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TOMOYO Linux Cross Reference
Linux/mm/zswap.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /*
  3  * zswap.c - zswap driver file
  4  *
  5  * zswap is a backend for frontswap that takes pages that are in the process
  6  * of being swapped out and attempts to compress and store them in a
  7  * RAM-based memory pool.  This can result in a significant I/O reduction on
  8  * the swap device and, in the case where decompressing from RAM is faster
  9  * than reading from the swap device, can also improve workload performance.
 10  *
 11  * Copyright (C) 2012  Seth Jennings <sjenning@linux.vnet.ibm.com>
 12 */
 13 
 14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 15 
 16 #include <linux/module.h>
 17 #include <linux/cpu.h>
 18 #include <linux/highmem.h>
 19 #include <linux/slab.h>
 20 #include <linux/spinlock.h>
 21 #include <linux/types.h>
 22 #include <linux/atomic.h>
 23 #include <linux/frontswap.h>
 24 #include <linux/rbtree.h>
 25 #include <linux/swap.h>
 26 #include <linux/crypto.h>
 27 #include <linux/scatterlist.h>
 28 #include <linux/mempool.h>
 29 #include <linux/zpool.h>
 30 #include <crypto/acompress.h>
 31 
 32 #include <linux/mm_types.h>
 33 #include <linux/page-flags.h>
 34 #include <linux/swapops.h>
 35 #include <linux/writeback.h>
 36 #include <linux/pagemap.h>
 37 #include <linux/workqueue.h>
 38 
 39 /*********************************
 40 * statistics
 41 **********************************/
 42 /* Total bytes used by the compressed storage */
 43 static u64 zswap_pool_total_size;
 44 /* The number of compressed pages currently stored in zswap */
 45 static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
 46 /* The number of same-value filled pages currently stored in zswap */
 47 static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);
 48 
 49 /*
 50  * The statistics below are not protected from concurrent access for
 51  * performance reasons so they may not be a 100% accurate.  However,
 52  * they do provide useful information on roughly how many times a
 53  * certain event is occurring.
 54 */
 55 
 56 /* Pool limit was hit (see zswap_max_pool_percent) */
 57 static u64 zswap_pool_limit_hit;
 58 /* Pages written back when pool limit was reached */
 59 static u64 zswap_written_back_pages;
 60 /* Store failed due to a reclaim failure after pool limit was reached */
 61 static u64 zswap_reject_reclaim_fail;
 62 /* Compressed page was too big for the allocator to (optimally) store */
 63 static u64 zswap_reject_compress_poor;
 64 /* Store failed because underlying allocator could not get memory */
 65 static u64 zswap_reject_alloc_fail;
 66 /* Store failed because the entry metadata could not be allocated (rare) */
 67 static u64 zswap_reject_kmemcache_fail;
 68 /* Duplicate store was encountered (rare) */
 69 static u64 zswap_duplicate_entry;
 70 
 71 /* Shrinker work queue */
 72 static struct workqueue_struct *shrink_wq;
 73 /* Pool limit was hit, we need to calm down */
 74 static bool zswap_pool_reached_full;
 75 
 76 /*********************************
 77 * tunables
 78 **********************************/
 79 
 80 #define ZSWAP_PARAM_UNSET ""
 81 
 82 /* Enable/disable zswap */
 83 static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON);
 84 static int zswap_enabled_param_set(const char *,
 85                                    const struct kernel_param *);
 86 static const struct kernel_param_ops zswap_enabled_param_ops = {
 87         .set =          zswap_enabled_param_set,
 88         .get =          param_get_bool,
 89 };
 90 module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
 91 
 92 /* Crypto compressor to use */
 93 static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
 94 static int zswap_compressor_param_set(const char *,
 95                                       const struct kernel_param *);
 96 static const struct kernel_param_ops zswap_compressor_param_ops = {
 97         .set =          zswap_compressor_param_set,
 98         .get =          param_get_charp,
 99         .free =         param_free_charp,
100 };
101 module_param_cb(compressor, &zswap_compressor_param_ops,
102                 &zswap_compressor, 0644);
103 
104 /* Compressed storage zpool to use */
105 static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
106 static int zswap_zpool_param_set(const char *, const struct kernel_param *);
107 static const struct kernel_param_ops zswap_zpool_param_ops = {
108         .set =          zswap_zpool_param_set,
109         .get =          param_get_charp,
110         .free =         param_free_charp,
111 };
112 module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
113 
114 /* The maximum percentage of memory that the compressed pool can occupy */
115 static unsigned int zswap_max_pool_percent = 20;
116 module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
117 
118 /* The threshold for accepting new pages after the max_pool_percent was hit */
119 static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */
120 module_param_named(accept_threshold_percent, zswap_accept_thr_percent,
121                    uint, 0644);
122 
123 /* Enable/disable handling same-value filled pages (enabled by default) */
124 static bool zswap_same_filled_pages_enabled = true;
125 module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
126                    bool, 0644);
127 
128 /*********************************
129 * data structures
130 **********************************/
131 
132 struct crypto_acomp_ctx {
133         struct crypto_acomp *acomp;
134         struct acomp_req *req;
135         struct crypto_wait wait;
136         u8 *dstmem;
137         struct mutex *mutex;
138 };
139 
140 struct zswap_pool {
141         struct zpool *zpool;
142         struct crypto_acomp_ctx __percpu *acomp_ctx;
143         struct kref kref;
144         struct list_head list;
145         struct work_struct release_work;
146         struct work_struct shrink_work;
147         struct hlist_node node;
148         char tfm_name[CRYPTO_MAX_ALG_NAME];
149 };
150 
151 /*
152  * struct zswap_entry
153  *
154  * This structure contains the metadata for tracking a single compressed
155  * page within zswap.
156  *
157  * rbnode - links the entry into red-black tree for the appropriate swap type
158  * offset - the swap offset for the entry.  Index into the red-black tree.
