1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 2008 Oracle. All rights reserved.
6 #include <linux/kernel.h>
8 #include <linux/file.h>
10 #include <linux/pagemap.h>
11 #include <linux/highmem.h>
12 #include <linux/time.h>
13 #include <linux/init.h>
14 #include <linux/string.h>
15 #include <linux/backing-dev.h>
16 #include <linux/writeback.h>
17 #include <linux/slab.h>
18 #include <linux/sched/mm.h>
19 #include <linux/log2.h>
20 #include <crypto/hash.h>
24 #include "transaction.h"
25 #include "btrfs_inode.h"
27 #include "ordered-data.h"
28 #include "compression.h"
29 #include "extent_io.h"
30 #include "extent_map.h"
32 int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
33 u64 start, struct page **pages, unsigned long *out_pages,
34 unsigned long *total_in, unsigned long *total_out);
35 int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb);
36 int zlib_decompress(struct list_head *ws, unsigned char *data_in,
37 struct page *dest_page, unsigned long start_byte, size_t srclen,
39 struct list_head *zlib_alloc_workspace(unsigned int level);
40 void zlib_free_workspace(struct list_head *ws);
41 struct list_head *zlib_get_workspace(unsigned int level);
43 int lzo_compress_pages(struct list_head *ws, struct address_space *mapping,
44 u64 start, struct page **pages, unsigned long *out_pages,
45 unsigned long *total_in, unsigned long *total_out);
46 int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb);
47 int lzo_decompress(struct list_head *ws, unsigned char *data_in,
48 struct page *dest_page, unsigned long start_byte, size_t srclen,
50 struct list_head *lzo_alloc_workspace(unsigned int level);
51 void lzo_free_workspace(struct list_head *ws);
53 int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
54 u64 start, struct page **pages, unsigned long *out_pages,
55 unsigned long *total_in, unsigned long *total_out);
56 int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb);
57 int zstd_decompress(struct list_head *ws, unsigned char *data_in,
58 struct page *dest_page, unsigned long start_byte, size_t srclen,
60 void zstd_init_workspace_manager(void);
61 void zstd_cleanup_workspace_manager(void);
62 struct list_head *zstd_alloc_workspace(unsigned int level);
63 void zstd_free_workspace(struct list_head *ws);
64 struct list_head *zstd_get_workspace(unsigned int level);
65 void zstd_put_workspace(struct list_head *ws);
67 static const char* const btrfs_compress_types[] = { "", "zlib", "lzo", "zstd" };
69 const char* btrfs_compress_type2str(enum btrfs_compression_type type)
72 case BTRFS_COMPRESS_ZLIB:
73 case BTRFS_COMPRESS_LZO:
74 case BTRFS_COMPRESS_ZSTD:
75 case BTRFS_COMPRESS_NONE:
76 return btrfs_compress_types[type];
84 bool btrfs_compress_is_valid_type(const char *str, size_t len)
88 for (i = 1; i < ARRAY_SIZE(btrfs_compress_types); i++) {
89 size_t comp_len = strlen(btrfs_compress_types[i]);
94 if (!strncmp(btrfs_compress_types[i], str, comp_len))
100 static int compression_compress_pages(int type, struct list_head *ws,
101 struct address_space *mapping, u64 start, struct page **pages,
102 unsigned long *out_pages, unsigned long *total_in,
103 unsigned long *total_out)
106 case BTRFS_COMPRESS_ZLIB:
107 return zlib_compress_pages(ws, mapping, start, pages,
108 out_pages, total_in, total_out);
109 case BTRFS_COMPRESS_LZO:
110 return lzo_compress_pages(ws, mapping, start, pages,
111 out_pages, total_in, total_out);
112 case BTRFS_COMPRESS_ZSTD:
113 return zstd_compress_pages(ws, mapping, start, pages,
114 out_pages, total_in, total_out);
115 case BTRFS_COMPRESS_NONE:
118 * This can't happen, the type is validated several times
119 * before we get here. As a sane fallback, return what the
120 * callers will understand as 'no compression happened'.
126 static int compression_decompress_bio(int type, struct list_head *ws,
127 struct compressed_bio *cb)
130 case BTRFS_COMPRESS_ZLIB: return zlib_decompress_bio(ws, cb);
131 case BTRFS_COMPRESS_LZO: return lzo_decompress_bio(ws, cb);
132 case BTRFS_COMPRESS_ZSTD: return zstd_decompress_bio(ws, cb);
133 case BTRFS_COMPRESS_NONE:
136 * This can't happen, the type is validated several times
137 * before we get here.
143 static int compression_decompress(int type, struct list_head *ws,
144 unsigned char *data_in, struct page *dest_page,
145 unsigned long start_byte, size_t srclen, size_t destlen)
148 case BTRFS_COMPRESS_ZLIB: return zlib_decompress(ws, data_in, dest_page,
149 start_byte, srclen, destlen);
150 case BTRFS_COMPRESS_LZO: return lzo_decompress(ws, data_in, dest_page,
151 start_byte, srclen, destlen);
152 case BTRFS_COMPRESS_ZSTD: return zstd_decompress(ws, data_in, dest_page,
153 start_byte, srclen, destlen);
154 case BTRFS_COMPRESS_NONE:
157 * This can't happen, the type is validated several times
158 * before we get here.
