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 /*********************************
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 /*********************************
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 /*********************************
113 **********************************/
117 struct crypto_comp * __percpu *tfm;
119 struct list_head list;
120 struct rcu_head rcu_head;
121 struct notifier_block notifier;
122 char tfm_name[CRYPTO_MAX_ALG_NAME];
128 * This structure contains the metadata for tracking a single compressed
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
141 * pool - the zswap_pool the entry's data is in
142 * handle - zpool allocation handle that stores the compressed page data
145 struct rb_node rbnode;
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:
160 * - the refcount field of each entry in the tree
163 struct rb_root rbroot;
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;
208 list_for_each_entry_rcu(pool, &zswap_pools, list)
209 total += zpool_get_total_size(pool->zpool);
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);
239 RB_CLEAR_NODE(&entry->rbnode);
243 static void zswap_entry_cache_free(struct zswap_entry *entry)
245 kmem_cache_free(zswap_entry_cache, entry);
248 /*********************************
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;
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;
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;
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;
290 rb_link_node(&entry->rbnode, parent, link);
291 rb_insert_color(&entry->rbnode, root);
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)
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);
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,
341 struct zswap_entry *entry;
343 entry = zswap_rb_search(root, offset);
345 zswap_entry_get(entry);
350 /*********************************
352 **********************************/
353 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
355 static int __zswap_cpu_dstmem_notifier(unsigned long action, unsigned long cpu)
361 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
363 pr_err("can't allocate compressor buffer\n");
366 per_cpu(zswap_dstmem, cpu) = dst;
369 case CPU_UP_CANCELED:
370 dst = per_cpu(zswap_dstmem, cpu);
372 per_cpu(zswap_dstmem, cpu) = NULL;
380 static int zswap_cpu_dstmem_notifier(struct notifier_block *nb,
381 unsigned long action, void *pcpu)
383 return __zswap_cpu_dstmem_notifier(action, (unsigned long)pcpu);
386 static struct notifier_block zswap_dstmem_notifier = {
387 .notifier_call = zswap_cpu_dstmem_notifier,
390 static int __init zswap_cpu_dstmem_init(void)
394 cpu_notifier_register_begin();
395 for_each_online_cpu(cpu)
396 if (__zswap_cpu_dstmem_notifier(CPU_UP_PREPARE, cpu) ==
399 __register_cpu_notifier(&zswap_dstmem_notifier);
400 cpu_notifier_register_done();
404 for_each_online_cpu(cpu)
405 __zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
406 cpu_notifier_register_done();
410 static void zswap_cpu_dstmem_destroy(void)
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();
421 static int __zswap_cpu_comp_notifier(struct zswap_pool *pool,
422 unsigned long action, unsigned long cpu)
424 struct crypto_comp *tfm;
428 if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
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));
436 *per_cpu_ptr(pool->tfm, cpu) = tfm;
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;
451 static int zswap_cpu_comp_notifier(struct notifier_block *nb,
452 unsigned long action, void *pcpu)
454 unsigned long cpu = (unsigned long)pcpu;
455 struct zswap_pool *pool = container_of(nb, typeof(*pool), notifier);
457 return __zswap_cpu_comp_notifier(pool, action, cpu);
460 static int zswap_cpu_comp_init(struct zswap_pool *pool)
464 memset(&pool->notifier, 0, sizeof(pool->notifier));
465 pool->notifier.notifier_call = zswap_cpu_comp_notifier;
467 cpu_notifier_register_begin();
468 for_each_online_cpu(cpu)
469 if (__zswap_cpu_comp_notifier(pool, CPU_UP_PREPARE, cpu) ==
472 __register_cpu_notifier(&pool->notifier);
473 cpu_notifier_register_done();
477 for_each_online_cpu(cpu)
478 __zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
479 cpu_notifier_register_done();
