1 /* 2 * z3fold.c 3 * 4 * Author: Vitaly Wool <vitaly.wool@konsulko.com> 5 * Copyright (C) 2016, Sony Mobile Communications Inc. 6 * 7 * This implementation is based on zbud written by Seth Jennings. 8 * 9 * z3fold is an special purpose allocator for storing compressed pages. It 10 * can store up to three compressed pages per page which improves the 11 * compression ratio of zbud while retaining its main concepts (e. g. always 12 * storing an integral number of objects per page) and simplicity. 13 * It still has simple and deterministic reclaim properties that make it 14 * preferable to a higher density approach (with no requirement on integral 15 * number of object per page) when reclaim is used. 16 * 17 * As in zbud, pages are divided into "chunks". The size of the chunks is 18 * fixed at compile time and is determined by NCHUNKS_ORDER below. 19 * 20 * z3fold doesn't export any API and is meant to be used via zpool API. 21 */ 22 23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 24 25 #include <linux/atomic.h> 26 #include <linux/sched.h> 27 #include <linux/list.h> 28 #include <linux/mm.h> 29 #include <linux/module.h> 30 #include <linux/percpu.h> 31 #include <linux/preempt.h> 32 #include <linux/workqueue.h> 33 #include <linux/slab.h> 34 #include <linux/spinlock.h> 35 #include <linux/zpool.h> 36 37 /***************** 38 * Structures 39 *****************/ 40 struct z3fold_pool; 41 struct z3fold_ops { 42 int (*evict)(struct z3fold_pool *pool, unsigned long handle); 43 }; 44 45 enum buddy { 46 HEADLESS = 0, 47 FIRST, 48 MIDDLE, 49 LAST, 50 BUDDIES_MAX 51 }; 52 53 /* 54 * struct z3fold_header - z3fold page metadata occupying first chunks of each 55 * z3fold page, except for HEADLESS pages 56 * @buddy: links the z3fold page into the relevant list in the 57 * pool 58 * @page_lock: per-page lock 59 * @refcount: reference count for the z3fold page 60 * @work: work_struct for page layout optimization 61 * @pool: pointer to the pool which this page belongs to 62 * @cpu: CPU which this page "belongs" to 63 * @first_chunks: the size of the first buddy in chunks, 0 if free 64 * @middle_chunks: the size of the middle buddy in chunks, 0 if free 65 * @last_chunks: the size of the last buddy in chunks, 0 if free 66 * @first_num: the starting number (for the first handle) 67 */ 68 struct z3fold_header { 69 struct list_head buddy; 70 spinlock_t page_lock; 71 struct kref refcount; 72 struct work_struct work; 73 struct z3fold_pool *pool; 74 short cpu; 75 unsigned short first_chunks; 76 unsigned short middle_chunks; 77 unsigned short last_chunks; 78 unsigned short start_middle; 79 unsigned short first_num:2; 80 }; 81 82 /* 83 * NCHUNKS_ORDER determines the internal allocation granularity, effectively 84 * adjusting internal fragmentation. It also determines the number of 85 * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the 86 * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks 87 * in the beginning of an allocated page are occupied by z3fold header, so 88 * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y), 89 * which shows the max number of free chunks in z3fold page, also there will 90 * be 63, or 62, respectively, freelists per pool. 91 */ 92 #define NCHUNKS_ORDER 6 93 94 #define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER) 95 #define CHUNK_SIZE (1 << CHUNK_SHIFT) 96 #define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE) 97 #define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT) 98 #define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT) 99 #define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT) 100 101 #define BUDDY_MASK (0x3) 102 103 /** 104 * struct z3fold_pool - stores metadata for each z3fold pool 105 * @name: pool name 106 * @lock: protects pool unbuddied/lru lists 107 * @stale_lock: protects pool stale page list 108 * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2- 109 * buddies; the list each z3fold page is added to depends on 110 * the size of its free region. 111 * @lru: list tracking the z3fold pages in LRU order by most recently 112 * added buddy. 