164 static int btrfs_decompress_bio(struct compressed_bio *cb);
166 static inline int compressed_bio_size(struct btrfs_fs_info *fs_info,
167 unsigned long disk_size)
169 u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
171 return sizeof(struct compressed_bio) +
172 (DIV_ROUND_UP(disk_size, fs_info->sectorsize)) * csum_size;
175 static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
178 struct btrfs_fs_info *fs_info = inode->root->fs_info;
179 SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
180 const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
184 u8 csum[BTRFS_CSUM_SIZE];
185 struct compressed_bio *cb = bio->bi_private;
186 u8 *cb_sum = cb->sums;
188 if (inode->flags & BTRFS_INODE_NODATASUM)
191 shash->tfm = fs_info->csum_shash;
193 for (i = 0; i < cb->nr_pages; i++) {
194 page = cb->compressed_pages[i];
196 kaddr = kmap_atomic(page);
197 crypto_shash_digest(shash, kaddr, PAGE_SIZE, csum);
198 kunmap_atomic(kaddr);
200 if (memcmp(&csum, cb_sum, csum_size)) {
201 btrfs_print_data_csum_error(inode, disk_start,
202 csum, cb_sum, cb->mirror_num);
203 if (btrfs_io_bio(bio)->device)
204 btrfs_dev_stat_inc_and_print(
205 btrfs_io_bio(bio)->device,
206 BTRFS_DEV_STAT_CORRUPTION_ERRS);
214 /* when we finish reading compressed pages from the disk, we
215 * decompress them and then run the bio end_io routines on the
216 * decompressed pages (in the inode address space).
218 * This allows the checksumming and other IO error handling routines
221 * The compressed pages are freed here, and it must be run
224 static void end_compressed_bio_read(struct bio *bio)
226 struct compressed_bio *cb = bio->bi_private;
230 unsigned int mirror = btrfs_io_bio(bio)->mirror_num;
236 /* if there are more bios still pending for this compressed
239 if (!refcount_dec_and_test(&cb->pending_bios))
243 * Record the correct mirror_num in cb->orig_bio so that
244 * read-repair can work properly.
246 btrfs_io_bio(cb->orig_bio)->mirror_num = mirror;
247 cb->mirror_num = mirror;
250 * Some IO in this cb have failed, just skip checksum as there
251 * is no way it could be correct.
257 ret = check_compressed_csum(BTRFS_I(inode), bio,
258 (u64)bio->bi_iter.bi_sector << 9);
262 /* ok, we're the last bio for this extent, lets start
265 ret = btrfs_decompress_bio(cb);
271 /* release the compressed pages */
273 for (index = 0; index < cb->nr_pages; index++) {
274 page = cb->compressed_pages[index];
275 page->mapping = NULL;
279 /* do io completion on the original bio */
281 bio_io_error(cb->orig_bio);
283 struct bio_vec *bvec;
284 struct bvec_iter_all iter_all;
287 * we have verified the checksum already, set page
288 * checked so the end_io handlers know about it
290 ASSERT(!bio_flagged(bio, BIO_CLONED));
291 bio_for_each_segment_all(bvec, cb->orig_bio, iter_all)
292 SetPageChecked(bvec->bv_page);
294 bio_endio(cb->orig_bio);
297 /* finally free the cb struct */
298 kfree(cb->compressed_pages);
305 * Clear the writeback bits on all of the file
306 * pages for a compressed write
308 static noinline void end_compressed_writeback(struct inode *inode,
309 const struct compressed_bio *cb)
311 unsigned long index = cb->start >> PAGE_SHIFT;
312 unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT;
313 struct page *pages[16];
314 unsigned long nr_pages = end_index - index + 1;
319 mapping_set_error(inode->i_mapping, -EIO);
321 while (nr_pages > 0) {
322 ret = find_get_pages_contig(inode->i_mapping, index,
324 nr_pages, ARRAY_SIZE(pages)), pages);
330 for (i = 0; i < ret; i++) {
332 SetPageError(pages[i]);
333 end_page_writeback(pages[i]);
339 /* the inode may be gone now */
343 * do the cleanup once all the compressed pages hit the disk.
344 * This will clear writeback on the file pages and free the compressed
347 * This also calls the writeback end hooks for the file pages so that
348 * metadata and checksums can be updated in the file.
350 static void end_compressed_bio_write(struct bio *bio)
352 struct compressed_bio *cb = bio->bi_private;
360 /* if there are more bios still pending for this compressed
363 if (!refcount_dec_and_test(&cb->pending_bios))
366 /* ok, we're the last bio for this extent, step one is to
367 * call back into the FS and do all the end_io operations
370 cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
371 btrfs_writepage_endio_finish_ordered(cb->compressed_pages[0],
372 cb->start, cb->start + cb->len - 1,
373 bio->bi_status == BLK_STS_OK);
374 cb->compressed_pages[0]->mapping = NULL;
376 end_compressed_writeback(inode, cb);
377 /* note, our inode could be gone now */
380 * release the compressed pages, these came from alloc_page and
381 * are not attached to the inode at all
384 for (index = 0; index < cb->nr_pages; index++) {
385 page = cb->compressed_pages[index];
386 page->mapping = NULL;
390 /* finally free the cb struct */
391 kfree(cb->compressed_pages);
398 * worker function to build and submit bios for previously compressed pages.
399 * The corresponding pages in the inode should be marked for writeback
400 * and the compressed pages should have a reference on them for dropping
401 * when the IO is complete.
