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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/zpool.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/* Total bytes used by the compressed storage */
49static u64 zswap_pool_total_size;
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
79/* Enable/disable zswap (disabled by default) */
80static bool zswap_enabled;
81module_param_named(enabled, zswap_enabled, bool, 0644);
82
83/* Crypto compressor to use */
84#define ZSWAP_COMPRESSOR_DEFAULT "lzo"
85static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
86static int zswap_compressor_param_set(const char *,
87 const struct kernel_param *);
88static struct kernel_param_ops zswap_compressor_param_ops = {
89 .set = zswap_compressor_param_set,
90 .get = param_get_charp,
91 .free = param_free_charp,
92};
93module_param_cb(compressor, &zswap_compressor_param_ops,
94 &zswap_compressor, 0644);
95
96/* Compressed storage zpool to use */
97#define ZSWAP_ZPOOL_DEFAULT "zbud"
98static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
99static int zswap_zpool_param_set(const char *, const struct kernel_param *);
100static struct kernel_param_ops zswap_zpool_param_ops = {
101 .set = zswap_zpool_param_set,
102 .get = param_get_charp,
103 .free = param_free_charp,
104};
105module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
106
107/* The maximum percentage of memory that the compressed pool can occupy */
108static unsigned int zswap_max_pool_percent = 20;
109module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
110
111/*********************************
112* data structures
113**********************************/
114
115struct zswap_pool {
116 struct zpool *zpool;
117 struct crypto_comp * __percpu *tfm;
118 struct kref kref;
119 struct list_head list;
120 struct rcu_head rcu_head;
121 struct notifier_block notifier;
122 char tfm_name[CRYPTO_MAX_ALG_NAME];
123};
124
125/*
126 * struct zswap_entry
127 *
128 * This structure contains the metadata for tracking a single compressed
129 * page within zswap.
130 *
131 * rbnode - links the entry into red-black tree for the appropriate swap type
132 * offset - the swap offset for the entry. Index into the red-black tree.
133 * refcount - the number of outstanding reference to the entry. This is needed
134 * to protect against premature freeing of the entry by code
135 * concurrent calls to load, invalidate, and writeback. The lock
136 * for the zswap_tree structure that contains the entry must
137 * be held while changing the refcount. Since the lock must
138 * be held, there is no reason to also make refcount atomic.
139 * length - the length in bytes of the compressed page data. Needed during
140 * decompression
141 * pool - the zswap_pool the entry's data is in
142 * handle - zpool allocation handle that stores the compressed page data
143 */
144struct zswap_entry {
145 struct rb_node rbnode;
146 pgoff_t offset;
147 int refcount;
148 unsigned int length;
149 struct zswap_pool *pool;
150 unsigned long handle;
151};
152
153struct zswap_header {
154 swp_entry_t swpentry;
155};
156
157/*
158 * The tree lock in the zswap_tree struct protects a few things:
159 * - the rbtree
160 * - the refcount field of each entry in the tree
161 */
162struct zswap_tree {
163 struct rb_root rbroot;
164 spinlock_t lock;
165};
166
167static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
168
169/* RCU-protected iteration */
170static LIST_HEAD(zswap_pools);
171/* protects zswap_pools list modification */
172static DEFINE_SPINLOCK(zswap_pools_lock);
173/* pool counter to provide unique names to zpool */
174static atomic_t zswap_pools_count = ATOMIC_INIT(0);
175
176/* used by param callback function */
177static bool zswap_init_started;
178
179/*********************************
180* helpers and fwd declarations
181**********************************/
182
183#define zswap_pool_debug(msg, p) \
184 pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \
185 zpool_get_type((p)->zpool))
186
187static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
188static int zswap_pool_get(struct zswap_pool *pool);
189static void zswap_pool_put(struct zswap_pool *pool);
190
191static const struct zpool_ops zswap_zpool_ops = {
192 .evict = zswap_writeback_entry
193};
194
195static bool zswap_is_full(void)
196{
197 return totalram_pages * zswap_max_pool_percent / 100 <
198 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
199}
200
201static void zswap_update_total_size(void)
