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 int btrfs_decompress_biovec(int type
, struct page
**pages_in
,
86 u64 disk_start
, struct bio_vec
*bvec
,
87 int vcnt
, size_t srclen
);
89 static inline int compressed_bio_size(struct btrfs_root
*root
,
90 unsigned long disk_size
)
92 u16 csum_size
= btrfs_super_csum_size(root
->fs_info
->super_copy
);
94 return sizeof(struct compressed_bio
) +
95 ((disk_size
+ root
->sectorsize
- 1) / root
->sectorsize
) *
99 static struct bio
*compressed_bio_alloc(struct block_device
*bdev
,
100 u64 first_byte
, gfp_t gfp_flags
)
104 nr_vecs
= bio_get_nr_vecs(bdev
);
105 return btrfs_bio_alloc(bdev
, first_byte
>> 9, nr_vecs
, gfp_flags
);
108 static int check_compressed_csum(struct inode
*inode
,
109 struct compressed_bio
*cb
,
117 u32
*cb_sum
= &cb
->sums
;
119 if (BTRFS_I(inode
)->flags
& BTRFS_INODE_NODATASUM
)
122 for (i
= 0; i
< cb
->nr_pages
; i
++) {
123 page
= cb
->compressed_pages
[i
];
126 kaddr
= kmap_atomic(page
);
127 csum
= btrfs_csum_data(kaddr
, csum
, PAGE_CACHE_SIZE
);
128 btrfs_csum_final(csum
, (char *)&csum
);
129 kunmap_atomic(kaddr
);
131 if (csum
!= *cb_sum
) {
132 printk(KERN_INFO
"btrfs csum failed ino %llu "
133 "extent %llu csum %u "
134 "wanted %u mirror %d\n",
135 btrfs_ino(inode
), disk_start
, csum
, *cb_sum
,
148 /* when we finish reading compressed pages from the disk, we
149 * decompress them and then run the bio end_io routines on the
150 * decompressed pages (in the inode address space).
152 * This allows the checksumming and other IO error handling routines
155 * The compressed pages are freed here, and it must be run
158 static void end_compressed_bio_read(struct bio
*bio
, int err
)
160 struct compressed_bio
*cb
= bio
->bi_private
;
169 /* if there are more bios still pending for this compressed
172 if (!atomic_dec_and_test(&cb
->pending_bios
))
176 ret
= check_compressed_csum(inode
, cb
, (u64
)bio
->bi_sector
<< 9);
180 /* ok, we're the last bio for this extent, lets start
183 ret
= btrfs_decompress_biovec(cb
->compress_type
,
184 cb
->compressed_pages
,
186 cb
->orig_bio
->bi_io_vec
,
187 cb
->orig_bio
->bi_vcnt
,
193 /* release the compressed pages */
195 for (index
= 0; index
< cb
->nr_pages
; index
++) {
196 page
= cb
->compressed_pages
[index
];
197 page
->mapping
= NULL
;
198 page_cache_release(page
);
201 /* do io completion on the original bio */
203 bio_io_error(cb
->orig_bio
);
206 struct bio_vec
*bvec
= cb
->orig_bio
->bi_io_vec
;
209 * we have verified the checksum already, set page
210 * checked so the end_io handlers know about it
212 while (bio_index
< cb
->orig_bio
->bi_vcnt
) {
213 SetPageChecked(bvec
->bv_page
);
217 bio_endio(cb
->orig_bio
, 0);
220 /* finally free the cb struct */
221 kfree(cb
->compressed_pages
);
228 * Clear the writeback bits on all of the file
229 * pages for a compressed write
231 static noinline
void end_compressed_writeback(struct inode
*inode
, u64 start
,
232 unsigned long ram_size
)
234 unsigned long index
= start
>> PAGE_CACHE_SHIFT
;
235 unsigned long end_index
= (start
+ ram_size
- 1) >> PAGE_CACHE_SHIFT
;
236 struct page
*pages
[16];
237 unsigned long nr_pages
= end_index
- index
+ 1;
241 while (nr_pages
> 0) {
242 ret
= find_get_pages_contig(inode
->i_mapping
, index
,
244 nr_pages
, ARRAY_SIZE(pages
)), pages
);
250 for (i
= 0; i
< ret
; i
++) {
251 end_page_writeback(pages
[i
]);
252 page_cache_release(pages
[i
]);
257 /* the inode may be gone now */
261 * do the cleanup once all the compressed pages hit the disk.
