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[firefly-linux-kernel-4.4.55.git] / mm / zswap.c
1 /*
2  * zswap.c - zswap driver file
3  *
4  * zswap is a backend for frontswap that takes pages that are in the process
5  * of being swapped out and attempts to compress and store them in a
6  * RAM-based memory pool.  This can result in a significant I/O reduction on
7  * the swap device and, in the case where decompressing from RAM is faster
8  * than reading from the swap device, can also improve workload performance.
9  *
10  * Copyright (C) 2012  Seth Jennings <sjenning@linux.vnet.ibm.com>
11  *
12  * This program is free software; you can redistribute it and/or
13  * modify it under the terms of the GNU General Public License
14  * as published by the Free Software Foundation; either version 2
15  * of the License, or (at your option) any later version.
16  *
17  * This program is distributed in the hope that it will be useful,
18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
20  * GNU General Public License for more details.
21 */
22
23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
24
25 #include <linux/module.h>
26 #include <linux/cpu.h>
27 #include <linux/highmem.h>
28 #include <linux/slab.h>
29 #include <linux/spinlock.h>
30 #include <linux/types.h>
31 #include <linux/atomic.h>
32 #include <linux/frontswap.h>
33 #include <linux/rbtree.h>
34 #include <linux/swap.h>
35 #include <linux/crypto.h>
36 #include <linux/mempool.h>
37 #include <linux/zpool.h>
38
39 #include <linux/mm_types.h>
40 #include <linux/page-flags.h>
41 #include <linux/swapops.h>
42 #include <linux/writeback.h>
43 #include <linux/pagemap.h>
44
45 /*********************************
46 * statistics
47 **********************************/
48 /* Total bytes used by the compressed storage */
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);
52
53 /*
54  * The statistics below are not protected from concurrent access for
55  * performance reasons so they may not be a 100% accurate.  However,
56  * they do provide useful information on roughly how many times a
57  * certain event is occurring.
58 */
59
60 /* Pool limit was hit (see zswap_max_pool_percent) */
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;
74
75 /*********************************
76 * tunables
77 **********************************/
78
79 /* Enable/disable zswap (disabled by default) */
80 static bool zswap_enabled;
81 module_param_named(enabled, zswap_enabled, bool, 0644);
82
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,
92 };
93 module_param_cb(compressor, &zswap_compressor_param_ops,
94                 &zswap_compressor, 0644);
95
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,
104 };
105 module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
106
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);
110
111 /*********************************
112 * data structures
113 **********************************/
114
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 rcu_head rcu_head;
121         struct notifier_block notifier;
122         char tfm_name[CRYPTO_MAX_ALG_NAME];
123 };
124
125 /*
126  * struct zswap_entry
127  *
128  * This structure contains the metadata for tracking a single compressed
129  * page within zswap.
130  *
131  * rbnode - links the entry into red-black tree for the appropriate swap type
132  * offset - the swap offset for the entry.  Index into the red-black tree.
133  * refcount - the number of outstanding reference to the entry. This is needed
134  *            to protect against premature freeing of the entry by code
135  *            concurrent calls to load, invalidate, and writeback.  The lock
136  *            for the zswap_tree structure that contains the entry must
137  *            be held while changing the refcount.  Since the lock must
138  *            be held, there is no reason to also make refcount atomic.
139  * length - the length in bytes of the compressed page data.  Needed during
140  *          decompression
141  * pool - the zswap_pool the entry's data is in
142  * handle - zpool allocation handle that stores the compressed page data
143  */
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;
151 };
152
153 struct zswap_header {
154         swp_entry_t swpentry;
155 };
156
157 /*
158  * The tree lock in the zswap_tree struct protects a few things:
159  * - the rbtree
160  * - the refcount field of each entry in the tree
161  */
162 struct zswap_tree {
163         struct rb_root rbroot;
164         spinlock_t lock;
165 };
166
167 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
168
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);
175
176 /* used by param callback function */
177 static bool zswap_init_started;
178
179 /*********************************
180 * helpers and fwd declarations
181 **********************************/
182
183 #define zswap_pool_debug(msg, p)                                \
184         pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,         \
185                  zpool_get_type((p)->zpool))
186
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);
190
191 static const struct zpool_ops zswap_zpool_ops = {
192         .evict = zswap_writeback_entry
193 };
194
195 static bool zswap_is_full(void)
196 {
197         return totalram_pages * zswap_max_pool_percent / 100 <
198                 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
199 }
200
201 static void zswap_update_total_size(void)
202 {
203         struct zswap_pool *pool;
204         u64 total = 0;
205
206         rcu_read_lock();
207
208         list_for_each_entry_rcu(pool, &zswap_pools, list)
