source: src/linux/universal/linux-4.9/mm/zsmalloc.c @ 31885

Last change on this file since 31885 was 31885, checked in by brainslayer, 3 months ago

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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_private2: identifies the last component page
28 *      PG_owner_priv_1: indentifies the huge component page
29 *
30 */
31
32#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
33
34#include <linux/module.h>
35#include <linux/kernel.h>
36#include <linux/sched.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 MAX(a, b) ((a) >= (b) ? (a) : (b))
120/* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
121#define ZS_MIN_ALLOC_SIZE \
122        MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
123/* each chunk includes extra space to keep handle */
124#define ZS_MAX_ALLOC_SIZE       PAGE_SIZE
125
126/*
127 * On systems with 4K page size, this gives 255 size classes! There is a
128 * trader-off here:
129 *  - Large number of size classes is potentially wasteful as free page are
130 *    spread across these classes
131 *  - Small number of size classes causes large internal fragmentation
132 *  - Probably its better to use specific size classes (empirically
133 *    determined). NOTE: all those class sizes must be set as multiple of
134 *    ZS_ALIGN to make sure link_free itself never has to span 2 pages.
135 *
136 *  ZS_MIN_ALLOC_SIZE and ZS_SIZE_CLASS_DELTA must be multiple of ZS_ALIGN
137 *  (reason above)
138 */
139#define ZS_SIZE_CLASS_DELTA     (PAGE_SIZE >> CLASS_BITS)
140
141enum fullness_group {
142        ZS_EMPTY,
143        ZS_ALMOST_EMPTY,
144        ZS_ALMOST_FULL,
145        ZS_FULL,
146        NR_ZS_FULLNESS,
147};
148
149enum zs_stat_type {
150        CLASS_EMPTY,
151        CLASS_ALMOST_EMPTY,
152        CLASS_ALMOST_FULL,
153        CLASS_FULL,
154        OBJ_ALLOCATED,
155        OBJ_USED,
156        NR_ZS_STAT_TYPE,
157};
158
159struct zs_size_stat {
160        unsigned long objs[NR_ZS_STAT_TYPE];
161};
162
163#ifdef CONFIG_ZSMALLOC_STAT
164static struct dentry *zs_stat_root;
165#endif
166
167#ifdef CONFIG_COMPACTION
168static struct vfsmount *zsmalloc_mnt;
169#endif
170
171/*
172 * number of size_classes
173 */
174static int zs_size_classes;
175
176/*
177 * We assign a page to ZS_ALMOST_EMPTY fullness group when:
178 *      n <= N / f, where
179 * n = number of allocated objects
180 * N = total number of objects zspage can store
181 * f = fullness_threshold_frac
182 *
183 * Similarly, we assign zspage to:
184 *      ZS_ALMOST_FULL  when n > N / f
185 *      ZS_EMPTY        when n == 0
186 *      ZS_FULL         when n == N
187 *
188 * (see: fix_fullness_group())
189 */
190static const int fullness_threshold_frac = 4;
191
192struct size_class {
193        spinlock_t lock;
194        struct list_head fullness_list[NR_ZS_FULLNESS];
195        /*
196         * Size of objects stored in this class. Must be multiple
197         * of ZS_ALIGN.
198         */
199        int size;
200        int objs_per_zspage;
201        /* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
202        int pages_per_zspage;
203
204        unsigned int index;
205        struct zs_size_stat stats;
206};
207
208/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
209static void SetPageHugeObject(struct page *page)
210{
211        SetPageOwnerPriv1(page);
212}
213
214static void ClearPageHugeObject(struct page *page)
215{
216        ClearPageOwnerPriv1(page);
217}
218
219static int PageHugeObject(struct page *page)
220{
221        return PageOwnerPriv1(page);
222}
223
224/*
225 * Placed within free objects to form a singly linked list.
226 * For every zspage, zspage->freeobj gives head of this list.
227 *
228 * This must be power of 2 and less than or equal to ZS_ALIGN
229 */
230struct link_free {
231        union {
232                /*
233                 * Free object index;
234                 * It's valid for non-allocated object
235                 */
236                unsigned long next;
237                /*
238                 * Handle of allocated object.
239                 */
240                unsigned long handle;
241        };
242};
243
244struct zs_pool {
245        const char *name;
246
247        struct size_class **size_class;
248        struct kmem_cache *handle_cachep;
249        struct kmem_cache *zspage_cachep;
250
251        atomic_long_t pages_allocated;
252
253        struct zs_pool_stats stats;
254
255        /* Compact classes */
256        struct shrinker shrinker;
257        /*
258         * To signify that register_shrinker() was successful
259         * and unregister_shrinker() will not Oops.
260         */
261        bool shrinker_enabled;
262#ifdef CONFIG_ZSMALLOC_STAT
263        struct dentry *stat_dentry;
264#endif
265#ifdef CONFIG_COMPACTION
266        struct inode *inode;
267        struct work_struct free_work;
268#endif
269};
270
271/*
272 * A zspage's class index and fullness group
273 * are encoded in its (first)page->mapping
274 */
275#define FULLNESS_BITS   2
276#define CLASS_BITS      8
277#define ISOLATED_BITS   3
278#define MAGIC_VAL_BITS  8
279
280struct zspage {
281        struct {
282                unsigned int fullness:FULLNESS_BITS;
283                unsigned int class:CLASS_BITS + 1;
284                unsigned int isolated:ISOLATED_BITS;
285                unsigned int magic:MAGIC_VAL_BITS;
286        };
287        unsigned int inuse;
288        unsigned int freeobj;
289        struct page *first_page;
290        struct list_head list; /* fullness list */
291#ifdef CONFIG_COMPACTION
292        rwlock_t lock;
293#endif
294};
295
296struct mapping_area {
297#ifdef CONFIG_PGTABLE_MAPPING
298        struct vm_struct *vm; /* vm area for mapping object that span pages */
299#else
300        char *vm_buf; /* copy buffer for objects that span pages */
301#endif
302        char *vm_addr; /* address of kmap_atomic()'ed pages */
303        enum zs_mapmode vm_mm; /* mapping mode */
304};
305
306#ifdef CONFIG_COMPACTION
307static int zs_register_migration(struct zs_pool *pool);
308static void zs_unregister_migration(struct zs_pool *pool);
309static void migrate_lock_init(struct zspage *zspage);
310static void migrate_read_lock(struct zspage *zspage);
311static void migrate_read_unlock(struct zspage *zspage);
312static void kick_deferred_free(struct zs_pool *pool);
313static void init_deferred_free(struct zs_pool *pool);
314static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage);
315#else
316static int zsmalloc_mount(void) { return 0; }
317static void zsmalloc_unmount(void) {}
318static int zs_register_migration(struct zs_pool *pool) { return 0; }
319static void zs_unregister_migration(struct zs_pool *pool) {}
320static void migrate_lock_init(struct zspage *zspage) {}
321static void migrate_read_lock(struct zspage *zspage) {}
322static void migrate_read_unlock(struct zspage *zspage) {}
323static void kick_deferred_free(struct zs_pool *pool) {}
324static void init_deferred_free(struct zs_pool *pool) {}
325static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage) {}
326#endif
327
328static int create_cache(struct zs_pool *pool)
329{
330        pool->handle_cachep = kmem_cache_create("zs_handle", ZS_HANDLE_SIZE,
331                                        0, 0, NULL);
332        if (!pool->handle_cachep)
333                return 1;
334
335        pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
336                                        0, 0, NULL);
337        if (!pool->zspage_cachep) {
338                kmem_cache_destroy(pool->handle_cachep);
339                pool->handle_cachep = NULL;
340                return 1;
341        }
342
343        return 0;
344}
345
346static void destroy_cache(struct zs_pool *pool)
347{
348        kmem_cache_destroy(pool->handle_cachep);
349        kmem_cache_destroy(pool->zspage_cachep);
350}
351
352static unsigned long cache_alloc_handle(struct zs_pool *pool, gfp_t gfp)
353{
354        return (unsigned long)kmem_cache_alloc(pool->handle_cachep,
355                        gfp & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
356}
357
358static void cache_free_handle(struct zs_pool *pool, unsigned long handle)
359{
360        kmem_cache_free(pool->handle_cachep, (void *)handle);
361}
362
363static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags)
364{
365        return kmem_cache_alloc(pool->zspage_cachep,
366                        flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
367};
368
369static void cache_free_zspage(struct zs_pool *pool, struct zspage *zspage)
370{
371        kmem_cache_free(pool->zspage_cachep, zspage);
372}
373
374static void record_obj(unsigned long handle, unsigned long obj)
375{
376        /*
377         * lsb of @obj represents handle lock while other bits
378         * represent object value the handle is pointing so
379         * updating shouldn't do store tearing.
380         */
381        WRITE_ONCE(*(unsigned long *)handle, obj);
382}
383
384/* zpool driver */
385
386#ifdef CONFIG_ZPOOL
387
388static void *zs_zpool_create(const char *name, gfp_t gfp,
389                             const struct zpool_ops *zpool_ops,
390                             struct zpool *zpool)
391{
392        /*
393         * Ignore global gfp flags: zs_malloc() may be invoked from
394         * different contexts and its caller must provide a valid
395         * gfp mask.
