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
38 static struct bio_set btrfs_compressed_bioset;
39
40 static const char* const btrfs_compress_types[] = { "", "zlib", "lzo", "zstd" };
41
42 const 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
57 static inline struct compressed_bio *to_compressed_bio(struct btrfs_bio *bbio)
58 {
59 return container_of(bbio, struct compressed_bio, bbio);
60 }
61
62 static 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
76 bool 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
92 static int compression_compress_pages(int type, struct list_head *ws,
93 struct address_space *mapping, u64 start,
94 struct folio **folios, unsigned long *out_folios,
95 unsigned long *total_in, unsigned long *total_out)
96 {
97 switch (type) {
98 case BTRFS_COMPRESS_ZLIB:
99 return zlib_compress_folios(ws, mapping, start, folios,
100 out_folios, total_in, total_out);
101 case BTRFS_COMPRESS_LZO:
102 return lzo_compress_folios(ws, mapping, start, folios,
103 out_folios, total_in, total_out);
104 case BTRFS_COMPRESS_ZSTD:
105 return zstd_compress_folios(ws, mapping, start, folios,
106 out_folios, 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_folios = 0;
119 return -E2BIG;
120 }
121 }
122
123 static 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
140 static 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
161 static void btrfs_free_compressed_folios(struct compressed_bio *cb)
162 {
163 for (unsigned int i = 0; i < cb->nr_folios; i++)
164 btrfs_free_compr_folio(cb->compressed_folios[i]);
165 kfree(cb->compressed_folios);
166 }
167
168 static int btrfs_decompress_bio(struct compressed_bio *cb);
169
170 /*
171 * Global cache of last unused pages for compression/decompression.
172 */
173 static 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
181 static 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
195 static 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 */
226 struct folio *btrfs_alloc_compr_folio(void)
227 {
228 struct folio *folio = NULL;
229
230 spin_lock(&compr_pool.lock);
231 if (compr_pool.count > 0) {
232 folio = list_first_entry(&compr_pool.list, struct folio, lru);
233 list_del_init(&folio->lru);
234 compr_pool.count--;
235 }
236 spin_unlock(&compr_pool.lock);
237
238 if (folio)
239 return folio;
240
241 return folio_alloc(GFP_NOFS, 0);
242 }
243
244 void btrfs_free_compr_folio(struct folio *folio)
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(&folio->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(folio_ref_count(folio) == 1);
261 folio_put(folio);
262 }
263
264 static void end_bbio_compressed_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_folios(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 */
281 static 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
314 static 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_folios(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 */
337 static void end_bbio_compressed_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
345 static void btrfs_add_compressed_bio_folios(struct compressed_bio *cb)
346 {
347 struct bio *bio = &cb->bbio.bio;
348 u32 offset = 0;
349
350 while (offset < cb->compressed_len) {
351 int ret;
352 u32 len = min_t(u32, cb->compressed_len - offset, PAGE_SIZE);
353
354 /* Maximum compressed extent is smaller than bio size limit. */
355 ret = bio_add_folio(bio, cb->compressed_folios[offset >> PAGE_SHIFT],
356 len, 0);
357 ASSERT(ret);
358 offset += len;
359 }
360 }
361
362 /*
363 * worker function to build and submit bios for previously compressed pages.
364 * The corresponding pages in the inode should be marked for writeback
365 * and the compressed pages should have a reference on them for dropping
366 * when the IO is complete.
367 *
368 * This also checksums the file bytes and gets things ready for
369 * the end io hooks.
370 */
371 void btrfs_submit_compressed_write(struct btrfs_ordered_extent *ordered,
372 struct folio **compressed_folios,
373 unsigned int nr_folios,
374 blk_opf_t write_flags,
375 bool writeback)
376 {
377 struct btrfs_inode *inode = ordered->inode;
378 struct btrfs_fs_info *fs_info = inode->root->fs_info;
379 struct compressed_bio *cb;
380
381 ASSERT(IS_ALIGNED(ordered->file_offset, fs_info->sectorsize));
382 ASSERT(IS_ALIGNED(ordered->num_bytes, fs_info->sectorsize));
383
384 cb = alloc_compressed_bio(inode, ordered->file_offset,
385 REQ_OP_WRITE | write_flags,
386 end_bbio_compressed_write);
387 cb->start = ordered->file_offset;
388 cb->len = ordered->num_bytes;
389 cb->compressed_folios = compressed_folios;
390 cb->compressed_len = ordered->disk_num_bytes;
391 cb->writeback = writeback;
392 INIT_WORK(&cb->write_end_work, btrfs_finish_compressed_write_work);
393 cb->nr_folios = nr_folios;
394 cb->bbio.bio.bi_iter.bi_sector = ordered->disk_bytenr >> SECTOR_SHIFT;
395 cb->bbio.ordered = ordered;
396 btrfs_add_compressed_bio_folios(cb);
397
398 btrfs_submit_bio(&cb->bbio, 0);
399 }
400
401 /*
402 * Add extra pages in the same compressed file extent so that we don't need to
403 * re-read the same extent again and again.
404 *
405 * NOTE: this won't work well for subpage, as for subpage read, we lock the
406 * full page then submit bio for each compressed/regular extents.
407 *
408 * This means, if we have several sectors in the same page points to the same
409 * on-disk compressed data, we will re-read the same extent many times and
410 * this function can only help for the next page.
411 */
412 static noinline int add_ra_bio_pages(struct inode *inode,
413 u64 compressed_end,
414 struct compressed_bio *cb,
415 int *memstall, unsigned long *pflags)
416 {
417 struct btrfs_fs_info *fs_info = inode_to_fs_info(inode);
418 unsigned long end_index;
419 struct bio *orig_bio = &cb->orig_bbio->bio;
420 u64 cur = cb->orig_bbio->file_offset + orig_bio->bi_iter.bi_size;
421 u64 isize = i_size_read(inode);
422 int ret;
423 struct page *page;
424 struct extent_map *em;
425 struct address_space *mapping = inode->i_mapping;
426 struct extent_map_tree *em_tree;
427 struct extent_io_tree *tree;
428 int sectors_missed = 0;
429
430 em_tree = &BTRFS_I(inode)->extent_tree;
431 tree = &BTRFS_I(inode)->io_tree;
432
433 if (isize == 0)
434 return 0;
435
436 /*
437 * For current subpage support, we only support 64K page size,
438 * which means maximum compressed extent size (128K) is just 2x page
439 * size.