262 * This will clear writeback on the file pages and free the compressed
265 * This also calls the writeback end hooks for the file pages so that
266 * metadata and checksums can be updated in the file.
268 static void end_compressed_bio_write(struct bio
*bio
, int err
)
270 struct extent_io_tree
*tree
;
271 struct compressed_bio
*cb
= bio
->bi_private
;
279 /* if there are more bios still pending for this compressed
282 if (!atomic_dec_and_test(&cb
->pending_bios
))
285 /* ok, we're the last bio for this extent, step one is to
286 * call back into the FS and do all the end_io operations
289 tree
= &BTRFS_I(inode
)->io_tree
;
290 cb
->compressed_pages
[0]->mapping
= cb
->inode
->i_mapping
;
291 tree
->ops
->writepage_end_io_hook(cb
->compressed_pages
[0],
293 cb
->start
+ cb
->len
- 1,
295 cb
->compressed_pages
[0]->mapping
= NULL
;
297 end_compressed_writeback(inode
, cb
->start
, cb
->len
);
298 /* note, our inode could be gone now */
301 * release the compressed pages, these came from alloc_page and
302 * are not attached to the inode at all
305 for (index
= 0; index
< cb
->nr_pages
; index
++) {
306 page
= cb
->compressed_pages
[index
];
307 page
->mapping
= NULL
;
308 page_cache_release(page
);
311 /* finally free the cb struct */
312 kfree(cb
->compressed_pages
);
319 * worker function to build and submit bios for previously compressed pages.
320 * The corresponding pages in the inode should be marked for writeback
321 * and the compressed pages should have a reference on them for dropping
322 * when the IO is complete.
324 * This also checksums the file bytes and gets things ready for
327 int btrfs_submit_compressed_write(struct inode
*inode
, u64 start
,
328 unsigned long len
, u64 disk_start
,
329 unsigned long compressed_len
,
330 struct page
**compressed_pages
,
331 unsigned long nr_pages
)
333 struct bio
*bio
= NULL
;
334 struct btrfs_root
*root
= BTRFS_I(inode
)->root
;
335 struct compressed_bio
*cb
;
336 unsigned long bytes_left
;
337 struct extent_io_tree
*io_tree
= &BTRFS_I(inode
)->io_tree
;
340 u64 first_byte
= disk_start
;
341 struct block_device
*bdev
;
343 int skip_sum
= BTRFS_I(inode
)->flags
& BTRFS_INODE_NODATASUM
;
345 WARN_ON(start
& ((u64
)PAGE_CACHE_SIZE
- 1));
346 cb
= kmalloc(compressed_bio_size(root
, compressed_len
), GFP_NOFS
);
349 atomic_set(&cb
->pending_bios
, 0);
355 cb
->compressed_pages
= compressed_pages
;
356 cb
->compressed_len
= compressed_len
;
358 cb
->nr_pages
= nr_pages
;
360 bdev
= BTRFS_I(inode
)->root
->fs_info
->fs_devices
->latest_bdev
;
362 bio
= compressed_bio_alloc(bdev
, first_byte
, GFP_NOFS
);
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
;
377 ret
= io_tree
->ops
->merge_bio_hook(WRITE
, page
, 0,
383 page
->mapping
= NULL
;
384 if (ret
|| bio_add_page(bio
, page
, PAGE_CACHE_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
, 0);
396 BUG_ON(ret
); /* -ENOMEM */
399 ret
= btrfs_csum_one_bio(root
, inode
, bio
,
401 BUG_ON(ret
); /* -ENOMEM */
404 ret
= btrfs_map_bio(root
, WRITE
, bio
, 0, 1);
405 BUG_ON(ret
); /* -ENOMEM */
