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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
36/*********************************
37* statistics
38**********************************/
39/* Total bytes used by the compressed storage */
40static u64 zswap_pool_total_size;
41/* The number of compressed pages currently stored in zswap */
42static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
43/* The number of same-value filled pages currently stored in zswap */
44static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);
45
46/*
47 * The statistics below are not protected from concurrent access for
48 * performance reasons so they may not be a 100% accurate. However,
49 * they do provide useful information on roughly how many times a
50 * certain event is occurring.
51*/
52
53/* Pool limit was hit (see zswap_max_pool_percent) */
54static u64 zswap_pool_limit_hit;
55/* Pages written back when pool limit was reached */
56static u64 zswap_written_back_pages;
57/* Store failed due to a reclaim failure after pool limit was reached */
58static u64 zswap_reject_reclaim_fail;
59/* Compressed page was too big for the allocator to (optimally) store */
60static u64 zswap_reject_compress_poor;
61/* Store failed because underlying allocator could not get memory */
62static u64 zswap_reject_alloc_fail;
63/* Store failed because the entry metadata could not be allocated (rare) */
64static u64 zswap_reject_kmemcache_fail;
65/* Duplicate store was encountered (rare) */
66static u64 zswap_duplicate_entry;
67
68/*********************************
69* tunables
70**********************************/
71
72#define ZSWAP_PARAM_UNSET ""
73
74/* Enable/disable zswap (disabled by default) */
75static bool zswap_enabled;
76static int zswap_enabled_param_set(const char *,
77 const struct kernel_param *);
78static struct kernel_param_ops zswap_enabled_param_ops = {
79 .set = zswap_enabled_param_set,
80 .get = param_get_bool,
81};
82module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
83
84/* Crypto compressor to use */
85#define ZSWAP_COMPRESSOR_DEFAULT "lzo"
86static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
87static int zswap_compressor_param_set(const char *,
88 const struct kernel_param *);
89static struct kernel_param_ops zswap_compressor_param_ops = {
90 .set = zswap_compressor_param_set,
91 .get = param_get_charp,
92 .free = param_free_charp,
93};
94module_param_cb(compressor, &zswap_compressor_param_ops,
95 &zswap_compressor, 0644);
96
97/* Compressed storage zpool to use */
98#define ZSWAP_ZPOOL_DEFAULT "zbud"
99static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
100static int zswap_zpool_param_set(const char *, const struct kernel_param *);
101static struct kernel_param_ops zswap_zpool_param_ops = {
102 .set = zswap_zpool_param_set,
103 .get = param_get_charp,
104 .free = param_free_charp,
105};
106module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
107
108/* The maximum percentage of memory that the compressed pool can occupy */
109static unsigned int zswap_max_pool_percent = 20;
110module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
111
112/* Enable/disable handling same-value filled pages (enabled by default) */
113static bool zswap_same_filled_pages_enabled = true;
114module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
115 bool, 0644);
116
117/*********************************
118* data structures
119**********************************/
120
121struct zswap_pool {
122 struct zpool *zpool;
123 struct crypto_comp * __percpu *tfm;
124 struct kref kref;
125 struct list_head list;
126 struct work_struct work;
127 struct hlist_node node;
128 char tfm_name[CRYPTO_MAX_ALG_NAME];
129};
130
131/*
132 * struct zswap_entry
133 *
134 * This structure contains the metadata for tracking a single compressed
135 * page within zswap.
136 *
137 * rbnode - links the entry into red-black tree for the appropriate swap type
138 * offset - the swap offset for the entry. Index into the red-black tree.
139 * refcount - the number of outstanding reference to the entry. This is needed
140 * to protect against premature freeing of the entry by code
141 * concurrent calls to load, invalidate, and writeback. The lock
142 * for the zswap_tree structure that contains the entry must
143 * be held while changing the refcount. Since the lock must
144 * be held, there is no reason to also make refcount atomic.
145 * length - the length in bytes of the compressed page data. Needed during
146 * decompression. For a same value filled page length is 0.
147 * pool - the zswap_pool the entry's data is in
148 * handle - zpool allocation handle that stores the compressed page data
149 * value - value of the same-value filled pages which have same content
150 */
151struct zswap_entry {
152 struct rb_node rbnode;
153 pgoff_t offset;
154 int refcount;
155 unsigned int length;
156 struct zswap_pool *pool;
157 union {
158 unsigned long handle;
159 unsigned long value;
160 };
161};
162
163struct zswap_header {
164 swp_entry_t swpentry;
165};
166
167/*
168 * The tree lock in the zswap_tree struct protects a few things:
169 * - the rbtree
170 * - the refcount field of each entry in the tree
171 */
172struct zswap_tree {
173 struct rb_root rbroot;
174 spinlock_t lock;
175};
176
177static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
178
179/* RCU-protected iteration */
180static LIST_HEAD(zswap_pools);
181/* protects zswap_pools list modification */
182static DEFINE_SPINLOCK(zswap_pools_lock);
183/* pool counter to provide unique names to zpool */
184static atomic_t zswap_pools_count = ATOMIC_INIT(0);
185
186/* used by param callback function */
187static bool zswap_init_started;
188
189/* fatal error during init */
190static bool zswap_init_failed;
191
192/* init completed, but couldn't create the initial pool */
193static bool zswap_has_pool;
194
195/*********************************
196* helpers and fwd declarations
197**********************************/
198
199#define zswap_pool_debug(msg, p) \
200 pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \
201 zpool_get_type((p)->zpool))
202
203static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
204static int zswap_pool_get(struct zswap_pool *pool);
205static void zswap_pool_put(struct zswap_pool *pool);
206
207static const struct zpool_ops zswap_zpool_ops = {
208 .evict = zswap_writeback_entry
209};
210
211static bool zswap_is_full(void)
212{
213 return totalram_pages() * zswap_max_pool_percent / 100 <
214 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
215}
216
217static void zswap_update_total_size(void)
218{
219 struct zswap_pool *pool;
220 u64 total = 0;
221
222 rcu_read_lock();
223
224 list_for_each_entry_rcu(pool, &zswap_pools, list)
225 total += zpool_get_total_size(pool->zpool);
226
227 rcu_read_unlock();
228
229 zswap_pool_total_size = total;
230}
231
232/*********************************
233* zswap entry functions
234**********************************/
235static struct kmem_cache *zswap_entry_cache;
236
237static int __init zswap_entry_cache_create(void)
238{
239 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
240 return zswap_entry_cache == NULL;
241}
242
243static void __init zswap_entry_cache_destroy(void)
244{
245 kmem_cache_destroy(zswap_entry_cache);
246}
247
248static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
249{
250 struct zswap_entry *entry;
251 entry = kmem_cache_alloc(zswap_entry_cache, gfp);
252 if (!entry)
253 return NULL;
254 entry->refcount = 1;
255 RB_CLEAR_NODE(&entry->rbnode);
256 return entry;
257}
258
259static void zswap_entry_cache_free(struct zswap_entry *entry)
260{
261 kmem_cache_free(zswap_entry_cache, entry);
262}
263
264/*********************************
265* rbtree functions
266**********************************/
267static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
268{
269 struct rb_node *node = root->rb_node;
270 struct zswap_entry *entry;
271
272 while (node) {
273 entry = rb_entry(node, struct zswap_entry, rbnode);
274 if (entry->offset > offset)
275 node = node->rb_left;
276 else if (entry->offset < offset)
277 node = node->rb_right;
278 else
279 return entry;
280 }
281 return NULL;
282}
283
284/*
285 * In the case that a entry with the same offset is found, a pointer to
286 * the existing entry is stored in dupentry and the function returns -EEXIST
287 */
288static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
289 struct zswap_entry **dupentry)
290{
291 struct rb_node **link = &root->rb_node, *parent = NULL;
292 struct zswap_entry *myentry;
293
294 while (*link) {
295 parent = *link;
296 myentry = rb_entry(parent, struct zswap_entry, rbnode);
297 if (myentry->offset > entry->offset)
298 link = &(*link)->rb_left;
299 else if (myentry->offset < entry->offset)
300 link = &(*link)->rb_right;
301 else {
302 *dupentry = myentry;
303 return -EEXIST;
304 }
305 }
306 rb_link_node(&entry->rbnode, parent, link);
307 rb_insert_color(&entry->rbnode, root);
308 return 0;
309}
310
311static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
312{
313 if (!RB_EMPTY_NODE(&entry->rbnode)) {
314 rb_erase(&entry->rbnode, root);
315 RB_CLEAR_NODE(&entry->rbnode);
316 }
317}
318
319/*
320 * Carries out the common pattern of freeing and entry's zpool allocation,
321 * freeing the entry itself, and decrementing the number of stored pages.