483 static void zswap_cpu_comp_destroy(struct zswap_pool *pool)
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();
494 /*********************************
496 **********************************/
498 static struct zswap_pool *__zswap_pool_current(void)
500 struct zswap_pool *pool;
502 pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
508 static struct zswap_pool *zswap_pool_current(void)
510 assert_spin_locked(&zswap_pools_lock);
512 return __zswap_pool_current();
515 static struct zswap_pool *zswap_pool_current_get(void)
517 struct zswap_pool *pool;
521 pool = __zswap_pool_current();
522 if (!pool || !zswap_pool_get(pool))
530 static struct zswap_pool *zswap_pool_last_get(void)
532 struct zswap_pool *pool, *last = NULL;
536 list_for_each_entry_rcu(pool, &zswap_pools, list)
538 if (!WARN_ON(!last) && !zswap_pool_get(last))
546 /* type and compressor must be null-terminated */
547 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
549 struct zswap_pool *pool;
551 assert_spin_locked(&zswap_pools_lock);
553 list_for_each_entry_rcu(pool, &zswap_pools, list) {
554 if (strcmp(pool->tfm_name, compressor))
556 if (strcmp(zpool_get_type(pool->zpool), type))
558 /* if we can't get it, it's about to be destroyed */
559 if (!zswap_pool_get(pool))
567 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
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;
573 pool = kzalloc(sizeof(*pool), GFP_KERNEL);
575 pr_err("pool alloc failed\n");
579 /* unique name for each pool specifically required by zsmalloc */
580 snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
582 pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
584 pr_err("%s zpool not available\n", type);
587 pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
589 strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
590 pool->tfm = alloc_percpu(struct crypto_comp *);
592 pr_err("percpu alloc failed\n");
596 if (zswap_cpu_comp_init(pool))
598 pr_debug("using %s compressor\n", pool->tfm_name);
600 /* being the current pool takes 1 ref; this func expects the
601 * caller to always add the new pool as the current pool
603 kref_init(&pool->kref);
604 INIT_LIST_HEAD(&pool->list);
606 zswap_pool_debug("created", pool);
611 free_percpu(pool->tfm);
613 zpool_destroy_pool(pool->zpool);
618 static __init struct zswap_pool *__zswap_pool_create_fallback(void)
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",
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;
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",
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;
643 return zswap_pool_create(zswap_zpool_type, zswap_compressor);
646 static void zswap_pool_destroy(struct zswap_pool *pool)
648 zswap_pool_debug("destroying", pool);
650 zswap_cpu_comp_destroy(pool);
651 free_percpu(pool->tfm);
652 zpool_destroy_pool(pool->zpool);
656 static int __must_check zswap_pool_get(struct zswap_pool *pool)
658 return kref_get_unless_zero(&pool->kref);
661 static void __zswap_pool_release(struct rcu_head *head)
663 struct zswap_pool *pool = container_of(head, typeof(*pool), rcu_head);
665 /* nobody should have been able to get a kref... */
666 WARN_ON(kref_get_unless_zero(&pool->kref));
668 /* pool is now off zswap_pools list and has no references. */
669 zswap_pool_destroy(pool);
672 static void __zswap_pool_empty(struct kref *kref)
674 struct zswap_pool *pool;
676 pool = container_of(kref, typeof(*pool), kref);
678 spin_lock(&zswap_pools_lock);
680 WARN_ON(pool == zswap_pool_current());
682 list_del_rcu(&pool->list);
683 call_rcu(&pool->rcu_head, __zswap_pool_release);
685 spin_unlock(&zswap_pools_lock);
688 static void zswap_pool_put(struct zswap_pool *pool)
690 kref_put(&pool->kref, __zswap_pool_empty);
693 /*********************************
695 **********************************/
697 /* val must be a null-terminated string */
698 static int __zswap_param_set(const char *val, const struct kernel_param *kp,
699 char *type, char *compressor)
701 struct zswap_pool *pool, *put_pool = NULL;
702 char *s = strstrip((char *)val);
705 /* no change required */
706 if (!strcmp(s, *(char **)kp->arg))
709 /* if this is load-time (pre-init) param setting,
710 * don't create a pool; that's done during init.