409 bio
= compressed_bio_alloc(bdev
, first_byte
, GFP_NOFS
);
411 bio
->bi_private
= cb
;
412 bio
->bi_end_io
= end_compressed_bio_write
;
413 bio_add_page(bio
, page
, PAGE_CACHE_SIZE
, 0);
415 if (bytes_left
< PAGE_CACHE_SIZE
) {
416 printk("bytes left %lu compress len %lu nr %lu\n",
417 bytes_left
, cb
->compressed_len
, cb
->nr_pages
);
419 bytes_left
-= PAGE_CACHE_SIZE
;
420 first_byte
+= PAGE_CACHE_SIZE
;
425 ret
= btrfs_bio_wq_end_io(root
->fs_info
, bio
, 0);
426 BUG_ON(ret
); /* -ENOMEM */
429 ret
= btrfs_csum_one_bio(root
, inode
, bio
, start
, 1);
430 BUG_ON(ret
); /* -ENOMEM */
433 ret
= btrfs_map_bio(root
, WRITE
, bio
, 0, 1);
434 BUG_ON(ret
); /* -ENOMEM */
440 static noinline
int add_ra_bio_pages(struct inode
*inode
,
442 struct compressed_bio
*cb
)
444 unsigned long end_index
;
445 unsigned long pg_index
;
447 u64 isize
= i_size_read(inode
);
450 unsigned long nr_pages
= 0;
451 struct extent_map
*em
;
452 struct address_space
*mapping
= inode
->i_mapping
;
453 struct extent_map_tree
*em_tree
;
454 struct extent_io_tree
*tree
;
458 page
= cb
->orig_bio
->bi_io_vec
[cb
->orig_bio
->bi_vcnt
- 1].bv_page
;
459 last_offset
= (page_offset(page
) + PAGE_CACHE_SIZE
);
460 em_tree
= &BTRFS_I(inode
)->extent_tree
;
461 tree
= &BTRFS_I(inode
)->io_tree
;
466 end_index
= (i_size_read(inode
) - 1) >> PAGE_CACHE_SHIFT
;
468 while (last_offset
< compressed_end
) {
469 pg_index
= last_offset
>> PAGE_CACHE_SHIFT
;
471 if (pg_index
> end_index
)
475 page
= radix_tree_lookup(&mapping
->page_tree
, pg_index
);
484 page
= __page_cache_alloc(mapping_gfp_mask(mapping
) &
489 if (add_to_page_cache_lru(page
, mapping
, pg_index
,
491 page_cache_release(page
);
495 end
= last_offset
+ PAGE_CACHE_SIZE
- 1;
497 * at this point, we have a locked page in the page cache
498 * for these bytes in the file. But, we have to make
499 * sure they map to this compressed extent on disk.
501 set_page_extent_mapped(page
);
502 lock_extent(tree
, last_offset
, end
);
503 read_lock(&em_tree
->lock
);
504 em
= lookup_extent_mapping(em_tree
, last_offset
,
506 read_unlock(&em_tree
->lock
);
508 if (!em
|| last_offset
< em
->start
||
509 (last_offset
+ PAGE_CACHE_SIZE
> extent_map_end(em
)) ||
510 (em
->block_start
>> 9) != cb
->orig_bio
->bi_sector
) {
512 unlock_extent(tree
, last_offset
, end
);
514 page_cache_release(page
);
519 if (page
->index
== end_index
) {
521 size_t zero_offset
= isize
& (PAGE_CACHE_SIZE
- 1);
525 zeros
= PAGE_CACHE_SIZE
- zero_offset
;
526 userpage
= kmap_atomic(page
);
527 memset(userpage
+ zero_offset
, 0, zeros
);
528 flush_dcache_page(page
);
529 kunmap_atomic(userpage
);
533 ret
= bio_add_page(cb
->orig_bio
, page
,
536 if (ret
== PAGE_CACHE_SIZE
) {
538 page_cache_release(page
);
540 unlock_extent(tree
, last_offset
, end
);
542 page_cache_release(page
);
546 last_offset
+= PAGE_CACHE_SIZE
;
552 * for a compressed read, the bio we get passed has all the inode pages
553 * in it. We don't actually do IO on those pages but allocate new ones
554 * to hold the compressed pages on disk.
