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09c434b8 1// SPDX-License-Identifier: GPL-2.0-only
9a001fc1
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2/*
3 * z3fold.c
4 *
5 * Author: Vitaly Wool <vitaly.wool@konsulko.com>
6 * Copyright (C) 2016, Sony Mobile Communications Inc.
7 *
8 * This implementation is based on zbud written by Seth Jennings.
9 *
10 * z3fold is an special purpose allocator for storing compressed pages. It
11 * can store up to three compressed pages per page which improves the
12 * compression ratio of zbud while retaining its main concepts (e. g. always
13 * storing an integral number of objects per page) and simplicity.
14 * It still has simple and deterministic reclaim properties that make it
15 * preferable to a higher density approach (with no requirement on integral
16 * number of object per page) when reclaim is used.
17 *
18 * As in zbud, pages are divided into "chunks". The size of the chunks is
19 * fixed at compile time and is determined by NCHUNKS_ORDER below.
20 *
21 * z3fold doesn't export any API and is meant to be used via zpool API.
22 */
23
24#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
25
26#include <linux/atomic.h>
d30561c5 27#include <linux/sched.h>
1f862989 28#include <linux/cpumask.h>
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29#include <linux/list.h>
30#include <linux/mm.h>
31#include <linux/module.h>
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32#include <linux/page-flags.h>
33#include <linux/migrate.h>
34#include <linux/node.h>
35#include <linux/compaction.h>
d30561c5 36#include <linux/percpu.h>
1f862989 37#include <linux/mount.h>
ea8157ab 38#include <linux/pseudo_fs.h>
1f862989 39#include <linux/fs.h>
9a001fc1 40#include <linux/preempt.h>
d30561c5 41#include <linux/workqueue.h>
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42#include <linux/slab.h>
43#include <linux/spinlock.h>
44#include <linux/zpool.h>
ea8157ab 45#include <linux/magic.h>
af4798a5 46#include <linux/kmemleak.h>
9a001fc1 47
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48/*
49 * NCHUNKS_ORDER determines the internal allocation granularity, effectively
50 * adjusting internal fragmentation. It also determines the number of
51 * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
52 * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
53 * in the beginning of an allocated page are occupied by z3fold header, so
54 * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
55 * which shows the max number of free chunks in z3fold page, also there will
56 * be 63, or 62, respectively, freelists per pool.
57 */
58#define NCHUNKS_ORDER 6
59
60#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
61#define CHUNK_SIZE (1 << CHUNK_SHIFT)
62#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
63#define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
64#define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
e3c0db4f 65#define NCHUNKS (TOTAL_CHUNKS - ZHDR_CHUNKS)
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66
67#define BUDDY_MASK (0x3)
68#define BUDDY_SHIFT 2
69#define SLOTS_ALIGN (0x40)
70
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71/*****************
72 * Structures
73*****************/
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74struct z3fold_pool;
75struct z3fold_ops {
76 int (*evict)(struct z3fold_pool *pool, unsigned long handle);
77};
78
79enum buddy {
80 HEADLESS = 0,
81 FIRST,
82 MIDDLE,
83 LAST,
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84 BUDDIES_MAX = LAST
85};
86
87struct z3fold_buddy_slots {
88 /*
89 * we are using BUDDY_MASK in handle_to_buddy etc. so there should
90 * be enough slots to hold all possible variants
91 */
92 unsigned long slot[BUDDY_MASK + 1];
fc548865 93 unsigned long pool; /* back link */
4a3ac931 94 rwlock_t lock;
ede93213 95};
7c2b8baa 96#define HANDLE_FLAG_MASK (0x03)
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97
98/*
d30561c5 99 * struct z3fold_header - z3fold page metadata occupying first chunks of each
ede93213 100 * z3fold page, except for HEADLESS pages
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101 * @buddy: links the z3fold page into the relevant list in the
102 * pool
2f1e5e4d 103 * @page_lock: per-page lock
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104 * @refcount: reference count for the z3fold page
105 * @work: work_struct for page layout optimization
7c2b8baa 106 * @slots: pointer to the structure holding buddy slots
bb9a374d 107 * @pool: pointer to the containing pool
d30561c5 108 * @cpu: CPU which this page "belongs" to
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109 * @first_chunks: the size of the first buddy in chunks, 0 if free
110 * @middle_chunks: the size of the middle buddy in chunks, 0 if free
111 * @last_chunks: the size of the last buddy in chunks, 0 if free
112 * @first_num: the starting number (for the first handle)
1f862989 113 * @mapped_count: the number of objects currently mapped
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114 */
115struct z3fold_header {
116 struct list_head buddy;
2f1e5e4d 117 spinlock_t page_lock;
5a27aa82 118 struct kref refcount;
d30561c5 119 struct work_struct work;
7c2b8baa 120 struct z3fold_buddy_slots *slots;
bb9a374d 121 struct z3fold_pool *pool;
d30561c5 122 short cpu;
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123 unsigned short first_chunks;
124 unsigned short middle_chunks;
125 unsigned short last_chunks;
126 unsigned short start_middle;
127 unsigned short first_num:2;
1f862989 128 unsigned short mapped_count:2;
4a3ac931 129 unsigned short foreign_handles:2;
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130};
131
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132/**
133 * struct z3fold_pool - stores metadata for each z3fold pool
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134 * @name: pool name
135 * @lock: protects pool unbuddied/lru lists
136 * @stale_lock: protects pool stale page list
137 * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2-
138 * buddies; the list each z3fold page is added to depends on
139 * the size of its free region.
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140 * @lru: list tracking the z3fold pages in LRU order by most recently
141 * added buddy.
d30561c5 142 * @stale: list of pages marked for freeing
9a001fc1 143 * @pages_nr: number of z3fold pages in the pool.
7c2b8baa 144 * @c_handle: cache for z3fold_buddy_slots allocation
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145 * @ops: pointer to a structure of user defined operations specified at
146 * pool creation time.
30522175
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147 * @zpool: zpool driver
148 * @zpool_ops: zpool operations structure with an evict callback
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149 * @compact_wq: workqueue for page layout background optimization
150 * @release_wq: workqueue for safe page release
151 * @work: work_struct for safe page release
1f862989 152 * @inode: inode for z3fold pseudo filesystem
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153 *
154 * This structure is allocated at pool creation time and maintains metadata
155 * pertaining to a particular z3fold pool.
