- 根目录:
- fs
- btrfs
- compression.c
/*
* Copyright (C) 2008 Oracle. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/buffer_head.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/mpage.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/bit_spinlock.h>
#include <linux/slab.h>
#include "compat.h"
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "volumes.h"
#include "ordered-data.h"
#include "compression.h"
#include "extent_io.h"
#include "extent_map.h"
struct compressed_bio {
/* number of bios pending for this compressed extent */
atomic_t pending_bios;
/* the pages with the compressed data on them */
struct page **compressed_pages;
/* inode that owns this data */
struct inode *inode;
/* starting offset in the inode for our pages */
u64 start;
/* number of bytes in the inode we're working on */
unsigned long len;
/* number of bytes on disk */
unsigned long compressed_len;
/* the compression algorithm for this bio */
int compress_type;
/* number of compressed pages in the array */
unsigned long nr_pages;
/* IO errors */
int errors;
int mirror_num;
/* for reads, this is the bio we are copying the data into */
struct bio *orig_bio;
/*
* the start of a variable length array of checksums only
* used by reads
*/
u32 sums;
};
static inline int compressed_bio_size(struct btrfs_root *root,
unsigned long disk_size)
{
u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
return sizeof(struct compressed_bio) +
((disk_size + root->sectorsize - 1) / root->sectorsize) *
csum_size;
}
static struct bio *compressed_bio_alloc(struct block_device *bdev,
u64 first_byte, gfp_t gfp_flags)
{
int nr_vecs;
nr_vecs = bio_get_nr_vecs(bdev);
return btrfs_bio_alloc(bdev, first_byte >> 9, nr_vecs, gfp_flags);
}
static int check_compressed_csum(struct inode *inode,
struct compressed_bio *cb,
u64 disk_start)
{
int ret;
struct btrfs_root *root = BTRFS_I(inode)->root;
struct page *page;
unsigned long i;
char *kaddr;
u32 csum;
u32 *cb_sum = &cb->sums;
if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
return 0;
for (i = 0; i < cb->nr_pages; i++) {
page = cb->compressed_pages[i];
csum = ~(u32)0;
kaddr = kmap_atomic(page, KM_USER0);
csum = btrfs_csum_data(root, kaddr, csum, PAGE_CACHE_SIZE);
btrfs_csum_final(csum, (char *)&csum);
kunmap_atomic(kaddr, KM_USER0);
if (csum != *cb_sum) {
printk(KERN_INFO "btrfs csum failed ino %lu "
"extent %llu csum %u "
"wanted %u mirror %d\n", inode->i_ino,
(unsigned long long)disk_start,
csum, *cb_sum, cb->mirror_num);
ret = -EIO;
goto fail;
}
cb_sum++;
}
ret = 0;
fail:
return ret;
}
/* when we finish reading compressed pages from the disk, we
* decompress them and then run the bio end_io routines on the
* decompressed pages (in the inode address space).
*
* This allows the checksumming and other IO error handling routines
* to work normally
*
* The compressed pages are freed here, and it must be run
* in process context
*/
static void end_compressed_bio_read(struct bio *bio, int err)
{
struct compressed_bio *cb = bio->bi_private;
struct inode *inode;
struct page *page;
unsigned long index;
int ret;
if (err)
cb->errors = 1;
/* if there are more bios still pending for this compressed
* extent, just exit
*/
if (!atomic_dec_and_test(&cb->pending_bios))
goto out;
inode = cb->inode;
ret = check_compressed_csum(inode, cb, (u64)bio->bi_sector << 9);
if (ret)
goto csum_failed;
/* ok, we're the last bio for this extent, lets start
* the decompression.