113 * @stale: list of pages marked for freeing 114 * @pages_nr: number of z3fold pages in the pool. 115 * @ops: pointer to a structure of user defined operations specified at 116 * pool creation time. 117 * @compact_wq: workqueue for page layout background optimization 118 * @release_wq: workqueue for safe page release 119 * @work: work_struct for safe page release 120 * 121 * This structure is allocated at pool creation time and maintains metadata 122 * pertaining to a particular z3fold pool. 123 */ 124 struct z3fold_pool { 125 const char *name; 126 spinlock_t lock; 127 spinlock_t stale_lock; 128 struct list_head *unbuddied; 129 struct list_head lru; 130 struct list_head stale; 131 atomic64_t pages_nr; 132 const struct z3fold_ops *ops; 133 struct zpool *zpool; 134 const struct zpool_ops *zpool_ops; 135 struct workqueue_struct *compact_wq; 136 struct workqueue_struct *release_wq; 137 struct work_struct work; 138 }; 139 140 /* 141 * Internal z3fold page flags 142 */ 143 enum z3fold_page_flags { 144 PAGE_HEADLESS = 0, 145 MIDDLE_CHUNK_MAPPED, 146 NEEDS_COMPACTING, 147 PAGE_STALE 148 }; 149 150 /***************** 151 * Helpers 152 *****************/ 153 154 /* Converts an allocation size in bytes to size in z3fold chunks */ 155 static int size_to_chunks(size_t size) 156 { 157 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT; 158 } 159 160 #define for_each_unbuddied_list(_iter, _begin) \ 161 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++) 162 163 static void compact_page_work(struct work_struct *w); 164 165 /* Initializes the z3fold header of a newly allocated z3fold page */ 166 static struct z3fold_header *init_z3fold_page(struct page *page, 167 struct z3fold_pool *pool) 168 { 169 struct z3fold_header *zhdr = page_address(page); 170 171 INIT_LIST_HEAD(&page->lru); 172 clear_bit(PAGE_HEADLESS, &page->private); 173 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private); 174 clear_bit(NEEDS_COMPACTING, &page->private); 175 clear_bit(PAGE_STALE, &page->private); 176 177 spin_lock_init(&zhdr->page_lock); 178 kref_init(&zhdr->refcount); 179 zhdr->first_chunks = 0; 180 zhdr->middle_chunks = 0; 181 zhdr->last_chunks = 0; 182 zhdr->first_num = 0; 183 zhdr->start_middle = 0; 184 zhdr->cpu = -1; 185 zhdr->pool = pool; 186 INIT_LIST_HEAD(&zhdr->buddy); 187 INIT_WORK(&zhdr->work, compact_page_work); 188 return zhdr; 189 } 190 191 /* Resets the struct page fields and frees the page */ 192 static void free_z3fold_page(struct page *page) 193 { 194 __free_page(page); 195 } 196 197 /* Lock a z3fold page */ 198 static inline void z3fold_page_lock(struct z3fold_header *zhdr) 199 { 200 spin_lock(&zhdr->page_lock); 201 } 202 203 /* Try to lock a z3fold page */ 204 static inline int z3fold_page_trylock(struct z3fold_header *zhdr) 205 { 206 return spin_trylock(&zhdr->page_lock); 207 } 208 209 /* Unlock a z3fold page */ 210 static inline void z3fold_page_unlock(struct z3fold_header *zhdr) 211 { 212 spin_unlock(&zhdr->page_lock); 213 } 214 215 /* 216 * Encodes the handle of a particular buddy within a z3fold page 217 * Pool lock should be held as this function accesses first_num 218 */ 219 static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud) 220 { 221 unsigned long handle; 222 223 handle = (unsigned long)zhdr; 224 if (bud != HEADLESS) 225 handle += (bud + zhdr->first_num) & BUDDY_MASK; 226 return handle; 227 } 228 229 /* Returns the z3fold page where a given handle is stored */ 230 static struct z3fold_header *handle_to_z3fold_header(unsigned long handle) 231 { 232 return (struct z3fold_header *)(handle & PAGE_MASK); 233 } 234 235 /* 236 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle 237 * but that doesn't matter. because the masking will result in the 238 * correct buddy number. 