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);
89 return sizeof(struct compressed_bio) +
90 ((disk_size + root->sectorsize - 1) / root->sectorsize) *
94 static struct bio *compressed_bio_alloc(struct block_device *bdev,
95 u64 first_byte, gfp_t gfp_flags)
99 nr_vecs = bio_get_nr_vecs(bdev);
100 return btrfs_bio_alloc(bdev, first_byte >> 9, nr_vecs, gfp_flags);
103 static int check_compressed_csum(struct inode *inode,
104 struct compressed_bio *cb,
108 struct btrfs_root *root = BTRFS_I(inode)->root;
113 u32 *cb_sum = &cb->sums;
115 if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
118 for (i = 0; i < cb->nr_pages; i++) {
119 page = cb->compressed_pages[i];
122 kaddr = kmap_atomic(page, KM_USER0);
123 csum = btrfs_csum_data(root, kaddr, csum, PAGE_CACHE_SIZE);
124 btrfs_csum_final(csum, (char *)&csum);
125 kunmap_atomic(kaddr, KM_USER0);
127 if (csum != *cb_sum) {
128 printk(KERN_INFO "btrfs csum failed ino %lu "
129 "extent %llu csum %u "
130 "wanted %u mirror %d\n", inode->i_ino,
131 (unsigned long long)disk_start,
132 csum, *cb_sum, cb->mirror_num);
144 /* when we finish reading compressed pages from the disk, we
145 * decompress them and then run the bio end_io routines on the
146 * decompressed pages (in the inode address space).
148 * This allows the checksumming and other IO error handling routines
151 * The compressed pages are freed here, and it must be run
154 static void end_compressed_bio_read(struct bio *bio, int err)
156 struct compressed_bio *cb = bio->bi_private;
165 /* if there are more bios still pending for this compressed
168 if (!atomic_dec_and_test(&cb->pending_bios))
172 ret = check_compressed_csum(inode, cb, (u64)bio->bi_sector << 9);
176 /* ok, we're the last bio for this extent, lets start
179 ret = btrfs_decompress_biovec(cb->compress_type,
180 cb->compressed_pages,
182 cb->orig_bio->bi_io_vec,
183 cb->orig_bio->bi_vcnt,
189 /* release the compressed pages */
191 for (index = 0; index < cb->nr_pages; index++) {
192 page = cb->compressed_pages[index];
193 page->mapping = NULL;
194 page_cache_release(page);
197 /* do io completion on the original bio */
199 bio_io_error(cb->orig_bio);
202 struct bio_vec *bvec = cb->orig_bio->bi_io_vec;
205 * we have verified the checksum already, set page
206 * checked so the end_io handlers know about it
208 while (bio_index < cb->orig_bio->bi_vcnt) {
209 SetPageChecked(bvec->bv_page);
213 bio_endio(cb->orig_bio, 0);
216 /* finally free the cb struct */
217 kfree(cb->compressed_pages);
224 * Clear the writeback bits on all of the file
225 * pages for a compressed write
227 static noinline int end_compressed_writeback(struct inode *inode, u64 start,
228 unsigned long ram_size)
230 unsigned long index = start >> PAGE_CACHE_SHIFT;
231 unsigned long end_index = (start + ram_size - 1) >> PAGE_CACHE_SHIFT;
232 struct page *pages[16];
233 unsigned long nr_pages = end_index - index + 1;
237 while (nr_pages > 0) {
238 ret = find_get_pages_contig(inode->i_mapping, index,
240 nr_pages, ARRAY_SIZE(pages)), pages);
246 for (i = 0; i < ret; i++) {
247 end_page_writeback(pages[i]);
248 page_cache_release(pages[i]);
253 /* the inode may be gone now */
258 * do the cleanup once all the compressed pages hit the disk.
259 * This will clear writeback on the file pages and free the compressed
262 * This also calls the writeback end hooks for the file pages so that
263 * metadata and checksums can be updated in the file.