403 * This also checksums the file bytes and gets things ready for
406 blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
407 unsigned long len, u64 disk_start,
408 unsigned long compressed_len,
409 struct page **compressed_pages,
410 unsigned long nr_pages,
411 unsigned int write_flags,
412 struct cgroup_subsys_state *blkcg_css)
414 struct btrfs_fs_info *fs_info = inode->root->fs_info;
415 struct bio *bio = NULL;
416 struct compressed_bio *cb;
417 unsigned long bytes_left;
420 u64 first_byte = disk_start;
422 int skip_sum = inode->flags & BTRFS_INODE_NODATASUM;
424 WARN_ON(!PAGE_ALIGNED(start));
425 cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
427 return BLK_STS_RESOURCE;
428 refcount_set(&cb->pending_bios, 0);
430 cb->inode = &inode->vfs_inode;
434 cb->compressed_pages = compressed_pages;
435 cb->compressed_len = compressed_len;
437 cb->nr_pages = nr_pages;
439 bio = btrfs_bio_alloc(first_byte);
440 bio->bi_opf = REQ_OP_WRITE | write_flags;
441 bio->bi_private = cb;
442 bio->bi_end_io = end_compressed_bio_write;
445 bio->bi_opf |= REQ_CGROUP_PUNT;
446 kthread_associate_blkcg(blkcg_css);
448 refcount_set(&cb->pending_bios, 1);
450 /* create and submit bios for the compressed pages */
451 bytes_left = compressed_len;
452 for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
455 page = compressed_pages[pg_index];
456 page->mapping = inode->vfs_inode.i_mapping;
457 if (bio->bi_iter.bi_size)
458 submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, bio,
461 page->mapping = NULL;
462 if (submit || bio_add_page(bio, page, PAGE_SIZE, 0) <
465 * inc the count before we submit the bio so
466 * we know the end IO handler won't happen before
467 * we inc the count. Otherwise, the cb might get
468 * freed before we're done setting it up
470 refcount_inc(&cb->pending_bios);
471 ret = btrfs_bio_wq_end_io(fs_info, bio,
472 BTRFS_WQ_ENDIO_DATA);
473 BUG_ON(ret); /* -ENOMEM */
476 ret = btrfs_csum_one_bio(inode, bio, start, 1);
477 BUG_ON(ret); /* -ENOMEM */
480 ret = btrfs_map_bio(fs_info, bio, 0);
482 bio->bi_status = ret;
486 bio = btrfs_bio_alloc(first_byte);
487 bio->bi_opf = REQ_OP_WRITE | write_flags;
488 bio->bi_private = cb;
489 bio->bi_end_io = end_compressed_bio_write;
491 bio->bi_opf |= REQ_CGROUP_PUNT;
492 bio_add_page(bio, page, PAGE_SIZE, 0);
494 if (bytes_left < PAGE_SIZE) {
496 "bytes left %lu compress len %lu nr %lu",
497 bytes_left, cb->compressed_len, cb->nr_pages);
499 bytes_left -= PAGE_SIZE;
500 first_byte += PAGE_SIZE;
504 ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
505 BUG_ON(ret); /* -ENOMEM */
508 ret = btrfs_csum_one_bio(inode, bio, start, 1);
509 BUG_ON(ret); /* -ENOMEM */
512 ret = btrfs_map_bio(fs_info, bio, 0);
514 bio->bi_status = ret;
519 kthread_associate_blkcg(NULL);
524 static u64 bio_end_offset(struct bio *bio)
526 struct bio_vec *last = bio_last_bvec_all(bio);
528 return page_offset(last->bv_page) + last->bv_len + last->bv_offset;
531 static noinline int add_ra_bio_pages(struct inode *inode,
533 struct compressed_bio *cb)
535 unsigned long end_index;
536 unsigned long pg_index;
538 u64 isize = i_size_read(inode);
541 unsigned long nr_pages = 0;
542 struct extent_map *em;
543 struct address_space *mapping = inode->i_mapping;
544 struct extent_map_tree *em_tree;
545 struct extent_io_tree *tree;
549 last_offset = bio_end_offset(cb->orig_bio);
550 em_tree = &BTRFS_I(inode)->extent_tree;
551 tree = &BTRFS_I(inode)->io_tree;
556 end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
558 while (last_offset < compressed_end) {
559 pg_index = last_offset >> PAGE_SHIFT;
561 if (pg_index > end_index)
564 page = xa_load(&mapping->i_pages, pg_index);
565 if (page && !xa_is_value(page)) {
572 page = __page_cache_alloc(mapping_gfp_constraint(mapping,
577 if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
582 end = last_offset + PAGE_SIZE - 1;
584 * at this point, we have a locked page in the page cache
585 * for these bytes in the file. But, we have to make
586 * sure they map to this compressed extent on disk.
588 set_page_extent_mapped(page);
589 lock_extent(tree, last_offset, end);
590 read_lock(&em_tree->lock);
591 em = lookup_extent_mapping(em_tree, last_offset,
593 read_unlock(&em_tree->lock);
595 if (!em || last_offset < em->start ||
596 (last_offset + PAGE_SIZE > extent_map_end(em)) ||
597 (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
599 unlock_extent(tree, last_offset, end);
606 if (page->index == end_index) {
608 size_t zero_offset = offset_in_page(isize);
612 zeros = PAGE_SIZE - zero_offset;
613 userpage = kmap_atomic(page);
614 memset(userpage + zero_offset, 0, zeros);
615 flush_dcache_page(page);
616 kunmap_atomic(userpage);
620 ret = bio_add_page(cb->orig_bio, page,
623 if (ret == PAGE_SIZE) {
627 unlock_extent(tree, last_offset, end);
633 last_offset += PAGE_SIZE;
639 * for a compressed read, the bio we get passed has all the inode pages
640 * in it. We don't actually do IO on those pages but allocate new ones
641 * to hold the compressed pages on disk.
