powerpc/mm/4k: don't allocate larger pmd page table for 4k
[linux/fpc-iii.git] / mm / zswap.c
blob067a0d62f31841d16913d36e38531a277ab59b01
1 /*
2 * zswap.c - zswap driver file
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.
10 * Copyright (C) 2012 Seth Jennings <sjenning@linux.vnet.ibm.com>
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.
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.
23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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>
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>
45 /*********************************
46 * statistics
47 **********************************/
48 /* Total bytes used by the compressed storage */
49 static u64 zswap_pool_total_size;
50 /* The number of compressed pages currently stored in zswap */
51 static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
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.
60 /* Pool limit was hit (see zswap_max_pool_percent) */
61 static u64 zswap_pool_limit_hit;
62 /* Pages written back when pool limit was reached */
63 static u64 zswap_written_back_pages;
64 /* Store failed due to a reclaim failure after pool limit was reached */
65 static u64 zswap_reject_reclaim_fail;
66 /* Compressed page was too big for the allocator to (optimally) store */
67 static u64 zswap_reject_compress_poor;
68 /* Store failed because underlying allocator could not get memory */
69 static u64 zswap_reject_alloc_fail;
70 /* Store failed because the entry metadata could not be allocated (rare) */
71 static u64 zswap_reject_kmemcache_fail;
72 /* Duplicate store was encountered (rare) */
73 static u64 zswap_duplicate_entry;
75 /*********************************
76 * tunables
77 **********************************/
79 /* Enable/disable zswap (disabled by default) */
80 static bool zswap_enabled;
81 module_param_named(enabled, zswap_enabled, bool, 0644);
83 /* Crypto compressor to use */
84 #define ZSWAP_COMPRESSOR_DEFAULT "lzo"
85 static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
86 static int zswap_compressor_param_set(const char *,
87 const struct kernel_param *);
88 static struct kernel_param_ops zswap_compressor_param_ops = {
89 .set = zswap_compressor_param_set,
90 .get = param_get_charp,
91 .free = param_free_charp,
93 module_param_cb(compressor, &zswap_compressor_param_ops,
94 &zswap_compressor, 0644);
96 /* Compressed storage zpool to use */
97 #define ZSWAP_ZPOOL_DEFAULT "zbud"
98 static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
99 static int zswap_zpool_param_set(const char *, const struct kernel_param *);
100 static struct kernel_param_ops zswap_zpool_param_ops = {
101 .set = zswap_zpool_param_set,
102 .get = param_get_charp,
103 .free = param_free_charp,
105 module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
107 /* The maximum percentage of memory that the compressed pool can occupy */
108 static unsigned int zswap_max_pool_percent = 20;
109 module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
111 /*********************************
112 * data structures
113 **********************************/
115 struct zswap_pool {
116 struct zpool *zpool;
117 struct crypto_comp * __percpu *tfm;
118 struct kref kref;
119 struct list_head list;
120 struct work_struct work;
121 struct hlist_node node;
122 char tfm_name[CRYPTO_MAX_ALG_NAME];
126 * struct zswap_entry
128 * This structure contains the metadata for tracking a single compressed
129 * page within zswap.