440 * This makes readahead less effective, so here disable readahead for
441 * subpage for now, until full compressed write is supported.
442 */
443 if (fs_info->sectorsize < PAGE_SIZE)
444 return 0;
445
446 end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
447
448 while (cur < compressed_end) {
449 u64 page_end;
450 u64 pg_index = cur >> PAGE_SHIFT;
451 u32 add_size;
452
453 if (pg_index > end_index)
454 break;
455
456 page = xa_load(&mapping->i_pages, pg_index);
457 if (page && !xa_is_value(page)) {
458 sectors_missed += (PAGE_SIZE - offset_in_page(cur)) >>
459 fs_info->sectorsize_bits;
460
461 /* Beyond threshold, no need to continue */
462 if (sectors_missed > 4)
463 break;
464
465 /*
466 * Jump to next page start as we already have page for
467 * current offset.
468 */
469 cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE;
470 continue;
471 }
472
473 page = __page_cache_alloc(mapping_gfp_constraint(mapping,
474 ~__GFP_FS));
475 if (!page)
476 break;
477
478 if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
479 put_page(page);
480 /* There is already a page, skip to page end */
481 cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE;
482 continue;
483 }
484
485 if (!*memstall && PageWorkingset(page)) {
486 psi_memstall_enter(pflags);
487 *memstall = 1;
488 }
489
490 ret = set_page_extent_mapped(page);
491 if (ret < 0) {
492 unlock_page(page);
493 put_page(page);
494 break;
495 }
496
497 page_end = (pg_index << PAGE_SHIFT) + PAGE_SIZE - 1;
498 lock_extent(tree, cur, page_end, NULL);
499 read_lock(&em_tree->lock);
500 em = lookup_extent_mapping(em_tree, cur, page_end + 1 - cur);
501 read_unlock(&em_tree->lock);
502
503 /*
504 * At this point, we have a locked page in the page cache for
505 * these bytes in the file. But, we have to make sure they map
506 * to this compressed extent on disk.
507 */
508 if (!em || cur < em->start ||
509 (cur + fs_info->sectorsize > extent_map_end(em)) ||
510 (extent_map_block_start(em) >> SECTOR_SHIFT) !=
511 orig_bio->bi_iter.bi_sector) {
512 free_extent_map(em);
513 unlock_extent(tree, cur, page_end, NULL);
514 unlock_page(page);
515 put_page(page);
516 break;
517 }
518 add_size = min(em->start + em->len, page_end + 1) - cur;
519 free_extent_map(em);
520
521 if (page->index == end_index) {
522 size_t zero_offset = offset_in_page(isize);
523
524 if (zero_offset) {
525 int zeros;
526 zeros = PAGE_SIZE - zero_offset;
527 memzero_page(page, zero_offset, zeros);
528 }
529 }
530
531 ret = bio_add_page(orig_bio, page, add_size, offset_in_page(cur));
532 if (ret != add_size) {
533 unlock_extent(tree, cur, page_end, NULL);
534 unlock_page(page);
535 put_page(page);
536 break;
537 }
538 /*
539 * If it's subpage, we also need to increase its
540 * subpage::readers number, as at endio we will decrease
541 * subpage::readers and to unlock the page.
542 */
543 if (fs_info->sectorsize < PAGE_SIZE)
544 btrfs_subpage_start_reader(fs_info, page_folio(page),
545 cur, add_size);
546 put_page(page);
547 cur += add_size;
548 }
549 return 0;
550 }
551
552 /*
553 * for a compressed read, the bio we get passed has all the inode pages
554 * in it. We don't actually do IO on those pages but allocate new ones
555 * to hold the compressed pages on disk.
556 *
557 * bio->bi_iter.bi_sector points to the compressed extent on disk
558 * bio->bi_io_vec points to all of the inode pages
559 *
560 * After the compressed pages are read, we copy the bytes into the
561 * bio we were passed and then call the bio end_io calls
562 */
563 void btrfs_submit_compressed_read(struct btrfs_bio *bbio)
564 {
565 struct btrfs_inode *inode = bbio->inode;
566 struct btrfs_fs_info *fs_info = inode->root->fs_info;
567 struct extent_map_tree *em_tree = &inode->extent_tree;
568 struct compressed_bio *cb;
569 unsigned int compressed_len;
570 u64 file_offset = bbio->file_offset;
571 u64 em_len;
572 u64 em_start;
573 struct extent_map *em;
574 unsigned long pflags;
575 int memstall = 0;
576 blk_status_t ret;
577 int ret2;
578
579 /* we need the actual starting offset of this extent in the file */
580 read_lock(&em_tree->lock);
581 em = lookup_extent_mapping(em_tree, file_offset, fs_info->sectorsize);
582 read_unlock(&em_tree->lock);
583 if (!em) {
584 ret = BLK_STS_IOERR;
585 goto out;
586 }
587
588 ASSERT(extent_map_is_compressed(em));
589 compressed_len = em->disk_num_bytes;
590
591 cb = alloc_compressed_bio(inode, file_offset, REQ_OP_READ,
592 end_bbio_compressed_read);
593
594 cb->start = em->start - em->offset;
595 em_len = em->len;
596 em_start = em->start;
597
598 cb->len = bbio->bio.bi_iter.bi_size;
599 cb->compressed_len = compressed_len;
600 cb->compress_type = extent_map_compression(em);
601 cb->orig_bbio = bbio;
602
603 free_extent_map(em);
604
605 cb->nr_folios = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
606 cb->compressed_folios = kcalloc(cb->nr_folios, sizeof(struct page *), GFP_NOFS);
607 if (!cb->compressed_folios) {
608 ret = BLK_STS_RESOURCE;
609 goto out_free_bio;
610 }
611
612 ret2 = btrfs_alloc_folio_array(cb->nr_folios, cb->compressed_folios);
613 if (ret2) {
614 ret = BLK_STS_RESOURCE;
615 goto out_free_compressed_pages;
616 }
617
618 add_ra_bio_pages(&inode->vfs_inode, em_start + em_len, cb, &memstall,
619 &pflags);
620
621 /* include any pages we added in add_ra-bio_pages */
622 cb->len = bbio->bio.bi_iter.bi_size;
623 cb->bbio.bio.bi_iter.bi_sector = bbio->bio.bi_iter.bi_sector;
624 btrfs_add_compressed_bio_folios(cb);
625
626 if (memstall)
627 psi_memstall_leave(&pflags);
628
629 btrfs_submit_bio(&cb->bbio, 0);
630 return;
631
632 out_free_compressed_pages:
633 kfree(cb->compressed_folios);
634 out_free_bio:
635 bio_put(&cb->bbio.bio);
636 out:
637 btrfs_bio_end_io(bbio, ret);
638 }
639
640 /*
641 * Heuristic uses systematic sampling to collect data from the input data
642 * range, the logic can be tuned by the following constants:
643 *
644 * @SAMPLING_READ_SIZE - how many bytes will be copied from for each sample
645 * @SAMPLING_INTERVAL - range from which the sampled data can be collected
646 */
647 #define SAMPLING_READ_SIZE (16)
648 #define SAMPLING_INTERVAL (256)
649
650 /*
651 * For statistical analysis of the input data we consider bytes that form a
652 * Galois Field of 256 objects. Each object has an attribute count, ie. how
653 * many times the object appeared in the sample.