322 */
323static void zswap_free_entry(struct zswap_entry *entry)
324{
325 if (!entry->length)
326 atomic_dec(&zswap_same_filled_pages);
327 else {
328 zpool_free(entry->pool->zpool, entry->handle);
329 zswap_pool_put(entry->pool);
330 }
331 zswap_entry_cache_free(entry);
332 atomic_dec(&zswap_stored_pages);
333 zswap_update_total_size();
334}
335
336/* caller must hold the tree lock */
337static void zswap_entry_get(struct zswap_entry *entry)
338{
339 entry->refcount++;
340}
341
342/* caller must hold the tree lock
343* remove from the tree and free it, if nobody reference the entry
344*/
345static void zswap_entry_put(struct zswap_tree *tree,
346 struct zswap_entry *entry)
347{
348 int refcount = --entry->refcount;
349
350 BUG_ON(refcount < 0);
351 if (refcount == 0) {
352 zswap_rb_erase(&tree->rbroot, entry);
353 zswap_free_entry(entry);
354 }
355}
356
357/* caller must hold the tree lock */
358static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
359 pgoff_t offset)
360{
361 struct zswap_entry *entry;
362
363 entry = zswap_rb_search(root, offset);
364 if (entry)
365 zswap_entry_get(entry);
366
367 return entry;
368}
369
370/*********************************
371* per-cpu code
372**********************************/
373static DEFINE_PER_CPU(u8 *, zswap_dstmem);
374
375static int zswap_dstmem_prepare(unsigned int cpu)
376{
377 u8 *dst;
378
379 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
380 if (!dst)
381 return -ENOMEM;
382
383 per_cpu(zswap_dstmem, cpu) = dst;
384 return 0;
385}
386
387static int zswap_dstmem_dead(unsigned int cpu)
388{
389 u8 *dst;
390
391 dst = per_cpu(zswap_dstmem, cpu);
392 kfree(dst);
393 per_cpu(zswap_dstmem, cpu) = NULL;
394
395 return 0;
396}
397
398static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
399{
400 struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
401 struct crypto_comp *tfm;
402
403 if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
404 return 0;
405
406 tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
407 if (IS_ERR_OR_NULL(tfm)) {
408 pr_err("could not alloc crypto comp %s : %ld\n",
409 pool->tfm_name, PTR_ERR(tfm));
410 return -ENOMEM;
411 }
412 *per_cpu_ptr(pool->tfm, cpu) = tfm;
413 return 0;
414}
415
416static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
417{
418 struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
419 struct crypto_comp *tfm;
420
421 tfm = *per_cpu_ptr(pool->tfm, cpu);
422 if (!IS_ERR_OR_NULL(tfm))
423 crypto_free_comp(tfm);
424 *per_cpu_ptr(pool->tfm, cpu) = NULL;
425 return 0;
426}
427
428/*********************************
429* pool functions
430**********************************/
431
432static struct zswap_pool *__zswap_pool_current(void)
433{
434 struct zswap_pool *pool;
435
436 pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
437 WARN_ONCE(!pool && zswap_has_pool,
438 "%s: no page storage pool!\n", __func__);
439
440 return pool;
441}
442
443static struct zswap_pool *zswap_pool_current(void)
444{
445 assert_spin_locked(&zswap_pools_lock);
446
447 return __zswap_pool_current();
448}
449
450static struct zswap_pool *zswap_pool_current_get(void)
451{
452 struct zswap_pool *pool;
453
454 rcu_read_lock();
455
456 pool = __zswap_pool_current();
457 if (!zswap_pool_get(pool))
458 pool = NULL;
459
460 rcu_read_unlock();
461
462 return pool;
463}
464
465static struct zswap_pool *zswap_pool_last_get(void)
466{
467 struct zswap_pool *pool, *last = NULL;
468
469 rcu_read_lock();
470
471 list_for_each_entry_rcu(pool, &zswap_pools, list)
472 last = pool;
473 WARN_ONCE(!last && zswap_has_pool,
474 "%s: no page storage pool!\n", __func__);
475 if (!zswap_pool_get(last))
476 last = NULL;
477
478 rcu_read_unlock();
479
480 return last;
481}
482
483/* type and compressor must be null-terminated */
484static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
485{
486 struct zswap_pool *pool;
487
488 assert_spin_locked(&zswap_pools_lock);
489
490 list_for_each_entry_rcu(pool, &zswap_pools, list) {
491 if (strcmp(pool->tfm_name, compressor))
492 continue;
493 if (strcmp(zpool_get_type(pool->zpool), type))
494 continue;
495 /* if we can't get it, it's about to be destroyed */
496 if (!zswap_pool_get(pool))
497 continue;
498 return pool;
499 }
500
501 return NULL;
502}
503
504static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
505{
506 struct zswap_pool *pool;
507 char name[38]; /* 'zswap' + 32 char (max) num + \0 */
508 gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
509 int ret;
510
511 if (!zswap_has_pool) {
512 /* if either are unset, pool initialization failed, and we
513 * need both params to be set correctly before trying to
514 * create a pool.
515 */
516 if (!strcmp(type, ZSWAP_PARAM_UNSET))
517 return NULL;
518 if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
519 return NULL;
520 }
521
522 pool = kzalloc(sizeof(*pool), GFP_KERNEL);
523 if (!pool)
524 return NULL;
525
526 /* unique name for each pool specifically required by zsmalloc */
527 snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
528
529 pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
530 if (!pool->zpool) {
531 pr_err("%s zpool not available\n", type);
532 goto error;
533 }
534 pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
535
536 strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
537 pool->tfm = alloc_percpu(struct crypto_comp *);
538 if (!pool->tfm) {
539 pr_err("percpu alloc failed\n");
540 goto error;
541 }
542
543 ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
544 &pool->node);
545 if (ret)
546 goto error;
547 pr_debug("using %s compressor\n", pool->tfm_name);
548
549 /* being the current pool takes 1 ref; this func expects the
550 * caller to always add the new pool as the current pool
551 */
552 kref_init(&pool->kref);
553 INIT_LIST_HEAD(&pool->list);
554
555 zswap_pool_debug("created", pool);
556
557 return pool;
558
559error:
560 free_percpu(pool->tfm);
561 if (pool->zpool)
562 zpool_destroy_pool(pool->zpool);
563 kfree(pool);
564 return NULL;
565}
566
567static __init struct zswap_pool *__zswap_pool_create_fallback(void)
568{
569 bool has_comp, has_zpool;
570
571 has_comp = crypto_has_comp(zswap_compressor, 0, 0);
572 if (!has_comp && strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {
573 pr_err("compressor %s not available, using default %s\n",
574 zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
575 param_free_charp(&zswap_compressor);
576 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
577 has_comp = crypto_has_comp(zswap_compressor, 0, 0);
578 }
579 if (!has_comp) {
580 pr_err("default compressor %s not available\n",
581 zswap_compressor);
582 param_free_charp(&zswap_compressor);
583 zswap_compressor = ZSWAP_PARAM_UNSET;
584 }
585
586 has_zpool = zpool_has_pool(zswap_zpool_type);
587 if (!has_zpool && strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
588 pr_err("zpool %s not available, using default %s\n",
589 zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
590 param_free_charp(&zswap_zpool_type);
591 zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
592 has_zpool = zpool_has_pool(zswap_zpool_type);
593 }
594 if (!has_zpool) {
595 pr_err("default zpool %s not available\n",
596 zswap_zpool_type);
597 param_free_charp(&zswap_zpool_type);
598 zswap_zpool_type = ZSWAP_PARAM_UNSET;
599 }
600
601 if (!has_comp || !has_zpool)
602 return NULL;
603
604 return zswap_pool_create(zswap_zpool_type, zswap_compressor);
605}
606
607static void zswap_pool_destroy(struct zswap_pool *pool)
608{
609 zswap_pool_debug("destroying", pool);
610
611 cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
612 free_percpu(pool->tfm);
613 zpool_destroy_pool(pool->zpool);
614 kfree(pool);
615}
616
617static int __must_check zswap_pool_get(struct zswap_pool *pool)
618{
619 if (!pool)
620 return 0;
621
622 return kref_get_unless_zero(&pool->kref);
623}
624
625static void __zswap_pool_release(struct work_struct *work)
626{
627 struct zswap_pool *pool = container_of(work, typeof(*pool), work);
628
629 synchronize_rcu();
630
631 /* nobody should have been able to get a kref... */
632 WARN_ON(kref_get_unless_zero(&pool->kref));
633
634 /* pool is now off zswap_pools list and has no references. */
635 zswap_pool_destroy(pool);
636}
637
638static void __zswap_pool_empty(struct kref *kref)
639{
640 struct zswap_pool *pool;
641
642 pool = container_of(kref, typeof(*pool), kref);
643
644 spin_lock(&zswap_pools_lock);
645
646 WARN_ON(pool == zswap_pool_current());
647
648 list_del_rcu(&pool->list);
649
650 INIT_WORK(&pool->work, __zswap_pool_release);
651 schedule_work(&pool->work);
652
653 spin_unlock(&zswap_pools_lock);
654}
655
656static void zswap_pool_put(struct zswap_pool *pool)
657{
658 kref_put(&pool->kref, __zswap_pool_empty);
659}
660
661/*********************************
662* param callbacks
663**********************************/
664
665/* val must be a null-terminated string */
666static int __zswap_param_set(const char *val, const struct kernel_param *kp,
667 char *type, char *compressor)
668{
669 struct zswap_pool *pool, *put_pool = NULL;
670 char *s = strstrip((char *)val);
671 int ret;
672
673 if (zswap_init_failed) {
674 pr_err("can't set param, initialization failed\n");
675 return -ENODEV;
676 }
677
678 /* no change required */
679 if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
680 return 0;
681
682 /* if this is load-time (pre-init) param setting,
683 * don't create a pool; that's done during init.
684 */
685 if (!zswap_init_started)
686 return param_set_charp(s, kp);
687
688 if (!type) {
689 if (!zpool_has_pool(s)) {
690 pr_err("zpool %s not available\n", s);
691 return -ENOENT;
692 }
693 type = s;
694 } else if (!compressor) {
695 if (!crypto_has_comp(s, 0, 0)) {
696 pr_err("compressor %s not available\n", s);
697 return -ENOENT;
698 }
699 compressor = s;
700 } else {
701 WARN_ON(1);
702 return -EINVAL;
703 }
704
705 spin_lock(&zswap_pools_lock);
706
707 pool = zswap_pool_find_get(type, compressor);
708 if (pool) {
709 zswap_pool_debug("using existing", pool);
710 WARN_ON(pool == zswap_pool_current());
711 list_del_rcu(&pool->list);
712 }
713
714 spin_unlock(&zswap_pools_lock);
715
716 if (!pool)
717 pool = zswap_pool_create(type, compressor);
718
719 if (pool)
720 ret = param_set_charp(s, kp);
721 else
722 ret = -EINVAL;
723
724 spin_lock(&zswap_pools_lock);
725
726 if (!ret) {
727 put_pool = zswap_pool_current();
728 list_add_rcu(&pool->list, &zswap_pools);
729 zswap_has_pool = true;
730 } else if (pool) {
731 /* add the possibly pre-existing pool to the end of the pools
732 * list; if it's new (and empty) then it'll be removed and
733 * destroyed by the put after we drop the lock
734 */
735 list_add_tail_rcu(&pool->list, &zswap_pools);
736 put_pool = pool;
737 }
738
739 spin_unlock(&zswap_pools_lock);
740
741 if (!zswap_has_pool && !pool) {
742 /* if initial pool creation failed, and this pool creation also
743 * failed, maybe both compressor and zpool params were bad.
744 * Allow changing this param, so pool creation will succeed
745 * when the other param is changed. We already verified this
746 * param is ok in the zpool_has_pool() or crypto_has_comp()
747 * checks above.
748 */
749 ret = param_set_charp(s, kp);
750 }
751
752 /* drop the ref from either the old current pool,
753 * or the new pool we failed to add
754 */
755 if (put_pool)
756 zswap_pool_put(put_pool);
757
758 return ret;
759}
760
761static int zswap_compressor_param_set(const char *val,
762 const struct kernel_param *kp)
763{
764 return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
765}
766
767static int zswap_zpool_param_set(const char *val,
768 const struct kernel_param *kp)
769{
770 return __zswap_param_set(val, kp, NULL, zswap_compressor);
771}
772
773static int zswap_enabled_param_set(const char *val,
774 const struct kernel_param *kp)
775{
776 if (zswap_init_failed) {
777 pr_err("can't enable, initialization failed\n");
778 return -ENODEV;
779 }
780 if (!zswap_has_pool && zswap_init_started) {
781 pr_err("can't enable, no pool configured\n");
782 return -ENODEV;
783 }
784
785 return param_set_bool(val, kp);
786}
787
788/*********************************
789* writeback code
790**********************************/
791/* return enum for zswap_get_swap_cache_page */
792enum zswap_get_swap_ret {
793 ZSWAP_SWAPCACHE_NEW,
794 ZSWAP_SWAPCACHE_EXIST,
795 ZSWAP_SWAPCACHE_FAIL,
796};
797
798/*
799 * zswap_get_swap_cache_page
800 *
801 * This is an adaption of read_swap_cache_async()
802 *
803 * This function tries to find a page with the given swap entry
804 * in the swapper_space address space (the swap cache). If the page
805 * is found, it is returned in retpage. Otherwise, a page is allocated,
806 * added to the swap cache, and returned in retpage.
