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[CRYPTO_MAX_ALG_NAME] = ZSWAP_COMPRESSOR_DEFAULT;
86 static struct kparam_string zswap_compressor_kparam = {
87 .string = zswap_compressor,
88 .maxlen = sizeof(zswap_compressor),
90 static int zswap_compressor_param_set(const char *,
91 const struct kernel_param *);
92 static struct kernel_param_ops zswap_compressor_param_ops = {
93 .set = zswap_compressor_param_set,
94 .get = param_get_string,
96 module_param_cb(compressor, &zswap_compressor_param_ops,
97 &zswap_compressor_kparam, 0644);
99 /* Compressed storage zpool to use */
100 #define ZSWAP_ZPOOL_DEFAULT "zbud"
101 static char zswap_zpool_type[32 /* arbitrary */] = ZSWAP_ZPOOL_DEFAULT;
102 static struct kparam_string zswap_zpool_kparam = {
103 .string = zswap_zpool_type,
104 .maxlen = sizeof(zswap_zpool_type),
106 static int zswap_zpool_param_set(const char *, const struct kernel_param *);
107 static struct kernel_param_ops zswap_zpool_param_ops = {
108 .set = zswap_zpool_param_set,
109 .get = param_get_string,
111 module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_kparam, 0644);
113 /* The maximum percentage of memory that the compressed pool can occupy */
114 static unsigned int zswap_max_pool_percent = 20;
115 module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
117 /*********************************
119 **********************************/
123 struct crypto_comp * __percpu *tfm;
125 struct list_head list;
126 struct rcu_head rcu_head;
127 struct notifier_block notifier;
128 char tfm_name[CRYPTO_MAX_ALG_NAME];
134 * This structure contains the metadata for tracking a single compressed
137 * rbnode - links the entry into red-black tree for the appropriate swap type
138 * offset - the swap offset for the entry. Index into the red-black tree.
139 * refcount - the number of outstanding reference to the entry. This is needed
140 * to protect against premature freeing of the entry by code
141 * concurrent calls to load, invalidate, and writeback. The lock
142 * for the zswap_tree structure that contains the entry must
143 * be held while changing the refcount. Since the lock must
144 * be held, there is no reason to also make refcount atomic.
145 * length - the length in bytes of the compressed page data. Needed during
147 * pool - the zswap_pool the entry's data is in
148 * handle - zpool allocation handle that stores the compressed page data
151 struct rb_node rbnode;
155 struct zswap_pool *pool;
156 unsigned long handle;
159 struct zswap_header {
160 swp_entry_t swpentry;
164 * The tree lock in the zswap_tree struct protects a few things:
166 * - the refcount field of each entry in the tree
169 struct rb_root rbroot;
173 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
175 /* RCU-protected iteration */
176 static LIST_HEAD(zswap_pools);
177 /* protects zswap_pools list modification */
178 static DEFINE_SPINLOCK(zswap_pools_lock);
180 /* used by param callback function */
181 static bool zswap_init_started;
183 /*********************************
184 * helpers and fwd declarations
185 **********************************/
187 #define zswap_pool_debug(msg, p) \
188 pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \
189 zpool_get_type((p)->zpool))
191 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
192 static int zswap_pool_get(struct zswap_pool *pool);
193 static void zswap_pool_put(struct zswap_pool *pool);
195 static const struct zpool_ops zswap_zpool_ops = {
196 .evict = zswap_writeback_entry
199 static bool zswap_is_full(void)
201 return totalram_pages * zswap_max_pool_percent / 100 <
202 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
205 static void zswap_update_total_size(void)
207 struct zswap_pool *pool;
212 list_for_each_entry_rcu(pool, &zswap_pools, list)
213 total += zpool_get_total_size(pool->zpool);
217 zswap_pool_total_size = total;
220 /*********************************
221 * zswap entry functions