159  * refcount - the number of outstanding reference to the entry. This is needed
160  *            to protect against premature freeing of the entry by code
161  *            concurrent calls to load, invalidate, and writeback.  The lock
162  *            for the zswap_tree structure that contains the entry must
163  *            be held while changing the refcount.  Since the lock must
164  *            be held, there is no reason to also make refcount atomic.
165  * length - the length in bytes of the compressed page data.  Needed during
166  *          decompression. For a same value filled page length is 0.
167  * pool - the zswap_pool the entry's data is in
168  * handle - zpool allocation handle that stores the compressed page data
169  * value - value of the same-value filled pages which have same content
170  */
171 struct zswap_entry {
172         struct rb_node rbnode;
173         pgoff_t offset;
174         int refcount;
175         unsigned int length;
176         struct zswap_pool *pool;
177         union {
178                 unsigned long handle;
179                 unsigned long value;
180         };
181 };
182 
183 struct zswap_header {
184         swp_entry_t swpentry;
185 };
186 
187 /*
188  * The tree lock in the zswap_tree struct protects a few things:
189  * - the rbtree
190  * - the refcount field of each entry in the tree
191  */
192 struct zswap_tree {
193         struct rb_root rbroot;
194         spinlock_t lock;
195 };
196 
197 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
198 
199 /* RCU-protected iteration */
200 static LIST_HEAD(zswap_pools);
201 /* protects zswap_pools list modification */
202 static DEFINE_SPINLOCK(zswap_pools_lock);
203 /* pool counter to provide unique names to zpool */
204 static atomic_t zswap_pools_count = ATOMIC_INIT(0);
205 
206 /* used by param callback function */
207 static bool zswap_init_started;
208 
209 /* fatal error during init */
210 static bool zswap_init_failed;
211 
212 /* init completed, but couldn't create the initial pool */
213 static bool zswap_has_pool;
214 
215 /*********************************
216 * helpers and fwd declarations
217 **********************************/
218 
219 #define zswap_pool_debug(msg, p)                                \
220         pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,         \
221                  zpool_get_type((p)->zpool))
222 
223 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
224 static int zswap_pool_get(struct zswap_pool *pool);
225 static void zswap_pool_put(struct zswap_pool *pool);
226 
227 static const struct zpool_ops zswap_zpool_ops = {
228         .evict = zswap_writeback_entry
229 };
230 
231 static bool zswap_is_full(void)
232 {
233         return totalram_pages() * zswap_max_pool_percent / 100 <
234                         DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
235 }
236 
237 static bool zswap_can_accept(void)
238 {
239         return totalram_pages() * zswap_accept_thr_percent / 100 *
240                                 zswap_max_pool_percent / 100 >
241                         DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
242 }
243 
244 static void zswap_update_total_size(void)
245 {
246         struct zswap_pool *pool;
247         u64 total = 0;
248 
249         rcu_read_lock();
250 
251         list_for_each_entry_rcu(pool, &zswap_pools, list)
252                 total += zpool_get_total_size(pool->zpool);
253 
254         rcu_read_unlock();
255 
256         zswap_pool_total_size = total;
257 }
258 
259 /*********************************
260 * zswap entry functions
261 **********************************/
262 static struct kmem_cache *zswap_entry_cache;
263 
264 static int __init zswap_entry_cache_create(void)
265 {
266         zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
267         return zswap_entry_cache == NULL;
268 }
269 
270 static void __init zswap_entry_cache_destroy(void)
271 {
272         kmem_cache_destroy(zswap_entry_cache);
273 }
274 
275 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
276 {
277         struct zswap_entry *entry;
278         entry = kmem_cache_alloc(zswap_entry_cache, gfp);
279         if (!entry)
280                 return NULL;
281         entry->refcount = 1;
282         RB_CLEAR_NODE(&entry->rbnode);
283         return entry;
284 }
285 
286 static void zswap_entry_cache_free(struct zswap_entry *entry)
287 {
288         kmem_cache_free(zswap_entry_cache, entry);
289 }
290 
291 /*********************************
292 * rbtree functions
293 **********************************/
294 static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
295 {
296         struct rb_node *node = root->rb_node;
297         struct zswap_entry *entry;
298 
299         while (node) {
300                 entry = rb_entry(node, struct zswap_entry, rbnode);
301                 if (entry->offset > offset)
302                         node = node->rb_left;
303                 else if (entry->offset < offset)
304                         node = node->rb_right;
305                 else
306                         return entry;
307         }
308         return NULL;
309 }
310 
311 /*
312  * In the case that a entry with the same offset is found, a pointer to
313  * the existing entry is stored in dupentry and the function returns -EEXIST
314  */
315 static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
316                         struct zswap_entry **dupentry)
317 {
318         struct rb_node **link = &root->rb_node, *parent = NULL;
319         struct zswap_entry *myentry;
320 
321         while (*link) {
322                 parent = *link;
323                 myentry = rb_entry(parent, struct zswap_entry, rbnode);
324                 if (myentry->offset > entry->offset)
325                         link = &(*link)->rb_left;
326                 else if (myentry->offset < entry->offset)
327                         link = &(*link)->rb_right;
328                 else {
329                         *dupentry = myentry;
330                         return -EEXIST;
331                 }
332         }
333         rb_link_node(&entry->rbnode, parent, link);
334         rb_insert_color(&entry->rbnode, root);
335         return 0;
336 }
337 
338 static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
339 {
340         if (!RB_EMPTY_NODE(&entry->rbnode)) {
341                 rb_erase(&entry->rbnode, root);
342                 RB_CLEAR_NODE(&entry->rbnode);
343         }
344 }
345 
346 /*
347  * Carries out the common pattern of freeing and entry's zpool allocation,
348  * freeing the entry itself, and decrementing the number of stored pages.
