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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 #include "swap.h"
 40 
 41 /*********************************
 42 * statistics
 43 **********************************/
 44 /* Total bytes used by the compressed storage */
 45 u64 zswap_pool_total_size;
 46 /* The number of compressed pages currently stored in zswap */
 47 atomic_t zswap_stored_pages = ATOMIC_INIT(0);
 48 /* The number of same-value filled pages currently stored in zswap */
 49 static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);
 50 
 51 /*
 52  * The statistics below are not protected from concurrent access for
 53  * performance reasons so they may not be a 100% accurate.  However,
 54  * they do provide useful information on roughly how many times a
 55  * certain event is occurring.
 56 */
 57 
 58 /* Pool limit was hit (see zswap_max_pool_percent) */
 59 static u64 zswap_pool_limit_hit;
 60 /* Pages written back when pool limit was reached */
 61 static u64 zswap_written_back_pages;
 62 /* Store failed due to a reclaim failure after pool limit was reached */
 63 static u64 zswap_reject_reclaim_fail;
 64 /* Compressed page was too big for the allocator to (optimally) store */
 65 static u64 zswap_reject_compress_poor;
 66 /* Store failed because underlying allocator could not get memory */
 67 static u64 zswap_reject_alloc_fail;
 68 /* Store failed because the entry metadata could not be allocated (rare) */
 69 static u64 zswap_reject_kmemcache_fail;
 70 /* Duplicate store was encountered (rare) */
 71 static u64 zswap_duplicate_entry;
 72 
 73 /* Shrinker work queue */
 74 static struct workqueue_struct *shrink_wq;
 75 /* Pool limit was hit, we need to calm down */
 76 static bool zswap_pool_reached_full;
 77 
 78 /*********************************
 79 * tunables
 80 **********************************/
 81 
 82 #define ZSWAP_PARAM_UNSET ""
 83 
 84 /* Enable/disable zswap */
 85 static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON);
 86 static int zswap_enabled_param_set(const char *,
 87                                    const struct kernel_param *);
 88 static const struct kernel_param_ops zswap_enabled_param_ops = {
 89         .set =          zswap_enabled_param_set,
 90         .get =          param_get_bool,
 91 };
 92 module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
 93 
 94 /* Crypto compressor to use */
 95 static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
 96 static int zswap_compressor_param_set(const char *,
 97                                       const struct kernel_param *);
 98 static const 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 static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
108 static int zswap_zpool_param_set(const char *, const struct kernel_param *);
109 static const struct kernel_param_ops zswap_zpool_param_ops = {
110         .set =          zswap_zpool_param_set,
111         .get =          param_get_charp,
112         .free =         param_free_charp,
113 };
114 module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
115 
116 /* The maximum percentage of memory that the compressed pool can occupy */
117 static unsigned int zswap_max_pool_percent = 20;
118 module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
119 
120 /* The threshold for accepting new pages after the max_pool_percent was hit */
121 static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */
122 module_param_named(accept_threshold_percent, zswap_accept_thr_percent,
123                    uint, 0644);
124 
125 /*
126  * Enable/disable handling same-value filled pages (enabled by default).
127  * If disabled every page is considered non-same-value filled.
128  */
129 static bool zswap_same_filled_pages_enabled = true;
130 module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
131                    bool, 0644);
132 
133 /* Enable/disable handling non-same-value filled pages (enabled by default) */
134 static bool zswap_non_same_filled_pages_enabled = true;
135 module_param_named(non_same_filled_pages_enabled, zswap_non_same_filled_pages_enabled,
136                    bool, 0644);
137 
138 /*********************************
139 * data structures
140 **********************************/
141 
142 struct crypto_acomp_ctx {
143         struct crypto_acomp *acomp;
144         struct acomp_req *req;
145         struct crypto_wait wait;
146         u8 *dstmem;
147         struct mutex *mutex;
148 };
149 
150 struct zswap_pool {
151         struct zpool *zpool;
152         struct crypto_acomp_ctx __percpu *acomp_ctx;
153         struct kref kref;
154         struct list_head list;
155         struct work_struct release_work;
156         struct work_struct shrink_work;
157         struct hlist_node node;
158         char tfm_name[CRYPTO_MAX_ALG_NAME];
159 };
160 
161 /*
162  * struct zswap_entry
163  *
164  * This structure contains the metadata for tracking a single compressed
165  * page within zswap.
166  *
167  * rbnode - links the entry into red-black tree for the appropriate swap type
168  * offset - the swap offset for the entry.  Index into the red-black tree.
169  * refcount - the number of outstanding reference to the entry. This is needed
170  *            to protect against premature freeing of the entry by code
171  *            concurrent calls to load, invalidate, and writeback.  The lock
172  *            for the zswap_tree structure that contains the entry must
173  *            be held while changing the refcount.  Since the lock must
174  *            be held, there is no reason to also make refcount atomic.
175  * length - the length in bytes of the compressed page data.  Needed during
176  *          decompression. For a same value filled page length is 0.
