1 /*
2 * zswap.c - zswap driver file
3 *
4 * zswap is a backend for frontswap that takes pages that are in the process
5 * of being swapped out and attempts to compress and store them in a
6 * RAM-based memory pool. This can result in a significant I/O reduction on
7 * the swap device and, in the case where decompressing from RAM is faster
8 * than reading from the swap device, can also improve workload performance.
9 *
10 * Copyright (C) 2012 Seth Jennings <sjenning@linux.vnet.ibm.com>
11 *
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation; either version 2
15 * of the License, or (at your option) any later version.
16 *
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
21 */
22
23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
24
25 #include <linux/module.h>
26 #include <linux/cpu.h>
27 #include <linux/highmem.h>
28 #include <linux/slab.h>
29 #include <linux/spinlock.h>
30 #include <linux/types.h>
31 #include <linux/atomic.h>
32 #include <linux/frontswap.h>
33 #include <linux/rbtree.h>
34 #include <linux/swap.h>
35 #include <linux/crypto.h>
36 #include <linux/mempool.h>
37 #include <linux/zpool.h>
38
39 #include <linux/mm_types.h>
40 #include <linux/page-flags.h>
41 #include <linux/swapops.h>
42 #include <linux/writeback.h>
43 #include <linux/pagemap.h>
44
45 /*********************************
46 * statistics
47 **********************************/
48 /* Total bytes used by the compressed storage */
49 static u64 zswap_pool_total_size;
50 /* The number of compressed pages currently stored in zswap */
51 static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
52
53 /*
54 * The statistics below are not protected from concurrent access for
55 * performance reasons so they may not be a 100% accurate. However,
56 * they do provide useful information on roughly how many times a
57 * certain event is occurring.
58 */
59
60 /* Pool limit was hit (see zswap_max_pool_percent) */
61 static u64 zswap_pool_limit_hit;
62 /* Pages written back when pool limit was reached */
63 static u64 zswap_written_back_pages;
64 /* Store failed due to a reclaim failure after pool limit was reached */
65 static u64 zswap_reject_reclaim_fail;
66 /* Compressed page was too big for the allocator to (optimally) store */
67 static u64 zswap_reject_compress_poor;
68 /* Store failed because underlying allocator could not get memory */
69 static u64 zswap_reject_alloc_fail;
70 /* Store failed because the entry metadata could not be allocated (rare) */
71 static u64 zswap_reject_kmemcache_fail;
72 /* Duplicate store was encountered (rare) */
73 static u64 zswap_duplicate_entry;
74
75 /*********************************
76 * tunables
77 **********************************/
78 /* Enable/disable zswap (disabled by default, fixed at boot for now) */
79 static bool zswap_enabled __read_mostly;
80 module_param_named(enabled, zswap_enabled, bool, 0444);
81
82 /* Compressor to be used by zswap (fixed at boot for now) */
83 #define ZSWAP_COMPRESSOR_DEFAULT "lzo"
84 static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
85 module_param_named(compressor, zswap_compressor, charp, 0444);
86
87 /* The maximum percentage of memory that the compressed pool can occupy */
88 static unsigned int zswap_max_pool_percent = 20;
89 module_param_named(max_pool_percent,
90 zswap_max_pool_percent, uint, 0644);
91
92 /* Compressed storage to use */
93 #define ZSWAP_ZPOOL_DEFAULT "zbud"
94 static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
95 module_param_named(zpool, zswap_zpool_type, charp, 0444);
96
97 /* zpool is shared by all of zswap backend */
98 static struct zpool *zswap_pool;
99
100 /*********************************
101 * compression functions
102 **********************************/
103 /* per-cpu compression transforms */
