_get_zspage(struct size_class *class)
1144 {
1145         int i;
1146         struct zspage *zspage;
1147
1148         for (i = ZS_ALMOST_FULL; i >= ZS_EMPTY; i--) {
1149                 zspage = list_first_entry_or_null(&class->fullness_list[i],
1150                                 struct zspage, list);
1151                 if (zspage)
1152                         break;
1153         }
1154
1155         return zspage;
1156 }
1157
1158 #ifdef CONFIG_PGTABLE_MAPPING
1159 static inline int __zs_cpu_up(struct mapping_area *area)
1160 {
1161         /*
1162          * Make sure we don't leak memory if a cpu UP notification
1163          * and zs_init() race and both call zs_cpu_up() on the same cpu
1164          */
1165         if (area->vm)
1166                 return 0;
1167         area->vm = alloc_vm_area(PAGE_SIZE * 2, NULL);
1168         if (!area->vm)
1169                 return -ENOMEM;
1170         return 0;
1171 }
1172
1173 static inline void __zs_cpu_down(struct mapping_area *area)
1174 {
1175         if (area->vm)
1176                 free_vm_area(area->vm);
1177         area->vm = NULL;
1178 }
1179
1180 static inline void *__zs_map_object(struct mapping_area *area,
1181                                 struct page *pages[2], int off, int size)
1182 {
1183         BUG_ON(map_vm_area(area->vm, PAGE_KERNEL, pages));
1184         area->vm_addr = area->vm->addr;
1185         return area->vm_addr + off;
1186 }
1187
1188 static inline void __zs_unmap_object(struct mapping_area *area,
1189                                 struct page *pages[2], int off, int size)
1190 {
1191         unsigned long addr = (unsigned long)area->vm_addr;
1192
1193         unmap_kernel_range(addr, PAGE_SIZE * 2);
1194 }
1195
1196 #else /* CONFIG_PGTABLE_MAPPING */
1197
1198 static inline int __zs_cpu_up(struct mapping_area *area)
1199 {
1200         /*
1201          * Make sure we don't leak memory if a cpu UP notification
1202          * and zs_init() race and both call zs_cpu_up() on the same cpu
1203          */
1204         if (area->vm_buf)
1205                 return 0;
1206         area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);
1207         if (!area->vm_buf)
1208                 return -ENOMEM;
1209         return 0;
1210 }
1211
1212 static inline void __zs_cpu_down(struct mapping_area *area)
1213 {
1214         kfree(area->vm_buf);
1215         area->vm_buf = NULL;
1216 }
1217
1218 static void *__zs_map_object(struct mapping_area *area,
1219                         struct page *pages[2], int off, int size)
1220 {
1221         int sizes[2];
1222         void *addr;
1223         char *buf = area->vm_buf;
1224
1225         /* disable page faults to match kmap_atomic() return conditions */
1226         pagefault_disable();
1227
1228         /* no read fastpath */
1229         if (area->vm_mm == ZS_MM_WO)
1230                 goto out;
1231
1232         sizes[0] = PAGE_SIZE - off;
1233         sizes[1] = size - sizes[0];
1234
1235         /* copy object to per-cpu buffer */
1236         addr = kmap_atomic(pages[0]);
1237         memcpy(buf, addr + off, sizes[0]);
1238         kunmap_atomic(addr);
1239         addr = kmap_atomic(pages[1]);
1240         memcpy(buf + sizes[0], addr, sizes[1]);
1241         kunmap_atomic(addr);
1242 out:
1243         return area->vm_buf;
1244 }
1245
1246 static void __zs_unmap_object(struct mapping_area *area,
1247                         struct page *pages[2], int off, int size)
1248 {
1249         int sizes[2];
1250         void *addr;
1251         char *buf;
1252
1253         /* no write fastpath */
1254         if (area->vm_mm == ZS_MM_RO)
1255                 goto out;
1256
1257         buf = area->vm_buf;
1258         buf = buf + ZS_HANDLE_SIZE;
1259         size -= ZS_HANDLE_SIZE;
1260         off += ZS_HANDLE_SIZE;
1261
1262         sizes[0] = PAGE_SIZE - off;
1263         sizes[1] = size - sizes[0];
1264
1265         /* copy per-cpu buffer to object */
1266         addr = kmap_atomic(pages[0]);
1267         memcpy(addr + off, buf, sizes[0]);
1268         kunmap_atomic(addr);
1269         addr = kmap_atomic(pages[1]);
1270         memcpy(addr, buf + sizes[0], sizes[1]);
1271         kunmap_atomic(addr);
1272
1273 out:
1274         /* enable page faults to match kunmap_atomic() return conditions */
1275         pagefault_enable();
1276 }
1277
1278 #endif /* CONFIG_PGTABLE_MAPPING */
1279
1280 static int zs_cpu_prepare(unsigned int cpu)
1281 {
1282         struct mapping_area *area;
1283
1284         area = &per_cpu(zs_map_area, cpu);
1285         return __zs_cpu_up(area);
1286 }
1287
1288 static int zs_cpu_dead(unsigned int cpu)
1289 {
1290         struct mapping_area *area;
1291
1292         area = &per_cpu(zs_map_area, cpu);
1293         __zs_cpu_down(area);
1294         return 0;
1295 }
1296
1297 static bool can_merge(struct size_class *prev, int pages_per_zspage,
1298                                         int objs_per_zspage)
1299 {
1300         if (prev->pages_per_zspage == pages_per_zspage &&
1301                 prev->objs_per_zspage == objs_per_zspage)
1302                 return true;
1303
1304         return false;
1305 }
1306
1307 static bool zspage_full(struct size_class *class, struct zspage *zspage)
1308 {
1309         return get_zspage_inuse(zspage) == class->objs_per_zspage;
1310 }
1311
1312 unsigned long zs_get_total_pages(struct zs_pool *pool)
1313 {
1314         return atomic_long_read(&pool->pages_allocated);
1315 }
1316 EXPORT_SYMBOL_GPL(zs_get_total_pages);
1317
1318 /**
1319  * zs_map_object - get address of allocated object from handle.
