spi-topcliff-pch: add recovery processing in case wait-event timeout
[zen-stable.git] / drivers / staging / zcache / zcache-main.c
blobdce04be1af30aeaeb55f7d7292cc0a906dc6817e
1 /*
2 * zcache.c
4 * Copyright (c) 2010,2011, Dan Magenheimer, Oracle Corp.
5 * Copyright (c) 2010,2011, Nitin Gupta
7 * Zcache provides an in-kernel "host implementation" for transcendent memory
8 * and, thus indirectly, for cleancache and frontswap. Zcache includes two
9 * page-accessible memory [1] interfaces, both utilizing lzo1x compression:
10 * 1) "compression buddies" ("zbud") is used for ephemeral pages
11 * 2) xvmalloc is used for persistent pages.
12 * Xvmalloc (based on the TLSF allocator) has very low fragmentation
13 * so maximizes space efficiency, while zbud allows pairs (and potentially,
14 * in the future, more than a pair of) compressed pages to be closely linked
15 * so that reclaiming can be done via the kernel's physical-page-oriented
16 * "shrinker" interface.
18 * [1] For a definition of page-accessible memory (aka PAM), see:
19 * http://marc.info/?l=linux-mm&m=127811271605009
22 #include <linux/module.h>
23 #include <linux/cpu.h>
24 #include <linux/highmem.h>
25 #include <linux/list.h>
26 #include <linux/lzo.h>
27 #include <linux/slab.h>
28 #include <linux/spinlock.h>
29 #include <linux/types.h>
30 #include <linux/atomic.h>
31 #include <linux/math64.h>
32 #include "tmem.h"
34 #include "../zram/xvmalloc.h" /* if built in drivers/staging */
36 #if (!defined(CONFIG_CLEANCACHE) && !defined(CONFIG_FRONTSWAP))
37 #error "zcache is useless without CONFIG_CLEANCACHE or CONFIG_FRONTSWAP"
38 #endif
39 #ifdef CONFIG_CLEANCACHE
40 #include <linux/cleancache.h>
41 #endif
42 #ifdef CONFIG_FRONTSWAP
43 #include <linux/frontswap.h>
44 #endif
46 #if 0
47 /* this is more aggressive but may cause other problems? */
48 #define ZCACHE_GFP_MASK (GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN)
49 #else
50 #define ZCACHE_GFP_MASK \
51 (__GFP_FS | __GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC)
52 #endif
54 #define MAX_POOLS_PER_CLIENT 16
56 #define MAX_CLIENTS 16
57 #define LOCAL_CLIENT ((uint16_t)-1)
59 MODULE_LICENSE("GPL");
61 struct zcache_client {
62 struct tmem_pool *tmem_pools[MAX_POOLS_PER_CLIENT];
63 struct xv_pool *xvpool;
64 bool allocated;
65 atomic_t refcount;
68 static struct zcache_client zcache_host;
69 static struct zcache_client zcache_clients[MAX_CLIENTS];
71 static inline uint16_t get_client_id_from_client(struct zcache_client *cli)
73 BUG_ON(cli == NULL);
74 if (cli == &zcache_host)
75 return LOCAL_CLIENT;
76 return cli - &zcache_clients[0];
79 static inline bool is_local_client(struct zcache_client *cli)
81 return cli == &zcache_host;
84 /**********
85 * Compression buddies ("zbud") provides for packing two (or, possibly
86 * in the future, more) compressed ephemeral pages into a single "raw"
87 * (physical) page and tracking them with data structures so that
88 * the raw pages can be easily reclaimed.
90 * A zbud page ("zbpg") is an aligned page containing a list_head,
91 * a lock, and two "zbud headers". The remainder of the physical
92 * page is divided up into aligned 64-byte "chunks" which contain
93 * the compressed data for zero, one, or two zbuds. Each zbpg
94 * resides on: (1) an "unused list" if it has no zbuds; (2) a
95 * "buddied" list if it is fully populated with two zbuds; or
96 * (3) one of PAGE_SIZE/64 "unbuddied" lists indexed by how many chunks
97 * the one unbuddied zbud uses. The data inside a zbpg cannot be
98 * read or written unless the zbpg's lock is held.
101 #define ZBH_SENTINEL 0x43214321
102 #define ZBPG_SENTINEL 0xdeadbeef
104 #define ZBUD_MAX_BUDS 2
106 struct zbud_hdr {
107 uint16_t client_id;
108 uint16_t pool_id;
109 struct tmem_oid oid;
110 uint32_t index;
111 uint16_t size; /* compressed size in bytes, zero means unused */
112 DECL_SENTINEL
115 struct zbud_page {
116 struct list_head bud_list;
117 spinlock_t lock;
118 struct zbud_hdr buddy[ZBUD_MAX_BUDS];
119 DECL_SENTINEL
120 /* followed by NUM_CHUNK aligned CHUNK_SIZE-byte chunks */
123 #define CHUNK_SHIFT 6
124 #define CHUNK_SIZE (1 << CHUNK_SHIFT)
125 #define CHUNK_MASK (~(CHUNK_SIZE-1))
126 #define NCHUNKS (((PAGE_SIZE - sizeof(struct zbud_page)) & \
127 CHUNK_MASK) >> CHUNK_SHIFT)
128 #define MAX_CHUNK (NCHUNKS-1)
130 static struct {
131 struct list_head list;
132 unsigned count;
133 } zbud_unbuddied[NCHUNKS];
134 /* list N contains pages with N chunks USED and NCHUNKS-N unused */
135 /* element 0 is never used but optimizing that isn't worth it */
136 static unsigned long zbud_cumul_chunk_counts[NCHUNKS];
138 struct list_head zbud_buddied_list;
139 static unsigned long zcache_zbud_buddied_count;
141 /* protects the buddied list and all unbuddied lists */
142 static DEFINE_SPINLOCK(zbud_budlists_spinlock);
144 static LIST_HEAD(zbpg_unused_list);
145 static unsigned long zcache_zbpg_unused_list_count;
147 /* protects the unused page list */
148 static DEFINE_SPINLOCK(zbpg_unused_list_spinlock);
150 static atomic_t zcache_zbud_curr_raw_pages;
151 static atomic_t zcache_zbud_curr_zpages;
152 static unsigned long zcache_zbud_curr_zbytes;
153 static unsigned long zcache_zbud_cumul_zpages;
154 static unsigned long zcache_zbud_cumul_zbytes;
155 static unsigned long zcache_compress_poor;
156 static unsigned long zcache_mean_compress_poor;
158 /* forward references */
159 static void *zcache_get_free_page(void);
160 static void zcache_free_page(void *p);
163 * zbud helper functions
166 static inline unsigned zbud_max_buddy_size(void)
168 return MAX_CHUNK << CHUNK_SHIFT;
171 static inline unsigned zbud_size_to_chunks(unsigned size)
173 BUG_ON(size == 0 || size > zbud_max_buddy_size());
174 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
177 static inline int zbud_budnum(struct zbud_hdr *zh)
179 unsigned offset = (unsigned long)zh & (PAGE_SIZE - 1);
180 struct zbud_page *zbpg = NULL;
181 unsigned budnum = -1U;
182 int i;
184 for (i = 0; i < ZBUD_MAX_BUDS; i++)
185 if (offset == offsetof(typeof(*zbpg), buddy[i])) {
186 budnum = i;
187 break;
189 BUG_ON(budnum == -1U);
190 return budnum;
193 static char *zbud_data(struct zbud_hdr *zh, unsigned size)
195 struct zbud_page *zbpg;
196 char *p;
197 unsigned budnum;
199 ASSERT_SENTINEL(zh, ZBH);
200 budnum = zbud_budnum(zh);
201 BUG_ON(size == 0 || size > zbud_max_buddy_size());
202 zbpg = container_of(zh, struct zbud_page, buddy[budnum]);
203 ASSERT_SPINLOCK(&zbpg->lock);
204 p = (char *)zbpg;
205 if (budnum == 0)
206 p += ((sizeof(struct zbud_page) + CHUNK_SIZE - 1) &
207 CHUNK_MASK);
208 else if (budnum == 1)
209 p += PAGE_SIZE - ((size + CHUNK_SIZE - 1) & CHUNK_MASK);
210 return p;
214 * zbud raw page management
217 static struct zbud_page *zbud_alloc_raw_page(void)
219 struct zbud_page *zbpg = NULL;
220 struct zbud_hdr *zh0, *zh1;
221 bool recycled = 0;
223 /* if any pages on the zbpg list, use one */
224 spin_lock(&zbpg_unused_list_spinlock);
225 if (!list_empty(&zbpg_unused_list)) {
226 zbpg = list_first_entry(&zbpg_unused_list,
227 struct zbud_page, bud_list);
228 list_del_init(&zbpg->bud_list);
229 zcache_zbpg_unused_list_count--;
230 recycled = 1;
232 spin_unlock(&zbpg_unused_list_spinlock);
233 if (zbpg == NULL)
234 /* none on zbpg list, try to get a kernel page */
235 zbpg = zcache_get_free_page();
236 if (likely(zbpg != NULL)) {
237 INIT_LIST_HEAD(&zbpg->bud_list);
238 zh0 = &zbpg->buddy[0]; zh1 = &zbpg->buddy[1];
239 spin_lock_init(&zbpg->lock);
240 if (recycled) {
241 ASSERT_INVERTED_SENTINEL(zbpg, ZBPG);
242 SET_SENTINEL(zbpg, ZBPG);
