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>
37 #include "transaction.h"
38 #include "btrfs_inode.h"
40 #include "ordered-data.h"
41 #include "compression.h"
42 #include "extent_io.h"
43 #include "extent_map.h"
45 struct compressed_bio {
46 /* number of bios pending for this compressed extent */
47 atomic_t pending_bios;
49 /* the pages with the compressed data on them */
50 struct page **compressed_pages;
52 /* inode that owns this data */
55 /* starting offset in the inode for our pages */
58 /* number of bytes in the inode we're working on */
61 /* number of bytes on disk */
62 unsigned long compressed_len;
64 /* the compression algorithm for this bio */
67 /* number of compressed pages in the array */
68 unsigned long nr_pages;
74 /* for reads, this is the bio we are copying the data into */
78 * the start of a variable length array of checksums only
84 static int btrfs_decompress_bio(int type, struct page **pages_in,
85 u64 disk_start, struct bio *orig_bio,
88 static inline int compressed_bio_size(struct btrfs_fs_info *fs_info,
89 unsigned long disk_size)
91 u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
93 return sizeof(struct compressed_bio) +
94 (DIV_ROUND_UP(disk_size, fs_info->sectorsize)) * csum_size;
97 static struct bio *compressed_bio_alloc(struct block_device *bdev,
98 u64 first_byte, gfp_t gfp_flags)
100 return btrfs_bio_alloc(bdev, first_byte >> 9, BIO_MAX_PAGES, gfp_flags);
103 static int check_compressed_csum(struct inode *inode,
104 struct compressed_bio *cb,
112 u32 *cb_sum = &cb->sums;
114 if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
117 for (i = 0; i < cb->nr_pages; i++) {
118 page = cb->compressed_pages[i];
121 kaddr = kmap_atomic(page);
122 csum = btrfs_csum_data(kaddr, csum, PAGE_SIZE);
123 btrfs_csum_final(csum, (u8 *)&csum);
124 kunmap_atomic(kaddr);
126 if (csum != *cb_sum) {
127 btrfs_info(BTRFS_I(inode)->root->fs_info,
128 "csum failed ino %llu extent %llu csum %u wanted %u mirror %d",
129 btrfs_ino(inode), disk_start, csum, *cb_sum,
142 /* when we finish reading compressed pages from the disk, we
143 * decompress them and then run the bio end_io routines on the
144 * decompressed pages (in the inode address space).
146 * This allows the checksumming and other IO error handling routines
149 * The compressed pages are freed here, and it must be run
152 static void end_compressed_bio_read(struct bio *bio)
154 struct compressed_bio *cb = bio->bi_private;
163 /* if there are more bios still pending for this compressed
166 if (!atomic_dec_and_test(&cb->pending_bios))
170 ret = check_compressed_csum(inode, cb,
171 (u64)bio->bi_iter.bi_sector << 9);
175 /* ok, we're the last bio for this extent, lets start
178 ret = btrfs_decompress_bio(cb->compress_type,
179 cb->compressed_pages,
187 /* release the compressed pages */
189 for (index = 0; index < cb->nr_pages; index++) {
190 page = cb->compressed_pages[index];
191 page->mapping = NULL;
195 /* do io completion on the original bio */
197 bio_io_error(cb->orig_bio);
200 struct bio_vec *bvec;
203 * we have verified the checksum already, set page
204 * checked so the end_io handlers know about it
206 bio_for_each_segment_all(bvec, cb->orig_bio, i)
207 SetPageChecked(bvec->bv_page);
209 bio_endio(cb->orig_bio);
212 /* finally free the cb struct */
213 kfree(cb->compressed_pages);
220 * Clear the writeback bits on all of the file
221 * pages for a compressed write
223 static noinline void end_compressed_writeback(struct inode *inode,
224 const struct compressed_bio *cb)
226 unsigned long index = cb->start >> PAGE_SHIFT;
227 unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT;
228 struct page *pages[16];
229 unsigned long nr_pages = end_index - index + 1;
234 mapping_set_error(inode->i_mapping, -EIO);
236 while (nr_pages > 0) {
237 ret = find_get_pages_contig(inode->i_mapping, index,
239 nr_pages, ARRAY_SIZE(pages)), pages);
245 for (i = 0; i < ret; i++) {
247 SetPageError(pages[i]);
248 end_page_writeback(pages[i]);
254 /* the inode may be gone now */
258 * do the cleanup once all the compressed pages hit the disk.