1320  * @pool: pool from which the object was allocated
1321  * @handle: handle returned from zs_malloc
1322  *
1323  * Before using an object allocated from zs_malloc, it must be mapped using
1324  * this function. When done with the object, it must be unmapped using
1325  * zs_unmap_object.
1326  *
1327  * Only one object can be mapped per cpu at a time. There is no protection
1328  * against nested mappings.
1329  *
1330  * This function returns with preemption and page faults disabled.
1331  */
1332 void *zs_map_object(struct zs_pool *pool, unsigned long handle,
1333                         enum zs_mapmode mm)
1334 {
1335         struct zspage *zspage;
1336         struct page *page;
1337         unsigned long obj, off;
1338         unsigned int obj_idx;
1339
1340         unsigned int class_idx;
1341         enum fullness_group fg;
1342         struct size_class *class;
1343         struct mapping_area *area;
1344         struct page *pages[2];
1345         void *ret;
1346
1347         /*
1348          * Because we use per-cpu mapping areas shared among the
1349          * pools/users, we can't allow mapping in interrupt context
1350          * because it can corrupt another users mappings.
1351          */
1352         BUG_ON(in_interrupt());
1353
1354         /* From now on, migration cannot move the object */
1355         pin_tag(handle);
1356
1357         obj = handle_to_obj(handle);
1358         obj_to_location(obj, &page, &obj_idx);
1359         zspage = get_zspage(page);
1360
1361         /* migration cannot move any subpage in this zspage */
1362         migrate_read_lock(zspage);
1363
1364         get_zspage_mapping(zspage, &class_idx, &fg);
1365         class = pool->size_class[class_idx];
1366         off = (class->size * obj_idx) & ~PAGE_MASK;
1367
1368         area = &get_cpu_var(zs_map_area);
1369         area->vm_mm = mm;
1370         if (off + class->size <= PAGE_SIZE) {
1371                 /* this object is contained entirely within a page */
1372                 area->vm_addr = kmap_atomic(page);
1373                 ret = area->vm_addr + off;
1374                 goto out;
1375         }
1376
1377         /* this object spans two pages */
1378         pages[0] = page;
1379         pages[1] = get_next_page(page);
1380         BUG_ON(!pages[1]);
1381
1382         ret = __zs_map_object(area, pages, off, class->size);
1383 out:
1384         if (likely(!PageHugeObject(page)))
1385                 ret += ZS_HANDLE_SIZE;
1386
1387         return ret;
1388 }
1389 EXPORT_SYMBOL_GPL(zs_map_object);
1390
1391 void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
1392 {
1393         struct zspage *zspage;
1394         struct page *page;
1395         unsigned long obj, off;
1396         unsigned int obj_idx;
1397
1398         unsigned int class_idx;
1399         enum fullness_group fg;
1400         struct size_class *class;
1401         struct mapping_area *area;
1402
1403         obj = handle_to_obj(handle);
1404         obj_to_location(obj, &page, &obj_idx);
1405         zspage = get_zspage(page);
1406         get_zspage_mapping(zspage, &class_idx, &fg);
1407         class = pool->size_class[class_idx];
1408         off = (class->size * obj_idx) & ~PAGE_MASK;
1409
1410         area = this_cpu_ptr(&zs_map_area);
1411         if (off + class->size <= PAGE_SIZE)
1412                 kunmap_atomic(area->vm_addr);
1413         else {
1414                 struct page *pages[2];
1415
1416                 pages[0] = page;
1417                 pages[1] = get_next_page(page);
1418                 BUG_ON(!pages[1]);
1419
1420                 __zs_unmap_object(area, pages, off, class->size);
1421         }
1422         put_cpu_var(zs_map_area);
1423
1424         migrate_read_unlock(zspage);
1425         unpin_tag(handle);
1426 }
1427 EXPORT_SYMBOL_GPL(zs_unmap_object);
1428
1429 static unsigned long obj_malloc(struct size_class *class,
1430                                 struct zspage *zspage, unsigned long handle)
1431 {
1432         int i, nr_page, offset;
1433         unsigned long obj;
1434         struct link_free *link;
1435
1436         struct page *m_page;
1437         unsigned long m_offset;
1438         void *vaddr;
1439
1440         handle |= OBJ_ALLOCATED_TAG;
1441         obj = get_freeobj(zspage);
1442
1443         offset = obj * class->size;
1444         nr_page = offset >> PAGE_SHIFT;
1445         m_offset = offset & ~PAGE_MASK;
1446         m_page = get_first_page(zspage);
1447
1448         for (i = 0; i < nr_page; i++)
1449                 m_page = get_next_page(m_page);
1450
1451         vaddr = kmap_atomic(m_page);
1452         link = (struct link_free *)vaddr + m_offset / sizeof(*link);
1453         set_freeobj(zspage, link->next >> OBJ_TAG_BITS);
1454         if (likely(!PageHugeObject(m_page)))
1455                 /* record handle in the header of allocated chunk */
1456                 link->handle = handle;
1457         else
1458                 /* record handle to page->index */
1459                 zspage->first_page->index = handle;
1460
1461         kunmap_atomic(vaddr);
1462         mod_zspage_inuse(zspage, 1);
1463         zs_stat_inc(class, OBJ_USED, 1);
1464
1465         obj = location_to_obj(m_page, obj);
1466
1467         return obj;
1468 }
1469
1470
1471 /**
1472  * zs_malloc - Allocate block of given size from pool.
