1// SPDX-License-Identifier: GPL-2.0 2/* 3 * Copyright (C) 2008 Oracle. All rights reserved. 4 */ 5 6#include <linux/kernel.h> 7#include <linux/bio.h> 8#include <linux/file.h> 9#include <linux/fs.h> 10#include <linux/pagemap.h> 11#include <linux/pagevec.h> 12#include <linux/highmem.h> 13#include <linux/kthread.h> 14#include <linux/time.h> 15#include <linux/init.h> 16#include <linux/string.h> 17#include <linux/backing-dev.h> 18#include <linux/writeback.h> 19#include <linux/psi.h> 20#include <linux/slab.h> 21#include <linux/sched/mm.h> 22#include <linux/log2.h> 23#include <linux/shrinker.h> 24#include <crypto/hash.h> 25#include "misc.h" 26#include "ctree.h" 27#include "fs.h" 28#include "btrfs_inode.h" 29#include "bio.h" 30#include "ordered-data.h" 31#include "compression.h" 32#include "extent_io.h" 33#include "extent_map.h" 34#include "subpage.h" 35#include "messages.h" 36#include "super.h" 37 38static struct bio_set btrfs_compressed_bioset; 39 40static const char* const btrfs_compress_types[] = { "", "zlib", "lzo", "zstd" }; 41 42const char* btrfs_compress_type2str(enum btrfs_compression_type type) 43{ 44 switch (type) { 45 case BTRFS_COMPRESS_ZLIB: 46 case BTRFS_COMPRESS_LZO: 47 case BTRFS_COMPRESS_ZSTD: 48 case BTRFS_COMPRESS_NONE: 49 return btrfs_compress_types[type]; 50 default: 51 break; 52 } 53 54 return NULL; 55} 56 57static inline struct compressed_bio *to_compressed_bio(struct btrfs_bio *bbio) 58{ 59 return container_of(bbio, struct compressed_bio, bbio); 60} 61 62static struct compressed_bio *alloc_compressed_bio(struct btrfs_inode *inode, 63 u64 start, blk_opf_t op, 64 btrfs_bio_end_io_t end_io) 65{ 66 struct btrfs_bio *bbio; 67 68 bbio = btrfs_bio(bio_alloc_bioset(NULL, BTRFS_MAX_COMPRESSED_PAGES, op, 69 GFP_NOFS, &btrfs_compressed_bioset)); 70 btrfs_bio_init(bbio, inode->root->fs_info, end_io, NULL); 71 bbio->inode = inode; 72 bbio->file_offset = start; 73 return to_compressed_bio(bbio); 74} 75 76bool btrfs_compress_is_valid_type(const char *str, size_t len) 77{ 78 int i; 79 80 for (i = 1; i < ARRAY_SIZE(btrfs_compress_types); i++) { 81 size_t comp_len = strlen(btrfs_compress_types[i]); 82 83 if (len < comp_len) 84 continue; 85 86 if (!strncmp(btrfs_compress_types[i], str, comp_len)) 87 return true; 88 } 89 return false; 90} 91 92static int compression_compress_pages(int type, struct list_head *ws, 93 struct address_space *mapping, u64 start, struct page **pages, 94 unsigned long *out_pages, unsigned long *total_in, 95 unsigned long *total_out) 96{ 97 switch (type) { 98 case BTRFS_COMPRESS_ZLIB: 99 return zlib_compress_pages(ws, mapping, start, pages, 100 out_pages, total_in, total_out); 101 case BTRFS_COMPRESS_LZO: 102 return lzo_compress_pages(ws, mapping, start, pages, 103 out_pages, total_in, total_out); 104 case BTRFS_COMPRESS_ZSTD: 105 return zstd_compress_pages(ws, mapping, start, pages, 106 out_pages, total_in, total_out); 107 case BTRFS_COMPRESS_NONE: 108 default: 109 /* 110 * This can happen when compression races with remount setting 111 * it to 'no compress', while caller doesn't call 112 * inode_need_compress() to check if we really need to 113 * compress. 114 * 115 * Not a big deal, just need to inform caller that we 116 * haven't allocated any pages yet. 117 */ 118 *out_pages = 0; 119 return -E2BIG; 120 } 121} 122 123static int compression_decompress_bio(struct list_head *ws, 124 struct compressed_bio *cb) 125{ 126 switch (cb->compress_type) { 127 case BTRFS_COMPRESS_ZLIB: return zlib_decompress_bio(ws, cb); 128 case BTRFS_COMPRESS_LZO: return lzo_decompress_bio(ws, cb); 129 case BTRFS_COMPRESS_ZSTD: return zstd_decompress_bio(ws, cb); 130 case BTRFS_COMPRESS_NONE: 131 default: 132 /* 133 * This can't happen, the type is validated several times 134 * before we get here. 135 */ 136 BUG(); 137 } 138} 139 140static int compression_decompress(int type, struct list_head *ws, 141 const u8 *data_in, struct page *dest_page, 142 unsigned long dest_pgoff, size_t srclen, size_t destlen) 143{ 144 switch (type) { 145 case BTRFS_COMPRESS_ZLIB: return zlib_decompress(ws, data_in, dest_page, 146 dest_pgoff, srclen, destlen); 147 case BTRFS_COMPRESS_LZO: return lzo_decompress(ws, data_in, dest_page, 148 dest_pgoff, srclen, destlen); 149 case BTRFS_COMPRESS_ZSTD: return zstd_decompress(ws, data_in, dest_page, 150 dest_pgoff, srclen, destlen); 151 case BTRFS_COMPRESS_NONE: 152 default: 153 /* 154 * This can't happen, the type is validated several times 155 * before we get here. 156 */ 157 BUG(); 158 } 159} 160 161static void btrfs_free_compressed_pages(struct compressed_bio *cb) 162{ 163 for (unsigned int i = 0; i < cb->nr_pages; i++) 164 btrfs_free_compr_page(cb->compressed_pages[i]); 165 kfree(cb->compressed_pages); 166} 167 168static int btrfs_decompress_bio(struct compressed_bio *cb); 169 170/* 171 * Global cache of last unused pages for compression/decompression. 172 */ 173static struct btrfs_compr_pool { 174 struct shrinker *shrinker; 175 spinlock_t lock; 176 struct list_head list; 177 int count; 178 int thresh; 179} compr_pool; 180 181static unsigned long btrfs_compr_pool_count(struct shrinker *sh, struct shrink_control *sc) 182{ 183 int ret; 184 185 /* 186 * We must not read the values more than once if 'ret' gets expanded in 187 * the return statement so we don't accidentally return a negative 188 * number, even if the first condition finds it positive. 