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TOMOYO Linux Cross Reference
Linux/mm/zswap.c

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

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