1473  * @pool: pool to allocate from
1474  * @size: size of block to allocate
1475  * @gfp: gfp flags when allocating object
1476  *
1477  * On success, handle to the allocated object is returned,
1478  * otherwise 0.
1479  * Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail.
1480  */
1481 unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
1482 {
1483         unsigned long handle, obj;
1484         struct size_class *class;
1485         enum fullness_group newfg;
1486         struct zspage *zspage;
1487
1488         if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
1489                 return 0;
1490
1491         handle = cache_alloc_handle(pool, gfp);
1492         if (!handle)
1493                 return 0;
1494
1495         /* extra space in chunk to keep the handle */
1496         size += ZS_HANDLE_SIZE;
1497         class = pool->size_class[get_size_class_index(size)];
1498
1499         spin_lock(&class->lock);
1500         zspage = find_get_zspage(class);
1501         if (likely(zspage)) {
1502                 obj = obj_malloc(class, zspage, handle);
1503                 /* Now move the zspage to another fullness group, if required */
1504                 fix_fullness_group(class, zspage);
1505                 record_obj(handle, obj);
1506                 spin_unlock(&class->lock);
1507
1508                 return handle;
1509         }
1510
1511         spin_unlock(&class->lock);
1512
1513         zspage = alloc_zspage(pool, class, gfp);
1514         if (!zspage) {
1515                 cache_free_handle(pool, handle);
1516                 return 0;
1517         }
1518
1519         spin_lock(&class->lock);
1520         obj = obj_malloc(class, zspage, handle);
1521         newfg = get_fullness_group(class, zspage);
1522         insert_zspage(class, zspage, newfg);
1523         set_zspage_mapping(zspage, class->index, newfg);
1524         record_obj(handle, obj);
1525         atomic_long_add(class->pages_per_zspage,
1526                                 &pool->pages_allocated);
1527         zs_stat_inc(class, OBJ_ALLOCATED, class->objs_per_zspage);
1528
1529         /* We completely set up zspage so mark them as movable */
1530         SetZsPageMovable(pool, zspage);
1531         spin_unlock(&class->lock);
1532
1533         return handle;
1534 }
1535 EXPORT_SYMBOL_GPL(zs_malloc);
1536
1537 static void obj_free(struct size_class *class, unsigned long obj)
1538 {
1539         struct link_free *link;
1540         struct zspage *zspage;
1541         struct page *f_page;
1542         unsigned long f_offset;
1543         unsigned int f_objidx;
1544         void *vaddr;
1545
1546         obj &= ~OBJ_ALLOCATED_TAG;
1547         obj_to_location(obj, &f_page, &f_objidx);
1548         f_offset = (class->size * f_objidx) & ~PAGE_MASK;
1549         zspage = get_zspage(f_page);
1550
1551         vaddr = kmap_atomic(f_page);
1552
1553         /* Insert this object in containing zspage's freelist */
1554         link = (struct link_free *)(vaddr + f_offset);
1555         link->next = get_freeobj(zspage) << OBJ_TAG_BITS;
1556         kunmap_atomic(vaddr);
1557         set_freeobj(zspage, f_objidx);
1558         mod_zspage_inuse(zspage, -1);
1559         zs_stat_dec(class, OBJ_USED, 1);
1560 }
1561
1562 void zs_free(struct zs_pool *pool, unsigned long handle)
1563 {
1564         struct zspage *zspage;
1565         struct page *f_page;
1566         unsigned long obj;
1567         unsigned int f_objidx;
1568         int class_idx;
1569         struct size_class *class;
1570         enum fullness_group fullness;
1571         bool isolated;
1572
1573         if (unlikely(!handle))
1574                 return;
1575
1576         pin_tag(handle);
1577         obj = handle_to_obj(handle);
1578         obj_to_location(obj, &f_page, &f_objidx);
1579         zspage = get_zspage(f_page);
1580
1581         migrate_read_lock(zspage);
1582
1583         get_zspage_mapping(zspage, &class_idx, &fullness);
1584         class = pool->size_class[class_idx];
1585
1586         spin_lock(&class->lock);
1587         obj_free(class, obj);
1588         fullness = fix_fullness_group(class, zspage);
1589         if (fullness != ZS_EMPTY) {
1590                 migrate_read_unlock(zspage);
1591                 goto out;
1592         }
1593
1594         isolated = is_zspage_isolated(zspage);
1595         migrate_read_unlock(zspage);
1596         /* If zspage is isolated, zs_page_putback will free the zspage */
1597         if (likely(!isolated))
1598                 free_zspage(pool, class, zspage);
1599 out:
1600
1601         spin_unlock(&class->lock);
1602         unpin_tag(handle);
1603         cache_free_handle(pool, handle);
1604 }
1605 EXPORT_SYMBOL_GPL(zs_free);
1606
1607 static void zs_object_copy(struct size_class *class, unsigned long dst,
1608                                 unsigned long src)
1609 {
1610         struct page *s_page, *d_page;
1611         unsigned int s_objidx, d_objidx;
1612         unsigned long s_off, d_off;
1613         void *s_addr, *d_addr;
1614         int s_size, d_size, size;
1615         int written = 0;