556 * bio->bi_sector points to the compressed extent on disk
557 * bio->bi_io_vec points to all of the inode pages
558 * bio->bi_vcnt is a count of pages
560 * After the compressed pages are read, we copy the bytes into the
561 * bio we were passed and then call the bio end_io calls
563 int btrfs_submit_compressed_read(struct inode
*inode
, struct bio
*bio
,
564 int mirror_num
, unsigned long bio_flags
)
566 struct extent_io_tree
*tree
;
567 struct extent_map_tree
*em_tree
;
568 struct compressed_bio
*cb
;
569 struct btrfs_root
*root
= BTRFS_I(inode
)->root
;
570 unsigned long uncompressed_len
= bio
->bi_vcnt
* PAGE_CACHE_SIZE
;
571 unsigned long compressed_len
;
572 unsigned long nr_pages
;
573 unsigned long pg_index
;
575 struct block_device
*bdev
;
576 struct bio
*comp_bio
;
577 u64 cur_disk_byte
= (u64
)bio
->bi_sector
<< 9;
580 struct extent_map
*em
;
585 tree
= &BTRFS_I(inode
)->io_tree
;
586 em_tree
= &BTRFS_I(inode
)->extent_tree
;
588 /* we need the actual starting offset of this extent in the file */
589 read_lock(&em_tree
->lock
);
590 em
= lookup_extent_mapping(em_tree
,
591 page_offset(bio
->bi_io_vec
->bv_page
),
593 read_unlock(&em_tree
->lock
);
597 compressed_len
= em
->block_len
;
598 cb
= kmalloc(compressed_bio_size(root
, compressed_len
), GFP_NOFS
);
602 atomic_set(&cb
->pending_bios
, 0);
605 cb
->mirror_num
= mirror_num
;
608 cb
->start
= em
->orig_start
;
610 em_start
= em
->start
;
615 cb
->len
= uncompressed_len
;
616 cb
->compressed_len
= compressed_len
;
617 cb
->compress_type
= extent_compress_type(bio_flags
);
620 nr_pages
= (compressed_len
+ PAGE_CACHE_SIZE
- 1) /
622 cb
->compressed_pages
= kzalloc(sizeof(struct page
*) * nr_pages
,
624 if (!cb
->compressed_pages
)
627 bdev
= BTRFS_I(inode
)->root
->fs_info
->fs_devices
->latest_bdev
;
629 for (pg_index
= 0; pg_index
< nr_pages
; pg_index
++) {
630 cb
->compressed_pages
[pg_index
] = alloc_page(GFP_NOFS
|
632 if (!cb
->compressed_pages
[pg_index
]) {
633 faili
= pg_index
- 1;
638 faili
= nr_pages
- 1;
639 cb
->nr_pages
= nr_pages
;
641 /* In the parent-locked case, we only locked the range we are
642 * interested in. In all other cases, we can opportunistically
643 * cache decompressed data that goes beyond the requested range. */
644 if (!(bio_flags
& EXTENT_BIO_PARENT_LOCKED
))
645 add_ra_bio_pages(inode
, em_start
+ em_len
, cb
);
647 /* include any pages we added in add_ra-bio_pages */
648 uncompressed_len
= bio
->bi_vcnt
* PAGE_CACHE_SIZE
;
649 cb
->len
= uncompressed_len
;
651 comp_bio
= compressed_bio_alloc(bdev
, cur_disk_byte
, GFP_NOFS
);
654 comp_bio
