2 * Copyright (C) 2008 Oracle. All rights reserved.
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public
6 * License v2 as published by the Free Software Foundation.
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
13 * You should have received a copy of the GNU General Public
14 * License along with this program; if not, write to the
15 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
16 * Boston, MA 021110-1307, USA.
19 #include <linux/kernel.h>
20 #include <linux/bio.h>
21 #include <linux/buffer_head.h>
22 #include <linux/file.h>
24 #include <linux/pagemap.h>
25 #include <linux/highmem.h>
26 #include <linux/time.h>
27 #include <linux/init.h>
28 #include <linux/string.h>
29 #include <linux/backing-dev.h>
30 #include <linux/mpage.h>
31 #include <linux/swap.h>
32 #include <linux/writeback.h>
33 #include <linux/bit_spinlock.h>
34 #include <linux/slab.h>
35 #include <linux/sched/mm.h>
38 #include "transaction.h"
39 #include "btrfs_inode.h"
41 #include "ordered-data.h"
42 #include "compression.h"
43 #include "extent_io.h"
44 #include "extent_map.h"
46 static int btrfs_decompress_bio(struct compressed_bio *cb);
48 static inline int compressed_bio_size(struct btrfs_fs_info *fs_info,
49 unsigned long disk_size)
51 u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
53 return sizeof(struct compressed_bio) +
54 (DIV_ROUND_UP(disk_size, fs_info->sectorsize)) * csum_size;
57 static int check_compressed_csum(struct btrfs_inode *inode,
58 struct compressed_bio *cb,
66 u32 *cb_sum = &cb->sums;
68 if (inode->flags & BTRFS_INODE_NODATASUM)
71 for (i = 0; i < cb->nr_pages; i++) {
72 page = cb->compressed_pages[i];
75 kaddr = kmap_atomic(page);
76 csum = btrfs_csum_data(kaddr, csum, PAGE_SIZE);
77 btrfs_csum_final(csum, (u8 *)&csum);
80 if (csum != *cb_sum) {
81 btrfs_print_data_csum_error(inode, disk_start, csum,
82 *cb_sum, cb->mirror_num);
94 /* when we finish reading compressed pages from the disk, we
95 * decompress them and then run the bio end_io routines on the
96 * decompressed pages (in the inode address space).
98 * This allows the checksumming and other IO error handling routines
101 * The compressed pages are freed here, and it must be run
104 static void end_compressed_bio_read(struct bio *bio)
106 struct compressed_bio *cb = bio->bi_private;
110 unsigned int mirror = btrfs_io_bio(bio)->mirror_num;
116 /* if there are more bios still pending for this compressed
119 if (!refcount_dec_and_test(&cb->pending_bios))
123 * Record the correct mirror_num in cb->orig_bio so that
124 * read-repair can work properly.
126 ASSERT(btrfs_io_bio(cb->orig_bio));
127 btrfs_io_bio(cb->orig_bio)->mirror_num = mirror;
128 cb->mirror_num = mirror;
131 * Some IO in this cb have failed, just skip checksum as there
132 * is no way it could be correct.
138 ret = check_compressed_csum(BTRFS_I(inode), cb,
139 (u64)bio->bi_iter.bi_sector << 9);
143 /* ok, we're the last bio for this extent, lets start
146 ret = btrfs_decompress_bio(cb);
152 /* release the compressed pages */
154 for (index = 0; index < cb->nr_pages; index++) {
155 page = cb->compressed_pages[index];
156 page->mapping = NULL;
160 /* do io completion on the original bio */
162 bio_io_error(cb->orig_bio);
165 struct bio_vec *bvec;
168 * we have verified the checksum already, set page
169 * checked so the end_io handlers know about it
171 ASSERT(!bio_flagged(bio, BIO_CLONED));
172 bio_for_each_segment_all(bvec, cb->orig_bio, i)
173 SetPageChecked(bvec->bv_page);
175 bio_endio(cb->orig_bio);
178 /* finally free the cb struct */
179 kfree(cb->compressed_pages);
186 * Clear the writeback bits on all of the file
187 * pages for a compressed write
189 static noinline void end_compressed_writeback(struct inode *inode,
190 const struct compressed_bio *cb)
192 unsigned long index = cb->start >> PAGE_SHIFT;
193 unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT;
194 struct page *pages[16];
195 unsigned long nr_pages = end_index - index + 1;
200 mapping_set_error(inode->i_mapping, -EIO);
202 while (nr_pages > 0) {
203 ret = find_get_pages_contig(inode->i_mapping, index,
205 nr_pages, ARRAY_SIZE(pages)), pages);
211 for (i = 0; i < ret; i++) {
213 SetPageError(pages[i]);
214 end_page_writeback(pages[i]);
220 /* the inode may be gone now */
224 * do the cleanup once all the compressed pages hit the disk.
