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_biovec(int type, struct page **pages_in,
85 u64 disk_start, struct bio_vec *bvec,
86 int vcnt, size_t srclen);
88 static inline int compressed_bio_size(struct btrfs_root *root,
89 unsigned long disk_size)
91 u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
93 return sizeof(struct compressed_bio) +
94 (DIV_ROUND_UP(disk_size, root->sectorsize)) * csum_size;
97 static struct bio *compressed_bio_alloc(struct block_device *bdev,
98 u64 first_byte, gfp_t gfp_flags)
102 nr_vecs = bio_get_nr_vecs(bdev);
103 return btrfs_bio_alloc(bdev, first_byte >> 9, nr_vecs, gfp_flags);
106 static int check_compressed_csum(struct inode *inode,
107 struct compressed_bio *cb,
115 u32 *cb_sum = &cb->sums;
117 if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
120 for (i = 0; i < cb->nr_pages; i++) {
121 page = cb->compressed_pages[i];
124 kaddr = kmap_atomic(page);
125 csum = btrfs_csum_data(kaddr, csum, PAGE_CACHE_SIZE);
126 btrfs_csum_final(csum, (char *)&csum);
127 kunmap_atomic(kaddr);
129 if (csum != *cb_sum) {
130 btrfs_info(BTRFS_I(inode)->root->fs_info,
131 "csum failed ino %llu extent %llu csum %u wanted %u mirror %d",
132 btrfs_ino(inode), disk_start, csum, *cb_sum,
145 /* when we finish reading compressed pages from the disk, we
146 * decompress them and then run the bio end_io routines on the
147 * decompressed pages (in the inode address space).
149 * This allows the checksumming and other IO error handling routines
152 * The compressed pages are freed here, and it must be run
155 static void end_compressed_bio_read(struct bio *bio, int err)
157 struct compressed_bio *cb = bio->bi_private;
166 /* if there are more bios still pending for this compressed
169 if (!atomic_dec_and_test(&cb->pending_bios))
173 ret = check_compressed_csum(inode, cb,
174 (u64)bio->bi_iter.bi_sector << 9);
178 /* ok, we're the last bio for this extent, lets start
181 ret = btrfs_decompress_biovec(cb->compress_type,
182 cb->compressed_pages,
184 cb->orig_bio->bi_io_vec,
185 cb->orig_bio->bi_vcnt,
191 /* release the compressed pages */
193 for (index = 0; index < cb->nr_pages; index++) {
194 page = cb->compressed_pages[index];
195 page->mapping = NULL;
196 page_cache_release(page);
199 /* do io completion on the original bio */
201 bio_io_error(cb->orig_bio);
204 struct bio_vec *bvec;
207 * we have verified the checksum already, set page
208 * checked so the end_io handlers know about it
210 bio_for_each_segment_all(bvec, cb->orig_bio, i)
211 SetPageChecked(bvec->bv_page);
213 bio_endio(cb->orig_bio, 0);
216 /* finally free the cb struct */
217 kfree(cb->compressed_pages);
224 * Clear the writeback bits on all of the file
225 * pages for a compressed write
227 static noinline void end_compressed_writeback(struct inode *inode, u64 start,
228 unsigned long ram_size)
230 unsigned long index = start >> PAGE_CACHE_SHIFT;
231 unsigned long end_index = (start + ram_size - 1) >> PAGE_CACHE_SHIFT;
232 struct page *pages[16];
233 unsigned long nr_pages = end_index - index + 1;
237 while (nr_pages > 0) {
238 ret = find_get_pages_contig(inode->i_mapping, index,
240 nr_pages, ARRAY_SIZE(pages)), pages);
246 for (i = 0; i < ret; i++) {
247 end_page_writeback(pages[i]);
248 page_cache_release(pages[i]);
253 /* the inode may be gone now */
257 * do the cleanup once all the compressed pages hit the disk.
258 * This will clear writeback on the file pages and free the compressed
261 * This also calls the writeback end hooks for the file pages so that
262 * metadata and checksums can be updated in the file.
