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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;
81static int zswap_enabled_param_set(const char *,
82 const struct kernel_param *);
83static struct kernel_param_ops zswap_enabled_param_ops = {
84 .set = zswap_enabled_param_set,
85 .get = param_get_bool,
86};
87module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
88
89/* Crypto compressor to use */
90#define ZSWAP_COMPRESSOR_DEFAULT "lzo"
91static char *zswap_compressor = 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 */
103#define ZSWAP_ZPOOL_DEFAULT "zbud"
104static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
105static int zswap_zpool_param_set(const char *, const struct kernel_param *);
106static struct kernel_param_ops zswap_zpool_param_ops = {
107 .set = zswap_zpool_param_set,
108 .get = param_get_charp,
109 .free = param_free_charp,
110};
111module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
112
113/* The maximum percentage of memory that the compressed pool can occupy */
114static unsigned int zswap_max_pool_percent = 20;
115module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 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 notifier_block notifier;
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
147 * pool - the zswap_pool the entry's data is in
148 * handle - zpool allocation handle that stores the compressed page data
149 */
150struct zswap_entry {
151 struct rb_node rbnode;
152 pgoff_t offset;
153 int refcount;
154 unsigned int length;
155 struct zswap_pool *pool;
156 unsigned long handle;
157};
158
159struct zswap_header {
160 swp_entry_t swpentry;
161};
162
163/*
164 * The tree lock in the zswap_tree struct protects a few things:
165 * - the rbtree
166 * - the refcount field of each entry in the tree
167 */
168struct zswap_tree {
169 struct rb_root rbroot;
170 spinlock_t lock;
171};
172
173static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
174
175/* RCU-protected iteration */
176static LIST_HEAD(zswap_pools);
177/* protects zswap_pools list modification */
178static DEFINE_SPINLOCK(zswap_pools_lock);
179/* pool counter to provide unique names to zpool */
180static atomic_t zswap_pools_count = ATOMIC_INIT(0);
181
182/* used by param callback function */
183static bool zswap_init_started;
184
185/* fatal error during init */
186static bool zswap_init_failed;
187
188/*********************************
189* helpers and fwd declarations
190**********************************/
191
192#define zswap_pool_debug(msg, p) \
193 pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \
194 zpool_get_type((p)->zpool))
195
196static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
197static int zswap_pool_get(struct zswap_pool *pool);
198static void zswap_pool_put(struct zswap_pool *pool);
199
200static const struct zpool_ops zswap_zpool_ops = {
201 .evict = zswap_writeback_entry
202};
203
204static bool zswap_is_full(void)
205{
206 return totalram_pages * zswap_max_pool_percent / 100 <
207 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
208}
209
210static void zswap_update_total_size(void)
211{
212 struct zswap_pool *pool;
213 u64 total = 0;
214
215 rcu_read_lock();
216
217 list_for_each_entry_rcu(pool, &zswap_pools, list)
218 total += zpool_get_total_size(pool->zpool);
219
220 rcu_read_unlock();
221
222 zswap_pool_total_size = total;
223}
224
225/*********************************
226* zswap entry functions
227**********************************/
228static struct kmem_cache *zswap_entry_cache;
229
230static int __init zswap_entry_cache_create(void)
231{
232 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
233 return zswap_entry_cache == NULL;
234}
235
236static void __init zswap_entry_cache_destroy(void)
237{
238 kmem_cache_destroy(zswap_entry_cache);
239}
240
241static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
242{
243 struct zswap_entry *entry;
244 entry = kmem_cache_alloc(zswap_entry_cache, gfp);
245 if (!entry)
246 return NULL;
247 entry->refcount = 1;
248 RB_CLEAR_NODE(&entry->rbnode);
249 return entry;
250}
251
252static void zswap_entry_cache_free(struct zswap_entry *entry)
253{
254 kmem_cache_free(zswap_entry_cache, entry);
255}
256
257/*********************************
258* rbtree functions
259**********************************/
260static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
261{
262 struct rb_node *node = root->rb_node;
263 struct zswap_entry *entry;
264
265 while (node) {
266 entry = rb_entry(node, struct zswap_entry, rbnode);
267 if (entry->offset > offset)
268 node = node->rb_left;
269 else if (entry->offset < offset)
270 node = node->rb_right;
271 else
272 return entry;
273 }
274 return NULL;
275}
276
277/*
278 * In the case that a entry with the same offset is found, a pointer to
279 * the existing entry is stored in dupentry and the function returns -EEXIST
280 */
281static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
282 struct zswap_entry **dupentry)
283{
284 struct rb_node **link = &root->rb_node, *parent = NULL;
285 struct zswap_entry *myentry;
286
287 while (*link) {
288 parent = *link;
289 myentry = rb_entry(parent, struct zswap_entry, rbnode);
290 if (myentry->offset > entry->offset)
291 link = &(*link)->rb_left;
292 else if (myentry->offset < entry->offset)
293 link = &(*link)->rb_right;
294 else {
295 *dupentry = myentry;
296 return -EEXIST;
297 }
298 }
299 rb_link_node(&entry->rbnode, parent, link);
300 rb_insert_color(&entry->rbnode, root);
301 return 0;
302}
303
304static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
305{
306 if (!RB_EMPTY_NODE(&entry->rbnode)) {
307 rb_erase(&entry->rbnode, root);
308 RB_CLEAR_NODE(&entry->rbnode);
309 }
310}
311
312/*
313 * Carries out the common pattern of freeing and entry's zpool allocation,
314 * freeing the entry itself, and decrementing the number of stored pages.