807 *
808 * If success, the swap cache page is returned in retpage
809 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
810 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
811 * the new page is added to swapcache and locked
812 * Returns ZSWAP_SWAPCACHE_FAIL on error
813 */
814static int zswap_get_swap_cache_page(swp_entry_t entry,
815 struct page **retpage)
816{
817 bool page_was_allocated;
818
819 *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
820 NULL, 0, &page_was_allocated);
821 if (page_was_allocated)
822 return ZSWAP_SWAPCACHE_NEW;
823 if (!*retpage)
824 return ZSWAP_SWAPCACHE_FAIL;
825 return ZSWAP_SWAPCACHE_EXIST;
826}
827
828/*
829 * Attempts to free an entry by adding a page to the swap cache,
830 * decompressing the entry data into the page, and issuing a
831 * bio write to write the page back to the swap device.
832 *
833 * This can be thought of as a "resumed writeback" of the page
834 * to the swap device. We are basically resuming the same swap
835 * writeback path that was intercepted with the frontswap_store()
836 * in the first place. After the page has been decompressed into
837 * the swap cache, the compressed version stored by zswap can be
838 * freed.
839 */
840static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
841{
842 struct zswap_header *zhdr;
843 swp_entry_t swpentry;
844 struct zswap_tree *tree;
845 pgoff_t offset;
846 struct zswap_entry *entry;
847 struct page *page;
848 struct crypto_comp *tfm;
849 u8 *src, *dst;
850 unsigned int dlen;
851 int ret;
852 struct writeback_control wbc = {
853 .sync_mode = WB_SYNC_NONE,
854 };
855
856 /* extract swpentry from data */
857 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
858 swpentry = zhdr->swpentry; /* here */
859 tree = zswap_trees[swp_type(swpentry)];
860 offset = swp_offset(swpentry);
861
862 /* find and ref zswap entry */
863 spin_lock(&tree->lock);
864 entry = zswap_entry_find_get(&tree->rbroot, offset);
865 if (!entry) {
866 /* entry was invalidated */
867 spin_unlock(&tree->lock);
868 zpool_unmap_handle(pool, handle);
869 return 0;
870 }
871 spin_unlock(&tree->lock);
872 BUG_ON(offset != entry->offset);
873
874 /* try to allocate swap cache page */
875 switch (zswap_get_swap_cache_page(swpentry, &page)) {
876 case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
877 ret = -ENOMEM;
878 goto fail;
879
880 case ZSWAP_SWAPCACHE_EXIST:
881 /* page is already in the swap cache, ignore for now */
882 put_page(page);
883 ret = -EEXIST;
884 goto fail;
885
886 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
887 /* decompress */
888 dlen = PAGE_SIZE;
889 src = (u8 *)zhdr + sizeof(struct zswap_header);
890 dst = kmap_atomic(page);
891 tfm = *get_cpu_ptr(entry->pool->tfm);
892 ret = crypto_comp_decompress(tfm, src, entry->length,
893 dst, &dlen);
894 put_cpu_ptr(entry->pool->tfm);
895 kunmap_atomic(dst);
896 BUG_ON(ret);
897 BUG_ON(dlen != PAGE_SIZE);
898
899 /* page is up to date */
900 SetPageUptodate(page);
901 }
902
903 /* move it to the tail of the inactive list after end_writeback */
904 SetPageReclaim(page);
905
906 /* start writeback */
907 __swap_writepage(page, &wbc, end_swap_bio_write);
908 put_page(page);
909 zswap_written_back_pages++;
910
911 spin_lock(&tree->lock);
912 /* drop local reference */
913 zswap_entry_put(tree, entry);
914
915 /*
916 * There are two possible situations for entry here:
917 * (1) refcount is 1(normal case), entry is valid and on the tree
918 * (2) refcount is 0, entry is freed and not on the tree
919 * because invalidate happened during writeback
920 * search the tree and free the entry if find entry
921 */
922 if (entry == zswap_rb_search(&tree->rbroot, offset))
923 zswap_entry_put(tree, entry);
924 spin_unlock(&tree->lock);
925
926 goto end;
927
928 /*
929 * if we get here due to ZSWAP_SWAPCACHE_EXIST
930 * a load may happening concurrently
931 * it is safe and okay to not free the entry
932 * if we free the entry in the following put
933 * it it either okay to return !0
934 */
935fail:
936 spin_lock(&tree->lock);
937 zswap_entry_put(tree, entry);
938 spin_unlock(&tree->lock);
939
940end:
941 zpool_unmap_handle(pool, handle);
942 return ret;
943}
944
945static int zswap_shrink(void)
946{
947 struct zswap_pool *pool;
948 int ret;
949
950 pool = zswap_pool_last_get();
951 if (!pool)
952 return -ENOENT;
953
954 ret = zpool_shrink(pool->zpool, 1, NULL);
955
956 zswap_pool_put(pool);
957
958 return ret;
959}
960
961static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
962{
963 unsigned int pos;
964 unsigned long *page;
965
966 page = (unsigned long *)ptr;
967 for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
968 if (page[pos] != page[0])
969 return 0;
970 }
971 *value = page[0];
972 return 1;
973}
974
975static void zswap_fill_page(void *ptr, unsigned long value)
976{
977 unsigned long *page;
978
979 page = (unsigned long *)ptr;
980 memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
981}
982
983/*********************************
984* frontswap hooks
985**********************************/
986/* attempts to compress and store an single page */
987static int zswap_frontswap_store(unsigned type, pgoff_t offset,
988 struct page *page)
989{
990 struct zswap_tree *tree = zswap_trees[type];
991 struct zswap_entry *entry, *dupentry;
992 struct crypto_comp *tfm;
993 int ret;
994 unsigned int hlen, dlen = PAGE_SIZE;
995 unsigned long handle, value;
996 char *buf;
997 u8 *src, *dst;
998 struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
999 gfp_t gfp;
1000
1001 /* THP isn't supported */
1002 if (PageTransHuge(page)) {
1003 ret = -EINVAL;
1004 goto reject;
1005 }
1006
1007 if (!zswap_enabled || !tree) {
1008 ret = -ENODEV;
1009 goto reject;
1010 }
1011
1012 /* reclaim space if needed */
1013 if (zswap_is_full()) {
1014 zswap_pool_limit_hit++;
1015 if (zswap_shrink()) {
1016 zswap_reject_reclaim_fail++;
1017 ret = -ENOMEM;
1018 goto reject;
1019 }
1020
1021 /* A second zswap_is_full() check after
1022 * zswap_shrink() to make sure it's now
1023 * under the max_pool_percent
1024 */
1025 if (zswap_is_full()) {
1026 ret = -ENOMEM;
1027 goto reject;
1028 }
1029 }
1030
1031 /* allocate entry */
1032 entry = zswap_entry_cache_alloc(GFP_KERNEL);
1033 if (!entry) {
1034 zswap_reject_kmemcache_fail++;
1035 ret = -ENOMEM;
1036 goto reject;
1037 }
1038
1039 if (zswap_same_filled_pages_enabled) {
1040 src = kmap_atomic(page);
1041 if (zswap_is_page_same_filled(src, &value)) {
1042 kunmap_atomic(src);
1043 entry->offset = offset;
1044 entry->length = 0;
1045 entry->value = value;
1046 atomic_inc(&zswap_same_filled_pages);
1047 goto insert_entry;
1048 }
1049 kunmap_atomic(src);
1050 }
1051
1052 /* if entry is successfully added, it keeps the reference */
1053 entry->pool = zswap_pool_current_get();
1054 if (!entry->pool) {
1055 ret = -EINVAL;
1056 goto freepage;
1057 }
1058
1059 /* compress */
1060 dst = get_cpu_var(zswap_dstmem);
1061 tfm = *get_cpu_ptr(entry->pool->tfm);
1062 src = kmap_atomic(page);
1063 ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
1064 kunmap_atomic(src);
1065 put_cpu_ptr(entry->pool->tfm);
1066 if (ret) {
1067 ret = -EINVAL;
1068 goto put_dstmem;
1069 }
1070
1071 /* store */
1072 hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
1073 gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
1074 if (zpool_malloc_support_movable(entry->pool->zpool))
1075 gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
1076 ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle);
1077 if (ret == -ENOSPC) {
1078 zswap_reject_compress_poor++;
1079 goto put_dstmem;
1080 }
1081 if (ret) {
1082 zswap_reject_alloc_fail++;
1083 goto put_dstmem;
1084 }
1085 buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
1086 memcpy(buf, &zhdr, hlen);
1087 memcpy(buf + hlen, dst, dlen);
1088 zpool_unmap_handle(entry->pool->zpool, handle);
1089 put_cpu_var(zswap_dstmem);
1090
1091 /* populate entry */
1092 entry->offset = offset;
1093 entry->handle = handle;
1094 entry->length = dlen;
1095
1096insert_entry:
1097 /* map */
1098 spin_lock(&tree->lock);
1099 do {
1100 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1101 if (ret == -EEXIST) {
1102 zswap_duplicate_entry++;
1103 /* remove from rbtree */
1104 zswap_rb_erase(&tree->rbroot, dupentry);
1105 zswap_entry_put(tree, dupentry);
1106 }
1107 } while (ret == -EEXIST);
1108 spin_unlock(&tree->lock);
1109
1110 /* update stats */
1111 atomic_inc(&zswap_stored_pages);
1112 zswap_update_total_size();
1113
1114 return 0;
1115
1116put_dstmem:
1117 put_cpu_var(zswap_dstmem);
1118 zswap_pool_put(entry->pool);
1119freepage:
1120 zswap_entry_cache_free(entry);
1121reject:
1122 return ret;
1123}
1124
1125/*
1126 * returns 0 if the page was successfully decompressed
1127 * return -1 on entry not found or error
1128*/
1129static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1130 struct page *page)
1131{
1132 struct zswap_tree *tree = zswap_trees[type];
1133 struct zswap_entry *entry;
1134 struct crypto_comp *tfm;
1135 u8 *src, *dst;
1136 unsigned int dlen;
1137 int ret;
1138
1139 /* find */
1140 spin_lock(&tree->lock);
1141 entry = zswap_entry_find_get(&tree->rbroot, offset);
1142 if (!entry) {
1143 /* entry was written back */
1144 spin_unlock(&tree->lock);
1145 return -1;
1146 }
1147 spin_unlock(&tree->lock);
1148
1149 if (!entry->length) {
1150 dst = kmap_atomic(page);
1151 zswap_fill_page(dst, entry->value);
1152 kunmap_atomic(dst);
1153 goto freeentry;
1154 }
1155
1156 /* decompress */
1157 dlen = PAGE_SIZE;
1158 src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
1159 if (zpool_evictable(entry->pool->zpool))