*/
ret = btrfs_decompress_biovec(cb->compress_type,
cb->compressed_pages,
cb->start,
cb->orig_bio->bi_io_vec,
cb->orig_bio->bi_vcnt,
cb->compressed_len);
csum_failed:
if (ret)
cb->errors = 1;
/* release the compressed pages */
index = 0;
for (index = 0; index < cb->nr_pages; index++) {
page = cb->compressed_pages[index];
page->mapping = NULL;
page_cache_release(page);
}
/* do io completion on the original bio */
if (cb->errors) {
bio_io_error(cb->orig_bio);
} else {
int bio_index = 0;
struct bio_vec *bvec = cb->orig_bio->bi_io_vec;
/*
* we have verified the checksum already, set page
* checked so the end_io handlers know about it
*/
while (bio_index < cb->orig_bio->bi_vcnt) {
SetPageChecked(bvec->bv_page);
bvec++;
bio_index++;
}
bio_endio(cb->orig_bio, 0);
}
/* finally free the cb struct */
kfree(cb->compressed_pages);
kfree(cb);
out:
bio_put(bio);
}
/*
* Clear the writeback bits on all of the file
* pages for a compressed write
*/
static noinline int end_compressed_writeback(struct inode *inode, u64 start,
unsigned long ram_size)
{
unsigned long index = start >> PAGE_CACHE_SHIFT;
unsigned long end_index = (start + ram_size - 1) >> PAGE_CACHE_SHIFT;
struct page *pages[16];
unsigned long nr_pages = end_index - index + 1;
int i;
int ret;
while (nr_pages > 0) {
ret = find_get_pages_contig(inode->i_mapping, index,
min_t(unsigned long,
nr_pages, ARRAY_SIZE(pages)), pages);
if (ret == 0) {
nr_pages -= 1;
index += 1;
continue;
}
for (i = 0; i < ret; i++) {
end_page_writeback(pages[i]);
page_cache_release(pages[i]);
}
nr_pages -= ret;
index += ret;
}
/* the inode may be gone now */
return 0;
}
/*
* do the cleanup once all the compressed pages hit the disk.
* This will clear writeback on the file pages and free the compressed
* pages.
*
* This also calls the writeback end hooks for the file pages so that
* metadata and checksums can be updated in the file.
*/
static void end_compressed_bio_write(struct bio *bio, int err)
{
struct extent_io_tree *tree;
struct compressed_bio *cb = bio->bi_private;
struct inode *inode;
struct page *page;
unsigned long index;
if (err)
cb->errors = 1;
/* if there are more bios still pending for this compressed
* extent, just exit
*/
if (!atomic_dec_and_test(&cb->pending_bios))
goto out;
/* ok, we're the last bio for this extent, step one is to
* call back into the FS and do all the end_io operations
*/
inode = cb->inode;
tree = &BTRFS_I(inode)->io_tree;
cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
cb->start,
cb->start + cb->len - 1,
NULL, 1);
cb->compressed_pages[0]->mapping = NULL;
end_compressed_writeback(inode, cb->start, cb->len);
/* note, our inode could be gone now */
/*
* release the compressed pages, these came from alloc_page and
* are not attached to the inode at all
*/
index = 0;
for (index = 0; index < cb->nr_pages; index++) {
page = cb->compressed_pages[index];
page->mapping = NULL;
page_cache_release(page);
}
/* finally free the cb struct */
kfree(cb->compressed_pages);
kfree(cb);
out:
bio_put(bio);
}
/*
* worker function to build and submit bios for previously compressed pages.
* The corresponding pages in the inode should be marked for writeback
* and the compressed pages should have a reference on them for dropping
* when the IO is complete.
*
* This also checksums the file bytes and gets things ready for
* the end io hooks.
*/
int btrfs_submit_compressed_write(struct inode *inode, u64 start,
unsigned long len, u64 disk_start,
unsigned long compressed_len,
struct page **compressed_pages,
unsigned long nr_pages)
{
struct bio *bio = NULL;
struct btrfs_root *root = BTRFS_I(inode)->root;
struct compressed_bio *cb;
unsigned long bytes_left;
struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
int page_index = 0;
struct page *page;
u64 first_byte = disk_start;
struct block_device *bdev;
int ret;
WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1));
cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
if (!cb)
return -ENOMEM;
atomic_set(&cb->pending_bios, 0);
cb->errors = 0;
cb->inode = inode;
cb->start = start;
cb->len = len;
cb->mirror_num = 0;
cb->compressed_pages = compressed_pages;
cb->compressed_len = compressed_len;
cb->orig_bio = NULL;
cb->nr_pages = nr_pages;
bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
if(!bio) {
kfree(cb);