396         */
397        return zs_create_pool(name);
398}
399
400static void zs_zpool_destroy(void *pool)
401{
402        zs_destroy_pool(pool);
403}
404
405static int zs_zpool_malloc(void *pool, size_t size, gfp_t gfp,
406                        unsigned long *handle)
407{
408        *handle = zs_malloc(pool, size, gfp);
409        return *handle ? 0 : -1;
410}
411static void zs_zpool_free(void *pool, unsigned long handle)
412{
413        zs_free(pool, handle);
414}
415
416static int zs_zpool_shrink(void *pool, unsigned int pages,
417                        unsigned int *reclaimed)
418{
419        return -EINVAL;
420}
421
422static void *zs_zpool_map(void *pool, unsigned long handle,
423                        enum zpool_mapmode mm)
424{
425        enum zs_mapmode zs_mm;
426
427        switch (mm) {
428        case ZPOOL_MM_RO:
429                zs_mm = ZS_MM_RO;
430                break;
431        case ZPOOL_MM_WO:
432                zs_mm = ZS_MM_WO;
433                break;
434        case ZPOOL_MM_RW: /* fallthru */
435        default:
436                zs_mm = ZS_MM_RW;
437                break;
438        }
439
440        return zs_map_object(pool, handle, zs_mm);
441}
442static void zs_zpool_unmap(void *pool, unsigned long handle)
443{
444        zs_unmap_object(pool, handle);
445}
446
447static u64 zs_zpool_total_size(void *pool)
448{
449        return zs_get_total_pages(pool) << PAGE_SHIFT;
450}
451
452static struct zpool_driver zs_zpool_driver = {
453        .type =         "zsmalloc",
454        .owner =        THIS_MODULE,
455        .create =       zs_zpool_create,
456        .destroy =      zs_zpool_destroy,
457        .malloc =       zs_zpool_malloc,
458        .free =         zs_zpool_free,
459        .shrink =       zs_zpool_shrink,
460        .map =          zs_zpool_map,
461        .unmap =        zs_zpool_unmap,
462        .total_size =   zs_zpool_total_size,
463};
464
465MODULE_ALIAS("zpool-zsmalloc");
466#endif /* CONFIG_ZPOOL */
467
468/* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
469static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
470
471static bool is_zspage_isolated(struct zspage *zspage)
472{
473        return zspage->isolated;
474}
475
476static int is_first_page(struct page *page)
477{
478        return PagePrivate(page);
479}
480
481/* Protected by class->lock */
482static inline int get_zspage_inuse(struct zspage *zspage)
483{
484        return zspage->inuse;
485}
486
487static inline void set_zspage_inuse(struct zspage *zspage, int val)
488{
489        zspage->inuse = val;
490}
491
492static inline void mod_zspage_inuse(struct zspage *zspage, int val)
493{
494        zspage->inuse += val;
495}
496
497static inline struct page *get_first_page(struct zspage *zspage)
498{
499        struct page *first_page = zspage->first_page;
500
501        VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
502        return first_page;
503}
504
505static inline int get_first_obj_offset(struct page *page)
506{
507        return page->units;
508}
509
510static inline void set_first_obj_offset(struct page *page, int offset)
511{
512        page->units = offset;
513}
514
515static inline unsigned int get_freeobj(struct zspage *zspage)
516{
517        return zspage->freeobj;
518}
519
520static inline void set_freeobj(struct zspage *zspage, unsigned int obj)
521{
522        zspage->freeobj = obj;
523}
524
525static void get_zspage_mapping(struct zspage *zspage,
526                                unsigned int *class_idx,
527                                enum fullness_group *fullness)
528{
529        BUG_ON(zspage->magic != ZSPAGE_MAGIC);
530
531        *fullness = zspage->fullness;
532        *class_idx = zspage->class;
533}
534
535static void set_zspage_mapping(struct zspage *zspage,
536                                unsigned int class_idx,
537                                enum fullness_group fullness)
538{
539        zspage->class = class_idx;
540        zspage->fullness = fullness;
541}
542
543/*
544 * zsmalloc divides the pool into various size classes where each
545 * class maintains a list of zspages where each zspage is divided
546 * into equal sized chunks. Each allocation falls into one of these
547 * classes depending on its size. This function returns index of the
548 * size class which has chunk size big enough to hold the give size.
549 */
550static int get_size_class_index(int size)
551{
552        int idx = 0;
553
554        if (likely(size > ZS_MIN_ALLOC_SIZE))
555                idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
556                                ZS_SIZE_CLASS_DELTA);
557
558        return min(zs_size_classes - 1, idx);
559}
560
561static inline void zs_stat_inc(struct size_class *class,
562                                enum zs_stat_type type, unsigned long cnt)
563{
564        class->stats.objs[type] += cnt;
565}
566
567static inline void zs_stat_dec(struct size_class *class,
568                                enum zs_stat_type type, unsigned long cnt)
569{
570        class->stats.objs[type] -= cnt;
571}
572
573static inline unsigned long zs_stat_get(struct size_class *class,
574                                enum zs_stat_type type)
575{
576        return class->stats.objs[type];
577}
578
579#ifdef CONFIG_ZSMALLOC_STAT
580
581static void __init zs_stat_init(void)
582{
583        if (!debugfs_initialized()) {
584                pr_warn("debugfs not available, stat dir not created\n");
585                return;
586        }
587
588        zs_stat_root = debugfs_create_dir("zsmalloc", NULL);
589        if (!zs_stat_root)
590                pr_warn("debugfs 'zsmalloc' stat dir creation failed\n");
591}
592
593static void __exit zs_stat_exit(void)
594{
595        debugfs_remove_recursive(zs_stat_root);
596}
597
598static unsigned long zs_can_compact(struct size_class *class);
599
600static int zs_stats_size_show(struct seq_file *s, void *v)
601{
602        int i;
603        struct zs_pool *pool = s->private;
604        struct size_class *class;
605        int objs_per_zspage;
606        unsigned long class_almost_full, class_almost_empty;
607        unsigned long obj_allocated, obj_used, pages_used, freeable;
608        unsigned long total_class_almost_full = 0, total_class_almost_empty = 0;
609        unsigned long total_objs = 0, total_used_objs = 0, total_pages = 0;
610        unsigned long total_freeable = 0;
611
612        seq_printf(s, " %5s %5s %11s %12s %13s %10s %10s %16s %8s\n",
613                        "class", "size", "almost_full", "almost_empty",
614                        "obj_allocated", "obj_used", "pages_used",
615                        "pages_per_zspage", "freeable");
616
617        for (i = 0; i < zs_size_classes; i++) {
618                class = pool->size_class[i];
619
620                if (class->index != i)
621                        continue;
622
623                spin_lock(&class->lock);
624                class_almost_full = zs_stat_get(class, CLASS_ALMOST_FULL);
625                class_almost_empty = zs_stat_get(class, CLASS_ALMOST_EMPTY);
626                obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
627                obj_used = zs_stat_get(class, OBJ_USED);
628                freeable = zs_can_compact(class);
629                spin_unlock(&class->lock);
630
631                objs_per_zspage = class->objs_per_zspage;
632                pages_used = obj_allocated / objs_per_zspage *
633                                class->pages_per_zspage;
634
635                seq_printf(s, " %5u %5u %11lu %12lu %13lu"
636                                " %10lu %10lu %16d %8lu\n",
637                        i, class->size, class_almost_full, class_almost_empty,
638                        obj_allocated, obj_used, pages_used,
639                        class->pages_per_zspage, freeable);
640
641                total_class_almost_full += class_almost_full;
642                total_class_almost_empty += class_almost_empty;
643                total_objs += obj_allocated;
644                total_used_objs += obj_used;
645                total_pages += pages_used;
646                total_freeable += freeable;
647        }
648
649        seq_puts(s, "\n");
650        seq_printf(s, " %5s %5s %11lu %12lu %13lu %10lu %10lu %16s %8lu\n",
651                        "Total", "", total_class_almost_full,
652                        total_class_almost_empty, total_objs,
653                        total_used_objs, total_pages, "", total_freeable);
654
655        return 0;
656}
657
658static int zs_stats_size_open(struct inode *inode, struct file *file)
659{
660        return single_open(file, zs_stats_size_show, inode->i_private);
661}
662
663static const struct file_operations zs_stat_size_ops = {
664        .open           = zs_stats_size_open,
665        .read           = seq_read,
666        .llseek         = seq_lseek,
667        .release        = single_release,
668};
669
670static void zs_pool_stat_create(struct zs_pool *pool, const char *name)
671{
672        struct dentry *entry;
673
674        if (!zs_stat_root) {
675                pr_warn("no root stat dir, not creating <%s> stat dir\n", name);
676                return;
677        }
678
679        entry = debugfs_create_dir(name, zs_stat_root);
680        if (!entry) {
681                pr_warn("debugfs dir <%s> creation failed\n", name);
682                return;
683        }
684        pool->stat_dentry = entry;
685
686        entry = debugfs_create_file("classes", S_IFREG | S_IRUGO,
687                        pool->stat_dentry, pool, &zs_stat_size_ops);
688        if (!entry) {
689                pr_warn("%s: debugfs file entry <%s> creation failed\n",
690                                name, "classes");
691                debugfs_remove_recursive(pool->stat_dentry);
692                pool->stat_dentry = NULL;
693        }
694}
695
696static void zs_pool_stat_destroy(struct zs_pool *pool)
697{
698        debugfs_remove_recursive(pool->stat_dentry);
699}
700
701#else /* CONFIG_ZSMALLOC_STAT */
702static void __init zs_stat_init(void)
703{
704}
705
706static void __exit zs_stat_exit(void)
707{
708}
709
710static inline void zs_pool_stat_create(struct zs_pool *pool, const char *name)
711{
712}
713
714static inline void zs_pool_stat_destroy(struct zs_pool *pool)
715{
716}
717#endif
718
719
720/*
721 * For each size class, zspages are divided into different groups
722 * depending on how "full" they are. This was done so that we could
723 * easily find empty or nearly empty zspages when we try to shrink
724 * the pool (not yet implemented). This function returns fullness
725 * status of the given page.
726 */
727static enum fullness_group get_fullness_group(struct size_class *class,
728                                                struct zspage *zspage)
729{
730        int inuse, objs_per_zspage;
731        enum fullness_group fg;
732
733        inuse = get_zspage_inuse(zspage);
734        objs_per_zspage = class->objs_per_zspage;
735
736        if (inuse == 0)
737                fg = ZS_EMPTY;
738        else if (inuse == objs_per_zspage)
739                fg = ZS_FULL;
740        else if (inuse <= 3 * objs_per_zspage / fullness_threshold_frac)
741                fg = ZS_ALMOST_EMPTY;
742        else
743                fg = ZS_ALMOST_FULL;
744
745        return fg;
746}
747
748/*
749 * Each size class maintains various freelists and zspages are assigned
750 * to one of these freelists based on the number of live objects they
751 * have. This functions inserts the given zspage into the freelist
752 * identified by <class, fullness_group>.