209                 total += zpool_get_total_size(pool->zpool);
210
211         rcu_read_unlock();
212
213         zswap_pool_total_size = total;
214 }
215
216 /*********************************
217 * zswap entry functions
218 **********************************/
219 static struct kmem_cache *zswap_entry_cache;
220
221 static int __init zswap_entry_cache_create(void)
222 {
223         zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
224         return zswap_entry_cache == NULL;
225 }
226
227 static void __init zswap_entry_cache_destroy(void)
228 {
229         kmem_cache_destroy(zswap_entry_cache);
230 }
231
232 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
233 {
234         struct zswap_entry *entry;
235         entry = kmem_cache_alloc(zswap_entry_cache, gfp);
236         if (!entry)
237                 return NULL;
238         entry->refcount = 1;
239         RB_CLEAR_NODE(&entry->rbnode);
240         return entry;
241 }
242
243 static void zswap_entry_cache_free(struct zswap_entry *entry)
244 {
245         kmem_cache_free(zswap_entry_cache, entry);
246 }
247
248 /*********************************
249 * rbtree functions
250 **********************************/
251 static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
252 {
253         struct rb_node *node = root->rb_node;
254         struct zswap_entry *entry;
255
256         while (node) {
257                 entry = rb_entry(node, struct zswap_entry, rbnode);
258                 if (entry->offset > offset)
259                         node = node->rb_left;
260                 else if (entry->offset < offset)
261                         node = node->rb_right;
262                 else
263                         return entry;
264         }
265         return NULL;
266 }
267
268 /*
269  * In the case that a entry with the same offset is found, a pointer to
270  * the existing entry is stored in dupentry and the function returns -EEXIST
271  */
272 static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
273                         struct zswap_entry **dupentry)
274 {
275         struct rb_node **link = &root->rb_node, *parent = NULL;
276         struct zswap_entry *myentry;
277
278         while (*link) {
279                 parent = *link;
280                 myentry = rb_entry(parent, struct zswap_entry, rbnode);
281                 if (myentry->offset > entry->offset)
282                         link = &(*link)->rb_left;
283                 else if (myentry->offset < entry->offset)
284                         link = &(*link)->rb_right;
285                 else {
286                         *dupentry = myentry;
287                         return -EEXIST;
288                 }
289         }
290         rb_link_node(&entry->rbnode, parent, link);
291         rb_insert_color(&entry->rbnode, root);
292         return 0;
293 }
294
295 static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
296 {
297         if (!RB_EMPTY_NODE(&entry->rbnode)) {
298                 rb_erase(&entry->rbnode, root);
299                 RB_CLEAR_NODE(&entry->rbnode);
300         }
301 }
302
303 /*
304  * Carries out the common pattern of freeing and entry's zpool allocation,
305  * freeing the entry itself, and decrementing the number of stored pages.
306  */
307 static void zswap_free_entry(struct zswap_entry *entry)
308 {
309         zpool_free(entry->pool->zpool, entry->handle);
310         zswap_pool_put(entry->pool);
311         zswap_entry_cache_free(entry);
312         atomic_dec(&zswap_stored_pages);
313         zswap_update_total_size();
314 }
315
316 /* caller must hold the tree lock */
317 static void zswap_entry_get(struct zswap_entry *entry)
318 {
319         entry->refcount++;
320 }
321
322 /* caller must hold the tree lock
323 * remove from the tree and free it, if nobody reference the entry
324 */
325 static void zswap_entry_put(struct zswap_tree *tree,
326                         struct zswap_entry *entry)
327 {
328         int refcount = --entry->refcount;
329
330         BUG_ON(refcount < 0);
331         if (refcount == 0) {
332                 zswap_rb_erase(&tree->rbroot, entry);
333                 zswap_free_entry(entry);
334         }
335 }
336
337 /* caller must hold the tree lock */
338 static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
339                                 pgoff_t offset)
340 {
341         struct zswap_entry *entry;
342
343         entry = zswap_rb_search(root, offset);
344         if (entry)
345                 zswap_entry_get(entry);
346
347         return entry;
348 }
349
350 /*********************************
351 * per-cpu code
352 **********************************/
353 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
354
355 static int __zswap_cpu_dstmem_notifier(unsigned long action, unsigned long cpu)
356 {
357         u8 *dst;
358
359         switch (action) {
360         case CPU_UP_PREPARE:
361                 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
362                 if (!dst) {
363                         pr_err("can't allocate compressor buffer\n");
364                         return NOTIFY_BAD;
365                 }
366                 per_cpu(zswap_dstmem, cpu) = dst;
367                 break;
368         case CPU_DEAD:
369         case CPU_UP_CANCELED:
370                 dst = per_cpu(zswap_dstmem, cpu);
371                 kfree(dst);
372                 per_cpu(zswap_dstmem, cpu) = NULL;
373                 break;
374         default:
375                 break;
376         }
377         return NOTIFY_OK;
378 }
379
380 static int zswap_cpu_dstmem_notifier(struct notifier_block *nb,