222 **********************************/
223 static struct kmem_cache *zswap_entry_cache;
225 static int __init zswap_entry_cache_create(void)
227 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
228 return zswap_entry_cache == NULL;
231 static void __init zswap_entry_cache_destroy(void)
233 kmem_cache_destroy(zswap_entry_cache);
236 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
238 struct zswap_entry *entry;
239 entry = kmem_cache_alloc(zswap_entry_cache, gfp);
243 RB_CLEAR_NODE(&entry->rbnode);
247 static void zswap_entry_cache_free(struct zswap_entry *entry)
249 kmem_cache_free(zswap_entry_cache, entry);
252 /*********************************
254 **********************************/
255 static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
257 struct rb_node *node = root->rb_node;
258 struct zswap_entry *entry;
261 entry = rb_entry(node, struct zswap_entry, rbnode);
262 if (entry->offset > offset)
263 node = node->rb_left;
264 else if (entry->offset < offset)
265 node = node->rb_right;
273 * In the case that a entry with the same offset is found, a pointer to
274 * the existing entry is stored in dupentry and the function returns -EEXIST
276 static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
277 struct zswap_entry **dupentry)
279 struct rb_node **link = &root->rb_node, *parent = NULL;
280 struct zswap_entry *myentry;
284 myentry = rb_entry(parent, struct zswap_entry, rbnode);
285 if (myentry->offset > entry->offset)
286 link = &(*link)->rb_left;
287 else if (myentry->offset < entry->offset)
288 link = &(*link)->rb_right;
294 rb_link_node(&entry->rbnode, parent, link);
295 rb_insert_color(&entry->rbnode, root);
299 static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
301 if (!RB_EMPTY_NODE(&entry->rbnode)) {
302 rb_erase(&entry->rbnode, root);
303 RB_CLEAR_NODE(&entry->rbnode);
308 * Carries out the common pattern of freeing and entry's zpool allocation,
309 * freeing the entry itself, and decrementing the number of stored pages.
311 static void zswap_free_entry(struct zswap_entry *entry)
313 zpool_free(entry->pool->zpool, entry->handle);
314 zswap_pool_put(entry->pool);
315 zswap_entry_cache_free(entry);
316 atomic_dec(&zswap_stored_pages);
317 zswap_update_total_size();
320 /* caller must hold the tree lock */
321 static void zswap_entry_get(struct zswap_entry *entry)
326 /* caller must hold the tree lock
327 * remove from the tree and free it, if nobody reference the entry
329 static void zswap_entry_put(struct zswap_tree *tree,
330 struct zswap_entry *entry)
332 int refcount = --entry->refcount;
334 BUG_ON(refcount < 0);
336 zswap_rb_erase(&tree->rbroot, entry);
337 zswap_free_entry(entry);
341 /* caller must hold the tree lock */
342 static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
345 struct zswap_entry *entry = NULL;
347 entry = zswap_rb_search(root, offset);
349 zswap_entry_get(entry);
354 /*********************************
356 **********************************/
357 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
359 static int __zswap_cpu_dstmem_notifier(unsigned long action, unsigned long cpu)
365 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
367 pr_err("can't allocate compressor buffer\n");
370 per_cpu(zswap_dstmem, cpu) = dst;
373 case CPU_UP_CANCELED:
374 dst = per_cpu(zswap_dstmem, cpu);
376 per_cpu(zswap_dstmem, cpu) = NULL;
384 static int zswap_cpu_dstmem_notifier(struct notifier_block *nb,
385 unsigned long action, void *pcpu)
387 return __zswap_cpu_dstmem_notifier(action, (unsigned long)pcpu);
390 static struct notifier_block zswap_dstmem_notifier = {
391 .notifier_call = zswap_cpu_dstmem_notifier,
394 static int __init zswap_cpu_dstmem_init(void)
398 cpu_notifier_register_begin();
399 for_each_online_cpu(cpu)
400 if (__zswap_cpu_dstmem_notifier(CPU_UP_PREPARE, cpu) ==
403 __register_cpu_notifier(&zswap_dstmem_notifier);
404 cpu_notifier_register_done();