259 * This will clear writeback on the file pages and free the compressed
262 * This also calls the writeback end hooks for the file pages so that
263 * metadata and checksums can be updated in the file.
265 static void end_compressed_bio_write(struct bio *bio)
267 struct extent_io_tree *tree;
268 struct compressed_bio *cb = bio->bi_private;
276 /* if there are more bios still pending for this compressed
279 if (!atomic_dec_and_test(&cb->pending_bios))
282 /* ok, we're the last bio for this extent, step one is to
283 * call back into the FS and do all the end_io operations
286 tree = &BTRFS_I(inode)->io_tree;
287 cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
288 tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
290 cb->start + cb->len - 1,
292 bio->bi_error ? 0 : 1);
293 cb->compressed_pages[0]->mapping = NULL;
295 end_compressed_writeback(inode, cb);
296 /* note, our inode could be gone now */
299 * release the compressed pages, these came from alloc_page and
300 * are not attached to the inode at all
303 for (index = 0; index < cb->nr_pages; index++) {
304 page = cb->compressed_pages[index];
305 page->mapping = NULL;
309 /* finally free the cb struct */
310 kfree(cb->compressed_pages);
317 * worker function to build and submit bios for previously compressed pages.
318 * The corresponding pages in the inode should be marked for writeback
319 * and the compressed pages should have a reference on them for dropping
320 * when the IO is complete.
322 * This also checksums the file bytes and gets things ready for
325 int btrfs_submit_compressed_write(struct inode *inode, u64 start,
326 unsigned long len, u64 disk_start,
327 unsigned long compressed_len,
328 struct page **compressed_pages,
329 unsigned long nr_pages)
331 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
332 struct bio *bio = NULL;
333 struct compressed_bio *cb;
334 unsigned long bytes_left;
335 struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
338 u64 first_byte = disk_start;
339 struct block_device *bdev;
341 int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
343 WARN_ON(start & ((u64)PAGE_SIZE - 1));
344 cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
347 atomic_set(&cb->pending_bios, 0);
353 cb->compressed_pages = compressed_pages;
354 cb->compressed_len = compressed_len;
356 cb->nr_pages = nr_pages;
358 bdev = fs_info->fs_devices->latest_bdev;
360 bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
365 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
366 bio->bi_private = cb;
367 bio->bi_end_io = end_compressed_bio_write;
368 atomic_inc(&cb->pending_bios);
370 /* create and submit bios for the compressed pages */
371 bytes_left = compressed_len;
372 for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
373 page = compressed_pages[pg_index];
374 page->mapping = inode->i_mapping;
375 if (bio->bi_iter.bi_size)
376 ret = io_tree->ops->merge_bio_hook(page, 0,
382 page->mapping = NULL;
383 if (ret || bio_add_page(bio, page, PAGE_SIZE, 0) <
388 * inc the count before we submit the bio so
389 * we know the end IO handler won't happen before
390 * we inc the count. Otherwise, the cb might get
391 * freed before we're done setting it up
393 atomic_inc(&cb->pending_bios);
394 ret = btrfs_bio_wq_end_io(fs_info, bio,
395 BTRFS_WQ_ENDIO_DATA);
396 BUG_ON(ret); /* -ENOMEM */
399 ret = btrfs_csum_one_bio(inode, bio, start, 1);
400 BUG_ON(ret); /* -ENOMEM */
403 ret = btrfs_map_bio(fs_info, bio, 0, 1);
411 bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
413 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
414 bio->bi_private = cb;
415 bio->bi_end_io = end_compressed_bio_write;
416 bio_add_page(bio, page, PAGE_SIZE, 0);
418 if (bytes_left < PAGE_SIZE) {
420 "bytes left %lu compress len %lu nr %lu",
421 bytes_left, cb->compressed_len, cb->nr_pages);