381                                      unsigned long action, void *pcpu)
382 {
383         return __zswap_cpu_dstmem_notifier(action, (unsigned long)pcpu);
384 }
385
386 static struct notifier_block zswap_dstmem_notifier = {
387         .notifier_call =        zswap_cpu_dstmem_notifier,
388 };
389
390 static int __init zswap_cpu_dstmem_init(void)
391 {
392         unsigned long cpu;
393
394         cpu_notifier_register_begin();
395         for_each_online_cpu(cpu)
396                 if (__zswap_cpu_dstmem_notifier(CPU_UP_PREPARE, cpu) ==
397                     NOTIFY_BAD)
398                         goto cleanup;
399         __register_cpu_notifier(&zswap_dstmem_notifier);
400         cpu_notifier_register_done();
401         return 0;
402
403 cleanup:
404         for_each_online_cpu(cpu)
405                 __zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
406         cpu_notifier_register_done();
407         return -ENOMEM;
408 }
409
410 static void zswap_cpu_dstmem_destroy(void)
411 {
412         unsigned long cpu;
413
414         cpu_notifier_register_begin();
415         for_each_online_cpu(cpu)
416                 __zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
417         __unregister_cpu_notifier(&zswap_dstmem_notifier);
418         cpu_notifier_register_done();
419 }
420
421 static int __zswap_cpu_comp_notifier(struct zswap_pool *pool,
422                                      unsigned long action, unsigned long cpu)
423 {
424         struct crypto_comp *tfm;
425
426         switch (action) {
427         case CPU_UP_PREPARE:
428                 if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
429                         break;
430                 tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
431                 if (IS_ERR_OR_NULL(tfm)) {
432                         pr_err("could not alloc crypto comp %s : %ld\n",
433                                pool->tfm_name, PTR_ERR(tfm));
434                         return NOTIFY_BAD;
435                 }
436                 *per_cpu_ptr(pool->tfm, cpu) = tfm;
437                 break;
438         case CPU_DEAD:
439         case CPU_UP_CANCELED:
440                 tfm = *per_cpu_ptr(pool->tfm, cpu);
441                 if (!IS_ERR_OR_NULL(tfm))
442                         crypto_free_comp(tfm);
443                 *per_cpu_ptr(pool->tfm, cpu) = NULL;
444                 break;
445         default:
446                 break;
447         }
448         return NOTIFY_OK;
449 }
450
451 static int zswap_cpu_comp_notifier(struct notifier_block *nb,
452                                    unsigned long action, void *pcpu)
453 {
454         unsigned long cpu = (unsigned long)pcpu;
455         struct zswap_pool *pool = container_of(nb, typeof(*pool), notifier);
456
457         return __zswap_cpu_comp_notifier(pool, action, cpu);
458 }
459
460 static int zswap_cpu_comp_init(struct zswap_pool *pool)
461 {
462         unsigned long cpu;
463
464         memset(&pool->notifier, 0, sizeof(pool->notifier));
465         pool->notifier.notifier_call = zswap_cpu_comp_notifier;
466
467         cpu_notifier_register_begin();
468         for_each_online_cpu(cpu)
469                 if (__zswap_cpu_comp_notifier(pool, CPU_UP_PREPARE, cpu) ==
470                     NOTIFY_BAD)
471                         goto cleanup;
472         __register_cpu_notifier(&pool->notifier);
473         cpu_notifier_register_done();
474         return 0;
475
476 cleanup:
477         for_each_online_cpu(cpu)
478                 __zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
479         cpu_notifier_register_done();
480         return -ENOMEM;
481 }
482
483 static void zswap_cpu_comp_destroy(struct zswap_pool *pool)
484 {
485         unsigned long cpu;
486
487         cpu_notifier_register_begin();
488         for_each_online_cpu(cpu)
489                 __zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
490         __unregister_cpu_notifier(&pool->notifier);
491         cpu_notifier_register_done();
492 }
493
494 /*********************************
495 * pool functions
496 **********************************/
497
498 static struct zswap_pool *__zswap_pool_current(void)
499 {
500         struct zswap_pool *pool;
501
502         pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
503         WARN_ON(!pool);
504
505         return pool;
506 }
507
508 static struct zswap_pool *zswap_pool_current(void)
509 {
510         assert_spin_locked(&zswap_pools_lock);
511
512         return __zswap_pool_current();
513 }
514
515 static struct zswap_pool *zswap_pool_current_get(void)
516 {
517         struct zswap_pool *pool;
518
519         rcu_read_lock();
520
521         pool = __zswap_pool_current();
522         if (!pool || !zswap_pool_get(pool))
523                 pool = NULL;
524
525         rcu_read_unlock();
526
527         return pool;
528 }
529
530 static struct zswap_pool *zswap_pool_last_get(void)
531 {
532         struct zswap_pool *pool, *last = NULL;
533
534         rcu_read_lock();
535
536         list_for_each_entry_rcu(pool, &zswap_pools, list)
537                 last = pool;
538         if (!WARN_ON(!last) && !zswap_pool_get(last))
539                 last = NULL;
540
541         rcu_read_unlock();
542
543         return last;
544 }
545
546 /* type and compressor must be null-terminated */
547 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
548 {
549         struct zswap_pool *pool;
550
551         assert_spin_locked(&zswap_pools_lock);
552
553         list_for_each_entry_rcu(pool, &zswap_pools, list) {
554                 if (strcmp(pool->tfm_name, compressor))
