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)
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, (char *)&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_biovec(cb->compress_type,
179 cb->compressed_pages,
181 cb->orig_bio->bi_io_vec,
182 cb->orig_bio->bi_vcnt,
188 /* release the compressed pages */
190 for (index = 0; index < cb->nr_pages; index++) {
191 page = cb->compressed_pages[index];
192 page->mapping = NULL;
196 /* do io completion on the original bio */
198 bio_io_error(cb->orig_bio);
201 struct bio_vec *bvec;
204 * we have verified the checksum already, set page
205 * checked so the end_io handlers know about it
207 bio_for_each_segment_all(bvec, cb->orig_bio, i)
208 SetPageChecked(bvec->bv_page);
210 bio_endio(cb->orig_bio);
213 /* finally free the cb struct */
214 kfree(cb->compressed_pages);
221 * Clear the writeback bits on all of the file
222 * pages for a compressed write
224 static noinline void end_compressed_writeback(struct inode *inode,
225 const struct compressed_bio *cb)
227 unsigned long index = cb->start >> PAGE_SHIFT;
228 unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT;
229 struct page *pages[16];
230 unsigned long nr_pages = end_index - index + 1;
235 mapping_set_error(inode->i_mapping, -EIO);
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++) {
248 SetPageError(pages[i]);
249 end_page_writeback(pages[i]);
255 /* the inode may be gone now */
259 * do the cleanup once all the compressed pages hit the disk.
260 * This will clear writeback on the file pages and free the compressed
263 * This also calls the writeback end hooks for the file pages so that
264 * metadata and checksums can be updated in the file.
266 static void end_compressed_bio_write(struct bio *bio)
268 struct extent_io_tree *tree;
269 struct compressed_bio *cb = bio->bi_private;
277 /* if there are more bios still pending for this compressed
280 if (!atomic_dec_and_test(&cb->pending_bios))
283 /* ok, we're the last bio for this extent, step one is to
284 * call back into the FS and do all the end_io operations
287 tree = &BTRFS_I(inode)->io_tree;
288 cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
289 tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
291 cb->start + cb->len - 1,
293 bio->bi_error ? 0 : 1);
294 cb->compressed_pages[0]->mapping = NULL;
296 end_compressed_writeback(inode, cb);
297 /* note, our inode could be gone now */
300 * release the compressed pages, these came from alloc_page and
301 * are not attached to the inode at all
304 for (index = 0; index < cb->nr_pages; index++) {
305 page = cb->compressed_pages[index];
306 page->mapping = NULL;
310 /* finally free the cb struct */
311 kfree(cb->compressed_pages);
318 * worker function to build and submit bios for previously compressed pages.
319 * The corresponding pages in the inode should be marked for writeback
320 * and the compressed pages should have a reference on them for dropping
321 * when the IO is complete.
323 * This also checksums the file bytes and gets things ready for
326 int btrfs_submit_compressed_write(struct inode *inode, u64 start,
327 unsigned long len, u64 disk_start,
328 unsigned long compressed_len,
329 struct page **compressed_pages,
330 unsigned long nr_pages)
332 struct bio *bio = NULL;
333 struct btrfs_root *root = BTRFS_I(inode)->root;
334 struct compressed_bio *cb;
335 unsigned long bytes_left;
336 struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
339 u64 first_byte = disk_start;
340 struct block_device *bdev;
342 int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
344 WARN_ON(start & ((u64)PAGE_SIZE - 1));
345 cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
348 atomic_set(&cb->pending_bios, 0);
354 cb->compressed_pages = compressed_pages;
355 cb->compressed_len = compressed_len;
357 cb->nr_pages = nr_pages;
359 bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
361 bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
