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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * zswap.c - zswap driver file
4 *
5 * zswap is a backend for frontswap that takes pages that are in the process
6 * of being swapped out and attempts to compress and store them in a
7 * RAM-based memory pool. This can result in a significant I/O reduction on
8 * the swap device and, in the case where decompressing from RAM is faster
9 * than reading from the swap device, can also improve workload performance.
10 *
11 * Copyright (C) 2012 Seth Jennings <sjenning@linux.vnet.ibm.com>
12*/
13
14#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15
16#include <linux/module.h>
17#include <linux/cpu.h>
18#include <linux/highmem.h>
19#include <linux/slab.h>
20#include <linux/spinlock.h>
21#include <linux/types.h>
22#include <linux/atomic.h>
23#include <linux/frontswap.h>
24#include <linux/rbtree.h>
25#include <linux/swap.h>
26#include <linux/crypto.h>
27#include <linux/mempool.h>
28#include <linux/zpool.h>
29
30#include <linux/mm_types.h>
31#include <linux/page-flags.h>
32#include <linux/swapops.h>
33#include <linux/writeback.h>
34#include <linux/pagemap.h>
35#include <linux/workqueue.h>
36
37/*********************************
38* statistics
39**********************************/
40/* Total bytes used by the compressed storage */
41static u64 zswap_pool_total_size;
42/* The number of compressed pages currently stored in zswap */
43static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
44/* The number of same-value filled pages currently stored in zswap */
45static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);
46
47/*
48 * The statistics below are not protected from concurrent access for
49 * performance reasons so they may not be a 100% accurate. However,
50 * they do provide useful information on roughly how many times a
51 * certain event is occurring.
52*/
53
54/* Pool limit was hit (see zswap_max_pool_percent) */
55static u64 zswap_pool_limit_hit;
56/* Pages written back when pool limit was reached */
57static u64 zswap_written_back_pages;
58/* Store failed due to a reclaim failure after pool limit was reached */
59static u64 zswap_reject_reclaim_fail;
60/* Compressed page was too big for the allocator to (optimally) store */
61static u64 zswap_reject_compress_poor;
62/* Store failed because underlying allocator could not get memory */
63static u64 zswap_reject_alloc_fail;
64/* Store failed because the entry metadata could not be allocated (rare) */
65static u64 zswap_reject_kmemcache_fail;
66/* Duplicate store was encountered (rare) */
67static u64 zswap_duplicate_entry;
68
69/* Shrinker work queue */
70static struct workqueue_struct *shrink_wq;
71/* Pool limit was hit, we need to calm down */
72static bool zswap_pool_reached_full;
73
74/*********************************
75* tunables
76**********************************/
77
78#define ZSWAP_PARAM_UNSET ""
79
80/* Enable/disable zswap */
81static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON);
82static int zswap_enabled_param_set(const char *,
83 const struct kernel_param *);
84static struct kernel_param_ops zswap_enabled_param_ops = {
85 .set = zswap_enabled_param_set,
86 .get = param_get_bool,
87};
88module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
89
90/* Crypto compressor to use */
91static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
92static int zswap_compressor_param_set(const char *,
93 const struct kernel_param *);
94static struct kernel_param_ops zswap_compressor_param_ops = {
95 .set = zswap_compressor_param_set,
96 .get = param_get_charp,
97 .free = param_free_charp,
98};
99module_param_cb(compressor, &zswap_compressor_param_ops,
100 &zswap_compressor, 0644);
101
102/* Compressed storage zpool to use */
103static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
104static int zswap_zpool_param_set(const char *, const struct kernel_param *);
105static struct kernel_param_ops zswap_zpool_param_ops = {
106 .set = zswap_zpool_param_set,
107 .get = param_get_charp,
108 .free = param_free_charp,
109};
110module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
111
112/* The maximum percentage of memory that the compressed pool can occupy */
113static unsigned int zswap_max_pool_percent = 20;
114module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
115
116/* The threshold for accepting new pages after the max_pool_percent was hit */
117static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */
118module_param_named(accept_threshold_percent, zswap_accept_thr_percent,
119 uint, 0644);
120
121/* Enable/disable handling same-value filled pages (enabled by default) */
122static bool zswap_same_filled_pages_enabled = true;
123module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
124 bool, 0644);
125
126/*********************************
127* data structures
128**********************************/
129
130struct zswap_pool {
131 struct zpool *zpool;
132 struct crypto_comp * __percpu *tfm;
133 struct kref kref;
134 struct list_head list;
135 struct work_struct release_work;
136 struct work_struct shrink_work;
137 struct hlist_node node;
138 char tfm_name[CRYPTO_MAX_ALG_NAME];
139};
140
141/*
142 * struct zswap_entry
143 *
144 * This structure contains the metadata for tracking a single compressed
145 * page within zswap.
146 *
147 * rbnode - links the entry into red-black tree for the appropriate swap type
148 * offset - the swap offset for the entry. Index into the red-black tree.
149 * refcount - the number of outstanding reference to the entry. This is needed
150 * to protect against premature freeing of the entry by code
151 * concurrent calls to load, invalidate, and writeback. The lock
152 * for the zswap_tree structure that contains the entry must
153 * be held while changing the refcount. Since the lock must
154 * be held, there is no reason to also make refcount atomic.
155 * length - the length in bytes of the compressed page data. Needed during
156 * decompression. For a same value filled page length is 0.
157 * pool - the zswap_pool the entry's data is in
158 * handle - zpool allocation handle that stores the compressed page data
159 * value - value of the same-value filled pages which have same content
160 */
161struct zswap_entry {
162 struct rb_node rbnode;
163 pgoff_t offset;
164 int refcount;
165 unsigned int length;
166 struct zswap_pool *pool;
167 union {
168 unsigned long handle;
169 unsigned long value;
170 };
171};
172
173struct zswap_header {
174 swp_entry_t swpentry;
175};
176
177/*
178 * The tree lock in the zswap_tree struct protects a few things:
179 * - the rbtree
180 * - the refcount field of each entry in the tree
181 */
182struct zswap_tree {
183 struct rb_root rbroot;
184 spinlock_t lock;
185};
186
187static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
188
189/* RCU-protected iteration */
190static LIST_HEAD(zswap_pools);
191/* protects zswap_pools list modification */
192static DEFINE_SPINLOCK(zswap_pools_lock);
193/* pool counter to provide unique names to zpool */
194static atomic_t zswap_pools_count = ATOMIC_INIT(0);
195
196/* used by param callback function */
197static bool zswap_init_started;
198
199/* fatal error during init */
200static bool zswap_init_failed;
201
202/* init completed, but couldn't create the initial pool */
203static bool zswap_has_pool;
204
205/*********************************
206* helpers and fwd declarations
207**********************************/
208
209#define zswap_pool_debug(msg, p) \
210 pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \
211 zpool_get_type((p)->zpool))
212
213static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
214static int zswap_pool_get(struct zswap_pool *pool);
215static void zswap_pool_put(struct zswap_pool *pool);
216
217static const struct zpool_ops zswap_zpool_ops = {
218 .evict = zswap_writeback_entry
219};
220
221static bool zswap_is_full(void)
222{
223 return totalram_pages() * zswap_max_pool_percent / 100 <
224 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
225}
226
227static bool zswap_can_accept(void)
228{
229 return totalram_pages() * zswap_accept_thr_percent / 100 *
230 zswap_max_pool_percent / 100 >
231 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
232}
233
234static void zswap_update_total_size(void)
235{
236 struct zswap_pool *pool;
237 u64 total = 0;
238
239 rcu_read_lock();
240
241 list_for_each_entry_rcu(pool, &zswap_pools, list)
242 total += zpool_get_total_size(pool->zpool);
243
244 rcu_read_unlock();
245
246 zswap_pool_total_size = total;
247}
248
249/*********************************
250* zswap entry functions
251**********************************/
252static struct kmem_cache *zswap_entry_cache;
253
254static int __init zswap_entry_cache_create(void)
255{
256 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
257 return zswap_entry_cache == NULL;
258}
259
260static void __init zswap_entry_cache_destroy(void)
261{
262 kmem_cache_destroy(zswap_entry_cache);
263}
264
265static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
266{
267 struct zswap_entry *entry;
268 entry = kmem_cache_alloc(zswap_entry_cache, gfp);
269 if (!entry)
270 return NULL;
271 entry->refcount = 1;
272 RB_CLEAR_NODE(&entry->rbnode);
273 return entry;
274}
275
276static void zswap_entry_cache_free(struct zswap_entry *entry)
277{
278 kmem_cache_free(zswap_entry_cache, entry);
279}
280
281/*********************************
282* rbtree functions
283**********************************/
284static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
285{
286 struct rb_node *node = root->rb_node;
287 struct zswap_entry *entry;
288
289 while (node) {
290 entry = rb_entry(node, struct zswap_entry, rbnode);
291 if (entry->offset > offset)
292 node = node->rb_left;
293 else if (entry->offset < offset)
294 node = node->rb_right;
295 else
296 return entry;
297 }
298 return NULL;
299}
300
301/*
302 * In the case that a entry with the same offset is found, a pointer to
303 * the existing entry is stored in dupentry and the function returns -EEXIST
304 */
305static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
306 struct zswap_entry **dupentry)
307{
308 struct rb_node **link = &root->rb_node, *parent = NULL;
309 struct zswap_entry *myentry;
310
311 while (*link) {
312 parent = *link;
313 myentry = rb_entry(parent, struct zswap_entry, rbnode);
314 if (myentry->offset > entry->offset)
315 link = &(*link)->rb_left;
316 else if (myentry->offset < entry->offset)
317 link = &(*link)->rb_right;
318 else {
319 *dupentry = myentry;
320 return -EEXIST;
321 }
322 }
323 rb_link_node(&entry->rbnode, parent, link);
324 rb_insert_color(&entry->rbnode, root);
325 return 0;
326}
327
328static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
329{
330 if (!RB_EMPTY_NODE(&entry->rbnode)) {
331 rb_erase(&entry->rbnode, root);
332 RB_CLEAR_NODE(&entry->rbnode);
333 }
334}
335
336/*
337 * Carries out the common pattern of freeing and entry's zpool allocation,
338 * freeing the entry itself, and decrementing the number of stored pages.