555                         continue;
556                 if (strcmp(zpool_get_type(pool->zpool), type))
557                         continue;
558                 /* if we can't get it, it's about to be destroyed */
559                 if (!zswap_pool_get(pool))
560                         continue;
561                 return pool;
562         }
563
564         return NULL;
565 }
566
567 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
568 {
569         struct zswap_pool *pool;
570         char name[38]; /* 'zswap' + 32 char (max) num + \0 */
571         gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
572
573         pool = kzalloc(sizeof(*pool), GFP_KERNEL);
574         if (!pool) {
575                 pr_err("pool alloc failed\n");
576                 return NULL;
577         }
578
579         /* unique name for each pool specifically required by zsmalloc */
580         snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
581
582         pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
583         if (!pool->zpool) {
584                 pr_err("%s zpool not available\n", type);
585                 goto error;
586         }
587         pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
588
589         strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
590         pool->tfm = alloc_percpu(struct crypto_comp *);
591         if (!pool->tfm) {
592                 pr_err("percpu alloc failed\n");
593                 goto error;
594         }
595
596         if (zswap_cpu_comp_init(pool))
597                 goto error;
598         pr_debug("using %s compressor\n", pool->tfm_name);
599
600         /* being the current pool takes 1 ref; this func expects the
601          * caller to always add the new pool as the current pool
602          */
603         kref_init(&pool->kref);
604         INIT_LIST_HEAD(&pool->list);
605
606         zswap_pool_debug("created", pool);
607
608         return pool;
609
610 error:
611         free_percpu(pool->tfm);
612         if (pool->zpool)
613                 zpool_destroy_pool(pool->zpool);
614         kfree(pool);
615         return NULL;
616 }
617
618 static __init struct zswap_pool *__zswap_pool_create_fallback(void)
619 {
620         if (!crypto_has_comp(zswap_compressor, 0, 0)) {
621                 if (!strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {
622                         pr_err("default compressor %s not available\n",
623                                zswap_compressor);
624                         return NULL;
625                 }
626                 pr_err("compressor %s not available, using default %s\n",
627                        zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
628                 param_free_charp(&zswap_compressor);
629                 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
630         }
631         if (!zpool_has_pool(zswap_zpool_type)) {
632                 if (!strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
633                         pr_err("default zpool %s not available\n",
634                                zswap_zpool_type);
635                         return NULL;
636                 }
637                 pr_err("zpool %s not available, using default %s\n",
638                        zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
639                 param_free_charp(&zswap_zpool_type);
640                 zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
641         }
642
643         return zswap_pool_create(zswap_zpool_type, zswap_compressor);
644 }
645
646 static void zswap_pool_destroy(struct zswap_pool *pool)
647 {
648         zswap_pool_debug("destroying", pool);
649
650         zswap_cpu_comp_destroy(pool);
651         free_percpu(pool->tfm);
652         zpool_destroy_pool(pool->zpool);
653         kfree(pool);
654 }
655
656 static int __must_check zswap_pool_get(struct zswap_pool *pool)
657 {
658         return kref_get_unless_zero(&pool->kref);
659 }
660
661 static void __zswap_pool_release(struct rcu_head *head)
662 {
663         struct zswap_pool *pool = container_of(head, typeof(*pool), rcu_head);
664
665         /* nobody should have been able to get a kref... */
666         WARN_ON(kref_get_unless_zero(&pool->kref));
667
668         /* pool is now off zswap_pools list and has no references. */
669         zswap_pool_destroy(pool);
670 }
671
672 static void __zswap_pool_empty(struct kref *kref)
673 {
674         struct zswap_pool *pool;
675
676         pool = container_of(kref, typeof(*pool), kref);
677
678         spin_lock(&zswap_pools_lock);
679
680         WARN_ON(pool == zswap_pool_current());
681
682         list_del_rcu(&pool->list);
683         call_rcu(&pool->rcu_head, __zswap_pool_release);
684
685         spin_unlock(&zswap_pools_lock);
686 }
687
688 static void zswap_pool_put(struct zswap_pool *pool)
689 {
690         kref_put(&pool->kref, __zswap_pool_empty);
691 }
692
693 /*********************************
694 * param callbacks
695 **********************************/
696
697 /* val must be a null-terminated string */
698 static int __zswap_param_set(const char *val, const struct kernel_param *kp,
699                              char *type, char *compressor)
700 {
701         struct zswap_pool *pool, *put_pool = NULL;
702         char *s = strstrip((char *)val);
703         int ret;
704
705         /* no change required */
706         if (!strcmp(s, *(char **)kp->arg))
707                 return 0;
708
709         /* if this is load-time (pre-init) param setting,
710          * don't create a pool; that's done during init.