104 static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms;
105
106 enum comp_op {
107 ZSWAP_COMPOP_COMPRESS,
108 ZSWAP_COMPOP_DECOMPRESS
109 };
110
zswap_comp_op(enum comp_op op,const u8 * src,unsigned int slen,u8 * dst,unsigned int * dlen)111 static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen,
112 u8 *dst, unsigned int *dlen)
113 {
114 struct crypto_comp *tfm;
115 int ret;
116
117 tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu());
118 switch (op) {
119 case ZSWAP_COMPOP_COMPRESS:
120 ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
121 break;
122 case ZSWAP_COMPOP_DECOMPRESS:
123 ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
124 break;
125 default:
126 ret = -EINVAL;
127 }
128
129 put_cpu();
130 return ret;
131 }
132
zswap_comp_init(void)133 static int __init zswap_comp_init(void)
134 {
135 if (!crypto_has_comp(zswap_compressor, 0, 0)) {
136 pr_info("%s compressor not available\n", zswap_compressor);
137 /* fall back to default compressor */
138 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
139 if (!crypto_has_comp(zswap_compressor, 0, 0))
140 /* can't even load the default compressor */
141 return -ENODEV;
142 }
143 pr_info("using %s compressor\n", zswap_compressor);
144
145 /* alloc percpu transforms */
146 zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
147 if (!zswap_comp_pcpu_tfms)
148 return -ENOMEM;
149 return 0;
150 }
151
zswap_comp_exit(void)152 static void zswap_comp_exit(void)
153 {
154 /* free percpu transforms */
155 if (zswap_comp_pcpu_tfms)
156 free_percpu(zswap_comp_pcpu_tfms);
157 }
158
159 /*********************************
160 * data structures
161 **********************************/
162 /*
163 * struct zswap_entry
164 *
165 * This structure contains the metadata for tracking a single compressed
166 * page within zswap.
167 *
168 * rbnode - links the entry into red-black tree for the appropriate swap type
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 * offset - the swap offset for the entry. Index into the red-black tree.
176 * handle - zpool allocation handle that stores the compressed page data
177 * length - the length in bytes of the compressed page data. Needed during
178 * decompression
179 */
180 struct zswap_entry {
181 struct rb_node rbnode;
182 pgoff_t offset;
183 int refcount;
184 unsigned int length;
185 unsigned long handle;
186 };
187
188 struct zswap_header {
189 swp_entry_t swpentry;
190 };
191
192 /*
193 * The tree lock in the zswap_tree struct protects a few things:
194 * - the rbtree
195 * - the refcount field of each entry in the tree
196 */
197 struct zswap_tree {
198 struct rb_root rbroot;
199 spinlock_t lock;
200 };
201
202 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
203
204 /*********************************
205 * zswap entry functions
206 **********************************/
207 static struct kmem_cache *zswap_entry_cache;
208
zswap_entry_cache_create(void)209 static int zswap_entry_cache_create(void)
210 {
211 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
212 return zswap_entry_cache == NULL;
213 }
214
zswap_entry_cache_destroy(void)215 static void __init zswap_entry_cache_destroy(void)
216 {
217 kmem_cache_destroy(zswap_entry_cache);
218 }
219
zswap_entry_cache_alloc(gfp_t gfp)220 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
221 {
222 struct zswap_entry *entry;
223 entry = kmem_cache_alloc(zswap_entry_cache, gfp);
224 if (!entry)
225 return NULL;
226 entry->refcount = 1;
227 RB_CLEAR_NODE(&entry->rbnode);
228 return entry;
229 }
230
zswap_entry_cache_free(struct zswap_entry * entry)231 static void zswap_entry_cache_free(struct zswap_entry *entry)
232 {
233 kmem_cache_free(zswap_entry_cache, entry);
234 }
235
236 /*********************************
