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/slab.h> 20 #include <linux/sched/mm.h> 21 #include <linux/log2.h> 22 #include <crypto/hash.h> 23 #include "misc.h" 24 #include "ctree.h" 25 #include "disk-io.h" 26 #include "transaction.h" 27 #include "btrfs_inode.h" 28 #include "volumes.h" 29 #include "ordered-data.h" 30 #include "compression.h" 31 #include "extent_io.h" 32 #include "extent_map.h" 33 #include "subpage.h" 34 #include "zoned.h" 35 36 static const char* const btrfs_compress_types[] = { "", "zlib", "lzo", "zstd" }; 37 38 const char* btrfs_compress_type2str(enum btrfs_compression_type type) 39 { 40 switch (type) { 41 case BTRFS_COMPRESS_ZLIB: 42 case BTRFS_COMPRESS_LZO: 43 case BTRFS_COMPRESS_ZSTD: 44 case BTRFS_COMPRESS_NONE: 45 return btrfs_compress_types[type]; 46 default: 47 break; 48 } 49 50 return NULL; 51 } 52 53 bool btrfs_compress_is_valid_type(const char *str, size_t len) 54 { 55 int i; 56 57 for (i = 1; i < ARRAY_SIZE(btrfs_compress_types); i++) { 58 size_t comp_len = strlen(btrfs_compress_types[i]); 59 60 if (len < comp_len) 61 continue; 62 63 if (!strncmp(btrfs_compress_types[i], str, comp_len)) 64 return true; 65 } 66 return false; 67 } 68 69 static int compression_compress_pages(int type, struct list_head *ws, 70 struct address_space *mapping, u64 start, struct page **pages, 71 unsigned long *out_pages, unsigned long *total_in, 72 unsigned long *total_out) 73 { 74 switch (type) { 75 case BTRFS_COMPRESS_ZLIB: 76 return zlib_compress_pages(ws, mapping, start, pages, 77 out_pages, total_in, total_out); 78 case BTRFS_COMPRESS_LZO: 79 return lzo_compress_pages(ws, mapping, start, pages, 80 out_pages, total_in, total_out); 81 case BTRFS_COMPRESS_ZSTD: 82 return zstd_compress_pages(ws, mapping, start, pages, 83 out_pages, total_in, total_out); 84 case BTRFS_COMPRESS_NONE: 85 default: 86 /* 87 * This can happen when compression races with remount setting 88 * it to 'no compress', while caller doesn't call 89 * inode_need_compress() to check if we really need to 90 * compress. 91 * 92 * Not a big deal, just need to inform caller that we 93 * haven't allocated any pages yet. 94 */ 95 *out_pages = 0; 96 return -E2BIG; 97 } 98 } 99 100 static int compression_decompress_bio(struct list_head *ws, 101 struct compressed_bio *cb) 102 { 103 switch (cb->compress_type) { 104 case BTRFS_COMPRESS_ZLIB: return zlib_decompress_bio(ws, cb); 105 case BTRFS_COMPRESS_LZO: return lzo_decompress_bio(ws, cb); 106 case BTRFS_COMPRESS_ZSTD: return zstd_decompress_bio(ws, cb); 107 case BTRFS_COMPRESS_NONE: 108 default: 109 /* 110 * This can't happen, the type is validated several times 111 * before we get here. 112 */ 113 BUG(); 114 } 115 } 116 117 static int compression_decompress(int type, struct list_head *ws, 118 unsigned char *data_in, struct page *dest_page, 119 unsigned long start_byte, size_t srclen, size_t destlen) 120 { 121 switch (type) { 122 case BTRFS_COMPRESS_ZLIB: return zlib_decompress(ws, data_in, dest_page, 123 start_byte, srclen, destlen); 124 case BTRFS_COMPRESS_LZO: return lzo_decompress(ws, data_in, dest_page, 125 start_byte, srclen, destlen); 126 case BTRFS_COMPRESS_ZSTD: return zstd_decompress(ws, data_in, dest_page, 127 start_byte, srclen, destlen); 128 case BTRFS_COMPRESS_NONE: 129 default: 130 /* 131 * This can't happen, the type is validated several times 132 * before we get here. 133 */ 134 BUG(); 135 } 136 } 137 138 static int btrfs_decompress_bio(struct compressed_bio *cb); 139 140 static void finish_compressed_bio_read(struct compressed_bio *cb) 141 { 142 unsigned int index; 143 struct page *page; 144 145 if (cb->status == BLK_STS_OK) 146 cb->status = errno_to_blk_status(btrfs_decompress_bio(cb)); 147 148 /* Release the compressed pages */ 149 for (index = 0; index < cb->nr_pages; index++) { 150 page = cb->compressed_pages[index]; 151 page->mapping = NULL; 152 put_page(page); 153 } 154 155 /* Do io completion on the original bio */ 156 if (cb->status != BLK_STS_OK) 157 cb->orig_bio->bi_status = cb->status; 158 bio_endio(cb->orig_bio); 159 160 /* Finally free the cb struct */ 161 kfree(cb->compressed_pages); 162 kfree(cb); 163 } 164 165 /* 166 * Verify the checksums and kick off repair if needed on the uncompressed data 167 * before decompressing it into the original bio and freeing the uncompressed 168 * pages. 169 */ 170 static void end_compressed_bio_read(struct bio *bio) 171 { 172 struct compressed_bio *cb = bio->bi_private; 173 struct inode *inode = cb->inode; 174 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); 175 struct btrfs_inode *bi = BTRFS_I(inode); 176 bool csum = !(bi->flags & BTRFS_INODE_NODATASUM) && 177 !test_bit(BTRFS_FS_STATE_NO_CSUMS, &fs_info->fs_state); 178 blk_status_t status = bio->bi_status; 179 struct btrfs_bio *bbio = btrfs_bio(bio); 180 struct bvec_iter iter; 181 struct bio_vec bv; 182 u32 offset; 183 184 btrfs_bio_for_each_sector(fs_info, bv, bbio, iter, offset) { 185 u64 start = bbio->file_offset + offset; 186 187 if (!status && 188 (!csum || !btrfs_check_data_csum(inode, bbio, offset, 189 bv.bv_page, bv.bv_offset))) { 190 clean_io_failure(fs_info, &bi->io_failure_tree, 191 &bi->io_tree, start, bv.bv_page, 192 btrfs_ino(bi), bv.bv_offset); 193 } else { 194 int ret; 195 196 refcount_inc(&cb->pending_ios); 197 ret = btrfs_repair_one_sector(inode, bbio, offset, 198 bv.bv_page, bv.bv_offset, 199 btrfs_submit_data_read_bio); 200 if (ret) { 201 refcount_dec(&cb->pending_ios); 202 status = errno_to_blk_status(ret); 203 } 204 } 205 } 206 207 if (status) 208 cb->status = status; 209 210 if (refcount_dec_and_test(&cb->pending_ios)) 211 finish_compressed_bio_read(cb); 212 btrfs_bio_free_csum(bbio); 213 bio_put(bio); 214 } 215 216 /* 217 * Clear the writeback bits on all of the file 218 * pages for a compressed write 219 */ 220 static noinline void end_compressed_writeback(struct inode *inode, 221 const struct compressed_bio *cb) 222 { 223 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); 224 unsigned long index = cb->start >> PAGE_SHIFT; 225 unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT; 226 struct folio_batch fbatch; 227 const int errno = blk_status_to_errno(cb->status); 228 int i; 229 int ret; 230 231 if (errno) 232 mapping_set_error(inode->i_mapping, errno); 233 234 folio_batch_init(&fbatch); 235 while (index <= end_index) { 236 ret = filemap_get_folios(inode->i_mapping, &index, end_index, 237 &fbatch); 238 239 if (ret == 0) 240 return; 241 242 for (i = 0; i < ret; i++) { 243 struct folio *folio = fbatch.folios[i]; 244 245 if (errno) 246 folio_set_error(folio); 247 btrfs_page_clamp_clear_writeback(fs_info, &folio->page, 248 cb->start, cb->len); 249 } 250 folio_batch_release(&fbatch); 251 } 252 /* the inode may be gone now */ 253 } 254 255 static void finish_compressed_bio_write(struct compressed_bio *cb) 256 { 257 struct inode *inode = cb->inode; 258 unsigned int index; 259 260 /* 261 * Ok, we're the last bio for this extent, step one is to call back 262 * into the FS and do all the end_io operations. 