243 BUG_ON(zh0->size != 0 || tmem_oid_valid(&zh0->oid));
244 BUG_ON(zh1->size != 0 || tmem_oid_valid(&zh1->oid));
245 } else {
246 atomic_inc(&zcache_zbud_curr_raw_pages);
247 INIT_LIST_HEAD(&zbpg->bud_list);
248 SET_SENTINEL(zbpg, ZBPG);
249 zh0->size = 0; zh1->size = 0;
250 tmem_oid_set_invalid(&zh0->oid);
251 tmem_oid_set_invalid(&zh1->oid);
254 return zbpg;
257 static void zbud_free_raw_page(struct zbud_page *zbpg)
259 struct zbud_hdr *zh0 = &zbpg->buddy[0], *zh1 = &zbpg->buddy[1];
261 ASSERT_SENTINEL(zbpg, ZBPG);
262 BUG_ON(!list_empty(&zbpg->bud_list));
263 ASSERT_SPINLOCK(&zbpg->lock);
264 BUG_ON(zh0->size != 0 || tmem_oid_valid(&zh0->oid));
265 BUG_ON(zh1->size != 0 || tmem_oid_valid(&zh1->oid));
266 INVERT_SENTINEL(zbpg, ZBPG);
267 spin_unlock(&zbpg->lock);
268 spin_lock(&zbpg_unused_list_spinlock);
269 list_add(&zbpg->bud_list, &zbpg_unused_list);
270 zcache_zbpg_unused_list_count++;
271 spin_unlock(&zbpg_unused_list_spinlock);
275 * core zbud handling routines
278 static unsigned zbud_free(struct zbud_hdr *zh)
280 unsigned size;
282 ASSERT_SENTINEL(zh, ZBH);
283 BUG_ON(!tmem_oid_valid(&zh->oid));
284 size = zh->size;
285 BUG_ON(zh->size == 0 || zh->size > zbud_max_buddy_size());
286 zh->size = 0;
287 tmem_oid_set_invalid(&zh->oid);
288 INVERT_SENTINEL(zh, ZBH);
289 zcache_zbud_curr_zbytes -= size;
290 atomic_dec(&zcache_zbud_curr_zpages);
291 return size;
294 static void zbud_free_and_delist(struct zbud_hdr *zh)
296 unsigned chunks;
297 struct zbud_hdr *zh_other;
298 unsigned budnum = zbud_budnum(zh), size;
299 struct zbud_page *zbpg =
300 container_of(zh, struct zbud_page, buddy[budnum]);
302 spin_lock(&zbud_budlists_spinlock);
303 spin_lock(&zbpg->lock);
304 if (list_empty(&zbpg->bud_list)) {
305 /* ignore zombie page... see zbud_evict_pages() */
306 spin_unlock(&zbpg->lock);
307 spin_unlock(&zbud_budlists_spinlock);
308 return;
310 size = zbud_free(zh);
311 ASSERT_SPINLOCK(&zbpg->lock);
312 zh_other = &zbpg->buddy[(budnum == 0) ? 1 : 0];
313 if (zh_other->size == 0) { /* was unbuddied: unlist and free */
314 chunks = zbud_size_to_chunks(size) ;
315 BUG_ON(list_empty(&zbud_unbuddied[chunks].list));
316 list_del_init(&zbpg->bud_list);
317 zbud_unbuddied[chunks].count--;
318 spin_unlock(&zbud_budlists_spinlock);
319 zbud_free_raw_page(zbpg);
320 } else { /* was buddied: move remaining buddy to unbuddied list */
321 chunks = zbud_size_to_chunks(zh_other->size) ;
322 list_del_init(&zbpg->bud_list);
323 zcache_zbud_buddied_count--;
324 list_add_tail(&zbpg->bud_list, &zbud_unbuddied[chunks].list);
325 zbud_unbuddied[chunks].count++;
326 spin_unlock(&zbud_budlists_spinlock);
327 spin_unlock(&zbpg->lock);
331 static struct zbud_hdr *zbud_create(uint16_t client_id, uint16_t pool_id,
332 struct tmem_oid *oid,
333 uint32_t index, struct page *page,
334 void *cdata, unsigned size)
336 struct zbud_hdr *zh0, *zh1, *zh = NULL;
337 struct zbud_page *zbpg = NULL, *ztmp;
338 unsigned nchunks;
339 char *to;
340 int i, found_good_buddy = 0;
342 nchunks = zbud_size_to_chunks(size) ;
343 for (i = MAX_CHUNK - nchunks + 1; i > 0; i--) {
344 spin_lock(&zbud_budlists_spinlock);
345 if (!list_empty(&zbud_unbuddied[i].list)) {
346 list_for_each_entry_safe(zbpg, ztmp,
347 &zbud_unbuddied[i].list, bud_list) {
348 if (spin_trylock(&zbpg->lock)) {
349 found_good_buddy = i;
350 goto found_unbuddied;
354 spin_unlock(&zbud_budlists_spinlock);
356 /* didn't find a good buddy, try allocating a new page */
357 zbpg = zbud_alloc_raw_page();
358 if (unlikely(zbpg == NULL))
359 goto out;
360 /* ok, have a page, now compress the data before taking locks */
361 spin_lock(&zbud_budlists_spinlock);
362 spin_lock(&zbpg->lock);
363 list_add_tail(&zbpg->bud_list, &zbud_unbuddied[nchunks].list);
364 zbud_unbuddied[nchunks].count++;
365 zh = &zbpg->buddy[0];
366 goto init_zh;
368 found_unbuddied:
369 ASSERT_SPINLOCK(&zbpg->lock);
370 zh0 = &zbpg->buddy[0]; zh1 = &zbpg->buddy[1];
371 BUG_ON(!((zh0->size == 0) ^ (zh1->size == 0)));
372 if (zh0->size != 0) { /* buddy0 in use, buddy1 is vacant */
373 ASSERT_SENTINEL(zh0, ZBH);
374 zh = zh1;
375 } else if (zh1->size != 0) { /* buddy1 in use, buddy0 is vacant */
376 ASSERT_SENTINEL(zh1, ZBH);
377 zh = zh0;
378 } else
379 BUG();
380 list_del_init(&zbpg->bud_list);
381 zbud_unbuddied[found_good_buddy].count--;
382 list_add_tail(&zbpg->bud_list, &zbud_buddied_list);
383 zcache_zbud_buddied_count++;
385 init_zh:
386 SET_SENTINEL(zh, ZBH);
387 zh->size = size;
388 zh->index = index;
389 zh->oid = *oid;
390 zh->pool_id = pool_id;
391 zh->client_id = client_id;
392 to = zbud_data(zh, size);
393 memcpy(to, cdata, size);
394 spin_unlock(&zbpg->lock);
395 spin_unlock(&zbud_budlists_spinlock);
397 zbud_cumul_chunk_counts[nchunks]++;
398 atomic_inc(&zcache_zbud_curr_zpages);
399 zcache_zbud_cumul_zpages++;
400 zcache_zbud_curr_zbytes += size;
401 zcache_zbud_cumul_zbytes += size;
402 out:
403 return zh;
406 static int zbud_decompress(struct page *page, struct zbud_hdr *zh)
408 struct zbud_page *zbpg;
409 unsigned budnum = zbud_budnum(zh);
410 size_t out_len = PAGE_SIZE;
411 char *to_va, *from_va;
412 unsigned size;
413 int ret = 0;
415 zbpg = container_of(zh, struct zbud_page, buddy[budnum]);
416 spin_lock(&zbpg->lock);
417 if (list_empty(&zbpg->bud_list)) {
418 /* ignore zombie page... see zbud_evict_pages() */
419 ret = -EINVAL;
420 goto out;
422 ASSERT_SENTINEL(zh, ZBH);
423 BUG_ON(zh->size == 0 || zh->size > zbud_max_buddy_size());
424 to_va = kmap_atomic(page, KM_USER0);
425 size = zh->size;
426 from_va = zbud_data(zh, size);
427 ret = lzo1x_decompress_safe(from_va, size, to_va, &out_len);
428 BUG_ON(ret != LZO_E_OK);
429 BUG_ON(out_len != PAGE_SIZE);
430 kunmap_atomic(to_va, KM_USER0);
431 out:
432 spin_unlock(&zbpg->lock);
433 return ret;
437 * The following routines handle shrinking of ephemeral pages by evicting
438 * pages "least valuable" first.
441 static unsigned long zcache_evicted_raw_pages;
442 static unsigned long zcache_evicted_buddied_pages;
443 static unsigned long zcache_evicted_unbuddied_pages;
445 static struct tmem_pool *zcache_get_pool_by_id(uint16_t cli_id,
446 uint16_t poolid);
447 static void zcache_put_pool(struct tmem_pool *pool);
450 * Flush and free all zbuds in a zbpg, then free the pageframe
452 static void zbud_evict_zbpg(struct zbud_page *zbpg)
454 struct zbud_hdr *zh;
455 int i, j;
456 uint32_t pool_id[ZBUD_MAX_BUDS], client_id[ZBUD_MAX_BUDS];
457 uint32_t index[ZBUD_MAX_BUDS];
458 struct tmem_oid oid[ZBUD_MAX_BUDS];
459 struct tmem_pool *pool;
461 ASSERT_SPINLOCK(&zbpg->lock);
462 BUG_ON(!list_empty(&zbpg->bud_list));
463 for (i = 0, j = 0; i < ZBUD_MAX_BUDS; i++) {
464 zh = &zbpg->buddy[i];
465 if (zh->size) {
466 client_id[j] = zh->client_id;
467 pool_id[j] = zh->pool_id;
468 oid[j] = zh->oid;
469 index[j] = zh->index;
470 j++;
471 zbud_free(zh);
474 spin_unlock(&zbpg->lock);
475 for (i = 0; i < j; i++) {
476 pool = zcache_get_pool_by_id(client_id[i], pool_id[i]);
477 if (pool != NULL) {
478 tmem_flush_page(pool, &oid[i], index[i]);
479 zcache_put_pool(pool);
482 ASSERT_SENTINEL(zbpg, ZBPG);
483 spin_lock(&zbpg->lock);
484 zbud_free_raw_page(zbpg);
488 * Free nr pages. This code is funky because we want to hold the locks
489 * protecting various lists for as short a time as possible, and in some
490 * circumstances the list may change asynchronously when the list lock is
491 * not held. In some cases we also trylock not only to avoid waiting on a
492 * page in use by another cpu, but also to avoid potential deadlock due to
493 * lock inversion.
