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
);
594 compressed_len
= em
->block_len
;
595 cb
= kmalloc(compressed_bio_size(root
, compressed_len
), GFP_NOFS
);
599 atomic_set(&cb
->pending_bios
, 0);
602 cb
->mirror_num
= mirror_num
;
605 cb
->start
= em
->orig_start
;
607 em_start
= em
->start
;
612 cb
->len
= uncompressed_len
;
613 cb
->compressed_len
= compressed_len
;
614 cb
->compress_type
= extent_compress_type(bio_flags
);
617 nr_pages
= (compressed_len
+ PAGE_CACHE_SIZE
- 1) /
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
])
632 cb
->nr_pages
= nr_pages
;
634 add_ra_bio_pages(inode
, em_start
+ em_len
, cb
);
636 /* include any pages we added in add_ra-bio_pages */
637 uncompressed_len
= bio
->bi_vcnt
* PAGE_CACHE_SIZE
;
638 cb
->len
= uncompressed_len
;
640 comp_bio
= compressed_bio_alloc(bdev
, cur_disk_byte
, GFP_NOFS
);
643 comp_bio
->bi_private
= cb
;
644 comp_bio
->bi_end_io
= end_compressed_bio_read
;
645 atomic_inc(&cb
->pending_bios
);
647 for (pg_index
= 0; pg_index
< nr_pages
; pg_index
++) {
648 page
= cb
->compressed_pages
[pg_index
];
649 page
->mapping
= inode
->i_mapping
;
650 page
->index
= em_start
>> PAGE_CACHE_SHIFT
;
652 if (comp_bio
->bi_size
)
653 ret
= tree
->ops
->merge_bio_hook(page
, 0,
659 page
->mapping
= NULL
;
660 if (ret
|| bio_add_page(comp_bio
, page
, PAGE_CACHE_SIZE
, 0) <
664 ret
= btrfs_bio_wq_end_io(root
->fs_info
, comp_bio
, 0);
668 * inc the count before we submit the bio so
669 * we know the end IO handler won't happen before
670 * we inc the count. Otherwise, the cb might get
671 * freed before we're done setting it up
673 atomic_inc(&cb
->pending_bios
);
675 if (!(BTRFS_I(inode
)->flags
& BTRFS_INODE_NODATASUM
)) {
676 ret
= btrfs_lookup_bio_sums(root
, inode
,
680 sums
+= (comp_bio
->bi_size
+ root
->sectorsize
- 1) /
683 ret
= btrfs_map_bio(root
, READ
, comp_bio
,
689 comp_bio
= compressed_bio_alloc(bdev
, cur_disk_byte
,
691 comp_bio
->bi_private
= cb
;
692 comp_bio
->bi_end_io
= end_compressed_bio_read
;
694 bio_add_page(comp_bio
, page
, PAGE_CACHE_SIZE
, 0);
696 cur_disk_byte
+= PAGE_CACHE_SIZE
;
700 ret
= btrfs_bio_wq_end_io(root
->fs_info
, comp_bio
, 0);
703 if (!(BTRFS_I(inode
)->flags
& BTRFS_INODE_NODATASUM
)) {
704 ret
= btrfs_lookup_bio_sums(root
, inode
, comp_bio
, sums
);
708 ret
= btrfs_map_bio(root
, READ
, comp_bio
, mirror_num
, 0);
715 for (pg_index
= 0; pg_index
< nr_pages
; pg_index
++)
716 free_page((unsigned long)cb
->compressed_pages
[pg_index
]);
718 kfree(cb
->compressed_pages
);
726 static struct list_head comp_idle_workspace
[BTRFS_COMPRESS_TYPES
];
727 static spinlock_t comp_workspace_lock
[BTRFS_COMPRESS_TYPES
];
728 static int comp_num_workspace
[BTRFS_COMPRESS_TYPES
];
729 static atomic_t comp_alloc_workspace
[BTRFS_COMPRESS_TYPES
];
730 static wait_queue_head_t comp_workspace_wait
[BTRFS_COMPRESS_TYPES
];
732 struct btrfs_compress_op
*btrfs_compress_op
[] = {
733 &btrfs_zlib_compress
,
737 int __init
btrfs_init_compress(void)
741 for (i
= 0; i
< BTRFS_COMPRESS_TYPES
; i
++) {
742 INIT_LIST_HEAD(&comp_idle_workspace
[i
]);
743 spin_lock_init(&comp_workspace_lock
[i
]);
744 atomic_set(&comp_alloc_workspace
[i
], 0);
745 init_waitqueue_head(&comp_workspace_wait
[i
]);
751 * this finds an available workspace or allocates a new one
752 * ERR_PTR is returned if things go bad.