366 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
367 bio->bi_private = cb;
368 bio->bi_end_io = end_compressed_bio_write;
369 atomic_inc(&cb->pending_bios);
371 /* create and submit bios for the compressed pages */
372 bytes_left = compressed_len;
373 for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
374 page = compressed_pages[pg_index];
375 page->mapping = inode->i_mapping;
376 if (bio->bi_iter.bi_size)
377 ret = io_tree->ops->merge_bio_hook(page, 0,
383 page->mapping = NULL;
384 if (ret || bio_add_page(bio, page, PAGE_SIZE, 0) <
389 * inc the count before we submit the bio so
390 * we know the end IO handler won't happen before
391 * we inc the count. Otherwise, the cb might get
392 * freed before we're done setting it up
394 atomic_inc(&cb->pending_bios);
395 ret = btrfs_bio_wq_end_io(root->fs_info, bio,
396 BTRFS_WQ_ENDIO_DATA);
397 BUG_ON(ret); /* -ENOMEM */
400 ret = btrfs_csum_one_bio(root, inode, bio,
402 BUG_ON(ret); /* -ENOMEM */
405 ret = btrfs_map_bio(root, bio, 0, 1);
406 BUG_ON(ret); /* -ENOMEM */
410 bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
412 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
413 bio->bi_private = cb;
414 bio->bi_end_io = end_compressed_bio_write;
415 bio_add_page(bio, page, PAGE_SIZE, 0);
417 if (bytes_left < PAGE_SIZE) {
418 btrfs_info(BTRFS_I(inode)->root->fs_info,
419 "bytes left %lu compress len %lu nr %lu",
420 bytes_left, cb->compressed_len, cb->nr_pages);
422 bytes_left -= PAGE_SIZE;
423 first_byte += PAGE_SIZE;
428 ret = btrfs_bio_wq_end_io(root->fs_info, bio, BTRFS_WQ_ENDIO_DATA);
429 BUG_ON(ret); /* -ENOMEM */
432 ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
433 BUG_ON(ret); /* -ENOMEM */
436 ret = btrfs_map_bio(root, bio, 0, 1);
437 BUG_ON(ret); /* -ENOMEM */
443 static noinline int add_ra_bio_pages(struct inode *inode,
445 struct compressed_bio *cb)
447 unsigned long end_index;
448 unsigned long pg_index;
450 u64 isize = i_size_read(inode);
453 unsigned long nr_pages = 0;
454 struct extent_map *em;
455 struct address_space *mapping = inode->i_mapping;
456 struct extent_map_tree *em_tree;
457 struct extent_io_tree *tree;
461 page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page;
462 last_offset = (page_offset(page) + PAGE_SIZE);
463 em_tree = &BTRFS_I(inode)->extent_tree;
464 tree = &BTRFS_I(inode)->io_tree;
469 end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
471 while (last_offset < compressed_end) {
472 pg_index = last_offset >> PAGE_SHIFT;
474 if (pg_index > end_index)
478 page = radix_tree_lookup(&mapping->page_tree, pg_index);
480 if (page && !radix_tree_exceptional_entry(page)) {
487 page = __page_cache_alloc(mapping_gfp_constraint(mapping,
492 if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
497 end = last_offset + PAGE_SIZE - 1;
499 * at this point, we have a locked page in the page cache
500 * for these bytes in the file. But, we have to make
501 * sure they map to this compressed extent on disk.
503 set_page_extent_mapped(page);
504 lock_extent(tree, last_offset, end);
505 read_lock(&em_tree->lock);
506 em = lookup_extent_mapping(em_tree, last_offset,
508 read_unlock(&em_tree->lock);
510 if (!em || last_offset < em->start ||
511 (last_offset + PAGE_SIZE > extent_map_end(em)) ||
512 (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
514 unlock_extent(tree, last_offset, end);
521 if (page->index == end_index) {
523 size_t zero_offset = isize & (PAGE_SIZE - 1);
527 zeros = PAGE_SIZE - zero_offset;
528 userpage = kmap_atomic(page);
529 memset(userpage + zero_offset, 0, zeros);
530 flush_dcache_page(page);
531 kunmap_atomic(userpage);
535 ret = bio_add_page(cb->orig_bio, page,
538 if (ret == PAGE_SIZE) {
542 unlock_extent(tree, last_offset, end);
548 last_offset += PAGE_SIZE;
554 * for a compressed read, the bio we get passed has all the inode pages
555 * in it. We don't actually do IO on those pages but allocate new ones
556 * to hold the compressed pages on disk.