264 static void end_compressed_bio_write(struct bio *bio, int err)
266 struct extent_io_tree *tree;
267 struct compressed_bio *cb = bio->bi_private;
275 /* if there are more bios still pending for this compressed
278 if (!atomic_dec_and_test(&cb->pending_bios))
281 /* ok, we're the last bio for this extent, step one is to
282 * call back into the FS and do all the end_io operations
285 tree = &BTRFS_I(inode)->io_tree;
286 cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
287 tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
289 cb->start + cb->len - 1,
291 cb->compressed_pages[0]->mapping = NULL;
293 end_compressed_writeback(inode, cb->start, cb->len);
294 /* note, our inode could be gone now */
297 * release the compressed pages, these came from alloc_page and
298 * are not attached to the inode at all
301 for (index = 0; index < cb->nr_pages; index++) {
302 page = cb->compressed_pages[index];
303 page->mapping = NULL;
304 page_cache_release(page);
307 /* finally free the cb struct */
308 kfree(cb->compressed_pages);
315 * worker function to build and submit bios for previously compressed pages.
316 * The corresponding pages in the inode should be marked for writeback
317 * and the compressed pages should have a reference on them for dropping
318 * when the IO is complete.
320 * This also checksums the file bytes and gets things ready for
323 int btrfs_submit_compressed_write(struct inode *inode, u64 start,
324 unsigned long len, u64 disk_start,
325 unsigned long compressed_len,
326 struct page **compressed_pages,
327 unsigned long nr_pages)
329 struct bio *bio = NULL;
330 struct btrfs_root *root = BTRFS_I(inode)->root;
331 struct compressed_bio *cb;
332 unsigned long bytes_left;
333 struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
336 u64 first_byte = disk_start;
337 struct block_device *bdev;
339 int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
341 WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1));
342 cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
345 atomic_set(&cb->pending_bios, 0);
351 cb->compressed_pages = compressed_pages;
352 cb->compressed_len = compressed_len;
354 cb->nr_pages = nr_pages;
356 bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
358 bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
363 bio->bi_private = cb;
364 bio->bi_end_io = end_compressed_bio_write;
365 atomic_inc(&cb->pending_bios);
367 /* create and submit bios for the compressed pages */
368 bytes_left = compressed_len;
369 for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
370 page = compressed_pages[pg_index];
371 page->mapping = inode->i_mapping;
372 if (bio->bi_iter.bi_size)
373 ret = io_tree->ops->merge_bio_hook(WRITE, page, 0,
379 page->mapping = NULL;
380 if (ret || bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) <
385 * inc the count before we submit the bio so
386 * we know the end IO handler won't happen before
387 * we inc the count. Otherwise, the cb might get
388 * freed before we're done setting it up
390 atomic_inc(&cb->pending_bios);
391 ret = btrfs_bio_wq_end_io(root->fs_info, bio,
392 BTRFS_WQ_ENDIO_DATA);
393 BUG_ON(ret); /* -ENOMEM */
396 ret = btrfs_csum_one_bio(root, inode, bio,
398 BUG_ON(ret); /* -ENOMEM */
401 ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
402 BUG_ON(ret); /* -ENOMEM */
406 bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
408 bio->bi_private = cb;
409 bio->bi_end_io = end_compressed_bio_write;
410 bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
412 if (bytes_left < PAGE_CACHE_SIZE) {
413 btrfs_info(BTRFS_I(inode)->root->fs_info,
414 "bytes left %lu compress len %lu nr %lu",
415 bytes_left, cb->compressed_len, cb->nr_pages);
417 bytes_left -= PAGE_CACHE_SIZE;
418 first_byte += PAGE_CACHE_SIZE;
423 ret = btrfs_bio_wq_end_io(root->fs_info, bio, BTRFS_WQ_ENDIO_DATA);
424 BUG_ON(ret); /* -ENOMEM */
427 ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
428 BUG_ON(ret); /* -ENOMEM */
431 ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
432 BUG_ON(ret); /* -ENOMEM */
438 static noinline int add_ra_bio_pages(struct inode *inode,
440 struct compressed_bio *cb)
442 unsigned long end_index;
443 unsigned long pg_index;
445 u64 isize = i_size_read(inode);
448 unsigned long nr_pages = 0;
449 struct extent_map *em;
450 struct address_space *mapping = inode->i_mapping;
451 struct extent_map_tree *em_tree;
452 struct extent_io_tree *tree;
456 page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page;
457 last_offset = (page_offset(page) + PAGE_CACHE_SIZE);
458 em_tree = &BTRFS_I(inode)->extent_tree;
459 tree = &BTRFS_I(inode)->io_tree;
464 end_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
466 while (last_offset < compressed_end) {
467 pg_index = last_offset >> PAGE_CACHE_SHIFT;
469 if (pg_index > end_index)
473 page = radix_tree_lookup(&mapping->page_tree, pg_index);
475 if (page && !radix_tree_exceptional_entry(page)) {
482 page = __page_cache_alloc(mapping_gfp_mask(mapping) &
487 if (add_to_page_cache_lru(page, mapping, pg_index,
489 page_cache_release(page);
493 end = last_offset + PAGE_CACHE_SIZE - 1;
495 * at this point, we have a locked page in the page cache
496 * for these bytes in the file. But, we have to make
497 * sure they map to this compressed extent on disk.