237 * rbtree functions
238 **********************************/
zswap_rb_search(struct rb_root * root,pgoff_t offset)239 static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
240 {
241 struct rb_node *node = root->rb_node;
242 struct zswap_entry *entry;
243
244 while (node) {
245 entry = rb_entry(node, struct zswap_entry, rbnode);
246 if (entry->offset > offset)
247 node = node->rb_left;
248 else if (entry->offset < offset)
249 node = node->rb_right;
250 else
251 return entry;
252 }
253 return NULL;
254 }
255
256 /*
257 * In the case that a entry with the same offset is found, a pointer to
258 * the existing entry is stored in dupentry and the function returns -EEXIST
259 */
zswap_rb_insert(struct rb_root * root,struct zswap_entry * entry,struct zswap_entry ** dupentry)260 static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
261 struct zswap_entry **dupentry)
262 {
263 struct rb_node **link = &root->rb_node, *parent = NULL;
264 struct zswap_entry *myentry;
265
266 while (*link) {
267 parent = *link;
268 myentry = rb_entry(parent, struct zswap_entry, rbnode);
269 if (myentry->offset > entry->offset)
270 link = &(*link)->rb_left;
271 else if (myentry->offset < entry->offset)
272 link = &(*link)->rb_right;
273 else {
274 *dupentry = myentry;
275 return -EEXIST;
276 }
277 }
278 rb_link_node(&entry->rbnode, parent, link);
279 rb_insert_color(&entry->rbnode, root);
280 return 0;
281 }
282
zswap_rb_erase(struct rb_root * root,struct zswap_entry * entry)283 static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
284 {
285 if (!RB_EMPTY_NODE(&entry->rbnode)) {
286 rb_erase(&entry->rbnode, root);
287 RB_CLEAR_NODE(&entry->rbnode);
288 }
289 }
290
291 /*
292 * Carries out the common pattern of freeing and entry's zpool allocation,
293 * freeing the entry itself, and decrementing the number of stored pages.
294 */
zswap_free_entry(struct zswap_entry * entry)295 static void zswap_free_entry(struct zswap_entry *entry)
296 {
297 zpool_free(zswap_pool, entry->handle);
298 zswap_entry_cache_free(entry);
299 atomic_dec(&zswap_stored_pages);
300 zswap_pool_total_size = zpool_get_total_size(zswap_pool);
301 }
302
303 /* caller must hold the tree lock */
zswap_entry_get(struct zswap_entry * entry)304 static void zswap_entry_get(struct zswap_entry *entry)
305 {
306 entry->refcount++;
307 }
308
309 /* caller must hold the tree lock
310 * remove from the tree and free it, if nobody reference the entry
311 */
zswap_entry_put(struct zswap_tree * tree,struct zswap_entry * entry)312 static void zswap_entry_put(struct zswap_tree *tree,
313 struct zswap_entry *entry)
314 {
315 int refcount = --entry->refcount;
316
317 BUG_ON(refcount < 0);
318 if (refcount == 0) {
319 zswap_rb_erase(&tree->rbroot, entry);
320 zswap_free_entry(entry);
321 }
322 }
323
324 /* caller must hold the tree lock */
zswap_entry_find_get(struct rb_root * root,pgoff_t offset)325 static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
326 pgoff_t offset)
327 {
328 struct zswap_entry *entry = NULL;
329
330 entry = zswap_rb_search(root, offset);
331 if (entry)
332 zswap_entry_get(entry);
333
334 return entry;
335 }
336
337 /*********************************
338 * per-cpu code
339 **********************************/
340 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
341
__zswap_cpu_notifier(unsigned long action,unsigned long cpu)342 static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu)
343 {
344 struct crypto_comp *tfm;
345 u8 *dst;
346
347 switch (action) {
348 case CPU_UP_PREPARE:
349 tfm = crypto_alloc_comp(zswap_compressor, 0, 0);
350 if (IS_ERR(tfm)) {
351 pr_err("can't allocate compressor transform\n");
352 return NOTIFY_BAD;
353 }
354 *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm;