225 * This will clear writeback on the file pages and free the compressed
228 * This also calls the writeback end hooks for the file pages so that
229 * metadata and checksums can be updated in the file.
231 static void end_compressed_bio_write(struct bio *bio)
233 struct extent_io_tree *tree;
234 struct compressed_bio *cb = bio->bi_private;
242 /* if there are more bios still pending for this compressed
245 if (!refcount_dec_and_test(&cb->pending_bios))
248 /* ok, we're the last bio for this extent, step one is to
249 * call back into the FS and do all the end_io operations
252 tree = &BTRFS_I(inode)->io_tree;
253 cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
254 tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
256 cb->start + cb->len - 1,
258 bio->bi_status ? 0 : 1);
259 cb->compressed_pages[0]->mapping = NULL;
261 end_compressed_writeback(inode, cb);
262 /* note, our inode could be gone now */
265 * release the compressed pages, these came from alloc_page and
266 * are not attached to the inode at all
269 for (index = 0; index < cb->nr_pages; index++) {
270 page = cb->compressed_pages[index];
271 page->mapping = NULL;
275 /* finally free the cb struct */
276 kfree(cb->compressed_pages);
283 * worker function to build and submit bios for previously compressed pages.
284 * The corresponding pages in the inode should be marked for writeback
285 * and the compressed pages should have a reference on them for dropping
286 * when the IO is complete.
288 * This also checksums the file bytes and gets things ready for
291 blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
292 unsigned long len, u64 disk_start,
293 unsigned long compressed_len,
294 struct page **compressed_pages,
295 unsigned long nr_pages)
297 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
298 struct bio *bio = NULL;
299 struct compressed_bio *cb;
300 unsigned long bytes_left;
301 struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
304 u64 first_byte = disk_start;
305 struct block_device *bdev;
307 int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
309 WARN_ON(start & ((u64)PAGE_SIZE - 1));
310 cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
312 return BLK_STS_RESOURCE;
313 refcount_set(&cb->pending_bios, 0);
319 cb->compressed_pages = compressed_pages;
320 cb->compressed_len = compressed_len;
322 cb->nr_pages = nr_pages;
324 bdev = fs_info->fs_devices->latest_bdev;
326 bio = btrfs_bio_alloc(bdev, first_byte);
327 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
328 bio->bi_private = cb;
329 bio->bi_end_io = end_compressed_bio_write;
330 refcount_set(&cb->pending_bios, 1);
332 /* create and submit bios for the compressed pages */
333 bytes_left = compressed_len;
334 for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
337 page = compressed_pages[pg_index];
338 page->mapping = inode->i_mapping;
339 if (bio->bi_iter.bi_size)
340 submit = io_tree->ops->merge_bio_hook(page, 0,
344 page->mapping = NULL;
345 if (submit || bio_add_page(bio, page, PAGE_SIZE, 0) <
350 * inc the count before we submit the bio so
351 * we know the end IO handler won't happen before
352 * we inc the count. Otherwise, the cb might get
353 * freed before we're done setting it up
355 refcount_inc(&cb->pending_bios);
356 ret = btrfs_bio_wq_end_io(fs_info, bio,
357 BTRFS_WQ_ENDIO_DATA);
358 BUG_ON(ret); /* -ENOMEM */
361 ret = btrfs_csum_one_bio(inode, bio, start, 1);
362 BUG_ON(ret); /* -ENOMEM */
365 ret = btrfs_map_bio(fs_info, bio, 0, 1);
367 bio->bi_status = ret;
373 bio = btrfs_bio_alloc(bdev, first_byte);
374 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
375 bio->bi_private = cb;
376 bio->bi_end_io = end_compressed_bio_write;
377 bio_add_page(bio, page, PAGE_SIZE, 0);
379 if (bytes_left < PAGE_SIZE) {
381 "bytes left %lu compress len %lu nr %lu",
382 bytes_left, cb->compressed_len, cb->nr_pages);
384 bytes_left -= PAGE_SIZE;