263 */ 264 btrfs_writepage_endio_finish_ordered(BTRFS_I(inode), NULL, 265 cb->start, cb->start + cb->len - 1, 266 cb->status == BLK_STS_OK); 267 268 if (cb->writeback) 269 end_compressed_writeback(inode, cb); 270 /* Note, our inode could be gone now */ 271 272 /* 273 * Release the compressed pages, these came from alloc_page and 274 * are not attached to the inode at all 275 */ 276 for (index = 0; index < cb->nr_pages; index++) { 277 struct page *page = cb->compressed_pages[index]; 278 279 page->mapping = NULL; 280 put_page(page); 281 } 282 283 /* Finally free the cb struct */ 284 kfree(cb->compressed_pages); 285 kfree(cb); 286 } 287 288 static void btrfs_finish_compressed_write_work(struct work_struct *work) 289 { 290 struct compressed_bio *cb = 291 container_of(work, struct compressed_bio, write_end_work); 292 293 finish_compressed_bio_write(cb); 294 } 295 296 /* 297 * Do the cleanup once all the compressed pages hit the disk. This will clear 298 * writeback on the file pages and free the compressed pages. 299 * 300 * This also calls the writeback end hooks for the file pages so that metadata 301 * and checksums can be updated in the file. 302 */ 303 static void end_compressed_bio_write(struct bio *bio) 304 { 305 struct compressed_bio *cb = bio->bi_private; 306 307 if (bio->bi_status) 308 cb->status = bio->bi_status; 309 310 if (refcount_dec_and_test(&cb->pending_ios)) { 311 struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb); 312 313 btrfs_record_physical_zoned(cb->inode, cb->start, bio); 314 queue_work(fs_info->compressed_write_workers, &cb->write_end_work); 315 } 316 bio_put(bio); 317 } 318 319 /* 320 * Allocate a compressed_bio, which will be used to read/write on-disk 321 * (aka, compressed) * data. 322 * 323 * @cb: The compressed_bio structure, which records all the needed 324 * information to bind the compressed data to the uncompressed 325 * page cache. 326 * @disk_byten: The logical bytenr where the compressed data will be read 327 * from or written to. 328 * @endio_func: The endio function to call after the IO for compressed data 329 * is finished. 330 * @next_stripe_start: Return value of logical bytenr of where next stripe starts. 331 * Let the caller know to only fill the bio up to the stripe 332 * boundary. 333 */ 334 335 336 static struct bio *alloc_compressed_bio(struct compressed_bio *cb, u64 disk_bytenr, 337 blk_opf_t opf, bio_end_io_t endio_func, 338 u64 *next_stripe_start) 339 { 340 struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb); 341 struct btrfs_io_geometry geom; 342 struct extent_map *em; 343 struct bio *bio; 344 int ret; 345 346 bio = btrfs_bio_alloc(BIO_MAX_VECS); 347 348 bio->bi_iter.bi_sector = disk_bytenr >> SECTOR_SHIFT; 349 bio->bi_opf = opf; 350 bio->bi_private = cb; 351 bio->bi_end_io = endio_func; 352 353 em = btrfs_get_chunk_map(fs_info, disk_bytenr, fs_info->sectorsize); 354 if (IS_ERR(em)) { 355 bio_put(bio); 356 return ERR_CAST(em); 357 } 358 359 if (bio_op(bio) == REQ_OP_ZONE_APPEND) 360 bio_set_dev(bio, em->map_lookup->stripes[0].dev->bdev); 361 362 ret = btrfs_get_io_geometry(fs_info, em, btrfs_op(bio), disk_bytenr, &geom); 363 free_extent_map(em); 364 if (ret < 0) { 365 bio_put(bio); 366 return ERR_PTR(ret); 367 } 368 *next_stripe_start = disk_bytenr + geom.len; 369 refcount_inc(&cb->pending_ios); 370 return bio; 371 } 372 373 /* 374 * worker function to build and submit bios for previously compressed pages. 375 * The corresponding pages in the inode should be marked for writeback 376 * and the compressed pages should have a reference on them for dropping 377 * when the IO is complete. 378 * 379 * This also checksums the file bytes and gets things ready for 380 * the end io hooks. 381 */ 382 blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start, 383 unsigned int len, u64 disk_start, 384 unsigned int compressed_len, 385 struct page **compressed_pages, 386 unsigned int nr_pages, 387 blk_opf_t write_flags, 388 struct cgroup_subsys_state *blkcg_css, 389 bool writeback) 390 { 391 struct btrfs_fs_info *fs_info = inode->root->fs_info; 392 struct bio *bio = NULL; 393 struct compressed_bio *cb; 394 u64 cur_disk_bytenr = disk_start; 395 u64 next_stripe_start; 396 blk_status_t ret = BLK_STS_OK; 397 int skip_sum = inode->flags & BTRFS_INODE_NODATASUM; 398 const bool use_append = btrfs_use_zone_append(inode, disk_start); 399 const enum req_op bio_op = use_append ? REQ_OP_ZONE_APPEND : REQ_OP_WRITE; 400 401 ASSERT(IS_ALIGNED(start, fs_info->sectorsize) && 402 IS_ALIGNED(len, fs_info->sectorsize)); 403 cb = kmalloc(sizeof(struct compressed_bio), GFP_NOFS); 404 if (!cb) 405 return BLK_STS_RESOURCE; 406 refcount_set(&cb->pending_ios, 1); 407 cb->status = BLK_STS_OK; 408 cb->inode = &inode->vfs_inode; 409 cb->start = start; 410 cb->len = len; 411 cb->compressed_pages = compressed_pages; 412 cb->compressed_len = compressed_len; 413 cb->writeback = writeback; 414 INIT_WORK(&cb->write_end_work, btrfs_finish_compressed_write_work); 415 cb->nr_pages = nr_pages; 416 417 if (blkcg_css) 418 kthread_associate_blkcg(blkcg_css); 419 420 while (cur_disk_bytenr < disk_start + compressed_len) { 421 u64 offset = cur_disk_bytenr - disk_start; 422 unsigned int index = offset >> PAGE_SHIFT; 423 unsigned int real_size; 424 unsigned int added; 425 struct page *page = compressed_pages[index]; 426 bool submit = false; 427 428 /* Allocate new bio if submitted or not yet allocated */ 429 if (!bio) { 430 bio = alloc_compressed_bio(cb, cur_disk_bytenr, 431 bio_op | write_flags, end_compressed_bio_write, 432 &next_stripe_start); 433 if (IS_ERR(bio)) { 434 ret = errno_to_blk_status(PTR_ERR(bio)); 435 break; 436 } 437 if (blkcg_css) 438 bio->bi_opf |= REQ_CGROUP_PUNT; 439 } 440 /* 441 * We should never reach next_stripe_start start as we will 442 * submit comp_bio when reach the boundary immediately. 