654 */
655 #define BUCKET_SIZE (256)
656
657 /*
658 * The size of the sample is based on a statistical sampling rule of thumb.
659 * The common way is to perform sampling tests as long as the number of
660 * elements in each cell is at least 5.
661 *
662 * Instead of 5, we choose 32 to obtain more accurate results.
663 * If the data contain the maximum number of symbols, which is 256, we obtain a
664 * sample size bound by 8192.
665 *
666 * For a sample of at most 8KB of data per data range: 16 consecutive bytes
667 * from up to 512 locations.
668 */
669 #define MAX_SAMPLE_SIZE (BTRFS_MAX_UNCOMPRESSED * \
670 SAMPLING_READ_SIZE / SAMPLING_INTERVAL)
671
672 struct bucket_item {
673 u32 count;
674 };
675
676 struct heuristic_ws {
677 /* Partial copy of input data */
678 u8 *sample;
679 u32 sample_size;
680 /* Buckets store counters for each byte value */
681 struct bucket_item *bucket;
682 /* Sorting buffer */
683 struct bucket_item *bucket_b;
684 struct list_head list;
685 };
686
687 static struct workspace_manager heuristic_wsm;
688
689 static void free_heuristic_ws(struct list_head *ws)
690 {
691 struct heuristic_ws *workspace;
692
693 workspace = list_entry(ws, struct heuristic_ws, list);
694
695 kvfree(workspace->sample);
696 kfree(workspace->bucket);
697 kfree(workspace->bucket_b);
698 kfree(workspace);
699 }
700
701 static struct list_head *alloc_heuristic_ws(unsigned int level)
702 {
703 struct heuristic_ws *ws;
704
705 ws = kzalloc(sizeof(*ws), GFP_KERNEL);
706 if (!ws)
707 return ERR_PTR(-ENOMEM);
708
709 ws->sample = kvmalloc(MAX_SAMPLE_SIZE, GFP_KERNEL);
710 if (!ws->sample)
711 goto fail;
712
713 ws->bucket = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket), GFP_KERNEL);
714 if (!ws->bucket)
715 goto fail;
716
717 ws->bucket_b = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket_b), GFP_KERNEL);
718 if (!ws->bucket_b)
719 goto fail;
720
721 INIT_LIST_HEAD(&ws->list);
722 return &ws->list;
723 fail:
724 free_heuristic_ws(&ws->list);
725 return ERR_PTR(-ENOMEM);
726 }
727
728 const struct btrfs_compress_op btrfs_heuristic_compress = {
729 .workspace_manager = &heuristic_wsm,
730 };
731
732 static const struct btrfs_compress_op * const btrfs_compress_op[] = {
733 /* The heuristic is represented as compression type 0 */
734 &btrfs_heuristic_compress,
735 &btrfs_zlib_compress,
736 &btrfs_lzo_compress,
737 &btrfs_zstd_compress,
738 };
739
740 static struct list_head *alloc_workspace(int type, unsigned int level)
741 {
742 switch (type) {
743 case BTRFS_COMPRESS_NONE: return alloc_heuristic_ws(level);
744 case BTRFS_COMPRESS_ZLIB: return zlib_alloc_workspace(level);
745 case BTRFS_COMPRESS_LZO: return lzo_alloc_workspace(level);
746 case BTRFS_COMPRESS_ZSTD: return zstd_alloc_workspace(level);
747 default:
748 /*
749 * This can't happen, the type is validated several times
750 * before we get here.
751 */
752 BUG();
753 }
754 }
755
756 static void free_workspace(int type, struct list_head *ws)
757 {
758 switch (type) {
759 case BTRFS_COMPRESS_NONE: return free_heuristic_ws(ws);
760 case BTRFS_COMPRESS_ZLIB: return zlib_free_workspace(ws);
761 case BTRFS_COMPRESS_LZO: return lzo_free_workspace(ws);
762 case BTRFS_COMPRESS_ZSTD: return zstd_free_workspace(ws);
763 default:
764 /*
765 * This can't happen, the type is validated several times
766 * before we get here.