349  */
350 static void zswap_free_entry(struct zswap_entry *entry)
351 {
352         if (!entry->length)
353                 atomic_dec(&zswap_same_filled_pages);
354         else {
355                 zpool_free(entry->pool->zpool, entry->handle);
356                 zswap_pool_put(entry->pool);
357         }
358         zswap_entry_cache_free(entry);
359         atomic_dec(&zswap_stored_pages);
360         zswap_update_total_size();
361 }
362 
363 /* caller must hold the tree lock */
364 static void zswap_entry_get(struct zswap_entry *entry)
365 {
366         entry->refcount++;
367 }
368 
369 /* caller must hold the tree lock
370 * remove from the tree and free it, if nobody reference the entry
371 */
372 static void zswap_entry_put(struct zswap_tree *tree,
373                         struct zswap_entry *entry)
374 {
375         int refcount = --entry->refcount;
376 
377         BUG_ON(refcount < 0);
378         if (refcount == 0) {
379                 zswap_rb_erase(&tree->rbroot, entry);
380                 zswap_free_entry(entry);
381         }
382 }
383 
384 /* caller must hold the tree lock */
385 static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
386                                 pgoff_t offset)
387 {
388         struct zswap_entry *entry;
389 
390         entry = zswap_rb_search(root, offset);
391         if (entry)
392                 zswap_entry_get(entry);
393 
394         return entry;
395 }
396 
397 /*********************************
398 * per-cpu code
399 **********************************/
400 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
401 /*
402  * If users dynamically change the zpool type and compressor at runtime, i.e.
403  * zswap is running, zswap can have more than one zpool on one cpu, but they
404  * are sharing dtsmem. So we need this mutex to be per-cpu.
405  */
406 static DEFINE_PER_CPU(struct mutex *, zswap_mutex);
407 
408 static int zswap_dstmem_prepare(unsigned int cpu)
409 {
410         struct mutex *mutex;
411         u8 *dst;
412 
413         dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
414         if (!dst)
415                 return -ENOMEM;
416 
417         mutex = kmalloc_node(sizeof(*mutex), GFP_KERNEL, cpu_to_node(cpu));
418         if (!mutex) {
419                 kfree(dst);
420                 return -ENOMEM;
421         }
422 
423         mutex_init(mutex);
424         per_cpu(zswap_dstmem, cpu) = dst;
425         per_cpu(zswap_mutex, cpu) = mutex;
426         return 0;
427 }
428 
429 static int zswap_dstmem_dead(unsigned int cpu)
430 {
431         struct mutex *mutex;
432         u8 *dst;
433 
434         mutex = per_cpu(zswap_mutex, cpu);
435         kfree(mutex);
436         per_cpu(zswap_mutex, cpu) = NULL;
437 
438         dst = per_cpu(zswap_dstmem, cpu);
439         kfree(dst);
440         per_cpu(zswap_dstmem, cpu) = NULL;
441 
442         return 0;
443 }
444 
445 static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
446 {
447         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
448         struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
449         struct crypto_acomp *acomp;
450         struct acomp_req *req;
451 
452         acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu));
453         if (IS_ERR(acomp)) {
454                 pr_err("could not alloc crypto acomp %s : %ld\n",
455                                 pool->tfm_name, PTR_ERR(acomp));
456                 return PTR_ERR(acomp);
457         }
458         acomp_ctx->acomp = acomp;
459 
460         req = acomp_request_alloc(acomp_ctx->acomp);
461         if (!req) {
462                 pr_err("could not alloc crypto acomp_request %s\n",
463                        pool->tfm_name);
464                 crypto_free_acomp(acomp_ctx->acomp);
465                 return -ENOMEM;
466         }
467         acomp_ctx->req = req;
468 
469         crypto_init_wait(&acomp_ctx->wait);
470         /*
471          * if the backend of acomp is async zip, crypto_req_done() will wakeup
472          * crypto_wait_req(); if the backend of acomp is scomp, the callback
473          * won't be called, crypto_wait_req() will return without blocking.
474          */
475         acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
476                                    crypto_req_done, &acomp_ctx->wait);
477 
478         acomp_ctx->mutex = per_cpu(zswap_mutex, cpu);
479         acomp_ctx->dstmem = per_cpu(zswap_dstmem, cpu);
480 
481         return 0;
482 }
483 
484 static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
485 {
486         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
487         struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
488 
489         if (!IS_ERR_OR_NULL(acomp_ctx)) {
490                 if (!IS_ERR_OR_NULL(acomp_ctx->req))
491                         acomp_request_free(acomp_ctx->req);
492                 if (!IS_ERR_OR_NULL(acomp_ctx->acomp))
493                         crypto_free_acomp(acomp_ctx->acomp);
494         }
495 
496         return 0;
497 }
498 
499 /*********************************
500 * pool functions
501 **********************************/
502 
503 static struct zswap_pool *__zswap_pool_current(void)
504 {
505         struct zswap_pool *pool;
506 
507         pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
508         WARN_ONCE(!pool && zswap_has_pool,
509                   "%s: no page storage pool!\n", __func__);
510 
511         return pool;
512 }
513 
514 static struct zswap_pool *zswap_pool_current(void)
515 {
516         assert_spin_locked(&zswap_pools_lock);
517 
518         return __zswap_pool_current();
519 }
520 
521 static struct zswap_pool *zswap_pool_current_get(void)
522 {
523         struct zswap_pool *pool;
524 
525         rcu_read_lock();
526 
527         pool = __zswap_pool_current();
528         if (!zswap_pool_get(pool))
529                 pool = NULL;
530 
531         rcu_read_unlock();
532 
533         return pool;
534 }
535 
536 static struct zswap_pool *zswap_pool_last_get(void)
537 {
538         struct zswap_pool *pool, *last = NULL;
539 
540         rcu_read_lock();
541 
542         list_for_each_entry_rcu(pool, &zswap_pools, list)
543                 last = pool;
544         WARN_ONCE(!last && zswap_has_pool,
545                   "%s: no page storage pool!\n", __func__);
546         if (!zswap_pool_get(last))
547                 last = NULL;
548 
549         rcu_read_unlock();
550 
551         return last;
552 }
553 
554 /* type and compressor must be null-terminated */
555 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
556 {
557         struct zswap_pool *pool;
558 
559         assert_spin_locked(&zswap_pools_lock);
560 
561         list_for_each_entry_rcu(pool, &zswap_pools, list) {
562                 if (strcmp(pool->tfm_name, compressor))
563                         continue;
564                 if (strcmp(zpool_get_type(pool->zpool), type))
565                         continue;
566                 /* if we can't get it, it's about to be destroyed */
567                 if (!zswap_pool_get(pool))
568                         continue;
569                 return pool;
570         }
571 
572         return NULL;
573 }
574 
575 static void shrink_worker(struct work_struct *w)
576 {
577         struct zswap_pool *pool = container_of(w, typeof(*pool),
578                                                 shrink_work);
579 
580         if (zpool_shrink(pool->zpool, 1, NULL))
581                 zswap_reject_reclaim_fail++;
582         zswap_pool_put(pool);
583 }
584 
585 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
586 {
587         struct zswap_pool *pool;
588         char name[38]; /* 'zswap' + 32 char (max) num + \0 */
589         gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
590         int ret;
591 
592         if (!zswap_has_pool) {
593                 /* if either are unset, pool initialization failed, and we
594                  * need both params to be set correctly before trying to
595                  * create a pool.