495 static void zbud_evict_pages(int nr)
497 struct zbud_page *zbpg;
498 int i;
500 /* first try freeing any pages on unused list */
501 retry_unused_list:
502 spin_lock_bh(&zbpg_unused_list_spinlock);
503 if (!list_empty(&zbpg_unused_list)) {
504 /* can't walk list here, since it may change when unlocked */
505 zbpg = list_first_entry(&zbpg_unused_list,
506 struct zbud_page, bud_list);
507 list_del_init(&zbpg->bud_list);
508 zcache_zbpg_unused_list_count--;
509 atomic_dec(&zcache_zbud_curr_raw_pages);
510 spin_unlock_bh(&zbpg_unused_list_spinlock);
511 zcache_free_page(zbpg);
512 zcache_evicted_raw_pages++;
513 if (--nr <= 0)
514 goto out;
515 goto retry_unused_list;
517 spin_unlock_bh(&zbpg_unused_list_spinlock);
519 /* now try freeing unbuddied pages, starting with least space avail */
520 for (i = 0; i < MAX_CHUNK; i++) {
521 retry_unbud_list_i:
522 spin_lock_bh(&zbud_budlists_spinlock);
523 if (list_empty(&zbud_unbuddied[i].list)) {
524 spin_unlock_bh(&zbud_budlists_spinlock);
525 continue;
527 list_for_each_entry(zbpg, &zbud_unbuddied[i].list, bud_list) {
528 if (unlikely(!spin_trylock(&zbpg->lock)))
529 continue;
530 list_del_init(&zbpg->bud_list);
531 zbud_unbuddied[i].count--;
532 spin_unlock(&zbud_budlists_spinlock);
533 zcache_evicted_unbuddied_pages++;
534 /* want budlists unlocked when doing zbpg eviction */
535 zbud_evict_zbpg(zbpg);
536 local_bh_enable();
537 if (--nr <= 0)
538 goto out;
539 goto retry_unbud_list_i;
541 spin_unlock_bh(&zbud_budlists_spinlock);
544 /* as a last resort, free buddied pages */
545 retry_bud_list:
546 spin_lock_bh(&zbud_budlists_spinlock);
547 if (list_empty(&zbud_buddied_list)) {
548 spin_unlock_bh(&zbud_budlists_spinlock);
549 goto out;
551 list_for_each_entry(zbpg, &zbud_buddied_list, bud_list) {
552 if (unlikely(!spin_trylock(&zbpg->lock)))
553 continue;
554 list_del_init(&zbpg->bud_list);
555 zcache_zbud_buddied_count--;
556 spin_unlock(&zbud_budlists_spinlock);
557 zcache_evicted_buddied_pages++;
558 /* want budlists unlocked when doing zbpg eviction */
559 zbud_evict_zbpg(zbpg);
560 local_bh_enable();
561 if (--nr <= 0)
562 goto out;
563 goto retry_bud_list;
565 spin_unlock_bh(&zbud_budlists_spinlock);
566 out:
567 return;
570 static void zbud_init(void)
572 int i;
574 INIT_LIST_HEAD(&zbud_buddied_list);
575 zcache_zbud_buddied_count = 0;
576 for (i = 0; i < NCHUNKS; i++) {
577 INIT_LIST_HEAD(&zbud_unbuddied[i].list);
578 zbud_unbuddied[i].count = 0;
582 #ifdef CONFIG_SYSFS
584 * These sysfs routines show a nice distribution of how many zbpg's are
585 * currently (and have ever been placed) in each unbuddied list. It's fun
586 * to watch but can probably go away before final merge.
588 static int zbud_show_unbuddied_list_counts(char *buf)
590 int i;
591 char *p = buf;
593 for (i = 0; i < NCHUNKS; i++)
594 p += sprintf(p, "%u ", zbud_unbuddied[i].count);
595 return p - buf;
598 static int zbud_show_cumul_chunk_counts(char *buf)
600 unsigned long i, chunks = 0, total_chunks = 0, sum_total_chunks = 0;
601 unsigned long total_chunks_lte_21 = 0, total_chunks_lte_32 = 0;
602 unsigned long total_chunks_lte_42 = 0;
603 char *p = buf;
605 for (i = 0; i < NCHUNKS; i++) {
606 p += sprintf(p, "%lu ", zbud_cumul_chunk_counts[i]);
607 chunks += zbud_cumul_chunk_counts[i];
608 total_chunks += zbud_cumul_chunk_counts[i];
609 sum_total_chunks += i * zbud_cumul_chunk_counts[i];
610 if (i == 21)
611 total_chunks_lte_21 = total_chunks;
612 if (i == 32)
613 total_chunks_lte_32 = total_chunks;
614 if (i == 42)
615 total_chunks_lte_42 = total_chunks;
617 p += sprintf(p, "<=21:%lu <=32:%lu <=42:%lu, mean:%lu\n",
618 total_chunks_lte_21, total_chunks_lte_32, total_chunks_lte_42,
619 chunks == 0 ? 0 : sum_total_chunks / chunks);
620 return p - buf;
622 #endif
624 /**********
625 * This "zv" PAM implementation combines the TLSF-based xvMalloc
626 * with lzo1x compression to maximize the amount of data that can
627 * be packed into a physical page.
629 * Zv represents a PAM page with the index and object (plus a "size" value
630 * necessary for decompression) immediately preceding the compressed data.
633 #define ZVH_SENTINEL 0x43214321
635 struct zv_hdr {
636 uint32_t pool_id;
637 struct tmem_oid oid;
638 uint32_t index;
639 DECL_SENTINEL
642 /* rudimentary policy limits */
643 /* total number of persistent pages may not exceed this percentage */
644 static unsigned int zv_page_count_policy_percent = 75;
646 * byte count defining poor compression; pages with greater zsize will be
647 * rejected
649 static unsigned int zv_max_zsize = (PAGE_SIZE / 8) * 7;
651 * byte count defining poor *mean* compression; pages with greater zsize
652 * will be rejected until sufficient better-compressed pages are accepted
653 * driving the mean below this threshold
655 static unsigned int zv_max_mean_zsize = (PAGE_SIZE / 8) * 5;
657 static atomic_t zv_curr_dist_counts[NCHUNKS];
658 static atomic_t zv_cumul_dist_counts[NCHUNKS];
660 static struct zv_hdr *zv_create(struct xv_pool *xvpool, uint32_t pool_id,
661 struct tmem_oid *oid, uint32_t index,
662 void *cdata, unsigned clen)
664 struct page *page;
665 struct zv_hdr *zv = NULL;
666 uint32_t offset;
667 int alloc_size = clen + sizeof(struct zv_hdr);
668 int chunks = (alloc_size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT;
669 int ret;
671 BUG_ON(!irqs_disabled());
672 BUG_ON(chunks >= NCHUNKS);
673 ret = xv_malloc(xvpool, alloc_size,
674 &page, &offset, ZCACHE_GFP_MASK);
675 if (unlikely(ret))
676 goto out;
677 atomic_inc(&zv_curr_dist_counts[chunks]);
678 atomic_inc(&zv_cumul_dist_counts[chunks]);
679 zv = kmap_atomic(page, KM_USER0) + offset;
680 zv->index = index;
681 zv->oid = *oid;
682 zv->pool_id = pool_id;
683 SET_SENTINEL(zv, ZVH);
684 memcpy((char *)zv + sizeof(struct zv_hdr), cdata, clen);
685 kunmap_atomic(zv, KM_USER0);
686 out:
687 return zv;
690 static void zv_free(struct xv_pool *xvpool, struct zv_hdr *zv)
692 unsigned long flags;
693 struct page *page;
694 uint32_t offset;
695 uint16_t size = xv_get_object_size(zv);
696 int chunks = (size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT;
698 ASSERT_SENTINEL(zv, ZVH);
699 BUG_ON(chunks >= NCHUNKS);
700 atomic_dec(&zv_curr_dist_counts[chunks]);
701 size -= sizeof(*zv);
702 BUG_ON(size == 0);
703 INVERT_SENTINEL(zv, ZVH);
704 page = virt_to_page(zv);
705 offset = (unsigned long)zv & ~PAGE_MASK;
706 local_irq_save(flags);
707 xv_free(xvpool, page, offset);
708 local_irq_restore(flags);
711 static void zv_decompress(struct page *page, struct zv_hdr *zv)
713 size_t clen = PAGE_SIZE;
714 char *to_va;
715 unsigned size;
716 int ret;
718 ASSERT_SENTINEL(zv, ZVH);
719 size = xv_get_object_size(zv) - sizeof(*zv);
720 BUG_ON(size == 0);
721 to_va = kmap_atomic(page, KM_USER0);
722 ret = lzo1x_decompress_safe((char *)zv + sizeof(*zv),
723 size, to_va, &clen);
724 kunmap_atomic(to_va, KM_USER0);
725 BUG_ON(ret != LZO_E_OK);
726 BUG_ON(clen != PAGE_SIZE);
729 #ifdef CONFIG_SYSFS
731 * show a distribution of compression stats for zv pages.