202{
203 struct zswap_pool *pool;
204 u64 total = 0;
205
206 rcu_read_lock();
207
208 list_for_each_entry_rcu(pool, &zswap_pools, list)
209 total += zpool_get_total_size(pool->zpool);
210
211 rcu_read_unlock();
212
213 zswap_pool_total_size = total;
214}
215
216/*********************************
217* zswap entry functions
218**********************************/
219static struct kmem_cache *zswap_entry_cache;
220
221static int __init zswap_entry_cache_create(void)
222{
223 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
224 return zswap_entry_cache == NULL;
225}
226
227static void __init zswap_entry_cache_destroy(void)
228{
229 kmem_cache_destroy(zswap_entry_cache);
230}
231
232static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
233{
234 struct zswap_entry *entry;
235 entry = kmem_cache_alloc(zswap_entry_cache, gfp);
236 if (!entry)
237 return NULL;
238 entry->refcount = 1;
239 RB_CLEAR_NODE(&entry->rbnode);
240 return entry;
241}
242
243static void zswap_entry_cache_free(struct zswap_entry *entry)
244{
245 kmem_cache_free(zswap_entry_cache, entry);
246}
247
248/*********************************
249* rbtree functions
250**********************************/
251static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
252{
253 struct rb_node *node = root->rb_node;
254 struct zswap_entry *entry;
255
256 while (node) {
257 entry = rb_entry(node, struct zswap_entry, rbnode);
258 if (entry->offset > offset)
259 node = node->rb_left;
260 else if (entry->offset < offset)
261 node = node->rb_right;
262 else
263 return entry;
264 }
265 return NULL;
266}
267
268/*
269 * In the case that a entry with the same offset is found, a pointer to
270 * the existing entry is stored in dupentry and the function returns -EEXIST
271 */
272static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
273 struct zswap_entry **dupentry)
274{
275 struct rb_node **link = &root->rb_node, *parent = NULL;
276 struct zswap_entry *myentry;
277
278 while (*link) {
279 parent = *link;
280 myentry = rb_entry(parent, struct zswap_entry, rbnode);
281 if (myentry->offset > entry->offset)
282 link = &(*link)->rb_left;
283 else if (myentry->offset < entry->offset)
284 link = &(*link)->rb_right;
285 else {
286 *dupentry = myentry;
287 return -EEXIST;
288 }
289 }
290 rb_link_node(&entry->rbnode, parent, link);
291 rb_insert_color(&entry->rbnode, root);
292 return 0;
293}
294
295static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
296{
297 if (!RB_EMPTY_NODE(&entry->rbnode)) {
298 rb_erase(&entry->rbnode, root);
299 RB_CLEAR_NODE(&entry->rbnode);
300 }
301}
302
303/*
304 * Carries out the common pattern of freeing and entry's zpool allocation,
305 * freeing the entry itself, and decrementing the number of stored pages.
306 */
307static void zswap_free_entry(struct zswap_entry *entry)
308{
309 zpool_free(entry->pool->zpool, entry->handle);
310 zswap_pool_put(entry->pool);
311 zswap_entry_cache_free(entry);
312 atomic_dec(&zswap_stored_pages);
313 zswap_update_total_size();
314}
315
316/* caller must hold the tree lock */
317static void zswap_entry_get(struct zswap_entry *entry)
318{
319 entry->refcount++;
320}
321
322/* caller must hold the tree lock
323* remove from the tree and free it, if nobody reference the entry
324*/
325static void zswap_entry_put(struct zswap_tree *tree,
326 struct zswap_entry *entry)
327{
328 int refcount = --entry->refcount;
329
330 BUG_ON(refcount < 0);
331 if (refcount == 0) {
332 zswap_rb_erase(&tree->rbroot, entry);
333 zswap_free_entry(entry);
334 }
335}
336
337/* caller must hold the tree lock */
338static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
339 pgoff_t offset)
340{
341 struct zswap_entry *entry;
342
343 entry = zswap_rb_search(root, offset);
344 if (entry)
345 zswap_entry_get(entry);
346
347 return entry;
348}
349
350/*********************************
351* per-cpu code
352**********************************/
353static DEFINE_PER_CPU(u8 *, zswap_dstmem);
354
355static int __zswap_cpu_dstmem_notifier(unsigned long action, unsigned long cpu)
356{
357 u8 *dst;
358
359 switch (action) {
360 case CPU_UP_PREPARE:
361 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
362 if (!dst) {
363 pr_err("can't allocate compressor buffer\n");
364 return NOTIFY_BAD;
365 }
366 per_cpu(zswap_dstmem, cpu) = dst;
367 break;
368 case CPU_DEAD:
369 case CPU_UP_CANCELED:
370 dst = per_cpu(zswap_dstmem, cpu);
371 kfree(dst);
372 per_cpu(zswap_dstmem, cpu) = NULL;
373 break;
374 default:
375 break;
376 }
377 return NOTIFY_OK;
378}
379
380static int zswap_cpu_dstmem_notifier(struct notifier_block *nb,
381 unsigned long action, void *pcpu)
382{
383 return __zswap_cpu_dstmem_notifier(action, (unsigned long)pcpu);
384}
385
386static struct notifier_block zswap_dstmem_notifier = {
387 .notifier_call = zswap_cpu_dstmem_notifier,
388};
389
390static int __init zswap_cpu_dstmem_init(void)
391{
392 unsigned long cpu;
393
394 cpu_notifier_register_begin();
395 for_each_online_cpu(cpu)
396 if (__zswap_cpu_dstmem_notifier(CPU_UP_PREPARE, cpu) ==
397 NOTIFY_BAD)
398 goto cleanup;
399 __register_cpu_notifier(&zswap_dstmem_notifier);
400 cpu_notifier_register_done();
401 return 0;
402
403cleanup:
404 for_each_online_cpu(cpu)
405 __zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
406 cpu_notifier_register_done();
407 return -ENOMEM;
408}
409
410static void zswap_cpu_dstmem_destroy(void)
411{
412 unsigned long cpu;
413
414 cpu_notifier_register_begin();
415 for_each_online_cpu(cpu)
416 __zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
417 __unregister_cpu_notifier(&zswap_dstmem_notifier);
418 cpu_notifier_register_done();
419}
420
421static int __zswap_cpu_comp_notifier(struct zswap_pool *pool,
422 unsigned long action, unsigned long cpu)
423{
424 struct crypto_comp *tfm;
425
426 switch (action) {
427 case CPU_UP_PREPARE:
428 if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
429 break;
430 tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
431 if (IS_ERR_OR_NULL(tfm)) {
432 pr_err("could not alloc crypto comp %s : %ld\n",
433 pool->tfm_name, PTR_ERR(tfm));
434 return NOTIFY_BAD;
435 }
436 *per_cpu_ptr(pool->tfm, cpu) = tfm;
437 break;
438 case CPU_DEAD:
439 case CPU_UP_CANCELED:
440 tfm = *per_cpu_ptr(pool->tfm, cpu);
441 if (!IS_ERR_OR_NULL(tfm))
442 crypto_free_comp(tfm);
443 *per_cpu_ptr(pool->tfm, cpu) = NULL;
444 break;
445 default:
446 break;
447 }
448 return NOTIFY_OK;
449}
450
451static int zswap_cpu_comp_notifier(struct notifier_block *nb,
452 unsigned long action, void *pcpu)
453{
454 unsigned long cpu = (unsigned long)pcpu;
455 struct zswap_pool *pool = container_of(nb, typeof(*pool), notifier);
456
457 return __zswap_cpu_comp_notifier(pool, action, cpu);
458}
459
460static int zswap_cpu_comp_init(struct zswap_pool *pool)
461{
462 unsigned long cpu;
463
464 memset(&pool->notifier, 0, sizeof(pool->notifier));
465 pool->notifier.notifier_call = zswap_cpu_comp_notifier;
466
467 cpu_notifier_register_begin();
468 for_each_online_cpu(cpu)
469 if (__zswap_cpu_comp_notifier(pool, CPU_UP_PREPARE, cpu) ==
470 NOTIFY_BAD)
471 goto cleanup;
472 __register_cpu_notifier(&pool->notifier);
473 cpu_notifier_register_done();
474 return 0;
475
476cleanup:
477 for_each_online_cpu(cpu)
478 __zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
479 cpu_notifier_register_done();
480 return -ENOMEM;
481}
482
483static void zswap_cpu_comp_destroy(struct zswap_pool *pool)
484{
485 unsigned long cpu;
486
487 cpu_notifier_register_begin();
488 for_each_online_cpu(cpu)
489 __zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
490 __unregister_cpu_notifier(&pool->notifier);
491 cpu_notifier_register_done();
492}
493
494/*********************************
495* pool functions
496**********************************/
497
498static struct zswap_pool *__zswap_pool_current(void)
499{
500 struct zswap_pool *pool;
501
502 pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
503 WARN_ON(!pool);
504
505 return pool;
506}
507
508static struct zswap_pool *zswap_pool_current(void)
509{
510 assert_spin_locked(&zswap_pools_lock);
511
512 return __zswap_pool_current();
513}
514
515static struct zswap_pool *zswap_pool_current_get(void)
516{
517 struct zswap_pool *pool;
518
519 rcu_read_lock();
520
521 pool = __zswap_pool_current();
522 if (!pool || !zswap_pool_get(pool))
523 pool = NULL;
524
525 rcu_read_unlock();
526
527 return pool;
528}
529
530static struct zswap_pool *zswap_pool_last_get(void)
531{
532 struct zswap_pool *pool, *last = NULL;
533
534 rcu_read_lock();
535
536 list_for_each_entry_rcu(pool, &zswap_pools, list)
537 last = pool;
538 if (!WARN_ON(!last) && !zswap_pool_get(last))
539 last = NULL;
540
541 rcu_read_unlock();
542
543 return last;
544}
545
546/* type and compressor must be null-terminated */
547static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
548{
549 struct zswap_pool *pool;
550
551 assert_spin_locked(&zswap_pools_lock);
552
553 list_for_each_entry_rcu(pool, &zswap_pools, list) {