767 */
768 BUG();
769 }
770 }
771
772 static void btrfs_init_workspace_manager(int type)
773 {
774 struct workspace_manager *wsm;
775 struct list_head *workspace;
776
777 wsm = btrfs_compress_op[type]->workspace_manager;
778 INIT_LIST_HEAD(&wsm->idle_ws);
779 spin_lock_init(&wsm->ws_lock);
780 atomic_set(&wsm->total_ws, 0);
781 init_waitqueue_head(&wsm->ws_wait);
782
783 /*
784 * Preallocate one workspace for each compression type so we can
785 * guarantee forward progress in the worst case
786 */
787 workspace = alloc_workspace(type, 0);
788 if (IS_ERR(workspace)) {
789 pr_warn(
790 "BTRFS: cannot preallocate compression workspace, will try later\n");
791 } else {
792 atomic_set(&wsm->total_ws, 1);
793 wsm->free_ws = 1;
794 list_add(workspace, &wsm->idle_ws);
795 }
796 }
797
798 static void btrfs_cleanup_workspace_manager(int type)
799 {
800 struct workspace_manager *wsman;
801 struct list_head *ws;
802
803 wsman = btrfs_compress_op[type]->workspace_manager;
804 while (!list_empty(&wsman->idle_ws)) {
805 ws = wsman->idle_ws.next;
806 list_del(ws);
807 free_workspace(type, ws);
808 atomic_dec(&wsman->total_ws);
809 }
810 }
811
812 /*
813 * This finds an available workspace or allocates a new one.
814 * If it's not possible to allocate a new one, waits until there's one.
815 * Preallocation makes a forward progress guarantees and we do not return
816 * errors.
817 */
818 struct list_head *btrfs_get_workspace(int type, unsigned int level)
819 {
820 struct workspace_manager *wsm;
821 struct list_head *workspace;
822 int cpus = num_online_cpus();
823 unsigned nofs_flag;
824 struct list_head *idle_ws;
825 spinlock_t *ws_lock;
826 atomic_t *total_ws;
827 wait_queue_head_t *ws_wait;
828 int *free_ws;
829
830 wsm = btrfs_compress_op[type]->workspace_manager;
831 idle_ws = &wsm->idle_ws;
832 ws_lock = &wsm->ws_lock;
833 total_ws = &wsm->total_ws;
834 ws_wait = &wsm->ws_wait;
835 free_ws = &wsm->free_ws;
836
837 again:
838 spin_lock(ws_lock);
839 if (!list_empty(idle_ws)) {
840 workspace = idle_ws->next;
841 list_del(workspace);
842 (*free_ws)--;
843 spin_unlock(ws_lock);
844 return workspace;
845
846 }
847 if (atomic_read(total_ws) > cpus) {
848 DEFINE_WAIT(wait);
849
850 spin_unlock(ws_lock);
851 prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE);
852 if (atomic_read(total_ws) > cpus && !*free_ws)
853 schedule();
854 finish_wait(ws_wait, &wait);
855 goto again;
856 }
857 atomic_inc(total_ws);
858 spin_unlock(ws_lock);
859
860 /*
861 * Allocation helpers call vmalloc that can't use GFP_NOFS, so we have
862 * to turn it off here because we might get called from the restricted
863 * context of btrfs_compress_bio/btrfs_compress_pages
864 */
865 nofs_flag = memalloc_nofs_save();
866 workspace = alloc_workspace(type, level);
867 memalloc_nofs_restore(nofs_flag);
868
869 if (IS_ERR(workspace)) {
870 atomic_dec(total_ws);
871 wake_up(ws_wait);
872
873 /*
874 * Do not return the error but go back to waiting. There's a
875 * workspace preallocated for each type and the compression
876 * time is bounded so we get to a workspace eventually. This
877 * makes our caller's life easier.
878 *
879 * To prevent silent and low-probability deadlocks (when the
880 * initial preallocation fails), check if there are any
881 * workspaces at all.
882 */
883 if (atomic_read(total_ws) == 0) {
884 static DEFINE_RATELIMIT_STATE(_rs,
885 /* once per minute */ 60 * HZ,
886 /* no burst */ 1);
887
888 if (__ratelimit(&_rs)) {
889 pr_warn("BTRFS: no compression workspaces, low memory, retrying\n");
890 }
891 }
892 goto again;
893 }
894 return workspace;
895 }
896
897 static struct list_head *get_workspace(int type, int level)
898 {
899 switch (type) {
900 case BTRFS_COMPRESS_NONE: return btrfs_get_workspace(type, level);
901 case BTRFS_COMPRESS_ZLIB: return zlib_get_workspace(level);
902 case BTRFS_COMPRESS_LZO: return btrfs_get_workspace(type, level);
903 case BTRFS_COMPRESS_ZSTD: return zstd_get_workspace(level);
904 default:
905 /*
906 * This can't happen, the type is validated several times
907 * before we get here.
908 */
909 BUG();
910 }
911 }
912
913 /*
914 * put a workspace struct back on the list or free it if we have enough
915 * idle ones sitting around
916 */
917 void btrfs_put_workspace(int type, struct list_head *ws)
918 {
919 struct workspace_manager *wsm;
920 struct list_head *idle_ws;
921 spinlock_t *ws_lock;
922 atomic_t *total_ws;
923 wait_queue_head_t *ws_wait;
924 int *free_ws;
925
926 wsm = btrfs_compress_op[type]->workspace_manager;
927 idle_ws = &wsm->idle_ws;
928 ws_lock = &wsm->ws_lock;
929 total_ws = &wsm->total_ws;
930 ws_wait = &wsm->ws_wait;
931 free_ws = &wsm->free_ws;
932
933 spin_lock(ws_lock);
934 if (*free_ws <= num_online_cpus()) {
935 list_add(ws, idle_ws);
936 (*free_ws)++;
937 spin_unlock(ws_lock);
938 goto wake;
939 }
940 spin_unlock(ws_lock);
941
942 free_workspace(type, ws);
943 atomic_dec(total_ws);
944 wake:
945 cond_wake_up(ws_wait);
946 }
947
948 static void put_workspace(int type, struct list_head *ws)
949 {
950 switch (type) {
951 case BTRFS_COMPRESS_NONE: return btrfs_put_workspace(type, ws);
952 case BTRFS_COMPRESS_ZLIB: return btrfs_put_workspace(type, ws);
953 case BTRFS_COMPRESS_LZO: return btrfs_put_workspace(type, ws);
954 case BTRFS_COMPRESS_ZSTD: return zstd_put_workspace(ws);
955 default:
956 /*
957 * This can't happen, the type is validated several times
958 * before we get here.