596                  */
597                 if (!strcmp(type, ZSWAP_PARAM_UNSET))
598                         return NULL;
599                 if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
600                         return NULL;
601         }
602 
603         pool = kzalloc(sizeof(*pool), GFP_KERNEL);
604         if (!pool)
605                 return NULL;
606 
607         /* unique name for each pool specifically required by zsmalloc */
608         snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
609 
610         pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
611         if (!pool->zpool) {
612                 pr_err("%s zpool not available\n", type);
613                 goto error;
614         }
615         pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
616 
617         strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
618 
619         pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx);
620         if (!pool->acomp_ctx) {
621                 pr_err("percpu alloc failed\n");
622                 goto error;
623         }
624 
625         ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
626                                        &pool->node);
627         if (ret)
628                 goto error;
629         pr_debug("using %s compressor\n", pool->tfm_name);
630 
631         /* being the current pool takes 1 ref; this func expects the
632          * caller to always add the new pool as the current pool
633          */
634         kref_init(&pool->kref);
635         INIT_LIST_HEAD(&pool->list);
636         INIT_WORK(&pool->shrink_work, shrink_worker);
637 
638         zswap_pool_debug("created", pool);
639 
640         return pool;
641 
642 error:
643         if (pool->acomp_ctx)
644                 free_percpu(pool->acomp_ctx);
645         if (pool->zpool)
646                 zpool_destroy_pool(pool->zpool);
647         kfree(pool);
648         return NULL;
649 }
650 
651 static __init struct zswap_pool *__zswap_pool_create_fallback(void)
652 {
653         bool has_comp, has_zpool;
654 
655         has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
656         if (!has_comp && strcmp(zswap_compressor,
657                                 CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
658                 pr_err("compressor %s not available, using default %s\n",
659                        zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
660                 param_free_charp(&zswap_compressor);
661                 zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
662                 has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
663         }
664         if (!has_comp) {
665                 pr_err("default compressor %s not available\n",
666                        zswap_compressor);
667                 param_free_charp(&zswap_compressor);
668                 zswap_compressor = ZSWAP_PARAM_UNSET;
669         }
670 
671         has_zpool = zpool_has_pool(zswap_zpool_type);
672         if (!has_zpool && strcmp(zswap_zpool_type,
673                                  CONFIG_ZSWAP_ZPOOL_DEFAULT)) {
674                 pr_err("zpool %s not available, using default %s\n",
675                        zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);
676                 param_free_charp(&zswap_zpool_type);
677                 zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
678                 has_zpool = zpool_has_pool(zswap_zpool_type);
679         }
680         if (!has_zpool) {
681                 pr_err("default zpool %s not available\n",
682                        zswap_zpool_type);
683                 param_free_charp(&zswap_zpool_type);
684                 zswap_zpool_type = ZSWAP_PARAM_UNSET;
685         }
686 
687         if (!has_comp || !has_zpool)
688                 return NULL;
689 
690         return zswap_pool_create(zswap_zpool_type, zswap_compressor);
691 }
692 
693 static void zswap_pool_destroy(struct zswap_pool *pool)
694 {
695         zswap_pool_debug("destroying", pool);
696 
697         cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
698         free_percpu(pool->acomp_ctx);
699         zpool_destroy_pool(pool->zpool);
700         kfree(pool);
701 }
702 
703 static int __must_check zswap_pool_get(struct zswap_pool *pool)
704 {
705         if (!pool)
706                 return 0;
707 
708         return kref_get_unless_zero(&pool->kref);
709 }
710 
711 static void __zswap_pool_release(struct work_struct *work)
712 {
713         struct zswap_pool *pool = container_of(work, typeof(*pool),
714                                                 release_work);
715 
716         synchronize_rcu();
717 
718         /* nobody should have been able to get a kref... */
719         WARN_ON(kref_get_unless_zero(&pool->kref));
720 
721         /* pool is now off zswap_pools list and has no references. */
722         zswap_pool_destroy(pool);
723 }
724 
725 static void __zswap_pool_empty(struct kref *kref)
726 {
727         struct zswap_pool *pool;
728 
729         pool = container_of(kref, typeof(*pool), kref);
730 
731         spin_lock(&zswap_pools_lock);
732 
733         WARN_ON(pool == zswap_pool_current());
734 
735         list_del_rcu(&pool->list);
736 
737         INIT_WORK(&pool->release_work, __zswap_pool_release);
738         schedule_work(&pool->release_work);
739 
740         spin_unlock(&zswap_pools_lock);
741 }
742 
743 static void zswap_pool_put(struct zswap_pool *pool)
744 {
745         kref_put(&pool->kref, __zswap_pool_empty);
746 }
747 
748 /*********************************
749 * param callbacks
750 **********************************/
751 
752 /* val must be a null-terminated string */
753 static int __zswap_param_set(const char *val, const struct kernel_param *kp,
754                              char *type, char *compressor)
755 {
756         struct zswap_pool *pool, *put_pool = NULL;
757         char *s = strstrip((char *)val);
758         int ret;
759 
760         if (zswap_init_failed) {
761                 pr_err("can't set param, initialization failed\n");
762                 return -ENODEV;
763         }
764 
765         /* no change required */
766         if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
767                 return 0;
768 
769         /* if this is load-time (pre-init) param setting,
770          * don't create a pool; that's done during init.