315 */
316static void zswap_free_entry(struct zswap_entry *entry)
317{
318 zpool_free(entry->pool->zpool, entry->handle);
319 zswap_pool_put(entry->pool);
320 zswap_entry_cache_free(entry);
321 atomic_dec(&zswap_stored_pages);
322 zswap_update_total_size();
323}
324
325/* caller must hold the tree lock */
326static void zswap_entry_get(struct zswap_entry *entry)
327{
328 entry->refcount++;
329}
330
331/* caller must hold the tree lock
332* remove from the tree and free it, if nobody reference the entry
333*/
334static void zswap_entry_put(struct zswap_tree *tree,
335 struct zswap_entry *entry)
336{
337 int refcount = --entry->refcount;
338
339 BUG_ON(refcount < 0);
340 if (refcount == 0) {
341 zswap_rb_erase(&tree->rbroot, entry);
342 zswap_free_entry(entry);
343 }
344}
345
346/* caller must hold the tree lock */
347static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
348 pgoff_t offset)
349{
350 struct zswap_entry *entry;
351
352 entry = zswap_rb_search(root, offset);
353 if (entry)
354 zswap_entry_get(entry);
355
356 return entry;
357}
358
359/*********************************
360* per-cpu code
361**********************************/
362static DEFINE_PER_CPU(u8 *, zswap_dstmem);
363
364static int __zswap_cpu_dstmem_notifier(unsigned long action, unsigned long cpu)
365{
366 u8 *dst;
367
368 switch (action) {
369 case CPU_UP_PREPARE:
370 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
371 if (!dst) {
372 pr_err("can't allocate compressor buffer\n");
373 return NOTIFY_BAD;
374 }
375 per_cpu(zswap_dstmem, cpu) = dst;
376 break;
377 case CPU_DEAD:
378 case CPU_UP_CANCELED:
379 dst = per_cpu(zswap_dstmem, cpu);
380 kfree(dst);
381 per_cpu(zswap_dstmem, cpu) = NULL;
382 break;
383 default:
384 break;
385 }
386 return NOTIFY_OK;
387}
388
389static int zswap_cpu_dstmem_notifier(struct notifier_block *nb,
390 unsigned long action, void *pcpu)
391{
392 return __zswap_cpu_dstmem_notifier(action, (unsigned long)pcpu);
393}
394
395static struct notifier_block zswap_dstmem_notifier = {
396 .notifier_call = zswap_cpu_dstmem_notifier,
397};
398
399static int __init zswap_cpu_dstmem_init(void)
400{
401 unsigned long cpu;
402
403 cpu_notifier_register_begin();
404 for_each_online_cpu(cpu)
405 if (__zswap_cpu_dstmem_notifier(CPU_UP_PREPARE, cpu) ==
406 NOTIFY_BAD)
407 goto cleanup;
408 __register_cpu_notifier(&zswap_dstmem_notifier);
409 cpu_notifier_register_done();
410 return 0;
411
412cleanup:
413 for_each_online_cpu(cpu)
414 __zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
415 cpu_notifier_register_done();
416 return -ENOMEM;
417}
418
419static void zswap_cpu_dstmem_destroy(void)
420{
421 unsigned long cpu;
422
423 cpu_notifier_register_begin();
424 for_each_online_cpu(cpu)
425 __zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
426 __unregister_cpu_notifier(&zswap_dstmem_notifier);
427 cpu_notifier_register_done();
428}
429
430static int __zswap_cpu_comp_notifier(struct zswap_pool *pool,
431 unsigned long action, unsigned long cpu)
432{
433 struct crypto_comp *tfm;
434
435 switch (action) {
436 case CPU_UP_PREPARE:
437 if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
438 break;
439 tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
440 if (IS_ERR_OR_NULL(tfm)) {
441 pr_err("could not alloc crypto comp %s : %ld\n",
442 pool->tfm_name, PTR_ERR(tfm));
443 return NOTIFY_BAD;
444 }
445 *per_cpu_ptr(pool->tfm, cpu) = tfm;
446 break;
447 case CPU_DEAD:
448 case CPU_UP_CANCELED:
449 tfm = *per_cpu_ptr(pool->tfm, cpu);
450 if (!IS_ERR_OR_NULL(tfm))
451 crypto_free_comp(tfm);
452 *per_cpu_ptr(pool->tfm, cpu) = NULL;
453 break;
454 default:
455 break;
456 }
457 return NOTIFY_OK;
458}
459
460static int zswap_cpu_comp_notifier(struct notifier_block *nb,
461 unsigned long action, void *pcpu)
462{
463 unsigned long cpu = (unsigned long)pcpu;
464 struct zswap_pool *pool = container_of(nb, typeof(*pool), notifier);
465
466 return __zswap_cpu_comp_notifier(pool, action, cpu);
467}
468
469static int zswap_cpu_comp_init(struct zswap_pool *pool)
470{
471 unsigned long cpu;
472
473 memset(&pool->notifier, 0, sizeof(pool->notifier));
474 pool->notifier.notifier_call = zswap_cpu_comp_notifier;
475
476 cpu_notifier_register_begin();
477 for_each_online_cpu(cpu)
478 if (__zswap_cpu_comp_notifier(pool, CPU_UP_PREPARE, cpu) ==
479 NOTIFY_BAD)
480 goto cleanup;
481 __register_cpu_notifier(&pool->notifier);
482 cpu_notifier_register_done();
483 return 0;
484
485cleanup:
486 for_each_online_cpu(cpu)
487 __zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
488 cpu_notifier_register_done();
489 return -ENOMEM;
490}
491
492static void zswap_cpu_comp_destroy(struct zswap_pool *pool)
493{
494 unsigned long cpu;
495
496 cpu_notifier_register_begin();
497 for_each_online_cpu(cpu)
498 __zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
499 __unregister_cpu_notifier(&pool->notifier);
500 cpu_notifier_register_done();
501}
502
503/*********************************
504* pool functions
505**********************************/
506
507static struct zswap_pool *__zswap_pool_current(void)
508{
509 struct zswap_pool *pool;
510
511 pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
512 WARN_ON(!pool);
513
514 return pool;
515}
516
517static struct zswap_pool *zswap_pool_current(void)
518{
519 assert_spin_locked(&zswap_pools_lock);
520
521 return __zswap_pool_current();
522}
523
524static struct zswap_pool *zswap_pool_current_get(void)
525{
526 struct zswap_pool *pool;
527
528 rcu_read_lock();
529
530 pool = __zswap_pool_current();
531 if (!pool || !zswap_pool_get(pool))
532 pool = NULL;
533
534 rcu_read_unlock();
535
536 return pool;
537}
538
539static struct zswap_pool *zswap_pool_last_get(void)
540{
541 struct zswap_pool *pool, *last = NULL;
542
543 rcu_read_lock();
544
545 list_for_each_entry_rcu(pool, &zswap_pools, list)
546 last = pool;
547 if (!WARN_ON(!last) && !zswap_pool_get(last))
548 last = NULL;
549
550 rcu_read_unlock();
551
552 return last;
553}
554
555/* type and compressor must be null-terminated */
556static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
557{
558 struct zswap_pool *pool;
559
560 assert_spin_locked(&zswap_pools_lock);
561
562 list_for_each_entry_rcu(pool, &zswap_pools, list) {
563 if (strcmp(pool->tfm_name, compressor))
564 continue;
565 if (strcmp(zpool_get_type(pool->zpool), type))
566 continue;
567 /* if we can't get it, it's about to be destroyed */
568 if (!zswap_pool_get(pool))
569 continue;
570 return pool;
571 }
572
573 return NULL;
574}
575
576static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
577{
578 struct zswap_pool *pool;
579 char name[38]; /* 'zswap' + 32 char (max) num + \0 */
580 gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
581
582 pool = kzalloc(sizeof(*pool), GFP_KERNEL);
583 if (!pool) {
584 pr_err("pool alloc failed\n");
585 return NULL;
586 }
587
588 /* unique name for each pool specifically required by zsmalloc */
589 snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
590
591 pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
592 if (!pool->zpool) {
593 pr_err("%s zpool not available\n", type);
594 goto error;
595 }
596 pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
597
598 strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