754 static struct list_head
*find_workspace(int type
)
756 struct list_head
*workspace
;
757 int cpus
= num_online_cpus();
760 struct list_head
*idle_workspace
= &comp_idle_workspace
[idx
];
761 spinlock_t
*workspace_lock
= &comp_workspace_lock
[idx
];
762 atomic_t
*alloc_workspace
= &comp_alloc_workspace
[idx
];
763 wait_queue_head_t
*workspace_wait
= &comp_workspace_wait
[idx
];
764 int *num_workspace
= &comp_num_workspace
[idx
];
766 spin_lock(workspace_lock
);
767 if (!list_empty(idle_workspace
)) {
768 workspace
= idle_workspace
->next
;
771 spin_unlock(workspace_lock
);
775 if (atomic_read(alloc_workspace
) > cpus
) {
778 spin_unlock(workspace_lock
);
779 prepare_to_wait(workspace_wait
, &wait
, TASK_UNINTERRUPTIBLE
);
780 if (atomic_read(alloc_workspace
) > cpus
&& !*num_workspace
)
782 finish_wait(workspace_wait
, &wait
);
785 atomic_inc(alloc_workspace
);
786 spin_unlock(workspace_lock
);
788 workspace
= btrfs_compress_op
[idx
]->alloc_workspace();
789 if (IS_ERR(workspace
)) {
790 atomic_dec(alloc_workspace
);
791 wake_up(workspace_wait
);
797 * put a workspace struct back on the list or free it if we have enough
798 * idle ones sitting around
800 static void free_workspace(int type
, struct list_head
*workspace
)
803 struct list_head
*idle_workspace
= &comp_idle_workspace
[idx
];
804 spinlock_t
*workspace_lock
= &comp_workspace_lock
[idx
];
805 atomic_t
*alloc_workspace
= &comp_alloc_workspace
[idx
];
806 wait_queue_head_t
*workspace_wait
= &comp_workspace_wait
[idx
];
807 int *num_workspace
= &comp_num_workspace
[idx
];
809 spin_lock(workspace_lock
);
810 if (*num_workspace
< num_online_cpus()) {
811 list_add_tail(workspace
, idle_workspace
);
813 spin_unlock(workspace_lock
);
816 spin_unlock(workspace_lock
);
818 btrfs_compress_op
[idx
]->free_workspace(workspace
);
819 atomic_dec(alloc_workspace
);
821 if (waitqueue_active(workspace_wait
))
822 wake_up(workspace_wait
);
826 * cleanup function for module exit
828 static void free_workspaces(void)
830 struct list_head
*workspace
;
833 for (i
= 0; i
< BTRFS_COMPRESS_TYPES
; i
++) {
834 while (!list_empty(&comp_idle_workspace
[i
])) {
835 workspace
= comp_idle_workspace
[i
].next
;
837 btrfs_compress_op
[i
]->free_workspace(workspace
);
838 atomic_dec(&comp_alloc_workspace
[i
]);
844 * given an address space and start/len, compress the bytes.
846 * pages are allocated to hold the compressed result and stored
849 * out_pages is used to return the number of pages allocated. There
850 * may be pages allocated even if we return an error
852 * total_in is used to return the number of bytes actually read. It
853 * may be smaller then len if we had to exit early because we
854 * ran out of room in the pages array or because we cross the
857 * total_out is used to return the total number of compressed bytes
859 * max_out tells us the max number of bytes that we're allowed to
862 int btrfs_compress_pages(int type
, struct address_space
*mapping
,
863 u64 start
, unsigned long len
,
865 unsigned long nr_dest_pages
,
866 unsigned long *out_pages
,
867 unsigned long *total_in
,
868 unsigned long *total_out
,
869 unsigned long max_out
)
871 struct list_head
*workspace
;
874 workspace
= find_workspace(type
);
875 if (IS_ERR(workspace
))
878 ret
= btrfs_compress_op
[type
-1]->compress_pages(workspace
, mapping
,
880 nr_dest_pages
, out_pages
,
883 free_workspace(type
, workspace
);
888 * pages_in is an array of pages with compressed data.