1616
1617         s_size = d_size = class->size;
1618
1619         obj_to_location(src, &s_page, &s_objidx);
1620         obj_to_location(dst, &d_page, &d_objidx);
1621
1622         s_off = (class->size * s_objidx) & ~PAGE_MASK;
1623         d_off = (class->size * d_objidx) & ~PAGE_MASK;
1624
1625         if (s_off + class->size > PAGE_SIZE)
1626                 s_size = PAGE_SIZE - s_off;
1627
1628         if (d_off + class->size > PAGE_SIZE)
1629                 d_size = PAGE_SIZE - d_off;
1630
1631         s_addr = kmap_atomic(s_page);
1632         d_addr = kmap_atomic(d_page);
1633
1634         while (1) {
1635                 size = min(s_size, d_size);
1636                 memcpy(d_addr + d_off, s_addr + s_off, size);
1637                 written += size;
1638
1639                 if (written == class->size)
1640                         break;
1641
1642                 s_off += size;
1643                 s_size -= size;
1644                 d_off += size;
1645                 d_size -= size;
1646
1647                 if (s_off >= PAGE_SIZE) {
1648                         kunmap_atomic(d_addr);
1649                         kunmap_atomic(s_addr);
1650                         s_page = get_next_page(s_page);
1651                         s_addr = kmap_atomic(s_page);
1652                         d_addr = kmap_atomic(d_page);
1653                         s_size = class->size - written;
1654                         s_off = 0;
1655                 }
1656
1657                 if (d_off >= PAGE_SIZE) {
1658                         kunmap_atomic(d_addr);
1659                         d_page = get_next_page(d_page);
1660                         d_addr = kmap_atomic(d_page);
1661                         d_size = class->size - written;
1662                         d_off = 0;
1663                 }
1664         }
1665
1666         kunmap_atomic(d_addr);
1667         kunmap_atomic(s_addr);
1668 }
1669
1670 /*
1671  * Find alloced object in zspage from index object and
1672  * return handle.
1673  */
1674 static unsigned long find_alloced_obj(struct size_class *class,
1675                                         struct page *page, int *obj_idx)
1676 {
1677         unsigned long head;
1678         int offset = 0;
1679         int index = *obj_idx;
1680         unsigned long handle = 0;
1681         void *addr = kmap_atomic(page);
1682
1683         offset = get_first_obj_offset(page);
1684         offset += class->size * index;
1685
1686         while (offset < PAGE_SIZE) {
1687                 head = obj_to_head(page, addr + offset);
1688                 if (head & OBJ_ALLOCATED_TAG) {
1689                         handle = head & ~OBJ_ALLOCATED_TAG;
1690                         if (trypin_tag(handle))
1691                                 break;
1692                         handle = 0;
1693                 }
1694
1695                 offset += class->size;
1696                 index++;
1697         }
1698
1699         kunmap_atomic(addr);
1700
1701         *obj_idx = index;
1702
1703         return handle;
1704 }
1705
1706 struct zs_compact_control {
1707         /* Source spage for migration which could be a subpage of zspage */
1708         struct page *s_page;
1709         /* Destination page for migration which should be a first page
1710          * of zspage. */
1711         struct page *d_page;
1712          /* Starting object index within @s_page which used for live object
1713           * in the subpage. */
1714         int obj_idx;
1715 };
1716
1717 static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
1718                                 struct zs_compact_control *cc)
1719 {
1720         unsigned long used_obj, free_obj;
1721         unsigned long handle;
1722         struct page *s_page = cc->s_page;
1723         struct page *d_page = cc->d_page;
1724         int obj_idx = cc->obj_idx;
1725         int ret = 0;
1726
1727         while (1) {
1728                 handle = find_alloced_obj(class, s_page, &obj_idx);
1729                 if (!handle) {
1730                         s_page = get_next_page(s_page);
1731                         if (!s_page)
1732                                 break;
1733                         obj_idx = 0;
1734                         continue;
1735                 }
1736
1737                 /* Stop if there is no more space */
1738                 if (zspage_full(class, get_zspage(d_page))) {
1739                         unpin_tag(handle);
1740                         ret = -ENOMEM;
1741                         break;
1742                 }
1743
1744                 used_obj = handle_to_obj(handle);
1745                 free_obj = obj_malloc(class, get_zspage(d_page), handle);
1746                 zs_object_copy(class, free_obj, used_obj);
1747                 obj_idx++;
1748                 /*
1749                  * record_obj updates handle's value to free_obj and it will
1750                  * invalidate lock bit(ie, HANDLE_PIN_BIT) of handle, which
1751                  * breaks synchronization using pin_tag(e,g, zs_free) so
1752                  * let's keep the lock bit.