599 pool->tfm = alloc_percpu(struct crypto_comp *);
600 if (!pool->tfm) {
601 pr_err("percpu alloc failed\n");
602 goto error;
603 }
604
605 if (zswap_cpu_comp_init(pool))
606 goto error;
607 pr_debug("using %s compressor\n", pool->tfm_name);
608
609 /* being the current pool takes 1 ref; this func expects the
610 * caller to always add the new pool as the current pool
611 */
612 kref_init(&pool->kref);
613 INIT_LIST_HEAD(&pool->list);
614
615 zswap_pool_debug("created", pool);
616
617 return pool;
618
619error:
620 free_percpu(pool->tfm);
621 if (pool->zpool)
622 zpool_destroy_pool(pool->zpool);
623 kfree(pool);
624 return NULL;
625}
626
627static __init struct zswap_pool *__zswap_pool_create_fallback(void)
628{
629 if (!crypto_has_comp(zswap_compressor, 0, 0)) {
630 if (!strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {
631 pr_err("default compressor %s not available\n",
632 zswap_compressor);
633 return NULL;
634 }
635 pr_err("compressor %s not available, using default %s\n",
636 zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
637 param_free_charp(&zswap_compressor);
638 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
639 }
640 if (!zpool_has_pool(zswap_zpool_type)) {
641 if (!strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
642 pr_err("default zpool %s not available\n",
643 zswap_zpool_type);
644 return NULL;
645 }
646 pr_err("zpool %s not available, using default %s\n",
647 zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
648 param_free_charp(&zswap_zpool_type);
649 zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
650 }
651
652 return zswap_pool_create(zswap_zpool_type, zswap_compressor);
653}
654
655static void zswap_pool_destroy(struct zswap_pool *pool)
656{
657 zswap_pool_debug("destroying", pool);
658
659 zswap_cpu_comp_destroy(pool);
660 free_percpu(pool->tfm);
661 zpool_destroy_pool(pool->zpool);
662 kfree(pool);
663}
664
665static int __must_check zswap_pool_get(struct zswap_pool *pool)
666{
667 return kref_get_unless_zero(&pool->kref);
668}
669
670static void __zswap_pool_release(struct work_struct *work)
671{
672 struct zswap_pool *pool = container_of(work, typeof(*pool), work);
673
674 synchronize_rcu();
675
676 /* nobody should have been able to get a kref... */
677 WARN_ON(kref_get_unless_zero(&pool->kref));
678
679 /* pool is now off zswap_pools list and has no references. */
680 zswap_pool_destroy(pool);
681}
682
683static void __zswap_pool_empty(struct kref *kref)
684{
685 struct zswap_pool *pool;
686
687 pool = container_of(kref, typeof(*pool), kref);
688
689 spin_lock(&zswap_pools_lock);
690
691 WARN_ON(pool == zswap_pool_current());
692
693 list_del_rcu(&pool->list);
694
695 INIT_WORK(&pool->work, __zswap_pool_release);
696 schedule_work(&pool->work);
697
698 spin_unlock(&zswap_pools_lock);
699}
700
701static void zswap_pool_put(struct zswap_pool *pool)
702{
703 kref_put(&pool->kref, __zswap_pool_empty);
704}
705
706/*********************************
707* param callbacks
708**********************************/
709
710/* val must be a null-terminated string */
711static int __zswap_param_set(const char *val, const struct kernel_param *kp,
712 char *type, char *compressor)
713{
714 struct zswap_pool *pool, *put_pool = NULL;
715 char *s = strstrip((char *)val);
716 int ret;
717
718 if (zswap_init_failed) {
719 pr_err("can't set param, initialization failed\n");
720 return -ENODEV;
721 }
722
723 /* no change required */
724 if (!strcmp(s, *(char **)kp->arg))
725 return 0;
726
727 /* if this is load-time (pre-init) param setting,
728 * don't create a pool; that's done during init.
