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/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 <crypto/hash.h>
28 #include "transaction.h"
29 #include "btrfs_inode.h"
31 #include "ordered-data.h"
32 #include "compression.h"
33 #include "extent_io.h"
34 #include "extent_map.h"
37 #include "file-item.h"
40 static const char* const btrfs_compress_types[] = { "", "zlib", "lzo", "zstd" };
42 const char* btrfs_compress_type2str(enum btrfs_compression_type 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];
57 bool btrfs_compress_is_valid_type(const char *str, size_t len)
61 for (i = 1; i < ARRAY_SIZE(btrfs_compress_types); i++) {
62 size_t comp_len = strlen(btrfs_compress_types[i]);
67 if (!strncmp(btrfs_compress_types[i], str, comp_len))
73 static int compression_compress_pages(int type, struct list_head *ws,
74 struct address_space *mapping, u64 start, struct page **pages,
75 unsigned long *out_pages, unsigned long *total_in,
76 unsigned long *total_out)
79 case BTRFS_COMPRESS_ZLIB:
80 return zlib_compress_pages(ws, mapping, start, pages,
81 out_pages, total_in, total_out);
82 case BTRFS_COMPRESS_LZO:
83 return lzo_compress_pages(ws, mapping, start, pages,
84 out_pages, total_in, total_out);
85 case BTRFS_COMPRESS_ZSTD:
86 return zstd_compress_pages(ws, mapping, start, pages,
87 out_pages, total_in, total_out);
88 case BTRFS_COMPRESS_NONE:
91 * This can happen when compression races with remount setting
92 * it to 'no compress', while caller doesn't call
93 * inode_need_compress() to check if we really need to
96 * Not a big deal, just need to inform caller that we
97 * haven't allocated any pages yet.
104 static int compression_decompress_bio(struct list_head *ws,
105 struct compressed_bio *cb)
107 switch (cb->compress_type) {
108 case BTRFS_COMPRESS_ZLIB: return zlib_decompress_bio(ws, cb);
109 case BTRFS_COMPRESS_LZO: return lzo_decompress_bio(ws, cb);
110 case BTRFS_COMPRESS_ZSTD: return zstd_decompress_bio(ws, cb);
111 case BTRFS_COMPRESS_NONE:
114 * This can't happen, the type is validated several times
115 * before we get here.
121 static int compression_decompress(int type, struct list_head *ws,
122 const u8 *data_in, struct page *dest_page,
123 unsigned long start_byte, size_t srclen, size_t destlen)
126 case BTRFS_COMPRESS_ZLIB: return zlib_decompress(ws, data_in, dest_page,
127 start_byte, srclen, destlen);
128 case BTRFS_COMPRESS_LZO: return lzo_decompress(ws, data_in, dest_page,
129 start_byte, srclen, destlen);
130 case BTRFS_COMPRESS_ZSTD: return zstd_decompress(ws, data_in, dest_page,
131 start_byte, srclen, destlen);
132 case BTRFS_COMPRESS_NONE:
135 * This can't happen, the type is validated several times
136 * before we get here.
142 static int btrfs_decompress_bio(struct compressed_bio *cb);
144 static void finish_compressed_bio_read(struct compressed_bio *cb)
149 if (cb->status == BLK_STS_OK)
150 cb->status = errno_to_blk_status(btrfs_decompress_bio(cb));
152 /* Release the compressed pages */
153 for (index = 0; index < cb->nr_pages; index++) {
154 page = cb->compressed_pages[index];
155 page->mapping = NULL;
159 /* Do io completion on the original bio */
160 btrfs_bio_end_io(btrfs_bio(cb->orig_bio), cb->status);
162 /* Finally free the cb struct */
163 kfree(cb->compressed_pages);
168 * Verify the checksums and kick off repair if needed on the uncompressed data
169 * before decompressing it into the original bio and freeing the uncompressed
172 static void end_compressed_bio_read(struct btrfs_bio *bbio)
174 struct compressed_bio *cb = bbio->private;
175 struct inode *inode = cb->inode;
176 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
177 struct btrfs_inode *bi = BTRFS_I(inode);
178 bool csum = !(bi->flags & BTRFS_INODE_NODATASUM) &&
179 !test_bit(BTRFS_FS_STATE_NO_CSUMS, &fs_info->fs_state);
180 blk_status_t status = bbio->bio.bi_status;
181 struct bvec_iter iter;
185 btrfs_bio_for_each_sector(fs_info, bv, bbio, iter, offset) {
186 u64 start = bbio->file_offset + offset;
189 (!csum || !btrfs_check_data_csum(bi, bbio, offset,
190 bv.bv_page, bv.bv_offset))) {
191 btrfs_clean_io_failure(bi, start, bv.bv_page,
196 refcount_inc(&cb->pending_ios);
197 ret = btrfs_repair_one_sector(BTRFS_I(inode), bbio, offset,
198 bv.bv_page, bv.bv_offset,
201 refcount_dec(&cb->pending_ios);
202 status = errno_to_blk_status(ret);
210 if (refcount_dec_and_test(&cb->pending_ios))
211 finish_compressed_bio_read(cb);
212 btrfs_bio_free_csum(bbio);
217 * Clear the writeback bits on all of the file
218 * pages for a compressed write
220 static noinline void end_compressed_writeback(struct inode *inode,
221 const struct compressed_bio *cb)
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);
232 mapping_set_error(inode->i_mapping, errno);
234 folio_batch_init(&fbatch);
235 while (index <= end_index) {
236 ret = filemap_get_folios(inode->i_mapping, &index, end_index,
242 for (i = 0; i < ret; i++) {
243 struct folio *folio = fbatch.folios[i];
246 folio_set_error(folio);
247 btrfs_page_clamp_clear_writeback(fs_info, &folio->page,
250 folio_batch_release(&fbatch);
252 /* the inode may be gone now */
255 static void finish_compressed_bio_write(struct compressed_bio *cb)
257 struct inode *inode = cb->inode;
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.