239 */ 240 static enum buddy handle_to_buddy(unsigned long handle) 241 { 242 struct z3fold_header *zhdr = handle_to_z3fold_header(handle); 243 return (handle - zhdr->first_num) & BUDDY_MASK; 244 } 245 246 static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked) 247 { 248 struct page *page = virt_to_page(zhdr); 249 struct z3fold_pool *pool = zhdr->pool; 250 251 WARN_ON(!list_empty(&zhdr->buddy)); 252 set_bit(PAGE_STALE, &page->private); 253 clear_bit(NEEDS_COMPACTING, &page->private); 254 spin_lock(&pool->lock); 255 if (!list_empty(&page->lru)) 256 list_del(&page->lru); 257 spin_unlock(&pool->lock); 258 if (locked) 259 z3fold_page_unlock(zhdr); 260 spin_lock(&pool->stale_lock); 261 list_add(&zhdr->buddy, &pool->stale); 262 queue_work(pool->release_wq, &pool->work); 263 spin_unlock(&pool->stale_lock); 264 } 265 266 static void __attribute__((__unused__)) 267 release_z3fold_page(struct kref *ref) 268 { 269 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, 270 refcount); 271 __release_z3fold_page(zhdr, false); 272 } 273 274 static void release_z3fold_page_locked(struct kref *ref) 275 { 276 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, 277 refcount); 278 WARN_ON(z3fold_page_trylock(zhdr)); 279 __release_z3fold_page(zhdr, true); 280 } 281 282 static void release_z3fold_page_locked_list(struct kref *ref) 283 { 284 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, 285 refcount); 286 spin_lock(&zhdr->pool->lock); 287 list_del_init(&zhdr->buddy); 288 spin_unlock(&zhdr->pool->lock); 289 290 WARN_ON(z3fold_page_trylock(zhdr)); 291 __release_z3fold_page(zhdr, true); 292 } 293 294 static void free_pages_work(struct work_struct *w) 295 { 296 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work); 297 298 spin_lock(&pool->stale_lock); 299 while (!list_empty(&pool->stale)) { 300 struct z3fold_header *zhdr = list_first_entry(&pool->stale, 301 struct z3fold_header, buddy); 302 struct page *page = virt_to_page(zhdr); 303 304 list_del(&zhdr->buddy); 305 if (WARN_ON(!test_bit(PAGE_STALE, &page->private))) 306 continue; 307 spin_unlock(&pool->stale_lock); 308 cancel_work_sync(&zhdr->work); 309 free_z3fold_page(page); 310 cond_resched(); 311 spin_lock(&pool->stale_lock); 312 } 313 spin_unlock(&pool->stale_lock); 314 } 315 316 /* 317 * Returns the number of free chunks in a z3fold page. 318 * NB: can't be used with HEADLESS pages. 319 */ 320 static int num_free_chunks(struct z3fold_header *zhdr) 321 { 322 int nfree; 323 /* 324 * If there is a middle object, pick up the bigger free space 325 * either before or after it. Otherwise just subtract the number 326 * of chunks occupied by the first and the last objects. 327 */ 328 if (zhdr->middle_chunks != 0) { 329 int nfree_before = zhdr->first_chunks ? 330 0 : zhdr->start_middle - ZHDR_CHUNKS; 331 int nfree_after = zhdr->last_chunks ? 332 0 : TOTAL_CHUNKS - 333 (zhdr->start_middle + zhdr->middle_chunks); 334 nfree = max(nfree_before, nfree_after); 335 } else 336 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks; 337 return nfree; 338 } 339 340 static inline void *mchunk_memmove(struct z3fold_header *zhdr, 341 unsigned short dst_chunk) 342 { 343 void *beg = zhdr; 344 return memmove(beg + (dst_chunk << CHUNK_SHIFT), 345 beg + (zhdr->start_middle << CHUNK_SHIFT), 346 zhdr->middle_chunks << CHUNK_SHIFT); 347 } 348 349 #define BIG_CHUNK_GAP 3 350 /* Has to be called with lock held */ 351 static int z3fold_compact_page(struct z3fold_header *zhdr) 352 { 353 struct page *page = virt_to_page(zhdr); 354 355 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private)) 356 return 0; /* can't move middle chunk, it's used */ 357 358 if (zhdr->middle_chunks == 0) 359 return 0; /* nothing to compact */ 360 361 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) { 362 /* move to the beginning */ 363 mchunk_memmove(zhdr, ZHDR_CHUNKS); 364 zhdr->first_chunks = zhdr->middle_chunks; 365 zhdr->middle_chunks = 0; 366 zhdr->start_middle = 0; 367 zhdr->first_num++; 368 return 1; 369 } 370 371 /* 372 * moving data is expensive, so let's only do that if 373 * there's substantial gain (at least BIG_CHUNK_GAP chunks) 374 */ 375 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 && 376 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >= 377 BIG_CHUNK_GAP) { 378 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS); 379 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS; 