156 */
157struct z3fold_pool {
d30561c5 158 const char *name;
9a001fc1 159 spinlock_t lock;
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160 spinlock_t stale_lock;
161 struct list_head *unbuddied;
9a001fc1 162 struct list_head lru;
d30561c5 163 struct list_head stale;
12d59ae6 164 atomic64_t pages_nr;
7c2b8baa 165 struct kmem_cache *c_handle;
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166 const struct z3fold_ops *ops;
167 struct zpool *zpool;
168 const struct zpool_ops *zpool_ops;
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169 struct workqueue_struct *compact_wq;
170 struct workqueue_struct *release_wq;
171 struct work_struct work;
1f862989 172 struct inode *inode;
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173};
174
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175/*
176 * Internal z3fold page flags
177 */
178enum z3fold_page_flags {
5a27aa82 179 PAGE_HEADLESS = 0,
9a001fc1 180 MIDDLE_CHUNK_MAPPED,
d30561c5 181 NEEDS_COMPACTING,
6098d7e1 182 PAGE_STALE,
ca0246bb 183 PAGE_CLAIMED, /* by either reclaim or free */
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184};
185
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186/*
187 * handle flags, go under HANDLE_FLAG_MASK
188 */
189enum z3fold_handle_flags {
190 HANDLES_NOFREE = 0,
191};
192
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193/*
194 * Forward declarations
195 */
196static struct z3fold_header *__z3fold_alloc(struct z3fold_pool *, size_t, bool);
197static void compact_page_work(struct work_struct *w);
198
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199/*****************
200 * Helpers
201*****************/
202
203/* Converts an allocation size in bytes to size in z3fold chunks */
204static int size_to_chunks(size_t size)
205{
206 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
207}
208
209#define for_each_unbuddied_list(_iter, _begin) \
210 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
211
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212static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
213 gfp_t gfp)
7c2b8baa 214{
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215 struct z3fold_buddy_slots *slots;
216
f94afee9 217 slots = kmem_cache_zalloc(pool->c_handle,
f1549cb5 218 (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
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219
220 if (slots) {
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221 /* It will be freed separately in free_handle(). */
222 kmemleak_not_leak(slots);
7c2b8baa 223 slots->pool = (unsigned long)pool;
4a3ac931 224 rwlock_init(&slots->lock);
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225 }
226
227 return slots;
228}
229
230static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
231{
232 return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
233}
234
235static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
236{
237 return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
238}
239
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240/* Lock a z3fold page */
241static inline void z3fold_page_lock(struct z3fold_header *zhdr)
242{
243 spin_lock(&zhdr->page_lock);
244}
245
246/* Try to lock a z3fold page */
247static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
248{
249 return spin_trylock(&zhdr->page_lock);
250}
251
252/* Unlock a z3fold page */
253static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
254{
255 spin_unlock(&zhdr->page_lock);
256}
257
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258/* return locked z3fold page if it's not headless */
259static inline struct z3fold_header *get_z3fold_header(unsigned long handle)
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260{
261 struct z3fold_buddy_slots *slots;
262 struct z3fold_header *zhdr;
263 int locked = 0;
264
265 if (!(handle & (1 << PAGE_HEADLESS))) {
266 slots = handle_to_slots(handle);
267 do {
268 unsigned long addr;
269
270 read_lock(&slots->lock);
271 addr = *(unsigned long *)handle;
272 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
767cc6c5 273 locked = z3fold_page_trylock(zhdr);
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274 read_unlock(&slots->lock);
275 if (locked)
276 break;
277 cpu_relax();
767cc6c5 278 } while (true);
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279 } else {
280 zhdr = (struct z3fold_header *)(handle & PAGE_MASK);
281 }
282
283 return zhdr;
284}
285
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286static inline void put_z3fold_header(struct z3fold_header *zhdr)
287{
288 struct page *page = virt_to_page(zhdr);
289
290 if (!test_bit(PAGE_HEADLESS, &page->private))
291 z3fold_page_unlock(zhdr);
292}
293
fc548865 294static inline void free_handle(unsigned long handle, struct z3fold_header *zhdr)
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295{
296 struct z3fold_buddy_slots *slots;
297 int i;
298 bool is_free;
299
300 if (handle & (1 << PAGE_HEADLESS))
301 return;
302
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303 if (WARN_ON(*(unsigned long *)handle == 0))
304 return;
305
7c2b8baa 306 slots = handle_to_slots(handle);
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307 write_lock(&slots->lock);
308 *(unsigned long *)handle = 0;
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309
310 if (test_bit(HANDLES_NOFREE, &slots->pool)) {
311 write_unlock(&slots->lock);
312 return; /* simple case, nothing else to do */
313 }
314
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315 if (zhdr->slots != slots)
316 zhdr->foreign_handles--;
4a3ac931 317
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318 is_free = true;
319 for (i = 0; i <= BUDDY_MASK; i++) {
320 if (slots->slot[i]) {
321 is_free = false;
322 break;
323 }
324 }
d8f117ab 325 write_unlock(&slots->lock);
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326
327 if (is_free) {
328 struct z3fold_pool *pool = slots_to_pool(slots);
329
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330 if (zhdr->slots == slots)
331 zhdr->slots = NULL;
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332 kmem_cache_free(pool->c_handle, slots);
333 }
334}
335
ea8157ab 336static int z3fold_init_fs_context(struct fs_context *fc)
1f862989 337{
ea8157ab 338 return init_pseudo(fc, Z3FOLD_MAGIC) ? 0 : -ENOMEM;
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339}
340
341static struct file_system_type z3fold_fs = {
342 .name = "z3fold",
ea8157ab 343 .init_fs_context = z3fold_init_fs_context,
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344 .kill_sb = kill_anon_super,
345};
346
347static struct vfsmount *z3fold_mnt;
348static int z3fold_mount(void)
349{
350 int ret = 0;
351
352 z3fold_mnt = kern_mount(&z3fold_fs);
353 if (IS_ERR(z3fold_mnt))
354 ret = PTR_ERR(z3fold_mnt);
355
356 return ret;
357}
358
359static void z3fold_unmount(void)
360{
361 kern_unmount(z3fold_mnt);
362}
363
364static const struct address_space_operations z3fold_aops;
365static int z3fold_register_migration(struct z3fold_pool *pool)
366{
367 pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
368 if (IS_ERR(pool->inode)) {
369 pool->inode = NULL;
370 return 1;
371 }
372
373 pool->inode->i_mapping->private_data = pool;
374 pool->inode->i_mapping->a_ops = &z3fold_aops;
375 return 0;
376}
377
378static void z3fold_unregister_migration(struct z3fold_pool *pool)
379{
380 if (pool->inode)
381 iput(pool->inode);
cb152a1a 382}
1f862989 383
9a001fc1 384/* Initializes the z3fold header of a newly allocated z3fold page */
63398413 385static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
bb9f6f63 386 struct z3fold_pool *pool, gfp_t gfp)
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387{
388 struct z3fold_header *zhdr = page_address(page);
63398413 389 struct z3fold_buddy_slots *slots;
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390
391 INIT_LIST_HEAD(&page->lru);
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392 clear_bit(PAGE_HEADLESS, &page->private);
393 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
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394 clear_bit(NEEDS_COMPACTING, &page->private);
395 clear_bit(PAGE_STALE, &page->private);
ca0246bb 396 clear_bit(PAGE_CLAIMED, &page->private);
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397 if (headless)
398 return zhdr;
399
400 slots = alloc_slots(pool, gfp);
401 if (!slots)
402 return NULL;
9a001fc1 403
c457cd96 404 memset(zhdr, 0, sizeof(*zhdr));
2f1e5e4d 405 spin_lock_init(&zhdr->page_lock);
5a27aa82 406 kref_init(&zhdr->refcount);
d30561c5 407 zhdr->cpu = -1;
7c2b8baa 408 zhdr->slots = slots;
bb9a374d 409 zhdr->pool = pool;
9a001fc1 410 INIT_LIST_HEAD(&zhdr->buddy);
d30561c5 411 INIT_WORK(&zhdr->work, compact_page_work);
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412 return zhdr;
413}
414
415/* Resets the struct page fields and frees the page */
1f862989 416static void free_z3fold_page(struct page *page, bool headless)
9a001fc1 417{
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418 if (!headless) {
419 lock_page(page);
420 __ClearPageMovable(page);
421 unlock_page(page);
422 }
423 ClearPagePrivate(page);
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424 __free_page(page);
425}
426
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427/* Helper function to build the index */
428static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
429{
430 return (bud + zhdr->first_num) & BUDDY_MASK;
431}
432
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433/*
434 * Encodes the handle of a particular buddy within a z3fold page
435 * Pool lock should be held as this function accesses first_num
436 */
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437static unsigned long __encode_handle(struct z3fold_header *zhdr,
438 struct z3fold_buddy_slots *slots,
439 enum buddy bud)
9a001fc1 440{
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441 unsigned long h = (unsigned long)zhdr;
442 int idx = 0;
9a001fc1 443
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444 /*
445 * For a headless page, its handle is its pointer with the extra
446 * PAGE_HEADLESS bit set
447 */
448 if (bud == HEADLESS)
449 return h | (1 << PAGE_HEADLESS);
450
451 /* otherwise, return pointer to encoded handle */
452 idx = __idx(zhdr, bud);
453 h += idx;
454 if (bud == LAST)
455 h |= (zhdr->last_chunks << BUDDY_SHIFT);
456
4a3ac931 457 write_lock(&slots->lock);
7c2b8baa 458 slots->slot[idx] = h;
4a3ac931 459 write_unlock(&slots->lock);
7c2b8baa 460 return (unsigned long)&slots->slot[idx];
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461}
462
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463static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
464{
465 return __encode_handle(zhdr, zhdr->slots, bud);
466}
467
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468/* only for LAST bud, returns zero otherwise */
469static unsigned short handle_to_chunks(unsigned long handle)
470{
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471 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
472 unsigned long addr;
7c2b8baa 473
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474 read_lock(&slots->lock);
475 addr = *(unsigned long *)handle;
476 read_unlock(&slots->lock);
7c2b8baa 477 return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
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478}
479
f201ebd8 480/*
481 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
482 * but that doesn't matter. because the masking will result in the
483 * correct buddy number.