189 */ 190 ret = READ_ONCE(compr_pool.count) - READ_ONCE(compr_pool.thresh); 191 192 return ret > 0 ? ret : 0; 193} 194 195static unsigned long btrfs_compr_pool_scan(struct shrinker *sh, struct shrink_control *sc) 196{ 197 struct list_head remove; 198 struct list_head *tmp, *next; 199 int freed; 200 201 if (compr_pool.count == 0) 202 return SHRINK_STOP; 203 204 INIT_LIST_HEAD(&remove); 205 206 /* For now, just simply drain the whole list. */ 207 spin_lock(&compr_pool.lock); 208 list_splice_init(&compr_pool.list, &remove); 209 freed = compr_pool.count; 210 compr_pool.count = 0; 211 spin_unlock(&compr_pool.lock); 212 213 list_for_each_safe(tmp, next, &remove) { 214 struct page *page = list_entry(tmp, struct page, lru); 215 216 ASSERT(page_ref_count(page) == 1); 217 put_page(page); 218 } 219 220 return freed; 221} 222 223/* 224 * Common wrappers for page allocation from compression wrappers 225 */ 226struct page *btrfs_alloc_compr_page(void) 227{ 228 struct page *page = NULL; 229 230 spin_lock(&compr_pool.lock); 231 if (compr_pool.count > 0) { 232 page = list_first_entry(&compr_pool.list, struct page, lru); 233 list_del_init(&page->lru); 234 compr_pool.count--; 235 } 236 spin_unlock(&compr_pool.lock); 237 238 if (page) 239 return page; 240 241 return alloc_page(GFP_NOFS); 242} 243 244void btrfs_free_compr_page(struct page *page) 245{ 246 bool do_free = false; 247 248 spin_lock(&compr_pool.lock); 249 if (compr_pool.count > compr_pool.thresh) { 250 do_free = true; 251 } else { 252 list_add(&page->lru, &compr_pool.list); 253 compr_pool.count++; 254 } 255 spin_unlock(&compr_pool.lock); 256 257 if (!do_free) 258 return; 259 260 ASSERT(page_ref_count(page) == 1); 261 put_page(page); 262} 263 264static void end_bbio_comprssed_read(struct btrfs_bio *bbio) 265{ 266 struct compressed_bio *cb = to_compressed_bio(bbio); 267 blk_status_t status = bbio->bio.bi_status; 268 269 if (!status) 270 status = errno_to_blk_status(btrfs_decompress_bio(cb)); 271 272 btrfs_free_compressed_pages(cb); 273 btrfs_bio_end_io(cb->orig_bbio, status); 274 bio_put(&bbio->bio); 275} 276 277/* 278 * Clear the writeback bits on all of the file 279 * pages for a compressed write 280 */ 281static noinline void end_compressed_writeback(const struct compressed_bio *cb) 282{ 283 struct inode *inode = &cb->bbio.inode->vfs_inode; 284 struct btrfs_fs_info *fs_info = inode_to_fs_info(inode); 285 unsigned long index = cb->start >> PAGE_SHIFT; 286 unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT; 287 struct folio_batch fbatch; 288 const int error = blk_status_to_errno(cb->bbio.bio.bi_status); 289 int i; 290 int ret; 291 292 if (error) 293 mapping_set_error(inode->i_mapping, error); 294 295 folio_batch_init(&fbatch); 296 while (index <= end_index) { 297 ret = filemap_get_folios(inode->i_mapping, &index, end_index, 298 &fbatch); 299 300 if (ret == 0) 301 return; 302 303 for (i = 0; i < ret; i++) { 304 struct folio *folio = fbatch.folios[i]; 305 306 btrfs_folio_clamp_clear_writeback(fs_info, folio, 307 cb->start, cb->len); 308 } 309 folio_batch_release(&fbatch); 310 } 311 /* the inode may be gone now */ 312} 313 314static void btrfs_finish_compressed_write_work(struct work_struct *work) 315{ 316 struct compressed_bio *cb = 317 container_of(work, struct compressed_bio, write_end_work); 318 319 btrfs_finish_ordered_extent(cb->bbio.ordered, NULL, cb->start, cb->len, 320 cb->bbio.bio.bi_status == BLK_STS_OK); 321 322 if (cb->writeback) 323 end_compressed_writeback(cb); 324 /* Note, our inode could be gone now */ 325 326 btrfs_free_compressed_pages(cb); 327 bio_put(&cb->bbio.bio); 328} 329 330/* 331 * Do the cleanup once all the compressed pages hit the disk. This will clear 332 * writeback on the file pages and free the compressed pages. 333 * 334 * This also calls the writeback end hooks for the file pages so that metadata 335 * and checksums can be updated in the file. 336 */ 337static void end_bbio_comprssed_write(struct btrfs_bio *bbio) 338{ 339 struct compressed_bio *cb = to_compressed_bio(bbio); 340 struct btrfs_fs_info *fs_info = bbio->inode->root->fs_info; 341 342 queue_work(fs_info->compressed_write_workers, &cb->write_end_work); 343} 344 345static void btrfs_add_compressed_bio_pages(struct compressed_bio *cb) 346{ 347 struct bio *bio = &cb->bbio.bio; 348 u32 offset = 0; 349 350 while (offset < cb->compressed_len) { 351 u32 len = min_t(u32, cb->compressed_len - offset, PAGE_SIZE); 352 353 /* Maximum compressed extent is smaller than bio size limit. */ 354 __bio_add_page(bio, cb->compressed_pages[offset >> PAGE_SHIFT], 355 len, 0); 356 offset += len; 357 } 358} 359 360/* 361 * worker function to build and submit bios for previously compressed pages. 362 * The corresponding pages in the inode should be marked for writeback 363 * and the compressed pages should have a reference on them for dropping 364 * when the IO is complete. 365 * 366 * This also checksums the file bytes and gets things ready for 367 * the end io hooks. 368 */ 369void btrfs_submit_compressed_write(struct btrfs_ordered_extent *ordered, 370 struct page **compressed_pages, 371 unsigned int nr_pages, 372 blk_opf_t write_flags, 373 bool writeback) 374{ 375 struct btrfs_inode *inode = BTRFS_I(ordered->inode); 376 struct btrfs_fs_info *fs_info = inode->root->fs_info; 377 struct compressed_bio *cb; 378 379 ASSERT(IS_ALIGNED(ordered->file_offset, fs_info->sectorsize)); 380 ASSERT(IS_ALIGNED(ordered->num_bytes, fs_info->sectorsize)); 381 382 cb = alloc_compressed_bio(inode, ordered->file_offset, 383 REQ_OP_WRITE | write_flags, 384 end_bbio_comprssed_write); 385 cb->start = ordered->file_offset; 386 cb->len = ordered->num_bytes; 387 cb->compressed_pages = compressed_pages; 388 cb->compressed_len = ordered->disk_num_bytes; 389 cb->writeback = writeback; 390 INIT_WORK(&cb->write_end_work, btrfs_finish_compressed_write_work); 391 cb->nr_pages = nr_pages; 392 cb->bbio.bio.bi_iter.bi_sector = ordered->disk_bytenr >> SECTOR_SHIFT; 393 cb->bbio.ordered = ordered; 394 btrfs_add_compressed_bio_pages(cb); 395 396 btrfs_submit_bio(&cb->bbio, 0); 397} 398 399/* 400 * Add extra pages in the same compressed file extent so that we don't need to 401 * re-read the same extent again and again. 402 * 403 * NOTE: this won't work well for subpage, as for subpage read, we lock the 404 * full page then submit bio for each compressed/regular extents. 