734 static int zv_curr_dist_counts_show(char *buf)
736 unsigned long i, n, chunks = 0, sum_total_chunks = 0;
737 char *p = buf;
739 for (i = 0; i < NCHUNKS; i++) {
740 n = atomic_read(&zv_curr_dist_counts[i]);
741 p += sprintf(p, "%lu ", n);
742 chunks += n;
743 sum_total_chunks += i * n;
745 p += sprintf(p, "mean:%lu\n",
746 chunks == 0 ? 0 : sum_total_chunks / chunks);
747 return p - buf;
750 static int zv_cumul_dist_counts_show(char *buf)
752 unsigned long i, n, chunks = 0, sum_total_chunks = 0;
753 char *p = buf;
755 for (i = 0; i < NCHUNKS; i++) {
756 n = atomic_read(&zv_cumul_dist_counts[i]);
757 p += sprintf(p, "%lu ", n);
758 chunks += n;
759 sum_total_chunks += i * n;
761 p += sprintf(p, "mean:%lu\n",
762 chunks == 0 ? 0 : sum_total_chunks / chunks);
763 return p - buf;
767 * setting zv_max_zsize via sysfs causes all persistent (e.g. swap)
768 * pages that don't compress to less than this value (including metadata
769 * overhead) to be rejected. We don't allow the value to get too close
770 * to PAGE_SIZE.
772 static ssize_t zv_max_zsize_show(struct kobject *kobj,
773 struct kobj_attribute *attr,
774 char *buf)
776 return sprintf(buf, "%u\n", zv_max_zsize);
779 static ssize_t zv_max_zsize_store(struct kobject *kobj,
780 struct kobj_attribute *attr,
781 const char *buf, size_t count)
783 unsigned long val;
784 int err;
786 if (!capable(CAP_SYS_ADMIN))
787 return -EPERM;
789 err = kstrtoul(buf, 10, &val);
790 if (err || (val == 0) || (val > (PAGE_SIZE / 8) * 7))
791 return -EINVAL;
792 zv_max_zsize = val;
793 return count;
797 * setting zv_max_mean_zsize via sysfs causes all persistent (e.g. swap)
798 * pages that don't compress to less than this value (including metadata
799 * overhead) to be rejected UNLESS the mean compression is also smaller
800 * than this value. In other words, we are load-balancing-by-zsize the
801 * accepted pages. Again, we don't allow the value to get too close
802 * to PAGE_SIZE.
804 static ssize_t zv_max_mean_zsize_show(struct kobject *kobj,
805 struct kobj_attribute *attr,
806 char *buf)
808 return sprintf(buf, "%u\n", zv_max_mean_zsize);
811 static ssize_t zv_max_mean_zsize_store(struct kobject *kobj,
812 struct kobj_attribute *attr,
813 const char *buf, size_t count)
815 unsigned long val;
816 int err;
818 if (!capable(CAP_SYS_ADMIN))
819 return -EPERM;
821 err = kstrtoul(buf, 10, &val);
822 if (err || (val == 0) || (val > (PAGE_SIZE / 8) * 7))
823 return -EINVAL;
824 zv_max_mean_zsize = val;
825 return count;
829 * setting zv_page_count_policy_percent via sysfs sets an upper bound of
830 * persistent (e.g. swap) pages that will be retained according to:
831 * (zv_page_count_policy_percent * totalram_pages) / 100)
832 * when that limit is reached, further puts will be rejected (until
833 * some pages have been flushed). Note that, due to compression,
834 * this number may exceed 100; it defaults to 75 and we set an
835 * arbitary limit of 150. A poor choice will almost certainly result
836 * in OOM's, so this value should only be changed prudently.
838 static ssize_t zv_page_count_policy_percent_show(struct kobject *kobj,
839 struct kobj_attribute *attr,
840 char *buf)
842 return sprintf(buf, "%u\n", zv_page_count_policy_percent);
845 static ssize_t zv_page_count_policy_percent_store(struct kobject *kobj,
846 struct kobj_attribute *attr,
847 const char *buf, size_t count)
849 unsigned long val;
850 int err;
852 if (!capable(CAP_SYS_ADMIN))
853 return -EPERM;
855 err = kstrtoul(buf, 10, &val);
856 if (err || (val == 0) || (val > 150))
857 return -EINVAL;
858 zv_page_count_policy_percent = val;
859 return count;
862 static struct kobj_attribute zcache_zv_max_zsize_attr = {
863 .attr = { .name = "zv_max_zsize", .mode = 0644 },
864 .show = zv_max_zsize_show,
865 .store = zv_max_zsize_store,
868 static struct kobj_attribute zcache_zv_max_mean_zsize_attr = {
869 .attr = { .name = "zv_max_mean_zsize", .mode = 0644 },
870 .show = zv_max_mean_zsize_show,
871 .store = zv_max_mean_zsize_store,
874 static struct kobj_attribute zcache_zv_page_count_policy_percent_attr = {
875 .attr = { .name = "zv_page_count_policy_percent",
876 .mode = 0644 },
877 .show = zv_page_count_policy_percent_show,
878 .store = zv_page_count_policy_percent_store,
880 #endif
883 * zcache core code starts here
886 /* useful stats not collected by cleancache or frontswap */
887 static unsigned long zcache_flush_total;
888 static unsigned long zcache_flush_found;
889 static unsigned long zcache_flobj_total;
890 static unsigned long zcache_flobj_found;
891 static unsigned long zcache_failed_eph_puts;
892 static unsigned long zcache_failed_pers_puts;
895 * Tmem operations assume the poolid implies the invoking client.
896 * Zcache only has one client (the kernel itself): LOCAL_CLIENT.
897 * RAMster has each client numbered by cluster node, and a KVM version
898 * of zcache would have one client per guest and each client might
899 * have a poolid==N.
901 static struct tmem_pool *zcache_get_pool_by_id(uint16_t cli_id, uint16_t poolid)
903 struct tmem_pool *pool = NULL;
904 struct zcache_client *cli = NULL;
906 if (cli_id == LOCAL_CLIENT)
907 cli = &zcache_host;
908 else {
909 if (cli_id >= MAX_CLIENTS)
910 goto out;
911 cli = &zcache_clients[cli_id];
912 if (cli == NULL)
913 goto out;
914 atomic_inc(&cli->refcount);
916 if (poolid < MAX_POOLS_PER_CLIENT) {
917 pool = cli->tmem_pools[poolid];
918 if (pool != NULL)
919 atomic_inc(&pool->refcount);
921 out:
922 return pool;
925 static void zcache_put_pool(struct tmem_pool *pool)
927 struct zcache_client *cli = NULL;
929 if (pool == NULL)
930 BUG();
931 cli = pool->client;
932 atomic_dec(&pool->refcount);
933 atomic_dec(&cli->refcount);
936 int zcache_new_client(uint16_t cli_id)
938 struct zcache_client *cli = NULL;
939 int ret = -1;
941 if (cli_id == LOCAL_CLIENT)
942 cli = &zcache_host;
943 else if ((unsigned int)cli_id < MAX_CLIENTS)
944 cli = &zcache_clients[cli_id];
945 if (cli == NULL)
946 goto out;
947 if (cli->allocated)
948 goto out;
949 cli->allocated = 1;
950 #ifdef CONFIG_FRONTSWAP
951 cli->xvpool = xv_create_pool();
952 if (cli->xvpool == NULL)
953 goto out;
954 #endif
955 ret = 0;
956 out:
957 return ret;
960 /* counters for debugging */
961 static unsigned long zcache_failed_get_free_pages;
962 static unsigned long zcache_failed_alloc;
963 static unsigned long zcache_put_to_flush;
966 * for now, used named slabs so can easily track usage; later can
967 * either just use kmalloc, or perhaps add a slab-like allocator
968 * to more carefully manage total memory utilization
970 static struct kmem_cache *zcache_objnode_cache;
971 static struct kmem_cache *zcache_obj_cache;
972 static atomic_t zcache_curr_obj_count = ATOMIC_INIT(0);
973 static unsigned long zcache_curr_obj_count_max;
974 static atomic_t zcache_curr_objnode_count = ATOMIC_INIT(0);
975 static unsigned long zcache_curr_objnode_count_max;
978 * to avoid memory allocation recursion (e.g. due to direct reclaim), we
979 * preload all necessary data structures so the hostops callbacks never
980 * actually do a malloc
982 struct zcache_preload {
983 void *page;
984 struct tmem_obj *obj;