->bi_private
= cb
;
655 comp_bio
->bi_end_io
= end_compressed_bio_read
;
656 atomic_inc(&cb
->pending_bios
);
658 for (pg_index
= 0; pg_index
< nr_pages
; pg_index
++) {
659 page
= cb
->compressed_pages
[pg_index
];
660 page
->mapping
= inode
->i_mapping
;
661 page
->index
= em_start
>> PAGE_CACHE_SHIFT
;
663 if (comp_bio
->bi_size
)
664 ret
= tree
->ops
->merge_bio_hook(READ
, page
, 0,
670 page
->mapping
= NULL
;
671 if (ret
|| bio_add_page(comp_bio
, page
, PAGE_CACHE_SIZE
, 0) <
675 ret
= btrfs_bio_wq_end_io(root
->fs_info
, comp_bio
, 0);
676 BUG_ON(ret
); /* -ENOMEM */
679 * inc the count before we submit the bio so
680 * we know the end IO handler won't happen before
681 * we inc the count. Otherwise, the cb might get
682 * freed before we're done setting it up
684 atomic_inc(&cb
->pending_bios
);
686 if (!(BTRFS_I(inode
)->flags
& BTRFS_INODE_NODATASUM
)) {
687 ret
= btrfs_lookup_bio_sums(root
, inode
,
689 BUG_ON(ret
); /* -ENOMEM */
691 sums
+= (comp_bio
->bi_size
+ root
->sectorsize
- 1) /
694 ret
= btrfs_map_bio(root
, READ
, comp_bio
,
697 bio_endio(comp_bio
, ret
);
701 comp_bio
= compressed_bio_alloc(bdev
, cur_disk_byte
,
704 comp_bio
->bi_private
= cb
;
705 comp_bio
->bi_end_io
= end_compressed_bio_read
;
707 bio_add_page(comp_bio
, page
, PAGE_CACHE_SIZE
, 0);
709 cur_disk_byte
+= PAGE_CACHE_SIZE
;
713 ret
= btrfs_bio_wq_end_io(root
->fs_info
, comp_bio
, 0);
714 BUG_ON(ret
); /* -ENOMEM */
716 if (!(BTRFS_I(inode
)->flags
& BTRFS_INODE_NODATASUM
)) {
717 ret
= btrfs_lookup_bio_sums(root
, inode
, comp_bio
, sums
);
718 BUG_ON(ret
); /* -ENOMEM */
721 ret
= btrfs_map_bio(root
, READ
, comp_bio
, mirror_num
, 0);
723 bio_endio(comp_bio
, ret
);
730 __free_page(cb
->compressed_pages
[faili
]);
734 kfree(cb
->compressed_pages
);
742 static struct list_head comp_idle_workspace
[BTRFS_COMPRESS_TYPES
];
743 static spinlock_t comp_workspace_lock
[BTRFS_COMPRESS_TYPES
];
744 static int comp_num_workspace
[BTRFS_COMPRESS_TYPES
];
745 static atomic_t comp_alloc_workspace
[BTRFS_COMPRESS_TYPES
];
746 static wait_queue_head_t comp_workspace_wait
[BTRFS_COMPRESS_TYPES
];
748 static struct btrfs_compress_op
*btrfs_compress_op
[] = {
749 &btrfs_zlib_compress
,
753 void __init
btrfs_init_compress(void)
757 for (i
= 0; i
< BTRFS_COMPRESS_TYPES
; i
++) {
758 INIT_LIST_HEAD(&comp_idle_workspace
[i
]);
759 spin_lock_init(&comp_workspace_lock
[i
]);
760 atomic_set(&comp_alloc_workspace
[i
], 0);
761 init_waitqueue_head(&comp_workspace_wait
[i
]);
766 * this finds an available workspace or allocates a new one
767 * ERR_PTR is returned if things go bad.
