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 if (!pool->unbuddied) 471 goto out_pool; 472 for_each_possible_cpu(cpu) { 473 struct list_head *unbuddied = 474 per_cpu_ptr(pool->unbuddied, cpu); 475 for_each_unbuddied_list(i, 0) 476 INIT_LIST_HEAD(&unbuddied[i]); 477 } 478 INIT_LIST_HEAD(&pool->lru); 479 INIT_LIST_HEAD(&pool->stale); 480 atomic64_set(&pool->pages_nr, 0); 481 pool->name = name; 482 pool->compact_wq = create_singlethread_workqueue(pool->name); 483 if (!pool->compact_wq) 484 goto out_unbuddied; 485 pool->release_wq = create_singlethread_workqueue(pool->name); 486 if (!pool->release_wq) 487 goto out_wq; 488 INIT_WORK(&pool->work, free_pages_work); 489 pool->ops = ops; 490 return pool; 491 492 out_wq: 493 destroy_workqueue(pool->compact_wq); 494 out_unbuddied: 495 free_percpu(pool->unbuddied); 496 out_pool: 497 kfree(pool); 498 out: 499 return NULL; 500 } 501 502 /** 503 * z3fold_destroy_pool() - destroys an existing z3fold pool 504 * @pool: the z3fold pool to be destroyed 505 * 506 * The pool should be emptied before this function is called. 507 */ 508 static void z3fold_destroy_pool(struct z3fold_pool *pool) 509 { 510 destroy_workqueue(pool->release_wq); 511 destroy_workqueue(pool->compact_wq); 512 kfree(pool); 513 } 514 515 /** 516 * z3fold_alloc() - allocates a region of a given size 517 * @pool: z3fold pool from which to allocate 518 * @size: size in bytes of the desired allocation 519 * @gfp: gfp flags used if the pool needs to grow 520 * @handle: handle of the new allocation 521 * 522 * This function will attempt to find a free region in the pool large enough to 523 * satisfy the allocation request. A search of the unbuddied lists is 524 * performed first. If no suitable free region is found, then a new page is 525 * allocated and added to the pool to satisfy the request. 526 * 527 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used 528 * as z3fold pool pages. 529 * 530 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or 531 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate 532 * a new page. 533 */ 534 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, 535 unsigned long *handle) 536 { 537 int chunks = 0, i, freechunks; 538 struct z3fold_header *zhdr = NULL; 539 struct page *page = NULL; 540 enum buddy bud; 541 bool can_sleep = gfpflags_allow_blocking(gfp); 542 543 if (!size || (gfp & __GFP_HIGHMEM)) 544 return -EINVAL; 545 546 if (size > PAGE_SIZE) 547 return -ENOSPC; 548 549 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE) 550 bud = HEADLESS; 551 else { 552 struct list_head *unbuddied; 553 chunks = size_to_chunks(size); 554 555 lookup: 556 /* First, try to find an unbuddied z3fold page. */ 557 unbuddied = get_cpu_ptr(pool->unbuddied); 558 for_each_unbuddied_list(i, chunks) { 559 struct list_head *l = &unbuddied[i]; 560 561 zhdr = list_first_entry_or_null(READ_ONCE(l), 562 struct z3fold_header, buddy); 563 564 if (!zhdr) 565 continue; 566 567 /* Re-check under lock. */ 568 spin_lock(&pool->lock); 569 l = &unbuddied[i]; 570 if (unlikely(zhdr != list_first_entry(READ_ONCE(l), 571 struct z3fold_header, buddy)) || 572 !z3fold_page_trylock(zhdr)) { 573 spin_unlock(&pool->lock); 574 put_cpu_ptr(pool->unbuddied); 575 goto lookup; 576 } 577 list_del_init(&zhdr->buddy); 578 zhdr->cpu = -1; 579 spin_unlock(&pool->lock); 580 581 page = virt_to_page(zhdr); 582 if (test_bit(NEEDS_COMPACTING, &page->private)) { 583 z3fold_page_unlock(zhdr); 584 zhdr = NULL; 585 put_cpu_ptr(pool->unbuddied); 586 if (can_sleep) 587 cond_resched(); 588 goto lookup; 589 } 590 591 /* 592 * this page could not be removed