753 */
754static void insert_zspage(struct size_class *class,
755                                struct zspage *zspage,
756                                enum fullness_group fullness)
757{
758        struct zspage *head;
759
760        zs_stat_inc(class, fullness, 1);
761        head = list_first_entry_or_null(&class->fullness_list[fullness],
762                                        struct zspage, list);
763        /*
764         * We want to see more ZS_FULL pages and less almost empty/full.
765         * Put pages with higher ->inuse first.
766         */
767        if (head) {
768                if (get_zspage_inuse(zspage) < get_zspage_inuse(head)) {
769                        list_add(&zspage->list, &head->list);
770                        return;
771                }
772        }
773        list_add(&zspage->list, &class->fullness_list[fullness]);
774}
775
776/*
777 * This function removes the given zspage from the freelist identified
778 * by <class, fullness_group>.
779 */
780static void remove_zspage(struct size_class *class,
781                                struct zspage *zspage,
782                                enum fullness_group fullness)
783{
784        VM_BUG_ON(list_empty(&class->fullness_list[fullness]));
785        VM_BUG_ON(is_zspage_isolated(zspage));
786
787        list_del_init(&zspage->list);
788        zs_stat_dec(class, fullness, 1);
789}
790
791/*
792 * Each size class maintains zspages in different fullness groups depending
793 * on the number of live objects they contain. When allocating or freeing
794 * objects, the fullness status of the page can change, say, from ALMOST_FULL
795 * to ALMOST_EMPTY when freeing an object. This function checks if such
796 * a status change has occurred for the given page and accordingly moves the
797 * page from the freelist of the old fullness group to that of the new
798 * fullness group.
799 */
800static enum fullness_group fix_fullness_group(struct size_class *class,
801                                                struct zspage *zspage)
802{
803        int class_idx;
804        enum fullness_group currfg, newfg;
805
806        get_zspage_mapping(zspage, &class_idx, &currfg);
807        newfg = get_fullness_group(class, zspage);
808        if (newfg == currfg)
809                goto out;
810
811        if (!is_zspage_isolated(zspage)) {
812                remove_zspage(class, zspage, currfg);
813                insert_zspage(class, zspage, newfg);
814        }
815
816        set_zspage_mapping(zspage, class_idx, newfg);
817
818out:
819        return newfg;
820}
821
822/*
823 * We have to decide on how many pages to link together
824 * to form a zspage for each size class. This is important
825 * to reduce wastage due to unusable space left at end of
826 * each zspage which is given as:
827 *     wastage = Zp % class_size
828 *     usage = Zp - wastage
829 * where Zp = zspage size = k * PAGE_SIZE where k = 1, 2, ...
830 *
831 * For example, for size class of 3/8 * PAGE_SIZE, we should
832 * link together 3 PAGE_SIZE sized pages to form a zspage
833 * since then we can perfectly fit in 8 such objects.
834 */
835static int get_pages_per_zspage(int class_size)
836{
837        int i, max_usedpc = 0;
838        /* zspage order which gives maximum used size per KB */
839        int max_usedpc_order = 1;
840
841        for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) {
842                int zspage_size;
843                int waste, usedpc;
844
845                zspage_size = i * PAGE_SIZE;
846                waste = zspage_size % class_size;
847                usedpc = (zspage_size - waste) * 100 / zspage_size;
848
849                if (usedpc > max_usedpc) {
850                        max_usedpc = usedpc;
851                        max_usedpc_order = i;
852                }
853        }
854
855        return max_usedpc_order;
856}
857
858static struct zspage *get_zspage(struct page *page)
859{
860        struct zspage *zspage = (struct zspage *)page->private;
861
862        BUG_ON(zspage->magic != ZSPAGE_MAGIC);
863        return zspage;
864}
865
866static struct page *get_next_page(struct page *page)
867{
868        if (unlikely(PageHugeObject(page)))
869                return NULL;
870
871        return page->freelist;
872}
873
874/**
875 * obj_to_location - get (<page>, <obj_idx>) from encoded object value
876 * @page: page object resides in zspage
877 * @obj_idx: object index
878 */
879static void obj_to_location(unsigned long obj, struct page **page,
880                                unsigned int *obj_idx)
881{
882        obj >>= OBJ_TAG_BITS;
883        *page = pfn_to_page(obj >> OBJ_INDEX_BITS);
884        *obj_idx = (obj & OBJ_INDEX_MASK);
885}
886
887/**
888 * location_to_obj - get obj value encoded from (<page>, <obj_idx>)
889 * @page: page object resides in zspage
890 * @obj_idx: object index
891 */
892static unsigned long location_to_obj(struct page *page, unsigned int obj_idx)
893{
894        unsigned long obj;
895
896        obj = page_to_pfn(page) << OBJ_INDEX_BITS;
897        obj |= obj_idx & OBJ_INDEX_MASK;
898        obj <<= OBJ_TAG_BITS;
899
900        return obj;
901}
902
903static unsigned long handle_to_obj(unsigned long handle)
904{
905        return *(unsigned long *)handle;
906}
907
908static unsigned long obj_to_head(struct page *page, void *obj)
909{
910        if (unlikely(PageHugeObject(page))) {
911                VM_BUG_ON_PAGE(!is_first_page(page), page);
912                return page->index;
913        } else
914                return *(unsigned long *)obj;
915}
916
917static inline int testpin_tag(unsigned long handle)
918{
919        return bit_spin_is_locked(HANDLE_PIN_BIT, (unsigned long *)handle);
920}
921
922static inline int trypin_tag(unsigned long handle)
923{
924        return bit_spin_trylock(HANDLE_PIN_BIT, (unsigned long *)handle);
925}
926
927static void pin_tag(unsigned long handle)
928{
929        bit_spin_lock(HANDLE_PIN_BIT, (unsigned long *)handle);
930}
931
932static void unpin_tag(unsigned long handle)
933{
934        bit_spin_unlock(HANDLE_PIN_BIT, (unsigned long *)handle);
935}
936
937static void reset_page(struct page *page)
938{
939        __ClearPageMovable(page);
940        ClearPagePrivate(page);
941        ClearPagePrivate2(page);
942        set_page_private(page, 0);
943        page_mapcount_reset(page);
944        ClearPageHugeObject(page);
945        page->freelist = NULL;
946}
947
948/*
949 * To prevent zspage destroy during migration, zspage freeing should
950 * hold locks of all pages in the zspage.
951 */
952void lock_zspage(struct zspage *zspage)
953{
954        struct page *page = get_first_page(zspage);
955
956        do {
957                lock_page(page);
958        } while ((page = get_next_page(page)) != NULL);
959}
960
961int trylock_zspage(struct zspage *zspage)
962{
963        struct page *cursor, *fail;
964
965        for (cursor = get_first_page(zspage); cursor != NULL; cursor =
966                                        get_next_page(cursor)) {
967                if (!trylock_page(cursor)) {
968                        fail = cursor;
969                        goto unlock;
970                }
971        }
972
973        return 1;
974unlock:
975        for (cursor = get_first_page(zspage); cursor != fail; cursor =
976                                        get_next_page(cursor))
977                unlock_page(cursor);
978
979        return 0;
980}
981
982static void __free_zspage(struct zs_pool *pool, struct size_class *class,
983                                struct zspage *zspage)
984{
985        struct page *page, *next;
986        enum fullness_group fg;
987        unsigned int class_idx;
988
989        get_zspage_mapping(zspage, &class_idx, &fg);
990
991        assert_spin_locked(&class->lock);
992
993        VM_BUG_ON(get_zspage_inuse(zspage));
994        VM_BUG_ON(fg != ZS_EMPTY);
995
996        next = page = get_first_page(zspage);
997        do {
998                VM_BUG_ON_PAGE(!PageLocked(page), page);
999                next = get_next_page(page);
1000                reset_page(page);
1001                unlock_page(page);
1002                dec_zone_page_state(page, NR_ZSPAGES);
1003                put_page(page);
1004                page = next;
1005        } while (page != NULL);
1006
1007        cache_free_zspage(pool, zspage);
1008
1009        zs_stat_dec(class, OBJ_ALLOCATED, class->objs_per_zspage);
1010        atomic_long_sub(class->pages_per_zspage,
1011                                        &pool->pages_allocated);
1012}
1013
1014static void free_zspage(struct zs_pool *pool, struct size_class *class,
1015                                struct zspage *zspage)
1016{
1017        VM_BUG_ON(get_zspage_inuse(zspage));
1018        VM_BUG_ON(list_empty(&zspage->list));
1019
1020        if (!trylock_zspage(zspage)) {
1021                kick_deferred_free(pool);
1022                return;
1023        }
1024
1025        remove_zspage(class, zspage, ZS_EMPTY);
1026        __free_zspage(pool, class, zspage);
1027}
1028
1029/* Initialize a newly allocated zspage */
1030static void init_zspage(struct size_class *class, struct zspage *zspage)
1031{
1032        unsigned int freeobj = 1;
1033        unsigned long off = 0;
1034        struct page *page = get_first_page(zspage);
1035
1036        while (page) {
1037                struct page *next_page;
1038                struct link_free *link;
1039                void *vaddr;
1040
1041                set_first_obj_offset(page, off);
1042
1043                vaddr = kmap_atomic(page);
1044                link = (struct link_free *)vaddr + off / sizeof(*link);
1045
1046                while ((off += class->size) < PAGE_SIZE) {
1047                        link->next = freeobj++ << OBJ_TAG_BITS;
1048                        link += class->size / sizeof(*link);
1049                }
1050
1051                /*
1052                 * We now come to the last (full or partial) object on this
1053                 * page, which must point to the first object on the next
1054                 * page (if present)
1055                 */
1056                next_page = get_next_page(page);
1057                if (next_page) {
1058                        link->next = freeobj++ << OBJ_TAG_BITS;
1059                } else {
1060                        /*
1061                         * Reset OBJ_TAG_BITS bit to last link to tell
1062                         * whether it's allocated object or not.