339 */
340static void zswap_free_entry(struct zswap_entry *entry)
341{
342 if (!entry->length)
343 atomic_dec(&zswap_same_filled_pages);
344 else {
345 zpool_free(entry->pool->zpool, entry->handle);
346 zswap_pool_put(entry->pool);
347 }
348 zswap_entry_cache_free(entry);
349 atomic_dec(&zswap_stored_pages);
350 zswap_update_total_size();
351}
352
353/* caller must hold the tree lock */
354static void zswap_entry_get(struct zswap_entry *entry)
355{
356 entry->refcount++;
357}
358
359/* caller must hold the tree lock
360* remove from the tree and free it, if nobody reference the entry
361*/
362static void zswap_entry_put(struct zswap_tree *tree,
363 struct zswap_entry *entry)
364{
365 int refcount = --entry->refcount;
366
367 BUG_ON(refcount < 0);
368 if (refcount == 0) {
369 zswap_rb_erase(&tree->rbroot, entry);
370 zswap_free_entry(entry);
371 }
372}
373
374/* caller must hold the tree lock */
375static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
376 pgoff_t offset)
377{
378 struct zswap_entry *entry;
379
380 entry = zswap_rb_search(root, offset);
381 if (entry)
382 zswap_entry_get(entry);
383
384 return entry;
385}
386
387/*********************************
388* per-cpu code
389**********************************/
390static DEFINE_PER_CPU(u8 *, zswap_dstmem);
391
392static int zswap_dstmem_prepare(unsigned int cpu)
393{
394 u8 *dst;
395
396 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
397 if (!dst)
398 return -ENOMEM;
399
400 per_cpu(zswap_dstmem, cpu) = dst;
401 return 0;
402}
403
404static int zswap_dstmem_dead(unsigned int cpu)
405{
406 u8 *dst;
407
408 dst = per_cpu(zswap_dstmem, cpu);
409 kfree(dst);
410 per_cpu(zswap_dstmem, cpu) = NULL;
411
412 return 0;
413}
414
415static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
416{
417 struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
418 struct crypto_comp *tfm;
419
420 if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
421 return 0;
422
423 tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
424 if (IS_ERR_OR_NULL(tfm)) {
425 pr_err("could not alloc crypto comp %s : %ld\n",
426 pool->tfm_name, PTR_ERR(tfm));
427 return -ENOMEM;
428 }
429 *per_cpu_ptr(pool->tfm, cpu) = tfm;
430 return 0;
431}
432
433static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
434{
435 struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
436 struct crypto_comp *tfm;
437
438 tfm = *per_cpu_ptr(pool->tfm, cpu);
439 if (!IS_ERR_OR_NULL(tfm))
440 crypto_free_comp(tfm);
441 *per_cpu_ptr(pool->tfm, cpu) = NULL;
442 return 0;
443}
444
445/*********************************
446* pool functions
447**********************************/
448
449static struct zswap_pool *__zswap_pool_current(void)
450{
451 struct zswap_pool *pool;
452
453 pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
454 WARN_ONCE(!pool && zswap_has_pool,
455 "%s: no page storage pool!\n", __func__);
456
457 return pool;
458}
459
460static struct zswap_pool *zswap_pool_current(void)
461{
462 assert_spin_locked(&zswap_pools_lock);
463
464 return __zswap_pool_current();
465}
466
467static struct zswap_pool *zswap_pool_current_get(void)
468{
469 struct zswap_pool *pool;
470
471 rcu_read_lock();
472
473 pool = __zswap_pool_current();
474 if (!zswap_pool_get(pool))
475 pool = NULL;
476
477 rcu_read_unlock();
478
479 return pool;
480}
481
482static struct zswap_pool *zswap_pool_last_get(void)
483{
484 struct zswap_pool *pool, *last = NULL;
485
486 rcu_read_lock();
487
488 list_for_each_entry_rcu(pool, &zswap_pools, list)
489 last = pool;
490 WARN_ONCE(!last && zswap_has_pool,
491 "%s: no page storage pool!\n", __func__);
492 if (!zswap_pool_get(last))
493 last = NULL;
494
495 rcu_read_unlock();
496
497 return last;
498}
499
500/* type and compressor must be null-terminated */
501static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
502{
503 struct zswap_pool *pool;
504
505 assert_spin_locked(&zswap_pools_lock);
506
507 list_for_each_entry_rcu(pool, &zswap_pools, list) {
508 if (strcmp(pool->tfm_name, compressor))
509 continue;
510 if (strcmp(zpool_get_type(pool->zpool), type))
511 continue;
512 /* if we can't get it, it's about to be destroyed */
513 if (!zswap_pool_get(pool))
514 continue;
515 return pool;
516 }
517
518 return NULL;
519}
520
521static void shrink_worker(struct work_struct *w)
522{
523 struct zswap_pool *pool = container_of(w, typeof(*pool),
524 shrink_work);
525
526 if (zpool_shrink(pool->zpool, 1, NULL))
527 zswap_reject_reclaim_fail++;
528 zswap_pool_put(pool);
529}
530
531static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
532{
533 struct zswap_pool *pool;
534 char name[38]; /* 'zswap' + 32 char (max) num + \0 */
535 gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
536 int ret;
537
538 if (!zswap_has_pool) {
539 /* if either are unset, pool initialization failed, and we
540 * need both params to be set correctly before trying to
541 * create a pool.
