blob: 5a63f78a5601aa63112f30b3338be6c413f02f4c [file] [log] [blame]
Seth Jennings2b281112013-07-10 16:05:03 -07001/*
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/zbud.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/* Number of memory pages used by the compressed pool */
49static u64 zswap_pool_pages;
50/* The number of compressed pages currently stored in zswap */
51static 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) */
61static u64 zswap_pool_limit_hit;
62/* Pages written back when pool limit was reached */
63static u64 zswap_written_back_pages;
64/* Store failed due to a reclaim failure after pool limit was reached */
65static u64 zswap_reject_reclaim_fail;
66/* Compressed page was too big for the allocator to (optimally) store */
67static u64 zswap_reject_compress_poor;
68/* Store failed because underlying allocator could not get memory */
69static u64 zswap_reject_alloc_fail;
70/* Store failed because the entry metadata could not be allocated (rare) */
71static u64 zswap_reject_kmemcache_fail;
72/* Duplicate store was encountered (rare) */
73static u64 zswap_duplicate_entry;
74
75/*********************************
76* tunables
77**********************************/
78/* Enable/disable zswap (disabled by default, fixed at boot for now) */
79static bool zswap_enabled __read_mostly;
80module_param_named(enabled, zswap_enabled, bool, 0);
81
82/* Compressor to be used by zswap (fixed at boot for now) */
83#define ZSWAP_COMPRESSOR_DEFAULT "lzo"
84static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
85module_param_named(compressor, zswap_compressor, charp, 0);
86
87/* The maximum percentage of memory that the compressed pool can occupy */
88static unsigned int zswap_max_pool_percent = 20;
89module_param_named(max_pool_percent,
90 zswap_max_pool_percent, uint, 0644);
91
92/*********************************
93* compression functions
94**********************************/
95/* per-cpu compression transforms */
96static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms;
97
98enum comp_op {
99 ZSWAP_COMPOP_COMPRESS,
100 ZSWAP_COMPOP_DECOMPRESS
101};
102
103static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen,
104 u8 *dst, unsigned int *dlen)
105{
106 struct crypto_comp *tfm;
107 int ret;
108
109 tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu());
110 switch (op) {
111 case ZSWAP_COMPOP_COMPRESS:
112 ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
113 break;
114 case ZSWAP_COMPOP_DECOMPRESS:
115 ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
116 break;
117 default:
118 ret = -EINVAL;
119 }
120
121 put_cpu();
122 return ret;
123}
124
125static int __init zswap_comp_init(void)
126{
127 if (!crypto_has_comp(zswap_compressor, 0, 0)) {
128 pr_info("%s compressor not available\n", zswap_compressor);
129 /* fall back to default compressor */
130 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
131 if (!crypto_has_comp(zswap_compressor, 0, 0))
132 /* can't even load the default compressor */
133 return -ENODEV;
134 }
135 pr_info("using %s compressor\n", zswap_compressor);
136
137 /* alloc percpu transforms */
138 zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
139 if (!zswap_comp_pcpu_tfms)
140 return -ENOMEM;
141 return 0;
142}
143
144static void zswap_comp_exit(void)
145{
146 /* free percpu transforms */
147 if (zswap_comp_pcpu_tfms)
148 free_percpu(zswap_comp_pcpu_tfms);
149}
150
151/*********************************
152* data structures
153**********************************/
154/*
155 * struct zswap_entry
156 *
157 * This structure contains the metadata for tracking a single compressed
158 * page within zswap.
159 *
160 * rbnode - links the entry into red-black tree for the appropriate swap type
161 * refcount - the number of outstanding reference to the entry. This is needed
162 * to protect against premature freeing of the entry by code
163 * concurent calls to load, invalidate, and writeback. The lock
164 * for the zswap_tree structure that contains the entry must
165 * be held while changing the refcount. Since the lock must
166 * be held, there is no reason to also make refcount atomic.
167 * offset - the swap offset for the entry. Index into the red-black tree.