711          */
712         if (!zswap_init_started)
713                 return param_set_charp(s, kp);
714
715         if (!type) {
716                 if (!zpool_has_pool(s)) {
717                         pr_err("zpool %s not available\n", s);
718                         return -ENOENT;
719                 }
720                 type = s;
721         } else if (!compressor) {
722                 if (!crypto_has_comp(s, 0, 0)) {
723                         pr_err("compressor %s not available\n", s);
724                         return -ENOENT;
725                 }
726                 compressor = s;
727         } else {
728                 WARN_ON(1);
729                 return -EINVAL;
730         }
731
732         spin_lock(&zswap_pools_lock);
733
734         pool = zswap_pool_find_get(type, compressor);
735         if (pool) {
736                 zswap_pool_debug("using existing", pool);
737                 list_del_rcu(&pool->list);
738         } else {
739                 spin_unlock(&zswap_pools_lock);
740                 pool = zswap_pool_create(type, compressor);
741                 spin_lock(&zswap_pools_lock);
742         }
743
744         if (pool)
745                 ret = param_set_charp(s, kp);
746         else
747                 ret = -EINVAL;
748
749         if (!ret) {
750                 put_pool = zswap_pool_current();
751                 list_add_rcu(&pool->list, &zswap_pools);
752         } else if (pool) {
753                 /* add the possibly pre-existing pool to the end of the pools
754                  * list; if it's new (and empty) then it'll be removed and
755                  * destroyed by the put after we drop the lock
756                  */
757                 list_add_tail_rcu(&pool->list, &zswap_pools);
758                 put_pool = pool;
759         }
760
761         spin_unlock(&zswap_pools_lock);
762
763         /* drop the ref from either the old current pool,
764          * or the new pool we failed to add
765          */
766         if (put_pool)
767                 zswap_pool_put(put_pool);
768
769         return ret;
770 }
771
772 static int zswap_compressor_param_set(const char *val,
773                                       const struct kernel_param *kp)
774 {
775         return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
776 }
777
778 static int zswap_zpool_param_set(const char *val,
779                                  const struct kernel_param *kp)
780 {
781         return __zswap_param_set(val, kp, NULL, zswap_compressor);
782 }
783
784 /*********************************
785 * writeback code
786 **********************************/
787 /* return enum for zswap_get_swap_cache_page */
788 enum zswap_get_swap_ret {
789         ZSWAP_SWAPCACHE_NEW,
790         ZSWAP_SWAPCACHE_EXIST,
791         ZSWAP_SWAPCACHE_FAIL,
792 };
793
794 /*
795  * zswap_get_swap_cache_page
796  *
797  * This is an adaption of read_swap_cache_async()
798  *
799  * This function tries to find a page with the given swap entry
800  * in the swapper_space address space (the swap cache).  If the page
801  * is found, it is returned in retpage.  Otherwise, a page is allocated,
802  * added to the swap cache, and returned in retpage.
803  *
804  * If success, the swap cache page is returned in retpage
805  * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
806  * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
807  *     the new page is added to swapcache and locked
808  * Returns ZSWAP_SWAPCACHE_FAIL on error
809  */
810 static int zswap_get_swap_cache_page(swp_entry_t entry,
811                                 struct page **retpage)
812 {
813         bool page_was_allocated;
814
815         *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
816                         NULL, 0, &page_was_allocated);
817         if (page_was_allocated)
818                 return ZSWAP_SWAPCACHE_NEW;
819         if (!*retpage)
820                 return ZSWAP_SWAPCACHE_FAIL;
821         return ZSWAP_SWAPCACHE_EXIST;
822 }
823
824 /*
825  * Attempts to free an entry by adding a page to the swap cache,
826  * decompressing the entry data into the page, and issuing a
827  * bio write to write the page back to the swap device.
828  *
829  * This can be thought of as a "resumed writeback" of the page
830  * to the swap device.  We are basically resuming the same swap
831  * writeback path that was intercepted with the frontswap_store()
832  * in the first place.  After the page has been decompressed into
833  * the swap cache, the compressed version stored by zswap can be
834  * freed.