558 * bio->bi_iter.bi_sector points to the compressed extent on disk
559 * bio->bi_io_vec points to all of the inode pages
560 * bio->bi_vcnt is a count of pages
562 * After the compressed pages are read, we copy the bytes into the
563 * bio we were passed and then call the bio end_io calls
565 int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
566 int mirror_num, unsigned long bio_flags)
568 struct extent_io_tree *tree;
569 struct extent_map_tree *em_tree;
570 struct compressed_bio *cb;
571 struct btrfs_root *root = BTRFS_I(inode)->root;
572 unsigned long uncompressed_len = bio->bi_vcnt * PAGE_SIZE;
573 unsigned long compressed_len;
574 unsigned long nr_pages;
575 unsigned long pg_index;
577 struct block_device *bdev;
578 struct bio *comp_bio;
579 u64 cur_disk_byte = (u64)bio->bi_iter.bi_sector << 9;
582 struct extent_map *em;
587 tree = &BTRFS_I(inode)->io_tree;
588 em_tree = &BTRFS_I(inode)->extent_tree;
590 /* we need the actual starting offset of this extent in the file */
591 read_lock(&em_tree->lock);
592 em = lookup_extent_mapping(em_tree,
593 page_offset(bio->bi_io_vec->bv_page),
595 read_unlock(&em_tree->lock);
599 compressed_len = em->block_len;
600 cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
604 atomic_set(&cb->pending_bios, 0);
607 cb->mirror_num = mirror_num;
610 cb->start = em->orig_start;
612 em_start = em->start;
617 cb->len = uncompressed_len;
618 cb->compressed_len = compressed_len;
619 cb->compress_type = extent_compress_type(bio_flags);
622 nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
623 cb->compressed_pages = kcalloc(nr_pages, sizeof(struct page *),
625 if (!cb->compressed_pages)
628 bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
630 for (pg_index = 0; pg_index < nr_pages; pg_index++) {
631 cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
633 if (!cb->compressed_pages[pg_index]) {
634 faili = pg_index - 1;
639 faili = nr_pages - 1;
640 cb->nr_pages = nr_pages;
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_SIZE;
646 cb->len = uncompressed_len;
648 comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
651 bio_set_op_attrs (comp_bio, REQ_OP_READ, 0);
652 comp_bio->bi_private = cb;
653 comp_bio->bi_end_io = end_compressed_bio_read;
654 atomic_inc(&cb->pending_bios);
656 for (pg_index = 0; pg_index < nr_pages; pg_index++) {
657 page = cb->compressed_pages[pg_index];
658 page->mapping = inode->i_mapping;
659 page->index = em_start >> PAGE_SHIFT;
661 if (comp_bio->bi_iter.bi_size)
662 ret = tree->ops->merge_bio_hook(page, 0,
668 page->mapping = NULL;
669 if (ret || bio_add_page(comp_bio, page, PAGE_SIZE, 0) <
673 ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio,
674 BTRFS_WQ_ENDIO_DATA);
675 BUG_ON(ret); /* -ENOMEM */
678 * inc the count before we submit the bio so
679 * we know the end IO handler won't happen before
680 * we inc the count. Otherwise, the cb might get
681 * freed before we're done setting it up
683 atomic_inc(&cb->pending_bios);
685 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
686 ret = btrfs_lookup_bio_sums(root, inode,
688 BUG_ON(ret); /* -ENOMEM */
690 sums += DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
693 ret = btrfs_map_bio(root, comp_bio, mirror_num, 0);
701 comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
704 bio_set_op_attrs(comp_bio, REQ_OP_READ, 0);
705 comp_bio->bi_private = cb;
706 comp_bio->bi_end_io = end_compressed_bio_read;
708 bio_add_page(comp_bio, page, PAGE_SIZE, 0);
710 cur_disk_byte += PAGE_SIZE;
714 ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio,
715 BTRFS_WQ_ENDIO_DATA);
716 BUG_ON(ret); /* -ENOMEM */
718 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
719 ret = btrfs_lookup_bio_sums(root, inode, comp_bio, sums);
720 BUG_ON(ret); /* -ENOMEM */
723 ret = btrfs_map_bio(root, comp_bio, mirror_num, 0);
734 __free_page(cb->compressed_pages[faili]);
738 kfree(cb->compressed_pages);
747 struct list_head idle_ws;
749 /* Number of free workspaces */
751 /* Total number of allocated workspaces */
753 /* Waiters for a free workspace */
754 wait_queue_head_t ws_wait;
755 } btrfs_comp_ws[BTRFS_COMPRESS_TYPES];
757 static const struct btrfs_compress_op * const btrfs_compress_op[] = {
758 &btrfs_zlib_compress,
762 void __init btrfs_init_compress(void)
766 for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
767 struct list_head *workspace;
769 INIT_LIST_HEAD(&btrfs_comp_ws[i].idle_ws);
770 spin_lock_init(&btrfs_comp_ws[i].ws_lock);
771 atomic_set(&btrfs_comp_ws[i].total_ws, 0);
772 init_waitqueue_head(&btrfs_comp_ws[i].ws_wait);
775 * Preallocate one workspace for each compression type so
776 * we can guarantee forward progress in the worst case
778 workspace = btrfs_compress_op[i]->alloc_workspace();
779 if (IS_ERR(workspace)) {
781 "BTRFS: cannot preallocate compression workspace, will try later");
783 atomic_set(&btrfs_comp_ws[i].total_ws, 1);
784 btrfs_comp_ws[i].free_ws = 1;
785 list_add(workspace, &btrfs_comp_ws[i].idle_ws);
791 * This finds an available workspace or allocates a new one.