1160 src += sizeof(struct zswap_header);
1161 dst = kmap_atomic(page);
1162 tfm = *get_cpu_ptr(entry->pool->tfm);
1163 ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
1164 put_cpu_ptr(entry->pool->tfm);
1165 kunmap_atomic(dst);
1166 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1167 BUG_ON(ret);
1168
1169freeentry:
1170 spin_lock(&tree->lock);
1171 zswap_entry_put(tree, entry);
1172 spin_unlock(&tree->lock);
1173
1174 return 0;
1175}
1176
1177/* frees an entry in zswap */
1178static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1179{
1180 struct zswap_tree *tree = zswap_trees[type];
1181 struct zswap_entry *entry;
1182
1183 /* find */
1184 spin_lock(&tree->lock);
1185 entry = zswap_rb_search(&tree->rbroot, offset);
1186 if (!entry) {
1187 /* entry was written back */
1188 spin_unlock(&tree->lock);
1189 return;
1190 }
1191
1192 /* remove from rbtree */
1193 zswap_rb_erase(&tree->rbroot, entry);
1194
1195 /* drop the initial reference from entry creation */
1196 zswap_entry_put(tree, entry);
1197
1198 spin_unlock(&tree->lock);
1199}
1200
1201/* frees all zswap entries for the given swap type */
1202static void zswap_frontswap_invalidate_area(unsigned type)
1203{
1204 struct zswap_tree *tree = zswap_trees[type];
1205 struct zswap_entry *entry, *n;
1206
1207 if (!tree)
1208 return;
1209
1210 /* walk the tree and free everything */
1211 spin_lock(&tree->lock);
1212 rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1213 zswap_free_entry(entry);
1214 tree->rbroot = RB_ROOT;
1215 spin_unlock(&tree->lock);
1216 kfree(tree);
1217 zswap_trees[type] = NULL;
1218}
1219
1220static void zswap_frontswap_init(unsigned type)
1221{
1222 struct zswap_tree *tree;
1223
1224 tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1225 if (!tree) {
1226 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1227 return;
1228 }
1229
1230 tree->rbroot = RB_ROOT;
1231 spin_lock_init(&tree->lock);
1232 zswap_trees[type] = tree;
1233}
1234
1235static struct frontswap_ops zswap_frontswap_ops = {
1236 .store = zswap_frontswap_store,
1237 .load = zswap_frontswap_load,
1238 .invalidate_page = zswap_frontswap_invalidate_page,
1239 .invalidate_area = zswap_frontswap_invalidate_area,
1240 .init = zswap_frontswap_init
1241};
1242
1243/*********************************
1244* debugfs functions
1245**********************************/
1246#ifdef CONFIG_DEBUG_FS
1247#include <linux/debugfs.h>
1248
1249static struct dentry *zswap_debugfs_root;
1250
1251static int __init zswap_debugfs_init(void)
1252{
1253 if (!debugfs_initialized())
1254 return -ENODEV;
1255
1256 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1257
1258 debugfs_create_u64("pool_limit_hit", 0444,
1259 zswap_debugfs_root, &zswap_pool_limit_hit);
1260 debugfs_create_u64("reject_reclaim_fail", 0444,
1261 zswap_debugfs_root, &zswap_reject_reclaim_fail);
1262 debugfs_create_u64("reject_alloc_fail", 0444,
1263 zswap_debugfs_root, &zswap_reject_alloc_fail);
1264 debugfs_create_u64("reject_kmemcache_fail", 0444,
1265 zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1266 debugfs_create_u64("reject_compress_poor", 0444,
1267 zswap_debugfs_root, &zswap_reject_compress_poor);
1268 debugfs_create_u64("written_back_pages", 0444,
1269 zswap_debugfs_root, &zswap_written_back_pages);
1270 debugfs_create_u64("duplicate_entry", 0444,
1271 zswap_debugfs_root, &zswap_duplicate_entry);
1272 debugfs_create_u64("pool_total_size", 0444,
1273 zswap_debugfs_root, &zswap_pool_total_size);
1274 debugfs_create_atomic_t("stored_pages", 0444,
1275 zswap_debugfs_root, &zswap_stored_pages);
1276 debugfs_create_atomic_t("same_filled_pages", 0444,
1277 zswap_debugfs_root, &zswap_same_filled_pages);
1278
1279 return 0;
1280}
1281
1282static void __exit zswap_debugfs_exit(void)
1283{
1284 debugfs_remove_recursive(zswap_debugfs_root);
1285}
1286#else
1287static int __init zswap_debugfs_init(void)
1288{
1289 return 0;
1290}
1291
1292static void __exit zswap_debugfs_exit(void) { }
1293#endif
1294
1295/*********************************
1296* module init and exit
1297**********************************/
1298static int __init init_zswap(void)
1299{
1300 struct zswap_pool *pool;
1301 int ret;
1302
1303 zswap_init_started = true;
1304
1305 if (zswap_entry_cache_create()) {
1306 pr_err("entry cache creation failed\n");
1307 goto cache_fail;
1308 }
1309
1310 ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1311 zswap_dstmem_prepare, zswap_dstmem_dead);
1312 if (ret) {
1313 pr_err("dstmem alloc failed\n");
1314 goto dstmem_fail;
1315 }
1316
1317 ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1318 "mm/zswap_pool:prepare",
1319 zswap_cpu_comp_prepare,
1320 zswap_cpu_comp_dead);
1321 if (ret)
1322 goto hp_fail;
1323
1324 pool = __zswap_pool_create_fallback();
1325 if (pool) {
1326 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1327 zpool_get_type(pool->zpool));
1328 list_add(&pool->list, &zswap_pools);
1329 zswap_has_pool = true;
1330 } else {
1331 pr_err("pool creation failed\n");
1332 zswap_enabled = false;
1333 }
1334
1335 frontswap_register_ops(&zswap_frontswap_ops);
1336 if (zswap_debugfs_init())
1337 pr_warn("debugfs initialization failed\n");
1338 return 0;
1339
1340hp_fail:
1341 cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1342dstmem_fail:
1343 zswap_entry_cache_destroy();
1344cache_fail:
1345 /* if built-in, we aren't unloaded on failure; don't allow use */
1346 zswap_init_failed = true;
1347 zswap_enabled = false;
1348 return -ENOMEM;
1349}
1350/* must be late so crypto has time to come up */
1351late_initcall(init_zswap);
1352
1353MODULE_LICENSE("GPL");
1354MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1355MODULE_DESCRIPTION("Compressed cache for swap pages");
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/scatterlist.h>
28#include <linux/mempool.h>
29#include <linux/zpool.h>
30#include <crypto/acompress.h>
31
32#include <linux/mm_types.h>
33#include <linux/page-flags.h>
34#include <linux/swapops.h>
35#include <linux/writeback.h>
36#include <linux/pagemap.h>
37#include <linux/workqueue.h>
38
39#include "swap.h"
40
41/*********************************
42* statistics
43**********************************/
44/* Total bytes used by the compressed storage */
45u64 zswap_pool_total_size;
46/* The number of compressed pages currently stored in zswap */
47atomic_t zswap_stored_pages = ATOMIC_INIT(0);
48/* The number of same-value filled pages currently stored in zswap */
49static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);
50
51/*
52 * The statistics below are not protected from concurrent access for
53 * performance reasons so they may not be a 100% accurate. However,
54 * they do provide useful information on roughly how many times a
55 * certain event is occurring.
56*/
57
58/* Pool limit was hit (see zswap_max_pool_percent) */
59static u64 zswap_pool_limit_hit;
60/* Pages written back when pool limit was reached */
61static u64 zswap_written_back_pages;
62/* Store failed due to a reclaim failure after pool limit was reached */
63static u64 zswap_reject_reclaim_fail;
64/* Compressed page was too big for the allocator to (optimally) store */
65static u64 zswap_reject_compress_poor;
66/* Store failed because underlying allocator could not get memory */
67static u64 zswap_reject_alloc_fail;
68/* Store failed because the entry metadata could not be allocated (rare) */
69static u64 zswap_reject_kmemcache_fail;
70/* Duplicate store was encountered (rare) */
71static u64 zswap_duplicate_entry;
72
73/* Shrinker work queue */
74static struct workqueue_struct *shrink_wq;
75/* Pool limit was hit, we need to calm down */
76static bool zswap_pool_reached_full;
77
78/*********************************
79* tunables
80**********************************/
81
82#define ZSWAP_PARAM_UNSET ""
83
84/* Enable/disable zswap */
85static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON);
86static int zswap_enabled_param_set(const char *,
87 const struct kernel_param *);
88static const struct kernel_param_ops zswap_enabled_param_ops = {
89 .set = zswap_enabled_param_set,
90 .get = param_get_bool,
91};
92module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
93
94/* Crypto compressor to use */
95static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
96static int zswap_compressor_param_set(const char *,
97 const struct kernel_param *);
98static const struct kernel_param_ops zswap_compressor_param_ops = {
99 .set = zswap_compressor_param_set,
100 .get = param_get_charp,
101 .free = param_free_charp,
102};
103module_param_cb(compressor, &zswap_compressor_param_ops,
104 &zswap_compressor, 0644);
105
106/* Compressed storage zpool to use */
107static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
108static int zswap_zpool_param_set(const char *, const struct kernel_param *);
109static const struct kernel_param_ops zswap_zpool_param_ops = {
110 .set = zswap_zpool_param_set,
111 .get = param_get_charp,
112 .free = param_free_charp,
113};
114module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
115
116/* The maximum percentage of memory that the compressed pool can occupy */
117static unsigned int zswap_max_pool_percent = 20;
118module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
119
120/* The threshold for accepting new pages after the max_pool_percent was hit */
121static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */
122module_param_named(accept_threshold_percent, zswap_accept_thr_percent,
123 uint, 0644);
124
125/*
126 * Enable/disable handling same-value filled pages (enabled by default).
127 * If disabled every page is considered non-same-value filled.