1753                  */
1754                 free_obj |= BIT(HANDLE_PIN_BIT);
1755                 record_obj(handle, free_obj);
1756                 unpin_tag(handle);
1757                 obj_free(class, used_obj);
1758         }
1759
1760         /* Remember last position in this iteration */
1761         cc->s_page = s_page;
1762         cc->obj_idx = obj_idx;
1763
1764         return ret;
1765 }
1766
1767 static struct zspage *isolate_zspage(struct size_class *class, bool source)
1768 {
1769         int i;
1770         struct zspage *zspage;
1771         enum fullness_group fg[2] = {ZS_ALMOST_EMPTY, ZS_ALMOST_FULL};
1772
1773         if (!source) {
1774                 fg[0] = ZS_ALMOST_FULL;
1775                 fg[1] = ZS_ALMOST_EMPTY;
1776         }
1777
1778         for (i = 0; i < 2; i++) {
1779                 zspage = list_first_entry_or_null(&class->fullness_list[fg[i]],
1780                                                         struct zspage, list);
1781                 if (zspage) {
1782                         VM_BUG_ON(is_zspage_isolated(zspage));
1783                         remove_zspage(class, zspage, fg[i]);
1784                         return zspage;
1785                 }
1786         }
1787
1788         return zspage;
1789 }
1790
1791 /*
1792  * putback_zspage - add @zspage into right class's fullness list
1793  * @class: destination class
1794  * @zspage: target page
1795  *
1796  * Return @zspage's fullness_group
1797  */
1798 static enum fullness_group putback_zspage(struct size_class *class,
1799                         struct zspage *zspage)
1800 {
1801         enum fullness_group fullness;
1802
1803         VM_BUG_ON(is_zspage_isolated(zspage));
1804
1805         fullness = get_fullness_group(class, zspage);
1806         insert_zspage(class, zspage, fullness);
1807         set_zspage_mapping(zspage, class->index, fullness);
1808
1809         return fullness;
1810 }
1811
1812 #ifdef CONFIG_COMPACTION
1813 static struct dentry *zs_mount(struct file_system_type *fs_type,
1814                                 int flags, const char *dev_name, void *data)
1815 {
1816         static const struct dentry_operations ops = {
1817                 .d_dname = simple_dname,
1818         };
1819
1820         return mount_pseudo(fs_type, "zsmalloc:", NULL, &ops, ZSMALLOC_MAGIC);
1821 }
1822
1823 static struct file_system_type zsmalloc_fs = {
1824         .name           = "zsmalloc",
1825         .mount          = zs_mount,
1826         .kill_sb        = kill_anon_super,
1827 };
1828
1829 static int zsmalloc_mount(void)
1830 {
1831         int ret = 0;
1832
1833         zsmalloc_mnt = kern_mount(&zsmalloc_fs);
1834         if (IS_ERR(zsmalloc_mnt))
1835                 ret = PTR_ERR(zsmalloc_mnt);
1836
1837         return ret;
1838 }
1839
1840 static void zsmalloc_unmount(void)
1841 {
1842         kern_unmount(zsmalloc_mnt);
1843 }
1844
1845 static void migrate_lock_init(struct zspage *zspage)
1846 {
1847         rwlock_init(&zspage->lock);
1848 }
1849
1850 static void migrate_read_lock(struct zspage *zspage)
1851 {
1852         read_lock(&zspage->lock);
1853 }
1854
1855 static void migrate_read_unlock(struct zspage *zspage)
1856 {
1857         read_unlock(&zspage->lock);
1858 }
1859
1860 static void migrate_write_lock(struct zspage *zspage)
1861 {
1862         write_lock(&zspage->lock);
1863 }
1864
1865 static void migrate_write_unlock(struct zspage *zspage)
1866 {
1867         write_unlock(&zspage->lock);
1868 }
1869
1870 /* Number of isolated subpage for *page migration* in this zspage */
1871 static void inc_zspage_isolation(struct zspage *zspage)
1872 {
1873         zspage->isolated++;
1874 }
1875
1876 static void dec_zspage_isolation(struct zspage *zspage)
1877 {
1878         zspage->isolated--;
1879 }
1880
1881 static void replace_sub_page(struct size_class *class, struct zspage *zspage,
1882                                 struct page *newpage, struct page *oldpage)
1883 {
1884         struct page *page;
1885         struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE] = {NULL, };
1886         int idx = 0;
1887
1888         page = get_first_page(zspage);
1889         do {
1890                 if (page == oldpage)
1891                         pages[idx] = newpage;
1892                 else
1893                         pages[idx] = page;
1894                 idx++;
1895         } while ((page = get_next_page(page)) != NULL);
1896
1897         create_page_chain(class, zspage, pages);
1898         set_first_obj_offset(newpage, get_first_obj_offset(oldpage));
1899         if (unlikely(PageHugeObject(oldpage)))
1900                 newpage->index = oldpage->index;
1901         __SetPageMovable(newpage, page_mapping(oldpage));
1902 }
1903
1904 bool zs_page_isolate(struct page *page, isolate_mode_t mode)
1905 {
1906         struct zs_pool *pool;
1907         struct size_class *class;
1908         int class_idx;
1909         enum fullness_group fullness;
1910         struct zspage *zspage;
1911         struct address_space *mapping;
1912
1913         /*
1914          * Page is locked so zspage couldn't be destroyed. For detail, look at
1915          * lock_zspage in free_zspage.
1916          */
1917         VM_BUG_ON_PAGE(!PageMovable(page), page);
1918         VM_BUG_ON_PAGE(PageIsolated(page), page);
1919
1920         zspage = get_zspage(page);
1921
1922         /*
1923          * Without class lock, fullness could be stale while class_idx is okay
1924          * because class_idx is constant unless page is freed so we should get
1925          * fullness again under class lock.
1926          */
1927         get_zspage_mapping(zspage, &class_idx, &fullness);
1928         mapping = page_mapping(page);
1929         pool = mapping->private_data;
1930         class = pool->size_class[class_idx];
1931
1932         spin_lock(&class->lock);
1933         if (get_zspage_inuse(zspage) == 0) {
1934                 spin_unlock(&class->lock);
1935                 return false;
1936         }
1937
1938         /* zspage is isolated for object migration */
1939         if (list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
1940                 spin_unlock(&class->lock);
1941                 return false;
1942         }
1943
1944         /*
1945          * If this is first time isolation for the zspage, isolate zspage from
1946          * size_class to prevent further object allocation from the zspage.