265 static void end_compressed_bio_write(struct bio *bio, int err)
267 struct extent_io_tree *tree;
268 struct compressed_bio *cb = bio->bi_private;
276 /* if there are more bios still pending for this compressed
279 if (!atomic_dec_and_test(&cb->pending_bios))
282 /* ok, we're the last bio for this extent, step one is to
283 * call back into the FS and do all the end_io operations
286 tree = &BTRFS_I(inode)->io_tree;
287 cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
288 tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
290 cb->start + cb->len - 1,
292 cb->compressed_pages[0]->mapping = NULL;
294 end_compressed_writeback(inode, cb->start, cb->len);
295 /* note, our inode could be gone now */
298 * release the compressed pages, these came from alloc_page and
299 * are not attached to the inode at all
302 for (index = 0; index < cb->nr_pages; index++) {
303 page = cb->compressed_pages[index];
304 page->mapping = NULL;
305 page_cache_release(page);
308 /* finally free the cb struct */
309 kfree(cb->compressed_pages);
316 * worker function to build and submit bios for previously compressed pages.
317 * The corresponding pages in the inode should be marked for writeback
318 * and the compressed pages should have a reference on them for dropping
319 * when the IO is complete.
321 * This also checksums the file bytes and gets things ready for
324 int btrfs_submit_compressed_write(struct inode *inode, u64 start,
325 unsigned long len, u64 disk_start,
326 unsigned long compressed_len,
327 struct page **compressed_pages,
328 unsigned long nr_pages)
330 struct bio *bio = NULL;
331 struct btrfs_root *root = BTRFS_I(inode)->root;
332 struct compressed_bio *cb;
333 unsigned long bytes_left;
334 struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
337 u64 first_byte = disk_start;
338 struct block_device *bdev;
341 WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1));
342 cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
343 atomic_set(&cb->pending_bios, 0);
349 cb->compressed_pages = compressed_pages;
350 cb->compressed_len = compressed_len;
352 cb->nr_pages = nr_pages;
354 bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
356 bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
357 bio->bi_private = cb;
358 bio->bi_end_io = end_compressed_bio_write;
359 atomic_inc(&cb->pending_bios);
361 /* create and submit bios for the compressed pages */
362 bytes_left = compressed_len;
363 for (page_index = 0; page_index < cb->nr_pages; page_index++) {
364 page = compressed_pages[page_index];
365 page->mapping = inode->i_mapping;
367 ret = io_tree->ops->merge_bio_hook(page, 0,
373 page->mapping = NULL;
374 if (ret || bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) <
379 * inc the count before we submit the bio so
380 * we know the end IO handler won't happen before
381 * we inc the count. Otherwise, the cb might get
382 * freed before we're done setting it up
384 atomic_inc(&cb->pending_bios);
385 ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
388 ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
391 ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
396 bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
397 bio->bi_private = cb;
398 bio->bi_end_io = end_compressed_bio_write;
399 bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
401 if (bytes_left < PAGE_CACHE_SIZE) {
402 printk("bytes left %lu compress len %lu nr %lu\n",
403 bytes_left, cb->compressed_len, cb->nr_pages);
405 bytes_left -= PAGE_CACHE_SIZE;
406 first_byte += PAGE_CACHE_SIZE;
411 ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
414 ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
417 ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
424 static noinline int add_ra_bio_pages(struct inode *inode,
426 struct compressed_bio *cb)
428 unsigned long end_index;
429 unsigned long page_index;
431 u64 isize = i_size_read(inode);
434 unsigned long nr_pages = 0;
435 struct extent_map *em;
436 struct address_space *mapping = inode->i_mapping;
437 struct extent_map_tree *em_tree;
438 struct extent_io_tree *tree;
442 page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page;
443 last_offset = (page_offset(page) + PAGE_CACHE_SIZE);
444 em_tree = &BTRFS_I(inode)->extent_tree;
445 tree = &BTRFS_I(inode)->io_tree;
450 end_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
452 while (last_offset < compressed_end) {
453 page_index = last_offset >> PAGE_CACHE_SHIFT;
455 if (page_index > end_index)
459 page = radix_tree_lookup(&mapping->page_tree, page_index);
468 page = __page_cache_alloc(mapping_gfp_mask(mapping) &
473 if (add_to_page_cache_lru(page, mapping, page_index,
475 page_cache_release(page);
479 end = last_offset + PAGE_CACHE_SIZE - 1;
481 * at this point, we have a locked page in the page cache
482 * for these bytes in the file. But, we have to make
483 * sure they map to this compressed extent on disk.