return -ENOMEM;
}
bio->bi_private = cb;
bio->bi_end_io = end_compressed_bio_write;
atomic_inc(&cb->pending_bios);
/* create and submit bios for the compressed pages */
bytes_left = compressed_len;
for (page_index = 0; page_index < cb->nr_pages; page_index++) {
page = compressed_pages[page_index];
page->mapping = inode->i_mapping;
if (bio->bi_size)
ret = io_tree->ops->merge_bio_hook(page, 0,
PAGE_CACHE_SIZE,
bio, 0);
else
ret = 0;
page->mapping = NULL;
if (ret || bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) <
PAGE_CACHE_SIZE) {
bio_get(bio);
/*
* inc the count before we submit the bio so
* we know the end IO handler won't happen before
* we inc the count. Otherwise, the cb might get
* freed before we're done setting it up
*/
atomic_inc(&cb->pending_bios);
ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
BUG_ON(ret);
ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
BUG_ON(ret);
ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
BUG_ON(ret);
bio_put(bio);
bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
bio->bi_private = cb;
bio->bi_end_io = end_compressed_bio_write;
bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
}
if (bytes_left < PAGE_CACHE_SIZE) {
printk("bytes left %lu compress len %lu nr %lu\n",
bytes_left, cb->compressed_len, cb->nr_pages);
}
bytes_left -= PAGE_CACHE_SIZE;
first_byte += PAGE_CACHE_SIZE;
cond_resched();
}
bio_get(bio);
ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
BUG_ON(ret);
ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
BUG_ON(ret);
ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
BUG_ON(ret);
bio_put(bio);
return 0;
}
static noinline int add_ra_bio_pages(struct inode *inode,
u64 compressed_end,
struct compressed_bio *cb)
{
unsigned long end_index;
unsigned long page_index;
u64 last_offset;
u64 isize = i_size_read(inode);
int ret;
struct page *page;
unsigned long nr_pages = 0;
struct extent_map *em;
struct address_space *mapping = inode->i_mapping;
struct extent_map_tree *em_tree;
struct extent_io_tree *tree;
u64 end;
int misses = 0;
page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page;
last_offset = (page_offset(page) + PAGE_CACHE_SIZE);
em_tree = &BTRFS_I(inode)->extent_tree;
tree = &BTRFS_I(inode)->io_tree;
if (isize == 0)
return 0;
end_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
while (last_offset < compressed_end) {
page_index = last_offset >> PAGE_CACHE_SHIFT;
if (page_index > end_index)
break;
rcu_read_lock();
page = radix_tree_lookup(&mapping->page_tree, page_index);
rcu_read_unlock();
if (page) {
misses++;
if (misses > 4)
break;
goto next;
}
page = __page_cache_alloc(mapping_gfp_mask(mapping) &
~__GFP_FS);
if (!page)
break;
if (add_to_page_cache_lru(page, mapping, page_index,
GFP_NOFS)) {
page_cache_release(page);
goto next;
}
end = last_offset + PAGE_CACHE_SIZE - 1;
/*
* at this point, we have a locked page in the page cache
* for these bytes in the file. But, we have to make
* sure they map to this compressed extent on disk.
*/
set_page_extent_mapped(page);
lock_extent(tree, last_offset, end, GFP_NOFS);
read_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree, last_offset,
PAGE_CACHE_SIZE);
read_unlock(&em_tree->lock);
if (!em || last_offset < em->start ||
(last_offset + PAGE_CACHE_SIZE > extent_map_end(em)) ||
(em->block_start >> 9) != cb->orig_bio->bi_sector) {
free_extent_map(em);
unlock_extent(tree, last_offset, end, GFP_NOFS);
unlock_page(page);
page_cache_release(page);
break;
}
free_extent_map(em);
if (page->index == end_index) {
char *userpage;
size_t zero_offset = isize & (PAGE_CACHE_SIZE - 1);
if (zero_offset) {
int zeros;
zeros = PAGE_CACHE_SIZE - zero_offset;
userpage = kmap_atomic(page, KM_USER0);
memset(userpage + zero_offset, 0, zeros);
flush_dcache_page(page);
kunmap_atomic(userpage, KM_USER0);
}
}
ret = bio_add_page(cb->orig_bio, page,
PAGE_CACHE_SIZE, 0);
if (ret == PAGE_CACHE_SIZE) {
nr_pages++;
page_cache_release(page);
} else {
unlock_extent(tree, last_offset, end, GFP_NOFS);
unlock_page(page);
page_cache_release(page);
break;
}
next:
last_offset += PAGE_CACHE_SIZE;
}
return 0;
}
/*
* for a compressed read, the bio we get passed has all the inode pages
* in it. We don't actually do IO on those pages but allocate new ones
* to hold the compressed pages on disk.