542 */
543 if (!strcmp(type, ZSWAP_PARAM_UNSET))
544 return NULL;
545 if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
546 return NULL;
547 }
548
549 pool = kzalloc(sizeof(*pool), GFP_KERNEL);
550 if (!pool)
551 return NULL;
552
553 /* unique name for each pool specifically required by zsmalloc */
554 snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
555
556 pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
557 if (!pool->zpool) {
558 pr_err("%s zpool not available\n", type);
559 goto error;
560 }
561 pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
562
563 strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
564 pool->tfm = alloc_percpu(struct crypto_comp *);
565 if (!pool->tfm) {
566 pr_err("percpu alloc failed\n");
567 goto error;
568 }
569
570 ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
571 &pool->node);
572 if (ret)
573 goto error;
574 pr_debug("using %s compressor\n", pool->tfm_name);
575
576 /* being the current pool takes 1 ref; this func expects the
577 * caller to always add the new pool as the current pool
578 */
579 kref_init(&pool->kref);
580 INIT_LIST_HEAD(&pool->list);
581 INIT_WORK(&pool->shrink_work, shrink_worker);
582
583 zswap_pool_debug("created", pool);
584
585 return pool;
586
587error:
588 free_percpu(pool->tfm);
589 if (pool->zpool)
590 zpool_destroy_pool(pool->zpool);
591 kfree(pool);
592 return NULL;
593}
594
595static __init struct zswap_pool *__zswap_pool_create_fallback(void)
596{
597 bool has_comp, has_zpool;
598
599 has_comp = crypto_has_comp(zswap_compressor, 0, 0);
600 if (!has_comp && strcmp(zswap_compressor,
601 CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
602 pr_err("compressor %s not available, using default %s\n",
603 zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
604 param_free_charp(&zswap_compressor);
605 zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
606 has_comp = crypto_has_comp(zswap_compressor, 0, 0);
607 }
608 if (!has_comp) {
609 pr_err("default compressor %s not available\n",
610 zswap_compressor);
611 param_free_charp(&zswap_compressor);
612 zswap_compressor = ZSWAP_PARAM_UNSET;
613 }
614
615 has_zpool = zpool_has_pool(zswap_zpool_type);
616 if (!has_zpool && strcmp(zswap_zpool_type,
617 CONFIG_ZSWAP_ZPOOL_DEFAULT)) {
618 pr_err("zpool %s not available, using default %s\n",
619 zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);
620 param_free_charp(&zswap_zpool_type);
621 zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
622 has_zpool = zpool_has_pool(zswap_zpool_type);
623 }
624 if (!has_zpool) {
625 pr_err("default zpool %s not available\n",
626 zswap_zpool_type);
627 param_free_charp(&zswap_zpool_type);
628 zswap_zpool_type = ZSWAP_PARAM_UNSET;
629 }
630
631 if (!has_comp || !has_zpool)
632 return NULL;
633
634 return zswap_pool_create(zswap_zpool_type, zswap_compressor);
635}
636
637static void zswap_pool_destroy(struct zswap_pool *pool)
638{
639 zswap_pool_debug("destroying", pool);
640
641 cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
642 free_percpu(pool->tfm);
643 zpool_destroy_pool(pool->zpool);
644 kfree(pool);
645}
646
647static int __must_check zswap_pool_get(struct zswap_pool *pool)
648{
649 if (!pool)
650 return 0;
651
652 return kref_get_unless_zero(&pool->kref);
653}
654
655static void __zswap_pool_release(struct work_struct *work)
656{
657 struct zswap_pool *pool = container_of(work, typeof(*pool),
658 release_work);
659
660 synchronize_rcu();
661
662 /* nobody should have been able to get a kref... */
663 WARN_ON(kref_get_unless_zero(&pool->kref));
664
665 /* pool is now off zswap_pools list and has no references. */
666 zswap_pool_destroy(pool);
667}
668
669static void __zswap_pool_empty(struct kref *kref)
670{
671 struct zswap_pool *pool;
672
673 pool = container_of(kref, typeof(*pool), kref);
674
675 spin_lock(&zswap_pools_lock);
676
677 WARN_ON(pool == zswap_pool_current());
678
679 list_del_rcu(&pool->list);
680
681 INIT_WORK(&pool->release_work, __zswap_pool_release);
682 schedule_work(&pool->release_work);
683
684 spin_unlock(&zswap_pools_lock);
685}
686
687static void zswap_pool_put(struct zswap_pool *pool)
688{
689 kref_put(&pool->kref, __zswap_pool_empty);
690}
691
692/*********************************
693* param callbacks
694**********************************/
695
696/* val must be a null-terminated string */
697static int __zswap_param_set(const char *val, const struct kernel_param *kp,
698 char *type, char *compressor)
699{
700 struct zswap_pool *pool, *put_pool = NULL;
701 char *s = strstrip((char *)val);
702 int ret;
703
704 if (zswap_init_failed) {
705 pr_err("can't set param, initialization failed\n");
706 return -ENODEV;
707 }
708
709 /* no change required */
710 if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
711 return 0;
712
713 /* if this is load-time (pre-init) param setting,
714 * don't create a pool; that's done during init.
715 */
716 if (!zswap_init_started)
717 return param_set_charp(s, kp);
718
719 if (!type) {
720 if (!zpool_has_pool(s)) {
721 pr_err("zpool %s not available\n", s);
722 return -ENOENT;
723 }
724 type = s;
725 } else if (!compressor) {
726 if (!crypto_has_comp(s, 0, 0)) {
727 pr_err("compressor %s not available\n", s);
728 return -ENOENT;
729 }
730 compressor = s;
731 } else {
732 WARN_ON(1);
733 return -EINVAL;
734 }
735
736 spin_lock(&zswap_pools_lock);
737
738 pool = zswap_pool_find_get(type, compressor);
739 if (pool) {
740 zswap_pool_debug("using existing", pool);
741 WARN_ON(pool == zswap_pool_current());
742 list_del_rcu(&pool->list);
743 }
744
745 spin_unlock(&zswap_pools_lock);
746
747 if (!pool)
748 pool = zswap_pool_create(type, compressor);
749
750 if (pool)
751 ret = param_set_charp(s, kp);
752 else
753 ret = -EINVAL;
754
755 spin_lock(&zswap_pools_lock);
756
757 if (!ret) {
758 put_pool = zswap_pool_current();
759 list_add_rcu(&pool->list, &zswap_pools);
760 zswap_has_pool = true;
761 } else if (pool) {
762 /* add the possibly pre-existing pool to the end of the pools
763 * list; if it's new (and empty) then it'll be removed and
764 * destroyed by the put after we drop the lock
765 */
766 list_add_tail_rcu(&pool->list, &zswap_pools);
767 put_pool = pool;
768 }
769
770 spin_unlock(&zswap_pools_lock);
771
772 if (!zswap_has_pool && !pool) {
773 /* if initial pool creation failed, and this pool creation also
774 * failed, maybe both compressor and zpool params were bad.
775 * Allow changing this param, so pool creation will succeed
776 * when the other param is changed. We already verified this
777 * param is ok in the zpool_has_pool() or crypto_has_comp()
778 * checks above.
779 */
780 ret = param_set_charp(s, kp);
781 }
782
783 /* drop the ref from either the old current pool,
784 * or the new pool we failed to add
785 */
786 if (put_pool)
787 zswap_pool_put(put_pool);
788
789 return ret;
790}
791
792static int zswap_compressor_param_set(const char *val,
793 const struct kernel_param *kp)
794{
795 return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
796}
797
798static int zswap_zpool_param_set(const char *val,
799 const struct kernel_param *kp)
800{
801 return __zswap_param_set(val, kp, NULL, zswap_compressor);
802}
803
804static int zswap_enabled_param_set(const char *val,
805 const struct kernel_param *kp)
806{
807 if (zswap_init_failed) {
808 pr_err("can't enable, initialization failed\n");
809 return -ENODEV;
810 }
811 if (!zswap_has_pool && zswap_init_started) {
812 pr_err("can't enable, no pool configured\n");
813 return -ENODEV;
814 }
815
816 return param_set_bool(val, kp);
817}
818
819/*********************************
820* writeback code
821**********************************/
822/* return enum for zswap_get_swap_cache_page */
823enum zswap_get_swap_ret {
824 ZSWAP_SWAPCACHE_NEW,
825 ZSWAP_SWAPCACHE_EXIST,
826 ZSWAP_SWAPCACHE_FAIL,
827};
828
829/*
830 * zswap_get_swap_cache_page
831 *
832 * This is an adaption of read_swap_cache_async()
833 *
834 * This function tries to find a page with the given swap entry
835 * in the swapper_space address space (the swap cache). If the page
836 * is found, it is returned in retpage. Otherwise, a page is allocated,
837 * added to the swap cache, and returned in retpage.
838 *
839 * If success, the swap cache page is returned in retpage
840 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
841 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
842 * the new page is added to swapcache and locked
843 * Returns ZSWAP_SWAPCACHE_FAIL on error
844 */
845static int zswap_get_swap_cache_page(swp_entry_t entry,
846 struct page **retpage)
847{
848 bool page_was_allocated;
849
850 *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
851 NULL, 0, &page_was_allocated);
852 if (page_was_allocated)
853 return ZSWAP_SWAPCACHE_NEW;
854 if (!*retpage)
855 return ZSWAP_SWAPCACHE_FAIL;
856 return ZSWAP_SWAPCACHE_EXIST;
857}
858
859/*
860 * Attempts to free an entry by adding a page to the swap cache,
861 * decompressing the entry data into the page, and issuing a
862 * bio write to write the page back to the swap device.
863 *
864 * This can be thought of as a "resumed writeback" of the page
865 * to the swap device. We are basically resuming the same swap
866 * writeback path that was intercepted with the frontswap_store()
867 * in the first place. After the page has been decompressed into
868 * the swap cache, the compressed version stored by zswap can be
869 * freed.