729 */
730 if (!zswap_init_started)
731 return param_set_charp(s, kp);
732
733 if (!type) {
734 if (!zpool_has_pool(s)) {
735 pr_err("zpool %s not available\n", s);
736 return -ENOENT;
737 }
738 type = s;
739 } else if (!compressor) {
740 if (!crypto_has_comp(s, 0, 0)) {
741 pr_err("compressor %s not available\n", s);
742 return -ENOENT;
743 }
744 compressor = s;
745 } else {
746 WARN_ON(1);
747 return -EINVAL;
748 }
749
750 spin_lock(&zswap_pools_lock);
751
752 pool = zswap_pool_find_get(type, compressor);
753 if (pool) {
754 zswap_pool_debug("using existing", pool);
755 WARN_ON(pool == zswap_pool_current());
756 list_del_rcu(&pool->list);
757 }
758
759 spin_unlock(&zswap_pools_lock);
760
761 if (!pool)
762 pool = zswap_pool_create(type, compressor);
763
764 if (pool)
765 ret = param_set_charp(s, kp);
766 else
767 ret = -EINVAL;
768
769 spin_lock(&zswap_pools_lock);
770
771 if (!ret) {
772 put_pool = zswap_pool_current();
773 list_add_rcu(&pool->list, &zswap_pools);
774 } else if (pool) {
775 /* add the possibly pre-existing pool to the end of the pools
776 * list; if it's new (and empty) then it'll be removed and
777 * destroyed by the put after we drop the lock
778 */
779 list_add_tail_rcu(&pool->list, &zswap_pools);
780 put_pool = pool;
781 }
782
783 spin_unlock(&zswap_pools_lock);
784
785 /* drop the ref from either the old current pool,
786 * or the new pool we failed to add
787 */
788 if (put_pool)
789 zswap_pool_put(put_pool);
790
791 return ret;
792}
793
794static int zswap_compressor_param_set(const char *val,
795 const struct kernel_param *kp)
796{
797 return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
798}
799
800static int zswap_zpool_param_set(const char *val,
801 const struct kernel_param *kp)
802{
803 return __zswap_param_set(val, kp, NULL, zswap_compressor);
804}
805
806static int zswap_enabled_param_set(const char *val,
807 const struct kernel_param *kp)
808{
809 if (zswap_init_failed) {
810 pr_err("can't enable, initialization failed\n");
811 return -ENODEV;
812 }
813
814 return param_set_bool(val, kp);
815}
816
817/*********************************
818* writeback code
819**********************************/
820/* return enum for zswap_get_swap_cache_page */
821enum zswap_get_swap_ret {
822 ZSWAP_SWAPCACHE_NEW,
823 ZSWAP_SWAPCACHE_EXIST,
824 ZSWAP_SWAPCACHE_FAIL,
825};
826
827/*
828 * zswap_get_swap_cache_page
829 *
830 * This is an adaption of read_swap_cache_async()
831 *
832 * This function tries to find a page with the given swap entry
833 * in the swapper_space address space (the swap cache). If the page
834 * is found, it is returned in retpage. Otherwise, a page is allocated,
835 * added to the swap cache, and returned in retpage.
836 *
837 * If success, the swap cache page is returned in retpage
838 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
839 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
840 * the new page is added to swapcache and locked
841 * Returns ZSWAP_SWAPCACHE_FAIL on error
842 */
843static int zswap_get_swap_cache_page(swp_entry_t entry,
844 struct page **retpage)
845{
846 bool page_was_allocated;
847
848 *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
849 NULL, 0, &page_was_allocated);
850 if (page_was_allocated)
851 return ZSWAP_SWAPCACHE_NEW;
852 if (!*retpage)
853 return ZSWAP_SWAPCACHE_FAIL;
854 return ZSWAP_SWAPCACHE_EXIST;
855}
856
857/*
858 * Attempts to free an entry by adding a page to the swap cache,
859 * decompressing the entry data into the page, and issuing a
860 * bio write to write the page back to the swap device.
861 *
862 * This can be thought of as a "resumed writeback" of the page
863 * to the swap device. We are basically resuming the same swap
864 * writeback path that was intercepted with the frontswap_store()
865 * in the first place. After the page has been decompressed into
866 * the swap cache, the compressed version stored by zswap can be
867 * freed.