959 */
960 BUG();
961 }
962 }
963
964 /*
965 * Adjust @level according to the limits of the compression algorithm or
966 * fallback to default
967 */
968 static unsigned int btrfs_compress_set_level(int type, unsigned level)
969 {
970 const struct btrfs_compress_op *ops = btrfs_compress_op[type];
971
972 if (level == 0)
973 level = ops->default_level;
974 else
975 level = min(level, ops->max_level);
976
977 return level;
978 }
979
980 /* Wrapper around find_get_page(), with extra error message. */
981 int btrfs_compress_filemap_get_folio(struct address_space *mapping, u64 start,
982 struct folio **in_folio_ret)
983 {
984 struct folio *in_folio;
985
986 /*
987 * The compressed write path should have the folio locked already, thus
988 * we only need to grab one reference.
989 */
990 in_folio = filemap_get_folio(mapping, start >> PAGE_SHIFT);
991 if (IS_ERR(in_folio)) {
992 struct btrfs_inode *inode = BTRFS_I(mapping->host);
993
994 btrfs_crit(inode->root->fs_info,
995 "failed to get page cache, root %lld ino %llu file offset %llu",
996 btrfs_root_id(inode->root), btrfs_ino(inode), start);
997 return -ENOENT;
998 }
999 *in_folio_ret = in_folio;
1000 return 0;
1001 }
1002
1003 /*
1004 * Given an address space and start and length, compress the bytes into @pages
1005 * that are allocated on demand.
1006 *
1007 * @type_level is encoded algorithm and level, where level 0 means whatever
1008 * default the algorithm chooses and is opaque here;
1009 * - compression algo are 0-3
1010 * - the level are bits 4-7
1011 *
1012 * @out_pages is an in/out parameter, holds maximum number of pages to allocate
1013 * and returns number of actually allocated pages
1014 *
1015 * @total_in is used to return the number of bytes actually read. It
1016 * may be smaller than the input length if we had to exit early because we
1017 * ran out of room in the pages array or because we cross the
1018 * max_out threshold.
1019 *
1020 * @total_out is an in/out parameter, must be set to the input length and will
1021 * be also used to return the total number of compressed bytes
1022 */
1023 int btrfs_compress_folios(unsigned int type_level, struct address_space *mapping,
1024 u64 start, struct folio **folios, unsigned long *out_folios,
1025 unsigned long *total_in, unsigned long *total_out)
1026 {
1027 int type = btrfs_compress_type(type_level);
1028 int level = btrfs_compress_level(type_level);
1029 struct list_head *workspace;
1030 int ret;
1031
1032 level = btrfs_compress_set_level(type, level);
1033 workspace = get_workspace(type, level);
1034 ret = compression_compress_pages(type, workspace, mapping, start, folios,
1035 out_folios, total_in, total_out);
1036 put_workspace(type, workspace);
1037 return ret;
1038 }
1039
1040 static int btrfs_decompress_bio(struct compressed_bio *cb)
1041 {
1042 struct list_head *workspace;
1043 int ret;
1044 int type = cb->compress_type;
1045
1046 workspace = get_workspace(type, 0);
1047 ret = compression_decompress_bio(workspace, cb);
1048 put_workspace(type, workspace);
1049
1050 if (!ret)
1051 zero_fill_bio(&cb->orig_bbio->bio);
1052 return ret;
1053 }
1054
1055 /*
1056 * a less complex decompression routine. Our compressed data fits in a
1057 * single page, and we want to read a single page out of it.
1058 * start_byte tells us the offset into the compressed data we're interested in
1059 */
1060 int btrfs_decompress(int type, const u8 *data_in, struct page *dest_page,
1061 unsigned long dest_pgoff, size_t srclen, size_t destlen)
1062 {
1063 struct btrfs_fs_info *fs_info = page_to_fs_info(dest_page);
1064 struct list_head *workspace;
1065 const u32 sectorsize = fs_info->sectorsize;
1066 int ret;
1067
1068 /*
1069 * The full destination page range should not exceed the page size.
1070 * And the @destlen should not exceed sectorsize, as this is only called for
1071 * inline file extents, which should not exceed sectorsize.
1072 */
1073 ASSERT(dest_pgoff + destlen <= PAGE_SIZE && destlen <= sectorsize);
1074
1075 workspace = get_workspace(type, 0);
1076 ret = compression_decompress(type, workspace, data_in, dest_page,
1077 dest_pgoff, srclen, destlen);
1078 put_workspace(type, workspace);
1079
1080 return ret;
1081 }
1082
1083 int __init btrfs_init_compress(void)
1084 {
1085 if (bioset_init(&btrfs_compressed_bioset, BIO_POOL_SIZE,
1086 offsetof(struct compressed_bio, bbio.bio),
1087 BIOSET_NEED_BVECS))
1088 return -ENOMEM;
1089
1090 compr_pool.shrinker = shrinker_alloc(SHRINKER_NONSLAB, "btrfs-compr-pages");
1091 if (!compr_pool.shrinker)
1092 return -ENOMEM;
1093
1094 btrfs_init_workspace_manager(BTRFS_COMPRESS_NONE);
1095 btrfs_init_workspace_manager(BTRFS_COMPRESS_ZLIB);
1096 btrfs_init_workspace_manager(BTRFS_COMPRESS_LZO);
1097 zstd_init_workspace_manager();
1098
1099 spin_lock_init(&compr_pool.lock);
1100 INIT_LIST_HEAD(&compr_pool.list);
1101 compr_pool.count = 0;
1102 /* 128K / 4K = 32, for 8 threads is 256 pages. */
1103 compr_pool.thresh = BTRFS_MAX_COMPRESSED / PAGE_SIZE * 8;
1104 compr_pool.shrinker->count_objects = btrfs_compr_pool_count;
1105 compr_pool.shrinker->scan_objects = btrfs_compr_pool_scan;
1106 compr_pool.shrinker->batch = 32;
1107 compr_pool.shrinker->seeks = DEFAULT_SEEKS;
1108 shrinker_register(compr_pool.shrinker);
1109
1110 return 0;
1111 }
1112
1113 void __cold btrfs_exit_compress(void)
1114 {
1115 /* For now scan drains all pages and does not touch the parameters. */
1116 btrfs_compr_pool_scan(NULL, NULL);
1117 shrinker_free(compr_pool.shrinker);
1118
1119 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_NONE);
1120 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_ZLIB);
1121 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_LZO);
1122 zstd_cleanup_workspace_manager();
1123 bioset_exit(&btrfs_compressed_bioset);
1124 }
1125
1126 /*
1127 * Copy decompressed data from working buffer to pages.