985 int nr;
986 struct tmem_objnode *objnodes[OBJNODE_TREE_MAX_PATH];
988 static DEFINE_PER_CPU(struct zcache_preload, zcache_preloads) = { 0, };
990 static int zcache_do_preload(struct tmem_pool *pool)
992 struct zcache_preload *kp;
993 struct tmem_objnode *objnode;
994 struct tmem_obj *obj;
995 void *page;
996 int ret = -ENOMEM;
998 if (unlikely(zcache_objnode_cache == NULL))
999 goto out;
1000 if (unlikely(zcache_obj_cache == NULL))
1001 goto out;
1002 preempt_disable();
1003 kp = &__get_cpu_var(zcache_preloads);
1004 while (kp->nr < ARRAY_SIZE(kp->objnodes)) {
1005 preempt_enable_no_resched();
1006 objnode = kmem_cache_alloc(zcache_objnode_cache,
1007 ZCACHE_GFP_MASK);
1008 if (unlikely(objnode == NULL)) {
1009 zcache_failed_alloc++;
1010 goto out;
1012 preempt_disable();
1013 kp = &__get_cpu_var(zcache_preloads);
1014 if (kp->nr < ARRAY_SIZE(kp->objnodes))
1015 kp->objnodes[kp->nr++] = objnode;
1016 else
1017 kmem_cache_free(zcache_objnode_cache, objnode);
1019 preempt_enable_no_resched();
1020 obj = kmem_cache_alloc(zcache_obj_cache, ZCACHE_GFP_MASK);
1021 if (unlikely(obj == NULL)) {
1022 zcache_failed_alloc++;
1023 goto out;
1025 page = (void *)__get_free_page(ZCACHE_GFP_MASK);
1026 if (unlikely(page == NULL)) {
1027 zcache_failed_get_free_pages++;
1028 kmem_cache_free(zcache_obj_cache, obj);
1029 goto out;
1031 preempt_disable();
1032 kp = &__get_cpu_var(zcache_preloads);
1033 if (kp->obj == NULL)
1034 kp->obj = obj;
1035 else
1036 kmem_cache_free(zcache_obj_cache, obj);
1037 if (kp->page == NULL)
1038 kp->page = page;
1039 else
1040 free_page((unsigned long)page);
1041 ret = 0;
1042 out:
1043 return ret;
1046 static void *zcache_get_free_page(void)
1048 struct zcache_preload *kp;
1049 void *page;
1051 kp = &__get_cpu_var(zcache_preloads);
1052 page = kp->page;
1053 BUG_ON(page == NULL);
1054 kp->page = NULL;
1055 return page;
1058 static void zcache_free_page(void *p)
1060 free_page((unsigned long)p);
1064 * zcache implementation for tmem host ops
1067 static struct tmem_objnode *zcache_objnode_alloc(struct tmem_pool *pool)
1069 struct tmem_objnode *objnode = NULL;
1070 unsigned long count;
1071 struct zcache_preload *kp;
1073 kp = &__get_cpu_var(zcache_preloads);
1074 if (kp->nr <= 0)
1075 goto out;
1076 objnode = kp->objnodes[kp->nr - 1];
1077 BUG_ON(objnode == NULL);
1078 kp->objnodes[kp->nr - 1] = NULL;
1079 kp->nr--;
1080 count = atomic_inc_return(&zcache_curr_objnode_count);
1081 if (count > zcache_curr_objnode_count_max)
1082 zcache_curr_objnode_count_max = count;
1083 out:
1084 return objnode;
1087 static void zcache_objnode_free(struct tmem_objnode *objnode,
1088 struct tmem_pool *pool)
1090 atomic_dec(&zcache_curr_objnode_count);
1091 BUG_ON(atomic_read(&zcache_curr_objnode_count) < 0);
1092 kmem_cache_free(zcache_objnode_cache, objnode);
1095 static struct tmem_obj *zcache_obj_alloc(struct tmem_pool *pool)
1097 struct tmem_obj *obj = NULL;
1098 unsigned long count;
1099 struct zcache_preload *kp;
1101 kp = &__get_cpu_var(zcache_preloads);
1102 obj = kp->obj;
1103 BUG_ON(obj == NULL);
1104 kp->obj = NULL;
1105 count = atomic_inc_return(&zcache_curr_obj_count);
1106 if (count > zcache_curr_obj_count_max)
1107 zcache_curr_obj_count_max = count;
1108 return obj;
1111 static void zcache_obj_free(struct tmem_obj *obj, struct tmem_pool *pool)
1113 atomic_dec(&zcache_curr_obj_count);
1114 BUG_ON(atomic_read(&zcache_curr_obj_count) < 0);
1115 kmem_cache_free(zcache_obj_cache, obj);
1118 static struct tmem_hostops zcache_hostops = {
1119 .obj_alloc = zcache_obj_alloc,
1120 .obj_free = zcache_obj_free,
1121 .objnode_alloc = zcache_objnode_alloc,
1122 .objnode_free = zcache_objnode_free,
1126 * zcache implementations for PAM page descriptor ops
1129 static atomic_t zcache_curr_eph_pampd_count = ATOMIC_INIT(0);
1130 static unsigned long zcache_curr_eph_pampd_count_max;
1131 static atomic_t zcache_curr_pers_pampd_count = ATOMIC_INIT(0);
1132 static unsigned long zcache_curr_pers_pampd_count_max;
1134 /* forward reference */
1135 static int zcache_compress(struct page *from, void **out_va, size_t *out_len);
1137 static void *zcache_pampd_create(char *data, size_t size, bool raw, int eph,
1138 struct tmem_pool *pool, struct tmem_oid *oid,
1139 uint32_t index)
1141 void *pampd = NULL, *cdata;
1142 size_t clen;
1143 int ret;
1144 unsigned long count;
1145 struct page *page = (struct page *)(data);
1146 struct zcache_client *cli = pool->client;
1147 uint16_t client_id = get_client_id_from_client(cli);
1148 unsigned long zv_mean_zsize;
1149 unsigned long curr_pers_pampd_count;
1150 u64 total_zsize;
1152 if (eph) {
1153 ret = zcache_compress(page, &cdata, &clen);
1154 if (ret == 0)
1155 goto out;
1156 if (clen == 0 || clen > zbud_max_buddy_size()) {
1157 zcache_compress_poor++;
1158 goto out;
1160 pampd = (void *)zbud_create(client_id, pool->pool_id, oid,
1161 index, page, cdata, clen);
1162 if (pampd != NULL) {
1163 count = atomic_inc_return(&zcache_curr_eph_pampd_count);
1164 if (count > zcache_curr_eph_pampd_count_max)
1165 zcache_curr_eph_pampd_count_max = count;
1167 } else {
1168 curr_pers_pampd_count =
1169 atomic_read(&zcache_curr_pers_pampd_count);
1170 if (curr_pers_pampd_count >
1171 (zv_page_count_policy_percent * totalram_pages) / 100)
1172 goto out;
1173 ret = zcache_compress(page, &cdata, &clen);
1174 if (ret == 0)
1175 goto out;
1176 /* reject if compression is too poor */
1177 if (clen > zv_max_zsize) {
1178 zcache_compress_poor++;
1179 goto out;
1181 /* reject if mean compression is too poor */
1182 if ((clen > zv_max_mean_zsize) && (curr_pers_pampd_count > 0)) {
1183 total_zsize = xv_get_total_size_bytes(cli->xvpool);
1184 zv_mean_zsize = div_u64(total_zsize,
1185 curr_pers_pampd_count);
1186 if (zv_mean_zsize > zv_max_mean_zsize) {
1187 zcache_mean_compress_poor++;
1188 goto out;
1191 pampd = (void *)zv_create(cli->xvpool, pool->pool_id,
1192 oid, index, cdata, clen);
1193 if (pampd == NULL)
1194 goto out;
1195 count = atomic_inc_return(&zcache_curr_pers_pampd_count);
1196 if (count > zcache_curr_pers_pampd_count_max)
1197 zcache_curr_pers_pampd_count_max = count;
1199 out:
1200 return pampd;
1204 * fill the pageframe corresponding to the struct page with the data
1205 * from the passed pampd
1207 static int zcache_pampd_get_data(char *data, size_t *bufsize, bool raw,
1208 void *pampd, struct tmem_pool *pool,
1209 struct tmem_oid *oid, uint32_t index)
1211 int ret = 0;
1213 BUG_ON(is_ephemeral(pool));
1214 zv_decompress((struct page *)(data), pampd);
1215 return ret;
1219 * fill the pageframe corresponding to the struct page with the data
1220 * from the passed pampd
1222 static int zcache_pampd_get_data_and_free(char *data, size_t *bufsize, bool raw,
1223 void *pampd, struct tmem_pool *pool,
1224 struct tmem_oid *oid, uint32_t index)
1226 int ret = 0;
1228 BUG_ON(!is_ephemeral(pool));
1229 zbud_decompress((struct page *)(data), pampd);
1230 zbud_free_and_delist((struct zbud_hdr *)pampd);
1231 atomic_dec(&zcache_curr_eph_pampd_count);
1232 return ret;
1236 * free the pampd and remove it from any zcache lists
1237 * pampd must no longer be pointed to from any tmem data structures!