443 */ 444 ASSERT(cur_disk_bytenr != next_stripe_start); 445 446 /* 447 * We have various limits on the real read size: 448 * - stripe boundary 449 * - page boundary 450 * - compressed length boundary 451 */ 452 real_size = min_t(u64, U32_MAX, next_stripe_start - cur_disk_bytenr); 453 real_size = min_t(u64, real_size, PAGE_SIZE - offset_in_page(offset)); 454 real_size = min_t(u64, real_size, compressed_len - offset); 455 ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize)); 456 457 if (use_append) 458 added = bio_add_zone_append_page(bio, page, real_size, 459 offset_in_page(offset)); 460 else 461 added = bio_add_page(bio, page, real_size, 462 offset_in_page(offset)); 463 /* Reached zoned boundary */ 464 if (added == 0) 465 submit = true; 466 467 cur_disk_bytenr += added; 468 /* Reached stripe boundary */ 469 if (cur_disk_bytenr == next_stripe_start) 470 submit = true; 471 472 /* Finished the range */ 473 if (cur_disk_bytenr == disk_start + compressed_len) 474 submit = true; 475 476 if (submit) { 477 if (!skip_sum) { 478 ret = btrfs_csum_one_bio(inode, bio, start, true); 479 if (ret) { 480 bio->bi_status = ret; 481 bio_endio(bio); 482 break; 483 } 484 } 485 486 ASSERT(bio->bi_iter.bi_size); 487 btrfs_submit_bio(fs_info, bio, 0); 488 bio = NULL; 489 } 490 cond_resched(); 491 } 492 493 if (blkcg_css) 494 kthread_associate_blkcg(NULL); 495 496 if (refcount_dec_and_test(&cb->pending_ios)) 497 finish_compressed_bio_write(cb); 498 return ret; 499 } 500 501 static u64 bio_end_offset(struct bio *bio) 502 { 503 struct bio_vec *last = bio_last_bvec_all(bio); 504 505 return page_offset(last->bv_page) + last->bv_len + last->bv_offset; 506 } 507 508 /* 509 * Add extra pages in the same compressed file extent so that we don't need to 510 * re-read the same extent again and again. 511 * 512 * NOTE: this won't work well for subpage, as for subpage read, we lock the 513 * full page then submit bio for each compressed/regular extents. 514 * 515 * This means, if we have several sectors in the same page points to the same 516 * on-disk compressed data, we will re-read the same extent many times and 517 * this function can only help for the next page. 518 */ 519 static noinline int add_ra_bio_pages(struct inode *inode, 520 u64 compressed_end, 521 struct compressed_bio *cb) 522 { 523 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); 524 unsigned long end_index; 525 u64 cur = bio_end_offset(cb->orig_bio); 526 u64 isize = i_size_read(inode); 527 int ret; 528 struct page *page; 529 struct extent_map *em; 530 struct address_space *mapping = inode->i_mapping; 531 struct extent_map_tree *em_tree; 532 struct extent_io_tree *tree; 533 int sectors_missed = 0; 534 535 em_tree = &BTRFS_I(inode)->extent_tree; 536 tree = &BTRFS_I(inode)->io_tree; 537 538 if (isize == 0) 539 return 0; 540 541 /* 542 * For current subpage support, we only support 64K page size, 543 * which means maximum compressed extent size (128K) is just 2x page 544 * size. 545 * This makes readahead less effective, so here disable readahead for 546 * subpage for now, until full compressed write is supported. 547 */ 548 if (btrfs_sb(inode->i_sb)->sectorsize < PAGE_SIZE) 549 return 0; 550 551 end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT; 552 553 while (cur < compressed_end) { 554 u64 page_end; 555 u64 pg_index = cur >> PAGE_SHIFT; 556 u32 add_size; 557 558 if (pg_index > end_index) 559 break; 560 561 page = xa_load(&mapping->i_pages, pg_index); 562 if (page && !xa_is_value(page)) { 563 sectors_missed += (PAGE_SIZE - offset_in_page(cur)) >> 564 fs_info->sectorsize_bits; 565 566 /* Beyond threshold, no need to continue */ 567 if (sectors_missed > 4) 568 break; 569 570 /* 571 * Jump to next page start as we already have page for 572 * current offset. 573 */ 574 cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE; 575 continue; 576 } 577 578 page = __page_cache_alloc(mapping_gfp_constraint(mapping, 579 ~__GFP_FS)); 580 if (!page) 581 break; 582 583 if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) { 584 put_page(page); 585 /* There is already a page, skip to page end */ 586 cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE; 587 continue; 588 } 589 590 ret = set_page_extent_mapped(page); 591 if (ret < 0) { 592 unlock_page(page); 593 put_page(page); 594 break; 595 } 596 597 page_end = (pg_index << PAGE_SHIFT) + PAGE_SIZE - 1; 598 lock_extent(tree, cur, page_end); 599 read_lock(&em_tree->lock); 600 em = lookup_extent_mapping(em_tree, cur, page_end + 1 - cur); 601 read_unlock(&em_tree->lock); 602 603 /* 604 * At this point, we have a locked page in the page cache for 605 * these bytes in the file. But, we have to make sure they map 606 * to this compressed extent on disk. 607 */ 608 if (!em || cur < em->start || 609 (cur + fs_info->sectorsize > extent_map_end(em)) || 610 (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) { 611 free_extent_map(em); 612 unlock_extent(tree, cur, page_end); 613 unlock_page(page); 614 put_page(page); 615 break; 616 } 617 free_extent_map(em); 618 619 if (page->index == end_index) { 620 size_t zero_offset = offset_in_page(isize); 621 622 if (zero_offset) { 623 int zeros; 624 zeros = PAGE_SIZE - zero_offset; 625 memzero_page(page, zero_offset, zeros); 626 } 627 } 628 629 add_size = min(em->start + em->len, page_end + 1) - cur; 630 ret = bio_add_page(cb->orig_bio, page, add_size, offset_in_page(cur)); 631 if (ret != add_size) { 632 unlock_extent(tree, cur, page_end); 633 unlock_page(page); 634 put_page(page); 635 break; 636 } 637 /* 638 * If it's subpage, we also need to increase its 639 * subpage::readers number, as at endio we will decrease 640 * subpage::readers and to unlock the page. 641 */ 642 if (fs_info->sectorsize < PAGE_SIZE) 643 btrfs_subpage_start_reader(fs_info, page, cur, add_size); 644 put_page(page); 645 cur += add_size; 646 } 647 return 0; 648 } 649 650 /* 651 * for a compressed read, the bio we get passed has all the inode pages 652 * in it. We don't actually do IO on those pages but allocate new ones 653 * to hold the compressed pages on disk. 654 * 655 * bio->bi_iter.bi_sector points to the compressed extent on disk 656 * bio->bi_io_vec points to all of the inode pages 657 * 658 * After the compressed pages are read, we copy the bytes into the 659 * bio we were passed and then call the bio end_io calls 660 */ 661 void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, 662 int mirror_num) 663 { 664 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); 