1063                         */
1064                        link->next = -1 << OBJ_TAG_BITS;
1065                }
1066                kunmap_atomic(vaddr);
1067                page = next_page;
1068                off %= PAGE_SIZE;
1069        }
1070
1071        set_freeobj(zspage, 0);
1072}
1073
1074static void create_page_chain(struct size_class *class, struct zspage *zspage,
1075                                struct page *pages[])
1076{
1077        int i;
1078        struct page *page;
1079        struct page *prev_page = NULL;
1080        int nr_pages = class->pages_per_zspage;
1081
1082        /*
1083         * Allocate individual pages and link them together as:
1084         * 1. all pages are linked together using page->freelist
1085         * 2. each sub-page point to zspage using page->private
1086         *
1087         * we set PG_private to identify the first page (i.e. no other sub-page
1088         * has this flag set) and PG_private_2 to identify the last page.
1089         */
1090        for (i = 0; i < nr_pages; i++) {
1091                page = pages[i];
1092                set_page_private(page, (unsigned long)zspage);
1093                page->freelist = NULL;
1094                if (i == 0) {
1095                        zspage->first_page = page;
1096                        SetPagePrivate(page);
1097                        if (unlikely(class->objs_per_zspage == 1 &&
1098                                        class->pages_per_zspage == 1))
1099                                SetPageHugeObject(page);
1100                } else {
1101                        prev_page->freelist = page;
1102                }
1103                if (i == nr_pages - 1)
1104                        SetPagePrivate2(page);
1105                prev_page = page;
1106        }
1107}
1108
1109/*
1110 * Allocate a zspage for the given size class
1111 */
1112static struct zspage *alloc_zspage(struct zs_pool *pool,
1113                                        struct size_class *class,
1114                                        gfp_t gfp)
1115{
1116        int i;
1117        struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE];
1118        struct zspage *zspage = cache_alloc_zspage(pool, gfp);
1119
1120        if (!zspage)
1121                return NULL;
1122
1123        memset(zspage, 0, sizeof(struct zspage));
1124        zspage->magic = ZSPAGE_MAGIC;
1125        migrate_lock_init(zspage);
1126
1127        for (i = 0; i < class->pages_per_zspage; i++) {
1128                struct page *page;
1129
1130                page = alloc_page(gfp);
1131                if (!page) {
1132                        while (--i >= 0) {
1133                                dec_zone_page_state(pages[i], NR_ZSPAGES);
1134                                __free_page(pages[i]);
1135                        }
1136                        cache_free_zspage(pool, zspage);
1137                        return NULL;
1138                }
1139
1140                inc_zone_page_state(page, NR_ZSPAGES);
1141                pages[i] = page;
1142        }
1143
1144        create_page_chain(class, zspage, pages);
1145        init_zspage(class, zspage);
1146
1147        return zspage;
1148}
1149
1150static struct zspage *find_get_zspage(struct size_class *class)
1151{
1152        int i;
1153        struct zspage *zspage;
1154
1155        for (i = ZS_ALMOST_FULL; i >= ZS_EMPTY; i--) {
1156                zspage = list_first_entry_or_null(&class->fullness_list[i],
1157                                struct zspage, list);
1158                if (zspage)
1159                        break;
1160        }
1161
1162        return zspage;
1163}
1164
1165#ifdef CONFIG_PGTABLE_MAPPING
1166static inline int __zs_cpu_up(struct mapping_area *area)
1167{
1168        /*
1169         * Make sure we don't leak memory if a cpu UP notification
1170         * and zs_init() race and both call zs_cpu_up() on the same cpu
1171         */
1172        if (area->vm)
1173                return 0;
1174        area->vm = alloc_vm_area(PAGE_SIZE * 2, NULL);
1175        if (!area->vm)
1176                return -ENOMEM;
1177        return 0;
1178}
1179
1180static inline void __zs_cpu_down(struct mapping_area *area)
1181{
1182        if (area->vm)
1183                free_vm_area(area->vm);
1184        area->vm = NULL;
1185}
1186
1187static inline void *__zs_map_object(struct mapping_area *area,
1188                                struct page *pages[2], int off, int size)
1189{
1190        BUG_ON(map_vm_area(area->vm, PAGE_KERNEL, pages));
1191        area->vm_addr = area->vm->addr;
1192        return area->vm_addr + off;
1193}
1194
1195static inline void __zs_unmap_object(struct mapping_area *area,
1196                                struct page *pages[2], int off, int size)
1197{
1198        unsigned long addr = (unsigned long)area->vm_addr;
1199
1200        unmap_kernel_range(addr, PAGE_SIZE * 2);
1201}
1202
1203#else /* CONFIG_PGTABLE_MAPPING */
1204
1205static inline int __zs_cpu_up(struct mapping_area *area)
1206{
1207        /*
1208         * Make sure we don't leak memory if a cpu UP notification
1209         * and zs_init() race and both call zs_cpu_up() on the same cpu
1210         */
1211        if (area->vm_buf)
1212                return 0;
1213        area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);
1214        if (!area->vm_buf)
1215                return -ENOMEM;
1216        return 0;
1217}
1218
1219static inline void __zs_cpu_down(struct mapping_area *area)
1220{
1221        kfree(area->vm_buf);
1222        area->vm_buf = NULL;
1223}
1224
1225static void *__zs_map_object(struct mapping_area *area,
1226                        struct page *pages[2], int off, int size)
1227{
1228        int sizes[2];
1229        void *addr;
1230        char *buf = area->vm_buf;
1231
1232        /* disable page faults to match kmap_atomic() return conditions */
1233        pagefault_disable();
1234
1235        /* no read fastpath */
1236        if (area->vm_mm == ZS_MM_WO)
1237                goto out;
1238
1239        sizes[0] = PAGE_SIZE - off;
1240        sizes[1] = size - sizes[0];
1241
1242        /* copy object to per-cpu buffer */
1243        addr = kmap_atomic(pages[0]);
1244        memcpy(buf, addr + off, sizes[0]);
1245        kunmap_atomic(addr);
1246        addr = kmap_atomic(pages[1]);
1247        memcpy(buf + sizes[0], addr, sizes[1]);
1248        kunmap_atomic(addr);
1249out:
1250        return area->vm_buf;
1251}
1252
1253static void __zs_unmap_object(struct mapping_area *area,
1254                        struct page *pages[2], int off, int size)
1255{
1256        int sizes[2];
1257        void *addr;
1258        char *buf;
1259
1260        /* no write fastpath */
1261        if (area->vm_mm == ZS_MM_RO)
1262                goto out;
1263
1264        buf = area->vm_buf;
1265        buf = buf + ZS_HANDLE_SIZE;
1266        size -= ZS_HANDLE_SIZE;
1267        off += ZS_HANDLE_SIZE;
1268
1269        sizes[0] = PAGE_SIZE - off;
1270        sizes[1] = size - sizes[0];
1271
1272        /* copy per-cpu buffer to object */
1273        addr = kmap_atomic(pages[0]);
1274        memcpy(addr + off, buf, sizes[0]);
1275        kunmap_atomic(addr);
1276        addr = kmap_atomic(pages[1]);
1277        memcpy(addr, buf + sizes[0], sizes[1]);
1278        kunmap_atomic(addr);
1279
1280out:
1281        /* enable page faults to match kunmap_atomic() return conditions */
1282        pagefault_enable();
1283}
1284
1285#endif /* CONFIG_PGTABLE_MAPPING */
1286
1287static int zs_cpu_notifier(struct notifier_block *nb, unsigned long action,
1288                                void *pcpu)
1289{
1290        int ret, cpu = (long)pcpu;
1291        struct mapping_area *area;
1292
1293        switch (action) {
1294        case CPU_UP_PREPARE:
1295                area = &per_cpu(zs_map_area, cpu);
1296                ret = __zs_cpu_up(area);
1297                if (ret)
1298                        return notifier_from_errno(ret);
1299                break;
1300        case CPU_DEAD:
1301        case CPU_UP_CANCELED:
1302                area = &per_cpu(zs_map_area, cpu);
1303                __zs_cpu_down(area);
1304                break;
1305        }
1306
1307        return NOTIFY_OK;
1308}
1309
1310static struct notifier_block zs_cpu_nb = {
1311        .notifier_call = zs_cpu_notifier
1312};
1313
1314static int zs_register_cpu_notifier(void)
1315{
1316        int cpu, uninitialized_var(ret);
1317
1318        cpu_notifier_register_begin();
1319
1320        __register_cpu_notifier(&zs_cpu_nb);
1321        for_each_online_cpu(cpu) {
1322                ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
1323                if (notifier_to_errno(ret))
1324                        break;
1325        }
1326
1327        cpu_notifier_register_done();
1328        return notifier_to_errno(ret);
1329}
1330
1331static void zs_unregister_cpu_notifier(void)
1332{
1333        int cpu;
1334
1335        cpu_notifier_register_begin();
1336
1337        for_each_online_cpu(cpu)
1338                zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu);
1339        __unregister_cpu_notifier(&zs_cpu_nb);
1340
1341        cpu_notifier_register_done();
1342}
1343
1344static void __init init_zs_size_classes(void)
1345{
1346        int nr;
1347
1348        nr = (ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1;
1349        if ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) % ZS_SIZE_CLASS_DELTA)
1350                nr += 1;
1351
1352        zs_size_classes = nr;
1353}
1354
1355static bool can_merge(struct size_class *prev, int pages_per_zspage,
1356                                        int objs_per_zspage)
1357{
1358        if (prev->pages_per_zspage == pages_per_zspage &&
1359                prev->objs_per_zspage == objs_per_zspage)
1360                return true;
1361
1362        return false;
1363}
1364
1365static bool zspage_full(struct size_class *class, struct zspage *zspage)
1366{
1367        return get_zspage_inuse(zspage) == class->objs_per_zspage;
1368}
1369
1370unsigned long zs_get_total_pages(struct zs_pool *pool)
1371{
1372        return atomic_long_read(&pool->pages_allocated);
1373}
1374EXPORT_SYMBOL_GPL(zs_get_total_pages);
1375
1376/**
1377 * zs_map_object - get address of allocated object from handle.