1239 static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
1240 struct tmem_oid *oid, uint32_t index)
1242 struct zcache_client *cli = pool->client;
1244 if (is_ephemeral(pool)) {
1245 zbud_free_and_delist((struct zbud_hdr *)pampd);
1246 atomic_dec(&zcache_curr_eph_pampd_count);
1247 BUG_ON(atomic_read(&zcache_curr_eph_pampd_count) < 0);
1248 } else {
1249 zv_free(cli->xvpool, (struct zv_hdr *)pampd);
1250 atomic_dec(&zcache_curr_pers_pampd_count);
1251 BUG_ON(atomic_read(&zcache_curr_pers_pampd_count) < 0);
1255 static void zcache_pampd_free_obj(struct tmem_pool *pool, struct tmem_obj *obj)
1259 static void zcache_pampd_new_obj(struct tmem_obj *obj)
1263 static int zcache_pampd_replace_in_obj(void *pampd, struct tmem_obj *obj)
1265 return -1;
1268 static bool zcache_pampd_is_remote(void *pampd)
1270 return 0;
1273 static struct tmem_pamops zcache_pamops = {
1274 .create = zcache_pampd_create,
1275 .get_data = zcache_pampd_get_data,
1276 .get_data_and_free = zcache_pampd_get_data_and_free,
1277 .free = zcache_pampd_free,
1278 .free_obj = zcache_pampd_free_obj,
1279 .new_obj = zcache_pampd_new_obj,
1280 .replace_in_obj = zcache_pampd_replace_in_obj,
1281 .is_remote = zcache_pampd_is_remote,
1285 * zcache compression/decompression and related per-cpu stuff
1288 #define LZO_WORKMEM_BYTES LZO1X_1_MEM_COMPRESS
1289 #define LZO_DSTMEM_PAGE_ORDER 1
1290 static DEFINE_PER_CPU(unsigned char *, zcache_workmem);
1291 static DEFINE_PER_CPU(unsigned char *, zcache_dstmem);
1293 static int zcache_compress(struct page *from, void **out_va, size_t *out_len)
1295 int ret = 0;
1296 unsigned char *dmem = __get_cpu_var(zcache_dstmem);
1297 unsigned char *wmem = __get_cpu_var(zcache_workmem);
1298 char *from_va;
1300 BUG_ON(!irqs_disabled());
1301 if (unlikely(dmem == NULL || wmem == NULL))
1302 goto out; /* no buffer, so can't compress */
1303 from_va = kmap_atomic(from, KM_USER0);
1304 mb();
1305 ret = lzo1x_1_compress(from_va, PAGE_SIZE, dmem, out_len, wmem);
1306 BUG_ON(ret != LZO_E_OK);
1307 *out_va = dmem;
1308 kunmap_atomic(from_va, KM_USER0);
1309 ret = 1;
1310 out:
1311 return ret;
1315 static int zcache_cpu_notifier(struct notifier_block *nb,
1316 unsigned long action, void *pcpu)
1318 int cpu = (long)pcpu;
1319 struct zcache_preload *kp;
1321 switch (action) {
1322 case CPU_UP_PREPARE:
1323 per_cpu(zcache_dstmem, cpu) = (void *)__get_free_pages(
1324 GFP_KERNEL | __GFP_REPEAT,
1325 LZO_DSTMEM_PAGE_ORDER),
1326 per_cpu(zcache_workmem, cpu) =
1327 kzalloc(LZO1X_MEM_COMPRESS,
1328 GFP_KERNEL | __GFP_REPEAT);
1329 break;
1330 case CPU_DEAD:
1331 case CPU_UP_CANCELED:
1332 free_pages((unsigned long)per_cpu(zcache_dstmem, cpu),
1333 LZO_DSTMEM_PAGE_ORDER);
1334 per_cpu(zcache_dstmem, cpu) = NULL;
1335 kfree(per_cpu(zcache_workmem, cpu));
1336 per_cpu(zcache_workmem, cpu) = NULL;
1337 kp = &per_cpu(zcache_preloads, cpu);
1338 while (kp->nr) {
1339 kmem_cache_free(zcache_objnode_cache,
1340 kp->objnodes[kp->nr - 1]);
1341 kp->objnodes[kp->nr - 1] = NULL;
1342 kp->nr--;
1344 if (kp->obj) {
1345 kmem_cache_free(zcache_obj_cache, kp->obj);
1346 kp->obj = NULL;
1348 if (kp->page) {
1349 free_page((unsigned long)kp->page);
1350 kp->page = NULL;
1352 break;
1353 default:
1354 break;
1356 return NOTIFY_OK;
1359 static struct notifier_block zcache_cpu_notifier_block = {
1360 .notifier_call = zcache_cpu_notifier
1363 #ifdef CONFIG_SYSFS
1364 #define ZCACHE_SYSFS_RO(_name) \
1365 static ssize_t zcache_##_name##_show(struct kobject *kobj, \
1366 struct kobj_attribute *attr, char *buf) \
1368 return sprintf(buf, "%lu\n", zcache_##_name); \
1370 static struct kobj_attribute zcache_##_name##_attr = { \
1371 .attr = { .name = __stringify(_name), .mode = 0444 }, \
1372 .show = zcache_##_name##_show, \
1375 #define ZCACHE_SYSFS_RO_ATOMIC(_name) \
1376 static ssize_t zcache_##_name##_show(struct kobject *kobj, \
1377 struct kobj_attribute *attr, char *buf) \
1379 return sprintf(buf, "%d\n", atomic_read(&zcache_##_name)); \
1381 static struct kobj_attribute zcache_##_name##_attr = { \
1382 .attr = { .name = __stringify(_name), .mode = 0444 }, \
1383 .show = zcache_##_name##_show, \
1386 #define ZCACHE_SYSFS_RO_CUSTOM(_name, _func) \
1387 static ssize_t zcache_##_name##_show(struct kobject *kobj, \
1388 struct kobj_attribute *attr, char *buf) \
1390 return _func(buf); \
1392 static struct kobj_attribute zcache_##_name##_attr = { \
1393 .attr = { .name = __stringify(_name), .mode = 0444 }, \
1394 .show = zcache_##_name##_show, \
1397 ZCACHE_SYSFS_RO(curr_obj_count_max);
1398 ZCACHE_SYSFS_RO(curr_objnode_count_max);
1399 ZCACHE_SYSFS_RO(flush_total);
1400 ZCACHE_SYSFS_RO(flush_found);
1401 ZCACHE_SYSFS_RO(flobj_total);
1402 ZCACHE_SYSFS_RO(flobj_found);
1403 ZCACHE_SYSFS_RO(failed_eph_puts);
1404 ZCACHE_SYSFS_RO(failed_pers_puts);
1405 ZCACHE_SYSFS_RO(zbud_curr_zbytes);
1406 ZCACHE_SYSFS_RO(zbud_cumul_zpages);
1407 ZCACHE_SYSFS_RO(zbud_cumul_zbytes);
1408 ZCACHE_SYSFS_RO(zbud_buddied_count);
1409 ZCACHE_SYSFS_RO(zbpg_unused_list_count);
1410 ZCACHE_SYSFS_RO(evicted_raw_pages);
1411 ZCACHE_SYSFS_RO(evicted_unbuddied_pages);
1412 ZCACHE_SYSFS_RO(evicted_buddied_pages);
1413 ZCACHE_SYSFS_RO(failed_get_free_pages);
1414 ZCACHE_SYSFS_RO(failed_alloc);
1415 ZCACHE_SYSFS_RO(put_to_flush);
1416 ZCACHE_SYSFS_RO(compress_poor);
1417 ZCACHE_SYSFS_RO(mean_compress_poor);
1418 ZCACHE_SYSFS_RO_ATOMIC(zbud_curr_raw_pages);
1419 ZCACHE_SYSFS_RO_ATOMIC(zbud_curr_zpages);
1420 ZCACHE_SYSFS_RO_ATOMIC(curr_obj_count);
1421 ZCACHE_SYSFS_RO_ATOMIC(curr_objnode_count);
1422 ZCACHE_SYSFS_RO_CUSTOM(zbud_unbuddied_list_counts,
1423 zbud_show_unbuddied_list_counts);
1424 ZCACHE_SYSFS_RO_CUSTOM(zbud_cumul_chunk_counts,
1425 zbud_show_cumul_chunk_counts);
1426 ZCACHE_SYSFS_RO_CUSTOM(zv_curr_dist_counts,
1427 zv_curr_dist_counts_show);
1428 ZCACHE_SYSFS_RO_CUSTOM(zv_cumul_dist_counts,
1429 zv_cumul_dist_counts_show);
1431 static struct attribute *zcache_attrs[] = {
1432 &zcache_curr_obj_count_attr.attr,
1433 &zcache_curr_obj_count_max_attr.attr,
1434 &zcache_curr_objnode_count_attr.attr,
1435 &zcache_curr_objnode_count_max_attr.attr,
1436 &zcache_flush_total_attr.attr,
1437 &zcache_flobj_total_attr.attr,
1438 &zcache_flush_found_attr.attr,
1439 &zcache_flobj_found_attr.attr,
1440 &zcache_failed_eph_puts_attr.attr,
1441 &zcache_failed_pers_puts_attr.attr,
1442 &zcache_compress_poor_attr.attr,
1443 &zcache_mean_compress_poor_attr.attr,
1444 &zcache_zbud_curr_raw_pages_attr.attr,
1445 &zcache_zbud_curr_zpages_attr.attr,
1446 &zcache_zbud_curr_zbytes_attr.attr,
1447 &zcache_zbud_cumul_zpages_attr.attr,
1448 &zcache_zbud_cumul_zbytes_attr.attr,
1449 &zcache_zbud_buddied_count_attr.attr,
1450 &zcache_zbpg_unused_list_count_attr.attr,
1451 &zcache_evicted_raw_pages_attr.attr,
1452 &zcache_evicted_unbuddied_pages_attr.attr,
1453 &zcache_evicted_buddied_pages_attr.attr,
1454 &zcache_failed_get_free_pages_attr.attr,
1455 &zcache_failed_alloc_attr.attr,
1456 &zcache_put_to_flush_attr.attr,
1457 &zcache_zbud_unbuddied_list_counts_attr.attr,
1458 &zcache_zbud_cumul_chunk_counts_attr.attr,
1459 &zcache_zv_curr_dist_counts_attr.attr,
1460 &zcache_zv_cumul_dist_counts_attr.attr,
1461 &zcache_zv_max_zsize_attr.attr,
1462 &zcache_zv_max_mean_zsize_attr.attr,
1463 &zcache_zv_page_count_policy_percent_attr.attr,
1464 NULL,
1467 static struct attribute_group zcache_attr_group = {
1468 .attrs = zcache_attrs,
1469 .name = "zcache",
1472 #endif /* CONFIG_SYSFS */
1474 * When zcache is disabled ("frozen"), pools can be created and destroyed,
1475 * but all puts (and thus all other operations that require memory allocation)
1476 * must fail. If zcache is unfrozen, accepts puts, then frozen again,
1477 * data consistency requires all puts while frozen to be converted into
1478 * flushes.