665 struct extent_map_tree *em_tree; 666 struct compressed_bio *cb; 667 unsigned int compressed_len; 668 struct bio *comp_bio = NULL; 669 const u64 disk_bytenr = bio->bi_iter.bi_sector << SECTOR_SHIFT; 670 u64 cur_disk_byte = disk_bytenr; 671 u64 next_stripe_start; 672 u64 file_offset; 673 u64 em_len; 674 u64 em_start; 675 struct extent_map *em; 676 blk_status_t ret; 677 int ret2; 678 int i; 679 680 em_tree = &BTRFS_I(inode)->extent_tree; 681 682 file_offset = bio_first_bvec_all(bio)->bv_offset + 683 page_offset(bio_first_page_all(bio)); 684 685 /* we need the actual starting offset of this extent in the file */ 686 read_lock(&em_tree->lock); 687 em = lookup_extent_mapping(em_tree, file_offset, fs_info->sectorsize); 688 read_unlock(&em_tree->lock); 689 if (!em) { 690 ret = BLK_STS_IOERR; 691 goto out; 692 } 693 694 ASSERT(em->compress_type != BTRFS_COMPRESS_NONE); 695 compressed_len = em->block_len; 696 cb = kmalloc(sizeof(struct compressed_bio), GFP_NOFS); 697 if (!cb) { 698 ret = BLK_STS_RESOURCE; 699 goto out; 700 } 701 702 refcount_set(&cb->pending_ios, 1); 703 cb->status = BLK_STS_OK; 704 cb->inode = inode; 705 706 cb->start = em->orig_start; 707 em_len = em->len; 708 em_start = em->start; 709 710 cb->len = bio->bi_iter.bi_size; 711 cb->compressed_len = compressed_len; 712 cb->compress_type = em->compress_type; 713 cb->orig_bio = bio; 714 715 free_extent_map(em); 716 em = NULL; 717 718 cb->nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE); 719 cb->compressed_pages = kcalloc(cb->nr_pages, sizeof(struct page *), GFP_NOFS); 720 if (!cb->compressed_pages) { 721 ret = BLK_STS_RESOURCE; 722 goto fail; 723 } 724 725 ret2 = btrfs_alloc_page_array(cb->nr_pages, cb->compressed_pages); 726 if (ret2) { 727 ret = BLK_STS_RESOURCE; 728 goto fail; 729 } 730 731 add_ra_bio_pages(inode, em_start + em_len, cb); 732 733 /* include any pages we added in add_ra-bio_pages */ 734 cb->len = bio->bi_iter.bi_size; 735 736 while (cur_disk_byte < disk_bytenr + compressed_len) { 737 u64 offset = cur_disk_byte - disk_bytenr; 738 unsigned int index = offset >> PAGE_SHIFT; 739 unsigned int real_size; 740 unsigned int added; 741 struct page *page = cb->compressed_pages[index]; 742 bool submit = false; 743 744 /* Allocate new bio if submitted or not yet allocated */ 745 if (!comp_bio) { 746 comp_bio = alloc_compressed_bio(cb, cur_disk_byte, 747 REQ_OP_READ, end_compressed_bio_read, 748 &next_stripe_start); 749 if (IS_ERR(comp_bio)) { 750 cb->status = errno_to_blk_status(PTR_ERR(comp_bio)); 751 break; 752 } 753 } 754 /* 755 * We should never reach next_stripe_start start as we will 756 * submit comp_bio when reach the boundary immediately. 757 */ 758 ASSERT(cur_disk_byte != next_stripe_start); 759 /* 760 * We have various limit on the real read size: 761 * - stripe boundary 762 * - page boundary 763 * - compressed length boundary 764 */ 765 real_size = min_t(u64, U32_MAX, next_stripe_start - cur_disk_byte); 766 real_size = min_t(u64, real_size, PAGE_SIZE - offset_in_page(offset)); 767 real_size = min_t(u64, real_size, compressed_len - offset); 768 ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize)); 769 770 added = bio_add_page(comp_bio, page, real_size, offset_in_page(offset)); 771 /* 772 * Maximum compressed extent is smaller than bio size limit, 773 * thus bio_add_page() should always success. 774 */ 775 ASSERT(added == real_size); 776 cur_disk_byte += added; 777 778 /* Reached stripe boundary, need to submit */ 779 if (cur_disk_byte == next_stripe_start) 780 submit = true; 781 782 /* Has finished the range, need to submit */ 783 if (cur_disk_byte == disk_bytenr + compressed_len) 784 submit = true; 785 786 if (submit) { 787 /* Save the original iter for read repair */ 788 if (bio_op(comp_bio) == REQ_OP_READ) 789 btrfs_bio(comp_bio)->iter = comp_bio->bi_iter; 790 791 /* 792 * Save the initial offset of this chunk, as there 793 * is no direct correlation between compressed pages and 794 * the original file offset. The field is only used for 795 * priting error messages. 796 */ 797 btrfs_bio(comp_bio)->file_offset = file_offset; 798 799 ret = btrfs_lookup_bio_sums(inode, comp_bio, NULL); 800 if (ret) { 801 comp_bio->bi_status = ret; 802 bio_endio(comp_bio); 803 break; 804 } 805 806 ASSERT(comp_bio->bi_iter.bi_size); 807 btrfs_submit_bio(fs_info, comp_bio, mirror_num); 808 comp_bio = NULL; 809 } 810 } 811 812 if (refcount_dec_and_test(&cb->pending_ios)) 813 finish_compressed_bio_read(cb); 814 return; 815 816 fail: 817 if (cb->compressed_pages) { 818 for (i = 0; i < cb->nr_pages; i++) { 819 if (cb->compressed_pages[i]) 820 __free_page(cb->compressed_pages[i]); 821 } 822 } 823 824 kfree(cb->compressed_pages); 825 kfree(cb); 826 out: 827 free_extent_map(em); 828 bio->bi_status = ret; 829 bio_endio(bio); 830 return; 831 } 832 833 /* 834 * Heuristic uses systematic sampling to collect data from the input data 835 * range, the logic can be tuned by the following constants: 836 * 837 * @SAMPLING_READ_SIZE - how many bytes will be copied from for each sample 838 * @SAMPLING_INTERVAL - range from which the sampled data can be collected 839 */ 840 #define SAMPLING_READ_SIZE (16) 841 #define SAMPLING_INTERVAL (256) 842 843 /* 844 * For statistical analysis of the input data we consider bytes that form a 845 * Galois Field of 256 objects. Each object has an attribute count, ie. how 846 * many times the object appeared in the sample. 847 */ 848 #define BUCKET_SIZE (256) 849 850 /* 851 * The size of the sample is based on a statistical sampling rule of thumb. 852 * The common way is to perform sampling tests as long as the number of 853 * elements in each cell is at least 5. 854 * 855 * Instead of 5, we choose 32 to obtain more accurate results. 856 * If the data contain the maximum number of symbols, which is 256, we obtain a 857 * sample size bound by 8192. 858 * 859 * For a sample of at most 8KB of data per data range: 16 consecutive bytes 860 * from up to 512 locations. 