1947          */
1948         if (!list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
1949                 get_zspage_mapping(zspage, &class_idx, &fullness);
1950                 remove_zspage(class, zspage, fullness);
1951         }
1952
1953         inc_zspage_isolation(zspage);
1954         spin_unlock(&class->lock);
1955
1956         return true;
1957 }
1958
1959 int zs_page_migrate(struct address_space *mapping, struct page *newpage,
1960                 struct page *page, enum migrate_mode mode)
1961 {
1962         struct zs_pool *pool;
1963         struct size_class *class;
1964         int class_idx;
1965         enum fullness_group fullness;
1966         struct zspage *zspage;
1967         struct page *dummy;
1968         void *s_addr, *d_addr, *addr;
1969         int offset, pos;
1970         unsigned long handle, head;
1971         unsigned long old_obj, new_obj;
1972         unsigned int obj_idx;
1973         int ret = -EAGAIN;
1974
1975         /*
1976          * We cannot support the _NO_COPY case here, because copy needs to
1977          * happen under the zs lock, which does not work with
1978          * MIGRATE_SYNC_NO_COPY workflow.
1979          */
1980         if (mode == MIGRATE_SYNC_NO_COPY)
1981                 return -EINVAL;
1982
1983         VM_BUG_ON_PAGE(!PageMovable(page), page);
1984         VM_BUG_ON_PAGE(!PageIsolated(page), page);
1985
1986         zspage = get_zspage(page);
1987
1988         /* Concurrent compactor cannot migrate any subpage in zspage */
1989         migrate_write_lock(zspage);
1990         get_zspage_mapping(zspage, &class_idx, &fullness);
1991         pool = mapping->private_data;
1992         class = pool->size_class[class_idx];
1993         offset = get_first_obj_offset(page);
1994
1995         spin_lock(&class->lock);
1996         if (!get_zspage_inuse(zspage)) {
1997                 /*
1998                  * Set "offset" to end of the page so that every loops
1999                  * skips unnecessary object scanning.
2000                  */
2001                 offset = PAGE_SIZE;
2002         }
2003
2004         pos = offset;
2005         s_addr = kmap_atomic(page);
2006         while (pos < PAGE_SIZE) {
2007                 head = obj_to_head(page, s_addr + pos);
2008                 if (head & OBJ_ALLOCATED_TAG) {
2009                         handle = head & ~OBJ_ALLOCATED_TAG;
2010                         if (!trypin_tag(handle))
2011                                 goto unpin_objects;
2012                 }
2013                 pos += class->size;
2014         }
2015
2016         /*
2017          * Here, any user cannot access all objects in the zspage so let's move.
2018          */
2019         d_addr = kmap_atomic(newpage);
2020         memcpy(d_addr, s_addr, PAGE_SIZE);
2021         kunmap_atomic(d_addr);
2022
2023         for (addr = s_addr + offset; addr < s_addr + pos;
2024                                         addr += class->size) {
2025                 head = obj_to_head(page, addr);
2026                 if (head & OBJ_ALLOCATED_TAG) {
2027                         handle = head & ~OBJ_ALLOCATED_TAG;
2028                         if (!testpin_tag(handle))
2029                                 BUG();
2030
2031                         old_obj = handle_to_obj(handle);
2032                         obj_to_location(old_obj, &dummy, &obj_idx);
2033                         new_obj = (unsigned long)location_to_obj(newpage,
2034                                                                 obj_idx);
2035                         new_obj |= BIT(HANDLE_PIN_BIT);
2036                         record_obj(handle, new_obj);
2037                 }
2038         }
2039
2040         replace_sub_page(class, zspage, newpage, page);
2041         get_page(newpage);
2042
2043         dec_zspage_isolation(zspage);
2044
2045         /*
2046          * Page migration is done so let's putback isolated zspage to
2047          * the list if @page is final isolated subpage in the zspage.
2048          */
2049         if (!is_zspage_isolated(zspage))
2050                 putback_zspage(class, zspage);
2051
2052         reset_page(page);
2053         put_page(page);
2054         page = newpage;
2055
2056         ret = MIGRATEPAGE_SUCCESS;
2057 unpin_objects:
2058         for (addr = s_addr + offset; addr < s_addr + pos;
2059                                                 addr += class->size) {
2060                 head = obj_to_head(page, addr);
2061                 if (head & OBJ_ALLOCATED_TAG) {
2062                         handle = head & ~OBJ_ALLOCATED_TAG;
2063                         if (!testpin_tag(handle))
2064                                 BUG();
2065                         unpin_tag(handle);
2066                 }
2067         }
2068         kunmap_atomic(s_addr);
2069         spin_unlock(&class->lock);
2070         migrate_write_unlock(zspage);
2071
2072         return ret;
2073 }
2074
2075 void zs_page_putback(struct page *page)
2076 {
2077         struct zs_pool *pool;
2078         struct size_class *class;
2079         int class_idx;
2080         enum fullness_group fg;
2081         struct address_space *mapping;
2082         struct zspage *zspage;
2083
2084         VM_BUG_ON_PAGE(!PageMovable(page), page);
2085         VM_BUG_ON_PAGE(!PageIsolated(page), page);
2086
2087         zspage = get_zspage(page);
2088         get_zspage_mapping(zspage, &class_idx, &fg);
2089         mapping = page_mapping(page);
2090         pool = mapping->private_data;
2091         class = pool->size_class[class_idx];
2092
2093         spin_lock(&class->lock);
2094         dec_zspage_isolation(zspage);
2095         if (!is_zspage_isolated(zspage)) {
2096                 fg = putback_zspage(class, zspage);
2097                 /*
2098                  * Due to page_lock, we cannot free zspage immediately
2099                  * so let's defer.