499 set_page_extent_mapped(page);
500 lock_extent(tree, last_offset, end);
501 read_lock(&em_tree->lock);
502 em = lookup_extent_mapping(em_tree, last_offset,
504 read_unlock(&em_tree->lock);
506 if (!em || last_offset < em->start ||
507 (last_offset + PAGE_CACHE_SIZE > extent_map_end(em)) ||
508 (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
510 unlock_extent(tree, last_offset, end);
512 page_cache_release(page);
517 if (page->index == end_index) {
519 size_t zero_offset = isize & (PAGE_CACHE_SIZE - 1);
523 zeros = PAGE_CACHE_SIZE - zero_offset;
524 userpage = kmap_atomic(page);
525 memset(userpage + zero_offset, 0, zeros);
526 flush_dcache_page(page);
527 kunmap_atomic(userpage);
531 ret = bio_add_page(cb->orig_bio, page,
534 if (ret == PAGE_CACHE_SIZE) {
536 page_cache_release(page);
538 unlock_extent(tree, last_offset, end);
540 page_cache_release(page);
544 last_offset += PAGE_CACHE_SIZE;
550 * for a compressed read, the bio we get passed has all the inode pages
551 * in it. We don't actually do IO on those pages but allocate new ones
552 * to hold the compressed pages on disk.
554 * bio->bi_iter.bi_sector points to the compressed extent on disk
555 * bio->bi_io_vec points to all of the inode pages
556 * bio->bi_vcnt is a count of pages
558 * After the compressed pages are read, we copy the bytes into the
559 * bio we were passed and then call the bio end_io calls
561 int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
562 int mirror_num, unsigned long bio_flags)
564 struct extent_io_tree *tree;
565 struct extent_map_tree *em_tree;
566 struct compressed_bio *cb;
567 struct btrfs_root *root = BTRFS_I(inode)->root;
568 unsigned long uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
569 unsigned long compressed_len;
570 unsigned long nr_pages;
571 unsigned long pg_index;
573 struct block_device *bdev;
574 struct bio *comp_bio;
575 u64 cur_disk_byte = (u64)bio->bi_iter.bi_sector << 9;
578 struct extent_map *em;
583 tree = &BTRFS_I(inode)->io_tree;
584 em_tree = &BTRFS_I(inode)->extent_tree;
586 /* we need the actual starting offset of this extent in the file */
587 read_lock(&em_tree->lock);
588 em = lookup_extent_mapping(em_tree,
589 page_offset(bio->bi_io_vec->bv_page),
591 read_unlock(&em_tree->lock);
595 compressed_len = em->block_len;
596 cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
600 atomic_set(&cb->pending_bios, 0);
603 cb->mirror_num = mirror_num;
606 cb->start = em->orig_start;
608 em_start = em->start;
613 cb->len = uncompressed_len;
614 cb->compressed_len = compressed_len;
615 cb->compress_type = extent_compress_type(bio_flags);
618 nr_pages = DIV_ROUND_UP(compressed_len, PAGE_CACHE_SIZE);
619 cb->compressed_pages = kzalloc(sizeof(struct page *) * nr_pages,
621 if (!cb->compressed_pages)
624 bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
626 for (pg_index = 0; pg_index < nr_pages; pg_index++) {
627 cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
629 if (!cb->compressed_pages[pg_index]) {
630 faili = pg_index - 1;
635 faili = nr_pages - 1;
636 cb->nr_pages = nr_pages;