355 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
356 if (!dst) {
357 pr_err("can't allocate compressor buffer\n");
358 crypto_free_comp(tfm);
359 *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
360 return NOTIFY_BAD;
361 }
362 per_cpu(zswap_dstmem, cpu) = dst;
363 break;
364 case CPU_DEAD:
365 case CPU_UP_CANCELED:
366 tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu);
367 if (tfm) {
368 crypto_free_comp(tfm);
369 *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
370 }
371 dst = per_cpu(zswap_dstmem, cpu);
372 kfree(dst);
373 per_cpu(zswap_dstmem, cpu) = NULL;
374 break;
375 default:
376 break;
377 }
378 return NOTIFY_OK;
379 }
380
zswap_cpu_notifier(struct notifier_block * nb,unsigned long action,void * pcpu)381 static int zswap_cpu_notifier(struct notifier_block *nb,
382 unsigned long action, void *pcpu)
383 {
384 unsigned long cpu = (unsigned long)pcpu;
385 return __zswap_cpu_notifier(action, cpu);
386 }
387
388 static struct notifier_block zswap_cpu_notifier_block = {
389 .notifier_call = zswap_cpu_notifier
390 };
391
zswap_cpu_init(void)392 static int zswap_cpu_init(void)
393 {
394 unsigned long cpu;
395
396 cpu_notifier_register_begin();
397 for_each_online_cpu(cpu)
398 if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
399 goto cleanup;
400 __register_cpu_notifier(&zswap_cpu_notifier_block);
401 cpu_notifier_register_done();
402 return 0;
403
404 cleanup:
405 for_each_online_cpu(cpu)
406 __zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
407 cpu_notifier_register_done();
408 return -ENOMEM;
409 }
410
411 /*********************************
412 * helpers
413 **********************************/
zswap_is_full(void)414 static bool zswap_is_full(void)
415 {
416 return totalram_pages * zswap_max_pool_percent / 100 <
417 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
418 }
419
420 /*********************************
421 * writeback code
422 **********************************/
423 /* return enum for zswap_get_swap_cache_page */
424 enum zswap_get_swap_ret {
425 ZSWAP_SWAPCACHE_NEW,
426 ZSWAP_SWAPCACHE_EXIST,
427 ZSWAP_SWAPCACHE_FAIL,
428 };
429
430 /*
431 * zswap_get_swap_cache_page
432 *
433 * This is an adaption of read_swap_cache_async()
434 *
435 * This function tries to find a page with the given swap entry
436 * in the swapper_space address space (the swap cache). If the page
437 * is found, it is returned in retpage. Otherwise, a page is allocated,
438 * added to the swap cache, and returned in retpage.
439 *
440 * If success, the swap cache page is returned in retpage
441 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
442 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
443 * the new page is added to swapcache and locked
444 * Returns ZSWAP_SWAPCACHE_FAIL on error
445 */
zswap_get_swap_cache_page(swp_entry_t entry,struct page ** retpage)446 static int zswap_get_swap_cache_page(swp_entry_t entry,
447 struct page **retpage)
448 {
449 struct page *found_page, *new_page = NULL;
450 struct address_space *swapper_space = swap_address_space(entry);
451 int err;
452
453 *retpage = NULL;
454 do {
455 /*
456 * First check the swap cache. Since this is normally
457 * called after lookup_swap_cache() failed, re-calling
458 * that would confuse statistics.
459 */
460 found_page = find_get_page(swapper_space, entry.val);
461 if (found_page)
462 break;
463
464 /*
465 * Get a new page to read into from swap.
466 */
467 if (!new_page) {
468 new_page = alloc_page(GFP_KERNEL);
469 if (!new_page)
470 break; /* Out of memory */
471 }
472
473 /*
474 * call radix_tree_preload() while we can wait.
475 */
476 err = radix_tree_preload(GFP_KERNEL);
477 if (err)
478 break;
479
480 /*
481 * Swap entry may have been freed since our caller observed it.