408 for_each_online_cpu(cpu)
409 __zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
410 cpu_notifier_register_done();
414 static void zswap_cpu_dstmem_destroy(void)
418 cpu_notifier_register_begin();
419 for_each_online_cpu(cpu)
420 __zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
421 __unregister_cpu_notifier(&zswap_dstmem_notifier);
422 cpu_notifier_register_done();
425 static int __zswap_cpu_comp_notifier(struct zswap_pool *pool,
426 unsigned long action, unsigned long cpu)
428 struct crypto_comp *tfm;
432 if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
434 tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
435 if (IS_ERR_OR_NULL(tfm)) {
436 pr_err("could not alloc crypto comp %s : %ld\n",
437 pool->tfm_name, PTR_ERR(tfm));
440 *per_cpu_ptr(pool->tfm, cpu) = tfm;
443 case CPU_UP_CANCELED:
444 tfm = *per_cpu_ptr(pool->tfm, cpu);
445 if (!IS_ERR_OR_NULL(tfm))
446 crypto_free_comp(tfm);
447 *per_cpu_ptr(pool->tfm, cpu) = NULL;
455 static int zswap_cpu_comp_notifier(struct notifier_block *nb,
456 unsigned long action, void *pcpu)
458 unsigned long cpu = (unsigned long)pcpu;
459 struct zswap_pool *pool = container_of(nb, typeof(*pool), notifier);
461 return __zswap_cpu_comp_notifier(pool, action, cpu);
464 static int zswap_cpu_comp_init(struct zswap_pool *pool)
468 memset(&pool->notifier, 0, sizeof(pool->notifier));
469 pool->notifier.notifier_call = zswap_cpu_comp_notifier;
471 cpu_notifier_register_begin();
472 for_each_online_cpu(cpu)
473 if (__zswap_cpu_comp_notifier(pool, CPU_UP_PREPARE, cpu) ==
476 __register_cpu_notifier(&pool->notifier);
477 cpu_notifier_register_done();
481 for_each_online_cpu(cpu)
482 __zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
483 cpu_notifier_register_done();
487 static void zswap_cpu_comp_destroy(struct zswap_pool *pool)
491 cpu_notifier_register_begin();
492 for_each_online_cpu(cpu)
493 __zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
494 __unregister_cpu_notifier(&pool->notifier);
495 cpu_notifier_register_done();
498 /*********************************
500 **********************************/
502 static struct zswap_pool *__zswap_pool_current(void)
504 struct zswap_pool *pool;
506 pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
512 static struct zswap_pool *zswap_pool_current(void)
514 assert_spin_locked(&zswap_pools_lock);
516 return __zswap_pool_current();
519 static struct zswap_pool *zswap_pool_current_get(void)
521 struct zswap_pool *pool;
525 pool = __zswap_pool_current();
526 if (!pool || !zswap_pool_get(pool))
534 static struct zswap_pool *zswap_pool_last_get(void)
536 struct zswap_pool *pool, *last = NULL;
540 list_for_each_entry_rcu(pool, &zswap_pools, list)
542 if (!WARN_ON(!last) && !zswap_pool_get(last))
550 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
552 struct zswap_pool *pool;
554 assert_spin_locked(&zswap_pools_lock);
556 list_for_each_entry_rcu(pool, &zswap_pools, list) {
557 if (strncmp(pool->tfm_name, compressor, sizeof(pool->tfm_name)))
559 if (strncmp(zpool_get_type(pool->zpool), type,
560 sizeof(zswap_zpool_type)))
562 /* if we can't get it, it's about to be destroyed */
563 if (!zswap_pool_get(pool))
571 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
573 struct zswap_pool *pool;
574 gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN;
576 pool = kzalloc(sizeof(*pool), GFP_KERNEL);
578 pr_err("pool alloc failed\n");
582 pool->zpool = zpool_create_pool(type, "zswap", 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 struct zswap_pool *__zswap_pool_create_fallback(void)
620 if (!crypto_has_comp(zswap_compressor, 0, 0)) {
621 pr_err("compressor %s not available, using default %s\n",
622 zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
623 strncpy(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT,
624 sizeof(zswap_compressor));
626 if (!zpool_has_pool(zswap_zpool_type)) {
627 pr_err("zpool %s not available, using default %s\n",