870 */
871static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
872{
873 struct zswap_header *zhdr;
874 swp_entry_t swpentry;
875 struct zswap_tree *tree;
876 pgoff_t offset;
877 struct zswap_entry *entry;
878 struct page *page;
879 struct crypto_comp *tfm;
880 u8 *src, *dst;
881 unsigned int dlen;
882 int ret;
883 struct writeback_control wbc = {
884 .sync_mode = WB_SYNC_NONE,
885 };
886
887 /* extract swpentry from data */
888 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
889 swpentry = zhdr->swpentry; /* here */
890 tree = zswap_trees[swp_type(swpentry)];
891 offset = swp_offset(swpentry);
892
893 /* find and ref zswap entry */
894 spin_lock(&tree->lock);
895 entry = zswap_entry_find_get(&tree->rbroot, offset);
896 if (!entry) {
897 /* entry was invalidated */
898 spin_unlock(&tree->lock);
899 zpool_unmap_handle(pool, handle);
900 return 0;
901 }
902 spin_unlock(&tree->lock);
903 BUG_ON(offset != entry->offset);
904
905 /* try to allocate swap cache page */
906 switch (zswap_get_swap_cache_page(swpentry, &page)) {
907 case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
908 ret = -ENOMEM;
909 goto fail;
910
911 case ZSWAP_SWAPCACHE_EXIST:
912 /* page is already in the swap cache, ignore for now */
913 put_page(page);
914 ret = -EEXIST;
915 goto fail;
916
917 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
918 /* decompress */
919 dlen = PAGE_SIZE;
920 src = (u8 *)zhdr + sizeof(struct zswap_header);
921 dst = kmap_atomic(page);
922 tfm = *get_cpu_ptr(entry->pool->tfm);
923 ret = crypto_comp_decompress(tfm, src, entry->length,
924 dst, &dlen);
925 put_cpu_ptr(entry->pool->tfm);
926 kunmap_atomic(dst);
927 BUG_ON(ret);
928 BUG_ON(dlen != PAGE_SIZE);
929
930 /* page is up to date */
931 SetPageUptodate(page);
932 }
933
934 /* move it to the tail of the inactive list after end_writeback */
935 SetPageReclaim(page);
936
937 /* start writeback */
938 __swap_writepage(page, &wbc, end_swap_bio_write);
939 put_page(page);
940 zswap_written_back_pages++;
941
942 spin_lock(&tree->lock);
943 /* drop local reference */
944 zswap_entry_put(tree, entry);
945
946 /*
947 * There are two possible situations for entry here:
948 * (1) refcount is 1(normal case), entry is valid and on the tree
949 * (2) refcount is 0, entry is freed and not on the tree
950 * because invalidate happened during writeback
951 * search the tree and free the entry if find entry
952 */
953 if (entry == zswap_rb_search(&tree->rbroot, offset))
954 zswap_entry_put(tree, entry);
955 spin_unlock(&tree->lock);
956
957 goto end;
958
959 /*
960 * if we get here due to ZSWAP_SWAPCACHE_EXIST
961 * a load may happening concurrently
962 * it is safe and okay to not free the entry
963 * if we free the entry in the following put
964 * it it either okay to return !0
965 */
966fail:
967 spin_lock(&tree->lock);
968 zswap_entry_put(tree, entry);
969 spin_unlock(&tree->lock);
970
971end:
972 zpool_unmap_handle(pool, handle);
973 return ret;
974}
975
976static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
977{
978 unsigned int pos;
979 unsigned long *page;
980
981 page = (unsigned long *)ptr;
982 for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
983 if (page[pos] != page[0])
984 return 0;
985 }
986 *value = page[0];
987 return 1;
988}
989
990static void zswap_fill_page(void *ptr, unsigned long value)
991{
992 unsigned long *page;
993
994 page = (unsigned long *)ptr;
995 memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
996}
997
998/*********************************
999* frontswap hooks
1000**********************************/
1001/* attempts to compress and store an single page */
1002static int zswap_frontswap_store(unsigned type, pgoff_t offset,
1003 struct page *page)
1004{
1005 struct zswap_tree *tree = zswap_trees[type];
1006 struct zswap_entry *entry, *dupentry;
1007 struct crypto_comp *tfm;
1008 int ret;
1009 unsigned int hlen, dlen = PAGE_SIZE;
1010 unsigned long handle, value;
1011 char *buf;
1012 u8 *src, *dst;
1013 struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
1014 gfp_t gfp;
1015
1016 /* THP isn't supported */
1017 if (PageTransHuge(page)) {
1018 ret = -EINVAL;
1019 goto reject;
1020 }
1021
1022 if (!zswap_enabled || !tree) {
1023 ret = -ENODEV;
1024 goto reject;
1025 }
1026
1027 /* reclaim space if needed */
1028 if (zswap_is_full()) {
1029 struct zswap_pool *pool;
1030
1031 zswap_pool_limit_hit++;
1032 zswap_pool_reached_full = true;
1033 pool = zswap_pool_last_get();
1034 if (pool)
1035 queue_work(shrink_wq, &pool->shrink_work);
1036 ret = -ENOMEM;
1037 goto reject;
1038 }
1039
1040 if (zswap_pool_reached_full) {
1041 if (!zswap_can_accept()) {
1042 ret = -ENOMEM;
1043 goto reject;
1044 } else
1045 zswap_pool_reached_full = false;
1046 }
1047
1048 /* allocate entry */
1049 entry = zswap_entry_cache_alloc(GFP_KERNEL);
1050 if (!entry) {
1051 zswap_reject_kmemcache_fail++;
1052 ret = -ENOMEM;
1053 goto reject;
1054 }
1055
1056 if (zswap_same_filled_pages_enabled) {
1057 src = kmap_atomic(page);
1058 if (zswap_is_page_same_filled(src, &value)) {
1059 kunmap_atomic(src);
1060 entry->offset = offset;
1061 entry->length = 0;
1062 entry->value = value;
1063 atomic_inc(&zswap_same_filled_pages);
1064 goto insert_entry;
1065 }
1066 kunmap_atomic(src);
1067 }
1068
1069 /* if entry is successfully added, it keeps the reference */
1070 entry->pool = zswap_pool_current_get();
1071 if (!entry->pool) {
1072 ret = -EINVAL;
1073 goto freepage;
1074 }
1075
1076 /* compress */
1077 dst = get_cpu_var(zswap_dstmem);
1078 tfm = *get_cpu_ptr(entry->pool->tfm);
1079 src = kmap_atomic(page);
1080 ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
1081 kunmap_atomic(src);
1082 put_cpu_ptr(entry->pool->tfm);
1083 if (ret) {
1084 ret = -EINVAL;
1085 goto put_dstmem;
1086 }
1087
1088 /* store */
1089 hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
1090 gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
1091 if (zpool_malloc_support_movable(entry->pool->zpool))
1092 gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
1093 ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle);
1094 if (ret == -ENOSPC) {
1095 zswap_reject_compress_poor++;
1096 goto put_dstmem;
1097 }
1098 if (ret) {
1099 zswap_reject_alloc_fail++;
1100 goto put_dstmem;
1101 }
1102 buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
1103 memcpy(buf, &zhdr, hlen);
1104 memcpy(buf + hlen, dst, dlen);
1105 zpool_unmap_handle(entry->pool->zpool, handle);
1106 put_cpu_var(zswap_dstmem);
1107
1108 /* populate entry */
1109 entry->offset = offset;
1110 entry->handle = handle;
1111 entry->length = dlen;
1112
1113insert_entry:
1114 /* map */
1115 spin_lock(&tree->lock);
1116 do {
1117 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1118 if (ret == -EEXIST) {
1119 zswap_duplicate_entry++;
1120 /* remove from rbtree */
1121 zswap_rb_erase(&tree->rbroot, dupentry);
1122 zswap_entry_put(tree, dupentry);
1123 }
1124 } while (ret == -EEXIST);
1125 spin_unlock(&tree->lock);
1126
1127 /* update stats */
1128 atomic_inc(&zswap_stored_pages);
1129 zswap_update_total_size();
1130
1131 return 0;
1132
1133put_dstmem:
1134 put_cpu_var(zswap_dstmem);
1135 zswap_pool_put(entry->pool);
1136freepage:
1137 zswap_entry_cache_free(entry);
1138reject:
1139 return ret;
1140}
1141
1142/*
1143 * returns 0 if the page was successfully decompressed
1144 * return -1 on entry not found or error
1145*/
1146static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1147 struct page *page)
1148{
1149 struct zswap_tree *tree = zswap_trees[type];
1150 struct zswap_entry *entry;
1151 struct crypto_comp *tfm;
1152 u8 *src, *dst;
1153 unsigned int dlen;
1154 int ret;
1155
1156 /* find */
1157 spin_lock(&tree->lock);
1158 entry = zswap_entry_find_get(&tree->rbroot, offset);
1159 if (!entry) {
1160 /* entry was written back */
1161 spin_unlock(&tree->lock);
1162 return -1;
1163 }
1164 spin_unlock(&tree->lock);
1165
1166 if (!entry->length) {
1167 dst = kmap_atomic(page);