128 */
129static bool zswap_same_filled_pages_enabled = true;
130module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
131 bool, 0644);
132
133/* Enable/disable handling non-same-value filled pages (enabled by default) */
134static bool zswap_non_same_filled_pages_enabled = true;
135module_param_named(non_same_filled_pages_enabled, zswap_non_same_filled_pages_enabled,
136 bool, 0644);
137
138/*********************************
139* data structures
140**********************************/
141
142struct crypto_acomp_ctx {
143 struct crypto_acomp *acomp;
144 struct acomp_req *req;
145 struct crypto_wait wait;
146 u8 *dstmem;
147 struct mutex *mutex;
148};
149
150struct zswap_pool {
151 struct zpool *zpool;
152 struct crypto_acomp_ctx __percpu *acomp_ctx;
153 struct kref kref;
154 struct list_head list;
155 struct work_struct release_work;
156 struct work_struct shrink_work;
157 struct hlist_node node;
158 char tfm_name[CRYPTO_MAX_ALG_NAME];
159};
160
161/*
162 * struct zswap_entry
163 *
164 * This structure contains the metadata for tracking a single compressed
165 * page within zswap.
166 *
167 * rbnode - links the entry into red-black tree for the appropriate swap type
168 * offset - the swap offset for the entry. Index into the red-black tree.
169 * refcount - the number of outstanding reference to the entry. This is needed
170 * to protect against premature freeing of the entry by code
171 * concurrent calls to load, invalidate, and writeback. The lock
172 * for the zswap_tree structure that contains the entry must
173 * be held while changing the refcount. Since the lock must
174 * be held, there is no reason to also make refcount atomic.
175 * length - the length in bytes of the compressed page data. Needed during
176 * decompression. For a same value filled page length is 0.
177 * pool - the zswap_pool the entry's data is in
178 * handle - zpool allocation handle that stores the compressed page data
179 * value - value of the same-value filled pages which have same content
180 */
181struct zswap_entry {
182 struct rb_node rbnode;
183 pgoff_t offset;
184 int refcount;
185 unsigned int length;
186 struct zswap_pool *pool;
187 union {
188 unsigned long handle;
189 unsigned long value;
190 };
191 struct obj_cgroup *objcg;
192};
193
194struct zswap_header {
195 swp_entry_t swpentry;
196};
197
198/*
199 * The tree lock in the zswap_tree struct protects a few things:
200 * - the rbtree
201 * - the refcount field of each entry in the tree
202 */
203struct zswap_tree {
204 struct rb_root rbroot;
205 spinlock_t lock;
206};
207
208static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
209
210/* RCU-protected iteration */
211static LIST_HEAD(zswap_pools);
212/* protects zswap_pools list modification */
213static DEFINE_SPINLOCK(zswap_pools_lock);
214/* pool counter to provide unique names to zpool */
215static atomic_t zswap_pools_count = ATOMIC_INIT(0);
216
217/* used by param callback function */
218static bool zswap_init_started;
219
220/* fatal error during init */
221static bool zswap_init_failed;
222
223/* init completed, but couldn't create the initial pool */
224static bool zswap_has_pool;
225
226/*********************************
227* helpers and fwd declarations
228**********************************/
229
230#define zswap_pool_debug(msg, p) \
231 pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \
232 zpool_get_type((p)->zpool))
233
234static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
235static int zswap_pool_get(struct zswap_pool *pool);
236static void zswap_pool_put(struct zswap_pool *pool);
237
238static const struct zpool_ops zswap_zpool_ops = {
239 .evict = zswap_writeback_entry
240};
241
242static bool zswap_is_full(void)
243{
244 return totalram_pages() * zswap_max_pool_percent / 100 <
245 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
246}
247
248static bool zswap_can_accept(void)
249{
250 return totalram_pages() * zswap_accept_thr_percent / 100 *
251 zswap_max_pool_percent / 100 >
252 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
253}
254
255static void zswap_update_total_size(void)
256{
257 struct zswap_pool *pool;
258 u64 total = 0;
259
260 rcu_read_lock();
261
262 list_for_each_entry_rcu(pool, &zswap_pools, list)
263 total += zpool_get_total_size(pool->zpool);
264
265 rcu_read_unlock();
266
267 zswap_pool_total_size = total;
268}
269
270/*********************************
271* zswap entry functions
272**********************************/
273static struct kmem_cache *zswap_entry_cache;
274
275static int __init zswap_entry_cache_create(void)
276{
277 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
278 return zswap_entry_cache == NULL;
279}
280
281static void __init zswap_entry_cache_destroy(void)
282{
283 kmem_cache_destroy(zswap_entry_cache);
284}
285
286static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
287{
288 struct zswap_entry *entry;
289 entry = kmem_cache_alloc(zswap_entry_cache, gfp);
290 if (!entry)
291 return NULL;
292 entry->refcount = 1;
293 RB_CLEAR_NODE(&entry->rbnode);
294 return entry;
295}
296
297static void zswap_entry_cache_free(struct zswap_entry *entry)
298{
299 kmem_cache_free(zswap_entry_cache, entry);
300}
301
302/*********************************
303* rbtree functions
304**********************************/
305static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
306{
307 struct rb_node *node = root->rb_node;
308 struct zswap_entry *entry;
309
310 while (node) {
311 entry = rb_entry(node, struct zswap_entry, rbnode);
312 if (entry->offset > offset)
313 node = node->rb_left;
314 else if (entry->offset < offset)
315 node = node->rb_right;
316 else
317 return entry;
318 }
319 return NULL;
320}
321
322/*
323 * In the case that a entry with the same offset is found, a pointer to
324 * the existing entry is stored in dupentry and the function returns -EEXIST
325 */
326static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
327 struct zswap_entry **dupentry)
328{
329 struct rb_node **link = &root->rb_node, *parent = NULL;
330 struct zswap_entry *myentry;
331
332 while (*link) {
333 parent = *link;
334 myentry = rb_entry(parent, struct zswap_entry, rbnode);
335 if (myentry->offset > entry->offset)
336 link = &(*link)->rb_left;
337 else if (myentry->offset < entry->offset)
338 link = &(*link)->rb_right;
339 else {
340 *dupentry = myentry;
341 return -EEXIST;
342 }
343 }
344 rb_link_node(&entry->rbnode, parent, link);
345 rb_insert_color(&entry->rbnode, root);
346 return 0;
347}
348
349static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
350{
351 if (!RB_EMPTY_NODE(&entry->rbnode)) {
352 rb_erase(&entry->rbnode, root);
353 RB_CLEAR_NODE(&entry->rbnode);
354 }
355}
356
357/*
358 * Carries out the common pattern of freeing and entry's zpool allocation,
359 * freeing the entry itself, and decrementing the number of stored pages.
360 */
361static void zswap_free_entry(struct zswap_entry *entry)
362{
363 if (entry->objcg) {
364 obj_cgroup_uncharge_zswap(entry->objcg, entry->length);
365 obj_cgroup_put(entry->objcg);
366 }
367 if (!entry->length)
368 atomic_dec(&zswap_same_filled_pages);
369 else {
370 zpool_free(entry->pool->zpool, entry->handle);
371 zswap_pool_put(entry->pool);
372 }
373 zswap_entry_cache_free(entry);
374 atomic_dec(&zswap_stored_pages);
375 zswap_update_total_size();
376}
377
378/* caller must hold the tree lock */
379static void zswap_entry_get(struct zswap_entry *entry)
380{
381 entry->refcount++;
382}
383
384/* caller must hold the tree lock
385* remove from the tree and free it, if nobody reference the entry
386*/
387static void zswap_entry_put(struct zswap_tree *tree,
388 struct zswap_entry *entry)
389{
390 int refcount = --entry->refcount;
391
392 BUG_ON(refcount < 0);
393 if (refcount == 0) {
394 zswap_rb_erase(&tree->rbroot, entry);
395 zswap_free_entry(entry);
396 }
397}
398
399/* caller must hold the tree lock */
400static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
401 pgoff_t offset)
402{
403 struct zswap_entry *entry;
404
405 entry = zswap_rb_search(root, offset);
406 if (entry)
407 zswap_entry_get(entry);
408
409 return entry;
410}
411
412/*********************************
413* per-cpu code
414**********************************/
415static DEFINE_PER_CPU(u8 *, zswap_dstmem);
416/*
417 * If users dynamically change the zpool type and compressor at runtime, i.e.
418 * zswap is running, zswap can have more than one zpool on one cpu, but they
419 * are sharing dtsmem. So we need this mutex to be per-cpu.
420 */
421static DEFINE_PER_CPU(struct mutex *, zswap_mutex);
422
423static int zswap_dstmem_prepare(unsigned int cpu)
424{
425 struct mutex *mutex;
426 u8 *dst;
427
428 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
429 if (!dst)
430 return -ENOMEM;
431
432 mutex = kmalloc_node(sizeof(*mutex), GFP_KERNEL, cpu_to_node(cpu));
433 if (!mutex) {
434 kfree(dst);
435 return -ENOMEM;
436 }
437
438 mutex_init(mutex);
439 per_cpu(zswap_dstmem, cpu) = dst;
440 per_cpu(zswap_mutex, cpu) = mutex;
441 return 0;
442}
443
444static int zswap_dstmem_dead(unsigned int cpu)
445{
446 struct mutex *mutex;
447 u8 *dst;
448
449 mutex = per_cpu(zswap_mutex, cpu);
450 kfree(mutex);
451 per_cpu(zswap_mutex, cpu) = NULL;
452
453 dst = per_cpu(zswap_dstmem, cpu);
454 kfree(dst);
455 per_cpu(zswap_dstmem, cpu) = NULL;
456
457 return 0;
458}
459
460static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
461{
462 struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
463 struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
464 struct crypto_acomp *acomp;
465 struct acomp_req *req;
466
467 acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu));
468 if (IS_ERR(acomp)) {
469 pr_err("could not alloc crypto acomp %s : %ld\n",
470 pool->tfm_name, PTR_ERR(acomp));
471 return PTR_ERR(acomp);
472 }
473 acomp_ctx->acomp = acomp;
474
475 req = acomp_request_alloc(acomp_ctx->acomp);
476 if (!req) {
477 pr_err("could not alloc crypto acomp_request %s\n",
478 pool->tfm_name);
479 crypto_free_acomp(acomp_ctx->acomp);
480 return -ENOMEM;
481 }
482 acomp_ctx->req = req;
483
484 crypto_init_wait(&acomp_ctx->wait);
485 /*
486 * if the backend of acomp is async zip, crypto_req_done() will wakeup
487 * crypto_wait_req(); if the backend of acomp is scomp, the callback
488 * won't be called, crypto_wait_req() will return without blocking.