712 if (!zswap_init_started)
713 return param_set_charp(s, kp);
716 if (!zpool_has_pool(s)) {
717 pr_err("zpool %s not available\n", s);
721 } else if (!compressor) {
722 if (!crypto_has_comp(s, 0, 0)) {
723 pr_err("compressor %s not available\n", s);
732 spin_lock(&zswap_pools_lock);
734 pool = zswap_pool_find_get(type, compressor);
736 zswap_pool_debug("using existing", pool);
737 list_del_rcu(&pool->list);
739 spin_unlock(&zswap_pools_lock);
740 pool = zswap_pool_create(type, compressor);
741 spin_lock(&zswap_pools_lock);
745 ret = param_set_charp(s, kp);
750 put_pool = zswap_pool_current();
751 list_add_rcu(&pool->list, &zswap_pools);
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
757 list_add_tail_rcu(&pool->list, &zswap_pools);
761 spin_unlock(&zswap_pools_lock);
763 /* drop the ref from either the old current pool,
764 * or the new pool we failed to add
767 zswap_pool_put(put_pool);
772 static int zswap_compressor_param_set(const char *val,
773 const struct kernel_param *kp)
775 return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
778 static int zswap_zpool_param_set(const char *val,
779 const struct kernel_param *kp)
781 return __zswap_param_set(val, kp, NULL, zswap_compressor);
784 /*********************************
786 **********************************/
787 /* return enum for zswap_get_swap_cache_page */
788 enum zswap_get_swap_ret {
790 ZSWAP_SWAPCACHE_EXIST,
791 ZSWAP_SWAPCACHE_FAIL,
795 * zswap_get_swap_cache_page
797 * This is an adaption of read_swap_cache_async()
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.
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
810 static int zswap_get_swap_cache_page(swp_entry_t entry,
811 struct page **retpage)
813 bool page_was_allocated;
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;
820 return ZSWAP_SWAPCACHE_FAIL;
821 return ZSWAP_SWAPCACHE_EXIST;
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.
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
836 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
838 struct zswap_header *zhdr;
839 swp_entry_t swpentry;
840 struct zswap_tree *tree;
842 struct zswap_entry *entry;
844 struct crypto_comp *tfm;
848 struct writeback_control wbc = {
849 .sync_mode = WB_SYNC_NONE,
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);
859 /* find and ref zswap entry */
860 spin_lock(&tree->lock);
861 entry = zswap_entry_find_get(&tree->rbroot, offset);
863 /* entry was invalidated */
864 spin_unlock(&tree->lock);
867 spin_unlock(&tree->lock);
868 BUG_ON(offset != entry->offset);
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 */
876 case ZSWAP_SWAPCACHE_EXIST:
877 /* page is already in the swap cache, ignore for now */
878 page_cache_release(page);
882 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
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,
891 put_cpu_ptr(entry->pool->tfm);
893 zpool_unmap_handle(entry->pool->zpool, entry->handle);
895 BUG_ON(dlen != PAGE_SIZE);
897 /* page is up to date */
898 SetPageUptodate(page);
901 /* move it to the tail of the inactive list after end_writeback */
902 SetPageReclaim(page);
904 /* start writeback */
905 __swap_writepage(page, &wbc, end_swap_bio_write);
906 page_cache_release(page);
907 zswap_written_back_pages++;
909 spin_lock(&tree->lock);
910 /* drop local reference */
911 zswap_entry_put(tree, entry);
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
920 if (entry == zswap_rb_search(&tree->rbroot, offset))
921 zswap_entry_put(tree, entry);
922 spin_unlock(&tree->lock);
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
934 spin_lock(&tree->lock);
935 zswap_entry_put(tree, entry);
936 spin_unlock(&tree->lock);
942 static int zswap_shrink(void)
944 struct zswap_pool *pool;
947 pool = zswap_pool_last_get();
951 ret = zpool_shrink(pool->zpool, 1, NULL);
953 zswap_pool_put(pool);
958 /*********************************
960 **********************************/
961 /* attempts to compress and store an single page */
962 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
965 struct zswap_tree *tree = zswap_trees[type];
966 struct zswap_entry *entry, *dupentry;
967 struct crypto_comp *tfm;
969 unsigned int dlen = PAGE_SIZE, len;
970 unsigned long handle;
973 struct zswap_header *zhdr;
975 if (!zswap_enabled || !tree) {
980 /* reclaim space if needed */
981 if (zswap_is_full()) {
982 zswap_pool_limit_hit++;
983 if (zswap_shrink()) {
984 zswap_reject_reclaim_fail++;
991 entry = zswap_entry_cache_alloc(GFP_KERNEL);