554 if (strcmp(pool->tfm_name, compressor))
555 continue;
556 if (strcmp(zpool_get_type(pool->zpool), type))
557 continue;
558 /* if we can't get it, it's about to be destroyed */
559 if (!zswap_pool_get(pool))
560 continue;
561 return pool;
562 }
563
564 return NULL;
565}
566
567static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
568{
569 struct zswap_pool *pool;
570 char name[38]; /* 'zswap' + 32 char (max) num + \0 */
571 gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
572
573 pool = kzalloc(sizeof(*pool), GFP_KERNEL);
574 if (!pool) {
575 pr_err("pool alloc failed\n");
576 return NULL;
577 }
578
579 /* unique name for each pool specifically required by zsmalloc */
580 snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
581
582 pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
583 if (!pool->zpool) {
584 pr_err("%s zpool not available\n", type);
585 goto error;
586 }
587 pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
588
589 strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
590 pool->tfm = alloc_percpu(struct crypto_comp *);
591 if (!pool->tfm) {
592 pr_err("percpu alloc failed\n");
593 goto error;
594 }
595
596 if (zswap_cpu_comp_init(pool))
597 goto error;
598 pr_debug("using %s compressor\n", pool->tfm_name);
599
600 /* being the current pool takes 1 ref; this func expects the
601 * caller to always add the new pool as the current pool
602 */
603 kref_init(&pool->kref);
604 INIT_LIST_HEAD(&pool->list);
605
606 zswap_pool_debug("created", pool);
607
608 return pool;
609
610error:
611 free_percpu(pool->tfm);
612 if (pool->zpool)
613 zpool_destroy_pool(pool->zpool);
614 kfree(pool);
615 return NULL;
616}
617
618static __init struct zswap_pool *__zswap_pool_create_fallback(void)
619{
620 if (!crypto_has_comp(zswap_compressor, 0, 0)) {
621 if (!strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {
622 pr_err("default compressor %s not available\n",
623 zswap_compressor);
624 return NULL;
625 }
626 pr_err("compressor %s not available, using default %s\n",
627 zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
628 param_free_charp(&zswap_compressor);
629 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
630 }
631 if (!zpool_has_pool(zswap_zpool_type)) {
632 if (!strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
633 pr_err("default zpool %s not available\n",
634 zswap_zpool_type);
635 return NULL;
636 }
637 pr_err("zpool %s not available, using default %s\n",
638 zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
639 param_free_charp(&zswap_zpool_type);
640 zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
641 }
642
643 return zswap_pool_create(zswap_zpool_type, zswap_compressor);
644}
645
646static void zswap_pool_destroy(struct zswap_pool *pool)
647{
648 zswap_pool_debug("destroying", pool);
649
650 zswap_cpu_comp_destroy(pool);
651 free_percpu(pool->tfm);
652 zpool_destroy_pool(pool->zpool);
653 kfree(pool);
654}
655
656static int __must_check zswap_pool_get(struct zswap_pool *pool)
657{
658 return kref_get_unless_zero(&pool->kref);
659}
660
661static void __zswap_pool_release(struct rcu_head *head)
662{
663 struct zswap_pool *pool = container_of(head, typeof(*pool), rcu_head);
664
665 /* nobody should have been able to get a kref... */
666 WARN_ON(kref_get_unless_zero(&pool->kref));
667
668 /* pool is now off zswap_pools list and has no references. */
669 zswap_pool_destroy(pool);
670}
671
672static void __zswap_pool_empty(struct kref *kref)
673{
674 struct zswap_pool *pool;
675
676 pool = container_of(kref, typeof(*pool), kref);
677
678 spin_lock(&zswap_pools_lock);
679
680 WARN_ON(pool == zswap_pool_current());
681
682 list_del_rcu(&pool->list);
683 call_rcu(&pool->rcu_head, __zswap_pool_release);
684
685 spin_unlock(&zswap_pools_lock);
686}
687
688static void zswap_pool_put(struct zswap_pool *pool)
689{
690 kref_put(&pool->kref, __zswap_pool_empty);
691}
692
693/*********************************
694* param callbacks
695**********************************/
696
697/* val must be a null-terminated string */
698static int __zswap_param_set(const char *val, const struct kernel_param *kp,
699 char *type, char *compressor)
700{
701 struct zswap_pool *pool, *put_pool = NULL;
702 char *s = strstrip((char *)val);
703 int ret;
704
705 /* no change required */
706 if (!strcmp(s, *(char **)kp->arg))
707 return 0;
708
709 /* if this is load-time (pre-init) param setting,
710 * don't create a pool; that's done during init.