482 */
483 err = swapcache_prepare(entry);
484 if (err == -EEXIST) { /* seems racy */
485 radix_tree_preload_end();
486 continue;
487 }
488 if (err) { /* swp entry is obsolete ? */
489 radix_tree_preload_end();
490 break;
491 }
492
493 /* May fail (-ENOMEM) if radix-tree node allocation failed. */
494 __set_page_locked(new_page);
495 SetPageSwapBacked(new_page);
496 err = __add_to_swap_cache(new_page, entry);
497 if (likely(!err)) {
498 radix_tree_preload_end();
499 lru_cache_add_anon(new_page);
500 *retpage = new_page;
501 return ZSWAP_SWAPCACHE_NEW;
502 }
503 radix_tree_preload_end();
504 ClearPageSwapBacked(new_page);
505 __clear_page_locked(new_page);
506 /*
507 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
508 * clear SWAP_HAS_CACHE flag.
509 */
510 swapcache_free(entry);
511 } while (err != -ENOMEM);
512
513 if (new_page)
514 page_cache_release(new_page);
515 if (!found_page)
516 return ZSWAP_SWAPCACHE_FAIL;
517 *retpage = found_page;
518 return ZSWAP_SWAPCACHE_EXIST;
519 }
520
521 /*
522 * Attempts to free an entry by adding a page to the swap cache,
523 * decompressing the entry data into the page, and issuing a
524 * bio write to write the page back to the swap device.
525 *
526 * This can be thought of as a "resumed writeback" of the page
527 * to the swap device. We are basically resuming the same swap
528 * writeback path that was intercepted with the frontswap_store()
529 * in the first place. After the page has been decompressed into
530 * the swap cache, the compressed version stored by zswap can be
531 * freed.
532 */
zswap_writeback_entry(struct zpool * pool,unsigned long handle)533 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
534 {
535 struct zswap_header *zhdr;
536 swp_entry_t swpentry;
537 struct zswap_tree *tree;
538 pgoff_t offset;
539 struct zswap_entry *entry;
540 struct page *page;
541 u8 *src, *dst;
542 unsigned int dlen;
543 int ret;
544 struct writeback_control wbc = {
545 .sync_mode = WB_SYNC_NONE,
546 };
547
548 /* extract swpentry from data */
549 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
550 swpentry = zhdr->swpentry; /* here */
551 zpool_unmap_handle(pool, handle);
552 tree = zswap_trees[swp_type(swpentry)];
553 offset = swp_offset(swpentry);
554
555 /* find and ref zswap entry */
556 spin_lock(&tree->lock);
557 entry = zswap_entry_find_get(&tree->rbroot, offset);
558 if (!entry) {
559 /* entry was invalidated */
560 spin_unlock(&tree->lock);
561 return 0;
562 }
563 spin_unlock(&tree->lock);
564 BUG_ON(offset != entry->offset);
565
566 /* try to allocate swap cache page */
567 switch (zswap_get_swap_cache_page(swpentry, &page)) {
568 case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
569 ret = -ENOMEM;
570 goto fail;
571
572 case ZSWAP_SWAPCACHE_EXIST:
573 /* page is already in the swap cache, ignore for now */
574 page_cache_release(page);
575 ret = -EEXIST;
576 goto fail;
577
578 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
579 /* decompress */
580 dlen = PAGE_SIZE;
581 src = (u8 *)zpool_map_handle(zswap_pool, entry->handle,
582 ZPOOL_MM_RO) + sizeof(struct zswap_header);
583 dst = kmap_atomic(page);
584 ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src,
585 entry->length, dst, &dlen);
586 kunmap_atomic(dst);
587 zpool_unmap_handle(zswap_pool, entry->handle);
588 BUG_ON(ret);
589 BUG_ON(dlen != PAGE_SIZE);
590
591 /* page is up to date */
592 SetPageUptodate(page);
593 }
594