405 * 406 * This means, if we have several sectors in the same page points to the same 407 * on-disk compressed data, we will re-read the same extent many times and 408 * this function can only help for the next page. 409 */ 410static noinline int add_ra_bio_pages(struct inode *inode, 411 u64 compressed_end, 412 struct compressed_bio *cb, 413 int *memstall, unsigned long *pflags) 414{ 415 struct btrfs_fs_info *fs_info = inode_to_fs_info(inode); 416 unsigned long end_index; 417 struct bio *orig_bio = &cb->orig_bbio->bio; 418 u64 cur = cb->orig_bbio->file_offset + orig_bio->bi_iter.bi_size; 419 u64 isize = i_size_read(inode); 420 int ret; 421 struct page *page; 422 struct extent_map *em; 423 struct address_space *mapping = inode->i_mapping; 424 struct extent_map_tree *em_tree; 425 struct extent_io_tree *tree; 426 int sectors_missed = 0; 427 428 em_tree = &BTRFS_I(inode)->extent_tree; 429 tree = &BTRFS_I(inode)->io_tree; 430 431 if (isize == 0) 432 return 0; 433 434 /* 435 * For current subpage support, we only support 64K page size, 436 * which means maximum compressed extent size (128K) is just 2x page 437 * size. 438 * This makes readahead less effective, so here disable readahead for 439 * subpage for now, until full compressed write is supported. 440 */ 441 if (fs_info->sectorsize < PAGE_SIZE) 442 return 0; 443 444 end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT; 445 446 while (cur < compressed_end) { 447 u64 page_end; 448 u64 pg_index = cur >> PAGE_SHIFT; 449 u32 add_size; 450 451 if (pg_index > end_index) 452 break; 453 454 page = xa_load(&mapping->i_pages, pg_index); 455 if (page && !xa_is_value(page)) { 456 sectors_missed += (PAGE_SIZE - offset_in_page(cur)) >> 457 fs_info->sectorsize_bits; 458 459 /* Beyond threshold, no need to continue */ 460 if (sectors_missed > 4) 461 break; 462 463 /* 464 * Jump to next page start as we already have page for 465 * current offset. 466 */ 467 cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE; 468 continue; 469 } 470 471 page = __page_cache_alloc(mapping_gfp_constraint(mapping, 472 ~__GFP_FS)); 473 if (!page) 474 break; 475 476 if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) { 477 put_page(page); 478 /* There is already a page, skip to page end */ 479 cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE; 480 continue; 481 } 482 483 if (!*memstall && PageWorkingset(page)) { 484 psi_memstall_enter(pflags); 485 *memstall = 1; 486 } 487 488 ret = set_page_extent_mapped(page); 489 if (ret < 0) { 490 unlock_page(page); 491 put_page(page); 492 break; 493 } 494 495 page_end = (pg_index << PAGE_SHIFT) + PAGE_SIZE - 1; 496 lock_extent(tree, cur, page_end, NULL); 497 read_lock(&em_tree->lock); 498 em = lookup_extent_mapping(em_tree, cur, page_end + 1 - cur); 499 read_unlock(&em_tree->lock); 500 501 /* 502 * At this point, we have a locked page in the page cache for 503 * these bytes in the file. But, we have to make sure they map 504 * to this compressed extent on disk. 505 */ 506 if (!em || cur < em->start || 507 (cur + fs_info->sectorsize > extent_map_end(em)) || 508 (em->block_start >> SECTOR_SHIFT) != orig_bio->bi_iter.bi_sector) { 509 free_extent_map(em); 510 unlock_extent(tree, cur, page_end, NULL); 511 unlock_page(page); 512 put_page(page); 513 break; 514 } 515 free_extent_map(em); 516 517 if (page->index == end_index) { 518 size_t zero_offset = offset_in_page(isize); 519 520 if (zero_offset) { 521 int zeros; 522 zeros = PAGE_SIZE - zero_offset; 523 memzero_page(page, zero_offset, zeros); 524 } 525 } 526 527 add_size = min(em->start + em->len, page_end + 1) - cur; 528 ret = bio_add_page(orig_bio, page, add_size, offset_in_page(cur)); 529 if (ret != add_size) { 530 unlock_extent(tree, cur, page_end, NULL); 531 unlock_page(page); 532 put_page(page); 533 break; 534 } 535 /* 536 * If it's subpage, we also need to increase its 537 * subpage::readers number, as at endio we will decrease 538 * subpage::readers and to unlock the page. 539 */ 540 if (fs_info->sectorsize < PAGE_SIZE) 541 btrfs_subpage_start_reader(fs_info, page_folio(page), 542 cur, add_size); 543 put_page(page); 544 cur += add_size; 545 } 546 return 0; 547} 548 549/* 550 * for a compressed read, the bio we get passed has all the inode pages 551 * in it. We don't actually do IO on those pages but allocate new ones 552 * to hold the compressed pages on disk. 553 * 554 * bio->bi_iter.bi_sector points to the compressed extent on disk 555 * bio->bi_io_vec points to all of the inode pages 556 * 557 * After the compressed pages are read, we copy the bytes into the 558 * bio we were passed and then call the bio end_io calls 559 */ 560void btrfs_submit_compressed_read(struct btrfs_bio *bbio) 561{ 562 struct btrfs_inode *inode = bbio->inode; 563 struct btrfs_fs_info *fs_info = inode->root->fs_info; 564 struct extent_map_tree *em_tree = &inode->extent_tree; 565 struct compressed_bio *cb; 566 unsigned int compressed_len; 567 u64 file_offset = bbio->file_offset; 568 u64 em_len; 569 u64 em_start; 570 struct extent_map *em; 571 unsigned long pflags; 572 int memstall = 0; 573 blk_status_t ret; 574 int ret2; 575 576 /* we need the actual starting offset of this extent in the file */ 577 read_lock(&em_tree->lock); 578 em = lookup_extent_mapping(em_tree, file_offset, fs_info->sectorsize); 579 read_unlock(&em_tree->lock); 580 if (!em) { 581 ret = BLK_STS_IOERR; 582 goto out; 583 } 584 585 ASSERT(extent_map_is_compressed(em)); 586 compressed_len = em->block_len; 587 588 cb = alloc_compressed_bio(inode, file_offset, REQ_OP_READ, 589 end_bbio_comprssed_read); 590 591 cb->start = em->orig_start; 592 em_len = em->len; 593 em_start = em->start; 594 595 cb->len = bbio->bio.bi_iter.bi_size; 596 cb->compressed_len = compressed_len; 597 cb->compress_type = extent_map_compression(em); 598 cb->orig_bbio = bbio; 599 600 