1480 static bool zcache_freeze;
1483 * zcache shrinker interface (only useful for ephemeral pages, so zbud only)
1485 static int shrink_zcache_memory(struct shrinker *shrink,
1486 struct shrink_control *sc)
1488 int ret = -1;
1489 int nr = sc->nr_to_scan;
1490 gfp_t gfp_mask = sc->gfp_mask;
1492 if (nr >= 0) {
1493 if (!(gfp_mask & __GFP_FS))
1494 /* does this case really need to be skipped? */
1495 goto out;
1496 zbud_evict_pages(nr);
1498 ret = (int)atomic_read(&zcache_zbud_curr_raw_pages);
1499 out:
1500 return ret;
1503 static struct shrinker zcache_shrinker = {
1504 .shrink = shrink_zcache_memory,
1505 .seeks = DEFAULT_SEEKS,
1509 * zcache shims between cleancache/frontswap ops and tmem
1512 static int zcache_put_page(int cli_id, int pool_id, struct tmem_oid *oidp,
1513 uint32_t index, struct page *page)
1515 struct tmem_pool *pool;
1516 int ret = -1;
1518 BUG_ON(!irqs_disabled());
1519 pool = zcache_get_pool_by_id(cli_id, pool_id);
1520 if (unlikely(pool == NULL))
1521 goto out;
1522 if (!zcache_freeze && zcache_do_preload(pool) == 0) {
1523 /* preload does preempt_disable on success */
1524 ret = tmem_put(pool, oidp, index, (char *)(page),
1525 PAGE_SIZE, 0, is_ephemeral(pool));
1526 if (ret < 0) {
1527 if (is_ephemeral(pool))
1528 zcache_failed_eph_puts++;
1529 else
1530 zcache_failed_pers_puts++;
1532 zcache_put_pool(pool);
1533 preempt_enable_no_resched();
1534 } else {
1535 zcache_put_to_flush++;
1536 if (atomic_read(&pool->obj_count) > 0)
1537 /* the put fails whether the flush succeeds or not */
1538 (void)tmem_flush_page(pool, oidp, index);
1539 zcache_put_pool(pool);
1541 out:
1542 return ret;
1545 static int zcache_get_page(int cli_id, int pool_id, struct tmem_oid *oidp,
1546 uint32_t index, struct page *page)
1548 struct tmem_pool *pool;
1549 int ret = -1;
1550 unsigned long flags;
1551 size_t size = PAGE_SIZE;
1553 local_irq_save(flags);
1554 pool = zcache_get_pool_by_id(cli_id, pool_id);
1555 if (likely(pool != NULL)) {
1556 if (atomic_read(&pool->obj_count) > 0)
1557 ret = tmem_get(pool, oidp, index, (char *)(page),
1558 &size, 0, is_ephemeral(pool));
1559 zcache_put_pool(pool);
1561 local_irq_restore(flags);
1562 return ret;
1565 static int zcache_flush_page(int cli_id, int pool_id,
1566 struct tmem_oid *oidp, uint32_t index)
1568 struct tmem_pool *pool;
1569 int ret = -1;
1570 unsigned long flags;
1572 local_irq_save(flags);
1573 zcache_flush_total++;
1574 pool = zcache_get_pool_by_id(cli_id, pool_id);
1575 if (likely(pool != NULL)) {
1576 if (atomic_read(&pool->obj_count) > 0)
1577 ret = tmem_flush_page(pool, oidp, index);
1578 zcache_put_pool(pool);
1580 if (ret >= 0)
1581 zcache_flush_found++;
1582 local_irq_restore(flags);
1583 return ret;
1586 static int zcache_flush_object(int cli_id, int pool_id,
1587 struct tmem_oid *oidp)
1589 struct tmem_pool *pool;
1590 int ret = -1;
1591 unsigned long flags;
1593 local_irq_save(flags);
1594 zcache_flobj_total++;
1595 pool = zcache_get_pool_by_id(cli_id, pool_id);
1596 if (likely(pool != NULL)) {
1597 if (atomic_read(&pool->obj_count) > 0)
1598 ret = tmem_flush_object(pool, oidp);
1599 zcache_put_pool(pool);
1601 if (ret >= 0)
1602 zcache_flobj_found++;
1603 local_irq_restore(flags);
1604 return ret;
1607 static int zcache_destroy_pool(int cli_id, int pool_id)
1609 struct tmem_pool *pool = NULL;
1610 struct zcache_client *cli = NULL;
1611 int ret = -1;
1613 if (pool_id < 0)
1614 goto out;
1615 if (cli_id == LOCAL_CLIENT)
1616 cli = &zcache_host;
1617 else if ((unsigned int)cli_id < MAX_CLIENTS)
1618 cli = &zcache_clients[cli_id];
1619 if (cli == NULL)
1620 goto out;
1621 atomic_inc(&cli->refcount);
1622 pool = cli->tmem_pools[pool_id];
1623 if (pool == NULL)
1624 goto out;
1625 cli->tmem_pools[pool_id] = NULL;
1626 /* wait for pool activity on other cpus to quiesce */
1627 while (atomic_read(&pool->refcount) != 0)
1629 atomic_dec(&cli->refcount);
1630 local_bh_disable();
1631 ret = tmem_destroy_pool(pool);
1632 local_bh_enable();
1633 kfree(pool);
1634 pr_info("zcache: destroyed pool id=%d, cli_id=%d\n",
1635 pool_id, cli_id);
1636 out:
1637 return ret;
1640 static int zcache_new_pool(uint16_t cli_id, uint32_t flags)
1642 int poolid = -1;
1643 struct tmem_pool *pool;
1644 struct zcache_client *cli = NULL;
1646 if (cli_id == LOCAL_CLIENT)
1647 cli = &zcache_host;
1648 else if ((unsigned int)cli_id < MAX_CLIENTS)
1649 cli = &zcache_clients[cli_id];
1650 if (cli == NULL)
1651 goto out;
1652 atomic_inc(&cli->refcount);
1653 pool = kmalloc(sizeof(struct tmem_pool), GFP_ATOMIC);
1654 if (pool == NULL) {
1655 pr_info("zcache: pool creation failed: out of memory\n");
1656 goto out;
1659 for (poolid = 0; poolid < MAX_POOLS_PER_CLIENT; poolid++)
1660 if (cli->tmem_pools[poolid] == NULL)
1661 break;
1662 if (poolid >= MAX_POOLS_PER_CLIENT) {
1663 pr_info("zcache: pool creation failed: max exceeded\n");
1664 kfree(pool);
1665 poolid = -1;
1666 goto out;
1668 atomic_set(&pool->refcount, 0);
1669 pool->client = cli;
1670 pool->pool_id = poolid;
1671 tmem_new_pool(pool, flags);
1672 cli->tmem_pools[poolid] = pool;
1673 pr_info("zcache: created %s tmem pool, id=%d, client=%d\n",
1674 flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
1675 poolid, cli_id);
1676 out:
1677 if (cli != NULL)
1678 atomic_dec(&cli->refcount);
1679 return poolid;
1682 /**********
1683 * Two kernel functionalities currently can be layered on top of tmem.
1684 * These are "cleancache" which is used as a second-chance cache for clean
1685 * page cache pages; and "frontswap" which is used for swap pages
1686 * to avoid writes to disk. A generic "shim" is provided here for each
1687 * to translate in-kernel semantics to zcache semantics.