484 */
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485static enum buddy handle_to_buddy(unsigned long handle)
486{
7c2b8baa 487 struct z3fold_header *zhdr;
4a3ac931 488 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
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489 unsigned long addr;
490
4a3ac931 491 read_lock(&slots->lock);
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492 WARN_ON(handle & (1 << PAGE_HEADLESS));
493 addr = *(unsigned long *)handle;
4a3ac931 494 read_unlock(&slots->lock);
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495 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
496 return (addr - zhdr->first_num) & BUDDY_MASK;
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497}
498
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499static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
500{
bb9a374d 501 return zhdr->pool;
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502}
503
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504static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
505{
506 struct page *page = virt_to_page(zhdr);
9050cce1 507 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
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508
509 WARN_ON(!list_empty(&zhdr->buddy));
510 set_bit(PAGE_STALE, &page->private);
35529357 511 clear_bit(NEEDS_COMPACTING, &page->private);
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512 spin_lock(&pool->lock);
513 if (!list_empty(&page->lru))
1f862989 514 list_del_init(&page->lru);
d30561c5 515 spin_unlock(&pool->lock);
4a3ac931 516
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517 if (locked)
518 z3fold_page_unlock(zhdr);
4a3ac931 519
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520 spin_lock(&pool->stale_lock);
521 list_add(&zhdr->buddy, &pool->stale);
522 queue_work(pool->release_wq, &pool->work);
523 spin_unlock(&pool->stale_lock);
524}
525
70ad3196 526static void release_z3fold_page(struct kref *ref)
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527{
528 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
529 refcount);
530 __release_z3fold_page(zhdr, false);
531}
532
533static void release_z3fold_page_locked(struct kref *ref)
534{
535 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
536 refcount);
537 WARN_ON(z3fold_page_trylock(zhdr));
538 __release_z3fold_page(zhdr, true);
539}
540
541static void release_z3fold_page_locked_list(struct kref *ref)
542{
543 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
544 refcount);
9050cce1 545 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
4a3ac931 546
9050cce1 547 spin_lock(&pool->lock);
d30561c5 548 list_del_init(&zhdr->buddy);
9050cce1 549 spin_unlock(&pool->lock);
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550
551 WARN_ON(z3fold_page_trylock(zhdr));
552 __release_z3fold_page(zhdr, true);
553}
554
555static void free_pages_work(struct work_struct *w)
556{
557 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
558
559 spin_lock(&pool->stale_lock);
560 while (!list_empty(&pool->stale)) {
561 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
562 struct z3fold_header, buddy);
563 struct page *page = virt_to_page(zhdr);
564
565 list_del(&zhdr->buddy);
566 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
567 continue;
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568 spin_unlock(&pool->stale_lock);
569 cancel_work_sync(&zhdr->work);
1f862989 570 free_z3fold_page(page, false);
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VW
571 cond_resched();
572 spin_lock(&pool->stale_lock);
573 }
574 spin_unlock(&pool->stale_lock);
575}
576
9a001fc1
VW
577/*
578 * Returns the number of free chunks in a z3fold page.
579 * NB: can't be used with HEADLESS pages.
580 */
581static int num_free_chunks(struct z3fold_header *zhdr)
582{
583 int nfree;
584 /*
585 * If there is a middle object, pick up the bigger free space
586 * either before or after it. Otherwise just subtract the number
587 * of chunks occupied by the first and the last objects.
588 */
589 if (zhdr->middle_chunks != 0) {
590 int nfree_before = zhdr->first_chunks ?
ede93213 591 0 : zhdr->start_middle - ZHDR_CHUNKS;
9a001fc1 592 int nfree_after = zhdr->last_chunks ?
ede93213
VW
593 0 : TOTAL_CHUNKS -
594 (zhdr->start_middle + zhdr->middle_chunks);
9a001fc1
VW
595 nfree = max(nfree_before, nfree_after);
596 } else
597 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
598 return nfree;
599}
600
9050cce1
VW
601/* Add to the appropriate unbuddied list */
602static inline void add_to_unbuddied(struct z3fold_pool *pool,
603 struct z3fold_header *zhdr)
604{
605 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
606 zhdr->middle_chunks == 0) {
135f97fd 607 struct list_head *unbuddied;
9050cce1 608 int freechunks = num_free_chunks(zhdr);
135f97fd
VW
609
610 migrate_disable();
611 unbuddied = this_cpu_ptr(pool->unbuddied);
9050cce1
VW
612 spin_lock(&pool->lock);
613 list_add(&zhdr->buddy, &unbuddied[freechunks]);
614 spin_unlock(&pool->lock);
615 zhdr->cpu = smp_processor_id();
135f97fd 616 migrate_enable();
9050cce1
VW
617 }
618}
619
dcf5aedb
VW
620static inline enum buddy get_free_buddy(struct z3fold_header *zhdr, int chunks)
621{
622 enum buddy bud = HEADLESS;
623
624 if (zhdr->middle_chunks) {
625 if (!zhdr->first_chunks &&
626 chunks <= zhdr->start_middle - ZHDR_CHUNKS)
627 bud = FIRST;
628 else if (!zhdr->last_chunks)
629 bud = LAST;
630 } else {
631 if (!zhdr->first_chunks)
632 bud = FIRST;
633 else if (!zhdr->last_chunks)
634 bud = LAST;
635 else
636 bud = MIDDLE;
637 }
638
639 return bud;
640}
641
ede93213
VW
642static inline void *mchunk_memmove(struct z3fold_header *zhdr,
643 unsigned short dst_chunk)
644{
645 void *beg = zhdr;
646 return memmove(beg + (dst_chunk << CHUNK_SHIFT),
647 beg + (zhdr->start_middle << CHUNK_SHIFT),
648 zhdr->middle_chunks << CHUNK_SHIFT);
649}
650
4a3ac931
VW
651static inline bool buddy_single(struct z3fold_header *zhdr)
652{
653 return !((zhdr->first_chunks && zhdr->middle_chunks) ||
654 (zhdr->first_chunks && zhdr->last_chunks) ||
655 (zhdr->middle_chunks && zhdr->last_chunks));
656}
657
658static struct z3fold_header *compact_single_buddy(struct z3fold_header *zhdr)
659{
660 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
661 void *p = zhdr;
662 unsigned long old_handle = 0;
663 size_t sz = 0;
664 struct z3fold_header *new_zhdr = NULL;
665 int first_idx = __idx(zhdr, FIRST);
666 int middle_idx = __idx(zhdr, MIDDLE);
667 int last_idx = __idx(zhdr, LAST);
668 unsigned short *moved_chunks = NULL;
669
670 /*
671 * No need to protect slots here -- all the slots are "local" and
672 * the page lock is already taken
673 */
674 if (zhdr->first_chunks && zhdr->slots->slot[first_idx]) {
675 p += ZHDR_SIZE_ALIGNED;
676 sz = zhdr->first_chunks << CHUNK_SHIFT;
677 old_handle = (unsigned long)&zhdr->slots->slot[first_idx];
678 moved_chunks = &zhdr->first_chunks;
679 } else if (zhdr->middle_chunks && zhdr->slots->slot[middle_idx]) {
680 p += zhdr->start_middle << CHUNK_SHIFT;
681 sz = zhdr->middle_chunks << CHUNK_SHIFT;
682 old_handle = (unsigned long)&zhdr->slots->slot[middle_idx];
683 moved_chunks = &zhdr->middle_chunks;
684 } else if (zhdr->last_chunks && zhdr->slots->slot[last_idx]) {
685 p += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
686 sz = zhdr->last_chunks << CHUNK_SHIFT;
687 old_handle = (unsigned long)&zhdr->slots->slot[last_idx];
688 moved_chunks = &zhdr->last_chunks;
689 }
690
691 if (sz > 0) {
692 enum buddy new_bud = HEADLESS;
693 short chunks = size_to_chunks(sz);
694 void *q;
695
696 new_zhdr = __z3fold_alloc(pool, sz, false);
697 if (!new_zhdr)
698 return NULL;
699