638 /* In the parent-locked case, we only locked the range we are
639 * interested in. In all other cases, we can opportunistically
640 * cache decompressed data that goes beyond the requested range. */
641 if (!(bio_flags & EXTENT_BIO_PARENT_LOCKED))
642 add_ra_bio_pages(inode, em_start + em_len, cb);
644 /* include any pages we added in add_ra-bio_pages */
645 uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
646 cb->len = uncompressed_len;
648 comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
651 comp_bio->bi_private = cb;
652 comp_bio->bi_end_io = end_compressed_bio_read;
653 atomic_inc(&cb->pending_bios);
655 for (pg_index = 0; pg_index < nr_pages; pg_index++) {
656 page = cb->compressed_pages[pg_index];
657 page->mapping = inode->i_mapping;
658 page->index = em_start >> PAGE_CACHE_SHIFT;
660 if (comp_bio->bi_iter.bi_size)
661 ret = tree->ops->merge_bio_hook(READ, page, 0,
667 page->mapping = NULL;
668 if (ret || bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0) <
672 ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio,
673 BTRFS_WQ_ENDIO_DATA);
674 BUG_ON(ret); /* -ENOMEM */
677 * inc the count before we submit the bio so
678 * we know the end IO handler won't happen before
679 * we inc the count. Otherwise, the cb might get
680 * freed before we're done setting it up
682 atomic_inc(&cb->pending_bios);
684 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
685 ret = btrfs_lookup_bio_sums(root, inode,
687 BUG_ON(ret); /* -ENOMEM */
689 sums += DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
692 ret = btrfs_map_bio(root, READ, comp_bio,
695 bio_endio(comp_bio, ret);
699 comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
702 comp_bio->bi_private = cb;
703 comp_bio->bi_end_io = end_compressed_bio_read;
705 bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0);
707 cur_disk_byte += PAGE_CACHE_SIZE;
711 ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio,
712 BTRFS_WQ_ENDIO_DATA);
713 BUG_ON(ret); /* -ENOMEM */
715 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
716 ret = btrfs_lookup_bio_sums(root, inode, comp_bio, sums);
717 BUG_ON(ret); /* -ENOMEM */
720 ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
722 bio_endio(comp_bio, ret);
729 __free_page(cb->compressed_pages[faili]);
733 kfree(cb->compressed_pages);
741 static struct list_head comp_idle_workspace[BTRFS_COMPRESS_TYPES];
742 static spinlock_t comp_workspace_lock[BTRFS_COMPRESS_TYPES];
743 static int comp_num_workspace[BTRFS_COMPRESS_TYPES];
744 static atomic_t comp_alloc_workspace[BTRFS_COMPRESS_TYPES];
745 static wait_queue_head_t comp_workspace_wait[BTRFS_COMPRESS_TYPES];
747 static struct btrfs_compress_op *btrfs_compress_op[] = {
748 &btrfs_zlib_compress,
752 void __init btrfs_init_compress(void)
756 for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
757 INIT_LIST_HEAD(&comp_idle_workspace[i]);
758 spin_lock_init(&comp_workspace_lock[i]);
759 atomic_set(&comp_alloc_workspace[i], 0);
760 init_waitqueue_head(&comp_workspace_wait[i]);
765 * this finds an available workspace or allocates a new one
766 * ERR_PTR is returned if things go bad.
