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>
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
struct compressed_bio {
47
/* number of bios pending for this compressed extent */
48
atomic_t pending_bios;
50
/* the pages with the compressed data on them */
51
struct page **compressed_pages;
53
/* inode that owns this data */
56
/* starting offset in the inode for our pages */
59
/* number of bytes in the inode we're working on */
62
/* number of bytes on disk */
63
unsigned long compressed_len;
65
/* the compression algorithm for this bio */
68
/* number of compressed pages in the array */
69
unsigned long nr_pages;
75
/* for reads, this is the bio we are copying the data into */
79
* the start of a variable length array of checksums only
85
static inline int compressed_bio_size(struct btrfs_root *root,
86
unsigned long disk_size)
88
u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
90
return sizeof(struct compressed_bio) +
91
((disk_size + root->sectorsize - 1) / root->sectorsize) *
95
static struct bio *compressed_bio_alloc(struct block_device *bdev,
96
u64 first_byte, gfp_t gfp_flags)
100
nr_vecs = bio_get_nr_vecs(bdev);
101
return btrfs_bio_alloc(bdev, first_byte >> 9, nr_vecs, gfp_flags);
104
static int check_compressed_csum(struct inode *inode,
105
struct compressed_bio *cb,
109
struct btrfs_root *root = BTRFS_I(inode)->root;
114
u32 *cb_sum = &cb->sums;
116
if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
119
for (i = 0; i < cb->nr_pages; i++) {
120
page = cb->compressed_pages[i];
123
kaddr = kmap_atomic(page, KM_USER0);
124
csum = btrfs_csum_data(root, kaddr, csum, PAGE_CACHE_SIZE);
125
btrfs_csum_final(csum, (char *)&csum);
126
kunmap_atomic(kaddr, KM_USER0);
128
if (csum != *cb_sum) {
129
printk(KERN_INFO "btrfs csum failed ino %llu "
130
"extent %llu csum %u "
131
"wanted %u mirror %d\n",
132
(unsigned long long)btrfs_ino(inode),
133
(unsigned long long)disk_start,
134
csum, *cb_sum, cb->mirror_num);
146
/* when we finish reading compressed pages from the disk, we
147
* decompress them and then run the bio end_io routines on the
148
* decompressed pages (in the inode address space).
150
* This allows the checksumming and other IO error handling routines
153
* The compressed pages are freed here, and it must be run
156
static void end_compressed_bio_read(struct bio *bio, int err)
158
struct compressed_bio *cb = bio->bi_private;
167
/* if there are more bios still pending for this compressed
170
if (!atomic_dec_and_test(&cb->pending_bios))
174
ret = check_compressed_csum(inode, cb, (u64)bio->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 = cb->orig_bio->bi_io_vec;
207
* we have verified the checksum already, set page
208
* checked so the end_io handlers know about it
210
while (bio_index < cb->orig_bio->bi_vcnt) {
211
SetPageChecked(bvec->bv_page);
215
bio_endio(cb->orig_bio, 0);
218
/* finally free the cb struct */
219
kfree(cb->compressed_pages);
226
* Clear the writeback bits on all of the file
227
* pages for a compressed write
229
static noinline int end_compressed_writeback(struct inode *inode, u64 start,
230
unsigned long ram_size)
232
unsigned long index = start >> PAGE_CACHE_SHIFT;
233
unsigned long end_index = (start + ram_size - 1) >> PAGE_CACHE_SHIFT;
234
struct page *pages[16];
235
unsigned long nr_pages = end_index - index + 1;
239
while (nr_pages > 0) {
240
ret = find_get_pages_contig(inode->i_mapping, index,
242
nr_pages, ARRAY_SIZE(pages)), pages);
248
for (i = 0; i < ret; i++) {
249
end_page_writeback(pages[i]);
250
page_cache_release(pages[i]);
255
/* the inode may be gone now */
260
* do the cleanup once all the compressed pages hit the disk.
261
* This will clear writeback on the file pages and free the compressed
264
* This also calls the writeback end hooks for the file pages so that
265
* metadata and checksums can be updated in the file.