628 zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
629 strncpy(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT,
630 sizeof(zswap_zpool_type));
633 return zswap_pool_create(zswap_zpool_type, zswap_compressor);
636 static void zswap_pool_destroy(struct zswap_pool *pool)
638 zswap_pool_debug("destroying", pool);
640 zswap_cpu_comp_destroy(pool);
641 free_percpu(pool->tfm);
642 zpool_destroy_pool(pool->zpool);
646 static int __must_check zswap_pool_get(struct zswap_pool *pool)
648 return kref_get_unless_zero(&pool->kref);
651 static void __zswap_pool_release(struct rcu_head *head)
653 struct zswap_pool *pool = container_of(head, typeof(*pool), rcu_head);
655 /* nobody should have been able to get a kref... */
656 WARN_ON(kref_get_unless_zero(&pool->kref));
658 /* pool is now off zswap_pools list and has no references. */
659 zswap_pool_destroy(pool);
662 static void __zswap_pool_empty(struct kref *kref)
664 struct zswap_pool *pool;
666 pool = container_of(kref, typeof(*pool), kref);
668 spin_lock(&zswap_pools_lock);
670 WARN_ON(pool == zswap_pool_current());
672 list_del_rcu(&pool->list);
673 call_rcu(&pool->rcu_head, __zswap_pool_release);
675 spin_unlock(&zswap_pools_lock);
678 static void zswap_pool_put(struct zswap_pool *pool)
680 kref_put(&pool->kref, __zswap_pool_empty);
683 /*********************************
685 **********************************/
687 static int __zswap_param_set(const char *val, const struct kernel_param *kp,
688 char *type, char *compressor)
690 struct zswap_pool *pool, *put_pool = NULL;
691 char str[kp->str->maxlen], *s;
695 * kp is either zswap_zpool_kparam or zswap_compressor_kparam, defined
696 * at the top of this file, so maxlen is CRYPTO_MAX_ALG_NAME (64) or
699 strlcpy(str, val, kp->str->maxlen);
702 /* if this is load-time (pre-init) param setting,
703 * don't create a pool; that's done during init.
705 if (!zswap_init_started)
706 return param_set_copystring(s, kp);
708 /* no change required */
709 if (!strncmp(kp->str->string, s, kp->str->maxlen))
714 if (!zpool_has_pool(type)) {
715 pr_err("zpool %s not available\n", type);
718 } else if (!compressor) {
720 if (!crypto_has_comp(compressor, 0, 0)) {
721 pr_err("compressor %s not available\n", compressor);
726 spin_lock(&zswap_pools_lock);
728 pool = zswap_pool_find_get(type, compressor);
730 zswap_pool_debug("using existing", pool);
731 list_del_rcu(&pool->list);
733 spin_unlock(&zswap_pools_lock);
734 pool = zswap_pool_create(type, compressor);
735 spin_lock(&zswap_pools_lock);
739 ret = param_set_copystring(s, kp);
744 put_pool = zswap_pool_current();
745 list_add_rcu(&pool->list, &zswap_pools);
747 /* add the possibly pre-existing pool to the end of the pools
748 * list; if it's new (and empty) then it'll be removed and
749 * destroyed by the put after we drop the lock
751 list_add_tail_rcu(&pool->list, &zswap_pools);
755 spin_unlock(&zswap_pools_lock);
757 /* drop the ref from either the old current pool,
758 * or the new pool we failed to add
761 zswap_pool_put(put_pool);
766 static int zswap_compressor_param_set(const char *val,
767 const struct kernel_param *kp)
769 return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
772 static int zswap_zpool_param_set(const char *val,
773 const struct kernel_param *kp)
775 return __zswap_param_set(val, kp, NULL, zswap_compressor);
778 /*********************************
780 **********************************/
781 /* return enum for zswap_get_swap_cache_page */
782 enum zswap_get_swap_ret {
784 ZSWAP_SWAPCACHE_EXIST,
785 ZSWAP_SWAPCACHE_FAIL,
789 * zswap_get_swap_cache_page
791 * This is an adaption of read_swap_cache_async()
793 * This function tries to find a page with the given swap entry
794 * in the swapper_space address space (the swap cache). If the page
795 * is found, it is returned in retpage. Otherwise, a page is allocated,
796 * added to the swap cache, and returned in retpage.