835  */
836 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
837 {
838         struct zswap_header *zhdr;
839         swp_entry_t swpentry;
840         struct zswap_tree *tree;
841         pgoff_t offset;
842         struct zswap_entry *entry;
843         struct page *page;
844         struct crypto_comp *tfm;
845         u8 *src, *dst;
846         unsigned int dlen;
847         int ret;
848         struct writeback_control wbc = {
849                 .sync_mode = WB_SYNC_NONE,
850         };
851
852         /* extract swpentry from data */
853         zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
854         swpentry = zhdr->swpentry; /* here */
855         zpool_unmap_handle(pool, handle);
856         tree = zswap_trees[swp_type(swpentry)];
857         offset = swp_offset(swpentry);
858
859         /* find and ref zswap entry */
860         spin_lock(&tree->lock);
861         entry = zswap_entry_find_get(&tree->rbroot, offset);
862         if (!entry) {
863                 /* entry was invalidated */
864                 spin_unlock(&tree->lock);
865                 return 0;
866         }
867         spin_unlock(&tree->lock);
868         BUG_ON(offset != entry->offset);
869
870         /* try to allocate swap cache page */
871         switch (zswap_get_swap_cache_page(swpentry, &page)) {
872         case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
873                 ret = -ENOMEM;
874                 goto fail;
875
876         case ZSWAP_SWAPCACHE_EXIST:
877                 /* page is already in the swap cache, ignore for now */
878                 page_cache_release(page);
879                 ret = -EEXIST;
880                 goto fail;
881
882         case ZSWAP_SWAPCACHE_NEW: /* page is locked */
883                 /* decompress */
884                 dlen = PAGE_SIZE;
885                 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
886                                 ZPOOL_MM_RO) + sizeof(struct zswap_header);
887                 dst = kmap_atomic(page);
888                 tfm = *get_cpu_ptr(entry->pool->tfm);
889                 ret = crypto_comp_decompress(tfm, src, entry->length,
890                                              dst, &dlen);
891                 put_cpu_ptr(entry->pool->tfm);
892                 kunmap_atomic(dst);
893                 zpool_unmap_handle(entry->pool->zpool, entry->handle);
894                 BUG_ON(ret);
895                 BUG_ON(dlen != PAGE_SIZE);
896
897                 /* page is up to date */
898                 SetPageUptodate(page);
899         }
900
901         /* move it to the tail of the inactive list after end_writeback */
902         SetPageReclaim(page);
903
904         /* start writeback */
905         __swap_writepage(page, &wbc, end_swap_bio_write);
906         page_cache_release(page);
907         zswap_written_back_pages++;
908
909         spin_lock(&tree->lock);
910         /* drop local reference */
911         zswap_entry_put(tree, entry);
912
913         /*
914         * There are two possible situations for entry here:
915         * (1) refcount is 1(normal case),  entry is valid and on the tree
916         * (2) refcount is 0, entry is freed and not on the tree
917         *     because invalidate happened during writeback
918         *  search the tree and free the entry if find entry
919         */
920         if (entry == zswap_rb_search(&tree->rbroot, offset))
921                 zswap_entry_put(tree, entry);
922         spin_unlock(&tree->lock);
923
924         goto end;
925
926         /*
927         * if we get here due to ZSWAP_SWAPCACHE_EXIST
928         * a load may happening concurrently
929         * it is safe and okay to not free the entry
930         * if we free the entry in the following put
931         * it it either okay to return !0
932         */
933 fail:
934         spin_lock(&tree->lock);
935         zswap_entry_put(tree, entry);
936         spin_unlock(&tree->lock);
937
938 end:
939         return ret;
940 }
941
942 static int zswap_shrink(void)
943 {
944         struct zswap_pool *pool;
945         int ret;
946
947         pool = zswap_pool_last_get();
948         if (!pool)
949                 return -ENOENT;
950
951         ret = zpool_shrink(pool->zpool, 1, NULL);
952
953         zswap_pool_put(pool);
954
955         return ret;
956 }
957
958 /*********************************
959 * frontswap hooks
960 **********************************/
961 /* attempts to compress and store an single page */
962 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
963                                 struct page *page)
964 {
965         struct zswap_tree *tree = zswap_trees[type];
966         struct zswap_entry *entry, *dupentry;
967         struct crypto_comp *tfm;
968         int ret;
969         unsigned int dlen = PAGE_SIZE, len;
970         unsigned long handle;
971         char *buf;
972         u8 *src, *dst;
973         struct zswap_header *zhdr;
974
975         if (!zswap_enabled || !tree) {
976                 ret = -ENODEV;
977                 goto reject;
978         }
979