264 btrfs_writepage_endio_finish_ordered(BTRFS_I(inode), NULL,
265 cb->start, cb->start + cb->len - 1,
266 cb->status == BLK_STS_OK);
269 end_compressed_writeback(inode, cb);
270 /* Note, our inode could be gone now */
273 * Release the compressed pages, these came from alloc_page and
274 * are not attached to the inode at all
276 for (index = 0; index < cb->nr_pages; index++) {
277 struct page *page = cb->compressed_pages[index];
279 page->mapping = NULL;
283 /* Finally free the cb struct */
284 kfree(cb->compressed_pages);
288 static void btrfs_finish_compressed_write_work(struct work_struct *work)
290 struct compressed_bio *cb =
291 container_of(work, struct compressed_bio, write_end_work);
293 finish_compressed_bio_write(cb);
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.
300 * This also calls the writeback end hooks for the file pages so that metadata
301 * and checksums can be updated in the file.
303 static void end_compressed_bio_write(struct btrfs_bio *bbio)
305 struct compressed_bio *cb = bbio->private;
307 if (bbio->bio.bi_status)
308 cb->status = bbio->bio.bi_status;
310 if (refcount_dec_and_test(&cb->pending_ios)) {
311 struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb);
313 btrfs_record_physical_zoned(cb->inode, cb->start, &bbio->bio);
314 queue_work(fs_info->compressed_write_workers, &cb->write_end_work);
320 * Allocate a compressed_bio, which will be used to read/write on-disk
321 * (aka, compressed) * data.
323 * @cb: The compressed_bio structure, which records all the needed
324 * information to bind the compressed data to the uncompressed
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
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
336 static struct bio *alloc_compressed_bio(struct compressed_bio *cb, u64 disk_bytenr,
338 btrfs_bio_end_io_t endio_func,
339 u64 *next_stripe_start)
341 struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb);
342 struct btrfs_io_geometry geom;
343 struct extent_map *em;
347 bio = btrfs_bio_alloc(BIO_MAX_VECS, opf, endio_func, cb);
348 bio->bi_iter.bi_sector = disk_bytenr >> SECTOR_SHIFT;
350 em = btrfs_get_chunk_map(fs_info, disk_bytenr, fs_info->sectorsize);
356 if (bio_op(bio) == REQ_OP_ZONE_APPEND)
357 bio_set_dev(bio, em->map_lookup->stripes[0].dev->bdev);
359 ret = btrfs_get_io_geometry(fs_info, em, btrfs_op(bio), disk_bytenr, &geom);
365 *next_stripe_start = disk_bytenr + geom.len;
366 refcount_inc(&cb->pending_ios);
371 * worker function to build and submit bios for previously compressed pages.
372 * The corresponding pages in the inode should be marked for writeback
373 * and the compressed pages should have a reference on them for dropping
374 * when the IO is complete.
376 * This also checksums the file bytes and gets things ready for
379 blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
380 unsigned int len, u64 disk_start,
381 unsigned int compressed_len,
382 struct page **compressed_pages,
383 unsigned int nr_pages,
384 blk_opf_t write_flags,
385 struct cgroup_subsys_state *blkcg_css,
388 struct btrfs_fs_info *fs_info = inode->root->fs_info;
389 struct bio *bio = NULL;
390 struct compressed_bio *cb;
391 u64 cur_disk_bytenr = disk_start;
392 u64 next_stripe_start;
393 blk_status_t ret = BLK_STS_OK;
394 int skip_sum = inode->flags & BTRFS_INODE_NODATASUM;
395 const bool use_append = btrfs_use_zone_append(inode, disk_start);
396 const enum req_op bio_op = use_append ? REQ_OP_ZONE_APPEND : REQ_OP_WRITE;
398 ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
399 IS_ALIGNED(len, fs_info->sectorsize));
400 cb = kmalloc(sizeof(struct compressed_bio), GFP_NOFS);
402 return BLK_STS_RESOURCE;
403 refcount_set(&cb->pending_ios, 1);
404 cb->status = BLK_STS_OK;
405 cb->inode = &inode->vfs_inode;
408 cb->compressed_pages = compressed_pages;
409 cb->compressed_len = compressed_len;
410 cb->writeback = writeback;
411 INIT_WORK(&cb->write_end_work, btrfs_finish_compressed_write_work);
412 cb->nr_pages = nr_pages;
415 kthread_associate_blkcg(blkcg_css);
417 while (cur_disk_bytenr < disk_start + compressed_len) {
418 u64 offset = cur_disk_bytenr - disk_start;
419 unsigned int index = offset >> PAGE_SHIFT;
420 unsigned int real_size;
422 struct page *page = compressed_pages[index];
425 /* Allocate new bio if submitted or not yet allocated */
427 bio = alloc_compressed_bio(cb, cur_disk_bytenr,
428 bio_op | write_flags, end_compressed_bio_write,
431 ret = errno_to_blk_status(PTR_ERR(bio));
435 bio->bi_opf |= REQ_CGROUP_PUNT;
438 * We should never reach next_stripe_start start as we will
439 * submit comp_bio when reach the boundary immediately.
441 ASSERT(cur_disk_bytenr != next_stripe_start);
444 * We have various limits on the real read size:
447 * - compressed length boundary
449 real_size = min_t(u64, U32_MAX, next_stripe_start - cur_disk_bytenr);
450 real_size = min_t(u64, real_size, PAGE_SIZE - offset_in_page(offset));
451 real_size = min_t(u64, real_size, compressed_len - offset);
452 ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize));
455 added = bio_add_zone_append_page(bio, page, real_size,
456 offset_in_page(offset));
458 added = bio_add_page(bio, page, real_size,
459 offset_in_page(offset));
460 /* Reached zoned boundary */
464 cur_disk_bytenr += added;
465 /* Reached stripe boundary */
466 if (cur_disk_bytenr == next_stripe_start)
469 /* Finished the range */
470 if (cur_disk_bytenr == disk_start + compressed_len)
475 ret = btrfs_csum_one_bio(inode, bio, start, true);
477 btrfs_bio_end_io(btrfs_bio(bio), ret);
482 ASSERT(bio->bi_iter.bi_size);
483 btrfs_submit_bio(fs_info, bio, 0);
490 kthread_associate_blkcg(NULL);
492 if (refcount_dec_and_test(&cb->pending_ios))
493 finish_compressed_bio_write(cb);
497 static u64 bio_end_offset(struct bio *bio)
499 struct bio_vec *last = bio_last_bvec_all(bio);
501 return page_offset(last->bv_page) + last->bv_len + last->bv_offset;
505 * Add extra pages in the same compressed file extent so that we don't need to
506 * re-read the same extent again and again.