489 */
490 acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
491 crypto_req_done, &acomp_ctx->wait);
492
493 acomp_ctx->mutex = per_cpu(zswap_mutex, cpu);
494 acomp_ctx->dstmem = per_cpu(zswap_dstmem, cpu);
495
496 return 0;
497}
498
499static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
500{
501 struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
502 struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
503
504 if (!IS_ERR_OR_NULL(acomp_ctx)) {
505 if (!IS_ERR_OR_NULL(acomp_ctx->req))
506 acomp_request_free(acomp_ctx->req);
507 if (!IS_ERR_OR_NULL(acomp_ctx->acomp))
508 crypto_free_acomp(acomp_ctx->acomp);
509 }
510
511 return 0;
512}
513
514/*********************************
515* pool functions
516**********************************/
517
518static struct zswap_pool *__zswap_pool_current(void)
519{
520 struct zswap_pool *pool;
521
522 pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
523 WARN_ONCE(!pool && zswap_has_pool,
524 "%s: no page storage pool!\n", __func__);
525
526 return pool;
527}
528
529static struct zswap_pool *zswap_pool_current(void)
530{
531 assert_spin_locked(&zswap_pools_lock);
532
533 return __zswap_pool_current();
534}
535
536static struct zswap_pool *zswap_pool_current_get(void)
537{
538 struct zswap_pool *pool;
539
540 rcu_read_lock();
541
542 pool = __zswap_pool_current();
543 if (!zswap_pool_get(pool))
544 pool = NULL;
545
546 rcu_read_unlock();
547
548 return pool;
549}
550
551static struct zswap_pool *zswap_pool_last_get(void)
552{
553 struct zswap_pool *pool, *last = NULL;
554
555 rcu_read_lock();
556
557 list_for_each_entry_rcu(pool, &zswap_pools, list)
558 last = pool;
559 WARN_ONCE(!last && zswap_has_pool,
560 "%s: no page storage pool!\n", __func__);
561 if (!zswap_pool_get(last))
562 last = NULL;
563
564 rcu_read_unlock();
565
566 return last;
567}
568
569/* type and compressor must be null-terminated */
570static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
571{
572 struct zswap_pool *pool;
573
574 assert_spin_locked(&zswap_pools_lock);
575
576 list_for_each_entry_rcu(pool, &zswap_pools, list) {
577 if (strcmp(pool->tfm_name, compressor))
578 continue;
579 if (strcmp(zpool_get_type(pool->zpool), type))
580 continue;
581 /* if we can't get it, it's about to be destroyed */
582 if (!zswap_pool_get(pool))
583 continue;
584 return pool;
585 }
586
587 return NULL;
588}
589
590static void shrink_worker(struct work_struct *w)
591{
592 struct zswap_pool *pool = container_of(w, typeof(*pool),
593 shrink_work);
594
595 if (zpool_shrink(pool->zpool, 1, NULL))
596 zswap_reject_reclaim_fail++;
597 zswap_pool_put(pool);
598}
599
600static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
601{
602 struct zswap_pool *pool;
603 char name[38]; /* 'zswap' + 32 char (max) num + \0 */
604 gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
605 int ret;
606
607 if (!zswap_has_pool) {
608 /* if either are unset, pool initialization failed, and we
609 * need both params to be set correctly before trying to
610 * create a pool.
611 */
612 if (!strcmp(type, ZSWAP_PARAM_UNSET))
613 return NULL;
614 if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
615 return NULL;
616 }
617
618 pool = kzalloc(sizeof(*pool), GFP_KERNEL);
619 if (!pool)
620 return NULL;
621
622 /* unique name for each pool specifically required by zsmalloc */
623 snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
624
625 pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
626 if (!pool->zpool) {
627 pr_err("%s zpool not available\n", type);
628 goto error;
629 }
630 pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
631
632 strscpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
633
634 pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx);
635 if (!pool->acomp_ctx) {
636 pr_err("percpu alloc failed\n");
637 goto error;
638 }
639
640 ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
641 &pool->node);
642 if (ret)
643 goto error;
644 pr_debug("using %s compressor\n", pool->tfm_name);
645
646 /* being the current pool takes 1 ref; this func expects the
647 * caller to always add the new pool as the current pool
648 */
649 kref_init(&pool->kref);
650 INIT_LIST_HEAD(&pool->list);
651 INIT_WORK(&pool->shrink_work, shrink_worker);
652
653 zswap_pool_debug("created", pool);
654
655 return pool;
656
657error:
658 if (pool->acomp_ctx)
659 free_percpu(pool->acomp_ctx);
660 if (pool->zpool)
661 zpool_destroy_pool(pool->zpool);
662 kfree(pool);
663 return NULL;
664}
665
666static __init struct zswap_pool *__zswap_pool_create_fallback(void)
667{
668 bool has_comp, has_zpool;
669
670 has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
671 if (!has_comp && strcmp(zswap_compressor,
672 CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
673 pr_err("compressor %s not available, using default %s\n",
674 zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
675 param_free_charp(&zswap_compressor);
676 zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
677 has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
678 }
679 if (!has_comp) {
680 pr_err("default compressor %s not available\n",
681 zswap_compressor);
682 param_free_charp(&zswap_compressor);
683 zswap_compressor = ZSWAP_PARAM_UNSET;
684 }
685
686 has_zpool = zpool_has_pool(zswap_zpool_type);
687 if (!has_zpool && strcmp(zswap_zpool_type,
688 CONFIG_ZSWAP_ZPOOL_DEFAULT)) {
689 pr_err("zpool %s not available, using default %s\n",
690 zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);
691 param_free_charp(&zswap_zpool_type);
692 zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
693 has_zpool = zpool_has_pool(zswap_zpool_type);
694 }
695 if (!has_zpool) {
696 pr_err("default zpool %s not available\n",
697 zswap_zpool_type);
698 param_free_charp(&zswap_zpool_type);
699 zswap_zpool_type = ZSWAP_PARAM_UNSET;
700 }
701
702 if (!has_comp || !has_zpool)
703 return NULL;
704
705 return zswap_pool_create(zswap_zpool_type, zswap_compressor);
706}
707
708static void zswap_pool_destroy(struct zswap_pool *pool)
709{
710 zswap_pool_debug("destroying", pool);
711
712 cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
713 free_percpu(pool->acomp_ctx);
714 zpool_destroy_pool(pool->zpool);
715 kfree(pool);
716}
717
718static int __must_check zswap_pool_get(struct zswap_pool *pool)
719{
720 if (!pool)
721 return 0;
722
723 return kref_get_unless_zero(&pool->kref);
724}
725
726static void __zswap_pool_release(struct work_struct *work)
727{
728 struct zswap_pool *pool = container_of(work, typeof(*pool),
729 release_work);
730
731 synchronize_rcu();
732
733 /* nobody should have been able to get a kref... */
734 WARN_ON(kref_get_unless_zero(&pool->kref));
735
736 /* pool is now off zswap_pools list and has no references. */
737 zswap_pool_destroy(pool);
738}
739
740static void __zswap_pool_empty(struct kref *kref)
741{
742 struct zswap_pool *pool;
743
744 pool = container_of(kref, typeof(*pool), kref);
745
746 spin_lock(&zswap_pools_lock);
747
748 WARN_ON(pool == zswap_pool_current());
749
750 list_del_rcu(&pool->list);
751
752 INIT_WORK(&pool->release_work, __zswap_pool_release);
753 schedule_work(&pool->release_work);
754
755 spin_unlock(&zswap_pools_lock);
756}
757
758static void zswap_pool_put(struct zswap_pool *pool)
759{
760 kref_put(&pool->kref, __zswap_pool_empty);
761}
762
763/*********************************
764* param callbacks
765**********************************/
766
767/* val must be a null-terminated string */
768static int __zswap_param_set(const char *val, const struct kernel_param *kp,
769 char *type, char *compressor)
770{
771 struct zswap_pool *pool, *put_pool = NULL;
772 char *s = strstrip((char *)val);
773 int ret;
774
775 if (zswap_init_failed) {
776 pr_err("can't set param, initialization failed\n");
777 return -ENODEV;
778 }
779
780 /* no change required */
781 if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
782 return 0;
783
784 /* if this is load-time (pre-init) param setting,
785 * don't create a pool; that's done during init.
786 */
787 if (!zswap_init_started)
788 return param_set_charp(s, kp);
789
790 if (!type) {
791 if (!zpool_has_pool(s)) {
792 pr_err("zpool %s not available\n", s);
793 return -ENOENT;
794 }
795 type = s;
796 } else if (!compressor) {
797 if (!crypto_has_acomp(s, 0, 0)) {
798 pr_err("compressor %s not available\n", s);
799 return -ENOENT;
800 }
801 compressor = s;
802 } else {
803 WARN_ON(1);
804 return -EINVAL;
805 }
806
807 spin_lock(&zswap_pools_lock);
808
809 pool = zswap_pool_find_get(type, compressor);
810 if (pool) {
811 zswap_pool_debug("using existing", pool);
812 WARN_ON(pool == zswap_pool_current());
813 list_del_rcu(&pool->list);
814 }
815
816 spin_unlock(&zswap_pools_lock);
817
818 if (!pool)
819 pool = zswap_pool_create(type, compressor);
820
821 if (pool)
822 ret = param_set_charp(s, kp);
823 else
824 ret = -EINVAL;
825
826 spin_lock(&zswap_pools_lock);
827
828 if (!ret) {
829 put_pool = zswap_pool_current();
830 list_add_rcu(&pool->list, &zswap_pools);
831 zswap_has_pool = true;
832 } else if (pool) {
833 /* add the possibly pre-existing pool to the end of the pools
834 * list; if it's new (and empty) then it'll be removed and
835 * destroyed by the put after we drop the lock
836 */
837 list_add_tail_rcu(&pool->list, &zswap_pools);
838 put_pool = pool;
839 }
840
841 spin_unlock(&zswap_pools_lock);
842
843 if (!zswap_has_pool && !pool) {
844 /* if initial pool creation failed, and this pool creation also
845 * failed, maybe both compressor and zpool params were bad.
846 * Allow changing this param, so pool creation will succeed
847 * when the other param is changed. We already verified this
848 * param is ok in the zpool_has_pool() or crypto_has_acomp()
849 * checks above.