798 * If success, the swap cache page is returned in retpage
799 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
800 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
801 * the new page is added to swapcache and locked
802 * Returns ZSWAP_SWAPCACHE_FAIL on error
804 static int zswap_get_swap_cache_page(swp_entry_t entry,
805 struct page **retpage)
807 bool page_was_allocated;
809 *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
810 NULL, 0, &page_was_allocated);
811 if (page_was_allocated)
812 return ZSWAP_SWAPCACHE_NEW;
814 return ZSWAP_SWAPCACHE_FAIL;
815 return ZSWAP_SWAPCACHE_EXIST;
819 * Attempts to free an entry by adding a page to the swap cache,
820 * decompressing the entry data into the page, and issuing a
821 * bio write to write the page back to the swap device.
823 * This can be thought of as a "resumed writeback" of the page
824 * to the swap device. We are basically resuming the same swap
825 * writeback path that was intercepted with the frontswap_store()
826 * in the first place. After the page has been decompressed into
827 * the swap cache, the compressed version stored by zswap can be
830 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
832 struct zswap_header *zhdr;
833 swp_entry_t swpentry;
834 struct zswap_tree *tree;
836 struct zswap_entry *entry;
838 struct crypto_comp *tfm;
842 struct writeback_control wbc = {
843 .sync_mode = WB_SYNC_NONE,
846 /* extract swpentry from data */
847 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
848 swpentry = zhdr->swpentry; /* here */
849 zpool_unmap_handle(pool, handle);
850 tree = zswap_trees[swp_type(swpentry)];
851 offset = swp_offset(swpentry);
853 /* find and ref zswap entry */
854 spin_lock(&tree->lock);
855 entry = zswap_entry_find_get(&tree->rbroot, offset);
857 /* entry was invalidated */
858 spin_unlock(&tree->lock);
861 spin_unlock(&tree->lock);
862 BUG_ON(offset != entry->offset);
864 /* try to allocate swap cache page */
865 switch (zswap_get_swap_cache_page(swpentry, &page)) {
866 case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
870 case ZSWAP_SWAPCACHE_EXIST:
871 /* page is already in the swap cache, ignore for now */
872 page_cache_release(page);
876 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
879 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
880 ZPOOL_MM_RO) + sizeof(struct zswap_header);
881 dst = kmap_atomic(page);
882 tfm = *get_cpu_ptr(entry->pool->tfm);
883 ret = crypto_comp_decompress(tfm, src, entry->length,
885 put_cpu_ptr(entry->pool->tfm);
887 zpool_unmap_handle(entry->pool->zpool, entry->handle);
889 BUG_ON(dlen != PAGE_SIZE);
891 /* page is up to date */
892 SetPageUptodate(page);
895 /* move it to the tail of the inactive list after end_writeback */
896 SetPageReclaim(page);
898 /* start writeback */
899 __swap_writepage(page, &wbc, end_swap_bio_write);
900 page_cache_release(page);
901 zswap_written_back_pages++;
903 spin_lock(&tree->lock);
904 /* drop local reference */
905 zswap_entry_put(tree, entry);
908 * There are two possible situations for entry here:
909 * (1) refcount is 1(normal case), entry is valid and on the tree
910 * (2) refcount is 0, entry is freed and not on the tree
911 * because invalidate happened during writeback
912 * search the tree and free the entry if find entry
914 if (entry == zswap_rb_search(&tree->rbroot, offset))
915 zswap_entry_put(tree, entry);
916 spin_unlock(&tree->lock);
921 * if we get here due to ZSWAP_SWAPCACHE_EXIST
922 * a load may happening concurrently
923 * it is safe and okay to not free the entry
924 * if we free the entry in the following put
925 * it it either okay to return !0
928 spin_lock(&tree->lock);