177  * pool - the zswap_pool the entry's data is in
178  * handle - zpool allocation handle that stores the compressed page data
179  * value - value of the same-value filled pages which have same content
180  */
181 struct zswap_entry {
182         struct rb_node rbnode;
183         pgoff_t offset;
184         int refcount;
185         unsigned int length;
186         struct zswap_pool *pool;
187         union {
188                 unsigned long handle;
189                 unsigned long value;
190         };
191         struct obj_cgroup *objcg;
192 };
193 
194 struct zswap_header {
195         swp_entry_t swpentry;
196 };
197 
198 /*
199  * The tree lock in the zswap_tree struct protects a few things:
200  * - the rbtree
201  * - the refcount field of each entry in the tree
202  */
203 struct zswap_tree {
204         struct rb_root rbroot;
205         spinlock_t lock;
206 };
207 
208 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
209 
210 /* RCU-protected iteration */
211 static LIST_HEAD(zswap_pools);
212 /* protects zswap_pools list modification */
213 static DEFINE_SPINLOCK(zswap_pools_lock);
214 /* pool counter to provide unique names to zpool */
215 static atomic_t zswap_pools_count = ATOMIC_INIT(0);
216 
217 /* used by param callback function */
218 static bool zswap_init_started;
219 
220 /* fatal error during init */
221 static bool zswap_init_failed;
222 
223 /* init completed, but couldn't create the initial pool */
224 static bool zswap_has_pool;
225 
226 /*********************************
227 * helpers and fwd declarations
228 **********************************/
229 
230 #define zswap_pool_debug(msg, p)                                \
231         pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,         \
232                  zpool_get_type((p)->zpool))
233 
234 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
235 static int zswap_pool_get(struct zswap_pool *pool);
236 static void zswap_pool_put(struct zswap_pool *pool);
237 
238 static const struct zpool_ops zswap_zpool_ops = {
239         .evict = zswap_writeback_entry
240 };
241 
242 static bool zswap_is_full(void)
243 {
244         return totalram_pages() * zswap_max_pool_percent / 100 <
245                         DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
246 }
247 
248 static bool zswap_can_accept(void)
249 {
250         return totalram_pages() * zswap_accept_thr_percent / 100 *
251                                 zswap_max_pool_percent / 100 >
252                         DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
253 }
254 
255 static void zswap_update_total_size(void)
256 {
257         struct zswap_pool *pool;
258         u64 total = 0;
259 
260         rcu_read_lock();
261 
262         list_for_each_entry_rcu(pool, &zswap_pools, list)
263                 total += zpool_get_total_size(pool->zpool);
264 
265         rcu_read_unlock();
266 
267         zswap_pool_total_size = total;
268 }
269 
270 /*********************************
271 * zswap entry functions
272 **********************************/
273 static struct kmem_cache *zswap_entry_cache;
274 
275 static int __init zswap_entry_cache_create(void)
276 {
277         zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
278         return zswap_entry_cache == NULL;
279 }
280 
281 static void __init zswap_entry_cache_destroy(void)
282 {
283         kmem_cache_destroy(zswap_entry_cache);
284 }
285 
286 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
287 {
288         struct zswap_entry *entry;
289         entry = kmem_cache_alloc(zswap_entry_cache, gfp);
290         if (!entry)
291                 return NULL;
292         entry->refcount = 1;
293         RB_CLEAR_NODE(&entry->rbnode);
294         return entry;
295 }
296 
297 static void zswap_entry_cache_free(struct zswap_entry *entry)
298 {
299         kmem_cache_free(zswap_entry_cache, entry);
300 }
301 
302 /*********************************
303 * rbtree functions
304 **********************************/
305 static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
306 {
307         struct rb_node *node = root->rb_node;
308         struct zswap_entry *entry;
309 
310         while (node) {
311                 entry = rb_entry(node, struct zswap_entry, rbnode);
312                 if (entry->offset > offset)
313                         node = node->rb_left;
314                 else if (entry->offset < offset)
315                         node = node->rb_right;
316                 else
317                         return entry;
318         }
319         return NULL;
320 }
321 
322 /*
323  * In the case that a entry with the same offset is found, a pointer to
324  * the existing entry is stored in dupentry and the function returns -EEXIST
325  */
326 static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
327                         struct zswap_entry **dupentry)
328 {
329         struct rb_node **link = &root->rb_node, *parent = NULL;
330         struct zswap_entry *myentry;
331 
332         while (*link) {
333                 parent = *link;
334                 myentry = rb_entry(parent, struct zswap_entry, rbnode);
335                 if (myentry->offset > entry->offset)
336                         link = &(*link)->rb_left;
337                 else if (myentry->offset < entry->offset)
338                         link = &(*link)->rb_right;
339                 else {
340                         *dupentry = myentry;
341                         return -EEXIST;
342                 }
343         }
344         rb_link_node(&entry->rbnode, parent, link);
345         rb_insert_color(&entry->rbnode, root);
346         return 0;
347 }
348 
349 static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
350 {
351         if (!RB_EMPTY_NODE(&entry->rbnode)) {
352                 rb_erase(&entry->rbnode, root);
353                 RB_CLEAR_NODE(&entry->rbnode);
354         }
355 }
356 
357 /*
358  * Carries out the common pattern of freeing and entry's zpool allocation,
359  * freeing the entry itself, and decrementing the number of stored pages.
360  */
361 static void zswap_free_entry(struct zswap_entry *entry)
362 {
363         if (entry->objcg) {
364                 obj_cgroup_uncharge_zswap(entry->objcg, entry->length);
365                 obj_cgroup_put(entry->objcg);
366         }
367         if (!entry->length)
368                 atomic_dec(&zswap_same_filled_pages);
369         else {
370                 zpool_free(entry->pool->zpool, entry->handle);
371                 zswap_pool_put(entry->pool);
372         }
373         zswap_entry_cache_free(entry);
374         atomic_dec(&zswap_stored_pages);
375         zswap_update_total_size();
376 }
377 
378 /* caller must hold the tree lock */
379 static void zswap_entry_get(struct zswap_entry *entry)
380 {
381         entry->refcount++;
382 }
383 
384 /* caller must hold the tree lock
385 * remove from the tree and free it, if nobody reference the entry
386 */
387 static void zswap_entry_put(struct zswap_tree *tree,
388                         struct zswap_entry *entry)
389 {
390         int refcount = --entry->refcount;
391 
392         BUG_ON(refcount < 0);
393         if (refcount == 0) {
394                 zswap_rb_erase(&tree->rbroot, entry);
395                 zswap_free_entry(entry);
396         }
397 }
398 
399 /* caller must hold the tree lock */
400 static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
401                                 pgoff_t offset)
402 {
403         struct zswap_entry *entry;
404 
405         entry = zswap_rb_search(root, offset);
406         if (entry)
407                 zswap_entry_get(entry);
408 
409         return entry;
410 }
411 
412 /*********************************
413 * per-cpu code
414 **********************************/
415 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
416 /*
417  * If users dynamically change the zpool type and compressor at runtime, i.e.
418  * zswap is running, zswap can have more than one zpool on one cpu, but they
419  * are sharing dtsmem. So we need this mutex to be per-cpu.