1128 *
1129 * @buf: The decompressed data buffer
1130 * @buf_len: The decompressed data length
1131 * @decompressed: Number of bytes that are already decompressed inside the
1132 * compressed extent
1133 * @cb: The compressed extent descriptor
1134 * @orig_bio: The original bio that the caller wants to read for
1135 *
1136 * An easier to understand graph is like below:
1137 *
1138 * |<- orig_bio ->| |<- orig_bio->|
1139 * |<------- full decompressed extent ----->|
1140 * |<----------- @cb range ---->|
1141 * | |<-- @buf_len -->|
1142 * |<--- @decompressed --->|
1143 *
1144 * Note that, @cb can be a subpage of the full decompressed extent, but
1145 * @cb->start always has the same as the orig_file_offset value of the full
1146 * decompressed extent.
1147 *
1148 * When reading compressed extent, we have to read the full compressed extent,
1149 * while @orig_bio may only want part of the range.
1150 * Thus this function will ensure only data covered by @orig_bio will be copied
1151 * to.
1152 *
1153 * Return 0 if we have copied all needed contents for @orig_bio.
1154 * Return >0 if we need continue decompress.
1155 */
1156 int btrfs_decompress_buf2page(const char *buf, u32 buf_len,
1157 struct compressed_bio *cb, u32 decompressed)
1158 {
1159 struct bio *orig_bio = &cb->orig_bbio->bio;
1160 /* Offset inside the full decompressed extent */
1161 u32 cur_offset;
1162
1163 cur_offset = decompressed;
1164 /* The main loop to do the copy */
1165 while (cur_offset < decompressed + buf_len) {
1166 struct bio_vec bvec;
1167 size_t copy_len;
1168 u32 copy_start;
1169 /* Offset inside the full decompressed extent */
1170 u32 bvec_offset;
1171
1172 bvec = bio_iter_iovec(orig_bio, orig_bio->bi_iter);
1173 /*
1174 * cb->start may underflow, but subtracting that value can still
1175 * give us correct offset inside the full decompressed extent.
1176 */
1177 bvec_offset = page_offset(bvec.bv_page) + bvec.bv_offset - cb->start;
1178
1179 /* Haven't reached the bvec range, exit */
1180 if (decompressed + buf_len <= bvec_offset)
1181 return 1;
1182
1183 copy_start = max(cur_offset, bvec_offset);
1184 copy_len = min(bvec_offset + bvec.bv_len,
1185 decompressed + buf_len) - copy_start;
1186 ASSERT(copy_len);
1187
1188 /*
1189 * Extra range check to ensure we didn't go beyond
1190 * @buf + @buf_len.
1191 */
1192 ASSERT(copy_start - decompressed < buf_len);
1193 memcpy_to_page(bvec.bv_page, bvec.bv_offset,
1194 buf + copy_start - decompressed, copy_len);
1195 cur_offset += copy_len;
1196
1197 bio_advance(orig_bio, copy_len);
1198 /* Finished the bio */
1199 if (!orig_bio->bi_iter.bi_size)
1200 return 0;
1201 }
1202 return 1;
1203 }
1204
1205 /*
1206 * Shannon Entropy calculation
1207 *
1208 * Pure byte distribution analysis fails to determine compressibility of data.
1209 * Try calculating entropy to estimate the average minimum number of bits
1210 * needed to encode the sampled data.
1211 *
1212 * For convenience, return the percentage of needed bits, instead of amount of
1213 * bits directly.
1214 *
1215 * @ENTROPY_LVL_ACEPTABLE - below that threshold, sample has low byte entropy
1216 * and can be compressible with high probability
1217 *
1218 * @ENTROPY_LVL_HIGH - data are not compressible with high probability
1219 *
1220 * Use of ilog2() decreases precision, we lower the LVL to 5 to compensate.
1221 */
1222 #define ENTROPY_LVL_ACEPTABLE (65)
1223 #define ENTROPY_LVL_HIGH (80)
1224
1225 /*
1226 * For increasead precision in shannon_entropy calculation,
1227 * let's do pow(n, M) to save more digits after comma:
1228 *
1229 * - maximum int bit length is 64
1230 * - ilog2(MAX_SAMPLE_SIZE) -> 13
1231 * - 13 * 4 = 52 < 64 -> M = 4
1232 *
1233 * So use pow(n, 4).