2100                  */
2101                 if (fg == ZS_EMPTY)
2102                         schedule_work(&pool->free_work);
2103         }
2104         spin_unlock(&class->lock);
2105 }
2106
2107 const struct address_space_operations zsmalloc_aops = {
2108         .isolate_page = zs_page_isolate,
2109         .migratepage = zs_page_migrate,
2110         .putback_page = zs_page_putback,
2111 };
2112
2113 static int zs_register_migration(struct zs_pool *pool)
2114 {
2115         pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb);
2116         if (IS_ERR(pool->inode)) {
2117                 pool->inode = NULL;
2118                 return 1;
2119         }
2120
2121         pool->inode->i_mapping->private_data = pool;
2122         pool->inode->i_mapping->a_ops = &zsmalloc_aops;
2123         return 0;
2124 }
2125
2126 static void zs_unregister_migration(struct zs_pool *pool)
2127 {
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 void __zs_compact(struct zs_pool *pool, struct size_class *class)
2214 {
2215         struct zs_compact_control cc;
2216         struct zspage *src_zspage;
2217         struct zspage *dst_zspage = NULL;
2218
2219         spin_lock(&class->lock);
2220         while ((src_zspage = isolate_zspage(class, true))) {
2221
2222                 if (!zs_can_compact(class))
2223                         break;
2224
2225                 cc.obj_idx = 0;
2226                 cc.s_page = get_first_page(src_zspage);
2227
2228                 while ((dst_zspage = isolate_zspage(class, false))) {
2229                         cc.d_page = get_first_page(dst_zspage);
2230                         /*
2231                          * If there is no more space in dst_page, resched
2232                          * and see if anyone had allocated another zspage.
2233                          */
2234                         if (!migrate_zspage(pool, class, &cc))
2235                                 break;
2236
2237                         putback_zspage(class, dst_zspage);
2238                 }
2239
2240                 /* Stop if we couldn't find slot */
2241                 if (dst_zspage == NULL)
2242                         break;
2243
2244                 putback_zspage(class, dst_zspage);
2245                 if (putback_zspage(class, src_zspage) == ZS_EMPTY) {
2246                         free_zspage(pool, class, src_zspage);
2247                         pool->stats.pages_compacted += class->pages_per_zspage;
2248                 }
2249                 spin_unlock(&class->lock);
2250                 cond_resched();
2251                 spin_lock(&class->lock);
2252         }
2253
2254         if (src_zspage)
2255                 putback_zspage(class, src_zspage);
2256
2257         spin_unlock(&class->lock);
2258 }
2259
2260 unsigned long zs_compact(struct zs_pool *pool)
2261 {
2262         int i;
2263         struct size_class *class;
2264
2265         for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2266                 class = pool->size_class[i];
2267                 if (!class)
2268                         continue;
2269                 if (class->index != i)
2270                         continue;
2271                 __zs_compact(pool, class);
2272         }
2273
2274         return pool->stats.pages_compacted;
2275 }
2276 EXPORT_SYMBOL_GPL(zs_compact);
2277
2278 void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats)
2279 {
2280         memcpy(stats, &pool->stats, sizeof(struct zs_pool_stats));
2281 }
2282 EXPORT_SYMBOL_GPL(zs_pool_stats);
2283
2284 static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
2285                 struct shrink_control *sc)
2286 {
2287         unsigned long pages_freed;
2288         struct zs_pool *pool = container_of(shrinker, struct zs_pool,
2289                         shrinker);
2290
2291         pages_freed = pool->stats.pages_compacted;
2292         /*
2293          * Compact classes and calculate compaction delta.
2294          * Can run concurrently with a manually triggered
2295          * (by user) compaction.
2296          */
2297         pages_freed = zs_compact(pool) - pages_freed;
2298
2299         return pages_freed ? pages_freed : SHRINK_STOP;
2300 }
2301
2302 static unsigned long zs_shrinker_count(struct shrinker *shrinker,
2303                 struct shrink_control *sc)
2304 {
2305         int i;
2306         struct size_class *class;
2307         unsigned long pages_to_free = 0;
2308         struct zs_pool *pool = container_of(shrinker, struct zs_pool,
2309                         shrinker);
2310
2311         for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2312                 class = pool->size_class[i];
2313                 if (!class)
2314                         continue;
2315                 if (class->index != i)
2316                         continue;
2317
2318                 pages_to_free += zs_can_compact(class);
2319         }
2320
2321         return pages_to_free;
2322 }
2323
2324 static void zs_unregister_shrinker(struct zs_pool *pool)
2325 {
2326         if (pool->shrinker_enabled) {
2327                 unregister_shrinker(&pool->shrinker);
2328                 pool->shrinker_enabled = false;
2329         }
2330 }
2331
2332 static int zs_register_shrinker(struct zs_pool *pool)
2333 {
2334         pool->shrinker.scan_objects = zs_shrinker_scan;
2335         pool->shrinker.count_objects = zs_shrinker_count;
2336         pool->shrinker.batch = 0;
2337         pool->shrinker.seeks = DEFAULT_SEEKS;
2338
2339         return register_shrinker(&pool->shrinker);
2340 }
2341
2342 /**
2343  * zs_create_pool - Creates an allocation pool to work from.
2344  * @name: pool name to be created
2345  *
2346  * This function must be called before anything when using
2347  * the zsmalloc allocator.