420  */
421 static DEFINE_PER_CPU(struct mutex *, zswap_mutex);
422 
423 static int zswap_dstmem_prepare(unsigned int cpu)
424 {
425         struct mutex *mutex;
426         u8 *dst;
427 
428         dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
429         if (!dst)
430                 return -ENOMEM;
431 
432         mutex = kmalloc_node(sizeof(*mutex), GFP_KERNEL, cpu_to_node(cpu));
433         if (!mutex) {
434                 kfree(dst);
435                 return -ENOMEM;
436         }
437 
438         mutex_init(mutex);
439         per_cpu(zswap_dstmem, cpu) = dst;
440         per_cpu(zswap_mutex, cpu) = mutex;
441         return 0;
442 }
443 
444 static int zswap_dstmem_dead(unsigned int cpu)
445 {
446         struct mutex *mutex;
447         u8 *dst;
448 
449         mutex = per_cpu(zswap_mutex, cpu);
450         kfree(mutex);
451         per_cpu(zswap_mutex, cpu) = NULL;
452 
453         dst = per_cpu(zswap_dstmem, cpu);
454         kfree(dst);
455         per_cpu(zswap_dstmem, cpu) = NULL;
456 
457         return 0;
458 }
459 
460 static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
461 {
462         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
463         struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
464         struct crypto_acomp *acomp;
465         struct acomp_req *req;
466 
467         acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu));
468         if (IS_ERR(acomp)) {
469                 pr_err("could not alloc crypto acomp %s : %ld\n",
470                                 pool->tfm_name, PTR_ERR(acomp));
471                 return PTR_ERR(acomp);
472         }
473         acomp_ctx->acomp = acomp;
474 
475         req = acomp_request_alloc(acomp_ctx->acomp);
476         if (!req) {
477                 pr_err("could not alloc crypto acomp_request %s\n",
478                        pool->tfm_name);
479                 crypto_free_acomp(acomp_ctx->acomp);
480                 return -ENOMEM;
481         }
482         acomp_ctx->req = req;
483 
484         crypto_init_wait(&acomp_ctx->wait);
485         /*
486          * if the backend of acomp is async zip, crypto_req_done() will wakeup
487          * crypto_wait_req(); if the backend of acomp is scomp, the callback
488          * won't be called, crypto_wait_req() will return without blocking.
489          */
490         acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
491                                    crypto_req_done, &acomp_ctx->wait);
492 
493         acomp_ctx->mutex = per_cpu(zswap_mutex, cpu);
494         acomp_ctx->dstmem = per_cpu(zswap_dstmem, cpu);
495 
496         return 0;
497 }
498 
499 static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
500 {
501         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
502         struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
503 
504         if (!IS_ERR_OR_NULL(acomp_ctx)) {
505                 if (!IS_ERR_OR_NULL(acomp_ctx->req))
506                         acomp_request_free(acomp_ctx->req);
507                 if (!IS_ERR_OR_NULL(acomp_ctx->acomp))
508                         crypto_free_acomp(acomp_ctx->acomp);
509         }
510 
511         return 0;
512 }
513 
514 /*********************************
515 * pool functions
516 **********************************/
517 
518 static struct zswap_pool *__zswap_pool_current(void)
519 {
520         struct zswap_pool *pool;
521 
522         pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
523         WARN_ONCE(!pool && zswap_has_pool,
524                   "%s: no page storage pool!\n", __func__);
525 
526         return pool;
527 }
528 
529 static struct zswap_pool *zswap_pool_current(void)
530 {
531         assert_spin_locked(&zswap_pools_lock);
532 
533         return __zswap_pool_current();
534 }
535 
536 static struct zswap_pool *zswap_pool_current_get(void)
537 {
538         struct zswap_pool *pool;
539 
540         rcu_read_lock();
541 
542         pool = __zswap_pool_current();
543         if (!zswap_pool_get(pool))
544                 pool = NULL;
545 
546         rcu_read_unlock();
547 
548         return pool;
549 }
550 
551 static struct zswap_pool *zswap_pool_last_get(void)
552 {
553         struct zswap_pool *pool, *last = NULL;
554 
555         rcu_read_lock();
556 
557         list_for_each_entry_rcu(pool, &zswap_pools, list)
558                 last = pool;
559         WARN_ONCE(!last && zswap_has_pool,
560                   "%s: no page storage pool!\n", __func__);
561         if (!zswap_pool_get(last))
562                 last = NULL;
563 
564         rcu_read_unlock();
565 
566         return last;
567 }
568 
569 /* type and compressor must be null-terminated */
570 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
571 {
572         struct zswap_pool *pool;
573 
574         assert_spin_locked(&zswap_pools_lock);
575 
576         list_for_each_entry_rcu(pool, &zswap_pools, list) {
577                 if (strcmp(pool->tfm_name, compressor))
578                         continue;
579                 if (strcmp(zpool_get_type(pool->zpool), type))
580                         continue;
581                 /* if we can't get it, it's about to be destroyed */
582                 if (!zswap_pool_get(pool))
583                         continue;
584                 return pool;
585         }
586 
587         return NULL;
588 }
589 
590 static void shrink_worker(struct work_struct *w)
591 {
592         struct zswap_pool *pool = container_of(w, typeof(*pool),
593                                                 shrink_work);
594 
595         if (zpool_shrink(pool->zpool, 1, NULL))
596                 zswap_reject_reclaim_fail++;
597         zswap_pool_put(pool);
598 }
599 
600 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
601 {
602         struct zswap_pool *pool;
603         char name[38]; /* 'zswap' + 32 char (max) num + \0 */
604         gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
605         int ret;
606 
607         if (!zswap_has_pool) {
608                 /* if either are unset, pool initialization failed, and we
609                  * need both params to be set correctly before trying to
610                  * create a pool.