1378 * @pool: pool from which the object was allocated
1379 * @handle: handle returned from zs_malloc
1380 *
1381 * Before using an object allocated from zs_malloc, it must be mapped using
1382 * this function. When done with the object, it must be unmapped using
1383 * zs_unmap_object.
1384 *
1385 * Only one object can be mapped per cpu at a time. There is no protection
1386 * against nested mappings.
1387 *
1388 * This function returns with preemption and page faults disabled.
1389 */
1390void *zs_map_object(struct zs_pool *pool, unsigned long handle,
1391                        enum zs_mapmode mm)
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        struct page *pages[2];
1403        void *ret;
1404
1405        /*
1406         * Because we use per-cpu mapping areas shared among the
1407         * pools/users, we can't allow mapping in interrupt context
1408         * because it can corrupt another users mappings.
1409         */
1410        WARN_ON_ONCE(in_interrupt());
1411
1412        /* From now on, migration cannot move the object */
1413        pin_tag(handle);
1414
1415        obj = handle_to_obj(handle);
1416        obj_to_location(obj, &page, &obj_idx);
1417        zspage = get_zspage(page);
1418
1419        /* migration cannot move any subpage in this zspage */
1420        migrate_read_lock(zspage);
1421
1422        get_zspage_mapping(zspage, &class_idx, &fg);
1423        class = pool->size_class[class_idx];
1424        off = (class->size * obj_idx) & ~PAGE_MASK;
1425
1426        area = &get_cpu_var(zs_map_area);
1427        area->vm_mm = mm;
1428        if (off + class->size <= PAGE_SIZE) {
1429                /* this object is contained entirely within a page */
1430                area->vm_addr = kmap_atomic(page);
1431                ret = area->vm_addr + off;
1432                goto out;
1433        }
1434
1435        /* this object spans two pages */
1436        pages[0] = page;
1437        pages[1] = get_next_page(page);
1438        BUG_ON(!pages[1]);
1439
1440        ret = __zs_map_object(area, pages, off, class->size);
1441out:
1442        if (likely(!PageHugeObject(page)))
1443                ret += ZS_HANDLE_SIZE;
1444
1445        return ret;
1446}
1447EXPORT_SYMBOL_GPL(zs_map_object);
1448
1449void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
1450{
1451        struct zspage *zspage;
1452        struct page *page;
1453        unsigned long obj, off;
1454        unsigned int obj_idx;
1455
1456        unsigned int class_idx;
1457        enum fullness_group fg;
1458        struct size_class *class;
1459        struct mapping_area *area;
1460
1461        obj = handle_to_obj(handle);
1462        obj_to_location(obj, &page, &obj_idx);
1463        zspage = get_zspage(page);
1464        get_zspage_mapping(zspage, &class_idx, &fg);
1465        class = pool->size_class[class_idx];
1466        off = (class->size * obj_idx) & ~PAGE_MASK;
1467
1468        area = this_cpu_ptr(&zs_map_area);
1469        if (off + class->size <= PAGE_SIZE)
1470                kunmap_atomic(area->vm_addr);
1471        else {
1472                struct page *pages[2];
1473
1474                pages[0] = page;
1475                pages[1] = get_next_page(page);
1476                BUG_ON(!pages[1]);
1477
1478                __zs_unmap_object(area, pages, off, class->size);
1479        }
1480        put_cpu_var(zs_map_area);
1481
1482        migrate_read_unlock(zspage);
1483        unpin_tag(handle);
1484}
1485EXPORT_SYMBOL_GPL(zs_unmap_object);
1486
1487static unsigned long obj_malloc(struct size_class *class,
1488                                struct zspage *zspage, unsigned long handle)
1489{
1490        int i, nr_page, offset;
1491        unsigned long obj;
1492        struct link_free *link;
1493
1494        struct page *m_page;
1495        unsigned long m_offset;
1496        void *vaddr;
1497
1498        handle |= OBJ_ALLOCATED_TAG;
1499        obj = get_freeobj(zspage);
1500
1501        offset = obj * class->size;
1502        nr_page = offset >> PAGE_SHIFT;
1503        m_offset = offset & ~PAGE_MASK;
1504        m_page = get_first_page(zspage);
1505
1506        for (i = 0; i < nr_page; i++)
1507                m_page = get_next_page(m_page);
1508
1509        vaddr = kmap_atomic(m_page);
1510        link = (struct link_free *)vaddr + m_offset / sizeof(*link);
1511        set_freeobj(zspage, link->next >> OBJ_TAG_BITS);
1512        if (likely(!PageHugeObject(m_page)))
1513                /* record handle in the header of allocated chunk */
1514                link->handle = handle;
1515        else
1516                /* record handle to page->index */
1517                zspage->first_page->index = handle;
1518
1519        kunmap_atomic(vaddr);
1520        mod_zspage_inuse(zspage, 1);
1521        zs_stat_inc(class, OBJ_USED, 1);
1522
1523        obj = location_to_obj(m_page, obj);
1524
1525        return obj;
1526}
1527
1528
1529/**
1530 * zs_malloc - Allocate block of given size from pool.
1531 * @pool: pool to allocate from
1532 * @size: size of block to allocate
1533 * @gfp: gfp flags when allocating object
1534 *
1535 * On success, handle to the allocated object is returned,
1536 * otherwise 0.
1537 * Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail.
1538 */
1539unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
1540{
1541        unsigned long handle, obj;
1542        struct size_class *class;
1543        enum fullness_group newfg;
1544        struct zspage *zspage;
1545
1546        if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
1547                return 0;
1548
1549        handle = cache_alloc_handle(pool, gfp);
1550        if (!handle)
1551                return 0;
1552
1553        /* extra space in chunk to keep the handle */
1554        size += ZS_HANDLE_SIZE;
1555        class = pool->size_class[get_size_class_index(size)];
1556
1557        spin_lock(&class->lock);
1558        zspage = find_get_zspage(class);
1559        if (likely(zspage)) {
1560                obj = obj_malloc(class, zspage, handle);
1561                /* Now move the zspage to another fullness group, if required */
1562                fix_fullness_group(class, zspage);
1563                record_obj(handle, obj);
1564                spin_unlock(&class->lock);
1565
1566                return handle;
1567        }
1568
1569        spin_unlock(&class->lock);
1570
1571        zspage = alloc_zspage(pool, class, gfp);
1572        if (!zspage) {
1573                cache_free_handle(pool, handle);
1574                return 0;
1575        }
1576
1577        spin_lock(&class->lock);
1578        obj = obj_malloc(class, zspage, handle);
1579        newfg = get_fullness_group(class, zspage);
1580        insert_zspage(class, zspage, newfg);
1581        set_zspage_mapping(zspage, class->index, newfg);
1582        record_obj(handle, obj);
1583        atomic_long_add(class->pages_per_zspage,
1584                                &pool->pages_allocated);
1585        zs_stat_inc(class, OBJ_ALLOCATED, class->objs_per_zspage);
1586
1587        /* We completely set up zspage so mark them as movable */
1588        SetZsPageMovable(pool, zspage);
1589        spin_unlock(&class->lock);
1590
1591        return handle;
1592}
1593EXPORT_SYMBOL_GPL(zs_malloc);
1594
1595static void obj_free(struct size_class *class, unsigned long obj)
1596{
1597        struct link_free *link;
1598        struct zspage *zspage;
1599        struct page *f_page;
1600        unsigned long f_offset;
1601        unsigned int f_objidx;
1602        void *vaddr;
1603
1604        obj &= ~OBJ_ALLOCATED_TAG;
1605        obj_to_location(obj, &f_page, &f_objidx);
1606        f_offset = (class->size * f_objidx) & ~PAGE_MASK;
1607        zspage = get_zspage(f_page);
1608
1609        vaddr = kmap_atomic(f_page);
1610
1611        /* Insert this object in containing zspage's freelist */
1612        link = (struct link_free *)(vaddr + f_offset);
1613        link->next = get_freeobj(zspage) << OBJ_TAG_BITS;
1614        kunmap_atomic(vaddr);
1615        set_freeobj(zspage, f_objidx);
1616        mod_zspage_inuse(zspage, -1);
1617        zs_stat_dec(class, OBJ_USED, 1);
1618}
1619
1620void zs_free(struct zs_pool *pool, unsigned long handle)
1621{
1622        struct zspage *zspage;
1623        struct page *f_page;
1624        unsigned long obj;
1625        unsigned int f_objidx;
1626        int class_idx;
1627        struct size_class *class;
1628        enum fullness_group fullness;
1629        bool isolated;
1630
1631        if (unlikely(!handle))
1632                return;
1633
1634        pin_tag(handle);
1635        obj = handle_to_obj(handle);
1636        obj_to_location(obj, &f_page, &f_objidx);
1637        zspage = get_zspage(f_page);
1638
1639        migrate_read_lock(zspage);
1640
1641        get_zspage_mapping(zspage, &class_idx, &fullness);
1642        class = pool->size_class[class_idx];
1643
1644        spin_lock(&class->lock);
1645        obj_free(class, obj);
1646        fullness = fix_fullness_group(class, zspage);
1647        if (fullness != ZS_EMPTY) {
1648                migrate_read_unlock(zspage);
1649                goto out;
1650        }
1651
1652        isolated = is_zspage_isolated(zspage);
1653        migrate_read_unlock(zspage);
1654        /* If zspage is isolated, zs_page_putback will free the zspage */
1655        if (likely(!isolated))
1656                free_zspage(pool, class, zspage);
1657out:
1658
1659        spin_unlock(&class->lock);
1660        unpin_tag(handle);
1661        cache_free_handle(pool, handle);
1662}
1663EXPORT_SYMBOL_GPL(zs_free);
1664
1665static void zs_object_copy(struct size_class *class, unsigned long dst,
1666                                unsigned long src)
1667{
1668        struct page *s_page, *d_page;
1669        unsigned int s_objidx, d_objidx;
1670        unsigned long s_off, d_off;
1671        void *s_addr, *d_addr;
1672        int s_size, d_size, size;
1673        int written = 0;
1674
1675        s_size = d_size = class->size;
1676
1677        obj_to_location(src, &s_page, &s_objidx);
1678        obj_to_location(dst, &d_page, &d_objidx);
1679
1680        s_off = (class->size * s_objidx) & ~PAGE_MASK;
1681        d_off = (class->size * d_objidx) & ~PAGE_MASK;
1682
1683        if (s_off + class->size > PAGE_SIZE)
1684                s_size = PAGE_SIZE - s_off;
1685
1686        if (d_off + class->size > PAGE_SIZE)
1687                d_size = PAGE_SIZE - d_off;
1688
1689        s_addr = kmap_atomic(s_page);
1690        d_addr = kmap_atomic(d_page);
1691
1692        while (1) {
1693                size = min(s_size, d_size);
1694                memcpy(d_addr + d_off, s_addr + s_off, size);
1695                written += size;
1696
1697                if (written == class->size)
1698                        break;
1699
1700                s_off += size;
1701                s_size -= size;
1702                d_off += size;
1703                d_size -= size;
1704
1705                if (s_off >= PAGE_SIZE) {
1706                        kunmap_atomic(d_addr);
1707                        kunmap_atomic(s_addr);
1708                        s_page = get_next_page(s_page);
1709                        s_addr = kmap_atomic(s_page);
1710                        d_addr = kmap_atomic(d_page);
1711                        s_size = class->size - written;
1712                        s_off = 0;
1713                }
1714
1715                if (d_off >= PAGE_SIZE) {
1716                        kunmap_atomic(d_addr);
1717                        d_page = get_next_page(d_page);
1718                        d_addr = kmap_atomic(d_page);
1719                        d_size = class->size - written;
1720                        d_off = 0;
1721                }
1722        }
1723
1724        kunmap_atomic(d_addr);
1725        kunmap_atomic(s_addr);
1726}
1727
1728/*
1729 * Find alloced object in zspage from index object and
1730 * return handle.