980         /* reclaim space if needed */
981         if (zswap_is_full()) {
982                 zswap_pool_limit_hit++;
983                 if (zswap_shrink()) {
984                         zswap_reject_reclaim_fail++;
985                         ret = -ENOMEM;
986                         goto reject;
987                 }
988         }
989
990         /* allocate entry */
991         entry = zswap_entry_cache_alloc(GFP_KERNEL);
992         if (!entry) {
993                 zswap_reject_kmemcache_fail++;
994                 ret = -ENOMEM;
995                 goto reject;
996         }
997
998         /* if entry is successfully added, it keeps the reference */
999         entry->pool = zswap_pool_current_get();
1000         if (!entry->pool) {
1001                 ret = -EINVAL;
1002                 goto freepage;
1003         }
1004
1005         /* compress */
1006         dst = get_cpu_var(zswap_dstmem);
1007         tfm = *get_cpu_ptr(entry->pool->tfm);
1008         src = kmap_atomic(page);
1009         ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
1010         kunmap_atomic(src);
1011         put_cpu_ptr(entry->pool->tfm);
1012         if (ret) {
1013                 ret = -EINVAL;
1014                 goto put_dstmem;
1015         }
1016
1017         /* store */
1018         len = dlen + sizeof(struct zswap_header);
1019         ret = zpool_malloc(entry->pool->zpool, len,
1020                            __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM,
1021                            &handle);
1022         if (ret == -ENOSPC) {
1023                 zswap_reject_compress_poor++;
1024                 goto put_dstmem;
1025         }
1026         if (ret) {
1027                 zswap_reject_alloc_fail++;
1028                 goto put_dstmem;
1029         }
1030         zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
1031         zhdr->swpentry = swp_entry(type, offset);
1032         buf = (u8 *)(zhdr + 1);
1033         memcpy(buf, dst, dlen);
1034         zpool_unmap_handle(entry->pool->zpool, handle);
1035         put_cpu_var(zswap_dstmem);
1036
1037         /* populate entry */
1038         entry->offset = offset;
1039         entry->handle = handle;
1040         entry->length = dlen;
1041
1042         /* map */
1043         spin_lock(&tree->lock);
1044         do {
1045                 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1046                 if (ret == -EEXIST) {
1047                         zswap_duplicate_entry++;
1048                         /* remove from rbtree */
1049                         zswap_rb_erase(&tree->rbroot, dupentry);
1050                         zswap_entry_put(tree, dupentry);
1051                 }
1052         } while (ret == -EEXIST);
1053         spin_unlock(&tree->lock);
1054
1055         /* update stats */
1056         atomic_inc(&zswap_stored_pages);
1057         zswap_update_total_size();
1058
1059         return 0;
1060
1061 put_dstmem:
1062         put_cpu_var(zswap_dstmem);
1063         zswap_pool_put(entry->pool);
1064 freepage:
1065         zswap_entry_cache_free(entry);
1066 reject:
1067         return ret;
1068 }
1069
1070 /*
1071  * returns 0 if the page was successfully decompressed
1072  * return -1 on entry not found or error
1073 */
1074 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1075                                 struct page *page)
1076 {
1077         struct zswap_tree *tree = zswap_trees[type];
1078         struct zswap_entry *entry;
1079         struct crypto_comp *tfm;
1080         u8 *src, *dst;
1081         unsigned int dlen;
1082         int ret;
1083
1084         /* find */
1085         spin_lock(&tree->lock);
1086         entry = zswap_entry_find_get(&tree->rbroot, offset);
1087         if (!entry) {
1088                 /* entry was written back */
1089                 spin_unlock(&tree->lock);
1090                 return -1;
1091         }
1092         spin_unlock(&tree->lock);
1093
1094         /* decompress */
1095         dlen = PAGE_SIZE;
1096         src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
1097                         ZPOOL_MM_RO) + sizeof(struct zswap_header);
1098         dst = kmap_atomic(page);
1099         tfm = *get_cpu_ptr(entry->pool->tfm);
1100         ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
1101         put_cpu_ptr(entry->pool->tfm);
1102         kunmap_atomic(dst);
1103         zpool_unmap_handle(entry->pool->zpool, entry->handle);
1104         BUG_ON(ret);
1105
1106         spin_lock(&tree->lock);
1107         zswap_entry_put(tree, entry);
1108         spin_unlock(&tree->lock);
1109
1110         return 0;
1111 }
1112
1113 /* frees an entry in zswap */
1114 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1115 {
1116         struct zswap_tree *tree = zswap_trees[type];
1117         struct zswap_entry *entry;
1118
1119         /* find */
1120         spin_lock(&tree->lock);
1121         entry = zswap_rb_search(&tree->rbroot, offset);
1122         if (!entry) {
1123                 /* entry was written back */
1124                 spin_unlock(&tree->lock);