*
* bio->bi_sector points to the compressed extent on disk
* bio->bi_io_vec points to all of the inode pages
* bio->bi_vcnt is a count of pages
*
* After the compressed pages are read, we copy the bytes into the
* bio we were passed and then call the bio end_io calls
*/
int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
int mirror_num, unsigned long bio_flags)
{
struct extent_io_tree *tree;
struct extent_map_tree *em_tree;
struct compressed_bio *cb;
struct btrfs_root *root = BTRFS_I(inode)->root;
unsigned long uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
unsigned long compressed_len;
unsigned long nr_pages;
unsigned long page_index;
struct page *page;
struct block_device *bdev;
struct bio *comp_bio;
u64 cur_disk_byte = (u64)bio->bi_sector << 9;
u64 em_len;
u64 em_start;
struct extent_map *em;
int ret = -ENOMEM;
u32 *sums;
tree = &BTRFS_I(inode)->io_tree;
em_tree = &BTRFS_I(inode)->extent_tree;
/* we need the actual starting offset of this extent in the file */
read_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree,
page_offset(bio->bi_io_vec->bv_page),
PAGE_CACHE_SIZE);
read_unlock(&em_tree->lock);
compressed_len = em->block_len;
cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
if (!cb)
goto out;
atomic_set(&cb->pending_bios, 0);
cb->errors = 0;
cb->inode = inode;
cb->mirror_num = mirror_num;
sums = &cb->sums;
cb->start = em->orig_start;
em_len = em->len;
em_start = em->start;
free_extent_map(em);
em = NULL;
cb->len = uncompressed_len;
cb->compressed_len = compressed_len;
cb->compress_type = extent_compress_type(bio_flags);
cb->orig_bio = bio;
nr_pages = (compressed_len + PAGE_CACHE_SIZE - 1) /
PAGE_CACHE_SIZE;
cb->compressed_pages = kzalloc(sizeof(struct page *) * nr_pages,
GFP_NOFS);
if (!cb->compressed_pages)
goto fail1;
bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
for (page_index = 0; page_index < nr_pages; page_index++) {
cb->compressed_pages[page_index] = alloc_page(GFP_NOFS |
__GFP_HIGHMEM);
if (!cb->compressed_pages[page_index])
goto fail2;
}
cb->nr_pages = nr_pages;
add_ra_bio_pages(inode, em_start + em_len, cb);
/* include any pages we added in add_ra-bio_pages */
uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
cb->len = uncompressed_len;
comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
if (!comp_bio)
goto fail2;
comp_bio->bi_private = cb;
comp_bio->bi_end_io = end_compressed_bio_read;
atomic_inc(&cb->pending_bios);
for (page_index = 0; page_index < nr_pages; page_index++) {
page = cb->compressed_pages[page_index];
page->mapping = inode->i_mapping;
page->index = em_start >> PAGE_CACHE_SHIFT;
if (comp_bio->bi_size)
ret = tree->ops->merge_bio_hook(page, 0,
PAGE_CACHE_SIZE,
comp_bio, 0);
else
ret = 0;
page->mapping = NULL;
if (ret || bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0) <
PAGE_CACHE_SIZE) {
bio_get(comp_bio);
ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
BUG_ON(ret);
/*
* inc the count before we submit the bio so
* we know the end IO handler won't happen before
* we inc the count. Otherwise, the cb might get
* freed before we're done setting it up
*/
atomic_inc(&cb->pending_bios);
if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
ret = btrfs_lookup_bio_sums(root, inode,
comp_bio, sums);
BUG_ON(ret);
}
sums += (comp_bio->bi_size + root->sectorsize - 1) /
root->sectorsize;
ret = btrfs_map_bio(root, READ, comp_bio,
mirror_num, 0);
BUG_ON(ret);
bio_put(comp_bio);
comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
GFP_NOFS);
comp_bio->bi_private = cb;
comp_bio->bi_end_io = end_compressed_bio_read;
bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0);
}
cur_disk_byte += PAGE_CACHE_SIZE;
}
bio_get(comp_bio);
ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
BUG_ON(ret);
if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
ret = btrfs_lookup_bio_sums(root, inode, comp_bio, sums);
BUG_ON(ret);
}
ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
BUG_ON(ret);
bio_put(comp_bio);
return 0;
fail2:
for (page_index = 0; page_index < nr_pages; page_index++)
free_page((unsigned long)cb->compressed_pages[page_index]);
kfree(cb->compressed_pages);
fail1:
kfree(cb);
out:
free_extent_map(em);
return ret;
}
static struct list_head comp_idle_workspace[BTRFS_COMPRESS_TYPES];
static spinlock_t comp_workspace_lock[BTRFS_COMPRESS_TYPES];
static int comp_num_workspace[BTRFS_COMPRESS_TYPES];
static atomic_t comp_alloc_workspace[BTRFS_COMPRESS_TYPES];
static wait_queue_head_t comp_workspace_wait[BTRFS_COMPRESS_TYPES];
struct btrfs_compress_op *btrfs_compress_op[] = {
&btrfs_zlib_compress,
&btrfs_lzo_compress,
};
int __init btrfs_init_compress(void)
{
int i;
for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
INIT_LIST_HEAD(&comp_idle_workspace[i]);
spin_lock_init(&comp_workspace_lock[i]);
atomic_set(&comp_alloc_workspace[i], 0);
init_waitqueue_head(&comp_workspace_wait[i]);
}
return 0;
}
/*
* this finds an available workspace or allocates a new one
* ERR_PTR is returned if things go bad.