267
static void end_compressed_bio_write(struct bio *bio, int err)
269
struct extent_io_tree *tree;
270
struct compressed_bio *cb = bio->bi_private;
278
/* if there are more bios still pending for this compressed
281
if (!atomic_dec_and_test(&cb->pending_bios))
284
/* ok, we're the last bio for this extent, step one is to
285
* call back into the FS and do all the end_io operations
288
tree = &BTRFS_I(inode)->io_tree;
289
cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
290
tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
292
cb->start + cb->len - 1,
294
cb->compressed_pages[0]->mapping = NULL;
296
end_compressed_writeback(inode, cb->start, cb->len);
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;
307
page_cache_release(page);
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_CACHE_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->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;
376
ret = io_tree->ops->merge_bio_hook(page, 0,
382
page->mapping = NULL;
383
if (ret || bio_add_page(bio, page, PAGE_CACHE_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(root->fs_info, bio, 0);
398
ret = btrfs_csum_one_bio(root, inode, bio,
403
ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
408
bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
409
bio->bi_private = cb;
410
bio->bi_end_io = end_compressed_bio_write;
411
bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
413
if (bytes_left < PAGE_CACHE_SIZE) {
414
printk("bytes left %lu compress len %lu nr %lu\n",
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, 0);
427
ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
431
ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
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);
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, GFP_NOFS);
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_sector) {
510
unlock_extent(tree, last_offset, end, GFP_NOFS);
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, KM_USER0);
525
memset(userpage + zero_offset, 0, zeros);
526
flush_dcache_page(page);
527
kunmap_atomic(userpage, KM_USER0);
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, GFP_NOFS);
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_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_sector << 9;
578
struct extent_map *em;
582
tree = &BTRFS_I(inode)->io_tree;
583
em_tree = &BTRFS_I(inode)->extent_tree;
585
/* we need the actual starting offset of this extent in the file */
586
read_lock(&em_tree->lock);
587
em = lookup_extent_mapping(em_tree,
588
page_offset(bio->bi_io_vec->bv_page),
590
read_unlock(&em_tree->lock);
592
compressed_len = em->block_len;
593
cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
597
atomic_set(&cb->pending_bios, 0);
600
cb->mirror_num = mirror_num;
603
cb->start = em->orig_start;
605
em_start = em->start;
610
cb->len = uncompressed_len;
611
cb->compressed_len = compressed_len;
612
cb->compress_type = extent_compress_type(bio_flags);
615
nr_pages = (compressed_len + PAGE_CACHE_SIZE - 1) /
617
cb->compressed_pages = kzalloc(sizeof(struct page *) * nr_pages,
619
if (!cb->compressed_pages)
622
bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
624
for (pg_index = 0; pg_index < nr_pages; pg_index++) {
625
cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
627
if (!cb->compressed_pages[pg_index])
630
cb->nr_pages = nr_pages;
632
add_ra_bio_pages(inode, em_start + em_len, cb);
634
/* include any pages we added in add_ra-bio_pages */
635
uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
636
cb->len = uncompressed_len;
638
comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
641
comp_bio->bi_private = cb;
642
comp_bio->bi_end_io = end_compressed_bio_read;
643
atomic_inc(&cb->pending_bios);
645
for (pg_index = 0; pg_index < nr_pages; pg_index++) {
646
page = cb->compressed_pages[pg_index];
647
page->mapping = inode->i_mapping;
648
page->index = em_start >> PAGE_CACHE_SHIFT;
650
if (comp_bio->bi_size)
651
ret = tree->ops->merge_bio_hook(page, 0,
657
page->mapping = NULL;
658
if (ret || bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0) <
662
ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
666
* inc the count before we submit the bio so
667
* we know the end IO handler won't happen before
668
* we inc the count. Otherwise, the cb might get
669
* freed before we're done setting it up
671
atomic_inc(&cb->pending_bios);
673
if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
674
ret = btrfs_lookup_bio_sums(root, inode,
678
sums += (comp_bio->bi_size + root->sectorsize - 1) /
681
ret = btrfs_map_bio(root, READ, comp_bio,
687
comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
689
comp_bio->bi_private = cb;
690
comp_bio->bi_end_io = end_compressed_bio_read;
692
bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0);
694
cur_disk_byte += PAGE_CACHE_SIZE;
698
ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
701
if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
702
ret = btrfs_lookup_bio_sums(root, inode, comp_bio, sums);
706
ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
713
for (pg_index = 0; pg_index < nr_pages; pg_index++)
714
free_page((unsigned long)cb->compressed_pages[pg_index]);
716
kfree(cb->compressed_pages);
724
static struct list_head comp_idle_workspace[BTRFS_COMPRESS_TYPES];
725
static spinlock_t comp_workspace_lock[BTRFS_COMPRESS_TYPES];
726
static int comp_num_workspace[BTRFS_COMPRESS_TYPES];
727
static atomic_t comp_alloc_workspace[BTRFS_COMPRESS_TYPES];
728
static wait_queue_head_t comp_workspace_wait[BTRFS_COMPRESS_TYPES];
730
struct btrfs_compress_op *btrfs_compress_op[] = {
731
&btrfs_zlib_compress,
735
int __init btrfs_init_compress(void)
739
for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
740
INIT_LIST_HEAD(&comp_idle_workspace[i]);
741
spin_lock_init(&comp_workspace_lock[i]);
742
atomic_set(&comp_alloc_workspace[i], 0);
743
init_waitqueue_head(&comp_workspace_wait[i]);
749
* this finds an available workspace or allocates a new one
750
* ERR_PTR is returned if things go bad.