380 return 1; 381 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 && 382 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle 383 + zhdr->middle_chunks) >= 384 BIG_CHUNK_GAP) { 385 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks - 386 zhdr->middle_chunks; 387 mchunk_memmove(zhdr, new_start); 388 zhdr->start_middle = new_start; 389 return 1; 390 } 391 392 return 0; 393 } 394 395 static void do_compact_page(struct z3fold_header *zhdr, bool locked) 396 { 397 struct z3fold_pool *pool = zhdr->pool; 398 struct page *page; 399 struct list_head *unbuddied; 400 int fchunks; 401 402 page = virt_to_page(zhdr); 403 if (locked) 404 WARN_ON(z3fold_page_trylock(zhdr)); 405 else 406 z3fold_page_lock(zhdr); 407 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) { 408 z3fold_page_unlock(zhdr); 409 return; 410 } 411 spin_lock(&pool->lock); 412 list_del_init(&zhdr->buddy); 413 spin_unlock(&pool->lock); 414 415 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) { 416 atomic64_dec(&pool->pages_nr); 417 return; 418 } 419 420 z3fold_compact_page(zhdr); 421 unbuddied = get_cpu_ptr(pool->unbuddied); 422 fchunks = num_free_chunks(zhdr); 423 if (fchunks < NCHUNKS && 424 (!zhdr->first_chunks || !zhdr->middle_chunks || 425 !zhdr->last_chunks)) { 426 /* the page's not completely free and it's unbuddied */ 427 spin_lock(&pool->lock); 428 list_add(&zhdr->buddy, &unbuddied[fchunks]); 429 spin_unlock(&pool->lock); 430 zhdr->cpu = smp_processor_id(); 431 } 432 put_cpu_ptr(pool->unbuddied); 433 z3fold_page_unlock(zhdr); 434 } 435 436 static void compact_page_work(struct work_struct *w) 437 { 438 struct z3fold_header *zhdr = container_of(w, struct z3fold_header, 439 work); 440 441 do_compact_page(zhdr, false); 442 } 443 444 445 /* 446 * API Functions 447 */ 448 449 /** 450 * z3fold_create_pool() - create a new z3fold pool 451 * @name: pool name 452 * @gfp: gfp flags when allocating the z3fold pool structure 453 * @ops: user-defined operations for the z3fold pool 454 * 455 * Return: pointer to the new z3fold pool or NULL if the metadata allocation 456 * failed. 457 */ 458 static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp, 459 const struct z3fold_ops *ops) 460 { 461 struct z3fold_pool *pool = NULL; 462 int i, cpu; 463 464 pool = kzalloc(sizeof(struct z3fold_pool), gfp); 465 if (!pool) 466 goto out; 467 spin_lock_init(&pool->lock); 468 spin_lock_init(&pool->stale_lock); 469 pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2); 470 for_each_possible_cpu(cpu) { 471 struct list_head *unbuddied = 472 per_cpu_ptr(pool->unbuddied, cpu); 473 for_each_unbuddied_list(i, 0) 474 INIT_LIST_HEAD(&unbuddied[i]); 475 } 476 INIT_LIST_HEAD(&pool->lru); 477 INIT_LIST_HEAD(&pool->stale); 478 atomic64_set(&pool->pages_nr, 0); 479 pool->name = name; 480 pool->compact_wq = create_singlethread_workqueue(pool->name); 481 if (!pool->compact_wq) 482 goto out; 483 pool->release_wq = create_singlethread_workqueue(pool->name); 484 if (!pool->release_wq) 485 goto out_wq; 486 INIT_WORK(&pool->work, free_pages_work); 487 pool->ops = ops; 488 return pool; 489 490 out_wq: 491 destroy_workqueue(pool->compact_wq); 492 out: 493 kfree(pool); 494 return NULL; 495 } 496 497 /** 498 * z3fold_destroy_pool() - destroys an existing z3fold pool 499 * @pool: the z3fold pool to be destroyed 500 * 501 * The pool should be emptied before this function is called. 502 */ 503 static void z3fold_destroy_pool(struct z3fold_pool *pool) 504 { 505 destroy_workqueue(pool->release_wq); 506 destroy_workqueue(pool->compact_wq); 507 kfree(pool); 508 } 509 510 /** 511 * z3fold_alloc() - allocates a region of a given size 512 * @pool: z3fold pool from which to allocate 513 * @size: size in bytes of the desired allocation 514 * @gfp: gfp flags used if the pool needs to grow 515 * @handle: handle of the new allocation 516 * 517 * This function will attempt to find a free region in the pool large enough to 518 * satisfy the allocation request. A search of the unbuddied lists is 519 * performed first. If no suitable free region is found, then a new page is 520 * allocated and added to the pool to satisfy the request. 