508 * NOTE: this won't work well for subpage, as for subpage read, we lock the
509 * full page then submit bio for each compressed/regular extents.
511 * This means, if we have several sectors in the same page points to the same
512 * on-disk compressed data, we will re-read the same extent many times and
513 * this function can only help for the next page.
515 static noinline int add_ra_bio_pages(struct inode *inode,
517 struct compressed_bio *cb,
518 int *memstall, unsigned long *pflags)
520 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
521 unsigned long end_index;
522 u64 cur = bio_end_offset(cb->orig_bio);
523 u64 isize = i_size_read(inode);
526 struct extent_map *em;
527 struct address_space *mapping = inode->i_mapping;
528 struct extent_map_tree *em_tree;
529 struct extent_io_tree *tree;
530 int sectors_missed = 0;
532 em_tree = &BTRFS_I(inode)->extent_tree;
533 tree = &BTRFS_I(inode)->io_tree;
539 * For current subpage support, we only support 64K page size,
540 * which means maximum compressed extent size (128K) is just 2x page
542 * This makes readahead less effective, so here disable readahead for
543 * subpage for now, until full compressed write is supported.
545 if (btrfs_sb(inode->i_sb)->sectorsize < PAGE_SIZE)
548 end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
550 while (cur < compressed_end) {
552 u64 pg_index = cur >> PAGE_SHIFT;
555 if (pg_index > end_index)
558 page = xa_load(&mapping->i_pages, pg_index);
559 if (page && !xa_is_value(page)) {
560 sectors_missed += (PAGE_SIZE - offset_in_page(cur)) >>
561 fs_info->sectorsize_bits;
563 /* Beyond threshold, no need to continue */
564 if (sectors_missed > 4)
568 * Jump to next page start as we already have page for
571 cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE;
575 page = __page_cache_alloc(mapping_gfp_constraint(mapping,
580 if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
582 /* There is already a page, skip to page end */
583 cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE;
587 if (!*memstall && PageWorkingset(page)) {
588 psi_memstall_enter(pflags);
592 ret = set_page_extent_mapped(page);
599 page_end = (pg_index << PAGE_SHIFT) + PAGE_SIZE - 1;
600 lock_extent(tree, cur, page_end, NULL);
601 read_lock(&em_tree->lock);
602 em = lookup_extent_mapping(em_tree, cur, page_end + 1 - cur);
603 read_unlock(&em_tree->lock);
606 * At this point, we have a locked page in the page cache for
607 * these bytes in the file. But, we have to make sure they map
608 * to this compressed extent on disk.
610 if (!em || cur < em->start ||
611 (cur + fs_info->sectorsize > extent_map_end(em)) ||
612 (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
614 unlock_extent(tree, cur, page_end, NULL);
621 if (page->index == end_index) {
622 size_t zero_offset = offset_in_page(isize);
626 zeros = PAGE_SIZE - zero_offset;
627 memzero_page(page, zero_offset, zeros);
631 add_size = min(em->start + em->len, page_end + 1) - cur;
632 ret = bio_add_page(cb->orig_bio, page, add_size, offset_in_page(cur));
633 if (ret != add_size) {
634 unlock_extent(tree, cur, page_end, NULL);
640 * If it's subpage, we also need to increase its
641 * subpage::readers number, as at endio we will decrease
642 * subpage::readers and to unlock the page.
644 if (fs_info->sectorsize < PAGE_SIZE)
645 btrfs_subpage_start_reader(fs_info, page, cur, add_size);
653 * for a compressed read, the bio we get passed has all the inode pages
654 * in it. We don't actually do IO on those pages but allocate new ones
655 * to hold the compressed pages on disk.
657 * bio->bi_iter.bi_sector points to the compressed extent on disk
658 * bio->bi_io_vec points to all of the inode pages
660 * After the compressed pages are read, we copy the bytes into the
661 * bio we were passed and then call the bio end_io calls
663 void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
666 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
667 struct extent_map_tree *em_tree;
668 struct compressed_bio *cb;
669 unsigned int compressed_len;
670 struct bio *comp_bio = NULL;
671 const u64 disk_bytenr = bio->bi_iter.bi_sector << SECTOR_SHIFT;
672 u64 cur_disk_byte = disk_bytenr;
673 u64 next_stripe_start;
677 struct extent_map *em;
678 unsigned long pflags;
684 em_tree = &BTRFS_I(inode)->extent_tree;
686 file_offset = bio_first_bvec_all(bio)->bv_offset +
687 page_offset(bio_first_page_all(bio));
689 /* we need the actual starting offset of this extent in the file */
690 read_lock(&em_tree->lock);
691 em = lookup_extent_mapping(em_tree, file_offset, fs_info->sectorsize);
692 read_unlock(&em_tree->lock);
698 ASSERT(em->compress_type != BTRFS_COMPRESS_NONE);
699 compressed_len = em->block_len;
700 cb = kmalloc(sizeof(struct compressed_bio), GFP_NOFS);
702 ret = BLK_STS_RESOURCE;
706 refcount_set(&cb->pending_ios, 1);
707 cb->status = BLK_STS_OK;
710 cb->start = em->orig_start;
712 em_start = em->start;
714 cb->len = bio->bi_iter.bi_size;
715 cb->compressed_len = compressed_len;
716 cb->compress_type = em->compress_type;
722 cb->nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
723 cb->compressed_pages = kcalloc(cb->nr_pages, sizeof(struct page *), GFP_NOFS);
724 if (!cb->compressed_pages) {
725 ret = BLK_STS_RESOURCE;
729 ret2 = btrfs_alloc_page_array(cb->nr_pages, cb->compressed_pages);
731 ret = BLK_STS_RESOURCE;
735 add_ra_bio_pages(inode, em_start + em_len, cb, &memstall, &pflags);
737 /* include any pages we added in add_ra-bio_pages */
738 cb->len = bio->bi_iter.bi_size;
740 while (cur_disk_byte < disk_bytenr + compressed_len) {
741 u64 offset = cur_disk_byte - disk_bytenr;
742 unsigned int index = offset >> PAGE_SHIFT;
743 unsigned int real_size;
745 struct page *page = cb->compressed_pages[index];
748 /* Allocate new bio if submitted or not yet allocated */
750 comp_bio = alloc_compressed_bio(cb, cur_disk_byte,
751 REQ_OP_READ, end_compressed_bio_read,
753 if (IS_ERR(comp_bio)) {
754 cb->status = errno_to_blk_status(PTR_ERR(comp_bio));
759 * We should never reach next_stripe_start start as we will
760 * submit comp_bio when reach the boundary immediately.