free_extent_map(em); 601 602 cb->nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE); 603 cb->compressed_pages = kcalloc(cb->nr_pages, sizeof(struct page *), GFP_NOFS); 604 if (!cb->compressed_pages) { 605 ret = BLK_STS_RESOURCE; 606 goto out_free_bio; 607 } 608 609 ret2 = btrfs_alloc_page_array(cb->nr_pages, cb->compressed_pages, 0); 610 if (ret2) { 611 ret = BLK_STS_RESOURCE; 612 goto out_free_compressed_pages; 613 } 614 615 add_ra_bio_pages(&inode->vfs_inode, em_start + em_len, cb, &memstall, 616 &pflags); 617 618 /* include any pages we added in add_ra-bio_pages */ 619 cb->len = bbio->bio.bi_iter.bi_size; 620 cb->bbio.bio.bi_iter.bi_sector = bbio->bio.bi_iter.bi_sector; 621 btrfs_add_compressed_bio_pages(cb); 622 623 if (memstall) 624 psi_memstall_leave(&pflags); 625 626 btrfs_submit_bio(&cb->bbio, 0); 627 return; 628 629out_free_compressed_pages: 630 kfree(cb->compressed_pages); 631out_free_bio: 632 bio_put(&cb->bbio.bio); 633out: 634 btrfs_bio_end_io(bbio, ret); 635} 636 637/* 638 * Heuristic uses systematic sampling to collect data from the input data 639 * range, the logic can be tuned by the following constants: 640 * 641 * @SAMPLING_READ_SIZE - how many bytes will be copied from for each sample 642 * @SAMPLING_INTERVAL - range from which the sampled data can be collected 643 */ 644#define SAMPLING_READ_SIZE (16) 645#define SAMPLING_INTERVAL (256) 646 647/* 648 * For statistical analysis of the input data we consider bytes that form a 649 * Galois Field of 256 objects. Each object has an attribute count, ie. how 650 * many times the object appeared in the sample. 651 */ 652#define BUCKET_SIZE (256) 653 654/* 655 * The size of the sample is based on a statistical sampling rule of thumb. 656 * The common way is to perform sampling tests as long as the number of 657 * elements in each cell is at least 5. 658 * 659 * Instead of 5, we choose 32 to obtain more accurate results. 660 * If the data contain the maximum number of symbols, which is 256, we obtain a 661 * sample size bound by 8192. 662 * 663 * For a sample of at most 8KB of data per data range: 16 consecutive bytes 664 * from up to 512 locations. 665 */ 666#define MAX_SAMPLE_SIZE (BTRFS_MAX_UNCOMPRESSED * \ 667 SAMPLING_READ_SIZE / SAMPLING_INTERVAL) 668 669struct bucket_item { 670 u32 count; 671}; 672 673struct heuristic_ws { 674 /* Partial copy of input data */ 675 u8 *sample; 676 u32 sample_size; 677 /* Buckets store counters for each byte value */ 678 struct bucket_item *bucket; 679 /* Sorting buffer */ 680 struct bucket_item *bucket_b; 681 struct list_head list; 682}; 683 684static struct workspace_manager heuristic_wsm; 685 686static void free_heuristic_ws(struct list_head *ws) 687{ 688 struct heuristic_ws *workspace; 689 690 workspace = list_entry(ws, struct heuristic_ws, list); 691 692 kvfree(workspace->sample); 693 kfree(workspace->bucket); 694 kfree(workspace->bucket_b); 695 kfree(workspace); 696} 697 698static struct list_head *alloc_heuristic_ws(unsigned int level) 699{ 700 struct heuristic_ws *ws; 701 702 ws = kzalloc(sizeof(*ws), GFP_KERNEL); 703 if (!ws) 704 return ERR_PTR(-ENOMEM); 705 706 ws->sample = kvmalloc(MAX_SAMPLE_SIZE, GFP_KERNEL); 707 if (!ws->sample) 708 goto fail; 709 710 ws->bucket = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket), GFP_KERNEL); 711 if (!ws->bucket) 712 goto fail; 713 714 ws->bucket_b = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket_b), GFP_KERNEL); 715 if (!ws->bucket_b) 716 goto fail; 717 718 INIT_LIST_HEAD(&ws->list); 719 return &ws->list; 720fail: 721 free_heuristic_ws(&ws->list); 722 return ERR_PTR(-ENOMEM); 723} 724 725const struct btrfs_compress_op btrfs_heuristic_compress = { 726 .workspace_manager = &heuristic_wsm, 727}; 728 729static const struct btrfs_compress_op * const btrfs_compress_op[] = { 730 /* The heuristic is represented as compression type 0 */ 731 &btrfs_heuristic_compress, 732 &btrfs_zlib_compress, 733 &btrfs_lzo_compress, 734 &btrfs_zstd_compress, 735}; 736 737static struct list_head *alloc_workspace(int type, unsigned int level) 738{ 739 switch (type) { 740 case BTRFS_COMPRESS_NONE: return alloc_heuristic_ws(level); 741 case BTRFS_COMPRESS_ZLIB: return zlib_alloc_workspace(level); 742 case BTRFS_COMPRESS_LZO: return lzo_alloc_workspace(level); 743 case BTRFS_COMPRESS_ZSTD: return zstd_alloc_workspace(level); 744 default: 745 /* 746 * This can't happen, the type is validated several times 747 * before we get here. 748 */ 749 BUG(); 750 } 751} 752 753static void free_workspace(int type, struct list_head *ws) 754{ 755 switch (type) { 756 case BTRFS_COMPRESS_NONE: return free_heuristic_ws(ws); 757 case BTRFS_COMPRESS_ZLIB: return zlib_free_workspace(ws); 758 case BTRFS_COMPRESS_LZO: return lzo_free_workspace(ws); 759 case BTRFS_COMPRESS_ZSTD: return zstd_free_workspace(ws); 760 default: 761 /* 762 * This can't happen, the type is validated several times 763 * before we get here. 764 */ 765 BUG(); 766 } 767} 768 769static void btrfs_init_workspace_manager(int type) 770{ 771 struct workspace_manager *wsm; 772 struct list_head *workspace; 773 774 wsm = btrfs_compress_op[type]->workspace_manager; 775 INIT_LIST_HEAD(&wsm->idle_ws); 776 spin_lock_init(&wsm->ws_lock); 777 atomic_set(&wsm->total_ws, 0); 778 init_waitqueue_head(&wsm->ws_wait); 779 780 /* 781 * Preallocate one workspace for each compression type so we can 782 * guarantee forward progress in the worst case 783 */ 784 workspace = alloc_workspace(type, 0); 785 if (IS_ERR(workspace)) { 786 pr_warn( 787 "BTRFS: cannot preallocate compression workspace, will try later\n"); 788 } else { 789 atomic_set(&wsm->total_ws, 1); 790 wsm->free_ws = 1; 791 list_add(workspace, &wsm->idle_ws); 792 } 793} 794 795static void btrfs_cleanup_workspace_manager(int type) 796{ 797 struct workspace_manager *wsman; 798 struct list_head *ws; 799 800 wsman = btrfs_compress_op[type]->workspace_manager; 801 while (!list_empty(&wsman->idle_ws)) { 802 ws = wsman->idle_ws.next; 803 list_del(ws); 804 free_workspace(type, ws); 805 atomic_dec(&wsman->total_ws); 806 } 807} 808 809/* 810 * This finds an available workspace or allocates a new one. 811 * If it's not possible to allocate a new one, waits until there's one. 812 * Preallocation makes a forward progress guarantees and we do not return 813 * errors. 