993 zswap_reject_kmemcache_fail++;
998 /* if entry is successfully added, it keeps the reference */
999 entry->pool = zswap_pool_current_get();
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);
1011 put_cpu_ptr(entry->pool->tfm);
1018 len = dlen + sizeof(struct zswap_header);
1019 ret = zpool_malloc(entry->pool->zpool, len,
1020 __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM,
1022 if (ret == -ENOSPC) {
1023 zswap_reject_compress_poor++;
1027 zswap_reject_alloc_fail++;
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);
1037 /* populate entry */
1038 entry->offset = offset;
1039 entry->handle = handle;
1040 entry->length = dlen;
1043 spin_lock(&tree->lock);
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);
1052 } while (ret == -EEXIST);
1053 spin_unlock(&tree->lock);
1056 atomic_inc(&zswap_stored_pages);
1057 zswap_update_total_size();
1062 put_cpu_var(zswap_dstmem);
1063 zswap_pool_put(entry->pool);
1065 zswap_entry_cache_free(entry);
1071 * returns 0 if the page was successfully decompressed
1072 * return -1 on entry not found or error
1074 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1077 struct zswap_tree *tree = zswap_trees[type];
1078 struct zswap_entry *entry;
1079 struct crypto_comp *tfm;
1085 spin_lock(&tree->lock);
1086 entry = zswap_entry_find_get(&tree->rbroot, offset);
1088 /* entry was written back */
1089 spin_unlock(&tree->lock);
1092 spin_unlock(&tree->lock);
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);
1103 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1106 spin_lock(&tree->lock);
1107 zswap_entry_put(tree, entry);
1108 spin_unlock(&tree->lock);
1113 /* frees an entry in zswap */
1114 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1116 struct zswap_tree *tree = zswap_trees[type];
1117 struct zswap_entry *entry;
1120 spin_lock(&tree->lock);
1121 entry = zswap_rb_search(&tree->rbroot, offset);
1123 /* entry was written back */
1124 spin_unlock(&tree->lock);
1128 /* remove from rbtree */
1129 zswap_rb_erase(&tree->rbroot, entry);
1131 /* drop the initial reference from entry creation */
1132 zswap_entry_put(tree, entry);
1134 spin_unlock(&tree->lock);
1137 /* frees all zswap entries for the given swap type */
1138 static void zswap_frontswap_invalidate_area(unsigned type)
1140 struct zswap_tree *tree = zswap_trees[type];
1141 struct zswap_entry *entry, *n;
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);
1153 zswap_trees[type] = NULL;
1156 static void zswap_frontswap_init(unsigned type)
1158 struct zswap_tree *tree;
1160 tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
1162 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1166 tree->rbroot = RB_ROOT;
1167 spin_lock_init(&tree->lock);
1168 zswap_trees[type] = tree;
1171 static 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
1179 /*********************************
1181 **********************************/
1182 #ifdef CONFIG_DEBUG_FS
1183 #include <linux/debugfs.h>
1185 static struct dentry *zswap_debugfs_root;
1187 static int __init zswap_debugfs_init(void)
1189 if (!debugfs_initialized())
1192 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1193 if (!zswap_debugfs_root)
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);
1218 static void __exit zswap_debugfs_exit(void)
1220 debugfs_remove_recursive(zswap_debugfs_root);
1223 static int __init zswap_debugfs_init(void)
1228 static void __exit zswap_debugfs_exit(void) { }
1231 /*********************************
1232 * module init and exit
1233 **********************************/
1234 static int __init init_zswap(void)
1236 struct zswap_pool *pool;
1238 zswap_init_started = true;
1240 if (zswap_entry_cache_create()) {
1241 pr_err("entry cache creation failed\n");
1245 if (zswap_cpu_dstmem_init()) {
1246 pr_err("dstmem alloc failed\n");
1250 pool = __zswap_pool_create_fallback();
1252 pr_err("pool creation failed\n");
1255 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1256 zpool_get_type(pool->zpool));
1258 list_add(&pool->list, &zswap_pools);
1260 frontswap_register_ops(&zswap_frontswap_ops);
1261 if (zswap_debugfs_init())
1262 pr_warn("debugfs initialization failed\n");
1266 zswap_cpu_dstmem_destroy();
1268 zswap_entry_cache_destroy();
1272 /* must be late so crypto has time to come up */
1273 late_initcall(init_zswap);
1275 MODULE_LICENSE("GPL");
1276 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1277 MODULE_DESCRIPTION("Compressed cache for swap pages");