611                  */
612                 if (!strcmp(type, ZSWAP_PARAM_UNSET))
613                         return NULL;
614                 if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
615                         return NULL;
616         }
617 
618         pool = kzalloc(sizeof(*pool), GFP_KERNEL);
619         if (!pool)
620                 return NULL;
621 
622         /* unique name for each pool specifically required by zsmalloc */
623         snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
624 
625         pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
626         if (!pool->zpool) {
627                 pr_err("%s zpool not available\n", type);
628                 goto error;
629         }
630         pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
631 
632         strscpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
633 
634         pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx);
635         if (!pool->acomp_ctx) {
636                 pr_err("percpu alloc failed\n");
637                 goto error;
638         }
639 
640         ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
641                                        &pool->node);
642         if (ret)
643                 goto error;
644         pr_debug("using %s compressor\n", pool->tfm_name);
645 
646         /* being the current pool takes 1 ref; this func expects the
647          * caller to always add the new pool as the current pool
648          */
649         kref_init(&pool->kref);
650         INIT_LIST_HEAD(&pool->list);
651         INIT_WORK(&pool->shrink_work, shrink_worker);
652 
653         zswap_pool_debug("created", pool);
654 
655         return pool;
656 
657 error:
658         if (pool->acomp_ctx)
659                 free_percpu(pool->acomp_ctx);
660         if (pool->zpool)
661                 zpool_destroy_pool(pool->zpool);
662         kfree(pool);
663         return NULL;
664 }
665 
666 static __init struct zswap_pool *__zswap_pool_create_fallback(void)
667 {
668         bool has_comp, has_zpool;
669 
670         has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
671         if (!has_comp && strcmp(zswap_compressor,
672                                 CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
673                 pr_err("compressor %s not available, using default %s\n",
674                        zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
675                 param_free_charp(&zswap_compressor);
676                 zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
677                 has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
678         }
679         if (!has_comp) {
680                 pr_err("default compressor %s not available\n",
681                        zswap_compressor);
682                 param_free_charp(&zswap_compressor);
683                 zswap_compressor = ZSWAP_PARAM_UNSET;
684         }
685 
686         has_zpool = zpool_has_pool(zswap_zpool_type);
687         if (!has_zpool && strcmp(zswap_zpool_type,
688                                  CONFIG_ZSWAP_ZPOOL_DEFAULT)) {
689                 pr_err("zpool %s not available, using default %s\n",
690                        zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);
691                 param_free_charp(&zswap_zpool_type);
692                 zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
693                 has_zpool = zpool_has_pool(zswap_zpool_type);
694         }
695         if (!has_zpool) {
696                 pr_err("default zpool %s not available\n",
697                        zswap_zpool_type);
698                 param_free_charp(&zswap_zpool_type);
699                 zswap_zpool_type = ZSWAP_PARAM_UNSET;
700         }
701 
702         if (!has_comp || !has_zpool)
703                 return NULL;
704 
705         return zswap_pool_create(zswap_zpool_type, zswap_compressor);
706 }
707 
708 static void zswap_pool_destroy(struct zswap_pool *pool)
709 {
710         zswap_pool_debug("destroying", pool);
711 
712         cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
713         free_percpu(pool->acomp_ctx);
714         zpool_destroy_pool(pool->zpool);
715         kfree(pool);
716 }
717 
718 static int __must_check zswap_pool_get(struct zswap_pool *pool)
719 {
720         if (!pool)
721                 return 0;
722 
723         return kref_get_unless_zero(&pool->kref);
724 }
725 
726 static void __zswap_pool_release(struct work_struct *work)
727 {
728         struct zswap_pool *pool = container_of(work, typeof(*pool),
729                                                 release_work);
730 
731         synchronize_rcu();
732 
733         /* nobody should have been able to get a kref... */
734         WARN_ON(kref_get_unless_zero(&pool->kref));
735 
736         /* pool is now off zswap_pools list and has no references. */
737         zswap_pool_destroy(pool);
738 }
739 
740 static void __zswap_pool_empty(struct kref *kref)
741 {
742         struct zswap_pool *pool;
743 
744         pool = container_of(kref, typeof(*pool), kref);
745 
746         spin_lock(&zswap_pools_lock);
747 
748         WARN_ON(pool == zswap_pool_current());
749 
750         list_del_rcu(&pool->list);
751 
752         INIT_WORK(&pool->release_work, __zswap_pool_release);
753         schedule_work(&pool->release_work);
754 
755         spin_unlock(&zswap_pools_lock);
756 }
757 
758 static void zswap_pool_put(struct zswap_pool *pool)
759 {
760         kref_put(&pool->kref, __zswap_pool_empty);
761 }
762 
763 /*********************************
764 * param callbacks
765 **********************************/
766 
767 /* val must be a null-terminated string */
768 static int __zswap_param_set(const char *val, const struct kernel_param *kp,
769                              char *type, char *compressor)
770 {
771         struct zswap_pool *pool, *put_pool = NULL;
772         char *s = strstrip((char *)val);
773         int ret;
774 
775         if (zswap_init_failed) {
776                 pr_err("can't set param, initialization failed\n");
777                 return -ENODEV;
778         }
779 
780         /* no change required */
781         if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
782                 return 0;
783 
784         /* if this is load-time (pre-init) param setting,
785          * don't create a pool; that's done during init.
786          */
787         if (!zswap_init_started)
788                 return param_set_charp(s, kp);
789 
790         if (!type) {
791                 if (!zpool_has_pool(s)) {
792                         pr_err("zpool %s not available\n", s);
793                         return -ENOENT;
794                 }
795                 type = s;
796         } else if (!compressor) {
797                 if (!crypto_has_acomp(s, 0, 0)) {
798                         pr_err("compressor %s not available\n", s);
799                         return -ENOENT;
800                 }
801                 compressor = s;
802         } else {
803                 WARN_ON(1);
804                 return -EINVAL;
805         }
806 
807         spin_lock(&zswap_pools_lock);
808 
809         pool = zswap_pool_find_get(type, compressor);
810         if (pool) {
811                 zswap_pool_debug("using existing", pool);
812                 WARN_ON(pool == zswap_pool_current());
813                 list_del_rcu(&pool->list);
814         }
815 
816         spin_unlock(&zswap_pools_lock);
817 
818         if (!pool)
819                 pool = zswap_pool_create(type, compressor);
820 
821         if (pool)
822                 ret = param_set_charp(s, kp);
823         else
824                 ret = -EINVAL;
825 
826         spin_lock(&zswap_pools_lock);
827 
828         if (!ret) {
829                 put_pool = zswap_pool_current();
830                 list_add_rcu(&pool->list, &zswap_pools);
831                 zswap_has_pool = true;
832         } else if (pool) {
833                 /* add the possibly pre-existing pool to the end of the pools
834                  * list; if it's new (and empty) then it'll be removed and
835                  * destroyed by the put after we drop the lock
836                  */
837                 list_add_tail_rcu(&pool->list, &zswap_pools);
838                 put_pool = pool;
839         }
840 
841         spin_unlock(&zswap_pools_lock);
842 
843         if (!zswap_has_pool && !pool) {
844                 /* if initial pool creation failed, and this pool creation also
845                  * failed, maybe both compressor and zpool params were bad.