814 */ 815struct list_head *btrfs_get_workspace(int type, unsigned int level) 816{ 817 struct workspace_manager *wsm; 818 struct list_head *workspace; 819 int cpus = num_online_cpus(); 820 unsigned nofs_flag; 821 struct list_head *idle_ws; 822 spinlock_t *ws_lock; 823 atomic_t *total_ws; 824 wait_queue_head_t *ws_wait; 825 int *free_ws; 826 827 wsm = btrfs_compress_op[type]->workspace_manager; 828 idle_ws = &wsm->idle_ws; 829 ws_lock = &wsm->ws_lock; 830 total_ws = &wsm->total_ws; 831 ws_wait = &wsm->ws_wait; 832 free_ws = &wsm->free_ws; 833 834again: 835 spin_lock(ws_lock); 836 if (!list_empty(idle_ws)) { 837 workspace = idle_ws->next; 838 list_del(workspace); 839 (*free_ws)--; 840 spin_unlock(ws_lock); 841 return workspace; 842 843 } 844 if (atomic_read(total_ws) > cpus) { 845 DEFINE_WAIT(wait); 846 847 spin_unlock(ws_lock); 848 prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE); 849 if (atomic_read(total_ws) > cpus && !*free_ws) 850 schedule(); 851 finish_wait(ws_wait, &wait); 852 goto again; 853 } 854 atomic_inc(total_ws); 855 spin_unlock(ws_lock); 856 857 /* 858 * Allocation helpers call vmalloc that can't use GFP_NOFS, so we have 859 * to turn it off here because we might get called from the restricted 860 * context of btrfs_compress_bio/btrfs_compress_pages 861 */ 862 nofs_flag = memalloc_nofs_save(); 863 workspace = alloc_workspace(type, level); 864 memalloc_nofs_restore(nofs_flag); 865 866 if (IS_ERR(workspace)) { 867 atomic_dec(total_ws); 868 wake_up(ws_wait); 869 870 /* 871 * Do not return the error but go back to waiting. There's a 872 * workspace preallocated for each type and the compression 873 * time is bounded so we get to a workspace eventually. This 874 * makes our caller's life easier. 875 * 876 * To prevent silent and low-probability deadlocks (when the 877 * initial preallocation fails), check if there are any 878 * workspaces at all. 879 */ 880 if (atomic_read(total_ws) == 0) { 881 static DEFINE_RATELIMIT_STATE(_rs, 882 /* once per minute */ 60 * HZ, 883 /* no burst */ 1); 884 885 if (__ratelimit(&_rs)) { 886 pr_warn("BTRFS: no compression workspaces, low memory, retrying\n"); 887 } 888 } 889 goto again; 890 } 891 return workspace; 892} 893 894static struct list_head *get_workspace(int type, int level) 895{ 896 switch (type) { 897 case BTRFS_COMPRESS_NONE: return btrfs_get_workspace(type, level); 898 case BTRFS_COMPRESS_ZLIB: return zlib_get_workspace(level); 899 case BTRFS_COMPRESS_LZO: return btrfs_get_workspace(type, level); 900 case BTRFS_COMPRESS_ZSTD: return zstd_get_workspace(level); 901 default: 902 /* 903 * This can't happen, the type is validated several times 904 * before we get here. 905 */ 906 BUG(); 907 } 908} 909 910/* 911 * put a workspace struct back on the list or free it if we have enough 912 * idle ones sitting around 913 */ 914void btrfs_put_workspace(int type, struct list_head *ws) 915{ 916 struct workspace_manager *wsm; 917 struct list_head *idle_ws; 918 spinlock_t *ws_lock; 919 atomic_t *total_ws; 920 wait_queue_head_t *ws_wait; 921 int *free_ws; 922 923 wsm = btrfs_compress_op[type]->workspace_manager; 924 idle_ws = &wsm->idle_ws; 925 ws_lock = &wsm->ws_lock; 926 total_ws = &wsm->total_ws; 927 ws_wait = &wsm->ws_wait; 928 free_ws = &wsm->free_ws; 929 930 spin_lock(ws_lock); 931 if (*free_ws <= num_online_cpus()) { 932 list_add(ws, idle_ws); 933 (*free_ws)++; 934 spin_unlock(ws_lock); 935 goto wake; 936 } 937 spin_unlock(ws_lock); 938 939 free_workspace(type, ws); 940 atomic_dec(total_ws); 941wake: 942 cond_wake_up(ws_wait); 943} 944 945static void put_workspace(int type, struct list_head *ws) 946{ 947 switch (type) { 948 case BTRFS_COMPRESS_NONE: return btrfs_put_workspace(type, ws); 949 case BTRFS_COMPRESS_ZLIB: return btrfs_put_workspace(type, ws); 950 case BTRFS_COMPRESS_LZO: return btrfs_put_workspace(type, ws); 951 case BTRFS_COMPRESS_ZSTD: return zstd_put_workspace(ws); 952 default: 953 /* 954 * This can't happen, the type is validated several times 955 * before we get here. 956 */ 957 BUG(); 958 } 959} 960 961/* 962 * Adjust @level according to the limits of the compression algorithm or 963 * fallback to default 964 */ 965static unsigned int btrfs_compress_set_level(int type, unsigned level) 966{ 967 const struct btrfs_compress_op *ops = btrfs_compress_op[type]; 968 969 if (level == 0) 970 level = ops->default_level; 971 else 972 level = min(level, ops->max_level); 973 974 return level; 975} 976 977/* 978 * Given an address space and start and length, compress the bytes into @pages 979 * that are allocated on demand. 980 * 981 * @type_level is encoded algorithm and level, where level 0 means whatever 982 * default the algorithm chooses and is opaque here; 983 * - compression algo are 0-3 984 * - the level are bits 4-7 985 * 986 * @out_pages is an in/out parameter, holds maximum number of pages to allocate 987 * and returns number of actually allocated pages 988 * 989 * @total_in is used to return the number of bytes actually read. It 990 * may be smaller than the input length if we had to exit early because we 991 * ran out of room in the pages array or because we cross the 992 * max_out threshold. 