168 * handle - zsmalloc allocation handle that stores the compressed page data
169 * length - the length in bytes of the compressed page data. Needed during
170 * decompression
171 */
172struct zswap_entry {
173 struct rb_node rbnode;
174 pgoff_t offset;
175 int refcount;
176 unsigned int length;
177 unsigned long handle;
178};
179
180struct zswap_header {
181 swp_entry_t swpentry;
182};
183
184/*
185 * The tree lock in the zswap_tree struct protects a few things:
186 * - the rbtree
187 * - the refcount field of each entry in the tree
188 */
189struct zswap_tree {
190 struct rb_root rbroot;
191 spinlock_t lock;
192 struct zbud_pool *pool;
193};
194
195static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
196
197/*********************************
198* zswap entry functions
199**********************************/
200static struct kmem_cache *zswap_entry_cache;
201
202static int zswap_entry_cache_create(void)
203{
204 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
205 return (zswap_entry_cache == NULL);
206}
207
208static void zswap_entry_cache_destory(void)
209{
210 kmem_cache_destroy(zswap_entry_cache);
211}
212
213static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
214{
215 struct zswap_entry *entry;
216 entry = kmem_cache_alloc(zswap_entry_cache, gfp);
217 if (!entry)
218 return NULL;
219 entry->refcount = 1;
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800220 RB_CLEAR_NODE(&entry->rbnode);
Seth Jennings2b281112013-07-10 16:05:03 -0700221 return entry;
222}
223
224static void zswap_entry_cache_free(struct zswap_entry *entry)
225{
226 kmem_cache_free(zswap_entry_cache, entry);
227}
228
Seth Jennings2b281112013-07-10 16:05:03 -0700229/*********************************
230* rbtree functions
231**********************************/
232static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
233{
234 struct rb_node *node = root->rb_node;
235 struct zswap_entry *entry;
236
237 while (node) {
238 entry = rb_entry(node, struct zswap_entry, rbnode);
239 if (entry->offset > offset)
240 node = node->rb_left;
241 else if (entry->offset < offset)
242 node = node->rb_right;
243 else
244 return entry;
245 }
246 return NULL;
247}
248
249/*
250 * In the case that a entry with the same offset is found, a pointer to
251 * the existing entry is stored in dupentry and the function returns -EEXIST
252 */
253static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
254 struct zswap_entry **dupentry)
255{
256 struct rb_node **link = &root->rb_node, *parent = NULL;
257 struct zswap_entry *myentry;
258
259 while (*link) {
260 parent = *link;
261 myentry = rb_entry(parent, struct zswap_entry, rbnode);
262 if (myentry->offset > entry->offset)
263 link = &(*link)->rb_left;
264 else if (myentry->offset < entry->offset)
265 link = &(*link)->rb_right;
266 else {
267 *dupentry = myentry;
268 return -EEXIST;
269 }
270 }
271 rb_link_node(&entry->rbnode, parent, link);
272 rb_insert_color(&entry->rbnode, root);
273 return 0;
274}
275
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800276static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
277{
278 if (!RB_EMPTY_NODE(&entry->rbnode)) {
279 rb_erase(&entry->rbnode, root);
280 RB_CLEAR_NODE(&entry->rbnode);
281 }
282}
283
284/*
285 * Carries out the common pattern of freeing and entry's zsmalloc allocation,
286 * freeing the entry itself, and decrementing the number of stored pages.
287 */
288static void zswap_free_entry(struct zswap_tree *tree,
289 struct zswap_entry *entry)
290{
291 zbud_free(tree->pool, entry->handle);
292 zswap_entry_cache_free(entry);
293 atomic_dec(&zswap_stored_pages);
294 zswap_pool_pages = zbud_get_pool_size(tree->pool);
295}
296
297/* caller must hold the tree lock */
298static void zswap_entry_get(struct zswap_entry *entry)
299{
300 entry->refcount++;
301}
302
303/* caller must hold the tree lock
304* remove from the tree and free it, if nobody reference the entry
305*/
306static void zswap_entry_put(struct zswap_tree *tree,
307 struct zswap_entry *entry)
308{
309 int refcount = --entry->refcount;
310
311 BUG_ON(refcount < 0);
312 if (refcount == 0) {
313 zswap_rb_erase(&tree->rbroot, entry);
314 zswap_free_entry(tree, entry);
315 }
316}
317
318/* caller must hold the tree lock */
319static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
320 pgoff_t offset)
321{