485 set_page_extent_mapped(page);
486 lock_extent(tree, last_offset, end, GFP_NOFS);
487 read_lock(&em_tree->lock);
488 em = lookup_extent_mapping(em_tree, last_offset,
490 read_unlock(&em_tree->lock);
492 if (!em || last_offset < em->start ||
493 (last_offset + PAGE_CACHE_SIZE > extent_map_end(em)) ||
494 (em->block_start >> 9) != cb->orig_bio->bi_sector) {
496 unlock_extent(tree, last_offset, end, GFP_NOFS);
498 page_cache_release(page);
503 if (page->index == end_index) {
505 size_t zero_offset = isize & (PAGE_CACHE_SIZE - 1);
509 zeros = PAGE_CACHE_SIZE - zero_offset;
510 userpage = kmap_atomic(page, KM_USER0);
511 memset(userpage + zero_offset, 0, zeros);
512 flush_dcache_page(page);
513 kunmap_atomic(userpage, KM_USER0);
517 ret = bio_add_page(cb->orig_bio, page,
520 if (ret == PAGE_CACHE_SIZE) {
522 page_cache_release(page);
524 unlock_extent(tree, last_offset, end, GFP_NOFS);
526 page_cache_release(page);
530 last_offset += PAGE_CACHE_SIZE;
536 * for a compressed read, the bio we get passed has all the inode pages
537 * in it. We don't actually do IO on those pages but allocate new ones
538 * to hold the compressed pages on disk.
540 * bio->bi_sector points to the compressed extent on disk
541 * bio->bi_io_vec points to all of the inode pages
542 * bio->bi_vcnt is a count of pages
544 * After the compressed pages are read, we copy the bytes into the
545 * bio we were passed and then call the bio end_io calls
547 int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
548 int mirror_num, unsigned long bio_flags)
550 struct extent_io_tree *tree;
551 struct extent_map_tree *em_tree;
552 struct compressed_bio *cb;
553 struct btrfs_root *root = BTRFS_I(inode)->root;
554 unsigned long uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
555 unsigned long compressed_len;
556 unsigned long nr_pages;
557 unsigned long page_index;
559 struct block_device *bdev;
560 struct bio *comp_bio;
561 u64 cur_disk_byte = (u64)bio->bi_sector << 9;
564 struct extent_map *em;
568 tree = &BTRFS_I(inode)->io_tree;
569 em_tree = &BTRFS_I(inode)->extent_tree;
571 /* we need the actual starting offset of this extent in the file */
572 read_lock(&em_tree->lock);
573 em = lookup_extent_mapping(em_tree,
574 page_offset(bio->bi_io_vec->bv_page),
576 read_unlock(&em_tree->lock);
578 compressed_len = em->block_len;
579 cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
580 atomic_set(&cb->pending_bios, 0);
583 cb->mirror_num = mirror_num;
586 cb->start = em->orig_start;
588 em_start = em->start;
593 cb->len = uncompressed_len;
594 cb->compressed_len = compressed_len;
595 cb->compress_type = extent_compress_type(bio_flags);
598 nr_pages = (compressed_len + PAGE_CACHE_SIZE - 1) /
600 cb->compressed_pages = kmalloc(sizeof(struct page *) * nr_pages,
602 bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
604 for (page_index = 0; page_index < nr_pages; page_index++) {
605 cb->compressed_pages[page_index] = alloc_page(GFP_NOFS |
608 cb->nr_pages = nr_pages;
610 add_ra_bio_pages(inode, em_start + em_len, cb);
612 /* include any pages we added in add_ra-bio_pages */
613 uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
614 cb->len = uncompressed_len;
616 comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
617 comp_bio->bi_private = cb;
618 comp_bio->bi_end_io = end_compressed_bio_read;
619 atomic_inc(&cb->pending_bios);
621 for (page_index = 0; page_index < nr_pages; page_index++) {
622 page = cb->compressed_pages[page_index];
623 page->mapping = inode->i_mapping;
624 page->index = em_start >> PAGE_CACHE_SHIFT;
626 if (comp_bio->bi_size)
627 ret = tree->ops->merge_bio_hook(page, 0,
633 page->mapping = NULL;
634 if (ret || bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0) <
638 ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
642 * inc the count before we submit the bio so
643 * we know the end IO handler won't happen before