595 /* move it to the tail of the inactive list after end_writeback */
596 SetPageReclaim(page);
597
598 /* start writeback */
599 __swap_writepage(page, &wbc, end_swap_bio_write);
600 page_cache_release(page);
601 zswap_written_back_pages++;
602
603 spin_lock(&tree->lock);
604 /* drop local reference */
605 zswap_entry_put(tree, entry);
606
607 /*
608 * There are two possible situations for entry here:
609 * (1) refcount is 1(normal case), entry is valid and on the tree
610 * (2) refcount is 0, entry is freed and not on the tree
611 * because invalidate happened during writeback
612 * search the tree and free the entry if find entry
613 */
614 if (entry == zswap_rb_search(&tree->rbroot, offset))
615 zswap_entry_put(tree, entry);
616 spin_unlock(&tree->lock);
617
618 goto end;
619
620 /*
621 * if we get here due to ZSWAP_SWAPCACHE_EXIST
622 * a load may happening concurrently
623 * it is safe and okay to not free the entry
624 * if we free the entry in the following put
625 * it it either okay to return !0
626 */
627 fail:
628 spin_lock(&tree->lock);
629 zswap_entry_put(tree, entry);
630 spin_unlock(&tree->lock);
631
632 end:
633 return ret;
634 }
635
636 /*********************************
637 * frontswap hooks
638 **********************************/
639 /* attempts to compress and store an single page */
zswap_frontswap_store(unsigned type,pgoff_t offset,struct page * page)640 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
641 struct page *page)
642 {
643 struct zswap_tree *tree = zswap_trees[type];
644 struct zswap_entry *entry, *dupentry;
645 int ret;
646 unsigned int dlen = PAGE_SIZE, len;
647 unsigned long handle;
648 char *buf;
649 u8 *src, *dst;
650 struct zswap_header *zhdr;
651
652 if (!tree) {
653 ret = -ENODEV;
654 goto reject;
655 }
656
657 /* reclaim space if needed */
658 if (zswap_is_full()) {
659 zswap_pool_limit_hit++;
660 if (zpool_shrink(zswap_pool, 1, NULL)) {
661 zswap_reject_reclaim_fail++;
662 ret = -ENOMEM;
663 goto reject;
664 }
665 }
666
667 /* allocate entry */
668 entry = zswap_entry_cache_alloc(GFP_KERNEL);
669 if (!entry) {
670 zswap_reject_kmemcache_fail++;
671 ret = -ENOMEM;
672 goto reject;
673 }
674
675 /* compress */
676 dst = get_cpu_var(zswap_dstmem);
677 src = kmap_atomic(page);
678 ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen);
679 kunmap_atomic(src);
680 if (ret) {
681 ret = -EINVAL;
682 goto freepage;
683 }
684
685 /* store */
686 len = dlen + sizeof(struct zswap_header);
687 ret = zpool_malloc(zswap_pool, len, __GFP_NORETRY | __GFP_NOWARN,
688 &handle);
689 if (ret == -ENOSPC) {
690 zswap_reject_compress_poor++;
691 goto freepage;
692 }
693 if (ret) {
694 zswap_reject_alloc_fail++;
695 goto freepage;
696 }
697 zhdr = zpool_map_handle(zswap_pool, handle, ZPOOL_MM_RW);
698 zhdr->swpentry = swp_entry(type, offset);
699 buf = (u8 *)(zhdr + 1);
700 memcpy(buf, dst, dlen);
701 zpool_unmap_handle(zswap_pool, handle);
702 put_cpu_var(zswap_dstmem);
703
704 /* populate entry */
705 entry->offset = offset;
706 entry->handle = handle;
707 entry->length = dlen;
708
709 /* map */
710 spin_lock(&tree->lock);
711 do {
712 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
713 if (ret == -EEXIST) {
714 zswap_duplicate_entry++;
715 /* remove from rbtree */
716 zswap_rb_erase(&tree->rbroot, dupentry);
717 zswap_entry_put(tree, dupentry);
718 }
719 } while (ret == -EEXIST);
720 spin_unlock(&tree->lock);
721
722 /* update stats */