1168 zswap_fill_page(dst, entry->value);
1169 kunmap_atomic(dst);
1170 goto freeentry;
1171 }
1172
1173 /* decompress */
1174 dlen = PAGE_SIZE;
1175 src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
1176 if (zpool_evictable(entry->pool->zpool))
1177 src += sizeof(struct zswap_header);
1178 dst = kmap_atomic(page);
1179 tfm = *get_cpu_ptr(entry->pool->tfm);
1180 ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
1181 put_cpu_ptr(entry->pool->tfm);
1182 kunmap_atomic(dst);
1183 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1184 BUG_ON(ret);
1185
1186freeentry:
1187 spin_lock(&tree->lock);
1188 zswap_entry_put(tree, entry);
1189 spin_unlock(&tree->lock);
1190
1191 return 0;
1192}
1193
1194/* frees an entry in zswap */
1195static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1196{
1197 struct zswap_tree *tree = zswap_trees[type];
1198 struct zswap_entry *entry;
1199
1200 /* find */
1201 spin_lock(&tree->lock);
1202 entry = zswap_rb_search(&tree->rbroot, offset);
1203 if (!entry) {
1204 /* entry was written back */
1205 spin_unlock(&tree->lock);
1206 return;
1207 }
1208
1209 /* remove from rbtree */
1210 zswap_rb_erase(&tree->rbroot, entry);
1211
1212 /* drop the initial reference from entry creation */
1213 zswap_entry_put(tree, entry);
1214
1215 spin_unlock(&tree->lock);
1216}
1217
1218/* frees all zswap entries for the given swap type */
1219static void zswap_frontswap_invalidate_area(unsigned type)
1220{
1221 struct zswap_tree *tree = zswap_trees[type];
1222 struct zswap_entry *entry, *n;
1223
1224 if (!tree)
1225 return;
1226
1227 /* walk the tree and free everything */
1228 spin_lock(&tree->lock);
1229 rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1230 zswap_free_entry(entry);
1231 tree->rbroot = RB_ROOT;
1232 spin_unlock(&tree->lock);
1233 kfree(tree);
1234 zswap_trees[type] = NULL;
1235}
1236
1237static void zswap_frontswap_init(unsigned type)
1238{
1239 struct zswap_tree *tree;
1240
1241 tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1242 if (!tree) {
1243 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1244 return;
1245 }
1246
1247 tree->rbroot = RB_ROOT;
1248 spin_lock_init(&tree->lock);
1249 zswap_trees[type] = tree;
1250}
1251
1252static struct frontswap_ops zswap_frontswap_ops = {
1253 .store = zswap_frontswap_store,
1254 .load = zswap_frontswap_load,
1255 .invalidate_page = zswap_frontswap_invalidate_page,
1256 .invalidate_area = zswap_frontswap_invalidate_area,
1257 .init = zswap_frontswap_init
1258};
1259
1260/*********************************
1261* debugfs functions
1262**********************************/
1263#ifdef CONFIG_DEBUG_FS
1264#include <linux/debugfs.h>
1265
1266static struct dentry *zswap_debugfs_root;
1267
1268static int __init zswap_debugfs_init(void)
1269{
1270 if (!debugfs_initialized())
1271 return -ENODEV;
1272
1273 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1274
1275 debugfs_create_u64("pool_limit_hit", 0444,
1276 zswap_debugfs_root, &zswap_pool_limit_hit);
1277 debugfs_create_u64("reject_reclaim_fail", 0444,
1278 zswap_debugfs_root, &zswap_reject_reclaim_fail);
1279 debugfs_create_u64("reject_alloc_fail", 0444,
1280 zswap_debugfs_root, &zswap_reject_alloc_fail);
1281 debugfs_create_u64("reject_kmemcache_fail", 0444,
1282 zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1283 debugfs_create_u64("reject_compress_poor", 0444,
1284 zswap_debugfs_root, &zswap_reject_compress_poor);
1285 debugfs_create_u64("written_back_pages", 0444,
1286 zswap_debugfs_root, &zswap_written_back_pages);
1287 debugfs_create_u64("duplicate_entry", 0444,
1288 zswap_debugfs_root, &zswap_duplicate_entry);
1289 debugfs_create_u64("pool_total_size", 0444,
1290 zswap_debugfs_root, &zswap_pool_total_size);
1291 debugfs_create_atomic_t("stored_pages", 0444,
1292 zswap_debugfs_root, &zswap_stored_pages);
1293 debugfs_create_atomic_t("same_filled_pages", 0444,
1294 zswap_debugfs_root, &zswap_same_filled_pages);
1295
1296 return 0;
1297}
1298
1299static void __exit zswap_debugfs_exit(void)
1300{
1301 debugfs_remove_recursive(zswap_debugfs_root);
1302}
1303#else
1304static int __init zswap_debugfs_init(void)
1305{
1306 return 0;
1307}
1308
1309static void __exit zswap_debugfs_exit(void) { }
1310#endif
1311
1312/*********************************
1313* module init and exit
1314**********************************/
1315static int __init init_zswap(void)
1316{
1317 struct zswap_pool *pool;
1318 int ret;
1319
1320 zswap_init_started = true;
1321
1322 if (zswap_entry_cache_create()) {
1323 pr_err("entry cache creation failed\n");
1324 goto cache_fail;
1325 }
1326
1327 ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1328 zswap_dstmem_prepare, zswap_dstmem_dead);
1329 if (ret) {
1330 pr_err("dstmem alloc failed\n");
1331 goto dstmem_fail;
1332 }
1333
1334 ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1335 "mm/zswap_pool:prepare",
1336 zswap_cpu_comp_prepare,
1337 zswap_cpu_comp_dead);
1338 if (ret)
1339 goto hp_fail;
1340
1341 pool = __zswap_pool_create_fallback();
1342 if (pool) {
1343 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1344 zpool_get_type(pool->zpool));
1345 list_add(&pool->list, &zswap_pools);
1346 zswap_has_pool = true;
1347 } else {
1348 pr_err("pool creation failed\n");
1349 zswap_enabled = false;
1350 }
1351
1352 shrink_wq = create_workqueue("zswap-shrink");
1353 if (!shrink_wq)
1354 goto fallback_fail;
1355
1356 frontswap_register_ops(&zswap_frontswap_ops);
1357 if (zswap_debugfs_init())
1358 pr_warn("debugfs initialization failed\n");
1359 return 0;
1360
1361fallback_fail:
1362 if (pool)
1363 zswap_pool_destroy(pool);
1364hp_fail:
1365 cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1366dstmem_fail:
1367 zswap_entry_cache_destroy();
1368cache_fail:
1369 /* if built-in, we aren't unloaded on failure; don't allow use */
1370 zswap_init_failed = true;
1371 zswap_enabled = false;
1372 return -ENOMEM;
1373}
1374/* must be late so crypto has time to come up */
1375late_initcall(init_zswap);
1376
1377MODULE_LICENSE("GPL");
1378MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1379MODULE_DESCRIPTION("Compressed cache for swap pages");
1/*
2 * zswap.c - zswap driver file
3 *
4 * zswap is a backend for frontswap that takes pages that are in the process
5 * of being swapped out and attempts to compress and store them in a
6 * RAM-based memory pool. This can result in a significant I/O reduction on
7 * the swap device and, in the case where decompressing from RAM is faster
8 * than reading from the swap device, can also improve workload performance.
9 *
10 * Copyright (C) 2012 Seth Jennings <sjenning@linux.vnet.ibm.com>
11 *
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation; either version 2
15 * of the License, or (at your option) any later version.
16 *
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
21*/
22
23#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
24
25#include <linux/module.h>
26#include <linux/cpu.h>
27#include <linux/highmem.h>
28#include <linux/slab.h>
29#include <linux/spinlock.h>
30#include <linux/types.h>
31#include <linux/atomic.h>
32#include <linux/frontswap.h>
33#include <linux/rbtree.h>
34#include <linux/swap.h>
35#include <linux/crypto.h>
36#include <linux/mempool.h>
37#include <linux/zbud.h>
38
39#include <linux/mm_types.h>
40#include <linux/page-flags.h>
41#include <linux/swapops.h>
42#include <linux/writeback.h>
43#include <linux/pagemap.h>
44
45/*********************************
46* statistics
47**********************************/
48/* Number of memory pages used by the compressed pool */
49static u64 zswap_pool_pages;
50/* The number of compressed pages currently stored in zswap */
51static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
52
53/*
54 * The statistics below are not protected from concurrent access for
55 * performance reasons so they may not be a 100% accurate. However,
56 * they do provide useful information on roughly how many times a
57 * certain event is occurring.