929 zswap_entry_put(tree, entry);
930 spin_unlock(&tree->lock);
936 static int zswap_shrink(void)
938 struct zswap_pool *pool;
941 pool = zswap_pool_last_get();
945 ret = zpool_shrink(pool->zpool, 1, NULL);
947 zswap_pool_put(pool);
952 /*********************************
954 **********************************/
955 /* attempts to compress and store an single page */
956 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
959 struct zswap_tree *tree = zswap_trees[type];
960 struct zswap_entry *entry, *dupentry;
961 struct crypto_comp *tfm;
963 unsigned int dlen = PAGE_SIZE, len;
964 unsigned long handle;
967 struct zswap_header *zhdr;
969 if (!zswap_enabled || !tree) {
974 /* reclaim space if needed */
975 if (zswap_is_full()) {
976 zswap_pool_limit_hit++;
977 if (zswap_shrink()) {
978 zswap_reject_reclaim_fail++;
985 entry = zswap_entry_cache_alloc(GFP_KERNEL);
987 zswap_reject_kmemcache_fail++;
992 /* if entry is successfully added, it keeps the reference */
993 entry->pool = zswap_pool_current_get();
1000 dst = get_cpu_var(zswap_dstmem);
1001 tfm = *get_cpu_ptr(entry->pool->tfm);
1002 src = kmap_atomic(page);
1003 ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
1005 put_cpu_ptr(entry->pool->tfm);
1012 len = dlen + sizeof(struct zswap_header);
1013 ret = zpool_malloc(entry->pool->zpool, len,
1014 __GFP_NORETRY | __GFP_NOWARN, &handle);
1015 if (ret == -ENOSPC) {
1016 zswap_reject_compress_poor++;
1020 zswap_reject_alloc_fail++;
1023 zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
1024 zhdr->swpentry = swp_entry(type, offset);
1025 buf = (u8 *)(zhdr + 1);
1026 memcpy(buf, dst, dlen);
1027 zpool_unmap_handle(entry->pool->zpool, handle);
1028 put_cpu_var(zswap_dstmem);
1030 /* populate entry */
1031 entry->offset = offset;
1032 entry->handle = handle;
1033 entry->length = dlen;
1036 spin_lock(&tree->lock);
1038 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1039 if (ret == -EEXIST) {
1040 zswap_duplicate_entry++;
1041 /* remove from rbtree */
1042 zswap_rb_erase(&tree->rbroot, dupentry);
1043 zswap_entry_put(tree, dupentry);
1045 } while (ret == -EEXIST);
1046 spin_unlock(&tree->lock);
1049 atomic_inc(&zswap_stored_pages);
1050 zswap_update_total_size();
1055 put_cpu_var(zswap_dstmem);
1056 zswap_pool_put(entry->pool);
1058 zswap_entry_cache_free(entry);
1064 * returns 0 if the page was successfully decompressed
1065 * return -1 on entry not found or error
1067 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1070 struct zswap_tree *tree = zswap_trees[type];
1071 struct zswap_entry *entry;
1072 struct crypto_comp *tfm;
1078 spin_lock(&tree->lock);
1079 entry = zswap_entry_find_get(&tree->rbroot, offset);
1081 /* entry was written back */
1082 spin_unlock(&tree->lock);
1085 spin_unlock(&tree->lock);
1089 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
1090 ZPOOL_MM_RO) + sizeof(struct zswap_header);
1091 dst = kmap_atomic(page);
1092 tfm = *get_cpu_ptr(entry->pool->tfm);
1093 ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
1094 put_cpu_ptr(entry->pool->tfm);
1096 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1099 spin_lock(&tree->lock);
1100 zswap_entry_put(tree, entry);
1101 spin_unlock(&tree->lock);
1106 /* frees an entry in zswap */
1107 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1109 struct zswap_tree *tree = zswap_trees[type];
1110 struct zswap_entry *entry;
1113 spin_lock(&tree->lock);
1114 entry = zswap_rb_search(&tree->rbroot, offset);
1116 /* entry was written back */
1117 spin_unlock(&tree->lock);
1121 /* remove from rbtree */
1122 zswap_rb_erase(&tree->rbroot, entry);
1124 /* drop the initial reference from entry creation */