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
144 struct 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;
153 struct zswap_header {
154 swp_entry_t swpentry;
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
162 struct zswap_tree {
163 struct rb_root rbroot;
164 spinlock_t lock;
167 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
169 /* RCU-protected iteration */
170 static LIST_HEAD(zswap_pools);
171 /* protects zswap_pools list modification */
172 static DEFINE_SPINLOCK(zswap_pools_lock);
173 /* pool counter to provide unique names to zpool */
174 static atomic_t zswap_pools_count = ATOMIC_INIT(0);
176 /* used by param callback function */
177 static bool zswap_init_started;
179 /*********************************
180 * helpers and fwd declarations
181 **********************************/
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))
187 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
188 static int zswap_pool_get(struct zswap_pool *pool);
189 static void zswap_pool_put(struct zswap_pool *pool);
191 static const struct zpool_ops zswap_zpool_ops = {
192 .evict = zswap_writeback_entry
195 static bool zswap_is_full(void)
197 return totalram_pages * zswap_max_pool_percent / 100 <
198 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
201 static void zswap_update_total_size(void)
203 struct zswap_pool *pool;
204 u64 total = 0;
206 rcu_read_lock();
208 list_for_each_entry_rcu(pool, &zswap_pools, list)
209 total += zpool_get_total_size(pool->zpool);
211 rcu_read_unlock();
213 zswap_pool_total_size = total;
216 /*********************************
217 * zswap entry functions
218 **********************************/
219 static struct kmem_cache *zswap_entry_cache;
221 static int __init zswap_entry_cache_create(void)
223 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
224 return zswap_entry_cache == NULL;
227 static void __init zswap_entry_cache_destroy(void)
229 kmem_cache_destroy(zswap_entry_cache);
232 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
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;
243 static void zswap_entry_cache_free(struct zswap_entry *entry)
245 kmem_cache_free(zswap_entry_cache, entry);
248 /*********************************
249 * rbtree functions
250 **********************************/
251 static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
253 struct rb_node *node = root->rb_node;
254 struct zswap_entry *entry;
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;
265 return NULL;
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
272 static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
273 struct zswap_entry **dupentry)
275 struct rb_node **link = &root->rb_node, *parent = NULL;
276 struct zswap_entry *myentry;
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;
290 rb_link_node(&entry->rbnode, parent, link);
291 rb_insert_color(&entry->rbnode, root);
292 return 0;
295 static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
297 if (!RB_EMPTY_NODE(&entry->rbnode)) {
298 rb_erase(&entry->rbnode, root);
299 RB_CLEAR_NODE(&entry->rbnode);
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.
307 static void zswap_free_entry(struct zswap_entry *entry)
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();
316 /* caller must hold the tree lock */
317 static void zswap_entry_get(struct zswap_entry *entry)
319 entry->refcount++;
322 /* caller must hold the tree lock
323 * remove from the tree and free it, if nobody reference the entry
325 static void zswap_entry_put(struct zswap_tree *tree,
326 struct zswap_entry *entry)
328 int refcount = --entry->refcount;
330 BUG_ON(refcount < 0);
331 if (refcount == 0) {
332 zswap_rb_erase(&tree->rbroot, entry);
333 zswap_free_entry(entry);
337 /* caller must hold the tree lock */
338 static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
339 pgoff_t offset)
341 struct zswap_entry *entry;
343 entry = zswap_rb_search(root, offset);
344 if (entry)
345 zswap_entry_get(entry);
347 return entry;
350 /*********************************
351 * per-cpu code
352 **********************************/
353 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
355 static int zswap_dstmem_prepare(unsigned int cpu)
357 u8 *dst;
359 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
360 if (!dst) {
361 pr_err("can't allocate compressor buffer\n");
362 return -ENOMEM;
364 per_cpu(zswap_dstmem, cpu) = dst;
365 return 0;
368 static int zswap_dstmem_dead(unsigned int cpu)
370 u8 *dst;
372 dst = per_cpu(zswap_dstmem, cpu);
373 kfree(dst);
374 per_cpu(zswap_dstmem, cpu) = NULL;
376 return 0;
379 static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
381 struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
382 struct crypto_comp *tfm;
384 if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
385 return 0;
387 tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
388 if (IS_ERR_OR_NULL(tfm)) {
389 pr_err("could not alloc crypto comp %s : %ld\n",
390 pool->tfm_name, PTR_ERR(tfm));
391 return -ENOMEM;
393 *per_cpu_ptr(pool->tfm, cpu) = tfm;
394 return 0;
397 static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
399 struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
400 struct crypto_comp *tfm;
402 tfm = *per_cpu_ptr(pool->tfm, cpu);
403 if (!IS_ERR_OR_NULL(tfm))
404 crypto_free_comp(tfm);
405 *per_cpu_ptr(pool->tfm, cpu) = NULL;
406 return 0;
409 /*********************************
410 * pool functions
411 **********************************/