723 atomic_inc(&zswap_stored_pages);
724 zswap_pool_total_size = zpool_get_total_size(zswap_pool);
725
726 return 0;
727
728 freepage:
729 put_cpu_var(zswap_dstmem);
730 zswap_entry_cache_free(entry);
731 reject:
732 return ret;
733 }
734
735 /*
736 * returns 0 if the page was successfully decompressed
737 * return -1 on entry not found or error
738 */
zswap_frontswap_load(unsigned type,pgoff_t offset,struct page * page)739 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
740 struct page *page)
741 {
742 struct zswap_tree *tree = zswap_trees[type];
743 struct zswap_entry *entry;
744 u8 *src, *dst;
745 unsigned int dlen;
746 int ret;
747
748 /* find */
749 spin_lock(&tree->lock);
750 entry = zswap_entry_find_get(&tree->rbroot, offset);
751 if (!entry) {
752 /* entry was written back */
753 spin_unlock(&tree->lock);
754 return -1;
755 }
756 spin_unlock(&tree->lock);
757
758 /* decompress */
759 dlen = PAGE_SIZE;
760 src = (u8 *)zpool_map_handle(zswap_pool, entry->handle,
761 ZPOOL_MM_RO) + sizeof(struct zswap_header);
762 dst = kmap_atomic(page);
763 ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
764 dst, &dlen);
765 kunmap_atomic(dst);
766 zpool_unmap_handle(zswap_pool, entry->handle);
767 BUG_ON(ret);
768
769 spin_lock(&tree->lock);
770 zswap_entry_put(tree, entry);
771 spin_unlock(&tree->lock);
772
773 return 0;
774 }
775
776 /* frees an entry in zswap */
zswap_frontswap_invalidate_page(unsigned type,pgoff_t offset)777 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
778 {
779 struct zswap_tree *tree = zswap_trees[type];
780 struct zswap_entry *entry;
781
782 /* find */
783 spin_lock(&tree->lock);
784 entry = zswap_rb_search(&tree->rbroot, offset);
785 if (!entry) {
786 /* entry was written back */
787 spin_unlock(&tree->lock);
788 return;
789 }
790
791 /* remove from rbtree */
792 zswap_rb_erase(&tree->rbroot, entry);
793
794 /* drop the initial reference from entry creation */
795 zswap_entry_put(tree, entry);
796
797 spin_unlock(&tree->lock);
798 }
799
800 /* frees all zswap entries for the given swap type */
zswap_frontswap_invalidate_area(unsigned type)801 static void zswap_frontswap_invalidate_area(unsigned type)
802 {
803 struct zswap_tree *tree = zswap_trees[type];
804 struct zswap_entry *entry, *n;
805
806 if (!tree)
807 return;
808
809 /* walk the tree and free everything */
810 spin_lock(&tree->lock);
811 rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
812 zswap_free_entry(entry);
813 tree->rbroot = RB_ROOT;
814 spin_unlock(&tree->lock);
815 kfree(tree);
816 zswap_trees[type] = NULL;
817 }
818
819 static struct zpool_ops zswap_zpool_ops = {
820 .evict = zswap_writeback_entry
821 };
822
zswap_frontswap_init(unsigned type)823 static void zswap_frontswap_init(unsigned type)
824 {
825 struct zswap_tree *tree;
826
827 tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
828 if (!tree) {
829 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
830 return;
831 }
832
833 tree->rbroot = RB_ROOT;
834 spin_lock_init(&tree->lock);
835 zswap_trees[type] = tree;
836 }
837
838 static struct frontswap_ops zswap_frontswap_ops = {
839 .store = zswap_frontswap_store,
840 .load = zswap_frontswap_load,
841 .invalidate_page = zswap_frontswap_invalidate_page,
842 .invalidate_area = zswap_frontswap_invalidate_area,
843 .init = zswap_frontswap_init
844 };
845
846 /*********************************
847 * debugfs functions
848 **********************************/