711 */
712 if (!zswap_init_started)
713 return param_set_charp(s, kp);
714
715 if (!type) {
716 if (!zpool_has_pool(s)) {
717 pr_err("zpool %s not available\n", s);
718 return -ENOENT;
719 }
720 type = s;
721 } else if (!compressor) {
722 if (!crypto_has_comp(s, 0, 0)) {
723 pr_err("compressor %s not available\n", s);
724 return -ENOENT;
725 }
726 compressor = s;
727 } else {
728 WARN_ON(1);
729 return -EINVAL;
730 }
731
732 spin_lock(&zswap_pools_lock);
733
734 pool = zswap_pool_find_get(type, compressor);
735 if (pool) {
736 zswap_pool_debug("using existing", pool);
737 list_del_rcu(&pool->list);
738 } else {
739 spin_unlock(&zswap_pools_lock);
740 pool = zswap_pool_create(type, compressor);
741 spin_lock(&zswap_pools_lock);
742 }
743
744 if (pool)
745 ret = param_set_charp(s, kp);
746 else
747 ret = -EINVAL;
748
749 if (!ret) {
750 put_pool = zswap_pool_current();
751 list_add_rcu(&pool->list, &zswap_pools);
752 } else if (pool) {
753 /* add the possibly pre-existing pool to the end of the pools
754 * list; if it's new (and empty) then it'll be removed and
755 * destroyed by the put after we drop the lock
756 */
757 list_add_tail_rcu(&pool->list, &zswap_pools);
758 put_pool = pool;
759 }
760
761 spin_unlock(&zswap_pools_lock);
762
763 /* drop the ref from either the old current pool,
764 * or the new pool we failed to add
765 */
766 if (put_pool)
767 zswap_pool_put(put_pool);
768
769 return ret;
770}
771
772static int zswap_compressor_param_set(const char *val,
773 const struct kernel_param *kp)
774{
775 return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
776}
777
778static int zswap_zpool_param_set(const char *val,
779 const struct kernel_param *kp)
780{
781 return __zswap_param_set(val, kp, NULL, zswap_compressor);
782}
783
784/*********************************
785* writeback code
786**********************************/
787/* return enum for zswap_get_swap_cache_page */
788enum zswap_get_swap_ret {
789 ZSWAP_SWAPCACHE_NEW,
790 ZSWAP_SWAPCACHE_EXIST,
791 ZSWAP_SWAPCACHE_FAIL,
792};
793
794/*
795 * zswap_get_swap_cache_page
796 *
797 * This is an adaption of read_swap_cache_async()
798 *
799 * This function tries to find a page with the given swap entry
800 * in the swapper_space address space (the swap cache). If the page
801 * is found, it is returned in retpage. Otherwise, a page is allocated,
802 * added to the swap cache, and returned in retpage.
803 *
804 * If success, the swap cache page is returned in retpage
805 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
806 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
807 * the new page is added to swapcache and locked
808 * Returns ZSWAP_SWAPCACHE_FAIL on error
809 */
810static int zswap_get_swap_cache_page(swp_entry_t entry,
811 struct page **retpage)
812{
813 bool page_was_allocated;
814
815 *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
816 NULL, 0, &page_was_allocated);
817 if (page_was_allocated)
818 return ZSWAP_SWAPCACHE_NEW;
819 if (!*retpage)
820 return ZSWAP_SWAPCACHE_FAIL;
821 return ZSWAP_SWAPCACHE_EXIST;
822}
823
824/*
825 * Attempts to free an entry by adding a page to the swap cache,
826 * decompressing the entry data into the page, and issuing a
827 * bio write to write the page back to the swap device.
828 *
829 * This can be thought of as a "resumed writeback" of the page
830 * to the swap device. We are basically resuming the same swap
831 * writeback path that was intercepted with the frontswap_store()
832 * in the first place. After the page has been decompressed into
833 * the swap cache, the compressed version stored by zswap can be
834 * freed.