868 */
869static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
870{
871 struct zswap_header *zhdr;
872 swp_entry_t swpentry;
873 struct zswap_tree *tree;
874 pgoff_t offset;
875 struct zswap_entry *entry;
876 struct page *page;
877 struct crypto_comp *tfm;
878 u8 *src, *dst;
879 unsigned int dlen;
880 int ret;
881 struct writeback_control wbc = {
882 .sync_mode = WB_SYNC_NONE,
883 };
884
885 /* extract swpentry from data */
886 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
887 swpentry = zhdr->swpentry; /* here */
888 zpool_unmap_handle(pool, handle);
889 tree = zswap_trees[swp_type(swpentry)];
890 offset = swp_offset(swpentry);
891
892 /* find and ref zswap entry */
893 spin_lock(&tree->lock);
894 entry = zswap_entry_find_get(&tree->rbroot, offset);
895 if (!entry) {
896 /* entry was invalidated */
897 spin_unlock(&tree->lock);
898 return 0;
899 }
900 spin_unlock(&tree->lock);
901 BUG_ON(offset != entry->offset);
902
903 /* try to allocate swap cache page */
904 switch (zswap_get_swap_cache_page(swpentry, &page)) {
905 case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
906 ret = -ENOMEM;
907 goto fail;
908
909 case ZSWAP_SWAPCACHE_EXIST:
910 /* page is already in the swap cache, ignore for now */
911 put_page(page);
912 ret = -EEXIST;
913 goto fail;
914
915 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
916 /* decompress */
917 dlen = PAGE_SIZE;
918 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
919 ZPOOL_MM_RO) + sizeof(struct zswap_header);
920 dst = kmap_atomic(page);
921 tfm = *get_cpu_ptr(entry->pool->tfm);
922 ret = crypto_comp_decompress(tfm, src, entry->length,
923 dst, &dlen);
924 put_cpu_ptr(entry->pool->tfm);
925 kunmap_atomic(dst);
926 zpool_unmap_handle(entry->pool->zpool, entry->handle);
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 return ret;
973}
974
975static int zswap_shrink(void)
976{
977 struct zswap_pool *pool;
978 int ret;
979
980 pool = zswap_pool_last_get();
981 if (!pool)
982 return -ENOENT;
983
984 ret = zpool_shrink(pool->zpool, 1, NULL);
985
986 zswap_pool_put(pool);
987
988 return ret;
989}
990
991/*********************************
992* frontswap hooks
993**********************************/
994/* attempts to compress and store an single page */
995static int zswap_frontswap_store(unsigned type, pgoff_t offset,
996 struct page *page)
997{
998 struct zswap_tree *tree = zswap_trees[type];
999 struct zswap_entry *entry, *dupentry;
1000 struct crypto_comp *tfm;
1001 int ret;
1002 unsigned int dlen = PAGE_SIZE, len;
1003 unsigned long handle;
1004 char *buf;
1005 u8 *src, *dst;
1006 struct zswap_header *zhdr;
1007
1008 if (!zswap_enabled || !tree) {
1009 ret = -ENODEV;
1010 goto reject;
1011 }
1012
1013 /* reclaim space if needed */
1014 if (zswap_is_full()) {
1015 zswap_pool_limit_hit++;
1016 if (zswap_shrink()) {
1017 zswap_reject_reclaim_fail++;
1018 ret = -ENOMEM;
1019 goto reject;
1020 }
1021
1022 /* A second zswap_is_full() check after
1023 * zswap_shrink() to make sure it's now
1024 * under the max_pool_percent
1025 */
1026 if (zswap_is_full()) {
1027 ret = -ENOMEM;
1028 goto reject;
1029 }
1030 }
1031
1032 /* allocate entry */
1033 entry = zswap_entry_cache_alloc(GFP_KERNEL);
1034 if (!entry) {
1035 zswap_reject_kmemcache_fail++;
1036 ret = -ENOMEM;
1037 goto reject;
1038 }
1039
1040 /* if entry is successfully added, it keeps the reference */
1041 entry->pool = zswap_pool_current_get();
1042 if (!entry->pool) {
1043 ret = -EINVAL;
1044 goto freepage;
1045 }
1046
1047 /* compress */
1048 dst = get_cpu_var(zswap_dstmem);
1049 tfm = *get_cpu_ptr(entry->pool->tfm);
1050 src = kmap_atomic(page);
1051 ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
1052 kunmap_atomic(src);
1053 put_cpu_ptr(entry->pool->tfm);
1054 if (ret) {