769 static struct list_head
*find_workspace(int type
)
771 struct list_head
*workspace
;
772 int cpus
= num_online_cpus();
775 struct list_head
*idle_workspace
= &comp_idle_workspace
[idx
];
776 spinlock_t
*workspace_lock
= &comp_workspace_lock
[idx
];
777 atomic_t
*alloc_workspace
= &comp_alloc_workspace
[idx
];
778 wait_queue_head_t
*workspace_wait
= &comp_workspace_wait
[idx
];
779 int *num_workspace
= &comp_num_workspace
[idx
];
781 spin_lock(workspace_lock
);
782 if (!list_empty(idle_workspace
)) {
783 workspace
= idle_workspace
->next
;
786 spin_unlock(workspace_lock
);
790 if (atomic_read(alloc_workspace
) > cpus
) {
793 spin_unlock(workspace_lock
);
794 prepare_to_wait(workspace_wait
, &wait
, TASK_UNINTERRUPTIBLE
);
795 if (atomic_read(alloc_workspace
) > cpus
&& !*num_workspace
)
797 finish_wait(workspace_wait
, &wait
);
800 atomic_inc(alloc_workspace
);
801 spin_unlock(workspace_lock
);
803 workspace
= btrfs_compress_op
[idx
]->alloc_workspace();
804 if (IS_ERR(workspace
)) {
805 atomic_dec(alloc_workspace
);
806 wake_up(workspace_wait
);
812 * put a workspace struct back on the list or free it if we have enough
813 * idle ones sitting around
815 static void free_workspace(int type
, struct list_head
*workspace
)
818 struct list_head
*idle_workspace
= &comp_idle_workspace
[idx
];
819 spinlock_t
*workspace_lock
= &comp_workspace_lock
[idx
];
820 atomic_t
*alloc_workspace
= &comp_alloc_workspace
[idx
];
821 wait_queue_head_t
*workspace_wait
= &comp_workspace_wait
[idx
];
822 int *num_workspace
= &comp_num_workspace
[idx
];
824 spin_lock(workspace_lock
);
825 if (*num_workspace
< num_online_cpus()) {
826 list_add_tail(workspace
, idle_workspace
);
828 spin_unlock(workspace_lock
);
831 spin_unlock(workspace_lock
);
833 btrfs_compress_op
[idx
]->free_workspace(workspace
);
834 atomic_dec(alloc_workspace
);
837 if (waitqueue_active(workspace_wait
))
838 wake_up(workspace_wait
);
842 * cleanup function for module exit
844 static void free_workspaces(void)
846 struct list_head
*workspace
;
849 for (i
= 0; i
< BTRFS_COMPRESS_TYPES
; i
++) {
850 while (!list_empty(&comp_idle_workspace
[i
])) {
851 workspace
= comp_idle_workspace
[i
].next
;
853 btrfs_compress_op
[i
]->free_workspace(workspace
);
854 atomic_dec(&comp_alloc_workspace
[i
]);
860 * given an address space and start/len, compress the bytes.
862 * pages are allocated to hold the compressed result and stored
865 * out_pages is used to return the number of pages allocated. There
866 * may be pages allocated even if we return an error
868 * total_in is used to return the number of bytes actually read. It
869 * may be smaller then len if we had to exit early because we
870 * ran out of room in the pages array or because we cross the
873 * total_out is used to return the total number of compressed bytes
875 * max_out tells us the max number of bytes that we're allowed to
878 int btrfs_compress_pages(int type
, struct address_space
*mapping
,
879 u64 start
, unsigned long len
,
881 unsigned long nr_dest_pages
,
882 unsigned long *out_pages
,
883 unsigned long *total_in
,
884 unsigned long *total_out
,
885 unsigned long max_out
)
887 struct list_head
*workspace
;
890 workspace
= find_workspace(type
);
891 if (IS_ERR(workspace
))
894 ret
= btrfs_compress_op
[type
-1]->compress_pages(workspace
, mapping
,
896 nr_dest_pages
, out_pages
,
899 free_workspace(type
, workspace
);
904 * pages_in is an array of pages with compressed data.
906 * disk_start is the starting logical offset of this array in the file
908 * bvec is a bio_vec of pages from the file that we want to decompress into
910 * vcnt is the count of pages in the biovec
912 * srclen is the number of bytes in pages_in
914 * The basic idea is that we have a bio that was created by readpages.
915 * The pages in the bio are for the uncompressed data, and they may not
916 * be contiguous. They all correspond to the range of bytes covered by
917 * the compressed extent.