521 * 522 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used 523 * as z3fold pool pages. 524 * 525 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or 526 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate 527 * a new page. 528 */ 529 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, 530 unsigned long *handle) 531 { 532 int chunks = 0, i, freechunks; 533 struct z3fold_header *zhdr = NULL; 534 struct page *page = NULL; 535 enum buddy bud; 536 bool can_sleep = (gfp & __GFP_RECLAIM) == __GFP_RECLAIM; 537 538 if (!size || (gfp & __GFP_HIGHMEM)) 539 return -EINVAL; 540 541 if (size > PAGE_SIZE) 542 return -ENOSPC; 543 544 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE) 545 bud = HEADLESS; 546 else { 547 struct list_head *unbuddied; 548 chunks = size_to_chunks(size); 549 550 lookup: 551 /* First, try to find an unbuddied z3fold page. */ 552 unbuddied = get_cpu_ptr(pool->unbuddied); 553 for_each_unbuddied_list(i, chunks) { 554 struct list_head *l = &unbuddied[i]; 555 556 zhdr = list_first_entry_or_null(READ_ONCE(l), 557 struct z3fold_header, buddy); 558 559 if (!zhdr) 560 continue; 561 562 /* Re-check under lock. */ 563 spin_lock(&pool->lock); 564 l = &unbuddied[i]; 565 if (unlikely(zhdr != list_first_entry(READ_ONCE(l), 566 struct z3fold_header, buddy)) || 567 !z3fold_page_trylock(zhdr)) { 568 spin_unlock(&pool->lock); 569 put_cpu_ptr(pool->unbuddied); 570 goto lookup; 571 } 572 list_del_init(&zhdr->buddy); 573 zhdr->cpu = -1; 574 spin_unlock(&pool->lock); 575 576 page = virt_to_page(zhdr); 577 if (test_bit(NEEDS_COMPACTING, &page->private)) { 578 z3fold_page_unlock(zhdr); 579 zhdr = NULL; 580 put_cpu_ptr(pool->unbuddied); 581 if (can_sleep) 582 cond_resched(); 583 goto lookup; 584 } 585 586 /* 587 * this page could not be removed from its unbuddied 588 * list while pool lock was held, and then we've taken 589 * page lock so kref_put could not be called before 590 * we got here, so it's safe to just call kref_get() 591 */ 592 kref_get(&zhdr->refcount); 593 break; 594 } 595 put_cpu_ptr(pool->unbuddied); 596 597 if (zhdr) { 598 if (zhdr->first_chunks == 0) { 599 if (zhdr->middle_chunks != 0 && 600 chunks >= zhdr->start_middle) 601 bud = LAST; 602 else 603 bud = FIRST; 604 } else if (zhdr->last_chunks == 0) 605 bud = LAST; 606 else if (zhdr->middle_chunks == 0) 607 bud = MIDDLE; 608 else { 609 if (kref_put(&zhdr->refcount, 610 release_z3fold_page_locked)) 611 atomic64_dec(&pool->pages_nr); 612 else 613 z3fold_page_unlock(zhdr); 614 pr_err("No free chunks in unbuddied\n"); 615 WARN_ON(1); 616 goto lookup; 617 } 618 goto found; 619 } 620 bud = FIRST; 621 } 622 623 spin_lock(&pool->stale_lock); 624 zhdr = list_first_entry_or_null(&pool->stale, 625 struct z3fold_header, buddy); 626 /* 627 * Before allocating a page, let's see if we can take one from the 628 * stale pages list. cancel_work_sync() can sleep so we must make 629 * sure it won't be called in case we're in atomic context. 630 */ 631 if (zhdr && (can_sleep || !work_pending(&zhdr->work))) { 632 list_del(&zhdr->buddy); 633 spin_unlock(&pool->stale_lock); 634 if (can_sleep) 635 cancel_work_sync(&zhdr->work); 636 page = virt_to_page(zhdr); 637 } else { 638 spin_unlock(&pool->stale_lock); 639 page = alloc_page(gfp); 640 } 641 642 if (!page) 643 return -ENOMEM; 644 645 atomic64_inc(&pool->pages_nr); 646 zhdr = init_z3fold_page(page, pool); 647 648 if (bud == HEADLESS) { 649 set_bit(PAGE_HEADLESS, &page->private); 650 goto headless; 651 } 652 z3fold_page_lock(zhdr); 653 654 found: 655 if (bud == FIRST) 656 zhdr->first_chunks = chunks; 657 else if (bud == LAST) 658 zhdr->last_chunks = chunks; 659 else { 660 zhdr->middle_chunks = chunks; 661 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS; 662 } 663 664 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 || 665 zhdr->middle_chunks == 0) { 666 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied); 667 668 /* Add to unbuddied list */ 669 freechunks = num_free_chunks(zhdr); 670 spin_lock(&pool->lock); 