768 static struct list_head *find_workspace(int type)
770 struct list_head *workspace;
771 int cpus = num_online_cpus();
774 struct list_head *idle_workspace = &comp_idle_workspace[idx];
775 spinlock_t *workspace_lock = &comp_workspace_lock[idx];
776 atomic_t *alloc_workspace = &comp_alloc_workspace[idx];
777 wait_queue_head_t *workspace_wait = &comp_workspace_wait[idx];
778 int *num_workspace = &comp_num_workspace[idx];
780 spin_lock(workspace_lock);
781 if (!list_empty(idle_workspace)) {
782 workspace = idle_workspace->next;
785 spin_unlock(workspace_lock);
789 if (atomic_read(alloc_workspace) > cpus) {
792 spin_unlock(workspace_lock);
793 prepare_to_wait(workspace_wait, &wait, TASK_UNINTERRUPTIBLE);
794 if (atomic_read(alloc_workspace) > cpus && !*num_workspace)
796 finish_wait(workspace_wait, &wait);
799 atomic_inc(alloc_workspace);
800 spin_unlock(workspace_lock);
802 workspace = btrfs_compress_op[idx]->alloc_workspace();
803 if (IS_ERR(workspace)) {
804 atomic_dec(alloc_workspace);
805 wake_up(workspace_wait);
811 * put a workspace struct back on the list or free it if we have enough
812 * idle ones sitting around
814 static void free_workspace(int type, struct list_head *workspace)
817 struct list_head *idle_workspace = &comp_idle_workspace[idx];
818 spinlock_t *workspace_lock = &comp_workspace_lock[idx];
819 atomic_t *alloc_workspace = &comp_alloc_workspace[idx];
820 wait_queue_head_t *workspace_wait = &comp_workspace_wait[idx];
821 int *num_workspace = &comp_num_workspace[idx];
823 spin_lock(workspace_lock);
824 if (*num_workspace < num_online_cpus()) {
825 list_add(workspace, idle_workspace);
827 spin_unlock(workspace_lock);
830 spin_unlock(workspace_lock);
832 btrfs_compress_op[idx]->free_workspace(workspace);
833 atomic_dec(alloc_workspace);
836 if (waitqueue_active(workspace_wait))
837 wake_up(workspace_wait);
841 * cleanup function for module exit
843 static void free_workspaces(void)
845 struct list_head *workspace;
848 for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
849 while (!list_empty(&comp_idle_workspace[i])) {
850 workspace = comp_idle_workspace[i].next;
852 btrfs_compress_op[i]->free_workspace(workspace);
853 atomic_dec(&comp_alloc_workspace[i]);
859 * given an address space and start/len, compress the bytes.
861 * pages are allocated to hold the compressed result and stored
864 * out_pages is used to return the number of pages allocated. There
865 * may be pages allocated even if we return an error
867 * total_in is used to return the number of bytes actually read. It
868 * may be smaller then len if we had to exit early because we
869 * ran out of room in the pages array or because we cross the
872 * total_out is used to return the total number of compressed bytes
874 * max_out tells us the max number of bytes that we're allowed to
877 int btrfs_compress_pages(int type, struct address_space *mapping,
878 u64 start, unsigned long len,
880 unsigned long nr_dest_pages,
881 unsigned long *out_pages,
882 unsigned long *total_in,
883 unsigned long *total_out,
884 unsigned long max_out)
886 struct list_head *workspace;
889 workspace = find_workspace(type);
890 if (IS_ERR(workspace))
891 return PTR_ERR(workspace);
893 ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping,
895 nr_dest_pages, out_pages,
898 free_workspace(type, workspace);
903 * pages_in is an array of pages with compressed data.
905 * disk_start is the starting logical offset of this array in the file
907 * bvec is a bio_vec of pages from the file that we want to decompress into
909 * vcnt is the count of pages in the biovec
911 * srclen is the number of bytes in pages_in
913 * The basic idea is that we have a bio that was created by readpages.
914 * The pages in the bio are for the uncompressed data, and they may not
915 * be contiguous. They all correspond to the range of bytes covered by
916 * the compressed extent.
918 static int btrfs_decompress_biovec(int type, struct page **pages_in,
919 u64 disk_start, struct bio_vec *bvec,
920 int vcnt, size_t srclen)
922 struct list_head *workspace;
925 workspace = find_workspace(type);
926 if (IS_ERR(workspace))
927 return PTR_ERR(workspace);
929 ret = btrfs_compress_op[type-1]->decompress_biovec(workspace, pages_in,
932 free_workspace(type, workspace);
937 * a less complex decompression routine. Our compressed data fits in a
938 * single page, and we want to read a single page out of it.