700 if (WARN_ON(new_zhdr == zhdr))
701 goto out_fail;
702
dcf5aedb 703 new_bud = get_free_buddy(new_zhdr, chunks);
4a3ac931
VW
704 q = new_zhdr;
705 switch (new_bud) {
706 case FIRST:
707 new_zhdr->first_chunks = chunks;
708 q += ZHDR_SIZE_ALIGNED;
709 break;
710 case MIDDLE:
711 new_zhdr->middle_chunks = chunks;
712 new_zhdr->start_middle =
713 new_zhdr->first_chunks + ZHDR_CHUNKS;
714 q += new_zhdr->start_middle << CHUNK_SHIFT;
715 break;
716 case LAST:
717 new_zhdr->last_chunks = chunks;
718 q += PAGE_SIZE - (new_zhdr->last_chunks << CHUNK_SHIFT);
719 break;
720 default:
721 goto out_fail;
722 }
723 new_zhdr->foreign_handles++;
724 memcpy(q, p, sz);
725 write_lock(&zhdr->slots->lock);
726 *(unsigned long *)old_handle = (unsigned long)new_zhdr +
727 __idx(new_zhdr, new_bud);
728 if (new_bud == LAST)
729 *(unsigned long *)old_handle |=
730 (new_zhdr->last_chunks << BUDDY_SHIFT);
731 write_unlock(&zhdr->slots->lock);
732 add_to_unbuddied(pool, new_zhdr);
733 z3fold_page_unlock(new_zhdr);
734
735 *moved_chunks = 0;
736 }
737
738 return new_zhdr;
739
740out_fail:
741 if (new_zhdr) {
742 if (kref_put(&new_zhdr->refcount, release_z3fold_page_locked))
743 atomic64_dec(&pool->pages_nr);
744 else {
745 add_to_unbuddied(pool, new_zhdr);
746 z3fold_page_unlock(new_zhdr);
747 }
748 }
749 return NULL;
750
751}
752
1b096e5a 753#define BIG_CHUNK_GAP 3
9a001fc1
VW
754/* Has to be called with lock held */
755static int z3fold_compact_page(struct z3fold_header *zhdr)
756{
757 struct page *page = virt_to_page(zhdr);
9a001fc1 758
ede93213
VW
759 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
760 return 0; /* can't move middle chunk, it's used */
9a001fc1 761
1f862989
VW
762 if (unlikely(PageIsolated(page)))
763 return 0;
764
ede93213
VW
765 if (zhdr->middle_chunks == 0)
766 return 0; /* nothing to compact */
767
768 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
769 /* move to the beginning */
770 mchunk_memmove(zhdr, ZHDR_CHUNKS);
9a001fc1
VW
771 zhdr->first_chunks = zhdr->middle_chunks;
772 zhdr->middle_chunks = 0;
773 zhdr->start_middle = 0;
774 zhdr->first_num++;
1b096e5a 775 return 1;
9a001fc1 776 }
1b096e5a
VW
777
778 /*
779 * moving data is expensive, so let's only do that if
780 * there's substantial gain (at least BIG_CHUNK_GAP chunks)
781 */
782 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
783 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
784 BIG_CHUNK_GAP) {
785 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
786 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
787 return 1;
788 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
789 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
790 + zhdr->middle_chunks) >=
791 BIG_CHUNK_GAP) {
792 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
793 zhdr->middle_chunks;
794 mchunk_memmove(zhdr, new_start);
795 zhdr->start_middle = new_start;
796 return 1;
797 }
798
799 return 0;
9a001fc1
VW
800}
801
d30561c5
VW
802static void do_compact_page(struct z3fold_header *zhdr, bool locked)
803{
9050cce1 804 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
d30561c5 805 struct page *page;
d30561c5
VW
806
807 page = virt_to_page(zhdr);
808 if (locked)
809 WARN_ON(z3fold_page_trylock(zhdr));
810 else
811 z3fold_page_lock(zhdr);
5d03a661 812 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
d30561c5
VW
813 z3fold_page_unlock(zhdr);
814 return;
815 }
816 spin_lock(&pool->lock);
817 list_del_init(&zhdr->buddy);
818 spin_unlock(&pool->lock);
819
5d03a661
VW
820 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
821 atomic64_dec(&pool->pages_nr);
822 return;
823 }
824
dcf5aedb
VW
825 if (test_bit(PAGE_STALE, &page->private) ||
826 test_and_set_bit(PAGE_CLAIMED, &page->private)) {
1f862989
VW
827 z3fold_page_unlock(zhdr);
828 return;
829 }
830
4a3ac931
VW
831 if (!zhdr->foreign_handles && buddy_single(zhdr) &&
832 zhdr->mapped_count == 0 && compact_single_buddy(zhdr)) {
833 if (kref_put(&zhdr->refcount, release_z3fold_page_locked))
834 atomic64_dec(&pool->pages_nr);
dcf5aedb
VW
835 else {
836 clear_bit(PAGE_CLAIMED, &page->private);
4a3ac931 837 z3fold_page_unlock(zhdr);
dcf5aedb 838 }
4a3ac931
VW
839 return;
840 }
841
d30561c5 842 z3fold_compact_page(zhdr);
9050cce1 843 add_to_unbuddied(pool, zhdr);
dcf5aedb 844 clear_bit(PAGE_CLAIMED, &page->private);
d30561c5
VW
845 z3fold_page_unlock(zhdr);
846}
847
848static void compact_page_work(struct work_struct *w)
849{
850 struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
851 work);
852
853 do_compact_page(zhdr, false);
854}
855
9050cce1
VW
856/* returns _locked_ z3fold page header or NULL */
857static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
858 size_t size, bool can_sleep)
859{
860 struct z3fold_header *zhdr = NULL;
861 struct page *page;
862 struct list_head *unbuddied;
863 int chunks = size_to_chunks(size), i;
864
865lookup:
135f97fd 866 migrate_disable();
9050cce1 867 /* First, try to find an unbuddied z3fold page. */
135f97fd 868 unbuddied = this_cpu_ptr(pool->unbuddied);
9050cce1
VW
869 for_each_unbuddied_list(i, chunks) {
870 struct list_head *l = &unbuddied[i];
871
872 zhdr = list_first_entry_or_null(READ_ONCE(l),
873 struct z3fold_header, buddy);
874
875 if (!zhdr)
876 continue;
877
878 /* Re-check under lock. */
879 spin_lock(&pool->lock);
880 l = &unbuddied[i];
881 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
882 struct z3fold_header, buddy)) ||
883 !z3fold_page_trylock(zhdr)) {
884 spin_unlock(&pool->lock);
885 zhdr = NULL;
135f97fd 886 migrate_enable();
9050cce1
VW
887 if (can_sleep)
888 cond_resched();
889 goto lookup;
890 }
891 list_del_init(&zhdr->buddy);
892 zhdr->cpu = -1;
893 spin_unlock(&pool->lock);
894
895 page = virt_to_page(zhdr);
4a3ac931
VW
896 if (test_bit(NEEDS_COMPACTING, &page->private) ||
897 test_bit(PAGE_CLAIMED, &page->private)) {
9050cce1
VW
898 z3fold_page_unlock(zhdr);
899 zhdr = NULL;
135f97fd 900 migrate_enable();
9050cce1
VW
901 if (can_sleep)
902 cond_resched();
903 goto lookup;
904 }
905
906 /*
907 * this page could not be removed from its unbuddied
908 * list while pool lock was held, and then we've taken
909 * page lock so kref_put could not be called before
910 * we got here, so it's safe to just call kref_get()
911 */
912 kref_get(&zhdr->refcount);
913 break;
914 }
135f97fd 915 migrate_enable();
9050cce1 916
351618b2
VW
917 if (!zhdr) {
918 int cpu;
919
920 /* look for _exact_ match on other cpus' lists */
921 for_each_online_cpu(cpu) {
922 struct list_head *l;
923
924 unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
925 spin_lock(&pool->lock);
926 l = &unbuddied[chunks];
927
928 zhdr = list_first_entry_or_null(READ_ONCE(l),
929 struct z3fold_header, buddy);
930
931 if (!zhdr || !z3fold_page_trylock(zhdr)) {
932 spin_unlock(&pool->lock);
933 zhdr = NULL;
934 continue;
935 }
936 list_del_init(&zhdr->buddy);
937 zhdr->cpu = -1;
938 spin_unlock(&pool->lock);
939
940 page = virt_to_page(zhdr);
4a3ac931
VW
941 if (test_bit(NEEDS_COMPACTING, &page->private) ||
942 test_bit(PAGE_CLAIMED, &page->private)) {
351618b2
VW
943 z3fold_page_unlock(zhdr);
944 zhdr = NULL;
945 if (can_sleep)
946 cond_resched();
947 continue;
948 }
949 kref_get(&zhdr->refcount);
950 break;
951 }
952 }
953
fc548865
VW
954 if (zhdr && !zhdr->slots)
955 zhdr->slots = alloc_slots(pool,
956 can_sleep ? GFP_NOIO : GFP_ATOMIC);
9050cce1
VW
957 return zhdr;
958}
d30561c5
VW
959
960/*
961 * API Functions
962 */
963
964/**
965 * z3fold_create_pool() - create a new z3fold pool
966 * @name: pool name
967 * @gfp: gfp flags when allocating the z3fold pool structure
968 * @ops: user-defined operations for the z3fold pool
969 *
970 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
971 * failed.