762 ASSERT(cur_disk_byte != next_stripe_start);
764 * We have various limit on the real read size:
767 * - compressed length boundary
769 real_size = min_t(u64, U32_MAX, next_stripe_start - cur_disk_byte);
770 real_size = min_t(u64, real_size, PAGE_SIZE - offset_in_page(offset));
771 real_size = min_t(u64, real_size, compressed_len - offset);
772 ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize));
774 added = bio_add_page(comp_bio, page, real_size, offset_in_page(offset));
776 * Maximum compressed extent is smaller than bio size limit,
777 * thus bio_add_page() should always success.
779 ASSERT(added == real_size);
780 cur_disk_byte += added;
782 /* Reached stripe boundary, need to submit */
783 if (cur_disk_byte == next_stripe_start)
786 /* Has finished the range, need to submit */
787 if (cur_disk_byte == disk_bytenr + compressed_len)
791 /* Save the original iter for read repair */
792 if (bio_op(comp_bio) == REQ_OP_READ)
793 btrfs_bio(comp_bio)->iter = comp_bio->bi_iter;
796 * Save the initial offset of this chunk, as there
797 * is no direct correlation between compressed pages and
798 * the original file offset. The field is only used for
799 * priting error messages.
801 btrfs_bio(comp_bio)->file_offset = file_offset;
803 ret = btrfs_lookup_bio_sums(inode, comp_bio, NULL);
805 btrfs_bio_end_io(btrfs_bio(comp_bio), ret);
809 ASSERT(comp_bio->bi_iter.bi_size);
810 btrfs_submit_bio(fs_info, comp_bio, mirror_num);
816 psi_memstall_leave(&pflags);
818 if (refcount_dec_and_test(&cb->pending_ios))
819 finish_compressed_bio_read(cb);
823 if (cb->compressed_pages) {
824 for (i = 0; i < cb->nr_pages; i++) {
825 if (cb->compressed_pages[i])
826 __free_page(cb->compressed_pages[i]);
830 kfree(cb->compressed_pages);
834 btrfs_bio_end_io(btrfs_bio(bio), ret);
839 * Heuristic uses systematic sampling to collect data from the input data
840 * range, the logic can be tuned by the following constants:
842 * @SAMPLING_READ_SIZE - how many bytes will be copied from for each sample
843 * @SAMPLING_INTERVAL - range from which the sampled data can be collected
845 #define SAMPLING_READ_SIZE (16)
846 #define SAMPLING_INTERVAL (256)
849 * For statistical analysis of the input data we consider bytes that form a
850 * Galois Field of 256 objects. Each object has an attribute count, ie. how
851 * many times the object appeared in the sample.
853 #define BUCKET_SIZE (256)
856 * The size of the sample is based on a statistical sampling rule of thumb.
857 * The common way is to perform sampling tests as long as the number of
858 * elements in each cell is at least 5.
860 * Instead of 5, we choose 32 to obtain more accurate results.
861 * If the data contain the maximum number of symbols, which is 256, we obtain a
862 * sample size bound by 8192.
864 * For a sample of at most 8KB of data per data range: 16 consecutive bytes
865 * from up to 512 locations.
867 #define MAX_SAMPLE_SIZE (BTRFS_MAX_UNCOMPRESSED * \
868 SAMPLING_READ_SIZE / SAMPLING_INTERVAL)
874 struct heuristic_ws {
875 /* Partial copy of input data */
878 /* Buckets store counters for each byte value */
879 struct bucket_item *bucket;
881 struct bucket_item *bucket_b;
882 struct list_head list;
885 static struct workspace_manager heuristic_wsm;
887 static void free_heuristic_ws(struct list_head *ws)
889 struct heuristic_ws *workspace;
891 workspace = list_entry(ws, struct heuristic_ws, list);
893 kvfree(workspace->sample);
894 kfree(workspace->bucket);
895 kfree(workspace->bucket_b);
899 static struct list_head *alloc_heuristic_ws(unsigned int level)
901 struct heuristic_ws *ws;
903 ws = kzalloc(sizeof(*ws), GFP_KERNEL);
905 return ERR_PTR(-ENOMEM);
907 ws->sample = kvmalloc(MAX_SAMPLE_SIZE, GFP_KERNEL);
911 ws->bucket = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket), GFP_KERNEL);
915 ws->bucket_b = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket_b), GFP_KERNEL);
919 INIT_LIST_HEAD(&ws->list);
922 free_heuristic_ws(&ws->list);
923 return ERR_PTR(-ENOMEM);
926 const struct btrfs_compress_op btrfs_heuristic_compress = {
927 .workspace_manager = &heuristic_wsm,
930 static const struct btrfs_compress_op * const btrfs_compress_op[] = {
931 /* The heuristic is represented as compression type 0 */
932 &btrfs_heuristic_compress,
933 &btrfs_zlib_compress,
935 &btrfs_zstd_compress,
938 static struct list_head *alloc_workspace(int type, unsigned int level)
941 case BTRFS_COMPRESS_NONE: return alloc_heuristic_ws(level);
942 case BTRFS_COMPRESS_ZLIB: return zlib_alloc_workspace(level);
943 case BTRFS_COMPRESS_LZO: return lzo_alloc_workspace(level);
944 case BTRFS_COMPRESS_ZSTD: return zstd_alloc_workspace(level);
947 * This can't happen, the type is validated several times
948 * before we get here.