385 first_byte += PAGE_SIZE;
390 ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
391 BUG_ON(ret); /* -ENOMEM */
394 ret = btrfs_csum_one_bio(inode, bio, start, 1);
395 BUG_ON(ret); /* -ENOMEM */
398 ret = btrfs_map_bio(fs_info, bio, 0, 1);
400 bio->bi_status = ret;
408 static u64 bio_end_offset(struct bio *bio)
410 struct bio_vec *last = &bio->bi_io_vec[bio->bi_vcnt - 1];
412 return page_offset(last->bv_page) + last->bv_len + last->bv_offset;
415 static noinline int add_ra_bio_pages(struct inode *inode,
417 struct compressed_bio *cb)
419 unsigned long end_index;
420 unsigned long pg_index;
422 u64 isize = i_size_read(inode);
425 unsigned long nr_pages = 0;
426 struct extent_map *em;
427 struct address_space *mapping = inode->i_mapping;
428 struct extent_map_tree *em_tree;
429 struct extent_io_tree *tree;
433 last_offset = bio_end_offset(cb->orig_bio);
434 em_tree = &BTRFS_I(inode)->extent_tree;
435 tree = &BTRFS_I(inode)->io_tree;
440 end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
442 while (last_offset < compressed_end) {
443 pg_index = last_offset >> PAGE_SHIFT;
445 if (pg_index > end_index)
449 page = radix_tree_lookup(&mapping->page_tree, pg_index);
451 if (page && !radix_tree_exceptional_entry(page)) {
458 page = __page_cache_alloc(mapping_gfp_constraint(mapping,
463 if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
468 end = last_offset + PAGE_SIZE - 1;
470 * at this point, we have a locked page in the page cache
471 * for these bytes in the file. But, we have to make
472 * sure they map to this compressed extent on disk.
474 set_page_extent_mapped(page);
475 lock_extent(tree, last_offset, end);
476 read_lock(&em_tree->lock);
477 em = lookup_extent_mapping(em_tree, last_offset,
479 read_unlock(&em_tree->lock);
481 if (!em || last_offset < em->start ||
482 (last_offset + PAGE_SIZE > extent_map_end(em)) ||
483 (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
485 unlock_extent(tree, last_offset, end);
492 if (page->index == end_index) {
494 size_t zero_offset = isize & (PAGE_SIZE - 1);
498 zeros = PAGE_SIZE - zero_offset;
499 userpage = kmap_atomic(page);
500 memset(userpage + zero_offset, 0, zeros);
501 flush_dcache_page(page);
502 kunmap_atomic(userpage);
506 ret = bio_add_page(cb->orig_bio, page,
509 if (ret == PAGE_SIZE) {
513 unlock_extent(tree, last_offset, end);
519 last_offset += PAGE_SIZE;
525 * for a compressed read, the bio we get passed has all the inode pages
526 * in it. We don't actually do IO on those pages but allocate new ones
527 * to hold the compressed pages on disk.
529 * bio->bi_iter.bi_sector points to the compressed extent on disk
530 * bio->bi_io_vec points to all of the inode pages
532 * After the compressed pages are read, we copy the bytes into the
533 * bio we were passed and then call the bio end_io calls
535 blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
536 int mirror_num, unsigned long bio_flags)
538 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
539 struct extent_io_tree *tree;
540 struct extent_map_tree *em_tree;
541 struct compressed_bio *cb;
542 unsigned long compressed_len;
543 unsigned long nr_pages;
544 unsigned long pg_index;
546 struct block_device *bdev;
547 struct bio *comp_bio;
548 u64 cur_disk_byte = (u64)bio->bi_iter.bi_sector << 9;
551 struct extent_map *em;
552 blk_status_t ret = BLK_STS_RESOURCE;
556 tree = &BTRFS_I(inode)->io_tree;
557 em_tree = &BTRFS_I(inode)->extent_tree;
559 /* we need the actual starting offset of this extent in the file */
560 read_lock(&em_tree->lock);
561 em = lookup_extent_mapping(em_tree,
562 page_offset(bio->bi_io_vec->bv_page),
564 read_unlock(&em_tree->lock);
566 return BLK_STS_IOERR;
568 compressed_len = em->block_len;
569 cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
573 refcount_set(&cb->pending_bios, 0);
576 cb->mirror_num = mirror_num;
579 cb->start = em->orig_start;
581 em_start = em->start;