939 * start_byte tells us the offset into the compressed data we're interested in
941 int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
942 unsigned long start_byte, size_t srclen, size_t destlen)
944 struct list_head *workspace;
947 workspace = find_workspace(type);
948 if (IS_ERR(workspace))
949 return PTR_ERR(workspace);
951 ret = btrfs_compress_op[type-1]->decompress(workspace, data_in,
952 dest_page, start_byte,
955 free_workspace(type, workspace);
959 void btrfs_exit_compress(void)
965 * Copy uncompressed data from working buffer to pages.
967 * buf_start is the byte offset we're of the start of our workspace buffer.
969 * total_out is the last byte of the buffer
971 int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
972 unsigned long total_out, u64 disk_start,
973 struct bio_vec *bvec, int vcnt,
974 unsigned long *pg_index,
975 unsigned long *pg_offset)
977 unsigned long buf_offset;
978 unsigned long current_buf_start;
979 unsigned long start_byte;
980 unsigned long working_bytes = total_out - buf_start;
983 struct page *page_out = bvec[*pg_index].bv_page;
986 * start byte is the first byte of the page we're currently
987 * copying into relative to the start of the compressed data.
989 start_byte = page_offset(page_out) - disk_start;
991 /* we haven't yet hit data corresponding to this page */
992 if (total_out <= start_byte)
996 * the start of the data we care about is offset into
997 * the middle of our working buffer
999 if (total_out > start_byte && buf_start < start_byte) {
1000 buf_offset = start_byte - buf_start;
1001 working_bytes -= buf_offset;
1005 current_buf_start = buf_start;
1007 /* copy bytes from the working buffer into the pages */
1008 while (working_bytes > 0) {
1009 bytes = min(PAGE_CACHE_SIZE - *pg_offset,
1010 PAGE_CACHE_SIZE - buf_offset);
1011 bytes = min(bytes, working_bytes);
1012 kaddr = kmap_atomic(page_out);
1013 memcpy(kaddr + *pg_offset, buf + buf_offset, bytes);
1014 kunmap_atomic(kaddr);
1015 flush_dcache_page(page_out);
1017 *pg_offset += bytes;
1018 buf_offset += bytes;
1019 working_bytes -= bytes;
1020 current_buf_start += bytes;
1022 /* check if we need to pick another page */
1023 if (*pg_offset == PAGE_CACHE_SIZE) {
1025 if (*pg_index >= vcnt)
1028 page_out = bvec[*pg_index].bv_page;
1030 start_byte = page_offset(page_out) - disk_start;
1033 * make sure our new page is covered by this
1036 if (total_out <= start_byte)
1040 * the next page in the biovec might not be adjacent
1041 * to the last page, but it might still be found
1042 * inside this working buffer. bump our offset pointer
1044 if (total_out > start_byte &&
1045 current_buf_start < start_byte) {
1046 buf_offset = start_byte - buf_start;
1047 working_bytes = total_out - start_byte;
1048 current_buf_start = buf_start + buf_offset;
1057 * When uncompressing data, we need to make sure and zero any parts of
1058 * the biovec that were not filled in by the decompression code. pg_index
1059 * and pg_offset indicate the last page and the last offset of that page
1060 * that have been filled in. This will zero everything remaining in the
1063 void btrfs_clear_biovec_end(struct bio_vec *bvec, int vcnt,
1064 unsigned long pg_index,
1065 unsigned long pg_offset)
1067 while (pg_index < vcnt) {
1068 struct page *page = bvec[pg_index].bv_page;
1069 unsigned long off = bvec[pg_index].bv_offset;
1070 unsigned long len = bvec[pg_index].bv_len;
1072 if (pg_offset < off)
1074 if (pg_offset < off + len) {
1075 unsigned long bytes = off + len - pg_offset;
1078 kaddr = kmap_atomic(page);
1079 memset(kaddr + pg_offset, 0, bytes);
1080 kunmap_atomic(kaddr);