from its unbuddied 593 * list while pool lock was held, and then we've taken 594 * page lock so kref_put could not be called before 595 * we got here, so it's safe to just call kref_get() 596 */ 597 kref_get(&zhdr->refcount); 598 break; 599 } 600 put_cpu_ptr(pool->unbuddied); 601 602 if (zhdr) { 603 if (zhdr->first_chunks == 0) { 604 if (zhdr->middle_chunks != 0 && 605 chunks >= zhdr->start_middle) 606 bud = LAST; 607 else 608 bud = FIRST; 609 } else if (zhdr->last_chunks == 0) 610 bud = LAST; 611 else if (zhdr->middle_chunks == 0) 612 bud = MIDDLE; 613 else { 614 if (kref_put(&zhdr->refcount, 615 release_z3fold_page_locked)) 616 atomic64_dec(&pool->pages_nr); 617 else 618 z3fold_page_unlock(zhdr); 619 pr_err("No free chunks in unbuddied\n"); 620 WARN_ON(1); 621 goto lookup; 622 } 623 goto found; 624 } 625 bud = FIRST; 626 } 627 628 page = NULL; 629 if (can_sleep) { 630 spin_lock(&pool->stale_lock); 631 zhdr = list_first_entry_or_null(&pool->stale, 632 struct z3fold_header, buddy); 633 /* 634 * Before allocating a page, let's see if we can take one from 635 * the stale pages list. cancel_work_sync() can sleep so we 636 * limit this case to the contexts where we can sleep 637 */ 638 if (zhdr) { 639 list_del(&zhdr->buddy); 640 spin_unlock(&pool->stale_lock); 641 cancel_work_sync(&zhdr->work); 642 page = virt_to_page(zhdr); 643 } else { 644 spin_unlock(&pool->stale_lock); 645 } 646 } 647 if (!page) 648 page = alloc_page(gfp); 649 650 if (!page) 651 return -ENOMEM; 652 653 atomic64_inc(&pool->pages_nr); 654 zhdr = init_z3fold_page(page, pool); 655 656 if (bud == HEADLESS) { 657 set_bit(PAGE_HEADLESS, &page->private); 658 goto headless; 659 } 660 z3fold_page_lock(zhdr); 661 662 found: 663 if (bud == FIRST) 664 zhdr->first_chunks = chunks; 665 else if (bud == LAST) 666 zhdr->last_chunks = chunks; 667 else { 668 zhdr->middle_chunks = chunks; 669 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS; 670 } 671 672 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 || 673 zhdr->middle_chunks == 0) { 674 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied); 675 676 /* Add to unbuddied list */ 677 freechunks = num_free_chunks(zhdr); 678 spin_lock(&pool->lock); 679 list_add(&zhdr->buddy, &unbuddied[freechunks]); 680 spin_unlock(&pool->lock); 681 zhdr->cpu = smp_processor_id(); 682 put_cpu_ptr(pool->unbuddied); 683 } 684 685 headless: 686 spin_lock(&pool->lock); 687 /* Add/move z3fold page to beginning of LRU */ 688 if (!list_empty(&page->lru)) 689 list_del(&page->lru); 690 691 list_add(&page->lru, &pool->lru); 692 693 *handle = encode_handle(zhdr, bud); 694 spin_unlock(&pool->lock); 695 if (bud != HEADLESS) 696 z3fold_page_unlock(zhdr); 697 698 return 0; 699 } 700 701 /** 702 * z3fold_free() - frees the allocation associated with the given handle 703 * @pool: pool in which the allocation resided 704 * @handle: handle associated with the allocation returned by z3fold_alloc() 705 * 706 * In the case that the z3fold page in which the allocation resides is under 707 * reclaim, as indicated by the PG_reclaim flag being set, this function 708 * only sets the first|last_chunks to 0. The page is actually freed 709 * once both buddies are evicted (see z3fold_reclaim_page() below). 