771          */
772         if (!zswap_init_started)
773                 return param_set_charp(s, kp);
774 
775         if (!type) {
776                 if (!zpool_has_pool(s)) {
777                         pr_err("zpool %s not available\n", s);
778                         return -ENOENT;
779                 }
780                 type = s;
781         } else if (!compressor) {
782                 if (!crypto_has_acomp(s, 0, 0)) {
783                         pr_err("compressor %s not available\n", s);
784                         return -ENOENT;
785                 }
786                 compressor = s;
787         } else {
788                 WARN_ON(1);
789                 return -EINVAL;
790         }
791 
792         spin_lock(&zswap_pools_lock);
793 
794         pool = zswap_pool_find_get(type, compressor);
795         if (pool) {
796                 zswap_pool_debug("using existing", pool);
797                 WARN_ON(pool == zswap_pool_current());
798                 list_del_rcu(&pool->list);
799         }
800 
801         spin_unlock(&zswap_pools_lock);
802 
803         if (!pool)
804                 pool = zswap_pool_create(type, compressor);
805 
806         if (pool)
807                 ret = param_set_charp(s, kp);
808         else
809                 ret = -EINVAL;
810 
811         spin_lock(&zswap_pools_lock);
812 
813         if (!ret) {
814                 put_pool = zswap_pool_current();
815                 list_add_rcu(&pool->list, &zswap_pools);
816                 zswap_has_pool = true;
817         } else if (pool) {
818                 /* add the possibly pre-existing pool to the end of the pools
819                  * list; if it's new (and empty) then it'll be removed and
820                  * destroyed by the put after we drop the lock
821                  */
822                 list_add_tail_rcu(&pool->list, &zswap_pools);
823                 put_pool = pool;
824         }
825 
826         spin_unlock(&zswap_pools_lock);
827 
828         if (!zswap_has_pool && !pool) {
829                 /* if initial pool creation failed, and this pool creation also
830                  * failed, maybe both compressor and zpool params were bad.
831                  * Allow changing this param, so pool creation will succeed
832                  * when the other param is changed. We already verified this
833                  * param is ok in the zpool_has_pool() or crypto_has_acomp()
834                  * checks above.
835                  */
836                 ret = param_set_charp(s, kp);
837         }
838 
839         /* drop the ref from either the old current pool,
840          * or the new pool we failed to add
841          */
842         if (put_pool)
843                 zswap_pool_put(put_pool);
844 
845         return ret;
846 }
847 
848 static int zswap_compressor_param_set(const char *val,
849                                       const struct kernel_param *kp)
850 {
851         return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
852 }
853 
854 static int zswap_zpool_param_set(const char *val,
855                                  const struct kernel_param *kp)
856 {
857         return __zswap_param_set(val, kp, NULL, zswap_compressor);
858 }
859 
860 static int zswap_enabled_param_set(const char *val,
861                                    const struct kernel_param *kp)
862 {
863         if (zswap_init_failed) {
864                 pr_err("can't enable, initialization failed\n");
865                 return -ENODEV;
866         }
867         if (!zswap_has_pool && zswap_init_started) {
868                 pr_err("can't enable, no pool configured\n");
869                 return -ENODEV;
870         }
871 
872         return param_set_bool(val, kp);
873 }
874 
875 /*********************************
876 * writeback code
877 **********************************/
878 /* return enum for zswap_get_swap_cache_page */
879 enum zswap_get_swap_ret {
880         ZSWAP_SWAPCACHE_NEW,
881         ZSWAP_SWAPCACHE_EXIST,
882         ZSWAP_SWAPCACHE_FAIL,
883 };
884 
885 /*
886  * zswap_get_swap_cache_page
887  *
888  * This is an adaption of read_swap_cache_async()
889  *
890  * This function tries to find a page with the given swap entry
891  * in the swapper_space address space (the swap cache).  If the page
892  * is found, it is returned in retpage.  Otherwise, a page is allocated,
893  * added to the swap cache, and returned in retpage.
894  *
895  * If success, the swap cache page is returned in retpage
896  * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
897  * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
898  *     the new page is added to swapcache and locked
899  * Returns ZSWAP_SWAPCACHE_FAIL on error
900  */
901 static int zswap_get_swap_cache_page(swp_entry_t entry,
902                                 struct page **retpage)
903 {
904         bool page_was_allocated;
905 
906         *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
907                         NULL, 0, &page_was_allocated);
908         if (page_was_allocated)
909                 return ZSWAP_SWAPCACHE_NEW;
910         if (!*retpage)
911                 return ZSWAP_SWAPCACHE_FAIL;
912         return ZSWAP_SWAPCACHE_EXIST;
913 }
914 
915 /*
916  * Attempts to free an entry by adding a page to the swap cache,
917  * decompressing the entry data into the page, and issuing a
918  * bio write to write the page back to the swap device.
919  *
920  * This can be thought of as a "resumed writeback" of the page
921  * to the swap device.  We are basically resuming the same swap
922  * writeback path that was intercepted with the frontswap_store()
923  * in the first place.  After the page has been decompressed into
924  * the swap cache, the compressed version stored by zswap can be
925  * freed.