993 * 994 * @total_out is an in/out parameter, must be set to the input length and will 995 * be also used to return the total number of compressed bytes 996 */ 997int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping, 998 u64 start, struct page **pages, 999 unsigned long *out_pages, 1000 unsigned long *total_in, 1001 unsigned long *total_out) 1002{ 1003 int type = btrfs_compress_type(type_level); 1004 int level = btrfs_compress_level(type_level); 1005 struct list_head *workspace; 1006 int ret; 1007 1008 level = btrfs_compress_set_level(type, level); 1009 workspace = get_workspace(type, level); 1010 ret = compression_compress_pages(type, workspace, mapping, start, pages, 1011 out_pages, total_in, total_out); 1012 put_workspace(type, workspace); 1013 return ret; 1014} 1015 1016static int btrfs_decompress_bio(struct compressed_bio *cb) 1017{ 1018 struct list_head *workspace; 1019 int ret; 1020 int type = cb->compress_type; 1021 1022 workspace = get_workspace(type, 0); 1023 ret = compression_decompress_bio(workspace, cb); 1024 put_workspace(type, workspace); 1025 1026 if (!ret) 1027 zero_fill_bio(&cb->orig_bbio->bio); 1028 return ret; 1029} 1030 1031/* 1032 * a less complex decompression routine. Our compressed data fits in a 1033 * single page, and we want to read a single page out of it. 1034 * start_byte tells us the offset into the compressed data we're interested in 1035 */ 1036int btrfs_decompress(int type, const u8 *data_in, struct page *dest_page, 1037 unsigned long dest_pgoff, size_t srclen, size_t destlen) 1038{ 1039 struct btrfs_fs_info *fs_info = page_to_fs_info(dest_page); 1040 struct list_head *workspace; 1041 const u32 sectorsize = fs_info->sectorsize; 1042 int ret; 1043 1044 /* 1045 * The full destination page range should not exceed the page size. 1046 * And the @destlen should not exceed sectorsize, as this is only called for 1047 * inline file extents, which should not exceed sectorsize. 1048 */ 1049 ASSERT(dest_pgoff + destlen <= PAGE_SIZE && destlen <= sectorsize); 1050 1051 workspace = get_workspace(type, 0); 1052 ret = compression_decompress(type, workspace, data_in, dest_page, 1053 dest_pgoff, srclen, destlen); 1054 put_workspace(type, workspace); 1055 1056 return ret; 1057} 1058 1059int __init btrfs_init_compress(void) 1060{ 1061 if (bioset_init(&btrfs_compressed_bioset, BIO_POOL_SIZE, 1062 offsetof(struct compressed_bio, bbio.bio), 1063 BIOSET_NEED_BVECS)) 1064 return -ENOMEM; 1065 1066 compr_pool.shrinker = shrinker_alloc(SHRINKER_NONSLAB, "btrfs-compr-pages"); 1067 if (!compr_pool.shrinker) 1068 return -ENOMEM; 1069 1070 btrfs_init_workspace_manager(BTRFS_COMPRESS_NONE); 1071 btrfs_init_workspace_manager(BTRFS_COMPRESS_ZLIB); 1072 btrfs_init_workspace_manager(BTRFS_COMPRESS_LZO); 1073 zstd_init_workspace_manager(); 1074 1075 spin_lock_init(&compr_pool.lock); 1076 INIT_LIST_HEAD(&compr_pool.list); 1077 compr_pool.count = 0; 1078 /* 128K / 4K = 32, for 8 threads is 256 pages. */ 1079 compr_pool.thresh = BTRFS_MAX_COMPRESSED / PAGE_SIZE * 8; 1080 compr_pool.shrinker->count_objects = btrfs_compr_pool_count; 1081 compr_pool.shrinker->scan_objects = btrfs_compr_pool_scan; 1082 compr_pool.shrinker->batch = 32; 1083 compr_pool.shrinker->seeks = DEFAULT_SEEKS; 1084 shrinker_register(compr_pool.shrinker); 1085 1086 return 0; 1087} 1088 1089void __cold btrfs_exit_compress(void) 1090{ 1091 /* For now scan drains all pages and does not touch the parameters. */ 1092 btrfs_compr_pool_scan(NULL, NULL); 1093 shrinker_free(compr_pool.shrinker); 1094 1095 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_NONE); 1096 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_ZLIB); 1097 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_LZO); 1098 zstd_cleanup_workspace_manager(); 1099 bioset_exit(&btrfs_compressed_bioset); 1100} 1101 1102/* 1103 * Copy decompressed data from working buffer to pages. 1104 * 1105 * @buf: The decompressed data buffer 1106 * @buf_len: The decompressed data length 1107 * @decompressed: Number of bytes that are already decompressed inside the 1108 * compressed extent 1109 * @cb: The compressed extent descriptor 1110 * @orig_bio: The original bio that the caller wants to read for 1111 * 1112 * An easier to understand graph is like below: 1113 * 1114 * |<- orig_bio ->| |<- orig_bio->| 1115 * |<------- full decompressed extent ----->| 1116 * |<----------- @cb range ---->| 1117 * | |<-- @buf_len -->| 1118 * |<--- @decompressed --->| 1119 * 1120 * Note that, @cb can be a subpage of the full decompressed extent, but 1121 * @cb->start always has the same as the orig_file_offset value of the full 1122 * decompressed extent. 1123 * 1124 * When reading compressed extent, we have to read the full compressed extent, 1125 * while @orig_bio may only want part of the range. 1126 * Thus this function will ensure only data covered by @orig_bio will be copied 1127 * to. 1128 * 1129 * Return 0 if we have copied all needed contents for @orig_bio. 1130 * Return >0 if we need continue decompress. 1131 */ 1132int btrfs_decompress_buf2page(const char *buf, u32 buf_len, 1133 struct compressed_bio *cb, u32 decompressed) 1134{ 1135 struct bio *orig_bio = &cb->orig_bbio->bio; 1136 /* Offset inside the full decompressed extent */ 1137 u32 cur_offset; 1138 1139 cur_offset = decompressed; 1140 /* The main loop to do the copy */ 1141 while (cur_offset < decompressed + buf_len) { 1142 struct bio_vec bvec; 1143 size_t copy_len; 1144 u32 copy_start; 1145 /* Offset inside the full decompressed extent */ 1146 u32 bvec_offset; 1147 1148 bvec = bio_iter_iovec(orig_bio, orig_bio->bi_iter); 1149 /* 1150 * cb->start may underflow, but subtracting that value can still 1151 * give us correct offset inside the full decompressed extent. 