322 struct zswap_entry *entry = NULL;
323
324 entry = zswap_rb_search(root, offset);
325 if (entry)
326 zswap_entry_get(entry);
327
328 return entry;
329}
330
Seth Jennings2b281112013-07-10 16:05:03 -0700331/*********************************
332* per-cpu code
333**********************************/
334static DEFINE_PER_CPU(u8 *, zswap_dstmem);
335
336static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu)
337{
338 struct crypto_comp *tfm;
339 u8 *dst;
340
341 switch (action) {
342 case CPU_UP_PREPARE:
343 tfm = crypto_alloc_comp(zswap_compressor, 0, 0);
344 if (IS_ERR(tfm)) {
345 pr_err("can't allocate compressor transform\n");
346 return NOTIFY_BAD;
347 }
348 *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm;
349 dst = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
350 if (!dst) {
351 pr_err("can't allocate compressor buffer\n");
352 crypto_free_comp(tfm);
353 *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
354 return NOTIFY_BAD;
355 }
356 per_cpu(zswap_dstmem, cpu) = dst;
357 break;
358 case CPU_DEAD:
359 case CPU_UP_CANCELED:
360 tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu);
361 if (tfm) {
362 crypto_free_comp(tfm);
363 *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
364 }
365 dst = per_cpu(zswap_dstmem, cpu);
366 kfree(dst);
367 per_cpu(zswap_dstmem, cpu) = NULL;
368 break;
369 default:
370 break;
371 }
372 return NOTIFY_OK;
373}
374
375static int zswap_cpu_notifier(struct notifier_block *nb,
376 unsigned long action, void *pcpu)
377{
378 unsigned long cpu = (unsigned long)pcpu;
379 return __zswap_cpu_notifier(action, cpu);
380}
381
382static struct notifier_block zswap_cpu_notifier_block = {
383 .notifier_call = zswap_cpu_notifier
384};
385
386static int zswap_cpu_init(void)
387{
388 unsigned long cpu;
389
390 get_online_cpus();
391 for_each_online_cpu(cpu)
392 if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
393 goto cleanup;
394 register_cpu_notifier(&zswap_cpu_notifier_block);
395 put_online_cpus();
396 return 0;
397
398cleanup:
399 for_each_online_cpu(cpu)
400 __zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
401 put_online_cpus();
402 return -ENOMEM;
403}
404
405/*********************************
406* helpers
407**********************************/
408static bool zswap_is_full(void)
409{
410 return (totalram_pages * zswap_max_pool_percent / 100 <
411 zswap_pool_pages);
412}
413
Seth Jennings2b281112013-07-10 16:05:03 -0700414/*********************************
415* writeback code
416**********************************/
417/* return enum for zswap_get_swap_cache_page */
418enum zswap_get_swap_ret {
419 ZSWAP_SWAPCACHE_NEW,
420 ZSWAP_SWAPCACHE_EXIST,
Weijie Yang67d13fe2013-11-12 15:08:26 -0800421 ZSWAP_SWAPCACHE_FAIL,
Seth Jennings2b281112013-07-10 16:05:03 -0700422};
423
424/*
425 * zswap_get_swap_cache_page
426 *
427 * This is an adaption of read_swap_cache_async()
428 *
429 * This function tries to find a page with the given swap entry
430 * in the swapper_space address space (the swap cache). If the page
431 * is found, it is returned in retpage. Otherwise, a page is allocated,
432 * added to the swap cache, and returned in retpage.
433 *
434 * If success, the swap cache page is returned in retpage
Weijie Yang67d13fe2013-11-12 15:08:26 -0800435 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
436 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
437 * the new page is added to swapcache and locked
438 * Returns ZSWAP_SWAPCACHE_FAIL on error
Seth Jennings2b281112013-07-10 16:05:03 -0700439 */
440static int zswap_get_swap_cache_page(swp_entry_t entry,
441 struct page **retpage)
442{
443 struct page *found_page, *new_page = NULL;
Sunghan Suh822518d2013-09-11 14:20:22 -0700444 struct address_space *swapper_space = swap_address_space(entry);
Seth Jennings2b281112013-07-10 16:05:03 -0700445 int err;
446
447 *retpage = NULL;
448 do {
449 /*
450 * First check the swap cache. Since this is normally
451 * called after lookup_swap_cache() failed, re-calling
452 * that would confuse statistics.
453 */
454 found_page = find_get_page(swapper_space, entry.val);
455 if (found_page)
456 break;
457
458 /*
459 * Get a new page to read into from swap.
460 */
461 if (!new_page) {
462 new_page = alloc_page(GFP_KERNEL);
463 if (!new_page)
464 break; /* Out of memory */
465 }
466
467 /*
468 * call radix_tree_preload() while we can wait.