671 list_add(&zhdr->buddy, &unbuddied[freechunks]); 672 spin_unlock(&pool->lock); 673 zhdr->cpu = smp_processor_id(); 674 put_cpu_ptr(pool->unbuddied); 675 } 676 677 headless: 678 spin_lock(&pool->lock); 679 /* Add/move z3fold page to beginning of LRU */ 680 if (!list_empty(&page->lru)) 681 list_del(&page->lru); 682 683 list_add(&page->lru, &pool->lru); 684 685 *handle = encode_handle(zhdr, bud); 686 spin_unlock(&pool->lock); 687 if (bud != HEADLESS) 688 z3fold_page_unlock(zhdr); 689 690 return 0; 691 } 692 693 /** 694 * z3fold_free() - frees the allocation associated with the given handle 695 * @pool: pool in which the allocation resided 696 * @handle: handle associated with the allocation returned by z3fold_alloc() 697 * 698 * In the case that the z3fold page in which the allocation resides is under 699 * reclaim, as indicated by the PG_reclaim flag being set, this function 700 * only sets the first|last_chunks to 0. The page is actually freed 701 * once both buddies are evicted (see z3fold_reclaim_page() below). 702 */ 703 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle) 704 { 705 struct z3fold_header *zhdr; 706 struct page *page; 707 enum buddy bud; 708 709 zhdr = handle_to_z3fold_header(handle); 710 page = virt_to_page(zhdr); 711 712 if (test_bit(PAGE_HEADLESS, &page->private)) { 713 /* HEADLESS page stored */ 714 bud = HEADLESS; 715 } else { 716 z3fold_page_lock(zhdr); 717 bud = handle_to_buddy(handle); 718 719 switch (bud) { 720 case FIRST: 721 zhdr->first_chunks = 0; 722 break; 723 case MIDDLE: 724 zhdr->middle_chunks = 0; 725 zhdr->start_middle = 0; 726 break; 727 case LAST: 728 zhdr->last_chunks = 0; 729 break; 730 default: 731 pr_err("%s: unknown bud %d\n", __func__, bud); 732 WARN_ON(1); 733 z3fold_page_unlock(zhdr); 734 return; 735 } 736 } 737 738 if (bud == HEADLESS) { 739 spin_lock(&pool->lock); 740 list_del(&page->lru); 741 spin_unlock(&pool->lock); 742 free_z3fold_page(page); 743 atomic64_dec(&pool->pages_nr); 744 return; 745 } 746 747 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) { 748 atomic64_dec(&pool->pages_nr); 749 return; 750 } 751 if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) { 752 z3fold_page_unlock(zhdr); 753 return; 754 } 755 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) { 756 spin_lock(&pool->lock); 757 list_del_init(&zhdr->buddy); 758 spin_unlock(&pool->lock); 759 zhdr->cpu = -1; 760 kref_get(&zhdr->refcount); 761 do_compact_page(zhdr, true); 762 return; 763 } 764 kref_get(&zhdr->refcount); 765 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work); 766 z3fold_page_unlock(zhdr); 767 } 768 769 /** 770 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it 771 * @pool: pool from which a page will attempt to be evicted 772 * @retires: number of pages on the LRU list for which eviction will 773 * be attempted before failing 774 * 775 * z3fold reclaim is different from normal system reclaim in that it is done 776 * from the bottom, up. This is because only the bottom layer, z3fold, has 777 * information on how the allocations are organized within each z3fold page. 778 * This has the potential to create interesting locking situations between 779 * z3fold and the user, however. 780 * 781 * To avoid these, this is how z3fold_reclaim_page() should be called: 782 783 * The user detects a page should be reclaimed and calls z3fold_reclaim_page(). 784 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and 785 * call the user-defined eviction handler with the pool and handle as 786 * arguments. 787 * 788 * If the handle can not be evicted, the eviction handler should return 789 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the 790 * appropriate list and try the next z3fold page on the LRU up to 791 * a user defined number of retries. 792 * 793 * If the handle is successfully evicted, the eviction handler should 794 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free() 795 * contains logic to delay freeing the page if the page is under reclaim, 796 * as indicated by the setting of the PG_reclaim flag on the underlying page. 797 * 798 * If all buddies in the z3fold page are successfully evicted, then the 799 * z3fold page can be freed. 