752
static struct list_head *find_workspace(int type)
754
struct list_head *workspace;
755
int cpus = num_online_cpus();
758
struct list_head *idle_workspace = &comp_idle_workspace[idx];
759
spinlock_t *workspace_lock = &comp_workspace_lock[idx];
760
atomic_t *alloc_workspace = &comp_alloc_workspace[idx];
761
wait_queue_head_t *workspace_wait = &comp_workspace_wait[idx];
762
int *num_workspace = &comp_num_workspace[idx];
764
spin_lock(workspace_lock);
765
if (!list_empty(idle_workspace)) {
766
workspace = idle_workspace->next;
769
spin_unlock(workspace_lock);
773
if (atomic_read(alloc_workspace) > cpus) {
776
spin_unlock(workspace_lock);
777
prepare_to_wait(workspace_wait, &wait, TASK_UNINTERRUPTIBLE);
778
if (atomic_read(alloc_workspace) > cpus && !*num_workspace)
780
finish_wait(workspace_wait, &wait);
783
atomic_inc(alloc_workspace);
784
spin_unlock(workspace_lock);
786
workspace = btrfs_compress_op[idx]->alloc_workspace();
787
if (IS_ERR(workspace)) {
788
atomic_dec(alloc_workspace);
789
wake_up(workspace_wait);
795
* put a workspace struct back on the list or free it if we have enough
796
* idle ones sitting around
798
static void free_workspace(int type, struct list_head *workspace)
801
struct list_head *idle_workspace = &comp_idle_workspace[idx];
802
spinlock_t *workspace_lock = &comp_workspace_lock[idx];
803
atomic_t *alloc_workspace = &comp_alloc_workspace[idx];
804
wait_queue_head_t *workspace_wait = &comp_workspace_wait[idx];
805
int *num_workspace = &comp_num_workspace[idx];
807
spin_lock(workspace_lock);
808
if (*num_workspace < num_online_cpus()) {
809
list_add_tail(workspace, idle_workspace);
811
spin_unlock(workspace_lock);
814
spin_unlock(workspace_lock);
816
btrfs_compress_op[idx]->free_workspace(workspace);
817
atomic_dec(alloc_workspace);
819
if (waitqueue_active(workspace_wait))
820
wake_up(workspace_wait);
824
* cleanup function for module exit
826
static void free_workspaces(void)
828
struct list_head *workspace;
831
for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
832
while (!list_empty(&comp_idle_workspace[i])) {
833
workspace = comp_idle_workspace[i].next;
835
btrfs_compress_op[i]->free_workspace(workspace);
836
atomic_dec(&comp_alloc_workspace[i]);
842
* given an address space and start/len, compress the bytes.
844
* pages are allocated to hold the compressed result and stored
847
* out_pages is used to return the number of pages allocated. There
848
* may be pages allocated even if we return an error
850
* total_in is used to return the number of bytes actually read. It
851
* may be smaller then len if we had to exit early because we
852
* ran out of room in the pages array or because we cross the
855
* total_out is used to return the total number of compressed bytes
857
* max_out tells us the max number of bytes that we're allowed to
860
int btrfs_compress_pages(int type, struct address_space *mapping,
861
u64 start, unsigned long len,
863
unsigned long nr_dest_pages,
864
unsigned long *out_pages,
865
unsigned long *total_in,
866
unsigned long *total_out,
867
unsigned long max_out)
869
struct list_head *workspace;
872
workspace = find_workspace(type);
873
if (IS_ERR(workspace))
876
ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping,
878
nr_dest_pages, out_pages,
881
free_workspace(type, workspace);
886
* pages_in is an array of pages with compressed data.