710 */ 711 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle) 712 { 713 struct z3fold_header *zhdr; 714 struct page *page; 715 enum buddy bud; 716 717 zhdr = handle_to_z3fold_header(handle); 718 page = virt_to_page(zhdr); 719 720 if (test_bit(PAGE_HEADLESS, &page->private)) { 721 /* HEADLESS page stored */ 722 bud = HEADLESS; 723 } else { 724 z3fold_page_lock(zhdr); 725 bud = handle_to_buddy(handle); 726 727 switch (bud) { 728 case FIRST: 729 zhdr->first_chunks = 0; 730 break; 731 case MIDDLE: 732 zhdr->middle_chunks = 0; 733 zhdr->start_middle = 0; 734 break; 735 case LAST: 736 zhdr->last_chunks = 0; 737 break; 738 default: 739 pr_err("%s: unknown bud %d\n", __func__, bud); 740 WARN_ON(1); 741 z3fold_page_unlock(zhdr); 742 return; 743 } 744 } 745 746 if (bud == HEADLESS) { 747 spin_lock(&pool->lock); 748 list_del(&page->lru); 749 spin_unlock(&pool->lock); 750 free_z3fold_page(page); 751 atomic64_dec(&pool->pages_nr); 752 return; 753 } 754 755 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) { 756 atomic64_dec(&pool->pages_nr); 757 return; 758 } 759 if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) { 760 z3fold_page_unlock(zhdr); 761 return; 762 } 763 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) { 764 spin_lock(&pool->lock); 765 list_del_init(&zhdr->buddy); 766 spin_unlock(&pool->lock); 767 zhdr->cpu = -1; 768 kref_get(&zhdr->refcount); 769 do_compact_page(zhdr, true); 770 return; 771 } 772 kref_get(&zhdr->refcount); 773 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work); 774 z3fold_page_unlock(zhdr); 775 } 776 777 /** 778 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it 779 * @pool: pool from which a page will attempt to be evicted 780 * @retries: number of pages on the LRU list for which eviction will 781 * be attempted before failing 782 * 783 * z3fold reclaim is different from normal system reclaim in that it is done 784 * from the bottom, up. This is because only the bottom layer, z3fold, has 785 * information on how the allocations are organized within each z3fold page. 786 * This has the potential to create interesting locking situations between 787 * z3fold and the user, however. 788 * 789 * To avoid these, this is how z3fold_reclaim_page() should be called: 790 * 791 * The user detects a page should be reclaimed and calls z3fold_reclaim_page(). 792 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and 793 * call the user-defined eviction handler with the pool and handle as 794 * arguments. 795 * 796 * If the handle can not be evicted, the eviction handler should return 797 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the 798 * appropriate list and try the next z3fold page on the LRU up to 799 * a user defined number of retries. 800 * 801 * If the handle is successfully evicted, the eviction handler should 802 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free() 803 * contains logic to delay freeing the page if the page is under reclaim, 804 * as indicated by the setting of the PG_reclaim flag on the underlying page. 805 * 806 * If all buddies in the z3fold page are successfully evicted, then the 807 * z3fold page can be freed. 808 * 809 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are 810 * no pages to evict or an eviction handler is not registered, -EAGAIN if 811 * the retry limit was hit. 812 */ 813 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) 814 { 815 int i, ret = 0; 816 struct z3fold_header *zhdr = NULL; 817 struct page *page = NULL; 818 struct list_head *pos; 819 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0; 820 821 spin_lock(&pool->lock); 822 if (!pool->ops || !pool->ops->evict || retries == 0) { 823 spin_unlock(&pool->lock); 824 return -EINVAL; 825 } 826 for (i = 0; i < retries; i++) { 827 if (list_empty(&pool->lru)) { 828 spin_unlock(&pool->lock); 829 return -EINVAL; 830 } 831 list_for_each_prev(pos, &pool->lru) { 832 page = list_entry(pos, struct page, lru); 833 if (test_bit(PAGE_HEADLESS, &page->private)) 