1731 */
1732static unsigned long find_alloced_obj(struct size_class *class,
1733                                        struct page *page, int *obj_idx)
1734{
1735        unsigned long head;
1736        int offset = 0;
1737        int index = *obj_idx;
1738        unsigned long handle = 0;
1739        void *addr = kmap_atomic(page);
1740
1741        offset = get_first_obj_offset(page);
1742        offset += class->size * index;
1743
1744        while (offset < PAGE_SIZE) {
1745                head = obj_to_head(page, addr + offset);
1746                if (head & OBJ_ALLOCATED_TAG) {
1747                        handle = head & ~OBJ_ALLOCATED_TAG;
1748                        if (trypin_tag(handle))
1749                                break;
1750                        handle = 0;
1751                }
1752
1753                offset += class->size;
1754                index++;
1755        }
1756
1757        kunmap_atomic(addr);
1758
1759        *obj_idx = index;
1760
1761        return handle;
1762}
1763
1764struct zs_compact_control {
1765        /* Source spage for migration which could be a subpage of zspage */
1766        struct page *s_page;
1767        /* Destination page for migration which should be a first page
1768         * of zspage. */
1769        struct page *d_page;
1770         /* Starting object index within @s_page which used for live object
1771          * in the subpage. */
1772        int obj_idx;
1773};
1774
1775static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
1776                                struct zs_compact_control *cc)
1777{
1778        unsigned long used_obj, free_obj;
1779        unsigned long handle;
1780        struct page *s_page = cc->s_page;
1781        struct page *d_page = cc->d_page;
1782        int obj_idx = cc->obj_idx;
1783        int ret = 0;
1784
1785        while (1) {
1786                handle = find_alloced_obj(class, s_page, &obj_idx);
1787                if (!handle) {
1788                        s_page = get_next_page(s_page);
1789                        if (!s_page)
1790                                break;
1791                        obj_idx = 0;
1792                        continue;
1793                }
1794
1795                /* Stop if there is no more space */
1796                if (zspage_full(class, get_zspage(d_page))) {
1797                        unpin_tag(handle);
1798                        ret = -ENOMEM;
1799                        break;
1800                }
1801
1802                used_obj = handle_to_obj(handle);
1803                free_obj = obj_malloc(class, get_zspage(d_page), handle);
1804                zs_object_copy(class, free_obj, used_obj);
1805                obj_idx++;
1806                /*
1807                 * record_obj updates handle's value to free_obj and it will
1808                 * invalidate lock bit(ie, HANDLE_PIN_BIT) of handle, which
1809                 * breaks synchronization using pin_tag(e,g, zs_free) so
1810                 * let's keep the lock bit.
1811                 */
1812                free_obj |= BIT(HANDLE_PIN_BIT);
1813                record_obj(handle, free_obj);
1814                unpin_tag(handle);
1815                obj_free(class, used_obj);
1816        }
1817
1818        /* Remember last position in this iteration */
1819        cc->s_page = s_page;
1820        cc->obj_idx = obj_idx;
1821
1822        return ret;
1823}
1824
1825static struct zspage *isolate_zspage(struct size_class *class, bool source)
1826{
1827        int i;
1828        struct zspage *zspage;
1829        enum fullness_group fg[2] = {ZS_ALMOST_EMPTY, ZS_ALMOST_FULL};
1830
1831        if (!source) {
1832                fg[0] = ZS_ALMOST_FULL;
1833                fg[1] = ZS_ALMOST_EMPTY;
1834        }
1835
1836        for (i = 0; i < 2; i++) {
1837                zspage = list_first_entry_or_null(&class->fullness_list[fg[i]],
1838                                                        struct zspage, list);
1839                if (zspage) {
1840                        VM_BUG_ON(is_zspage_isolated(zspage));
1841                        remove_zspage(class, zspage, fg[i]);
1842                        return zspage;
1843                }
1844        }
1845
1846        return zspage;
1847}
1848
1849/*
1850 * putback_zspage - add @zspage into right class's fullness list
1851 * @class: destination class
1852 * @zspage: target page
1853 *
1854 * Return @zspage's fullness_group
1855 */
1856static enum fullness_group putback_zspage(struct size_class *class,
1857                        struct zspage *zspage)
1858{
1859        enum fullness_group fullness;
1860
1861        VM_BUG_ON(is_zspage_isolated(zspage));
1862
1863        fullness = get_fullness_group(class, zspage);
1864        insert_zspage(class, zspage, fullness);
1865        set_zspage_mapping(zspage, class->index, fullness);
1866
1867        return fullness;
1868}
1869
1870#ifdef CONFIG_COMPACTION
1871static struct dentry *zs_mount(struct file_system_type *fs_type,
1872                                int flags, const char *dev_name, void *data)
1873{
1874        static const struct dentry_operations ops = {
1875                .d_dname = simple_dname,
1876        };
1877
1878        return mount_pseudo(fs_type, "zsmalloc:", NULL, &ops, ZSMALLOC_MAGIC);
1879}
1880
1881static struct file_system_type zsmalloc_fs = {
1882        .name           = "zsmalloc",
1883        .mount          = zs_mount,
1884        .kill_sb        = kill_anon_super,
1885};
1886
1887static int zsmalloc_mount(void)
1888{
1889        int ret = 0;
1890
1891        zsmalloc_mnt = kern_mount(&zsmalloc_fs);
1892        if (IS_ERR(zsmalloc_mnt))
1893                ret = PTR_ERR(zsmalloc_mnt);
1894
1895        return ret;
1896}
1897
1898static void zsmalloc_unmount(void)
1899{
1900        kern_unmount(zsmalloc_mnt);
1901}
1902
1903static void migrate_lock_init(struct zspage *zspage)
1904{
1905        rwlock_init(&zspage->lock);
1906}
1907
1908static void migrate_read_lock(struct zspage *zspage)
1909{
1910        read_lock(&zspage->lock);
1911}
1912
1913static void migrate_read_unlock(struct zspage *zspage)
1914{
1915        read_unlock(&zspage->lock);
1916}
1917
1918static void migrate_write_lock(struct zspage *zspage)
1919{
1920        write_lock(&zspage->lock);
1921}
1922
1923static void migrate_write_unlock(struct zspage *zspage)
1924{
1925        write_unlock(&zspage->lock);
1926}
1927
1928/* Number of isolated subpage for *page migration* in this zspage */
1929static void inc_zspage_isolation(struct zspage *zspage)
1930{
1931        zspage->isolated++;
1932}
1933
1934static void dec_zspage_isolation(struct zspage *zspage)
1935{
1936        zspage->isolated--;
1937}
1938
1939static void replace_sub_page(struct size_class *class, struct zspage *zspage,
1940                                struct page *newpage, struct page *oldpage)
1941{
1942        struct page *page;
1943        struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE] = {NULL, };
1944        int idx = 0;
1945
1946        page = get_first_page(zspage);
1947        do {
1948                if (page == oldpage)
1949                        pages[idx] = newpage;
1950                else
1951                        pages[idx] = page;
1952                idx++;
1953        } while ((page = get_next_page(page)) != NULL);
1954
1955        create_page_chain(class, zspage, pages);
1956        set_first_obj_offset(newpage, get_first_obj_offset(oldpage));
1957        if (unlikely(PageHugeObject(oldpage)))
1958                newpage->index = oldpage->index;
1959        __SetPageMovable(newpage, page_mapping(oldpage));
1960}
1961
1962bool zs_page_isolate(struct page *page, isolate_mode_t mode)
1963{
1964        struct zs_pool *pool;
1965        struct size_class *class;
1966        int class_idx;
1967        enum fullness_group fullness;
1968        struct zspage *zspage;
1969        struct address_space *mapping;
1970
1971        /*
1972         * Page is locked so zspage couldn't be destroyed. For detail, look at
1973         * lock_zspage in free_zspage.