58*/
59
60/* Pool limit was hit (see zswap_max_pool_percent) */
61static u64 zswap_pool_limit_hit;
62/* Pages written back when pool limit was reached */
63static u64 zswap_written_back_pages;
64/* Store failed due to a reclaim failure after pool limit was reached */
65static u64 zswap_reject_reclaim_fail;
66/* Compressed page was too big for the allocator to (optimally) store */
67static u64 zswap_reject_compress_poor;
68/* Store failed because underlying allocator could not get memory */
69static u64 zswap_reject_alloc_fail;
70/* Store failed because the entry metadata could not be allocated (rare) */
71static u64 zswap_reject_kmemcache_fail;
72/* Duplicate store was encountered (rare) */
73static u64 zswap_duplicate_entry;
74
75/*********************************
76* tunables
77**********************************/
78/* Enable/disable zswap (disabled by default, fixed at boot for now) */
79static bool zswap_enabled __read_mostly;
80module_param_named(enabled, zswap_enabled, bool, 0444);
81
82/* Compressor to be used by zswap (fixed at boot for now) */
83#define ZSWAP_COMPRESSOR_DEFAULT "lzo"
84static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
85module_param_named(compressor, zswap_compressor, charp, 0444);
86
87/* The maximum percentage of memory that the compressed pool can occupy */
88static unsigned int zswap_max_pool_percent = 20;
89module_param_named(max_pool_percent,
90 zswap_max_pool_percent, uint, 0644);
91
92/* zbud_pool is shared by all of zswap backend */
93static struct zbud_pool *zswap_pool;
94
95/*********************************
96* compression functions
97**********************************/
98/* per-cpu compression transforms */
99static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms;
100
101enum comp_op {
102 ZSWAP_COMPOP_COMPRESS,
103 ZSWAP_COMPOP_DECOMPRESS
104};
105
106static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen,
107 u8 *dst, unsigned int *dlen)
108{
109 struct crypto_comp *tfm;
110 int ret;
111
112 tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu());
113 switch (op) {
114 case ZSWAP_COMPOP_COMPRESS:
115 ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
116 break;
117 case ZSWAP_COMPOP_DECOMPRESS:
118 ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
119 break;
120 default:
121 ret = -EINVAL;
122 }
123
124 put_cpu();
125 return ret;
126}
127
128static int __init zswap_comp_init(void)
129{
130 if (!crypto_has_comp(zswap_compressor, 0, 0)) {
131 pr_info("%s compressor not available\n", zswap_compressor);
132 /* fall back to default compressor */
133 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
134 if (!crypto_has_comp(zswap_compressor, 0, 0))
135 /* can't even load the default compressor */
136 return -ENODEV;
137 }
138 pr_info("using %s compressor\n", zswap_compressor);
139
140 /* alloc percpu transforms */
141 zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
142 if (!zswap_comp_pcpu_tfms)
143 return -ENOMEM;
144 return 0;
145}
146
147static void zswap_comp_exit(void)
148{
149 /* free percpu transforms */
150 if (zswap_comp_pcpu_tfms)
151 free_percpu(zswap_comp_pcpu_tfms);
152}
153
154/*********************************
155* data structures
156**********************************/
157/*
158 * struct zswap_entry
159 *
160 * This structure contains the metadata for tracking a single compressed
161 * page within zswap.
162 *
163 * rbnode - links the entry into red-black tree for the appropriate swap type
164 * refcount - the number of outstanding reference to the entry. This is needed
165 * to protect against premature freeing of the entry by code
166 * concurrent calls to load, invalidate, and writeback. The lock
167 * for the zswap_tree structure that contains the entry must
168 * be held while changing the refcount. Since the lock must
169 * be held, there is no reason to also make refcount atomic.
170 * offset - the swap offset for the entry. Index into the red-black tree.
171 * handle - zbud allocation handle that stores the compressed page data
172 * length - the length in bytes of the compressed page data. Needed during
173 * decompression
174 */
175struct zswap_entry {
176 struct rb_node rbnode;
177 pgoff_t offset;
178 int refcount;
179 unsigned int length;
180 unsigned long handle;
181};
182
183struct zswap_header {
184 swp_entry_t swpentry;
185};
186
187/*
188 * The tree lock in the zswap_tree struct protects a few things:
189 * - the rbtree
190 * - the refcount field of each entry in the tree
191 */
192struct zswap_tree {
193 struct rb_root rbroot;
194 spinlock_t lock;
195};
196
197static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
198
199/*********************************
200* zswap entry functions
201**********************************/
202static struct kmem_cache *zswap_entry_cache;
203
204static int zswap_entry_cache_create(void)
205{
206 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
207 return zswap_entry_cache == NULL;
208}
209
210static void zswap_entry_cache_destory(void)
211{
212 kmem_cache_destroy(zswap_entry_cache);
213}
214
215static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
216{
217 struct zswap_entry *entry;
218 entry = kmem_cache_alloc(zswap_entry_cache, gfp);
219 if (!entry)
220 return NULL;
221 entry->refcount = 1;
222 RB_CLEAR_NODE(&entry->rbnode);
223 return entry;
224}
225
226static void zswap_entry_cache_free(struct zswap_entry *entry)
227{
228 kmem_cache_free(zswap_entry_cache, entry);
229}
230
231/*********************************
232* rbtree functions
233**********************************/
234static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
235{
236 struct rb_node *node = root->rb_node;
237 struct zswap_entry *entry;
238
239 while (node) {
240 entry = rb_entry(node, struct zswap_entry, rbnode);
241 if (entry->offset > offset)
242 node = node->rb_left;
243 else if (entry->offset < offset)
244 node = node->rb_right;
245 else
246 return entry;
247 }
248 return NULL;
249}
250
251/*
252 * In the case that a entry with the same offset is found, a pointer to
253 * the existing entry is stored in dupentry and the function returns -EEXIST
254 */
255static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
256 struct zswap_entry **dupentry)
257{
258 struct rb_node **link = &root->rb_node, *parent = NULL;
259 struct zswap_entry *myentry;
260
261 while (*link) {
262 parent = *link;
263 myentry = rb_entry(parent, struct zswap_entry, rbnode);
264 if (myentry->offset > entry->offset)
265 link = &(*link)->rb_left;
266 else if (myentry->offset < entry->offset)
267 link = &(*link)->rb_right;
268 else {
269 *dupentry = myentry;
270 return -EEXIST;
271 }
272 }
273 rb_link_node(&entry->rbnode, parent, link);
274 rb_insert_color(&entry->rbnode, root);
275 return 0;
276}
277
278static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
279{
280 if (!RB_EMPTY_NODE(&entry->rbnode)) {
281 rb_erase(&entry->rbnode, root);
282 RB_CLEAR_NODE(&entry->rbnode);
283 }
284}
285
286/*
287 * Carries out the common pattern of freeing and entry's zbud allocation,
288 * freeing the entry itself, and decrementing the number of stored pages.
289 */
290static void zswap_free_entry(struct zswap_entry *entry)
291{
292 zbud_free(zswap_pool, entry->handle);
293 zswap_entry_cache_free(entry);
294 atomic_dec(&zswap_stored_pages);
295 zswap_pool_pages = zbud_get_pool_size(zswap_pool);
296}
297
298/* caller must hold the tree lock */
299static void zswap_entry_get(struct zswap_entry *entry)
300{
301 entry->refcount++;
302}
303
304/* caller must hold the tree lock
305* remove from the tree and free it, if nobody reference the entry
306*/
307static void zswap_entry_put(struct zswap_tree *tree,
308 struct zswap_entry *entry)
309{
310 int refcount = --entry->refcount;
311
312 BUG_ON(refcount < 0);
313 if (refcount == 0) {
314 zswap_rb_erase(&tree->rbroot, entry);
315 zswap_free_entry(entry);
316 }
317}
318
319/* caller must hold the tree lock */
320static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
321 pgoff_t offset)
322{
323 struct zswap_entry *entry = NULL;
324
325 entry = zswap_rb_search(root, offset);
326 if (entry)
327 zswap_entry_get(entry);
328
329 return entry;
330}
331
332/*********************************
333* per-cpu code
334**********************************/
335static DEFINE_PER_CPU(u8 *, zswap_dstmem);
336
337static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu)
338{
339 struct crypto_comp *tfm;
340 u8 *dst;
341
342 switch (action) {
343 case CPU_UP_PREPARE:
344 tfm = crypto_alloc_comp(zswap_compressor, 0, 0);
345 if (IS_ERR(tfm)) {
346 pr_err("can't allocate compressor transform\n");
347 return NOTIFY_BAD;
348 }
349 *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm;
350 dst = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
351 if (!dst) {
352 pr_err("can't allocate compressor buffer\n");
353 crypto_free_comp(tfm);
354 *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
355 return NOTIFY_BAD;
356 }
357 per_cpu(zswap_dstmem, cpu) = dst;
358 break;
359 case CPU_DEAD:
360 case CPU_UP_CANCELED:
361 tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu);
362 if (tfm) {
363 crypto_free_comp(tfm);
364 *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
365 }
366 dst = per_cpu(zswap_dstmem, cpu);
367 kfree(dst);
368 per_cpu(zswap_dstmem, cpu) = NULL;
369 break;
370 default:
371 break;
372 }
373 return NOTIFY_OK;
374}
375
376static int zswap_cpu_notifier(struct notifier_block *nb,
377 unsigned long action, void *pcpu)
378{
379 unsigned long cpu = (unsigned long)pcpu;
380 return __zswap_cpu_notifier(action, cpu);
381}
382
383static struct notifier_block zswap_cpu_notifier_block = {
384 .notifier_call = zswap_cpu_notifier
385};
386
387static int zswap_cpu_init(void)
388{
389 unsigned long cpu;
390
391 cpu_notifier_register_begin();
392 for_each_online_cpu(cpu)
393 if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
394 goto cleanup;
395 __register_cpu_notifier(&zswap_cpu_notifier_block);
396 cpu_notifier_register_done();
397 return 0;
398
399cleanup:
400 for_each_online_cpu(cpu)
401 __zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
402 cpu_notifier_register_done();
403 return -ENOMEM;
404}
405
406/*********************************
407* helpers
408**********************************/
409static bool zswap_is_full(void)
410{
411 return totalram_pages * zswap_max_pool_percent / 100 <
412 zswap_pool_pages;
413}
414
415/*********************************
416* writeback code
417**********************************/
418/* return enum for zswap_get_swap_cache_page */
419enum zswap_get_swap_ret {
420 ZSWAP_SWAPCACHE_NEW,
421 ZSWAP_SWAPCACHE_EXIST,
422 ZSWAP_SWAPCACHE_FAIL,
423};
424
425/*
426 * zswap_get_swap_cache_page
427 *
428 * This is an adaption of read_swap_cache_async()
429 *
430 * This function tries to find a page with the given swap entry
431 * in the swapper_space address space (the swap cache). If the page
432 * is found, it is returned in retpage. Otherwise, a page is allocated,
433 * added to the swap cache, and returned in retpage.