423 bytes_left -= PAGE_SIZE;
424 first_byte += PAGE_SIZE;
429 ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
430 BUG_ON(ret); /* -ENOMEM */
433 ret = btrfs_csum_one_bio(inode, bio, start, 1);
434 BUG_ON(ret); /* -ENOMEM */
437 ret = btrfs_map_bio(fs_info, bio, 0, 1);
447 static u64 bio_end_offset(struct bio *bio)
449 struct bio_vec *last = &bio->bi_io_vec[bio->bi_vcnt - 1];
451 return page_offset(last->bv_page) + last->bv_len + last->bv_offset;
454 static noinline int add_ra_bio_pages(struct inode *inode,
456 struct compressed_bio *cb)
458 unsigned long end_index;
459 unsigned long pg_index;
461 u64 isize = i_size_read(inode);
464 unsigned long nr_pages = 0;
465 struct extent_map *em;
466 struct address_space *mapping = inode->i_mapping;
467 struct extent_map_tree *em_tree;
468 struct extent_io_tree *tree;
472 last_offset = bio_end_offset(cb->orig_bio);
473 em_tree = &BTRFS_I(inode)->extent_tree;
474 tree = &BTRFS_I(inode)->io_tree;
479 end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
481 while (last_offset < compressed_end) {
482 pg_index = last_offset >> PAGE_SHIFT;
484 if (pg_index > end_index)
488 page = radix_tree_lookup(&mapping->page_tree, pg_index);
490 if (page && !radix_tree_exceptional_entry(page)) {
497 page = __page_cache_alloc(mapping_gfp_constraint(mapping,
502 if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
507 end = last_offset + PAGE_SIZE - 1;
509 * at this point, we have a locked page in the page cache
510 * for these bytes in the file. But, we have to make
511 * sure they map to this compressed extent on disk.
513 set_page_extent_mapped(page);
514 lock_extent(tree, last_offset, end);
515 read_lock(&em_tree->lock);
516 em = lookup_extent_mapping(em_tree, last_offset,
518 read_unlock(&em_tree->lock);
520 if (!em || last_offset < em->start ||
521 (last_offset + PAGE_SIZE > extent_map_end(em)) ||
522 (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
524 unlock_extent(tree, last_offset, end);
531 if (page->index == end_index) {
533 size_t zero_offset = isize & (PAGE_SIZE - 1);
537 zeros = PAGE_SIZE - zero_offset;
538 userpage = kmap_atomic(page);
539 memset(userpage + zero_offset, 0, zeros);
540 flush_dcache_page(page);
541 kunmap_atomic(userpage);
545 ret = bio_add_page(cb->orig_bio, page,
548 if (ret == PAGE_SIZE) {
552 unlock_extent(tree, last_offset, end);
558 last_offset += PAGE_SIZE;
564 * for a compressed read, the bio we get passed has all the inode pages
565 * in it. We don't actually do IO on those pages but allocate new ones
566 * to hold the compressed pages on disk.
568 * bio->bi_iter.bi_sector points to the compressed extent on disk
569 * bio->bi_io_vec points to all of the inode pages
571 * After the compressed pages are read, we copy the bytes into the
572 * bio we were passed and then call the bio end_io calls
574 int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
575 int mirror_num, unsigned long bio_flags)
577 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
578 struct extent_io_tree *tree;
579 struct extent_map_tree *em_tree;
580 struct compressed_bio *cb;
581 unsigned long compressed_len;
582 unsigned long nr_pages;
583 unsigned long pg_index;
585 struct block_device *bdev;
586 struct bio *comp_bio;
587 u64 cur_disk_byte = (u64)bio->bi_iter.bi_sector << 9;
590 struct extent_map *em;
595 tree = &BTRFS_I(inode)->io_tree;
596 em_tree = &BTRFS_I(inode)->extent_tree;
598 /* we need the actual starting offset of this extent in the file */
599 read_lock(&em_tree->lock);
600 em = lookup_extent_mapping(em_tree,
601 page_offset(bio->bi_io_vec->bv_page),
603 read_unlock(&em_tree->lock);
607 compressed_len = em->block_len;
608 cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
612 atomic_set(&cb->pending_bios, 0);
615 cb->mirror_num = mirror_num;