926  */
927 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
928 {
929         struct zswap_header *zhdr;
930         swp_entry_t swpentry;
931         struct zswap_tree *tree;
932         pgoff_t offset;
933         struct zswap_entry *entry;
934         struct page *page;
935         struct scatterlist input, output;
936         struct crypto_acomp_ctx *acomp_ctx;
937 
938         u8 *src;
939         unsigned int dlen;
940         int ret;
941         struct writeback_control wbc = {
942                 .sync_mode = WB_SYNC_NONE,
943         };
944 
945         /* extract swpentry from data */
946         zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
947         swpentry = zhdr->swpentry; /* here */
948         tree = zswap_trees[swp_type(swpentry)];
949         offset = swp_offset(swpentry);
950 
951         /* find and ref zswap entry */
952         spin_lock(&tree->lock);
953         entry = zswap_entry_find_get(&tree->rbroot, offset);
954         if (!entry) {
955                 /* entry was invalidated */
956                 spin_unlock(&tree->lock);
957                 zpool_unmap_handle(pool, handle);
958                 return 0;
959         }
960         spin_unlock(&tree->lock);
961         BUG_ON(offset != entry->offset);
962 
963         /* try to allocate swap cache page */
964         switch (zswap_get_swap_cache_page(swpentry, &page)) {
965         case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
966                 ret = -ENOMEM;
967                 goto fail;
968 
969         case ZSWAP_SWAPCACHE_EXIST:
970                 /* page is already in the swap cache, ignore for now */
971                 put_page(page);
972                 ret = -EEXIST;
973                 goto fail;
974 
975         case ZSWAP_SWAPCACHE_NEW: /* page is locked */
976                 /* decompress */
977                 acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
978 
979                 dlen = PAGE_SIZE;
980                 src = (u8 *)zhdr + sizeof(struct zswap_header);
981 
982                 mutex_lock(acomp_ctx->mutex);
983                 sg_init_one(&input, src, entry->length);
984                 sg_init_table(&output, 1);
985                 sg_set_page(&output, page, PAGE_SIZE, 0);
986                 acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
987                 ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
988                 dlen = acomp_ctx->req->dlen;
989                 mutex_unlock(acomp_ctx->mutex);
990 
991                 BUG_ON(ret);
992                 BUG_ON(dlen != PAGE_SIZE);
993 
994                 /* page is up to date */
995                 SetPageUptodate(page);
996         }
997 
998         /* move it to the tail of the inactive list after end_writeback */
999         SetPageReclaim(page);
1000 
1001         /* start writeback */
1002         __swap_writepage(page, &wbc, end_swap_bio_write);
1003         put_page(page);
1004         zswap_written_back_pages++;
1005 
1006         spin_lock(&tree->lock);
1007         /* drop local reference */
1008         zswap_entry_put(tree, entry);
1009 
1010         /*
1011         * There are two possible situations for entry here:
1012         * (1) refcount is 1(normal case),  entry is valid and on the tree
1013         * (2) refcount is 0, entry is freed and not on the tree
1014         *     because invalidate happened during writeback
1015         *  search the tree and free the entry if find entry
1016         */
1017         if (entry == zswap_rb_search(&tree->rbroot, offset))
1018                 zswap_entry_put(tree, entry);
1019         spin_unlock(&tree->lock);
1020 
1021         goto end;
1022 
1023         /*
1024         * if we get here due to ZSWAP_SWAPCACHE_EXIST
1025         * a load may happening concurrently
1026         * it is safe and okay to not free the entry
1027         * if we free the entry in the following put
1028         * it it either okay to return !0
1029         */
1030 fail:
1031         spin_lock(&tree->lock);
1032         zswap_entry_put(tree, entry);
1033         spin_unlock(&tree->lock);
1034 
1035 end:
1036         zpool_unmap_handle(pool, handle);
1037         return ret;
1038 }
1039 
1040 static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
1041 {
1042         unsigned int pos;
1043         unsigned long *page;
1044 
1045         page = (unsigned long *)ptr;
1046         for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
1047                 if (page[pos] != page[0])
1048                         return 0;
1049         }
1050         *value = page[0];
1051         return 1;
1052 }
1053 
1054 static void zswap_fill_page(void *ptr, unsigned long value)
1055 {
1056         unsigned long *page;
1057 
1058         page = (unsigned long *)ptr;
1059         memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
1060 }
1061 
1062 /*********************************
1063 * frontswap hooks
1064 **********************************/
1065 /* attempts to compress and store an single page */
1066 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
1067                                 struct page *page)
1068 {
1069         struct zswap_tree *tree = zswap_trees[type];
1070         struct zswap_entry *entry, *dupentry;
1071         struct scatterlist input, output;
1072         struct crypto_acomp_ctx *acomp_ctx;
1073         int ret;
1074         unsigned int hlen, dlen = PAGE_SIZE;
1075         unsigned long handle, value;
1076         char *buf;
1077         u8 *src, *dst;
1078         struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
1079         gfp_t gfp;
1080 
1081         /* THP isn't supported */
1082         if (PageTransHuge(page)) {
1083                 ret = -EINVAL;
1084                 goto reject;
1085         }
1086 
1087         if (!zswap_enabled || !tree) {
1088                 ret = -ENODEV;
1089                 goto reject;
1090         }
1091 
1092         /* reclaim space if needed */
1093         if (zswap_is_full()) {
1094                 struct zswap_pool *pool;
1095 
1096                 zswap_pool_limit_hit++;
1097                 zswap_pool_reached_full = true;
1098                 pool = zswap_pool_last_get();
1099                 if (pool)
1100                         queue_work(shrink_wq, &pool->shrink_work);
1101                 ret = -ENOMEM;
1102                 goto reject;
1103         }
1104 
1105         if (zswap_pool_reached_full) {
1106                if (!zswap_can_accept()) {
1107                         ret = -ENOMEM;
1108                         goto reject;
1109                 } else
1110                         zswap_pool_reached_full = false;
1111         }
1112 
1113         /* allocate entry */
1114         entry = zswap_entry_cache_alloc(GFP_KERNEL);
1115         if (!entry) {
1116                 zswap_reject_kmemcache_fail++;
1117                 ret = -ENOMEM;
1118                 goto reject;
1119         }
1120 
1121         if (zswap_same_filled_pages_enabled) {
1122                 src = kmap_atomic(page);
1123                 if (zswap_is_page_same_filled(src, &value)) {
1124                         kunmap_atomic(src);
1125                         entry->offset = offset;
1126                         entry->length = 0;
1127                         entry->value = value;
1128                         atomic_inc(&zswap_same_filled_pages);
1129                         goto insert_entry;
1130                 }
1131                 kunmap_atomic(src);
1132         }
1133 
1134         /* if entry is successfully added, it keeps the reference */
1135         entry->pool = zswap_pool_current_get();
1136         if (!entry->pool) {
1137                 ret = -EINVAL;
1138                 goto freepage;
1139         }
1140 
1141         /* compress */
1142         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1143 
1144         mutex_lock(acomp_ctx->mutex);
1145 
1146         dst = acomp_ctx->dstmem;
1147         sg_init_table(&input, 1);
1148         sg_set_page(&input, page, PAGE_SIZE, 0);
1149 
1150         /* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */
1151         sg_init_one(&output, dst, PAGE_SIZE * 2);
1152         acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);
1153         /*
1154          * it maybe looks a little bit silly that we send an asynchronous request,
1155          * then wait for its completion synchronously. This makes the process look
1156          * synchronous in fact.