1055 ret = -EINVAL;
1056 goto put_dstmem;
1057 }
1058
1059 /* store */
1060 len = dlen + sizeof(struct zswap_header);
1061 ret = zpool_malloc(entry->pool->zpool, len,
1062 __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM,
1063 &handle);
1064 if (ret == -ENOSPC) {
1065 zswap_reject_compress_poor++;
1066 goto put_dstmem;
1067 }
1068 if (ret) {
1069 zswap_reject_alloc_fail++;
1070 goto put_dstmem;
1071 }
1072 zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
1073 zhdr->swpentry = swp_entry(type, offset);
1074 buf = (u8 *)(zhdr + 1);
1075 memcpy(buf, dst, dlen);
1076 zpool_unmap_handle(entry->pool->zpool, handle);
1077 put_cpu_var(zswap_dstmem);
1078
1079 /* populate entry */
1080 entry->offset = offset;
1081 entry->handle = handle;
1082 entry->length = dlen;
1083
1084 /* map */
1085 spin_lock(&tree->lock);
1086 do {
1087 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1088 if (ret == -EEXIST) {
1089 zswap_duplicate_entry++;
1090 /* remove from rbtree */
1091 zswap_rb_erase(&tree->rbroot, dupentry);
1092 zswap_entry_put(tree, dupentry);
1093 }
1094 } while (ret == -EEXIST);
1095 spin_unlock(&tree->lock);
1096
1097 /* update stats */
1098 atomic_inc(&zswap_stored_pages);
1099 zswap_update_total_size();
1100
1101 return 0;
1102
1103put_dstmem:
1104 put_cpu_var(zswap_dstmem);
1105 zswap_pool_put(entry->pool);
1106freepage:
1107 zswap_entry_cache_free(entry);
1108reject:
1109 return ret;
1110}
1111
1112/*
1113 * returns 0 if the page was successfully decompressed
1114 * return -1 on entry not found or error
1115*/
1116static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1117 struct page *page)
1118{
1119 struct zswap_tree *tree = zswap_trees[type];
1120 struct zswap_entry *entry;
1121 struct crypto_comp *tfm;
1122 u8 *src, *dst;
1123 unsigned int dlen;
1124 int ret;
1125
1126 /* find */
1127 spin_lock(&tree->lock);
1128 entry = zswap_entry_find_get(&tree->rbroot, offset);
1129 if (!entry) {
1130 /* entry was written back */
1131 spin_unlock(&tree->lock);
1132 return -1;
1133 }
1134 spin_unlock(&tree->lock);
1135
1136 /* decompress */
1137 dlen = PAGE_SIZE;
1138 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
1139 ZPOOL_MM_RO) + sizeof(struct zswap_header);
1140 dst = kmap_atomic(page);
1141 tfm = *get_cpu_ptr(entry->pool->tfm);
1142 ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
1143 put_cpu_ptr(entry->pool->tfm);
1144 kunmap_atomic(dst);
1145 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1146 BUG_ON(ret);
1147
1148 spin_lock(&tree->lock);
1149 zswap_entry_put(tree, entry);
1150 spin_unlock(&tree->lock);
1151
1152 return 0;
1153}
1154
1155/* frees an entry in zswap */
1156static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1157{
1158 struct zswap_tree *tree = zswap_trees[type];
1159 struct zswap_entry *entry;
1160
1161 /* find */
1162 spin_lock(&tree->lock);
1163 entry = zswap_rb_search(&tree->rbroot, offset);
1164 if (!entry) {
1165 /* entry was written back */
1166 spin_unlock(&tree->lock);
1167 return;
1168 }
1169
1170 /* remove from rbtree */
1171 zswap_rb_erase(&tree->rbroot, entry);
1172
1173 /* drop the initial reference from entry creation */
1174 zswap_entry_put(tree, entry);
1175
1176 spin_unlock(&tree->lock);
1177}
1178
1179/* frees all zswap entries for the given swap type */
1180static void zswap_frontswap_invalidate_area(unsigned type)
1181{
1182 struct zswap_tree *tree = zswap_trees[type];
1183 struct zswap_entry *entry, *n;
1184
1185 if (!tree)
1186 return;
1187
1188 /* walk the tree and free everything */
1189 spin_lock(&tree->lock);
1190 rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1191 zswap_free_entry(entry);
1192 tree->rbroot = RB_ROOT;
1193 spin_unlock(&tree->lock);
1194 kfree(tree);
1195 zswap_trees[type] = NULL;
1196}
1197