618 cb->start = em->orig_start;
620 em_start = em->start;
625 cb->len = bio->bi_iter.bi_size;
626 cb->compressed_len = compressed_len;
627 cb->compress_type = extent_compress_type(bio_flags);
630 nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
631 cb->compressed_pages = kcalloc(nr_pages, sizeof(struct page *),
633 if (!cb->compressed_pages)
636 bdev = fs_info->fs_devices->latest_bdev;
638 for (pg_index = 0; pg_index < nr_pages; pg_index++) {
639 cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
641 if (!cb->compressed_pages[pg_index]) {
642 faili = pg_index - 1;
647 faili = nr_pages - 1;
648 cb->nr_pages = nr_pages;
650 add_ra_bio_pages(inode, em_start + em_len, cb);
652 /* include any pages we added in add_ra-bio_pages */
653 cb->len = bio->bi_iter.bi_size;
655 comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
658 bio_set_op_attrs (comp_bio, REQ_OP_READ, 0);
659 comp_bio->bi_private = cb;
660 comp_bio->bi_end_io = end_compressed_bio_read;
661 atomic_inc(&cb->pending_bios);
663 for (pg_index = 0; pg_index < nr_pages; pg_index++) {
664 page = cb->compressed_pages[pg_index];
665 page->mapping = inode->i_mapping;
666 page->index = em_start >> PAGE_SHIFT;
668 if (comp_bio->bi_iter.bi_size)
669 ret = tree->ops->merge_bio_hook(page, 0,
675 page->mapping = NULL;
676 if (ret || bio_add_page(comp_bio, page, PAGE_SIZE, 0) <
680 ret = btrfs_bio_wq_end_io(fs_info, comp_bio,
681 BTRFS_WQ_ENDIO_DATA);
682 BUG_ON(ret); /* -ENOMEM */
685 * inc the count before we submit the bio so
686 * we know the end IO handler won't happen before
687 * we inc the count. Otherwise, the cb might get
688 * freed before we're done setting it up
690 atomic_inc(&cb->pending_bios);
692 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
693 ret = btrfs_lookup_bio_sums(inode, comp_bio,
695 BUG_ON(ret); /* -ENOMEM */
697 sums += DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
698 fs_info->sectorsize);
700 ret = btrfs_map_bio(fs_info, comp_bio, mirror_num, 0);
702 comp_bio->bi_error = ret;
708 comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
711 bio_set_op_attrs(comp_bio, REQ_OP_READ, 0);
712 comp_bio->bi_private = cb;
713 comp_bio->bi_end_io = end_compressed_bio_read;
715 bio_add_page(comp_bio, page, PAGE_SIZE, 0);
717 cur_disk_byte += PAGE_SIZE;
721 ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA);
722 BUG_ON(ret); /* -ENOMEM */
724 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
725 ret = btrfs_lookup_bio_sums(inode, comp_bio, sums);
726 BUG_ON(ret); /* -ENOMEM */
729 ret = btrfs_map_bio(fs_info, comp_bio, mirror_num, 0);
731 comp_bio->bi_error = ret;
740 __free_page(cb->compressed_pages[faili]);
744 kfree(cb->compressed_pages);
753 struct list_head idle_ws;
755 /* Number of free workspaces */
757 /* Total number of allocated workspaces */
759 /* Waiters for a free workspace */
760 wait_queue_head_t ws_wait;
761 } btrfs_comp_ws[BTRFS_COMPRESS_TYPES];
763 static const struct btrfs_compress_op * const btrfs_compress_op[] = {
764 &btrfs_zlib_compress,
768 void __init btrfs_init_compress(void)
772 for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
773 struct list_head *workspace;
775 INIT_LIST_HEAD(&btrfs_comp_ws[i].idle_ws);
776 spin_lock_init(&btrfs_comp_ws[i].ws_lock);
777 atomic_set(&btrfs_comp_ws[i].total_ws, 0);
778 init_waitqueue_head(&btrfs_comp_ws[i].ws_wait);
781 * Preallocate one workspace for each compression type so
782 * we can guarantee forward progress in the worst case
784 workspace = btrfs_compress_op[i]->alloc_workspace();
785 if (IS_ERR(workspace)) {
786 pr_warn("BTRFS: cannot preallocate compression workspace, will try later\n");
788 atomic_set(&btrfs_comp_ws[i].total_ws, 1);
789 btrfs_comp_ws[i].free_ws = 1;
790 list_add(workspace, &btrfs_comp_ws[i].idle_ws);
796 * This finds an available workspace or allocates a new one.