1152 */ 1153 bvec_offset = page_offset(bvec.bv_page) + bvec.bv_offset - cb->start; 1154 1155 /* Haven't reached the bvec range, exit */ 1156 if (decompressed + buf_len <= bvec_offset) 1157 return 1; 1158 1159 copy_start = max(cur_offset, bvec_offset); 1160 copy_len = min(bvec_offset + bvec.bv_len, 1161 decompressed + buf_len) - copy_start; 1162 ASSERT(copy_len); 1163 1164 /* 1165 * Extra range check to ensure we didn't go beyond 1166 * @buf + @buf_len. 1167 */ 1168 ASSERT(copy_start - decompressed < buf_len); 1169 memcpy_to_page(bvec.bv_page, bvec.bv_offset, 1170 buf + copy_start - decompressed, copy_len); 1171 cur_offset += copy_len; 1172 1173 bio_advance(orig_bio, copy_len); 1174 /* Finished the bio */ 1175 if (!orig_bio->bi_iter.bi_size) 1176 return 0; 1177 } 1178 return 1; 1179} 1180 1181/* 1182 * Shannon Entropy calculation 1183 * 1184 * Pure byte distribution analysis fails to determine compressibility of data. 1185 * Try calculating entropy to estimate the average minimum number of bits 1186 * needed to encode the sampled data. 1187 * 1188 * For convenience, return the percentage of needed bits, instead of amount of 1189 * bits directly. 1190 * 1191 * @ENTROPY_LVL_ACEPTABLE - below that threshold, sample has low byte entropy 1192 * and can be compressible with high probability 1193 * 1194 * @ENTROPY_LVL_HIGH - data are not compressible with high probability 1195 * 1196 * Use of ilog2() decreases precision, we lower the LVL to 5 to compensate. 1197 */ 1198#define ENTROPY_LVL_ACEPTABLE (65) 1199#define ENTROPY_LVL_HIGH (80) 1200 1201/* 1202 * For increasead precision in shannon_entropy calculation, 1203 * let's do pow(n, M) to save more digits after comma: 1204 * 1205 * - maximum int bit length is 64 1206 * - ilog2(MAX_SAMPLE_SIZE) -> 13 1207 * - 13 * 4 = 52 < 64 -> M = 4 1208 * 1209 * So use pow(n, 4). 1210 */ 1211static inline u32 ilog2_w(u64 n) 1212{ 1213 return ilog2(n * n * n * n); 1214} 1215 1216static u32 shannon_entropy(struct heuristic_ws *ws) 1217{ 1218 const u32 entropy_max = 8 * ilog2_w(2); 1219 u32 entropy_sum = 0; 1220 u32 p, p_base, sz_base; 1221 u32 i; 1222 1223 sz_base = ilog2_w(ws->sample_size); 1224 for (i = 0; i < BUCKET_SIZE && ws->bucket[i].count > 0; i++) { 1225 p = ws->bucket[i].count; 1226 p_base = ilog2_w(p); 1227 entropy_sum += p * (sz_base - p_base); 1228 } 1229 1230 entropy_sum /= ws->sample_size; 1231 return entropy_sum * 100 / entropy_max; 1232} 1233 1234#define RADIX_BASE 4U 1235#define COUNTERS_SIZE (1U << RADIX_BASE) 1236 1237static u8 get4bits(u64 num, int shift) { 1238 u8 low4bits; 1239 1240 num >>= shift; 1241 /* Reverse order */ 1242 low4bits = (COUNTERS_SIZE - 1) - (num % COUNTERS_SIZE); 1243 return low4bits; 1244} 1245 1246/* 1247 * Use 4 bits as radix base 1248 * Use 16 u32 counters for calculating new position in buf array 1249 * 1250 * @array - array that will be sorted 1251 * @array_buf - buffer array to store sorting results 1252 * must be equal in size to @array 1253 * @num - array size 1254 */ 1255static void radix_sort(struct bucket_item *array, struct bucket_item *array_buf, 1256 int num) 1257{ 1258 u64 max_num; 1259 u64 buf_num; 1260 u32 counters[COUNTERS_SIZE]; 1261 u32 new_addr; 1262 u32 addr; 1263 int bitlen; 1264 int shift; 1265 int i; 1266 1267 /* 1268 * Try avoid useless loop iterations for small numbers stored in big 1269 * counters. Example: 48 33 4 ... in 64bit array 1270 */ 1271 max_num = array[0].count; 1272 for (i = 1; i < num; i++) { 1273 buf_num = array[i].count; 1274 if (buf_num > max_num) 1275 max_num = buf_num; 1276 } 1277 1278 buf_num = ilog2(max_num); 1279 bitlen = ALIGN(buf_num, RADIX_BASE * 2); 1280 1281 shift = 0; 1282 while (shift < bitlen) { 1283 memset(counters, 0, sizeof(counters)); 1284 1285 for (i = 0; i < num; i++) { 1286 buf_num = array[i].count; 1287 addr = get4bits(buf_num, shift); 1288 counters[addr]++; 1289 } 1290 1291 for (i = 1; i < COUNTERS_SIZE; i++) 1292 counters[i] += counters[i - 1]; 1293 1294 for (i = num - 1; i >= 0; i--) { 1295 buf_num = array[i].count; 1296 addr = get4bits(buf_num, shift); 1297 counters[addr]--; 1298 new_addr = counters[addr]; 1299 array_buf[new_addr] = array[i]; 1300 } 1301 1302 shift += RADIX_BASE; 1303 1304 /* 1305 * Normal radix expects to move data from a temporary array, to 1306 * the main one. But that requires some CPU time. Avoid that 1307 * by doing another sort iteration to original array instead of 1308 * memcpy() 1309 */ 1310 memset(counters, 0, sizeof(counters)); 1311 1312 for (i = 0; i < num; i ++) { 1313 buf_num = array_buf[i].count; 1314 addr = get4bits(buf_num, shift); 1315 counters[addr]++; 1316 } 1317 1318 for (i = 1; i < COUNTERS_SIZE; i++) 1319 counters[i] += counters[i - 1]; 1320 1321 for (i = num - 1; i >= 0; i--) { 1322 buf_num = array_buf[i].count; 1323 addr = get4bits(buf_num, shift); 1324 counters[addr]--; 1325 new_addr = counters[addr]; 1326 array[new_addr] = array_buf[i]; 1327 } 1328 1329 shift += RADIX_BASE; 1330 } 1331} 1332 1333/* 1334 * Size of the core byte set - how many bytes cover 90% of the sample 1335 * 1336 * There are several types of structured binary data that use nearly all byte 1337 * values. The distribution can be uniform and counts in all buckets will be 1338 * nearly the same (eg. encrypted data). Unlikely to be compressible. 1339 * 1340 * Other possibility is normal (Gaussian) distribution, where the data could 1341 * be potentially compressible, but we have to take a few more steps to decide 1342 * how much. 1343 * 1344 * @BYTE_CORE_SET_LOW - main part of byte values repeated frequently, 1345 * compression algo can easy fix that 1346 * @BYTE_CORE_SET_HIGH - data have uniform distribution and with high 1347 * probability is not compressible 1348 */ 1349#define BYTE_CORE_SET_LOW (64) 1350#define BYTE_CORE_SET_HIGH (200) 1351 1352static int byte_core_set_size(struct heuristic_ws *ws) 1353{ 1354 u32 i; 1355 u32 coreset_sum = 0; 1356 const u32 core_set_threshold = ws->sample_size * 90 / 100; 1357 struct bucket_item *bucket = ws->bucket; 1358 1359 /* Sort in reverse order */ 1360 radix_sort(ws->bucket, ws->bucket_b, BUCKET_SIZE); 1361 1362 for (i = 0; i < BYTE_CORE_SET_LOW; i++) 1363 coreset_sum += bucket[i].count; 1364 1365 if (coreset_sum > core_set_threshold) 1366 return i; 1367 1368 for (; i < BYTE_CORE_SET_HIGH && bucket[i].count > 0; i++) { 1369 coreset_sum += bucket[i].count; 1370 if (coreset_sum > core_set_threshold) 1371 break; 1372 } 1373 1374 return i; 1375} 1376 1377/* 1378 * Count byte values in buckets. 