792 * If it's not possible to allocate a new one, waits until there's one.
793 * Preallocation makes a forward progress guarantees and we do not return
796 static struct list_head *find_workspace(int type)
798 struct list_head *workspace;
799 int cpus = num_online_cpus();
802 struct list_head *idle_ws = &btrfs_comp_ws[idx].idle_ws;
803 spinlock_t *ws_lock = &btrfs_comp_ws[idx].ws_lock;
804 atomic_t *total_ws = &btrfs_comp_ws[idx].total_ws;
805 wait_queue_head_t *ws_wait = &btrfs_comp_ws[idx].ws_wait;
806 int *free_ws = &btrfs_comp_ws[idx].free_ws;
809 if (!list_empty(idle_ws)) {
810 workspace = idle_ws->next;
813 spin_unlock(ws_lock);
817 if (atomic_read(total_ws) > cpus) {
820 spin_unlock(ws_lock);
821 prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE);
822 if (atomic_read(total_ws) > cpus && !*free_ws)
824 finish_wait(ws_wait, &wait);
827 atomic_inc(total_ws);
828 spin_unlock(ws_lock);
830 workspace = btrfs_compress_op[idx]->alloc_workspace();
831 if (IS_ERR(workspace)) {
832 atomic_dec(total_ws);
836 * Do not return the error but go back to waiting. There's a
837 * workspace preallocated for each type and the compression
838 * time is bounded so we get to a workspace eventually. This
839 * makes our caller's life easier.
841 * To prevent silent and low-probability deadlocks (when the
842 * initial preallocation fails), check if there are any
845 if (atomic_read(total_ws) == 0) {
846 static DEFINE_RATELIMIT_STATE(_rs,
847 /* once per minute */ 60 * HZ,
850 if (__ratelimit(&_rs)) {
852 "no compression workspaces, low memory, retrying");
861 * put a workspace struct back on the list or free it if we have enough
862 * idle ones sitting around
864 static void free_workspace(int type, struct list_head *workspace)
867 struct list_head *idle_ws = &btrfs_comp_ws[idx].idle_ws;
868 spinlock_t *ws_lock = &btrfs_comp_ws[idx].ws_lock;
869 atomic_t *total_ws = &btrfs_comp_ws[idx].total_ws;
870 wait_queue_head_t *ws_wait = &btrfs_comp_ws[idx].ws_wait;
871 int *free_ws = &btrfs_comp_ws[idx].free_ws;
874 if (*free_ws < num_online_cpus()) {
875 list_add(workspace, idle_ws);
877 spin_unlock(ws_lock);
880 spin_unlock(ws_lock);
882 btrfs_compress_op[idx]->free_workspace(workspace);
883 atomic_dec(total_ws);
886 * Make sure counter is updated before we wake up waiters.
889 if (waitqueue_active(ws_wait))
894 * cleanup function for module exit
896 static void free_workspaces(void)
898 struct list_head *workspace;
901 for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
902 while (!list_empty(&btrfs_comp_ws[i].idle_ws)) {
903 workspace = btrfs_comp_ws[i].idle_ws.next;
905 btrfs_compress_op[i]->free_workspace(workspace);
906 atomic_dec(&btrfs_comp_ws[i].total_ws);
912 * given an address space and start/len, compress the bytes.
914 * pages are allocated to hold the compressed result and stored
917 * out_pages is used to return the number of pages allocated. There
918 * may be pages allocated even if we return an error
920 * total_in is used to return the number of bytes actually read. It
921 * may be smaller then len if we had to exit early because we
922 * ran out of room in the pages array or because we cross the
925 * total_out is used to return the total number of compressed bytes
927 * max_out tells us the max number of bytes that we're allowed to
930 int btrfs_compress_pages(int type, struct address_space *mapping,
931 u64 start, unsigned long len,
933 unsigned long nr_dest_pages,
934 unsigned long *out_pages,
935 unsigned long *total_in,
936 unsigned long *total_out,
937 unsigned long max_out)
939 struct list_head *workspace;
942 workspace = find_workspace(type);
944 ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping,
946 nr_dest_pages, out_pages,
949 free_workspace(type, workspace);
954 * pages_in is an array of pages with compressed data.