469 */
470 err = radix_tree_preload(GFP_KERNEL);
471 if (err)
472 break;
473
474 /*
475 * Swap entry may have been freed since our caller observed it.
476 */
477 err = swapcache_prepare(entry);
478 if (err == -EEXIST) { /* seems racy */
479 radix_tree_preload_end();
480 continue;
481 }
482 if (err) { /* swp entry is obsolete ? */
483 radix_tree_preload_end();
484 break;
485 }
486
487 /* May fail (-ENOMEM) if radix-tree node allocation failed. */
488 __set_page_locked(new_page);
489 SetPageSwapBacked(new_page);
490 err = __add_to_swap_cache(new_page, entry);
491 if (likely(!err)) {
492 radix_tree_preload_end();
493 lru_cache_add_anon(new_page);
494 *retpage = new_page;
495 return ZSWAP_SWAPCACHE_NEW;
496 }
497 radix_tree_preload_end();
498 ClearPageSwapBacked(new_page);
499 __clear_page_locked(new_page);
500 /*
501 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
502 * clear SWAP_HAS_CACHE flag.
503 */
504 swapcache_free(entry, NULL);
505 } while (err != -ENOMEM);
506
507 if (new_page)
508 page_cache_release(new_page);
509 if (!found_page)
Weijie Yang67d13fe2013-11-12 15:08:26 -0800510 return ZSWAP_SWAPCACHE_FAIL;
Seth Jennings2b281112013-07-10 16:05:03 -0700511 *retpage = found_page;
512 return ZSWAP_SWAPCACHE_EXIST;
513}
514
515/*
516 * Attempts to free an entry by adding a page to the swap cache,
517 * decompressing the entry data into the page, and issuing a
518 * bio write to write the page back to the swap device.
519 *
520 * This can be thought of as a "resumed writeback" of the page
521 * to the swap device. We are basically resuming the same swap
522 * writeback path that was intercepted with the frontswap_store()
523 * in the first place. After the page has been decompressed into
524 * the swap cache, the compressed version stored by zswap can be
525 * freed.
526 */
527static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle)
528{
529 struct zswap_header *zhdr;
530 swp_entry_t swpentry;
531 struct zswap_tree *tree;
532 pgoff_t offset;
533 struct zswap_entry *entry;
534 struct page *page;
535 u8 *src, *dst;
536 unsigned int dlen;
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800537 int ret;
Seth Jennings2b281112013-07-10 16:05:03 -0700538 struct writeback_control wbc = {
539 .sync_mode = WB_SYNC_NONE,
540 };
541
542 /* extract swpentry from data */
543 zhdr = zbud_map(pool, handle);
544 swpentry = zhdr->swpentry; /* here */
545 zbud_unmap(pool, handle);
546 tree = zswap_trees[swp_type(swpentry)];
547 offset = swp_offset(swpentry);
548 BUG_ON(pool != tree->pool);
549
550 /* find and ref zswap entry */
551 spin_lock(&tree->lock);
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800552 entry = zswap_entry_find_get(&tree->rbroot, offset);
Seth Jennings2b281112013-07-10 16:05:03 -0700553 if (!entry) {
554 /* entry was invalidated */
555 spin_unlock(&tree->lock);
556 return 0;
557 }
Seth Jennings2b281112013-07-10 16:05:03 -0700558 spin_unlock(&tree->lock);
559 BUG_ON(offset != entry->offset);
560
561 /* try to allocate swap cache page */
562 switch (zswap_get_swap_cache_page(swpentry, &page)) {
Weijie Yang67d13fe2013-11-12 15:08:26 -0800563 case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
Seth Jennings2b281112013-07-10 16:05:03 -0700564 ret = -ENOMEM;
565 goto fail;
566
Weijie Yang67d13fe2013-11-12 15:08:26 -0800567 case ZSWAP_SWAPCACHE_EXIST:
Seth Jennings2b281112013-07-10 16:05:03 -0700568 /* page is already in the swap cache, ignore for now */
569 page_cache_release(page);
570 ret = -EEXIST;
571 goto fail;
572
573 case ZSWAP_SWAPCACHE_NEW: /* page is locked */
574 /* decompress */
575 dlen = PAGE_SIZE;
576 src = (u8 *)zbud_map(tree->pool, entry->handle) +
577 sizeof(struct zswap_header);
578 dst = kmap_atomic(page);
579 ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src,