643 * bio->bi_iter.bi_sector points to the compressed extent on disk
644 * bio->bi_io_vec points to all of the inode pages
646 * After the compressed pages are read, we copy the bytes into the
647 * bio we were passed and then call the bio end_io calls
649 blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
650 int mirror_num, unsigned long bio_flags)
652 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
653 struct extent_map_tree *em_tree;
654 struct compressed_bio *cb;
655 unsigned long compressed_len;
656 unsigned long nr_pages;
657 unsigned long pg_index;
659 struct bio *comp_bio;
660 u64 cur_disk_byte = (u64)bio->bi_iter.bi_sector << 9;
663 struct extent_map *em;
664 blk_status_t ret = BLK_STS_RESOURCE;
666 const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
669 em_tree = &BTRFS_I(inode)->extent_tree;
671 /* we need the actual starting offset of this extent in the file */
672 read_lock(&em_tree->lock);
673 em = lookup_extent_mapping(em_tree,
674 page_offset(bio_first_page_all(bio)),
676 read_unlock(&em_tree->lock);
678 return BLK_STS_IOERR;
680 compressed_len = em->block_len;
681 cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
685 refcount_set(&cb->pending_bios, 0);
688 cb->mirror_num = mirror_num;
691 cb->start = em->orig_start;
693 em_start = em->start;
698 cb->len = bio->bi_iter.bi_size;
699 cb->compressed_len = compressed_len;
700 cb->compress_type = extent_compress_type(bio_flags);
703 nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
704 cb->compressed_pages = kcalloc(nr_pages, sizeof(struct page *),
706 if (!cb->compressed_pages)
709 for (pg_index = 0; pg_index < nr_pages; pg_index++) {
710 cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
712 if (!cb->compressed_pages[pg_index]) {
713 faili = pg_index - 1;
714 ret = BLK_STS_RESOURCE;
718 faili = nr_pages - 1;
719 cb->nr_pages = nr_pages;
721 add_ra_bio_pages(inode, em_start + em_len, cb);
723 /* include any pages we added in add_ra-bio_pages */
724 cb->len = bio->bi_iter.bi_size;
726 comp_bio = btrfs_bio_alloc(cur_disk_byte);
727 comp_bio->bi_opf = REQ_OP_READ;
728 comp_bio->bi_private = cb;
729 comp_bio->bi_end_io = end_compressed_bio_read;
730 refcount_set(&cb->pending_bios, 1);
732 for (pg_index = 0; pg_index < nr_pages; pg_index++) {
735 page = cb->compressed_pages[pg_index];
736 page->mapping = inode->i_mapping;
737 page->index = em_start >> PAGE_SHIFT;
739 if (comp_bio->bi_iter.bi_size)
740 submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE,
743 page->mapping = NULL;
744 if (submit || bio_add_page(comp_bio, page, PAGE_SIZE, 0) <
746 unsigned int nr_sectors;
748 ret = btrfs_bio_wq_end_io(fs_info, comp_bio,
749 BTRFS_WQ_ENDIO_DATA);
750 BUG_ON(ret); /* -ENOMEM */
753 * inc the count before we submit the bio so
754 * we know the end IO handler won't happen before
755 * we inc the count. Otherwise, the cb might get
756 * freed before we're done setting it up
758 refcount_inc(&cb->pending_bios);
760 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
761 ret = btrfs_lookup_bio_sums(inode, comp_bio,
763 BUG_ON(ret); /* -ENOMEM */
766 nr_sectors = DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
767 fs_info->sectorsize);
768 sums += csum_size * nr_sectors;
770 ret = btrfs_map_bio(fs_info, comp_bio, mirror_num);
772 comp_bio->bi_status = ret;
776 comp_bio = btrfs_bio_alloc(cur_disk_byte);
777 comp_bio->bi_opf = REQ_OP_READ;
778 comp_bio->bi_private = cb;
779 comp_bio->bi_end_io = end_compressed_bio_read;
781 bio_add_page(comp_bio, page, PAGE_SIZE, 0);
783 cur_disk_byte += PAGE_SIZE;
786 ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA);
787 BUG_ON(ret); /* -ENOMEM */
789 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
790 ret = btrfs_lookup_bio_sums(inode, comp_bio, (u64)-1, sums);
791 BUG_ON(ret); /* -ENOMEM */
794 ret = btrfs_map_bio(fs_info, comp_bio, mirror_num);
796 comp_bio->bi_status = ret;
804 __free_page(cb->compressed_pages[faili]);
808 kfree(cb->compressed_pages);
817 * Heuristic uses systematic sampling to collect data from the input data
818 * range, the logic can be tuned by the following constants:
820 * @SAMPLING_READ_SIZE - how many bytes will be copied from for each sample
821 * @SAMPLING_INTERVAL - range from which the sampled data can be collected
823 #define SAMPLING_READ_SIZE (16)
824 #define SAMPLING_INTERVAL (256)
827 * For statistical analysis of the input data we consider bytes that form a
828 * Galois Field of 256 objects. Each object has an attribute count, ie. how
829 * many times the object appeared in the sample.
831 #define BUCKET_SIZE (256)
834 * The size of the sample is based on a statistical sampling rule of thumb.
835 * The common way is to perform sampling tests as long as the number of
836 * elements in each cell is at least 5.
838 * Instead of 5, we choose 32 to obtain more accurate results.
839 * If the data contain the maximum number of symbols, which is 256, we obtain a
840 * sample size bound by 8192.
842 * For a sample of at most 8KB of data per data range: 16 consecutive bytes
843 * from up to 512 locations.
845 #define MAX_SAMPLE_SIZE (BTRFS_MAX_UNCOMPRESSED * \
846 SAMPLING_READ_SIZE / SAMPLING_INTERVAL)
852 struct heuristic_ws {
853 /* Partial copy of input data */
856 /* Buckets store counters for each byte value */
857 struct bucket_item *bucket;
859 struct bucket_item *bucket_b;
860 struct list_head list;
863 static struct workspace_manager heuristic_wsm;
865 static void free_heuristic_ws(struct list_head *ws)
867 struct heuristic_ws *workspace;
869 workspace = list_entry(ws, struct heuristic_ws, list);
871 kvfree(workspace->sample);
872 kfree(workspace->bucket);
873 kfree(workspace->bucket_b);
877 static struct list_head *alloc_heuristic_ws(unsigned int level)
879 struct heuristic_ws *ws;
881 ws = kzalloc(sizeof(*ws), GFP_KERNEL);
883 return ERR_PTR(-ENOMEM);
885 ws->sample = kvmalloc(MAX_SAMPLE_SIZE, GFP_KERNEL);
889 ws->bucket = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket), GFP_KERNEL);
893 ws->bucket_b = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket_b), GFP_KERNEL);
897 INIT_LIST_HEAD(&ws->list);
900 free_heuristic_ws(&ws->list);
901 return ERR_PTR(-ENOMEM);
904 const struct btrfs_compress_op btrfs_heuristic_compress = {
905 .workspace_manager = &heuristic_wsm,
908 static const struct btrfs_compress_op * const btrfs_compress_op[] = {
909 /* The heuristic is represented as compression type 0 */
910 &btrfs_heuristic_compress,
911 &btrfs_zlib_compress,
913 &btrfs_zstd_compress,
916 static struct list_head *alloc_workspace(int type, unsigned int level)
919 case BTRFS_COMPRESS_NONE: return alloc_heuristic_ws(level);
920 case BTRFS_COMPRESS_ZLIB: return zlib_alloc_workspace(level);
921 case BTRFS_COMPRESS_LZO: return lzo_alloc_workspace(level);
922 case BTRFS_COMPRESS_ZSTD: return zstd_alloc_workspace(level);
925 * This can't happen, the type is validated several times
926 * before we get here.