861 */ 862 #define MAX_SAMPLE_SIZE (BTRFS_MAX_UNCOMPRESSED * \ 863 SAMPLING_READ_SIZE / SAMPLING_INTERVAL) 864 865 struct bucket_item { 866 u32 count; 867 }; 868 869 struct heuristic_ws { 870 /* Partial copy of input data */ 871 u8 *sample; 872 u32 sample_size; 873 /* Buckets store counters for each byte value */ 874 struct bucket_item *bucket; 875 /* Sorting buffer */ 876 struct bucket_item *bucket_b; 877 struct list_head list; 878 }; 879 880 static struct workspace_manager heuristic_wsm; 881 882 static void free_heuristic_ws(struct list_head *ws) 883 { 884 struct heuristic_ws *workspace; 885 886 workspace = list_entry(ws, struct heuristic_ws, list); 887 888 kvfree(workspace->sample); 889 kfree(workspace->bucket); 890 kfree(workspace->bucket_b); 891 kfree(workspace); 892 } 893 894 static struct list_head *alloc_heuristic_ws(unsigned int level) 895 { 896 struct heuristic_ws *ws; 897 898 ws = kzalloc(sizeof(*ws), GFP_KERNEL); 899 if (!ws) 900 return ERR_PTR(-ENOMEM); 901 902 ws->sample = kvmalloc(MAX_SAMPLE_SIZE, GFP_KERNEL); 903 if (!ws->sample) 904 goto fail; 905 906 ws->bucket = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket), GFP_KERNEL); 907 if (!ws->bucket) 908 goto fail; 909 910 ws->bucket_b = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket_b), GFP_KERNEL); 911 if (!ws->bucket_b) 912 goto fail; 913 914 INIT_LIST_HEAD(&ws->list); 915 return &ws->list; 916 fail: 917 free_heuristic_ws(&ws->list); 918 return ERR_PTR(-ENOMEM); 919 } 920 921 const struct btrfs_compress_op btrfs_heuristic_compress = { 922 .workspace_manager = &heuristic_wsm, 923 }; 924 925 static const struct btrfs_compress_op * const btrfs_compress_op[] = { 926 /* The heuristic is represented as compression type 0 */ 927 &btrfs_heuristic_compress, 928 &btrfs_zlib_compress, 929 &btrfs_lzo_compress, 930 &btrfs_zstd_compress, 931 }; 932 933 static struct list_head *alloc_workspace(int type, unsigned int level) 934 { 935 switch (type) { 936 case BTRFS_COMPRESS_NONE: return alloc_heuristic_ws(level); 937 case BTRFS_COMPRESS_ZLIB: return zlib_alloc_workspace(level); 938 case BTRFS_COMPRESS_LZO: return lzo_alloc_workspace(level); 939 case BTRFS_COMPRESS_ZSTD: return zstd_alloc_workspace(level); 940 default: 941 /* 942 * This can't happen, the type is validated several times 943 * before we get here. 944 */ 945 BUG(); 946 } 947 } 948 949 static void free_workspace(int type, struct list_head *ws) 950 { 951 switch (type) { 952 case BTRFS_COMPRESS_NONE: return free_heuristic_ws(ws); 953 case BTRFS_COMPRESS_ZLIB: return zlib_free_workspace(ws); 954 case BTRFS_COMPRESS_LZO: return lzo_free_workspace(ws); 955 case BTRFS_COMPRESS_ZSTD: return zstd_free_workspace(ws); 956 default: 957 /* 958 * This can't happen, the type is validated several times 959 * before we get here. 960 */ 961 BUG(); 962 } 963 } 964 965 static void btrfs_init_workspace_manager(int type) 966 { 967 struct workspace_manager *wsm; 968 struct list_head *workspace; 969 970 wsm = btrfs_compress_op[type]->workspace_manager; 971 INIT_LIST_HEAD(&wsm->idle_ws); 972 spin_lock_init(&wsm->ws_lock); 973 atomic_set(&wsm->total_ws, 0); 974 init_waitqueue_head(&wsm->ws_wait); 975 976 /* 977 * Preallocate one workspace for each compression type so we can 978 * guarantee forward progress in the worst case 979 */ 980 workspace = alloc_workspace(type, 0); 981 if (IS_ERR(workspace)) { 982 pr_warn( 983 "BTRFS: cannot preallocate compression workspace, will try later\n"); 984 } else { 985 atomic_set(&wsm->total_ws, 1); 986 wsm->free_ws = 1; 987 list_add(workspace, &wsm->idle_ws); 988 } 989 } 990 991 static void btrfs_cleanup_workspace_manager(int type) 992 { 993 struct workspace_manager *wsman; 994 struct list_head *ws; 995 996 wsman = btrfs_compress_op[type]->workspace_manager; 997 while (!list_empty(&wsman->idle_ws)) { 998 ws = wsman->idle_ws.next; 999 list_del(ws); 1000 free_workspace(type, ws); 1001 atomic_dec(&wsman->total_ws); 1002 } 1003 } 1004 1005 /* 1006 * This finds an available workspace or allocates a new one. 1007 * If it's not possible to allocate a new one, waits until there's one. 1008 * Preallocation makes a forward progress guarantees and we do not return 1009 * errors. 1010 */ 1011 struct list_head *btrfs_get_workspace(int type, unsigned int level) 1012 { 1013 struct workspace_manager *wsm; 1014 struct list_head *workspace; 1015 int cpus = num_online_cpus(); 1016 unsigned nofs_flag; 1017 struct list_head *idle_ws; 1018 spinlock_t *ws_lock; 1019 atomic_t *total_ws; 1020 wait_queue_head_t *ws_wait; 1021 int *free_ws; 1022 1023 wsm = btrfs_compress_op[type]->workspace_manager; 1024 idle_ws = &wsm->idle_ws; 1025 ws_lock = &wsm->ws_lock; 1026 total_ws = &wsm->total_ws; 1027 ws_wait = &wsm->ws_wait; 1028 free_ws = &wsm->free_ws; 1029 1030 again: 1031 spin_lock(ws_lock); 1032 if (!list_empty(idle_ws)) { 1033 workspace = idle_ws->next; 1034 list_del(workspace); 1035 (*free_ws)--; 1036 spin_unlock(ws_lock); 1037 return workspace; 1038 1039 } 1040 if (atomic_read(total_ws) > cpus) { 1041 DEFINE_WAIT(wait); 1042 1043 spin_unlock(ws_lock); 1044 prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE); 1045 if (atomic_read(total_ws) > cpus && !*free_ws) 1046 schedule(); 1047 finish_wait(ws_wait, &wait); 1048 goto again; 1049 } 1050 atomic_inc(total_ws); 1051 spin_unlock(ws_lock); 1052 1053 /* 1054 * Allocation helpers call vmalloc that can't use GFP_NOFS, so we have 1055 * to turn it off here because we might get called from the restricted 1056 * context of btrfs_compress_bio/btrfs_compress_pages 1057 */ 1058 nofs_flag = memalloc_nofs_save(); 1059 workspace = alloc_workspace(type, level); 1060 memalloc_nofs_restore(nofs_flag); 1061 1062 if (IS_ERR(workspace)) { 1063 atomic_dec(total_ws); 1064 wake_up(ws_wait); 1065 1066 /* 1067 * Do not return the error but go back to waiting. There's a 1068 * workspace preallocated for each type and the compression 1069 * time is bounded so we get to a workspace eventually. This 1070 * makes our caller's life easier. 