972 */
973static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
974 const struct z3fold_ops *ops)
975{
976 struct z3fold_pool *pool = NULL;
977 int i, cpu;
978
979 pool = kzalloc(sizeof(struct z3fold_pool), gfp);
980 if (!pool)
981 goto out;
7c2b8baa
VW
982 pool->c_handle = kmem_cache_create("z3fold_handle",
983 sizeof(struct z3fold_buddy_slots),
984 SLOTS_ALIGN, 0, NULL);
985 if (!pool->c_handle)
986 goto out_c;
d30561c5
VW
987 spin_lock_init(&pool->lock);
988 spin_lock_init(&pool->stale_lock);
e891f60e
ML
989 pool->unbuddied = __alloc_percpu(sizeof(struct list_head) * NCHUNKS,
990 __alignof__(struct list_head));
1ec6995d
XW
991 if (!pool->unbuddied)
992 goto out_pool;
d30561c5
VW
993 for_each_possible_cpu(cpu) {
994 struct list_head *unbuddied =
995 per_cpu_ptr(pool->unbuddied, cpu);
996 for_each_unbuddied_list(i, 0)
997 INIT_LIST_HEAD(&unbuddied[i]);
998 }
999 INIT_LIST_HEAD(&pool->lru);
1000 INIT_LIST_HEAD(&pool->stale);
1001 atomic64_set(&pool->pages_nr, 0);
1002 pool->name = name;
1003 pool->compact_wq = create_singlethread_workqueue(pool->name);
1004 if (!pool->compact_wq)
1ec6995d 1005 goto out_unbuddied;
d30561c5
VW
1006 pool->release_wq = create_singlethread_workqueue(pool->name);
1007 if (!pool->release_wq)
1008 goto out_wq;
1f862989
VW
1009 if (z3fold_register_migration(pool))
1010 goto out_rwq;
d30561c5
VW
1011 INIT_WORK(&pool->work, free_pages_work);
1012 pool->ops = ops;
1013 return pool;
1014
1f862989
VW
1015out_rwq:
1016 destroy_workqueue(pool->release_wq);
d30561c5
VW
1017out_wq:
1018 destroy_workqueue(pool->compact_wq);
1ec6995d
XW
1019out_unbuddied:
1020 free_percpu(pool->unbuddied);
1021out_pool:
7c2b8baa
VW
1022 kmem_cache_destroy(pool->c_handle);
1023out_c:
d30561c5 1024 kfree(pool);
1ec6995d 1025out:
d30561c5
VW
1026 return NULL;
1027}
1028
1029/**
1030 * z3fold_destroy_pool() - destroys an existing z3fold pool
1031 * @pool: the z3fold pool to be destroyed
1032 *
1033 * The pool should be emptied before this function is called.
1034 */
1035static void z3fold_destroy_pool(struct z3fold_pool *pool)
1036{
7c2b8baa 1037 kmem_cache_destroy(pool->c_handle);
6051d3bd
HB
1038
1039 /*
1040 * We need to destroy pool->compact_wq before pool->release_wq,
1041 * as any pending work on pool->compact_wq will call
1042 * queue_work(pool->release_wq, &pool->work).
b997052b
HB
1043 *
1044 * There are still outstanding pages until both workqueues are drained,
1045 * so we cannot unregister migration until then.
6051d3bd
HB
1046 */
1047
d30561c5 1048 destroy_workqueue(pool->compact_wq);
6051d3bd 1049 destroy_workqueue(pool->release_wq);
b997052b 1050 z3fold_unregister_migration(pool);
dac0d1cf 1051 free_percpu(pool->unbuddied);
d30561c5
VW
1052 kfree(pool);
1053}
1054
9a001fc1
VW
1055/**
1056 * z3fold_alloc() - allocates a region of a given size
1057 * @pool: z3fold pool from which to allocate
1058 * @size: size in bytes of the desired allocation
1059 * @gfp: gfp flags used if the pool needs to grow
1060 * @handle: handle of the new allocation
1061 *
1062 * This function will attempt to find a free region in the pool large enough to
1063 * satisfy the allocation request. A search of the unbuddied lists is
1064 * performed first. If no suitable free region is found, then a new page is
1065 * allocated and added to the pool to satisfy the request.
1066 *
1067 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
1068 * as z3fold pool pages.
1069 *
1070 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
1071 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
1072 * a new page.
1073 */
1074static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
1075 unsigned long *handle)
1076{
9050cce1 1077 int chunks = size_to_chunks(size);
9a001fc1 1078 struct z3fold_header *zhdr = NULL;
d30561c5 1079 struct page *page = NULL;
9a001fc1 1080 enum buddy bud;
8a97ea54 1081 bool can_sleep = gfpflags_allow_blocking(gfp);
9a001fc1 1082
f1549cb5 1083 if (!size)
9a001fc1
VW
1084 return -EINVAL;
1085
1086 if (size > PAGE_SIZE)
1087 return -ENOSPC;
1088
1089 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
1090 bud = HEADLESS;
1091 else {
9050cce1
VW
1092retry:
1093 zhdr = __z3fold_alloc(pool, size, can_sleep);
d30561c5 1094 if (zhdr) {
dcf5aedb
VW
1095 bud = get_free_buddy(zhdr, chunks);
1096 if (bud == HEADLESS) {
5a27aa82 1097 if (kref_put(&zhdr->refcount,
d30561c5 1098 release_z3fold_page_locked))
5a27aa82 1099 atomic64_dec(&pool->pages_nr);
d30561c5
VW
1100 else
1101 z3fold_page_unlock(zhdr);
2f1e5e4d
VW
1102 pr_err("No free chunks in unbuddied\n");
1103 WARN_ON(1);
9050cce1 1104 goto retry;
9a001fc1 1105 }
9050cce1 1106 page = virt_to_page(zhdr);
2f1e5e4d 1107 goto found;
9a001fc1
VW
1108 }
1109 bud = FIRST;
9a001fc1
VW
1110 }
1111
5c9bab59
VW
1112 page = NULL;
1113 if (can_sleep) {
1114 spin_lock(&pool->stale_lock);
1115 zhdr = list_first_entry_or_null(&pool->stale,
1116 struct z3fold_header, buddy);
1117 /*
1118 * Before allocating a page, let's see if we can take one from
1119 * the stale pages list. cancel_work_sync() can sleep so we
1120 * limit this case to the contexts where we can sleep
1121 */
1122 if (zhdr) {
1123 list_del(&zhdr->buddy);
1124 spin_unlock(&pool->stale_lock);
d30561c5 1125 cancel_work_sync(&zhdr->work);
5c9bab59
VW
1126 page = virt_to_page(zhdr);
1127 } else {
1128 spin_unlock(&pool->stale_lock);
1129 }
d30561c5 1130 }
5c9bab59
VW
1131 if (!page)
1132 page = alloc_page(gfp);
d30561c5 1133
9a001fc1
VW
1134 if (!page)
1135 return -ENOMEM;
2f1e5e4d 1136
63398413 1137 zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
9050cce1
VW
1138 if (!zhdr) {
1139 __free_page(page);
1140 return -ENOMEM;
1141 }
1142 atomic64_inc(&pool->pages_nr);
9a001fc1
VW
1143
1144 if (bud == HEADLESS) {
1145 set_bit(PAGE_HEADLESS, &page->private);
1146 goto headless;
1147 }
810481a2
HB
1148 if (can_sleep) {
1149 lock_page(page);
1150 __SetPageMovable(page, pool->inode->i_mapping);
1151 unlock_page(page);
1152 } else {
1153 if (trylock_page(page)) {
1154 __SetPageMovable(page, pool->inode->i_mapping);
1155 unlock_page(page);
1156 }
1157 }
2f1e5e4d 1158 z3fold_page_lock(zhdr);
9a001fc1
VW
1159
1160found:
1161 if (bud == FIRST)
1162 zhdr->first_chunks = chunks;
1163 else if (bud == LAST)
1164 zhdr->last_chunks = chunks;
1165 else {
1166 zhdr->middle_chunks = chunks;
ede93213 1167 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
9a001fc1 1168 }
9050cce1 1169 add_to_unbuddied(pool, zhdr);
9a001fc1
VW
1170
1171headless:
d30561c5 1172 spin_lock(&pool->lock);
9a001fc1
VW
1173 /* Add/move z3fold page to beginning of LRU */
1174 if (!list_empty(&page->lru))
1175 list_del(&page->lru);
1176
1177 list_add(&page->lru, &pool->lru);
1178
1179 *handle = encode_handle(zhdr, bud);
1180 spin_unlock(&pool->lock);
2f1e5e4d
VW
1181 if (bud != HEADLESS)
1182 z3fold_page_unlock(zhdr);
9a001fc1
VW
1183
1184 return 0;
1185}
1186
1187/**
1188 * z3fold_free() - frees the allocation associated with the given handle
1189 * @pool: pool in which the allocation resided
1190 * @handle: handle associated with the allocation returned by z3fold_alloc()
1191 *
1192 * In the case that the z3fold page in which the allocation resides is under
1193 * reclaim, as indicated by the PG_reclaim flag being set, this function
1194 * only sets the first|last_chunks to 0. The page is actually freed
1195 * once both buddies are evicted (see z3fold_reclaim_page() below).