413 static struct zswap_pool *__zswap_pool_current(void)
415 struct zswap_pool *pool;
417 pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
418 WARN_ON(!pool);
420 return pool;
423 static struct zswap_pool *zswap_pool_current(void)
425 assert_spin_locked(&zswap_pools_lock);
427 return __zswap_pool_current();
430 static struct zswap_pool *zswap_pool_current_get(void)
432 struct zswap_pool *pool;
434 rcu_read_lock();
436 pool = __zswap_pool_current();
437 if (!pool || !zswap_pool_get(pool))
438 pool = NULL;
440 rcu_read_unlock();
442 return pool;
445 static struct zswap_pool *zswap_pool_last_get(void)
447 struct zswap_pool *pool, *last = NULL;
449 rcu_read_lock();
451 list_for_each_entry_rcu(pool, &zswap_pools, list)
452 last = pool;
453 if (!WARN_ON(!last) && !zswap_pool_get(last))
454 last = NULL;
456 rcu_read_unlock();
458 return last;
461 /* type and compressor must be null-terminated */
462 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
464 struct zswap_pool *pool;
466 assert_spin_locked(&zswap_pools_lock);
468 list_for_each_entry_rcu(pool, &zswap_pools, list) {
469 if (strcmp(pool->tfm_name, compressor))
470 continue;
471 if (strcmp(zpool_get_type(pool->zpool), type))
472 continue;
473 /* if we can't get it, it's about to be destroyed */
474 if (!zswap_pool_get(pool))
475 continue;
476 return pool;
479 return NULL;
482 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
484 struct zswap_pool *pool;
485 char name[38]; /* 'zswap' + 32 char (max) num + \0 */
486 gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
487 int ret;
489 pool = kzalloc(sizeof(*pool), GFP_KERNEL);
490 if (!pool) {
491 pr_err("pool alloc failed\n");
492 return NULL;
495 /* unique name for each pool specifically required by zsmalloc */
496 snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
498 pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
499 if (!pool->zpool) {
500 pr_err("%s zpool not available\n", type);
501 goto error;
503 pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
505 strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
506 pool->tfm = alloc_percpu(struct crypto_comp *);
507 if (!pool->tfm) {
508 pr_err("percpu alloc failed\n");
509 goto error;
512 ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
513 &pool->node);
514 if (ret)
515 goto error;
516 pr_debug("using %s compressor\n", pool->tfm_name);
518 /* being the current pool takes 1 ref; this func expects the
519 * caller to always add the new pool as the current pool
521 kref_init(&pool->kref);
522 INIT_LIST_HEAD(&pool->list);
524 zswap_pool_debug("created", pool);
526 return pool;
528 error:
529 free_percpu(pool->tfm);
530 if (pool->zpool)
531 zpool_destroy_pool(pool->zpool);
532 kfree(pool);
533 return NULL;
536 static __init struct zswap_pool *__zswap_pool_create_fallback(void)
538 if (!crypto_has_comp(zswap_compressor, 0, 0)) {
539 if (!strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {
540 pr_err("default compressor %s not available\n",
541 zswap_compressor);
542 return NULL;
544 pr_err("compressor %s not available, using default %s\n",
545 zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
546 param_free_charp(&zswap_compressor);
547 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
549 if (!zpool_has_pool(zswap_zpool_type)) {
550 if (!strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
551 pr_err("default zpool %s not available\n",
552 zswap_zpool_type);
553 return NULL;
555 pr_err("zpool %s not available, using default %s\n",
556 zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
557 param_free_charp(&zswap_zpool_type);
558 zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
561 return zswap_pool_create(zswap_zpool_type, zswap_compressor);
564 static void zswap_pool_destroy(struct zswap_pool *pool)
566 zswap_pool_debug("destroying", pool);
568 cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
569 free_percpu(pool->tfm);
570 zpool_destroy_pool(pool->zpool);
571 kfree(pool);
574 static int __must_check zswap_pool_get(struct zswap_pool *pool)
576 return kref_get_unless_zero(&pool->kref);
579 static void __zswap_pool_release(struct work_struct *work)
581 struct zswap_pool *pool = container_of(work, typeof(*pool), work);
583 synchronize_rcu();
585 /* nobody should have been able to get a kref... */
586 WARN_ON(kref_get_unless_zero(&pool->kref));
588 /* pool is now off zswap_pools list and has no references. */
589 zswap_pool_destroy(pool);
592 static void __zswap_pool_empty(struct kref *kref)
594 struct zswap_pool *pool;
596 pool = container_of(kref, typeof(*pool), kref);
598 spin_lock(&zswap_pools_lock);
600 WARN_ON(pool == zswap_pool_current());
602 list_del_rcu(&pool->list);
604 INIT_WORK(&pool->work, __zswap_pool_release);
605 schedule_work(&pool->work);
607 spin_unlock(&zswap_pools_lock);
610 static void zswap_pool_put(struct zswap_pool *pool)
612 kref_put(&pool->kref, __zswap_pool_empty);
615 /*********************************
616 * param callbacks
617 **********************************/
619 /* val must be a null-terminated string */
620 static int __zswap_param_set(const char *val, const struct kernel_param *kp,
621 char *type, char *compressor)
623 struct zswap_pool *pool, *put_pool = NULL;
624 char *s = strstrip((char *)val);
625 int ret;
627 /* no change required */
628 if (!strcmp(s, *(char **)kp->arg))
629 return 0;
631 /* if this is load-time (pre-init) param setting,
632 * don't create a pool; that's done during init.