1974         */
1975        VM_BUG_ON_PAGE(!PageMovable(page), page);
1976        VM_BUG_ON_PAGE(PageIsolated(page), page);
1977
1978        zspage = get_zspage(page);
1979
1980        /*
1981         * Without class lock, fullness could be stale while class_idx is okay
1982         * because class_idx is constant unless page is freed so we should get
1983         * fullness again under class lock.
1984         */
1985        get_zspage_mapping(zspage, &class_idx, &fullness);
1986        mapping = page_mapping(page);
1987        pool = mapping->private_data;
1988        class = pool->size_class[class_idx];
1989
1990        spin_lock(&class->lock);
1991        if (get_zspage_inuse(zspage) == 0) {
1992                spin_unlock(&class->lock);
1993                return false;
1994        }
1995
1996        /* zspage is isolated for object migration */
1997        if (list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
1998                spin_unlock(&class->lock);
1999                return false;
2000        }
2001
2002        /*
2003         * If this is first time isolation for the zspage, isolate zspage from
2004         * size_class to prevent further object allocation from the zspage.
2005         */
2006        if (!list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
2007                get_zspage_mapping(zspage, &class_idx, &fullness);
2008                remove_zspage(class, zspage, fullness);
2009        }
2010
2011        inc_zspage_isolation(zspage);
2012        spin_unlock(&class->lock);
2013
2014        return true;
2015}
2016
2017int zs_page_migrate(struct address_space *mapping, struct page *newpage,
2018                struct page *page, enum migrate_mode mode)
2019{
2020        struct zs_pool *pool;
2021        struct size_class *class;
2022        int class_idx;
2023        enum fullness_group fullness;
2024        struct zspage *zspage;
2025        struct page *dummy;
2026        void *s_addr, *d_addr, *addr;
2027        int offset, pos;
2028        unsigned long handle, head;
2029        unsigned long old_obj, new_obj;
2030        unsigned int obj_idx;
2031        int ret = -EAGAIN;
2032
2033        VM_BUG_ON_PAGE(!PageMovable(page), page);
2034        VM_BUG_ON_PAGE(!PageIsolated(page), page);
2035
2036        zspage = get_zspage(page);
2037
2038        /* Concurrent compactor cannot migrate any subpage in zspage */
2039        migrate_write_lock(zspage);
2040        get_zspage_mapping(zspage, &class_idx, &fullness);
2041        pool = mapping->private_data;
2042        class = pool->size_class[class_idx];
2043        offset = get_first_obj_offset(page);
2044
2045        spin_lock(&class->lock);
2046        if (!get_zspage_inuse(zspage)) {
2047                ret = -EBUSY;
2048                goto unlock_class;
2049        }
2050
2051        pos = offset;
2052        s_addr = kmap_atomic(page);
2053        while (pos < PAGE_SIZE) {
2054                head = obj_to_head(page, s_addr + pos);
2055                if (head & OBJ_ALLOCATED_TAG) {
2056                        handle = head & ~OBJ_ALLOCATED_TAG;
2057                        if (!trypin_tag(handle))
2058                                goto unpin_objects;
2059                }
2060                pos += class->size;
2061        }
2062
2063        /*
2064         * Here, any user cannot access all objects in the zspage so let's move.
2065         */
2066        d_addr = kmap_atomic(newpage);
2067        memcpy(d_addr, s_addr, PAGE_SIZE);
2068        kunmap_atomic(d_addr);
2069
2070        for (addr = s_addr + offset; addr < s_addr + pos;
2071                                        addr += class->size) {
2072                head = obj_to_head(page, addr);
2073                if (head & OBJ_ALLOCATED_TAG) {
2074                        handle = head & ~OBJ_ALLOCATED_TAG;
2075                        if (!testpin_tag(handle))
2076                                BUG();
2077
2078                        old_obj = handle_to_obj(handle);
2079                        obj_to_location(old_obj, &dummy, &obj_idx);
2080                        new_obj = (unsigned long)location_to_obj(newpage,
2081                                                                obj_idx);
2082                        new_obj |= BIT(HANDLE_PIN_BIT);
2083                        record_obj(handle, new_obj);
2084                }
2085        }
2086
2087        replace_sub_page(class, zspage, newpage, page);
2088        get_page(newpage);
2089
2090        dec_zspage_isolation(zspage);
2091
2092        /*
2093         * Page migration is done so let's putback isolated zspage to
2094         * the list if @page is final isolated subpage in the zspage.
2095         */
2096        if (!is_zspage_isolated(zspage))
2097                putback_zspage(class, zspage);
2098
2099        reset_page(page);
2100        put_page(page);
2101        page = newpage;
2102
2103        ret = MIGRATEPAGE_SUCCESS;
2104unpin_objects:
2105        for (addr = s_addr + offset; addr < s_addr + pos;
2106                                                addr += class->size) {
2107                head = obj_to_head(page, addr);
2108                if (head & OBJ_ALLOCATED_TAG) {
2109                        handle = head & ~OBJ_ALLOCATED_TAG;
2110                        if (!testpin_tag(handle))
2111                                BUG();
2112                        unpin_tag(handle);
2113                }
2114        }
2115        kunmap_atomic(s_addr);
2116unlock_class:
2117        spin_unlock(&class->lock);
2118        migrate_write_unlock(zspage);
2119
2120        return ret;
2121}
2122
2123void zs_page_putback(struct page *page)
2124{
2125        struct zs_pool *pool;
2126        struct size_class *class;
2127        int class_idx;
2128        enum fullness_group fg;
2129        struct address_space *mapping;
2130        struct zspage *zspage;
2131
2132        VM_BUG_ON_PAGE(!PageMovable(page), page);
2133        VM_BUG_ON_PAGE(!PageIsolated(page), page);
2134
2135        zspage = get_zspage(page);
2136        get_zspage_mapping(zspage, &class_idx, &fg);
2137        mapping = page_mapping(page);
2138        pool = mapping->private_data;
2139        class = pool->size_class[class_idx];
2140
2141        spin_lock(&class->lock);
2142        dec_zspage_isolation(zspage);
2143        if (!is_zspage_isolated(zspage)) {
2144                fg = putback_zspage(class, zspage);
2145                /*
2146                 * Due to page_lock, we cannot free zspage immediately
2147                 * so let's defer.
2148                 */
2149                if (fg == ZS_EMPTY)
2150                        schedule_work(&pool->free_work);
2151        }
2152        spin_unlock(&class->lock);
2153}
2154
2155const struct address_space_operations zsmalloc_aops = {
2156        .isolate_page = zs_page_isolate,
2157        .migratepage = zs_page_migrate,
2158        .putback_page = zs_page_putback,
2159};
2160
2161static int zs_register_migration(struct zs_pool *pool)
2162{
2163        pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb);
2164        if (IS_ERR(pool->inode)) {
2165                pool->inode = NULL;
2166                return 1;
2167        }
2168
2169        pool->inode->i_mapping->private_data = pool;
2170        pool->inode->i_mapping->a_ops = &zsmalloc_aops;
2171        return 0;
2172}
2173
2174static void zs_unregister_migration(struct zs_pool *pool)
2175{
2176        flush_work(&pool->free_work);
2177        iput(pool->inode);
2178}
2179
2180/*
2181 * Caller should hold page_lock of all pages in the zspage
2182 * In here, we cannot use zspage meta data.
2183 */
2184static void async_free_zspage(struct work_struct *work)
2185{
2186        int i;
2187        struct size_class *class;
2188        unsigned int class_idx;
2189        enum fullness_group fullness;
2190        struct zspage *zspage, *tmp;
2191        LIST_HEAD(free_pages);
2192        struct zs_pool *pool = container_of(work, struct zs_pool,
2193                                        free_work);
2194
2195        for (i = 0; i < zs_size_classes; i++) {
2196                class = pool->size_class[i];
2197                if (class->index != i)
2198                        continue;
2199
2200                spin_lock(&class->lock);
2201                list_splice_init(&class->fullness_list[ZS_EMPTY], &free_pages);
2202                spin_unlock(&class->lock);
2203        }
2204
2205
2206        list_for_each_entry_safe(zspage, tmp, &free_pages, list) {
2207                list_del(&zspage->list);
2208                lock_zspage(zspage);
2209
2210                get_zspage_mapping(zspage, &class_idx, &fullness);
2211                VM_BUG_ON(fullness != ZS_EMPTY);
2212                class = pool->size_class[class_idx];
2213                spin_lock(&class->lock);
2214                __free_zspage(pool, pool->size_class[class_idx], zspage);
2215                spin_unlock(&class->lock);
2216        }
2217};
2218
2219static void kick_deferred_free(struct zs_pool *pool)
2220{
2221        schedule_work(&pool->free_work);
2222}
2223
2224static void init_deferred_free(struct zs_pool *pool)
2225{
2226        INIT_WORK(&pool->free_work, async_free_zspage);
2227}
2228
2229static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage)
2230{
2231        struct page *page = get_first_page(zspage);
2232
2233        do {
2234                WARN_ON(!trylock_page(page));
2235                __SetPageMovable(page, pool->inode->i_mapping);
2236                unlock_page(page);
2237        } while ((page = get_next_page(page)) != NULL);
2238}
2239#endif
2240
2241/*
2242 *
2243 * Based on the number of unused allocated objects calculate
2244 * and return the number of pages that we can free.
