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