586 cb->len = bio->bi_iter.bi_size;
587 cb->compressed_len = compressed_len;
588 cb->compress_type = extent_compress_type(bio_flags);
591 nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
592 cb->compressed_pages = kcalloc(nr_pages, sizeof(struct page *),
594 if (!cb->compressed_pages)
597 bdev = fs_info->fs_devices->latest_bdev;
599 for (pg_index = 0; pg_index < nr_pages; pg_index++) {
600 cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
602 if (!cb->compressed_pages[pg_index]) {
603 faili = pg_index - 1;
604 ret = BLK_STS_RESOURCE;
608 faili = nr_pages - 1;
609 cb->nr_pages = nr_pages;
611 add_ra_bio_pages(inode, em_start + em_len, cb);
613 /* include any pages we added in add_ra-bio_pages */
614 cb->len = bio->bi_iter.bi_size;
616 comp_bio = btrfs_bio_alloc(bdev, cur_disk_byte);
617 bio_set_op_attrs (comp_bio, REQ_OP_READ, 0);
618 comp_bio->bi_private = cb;
619 comp_bio->bi_end_io = end_compressed_bio_read;
620 refcount_set(&cb->pending_bios, 1);
622 for (pg_index = 0; pg_index < nr_pages; pg_index++) {
625 page = cb->compressed_pages[pg_index];
626 page->mapping = inode->i_mapping;
627 page->index = em_start >> PAGE_SHIFT;
629 if (comp_bio->bi_iter.bi_size)
630 submit = tree->ops->merge_bio_hook(page, 0,
634 page->mapping = NULL;
635 if (submit || bio_add_page(comp_bio, page, PAGE_SIZE, 0) <
639 ret = btrfs_bio_wq_end_io(fs_info, comp_bio,
640 BTRFS_WQ_ENDIO_DATA);
641 BUG_ON(ret); /* -ENOMEM */
644 * inc the count before we submit the bio so
645 * we know the end IO handler won't happen before
646 * we inc the count. Otherwise, the cb might get
647 * freed before we're done setting it up
649 refcount_inc(&cb->pending_bios);
651 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
652 ret = btrfs_lookup_bio_sums(inode, comp_bio,
654 BUG_ON(ret); /* -ENOMEM */
656 sums += DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
657 fs_info->sectorsize);
659 ret = btrfs_map_bio(fs_info, comp_bio, mirror_num, 0);
661 comp_bio->bi_status = ret;
667 comp_bio = btrfs_bio_alloc(bdev, cur_disk_byte);
668 bio_set_op_attrs(comp_bio, REQ_OP_READ, 0);
669 comp_bio->bi_private = cb;
670 comp_bio->bi_end_io = end_compressed_bio_read;
672 bio_add_page(comp_bio, page, PAGE_SIZE, 0);
674 cur_disk_byte += PAGE_SIZE;
678 ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA);
679 BUG_ON(ret); /* -ENOMEM */
681 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
682 ret = btrfs_lookup_bio_sums(inode, comp_bio, sums);
683 BUG_ON(ret); /* -ENOMEM */
686 ret = btrfs_map_bio(fs_info, comp_bio, mirror_num, 0);
688 comp_bio->bi_status = ret;
697 __free_page(cb->compressed_pages[faili]);
701 kfree(cb->compressed_pages);
710 struct list_head idle_ws;
712 /* Number of free workspaces */
714 /* Total number of allocated workspaces */
716 /* Waiters for a free workspace */
717 wait_queue_head_t ws_wait;
718 } btrfs_comp_ws[BTRFS_COMPRESS_TYPES];
720 static const struct btrfs_compress_op * const btrfs_compress_op[] = {
721 &btrfs_zlib_compress,
723 &btrfs_zstd_compress,
726 void __init btrfs_init_compress(void)
730 for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
731 struct list_head *workspace;
733 INIT_LIST_HEAD(&btrfs_comp_ws[i].idle_ws);
734 spin_lock_init(&btrfs_comp_ws[i].ws_lock);
735 atomic_set(&btrfs_comp_ws[i].total_ws, 0);
736 init_waitqueue_head(&btrfs_comp_ws[i].ws_wait);
739 * Preallocate one workspace for each compression type so
740 * we can guarantee forward progress in the worst case
742 workspace = btrfs_compress_op[i]->alloc_workspace();
743 if (IS_ERR(workspace)) {
744 pr_warn("BTRFS: cannot preallocate compression workspace, will try later\n");
746 atomic_set(&btrfs_comp_ws[i].total_ws, 1);
747 btrfs_comp_ws[i].free_ws = 1;
748 list_add(workspace, &btrfs_comp_ws[i].idle_ws);
754 * This finds an available workspace or allocates a new one.
755 * If it's not possible to allocate a new one, waits until there's one.