1157          * Theoretically, acomp supports users send multiple acomp requests in one
1158          * acomp instance, then get those requests done simultaneously. but in this
1159          * case, frontswap actually does store and load page by page, there is no
1160          * existing method to send the second page before the first page is done
1161          * in one thread doing frontswap.
1162          * but in different threads running on different cpu, we have different
1163          * acomp instance, so multiple threads can do (de)compression in parallel.
1164          */
1165         ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
1166         dlen = acomp_ctx->req->dlen;
1167 
1168         if (ret) {
1169                 ret = -EINVAL;
1170                 goto put_dstmem;
1171         }
1172 
1173         /* store */
1174         hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
1175         gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
1176         if (zpool_malloc_support_movable(entry->pool->zpool))
1177                 gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
1178         ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle);
1179         if (ret == -ENOSPC) {
1180                 zswap_reject_compress_poor++;
1181                 goto put_dstmem;
1182         }
1183         if (ret) {
1184                 zswap_reject_alloc_fail++;
1185                 goto put_dstmem;
1186         }
1187         buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
1188         memcpy(buf, &zhdr, hlen);
1189         memcpy(buf + hlen, dst, dlen);
1190         zpool_unmap_handle(entry->pool->zpool, handle);
1191         mutex_unlock(acomp_ctx->mutex);
1192 
1193         /* populate entry */
1194         entry->offset = offset;
1195         entry->handle = handle;
1196         entry->length = dlen;
1197 
1198 insert_entry:
1199         /* map */
1200         spin_lock(&tree->lock);
1201         do {
1202                 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1203                 if (ret == -EEXIST) {
1204                         zswap_duplicate_entry++;
1205                         /* remove from rbtree */
1206                         zswap_rb_erase(&tree->rbroot, dupentry);
1207                         zswap_entry_put(tree, dupentry);
1208                 }
1209         } while (ret == -EEXIST);
1210         spin_unlock(&tree->lock);
1211 
1212         /* update stats */
1213         atomic_inc(&zswap_stored_pages);
1214         zswap_update_total_size();
1215 
1216         return 0;
1217 
1218 put_dstmem:
1219         mutex_unlock(acomp_ctx->mutex);
1220         zswap_pool_put(entry->pool);
1221 freepage:
1222         zswap_entry_cache_free(entry);
1223 reject:
1224         return ret;
1225 }
1226 
1227 /*
1228  * returns 0 if the page was successfully decompressed
1229  * return -1 on entry not found or error
1230 */
1231 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1232                                 struct page *page)
1233 {
1234         struct zswap_tree *tree = zswap_trees[type];
1235         struct zswap_entry *entry;
1236         struct scatterlist input, output;
1237         struct crypto_acomp_ctx *acomp_ctx;
1238         u8 *src, *dst;
1239         unsigned int dlen;
1240         int ret;
1241 
1242         /* find */
1243         spin_lock(&tree->lock);
1244         entry = zswap_entry_find_get(&tree->rbroot, offset);
1245         if (!entry) {
1246                 /* entry was written back */
1247                 spin_unlock(&tree->lock);
1248                 return -1;
1249         }
1250         spin_unlock(&tree->lock);
1251 
1252         if (!entry->length) {
1253                 dst = kmap_atomic(page);
1254                 zswap_fill_page(dst, entry->value);
1255                 kunmap_atomic(dst);
1256                 goto freeentry;
1257         }
1258 
1259         /* decompress */
1260         dlen = PAGE_SIZE;
1261         src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
1262         if (zpool_evictable(entry->pool->zpool))
1263                 src += sizeof(struct zswap_header);
1264 
1265         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1266         mutex_lock(acomp_ctx->mutex);
1267         sg_init_one(&input, src, entry->length);
1268         sg_init_table(&output, 1);
1269         sg_set_page(&output, page, PAGE_SIZE, 0);
1270         acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1271         ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1272         mutex_unlock(acomp_ctx->mutex);
1273 
1274         zpool_unmap_handle(entry->pool->zpool, entry->handle);
1275         BUG_ON(ret);
1276 
1277 freeentry:
1278         spin_lock(&tree->lock);
1279         zswap_entry_put(tree, entry);
1280         spin_unlock(&tree->lock);
1281 
1282         return 0;
1283 }
1284 
1285 /* frees an entry in zswap */
1286 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1287 {
1288         struct zswap_tree *tree = zswap_trees[type];
1289         struct zswap_entry *entry;
1290 
1291         /* find */
1292         spin_lock(&tree->lock);
1293         entry = zswap_rb_search(&tree->rbroot, offset);
1294         if (!entry) {
1295                 /* entry was written back */
1296                 spin_unlock(&tree->lock);
1297                 return;
1298         }
1299 
1300         /* remove from rbtree */
1301         zswap_rb_erase(&tree->rbroot, entry);
1302 
1303         /* drop the initial reference from entry creation */
1304         zswap_entry_put(tree, entry);
1305 
1306         spin_unlock(&tree->lock);
1307 }
1308 
1309 /* frees all zswap entries for the given swap type */
1310 static void zswap_frontswap_invalidate_area(unsigned type)
1311 {
1312         struct zswap_tree *tree = zswap_trees[type];
1313         struct zswap_entry *entry, *n;
1314 
1315         if (!tree)