1690 #ifdef CONFIG_CLEANCACHE
1691 static void zcache_cleancache_put_page(int pool_id,
1692 struct cleancache_filekey key,
1693 pgoff_t index, struct page *page)
1695 u32 ind = (u32) index;
1696 struct tmem_oid oid = *(struct tmem_oid *)&key;
1698 if (likely(ind == index))
1699 (void)zcache_put_page(LOCAL_CLIENT, pool_id, &oid, index, page);
1702 static int zcache_cleancache_get_page(int pool_id,
1703 struct cleancache_filekey key,
1704 pgoff_t index, struct page *page)
1706 u32 ind = (u32) index;
1707 struct tmem_oid oid = *(struct tmem_oid *)&key;
1708 int ret = -1;
1710 if (likely(ind == index))
1711 ret = zcache_get_page(LOCAL_CLIENT, pool_id, &oid, index, page);
1712 return ret;
1715 static void zcache_cleancache_flush_page(int pool_id,
1716 struct cleancache_filekey key,
1717 pgoff_t index)
1719 u32 ind = (u32) index;
1720 struct tmem_oid oid = *(struct tmem_oid *)&key;
1722 if (likely(ind == index))
1723 (void)zcache_flush_page(LOCAL_CLIENT, pool_id, &oid, ind);
1726 static void zcache_cleancache_flush_inode(int pool_id,
1727 struct cleancache_filekey key)
1729 struct tmem_oid oid = *(struct tmem_oid *)&key;
1731 (void)zcache_flush_object(LOCAL_CLIENT, pool_id, &oid);
1734 static void zcache_cleancache_flush_fs(int pool_id)
1736 if (pool_id >= 0)
1737 (void)zcache_destroy_pool(LOCAL_CLIENT, pool_id);
1740 static int zcache_cleancache_init_fs(size_t pagesize)
1742 BUG_ON(sizeof(struct cleancache_filekey) !=
1743 sizeof(struct tmem_oid));
1744 BUG_ON(pagesize != PAGE_SIZE);
1745 return zcache_new_pool(LOCAL_CLIENT, 0);
1748 static int zcache_cleancache_init_shared_fs(char *uuid, size_t pagesize)
1750 /* shared pools are unsupported and map to private */
1751 BUG_ON(sizeof(struct cleancache_filekey) !=
1752 sizeof(struct tmem_oid));
1753 BUG_ON(pagesize != PAGE_SIZE);
1754 return zcache_new_pool(LOCAL_CLIENT, 0);
1757 static struct cleancache_ops zcache_cleancache_ops = {
1758 .put_page = zcache_cleancache_put_page,
1759 .get_page = zcache_cleancache_get_page,
1760 .flush_page = zcache_cleancache_flush_page,
1761 .flush_inode = zcache_cleancache_flush_inode,
1762 .flush_fs = zcache_cleancache_flush_fs,
1763 .init_shared_fs = zcache_cleancache_init_shared_fs,
1764 .init_fs = zcache_cleancache_init_fs
1767 struct cleancache_ops zcache_cleancache_register_ops(void)
1769 struct cleancache_ops old_ops =
1770 cleancache_register_ops(&zcache_cleancache_ops);
1772 return old_ops;
1774 #endif
1776 #ifdef CONFIG_FRONTSWAP
1777 /* a single tmem poolid is used for all frontswap "types" (swapfiles) */
1778 static int zcache_frontswap_poolid = -1;
1781 * Swizzling increases objects per swaptype, increasing tmem concurrency
1782 * for heavy swaploads. Later, larger nr_cpus -> larger SWIZ_BITS
1783 * Setting SWIZ_BITS to 27 basically reconstructs the swap entry from
1784 * frontswap_get_page(), but has side-effects. Hence using 8.
1786 #define SWIZ_BITS 8
1787 #define SWIZ_MASK ((1 << SWIZ_BITS) - 1)
1788 #define _oswiz(_type, _ind) ((_type << SWIZ_BITS) | (_ind & SWIZ_MASK))
1789 #define iswiz(_ind) (_ind >> SWIZ_BITS)
1791 static inline struct tmem_oid oswiz(unsigned type, u32 ind)
1793 struct tmem_oid oid = { .oid = { 0 } };
1794 oid.oid[0] = _oswiz(type, ind);
1795 return oid;
1798 static int zcache_frontswap_put_page(unsigned type, pgoff_t offset,
1799 struct page *page)
1801 u64 ind64 = (u64)offset;
1802 u32 ind = (u32)offset;
1803 struct tmem_oid oid = oswiz(type, ind);
1804 int ret = -1;
1805 unsigned long flags;
1807 BUG_ON(!PageLocked(page));
1808 if (likely(ind64 == ind)) {
1809 local_irq_save(flags);
1810 ret = zcache_put_page(LOCAL_CLIENT, zcache_frontswap_poolid,
1811 &oid, iswiz(ind), page);
1812 local_irq_restore(flags);
1814 return ret;
1817 /* returns 0 if the page was successfully gotten from frontswap, -1 if
1818 * was not present (should never happen!) */
1819 static int zcache_frontswap_get_page(unsigned type, pgoff_t offset,
1820 struct page *page)
1822 u64 ind64 = (u64)offset;
1823 u32 ind = (u32)offset;
1824 struct tmem_oid oid = oswiz(type, ind);
1825 int ret = -1;
1827 BUG_ON(!PageLocked(page));
1828 if (likely(ind64 == ind))
1829 ret = zcache_get_page(LOCAL_CLIENT, zcache_frontswap_poolid,
1830 &oid, iswiz(ind), page);
1831 return ret;
1834 /* flush a single page from frontswap */
1835 static void zcache_frontswap_flush_page(unsigned type, pgoff_t offset)
1837 u64 ind64 = (u64)offset;
1838 u32 ind = (u32)offset;
1839 struct tmem_oid oid = oswiz(type, ind);
1841 if (likely(ind64 == ind))
1842 (void)zcache_flush_page(LOCAL_CLIENT, zcache_frontswap_poolid,
1843 &oid, iswiz(ind));
1846 /* flush all pages from the passed swaptype */
1847 static void zcache_frontswap_flush_area(unsigned type)
1849 struct tmem_oid oid;
1850 int ind;
1852 for (ind = SWIZ_MASK; ind >= 0; ind--) {
1853 oid = oswiz(type, ind);
1854 (void)zcache_flush_object(LOCAL_CLIENT,
1855 zcache_frontswap_poolid, &oid);
1859 static void zcache_frontswap_init(unsigned ignored)
1861 /* a single tmem poolid is used for all frontswap "types" (swapfiles) */
1862 if (zcache_frontswap_poolid < 0)
1863 zcache_frontswap_poolid =
1864 zcache_new_pool(LOCAL_CLIENT, TMEM_POOL_PERSIST);
1867 static struct frontswap_ops zcache_frontswap_ops = {
1868 .put_page = zcache_frontswap_put_page,
1869 .get_page = zcache_frontswap_get_page,
1870 .flush_page = zcache_frontswap_flush_page,
1871 .flush_area = zcache_frontswap_flush_area,
1872 .init = zcache_frontswap_init
1875 struct frontswap_ops zcache_frontswap_register_ops(void)
1877 struct frontswap_ops old_ops =
1878 frontswap_register_ops(&zcache_frontswap_ops);
1880 return old_ops;
1882 #endif
1885 * zcache initialization
1886 * NOTE FOR NOW zcache MUST BE PROVIDED AS A KERNEL BOOT PARAMETER OR
1887 * NOTHING HAPPENS!
1890 static int zcache_enabled;
1892 static int __init enable_zcache(char *s)
1894 zcache_enabled = 1;
1895 return 1;
1897 __setup("zcache", enable_zcache);
1899 /* allow independent dynamic disabling of cleancache and frontswap */
1901 static int use_cleancache = 1;
1903 static int __init no_cleancache(char *s)
1905 use_cleancache = 0;
1906 return 1;
1909 __setup("nocleancache", no_cleancache);
1911 static int use_frontswap = 1;
1913 static int __init no_frontswap(char *s)
1915 use_frontswap = 0;
1916 return 1;
1919 __setup("nofrontswap", no_frontswap);
1921 static int __init zcache_init(void)
1923 int ret = 0;
1925 #ifdef CONFIG_SYSFS
1926 ret = sysfs_create_group(mm_kobj, &zcache_attr_group);
1927 if (ret) {
1928 pr_err("zcache: can't create sysfs\n");
1929 goto out;
1931 #endif /* CONFIG_SYSFS */
1932 #if defined(CONFIG_CLEANCACHE) || defined(CONFIG_FRONTSWAP)
1933 if (zcache_enabled) {
1934 unsigned int cpu;
1936 tmem_register_hostops(&zcache_hostops);
1937 tmem_register_pamops(&zcache_pamops);
1938 ret = register_cpu_notifier(&zcache_cpu_notifier_block);
1939 if (ret) {
1940 pr_err("zcache: can't register cpu notifier\n");
1941 goto out;
1943 for_each_online_cpu(cpu) {
1944 void *pcpu = (void *)(long)cpu;
1945 zcache_cpu_notifier(&zcache_cpu_notifier_block,
1946 CPU_UP_PREPARE, pcpu);
1949 zcache_objnode_cache = kmem_cache_create("zcache_objnode",
1950 sizeof(struct tmem_objnode), 0, 0, NULL);
1951 zcache_obj_cache = kmem_cache_create("zcache_obj",
1952 sizeof(struct tmem_obj), 0, 0, NULL);
1953 ret = zcache_new_client(LOCAL_CLIENT);
1954 if (ret) {
1955 pr_err("zcache: can't create client\n");
1956 goto out;
1958 #endif
1959 #ifdef CONFIG_CLEANCACHE
1960 if (zcache_enabled && use_cleancache) {
1961 struct cleancache_ops old_ops;
1963 zbud_init();
1964 register_shrinker(&zcache_shrinker);
1965 old_ops = zcache_cleancache_register_ops();
1966 pr_info("zcache: cleancache enabled using kernel "
1967 "transcendent memory and compression buddies\n");
1968 if (old_ops.init_fs != NULL)
1969 pr_warning("zcache: cleancache_ops overridden");
1971 #endif
1972 #ifdef CONFIG_FRONTSWAP
1973 if (zcache_enabled && use_frontswap) {
1974 struct frontswap_ops old_ops;
1976 old_ops = zcache_frontswap_register_ops();
1977 pr_info("zcache: frontswap enabled using kernel "
1978 "transcendent memory and xvmalloc\n");
1979 if (old_ops.init != NULL)
1980 pr_warning("zcache: frontswap_ops overridden");
1982 #endif
1983 out:
1984 return ret;
1987 module_init(zcache_init)