846                  * Allow changing this param, so pool creation will succeed
847                  * when the other param is changed. We already verified this
848                  * param is ok in the zpool_has_pool() or crypto_has_acomp()
849                  * checks above.
850                  */
851                 ret = param_set_charp(s, kp);
852         }
853 
854         /* drop the ref from either the old current pool,
855          * or the new pool we failed to add
856          */
857         if (put_pool)
858                 zswap_pool_put(put_pool);
859 
860         return ret;
861 }
862 
863 static int zswap_compressor_param_set(const char *val,
864                                       const struct kernel_param *kp)
865 {
866         return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
867 }
868 
869 static int zswap_zpool_param_set(const char *val,
870                                  const struct kernel_param *kp)
871 {
872         return __zswap_param_set(val, kp, NULL, zswap_compressor);
873 }
874 
875 static int zswap_enabled_param_set(const char *val,
876                                    const struct kernel_param *kp)
877 {
878         if (zswap_init_failed) {
879                 pr_err("can't enable, initialization failed\n");
880                 return -ENODEV;
881         }
882         if (!zswap_has_pool && zswap_init_started) {
883                 pr_err("can't enable, no pool configured\n");
884                 return -ENODEV;
885         }
886 
887         return param_set_bool(val, kp);
888 }
889 
890 /*********************************
891 * writeback code
892 **********************************/
893 /* return enum for zswap_get_swap_cache_page */
894 enum zswap_get_swap_ret {
895         ZSWAP_SWAPCACHE_NEW,
896         ZSWAP_SWAPCACHE_EXIST,
897         ZSWAP_SWAPCACHE_FAIL,
898 };
899 
900 /*
901  * zswap_get_swap_cache_page
902  *
903  * This is an adaption of read_swap_cache_async()
904  *
905  * This function tries to find a page with the given swap entry
906  * in the swapper_space address space (the swap cache).  If the page
907  * is found, it is returned in retpage.  Otherwise, a page is allocated,
908  * added to the swap cache, and returned in retpage.
909  *
910  * If success, the swap cache page is returned in retpage
911  * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
912  * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
913  *     the new page is added to swapcache and locked
914  * Returns ZSWAP_SWAPCACHE_FAIL on error
915  */
916 static int zswap_get_swap_cache_page(swp_entry_t entry,
917                                 struct page **retpage)
918 {
919         bool page_was_allocated;
920 
921         *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
922                         NULL, 0, &page_was_allocated);
923         if (page_was_allocated)
924                 return ZSWAP_SWAPCACHE_NEW;
925         if (!*retpage)
926                 return ZSWAP_SWAPCACHE_FAIL;
927         return ZSWAP_SWAPCACHE_EXIST;
928 }
929 
930 /*
931  * Attempts to free an entry by adding a page to the swap cache,
932  * decompressing the entry data into the page, and issuing a
933  * bio write to write the page back to the swap device.
934  *
935  * This can be thought of as a "resumed writeback" of the page
936  * to the swap device.  We are basically resuming the same swap
937  * writeback path that was intercepted with the frontswap_store()
938  * in the first place.  After the page has been decompressed into
939  * the swap cache, the compressed version stored by zswap can be
940  * freed.
941  */
942 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
943 {
944         struct zswap_header *zhdr;
945         swp_entry_t swpentry;
946         struct zswap_tree *tree;
947         pgoff_t offset;
948         struct zswap_entry *entry;
949         struct page *page;
950         struct scatterlist input, output;
951         struct crypto_acomp_ctx *acomp_ctx;
952 
953         u8 *src, *tmp = NULL;
954         unsigned int dlen;
955         int ret;
956         struct writeback_control wbc = {
957                 .sync_mode = WB_SYNC_NONE,
958         };
959 
960         if (!zpool_can_sleep_mapped(pool)) {
961                 tmp = kmalloc(PAGE_SIZE, GFP_ATOMIC);
962                 if (!tmp)
963                         return -ENOMEM;
964         }
965 
966         /* extract swpentry from data */
967         zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
968         swpentry = zhdr->swpentry; /* here */
969         tree = zswap_trees[swp_type(swpentry)];
970         offset = swp_offset(swpentry);
971 
972         /* find and ref zswap entry */
973         spin_lock(&tree->lock);
974         entry = zswap_entry_find_get(&tree->rbroot, offset);
975         if (!entry) {
976                 /* entry was invalidated */
977                 spin_unlock(&tree->lock);
978                 zpool_unmap_handle(pool, handle);
979                 kfree(tmp);
980                 return 0;
981         }
982         spin_unlock(&tree->lock);
983         BUG_ON(offset != entry->offset);
984 
985         src = (u8 *)zhdr + sizeof(struct zswap_header);
986         if (!zpool_can_sleep_mapped(pool)) {
987                 memcpy(tmp, src, entry->length);
988                 src = tmp;
989                 zpool_unmap_handle(pool, handle);
990         }
991 
992         /* try to allocate swap cache page */
993         switch (zswap_get_swap_cache_page(swpentry, &page)) {
994         case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
995                 ret = -ENOMEM;
996                 goto fail;
997 
998         case ZSWAP_SWAPCACHE_EXIST:
999                 /* page is already in the swap cache, ignore for now */
1000                 put_page(page);
1001                 ret = -EEXIST;
1002                 goto fail;
1003 
1004         case ZSWAP_SWAPCACHE_NEW: /* page is locked */
1005                 /* decompress */
1006                 acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1007                 dlen = PAGE_SIZE;
1008 
1009                 mutex_lock(acomp_ctx->mutex);
1010                 sg_init_one(&input, src, entry->length);
1011                 sg_init_table(&output, 1);
1012                 sg_set_page(&output, page, PAGE_SIZE, 0);