850 */
851 ret = param_set_charp(s, kp);
852 }
853
854 /* drop the ref from either the old current pool,
855 * or the new pool we failed to add
856 */
857 if (put_pool)
858 zswap_pool_put(put_pool);
859
860 return ret;
861}
862
863static int zswap_compressor_param_set(const char *val,
864 const struct kernel_param *kp)
865{
866 return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
867}
868
869static int zswap_zpool_param_set(const char *val,
870 const struct kernel_param *kp)
871{
872 return __zswap_param_set(val, kp, NULL, zswap_compressor);
873}
874
875static int zswap_enabled_param_set(const char *val,
876 const struct kernel_param *kp)
877{
878 if (zswap_init_failed) {
879 pr_err("can't enable, initialization failed\n");
880 return -ENODEV;
881 }
882 if (!zswap_has_pool && zswap_init_started) {
883 pr_err("can't enable, no pool configured\n");
884 return -ENODEV;
885 }
886
887 return param_set_bool(val, kp);
888}
889
890/*********************************
891* writeback code
892**********************************/
893/* return enum for zswap_get_swap_cache_page */
894enum zswap_get_swap_ret {
895 ZSWAP_SWAPCACHE_NEW,
896 ZSWAP_SWAPCACHE_EXIST,
897 ZSWAP_SWAPCACHE_FAIL,
898};
899
900/*
901 * zswap_get_swap_cache_page
902 *
903 * This is an adaption of read_swap_cache_async()
904 *
905 * This function tries to find a page with the given swap entry
906 * in the swapper_space address space (the swap cache). If the page
907 * is found, it is returned in retpage. Otherwise, a page is allocated,
908 * added to the swap cache, and returned in retpage.
909 *
910 * If success, the swap cache page is returned in retpage
911 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
912 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
913 * the new page is added to swapcache and locked
914 * Returns ZSWAP_SWAPCACHE_FAIL on error
915 */
916static int zswap_get_swap_cache_page(swp_entry_t entry,
917 struct page **retpage)
918{
919 bool page_was_allocated;
920
921 *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
922 NULL, 0, &page_was_allocated);
923 if (page_was_allocated)
924 return ZSWAP_SWAPCACHE_NEW;
925 if (!*retpage)
926 return ZSWAP_SWAPCACHE_FAIL;
927 return ZSWAP_SWAPCACHE_EXIST;
928}
929
930/*
931 * Attempts to free an entry by adding a page to the swap cache,
932 * decompressing the entry data into the page, and issuing a
933 * bio write to write the page back to the swap device.
934 *
935 * This can be thought of as a "resumed writeback" of the page
936 * to the swap device. We are basically resuming the same swap
937 * writeback path that was intercepted with the frontswap_store()
938 * in the first place. After the page has been decompressed into
939 * the swap cache, the compressed version stored by zswap can be
940 * freed.
941 */
942static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
943{
944 struct zswap_header *zhdr;
945 swp_entry_t swpentry;
946 struct zswap_tree *tree;
947 pgoff_t offset;
948 struct zswap_entry *entry;
949 struct page *page;
950 struct scatterlist input, output;
951 struct crypto_acomp_ctx *acomp_ctx;
952
953 u8 *src, *tmp = NULL;
954 unsigned int dlen;
955 int ret;
956 struct writeback_control wbc = {
957 .sync_mode = WB_SYNC_NONE,
958 };
959
960 if (!zpool_can_sleep_mapped(pool)) {
961 tmp = kmalloc(PAGE_SIZE, GFP_KERNEL);
962 if (!tmp)
963 return -ENOMEM;
964 }
965
966 /* extract swpentry from data */
967 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
968 swpentry = zhdr->swpentry; /* here */
969 tree = zswap_trees[swp_type(swpentry)];
970 offset = swp_offset(swpentry);
971 zpool_unmap_handle(pool, handle);
972
973 /* find and ref zswap entry */
974 spin_lock(&tree->lock);
975 entry = zswap_entry_find_get(&tree->rbroot, offset);
976 if (!entry) {
977 /* entry was invalidated */
978 spin_unlock(&tree->lock);
979 kfree(tmp);
980 return 0;
981 }
982 spin_unlock(&tree->lock);
983 BUG_ON(offset != entry->offset);
984
985 /* try to allocate swap cache page */
986 switch (zswap_get_swap_cache_page(swpentry, &page)) {
987 case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
988 ret = -ENOMEM;
989 goto fail;
990
991 case ZSWAP_SWAPCACHE_EXIST:
992 /* page is already in the swap cache, ignore for now */
993 put_page(page);
994 ret = -EEXIST;
995 goto fail;
996
997 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
998 /* decompress */
999 acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1000 dlen = PAGE_SIZE;
1001
1002 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
1003 src = (u8 *)zhdr + sizeof(struct zswap_header);
1004 if (!zpool_can_sleep_mapped(pool)) {
1005 memcpy(tmp, src, entry->length);
1006 src = tmp;
1007 zpool_unmap_handle(pool, handle);
1008 }
1009
1010 mutex_lock(acomp_ctx->mutex);
1011 sg_init_one(&input, src, entry->length);
1012 sg_init_table(&output, 1);
1013 sg_set_page(&output, page, PAGE_SIZE, 0);
1014 acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1015 ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1016 dlen = acomp_ctx->req->dlen;
1017 mutex_unlock(acomp_ctx->mutex);
1018
1019 if (!zpool_can_sleep_mapped(pool))
1020 kfree(tmp);
1021 else
1022 zpool_unmap_handle(pool, handle);
1023
1024 BUG_ON(ret);
1025 BUG_ON(dlen != PAGE_SIZE);
1026
1027 /* page is up to date */
1028 SetPageUptodate(page);
1029 }
1030
1031 /* move it to the tail of the inactive list after end_writeback */
1032 SetPageReclaim(page);
1033
1034 /* start writeback */
1035 __swap_writepage(page, &wbc);
1036 put_page(page);
1037 zswap_written_back_pages++;
1038
1039 spin_lock(&tree->lock);
1040 /* drop local reference */
1041 zswap_entry_put(tree, entry);
1042
1043 /*
1044 * There are two possible situations for entry here:
1045 * (1) refcount is 1(normal case), entry is valid and on the tree
1046 * (2) refcount is 0, entry is freed and not on the tree
1047 * because invalidate happened during writeback
1048 * search the tree and free the entry if find entry
1049 */
1050 if (entry == zswap_rb_search(&tree->rbroot, offset))
1051 zswap_entry_put(tree, entry);
1052 spin_unlock(&tree->lock);
1053
1054 return ret;
1055
1056fail:
1057 if (!zpool_can_sleep_mapped(pool))
1058 kfree(tmp);
1059
1060 /*
1061 * if we get here due to ZSWAP_SWAPCACHE_EXIST
1062 * a load may be happening concurrently.
1063 * it is safe and okay to not free the entry.
1064 * if we free the entry in the following put
1065 * it is also okay to return !0
1066 */
1067 spin_lock(&tree->lock);
1068 zswap_entry_put(tree, entry);
1069 spin_unlock(&tree->lock);
1070
1071 return ret;
1072}
1073
1074static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
1075{
1076 unsigned int pos;
1077 unsigned long *page;
1078
1079 page = (unsigned long *)ptr;
1080 for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
1081 if (page[pos] != page[0])
1082 return 0;
1083 }
1084 *value = page[0];
1085 return 1;
1086}
1087
1088static void zswap_fill_page(void *ptr, unsigned long value)
1089{
1090 unsigned long *page;
1091
1092 page = (unsigned long *)ptr;
1093 memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
1094}
1095
1096/*********************************
1097* frontswap hooks
1098**********************************/
1099/* attempts to compress and store an single page */
1100static int zswap_frontswap_store(unsigned type, pgoff_t offset,
1101 struct page *page)
1102{
1103 struct zswap_tree *tree = zswap_trees[type];
1104 struct zswap_entry *entry, *dupentry;
1105 struct scatterlist input, output;
1106 struct crypto_acomp_ctx *acomp_ctx;
1107 struct obj_cgroup *objcg = NULL;
1108 struct zswap_pool *pool;
1109 int ret;
1110 unsigned int hlen, dlen = PAGE_SIZE;
1111 unsigned long handle, value;
1112 char *buf;
1113 u8 *src, *dst;
1114 struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
1115 gfp_t gfp;
1116
1117 /* THP isn't supported */
1118 if (PageTransHuge(page)) {
1119 ret = -EINVAL;
1120 goto reject;
1121 }
1122
1123 if (!zswap_enabled || !tree) {
1124 ret = -ENODEV;
1125 goto reject;
1126 }
1127
1128 objcg = get_obj_cgroup_from_page(page);
1129 if (objcg && !obj_cgroup_may_zswap(objcg))
1130 goto shrink;
1131
1132 /* reclaim space if needed */
1133 if (zswap_is_full()) {
1134 zswap_pool_limit_hit++;
1135 zswap_pool_reached_full = true;
1136 goto shrink;
1137 }
1138
1139 if (zswap_pool_reached_full) {
1140 if (!zswap_can_accept()) {
1141 ret = -ENOMEM;
1142 goto reject;
1143 } else
1144 zswap_pool_reached_full = false;
1145 }
1146
1147 /* allocate entry */
1148 entry = zswap_entry_cache_alloc(GFP_KERNEL);
1149 if (!entry) {
1150 zswap_reject_kmemcache_fail++;
1151 ret = -ENOMEM;
1152 goto reject;
1153 }
1154
1155 if (zswap_same_filled_pages_enabled) {
1156 src = kmap_atomic(page);
1157 if (zswap_is_page_same_filled(src, &value)) {
1158 kunmap_atomic(src);
1159 entry->offset = offset;
1160 entry->length = 0;
1161 entry->value = value;
1162 atomic_inc(&zswap_same_filled_pages);
1163 goto insert_entry;
1164 }
1165 kunmap_atomic(src);
1166 }
1167
1168 if (!zswap_non_same_filled_pages_enabled) {
1169 ret = -EINVAL;
1170 goto freepage;
1171 }
1172
1173 /* if entry is successfully added, it keeps the reference */
1174 entry->pool = zswap_pool_current_get();
1175 if (!entry->pool) {
1176 ret = -EINVAL;
1177 goto freepage;
1178 }
1179
1180 /* compress */
1181 acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1182
1183 mutex_lock(acomp_ctx->mutex);
1184
1185 dst = acomp_ctx->dstmem;
1186 sg_init_table(&input, 1);
1187 sg_set_page(&input, page, PAGE_SIZE, 0);
1188
1189 /* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */
1190 sg_init_one(&output, dst, PAGE_SIZE * 2);
1191 acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);
1192 /*
1193 * it maybe looks a little bit silly that we send an asynchronous request,
1194 * then wait for its completion synchronously. This makes the process look
1195 * synchronous in fact.
1196 * Theoretically, acomp supports users send multiple acomp requests in one
1197 * acomp instance, then get those requests done simultaneously. but in this
1198 * case, frontswap actually does store and load page by page, there is no
1199 * existing method to send the second page before the first page is done
1200 * in one thread doing frontswap.
1201 * but in different threads running on different cpu, we have different
1202 * acomp instance, so multiple threads can do (de)compression in parallel.