1071 * 1072 * To prevent silent and low-probability deadlocks (when the 1073 * initial preallocation fails), check if there are any 1074 * workspaces at all. 1075 */ 1076 if (atomic_read(total_ws) == 0) { 1077 static DEFINE_RATELIMIT_STATE(_rs, 1078 /* once per minute */ 60 * HZ, 1079 /* no burst */ 1); 1080 1081 if (__ratelimit(&_rs)) { 1082 pr_warn("BTRFS: no compression workspaces, low memory, retrying\n"); 1083 } 1084 } 1085 goto again; 1086 } 1087 return workspace; 1088 } 1089 1090 static struct list_head *get_workspace(int type, int level) 1091 { 1092 switch (type) { 1093 case BTRFS_COMPRESS_NONE: return btrfs_get_workspace(type, level); 1094 case BTRFS_COMPRESS_ZLIB: return zlib_get_workspace(level); 1095 case BTRFS_COMPRESS_LZO: return btrfs_get_workspace(type, level); 1096 case BTRFS_COMPRESS_ZSTD: return zstd_get_workspace(level); 1097 default: 1098 /* 1099 * This can't happen, the type is validated several times 1100 * before we get here. 1101 */ 1102 BUG(); 1103 } 1104 } 1105 1106 /* 1107 * put a workspace struct back on the list or free it if we have enough 1108 * idle ones sitting around 1109 */ 1110 void btrfs_put_workspace(int type, struct list_head *ws) 1111 { 1112 struct workspace_manager *wsm; 1113 struct list_head *idle_ws; 1114 spinlock_t *ws_lock; 1115 atomic_t *total_ws; 1116 wait_queue_head_t *ws_wait; 1117 int *free_ws; 1118 1119 wsm = btrfs_compress_op[type]->workspace_manager; 1120 idle_ws = &wsm->idle_ws; 1121 ws_lock = &wsm->ws_lock; 1122 total_ws = &wsm->total_ws; 1123 ws_wait = &wsm->ws_wait; 1124 free_ws = &wsm->free_ws; 1125 1126 spin_lock(ws_lock); 1127 if (*free_ws <= num_online_cpus()) { 1128 list_add(ws, idle_ws); 1129 (*free_ws)++; 1130 spin_unlock(ws_lock); 1131 goto wake; 1132 } 1133 spin_unlock(ws_lock); 1134 1135 free_workspace(type, ws); 1136 atomic_dec(total_ws); 1137 wake: 1138 cond_wake_up(ws_wait); 1139 } 1140 1141 static void put_workspace(int type, struct list_head *ws) 1142 { 1143 switch (type) { 1144 case BTRFS_COMPRESS_NONE: return btrfs_put_workspace(type, ws); 1145 case BTRFS_COMPRESS_ZLIB: return btrfs_put_workspace(type, ws); 1146 case BTRFS_COMPRESS_LZO: return btrfs_put_workspace(type, ws); 1147 case BTRFS_COMPRESS_ZSTD: return zstd_put_workspace(ws); 1148 default: 1149 /* 1150 * This can't happen, the type is validated several times 1151 * before we get here. 1152 */ 1153 BUG(); 1154 } 1155 } 1156 1157 /* 1158 * Adjust @level according to the limits of the compression algorithm or 1159 * fallback to default 1160 */ 1161 static unsigned int btrfs_compress_set_level(int type, unsigned level) 1162 { 1163 const struct btrfs_compress_op *ops = btrfs_compress_op[type]; 1164 1165 if (level == 0) 1166 level = ops->default_level; 1167 else 1168 level = min(level, ops->max_level); 1169 1170 return level; 1171 } 1172 1173 /* 1174 * Given an address space and start and length, compress the bytes into @pages 1175 * that are allocated on demand. 1176 * 1177 * @type_level is encoded algorithm and level, where level 0 means whatever 1178 * default the algorithm chooses and is opaque here; 1179 * - compression algo are 0-3 1180 * - the level are bits 4-7 1181 * 1182 * @out_pages is an in/out parameter, holds maximum number of pages to allocate 1183 * and returns number of actually allocated pages 1184 * 1185 * @total_in is used to return the number of bytes actually read. It 1186 * may be smaller than the input length if we had to exit early because we 1187 * ran out of room in the pages array or because we cross the 1188 * max_out threshold. 1189 * 1190 * @total_out is an in/out parameter, must be set to the input length and will 1191 * be also used to return the total number of compressed bytes 1192 */ 1193 int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping, 1194 u64 start, struct page **pages, 1195 unsigned long *out_pages, 1196 unsigned long *total_in, 1197 unsigned long *total_out) 1198 { 1199 int type = btrfs_compress_type(type_level); 1200 int level = btrfs_compress_level(type_level); 1201 struct list_head *workspace; 1202 int ret; 1203 1204 level = btrfs_compress_set_level(type, level); 1205 workspace = get_workspace(type, level); 1206 ret = compression_compress_pages(type, workspace, mapping, start, pages, 1207 out_pages, total_in, total_out); 1208 put_workspace(type, workspace); 1209 return ret; 1210 } 1211 1212 static int btrfs_decompress_bio(struct compressed_bio *cb) 1213 { 1214 struct list_head *workspace; 1215 int ret; 1216 int type = cb->compress_type; 1217 1218 workspace = get_workspace(type, 0); 1219 ret = compression_decompress_bio(workspace, cb); 1220 put_workspace(type, workspace); 1221 1222 return ret; 1223 } 1224 1225 /* 1226 * a less complex decompression routine. Our compressed data fits in a 1227 * single page, and we want to read a single page out of it. 1228 * start_byte tells us the offset into the compressed data we're interested in 1229 */ 1230 int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page, 1231 unsigned long start_byte, size_t srclen, size_t destlen) 1232 { 1233 struct list_head *workspace; 1234 int ret; 1235 1236 workspace = get_workspace(type, 0); 1237 ret = compression_decompress(type, workspace, data_in, dest_page, 1238 start_byte, srclen, destlen); 1239 put_workspace(type, workspace); 1240 1241 return ret; 1242 } 1243 1244 void __init btrfs_init_compress(void) 1245 { 1246 btrfs_init_workspace_manager(BTRFS_COMPRESS_NONE); 1247 btrfs_init_workspace_manager(BTRFS_COMPRESS_ZLIB); 1248 btrfs_init_workspace_manager(BTRFS_COMPRESS_LZO); 1249 zstd_init_workspace_manager(); 1250 } 1251 1252 void __cold btrfs_exit_compress(void) 1253 { 1254 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_NONE); 1255 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_ZLIB); 1256 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_LZO); 1257 zstd_cleanup_workspace_manager(); 1258 } 1259 1260 /* 1261 * Copy decompressed data from working buffer to pages. 1262 * 1263 * @buf: The decompressed data buffer 1264 * @buf_len: The decompressed data length 1265 * @decompressed: Number of bytes that are already decompressed inside the 1266 * compressed extent 1267 * @cb: The compressed extent descriptor 1268 * @orig_bio: The original bio that the caller wants to read for 1269 * 1270 * An easier to understand graph is like below: 1271 * 1272 * |<- orig_bio ->| |<- orig_bio->| 1273 * |<------- full decompressed extent ----->| 1274 * |<----------- @cb range ---->| 1275 * | |<-- @buf_len -->| 1276 * |<--- @decompressed --->| 1277 * 1278 * Note that, @cb can be a subpage of the full decompressed extent, but 1279 * @cb->start always has the same as the orig_file_offset value of the full 1280 * decompressed extent. 1281 * 1282 * When reading compressed extent, we have to read the full compressed extent, 1283 * while @orig_bio may only want part of the range. 1284 * Thus this function will ensure only data covered by @orig_bio will be copied 1285 * to. 1286 * 1287 * Return 0 if we have copied all needed contents for @orig_bio. 1288 * Return >0 if we need continue decompress. 