1196 */
1197static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
1198{
1199 struct z3fold_header *zhdr;
9a001fc1
VW
1200 struct page *page;
1201 enum buddy bud;
5b6807de 1202 bool page_claimed;
9a001fc1 1203
4a3ac931 1204 zhdr = get_z3fold_header(handle);
9a001fc1 1205 page = virt_to_page(zhdr);
5b6807de 1206 page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
9a001fc1
VW
1207
1208 if (test_bit(PAGE_HEADLESS, &page->private)) {
ca0246bb
VW
1209 /* if a headless page is under reclaim, just leave.
1210 * NB: we use test_and_set_bit for a reason: if the bit
1211 * has not been set before, we release this page
1212 * immediately so we don't care about its value any more.
1213 */
5b6807de 1214 if (!page_claimed) {
ca0246bb
VW
1215 spin_lock(&pool->lock);
1216 list_del(&page->lru);
1217 spin_unlock(&pool->lock);
4a3ac931 1218 put_z3fold_header(zhdr);
1f862989 1219 free_z3fold_page(page, true);
ca0246bb 1220 atomic64_dec(&pool->pages_nr);
9a001fc1 1221 }
ca0246bb 1222 return;
9a001fc1
VW
1223 }
1224
ca0246bb 1225 /* Non-headless case */
ca0246bb
VW
1226 bud = handle_to_buddy(handle);
1227
1228 switch (bud) {
1229 case FIRST:
1230 zhdr->first_chunks = 0;
1231 break;
1232 case MIDDLE:
1233 zhdr->middle_chunks = 0;
1234 break;
1235 case LAST:
1236 zhdr->last_chunks = 0;
1237 break;
1238 default:
1239 pr_err("%s: unknown bud %d\n", __func__, bud);
1240 WARN_ON(1);
4a3ac931 1241 put_z3fold_header(zhdr);
d30561c5
VW
1242 return;
1243 }
1244
4a3ac931 1245 if (!page_claimed)
fc548865 1246 free_handle(handle, zhdr);
d30561c5
VW
1247 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
1248 atomic64_dec(&pool->pages_nr);
1249 return;
1250 }
5b6807de
VW
1251 if (page_claimed) {
1252 /* the page has not been claimed by us */
6098d7e1
VW
1253 z3fold_page_unlock(zhdr);
1254 return;
1255 }
dcf5aedb 1256 if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
4a3ac931 1257 put_z3fold_header(zhdr);
5b6807de 1258 clear_bit(PAGE_CLAIMED, &page->private);
d30561c5
VW
1259 return;
1260 }
1261 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
2f1e5e4d 1262 spin_lock(&pool->lock);
d30561c5 1263 list_del_init(&zhdr->buddy);
2f1e5e4d 1264 spin_unlock(&pool->lock);
d30561c5 1265 zhdr->cpu = -1;
5d03a661 1266 kref_get(&zhdr->refcount);
5b6807de 1267 clear_bit(PAGE_CLAIMED, &page->private);
4a3ac931 1268 do_compact_page(zhdr, true);
d30561c5 1269 return;
9a001fc1 1270 }
5d03a661 1271 kref_get(&zhdr->refcount);
5b6807de 1272 clear_bit(PAGE_CLAIMED, &page->private);
4a3ac931
VW
1273 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1274 put_z3fold_header(zhdr);
9a001fc1
VW
1275}
1276
1277/**
1278 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1279 * @pool: pool from which a page will attempt to be evicted
f144c390 1280 * @retries: number of pages on the LRU list for which eviction will
9a001fc1
VW
1281 * be attempted before failing
1282 *
1283 * z3fold reclaim is different from normal system reclaim in that it is done
1284 * from the bottom, up. This is because only the bottom layer, z3fold, has
1285 * information on how the allocations are organized within each z3fold page.
1286 * This has the potential to create interesting locking situations between
1287 * z3fold and the user, however.
1288 *
1289 * To avoid these, this is how z3fold_reclaim_page() should be called:
f144c390 1290 *
9a001fc1
VW
1291 * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1292 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1293 * call the user-defined eviction handler with the pool and handle as
1294 * arguments.
1295 *
1296 * If the handle can not be evicted, the eviction handler should return
1297 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1298 * appropriate list and try the next z3fold page on the LRU up to
1299 * a user defined number of retries.
1300 *
1301 * If the handle is successfully evicted, the eviction handler should
1302 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1303 * contains logic to delay freeing the page if the page is under reclaim,
1304 * as indicated by the setting of the PG_reclaim flag on the underlying page.
1305 *
1306 * If all buddies in the z3fold page are successfully evicted, then the
1307 * z3fold page can be freed.
1308 *
1309 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1310 * no pages to evict or an eviction handler is not registered, -EAGAIN if
1311 * the retry limit was hit.
1312 */
1313static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1314{
4a3ac931 1315 int i, ret = -1;
d30561c5
VW
1316 struct z3fold_header *zhdr = NULL;
1317 struct page *page = NULL;
1318 struct list_head *pos;
9a001fc1 1319 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
dcf5aedb
VW
1320 struct z3fold_buddy_slots slots __attribute__((aligned(SLOTS_ALIGN)));
1321
1322 rwlock_init(&slots.lock);
1323 slots.pool = (unsigned long)pool | (1 << HANDLES_NOFREE);
9a001fc1
VW
1324
1325 spin_lock(&pool->lock);
2f1e5e4d 1326 if (!pool->ops || !pool->ops->evict || retries == 0) {
9a001fc1
VW
1327 spin_unlock(&pool->lock);
1328 return -EINVAL;
1329 }
1330 for (i = 0; i < retries; i++) {
2f1e5e4d
VW
1331 if (list_empty(&pool->lru)) {
1332 spin_unlock(&pool->lock);
1333 return -EINVAL;
1334 }
d30561c5
VW
1335 list_for_each_prev(pos, &pool->lru) {
1336 page = list_entry(pos, struct page, lru);
ca0246bb 1337
3f9d2b57 1338 zhdr = page_address(page);
6d679578
TH
1339 if (test_bit(PAGE_HEADLESS, &page->private)) {
1340 /*
1341 * For non-headless pages, we wait to do this
1342 * until we have the page lock to avoid racing
1343 * with __z3fold_alloc(). Headless pages don't
1344 * have a lock (and __z3fold_alloc() will never
1345 * see them), but we still need to test and set
1346 * PAGE_CLAIMED to avoid racing with
1347 * z3fold_free(), so just do it now before
1348 * leaving the loop.