797 * If it's not possible to allocate a new one, waits until there's one.
798 * Preallocation makes a forward progress guarantees and we do not return
801 static struct list_head *find_workspace(int type)
803 struct list_head *workspace;
804 int cpus = num_online_cpus();
807 struct list_head *idle_ws = &btrfs_comp_ws[idx].idle_ws;
808 spinlock_t *ws_lock = &btrfs_comp_ws[idx].ws_lock;
809 atomic_t *total_ws = &btrfs_comp_ws[idx].total_ws;
810 wait_queue_head_t *ws_wait = &btrfs_comp_ws[idx].ws_wait;
811 int *free_ws = &btrfs_comp_ws[idx].free_ws;
814 if (!list_empty(idle_ws)) {
815 workspace = idle_ws->next;
818 spin_unlock(ws_lock);
822 if (atomic_read(total_ws) > cpus) {
825 spin_unlock(ws_lock);
826 prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE);
827 if (atomic_read(total_ws) > cpus && !*free_ws)
829 finish_wait(ws_wait, &wait);
832 atomic_inc(total_ws);
833 spin_unlock(ws_lock);
835 workspace = btrfs_compress_op[idx]->alloc_workspace();
836 if (IS_ERR(workspace)) {
837 atomic_dec(total_ws);
841 * Do not return the error but go back to waiting. There's a
842 * workspace preallocated for each type and the compression
843 * time is bounded so we get to a workspace eventually. This
844 * makes our caller's life easier.
846 * To prevent silent and low-probability deadlocks (when the
847 * initial preallocation fails), check if there are any
850 if (atomic_read(total_ws) == 0) {
851 static DEFINE_RATELIMIT_STATE(_rs,
852 /* once per minute */ 60 * HZ,
855 if (__ratelimit(&_rs)) {
856 pr_warn("BTRFS: no compression workspaces, low memory, retrying\n");
865 * put a workspace struct back on the list or free it if we have enough
866 * idle ones sitting around
868 static void free_workspace(int type, struct list_head *workspace)
871 struct list_head *idle_ws = &btrfs_comp_ws[idx].idle_ws;
872 spinlock_t *ws_lock = &btrfs_comp_ws[idx].ws_lock;
873 atomic_t *total_ws = &btrfs_comp_ws[idx].total_ws;
874 wait_queue_head_t *ws_wait = &btrfs_comp_ws[idx].ws_wait;
875 int *free_ws = &btrfs_comp_ws[idx].free_ws;
878 if (*free_ws < num_online_cpus()) {
879 list_add(workspace, idle_ws);
881 spin_unlock(ws_lock);
884 spin_unlock(ws_lock);
886 btrfs_compress_op[idx]->free_workspace(workspace);
887 atomic_dec(total_ws);
890 * Make sure counter is updated before we wake up waiters.
893 if (waitqueue_active(ws_wait))
898 * cleanup function for module exit
900 static void free_workspaces(void)
902 struct list_head *workspace;
905 for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
906 while (!list_empty(&btrfs_comp_ws[i].idle_ws)) {
907 workspace = btrfs_comp_ws[i].idle_ws.next;
909 btrfs_compress_op[i]->free_workspace(workspace);
910 atomic_dec(&btrfs_comp_ws[i].total_ws);
916 * given an address space and start/len, compress the bytes.