644 * we inc the count. Otherwise, the cb might get
645 * freed before we're done setting it up
647 atomic_inc(&cb->pending_bios);
649 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
650 btrfs_lookup_bio_sums(root, inode, comp_bio,
653 sums += (comp_bio->bi_size + root->sectorsize - 1) /
656 ret = btrfs_map_bio(root, READ, comp_bio,
662 comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
664 comp_bio->bi_private = cb;
665 comp_bio->bi_end_io = end_compressed_bio_read;
667 bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0);
669 cur_disk_byte += PAGE_CACHE_SIZE;
673 ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
676 if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM))
677 btrfs_lookup_bio_sums(root, inode, comp_bio, sums);
679 ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
686 static struct list_head comp_idle_workspace[BTRFS_COMPRESS_TYPES];
687 static spinlock_t comp_workspace_lock[BTRFS_COMPRESS_TYPES];
688 static int comp_num_workspace[BTRFS_COMPRESS_TYPES];
689 static atomic_t comp_alloc_workspace[BTRFS_COMPRESS_TYPES];
690 static wait_queue_head_t comp_workspace_wait[BTRFS_COMPRESS_TYPES];
692 struct btrfs_compress_op *btrfs_compress_op[] = {
693 &btrfs_zlib_compress,
697 int __init btrfs_init_compress(void)
701 for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
702 INIT_LIST_HEAD(&comp_idle_workspace[i]);
703 spin_lock_init(&comp_workspace_lock[i]);
704 atomic_set(&comp_alloc_workspace[i], 0);
705 init_waitqueue_head(&comp_workspace_wait[i]);
711 * this finds an available workspace or allocates a new one
712 * ERR_PTR is returned if things go bad.
714 static struct list_head *find_workspace(int type)
716 struct list_head *workspace;
717 int cpus = num_online_cpus();
720 struct list_head *idle_workspace = &comp_idle_workspace[idx];
721 spinlock_t *workspace_lock = &comp_workspace_lock[idx];
722 atomic_t *alloc_workspace = &comp_alloc_workspace[idx];
723 wait_queue_head_t *workspace_wait = &comp_workspace_wait[idx];
724 int *num_workspace = &comp_num_workspace[idx];
726 spin_lock(workspace_lock);
727 if (!list_empty(idle_workspace)) {
728 workspace = idle_workspace->next;
731 spin_unlock(workspace_lock);
735 if (atomic_read(alloc_workspace) > cpus) {
738 spin_unlock(workspace_lock);
739 prepare_to_wait(workspace_wait, &wait, TASK_UNINTERRUPTIBLE);
740 if (atomic_read(alloc_workspace) > cpus && !*num_workspace)
742 finish_wait(workspace_wait, &wait);
745 atomic_inc(alloc_workspace);
746 spin_unlock(workspace_lock);
748 workspace = btrfs_compress_op[idx]->alloc_workspace();
749 if (IS_ERR(workspace)) {
750 atomic_dec(alloc_workspace);
751 wake_up(workspace_wait);
757 * put a workspace struct back on the list or free it if we have enough
758 * idle ones sitting around
760 static void free_workspace(int type, struct list_head *workspace)
763 struct list_head *idle_workspace = &comp_idle_workspace[idx];
764 spinlock_t *workspace_lock = &comp_workspace_lock[idx];
765 atomic_t *alloc_workspace = &comp_alloc_workspace[idx];
766 wait_queue_head_t *workspace_wait = &comp_workspace_wait[idx];
767 int *num_workspace = &comp_num_workspace[idx];
769 spin_lock(workspace_lock);
770 if (*num_workspace < num_online_cpus()) {
771 list_add_tail(workspace, idle_workspace);
773 spin_unlock(workspace_lock);
776 spin_unlock(workspace_lock);
778 btrfs_compress_op[idx]->free_workspace(workspace);
779 atomic_dec(alloc_workspace);
781 if (waitqueue_active(workspace_wait))
782 wake_up(workspace_wait);
786 * cleanup function for module exit
788 static void free_workspaces(void)
790 struct list_head *workspace;
793 for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
794 while (!list_empty(&comp_idle_workspace[i])) {
795 workspace = comp_idle_workspace[i].next;
797 btrfs_compress_op[i]->free_workspace(workspace);
798 atomic_dec(&comp_alloc_workspace[i]);
804 * given an address space and start/len, compress the bytes.