932 static void free_workspace(int type, struct list_head *ws)
935 case BTRFS_COMPRESS_NONE: return free_heuristic_ws(ws);
936 case BTRFS_COMPRESS_ZLIB: return zlib_free_workspace(ws);
937 case BTRFS_COMPRESS_LZO: return lzo_free_workspace(ws);
938 case BTRFS_COMPRESS_ZSTD: return zstd_free_workspace(ws);
941 * This can't happen, the type is validated several times
942 * before we get here.
948 static void btrfs_init_workspace_manager(int type)
950 struct workspace_manager *wsm;
951 struct list_head *workspace;
953 wsm = btrfs_compress_op[type]->workspace_manager;
954 INIT_LIST_HEAD(&wsm->idle_ws);
955 spin_lock_init(&wsm->ws_lock);
956 atomic_set(&wsm->total_ws, 0);
957 init_waitqueue_head(&wsm->ws_wait);
960 * Preallocate one workspace for each compression type so we can
961 * guarantee forward progress in the worst case
963 workspace = alloc_workspace(type, 0);
964 if (IS_ERR(workspace)) {
966 "BTRFS: cannot preallocate compression workspace, will try later\n");
968 atomic_set(&wsm->total_ws, 1);
970 list_add(workspace, &wsm->idle_ws);
974 static void btrfs_cleanup_workspace_manager(int type)
976 struct workspace_manager *wsman;
977 struct list_head *ws;
979 wsman = btrfs_compress_op[type]->workspace_manager;
980 while (!list_empty(&wsman->idle_ws)) {
981 ws = wsman->idle_ws.next;
983 free_workspace(type, ws);
984 atomic_dec(&wsman->total_ws);
989 * This finds an available workspace or allocates a new one.
990 * If it's not possible to allocate a new one, waits until there's one.
991 * Preallocation makes a forward progress guarantees and we do not return
994 struct list_head *btrfs_get_workspace(int type, unsigned int level)
996 struct workspace_manager *wsm;
997 struct list_head *workspace;
998 int cpus = num_online_cpus();
1000 struct list_head *idle_ws;
1001 spinlock_t *ws_lock;
1003 wait_queue_head_t *ws_wait;
1006 wsm = btrfs_compress_op[type]->workspace_manager;
1007 idle_ws = &wsm->idle_ws;
1008 ws_lock = &wsm->ws_lock;
1009 total_ws = &wsm->total_ws;
1010 ws_wait = &wsm->ws_wait;
1011 free_ws = &wsm->free_ws;
1015 if (!list_empty(idle_ws)) {
1016 workspace = idle_ws->next;
1017 list_del(workspace);
1019 spin_unlock(ws_lock);
1023 if (atomic_read(total_ws) > cpus) {
1026 spin_unlock(ws_lock);
1027 prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE);
1028 if (atomic_read(total_ws) > cpus && !*free_ws)
1030 finish_wait(ws_wait, &wait);
1033 atomic_inc(total_ws);
1034 spin_unlock(ws_lock);
1037 * Allocation helpers call vmalloc that can't use GFP_NOFS, so we have
1038 * to turn it off here because we might get called from the restricted
1039 * context of btrfs_compress_bio/btrfs_compress_pages
1041 nofs_flag = memalloc_nofs_save();
1042 workspace = alloc_workspace(type, level);
1043 memalloc_nofs_restore(nofs_flag);
1045 if (IS_ERR(workspace)) {
1046 atomic_dec(total_ws);
1050 * Do not return the error but go back to waiting. There's a
1051 * workspace preallocated for each type and the compression
1052 * time is bounded so we get to a workspace eventually. This
1053 * makes our caller's life easier.
1055 * To prevent silent and low-probability deadlocks (when the
1056 * initial preallocation fails), check if there are any
1057 * workspaces at all.
1059 if (atomic_read(total_ws) == 0) {
1060 static DEFINE_RATELIMIT_STATE(_rs,
1061 /* once per minute */ 60 * HZ,
1064 if (__ratelimit(&_rs)) {
1065 pr_warn("BTRFS: no compression workspaces, low memory, retrying\n");
1073 static struct list_head *get_workspace(int type, int level)
1076 case BTRFS_COMPRESS_NONE: return btrfs_get_workspace(type, level);
1077 case BTRFS_COMPRESS_ZLIB: return zlib_get_workspace(level);
1078 case BTRFS_COMPRESS_LZO: return btrfs_get_workspace(type, level);
1079 case BTRFS_COMPRESS_ZSTD: return zstd_get_workspace(level);
1082 * This can't happen, the type is validated several times
1083 * before we get here.