954 static void free_workspace(int type, struct list_head *ws)
957 case BTRFS_COMPRESS_NONE: return free_heuristic_ws(ws);
958 case BTRFS_COMPRESS_ZLIB: return zlib_free_workspace(ws);
959 case BTRFS_COMPRESS_LZO: return lzo_free_workspace(ws);
960 case BTRFS_COMPRESS_ZSTD: return zstd_free_workspace(ws);
963 * This can't happen, the type is validated several times
964 * before we get here.
970 static void btrfs_init_workspace_manager(int type)
972 struct workspace_manager *wsm;
973 struct list_head *workspace;
975 wsm = btrfs_compress_op[type]->workspace_manager;
976 INIT_LIST_HEAD(&wsm->idle_ws);
977 spin_lock_init(&wsm->ws_lock);
978 atomic_set(&wsm->total_ws, 0);
979 init_waitqueue_head(&wsm->ws_wait);
982 * Preallocate one workspace for each compression type so we can
983 * guarantee forward progress in the worst case
985 workspace = alloc_workspace(type, 0);
986 if (IS_ERR(workspace)) {
988 "BTRFS: cannot preallocate compression workspace, will try later\n");
990 atomic_set(&wsm->total_ws, 1);
992 list_add(workspace, &wsm->idle_ws);
996 static void btrfs_cleanup_workspace_manager(int type)
998 struct workspace_manager *wsman;
999 struct list_head *ws;
1001 wsman = btrfs_compress_op[type]->workspace_manager;
1002 while (!list_empty(&wsman->idle_ws)) {
1003 ws = wsman->idle_ws.next;
1005 free_workspace(type, ws);
1006 atomic_dec(&wsman->total_ws);
1011 * This finds an available workspace or allocates a new one.
1012 * If it's not possible to allocate a new one, waits until there's one.
1013 * Preallocation makes a forward progress guarantees and we do not return
1016 struct list_head *btrfs_get_workspace(int type, unsigned int level)
1018 struct workspace_manager *wsm;
1019 struct list_head *workspace;
1020 int cpus = num_online_cpus();
1022 struct list_head *idle_ws;
1023 spinlock_t *ws_lock;
1025 wait_queue_head_t *ws_wait;
1028 wsm = btrfs_compress_op[type]->workspace_manager;
1029 idle_ws = &wsm->idle_ws;
1030 ws_lock = &wsm->ws_lock;
1031 total_ws = &wsm->total_ws;
1032 ws_wait = &wsm->ws_wait;
1033 free_ws = &wsm->free_ws;
1037 if (!list_empty(idle_ws)) {
1038 workspace = idle_ws->next;
1039 list_del(workspace);
1041 spin_unlock(ws_lock);
1045 if (atomic_read(total_ws) > cpus) {
1048 spin_unlock(ws_lock);
1049 prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE);
1050 if (atomic_read(total_ws) > cpus && !*free_ws)
1052 finish_wait(ws_wait, &wait);
1055 atomic_inc(total_ws);
1056 spin_unlock(ws_lock);
1059 * Allocation helpers call vmalloc that can't use GFP_NOFS, so we have
1060 * to turn it off here because we might get called from the restricted
1061 * context of btrfs_compress_bio/btrfs_compress_pages
1063 nofs_flag = memalloc_nofs_save();
1064 workspace = alloc_workspace(type, level);
1065 memalloc_nofs_restore(nofs_flag);
1067 if (IS_ERR(workspace)) {
1068 atomic_dec(total_ws);
1072 * Do not return the error but go back to waiting. There's a
1073 * workspace preallocated for each type and the compression
1074 * time is bounded so we get to a workspace eventually. This
1075 * makes our caller's life easier.
1077 * To prevent silent and low-probability deadlocks (when the
1078 * initial preallocation fails), check if there are any
1079 * workspaces at all.
1081 if (atomic_read(total_ws) == 0) {
1082 static DEFINE_RATELIMIT_STATE(_rs,
1083 /* once per minute */ 60 * HZ,
1086 if (__ratelimit(&_rs)) {
1087 pr_warn("BTRFS: no compression workspaces, low memory, retrying\n");
1095 static struct list_head *get_workspace(int type, int level)
1098 case BTRFS_COMPRESS_NONE: return btrfs_get_workspace(type, level);
1099 case BTRFS_COMPRESS_ZLIB: return zlib_get_workspace(level);
1100 case BTRFS_COMPRESS_LZO: return btrfs_get_workspace(type, level);
1101 case BTRFS_COMPRESS_ZSTD: return zstd_get_workspace(level);
1104 * This can't happen, the type is validated several times
1105 * before we get here.