849 #ifdef CONFIG_DEBUG_FS
850 #include <linux/debugfs.h>
851
852 static struct dentry *zswap_debugfs_root;
853
zswap_debugfs_init(void)854 static int __init zswap_debugfs_init(void)
855 {
856 if (!debugfs_initialized())
857 return -ENODEV;
858
859 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
860 if (!zswap_debugfs_root)
861 return -ENOMEM;
862
863 debugfs_create_u64("pool_limit_hit", S_IRUGO,
864 zswap_debugfs_root, &zswap_pool_limit_hit);
865 debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
866 zswap_debugfs_root, &zswap_reject_reclaim_fail);
867 debugfs_create_u64("reject_alloc_fail", S_IRUGO,
868 zswap_debugfs_root, &zswap_reject_alloc_fail);
869 debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
870 zswap_debugfs_root, &zswap_reject_kmemcache_fail);
871 debugfs_create_u64("reject_compress_poor", S_IRUGO,
872 zswap_debugfs_root, &zswap_reject_compress_poor);
873 debugfs_create_u64("written_back_pages", S_IRUGO,
874 zswap_debugfs_root, &zswap_written_back_pages);
875 debugfs_create_u64("duplicate_entry", S_IRUGO,
876 zswap_debugfs_root, &zswap_duplicate_entry);
877 debugfs_create_u64("pool_total_size", S_IRUGO,
878 zswap_debugfs_root, &zswap_pool_total_size);
879 debugfs_create_atomic_t("stored_pages", S_IRUGO,
880 zswap_debugfs_root, &zswap_stored_pages);
881
882 return 0;
883 }
884
zswap_debugfs_exit(void)885 static void __exit zswap_debugfs_exit(void)
886 {
887 debugfs_remove_recursive(zswap_debugfs_root);
888 }
889 #else
zswap_debugfs_init(void)890 static int __init zswap_debugfs_init(void)
891 {
892 return 0;
893 }
894
zswap_debugfs_exit(void)895 static void __exit zswap_debugfs_exit(void) { }
896 #endif
897
898 /*********************************
899 * module init and exit
900 **********************************/
init_zswap(void)901 static int __init init_zswap(void)
902 {
903 gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN;
904
905 if (!zswap_enabled)
906 return 0;
907
908 pr_info("loading zswap\n");
909
910 zswap_pool = zpool_create_pool(zswap_zpool_type, "zswap", gfp,
911 &zswap_zpool_ops);
912 if (!zswap_pool && strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
913 pr_info("%s zpool not available\n", zswap_zpool_type);
914 zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
915 zswap_pool = zpool_create_pool(zswap_zpool_type, "zswap", gfp,
916 &zswap_zpool_ops);
917 }
918 if (!zswap_pool) {
919 pr_err("%s zpool not available\n", zswap_zpool_type);
920 pr_err("zpool creation failed\n");
921 goto error;
922 }
923 pr_info("using %s pool\n", zswap_zpool_type);
924
925 if (zswap_entry_cache_create()) {
926 pr_err("entry cache creation failed\n");
927 goto cachefail;
928 }
929 if (zswap_comp_init()) {
930 pr_err("compressor initialization failed\n");
931 goto compfail;
932 }
933 if (zswap_cpu_init()) {
934 pr_err("per-cpu initialization failed\n");
935 goto pcpufail;
936 }
937
938 frontswap_register_ops(&zswap_frontswap_ops);
939 if (zswap_debugfs_init())
940 pr_warn("debugfs initialization failed\n");
941 return 0;
942 pcpufail:
943 zswap_comp_exit();
944 compfail:
945 zswap_entry_cache_destroy();
946 cachefail:
947 zpool_destroy_pool(zswap_pool);
948 error:
949 return -ENOMEM;
950 }
951 /* must be late so crypto has time to come up */
952 late_initcall(init_zswap);
953
954 MODULE_LICENSE("GPL");
955 MODULE_AUTHOR("Seth Jennings <sjenning@linux.vnet.ibm.com>");
956 MODULE_DESCRIPTION("Compressed cache for swap pages");
957