1013                 acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1014                 ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1015                 dlen = acomp_ctx->req->dlen;
1016                 mutex_unlock(acomp_ctx->mutex);
1017 
1018                 BUG_ON(ret);
1019                 BUG_ON(dlen != PAGE_SIZE);
1020 
1021                 /* page is up to date */
1022                 SetPageUptodate(page);
1023         }
1024 
1025         /* move it to the tail of the inactive list after end_writeback */
1026         SetPageReclaim(page);
1027 
1028         /* start writeback */
1029         __swap_writepage(page, &wbc, end_swap_bio_write);
1030         put_page(page);
1031         zswap_written_back_pages++;
1032 
1033         spin_lock(&tree->lock);
1034         /* drop local reference */
1035         zswap_entry_put(tree, entry);
1036 
1037         /*
1038         * There are two possible situations for entry here:
1039         * (1) refcount is 1(normal case),  entry is valid and on the tree
1040         * (2) refcount is 0, entry is freed and not on the tree
1041         *     because invalidate happened during writeback
1042         *  search the tree and free the entry if find entry
1043         */
1044         if (entry == zswap_rb_search(&tree->rbroot, offset))
1045                 zswap_entry_put(tree, entry);
1046         spin_unlock(&tree->lock);
1047 
1048         goto end;
1049 
1050         /*
1051         * if we get here due to ZSWAP_SWAPCACHE_EXIST
1052         * a load may be happening concurrently.
1053         * it is safe and okay to not free the entry.
1054         * if we free the entry in the following put
1055         * it is also okay to return !0
1056         */
1057 fail:
1058         spin_lock(&tree->lock);
1059         zswap_entry_put(tree, entry);
1060         spin_unlock(&tree->lock);
1061 
1062 end:
1063         if (zpool_can_sleep_mapped(pool))
1064                 zpool_unmap_handle(pool, handle);
1065         else
1066                 kfree(tmp);
1067 
1068         return ret;
1069 }
1070 
1071 static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
1072 {
1073         unsigned int pos;
1074         unsigned long *page;
1075 
1076         page = (unsigned long *)ptr;
1077         for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
1078                 if (page[pos] != page[0])
1079                         return 0;
1080         }
1081         *value = page[0];
1082         return 1;
1083 }
1084 
1085 static void zswap_fill_page(void *ptr, unsigned long value)
1086 {
1087         unsigned long *page;
1088 
1089         page = (unsigned long *)ptr;
1090         memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
1091 }
1092 
1093 /*********************************
1094 * frontswap hooks
1095 **********************************/
1096 /* attempts to compress and store an single page */
1097 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
1098                                 struct page *page)
1099 {
1100         struct zswap_tree *tree = zswap_trees[type];
1101         struct zswap_entry *entry, *dupentry;
1102         struct scatterlist input, output;
1103         struct crypto_acomp_ctx *acomp_ctx;
1104         struct obj_cgroup *objcg = NULL;
1105         struct zswap_pool *pool;
1106         int ret;
1107         unsigned int hlen, dlen = PAGE_SIZE;
1108         unsigned long handle, value;
1109         char *buf;
1110         u8 *src, *dst;
1111         struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
1112         gfp_t gfp;
1113 
1114         /* THP isn't supported */
1115         if (PageTransHuge(page)) {
1116                 ret = -EINVAL;
1117                 goto reject;
1118         }
1119 
1120         if (!zswap_enabled || !tree) {
1121                 ret = -ENODEV;
1122                 goto reject;
1123         }
1124 
1125         objcg = get_obj_cgroup_from_page(page);
1126         if (objcg && !obj_cgroup_may_zswap(objcg))
1127                 goto shrink;
1128 
1129         /* reclaim space if needed */
1130         if (zswap_is_full()) {
1131                 zswap_pool_limit_hit++;
1132                 zswap_pool_reached_full = true;
1133                 goto shrink;
1134         }
1135 
1136         if (zswap_pool_reached_full) {
1137                if (!zswap_can_accept()) {
1138                         ret = -ENOMEM;
1139                         goto reject;
1140                 } else
1141                         zswap_pool_reached_full = false;
1142         }
1143 
1144         /* allocate entry */
1145         entry = zswap_entry_cache_alloc(GFP_KERNEL);
1146         if (!entry) {
1147                 zswap_reject_kmemcache_fail++;
1148                 ret = -ENOMEM;
1149                 goto reject;
1150         }
1151 
1152         if (zswap_same_filled_pages_enabled) {
1153                 src = kmap_atomic(page);
1154                 if (zswap_is_page_same_filled(src, &value)) {
1155                         kunmap_atomic(src);
1156                         entry->offset = offset;
1157                         entry->length = 0;
1158                         entry->value = value;
1159                         atomic_inc(&zswap_same_filled_pages);
1160                         goto insert_entry;
1161                 }
1162                 kunmap_atomic(src);
1163         }
1164 
1165         if (!zswap_non_same_filled_pages_enabled) {
1166                 ret = -EINVAL;
1167                 goto freepage;
1168         }
1169 
1170         /* if entry is successfully added, it keeps the reference */
1171         entry->pool = zswap_pool_current_get();
1172         if (!entry->pool) {
1173                 ret = -EINVAL;
1174                 goto freepage;
1175         }
1176 
1177         /* compress */
1178         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1179 
1180         mutex_lock(acomp_ctx->mutex);
1181 
1182         dst = acomp_ctx->dstmem;
1183         sg_init_table(&input, 1);
1184         sg_set_page(&input, page, PAGE_SIZE, 0);
1185 
1186         /* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */
1187         sg_init_one(&output, dst, PAGE_SIZE * 2);
1188         acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);
1189         /*
1190          * it maybe looks a little bit silly that we send an asynchronous request,
1191          * then wait for its completion synchronously. This makes the process look
1192          * synchronous in fact.