*/
static struct list_head *find_workspace(int type)
{
struct list_head *workspace;
int cpus = num_online_cpus();
int idx = type - 1;
struct list_head *idle_workspace = &comp_idle_workspace[idx];
spinlock_t *workspace_lock = &comp_workspace_lock[idx];
atomic_t *alloc_workspace = &comp_alloc_workspace[idx];
wait_queue_head_t *workspace_wait = &comp_workspace_wait[idx];
int *num_workspace = &comp_num_workspace[idx];
again:
spin_lock(workspace_lock);
if (!list_empty(idle_workspace)) {
workspace = idle_workspace->next;
list_del(workspace);
(*num_workspace)--;
spin_unlock(workspace_lock);
return workspace;
}
if (atomic_read(alloc_workspace) > cpus) {
DEFINE_WAIT(wait);
spin_unlock(workspace_lock);
prepare_to_wait(workspace_wait, &wait, TASK_UNINTERRUPTIBLE);
if (atomic_read(alloc_workspace) > cpus && !*num_workspace)
schedule();
finish_wait(workspace_wait, &wait);
goto again;
}
atomic_inc(alloc_workspace);
spin_unlock(workspace_lock);
workspace = btrfs_compress_op[idx]->alloc_workspace();
if (IS_ERR(workspace)) {
atomic_dec(alloc_workspace);
wake_up(workspace_wait);
}
return workspace;
}
/*
* put a workspace struct back on the list or free it if we have enough
* idle ones sitting around
*/
static void free_workspace(int type, struct list_head *workspace)
{
int idx = type - 1;
struct list_head *idle_workspace = &comp_idle_workspace[idx];
spinlock_t *workspace_lock = &comp_workspace_lock[idx];
atomic_t *alloc_workspace = &comp_alloc_workspace[idx];
wait_queue_head_t *workspace_wait = &comp_workspace_wait[idx];
int *num_workspace = &comp_num_workspace[idx];
spin_lock(workspace_lock);
if (*num_workspace < num_online_cpus()) {
list_add_tail(workspace, idle_workspace);
(*num_workspace)++;
spin_unlock(workspace_lock);
goto wake;
}
spin_unlock(workspace_lock);
btrfs_compress_op[idx]->free_workspace(workspace);
atomic_dec(alloc_workspace);
wake:
if (waitqueue_active(workspace_wait))
wake_up(workspace_wait);
}
/*
* cleanup function for module exit
*/
static void free_workspaces(void)
{
struct list_head *workspace;
int i;
for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
while (!list_empty(&comp_idle_workspace[i])) {
workspace = comp_idle_workspace[i].next;
list_del(workspace);
btrfs_compress_op[i]->free_workspace(workspace);
atomic_dec(&comp_alloc_workspace[i]);
}
}
}
/*
* given an address space and start/len, compress the bytes.
*
* pages are allocated to hold the compressed result and stored
* in 'pages'
*
* out_pages is used to return the number of pages allocated. There
* may be pages allocated even if we return an error
*
* total_in is used to return the number of bytes actually read. It
* may be smaller then len if we had to exit early because we
* ran out of room in the pages array or because we cross the
* max_out threshold.