756 * Preallocation makes a forward progress guarantees and we do not return
759 static struct list_head *find_workspace(int type)
761 struct list_head *workspace;
762 int cpus = num_online_cpus();
766 struct list_head *idle_ws = &btrfs_comp_ws[idx].idle_ws;
767 spinlock_t *ws_lock = &btrfs_comp_ws[idx].ws_lock;
768 atomic_t *total_ws = &btrfs_comp_ws[idx].total_ws;
769 wait_queue_head_t *ws_wait = &btrfs_comp_ws[idx].ws_wait;
770 int *free_ws = &btrfs_comp_ws[idx].free_ws;
773 if (!list_empty(idle_ws)) {
774 workspace = idle_ws->next;
777 spin_unlock(ws_lock);
781 if (atomic_read(total_ws) > cpus) {
784 spin_unlock(ws_lock);
785 prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE);
786 if (atomic_read(total_ws) > cpus && !*free_ws)
788 finish_wait(ws_wait, &wait);
791 atomic_inc(total_ws);
792 spin_unlock(ws_lock);
795 * Allocation helpers call vmalloc that can't use GFP_NOFS, so we have
796 * to turn it off here because we might get called from the restricted
797 * context of btrfs_compress_bio/btrfs_compress_pages
799 nofs_flag = memalloc_nofs_save();
800 workspace = btrfs_compress_op[idx]->alloc_workspace();
801 memalloc_nofs_restore(nofs_flag);
803 if (IS_ERR(workspace)) {
804 atomic_dec(total_ws);
808 * Do not return the error but go back to waiting. There's a
809 * workspace preallocated for each type and the compression
810 * time is bounded so we get to a workspace eventually. This
811 * makes our caller's life easier.
813 * To prevent silent and low-probability deadlocks (when the
814 * initial preallocation fails), check if there are any
817 if (atomic_read(total_ws) == 0) {
818 static DEFINE_RATELIMIT_STATE(_rs,
819 /* once per minute */ 60 * HZ,
822 if (__ratelimit(&_rs)) {
823 pr_warn("BTRFS: no compression workspaces, low memory, retrying\n");
832 * put a workspace struct back on the list or free it if we have enough
833 * idle ones sitting around
835 static void free_workspace(int type, struct list_head *workspace)
838 struct list_head *idle_ws = &btrfs_comp_ws[idx].idle_ws;
839 spinlock_t *ws_lock = &btrfs_comp_ws[idx].ws_lock;
840 atomic_t *total_ws = &btrfs_comp_ws[idx].total_ws;
841 wait_queue_head_t *ws_wait = &btrfs_comp_ws[idx].ws_wait;
842 int *free_ws = &btrfs_comp_ws[idx].free_ws;
845 if (*free_ws <= num_online_cpus()) {
846 list_add(workspace, idle_ws);
848 spin_unlock(ws_lock);
851 spin_unlock(ws_lock);
853 btrfs_compress_op[idx]->free_workspace(workspace);
854 atomic_dec(total_ws);
857 * Make sure counter is updated before we wake up waiters.
860 if (waitqueue_active(ws_wait))
865 * cleanup function for module exit
867 static void free_workspaces(void)
869 struct list_head *workspace;
872 for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
873 while (!list_empty(&btrfs_comp_ws[i].idle_ws)) {
874 workspace = btrfs_comp_ws[i].idle_ws.next;
876 btrfs_compress_op[i]->free_workspace(workspace);
877 atomic_dec(&btrfs_comp_ws[i].total_ws);
883 * Given an address space and start and length, compress the bytes into @pages
884 * that are allocated on demand.
886 * @out_pages is an in/out parameter, holds maximum number of pages to allocate
887 * and returns number of actually allocated pages
889 * @total_in is used to return the number of bytes actually read. It
890 * may be smaller than the input length if we had to exit early because we
891 * ran out of room in the pages array or because we cross the
894 * @total_out is an in/out parameter, must be set to the input length and will
895 * be also used to return the total number of compressed bytes
897 * @max_out tells us the max number of bytes that we're allowed to
900 int btrfs_compress_pages(int type, struct address_space *mapping,
901 u64 start, struct page **pages,
902 unsigned long *out_pages,
903 unsigned long *total_in,
904 unsigned long *total_out)
906 struct list_head *workspace;
909 workspace = find_workspace(type);
911 ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping,
914 total_in, total_out);
915 free_workspace(type, workspace);
920 * pages_in is an array of pages with compressed data.