1193          * Theoretically, acomp supports users send multiple acomp requests in one
1194          * acomp instance, then get those requests done simultaneously. but in this
1195          * case, frontswap actually does store and load page by page, there is no
1196          * existing method to send the second page before the first page is done
1197          * in one thread doing frontswap.
1198          * but in different threads running on different cpu, we have different
1199          * acomp instance, so multiple threads can do (de)compression in parallel.
1200          */
1201         ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
1202         dlen = acomp_ctx->req->dlen;
1203 
1204         if (ret) {
1205                 ret = -EINVAL;
1206                 goto put_dstmem;
1207         }
1208 
1209         /* store */
1210         hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
1211         gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
1212         if (zpool_malloc_support_movable(entry->pool->zpool))
1213                 gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
1214         ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle);
1215         if (ret == -ENOSPC) {
1216                 zswap_reject_compress_poor++;
1217                 goto put_dstmem;
1218         }
1219         if (ret) {
1220                 zswap_reject_alloc_fail++;
1221                 goto put_dstmem;
1222         }
1223         buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_WO);
1224         memcpy(buf, &zhdr, hlen);
1225         memcpy(buf + hlen, dst, dlen);
1226         zpool_unmap_handle(entry->pool->zpool, handle);
1227         mutex_unlock(acomp_ctx->mutex);
1228 
1229         /* populate entry */
1230         entry->offset = offset;
1231         entry->handle = handle;
1232         entry->length = dlen;
1233 
1234 insert_entry:
1235         entry->objcg = objcg;
1236         if (objcg) {
1237                 obj_cgroup_charge_zswap(objcg, entry->length);
1238                 /* Account before objcg ref is moved to tree */
1239                 count_objcg_event(objcg, ZSWPOUT);
1240         }
1241 
1242         /* map */
1243         spin_lock(&tree->lock);
1244         do {
1245                 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1246                 if (ret == -EEXIST) {
1247                         zswap_duplicate_entry++;
1248                         /* remove from rbtree */
1249                         zswap_rb_erase(&tree->rbroot, dupentry);
1250                         zswap_entry_put(tree, dupentry);
1251                 }
1252         } while (ret == -EEXIST);
1253         spin_unlock(&tree->lock);
1254 
1255         /* update stats */
1256         atomic_inc(&zswap_stored_pages);
1257         zswap_update_total_size();
1258         count_vm_event(ZSWPOUT);
1259 
1260         return 0;
1261 
1262 put_dstmem:
1263         mutex_unlock(acomp_ctx->mutex);
1264         zswap_pool_put(entry->pool);
1265 freepage:
1266         zswap_entry_cache_free(entry);
1267 reject:
1268         if (objcg)
1269                 obj_cgroup_put(objcg);
1270         return ret;
1271 
1272 shrink:
1273         pool = zswap_pool_last_get();
1274         if (pool)
1275                 queue_work(shrink_wq, &pool->shrink_work);
1276         ret = -ENOMEM;
1277         goto reject;
1278 }
1279 
1280 /*
1281  * returns 0 if the page was successfully decompressed
1282  * return -1 on entry not found or error
1283 */
1284 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1285                                 struct page *page)
1286 {
1287         struct zswap_tree *tree = zswap_trees[type];
1288         struct zswap_entry *entry;
1289         struct scatterlist input, output;
1290         struct crypto_acomp_ctx *acomp_ctx;
1291         u8 *src, *dst, *tmp;
1292         unsigned int dlen;
1293         int ret;
1294 
1295         /* find */
1296         spin_lock(&tree->lock);
1297         entry = zswap_entry_find_get(&tree->rbroot, offset);
1298         if (!entry) {
1299                 /* entry was written back */
1300                 spin_unlock(&tree->lock);
1301                 return -1;
1302         }
1303         spin_unlock(&tree->lock);
1304 
1305         if (!entry->length) {
1306                 dst = kmap_atomic(page);
1307                 zswap_fill_page(dst, entry->value);
1308                 kunmap_atomic(dst);
1309                 ret = 0;
1310                 goto stats;
1311         }
1312 
1313         if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
1314                 tmp = kmalloc(entry->length, GFP_ATOMIC);
1315                 if (!tmp) {
1316                         ret = -ENOMEM;
1317                         goto freeentry;
1318                 }
1319         }
1320 
1321         /* decompress */
1322         dlen = PAGE_SIZE;
1323         src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
1324         if (zpool_evictable(entry->pool->zpool))
1325                 src += sizeof(struct zswap_header);
1326 
1327         if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
1328                 memcpy(tmp, src, entry->length);
1329                 src = tmp;
1330                 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1331         }
1332 
1333         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1334         mutex_lock(acomp_ctx->mutex);
1335         sg_init_one(&input, src, entry->length);
1336         sg_init_table(&output, 1);
1337         sg_set_page(&output, page, PAGE_SIZE, 0);
1338         acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1339         ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1340         mutex_unlock(acomp_ctx->mutex);
1341 
1342         if (zpool_can_sleep_mapped(entry->pool->zpool))
1343                 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1344         else
1345                 kfree(tmp);
1346 
1347         BUG_ON(ret);
1348 stats:
1349         count_vm_event(ZSWPIN);
1350         if (entry->objcg)
1351                 count_objcg_event(entry->objcg, ZSWPIN);
1352 freeentry:
1353         spin_lock(&tree->lock);
1354         zswap_entry_put(tree, entry);
1355         spin_unlock(&tree->lock);
1356 
1357         return ret;
1358 }
1359 
1360 /* frees an entry in zswap */
1361 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1362 {
1363         struct zswap_tree *tree = zswap_trees[type];
1364         struct zswap_entry *entry;
1365 
1366         /* find */
1367         spin_lock(&tree->lock);