434 *
435 * If success, the swap cache page is returned in retpage
436 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
437 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
438 * the new page is added to swapcache and locked
439 * Returns ZSWAP_SWAPCACHE_FAIL on error
440 */
441static int zswap_get_swap_cache_page(swp_entry_t entry,
442 struct page **retpage)
443{
444 struct page *found_page, *new_page = NULL;
445 struct address_space *swapper_space = swap_address_space(entry);
446 int err;
447
448 *retpage = NULL;
449 do {
450 /*
451 * First check the swap cache. Since this is normally
452 * called after lookup_swap_cache() failed, re-calling
453 * that would confuse statistics.
454 */
455 found_page = find_get_page(swapper_space, entry.val);
456 if (found_page)
457 break;
458
459 /*
460 * Get a new page to read into from swap.
461 */
462 if (!new_page) {
463 new_page = alloc_page(GFP_KERNEL);
464 if (!new_page)
465 break; /* Out of memory */
466 }
467
468 /*
469 * call radix_tree_preload() while we can wait.
470 */
471 err = radix_tree_preload(GFP_KERNEL);
472 if (err)
473 break;
474
475 /*
476 * Swap entry may have been freed since our caller observed it.
477 */
478 err = swapcache_prepare(entry);
479 if (err == -EEXIST) { /* seems racy */
480 radix_tree_preload_end();
481 continue;
482 }
483 if (err) { /* swp entry is obsolete ? */
484 radix_tree_preload_end();
485 break;
486 }
487
488 /* May fail (-ENOMEM) if radix-tree node allocation failed. */
489 __set_page_locked(new_page);
490 SetPageSwapBacked(new_page);
491 err = __add_to_swap_cache(new_page, entry);
492 if (likely(!err)) {
493 radix_tree_preload_end();
494 lru_cache_add_anon(new_page);
495 *retpage = new_page;
496 return ZSWAP_SWAPCACHE_NEW;
497 }
498 radix_tree_preload_end();
499 ClearPageSwapBacked(new_page);
500 __clear_page_locked(new_page);
501 /*
502 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
503 * clear SWAP_HAS_CACHE flag.
504 */
505 swapcache_free(entry, NULL);
506 } while (err != -ENOMEM);
507
508 if (new_page)
509 page_cache_release(new_page);
510 if (!found_page)
511 return ZSWAP_SWAPCACHE_FAIL;
512 *retpage = found_page;
513 return ZSWAP_SWAPCACHE_EXIST;
514}
515
516/*
517 * Attempts to free an entry by adding a page to the swap cache,
518 * decompressing the entry data into the page, and issuing a
519 * bio write to write the page back to the swap device.
520 *
521 * This can be thought of as a "resumed writeback" of the page
522 * to the swap device. We are basically resuming the same swap
523 * writeback path that was intercepted with the frontswap_store()
524 * in the first place. After the page has been decompressed into
525 * the swap cache, the compressed version stored by zswap can be
526 * freed.
527 */
528static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle)
529{
530 struct zswap_header *zhdr;
531 swp_entry_t swpentry;
532 struct zswap_tree *tree;
533 pgoff_t offset;
534 struct zswap_entry *entry;
535 struct page *page;
536 u8 *src, *dst;
537 unsigned int dlen;
538 int ret;
539 struct writeback_control wbc = {
540 .sync_mode = WB_SYNC_NONE,
541 };
542
543 /* extract swpentry from data */
544 zhdr = zbud_map(pool, handle);
545 swpentry = zhdr->swpentry; /* here */
546 zbud_unmap(pool, handle);
547 tree = zswap_trees[swp_type(swpentry)];
548 offset = swp_offset(swpentry);
549
550 /* find and ref zswap entry */
551 spin_lock(&tree->lock);
552 entry = zswap_entry_find_get(&tree->rbroot, offset);
553 if (!entry) {
554 /* entry was invalidated */
555 spin_unlock(&tree->lock);
556 return 0;
557 }
558 spin_unlock(&tree->lock);
559 BUG_ON(offset != entry->offset);
560
561 /* try to allocate swap cache page */
562 switch (zswap_get_swap_cache_page(swpentry, &page)) {
563 case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
564 ret = -ENOMEM;
565 goto fail;
566
567 case ZSWAP_SWAPCACHE_EXIST:
568 /* page is already in the swap cache, ignore for now */
569 page_cache_release(page);
570 ret = -EEXIST;
571 goto fail;
572
573 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
574 /* decompress */
575 dlen = PAGE_SIZE;
576 src = (u8 *)zbud_map(zswap_pool, entry->handle) +
577 sizeof(struct zswap_header);
578 dst = kmap_atomic(page);
579 ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src,
580 entry->length, dst, &dlen);
581 kunmap_atomic(dst);
582 zbud_unmap(zswap_pool, entry->handle);
583 BUG_ON(ret);
584 BUG_ON(dlen != PAGE_SIZE);
585
586 /* page is up to date */
587 SetPageUptodate(page);
588 }
589
590 /* move it to the tail of the inactive list after end_writeback */
591 SetPageReclaim(page);
592
593 /* start writeback */
594 __swap_writepage(page, &wbc, end_swap_bio_write);
595 page_cache_release(page);
596 zswap_written_back_pages++;
597
598 spin_lock(&tree->lock);
599 /* drop local reference */
600 zswap_entry_put(tree, entry);
601
602 /*
603 * There are two possible situations for entry here:
604 * (1) refcount is 1(normal case), entry is valid and on the tree
605 * (2) refcount is 0, entry is freed and not on the tree
606 * because invalidate happened during writeback
607 * search the tree and free the entry if find entry
608 */
609 if (entry == zswap_rb_search(&tree->rbroot, offset))
610 zswap_entry_put(tree, entry);
611 spin_unlock(&tree->lock);
612
613 goto end;
614
615 /*
616 * if we get here due to ZSWAP_SWAPCACHE_EXIST
617 * a load may happening concurrently
618 * it is safe and okay to not free the entry
619 * if we free the entry in the following put
620 * it it either okay to return !0
621 */
622fail:
623 spin_lock(&tree->lock);
624 zswap_entry_put(tree, entry);
625 spin_unlock(&tree->lock);
626
627end:
628 return ret;
629}
630
631/*********************************
632* frontswap hooks
633**********************************/
634/* attempts to compress and store an single page */
635static int zswap_frontswap_store(unsigned type, pgoff_t offset,
636 struct page *page)
637{
638 struct zswap_tree *tree = zswap_trees[type];
639 struct zswap_entry *entry, *dupentry;
640 int ret;
641 unsigned int dlen = PAGE_SIZE, len;
642 unsigned long handle;
643 char *buf;
644 u8 *src, *dst;
645 struct zswap_header *zhdr;
646
647 if (!tree) {
648 ret = -ENODEV;
649 goto reject;
650 }
651
652 /* reclaim space if needed */
653 if (zswap_is_full()) {
654 zswap_pool_limit_hit++;
655 if (zbud_reclaim_page(zswap_pool, 8)) {
656 zswap_reject_reclaim_fail++;
657 ret = -ENOMEM;
658 goto reject;
659 }
660 }
661
662 /* allocate entry */
663 entry = zswap_entry_cache_alloc(GFP_KERNEL);
664 if (!entry) {
665 zswap_reject_kmemcache_fail++;
666 ret = -ENOMEM;
667 goto reject;
668 }
669
670 /* compress */
671 dst = get_cpu_var(zswap_dstmem);
672 src = kmap_atomic(page);
673 ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen);
674 kunmap_atomic(src);
675 if (ret) {
676 ret = -EINVAL;
677 goto freepage;
678 }
679
680 /* store */
681 len = dlen + sizeof(struct zswap_header);