1234 */
1235 static inline u32 ilog2_w(u64 n)
1236 {
1237 return ilog2(n * n * n * n);
1238 }
1239
1240 static u32 shannon_entropy(struct heuristic_ws *ws)
1241 {
1242 const u32 entropy_max = 8 * ilog2_w(2);
1243 u32 entropy_sum = 0;
1244 u32 p, p_base, sz_base;
1245 u32 i;
1246
1247 sz_base = ilog2_w(ws->sample_size);
1248 for (i = 0; i < BUCKET_SIZE && ws->bucket[i].count > 0; i++) {
1249 p = ws->bucket[i].count;
1250 p_base = ilog2_w(p);
1251 entropy_sum += p * (sz_base - p_base);
1252 }
1253
1254 entropy_sum /= ws->sample_size;
1255 return entropy_sum * 100 / entropy_max;
1256 }
1257
1258 #define RADIX_BASE 4U
1259 #define COUNTERS_SIZE (1U << RADIX_BASE)
1260
1261 static u8 get4bits(u64 num, int shift) {
1262 u8 low4bits;
1263
1264 num >>= shift;
1265 /* Reverse order */
1266 low4bits = (COUNTERS_SIZE - 1) - (num % COUNTERS_SIZE);
1267 return low4bits;
1268 }
1269
1270 /*
1271 * Use 4 bits as radix base
1272 * Use 16 u32 counters for calculating new position in buf array
1273 *
1274 * @array - array that will be sorted
1275 * @array_buf - buffer array to store sorting results
1276 * must be equal in size to @array
1277 * @num - array size
1278 */
1279 static void radix_sort(struct bucket_item *array, struct bucket_item *array_buf,
1280 int num)
1281 {
1282 u64 max_num;
1283 u64 buf_num;
1284 u32 counters[COUNTERS_SIZE];
1285 u32 new_addr;
1286 u32 addr;
1287 int bitlen;
1288 int shift;
1289 int i;
1290
1291 /*
1292 * Try avoid useless loop iterations for small numbers stored in big
1293 * counters. Example: 48 33 4 ... in 64bit array
1294 */
1295 max_num = array[0].count;
1296 for (i = 1; i < num; i++) {
1297 buf_num = array[i].count;
1298 if (buf_num > max_num)
1299 max_num = buf_num;
1300 }
1301
1302 buf_num = ilog2(max_num);
1303 bitlen = ALIGN(buf_num, RADIX_BASE * 2);
1304
1305 shift = 0;
1306 while (shift < bitlen) {
1307 memset(counters, 0, sizeof(counters));
1308
1309 for (i = 0; i < num; i++) {
1310 buf_num = array[i].count;
1311 addr = get4bits(buf_num, shift);
1312 counters[addr]++;
1313 }
1314
1315 for (i = 1; i < COUNTERS_SIZE; i++)
1316 counters[i] += counters[i - 1];
1317
1318 for (i = num - 1; i >= 0; i--) {
1319 buf_num = array[i].count;
1320 addr = get4bits(buf_num, shift);
1321 counters[addr]--;
1322 new_addr = counters[addr];
1323 array_buf[new_addr] = array[i];
1324 }
1325
1326 shift += RADIX_BASE;
1327
1328 /*
1329 * Normal radix expects to move data from a temporary array, to
1330 * the main one. But that requires some CPU time. Avoid that
1331 * by doing another sort iteration to original array instead of
1332 * memcpy()
1333 */
1334 memset(counters, 0, sizeof(counters));
1335
1336 for (i = 0; i < num; i ++) {
1337 buf_num = array_buf[i].count;
1338 addr = get4bits(buf_num, shift);
1339 counters[addr]++;
1340 }
1341
1342 for (i = 1; i < COUNTERS_SIZE; i++)
1343 counters[i] += counters[i - 1];
1344
1345 for (i = num - 1; i >= 0; i--) {
1346 buf_num = array_buf[i].count;
1347 addr = get4bits(buf_num, shift);
1348 counters[addr]--;
1349 new_addr = counters[addr];
1350 array[new_addr] = array_buf[i];
1351 }
1352
1353 shift += RADIX_BASE;
1354 }
1355 }
1356
1357 /*
1358 * Size of the core byte set - how many bytes cover 90% of the sample
1359 *
1360 * There are several types of structured binary data that use nearly all byte
1361 * values. The distribution can be uniform and counts in all buckets will be
1362 * nearly the same (eg. encrypted data). Unlikely to be compressible.
1363 *
1364 * Other possibility is normal (Gaussian) distribution, where the data could
1365 * be potentially compressible, but we have to take a few more steps to decide
1366 * how much.
1367 *
1368 * @BYTE_CORE_SET_LOW - main part of byte values repeated frequently,
1369 * compression algo can easy fix that
1370 * @BYTE_CORE_SET_HIGH - data have uniform distribution and with high
1371 * probability is not compressible
1372 */
1373 #define BYTE_CORE_SET_LOW (64)
1374 #define BYTE_CORE_SET_HIGH (200)
1375
1376 static int byte_core_set_size(struct heuristic_ws *ws)
1377 {
1378 u32 i;
1379 u32 coreset_sum = 0;
1380 const u32 core_set_threshold = ws->sample_size * 90 / 100;
1381 struct bucket_item *bucket = ws->bucket;
1382
1383 /* Sort in reverse order */
1384 radix_sort(ws->bucket, ws->bucket_b, BUCKET_SIZE);
1385
1386 for (i = 0; i < BYTE_CORE_SET_LOW; i++)
1387 coreset_sum += bucket[i].count;
1388
1389 if (coreset_sum > core_set_threshold)
1390 return i;
1391
1392 for (; i < BYTE_CORE_SET_HIGH && bucket[i].count > 0; i++) {
1393 coreset_sum += bucket[i].count;
1394 if (coreset_sum > core_set_threshold)
1395 break;
1396 }
1397
1398 return i;
1399 }
1400
1401 /*
1402 * Count byte values in buckets.
1403 * This heuristic can detect textual data (configs, xml, json, html, etc).
1404 * Because in most text-like data byte set is restricted to limited number of
1405 * possible characters, and that restriction in most cases makes data easy to
1406 * compress.
1407 *
1408 * @BYTE_SET_THRESHOLD - consider all data within this byte set size:
1409 * less - compressible
1410 * more - need additional analysis
1411 */
1412 #define BYTE_SET_THRESHOLD (64)
1413
1414 static u32 byte_set_size(const struct heuristic_ws *ws)
1415 {
1416 u32 i;
1417 u32 byte_set_size = 0;
1418
1419 for (i = 0; i < BYTE_SET_THRESHOLD; i++) {
1420 if (ws->bucket[i].count > 0)
1421 byte_set_size++;
1422 }
1423
1424 /*
1425 * Continue collecting count of byte values in buckets. If the byte
1426 * set size is bigger then the threshold, it's pointless to continue,
1427 * the detection technique would fail for this type of data.