834 /* candidate found */ 835 break; 836 837 zhdr = page_address(page); 838 if (!z3fold_page_trylock(zhdr)) 839 continue; /* can't evict at this point */ 840 kref_get(&zhdr->refcount); 841 list_del_init(&zhdr->buddy); 842 zhdr->cpu = -1; 843 } 844 845 list_del_init(&page->lru); 846 spin_unlock(&pool->lock); 847 848 if (!test_bit(PAGE_HEADLESS, &page->private)) { 849 /* 850 * We need encode the handles before unlocking, since 851 * we can race with free that will set 852 * (first|last)_chunks to 0 853 */ 854 first_handle = 0; 855 last_handle = 0; 856 middle_handle = 0; 857 if (zhdr->first_chunks) 858 first_handle = encode_handle(zhdr, FIRST); 859 if (zhdr->middle_chunks) 860 middle_handle = encode_handle(zhdr, MIDDLE); 861 if (zhdr->last_chunks) 862 last_handle = encode_handle(zhdr, LAST); 863 /* 864 * it's safe to unlock here because we hold a 865 * reference to this page 866 */ 867 z3fold_page_unlock(zhdr); 868 } else { 869 first_handle = encode_handle(zhdr, HEADLESS); 870 last_handle = middle_handle = 0; 871 } 872 873 /* Issue the eviction callback(s) */ 874 if (middle_handle) { 875 ret = pool->ops->evict(pool, middle_handle); 876 if (ret) 877 goto next; 878 } 879 if (first_handle) { 880 ret = pool->ops->evict(pool, first_handle); 881 if (ret) 882 goto next; 883 } 884 if (last_handle) { 885 ret = pool->ops->evict(pool, last_handle); 886 if (ret) 887 goto next; 888 } 889 next: 890 spin_lock(&pool->lock); 891 if (test_bit(PAGE_HEADLESS, &page->private)) { 892 if (ret == 0) { 893 spin_unlock(&pool->lock); 894 free_z3fold_page(page); 895 return 0; 896 } 897 } else if (kref_put(&zhdr->refcount, release_z3fold_page)) { 898 atomic64_dec(&pool->pages_nr); 899 spin_unlock(&pool->lock); 900 return 0; 901 } 902 903 /* 904 * Add to the beginning of LRU. 905 * Pool lock has to be kept here to ensure the page has 906 * not already been released 907 */ 908 list_add(&page->lru, &pool->lru); 909 } 910 spin_unlock(&pool->lock); 911 return -EAGAIN; 912 } 913 914 /** 915 * z3fold_map() - maps the allocation associated with the given handle 916 * @pool: pool in which the allocation resides 917 * @handle: handle associated with the allocation to be mapped 918 * 919 * Extracts the buddy number from handle and constructs the pointer to the 920 * correct starting chunk within the page. 921 * 922 * Returns: a pointer to the mapped allocation 923 */ 924 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle) 925 { 926 struct z3fold_header *zhdr; 927 struct page *page; 928 void *addr; 929 enum buddy buddy; 930 931 zhdr = handle_to_z3fold_header(handle); 932 addr = zhdr; 933 page = virt_to_page(zhdr); 934 935 if (test_bit(PAGE_HEADLESS, &page->private)) 936 goto out; 937 938 z3fold_page_lock(zhdr); 939 buddy = handle_to_buddy(handle); 940 switch (buddy) { 941 case FIRST: 942 addr += ZHDR_SIZE_ALIGNED; 943 break; 944 case MIDDLE: 945 addr += zhdr->start_middle << CHUNK_SHIFT; 946 set_bit(MIDDLE_CHUNK_MAPPED, &page->private); 947 break; 948 case LAST: 949 addr += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT); 950 break; 951 default: 952 pr_err("unknown buddy id %d\n", buddy); 953 WARN_ON(1); 954 addr = NULL; 955 break; 956 } 957 958 z3fold_page_unlock(zhdr); 959 out: 960 return addr; 961 } 962 963 /** 964 * z3fold_unmap() - unmaps the allocation associated with the given handle 965 * @pool: pool in which the allocation resides 966 * @handle: handle associated with the allocation to be unmapped 967 */ 968 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle) 969 { 970 struct z3fold_header *zhdr; 971 struct page *page; 972 enum buddy buddy; 973 