580 entry->length, dst, &dlen);
581 kunmap_atomic(dst);
582 zbud_unmap(tree->pool, entry->handle);
583 BUG_ON(ret);
584 BUG_ON(dlen != PAGE_SIZE);
585
586 /* page is up to date */
587 SetPageUptodate(page);
588 }
589
Weijie Yangb349acc2013-11-12 15:07:52 -0800590 /* move it to the tail of the inactive list after end_writeback */
591 SetPageReclaim(page);
592
Seth Jennings2b281112013-07-10 16:05:03 -0700593 /* start writeback */
594 __swap_writepage(page, &wbc, end_swap_bio_write);
595 page_cache_release(page);
596 zswap_written_back_pages++;
597
598 spin_lock(&tree->lock);
Seth Jennings2b281112013-07-10 16:05:03 -0700599 /* drop local reference */
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800600 zswap_entry_put(tree, entry);
Seth Jennings2b281112013-07-10 16:05:03 -0700601
602 /*
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800603 * There are two possible situations for entry here:
604 * (1) refcount is 1(normal case), entry is valid and on the tree
605 * (2) refcount is 0, entry is freed and not on the tree
606 * because invalidate happened during writeback
607 * search the tree and free the entry if find entry
608 */
609 if (entry == zswap_rb_search(&tree->rbroot, offset))
610 zswap_entry_put(tree, entry);
Seth Jennings2b281112013-07-10 16:05:03 -0700611 spin_unlock(&tree->lock);
Seth Jennings2b281112013-07-10 16:05:03 -0700612
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800613 goto end;
614
615 /*
616 * if we get here due to ZSWAP_SWAPCACHE_EXIST
617 * a load may happening concurrently
618 * it is safe and okay to not free the entry
619 * if we free the entry in the following put
620 * it it either okay to return !0
621 */
Seth Jennings2b281112013-07-10 16:05:03 -0700622fail:
623 spin_lock(&tree->lock);
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800624 zswap_entry_put(tree, entry);
Seth Jennings2b281112013-07-10 16:05:03 -0700625 spin_unlock(&tree->lock);
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800626
627end:
Seth Jennings2b281112013-07-10 16:05:03 -0700628 return ret;
629}
630
631/*********************************
632* frontswap hooks
633**********************************/
634/* attempts to compress and store an single page */
635static int zswap_frontswap_store(unsigned type, pgoff_t offset,
636 struct page *page)
637{
638 struct zswap_tree *tree = zswap_trees[type];
639 struct zswap_entry *entry, *dupentry;
640 int ret;
641 unsigned int dlen = PAGE_SIZE, len;
642 unsigned long handle;
643 char *buf;
644 u8 *src, *dst;
645 struct zswap_header *zhdr;
646
647 if (!tree) {
648 ret = -ENODEV;
649 goto reject;
650 }
651
652 /* reclaim space if needed */
653 if (zswap_is_full()) {
654 zswap_pool_limit_hit++;
655 if (zbud_reclaim_page(tree->pool, 8)) {
656 zswap_reject_reclaim_fail++;
657 ret = -ENOMEM;
658 goto reject;
659 }
660 }
661
662 /* allocate entry */
663 entry = zswap_entry_cache_alloc(GFP_KERNEL);
664 if (!entry) {
665 zswap_reject_kmemcache_fail++;
666 ret = -ENOMEM;
667 goto reject;
668 }
669
670 /* compress */
671 dst = get_cpu_var(zswap_dstmem);
672 src = kmap_atomic(page);
673 ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen);
674 kunmap_atomic(src);
675 if (ret) {
676 ret = -EINVAL;
677 goto freepage;
678 }
679
680 /* store */
681 len = dlen + sizeof(struct zswap_header);
682 ret = zbud_alloc(tree->pool, len, __GFP_NORETRY | __GFP_NOWARN,
683 &handle);
684 if (ret == -ENOSPC) {
685 zswap_reject_compress_poor++;
686 goto freepage;
687 }
688 if (ret) {
689 zswap_reject_alloc_fail++;
690 goto freepage;
691 }
692 zhdr = zbud_map(tree->pool, handle);
693 zhdr->swpentry = swp_entry(type, offset);
694 buf = (u8 *)(zhdr + 1);
695 memcpy(buf, dst, dlen);
696 zbud_unmap(tree->pool, handle);