806 * pages are allocated to hold the compressed result and stored
809 * out_pages is used to return the number of pages allocated. There
810 * may be pages allocated even if we return an error
812 * total_in is used to return the number of bytes actually read. It
813 * may be smaller then len if we had to exit early because we
814 * ran out of room in the pages array or because we cross the
817 * total_out is used to return the total number of compressed bytes
819 * max_out tells us the max number of bytes that we're allowed to
822 int btrfs_compress_pages(int type, struct address_space *mapping,
823 u64 start, unsigned long len,
825 unsigned long nr_dest_pages,
826 unsigned long *out_pages,
827 unsigned long *total_in,
828 unsigned long *total_out,
829 unsigned long max_out)
831 struct list_head *workspace;
834 workspace = find_workspace(type);
835 if (IS_ERR(workspace))
838 ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping,
840 nr_dest_pages, out_pages,
843 free_workspace(type, workspace);
848 * pages_in is an array of pages with compressed data.
850 * disk_start is the starting logical offset of this array in the file
852 * bvec is a bio_vec of pages from the file that we want to decompress into
854 * vcnt is the count of pages in the biovec
856 * srclen is the number of bytes in pages_in
858 * The basic idea is that we have a bio that was created by readpages.
859 * The pages in the bio are for the uncompressed data, and they may not
860 * be contiguous. They all correspond to the range of bytes covered by
861 * the compressed extent.
863 int btrfs_decompress_biovec(int type, struct page **pages_in, u64 disk_start,
864 struct bio_vec *bvec, int vcnt, size_t srclen)
866 struct list_head *workspace;
869 workspace = find_workspace(type);
870 if (IS_ERR(workspace))
873 ret = btrfs_compress_op[type-1]->decompress_biovec(workspace, pages_in,
876 free_workspace(type, workspace);
881 * a less complex decompression routine. Our compressed data fits in a
882 * single page, and we want to read a single page out of it.
883 * start_byte tells us the offset into the compressed data we're interested in
885 int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
886 unsigned long start_byte, size_t srclen, size_t destlen)
888 struct list_head *workspace;
891 workspace = find_workspace(type);
892 if (IS_ERR(workspace))
895 ret = btrfs_compress_op[type-1]->decompress(workspace, data_in,
896 dest_page, start_byte,
899 free_workspace(type, workspace);
903 void __exit btrfs_exit_compress(void)
909 * Copy uncompressed data from working buffer to pages.
911 * buf_start is the byte offset we're of the start of our workspace buffer.
913 * total_out is the last byte of the buffer
915 int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
916 unsigned long total_out, u64 disk_start,
917 struct bio_vec *bvec, int vcnt,
918 unsigned long *page_index,
919 unsigned long *pg_offset)
921 unsigned long buf_offset;
922 unsigned long current_buf_start;
923 unsigned long start_byte;
924 unsigned long working_bytes = total_out - buf_start;
927 struct page *page_out = bvec[*page_index].bv_page;
930 * start byte is the first byte of the page we're currently
931 * copying into relative to the start of the compressed data.
933 start_byte = page_offset(page_out) - disk_start;
935 /* we haven't yet hit data corresponding to this page */
936 if (total_out <= start_byte)
940 * the start of the data we care about is offset into
941 * the middle of our working buffer
943 if (total_out > start_byte && buf_start < start_byte) {
944 buf_offset = start_byte - buf_start;
945 working_bytes -= buf_offset;
949 current_buf_start = buf_start;
951 /* copy bytes from the working buffer into the pages */
952 while (working_bytes > 0) {
953 bytes = min(PAGE_CACHE_SIZE - *pg_offset,
954 PAGE_CACHE_SIZE - buf_offset);
955 bytes = min(bytes, working_bytes);
956 kaddr = kmap_atomic(page_out, KM_USER0);
957 memcpy(kaddr + *pg_offset, buf + buf_offset, bytes);
958 kunmap_atomic(kaddr, KM_USER0);
959 flush_dcache_page(page_out);
963 working_bytes -= bytes;
964 current_buf_start += bytes;
966 /* check if we need to pick another page */
967 if (*pg_offset == PAGE_CACHE_SIZE) {
969 if (*page_index >= vcnt)
972 page_out = bvec[*page_index].bv_page;
974 start_byte = page_offset(page_out) - disk_start;
977 * make sure our new page is covered by this
980 if (total_out <= start_byte)
984 * the next page in the biovec might not be adjacent
985 * to the last page, but it might still be found
986 * inside this working buffer. bump our offset pointer
988 if (total_out > start_byte &&
989 current_buf_start < start_byte) {
990 buf_offset = start_byte - buf_start;
991 working_bytes = total_out - start_byte;
992 current_buf_start = buf_start + buf_offset;