682 ret = zbud_alloc(zswap_pool, len, __GFP_NORETRY | __GFP_NOWARN,
683 &handle);
684 if (ret == -ENOSPC) {
685 zswap_reject_compress_poor++;
686 goto freepage;
687 }
688 if (ret) {
689 zswap_reject_alloc_fail++;
690 goto freepage;
691 }
692 zhdr = zbud_map(zswap_pool, handle);
693 zhdr->swpentry = swp_entry(type, offset);
694 buf = (u8 *)(zhdr + 1);
695 memcpy(buf, dst, dlen);
696 zbud_unmap(zswap_pool, handle);
697 put_cpu_var(zswap_dstmem);
698
699 /* populate entry */
700 entry->offset = offset;
701 entry->handle = handle;
702 entry->length = dlen;
703
704 /* map */
705 spin_lock(&tree->lock);
706 do {
707 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
708 if (ret == -EEXIST) {
709 zswap_duplicate_entry++;
710 /* remove from rbtree */
711 zswap_rb_erase(&tree->rbroot, dupentry);
712 zswap_entry_put(tree, dupentry);
713 }
714 } while (ret == -EEXIST);
715 spin_unlock(&tree->lock);
716
717 /* update stats */
718 atomic_inc(&zswap_stored_pages);
719 zswap_pool_pages = zbud_get_pool_size(zswap_pool);
720
721 return 0;
722
723freepage:
724 put_cpu_var(zswap_dstmem);
725 zswap_entry_cache_free(entry);
726reject:
727 return ret;
728}
729
730/*
731 * returns 0 if the page was successfully decompressed
732 * return -1 on entry not found or error
733*/
734static int zswap_frontswap_load(unsigned type, pgoff_t offset,
735 struct page *page)
736{
737 struct zswap_tree *tree = zswap_trees[type];
738 struct zswap_entry *entry;
739 u8 *src, *dst;
740 unsigned int dlen;
741 int ret;
742
743 /* find */
744 spin_lock(&tree->lock);
745 entry = zswap_entry_find_get(&tree->rbroot, offset);
746 if (!entry) {
747 /* entry was written back */
748 spin_unlock(&tree->lock);
749 return -1;
750 }
751 spin_unlock(&tree->lock);
752
753 /* decompress */
754 dlen = PAGE_SIZE;
755 src = (u8 *)zbud_map(zswap_pool, entry->handle) +
756 sizeof(struct zswap_header);
757 dst = kmap_atomic(page);
758 ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
759 dst, &dlen);
760 kunmap_atomic(dst);
761 zbud_unmap(zswap_pool, entry->handle);
762 BUG_ON(ret);
763
764 spin_lock(&tree->lock);
765 zswap_entry_put(tree, entry);
766 spin_unlock(&tree->lock);
767
768 return 0;
769}
770
771/* frees an entry in zswap */
772static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
773{
774 struct zswap_tree *tree = zswap_trees[type];
775 struct zswap_entry *entry;
776
777 /* find */
778 spin_lock(&tree->lock);
779 entry = zswap_rb_search(&tree->rbroot, offset);
780 if (!entry) {
781 /* entry was written back */
782 spin_unlock(&tree->lock);
783 return;
784 }
785
786 /* remove from rbtree */
787 zswap_rb_erase(&tree->rbroot, entry);
788
789 /* drop the initial reference from entry creation */
790 zswap_entry_put(tree, entry);
791
792 spin_unlock(&tree->lock);
793}
794
795/* frees all zswap entries for the given swap type */
796static void zswap_frontswap_invalidate_area(unsigned type)
797{
798 struct zswap_tree *tree = zswap_trees[type];
799 struct zswap_entry *entry, *n;
800
801 if (!tree)
802 return;
803
804 /* walk the tree and free everything */
805 spin_lock(&tree->lock);
806 rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
807 zswap_free_entry(entry);
808 tree->rbroot = RB_ROOT;
809 spin_unlock(&tree->lock);
810 kfree(tree);
811 zswap_trees[type] = NULL;
812}
813
814static struct zbud_ops zswap_zbud_ops = {
815 .evict = zswap_writeback_entry
816};
817
818static void zswap_frontswap_init(unsigned type)
819{
820 struct zswap_tree *tree;
821
822 tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
823 if (!tree) {
824 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
825 return;
826 }
827
828 tree->rbroot = RB_ROOT;
829 spin_lock_init(&tree->lock);
830 zswap_trees[type] = tree;
831}
832
833static struct frontswap_ops zswap_frontswap_ops = {
834 .store = zswap_frontswap_store,
835 .load = zswap_frontswap_load,
836 .invalidate_page = zswap_frontswap_invalidate_page,
837 .invalidate_area = zswap_frontswap_invalidate_area,
838 .init = zswap_frontswap_init
839};
840
841/*********************************
842* debugfs functions
843**********************************/
844#ifdef CONFIG_DEBUG_FS
845#include <linux/debugfs.h>
846
847static struct dentry *zswap_debugfs_root;
848
849static int __init zswap_debugfs_init(void)
850{
851 if (!debugfs_initialized())
852 return -ENODEV;
853
854 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
855 if (!zswap_debugfs_root)
856 return -ENOMEM;
857
858 debugfs_create_u64("pool_limit_hit", S_IRUGO,
859 zswap_debugfs_root, &zswap_pool_limit_hit);
860 debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
861 zswap_debugfs_root, &zswap_reject_reclaim_fail);
862 debugfs_create_u64("reject_alloc_fail", S_IRUGO,
863 zswap_debugfs_root, &zswap_reject_alloc_fail);
864 debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
865 zswap_debugfs_root, &zswap_reject_kmemcache_fail);
866 debugfs_create_u64("reject_compress_poor", S_IRUGO,
867 zswap_debugfs_root, &zswap_reject_compress_poor);
868 debugfs_create_u64("written_back_pages", S_IRUGO,
869 zswap_debugfs_root, &zswap_written_back_pages);
870 debugfs_create_u64("duplicate_entry", S_IRUGO,
871 zswap_debugfs_root, &zswap_duplicate_entry);
872 debugfs_create_u64("pool_pages", S_IRUGO,
873 zswap_debugfs_root, &zswap_pool_pages);
874 debugfs_create_atomic_t("stored_pages", S_IRUGO,
875 zswap_debugfs_root, &zswap_stored_pages);
876
877 return 0;
878}
879
880static void __exit zswap_debugfs_exit(void)
881{
882 debugfs_remove_recursive(zswap_debugfs_root);
883}
884#else
885static int __init zswap_debugfs_init(void)
886{
887 return 0;
888}
889
890static void __exit zswap_debugfs_exit(void) { }
891#endif
892
893/*********************************
894* module init and exit
895**********************************/
896static int __init init_zswap(void)
897{
898 if (!zswap_enabled)
899 return 0;
900
901 pr_info("loading zswap\n");
902
903 zswap_pool = zbud_create_pool(GFP_KERNEL, &zswap_zbud_ops);
904 if (!zswap_pool) {
905 pr_err("zbud pool creation failed\n");
906 goto error;
907 }
908
909 if (zswap_entry_cache_create()) {
910 pr_err("entry cache creation failed\n");
911 goto cachefail;
912 }
913 if (zswap_comp_init()) {
914 pr_err("compressor initialization failed\n");
915 goto compfail;
916 }
917 if (zswap_cpu_init()) {
918 pr_err("per-cpu initialization failed\n");
919 goto pcpufail;
920 }
921
922 frontswap_register_ops(&zswap_frontswap_ops);
923 if (zswap_debugfs_init())
924 pr_warn("debugfs initialization failed\n");
925 return 0;
926pcpufail:
927 zswap_comp_exit();
928compfail:
929 zswap_entry_cache_destory();
930cachefail:
931 zbud_destroy_pool(zswap_pool);
932error:
933 return -ENOMEM;
934}
935/* must be late so crypto has time to come up */
936late_initcall(init_zswap);
937
938MODULE_LICENSE("GPL");
939MODULE_AUTHOR("Seth Jennings <sjenning@linux.vnet.ibm.com>");
940MODULE_DESCRIPTION("Compressed cache for swap pages");