634 if (!zswap_init_started)
635 return param_set_charp(s, kp);
637 if (!type) {
638 if (!zpool_has_pool(s)) {
639 pr_err("zpool %s not available\n", s);
640 return -ENOENT;
642 type = s;
643 } else if (!compressor) {
644 if (!crypto_has_comp(s, 0, 0)) {
645 pr_err("compressor %s not available\n", s);
646 return -ENOENT;
648 compressor = s;
649 } else {
650 WARN_ON(1);
651 return -EINVAL;
654 spin_lock(&zswap_pools_lock);
656 pool = zswap_pool_find_get(type, compressor);
657 if (pool) {
658 zswap_pool_debug("using existing", pool);
659 list_del_rcu(&pool->list);
660 } else {
661 spin_unlock(&zswap_pools_lock);
662 pool = zswap_pool_create(type, compressor);
663 spin_lock(&zswap_pools_lock);
666 if (pool)
667 ret = param_set_charp(s, kp);
668 else
669 ret = -EINVAL;
671 if (!ret) {
672 put_pool = zswap_pool_current();
673 list_add_rcu(&pool->list, &zswap_pools);
674 } else if (pool) {
675 /* add the possibly pre-existing pool to the end of the pools
676 * list; if it's new (and empty) then it'll be removed and
677 * destroyed by the put after we drop the lock
679 list_add_tail_rcu(&pool->list, &zswap_pools);
680 put_pool = pool;
683 spin_unlock(&zswap_pools_lock);
685 /* drop the ref from either the old current pool,
686 * or the new pool we failed to add
688 if (put_pool)
689 zswap_pool_put(put_pool);
691 return ret;
694 static int zswap_compressor_param_set(const char *val,
695 const struct kernel_param *kp)
697 return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
700 static int zswap_zpool_param_set(const char *val,
701 const struct kernel_param *kp)
703 return __zswap_param_set(val, kp, NULL, zswap_compressor);
706 /*********************************
707 * writeback code
708 **********************************/
709 /* return enum for zswap_get_swap_cache_page */
710 enum zswap_get_swap_ret {
711 ZSWAP_SWAPCACHE_NEW,
712 ZSWAP_SWAPCACHE_EXIST,
713 ZSWAP_SWAPCACHE_FAIL,
717 * zswap_get_swap_cache_page
719 * This is an adaption of read_swap_cache_async()
721 * This function tries to find a page with the given swap entry
722 * in the swapper_space address space (the swap cache). If the page
723 * is found, it is returned in retpage. Otherwise, a page is allocated,
724 * added to the swap cache, and returned in retpage.
726 * If success, the swap cache page is returned in retpage
727 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
728 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
729 * the new page is added to swapcache and locked
730 * Returns ZSWAP_SWAPCACHE_FAIL on error
732 static int zswap_get_swap_cache_page(swp_entry_t entry,
733 struct page **retpage)
735 bool page_was_allocated;
737 *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
738 NULL, 0, &page_was_allocated);
739 if (page_was_allocated)
740 return ZSWAP_SWAPCACHE_NEW;
741 if (!*retpage)
742 return ZSWAP_SWAPCACHE_FAIL;
743 return ZSWAP_SWAPCACHE_EXIST;
747 * Attempts to free an entry by adding a page to the swap cache,
748 * decompressing the entry data into the page, and issuing a
749 * bio write to write the page back to the swap device.
751 * This can be thought of as a "resumed writeback" of the page
752 * to the swap device. We are basically resuming the same swap
753 * writeback path that was intercepted with the frontswap_store()
754 * in the first place. After the page has been decompressed into
755 * the swap cache, the compressed version stored by zswap can be
756 * freed.
