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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/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");