1112 * put a workspace struct back on the list or free it if we have enough
1113 * idle ones sitting around
1115 void btrfs_put_workspace(int type, struct list_head *ws)
1117 struct workspace_manager *wsm;
1118 struct list_head *idle_ws;
1119 spinlock_t *ws_lock;
1121 wait_queue_head_t *ws_wait;
1124 wsm = btrfs_compress_op[type]->workspace_manager;
1125 idle_ws = &wsm->idle_ws;
1126 ws_lock = &wsm->ws_lock;
1127 total_ws = &wsm->total_ws;
1128 ws_wait = &wsm->ws_wait;
1129 free_ws = &wsm->free_ws;
1132 if (*free_ws <= num_online_cpus()) {
1133 list_add(ws, idle_ws);
1135 spin_unlock(ws_lock);
1138 spin_unlock(ws_lock);
1140 free_workspace(type, ws);
1141 atomic_dec(total_ws);
1143 cond_wake_up(ws_wait);
1146 static void put_workspace(int type, struct list_head *ws)
1149 case BTRFS_COMPRESS_NONE: return btrfs_put_workspace(type, ws);
1150 case BTRFS_COMPRESS_ZLIB: return btrfs_put_workspace(type, ws);
1151 case BTRFS_COMPRESS_LZO: return btrfs_put_workspace(type, ws);
1152 case BTRFS_COMPRESS_ZSTD: return zstd_put_workspace(ws);
1155 * This can't happen, the type is validated several times
1156 * before we get here.
1163 * Adjust @level according to the limits of the compression algorithm or
1164 * fallback to default
1166 static unsigned int btrfs_compress_set_level(int type, unsigned level)
1168 const struct btrfs_compress_op *ops = btrfs_compress_op[type];
1171 level = ops->default_level;
1173 level = min(level, ops->max_level);
1179 * Given an address space and start and length, compress the bytes into @pages
1180 * that are allocated on demand.
1182 * @type_level is encoded algorithm and level, where level 0 means whatever
1183 * default the algorithm chooses and is opaque here;
1184 * - compression algo are 0-3
1185 * - the level are bits 4-7
1187 * @out_pages is an in/out parameter, holds maximum number of pages to allocate
1188 * and returns number of actually allocated pages
1190 * @total_in is used to return the number of bytes actually read. It
1191 * may be smaller than the input length if we had to exit early because we
1192 * ran out of room in the pages array or because we cross the
1193 * max_out threshold.
1195 * @total_out is an in/out parameter, must be set to the input length and will
1196 * be also used to return the total number of compressed bytes
1198 int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
1199 u64 start, struct page **pages,
1200 unsigned long *out_pages,
1201 unsigned long *total_in,
1202 unsigned long *total_out)
1204 int type = btrfs_compress_type(type_level);
1205 int level = btrfs_compress_level(type_level);
1206 struct list_head *workspace;
1209 level = btrfs_compress_set_level(type, level);
1210 workspace = get_workspace(type, level);
1211 ret = compression_compress_pages(type, workspace, mapping, start, pages,
1212 out_pages, total_in, total_out);
1213 put_workspace(type, workspace);
1217 static int btrfs_decompress_bio(struct compressed_bio *cb)
1219 struct list_head *workspace;
1221 int type = cb->compress_type;
1223 workspace = get_workspace(type, 0);
1224 ret = compression_decompress_bio(workspace, cb);
1225 put_workspace(type, workspace);
1231 * a less complex decompression routine. Our compressed data fits in a
1232 * single page, and we want to read a single page out of it.
1233 * start_byte tells us the offset into the compressed data we're interested in
1235 int btrfs_decompress(int type, const u8 *data_in, struct page *dest_page,
1236 unsigned long start_byte, size_t srclen, size_t destlen)
1238 struct list_head *workspace;
1241 workspace = get_workspace(type, 0);
1242 ret = compression_decompress(type, workspace, data_in, dest_page,
1243 start_byte, srclen, destlen);
1244 put_workspace(type, workspace);
1249 int __init btrfs_init_compress(void)
1251 btrfs_init_workspace_manager(BTRFS_COMPRESS_NONE);
1252 btrfs_init_workspace_manager(BTRFS_COMPRESS_ZLIB);
1253 btrfs_init_workspace_manager(BTRFS_COMPRESS_LZO);
1254 zstd_init_workspace_manager();
1258 void __cold btrfs_exit_compress(void)
1260 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_NONE);
1261 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_ZLIB);
1262 btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_LZO);
1263 zstd_cleanup_workspace_manager();
1267 * Copy decompressed data from working buffer to pages.
1269 * @buf: The decompressed data buffer
1270 * @buf_len: The decompressed data length
1271 * @decompressed: Number of bytes that are already decompressed inside the
1273 * @cb: The compressed extent descriptor
1274 * @orig_bio: The original bio that the caller wants to read for
1276 * An easier to understand graph is like below:
1278 * |<- orig_bio ->| |<- orig_bio->|
1279 * |<------- full decompressed extent ----->|
1280 * |<----------- @cb range ---->|
1281 * | |<-- @buf_len -->|
1282 * |<--- @decompressed --->|
1284 * Note that, @cb can be a subpage of the full decompressed extent, but
1285 * @cb->start always has the same as the orig_file_offset value of the full
1286 * decompressed extent.
1288 * When reading compressed extent, we have to read the full compressed extent,
1289 * while @orig_bio may only want part of the range.
1290 * Thus this function will ensure only data covered by @orig_bio will be copied
1293 * Return 0 if we have copied all needed contents for @orig_bio.
1294 * Return >0 if we need continue decompress.
1296 int btrfs_decompress_buf2page(const char *buf, u32 buf_len,
1297 struct compressed_bio *cb, u32 decompressed)
1299 struct bio *orig_bio = cb->orig_bio;
1300 /* Offset inside the full decompressed extent */
1303 cur_offset = decompressed;
1304 /* The main loop to do the copy */
1305 while (cur_offset < decompressed + buf_len) {
1306 struct bio_vec bvec;
1309 /* Offset inside the full decompressed extent */
1312 bvec = bio_iter_iovec(orig_bio, orig_bio->bi_iter);
1314 * cb->start may underflow, but subtracting that value can still
1315 * give us correct offset inside the full decompressed extent.