1289 */ 1290 int btrfs_decompress_buf2page(const char *buf, u32 buf_len, 1291 struct compressed_bio *cb, u32 decompressed) 1292 { 1293 struct bio *orig_bio = cb->orig_bio; 1294 /* Offset inside the full decompressed extent */ 1295 u32 cur_offset; 1296 1297 cur_offset = decompressed; 1298 /* The main loop to do the copy */ 1299 while (cur_offset < decompressed + buf_len) { 1300 struct bio_vec bvec; 1301 size_t copy_len; 1302 u32 copy_start; 1303 /* Offset inside the full decompressed extent */ 1304 u32 bvec_offset; 1305 1306 bvec = bio_iter_iovec(orig_bio, orig_bio->bi_iter); 1307 /* 1308 * cb->start may underflow, but subtracting that value can still 1309 * give us correct offset inside the full decompressed extent. 1310 */ 1311 bvec_offset = page_offset(bvec.bv_page) + bvec.bv_offset - cb->start; 1312 1313 /* Haven't reached the bvec range, exit */ 1314 if (decompressed + buf_len <= bvec_offset) 1315 return 1; 1316 1317 copy_start = max(cur_offset, bvec_offset); 1318 copy_len = min(bvec_offset + bvec.bv_len, 1319 decompressed + buf_len) - copy_start; 1320 ASSERT(copy_len); 1321 1322 /* 1323 * Extra range check to ensure we didn't go beyond 1324 * @buf + @buf_len. 1325 */ 1326 ASSERT(copy_start - decompressed < buf_len); 1327 memcpy_to_page(bvec.bv_page, bvec.bv_offset, 1328 buf + copy_start - decompressed, copy_len); 1329 cur_offset += copy_len; 1330 1331 bio_advance(orig_bio, copy_len); 1332 /* Finished the bio */ 1333 if (!orig_bio->bi_iter.bi_size) 1334 return 0; 1335 } 1336 return 1; 1337 } 1338 1339 /* 1340 * Shannon Entropy calculation 1341 * 1342 * Pure byte distribution analysis fails to determine compressibility of data. 1343 * Try calculating entropy to estimate the average minimum number of bits 1344 * needed to encode the sampled data. 1345 * 1346 * For convenience, return the percentage of needed bits, instead of amount of 1347 * bits directly. 1348 * 1349 * @ENTROPY_LVL_ACEPTABLE - below that threshold, sample has low byte entropy 1350 * and can be compressible with high probability 1351 * 1352 * @ENTROPY_LVL_HIGH - data are not compressible with high probability 1353 * 1354 * Use of ilog2() decreases precision, we lower the LVL to 5 to compensate. 1355 */ 1356 #define ENTROPY_LVL_ACEPTABLE (65) 1357 #define ENTROPY_LVL_HIGH (80) 1358 1359 /* 1360 * For increasead precision in shannon_entropy calculation, 1361 * let's do pow(n, M) to save more digits after comma: 1362 * 1363 * - maximum int bit length is 64 1364 * - ilog2(MAX_SAMPLE_SIZE) -> 13 1365 * - 13 * 4 = 52 < 64 -> M = 4 1366 * 1367 * So use pow(n, 4). 1368 */ 1369 static inline u32 ilog2_w(u64 n) 1370 { 1371 return ilog2(n * n * n * n); 1372 } 1373 1374 static u32 shannon_entropy(struct heuristic_ws *ws) 1375 { 1376 const u32 entropy_max = 8 * ilog2_w(2); 1377 u32 entropy_sum = 0; 1378 u32 p, p_base, sz_base; 1379 u32 i; 1380 1381 sz_base = ilog2_w(ws->sample_size); 1382 for (i = 0; i < BUCKET_SIZE && ws->bucket[i].count > 0; i++) { 1383 p = ws->bucket[i].count; 1384 p_base = ilog2_w(p); 1385 entropy_sum += p * (sz_base - p_base); 1386 } 1387 1388 entropy_sum /= ws->sample_size; 1389 return entropy_sum * 100 / entropy_max; 1390 } 1391 1392 #define RADIX_BASE 4U 1393 #define COUNTERS_SIZE (1U << RADIX_BASE) 1394 1395 static u8 get4bits(u64 num, int shift) { 1396 u8 low4bits; 1397 1398 num >>= shift; 1399 /* Reverse order */ 1400 low4bits = (COUNTERS_SIZE - 1) - (num % COUNTERS_SIZE); 1401 return low4bits; 1402 } 1403 1404 /* 1405 * Use 4 bits as radix base 1406 * Use 16 u32 counters for calculating new position in buf array 1407 * 1408 * @array - array that will be sorted 1409 * @array_buf - buffer array to store sorting results 1410 * must be equal in size to @array 1411 * @num - array size 1412 */ 1413 static void radix_sort(struct bucket_item *array, struct bucket_item *array_buf, 1414 int num) 1415 { 1416 u64 max_num; 1417 u64 buf_num; 1418 u32 counters[COUNTERS_SIZE]; 1419 u32 new_addr; 1420 u32 addr; 1421 int bitlen; 1422 int shift; 1423 int i; 1424 1425 /* 1426 * Try avoid useless loop iterations for small numbers stored in big 1427 * counters. Example: 48 33 4 ... in 64bit array 1428 */ 1429 max_num = array[0].count; 1430 for (i = 1; i < num; i++) { 1431 buf_num = array[i].count; 1432 if (buf_num > max_num) 1433 max_num = buf_num; 1434 } 1435 1436 buf_num = ilog2(max_num); 1437 bitlen = ALIGN(buf_num, RADIX_BASE * 2); 1438 1439 shift = 0; 1440 while (shift < bitlen) { 1441 memset(counters, 0, sizeof(counters)); 1442 1443 for (i = 0; i < num; i++) { 1444 buf_num = array[i].count; 1445 addr = get4bits(buf_num, shift); 1446 counters[addr]++; 1447 } 1448 1449 for (i = 1; i < COUNTERS_SIZE; i++) 1450 counters[i] += counters[i - 1]; 1451 1452 for (i = num - 1; i >= 0; i--) { 1453 buf_num = array[i].count; 1454 addr = get4bits(buf_num, shift); 1455 counters[addr]--; 1456 new_addr = counters[addr]; 1457 array_buf[new_addr] = array[i]; 1458 } 1459 1460 shift += RADIX_BASE; 1461 1462 /* 1463 * Normal radix expects to move data from a temporary array, to 1464 * the main one. But that requires some CPU time. Avoid that 1465 * by doing another sort iteration to original array instead of 1466 * memcpy() 1467 */ 1468 memset(counters, 0, sizeof(counters)); 1469 1470 for (i = 0; i < num; i ++) { 1471 buf_num = array_buf[i].count; 1472 addr = get4bits(buf_num, shift); 1473 counters[addr]++; 1474 } 1475 1476 for (i = 1; i < COUNTERS_SIZE; i++) 1477 counters[i] += counters[i - 1]; 1478 1479 for (i = num - 1; i >= 0; i--) { 1480 buf_num = array_buf[i].count; 1481 addr = get4bits(buf_num, shift); 1482 counters[addr]--; 1483 new_addr = counters[addr]; 1484 array[new_addr] = array_buf[i]; 1485 } 1486 1487 shift += RADIX_BASE; 1488 } 1489 } 1490 1491 /* 1492 * Size of the core byte set - how many bytes cover 90% of the sample 1493 * 1494 * There are several types of structured binary data that use nearly all byte 1495 * values. The distribution can be uniform and counts in all buckets will be 1496 * nearly the same (eg. encrypted data). Unlikely to be compressible. 1497 * 1498 * Other possibility is normal (Gaussian) distribution, where the data could 1499 * be potentially compressible, but we have to take a few more steps to decide 1500 * how much. 1501 * 1502 * @BYTE_CORE_SET_LOW - main part of byte values repeated frequently, 1503 * compression algo can easy fix that 1504 * @BYTE_CORE_SET_HIGH - data have uniform distribution and with high 1505 * probability is not compressible 1506 */ 1507 #define BYTE_CORE_SET_LOW (64) 1508 #define BYTE_CORE_SET_HIGH (200) 1509 1510 static int byte_core_set_size(struct heuristic_ws *ws) 1511 { 1512 u32 i; 1513 u32 coreset_sum = 0; 1514 const u32 core_set_threshold = ws->sample_size * 90 / 100; 1515 struct bucket_item *bucket = ws->bucket; 1516 1517 /* Sort in reverse order */ 1518 radix_sort(ws->bucket, ws->bucket_b, BUCKET_SIZE); 1519 1520 for (i = 0; i < BYTE_CORE_SET_LOW; i++) 1521 coreset_sum += bucket[i].count; 1522 1523 if (coreset_sum > core_set_threshold) 1524 return i; 1525 1526 for (; i < BYTE_CORE_SET_HIGH && bucket[i].count > 0; i++) { 1527 coreset_sum += bucket[i].count; 1528 if (coreset_sum > core_set_threshold) 1529 break; 1530 } 1531 1532 return i; 1533 } 1534 1535 /* 1536 * Count byte values in buckets. 