918 * pages are allocated to hold the compressed result and stored
921 * out_pages is used to return the number of pages allocated. There
922 * may be pages allocated even if we return an error
924 * total_in is used to return the number of bytes actually read. It
925 * may be smaller then len if we had to exit early because we
926 * ran out of room in the pages array or because we cross the
929 * total_out is used to return the total number of compressed bytes
931 * max_out tells us the max number of bytes that we're allowed to
934 int btrfs_compress_pages(int type, struct address_space *mapping,
935 u64 start, unsigned long len,
937 unsigned long nr_dest_pages,
938 unsigned long *out_pages,
939 unsigned long *total_in,
940 unsigned long *total_out,
941 unsigned long max_out)
943 struct list_head *workspace;
946 workspace = find_workspace(type);
948 ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping,
950 nr_dest_pages, out_pages,
953 free_workspace(type, workspace);
958 * pages_in is an array of pages with compressed data.
960 * disk_start is the starting logical offset of this array in the file
962 * orig_bio contains the pages from the file that we want to decompress into
964 * srclen is the number of bytes in pages_in
966 * The basic idea is that we have a bio that was created by readpages.
967 * The pages in the bio are for the uncompressed data, and they may not
968 * be contiguous. They all correspond to the range of bytes covered by
969 * the compressed extent.
971 static int btrfs_decompress_bio(int type, struct page **pages_in,
972 u64 disk_start, struct bio *orig_bio,
975 struct list_head *workspace;
978 workspace = find_workspace(type);
980 ret = btrfs_compress_op[type-1]->decompress_bio(workspace, pages_in,
981 disk_start, orig_bio,
983 free_workspace(type, workspace);
988 * a less complex decompression routine. Our compressed data fits in a
989 * single page, and we want to read a single page out of it.
990 * start_byte tells us the offset into the compressed data we're interested in
992 int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
993 unsigned long start_byte, size_t srclen, size_t destlen)
995 struct list_head *workspace;
998 workspace = find_workspace(type);
1000 ret = btrfs_compress_op[type-1]->decompress(workspace, data_in,
1001 dest_page, start_byte,
1004 free_workspace(type, workspace);
1008 void btrfs_exit_compress(void)
1014 * Copy uncompressed data from working buffer to pages.
1016 * buf_start is the byte offset we're of the start of our workspace buffer.
1018 * total_out is the last byte of the buffer
1020 int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
1021 unsigned long total_out, u64 disk_start,
1024 unsigned long buf_offset;
1025 unsigned long current_buf_start;
1026 unsigned long start_byte;
1027 unsigned long working_bytes = total_out - buf_start;
1028 unsigned long bytes;
1030 struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter);
1033 * start byte is the first byte of the page we're currently
1034 * copying into relative to the start of the compressed data.
1036 start_byte = page_offset(bvec.bv_page) - disk_start;
1038 /* we haven't yet hit data corresponding to this page */
1039 if (total_out <= start_byte)
1043 * the start of the data we care about is offset into
1044 * the middle of our working buffer
1046 if (total_out > start_byte && buf_start < start_byte) {
1047 buf_offset = start_byte - buf_start;
1048 working_bytes -= buf_offset;
1052 current_buf_start = buf_start;
1054 /* copy bytes from the working buffer into the pages */
1055 while (working_bytes > 0) {
1056 bytes = min_t(unsigned long, bvec.bv_len,
1057 PAGE_SIZE - buf_offset);
1058 bytes = min(bytes, working_bytes);
1060 kaddr = kmap_atomic(bvec.bv_page);
1061 memcpy(kaddr + bvec.bv_offset, buf + buf_offset, bytes);
1062 kunmap_atomic(kaddr);
1063 flush_dcache_page(bvec.bv_page);
1065 buf_offset += bytes;
1066 working_bytes -= bytes;
1067 current_buf_start += bytes;
1069 /* check if we need to pick another page */
1070 bio_advance(bio, bytes);
1071 if (!bio->bi_iter.bi_size)
1073 bvec = bio_iter_iovec(bio, bio->bi_iter);
1075 start_byte = page_offset(bvec.bv_page) - disk_start;
1078 * make sure our new page is covered by this
1081 if (total_out <= start_byte)
1085 * the next page in the biovec might not be adjacent
1086 * to the last page, but it might still be found
1087 * inside this working buffer. bump our offset pointer
1089 if (total_out > start_byte &&
1090 current_buf_start < start_byte) {
1091 buf_offset = start_byte - buf_start;
1092 working_bytes = total_out - start_byte;
1093 current_buf_start = buf_start + buf_offset;