835 */
836static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
837{
838 struct zswap_header *zhdr;
839 swp_entry_t swpentry;
840 struct zswap_tree *tree;
841 pgoff_t offset;
842 struct zswap_entry *entry;
843 struct page *page;
844 struct crypto_comp *tfm;
845 u8 *src, *dst;
846 unsigned int dlen;
847 int ret;
848 struct writeback_control wbc = {
849 .sync_mode = WB_SYNC_NONE,
850 };
851
852 /* extract swpentry from data */
853 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
854 swpentry = zhdr->swpentry; /* here */
855 zpool_unmap_handle(pool, handle);
856 tree = zswap_trees[swp_type(swpentry)];
857 offset = swp_offset(swpentry);
858
859 /* find and ref zswap entry */
860 spin_lock(&tree->lock);
861 entry = zswap_entry_find_get(&tree->rbroot, offset);
862 if (!entry) {
863 /* entry was invalidated */
864 spin_unlock(&tree->lock);
865 return 0;
866 }
867 spin_unlock(&tree->lock);
868 BUG_ON(offset != entry->offset);
869
870 /* try to allocate swap cache page */
871 switch (zswap_get_swap_cache_page(swpentry, &page)) {
872 case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
873 ret = -ENOMEM;
874 goto fail;
875
876 case ZSWAP_SWAPCACHE_EXIST:
877 /* page is already in the swap cache, ignore for now */
878 put_page(page);
879 ret = -EEXIST;
880 goto fail;
881
882 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
883 /* decompress */
884 dlen = PAGE_SIZE;
885 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
886 ZPOOL_MM_RO) + sizeof(struct zswap_header);
887 dst = kmap_atomic(page);
888 tfm = *get_cpu_ptr(entry->pool->tfm);
889 ret = crypto_comp_decompress(tfm, src, entry->length,
890 dst, &dlen);
891 put_cpu_ptr(entry->pool->tfm);
892 kunmap_atomic(dst);
893 zpool_unmap_handle(entry->pool->zpool, entry->handle);
894 BUG_ON(ret);
895 BUG_ON(dlen != PAGE_SIZE);
896
897 /* page is up to date */
898 SetPageUptodate(page);
899 }
900
901 /* move it to the tail of the inactive list after end_writeback */
902 SetPageReclaim(page);
903
904 /* start writeback */
905 __swap_writepage(page, &wbc, end_swap_bio_write);
906 put_page(page);
907 zswap_written_back_pages++;
908
909 spin_lock(&tree->lock);
910 /* drop local reference */
911 zswap_entry_put(tree, entry);
912
913 /*
914 * There are two possible situations for entry here:
915 * (1) refcount is 1(normal case), entry is valid and on the tree
916 * (2) refcount is 0, entry is freed and not on the tree
917 * because invalidate happened during writeback
918 * search the tree and free the entry if find entry
919 */
920 if (entry == zswap_rb_search(&tree->rbroot, offset))
921 zswap_entry_put(tree, entry);
922 spin_unlock(&tree->lock);
923
924 goto end;
925
926 /*
927 * if we get here due to ZSWAP_SWAPCACHE_EXIST
928 * a load may happening concurrently
929 * it is safe and okay to not free the entry
930 * if we free the entry in the following put
931 * it it either okay to return !0
932 */
933fail:
934 spin_lock(&tree->lock);
935 zswap_entry_put(tree, entry);
936 spin_unlock(&tree->lock);
937
938end:
939 return ret;
940}
941
942static int zswap_shrink(void)
943{
944 struct zswap_pool *pool;
945 int ret;
946
947 pool = zswap_pool_last_get();
948 if (!pool)
949 return -ENOENT;
950
951 ret = zpool_shrink(pool->zpool, 1, NULL);
952
953 zswap_pool_put(pool);
954
955 return ret;
956}
957
958/*********************************
959* frontswap hooks
960**********************************/
961/* attempts to compress and store an single page */
962static int zswap_frontswap_store(unsigned type, pgoff_t offset,
963 struct page *page)
964{
965 struct zswap_tree *tree = zswap_trees[type];
966 struct zswap_entry *entry, *dupentry;
967 struct crypto_comp *tfm;
968 int ret;
969 unsigned int dlen = PAGE_SIZE, len;
970 unsigned long handle;
971 char *buf;
972 u8 *src, *dst;
973 struct zswap_header *zhdr;
974
975 if (!zswap_enabled || !tree) {
976 ret = -ENODEV;
977 goto reject;
978 }
979
980 /* reclaim space if needed */
981 if (zswap_is_full()) {
982 zswap_pool_limit_hit++;
983 if (zswap_shrink()) {
984 zswap_reject_reclaim_fail++;