758 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
760 struct zswap_header *zhdr;
761 swp_entry_t swpentry;
762 struct zswap_tree *tree;
763 pgoff_t offset;
764 struct zswap_entry *entry;
765 struct page *page;
766 struct crypto_comp *tfm;
767 u8 *src, *dst;
768 unsigned int dlen;
769 int ret;
770 struct writeback_control wbc = {
771 .sync_mode = WB_SYNC_NONE,
774 /* extract swpentry from data */
775 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
776 swpentry = zhdr->swpentry; /* here */
777 zpool_unmap_handle(pool, handle);
778 tree = zswap_trees[swp_type(swpentry)];
779 offset = swp_offset(swpentry);
781 /* find and ref zswap entry */
782 spin_lock(&tree->lock);
783 entry = zswap_entry_find_get(&tree->rbroot, offset);
784 if (!entry) {
785 /* entry was invalidated */
786 spin_unlock(&tree->lock);
787 return 0;
789 spin_unlock(&tree->lock);
790 BUG_ON(offset != entry->offset);
792 /* try to allocate swap cache page */
793 switch (zswap_get_swap_cache_page(swpentry, &page)) {
794 case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
795 ret = -ENOMEM;
796 goto fail;
798 case ZSWAP_SWAPCACHE_EXIST:
799 /* page is already in the swap cache, ignore for now */
800 put_page(page);
801 ret = -EEXIST;
802 goto fail;
804 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
805 /* decompress */
806 dlen = PAGE_SIZE;
807 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
808 ZPOOL_MM_RO) + sizeof(struct zswap_header);
809 dst = kmap_atomic(page);
810 tfm = *get_cpu_ptr(entry->pool->tfm);
811 ret = crypto_comp_decompress(tfm, src, entry->length,
812 dst, &dlen);
813 put_cpu_ptr(entry->pool->tfm);
814 kunmap_atomic(dst);
815 zpool_unmap_handle(entry->pool->zpool, entry->handle);
816 BUG_ON(ret);
817 BUG_ON(dlen != PAGE_SIZE);
819 /* page is up to date */
820 SetPageUptodate(page);
823 /* move it to the tail of the inactive list after end_writeback */
824 SetPageReclaim(page);
826 /* start writeback */
827 __swap_writepage(page, &wbc, end_swap_bio_write);
828 put_page(page);
829 zswap_written_back_pages++;
831 spin_lock(&tree->lock);
832 /* drop local reference */
833 zswap_entry_put(tree, entry);
836 * There are two possible situations for entry here:
837 * (1) refcount is 1(normal case), entry is valid and on the tree
838 * (2) refcount is 0, entry is freed and not on the tree
839 * because invalidate happened during writeback
840 * search the tree and free the entry if find entry
842 if (entry == zswap_rb_search(&tree->rbroot, offset))
843 zswap_entry_put(tree, entry);
844 spin_unlock(&tree->lock);
846 goto end;
849 * if we get here due to ZSWAP_SWAPCACHE_EXIST
850 * a load may happening concurrently
851 * it is safe and okay to not free the entry
852 * if we free the entry in the following put
853 * it it either okay to return !0
855 fail:
856 spin_lock(&tree->lock);
857 zswap_entry_put(tree, entry);
858 spin_unlock(&tree->lock);
860 end:
861 return ret;
864 static int zswap_shrink(void)
866 struct zswap_pool *pool;
867 int ret;
869 pool = zswap_pool_last_get();
870 if (!pool)
871 return -ENOENT;
873 ret = zpool_shrink(pool->zpool, 1, NULL);
875 zswap_pool_put(pool);
877 return ret;
880 /*********************************
881 * frontswap hooks
882 **********************************/
883 /* attempts to compress and store an single page */
884 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
885 struct page *page)
887 struct zswap_tree *tree = zswap_trees[type];
888 struct zswap_entry *entry, *dupentry;
889 struct crypto_comp *tfm;
890 int ret;
891 unsigned int dlen = PAGE_SIZE, len;
892 unsigned long handle;
893 char *buf;
894 u8 *src, *dst;
895 struct zswap_header *zhdr;
897 if (!zswap_enabled || !tree) {
898 ret = -ENODEV;
899 goto reject;
902 /* reclaim space if needed */
903 if (zswap_is_full()) {
904 zswap_pool_limit_hit++;
905 if (zswap_shrink()) {
906 zswap_reject_reclaim_fail++;
907 ret = -ENOMEM;
908 goto reject;
912 /* allocate entry */