1203 */
1204 ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
1205 dlen = acomp_ctx->req->dlen;
1206
1207 if (ret) {
1208 ret = -EINVAL;
1209 goto put_dstmem;
1210 }
1211
1212 /* store */
1213 hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
1214 gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
1215 if (zpool_malloc_support_movable(entry->pool->zpool))
1216 gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
1217 ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle);
1218 if (ret == -ENOSPC) {
1219 zswap_reject_compress_poor++;
1220 goto put_dstmem;
1221 }
1222 if (ret) {
1223 zswap_reject_alloc_fail++;
1224 goto put_dstmem;
1225 }
1226 buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_WO);
1227 memcpy(buf, &zhdr, hlen);
1228 memcpy(buf + hlen, dst, dlen);
1229 zpool_unmap_handle(entry->pool->zpool, handle);
1230 mutex_unlock(acomp_ctx->mutex);
1231
1232 /* populate entry */
1233 entry->offset = offset;
1234 entry->handle = handle;
1235 entry->length = dlen;
1236
1237insert_entry:
1238 entry->objcg = objcg;
1239 if (objcg) {
1240 obj_cgroup_charge_zswap(objcg, entry->length);
1241 /* Account before objcg ref is moved to tree */
1242 count_objcg_event(objcg, ZSWPOUT);
1243 }
1244
1245 /* map */
1246 spin_lock(&tree->lock);
1247 do {
1248 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1249 if (ret == -EEXIST) {
1250 zswap_duplicate_entry++;
1251 /* remove from rbtree */
1252 zswap_rb_erase(&tree->rbroot, dupentry);
1253 zswap_entry_put(tree, dupentry);
1254 }
1255 } while (ret == -EEXIST);
1256 spin_unlock(&tree->lock);
1257
1258 /* update stats */
1259 atomic_inc(&zswap_stored_pages);
1260 zswap_update_total_size();
1261 count_vm_event(ZSWPOUT);
1262
1263 return 0;
1264
1265put_dstmem:
1266 mutex_unlock(acomp_ctx->mutex);
1267 zswap_pool_put(entry->pool);
1268freepage:
1269 zswap_entry_cache_free(entry);
1270reject:
1271 if (objcg)
1272 obj_cgroup_put(objcg);
1273 return ret;
1274
1275shrink:
1276 pool = zswap_pool_last_get();
1277 if (pool)
1278 queue_work(shrink_wq, &pool->shrink_work);
1279 ret = -ENOMEM;
1280 goto reject;
1281}
1282
1283/*
1284 * returns 0 if the page was successfully decompressed
1285 * return -1 on entry not found or error
1286*/
1287static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1288 struct page *page)
1289{
1290 struct zswap_tree *tree = zswap_trees[type];
1291 struct zswap_entry *entry;
1292 struct scatterlist input, output;
1293 struct crypto_acomp_ctx *acomp_ctx;
1294 u8 *src, *dst, *tmp;
1295 unsigned int dlen;
1296 int ret;
1297
1298 /* find */
1299 spin_lock(&tree->lock);
1300 entry = zswap_entry_find_get(&tree->rbroot, offset);
1301 if (!entry) {
1302 /* entry was written back */
1303 spin_unlock(&tree->lock);
1304 return -1;
1305 }
1306 spin_unlock(&tree->lock);
1307
1308 if (!entry->length) {
1309 dst = kmap_atomic(page);
1310 zswap_fill_page(dst, entry->value);
1311 kunmap_atomic(dst);
1312 ret = 0;
1313 goto stats;
1314 }
1315
1316 if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
1317 tmp = kmalloc(entry->length, GFP_KERNEL);
1318 if (!tmp) {
1319 ret = -ENOMEM;
1320 goto freeentry;
1321 }
1322 }
1323
1324 /* decompress */
1325 dlen = PAGE_SIZE;
1326 src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
1327 if (zpool_evictable(entry->pool->zpool))
1328 src += sizeof(struct zswap_header);
1329
1330 if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
1331 memcpy(tmp, src, entry->length);
1332 src = tmp;
1333 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1334 }
1335
1336 acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1337 mutex_lock(acomp_ctx->mutex);
1338 sg_init_one(&input, src, entry->length);
1339 sg_init_table(&output, 1);
1340 sg_set_page(&output, page, PAGE_SIZE, 0);
1341 acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1342 ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1343 mutex_unlock(acomp_ctx->mutex);
1344
1345 if (zpool_can_sleep_mapped(entry->pool->zpool))
1346 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1347 else
1348 kfree(tmp);
1349
1350 BUG_ON(ret);
1351stats:
1352 count_vm_event(ZSWPIN);
1353 if (entry->objcg)
1354 count_objcg_event(entry->objcg, ZSWPIN);
1355freeentry:
1356 spin_lock(&tree->lock);
1357 zswap_entry_put(tree, entry);
1358 spin_unlock(&tree->lock);
1359
1360 return ret;
1361}
1362
1363/* frees an entry in zswap */
1364static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1365{
1366 struct zswap_tree *tree = zswap_trees[type];
1367 struct zswap_entry *entry;
1368
1369 /* find */
1370 spin_lock(&tree->lock);
1371 entry = zswap_rb_search(&tree->rbroot, offset);
1372 if (!entry) {
1373 /* entry was written back */
1374 spin_unlock(&tree->lock);
1375 return;
1376 }
1377
1378 /* remove from rbtree */
1379 zswap_rb_erase(&tree->rbroot, entry);
1380
1381 /* drop the initial reference from entry creation */
1382 zswap_entry_put(tree, entry);
1383
1384 spin_unlock(&tree->lock);
1385}
1386
1387/* frees all zswap entries for the given swap type */
1388static void zswap_frontswap_invalidate_area(unsigned type)
1389{
1390 struct zswap_tree *tree = zswap_trees[type];
1391 struct zswap_entry *entry, *n;
1392
1393 if (!tree)
1394 return;
1395
1396 /* walk the tree and free everything */
1397 spin_lock(&tree->lock);
1398 rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1399 zswap_free_entry(entry);
1400 tree->rbroot = RB_ROOT;
1401 spin_unlock(&tree->lock);
1402 kfree(tree);
1403 zswap_trees[type] = NULL;
1404}
1405
1406static void zswap_frontswap_init(unsigned type)
1407{
1408 struct zswap_tree *tree;
1409
1410 tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1411 if (!tree) {
1412 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1413 return;
1414 }
1415
1416 tree->rbroot = RB_ROOT;
1417 spin_lock_init(&tree->lock);
1418 zswap_trees[type] = tree;
1419}
1420
1421static const struct frontswap_ops zswap_frontswap_ops = {
1422 .store = zswap_frontswap_store,
1423 .load = zswap_frontswap_load,
1424 .invalidate_page = zswap_frontswap_invalidate_page,
1425 .invalidate_area = zswap_frontswap_invalidate_area,
1426 .init = zswap_frontswap_init
1427};
1428
1429/*********************************
1430* debugfs functions
1431**********************************/
1432#ifdef CONFIG_DEBUG_FS
1433#include <linux/debugfs.h>
1434
1435static struct dentry *zswap_debugfs_root;
1436
1437static int __init zswap_debugfs_init(void)
1438{
1439 if (!debugfs_initialized())
1440 return -ENODEV;
1441
1442 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1443
1444 debugfs_create_u64("pool_limit_hit", 0444,
1445 zswap_debugfs_root, &zswap_pool_limit_hit);
1446 debugfs_create_u64("reject_reclaim_fail", 0444,
1447 zswap_debugfs_root, &zswap_reject_reclaim_fail);
1448 debugfs_create_u64("reject_alloc_fail", 0444,
1449 zswap_debugfs_root, &zswap_reject_alloc_fail);
1450 debugfs_create_u64("reject_kmemcache_fail", 0444,
1451 zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1452 debugfs_create_u64("reject_compress_poor", 0444,
1453 zswap_debugfs_root, &zswap_reject_compress_poor);
1454 debugfs_create_u64("written_back_pages", 0444,
1455 zswap_debugfs_root, &zswap_written_back_pages);
1456 debugfs_create_u64("duplicate_entry", 0444,
1457 zswap_debugfs_root, &zswap_duplicate_entry);
1458 debugfs_create_u64("pool_total_size", 0444,
1459 zswap_debugfs_root, &zswap_pool_total_size);
1460 debugfs_create_atomic_t("stored_pages", 0444,
1461 zswap_debugfs_root, &zswap_stored_pages);
1462 debugfs_create_atomic_t("same_filled_pages", 0444,
1463 zswap_debugfs_root, &zswap_same_filled_pages);
1464
1465 return 0;
1466}
1467#else
1468static int __init zswap_debugfs_init(void)
1469{
1470 return 0;
1471}
1472#endif
1473
1474/*********************************
1475* module init and exit
1476**********************************/
1477static int __init init_zswap(void)
1478{
1479 struct zswap_pool *pool;
1480 int ret;
1481
1482 zswap_init_started = true;
1483
1484 if (zswap_entry_cache_create()) {
1485 pr_err("entry cache creation failed\n");
1486 goto cache_fail;
1487 }
1488
1489 ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1490 zswap_dstmem_prepare, zswap_dstmem_dead);
1491 if (ret) {
1492 pr_err("dstmem alloc failed\n");
1493 goto dstmem_fail;
1494 }
1495
1496 ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1497 "mm/zswap_pool:prepare",
1498 zswap_cpu_comp_prepare,
1499 zswap_cpu_comp_dead);
1500 if (ret)
1501 goto hp_fail;
1502
1503 pool = __zswap_pool_create_fallback();
1504 if (pool) {
1505 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1506 zpool_get_type(pool->zpool));
1507 list_add(&pool->list, &zswap_pools);
1508 zswap_has_pool = true;
1509 } else {
1510 pr_err("pool creation failed\n");
1511 zswap_enabled = false;
1512 }
1513
1514 shrink_wq = create_workqueue("zswap-shrink");
1515 if (!shrink_wq)
1516 goto fallback_fail;
1517
1518 ret = frontswap_register_ops(&zswap_frontswap_ops);
1519 if (ret)
1520 goto destroy_wq;
1521 if (zswap_debugfs_init())
1522 pr_warn("debugfs initialization failed\n");
1523 return 0;
1524
1525destroy_wq:
1526 destroy_workqueue(shrink_wq);
1527fallback_fail:
1528 if (pool)
1529 zswap_pool_destroy(pool);
1530hp_fail:
1531 cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1532dstmem_fail:
1533 zswap_entry_cache_destroy();
1534cache_fail:
1535 /* if built-in, we aren't unloaded on failure; don't allow use */
1536 zswap_init_failed = true;
1537 zswap_enabled = false;
1538 return -ENOMEM;
1539}
1540/* must be late so crypto has time to come up */
1541late_initcall(init_zswap);
1542
1543MODULE_LICENSE("GPL");
1544MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1545MODULE_DESCRIPTION("Compressed cache for swap pages");