1125                 return;
1126         }
1127
1128         /* remove from rbtree */
1129         zswap_rb_erase(&tree->rbroot, entry);
1130
1131         /* drop the initial reference from entry creation */
1132         zswap_entry_put(tree, entry);
1133
1134         spin_unlock(&tree->lock);
1135 }
1136
1137 /* frees all zswap entries for the given swap type */
1138 static void zswap_frontswap_invalidate_area(unsigned type)
1139 {
1140         struct zswap_tree *tree = zswap_trees[type];
1141         struct zswap_entry *entry, *n;
1142
1143         if (!tree)
1144                 return;
1145
1146         /* walk the tree and free everything */
1147         spin_lock(&tree->lock);
1148         rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1149                 zswap_free_entry(entry);
1150         tree->rbroot = RB_ROOT;
1151         spin_unlock(&tree->lock);
1152         kfree(tree);
1153         zswap_trees[type] = NULL;
1154 }
1155
1156 static void zswap_frontswap_init(unsigned type)
1157 {
1158         struct zswap_tree *tree;
1159
1160         tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
1161         if (!tree) {
1162                 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1163                 return;
1164         }
1165
1166         tree->rbroot = RB_ROOT;
1167         spin_lock_init(&tree->lock);
1168         zswap_trees[type] = tree;
1169 }
1170
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
1177 };
1178
1179 /*********************************
1180 * debugfs functions
1181 **********************************/
1182 #ifdef CONFIG_DEBUG_FS
1183 #include <linux/debugfs.h>
1184
1185 static struct dentry *zswap_debugfs_root;
1186
1187 static int __init zswap_debugfs_init(void)
1188 {
1189         if (!debugfs_initialized())
1190                 return -ENODEV;
1191
1192         zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1193         if (!zswap_debugfs_root)
1194                 return -ENOMEM;
1195
1196         debugfs_create_u64("pool_limit_hit", S_IRUGO,
1197                         zswap_debugfs_root, &zswap_pool_limit_hit);
1198         debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
1199                         zswap_debugfs_root, &zswap_reject_reclaim_fail);
1200         debugfs_create_u64("reject_alloc_fail", S_IRUGO,
1201                         zswap_debugfs_root, &zswap_reject_alloc_fail);
1202         debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
1203                         zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1204         debugfs_create_u64("reject_compress_poor", S_IRUGO,
1205                         zswap_debugfs_root, &zswap_reject_compress_poor);
1206         debugfs_create_u64("written_back_pages", S_IRUGO,
1207                         zswap_debugfs_root, &zswap_written_back_pages);
1208         debugfs_create_u64("duplicate_entry", S_IRUGO,
1209                         zswap_debugfs_root, &zswap_duplicate_entry);
1210         debugfs_create_u64("pool_total_size", S_IRUGO,
1211                         zswap_debugfs_root, &zswap_pool_total_size);
1212         debugfs_create_atomic_t("stored_pages", S_IRUGO,
1213                         zswap_debugfs_root, &zswap_stored_pages);
1214
1215         return 0;
1216 }
1217
1218 static void __exit zswap_debugfs_exit(void)
1219 {
1220         debugfs_remove_recursive(zswap_debugfs_root);
1221 }
1222 #else
1223 static int __init zswap_debugfs_init(void)
1224 {
1225         return 0;
1226 }
1227
1228 static void __exit zswap_debugfs_exit(void) { }
1229 #endif
1230
1231 /*********************************
1232 * module init and exit
1233 **********************************/
1234 static int __init init_zswap(void)
1235 {
1236         struct zswap_pool *pool;
1237
1238         zswap_init_started = true;
1239
1240         if (zswap_entry_cache_create()) {
1241                 pr_err("entry cache creation failed\n");
1242                 goto cache_fail;
1243         }
1244
1245         if (zswap_cpu_dstmem_init()) {
1246                 pr_err("dstmem alloc failed\n");
1247                 goto dstmem_fail;
1248         }
1249
1250         pool = __zswap_pool_create_fallback();
1251         if (!pool) {
1252                 pr_err("pool creation failed\n");
1253                 goto pool_fail;
1254         }
1255         pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1256                 zpool_get_type(pool->zpool));
1257
1258         list_add(&pool->list, &zswap_pools);
1259
1260         frontswap_register_ops(&zswap_frontswap_ops);
1261         if (zswap_debugfs_init())
1262                 pr_warn("debugfs initialization failed\n");
1263         return 0;
1264
1265 pool_fail:
1266         zswap_cpu_dstmem_destroy();
1267 dstmem_fail:
1268         zswap_entry_cache_destroy();
1269 cache_fail:
1270         return -ENOMEM;
1271 }
1272 /* must be late so crypto has time to come up */
1273 late_initcall(init_zswap);
1274
1275 MODULE_LICENSE("GPL");
1276 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1277 MODULE_DESCRIPTION("Compressed cache for swap pages");