913 entry = zswap_entry_cache_alloc(GFP_KERNEL);
914 if (!entry) {
915 zswap_reject_kmemcache_fail++;
916 ret = -ENOMEM;
917 goto reject;
920 /* if entry is successfully added, it keeps the reference */
921 entry->pool = zswap_pool_current_get();
922 if (!entry->pool) {
923 ret = -EINVAL;
924 goto freepage;
927 /* compress */
928 dst = get_cpu_var(zswap_dstmem);
929 tfm = *get_cpu_ptr(entry->pool->tfm);
930 src = kmap_atomic(page);
931 ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
932 kunmap_atomic(src);
933 put_cpu_ptr(entry->pool->tfm);
934 if (ret) {
935 ret = -EINVAL;
936 goto put_dstmem;
939 /* store */
940 len = dlen + sizeof(struct zswap_header);
941 ret = zpool_malloc(entry->pool->zpool, len,
942 __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM,
943 &handle);
944 if (ret == -ENOSPC) {
945 zswap_reject_compress_poor++;
946 goto put_dstmem;
948 if (ret) {
949 zswap_reject_alloc_fail++;
950 goto put_dstmem;
952 zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
953 zhdr->swpentry = swp_entry(type, offset);
954 buf = (u8 *)(zhdr + 1);
955 memcpy(buf, dst, dlen);
956 zpool_unmap_handle(entry->pool->zpool, handle);
957 put_cpu_var(zswap_dstmem);
959 /* populate entry */
960 entry->offset = offset;
961 entry->handle = handle;
962 entry->length = dlen;
964 /* map */
965 spin_lock(&tree->lock);
966 do {
967 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
968 if (ret == -EEXIST) {
969 zswap_duplicate_entry++;
970 /* remove from rbtree */
971 zswap_rb_erase(&tree->rbroot, dupentry);
972 zswap_entry_put(tree, dupentry);
974 } while (ret == -EEXIST);
975 spin_unlock(&tree->lock);
977 /* update stats */
978 atomic_inc(&zswap_stored_pages);
979 zswap_update_total_size();
981 return 0;
983 put_dstmem:
984 put_cpu_var(zswap_dstmem);
985 zswap_pool_put(entry->pool);
986 freepage:
987 zswap_entry_cache_free(entry);
988 reject:
989 return ret;
993 * returns 0 if the page was successfully decompressed
994 * return -1 on entry not found or error
996 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
997 struct page *page)
999 struct zswap_tree *tree = zswap_trees[type];
1000 struct zswap_entry *entry;
1001 struct crypto_comp *tfm;
1002 u8 *src, *dst;
1003 unsigned int dlen;
1004 int ret;
1006 /* find */
1007 spin_lock(&tree->lock);
1008 entry = zswap_entry_find_get(&tree->rbroot, offset);
1009 if (!entry) {
1010 /* entry was written back */
1011 spin_unlock(&tree->lock);
1012 return -1;
1014 spin_unlock(&tree->lock);
1016 /* decompress */
1017 dlen = PAGE_SIZE;
1018 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
1019 ZPOOL_MM_RO) + sizeof(struct zswap_header);
1020 dst = kmap_atomic(page);
1021 tfm = *get_cpu_ptr(entry->pool->tfm);
1022 ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
1023 put_cpu_ptr(entry->pool->tfm);
1024 kunmap_atomic(dst);
1025 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1026 BUG_ON(ret);
1028 spin_lock(&tree->lock);
1029 zswap_entry_put(tree, entry);
1030 spin_unlock(&tree->lock);
1032 return 0;
1035 /* frees an entry in zswap */
1036 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1038 struct zswap_tree *tree = zswap_trees[type];
1039 struct zswap_entry *entry;
1041 /* find */
1042 spin_lock(&tree->lock);
1043 entry = zswap_rb_search(&tree->rbroot, offset);
1044 if (!entry) {
1045 /* entry was written back */
1046 spin_unlock(&tree->lock);
1047 return;
1050 /* remove from rbtree */
1051 zswap_rb_erase(&tree->rbroot, entry);
1053 /* drop the initial reference from entry creation */
1054 zswap_entry_put(tree, entry);
1056 spin_unlock(&tree->lock);
1059 /* frees all zswap entries for the given swap type */
1060 static void zswap_frontswap_invalidate_area(unsigned type)
1062 struct zswap_tree *tree = zswap_trees[type];
1063 struct zswap_entry *entry, *n;
1065 if (!tree)
1066 return;
1068 /* walk the tree and free everything */
1069 spin_lock(&tree->lock);
1070 rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1071 zswap_free_entry(entry);