697 put_cpu_var(zswap_dstmem);
698
699 /* populate entry */
700 entry->offset = offset;
701 entry->handle = handle;
702 entry->length = dlen;
703
704 /* map */
705 spin_lock(&tree->lock);
706 do {
707 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
708 if (ret == -EEXIST) {
709 zswap_duplicate_entry++;
710 /* remove from rbtree */
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800711 zswap_rb_erase(&tree->rbroot, dupentry);
712 zswap_entry_put(tree, dupentry);
Seth Jennings2b281112013-07-10 16:05:03 -0700713 }
714 } while (ret == -EEXIST);
715 spin_unlock(&tree->lock);
716
717 /* update stats */
718 atomic_inc(&zswap_stored_pages);
719 zswap_pool_pages = zbud_get_pool_size(tree->pool);
720
721 return 0;
722
723freepage:
724 put_cpu_var(zswap_dstmem);
725 zswap_entry_cache_free(entry);
726reject:
727 return ret;
728}
729
730/*
731 * returns 0 if the page was successfully decompressed
732 * return -1 on entry not found or error
733*/
734static int zswap_frontswap_load(unsigned type, pgoff_t offset,
735 struct page *page)
736{
737 struct zswap_tree *tree = zswap_trees[type];
738 struct zswap_entry *entry;
739 u8 *src, *dst;
740 unsigned int dlen;
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800741 int ret;
Seth Jennings2b281112013-07-10 16:05:03 -0700742
743 /* find */
744 spin_lock(&tree->lock);
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800745 entry = zswap_entry_find_get(&tree->rbroot, offset);
Seth Jennings2b281112013-07-10 16:05:03 -0700746 if (!entry) {
747 /* entry was written back */
748 spin_unlock(&tree->lock);
749 return -1;
750 }
Seth Jennings2b281112013-07-10 16:05:03 -0700751 spin_unlock(&tree->lock);
752
753 /* decompress */
754 dlen = PAGE_SIZE;
755 src = (u8 *)zbud_map(tree->pool, entry->handle) +
756 sizeof(struct zswap_header);
757 dst = kmap_atomic(page);
758 ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
759 dst, &dlen);
760 kunmap_atomic(dst);
761 zbud_unmap(tree->pool, entry->handle);
762 BUG_ON(ret);
763
764 spin_lock(&tree->lock);
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800765 zswap_entry_put(tree, entry);
Seth Jennings2b281112013-07-10 16:05:03 -0700766 spin_unlock(&tree->lock);
767
Seth Jennings2b281112013-07-10 16:05:03 -0700768 return 0;
769}
770
771/* frees an entry in zswap */
772static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
773{
774 struct zswap_tree *tree = zswap_trees[type];
775 struct zswap_entry *entry;
Seth Jennings2b281112013-07-10 16:05:03 -0700776
777 /* find */
778 spin_lock(&tree->lock);
779 entry = zswap_rb_search(&tree->rbroot, offset);
780 if (!entry) {
781 /* entry was written back */
782 spin_unlock(&tree->lock);
783 return;
784 }
785
786 /* remove from rbtree */
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800787 zswap_rb_erase(&tree->rbroot, entry);
Seth Jennings2b281112013-07-10 16:05:03 -0700788
789 /* drop the initial reference from entry creation */
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800790 zswap_entry_put(tree, entry);
Seth Jennings2b281112013-07-10 16:05:03 -0700791
792 spin_unlock(&tree->lock);
Seth Jennings2b281112013-07-10 16:05:03 -0700793}
794
795/* frees all zswap entries for the given swap type */
796static void zswap_frontswap_invalidate_area(unsigned type)
797{
798 struct zswap_tree *tree = zswap_trees[type];
Cody P Schafer0bd42132013-09-11 14:25:33 -0700799 struct zswap_entry *entry, *n;
Seth Jennings2b281112013-07-10 16:05:03 -0700800
801 if (!tree)
802 return;
803
804 /* walk the tree and free everything */
805 spin_lock(&tree->lock);
Weijie Yang0ab0abc2013-11-12 15:08:27 -0800806 rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
807 zswap_free_entry(tree, entry);
Seth Jennings2b281112013-07-10 16:05:03 -0700808 tree->rbroot = RB_ROOT;