974 zhdr = handle_to_z3fold_header(handle); 975 page = virt_to_page(zhdr); 976 977 if (test_bit(PAGE_HEADLESS, &page->private)) 978 return; 979 980 z3fold_page_lock(zhdr); 981 buddy = handle_to_buddy(handle); 982 if (buddy == MIDDLE) 983 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private); 984 z3fold_page_unlock(zhdr); 985 } 986 987 /** 988 * z3fold_get_pool_size() - gets the z3fold pool size in pages 989 * @pool: pool whose size is being queried 990 * 991 * Returns: size in pages of the given pool. 992 */ 993 static u64 z3fold_get_pool_size(struct z3fold_pool *pool) 994 { 995 return atomic64_read(&pool->pages_nr); 996 } 997 998 /***************** 999 * zpool 1000 ****************/ 1001 1002 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle) 1003 { 1004 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict) 1005 return pool->zpool_ops->evict(pool->zpool, handle); 1006 else 1007 return -ENOENT; 1008 } 1009 1010 static const struct z3fold_ops z3fold_zpool_ops = { 1011 .evict = z3fold_zpool_evict 1012 }; 1013 1014 static void *z3fold_zpool_create(const char *name, gfp_t gfp, 1015 const struct zpool_ops *zpool_ops, 1016 struct zpool *zpool) 1017 { 1018 struct z3fold_pool *pool; 1019 1020 pool = z3fold_create_pool(name, gfp, 1021 zpool_ops ? &z3fold_zpool_ops : NULL); 1022 if (pool) { 1023 pool->zpool = zpool; 1024 pool->zpool_ops = zpool_ops; 1025 } 1026 return pool; 1027 } 1028 1029 static void z3fold_zpool_destroy(void *pool) 1030 { 1031 z3fold_destroy_pool(pool); 1032 } 1033 1034 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp, 1035 unsigned long *handle) 1036 { 1037 return z3fold_alloc(pool, size, gfp, handle); 1038 } 1039 static void z3fold_zpool_free(void *pool, unsigned long handle) 1040 { 1041 z3fold_free(pool, handle); 1042 } 1043 1044 static int z3fold_zpool_shrink(void *pool, unsigned int pages, 1045 unsigned int *reclaimed) 1046 { 1047 unsigned int total = 0; 1048 int ret = -EINVAL; 1049 1050 while (total < pages) { 1051 ret = z3fold_reclaim_page(pool, 8); 1052 if (ret < 0) 1053 break; 1054 total++; 1055 } 1056 1057 if (reclaimed) 1058 *reclaimed = total; 1059 1060 return ret; 1061 } 1062 1063 static void *z3fold_zpool_map(void *pool, unsigned long handle, 1064 enum zpool_mapmode mm) 1065 { 1066 return z3fold_map(pool, handle); 1067 } 1068 static void z3fold_zpool_unmap(void *pool, unsigned long handle) 1069 { 1070 z3fold_unmap(pool, handle); 1071 } 1072 1073 static u64 z3fold_zpool_total_size(void *pool) 1074 { 1075 return z3fold_get_pool_size(pool) * PAGE_SIZE; 1076 } 1077 1078 static struct zpool_driver z3fold_zpool_driver = { 1079 .type = "z3fold", 1080 .owner = THIS_MODULE, 1081 .create = z3fold_zpool_create, 1082 .destroy = z3fold_zpool_destroy, 1083 .malloc = z3fold_zpool_malloc, 1084 .free = z3fold_zpool_free, 1085 .shrink = z3fold_zpool_shrink, 1086 .map = z3fold_zpool_map, 1087 .unmap = z3fold_zpool_unmap, 1088 .total_size = z3fold_zpool_total_size, 1089 }; 1090 1091 MODULE_ALIAS("zpool-z3fold"); 1092 1093 static int __init init_z3fold(void) 1094 { 1095 /* Make sure the z3fold header is not larger than the page size */ 1096 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE); 1097 zpool_register_driver(&z3fold_zpool_driver); 1098 1099 return 0; 1100 } 1101 1102 static void __exit exit_z3fold(void) 1103 { 1104 zpool_unregister_driver(&z3fold_zpool_driver); 1105 } 1106 1107 module_init(init_z3fold); 1108 module_exit(exit_z3fold); 1109 1110 MODULE_LICENSE("GPL"); 1111 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>"); 1112 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages"); 1113