888
* disk_start is the starting logical offset of this array in the file
890
* bvec is a bio_vec of pages from the file that we want to decompress into
892
* vcnt is the count of pages in the biovec
894
* srclen is the number of bytes in pages_in
896
* The basic idea is that we have a bio that was created by readpages.
897
* The pages in the bio are for the uncompressed data, and they may not
898
* be contiguous. They all correspond to the range of bytes covered by
899
* the compressed extent.
901
int btrfs_decompress_biovec(int type, struct page **pages_in, u64 disk_start,
902
struct bio_vec *bvec, int vcnt, size_t srclen)
904
struct list_head *workspace;
907
workspace = find_workspace(type);
908
if (IS_ERR(workspace))
911
ret = btrfs_compress_op[type-1]->decompress_biovec(workspace, pages_in,
914
free_workspace(type, workspace);
919
* a less complex decompression routine. Our compressed data fits in a
920
* single page, and we want to read a single page out of it.
921
* start_byte tells us the offset into the compressed data we're interested in
923
int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
924
unsigned long start_byte, size_t srclen, size_t destlen)
926
struct list_head *workspace;
929
workspace = find_workspace(type);
930
if (IS_ERR(workspace))
933
ret = btrfs_compress_op[type-1]->decompress(workspace, data_in,
934
dest_page, start_byte,
937
free_workspace(type, workspace);
941
void btrfs_exit_compress(void)
947
* Copy uncompressed data from working buffer to pages.
949
* buf_start is the byte offset we're of the start of our workspace buffer.
951
* total_out is the last byte of the buffer
953
int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
954
unsigned long total_out, u64 disk_start,
955
struct bio_vec *bvec, int vcnt,
956
unsigned long *pg_index,
957
unsigned long *pg_offset)
959
unsigned long buf_offset;
960
unsigned long current_buf_start;
961
unsigned long start_byte;
962
unsigned long working_bytes = total_out - buf_start;
965
struct page *page_out = bvec[*pg_index].bv_page;
968
* start byte is the first byte of the page we're currently
969
* copying into relative to the start of the compressed data.
971
start_byte = page_offset(page_out) - disk_start;
973
/* we haven't yet hit data corresponding to this page */
974
if (total_out <= start_byte)
978
* the start of the data we care about is offset into
979
* the middle of our working buffer
981
if (total_out > start_byte && buf_start < start_byte) {
982
buf_offset = start_byte - buf_start;
983
working_bytes -= buf_offset;
987
current_buf_start = buf_start;
989
/* copy bytes from the working buffer into the pages */
990
while (working_bytes > 0) {
991
bytes = min(PAGE_CACHE_SIZE - *pg_offset,
992
PAGE_CACHE_SIZE - buf_offset);
993
bytes = min(bytes, working_bytes);
994
kaddr = kmap_atomic(page_out, KM_USER0);
995
memcpy(kaddr + *pg_offset, buf + buf_offset, bytes);
996
kunmap_atomic(kaddr, KM_USER0);
997
flush_dcache_page(page_out);
1000
buf_offset += bytes;
1001
working_bytes -= bytes;
1002
current_buf_start += bytes;
1004
/* check if we need to pick another page */
1005
if (*pg_offset == PAGE_CACHE_SIZE) {
1007
if (*pg_index >= vcnt)
1010
page_out = bvec[*pg_index].bv_page;
1012
start_byte = page_offset(page_out) - disk_start;
1015
* make sure our new page is covered by this
1018
if (total_out <= start_byte)
1022
* the next page in the biovec might not be adjacent
1023
* to the last page, but it might still be found
1024
* inside this working buffer. bump our offset pointer
1026
if (total_out > start_byte &&
1027
current_buf_start < start_byte) {
1028
buf_offset = start_byte - buf_start;
1029
working_bytes = total_out - start_byte;
1030
current_buf_start = buf_start + buf_offset;