1349 */
1350 if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1351 continue;
1352
d30561c5 1353 break;
6d679578 1354 }
d30561c5 1355
dcf5aedb
VW
1356 if (kref_get_unless_zero(&zhdr->refcount) == 0) {
1357 zhdr = NULL;
1358 break;
1359 }
ca0246bb 1360 if (!z3fold_page_trylock(zhdr)) {
dcf5aedb
VW
1361 if (kref_put(&zhdr->refcount,
1362 release_z3fold_page))
1363 atomic64_dec(&pool->pages_nr);
ca0246bb 1364 zhdr = NULL;
d30561c5 1365 continue; /* can't evict at this point */
ca0246bb 1366 }
dcf5aedb
VW
1367
1368 /* test_and_set_bit is of course atomic, but we still
1369 * need to do it under page lock, otherwise checking
1370 * that bit in __z3fold_alloc wouldn't make sense
1371 */
1372 if (zhdr->foreign_handles ||
1373 test_and_set_bit(PAGE_CLAIMED, &page->private)) {
1374 if (kref_put(&zhdr->refcount,
28473d91 1375 release_z3fold_page_locked))
dcf5aedb
VW
1376 atomic64_dec(&pool->pages_nr);
1377 else
1378 z3fold_page_unlock(zhdr);
4a3ac931
VW
1379 zhdr = NULL;
1380 continue; /* can't evict such page */
1381 }
d30561c5
VW
1382 list_del_init(&zhdr->buddy);
1383 zhdr->cpu = -1;
6098d7e1 1384 break;
d30561c5
VW
1385 }
1386
ca0246bb
VW
1387 if (!zhdr)
1388 break;
1389
5a27aa82 1390 list_del_init(&page->lru);
d30561c5 1391 spin_unlock(&pool->lock);
9a001fc1 1392
9a001fc1 1393 if (!test_bit(PAGE_HEADLESS, &page->private)) {
9a001fc1 1394 /*
3f9d2b57
VW
1395 * We need encode the handles before unlocking, and
1396 * use our local slots structure because z3fold_free
1397 * can zero out zhdr->slots and we can't do much
1398 * about that
9a001fc1
VW
1399 */
1400 first_handle = 0;
1401 last_handle = 0;
1402 middle_handle = 0;
dcf5aedb 1403 memset(slots.slot, 0, sizeof(slots.slot));
9a001fc1 1404 if (zhdr->first_chunks)
dcf5aedb
VW
1405 first_handle = __encode_handle(zhdr, &slots,
1406 FIRST);
9a001fc1 1407 if (zhdr->middle_chunks)
dcf5aedb
VW
1408 middle_handle = __encode_handle(zhdr, &slots,
1409 MIDDLE);
9a001fc1 1410 if (zhdr->last_chunks)
dcf5aedb
VW
1411 last_handle = __encode_handle(zhdr, &slots,
1412 LAST);
d30561c5
VW
1413 /*
1414 * it's safe to unlock here because we hold a
1415 * reference to this page
1416 */
2f1e5e4d 1417 z3fold_page_unlock(zhdr);
9a001fc1 1418 } else {
4a3ac931 1419 first_handle = encode_handle(zhdr, HEADLESS);
9a001fc1
VW
1420 last_handle = middle_handle = 0;
1421 }
9a001fc1
VW
1422 /* Issue the eviction callback(s) */
1423 if (middle_handle) {
1424 ret = pool->ops->evict(pool, middle_handle);
1425 if (ret)
1426 goto next;
1427 }
1428 if (first_handle) {
1429 ret = pool->ops->evict(pool, first_handle);
1430 if (ret)
1431 goto next;
1432 }
1433 if (last_handle) {
1434 ret = pool->ops->evict(pool, last_handle);
1435 if (ret)
1436 goto next;
1437 }
1438next:
5a27aa82
VW
1439 if (test_bit(PAGE_HEADLESS, &page->private)) {
1440 if (ret == 0) {
1f862989 1441 free_z3fold_page(page, true);
ca0246bb 1442 atomic64_dec(&pool->pages_nr);
5a27aa82 1443 return 0;
5a27aa82 1444 }
6098d7e1
VW
1445 spin_lock(&pool->lock);
1446 list_add(&page->lru, &pool->lru);
1447 spin_unlock(&pool->lock);
3f9d2b57 1448 clear_bit(PAGE_CLAIMED, &page->private);
6098d7e1 1449 } else {
dcf5aedb 1450 struct z3fold_buddy_slots *slots = zhdr->slots;
6098d7e1 1451 z3fold_page_lock(zhdr);
6098d7e1
VW
1452 if (kref_put(&zhdr->refcount,
1453 release_z3fold_page_locked)) {
dcf5aedb 1454 kmem_cache_free(pool->c_handle, slots);
6098d7e1
VW
1455 atomic64_dec(&pool->pages_nr);
1456 return 0;
1457 }
1458 /*
1459 * if we are here, the page is still not completely
1460 * free. Take the global pool lock then to be able
1461 * to add it back to the lru list
1462 */
1463 spin_lock(&pool->lock);
1464 list_add(&page->lru, &pool->lru);
d5567c9d 1465 spin_unlock(&pool->lock);
6098d7e1 1466 z3fold_page_unlock(zhdr);
3f9d2b57 1467 clear_bit(PAGE_CLAIMED, &page->private);
5a27aa82 1468 }
2f1e5e4d 1469
6098d7e1
VW
1470 /* We started off locked to we need to lock the pool back */
1471 spin_lock(&pool->lock);
9a001fc1
VW
1472 }
1473 spin_unlock(&pool->lock);
1474 return -EAGAIN;
1475}
1476
1477/**
1478 * z3fold_map() - maps the allocation associated with the given handle
1479 * @pool: pool in which the allocation resides
1480 * @handle: handle associated with the allocation to be mapped
1481 *
1482 * Extracts the buddy number from handle and constructs the pointer to the
1483 * correct starting chunk within the page.
1484 *
1485 * Returns: a pointer to the mapped allocation
1486 */
1487static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1488{
1489 struct z3fold_header *zhdr;
1490 struct page *page;
1491 void *addr;
1492 enum buddy buddy;
1493
4a3ac931 1494 zhdr = get_z3fold_header(handle);
9a001fc1
VW
1495 addr = zhdr;
1496 page = virt_to_page(zhdr);
1497
1498 if (test_bit(PAGE_HEADLESS, &page->private))
1499 goto out;
1500
1501 buddy = handle_to_buddy(handle);
1502 switch (buddy) {
1503 case FIRST:
1504 addr += ZHDR_SIZE_ALIGNED;
1505 break;
1506 case MIDDLE:
1507 addr += zhdr->start_middle << CHUNK_SHIFT;
1508 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1509 break;
1510 case LAST:
ca0246bb 1511 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
9a001fc1
VW
1512 break;
1513 default:
1514 pr_err("unknown buddy id %d\n", buddy);
1515 WARN_ON(1);
1516 addr = NULL;
1517 break;
1518 }
2f1e5e4d 1519
1f862989
VW
1520 if (addr)
1521 zhdr->mapped_count++;
9a001fc1 1522out:
4a3ac931 1523 put_z3fold_header(zhdr);
9a001fc1
VW
1524 return addr;
1525}
1526
1527/**
1528 * z3fold_unmap() - unmaps the allocation associated with the given handle
1529 * @pool: pool in which the allocation resides
1530 * @handle: handle associated with the allocation to be unmapped
1531 */
1532static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1533{
1534 struct z3fold_header *zhdr;
1535 struct page *page;
1536 enum buddy buddy;
1537
4a3ac931 1538 zhdr = get_z3fold_header(handle);
9a001fc1
VW
1539 page = virt_to_page(zhdr);
1540
2f1e5e4d 1541 if (test_bit(PAGE_HEADLESS, &page->private))
9a001fc1 1542 return;
9a001fc1
VW
1543
1544 buddy = handle_to_buddy(handle);
1545 if (buddy == MIDDLE)
1546 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1f862989 1547 zhdr->mapped_count--;
4a3ac931 1548 put_z3fold_header(zhdr);
9a001fc1
VW
1549}
1550
1551/**
1552 * z3fold_get_pool_size() - gets the z3fold pool size in pages
1553 * @pool: pool whose size is being queried
1554 *
12d59ae6 1555 * Returns: size in pages of the given pool.