985 ret = -ENOMEM;
986 goto reject;
987 }
988 }
989
990 /* allocate entry */
991 entry = zswap_entry_cache_alloc(GFP_KERNEL);
992 if (!entry) {
993 zswap_reject_kmemcache_fail++;
994 ret = -ENOMEM;
995 goto reject;
996 }
997
998 /* if entry is successfully added, it keeps the reference */
999 entry->pool = zswap_pool_current_get();
1000 if (!entry->pool) {
1001 ret = -EINVAL;
1002 goto freepage;
1003 }
1004
1005 /* compress */
1006 dst = get_cpu_var(zswap_dstmem);
1007 tfm = *get_cpu_ptr(entry->pool->tfm);
1008 src = kmap_atomic(page);
1009 ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
1010 kunmap_atomic(src);
1011 put_cpu_ptr(entry->pool->tfm);
1012 if (ret) {
1013 ret = -EINVAL;
1014 goto put_dstmem;
1015 }
1016
1017 /* store */
1018 len = dlen + sizeof(struct zswap_header);
1019 ret = zpool_malloc(entry->pool->zpool, len,
1020 __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM,
1021 &handle);
1022 if (ret == -ENOSPC) {
1023 zswap_reject_compress_poor++;
1024 goto put_dstmem;
1025 }
1026 if (ret) {
1027 zswap_reject_alloc_fail++;
1028 goto put_dstmem;
1029 }
1030 zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
1031 zhdr->swpentry = swp_entry(type, offset);
1032 buf = (u8 *)(zhdr + 1);
1033 memcpy(buf, dst, dlen);
1034 zpool_unmap_handle(entry->pool->zpool, handle);
1035 put_cpu_var(zswap_dstmem);
1036
1037 /* populate entry */
1038 entry->offset = offset;
1039 entry->handle = handle;
1040 entry->length = dlen;
1041
1042 /* map */
1043 spin_lock(&tree->lock);
1044 do {
1045 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1046 if (ret == -EEXIST) {
1047 zswap_duplicate_entry++;
1048 /* remove from rbtree */
1049 zswap_rb_erase(&tree->rbroot, dupentry);
1050 zswap_entry_put(tree, dupentry);
1051 }
1052 } while (ret == -EEXIST);
1053 spin_unlock(&tree->lock);
1054
1055 /* update stats */
1056 atomic_inc(&zswap_stored_pages);
1057 zswap_update_total_size();
1058
1059 return 0;
1060
1061put_dstmem:
1062 put_cpu_var(zswap_dstmem);
1063 zswap_pool_put(entry->pool);
1064freepage:
1065 zswap_entry_cache_free(entry);
1066reject:
1067 return ret;
1068}
1069
1070/*
1071 * returns 0 if the page was successfully decompressed
1072 * return -1 on entry not found or error
1073*/
1074static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1075 struct page *page)
1076{
1077 struct zswap_tree *tree = zswap_trees[type];
1078 struct zswap_entry *entry;
1079 struct crypto_comp *tfm;
1080 u8 *src, *dst;
1081 unsigned int dlen;
1082 int ret;
1083
1084 /* find */
1085 spin_lock(&tree->lock);
1086 entry = zswap_entry_find_get(&tree->rbroot, offset);
1087 if (!entry) {
1088 /* entry was written back */
1089 spin_unlock(&tree->lock);
1090 return -1;
1091 }
1092 spin_unlock(&tree->lock);
1093
1094 /* decompress */
1095 dlen = PAGE_SIZE;
1096 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
1097 ZPOOL_MM_RO) + sizeof(struct zswap_header);
1098 dst = kmap_atomic(page);
1099 tfm = *get_cpu_ptr(entry->pool->tfm);
1100 ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
1101 put_cpu_ptr(entry->pool->tfm);
1102 kunmap_atomic(dst);
1103 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1104 BUG_ON(ret);
1105
1106 spin_lock(&tree->lock);
1107 zswap_entry_put(tree, entry);
1108 spin_unlock(&tree->lock);
1109
1110 return 0;
1111}
1112
1113/* frees an entry in zswap */
1114static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1115{
1116 struct zswap_tree *tree = zswap_trees[type];
1117 struct zswap_entry *entry;
1118
1119 /* find */
1120 spin_lock(&tree->lock);
1121 entry = zswap_rb_search(&tree->rbroot, offset);
1122 if (!entry) {
1123 /* entry was written back */
1124 spin_unlock(&tree->lock);
1125 return;
1126 }
1127
1128 /* remove from rbtree */
1129 zswap_rb_erase(&tree->rbroot, entry);
1130
1131 /* drop the initial reference from entry creation */
1132 zswap_entry_put(tree, entry);
1133
1134 spin_unlock(&tree->lock);
1135}
1136
1137/* frees all zswap entries for the given swap type */
1138static void zswap_frontswap_invalidate_area(unsigned type)