890 * disk_start is the starting logical offset of this array in the file
892 * bvec is a bio_vec of pages from the file that we want to decompress into
894 * vcnt is the count of pages in the biovec
896 * srclen is the number of bytes in pages_in
898 * The basic idea is that we have a bio that was created by readpages.
899 * The pages in the bio are for the uncompressed data, and they may not
900 * be contiguous. They all correspond to the range of bytes covered by
901 * the compressed extent.
903 int btrfs_decompress_biovec(int type
, struct page
**pages_in
, u64 disk_start
,
904 struct bio_vec
*bvec
, int vcnt
, size_t srclen
)
906 struct list_head
*workspace
;
909 workspace
= find_workspace(type
);
910 if (IS_ERR(workspace
))
913 ret
= btrfs_compress_op
[type
-1]->decompress_biovec(workspace
, pages_in
,
916 free_workspace(type
, workspace
);
921 * a less complex decompression routine. Our compressed data fits in a
922 * single page, and we want to read a single page out of it.
923 * start_byte tells us the offset into the compressed data we're interested in
925 int btrfs_decompress(int type
, unsigned char *data_in
, struct page
*dest_page
,
926 unsigned long start_byte
, size_t srclen
, size_t destlen
)
928 struct list_head
*workspace
;
931 workspace
= find_workspace(type
);
932 if (IS_ERR(workspace
))
935 ret
= btrfs_compress_op
[type
-1]->decompress(workspace
, data_in
,
936 dest_page
, start_byte
,
939 free_workspace(type
, workspace
);
943 void btrfs_exit_compress(void)
949 * Copy uncompressed data from working buffer to pages.
951 * buf_start is the byte offset we're of the start of our workspace buffer.
953 * total_out is the last byte of the buffer
955 int btrfs_decompress_buf2page(char *buf
, unsigned long buf_start
,
956 unsigned long total_out
, u64 disk_start
,
957 struct bio_vec
*bvec
, int vcnt
,
958 unsigned long *pg_index
,
959 unsigned long *pg_offset
)
961 unsigned long buf_offset
;
962 unsigned long current_buf_start
;
963 unsigned long start_byte
;
964 unsigned long working_bytes
= total_out
- buf_start
;
967 struct page
*page_out
= bvec
[*pg_index
].bv_page
;
970 * start byte is the first byte of the page we're currently
971 * copying into relative to the start of the compressed data.
973 start_byte
= page_offset(page_out
) - disk_start
;
975 /* we haven't yet hit data corresponding to this page */
976 if (total_out
<= start_byte
)
980 * the start of the data we care about is offset into
981 * the middle of our working buffer
983 if (total_out
> start_byte
&& buf_start
< start_byte
) {
984 buf_offset
= start_byte
- buf_start
;
985 working_bytes
-= buf_offset
;
989 current_buf_start
= buf_start
;
991 /* copy bytes from the working buffer into the pages */
992 while (working_bytes
> 0) {
993 bytes
= min(PAGE_CACHE_SIZE
- *pg_offset
,
994 PAGE_CACHE_SIZE
- buf_offset
);
995 bytes
= min(bytes
, working_bytes
);
996 kaddr
= kmap_atomic(page_out
, KM_USER0
);
997 memcpy(kaddr
+ *pg_offset
, buf
+ buf_offset
, bytes
);
998 kunmap_atomic(kaddr
, KM_USER0
);
999 flush_dcache_page(page_out
);
1001 *pg_offset
+= bytes
;
1002 buf_offset
+= bytes
;
1003 working_bytes
-= bytes
;
1004 current_buf_start
+= bytes
;
1006 /* check if we need to pick another page */
1007 if (*pg_offset
== PAGE_CACHE_SIZE
) {
1009 if (*pg_index
>= vcnt
)
1012 page_out
= bvec
[*pg_index
].bv_page
;
1014 start_byte
= page_offset(page_out
) - disk_start
;
1017 * make sure our new page is covered by this
1020 if (total_out
<= start_byte
)
1024 * the next page in the biovec might not be adjacent
1025 * to the last page, but it might still be found
1026 * inside this working buffer. bump our offset pointer
1028 if (total_out
> start_byte
&&
1029 current_buf_start
< start_byte
) {
1030 buf_offset
= start_byte
- buf_start
;
1031 working_bytes
= total_out
- start_byte
;
1032 current_buf_start
= buf_start
+ buf_offset
;