2348  *
2349  * On success, a pointer to the newly created pool is returned,
2350  * otherwise NULL.
2351  */
2352 struct zs_pool *zs_create_pool(const char *name)
2353 {
2354         int i;
2355         struct zs_pool *pool;
2356         struct size_class *prev_class = NULL;
2357
2358         pool = kzalloc(sizeof(*pool), GFP_KERNEL);
2359         if (!pool)
2360                 return NULL;
2361
2362         init_deferred_free(pool);
2363
2364         pool->name = kstrdup(name, GFP_KERNEL);
2365         if (!pool->name)
2366                 goto err;
2367
2368         if (create_cache(pool))
2369                 goto err;
2370
2371         /*
2372          * Iterate reversely, because, size of size_class that we want to use
2373          * for merging should be larger or equal to current size.
2374          */
2375         for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2376                 int size;
2377                 int pages_per_zspage;
2378                 int objs_per_zspage;
2379                 struct size_class *class;
2380                 int fullness = 0;
2381
2382                 size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
2383                 if (size > ZS_MAX_ALLOC_SIZE)
2384                         size = ZS_MAX_ALLOC_SIZE;
2385                 pages_per_zspage = get_pages_per_zspage(size);
2386                 objs_per_zspage = pages_per_zspage * PAGE_SIZE / size;
2387
2388                 /*
2389                  * size_class is used for normal zsmalloc operation such
2390                  * as alloc/free for that size. Although it is natural that we
2391                  * have one size_class for each size, there is a chance that we
2392                  * can get more memory utilization if we use one size_class for
2393                  * many different sizes whose size_class have same
2394                  * characteristics. So, we makes size_class point to
2395                  * previous size_class if possible.
2396                  */
2397                 if (prev_class) {
2398                         if (can_merge(prev_class, pages_per_zspage, objs_per_zspage)) {
2399                                 pool->size_class[i] = prev_class;
2400                                 continue;
2401                         }
2402                 }
2403
2404                 class = kzalloc(sizeof(struct size_class), GFP_KERNEL);
2405                 if (!class)
2406                         goto err;
2407
2408                 class->size = size;
2409                 class->index = i;
2410                 class->pages_per_zspage = pages_per_zspage;
2411                 class->objs_per_zspage = objs_per_zspage;
2412                 spin_lock_init(&class->lock);
2413                 pool->size_class[i] = class;
2414                 for (fullness = ZS_EMPTY; fullness < NR_ZS_FULLNESS;
2415                                                         fullness++)
2416                         INIT_LIST_HEAD(&class->fullness_list[fullness]);
2417
2418                 prev_class = class;
2419         }
2420
2421         /* debug only, don't abort if it fails */
2422         zs_pool_stat_create(pool, name);
2423
2424         if (zs_register_migration(pool))
2425                 goto err;
2426
2427         /*
2428          * Not critical, we still can use the pool
2429          * and user can trigger compaction manually.
2430          */
2431         if (zs_register_shrinker(pool) == 0)
2432                 pool->shrinker_enabled = true;
2433         return pool;
2434
2435 err:
2436         zs_destroy_pool(pool);
2437         return NULL;
2438 }
2439 EXPORT_SYMBOL_GPL(zs_create_pool);
2440
2441 void zs_destroy_pool(struct zs_pool *pool)
2442 {
2443         int i;
2444
2445         zs_unregister_shrinker(pool);
2446         zs_unregister_migration(pool);
2447         zs_pool_stat_destroy(pool);
2448
2449         for (i = 0; i < ZS_SIZE_CLASSES; i++) {
2450                 int fg;
2451                 struct size_class *class = pool->size_class[i];
2452
2453                 if (!class)
2454                         continue;
2455
2456                 if (class->index != i)
2457                         continue;
2458
2459                 for (fg = ZS_EMPTY; fg < NR_ZS_FULLNESS; fg++) {
2460                         if (!list_empty(&class->fullness_list[fg])) {
2461                                 pr_info("Freeing non-empty class with size %db, fullness group %d\n",
2462                                         class->size, fg);
2463                         }
2464                 }
2465                 kfree(class);
2466         }
2467
2468         destroy_cache(pool);
2469         kfree(pool->name);
2470         kfree(pool);
2471 }
2472 EXPORT_SYMBOL_GPL(zs_destroy_pool);
2473
2474 static int __init zs_init(void)
2475 {
2476         int ret;
2477
2478         ret = zsmalloc_mount();
2479         if (ret)
2480                 goto out;
2481
2482         ret = cpuhp_setup_state(CPUHP_MM_ZS_PREPARE, "mm/zsmalloc:prepare",
2483                                 zs_cpu_prepare, zs_cpu_dead);
2484         if (ret)
2485                 goto hp_setup_fail;
2486
2487 #ifdef CONFIG_ZPOOL
2488         zpool_register_driver(&zs_zpool_driver);
2489 #endif
2490
2491         zs_stat_init();
2492
2493         return 0;
2494
2495 hp_setup_fail:
2496         zsmalloc_unmount();
2497 out:
2498         return ret;
2499 }
2500
2501 static void __exit zs_exit(void)
2502 {
2503 #ifdef CONFIG_ZPOOL
2504         zpool_unregister_driver(&zs_zpool_driver);
2505 #endif
2506         zsmalloc_unmount();
2507         cpuhp_remove_state(CPUHP_MM_ZS_PREPARE);
2508
2509         zs_stat_exit();
2510 }
2511
2512 module_init(zs_init);
2513 module_exit(zs_exit);
2514
2515 MODULE_LICENSE("Dual BSD/GPL");
2516 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");