922 * disk_start is the starting logical offset of this array in the file
924 * orig_bio contains the pages from the file that we want to decompress into
926 * srclen is the number of bytes in pages_in
928 * The basic idea is that we have a bio that was created by readpages.
929 * The pages in the bio are for the uncompressed data, and they may not
930 * be contiguous. They all correspond to the range of bytes covered by
931 * the compressed extent.
933 static int btrfs_decompress_bio(struct compressed_bio *cb)
935 struct list_head *workspace;
937 int type = cb->compress_type;
939 workspace = find_workspace(type);
940 ret = btrfs_compress_op[type - 1]->decompress_bio(workspace, cb);
941 free_workspace(type, workspace);
947 * a less complex decompression routine. Our compressed data fits in a
948 * single page, and we want to read a single page out of it.
949 * start_byte tells us the offset into the compressed data we're interested in
951 int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
952 unsigned long start_byte, size_t srclen, size_t destlen)
954 struct list_head *workspace;
957 workspace = find_workspace(type);
959 ret = btrfs_compress_op[type-1]->decompress(workspace, data_in,
960 dest_page, start_byte,
963 free_workspace(type, workspace);
967 void btrfs_exit_compress(void)
973 * Copy uncompressed data from working buffer to pages.
975 * buf_start is the byte offset we're of the start of our workspace buffer.
977 * total_out is the last byte of the buffer
979 int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
980 unsigned long total_out, u64 disk_start,
983 unsigned long buf_offset;
984 unsigned long current_buf_start;
985 unsigned long start_byte;
986 unsigned long prev_start_byte;
987 unsigned long working_bytes = total_out - buf_start;
990 struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter);
993 * start byte is the first byte of the page we're currently
994 * copying into relative to the start of the compressed data.
996 start_byte = page_offset(bvec.bv_page) - disk_start;
998 /* we haven't yet hit data corresponding to this page */
999 if (total_out <= start_byte)
1003 * the start of the data we care about is offset into
1004 * the middle of our working buffer
1006 if (total_out > start_byte && buf_start < start_byte) {
1007 buf_offset = start_byte - buf_start;
1008 working_bytes -= buf_offset;
1012 current_buf_start = buf_start;
1014 /* copy bytes from the working buffer into the pages */
1015 while (working_bytes > 0) {
1016 bytes = min_t(unsigned long, bvec.bv_len,
1017 PAGE_SIZE - buf_offset);
1018 bytes = min(bytes, working_bytes);
1020 kaddr = kmap_atomic(bvec.bv_page);
1021 memcpy(kaddr + bvec.bv_offset, buf + buf_offset, bytes);
1022 kunmap_atomic(kaddr);
1023 flush_dcache_page(bvec.bv_page);
1025 buf_offset += bytes;
1026 working_bytes -= bytes;
1027 current_buf_start += bytes;
1029 /* check if we need to pick another page */
1030 bio_advance(bio, bytes);
1031 if (!bio->bi_iter.bi_size)
1033 bvec = bio_iter_iovec(bio, bio->bi_iter);
1034 prev_start_byte = start_byte;
1035 start_byte = page_offset(bvec.bv_page) - disk_start;
1038 * We need to make sure we're only adjusting
1039 * our offset into compression working buffer when
1040 * we're switching pages. Otherwise we can incorrectly
1041 * keep copying when we were actually done.
1043 if (start_byte != prev_start_byte) {
1045 * make sure our new page is covered by this
1048 if (total_out <= start_byte)
1052 * the next page in the biovec might not be adjacent
1053 * to the last page, but it might still be found
1054 * inside this working buffer. bump our offset pointer
1056 if (total_out > start_byte &&
1057 current_buf_start < start_byte) {
1058 buf_offset = start_byte - buf_start;
1059 working_bytes = total_out - start_byte;
1060 current_buf_start = buf_start + buf_offset;
1069 * Compression heuristic.
1071 * For now is's a naive and optimistic 'return true', we'll extend the logic to
1072 * quickly (compared to direct compression) detect data characteristics
1073 * (compressible/uncompressible) to avoid wasting CPU time on uncompressible
1076 * The following types of analysis can be performed:
1077 * - detect mostly zero data
1078 * - detect data with low "byte set" size (text, etc)
1079 * - detect data with low/high "core byte" set
1081 * Return non-zero if the compression should be done, 0 otherwise.
1083 int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
1085 u64 index = start >> PAGE_SHIFT;
1086 u64 end_index = end >> PAGE_SHIFT;
1090 while (index <= end_index) {
1091 page = find_get_page(inode->i_mapping, index);