*
* total_out is used to return the total number of compressed bytes
*
* max_out tells us the max number of bytes that we're allowed to
* stuff into pages
*/
int btrfs_compress_pages(int type, struct address_space *mapping,
u64 start, unsigned long len,
struct page **pages,
unsigned long nr_dest_pages,
unsigned long *out_pages,
unsigned long *total_in,
unsigned long *total_out,
unsigned long max_out)
{
struct list_head *workspace;
int ret;
workspace = find_workspace(type);
if (IS_ERR(workspace))
return -1;
ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping,
start, len, pages,
nr_dest_pages, out_pages,
total_in, total_out,
max_out);
free_workspace(type, workspace);
return ret;
}
/*
* pages_in is an array of pages with compressed data.
*
* disk_start is the starting logical offset of this array in the file
*
* bvec is a bio_vec of pages from the file that we want to decompress into
*
* vcnt is the count of pages in the biovec
*
* srclen is the number of bytes in pages_in
*
* The basic idea is that we have a bio that was created by readpages.
* The pages in the bio are for the uncompressed data, and they may not
* be contiguous. They all correspond to the range of bytes covered by
* the compressed extent.
*/
int btrfs_decompress_biovec(int type, struct page **pages_in, u64 disk_start,
struct bio_vec *bvec, int vcnt, size_t srclen)
{
struct list_head *workspace;
int ret;
workspace = find_workspace(type);
if (IS_ERR(workspace))
return -ENOMEM;
ret = btrfs_compress_op[type-1]->decompress_biovec(workspace, pages_in,
disk_start,
bvec, vcnt, srclen);
free_workspace(type, workspace);
return ret;
}
/*
* a less complex decompression routine. Our compressed data fits in a
* single page, and we want to read a single page out of it.
* start_byte tells us the offset into the compressed data we're interested in
*/
int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
unsigned long start_byte, size_t srclen, size_t destlen)
{
struct list_head *workspace;
int ret;
workspace = find_workspace(type);
if (IS_ERR(workspace))
return -ENOMEM;
ret = btrfs_compress_op[type-1]->decompress(workspace, data_in,
dest_page, start_byte,
srclen, destlen);
free_workspace(type, workspace);
return ret;
}
void btrfs_exit_compress(void)
{
free_workspaces();
}
/*
* Copy uncompressed data from working buffer to pages.
*
* buf_start is the byte offset we're of the start of our workspace buffer.
*
* total_out is the last byte of the buffer
*/
int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
unsigned long total_out, u64 disk_start,
struct bio_vec *bvec, int vcnt,
unsigned long *page_index,
unsigned long *pg_offset)
{
unsigned long buf_offset;
unsigned long current_buf_start;
unsigned long start_byte;
unsigned long working_bytes = total_out - buf_start;
unsigned long bytes;
char *kaddr;
struct page *page_out = bvec[*page_index].bv_page;
/*
* start byte is the first byte of the page we're currently
* copying into relative to the start of the compressed data.
*/
start_byte = page_offset(page_out) - disk_start;
/* we haven't yet hit data corresponding to this page */
if (total_out <= start_byte)
return 1;
/*
* the start of the data we care about is offset into
* the middle of our working buffer
*/
if (total_out > start_byte && buf_start < start_byte) {
buf_offset = start_byte - buf_start;
working_bytes -= buf_offset;
} else {
buf_offset = 0;
}
current_buf_start = buf_start;
/* copy bytes from the working buffer into the pages */
while (working_bytes > 0) {
bytes = min(PAGE_CACHE_SIZE - *pg_offset,
PAGE_CACHE_SIZE - buf_offset);
bytes = min(bytes, working_bytes);
kaddr = kmap_atomic(page_out, KM_USER0);
memcpy(kaddr + *pg_offset, buf + buf_offset, bytes);
kunmap_atomic(kaddr, KM_USER0);
flush_dcache_page(page_out);
*pg_offset += bytes;
buf_offset += bytes;
working_bytes -= bytes;
current_buf_start += bytes;
/* check if we need to pick another page */
if (*pg_offset == PAGE_CACHE_SIZE) {
(*page_index)++;
if (*page_index >= vcnt)
return 0;
page_out = bvec[*page_index].bv_page;
*pg_offset = 0;
start_byte = page_offset(page_out) - disk_start;
/*
* make sure our new page is covered by this
* working buffer
*/
if (total_out <= start_byte)
return 1;
/*
* the next page in the biovec might not be adjacent
* to the last page, but it might still be found
* inside this working buffer. bump our offset pointer
*/
if (total_out > start_byte &&
current_buf_start < start_byte) {
buf_offset = start_byte - buf_start;
working_bytes = total_out - start_byte;
current_buf_start = buf_start + buf_offset;
}
}
}
return 1;
}