1368         entry = zswap_rb_search(&tree->rbroot, offset);
1369         if (!entry) {
1370                 /* entry was written back */
1371                 spin_unlock(&tree->lock);
1372                 return;
1373         }
1374 
1375         /* remove from rbtree */
1376         zswap_rb_erase(&tree->rbroot, entry);
1377 
1378         /* drop the initial reference from entry creation */
1379         zswap_entry_put(tree, entry);
1380 
1381         spin_unlock(&tree->lock);
1382 }
1383 
1384 /* frees all zswap entries for the given swap type */
1385 static void zswap_frontswap_invalidate_area(unsigned type)
1386 {
1387         struct zswap_tree *tree = zswap_trees[type];
1388         struct zswap_entry *entry, *n;
1389 
1390         if (!tree)
1391                 return;
1392 
1393         /* walk the tree and free everything */
1394         spin_lock(&tree->lock);
1395         rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1396                 zswap_free_entry(entry);
1397         tree->rbroot = RB_ROOT;
1398         spin_unlock(&tree->lock);
1399         kfree(tree);
1400         zswap_trees[type] = NULL;
1401 }
1402 
1403 static void zswap_frontswap_init(unsigned type)
1404 {
1405         struct zswap_tree *tree;
1406 
1407         tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1408         if (!tree) {
1409                 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1410                 return;
1411         }
1412 
1413         tree->rbroot = RB_ROOT;
1414         spin_lock_init(&tree->lock);
1415         zswap_trees[type] = tree;
1416 }
1417 
1418 static const struct frontswap_ops zswap_frontswap_ops = {
1419         .store = zswap_frontswap_store,
1420         .load = zswap_frontswap_load,
1421         .invalidate_page = zswap_frontswap_invalidate_page,
1422         .invalidate_area = zswap_frontswap_invalidate_area,
1423         .init = zswap_frontswap_init
1424 };
1425 
1426 /*********************************
1427 * debugfs functions
1428 **********************************/
1429 #ifdef CONFIG_DEBUG_FS
1430 #include <linux/debugfs.h>
1431 
1432 static struct dentry *zswap_debugfs_root;
1433 
1434 static int __init zswap_debugfs_init(void)
1435 {
1436         if (!debugfs_initialized())
1437                 return -ENODEV;
1438 
1439         zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1440 
1441         debugfs_create_u64("pool_limit_hit", 0444,
1442                            zswap_debugfs_root, &zswap_pool_limit_hit);
1443         debugfs_create_u64("reject_reclaim_fail", 0444,
1444                            zswap_debugfs_root, &zswap_reject_reclaim_fail);
1445         debugfs_create_u64("reject_alloc_fail", 0444,
1446                            zswap_debugfs_root, &zswap_reject_alloc_fail);
1447         debugfs_create_u64("reject_kmemcache_fail", 0444,
1448                            zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1449         debugfs_create_u64("reject_compress_poor", 0444,
1450                            zswap_debugfs_root, &zswap_reject_compress_poor);
1451         debugfs_create_u64("written_back_pages", 0444,
1452                            zswap_debugfs_root, &zswap_written_back_pages);
1453         debugfs_create_u64("duplicate_entry", 0444,
1454                            zswap_debugfs_root, &zswap_duplicate_entry);
1455         debugfs_create_u64("pool_total_size", 0444,
1456                            zswap_debugfs_root, &zswap_pool_total_size);
1457         debugfs_create_atomic_t("stored_pages", 0444,
1458                                 zswap_debugfs_root, &zswap_stored_pages);
1459         debugfs_create_atomic_t("same_filled_pages", 0444,
1460                                 zswap_debugfs_root, &zswap_same_filled_pages);
1461 
1462         return 0;
1463 }
1464 #else
1465 static int __init zswap_debugfs_init(void)
1466 {
1467         return 0;
1468 }
1469 #endif
1470 
1471 /*********************************
1472 * module init and exit
1473 **********************************/
1474 static int __init init_zswap(void)
1475 {
1476         struct zswap_pool *pool;
1477         int ret;
1478 
1479         zswap_init_started = true;
1480 
1481         if (zswap_entry_cache_create()) {
1482                 pr_err("entry cache creation failed\n");
1483                 goto cache_fail;
1484         }
1485 
1486         ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1487                                 zswap_dstmem_prepare, zswap_dstmem_dead);
1488         if (ret) {
1489                 pr_err("dstmem alloc failed\n");
1490                 goto dstmem_fail;
1491         }
1492 
1493         ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1494                                       "mm/zswap_pool:prepare",
1495                                       zswap_cpu_comp_prepare,
1496                                       zswap_cpu_comp_dead);
1497         if (ret)
1498                 goto hp_fail;
1499 
1500         pool = __zswap_pool_create_fallback();
1501         if (pool) {
1502                 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1503                         zpool_get_type(pool->zpool));
1504                 list_add(&pool->list, &zswap_pools);
1505                 zswap_has_pool = true;
1506         } else {
1507                 pr_err("pool creation failed\n");
1508                 zswap_enabled = false;
1509         }
1510 
1511         shrink_wq = create_workqueue("zswap-shrink");
1512         if (!shrink_wq)
1513                 goto fallback_fail;
1514 
1515         ret = frontswap_register_ops(&zswap_frontswap_ops);
1516         if (ret)
1517                 goto destroy_wq;
1518         if (zswap_debugfs_init())
1519                 pr_warn("debugfs initialization failed\n");
1520         return 0;
1521 
1522 destroy_wq:
1523         destroy_workqueue(shrink_wq);
1524 fallback_fail:
1525         if (pool)
1526                 zswap_pool_destroy(pool);
1527 hp_fail:
1528         cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1529 dstmem_fail:
1530         zswap_entry_cache_destroy();
1531 cache_fail:
1532         /* if built-in, we aren't unloaded on failure; don't allow use */
1533         zswap_init_failed = true;
1534         zswap_enabled = false;
1535         return -ENOMEM;
1536 }
1537 /* must be late so crypto has time to come up */
1538 late_initcall(init_zswap);
1539 
1540 MODULE_LICENSE("GPL");
1541 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1542 MODULE_DESCRIPTION("Compressed cache for swap pages");
1543 

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