800 * 801 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are 802 * no pages to evict or an eviction handler is not registered, -EAGAIN if 803 * the retry limit was hit. 804 */ 805 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) 806 { 807 int i, ret = 0; 808 struct z3fold_header *zhdr = NULL; 809 struct page *page = NULL; 810 struct list_head *pos; 811 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0; 812 813 spin_lock(&pool->lock); 814 if (!pool->ops || !pool->ops->evict || retries == 0) { 815 spin_unlock(&pool->lock); 816 return -EINVAL; 817 } 818 for (i = 0; i < retries; i++) { 819 if (list_empty(&pool->lru)) { 820 spin_unlock(&pool->lock); 821 return -EINVAL; 822 } 823 list_for_each_prev(pos, &pool->lru) { 824 page = list_entry(pos, struct page, lru); 825 if (test_bit(PAGE_HEADLESS, &page->private)) 826 /* candidate found */ 827 break; 828 829 zhdr = page_address(page); 830 if (!z3fold_page_trylock(zhdr)) 831 continue; /* can't evict at this point */ 832 kref_get(&zhdr->refcount); 833 list_del_init(&zhdr->buddy); 834 zhdr->cpu = -1; 835 } 836 837 list_del_init(&page->lru); 838 spin_unlock(&pool->lock); 839 840 if (!test_bit(PAGE_HEADLESS, &page->private)) { 841 /* 842 * We need encode the handles before unlocking, since 843 * we can race with free that will set 844 * (first|last)_chunks to 0 845 */ 846 first_handle = 0; 847 last_handle = 0; 848 middle_handle = 0; 849 if (zhdr->first_chunks) 850 first_handle = encode_handle(zhdr, FIRST); 851 if (zhdr->middle_chunks) 852 middle_handle = encode_handle(zhdr, MIDDLE); 853 if (zhdr->last_chunks) 854 last_handle = encode_handle(zhdr, LAST); 855 /* 856 * it's safe to unlock here because we hold a 857 * reference to this page 858 */ 859 z3fold_page_unlock(zhdr); 860 } else { 861 first_handle = encode_handle(zhdr, HEADLESS); 862 last_handle = middle_handle = 0; 863 } 864 865 /* Issue the eviction callback(s) */ 866 if (middle_handle) { 867 ret = pool->ops->evict(pool, middle_handle); 868 if (ret) 869 goto next; 870 } 871 if (first_handle) { 872 ret = pool->ops->evict(pool, first_handle); 873 if (ret) 874 goto next; 875 } 876 if (last_handle) { 877 ret = pool->ops->evict(pool, last_handle); 878 if (ret) 879 goto next; 880 } 881 next: 882 spin_lock(&pool->lock); 883 if (test_bit(PAGE_HEADLESS, &page->private)) { 884 if (ret == 0) { 885 spin_unlock(&pool->lock); 886 free_z3fold_page(page); 887 return 0; 888 } 889 } else if (kref_put(&zhdr->refcount, release_z3fold_page)) { 890 atomic64_dec(&pool->pages_nr); 891 spin_unlock(&pool->lock); 892 return 0; 893 } 894 895 /* 896 * Add to the beginning of LRU. 897 * Pool lock has to be kept here to ensure the page has 898 * not already been released 899 */ 900 list_add(&page->lru, &pool->lru); 901 } 902 spin_unlock(&pool->lock); 903 return -EAGAIN; 904 } 905 906 /** 907 * z3fold_map() - maps the allocation associated with the given handle 908 * @pool: pool in which the allocation resides 909 * @handle: handle associated with the allocation to be mapped 910 * 911 * Extracts the buddy number from handle and constructs the pointer to the 912 * correct starting chunk within the page. 913 * 914 * Returns: a pointer to the mapped allocation 915 */ 916 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle) 917 { 918 struct z3fold_header *zhdr; 919 struct page *page; 920 void *addr; 921 enum buddy buddy; 922 923 zhdr = handle_to_z3fold_header(handle); 924 addr = zhdr; 925 page = virt_to_page(zhdr); 926 927 if (test_bit(PAGE_HEADLESS, &page->private)) 928 goto out; 929 930 z3fold_page_lock(zhdr); 931 buddy = handle_to_buddy(handle); 932 switch (buddy) { 933 case FIRST: 934 addr += ZHDR_SIZE_ALIGNED; 935 break; 936 case MIDDLE: 937 addr += zhdr->start_middle << CHUNK_SHIFT; 938 set_bit(MIDDLE_CHUNK_MAPPED, &page->private); 939 break; 940 case LAST: 941 addr += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT); 942 break; 943 default: 944 pr_err("unknown buddy id %d\n", buddy); 945 