1379 * This heuristic can detect textual data (configs, xml, json, html, etc). 1380 * Because in most text-like data byte set is restricted to limited number of 1381 * possible characters, and that restriction in most cases makes data easy to 1382 * compress. 1383 * 1384 * @BYTE_SET_THRESHOLD - consider all data within this byte set size: 1385 * less - compressible 1386 * more - need additional analysis 1387 */ 1388#define BYTE_SET_THRESHOLD (64) 1389 1390static u32 byte_set_size(const struct heuristic_ws *ws) 1391{ 1392 u32 i; 1393 u32 byte_set_size = 0; 1394 1395 for (i = 0; i < BYTE_SET_THRESHOLD; i++) { 1396 if (ws->bucket[i].count > 0) 1397 byte_set_size++; 1398 } 1399 1400 /* 1401 * Continue collecting count of byte values in buckets. If the byte 1402 * set size is bigger then the threshold, it's pointless to continue, 1403 * the detection technique would fail for this type of data. 1404 */ 1405 for (; i < BUCKET_SIZE; i++) { 1406 if (ws->bucket[i].count > 0) { 1407 byte_set_size++; 1408 if (byte_set_size > BYTE_SET_THRESHOLD) 1409 return byte_set_size; 1410 } 1411 } 1412 1413 return byte_set_size; 1414} 1415 1416static bool sample_repeated_patterns(struct heuristic_ws *ws) 1417{ 1418 const u32 half_of_sample = ws->sample_size / 2; 1419 const u8 *data = ws->sample; 1420 1421 return memcmp(&data[0], &data[half_of_sample], half_of_sample) == 0; 1422} 1423 1424static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end, 1425 struct heuristic_ws *ws) 1426{ 1427 struct page *page; 1428 u64 index, index_end; 1429 u32 i, curr_sample_pos; 1430 u8 *in_data; 1431 1432 /* 1433 * Compression handles the input data by chunks of 128KiB 1434 * (defined by BTRFS_MAX_UNCOMPRESSED) 1435 * 1436 * We do the same for the heuristic and loop over the whole range. 1437 * 1438 * MAX_SAMPLE_SIZE - calculated under assumption that heuristic will 1439 * process no more than BTRFS_MAX_UNCOMPRESSED at a time. 1440 */ 1441 if (end - start > BTRFS_MAX_UNCOMPRESSED) 1442 end = start + BTRFS_MAX_UNCOMPRESSED; 1443 1444 index = start >> PAGE_SHIFT; 1445 index_end = end >> PAGE_SHIFT; 1446 1447 /* Don't miss unaligned end */ 1448 if (!PAGE_ALIGNED(end)) 1449 index_end++; 1450 1451 curr_sample_pos = 0; 1452 while (index < index_end) { 1453 page = find_get_page(inode->i_mapping, index); 1454 in_data = kmap_local_page(page); 1455 /* Handle case where the start is not aligned to PAGE_SIZE */ 1456 i = start % PAGE_SIZE; 1457 while (i < PAGE_SIZE - SAMPLING_READ_SIZE) { 1458 /* Don't sample any garbage from the last page */ 1459 if (start > end - SAMPLING_READ_SIZE) 1460 break; 1461 memcpy(&ws->sample[curr_sample_pos], &in_data[i], 1462 SAMPLING_READ_SIZE); 1463 i += SAMPLING_INTERVAL; 1464 start += SAMPLING_INTERVAL; 1465 curr_sample_pos += SAMPLING_READ_SIZE; 1466 } 1467 kunmap_local(in_data); 1468 put_page(page); 1469 1470 index++; 1471 } 1472 1473 ws->sample_size = curr_sample_pos; 1474} 1475 1476/* 1477 * Compression heuristic. 1478 * 1479 * The following types of analysis can be performed: 1480 * - detect mostly zero data 1481 * - detect data with low "byte set" size (text, etc) 1482 * - detect data with low/high "core byte" set 1483 * 1484 * Return non-zero if the compression should be done, 0 otherwise. 1485 */ 1486int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end) 1487{ 1488 struct list_head *ws_list = get_workspace(0, 0); 1489 struct heuristic_ws *ws; 1490 u32 i; 1491 u8 byte; 1492 int ret = 0; 1493 1494 ws = list_entry(ws_list, struct heuristic_ws, list); 1495 1496 heuristic_collect_sample(inode, start, end, ws); 1497 1498 if (sample_repeated_patterns(ws)) { 1499 ret = 1; 1500 goto out; 1501 } 1502 1503 memset(ws->bucket, 0, sizeof(*ws->bucket)*BUCKET_SIZE); 1504 1505 for (i = 0; i < ws->sample_size; i++) { 1506 byte = ws->sample[i]; 1507 ws->bucket[byte].count++; 1508 } 1509 1510 i = byte_set_size(ws); 1511 if (i < BYTE_SET_THRESHOLD) { 1512 ret = 2; 1513 goto out; 1514 } 1515 1516 i = byte_core_set_size(ws); 1517 if (i <= BYTE_CORE_SET_LOW) { 1518 ret = 3; 1519 goto out; 1520 } 1521 1522 if (i >= BYTE_CORE_SET_HIGH) { 1523 ret = 0; 1524 goto out; 1525 } 1526 1527 i = shannon_entropy(ws); 1528 if (i <= ENTROPY_LVL_ACEPTABLE) { 1529 ret = 4; 1530 goto out; 1531 } 1532 1533 /* 1534 * For the levels below ENTROPY_LVL_HIGH, additional analysis would be 1535 * needed to give green light to compression. 1536 * 1537 * For now just assume that compression at that level is not worth the 1538 * resources because: 1539 * 1540 * 1. it is possible to defrag the data later 1541 * 1542 * 2. the data would turn out to be hardly compressible, eg. 150 byte 1543 * values, every bucket has counter at level ~54. The heuristic would 1544 * be confused. This can happen when data have some internal repeated 1545 * patterns like "abbacbbc...". This can be detected by analyzing 1546 * pairs of bytes, which is too costly. 1547 */ 1548 if (i < ENTROPY_LVL_HIGH) { 1549 ret = 5; 1550 goto out; 1551 } else { 1552 ret = 0; 1553 goto out; 1554 } 1555 1556out: 1557 put_workspace(0, ws_list); 1558 return ret; 1559} 1560 1561/* 1562 * Convert the compression suffix (eg. after "zlib" starting with ":") to 1563 * level, unrecognized string will set the default level 1564 */ 1565unsigned int btrfs_compress_str2level(unsigned int type, const char *str) 1566{ 1567 unsigned int level = 0; 1568 int ret; 1569 1570 if (!type) 1571 return 0; 1572 1573 if (str[0] == ':') { 1574 ret = kstrtouint(str + 1, 10, &level); 1575 if (ret) 1576 level = 0; 1577 } 1578 1579 level = btrfs_compress_set_level(type, level); 1580 1581 return level; 1582} 1583