1537 * This heuristic can detect textual data (configs, xml, json, html, etc). 1538 * Because in most text-like data byte set is restricted to limited number of 1539 * possible characters, and that restriction in most cases makes data easy to 1540 * compress. 1541 * 1542 * @BYTE_SET_THRESHOLD - consider all data within this byte set size: 1543 * less - compressible 1544 * more - need additional analysis 1545 */ 1546 #define BYTE_SET_THRESHOLD (64) 1547 1548 static u32 byte_set_size(const struct heuristic_ws *ws) 1549 { 1550 u32 i; 1551 u32 byte_set_size = 0; 1552 1553 for (i = 0; i < BYTE_SET_THRESHOLD; i++) { 1554 if (ws->bucket[i].count > 0) 1555 byte_set_size++; 1556 } 1557 1558 /* 1559 * Continue collecting count of byte values in buckets. If the byte 1560 * set size is bigger then the threshold, it's pointless to continue, 1561 * the detection technique would fail for this type of data. 1562 */ 1563 for (; i < BUCKET_SIZE; i++) { 1564 if (ws->bucket[i].count > 0) { 1565 byte_set_size++; 1566 if (byte_set_size > BYTE_SET_THRESHOLD) 1567 return byte_set_size; 1568 } 1569 } 1570 1571 return byte_set_size; 1572 } 1573 1574 static bool sample_repeated_patterns(struct heuristic_ws *ws) 1575 { 1576 const u32 half_of_sample = ws->sample_size / 2; 1577 const u8 *data = ws->sample; 1578 1579 return memcmp(&data[0], &data[half_of_sample], half_of_sample) == 0; 1580 } 1581 1582 static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end, 1583 struct heuristic_ws *ws) 1584 { 1585 struct page *page; 1586 u64 index, index_end; 1587 u32 i, curr_sample_pos; 1588 u8 *in_data; 1589 1590 /* 1591 * Compression handles the input data by chunks of 128KiB 1592 * (defined by BTRFS_MAX_UNCOMPRESSED) 1593 * 1594 * We do the same for the heuristic and loop over the whole range. 1595 * 1596 * MAX_SAMPLE_SIZE - calculated under assumption that heuristic will 1597 * process no more than BTRFS_MAX_UNCOMPRESSED at a time. 1598 */ 1599 if (end - start > BTRFS_MAX_UNCOMPRESSED) 1600 end = start + BTRFS_MAX_UNCOMPRESSED; 1601 1602 index = start >> PAGE_SHIFT; 1603 index_end = end >> PAGE_SHIFT; 1604 1605 /* Don't miss unaligned end */ 1606 if (!IS_ALIGNED(end, PAGE_SIZE)) 1607 index_end++; 1608 1609 curr_sample_pos = 0; 1610 while (index < index_end) { 1611 page = find_get_page(inode->i_mapping, index); 1612 in_data = kmap_local_page(page); 1613 /* Handle case where the start is not aligned to PAGE_SIZE */ 1614 i = start % PAGE_SIZE; 1615 while (i < PAGE_SIZE - SAMPLING_READ_SIZE) { 1616 /* Don't sample any garbage from the last page */ 1617 if (start > end - SAMPLING_READ_SIZE) 1618 break; 1619 memcpy(&ws->sample[curr_sample_pos], &in_data[i], 1620 SAMPLING_READ_SIZE); 1621 i += SAMPLING_INTERVAL; 1622 start += SAMPLING_INTERVAL; 1623 curr_sample_pos += SAMPLING_READ_SIZE; 1624 } 1625 kunmap_local(in_data); 1626 put_page(page); 1627 1628 index++; 1629 } 1630 1631 ws->sample_size = curr_sample_pos; 1632 } 1633 1634 /* 1635 * Compression heuristic. 1636 * 1637 * For now is's a naive and optimistic 'return true', we'll extend the logic to 1638 * quickly (compared to direct compression) detect data characteristics 1639 * (compressible/uncompressible) to avoid wasting CPU time on uncompressible 1640 * data. 1641 * 1642 * The following types of analysis can be performed: 1643 * - detect mostly zero data 1644 * - detect data with low "byte set" size (text, etc) 1645 * - detect data with low/high "core byte" set 1646 * 1647 * Return non-zero if the compression should be done, 0 otherwise. 1648 */ 1649 int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end) 1650 { 1651 struct list_head *ws_list = get_workspace(0, 0); 1652 struct heuristic_ws *ws; 1653 u32 i; 1654 u8 byte; 1655 int ret = 0; 1656 1657 ws = list_entry(ws_list, struct heuristic_ws, list); 1658 1659 heuristic_collect_sample(inode, start, end, ws); 1660 1661 if (sample_repeated_patterns(ws)) { 1662 ret = 1; 1663 goto out; 1664 } 1665 1666 memset(ws->bucket, 0, sizeof(*ws->bucket)*BUCKET_SIZE); 1667 1668 for (i = 0; i < ws->sample_size; i++) { 1669 byte = ws->sample[i]; 1670 ws->bucket[byte].count++; 1671 } 1672 1673 i = byte_set_size(ws); 1674 if (i < BYTE_SET_THRESHOLD) { 1675 ret = 2; 1676 goto out; 1677 } 1678 1679 i = byte_core_set_size(ws); 1680 if (i <= BYTE_CORE_SET_LOW) { 1681 ret = 3; 1682 goto out; 1683 } 1684 1685 if (i >= BYTE_CORE_SET_HIGH) { 1686 ret = 0; 1687 goto out; 1688 } 1689 1690 i = shannon_entropy(ws); 1691 if (i <= ENTROPY_LVL_ACEPTABLE) { 1692 ret = 4; 1693 goto out; 1694 } 1695 1696 /* 1697 * For the levels below ENTROPY_LVL_HIGH, additional analysis would be 1698 * needed to give green light to compression. 1699 * 1700 * For now just assume that compression at that level is not worth the 1701 * resources because: 1702 * 1703 * 1. it is possible to defrag the data later 1704 * 1705 * 2. the data would turn out to be hardly compressible, eg. 150 byte 1706 * values, every bucket has counter at level ~54. The heuristic would 1707 * be confused. This can happen when data have some internal repeated 1708 * patterns like "abbacbbc...". This can be detected by analyzing 1709 * pairs of bytes, which is too costly. 1710 */ 1711 if (i < ENTROPY_LVL_HIGH) { 1712 ret = 5; 1713 goto out; 1714 } else { 1715 ret = 0; 1716 goto out; 1717 } 1718 1719 out: 1720 put_workspace(0, ws_list); 1721 return ret; 1722 } 1723 1724 /* 1725 * Convert the compression suffix (eg. after "zlib" starting with ":") to 1726 * level, unrecognized string will set the default level 1727 */ 1728 unsigned int btrfs_compress_str2level(unsigned int type, const char *str) 1729 { 1730 unsigned int level = 0; 1731 int ret; 1732 1733 if (!type) 1734 return 0; 1735 1736 if (str[0] == ':') { 1737 ret = kstrtouint(str + 1, 10, &level); 1738 if (ret) 1739 level = 0; 1740 } 1741 1742 level = btrfs_compress_set_level(type, level); 1743 1744 return level; 1745 } 1746