1090 * put a workspace struct back on the list or free it if we have enough
1091 * idle ones sitting around
1093 void btrfs_put_workspace(int type, struct list_head *ws)
1095 struct workspace_manager *wsm;
1096 struct list_head *idle_ws;
1097 spinlock_t *ws_lock;
1099 wait_queue_head_t *ws_wait;
1102 wsm = btrfs_compress_op[type]->workspace_manager;
1103 idle_ws = &wsm->idle_ws;
1104 ws_lock = &wsm->ws_lock;
1105 total_ws = &wsm->total_ws;
1106 ws_wait = &wsm->ws_wait;
1107 free_ws = &wsm->free_ws;
1110 if (*free_ws <= num_online_cpus()) {
1111 list_add(ws, idle_ws);
1113 spin_unlock(ws_lock);
1116 spin_unlock(ws_lock);
1118 free_workspace(type, ws);
1119 atomic_dec(total_ws);
1121 cond_wake_up(ws_wait);
1124 static void put_workspace(int type, struct list_head *ws)
1127 case BTRFS_COMPRESS_NONE: return btrfs_put_workspace(type, ws);
1128 case BTRFS_COMPRESS_ZLIB: return btrfs_put_workspace(type, ws);
1129 case BTRFS_COMPRESS_LZO: return btrfs_put_workspace(type, ws);
1130 case BTRFS_COMPRESS_ZSTD: return zstd_put_workspace(ws);
1133 * This can't happen, the type is validated several times
1134 * before we get here.
1141 * Adjust @level according to the limits of the compression algorithm or
1142 * fallback to default
1144 static unsigned int btrfs_compress_set_level(int type, unsigned level)
1146 const struct btrfs_compress_op *ops = btrfs_compress_op[type];
1149 level = ops->default_level;
1151 level = min(level, ops->max_level);
1157 * Given an address space and start and length, compress the bytes into @pages
1158 * that are allocated on demand.
1160 * @type_level is encoded algorithm and level, where level 0 means whatever
1161 * default the algorithm chooses and is opaque here;
1162 * - compression algo are 0-3
1163 * - the level are bits 4-7
1165 * @out_pages is an in/out parameter, holds maximum number of pages to allocate
1166 * and returns number of actually allocated pages
1168 * @total_in is used to return the number of bytes actually read. It
1169 * may be smaller than the input length if we had to exit early because we
1170 * ran out of room in the pages array or because we cross the
1171 * max_out threshold.
1173 * @total_out is an in/out parameter, must be set to the input length and will
1174 * be also used to return the total number of compressed bytes
1176 * @max_out tells us the max number of bytes that we're allowed to
1179 int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
1180 u64 start, struct page **pages,
1181 unsigned long *out_pages,
1182 unsigned long *total_in,
1183 unsigned long *total_out)
1185 int type = btrfs_compress_type(type_level);
1186 int level = btrfs_compress_level(type_level);
1187 struct list_head *workspace;
1190 level = btrfs_compress_set_level(type, level);
1191 workspace = get_workspace(type, level);
1192 ret = compression_compress_pages(type, workspace, mapping, start, pages,
1193 out_pages, total_in, total_out);
1194 put_workspace(type, workspace);
1199 * pages_in is an array of pages with compressed data.
1201 * disk_start is the starting logical offset of this array in the file
1203 * orig_bio contains the pages from the file that we want to decompress into
1205 * srclen is the number of bytes in pages_in
1207 * The basic idea is that we have a bio that was created by readpages.
1208 * The pages in the bio are for the uncompressed data, and they may not
1209 * be contiguous. They all correspond to the range of bytes covered by
1210 * the compressed extent.
1212 static int btrfs_decompress_bio(struct compressed_bio *cb)
1214 struct list_head *workspace;
1216 int type = cb->compress_type;
1218 workspace = get_workspace(type, 0);
1219 ret = compression_decompress_bio(type, workspace, cb);
1220 put_workspace(type, workspace);
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
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)
1233 struct list_head *workspace;
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);
1244 void __init btrfs_init_compress(void)
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();
1252 void __cold btrfs_exit_compress(void)
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();
1261 * Copy uncompressed data from working buffer to pages.
1263 * buf_start is the byte offset we're of the start of our workspace buffer.
1265 * total_out is the last byte of the buffer
1267 int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
1268 unsigned long total_out, u64 disk_start,
1271 unsigned long buf_offset;
1272 unsigned long current_buf_start;
1273 unsigned long start_byte;
1274 unsigned long prev_start_byte;
1275 unsigned long working_bytes = total_out - buf_start;
1276 unsigned long bytes;
1278 struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter);
1281 * start byte is the first byte of the page we're currently
1282 * copying into relative to the start of the compressed data.
1284 start_byte = page_offset(bvec.bv_page) - disk_start;
1286 /* we haven't yet hit data corresponding to this page */
1287 if (total_out <= start_byte)
1291 * the start of the data we care about is offset into
1292 * the middle of our working buffer
1294 if (total_out > start_byte && buf_start < start_byte) {
1295 buf_offset = start_byte - buf_start;
1296 working_bytes -= buf_offset;
1300 current_buf_start = buf_start;
1302 /* copy bytes from the working buffer into the pages */
1303 while (working_bytes > 0) {
1304 bytes = min_t(unsigned long, bvec.bv_len,
1305 PAGE_SIZE - (buf_offset % PAGE_SIZE));
1306 bytes = min(bytes, working_bytes);
1308 kaddr = kmap_atomic(bvec.bv_page);
1309 memcpy(kaddr + bvec.bv_offset, buf + buf_offset, bytes);
1310 kunmap_atomic(kaddr);
1311 flush_dcache_page(bvec.bv_page);
1313 buf_offset += bytes;
1314 working_bytes -= bytes;
1315 current_buf_start += bytes;
1317 /* check if we need to pick another page */
1318 bio_advance(bio, bytes);
1319 if (!bio->bi_iter.bi_size)
1321 bvec = bio_iter_iovec(bio, bio->bi_iter);
1322 prev_start_byte = start_byte;
1323 start_byte = page_offset(bvec.bv_page) - disk_start;
1326 * We need to make sure we're only adjusting
1327 * our offset into compression working buffer when
1328 * we're switching pages. Otherwise we can incorrectly
1329 * keep copying when we were actually done.