1072 tree->rbroot = RB_ROOT;
1073 spin_unlock(&tree->lock);
1074 kfree(tree);
1075 zswap_trees[type] = NULL;
1078 static void zswap_frontswap_init(unsigned type)
1080 struct zswap_tree *tree;
1082 tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
1083 if (!tree) {
1084 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1085 return;
1088 tree->rbroot = RB_ROOT;
1089 spin_lock_init(&tree->lock);
1090 zswap_trees[type] = tree;
1093 static struct frontswap_ops zswap_frontswap_ops = {
1094 .store = zswap_frontswap_store,
1095 .load = zswap_frontswap_load,
1096 .invalidate_page = zswap_frontswap_invalidate_page,
1097 .invalidate_area = zswap_frontswap_invalidate_area,
1098 .init = zswap_frontswap_init
1101 /*********************************
1102 * debugfs functions
1103 **********************************/
1104 #ifdef CONFIG_DEBUG_FS
1105 #include <linux/debugfs.h>
1107 static struct dentry *zswap_debugfs_root;
1109 static int __init zswap_debugfs_init(void)
1111 if (!debugfs_initialized())
1112 return -ENODEV;
1114 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1115 if (!zswap_debugfs_root)
1116 return -ENOMEM;
1118 debugfs_create_u64("pool_limit_hit", S_IRUGO,
1119 zswap_debugfs_root, &zswap_pool_limit_hit);
1120 debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
1121 zswap_debugfs_root, &zswap_reject_reclaim_fail);
1122 debugfs_create_u64("reject_alloc_fail", S_IRUGO,
1123 zswap_debugfs_root, &zswap_reject_alloc_fail);
1124 debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
1125 zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1126 debugfs_create_u64("reject_compress_poor", S_IRUGO,
1127 zswap_debugfs_root, &zswap_reject_compress_poor);
1128 debugfs_create_u64("written_back_pages", S_IRUGO,
1129 zswap_debugfs_root, &zswap_written_back_pages);
1130 debugfs_create_u64("duplicate_entry", S_IRUGO,
1131 zswap_debugfs_root, &zswap_duplicate_entry);
1132 debugfs_create_u64("pool_total_size", S_IRUGO,
1133 zswap_debugfs_root, &zswap_pool_total_size);
1134 debugfs_create_atomic_t("stored_pages", S_IRUGO,
1135 zswap_debugfs_root, &zswap_stored_pages);
1137 return 0;
1140 static void __exit zswap_debugfs_exit(void)
1142 debugfs_remove_recursive(zswap_debugfs_root);
1144 #else
1145 static int __init zswap_debugfs_init(void)
1147 return 0;
1150 static void __exit zswap_debugfs_exit(void) { }
1151 #endif
1153 /*********************************
1154 * module init and exit
1155 **********************************/
1156 static int __init init_zswap(void)
1158 struct zswap_pool *pool;
1159 int ret;
1161 zswap_init_started = true;
1163 if (zswap_entry_cache_create()) {
1164 pr_err("entry cache creation failed\n");
1165 goto cache_fail;
1168 ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1169 zswap_dstmem_prepare, zswap_dstmem_dead);
1170 if (ret) {
1171 pr_err("dstmem alloc failed\n");
1172 goto dstmem_fail;
1175 ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1176 "mm/zswap_pool:prepare",
1177 zswap_cpu_comp_prepare,
1178 zswap_cpu_comp_dead);
1179 if (ret)
1180 goto hp_fail;
1182 pool = __zswap_pool_create_fallback();
1183 if (!pool) {
1184 pr_err("pool creation failed\n");
1185 goto pool_fail;
1187 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1188 zpool_get_type(pool->zpool));
1190 list_add(&pool->list, &zswap_pools);
1192 frontswap_register_ops(&zswap_frontswap_ops);
1193 if (zswap_debugfs_init())
1194 pr_warn("debugfs initialization failed\n");
1195 return 0;
1197 pool_fail:
1198 cpuhp_remove_state_nocalls(CPUHP_MM_ZSWP_POOL_PREPARE);
1199 hp_fail:
1200 cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1201 dstmem_fail:
1202 zswap_entry_cache_destroy();
1203 cache_fail:
1204 return -ENOMEM;
1206 /* must be late so crypto has time to come up */
1207 late_initcall(init_zswap);
1209 MODULE_LICENSE("GPL");
1210 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1211 MODULE_DESCRIPTION("Compressed cache for swap pages");