1428 */
1429 for (; i < BUCKET_SIZE; i++) {
1430 if (ws->bucket[i].count > 0) {
1431 byte_set_size++;
1432 if (byte_set_size > BYTE_SET_THRESHOLD)
1433 return byte_set_size;
1434 }
1435 }
1436
1437 return byte_set_size;
1438 }
1439
1440 static bool sample_repeated_patterns(struct heuristic_ws *ws)
1441 {
1442 const u32 half_of_sample = ws->sample_size / 2;
1443 const u8 *data = ws->sample;
1444
1445 return memcmp(&data[0], &data[half_of_sample], half_of_sample) == 0;
1446 }
1447
1448 static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end,
1449 struct heuristic_ws *ws)
1450 {
1451 struct page *page;
1452 u64 index, index_end;
1453 u32 i, curr_sample_pos;
1454 u8 *in_data;
1455
1456 /*
1457 * Compression handles the input data by chunks of 128KiB
1458 * (defined by BTRFS_MAX_UNCOMPRESSED)
1459 *
1460 * We do the same for the heuristic and loop over the whole range.
1461 *
1462 * MAX_SAMPLE_SIZE - calculated under assumption that heuristic will
1463 * process no more than BTRFS_MAX_UNCOMPRESSED at a time.
1464 */
1465 if (end - start > BTRFS_MAX_UNCOMPRESSED)
1466 end = start + BTRFS_MAX_UNCOMPRESSED;
1467
1468 index = start >> PAGE_SHIFT;
1469 index_end = end >> PAGE_SHIFT;
1470
1471 /* Don't miss unaligned end */
1472 if (!PAGE_ALIGNED(end))
1473 index_end++;
1474
1475 curr_sample_pos = 0;
1476 while (index < index_end) {
1477 page = find_get_page(inode->i_mapping, index);
1478 in_data = kmap_local_page(page);
1479 /* Handle case where the start is not aligned to PAGE_SIZE */
1480 i = start % PAGE_SIZE;
1481 while (i < PAGE_SIZE - SAMPLING_READ_SIZE) {
1482 /* Don't sample any garbage from the last page */
1483 if (start > end - SAMPLING_READ_SIZE)
1484 break;
1485 memcpy(&ws->sample[curr_sample_pos], &in_data[i],
1486 SAMPLING_READ_SIZE);
1487 i += SAMPLING_INTERVAL;
1488 start += SAMPLING_INTERVAL;
1489 curr_sample_pos += SAMPLING_READ_SIZE;
1490 }
1491 kunmap_local(in_data);
1492 put_page(page);
1493
1494 index++;
1495 }
1496
1497 ws->sample_size = curr_sample_pos;
1498 }
1499
1500 /*
1501 * Compression heuristic.
1502 *
1503 * The following types of analysis can be performed:
1504 * - detect mostly zero data
1505 * - detect data with low "byte set" size (text, etc)
1506 * - detect data with low/high "core byte" set
1507 *
1508 * Return non-zero if the compression should be done, 0 otherwise.
1509 */
1510 int btrfs_compress_heuristic(struct btrfs_inode *inode, u64 start, u64 end)
1511 {
1512 struct list_head *ws_list = get_workspace(0, 0);
1513 struct heuristic_ws *ws;
1514 u32 i;
1515 u8 byte;
1516 int ret = 0;
1517
1518 ws = list_entry(ws_list, struct heuristic_ws, list);
1519
1520 heuristic_collect_sample(&inode->vfs_inode, start, end, ws);
1521
1522 if (sample_repeated_patterns(ws)) {
1523 ret = 1;
1524 goto out;
1525 }
1526
1527 memset(ws->bucket, 0, sizeof(*ws->bucket)*BUCKET_SIZE);
1528
1529 for (i = 0; i < ws->sample_size; i++) {
1530 byte = ws->sample[i];
1531 ws->bucket[byte].count++;
1532 }
1533
1534 i = byte_set_size(ws);
1535 if (i < BYTE_SET_THRESHOLD) {
1536 ret = 2;
1537 goto out;
1538 }
1539
1540 i = byte_core_set_size(ws);
1541 if (i <= BYTE_CORE_SET_LOW) {
1542 ret = 3;
1543 goto out;
1544 }
1545
1546 if (i >= BYTE_CORE_SET_HIGH) {
1547 ret = 0;
1548 goto out;
1549 }
1550
1551 i = shannon_entropy(ws);
1552 if (i <= ENTROPY_LVL_ACEPTABLE) {
1553 ret = 4;
1554 goto out;
1555 }
1556
1557 /*
1558 * For the levels below ENTROPY_LVL_HIGH, additional analysis would be
1559 * needed to give green light to compression.
1560 *
1561 * For now just assume that compression at that level is not worth the
1562 * resources because:
1563 *
1564 * 1. it is possible to defrag the data later
1565 *
1566 * 2. the data would turn out to be hardly compressible, eg. 150 byte
1567 * values, every bucket has counter at level ~54. The heuristic would
1568 * be confused. This can happen when data have some internal repeated
1569 * patterns like "abbacbbc...". This can be detected by analyzing
1570 * pairs of bytes, which is too costly.
1571 */
1572 if (i < ENTROPY_LVL_HIGH) {
1573 ret = 5;
1574 goto out;
1575 } else {
1576 ret = 0;
1577 goto out;
1578 }
1579
1580 out:
1581 put_workspace(0, ws_list);
1582 return ret;
1583 }
1584
1585 /*
1586 * Convert the compression suffix (eg. after "zlib" starting with ":") to
1587 * level, unrecognized string will set the default level
1588 */
1589 unsigned int btrfs_compress_str2level(unsigned int type, const char *str)
1590 {
1591 unsigned int level = 0;
1592 int ret;
1593
1594 if (!type)
1595 return 0;
1596
1597 if (str[0] == ':') {
1598 ret = kstrtouint(str + 1, 10, &level);
1599 if (ret)
1600 level = 0;
1601 }
1602
1603 level = btrfs_compress_set_level(type, level);
1604
1605 return level;
1606 }
1607
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