1316                 return;
1317 
1318         /* walk the tree and free everything */
1319         spin_lock(&tree->lock);
1320         rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1321                 zswap_free_entry(entry);
1322         tree->rbroot = RB_ROOT;
1323         spin_unlock(&tree->lock);
1324         kfree(tree);
1325         zswap_trees[type] = NULL;
1326 }
1327 
1328 static void zswap_frontswap_init(unsigned type)
1329 {
1330         struct zswap_tree *tree;
1331 
1332         tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1333         if (!tree) {
1334                 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1335                 return;
1336         }
1337 
1338         tree->rbroot = RB_ROOT;
1339         spin_lock_init(&tree->lock);
1340         zswap_trees[type] = tree;
1341 }
1342 
1343 static struct frontswap_ops zswap_frontswap_ops = {
1344         .store = zswap_frontswap_store,
1345         .load = zswap_frontswap_load,
1346         .invalidate_page = zswap_frontswap_invalidate_page,
1347         .invalidate_area = zswap_frontswap_invalidate_area,
1348         .init = zswap_frontswap_init
1349 };
1350 
1351 /*********************************
1352 * debugfs functions
1353 **********************************/
1354 #ifdef CONFIG_DEBUG_FS
1355 #include <linux/debugfs.h>
1356 
1357 static struct dentry *zswap_debugfs_root;
1358 
1359 static int __init zswap_debugfs_init(void)
1360 {
1361         if (!debugfs_initialized())
1362                 return -ENODEV;
1363 
1364         zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1365 
1366         debugfs_create_u64("pool_limit_hit", 0444,
1367                            zswap_debugfs_root, &zswap_pool_limit_hit);
1368         debugfs_create_u64("reject_reclaim_fail", 0444,
1369                            zswap_debugfs_root, &zswap_reject_reclaim_fail);
1370         debugfs_create_u64("reject_alloc_fail", 0444,
1371                            zswap_debugfs_root, &zswap_reject_alloc_fail);
1372         debugfs_create_u64("reject_kmemcache_fail", 0444,
1373                            zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1374         debugfs_create_u64("reject_compress_poor", 0444,
1375                            zswap_debugfs_root, &zswap_reject_compress_poor);
1376         debugfs_create_u64("written_back_pages", 0444,
1377                            zswap_debugfs_root, &zswap_written_back_pages);
1378         debugfs_create_u64("duplicate_entry", 0444,
1379                            zswap_debugfs_root, &zswap_duplicate_entry);
1380         debugfs_create_u64("pool_total_size", 0444,
1381                            zswap_debugfs_root, &zswap_pool_total_size);
1382         debugfs_create_atomic_t("stored_pages", 0444,
1383                                 zswap_debugfs_root, &zswap_stored_pages);
1384         debugfs_create_atomic_t("same_filled_pages", 0444,
1385                                 zswap_debugfs_root, &zswap_same_filled_pages);
1386 
1387         return 0;
1388 }
1389 
1390 static void __exit zswap_debugfs_exit(void)
1391 {
1392         debugfs_remove_recursive(zswap_debugfs_root);
1393 }
1394 #else
1395 static int __init zswap_debugfs_init(void)
1396 {
1397         return 0;
1398 }
1399 
1400 static void __exit zswap_debugfs_exit(void) { }
1401 #endif
1402 
1403 /*********************************
1404 * module init and exit
1405 **********************************/
1406 static int __init init_zswap(void)
1407 {
1408         struct zswap_pool *pool;
1409         int ret;
1410 
1411         zswap_init_started = true;
1412 
1413         if (zswap_entry_cache_create()) {
1414                 pr_err("entry cache creation failed\n");
1415                 goto cache_fail;
1416         }
1417 
1418         ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1419                                 zswap_dstmem_prepare, zswap_dstmem_dead);
1420         if (ret) {
1421                 pr_err("dstmem alloc failed\n");
1422                 goto dstmem_fail;
1423         }
1424 
1425         ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1426                                       "mm/zswap_pool:prepare",
1427                                       zswap_cpu_comp_prepare,
1428                                       zswap_cpu_comp_dead);
1429         if (ret)
1430                 goto hp_fail;
1431 
1432         pool = __zswap_pool_create_fallback();
1433         if (pool) {
1434                 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1435                         zpool_get_type(pool->zpool));
1436                 list_add(&pool->list, &zswap_pools);
1437                 zswap_has_pool = true;
1438         } else {
1439                 pr_err("pool creation failed\n");
1440                 zswap_enabled = false;
1441         }
1442 
1443         shrink_wq = create_workqueue("zswap-shrink");
1444         if (!shrink_wq)
1445                 goto fallback_fail;
1446 
1447         frontswap_register_ops(&zswap_frontswap_ops);
1448         if (zswap_debugfs_init())
1449                 pr_warn("debugfs initialization failed\n");
1450         return 0;
1451 
1452 fallback_fail:
1453         if (pool)
1454                 zswap_pool_destroy(pool);
1455 hp_fail:
1456         cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1457 dstmem_fail:
1458         zswap_entry_cache_destroy();
1459 cache_fail:
1460         /* if built-in, we aren't unloaded on failure; don't allow use */
1461         zswap_init_failed = true;
1462         zswap_enabled = false;
1463         return -ENOMEM;
1464 }
1465 /* must be late so crypto has time to come up */
1466 late_initcall(init_zswap);
1467 
1468 MODULE_LICENSE("GPL");
1469 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1470 MODULE_DESCRIPTION("Compressed cache for swap pages");
1471 

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