1317 bvec_offset = page_offset(bvec.bv_page) + bvec.bv_offset - cb->start;
1319 /* Haven't reached the bvec range, exit */
1320 if (decompressed + buf_len <= bvec_offset)
1323 copy_start = max(cur_offset, bvec_offset);
1324 copy_len = min(bvec_offset + bvec.bv_len,
1325 decompressed + buf_len) - copy_start;
1329 * Extra range check to ensure we didn't go beyond
1332 ASSERT(copy_start - decompressed < buf_len);
1333 memcpy_to_page(bvec.bv_page, bvec.bv_offset,
1334 buf + copy_start - decompressed, copy_len);
1335 cur_offset += copy_len;
1337 bio_advance(orig_bio, copy_len);
1338 /* Finished the bio */
1339 if (!orig_bio->bi_iter.bi_size)
1346 * Shannon Entropy calculation
1348 * Pure byte distribution analysis fails to determine compressibility of data.
1349 * Try calculating entropy to estimate the average minimum number of bits
1350 * needed to encode the sampled data.
1352 * For convenience, return the percentage of needed bits, instead of amount of
1355 * @ENTROPY_LVL_ACEPTABLE - below that threshold, sample has low byte entropy
1356 * and can be compressible with high probability
1358 * @ENTROPY_LVL_HIGH - data are not compressible with high probability
1360 * Use of ilog2() decreases precision, we lower the LVL to 5 to compensate.
1362 #define ENTROPY_LVL_ACEPTABLE (65)
1363 #define ENTROPY_LVL_HIGH (80)
1366 * For increasead precision in shannon_entropy calculation,
1367 * let's do pow(n, M) to save more digits after comma:
1369 * - maximum int bit length is 64
1370 * - ilog2(MAX_SAMPLE_SIZE) -> 13
1371 * - 13 * 4 = 52 < 64 -> M = 4
1375 static inline u32 ilog2_w(u64 n)
1377 return ilog2(n * n * n * n);
1380 static u32 shannon_entropy(struct heuristic_ws *ws)
1382 const u32 entropy_max = 8 * ilog2_w(2);
1383 u32 entropy_sum = 0;
1384 u32 p, p_base, sz_base;
1387 sz_base = ilog2_w(ws->sample_size);
1388 for (i = 0; i < BUCKET_SIZE && ws->bucket[i].count > 0; i++) {
1389 p = ws->bucket[i].count;
1390 p_base = ilog2_w(p);
1391 entropy_sum += p * (sz_base - p_base);
1394 entropy_sum /= ws->sample_size;
1395 return entropy_sum * 100 / entropy_max;
1398 #define RADIX_BASE 4U
1399 #define COUNTERS_SIZE (1U << RADIX_BASE)
1401 static u8 get4bits(u64 num, int shift) {
1406 low4bits = (COUNTERS_SIZE - 1) - (num % COUNTERS_SIZE);
1411 * Use 4 bits as radix base
1412 * Use 16 u32 counters for calculating new position in buf array
1414 * @array - array that will be sorted
1415 * @array_buf - buffer array to store sorting results
1416 * must be equal in size to @array
1419 static void radix_sort(struct bucket_item *array, struct bucket_item *array_buf,
1424 u32 counters[COUNTERS_SIZE];
1432 * Try avoid useless loop iterations for small numbers stored in big
1433 * counters. Example: 48 33 4 ... in 64bit array
1435 max_num = array[0].count;
1436 for (i = 1; i < num; i++) {
1437 buf_num = array[i].count;
1438 if (buf_num > max_num)
1442 buf_num = ilog2(max_num);
1443 bitlen = ALIGN(buf_num, RADIX_BASE * 2);
1446 while (shift < bitlen) {
1447 memset(counters, 0, sizeof(counters));
1449 for (i = 0; i < num; i++) {
1450 buf_num = array[i].count;
1451 addr = get4bits(buf_num, shift);
1455 for (i = 1; i < COUNTERS_SIZE; i++)
1456 counters[i] += counters[i - 1];
1458 for (i = num - 1; i >= 0; i--) {
1459 buf_num = array[i].count;
1460 addr = get4bits(buf_num, shift);
1462 new_addr = counters[addr];
1463 array_buf[new_addr] = array[i];
1466 shift += RADIX_BASE;
1469 * Normal radix expects to move data from a temporary array, to
1470 * the main one. But that requires some CPU time. Avoid that
1471 * by doing another sort iteration to original array instead of
1474 memset(counters, 0, sizeof(counters));
1476 for (i = 0; i < num; i ++) {
1477 buf_num = array_buf[i].count;
1478 addr = get4bits(buf_num, shift);
1482 for (i = 1; i < COUNTERS_SIZE; i++)
1483 counters[i] += counters[i - 1];
1485 for (i = num - 1; i >= 0; i--) {
1486 buf_num = array_buf[i].count;
1487 addr = get4bits(buf_num, shift);
1489 new_addr = counters[addr];
1490 array[new_addr] = array_buf[i];
1493 shift += RADIX_BASE;
1498 * Size of the core byte set - how many bytes cover 90% of the sample
1500 * There are several types of structured binary data that use nearly all byte
1501 * values. The distribution can be uniform and counts in all buckets will be
1502 * nearly the same (eg. encrypted data). Unlikely to be compressible.
1504 * Other possibility is normal (Gaussian) distribution, where the data could
1505 * be potentially compressible, but we have to take a few more steps to decide
1508 * @BYTE_CORE_SET_LOW - main part of byte values repeated frequently,
1509 * compression algo can easy fix that
1510 * @BYTE_CORE_SET_HIGH - data have uniform distribution and with high
1511 * probability is not compressible
1513 #define BYTE_CORE_SET_LOW (64)
1514 #define BYTE_CORE_SET_HIGH (200)
1516 static int byte_core_set_size(struct heuristic_ws *ws)
1519 u32 coreset_sum = 0;
1520 const u32 core_set_threshold = ws->sample_size * 90 / 100;
1521 struct bucket_item *bucket = ws->bucket;
1523 /* Sort in reverse order */
1524 radix_sort(ws->bucket, ws->bucket_b, BUCKET_SIZE);
1526 for (i = 0; i < BYTE_CORE_SET_LOW; i++)
1527 coreset_sum += bucket[i].count;
1529 if (coreset_sum > core_set_threshold)
1532 for (; i < BYTE_CORE_SET_HIGH && bucket[i].count > 0; i++) {
1533 coreset_sum += bucket[i].count;
1534 if (coreset_sum > core_set_threshold)
1542 * Count byte values in buckets.