WARN_ON(1); 946 addr = NULL; 947 break; 948 } 949 950 z3fold_page_unlock(zhdr); 951 out: 952 return addr; 953 } 954 955 /** 956 * z3fold_unmap() - unmaps the allocation associated with the given handle 957 * @pool: pool in which the allocation resides 958 * @handle: handle associated with the allocation to be unmapped 959 */ 960 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle) 961 { 962 struct z3fold_header *zhdr; 963 struct page *page; 964 enum buddy buddy; 965 966 zhdr = handle_to_z3fold_header(handle); 967 page = virt_to_page(zhdr); 968 969 if (test_bit(PAGE_HEADLESS, &page->private)) 970 return; 971 972 z3fold_page_lock(zhdr); 973 buddy = handle_to_buddy(handle); 974 if (buddy == MIDDLE) 975 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private); 976 z3fold_page_unlock(zhdr); 977 } 978 979 /** 980 * z3fold_get_pool_size() - gets the z3fold pool size in pages 981 * @pool: pool whose size is being queried 982 * 983 * Returns: size in pages of the given pool. 984 */ 985 static u64 z3fold_get_pool_size(struct z3fold_pool *pool) 986 { 987 return atomic64_read(&pool->pages_nr); 988 } 989 990 /***************** 991 * zpool 992 ****************/ 993 994 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle) 995 { 996 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict) 997 return pool->zpool_ops->evict(pool->zpool, handle); 998 else 999 return -ENOENT; 1000 } 1001 1002 static const struct z3fold_ops z3fold_zpool_ops = { 1003 .evict = z3fold_zpool_evict 1004 }; 1005 1006 static void *z3fold_zpool_create(const char *name, gfp_t gfp, 1007 const struct zpool_ops *zpool_ops, 1008 struct zpool *zpool) 1009 { 1010 struct z3fold_pool *pool; 1011 1012 pool = z3fold_create_pool(name, gfp, 1013 zpool_ops ? &z3fold_zpool_ops : NULL); 1014 if (pool) { 1015 pool->zpool = zpool; 1016 pool->zpool_ops = zpool_ops; 1017 } 1018 return pool; 1019 } 1020 1021 static void z3fold_zpool_destroy(void *pool) 1022 { 1023 z3fold_destroy_pool(pool); 1024 } 1025 1026 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp, 1027 unsigned long *handle) 1028 { 1029 return z3fold_alloc(pool, size, gfp, handle); 1030 } 1031 static void z3fold_zpool_free(void *pool, unsigned long handle) 1032 { 1033 z3fold_free(pool, handle); 1034 } 1035 1036 static int z3fold_zpool_shrink(void *pool, unsigned int pages, 1037 unsigned int *reclaimed) 1038 { 1039 unsigned int total = 0; 1040 int ret = -EINVAL; 1041 1042 while (total < pages) { 1043 ret = z3fold_reclaim_page(pool, 8); 1044 if (ret < 0) 1045 break; 1046 total++; 1047 } 1048 1049 if (reclaimed) 1050 *reclaimed = total; 1051 1052 return ret; 1053 } 1054 1055 static void *z3fold_zpool_map(void *pool, unsigned long handle, 1056 enum zpool_mapmode mm) 1057 { 1058 return z3fold_map(pool, handle); 1059 } 1060 static void z3fold_zpool_unmap(void *pool, unsigned long handle) 1061 { 1062 z3fold_unmap(pool, handle); 1063 } 1064 1065 static u64 z3fold_zpool_total_size(void *pool) 1066 { 1067 return z3fold_get_pool_size(pool) * PAGE_SIZE; 1068 } 1069 1070 static struct zpool_driver z3fold_zpool_driver = { 1071 .type = "z3fold", 1072 .owner = THIS_MODULE, 1073 .create = z3fold_zpool_create, 1074 .destroy = z3fold_zpool_destroy, 1075 .malloc = z3fold_zpool_malloc, 1076 .free = z3fold_zpool_free, 1077 .shrink = z3fold_zpool_shrink, 1078 .map = z3fold_zpool_map, 1079 .unmap = z3fold_zpool_unmap, 1080 .total_size = z3fold_zpool_total_size, 1081 }; 1082 1083 MODULE_ALIAS("zpool-z3fold"); 1084 1085 static int __init init_z3fold(void) 1086 { 1087 /* Make sure the z3fold header is not larger than the page size */ 1088 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE); 1089 zpool_register_driver(&z3fold_zpool_driver); 1090 1091 return 0; 1092 } 1093 1094 static void __exit exit_z3fold(void) 1095 { 1096 zpool_unregister_driver(&z3fold_zpool_driver); 1097 } 1098 1099 module_init(init_z3fold); 1100 module_exit(exit_z3fold); 1101 1102 MODULE_LICENSE("GPL"); 1103 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>"); 1104 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages"); 1105