1198static void zswap_frontswap_init(unsigned type)
1199{
1200 struct zswap_tree *tree;
1201
1202 tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
1203 if (!tree) {
1204 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1205 return;
1206 }
1207
1208 tree->rbroot = RB_ROOT;
1209 spin_lock_init(&tree->lock);
1210 zswap_trees[type] = tree;
1211}
1212
1213static struct frontswap_ops zswap_frontswap_ops = {
1214 .store = zswap_frontswap_store,
1215 .load = zswap_frontswap_load,
1216 .invalidate_page = zswap_frontswap_invalidate_page,
1217 .invalidate_area = zswap_frontswap_invalidate_area,
1218 .init = zswap_frontswap_init
1219};
1220
1221/*********************************
1222* debugfs functions
1223**********************************/
1224#ifdef CONFIG_DEBUG_FS
1225#include <linux/debugfs.h>
1226
1227static struct dentry *zswap_debugfs_root;
1228
1229static int __init zswap_debugfs_init(void)
1230{
1231 if (!debugfs_initialized())
1232 return -ENODEV;
1233
1234 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1235 if (!zswap_debugfs_root)
1236 return -ENOMEM;
1237
1238 debugfs_create_u64("pool_limit_hit", S_IRUGO,
1239 zswap_debugfs_root, &zswap_pool_limit_hit);
1240 debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
1241 zswap_debugfs_root, &zswap_reject_reclaim_fail);
1242 debugfs_create_u64("reject_alloc_fail", S_IRUGO,
1243 zswap_debugfs_root, &zswap_reject_alloc_fail);
1244 debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
1245 zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1246 debugfs_create_u64("reject_compress_poor", S_IRUGO,
1247 zswap_debugfs_root, &zswap_reject_compress_poor);
1248 debugfs_create_u64("written_back_pages", S_IRUGO,
1249 zswap_debugfs_root, &zswap_written_back_pages);
1250 debugfs_create_u64("duplicate_entry", S_IRUGO,
1251 zswap_debugfs_root, &zswap_duplicate_entry);
1252 debugfs_create_u64("pool_total_size", S_IRUGO,
1253 zswap_debugfs_root, &zswap_pool_total_size);
1254 debugfs_create_atomic_t("stored_pages", S_IRUGO,
1255 zswap_debugfs_root, &zswap_stored_pages);
1256
1257 return 0;
1258}
1259
1260static void __exit zswap_debugfs_exit(void)
1261{
1262 debugfs_remove_recursive(zswap_debugfs_root);
1263}
1264#else
1265static int __init zswap_debugfs_init(void)
1266{
1267 return 0;
1268}
1269
1270static void __exit zswap_debugfs_exit(void) { }
1271#endif
1272
1273/*********************************
1274* module init and exit
1275**********************************/
1276static int __init init_zswap(void)
1277{
1278 struct zswap_pool *pool;
1279
1280 zswap_init_started = true;
1281
1282 if (zswap_entry_cache_create()) {
1283 pr_err("entry cache creation failed\n");
1284 goto cache_fail;
1285 }
1286
1287 if (zswap_cpu_dstmem_init()) {
1288 pr_err("dstmem alloc failed\n");
1289 goto dstmem_fail;
1290 }
1291
1292 pool = __zswap_pool_create_fallback();
1293 if (!pool) {
1294 pr_err("pool creation failed\n");
1295 goto pool_fail;
1296 }
1297 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1298 zpool_get_type(pool->zpool));
1299
1300 list_add(&pool->list, &zswap_pools);
1301
1302 frontswap_register_ops(&zswap_frontswap_ops);
1303 if (zswap_debugfs_init())
1304 pr_warn("debugfs initialization failed\n");
1305 return 0;
1306
1307pool_fail:
1308 zswap_cpu_dstmem_destroy();
1309dstmem_fail:
1310 zswap_entry_cache_destroy();
1311cache_fail:
1312 /* if built-in, we aren't unloaded on failure; don't allow use */
1313 zswap_init_failed = true;
1314 zswap_enabled = false;
1315 return -ENOMEM;
1316}
1317/* must be late so crypto has time to come up */
1318late_initcall(init_zswap);
1319
1320MODULE_LICENSE("GPL");
1321MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1322MODULE_DESCRIPTION("Compressed cache for swap pages");
1323
generated by cgit at 2024-05-18 14:16:22 (GMT)