9a001fc1
VW
1556 */
1557static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1558{
12d59ae6 1559 return atomic64_read(&pool->pages_nr);
9a001fc1
VW
1560}
1561
1f862989
VW
1562static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1563{
1564 struct z3fold_header *zhdr;
1565 struct z3fold_pool *pool;
1566
1567 VM_BUG_ON_PAGE(!PageMovable(page), page);
1568 VM_BUG_ON_PAGE(PageIsolated(page), page);
1569
dcf5aedb 1570 if (test_bit(PAGE_HEADLESS, &page->private))
1f862989
VW
1571 return false;
1572
1573 zhdr = page_address(page);
1574 z3fold_page_lock(zhdr);
1575 if (test_bit(NEEDS_COMPACTING, &page->private) ||
1576 test_bit(PAGE_STALE, &page->private))
1577 goto out;
1578
4a3ac931
VW
1579 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
1580 goto out;
1581
dcf5aedb
VW
1582 if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1583 goto out;
1f862989 1584 pool = zhdr_to_pool(zhdr);
4a3ac931
VW
1585 spin_lock(&pool->lock);
1586 if (!list_empty(&zhdr->buddy))
1587 list_del_init(&zhdr->buddy);
1588 if (!list_empty(&page->lru))
1589 list_del_init(&page->lru);
1590 spin_unlock(&pool->lock);
1591
1592 kref_get(&zhdr->refcount);
1593 z3fold_page_unlock(zhdr);
1594 return true;
1f862989 1595
1f862989
VW
1596out:
1597 z3fold_page_unlock(zhdr);
1598 return false;
1599}
1600
1601static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
1602 struct page *page, enum migrate_mode mode)
1603{
1604 struct z3fold_header *zhdr, *new_zhdr;
1605 struct z3fold_pool *pool;
1606 struct address_space *new_mapping;
1607
1608 VM_BUG_ON_PAGE(!PageMovable(page), page);
1609 VM_BUG_ON_PAGE(!PageIsolated(page), page);
dcf5aedb 1610 VM_BUG_ON_PAGE(!test_bit(PAGE_CLAIMED, &page->private), page);
810481a2 1611 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1f862989
VW
1612
1613 zhdr = page_address(page);
1614 pool = zhdr_to_pool(zhdr);
1615
dcf5aedb 1616 if (!z3fold_page_trylock(zhdr))
1f862989 1617 return -EAGAIN;
4a3ac931 1618 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
1f862989 1619 z3fold_page_unlock(zhdr);
dcf5aedb 1620 clear_bit(PAGE_CLAIMED, &page->private);
1f862989
VW
1621 return -EBUSY;
1622 }
c92d2f38
HB
1623 if (work_pending(&zhdr->work)) {
1624 z3fold_page_unlock(zhdr);
1625 return -EAGAIN;
1626 }
1f862989
VW
1627 new_zhdr = page_address(newpage);
1628 memcpy(new_zhdr, zhdr, PAGE_SIZE);
1629 newpage->private = page->private;
1630 page->private = 0;
1631 z3fold_page_unlock(zhdr);
1632 spin_lock_init(&new_zhdr->page_lock);
c92d2f38
HB
1633 INIT_WORK(&new_zhdr->work, compact_page_work);
1634 /*
1635 * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1636 * so we only have to reinitialize it.
1637 */
1638 INIT_LIST_HEAD(&new_zhdr->buddy);
1f862989
VW
1639 new_mapping = page_mapping(page);
1640 __ClearPageMovable(page);
1641 ClearPagePrivate(page);
1642
1643 get_page(newpage);
1644 z3fold_page_lock(new_zhdr);
1645 if (new_zhdr->first_chunks)
1646 encode_handle(new_zhdr, FIRST);
1647 if (new_zhdr->last_chunks)
1648 encode_handle(new_zhdr, LAST);
1649 if (new_zhdr->middle_chunks)
1650 encode_handle(new_zhdr, MIDDLE);
1651 set_bit(NEEDS_COMPACTING, &newpage->private);
1652 new_zhdr->cpu = smp_processor_id();
1653 spin_lock(&pool->lock);
1654 list_add(&newpage->lru, &pool->lru);
1655 spin_unlock(&pool->lock);
1656 __SetPageMovable(newpage, new_mapping);
1657 z3fold_page_unlock(new_zhdr);
1658
1659 queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1660
1661 page_mapcount_reset(page);
dcf5aedb 1662 clear_bit(PAGE_CLAIMED, &page->private);
1f862989
VW
1663 put_page(page);
1664 return 0;
1665}
1666
1667static void z3fold_page_putback(struct page *page)
1668{
1669 struct z3fold_header *zhdr;
1670 struct z3fold_pool *pool;
1671
1672 zhdr = page_address(page);
1673 pool = zhdr_to_pool(zhdr);
1674
1675 z3fold_page_lock(zhdr);
1676 if (!list_empty(&zhdr->buddy))
1677 list_del_init(&zhdr->buddy);
1678 INIT_LIST_HEAD(&page->lru);
1679 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
1680 atomic64_dec(&pool->pages_nr);
1681 return;
1682 }
1683 spin_lock(&pool->lock);
1684 list_add(&page->lru, &pool->lru);
1685 spin_unlock(&pool->lock);
dcf5aedb 1686 clear_bit(PAGE_CLAIMED, &page->private);
1f862989
VW
1687 z3fold_page_unlock(zhdr);
1688}
1689
1690static const struct address_space_operations z3fold_aops = {
1691 .isolate_page = z3fold_page_isolate,
1692 .migratepage = z3fold_page_migrate,
1693 .putback_page = z3fold_page_putback,
1694};
1695
9a001fc1
VW
1696/*****************
1697 * zpool
1698 ****************/
1699
1700static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1701{
1702 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1703 return pool->zpool_ops->evict(pool->zpool, handle);
1704 else
1705 return -ENOENT;
1706}
1707
1708static const struct z3fold_ops z3fold_zpool_ops = {
1709 .evict = z3fold_zpool_evict
1710};
1711
1712static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1713 const struct zpool_ops *zpool_ops,
1714 struct zpool *zpool)
1715{
1716 struct z3fold_pool *pool;
1717
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1718 pool = z3fold_create_pool(name, gfp,
1719 zpool_ops ? &z3fold_zpool_ops : NULL);
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1720 if (pool) {
1721 pool->zpool = zpool;
1722 pool->zpool_ops = zpool_ops;
1723 }
1724 return pool;
1725}
1726
1727static void z3fold_zpool_destroy(void *pool)
1728{
1729 z3fold_destroy_pool(pool);
1730}
1731
1732static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1733 unsigned long *handle)
1734{
1735 return z3fold_alloc(pool, size, gfp, handle);
1736}
1737static void z3fold_zpool_free(void *pool, unsigned long handle)
1738{
1739 z3fold_free(pool, handle);
1740}
1741
1742static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1743 unsigned int *reclaimed)
1744{
1745 unsigned int total = 0;
1746 int ret = -EINVAL;
1747
1748 while (total < pages) {
1749 ret = z3fold_reclaim_page(pool, 8);
1750 if (ret < 0)
1751 break;
1752 total++;
1753 }
1754
1755 if (reclaimed)
1756 *reclaimed = total;
1757
1758 return ret;
1759}
1760
1761static void *z3fold_zpool_map(void *pool, unsigned long handle,
1762 enum zpool_mapmode mm)
1763{
1764 return z3fold_map(pool, handle);
1765}
1766static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1767{
1768 z3fold_unmap(pool, handle);
1769}
1770
1771static u64 z3fold_zpool_total_size(void *pool)
1772{
1773 return z3fold_get_pool_size(pool) * PAGE_SIZE;
1774}
1775
1776static struct zpool_driver z3fold_zpool_driver = {
1777 .type = "z3fold",
e818e820 1778 .sleep_mapped = true,
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1779 .owner = THIS_MODULE,
1780 .create = z3fold_zpool_create,
1781 .destroy = z3fold_zpool_destroy,
1782 .malloc = z3fold_zpool_malloc,
1783 .free = z3fold_zpool_free,
1784 .shrink = z3fold_zpool_shrink,
1785 .map = z3fold_zpool_map,
1786 .unmap = z3fold_zpool_unmap,
1787 .total_size = z3fold_zpool_total_size,
1788};
1789
1790MODULE_ALIAS("zpool-z3fold");
1791
1792static int __init init_z3fold(void)
1793{
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1794 int ret;
1795
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1796 /*
1797 * Make sure the z3fold header is not larger than the page size and
1798 * there has remaining spaces for its buddy.
1799 */
1800 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE - CHUNK_SIZE);
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1801 ret = z3fold_mount();
1802 if (ret)
1803 return ret;
1804
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1805 zpool_register_driver(&z3fold_zpool_driver);
1806
1807 return 0;
1808}
1809
1810static void __exit exit_z3fold(void)
1811{
1f862989 1812 z3fold_unmount();
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1813 zpool_unregister_driver(&z3fold_zpool_driver);
1814}
1815
1816module_init(init_z3fold);
1817module_exit(exit_z3fold);
1818
1819MODULE_LICENSE("GPL");
1820MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1821MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");