2245 */
2246static unsigned long zs_can_compact(struct size_class *class)
2247{
2248        unsigned long obj_wasted;
2249        unsigned long obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
2250        unsigned long obj_used = zs_stat_get(class, OBJ_USED);
2251
2252        if (obj_allocated <= obj_used)
2253                return 0;
2254
2255        obj_wasted = obj_allocated - obj_used;
2256        obj_wasted /= class->objs_per_zspage;
2257
2258        return obj_wasted * class->pages_per_zspage;
2259}
2260
2261static void __zs_compact(struct zs_pool *pool, struct size_class *class)
2262{
2263        struct zs_compact_control cc;
2264        struct zspage *src_zspage;
2265        struct zspage *dst_zspage = NULL;
2266
2267        spin_lock(&class->lock);
2268        while ((src_zspage = isolate_zspage(class, true))) {
2269
2270                if (!zs_can_compact(class))
2271                        break;
2272
2273                cc.obj_idx = 0;
2274                cc.s_page = get_first_page(src_zspage);
2275
2276                while ((dst_zspage = isolate_zspage(class, false))) {
2277                        cc.d_page = get_first_page(dst_zspage);
2278                        /*
2279                         * If there is no more space in dst_page, resched
2280                         * and see if anyone had allocated another zspage.
2281                         */
2282                        if (!migrate_zspage(pool, class, &cc))
2283                                break;
2284
2285                        putback_zspage(class, dst_zspage);
2286                }
2287
2288                /* Stop if we couldn't find slot */
2289                if (dst_zspage == NULL)
2290                        break;
2291
2292                putback_zspage(class, dst_zspage);
2293                if (putback_zspage(class, src_zspage) == ZS_EMPTY) {
2294                        free_zspage(pool, class, src_zspage);
2295                        pool->stats.pages_compacted += class->pages_per_zspage;
2296                }
2297                spin_unlock(&class->lock);
2298                cond_resched();
2299                spin_lock(&class->lock);
2300        }
2301
2302        if (src_zspage)
2303                putback_zspage(class, src_zspage);
2304
2305        spin_unlock(&class->lock);
2306}
2307
2308unsigned long zs_compact(struct zs_pool *pool)
2309{
2310        int i;
2311        struct size_class *class;
2312
2313        for (i = zs_size_classes - 1; i >= 0; i--) {
2314                class = pool->size_class[i];
2315                if (!class)
2316                        continue;
2317                if (class->index != i)
2318                        continue;
2319                __zs_compact(pool, class);
2320        }
2321
2322        return pool->stats.pages_compacted;
2323}
2324EXPORT_SYMBOL_GPL(zs_compact);
2325
2326void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats)
2327{
2328        memcpy(stats, &pool->stats, sizeof(struct zs_pool_stats));
2329}
2330EXPORT_SYMBOL_GPL(zs_pool_stats);
2331
2332static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
2333                struct shrink_control *sc)
2334{
2335        unsigned long pages_freed;
2336        struct zs_pool *pool = container_of(shrinker, struct zs_pool,
2337                        shrinker);
2338
2339        pages_freed = pool->stats.pages_compacted;
2340        /*
2341         * Compact classes and calculate compaction delta.
2342         * Can run concurrently with a manually triggered
2343         * (by user) compaction.
2344         */
2345        pages_freed = zs_compact(pool) - pages_freed;
2346
2347        return pages_freed ? pages_freed : SHRINK_STOP;
2348}
2349
2350static unsigned long zs_shrinker_count(struct shrinker *shrinker,
2351                struct shrink_control *sc)
2352{
2353        int i;
2354        struct size_class *class;
2355        unsigned long pages_to_free = 0;
2356        struct zs_pool *pool = container_of(shrinker, struct zs_pool,
2357                        shrinker);
2358
2359        for (i = zs_size_classes - 1; i >= 0; i--) {
2360                class = pool->size_class[i];
2361                if (!class)
2362                        continue;
2363                if (class->index != i)
2364                        continue;
2365
2366                pages_to_free += zs_can_compact(class);
2367        }
2368
2369        return pages_to_free;
2370}
2371
2372static void zs_unregister_shrinker(struct zs_pool *pool)
2373{
2374        if (pool->shrinker_enabled) {
2375                unregister_shrinker(&pool->shrinker);
2376                pool->shrinker_enabled = false;
2377        }
2378}
2379
2380static int zs_register_shrinker(struct zs_pool *pool)
2381{
2382        pool->shrinker.scan_objects = zs_shrinker_scan;
2383        pool->shrinker.count_objects = zs_shrinker_count;
2384        pool->shrinker.batch = 0;
2385        pool->shrinker.seeks = DEFAULT_SEEKS;
2386
2387        return register_shrinker(&pool->shrinker);
2388}
2389
2390/**
2391 * zs_create_pool - Creates an allocation pool to work from.
2392 * @name: pool name to be created
2393 *
2394 * This function must be called before anything when using
2395 * the zsmalloc allocator.
2396 *
2397 * On success, a pointer to the newly created pool is returned,
2398 * otherwise NULL.
2399 */
2400struct zs_pool *zs_create_pool(const char *name)
2401{
2402        int i;
2403        struct zs_pool *pool;
2404        struct size_class *prev_class = NULL;
2405
2406        pool = kzalloc(sizeof(*pool), GFP_KERNEL);
2407        if (!pool)
2408                return NULL;
2409
2410        init_deferred_free(pool);
2411        pool->size_class = kcalloc(zs_size_classes, sizeof(struct size_class *),
2412                        GFP_KERNEL);
2413        if (!pool->size_class) {
2414                kfree(pool);
2415                return NULL;
2416        }
2417
2418        pool->name = kstrdup(name, GFP_KERNEL);
2419        if (!pool->name)
2420                goto err;
2421
2422        if (create_cache(pool))
2423                goto err;
2424
2425        /*
2426         * Iterate reversly, because, size of size_class that we want to use
2427         * for merging should be larger or equal to current size.
2428         */
2429        for (i = zs_size_classes - 1; i >= 0; i--) {
2430                int size;
2431                int pages_per_zspage;
2432                int objs_per_zspage;
2433                struct size_class *class;
2434                int fullness = 0;
2435
2436                size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
2437                if (size > ZS_MAX_ALLOC_SIZE)
2438                        size = ZS_MAX_ALLOC_SIZE;
2439                pages_per_zspage = get_pages_per_zspage(size);
2440                objs_per_zspage = pages_per_zspage * PAGE_SIZE / size;
2441
2442                /*
2443                 * size_class is used for normal zsmalloc operation such
2444                 * as alloc/free for that size. Although it is natural that we
2445                 * have one size_class for each size, there is a chance that we
2446                 * can get more memory utilization if we use one size_class for
2447                 * many different sizes whose size_class have same
2448                 * characteristics. So, we makes size_class point to
2449                 * previous size_class if possible.
2450                 */
2451                if (prev_class) {
2452                        if (can_merge(prev_class, pages_per_zspage, objs_per_zspage)) {
2453                                pool->size_class[i] = prev_class;
2454                                continue;
2455                        }
2456                }
2457
2458                class = kzalloc(sizeof(struct size_class), GFP_KERNEL);
2459                if (!class)
2460                        goto err;
2461
2462                class->size = size;
2463                class->index = i;
2464                class->pages_per_zspage = pages_per_zspage;
2465                class->objs_per_zspage = objs_per_zspage;
2466                spin_lock_init(&class->lock);
2467                pool->size_class[i] = class;
2468                for (fullness = ZS_EMPTY; fullness < NR_ZS_FULLNESS;
2469                                                        fullness++)
2470                        INIT_LIST_HEAD(&class->fullness_list[fullness]);
2471
2472                prev_class = class;
2473        }
2474
2475        /* debug only, don't abort if it fails */
2476        zs_pool_stat_create(pool, name);
2477
2478        if (zs_register_migration(pool))
2479                goto err;
2480
2481        /*
2482         * Not critical, we still can use the pool
2483         * and user can trigger compaction manually.
2484         */
2485        if (zs_register_shrinker(pool) == 0)
2486                pool->shrinker_enabled = true;
2487        return pool;
2488
2489err:
2490        zs_destroy_pool(pool);
2491        return NULL;
2492}
2493EXPORT_SYMBOL_GPL(zs_create_pool);
2494
2495void zs_destroy_pool(struct zs_pool *pool)
2496{
2497        int i;
2498
2499        zs_unregister_shrinker(pool);
2500        zs_unregister_migration(pool);
2501        zs_pool_stat_destroy(pool);
2502
2503        for (i = 0; i < zs_size_classes; i++) {
2504                int fg;
2505                struct size_class *class = pool->size_class[i];
2506
2507                if (!class)
2508                        continue;
2509
2510                if (class->index != i)
2511                        continue;
2512
2513                for (fg = ZS_EMPTY; fg < NR_ZS_FULLNESS; fg++) {
2514                        if (!list_empty(&class->fullness_list[fg])) {
2515                                pr_info("Freeing non-empty class with size %db, fullness group %d\n",
2516                                        class->size, fg);
2517                        }
2518                }
2519                kfree(class);
2520        }
2521
2522        destroy_cache(pool);
2523        kfree(pool->size_class);
2524        kfree(pool->name);
2525        kfree(pool);
2526}
2527EXPORT_SYMBOL_GPL(zs_destroy_pool);
2528
2529static int __init zs_init(void)
2530{
2531        int ret;
2532
2533        ret = zsmalloc_mount();
2534        if (ret)
2535                goto out;
2536
2537        ret = zs_register_cpu_notifier();
2538
2539        if (ret)
2540                goto notifier_fail;
2541
2542        init_zs_size_classes();
2543
2544#ifdef CONFIG_ZPOOL
2545        zpool_register_driver(&zs_zpool_driver);
2546#endif
2547
2548        zs_stat_init();
2549
2550        return 0;
2551
2552notifier_fail:
2553        zs_unregister_cpu_notifier();
2554        zsmalloc_unmount();
2555out:
2556        return ret;
2557}
2558
2559static void __exit zs_exit(void)
2560{
2561#ifdef CONFIG_ZPOOL
2562        zpool_unregister_driver(&zs_zpool_driver);
2563#endif
2564        zsmalloc_unmount();
2565        zs_unregister_cpu_notifier();
2566
2567        zs_stat_exit();
2568}
2569
2570module_init(zs_init);
2571module_exit(zs_exit);
2572
2573MODULE_LICENSE("Dual BSD/GPL");
2574MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
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