809 spin_unlock(&tree->lock);
Weijie Yangaa9bca02013-10-16 13:46:54 -0700810
811 zbud_destroy_pool(tree->pool);
812 kfree(tree);
813 zswap_trees[type] = NULL;
Seth Jennings2b281112013-07-10 16:05:03 -0700814}
815
816static struct zbud_ops zswap_zbud_ops = {
817 .evict = zswap_writeback_entry
818};
819
820static void zswap_frontswap_init(unsigned type)
821{
822 struct zswap_tree *tree;
823
824 tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
825 if (!tree)
826 goto err;
827 tree->pool = zbud_create_pool(GFP_KERNEL, &zswap_zbud_ops);
828 if (!tree->pool)
829 goto freetree;
830 tree->rbroot = RB_ROOT;
831 spin_lock_init(&tree->lock);
832 zswap_trees[type] = tree;
833 return;
834
835freetree:
836 kfree(tree);
837err:
838 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
839}
840
841static struct frontswap_ops zswap_frontswap_ops = {
842 .store = zswap_frontswap_store,
843 .load = zswap_frontswap_load,
844 .invalidate_page = zswap_frontswap_invalidate_page,
845 .invalidate_area = zswap_frontswap_invalidate_area,
846 .init = zswap_frontswap_init
847};
848
849/*********************************
850* debugfs functions
851**********************************/
852#ifdef CONFIG_DEBUG_FS
853#include <linux/debugfs.h>
854
855static struct dentry *zswap_debugfs_root;
856
857static int __init zswap_debugfs_init(void)
858{
859 if (!debugfs_initialized())
860 return -ENODEV;
861
862 zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
863 if (!zswap_debugfs_root)
864 return -ENOMEM;
865
866 debugfs_create_u64("pool_limit_hit", S_IRUGO,
867 zswap_debugfs_root, &zswap_pool_limit_hit);
868 debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
869 zswap_debugfs_root, &zswap_reject_reclaim_fail);
870 debugfs_create_u64("reject_alloc_fail", S_IRUGO,
871 zswap_debugfs_root, &zswap_reject_alloc_fail);
872 debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
873 zswap_debugfs_root, &zswap_reject_kmemcache_fail);
874 debugfs_create_u64("reject_compress_poor", S_IRUGO,
875 zswap_debugfs_root, &zswap_reject_compress_poor);
876 debugfs_create_u64("written_back_pages", S_IRUGO,
877 zswap_debugfs_root, &zswap_written_back_pages);
878 debugfs_create_u64("duplicate_entry", S_IRUGO,
879 zswap_debugfs_root, &zswap_duplicate_entry);
880 debugfs_create_u64("pool_pages", S_IRUGO,
881 zswap_debugfs_root, &zswap_pool_pages);
882 debugfs_create_atomic_t("stored_pages", S_IRUGO,
883 zswap_debugfs_root, &zswap_stored_pages);
884
885 return 0;
886}
887
888static void __exit zswap_debugfs_exit(void)
889{
890 debugfs_remove_recursive(zswap_debugfs_root);
891}
892#else
893static int __init zswap_debugfs_init(void)
894{
895 return 0;
896}
897
898static void __exit zswap_debugfs_exit(void) { }
899#endif
900
901/*********************************
902* module init and exit
903**********************************/
904static int __init init_zswap(void)
905{
906 if (!zswap_enabled)
907 return 0;
908
909 pr_info("loading zswap\n");
910 if (zswap_entry_cache_create()) {
911 pr_err("entry cache creation failed\n");
912 goto error;
913 }
914 if (zswap_comp_init()) {
915 pr_err("compressor initialization failed\n");
916 goto compfail;
917 }
918 if (zswap_cpu_init()) {
919 pr_err("per-cpu initialization failed\n");
920 goto pcpufail;
921 }
922 frontswap_register_ops(&zswap_frontswap_ops);
923 if (zswap_debugfs_init())
924 pr_warn("debugfs initialization failed\n");
925 return 0;
926pcpufail:
927 zswap_comp_exit();
928compfail:
929 zswap_entry_cache_destory();
930error:
931 return -ENOMEM;
932}
933/* must be late so crypto has time to come up */
934late_initcall(init_zswap);
935
936MODULE_LICENSE("GPL");
937MODULE_AUTHOR("Seth Jennings <sjenning@linux.vnet.ibm.com>");
938MODULE_DESCRIPTION("Compressed cache for swap pages");