919 static int btrfs_decompress_biovec(int type
, struct page
**pages_in
,
920 u64 disk_start
, struct bio_vec
*bvec
,
921 int vcnt
, size_t srclen
)
923 struct list_head
*workspace
;
926 workspace
= find_workspace(type
);
927 if (IS_ERR(workspace
))
930 ret
= btrfs_compress_op
[type
-1]->decompress_biovec(workspace
, pages_in
,
933 free_workspace(type
, workspace
);
938 * a less complex decompression routine. Our compressed data fits in a
939 * single page, and we want to read a single page out of it.
940 * start_byte tells us the offset into the compressed data we're interested in
942 int btrfs_decompress(int type
, unsigned char *data_in
, struct page
*dest_page
,
943 unsigned long start_byte
, size_t srclen
, size_t destlen
)
945 struct list_head
*workspace
;
948 workspace
= find_workspace(type
);
949 if (IS_ERR(workspace
))
952 ret
= btrfs_compress_op
[type
-1]->decompress(workspace
, data_in
,
953 dest_page
, start_byte
,
956 free_workspace(type
, workspace
);
960 void btrfs_exit_compress(void)
966 * Copy uncompressed data from working buffer to pages.
968 * buf_start is the byte offset we're of the start of our workspace buffer.
970 * total_out is the last byte of the buffer
972 int btrfs_decompress_buf2page(char *buf
, unsigned long buf_start
,
973 unsigned long total_out
, u64 disk_start
,
974 struct bio_vec
*bvec
, int vcnt
,
975 unsigned long *pg_index
,
976 unsigned long *pg_offset
)
978 unsigned long buf_offset
;
979 unsigned long current_buf_start
;
980 unsigned long start_byte
;
981 unsigned long working_bytes
= total_out
- buf_start
;
984 struct page
*page_out
= bvec
[*pg_index
].bv_page
;
987 * start byte is the first byte of the page we're currently
988 * copying into relative to the start of the compressed data.
990 start_byte
= page_offset(page_out
) - disk_start
;
992 /* we haven't yet hit data corresponding to this page */
993 if (total_out
<= start_byte
)
997 * the start of the data we care about is offset into
998 * the middle of our working buffer
1000 if (total_out
> start_byte
&& buf_start
< start_byte
) {
1001 buf_offset
= start_byte
- buf_start
;
1002 working_bytes
-= buf_offset
;
1006 current_buf_start
= buf_start
;
1008 /* copy bytes from the working buffer into the pages */
1009 while (working_bytes
> 0) {
1010 bytes
= min(PAGE_CACHE_SIZE
- *pg_offset
,
1011 PAGE_CACHE_SIZE
- buf_offset
);
1012 bytes
= min(bytes
, working_bytes
);
1013 kaddr
= kmap_atomic(page_out
);
1014 memcpy(kaddr
+ *pg_offset
, buf
+ buf_offset
, bytes
);
1015 if (*pg_index
== (vcnt
- 1) && *pg_offset
== 0)
1016 memset(kaddr
+ bytes
, 0, PAGE_CACHE_SIZE
- bytes
);
1017 kunmap_atomic(kaddr
);
1018 flush_dcache_page(page_out
);
1020 *pg_offset
+= bytes
;
1021 buf_offset
+= bytes
;
1022 working_bytes
-= bytes
;
1023 current_buf_start
+= bytes
;
1025 /* check if we need to pick another page */
1026 if (*pg_offset
== PAGE_CACHE_SIZE
) {
1028 if (*pg_index
>= vcnt
)
1031 page_out
= bvec
[*pg_index
].bv_page
;
1033 start_byte
= page_offset(page_out
) - disk_start
;
1036 * make sure our new page is covered by this
1039 if (total_out
<= start_byte
)
1043 * the next page in the biovec might not be adjacent
1044 * to the last page, but it might still be found
1045 * inside this working buffer. bump our offset pointer
1047 if (total_out
> start_byte
&&
1048 current_buf_start
< start_byte
) {
1049 buf_offset
= start_byte
- buf_start
;
1050 working_bytes
= total_out
- start_byte
;
1051 current_buf_start
= buf_start
+ buf_offset
;