1331 if (start_byte != prev_start_byte) {
1333 * make sure our new page is covered by this
1336 if (total_out <= start_byte)
1340 * the next page in the biovec might not be adjacent
1341 * to the last page, but it might still be found
1342 * inside this working buffer. bump our offset pointer
1344 if (total_out > start_byte &&
1345 current_buf_start < start_byte) {
1346 buf_offset = start_byte - buf_start;
1347 working_bytes = total_out - start_byte;
1348 current_buf_start = buf_start + buf_offset;
1357 * Shannon Entropy calculation
1359 * Pure byte distribution analysis fails to determine compressibility of data.
1360 * Try calculating entropy to estimate the average minimum number of bits
1361 * needed to encode the sampled data.
1363 * For convenience, return the percentage of needed bits, instead of amount of
1366 * @ENTROPY_LVL_ACEPTABLE - below that threshold, sample has low byte entropy
1367 * and can be compressible with high probability
1369 * @ENTROPY_LVL_HIGH - data are not compressible with high probability
1371 * Use of ilog2() decreases precision, we lower the LVL to 5 to compensate.
1373 #define ENTROPY_LVL_ACEPTABLE (65)
1374 #define ENTROPY_LVL_HIGH (80)
1377 * For increasead precision in shannon_entropy calculation,
1378 * let's do pow(n, M) to save more digits after comma:
1380 * - maximum int bit length is 64
1381 * - ilog2(MAX_SAMPLE_SIZE) -> 13
1382 * - 13 * 4 = 52 < 64 -> M = 4
1386 static inline u32 ilog2_w(u64 n)
1388 return ilog2(n * n * n * n);
1391 static u32 shannon_entropy(struct heuristic_ws *ws)
1393 const u32 entropy_max = 8 * ilog2_w(2);
1394 u32 entropy_sum = 0;
1395 u32 p, p_base, sz_base;
1398 sz_base = ilog2_w(ws->sample_size);
1399 for (i = 0; i < BUCKET_SIZE && ws->bucket[i].count > 0; i++) {
1400 p = ws->bucket[i].count;
1401 p_base = ilog2_w(p);
1402 entropy_sum += p * (sz_base - p_base);
1405 entropy_sum /= ws->sample_size;
1406 return entropy_sum * 100 / entropy_max;
1409 #define RADIX_BASE 4U
1410 #define COUNTERS_SIZE (1U << RADIX_BASE)
1412 static u8 get4bits(u64 num, int shift) {
1417 low4bits = (COUNTERS_SIZE - 1) - (num % COUNTERS_SIZE);
1422 * Use 4 bits as radix base
1423 * Use 16 u32 counters for calculating new position in buf array
1425 * @array - array that will be sorted
1426 * @array_buf - buffer array to store sorting results
1427 * must be equal in size to @array
1430 static void radix_sort(struct bucket_item *array, struct bucket_item *array_buf,
1435 u32 counters[COUNTERS_SIZE];
1443 * Try avoid useless loop iterations for small numbers stored in big
1444 * counters. Example: 48 33 4 ... in 64bit array
1446 max_num = array[0].count;
1447 for (i = 1; i < num; i++) {
1448 buf_num = array[i].count;
1449 if (buf_num > max_num)
1453 buf_num = ilog2(max_num);
1454 bitlen = ALIGN(buf_num, RADIX_BASE * 2);
1457 while (shift < bitlen) {
1458 memset(counters, 0, sizeof(counters));
1460 for (i = 0; i < num; i++) {
1461 buf_num = array[i].count;
1462 addr = get4bits(buf_num, shift);
1466 for (i = 1; i < COUNTERS_SIZE; i++)
1467 counters[i] += counters[i - 1];
1469 for (i = num - 1; i >= 0; i--) {
1470 buf_num = array[i].count;
1471 addr = get4bits(buf_num, shift);
1473 new_addr = counters[addr];
1474 array_buf[new_addr] = array[i];
1477 shift += RADIX_BASE;
1480 * Normal radix expects to move data from a temporary array, to
1481 * the main one. But that requires some CPU time. Avoid that
1482 * by doing another sort iteration to original array instead of
1485 memset(counters, 0, sizeof(counters));
1487 for (i = 0; i < num; i ++) {
1488 buf_num = array_buf[i].count;
1489 addr = get4bits(buf_num, shift);
1493 for (i = 1; i < COUNTERS_SIZE; i++)
1494 counters[i] += counters[i - 1];
1496 for (i = num - 1; i >= 0; i--) {
1497 buf_num = array_buf[i].count;
1498 addr = get4bits(buf_num, shift);
1500 new_addr = counters[addr];
1501 array[new_addr] = array_buf[i];
1504 shift += RADIX_BASE;
1509 * Size of the core byte set - how many bytes cover 90% of the sample
1511 * There are several types of structured binary data that use nearly all byte
1512 * values. The distribution can be uniform and counts in all buckets will be
1513 * nearly the same (eg. encrypted data). Unlikely to be compressible.
1515 * Other possibility is normal (Gaussian) distribution, where the data could
1516 * be potentially compressible, but we have to take a few more steps to decide
1519 * @BYTE_CORE_SET_LOW - main part of byte values repeated frequently,
1520 * compression algo can easy fix that
1521 * @BYTE_CORE_SET_HIGH - data have uniform distribution and with high
1522 * probability is not compressible
1524 #define BYTE_CORE_SET_LOW (64)
1525 #define BYTE_CORE_SET_HIGH (200)
1527 static int byte_core_set_size(struct heuristic_ws *ws)
1530 u32 coreset_sum = 0;
1531 const u32 core_set_threshold = ws->sample_size * 90 / 100;
1532 struct bucket_item *bucket = ws->bucket;
1534 /* Sort in reverse order */
1535 radix_sort(ws->bucket, ws->bucket_b, BUCKET_SIZE);
1537 for (i = 0; i < BYTE_CORE_SET_LOW; i++)
1538 coreset_sum += bucket[i].count;
1540 if (coreset_sum > core_set_threshold)
1543 for (; i < BYTE_CORE_SET_HIGH && bucket[i].count > 0; i++) {
1544 coreset_sum += bucket[i].count;
1545 if (coreset_sum > core_set_threshold)
1553 * Count byte values in buckets.
