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