1125 zswap_entry_put(tree, entry);
1127 spin_unlock(&tree->lock);
1130 /* frees all zswap entries for the given swap type */
1131 static void zswap_frontswap_invalidate_area(unsigned type)
1133 struct zswap_tree *tree = zswap_trees[type];
1134 struct zswap_entry *entry, *n;
1139 /* walk the tree and free everything */
1140 spin_lock(&tree->lock);
1141 rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1142 zswap_free_entry(entry);
1143 tree->rbroot = RB_ROOT;
1144 spin_unlock(&tree->lock);
1146 zswap_trees[type] = NULL;
1149 static void zswap_frontswap_init(unsigned type)
1151 struct zswap_tree *tree;
1153 tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
1155 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1159 tree->rbroot = RB_ROOT;
1160 spin_lock_init(&tree->lock);
1161 zswap_trees[type] = tree;
1164 static struct frontswap_ops zswap_frontswap_ops = {
1165 .store = zswap_frontswap_store,
1166 .load = zswap_frontswap_load,
1167 .invalidate_page = zswap_frontswap_invalidate_page,
1168 .invalidate_area = zswap_frontswap_invalidate_area,
1169 .init = zswap_frontswap_init
1172 /*********************************
1174 **********************************/
1175 #ifdef CONFIG_DEBUG_FS
1176 #include <linux/debugfs.h>
1178 static struct dentry *zswap_debugfs_root;
1180 static int __init zswap_debugfs_init(void)
1182 if (!debugfs_initialized())
1185 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1186 if (!zswap_debugfs_root)
1189 debugfs_create_u64("pool_limit_hit", S_IRUGO,
1190 zswap_debugfs_root, &zswap_pool_limit_hit);
1191 debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
1192 zswap_debugfs_root, &zswap_reject_reclaim_fail);
1193 debugfs_create_u64("reject_alloc_fail", S_IRUGO,
1194 zswap_debugfs_root, &zswap_reject_alloc_fail);
1195 debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
1196 zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1197 debugfs_create_u64("reject_compress_poor", S_IRUGO,
1198 zswap_debugfs_root, &zswap_reject_compress_poor);
1199 debugfs_create_u64("written_back_pages", S_IRUGO,
1200 zswap_debugfs_root, &zswap_written_back_pages);
1201 debugfs_create_u64("duplicate_entry", S_IRUGO,
1202 zswap_debugfs_root, &zswap_duplicate_entry);
1203 debugfs_create_u64("pool_total_size", S_IRUGO,
1204 zswap_debugfs_root, &zswap_pool_total_size);
1205 debugfs_create_atomic_t("stored_pages", S_IRUGO,
1206 zswap_debugfs_root, &zswap_stored_pages);
1211 static void __exit zswap_debugfs_exit(void)
1213 debugfs_remove_recursive(zswap_debugfs_root);
1216 static int __init zswap_debugfs_init(void)
1221 static void __exit zswap_debugfs_exit(void) { }
1224 /*********************************
1225 * module init and exit
1226 **********************************/
1227 static int __init init_zswap(void)
1229 struct zswap_pool *pool;
1231 zswap_init_started = true;
1233 if (zswap_entry_cache_create()) {
1234 pr_err("entry cache creation failed\n");
1238 if (zswap_cpu_dstmem_init()) {
1239 pr_err("dstmem alloc failed\n");
1243 pool = __zswap_pool_create_fallback();
1245 pr_err("pool creation failed\n");
1248 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1249 zpool_get_type(pool->zpool));
1251 list_add(&pool->list, &zswap_pools);
1253 frontswap_register_ops(&zswap_frontswap_ops);
1254 if (zswap_debugfs_init())
1255 pr_warn("debugfs initialization failed\n");
1259 zswap_cpu_dstmem_destroy();
1261 zswap_entry_cache_destroy();
1265 /* must be late so crypto has time to come up */
1266 late_initcall(init_zswap);
1268 MODULE_LICENSE("GPL");
1269 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1270 MODULE_DESCRIPTION("Compressed cache for swap pages");