1554 * This heuristic can detect textual data (configs, xml, json, html, etc).
1555 * Because in most text-like data byte set is restricted to limited number of
1556 * possible characters, and that restriction in most cases makes data easy to
1559 * @BYTE_SET_THRESHOLD - consider all data within this byte set size:
1560 * less - compressible
1561 * more - need additional analysis
1563 #define BYTE_SET_THRESHOLD (64)
1565 static u32 byte_set_size(const struct heuristic_ws *ws)
1568 u32 byte_set_size = 0;
1570 for (i = 0; i < BYTE_SET_THRESHOLD; i++) {
1571 if (ws->bucket[i].count > 0)
1576 * Continue collecting count of byte values in buckets. If the byte
1577 * set size is bigger then the threshold, it's pointless to continue,
1578 * the detection technique would fail for this type of data.
1580 for (; i < BUCKET_SIZE; i++) {
1581 if (ws->bucket[i].count > 0) {
1583 if (byte_set_size > BYTE_SET_THRESHOLD)
1584 return byte_set_size;
1588 return byte_set_size;
1591 static bool sample_repeated_patterns(struct heuristic_ws *ws)
1593 const u32 half_of_sample = ws->sample_size / 2;
1594 const u8 *data = ws->sample;
1596 return memcmp(&data[0], &data[half_of_sample], half_of_sample) == 0;
1599 static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end,
1600 struct heuristic_ws *ws)
1603 u64 index, index_end;
1604 u32 i, curr_sample_pos;
1608 * Compression handles the input data by chunks of 128KiB
1609 * (defined by BTRFS_MAX_UNCOMPRESSED)
1611 * We do the same for the heuristic and loop over the whole range.
1613 * MAX_SAMPLE_SIZE - calculated under assumption that heuristic will
1614 * process no more than BTRFS_MAX_UNCOMPRESSED at a time.
1616 if (end - start > BTRFS_MAX_UNCOMPRESSED)
1617 end = start + BTRFS_MAX_UNCOMPRESSED;
1619 index = start >> PAGE_SHIFT;
1620 index_end = end >> PAGE_SHIFT;
1622 /* Don't miss unaligned end */
1623 if (!IS_ALIGNED(end, PAGE_SIZE))
1626 curr_sample_pos = 0;
1627 while (index < index_end) {
1628 page = find_get_page(inode->i_mapping, index);
1629 in_data = kmap(page);
1630 /* Handle case where the start is not aligned to PAGE_SIZE */
1631 i = start % PAGE_SIZE;
1632 while (i < PAGE_SIZE - SAMPLING_READ_SIZE) {
1633 /* Don't sample any garbage from the last page */
1634 if (start > end - SAMPLING_READ_SIZE)
1636 memcpy(&ws->sample[curr_sample_pos], &in_data[i],
1637 SAMPLING_READ_SIZE);
1638 i += SAMPLING_INTERVAL;
1639 start += SAMPLING_INTERVAL;
1640 curr_sample_pos += SAMPLING_READ_SIZE;
1648 ws->sample_size = curr_sample_pos;
1652 * Compression heuristic.
1654 * For now is's a naive and optimistic 'return true', we'll extend the logic to
1655 * quickly (compared to direct compression) detect data characteristics
1656 * (compressible/uncompressible) to avoid wasting CPU time on uncompressible
1659 * The following types of analysis can be performed:
1660 * - detect mostly zero data
1661 * - detect data with low "byte set" size (text, etc)
1662 * - detect data with low/high "core byte" set
1664 * Return non-zero if the compression should be done, 0 otherwise.
1666 int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
1668 struct list_head *ws_list = get_workspace(0, 0);
1669 struct heuristic_ws *ws;
1674 ws = list_entry(ws_list, struct heuristic_ws, list);
1676 heuristic_collect_sample(inode, start, end, ws);
1678 if (sample_repeated_patterns(ws)) {
1683 memset(ws->bucket, 0, sizeof(*ws->bucket)*BUCKET_SIZE);
1685 for (i = 0; i < ws->sample_size; i++) {
1686 byte = ws->sample[i];
1687 ws->bucket[byte].count++;
1690 i = byte_set_size(ws);
1691 if (i < BYTE_SET_THRESHOLD) {
1696 i = byte_core_set_size(ws);
1697 if (i <= BYTE_CORE_SET_LOW) {
1702 if (i >= BYTE_CORE_SET_HIGH) {
1707 i = shannon_entropy(ws);
1708 if (i <= ENTROPY_LVL_ACEPTABLE) {
1714 * For the levels below ENTROPY_LVL_HIGH, additional analysis would be
1715 * needed to give green light to compression.
1717 * For now just assume that compression at that level is not worth the
1718 * resources because:
1720 * 1. it is possible to defrag the data later
1722 * 2. the data would turn out to be hardly compressible, eg. 150 byte
1723 * values, every bucket has counter at level ~54. The heuristic would
1724 * be confused. This can happen when data have some internal repeated
1725 * patterns like "abbacbbc...". This can be detected by analyzing
1726 * pairs of bytes, which is too costly.
1728 if (i < ENTROPY_LVL_HIGH) {
1737 put_workspace(0, ws_list);
1742 * Convert the compression suffix (eg. after "zlib" starting with ":") to
1743 * level, unrecognized string will set the default level
1745 unsigned int btrfs_compress_str2level(unsigned int type, const char *str)
1747 unsigned int level = 0;
1753 if (str[0] == ':') {
1754 ret = kstrtouint(str + 1, 10, &level);
1759 level = btrfs_compress_set_level(type, level);