1543 * This heuristic can detect textual data (configs, xml, json, html, etc).
1544 * Because in most text-like data byte set is restricted to limited number of
1545 * possible characters, and that restriction in most cases makes data easy to
1548 * @BYTE_SET_THRESHOLD - consider all data within this byte set size:
1549 * less - compressible
1550 * more - need additional analysis
1552 #define BYTE_SET_THRESHOLD (64)
1554 static u32 byte_set_size(const struct heuristic_ws *ws)
1557 u32 byte_set_size = 0;
1559 for (i = 0; i < BYTE_SET_THRESHOLD; i++) {
1560 if (ws->bucket[i].count > 0)
1565 * Continue collecting count of byte values in buckets. If the byte
1566 * set size is bigger then the threshold, it's pointless to continue,
1567 * the detection technique would fail for this type of data.
1569 for (; i < BUCKET_SIZE; i++) {
1570 if (ws->bucket[i].count > 0) {
1572 if (byte_set_size > BYTE_SET_THRESHOLD)
1573 return byte_set_size;
1577 return byte_set_size;
1580 static bool sample_repeated_patterns(struct heuristic_ws *ws)
1582 const u32 half_of_sample = ws->sample_size / 2;
1583 const u8 *data = ws->sample;
1585 return memcmp(&data[0], &data[half_of_sample], half_of_sample) == 0;
1588 static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end,
1589 struct heuristic_ws *ws)
1592 u64 index, index_end;
1593 u32 i, curr_sample_pos;
1597 * Compression handles the input data by chunks of 128KiB
1598 * (defined by BTRFS_MAX_UNCOMPRESSED)
1600 * We do the same for the heuristic and loop over the whole range.
1602 * MAX_SAMPLE_SIZE - calculated under assumption that heuristic will
1603 * process no more than BTRFS_MAX_UNCOMPRESSED at a time.
1605 if (end - start > BTRFS_MAX_UNCOMPRESSED)
1606 end = start + BTRFS_MAX_UNCOMPRESSED;
1608 index = start >> PAGE_SHIFT;
1609 index_end = end >> PAGE_SHIFT;
1611 /* Don't miss unaligned end */
1612 if (!IS_ALIGNED(end, PAGE_SIZE))
1615 curr_sample_pos = 0;
1616 while (index < index_end) {
1617 page = find_get_page(inode->i_mapping, index);
1618 in_data = kmap_local_page(page);
1619 /* Handle case where the start is not aligned to PAGE_SIZE */
1620 i = start % PAGE_SIZE;
1621 while (i < PAGE_SIZE - SAMPLING_READ_SIZE) {
1622 /* Don't sample any garbage from the last page */
1623 if (start > end - SAMPLING_READ_SIZE)
1625 memcpy(&ws->sample[curr_sample_pos], &in_data[i],
1626 SAMPLING_READ_SIZE);
1627 i += SAMPLING_INTERVAL;
1628 start += SAMPLING_INTERVAL;
1629 curr_sample_pos += SAMPLING_READ_SIZE;
1631 kunmap_local(in_data);
1637 ws->sample_size = curr_sample_pos;
1641 * Compression heuristic.
1643 * For now is's a naive and optimistic 'return true', we'll extend the logic to
1644 * quickly (compared to direct compression) detect data characteristics
1645 * (compressible/uncompressible) to avoid wasting CPU time on uncompressible
1648 * The following types of analysis can be performed:
1649 * - detect mostly zero data
1650 * - detect data with low "byte set" size (text, etc)
1651 * - detect data with low/high "core byte" set
1653 * Return non-zero if the compression should be done, 0 otherwise.
1655 int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
1657 struct list_head *ws_list = get_workspace(0, 0);
1658 struct heuristic_ws *ws;
1663 ws = list_entry(ws_list, struct heuristic_ws, list);
1665 heuristic_collect_sample(inode, start, end, ws);
1667 if (sample_repeated_patterns(ws)) {
1672 memset(ws->bucket, 0, sizeof(*ws->bucket)*BUCKET_SIZE);
1674 for (i = 0; i < ws->sample_size; i++) {
1675 byte = ws->sample[i];
1676 ws->bucket[byte].count++;
1679 i = byte_set_size(ws);
1680 if (i < BYTE_SET_THRESHOLD) {
1685 i = byte_core_set_size(ws);
1686 if (i <= BYTE_CORE_SET_LOW) {
1691 if (i >= BYTE_CORE_SET_HIGH) {
1696 i = shannon_entropy(ws);
1697 if (i <= ENTROPY_LVL_ACEPTABLE) {
1703 * For the levels below ENTROPY_LVL_HIGH, additional analysis would be
1704 * needed to give green light to compression.
1706 * For now just assume that compression at that level is not worth the
1707 * resources because:
1709 * 1. it is possible to defrag the data later
1711 * 2. the data would turn out to be hardly compressible, eg. 150 byte
1712 * values, every bucket has counter at level ~54. The heuristic would
1713 * be confused. This can happen when data have some internal repeated
1714 * patterns like "abbacbbc...". This can be detected by analyzing
1715 * pairs of bytes, which is too costly.
1717 if (i < ENTROPY_LVL_HIGH) {
1726 put_workspace(0, ws_list);
1731 * Convert the compression suffix (eg. after "zlib" starting with ":") to
1732 * level, unrecognized string will set the default level
1734 unsigned int btrfs_compress_str2level(unsigned int type, const char *str)
1736 unsigned int level = 0;
1742 if (str[0] == ':') {
1743 ret = kstrtouint(str + 1, 10, &level);
1748 level = btrfs_compress_set_level(type, level);