1139{
1140 struct zswap_tree *tree = zswap_trees[type];
1141 struct zswap_entry *entry, *n;
1142
1143 if (!tree)
1144 return;
1145
1146 /* walk the tree and free everything */
1147 spin_lock(&tree->lock);
1148 rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1149 zswap_free_entry(entry);
1150 tree->rbroot = RB_ROOT;
1151 spin_unlock(&tree->lock);
1152 kfree(tree);
1153 zswap_trees[type] = NULL;
1154}
1155
1156static void zswap_frontswap_init(unsigned type)
1157{
1158 struct zswap_tree *tree;
1159
1160 tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
1161 if (!tree) {
1162 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1163 return;
1164 }
1165
1166 tree->rbroot = RB_ROOT;
1167 spin_lock_init(&tree->lock);
1168 zswap_trees[type] = tree;
1169}
1170
1171static struct frontswap_ops zswap_frontswap_ops = {
1172 .store = zswap_frontswap_store,
1173 .load = zswap_frontswap_load,
1174 .invalidate_page = zswap_frontswap_invalidate_page,
1175 .invalidate_area = zswap_frontswap_invalidate_area,
1176 .init = zswap_frontswap_init
1177};
1178
1179/*********************************
1180* debugfs functions
1181**********************************/
1182#ifdef CONFIG_DEBUG_FS
1183#include <linux/debugfs.h>
1184
1185static struct dentry *zswap_debugfs_root;
1186
1187static int __init zswap_debugfs_init(void)
1188{
1189 if (!debugfs_initialized())
1190 return -ENODEV;
1191
1192 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1193 if (!zswap_debugfs_root)
1194 return -ENOMEM;
1195
1196 debugfs_create_u64("pool_limit_hit", S_IRUGO,
1197 zswap_debugfs_root, &zswap_pool_limit_hit);
1198 debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
1199 zswap_debugfs_root, &zswap_reject_reclaim_fail);
1200 debugfs_create_u64("reject_alloc_fail", S_IRUGO,
1201 zswap_debugfs_root, &zswap_reject_alloc_fail);
1202 debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
1203 zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1204 debugfs_create_u64("reject_compress_poor", S_IRUGO,
1205 zswap_debugfs_root, &zswap_reject_compress_poor);
1206 debugfs_create_u64("written_back_pages", S_IRUGO,
1207 zswap_debugfs_root, &zswap_written_back_pages);
1208 debugfs_create_u64("duplicate_entry", S_IRUGO,
1209 zswap_debugfs_root, &zswap_duplicate_entry);
1210 debugfs_create_u64("pool_total_size", S_IRUGO,
1211 zswap_debugfs_root, &zswap_pool_total_size);
1212 debugfs_create_atomic_t("stored_pages", S_IRUGO,
1213 zswap_debugfs_root, &zswap_stored_pages);
1214
1215 return 0;
1216}
1217
1218static void __exit zswap_debugfs_exit(void)
1219{
1220 debugfs_remove_recursive(zswap_debugfs_root);
1221}
1222#else
1223static int __init zswap_debugfs_init(void)
1224{
1225 return 0;
1226}
1227
1228static void __exit zswap_debugfs_exit(void) { }
1229#endif
1230
1231/*********************************
1232* module init and exit
1233**********************************/
1234static int __init init_zswap(void)
1235{
1236 struct zswap_pool *pool;
1237
1238 zswap_init_started = true;
1239
1240 if (zswap_entry_cache_create()) {
1241 pr_err("entry cache creation failed\n");
1242 goto cache_fail;
1243 }
1244
1245 if (zswap_cpu_dstmem_init()) {
1246 pr_err("dstmem alloc failed\n");
1247 goto dstmem_fail;
1248 }
1249
1250 pool = __zswap_pool_create_fallback();
1251 if (!pool) {
1252 pr_err("pool creation failed\n");
1253 goto pool_fail;
1254 }
1255 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1256 zpool_get_type(pool->zpool));
1257
1258 list_add(&pool->list, &zswap_pools);
1259
1260 frontswap_register_ops(&zswap_frontswap_ops);
1261 if (zswap_debugfs_init())
1262 pr_warn("debugfs initialization failed\n");
1263 return 0;
1264
1265pool_fail:
1266 zswap_cpu_dstmem_destroy();
1267dstmem_fail:
1268 zswap_entry_cache_destroy();
1269cache_fail:
1270 return -ENOMEM;
1271}
1272/* must be late so crypto has time to come up */
1273late_initcall(init_zswap);
1274
1275MODULE_LICENSE("GPL");
1276MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1277MODULE_DESCRIPTION("Compressed cache for swap pages");