956 * disk_start is the starting logical offset of this array in the file
958 * bvec is a bio_vec of pages from the file that we want to decompress into
960 * vcnt is the count of pages in the biovec
962 * srclen is the number of bytes in pages_in
964 * The basic idea is that we have a bio that was created by readpages.
965 * The pages in the bio are for the uncompressed data, and they may not
966 * be contiguous. They all correspond to the range of bytes covered by
967 * the compressed extent.
969 static int btrfs_decompress_biovec(int type, struct page **pages_in,
970 u64 disk_start, struct bio_vec *bvec,
971 int vcnt, size_t srclen)
973 struct list_head *workspace;
976 workspace = find_workspace(type);
978 ret = btrfs_compress_op[type-1]->decompress_biovec(workspace, pages_in,
981 free_workspace(type, workspace);
986 * a less complex decompression routine. Our compressed data fits in a
987 * single page, and we want to read a single page out of it.
988 * start_byte tells us the offset into the compressed data we're interested in
990 int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
991 unsigned long start_byte, size_t srclen, size_t destlen)
993 struct list_head *workspace;
996 workspace = find_workspace(type);
998 ret = btrfs_compress_op[type-1]->decompress(workspace, data_in,
999 dest_page, start_byte,
1002 free_workspace(type, workspace);
1006 void btrfs_exit_compress(void)
1012 * Copy uncompressed data from working buffer to pages.
1014 * buf_start is the byte offset we're of the start of our workspace buffer.
1016 * total_out is the last byte of the buffer
1018 int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
1019 unsigned long total_out, u64 disk_start,
1020 struct bio_vec *bvec, int vcnt,
1021 unsigned long *pg_index,
1022 unsigned long *pg_offset)
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 page *page_out = bvec[*pg_index].bv_page;
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(page_out) - 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(PAGE_SIZE - *pg_offset,
1057 PAGE_SIZE - buf_offset);
1058 bytes = min(bytes, working_bytes);
1059 kaddr = kmap_atomic(page_out);
1060 memcpy(kaddr + *pg_offset, buf + buf_offset, bytes);
1061 kunmap_atomic(kaddr);
1062 flush_dcache_page(page_out);
1064 *pg_offset += bytes;
1065 buf_offset += bytes;
1066 working_bytes -= bytes;
1067 current_buf_start += bytes;
1069 /* check if we need to pick another page */
1070 if (*pg_offset == PAGE_SIZE) {
1072 if (*pg_index >= vcnt)
1075 page_out = bvec[*pg_index].bv_page;
1077 start_byte = page_offset(page_out) - disk_start;
1080 * make sure our new page is covered by this
1083 if (total_out <= start_byte)
1087 * the next page in the biovec might not be adjacent
1088 * to the last page, but it might still be found
1089 * inside this working buffer. bump our offset pointer
1091 if (total_out > start_byte &&
1092 current_buf_start < start_byte) {
1093 buf_offset = start_byte - buf_start;
1094 working_bytes = total_out - start_byte;
1095 current_buf_start = buf_start + buf_offset;
1104 * When uncompressing data, we need to make sure and zero any parts of
1105 * the biovec that were not filled in by the decompression code. pg_index
1106 * and pg_offset indicate the last page and the last offset of that page
1107 * that have been filled in. This will zero everything remaining in the
1110 void btrfs_clear_biovec_end(struct bio_vec *bvec, int vcnt,
1111 unsigned long pg_index,
1112 unsigned long pg_offset)
1114 while (pg_index < vcnt) {
1115 struct page *page = bvec[pg_index].bv_page;
1116 unsigned long off = bvec[pg_index].bv_offset;
1117 unsigned long len = bvec[pg_index].bv_len;
1119 if (pg_offset < off)
1121 if (pg_offset < off + len) {
1122 unsigned long bytes = off + len - pg_offset;
1125 kaddr = kmap_atomic(page);
1126 memset(kaddr + pg_offset, 0, bytes);
1127 kunmap_atomic(kaddr);