linux/fs/btrfs/compression.c
Filipe David Borba Manana a2aa75e18a Btrfs: fix data corruption when reading/updating compressed extents
When using a mix of compressed file extents and prealloc extents, it
is possible to fill a page of a file with random, garbage data from
some unrelated previous use of the page, instead of a sequence of zeroes.

A simple sequence of steps to get into such case, taken from the test
case I made for xfstests, is:

   _scratch_mkfs
   _scratch_mount "-o compress-force=lzo"
   $XFS_IO_PROG -f -c "pwrite -S 0x06 -b 18670 266978 18670" $SCRATCH_MNT/foobar
   $XFS_IO_PROG -c "falloc 26450 665194" $SCRATCH_MNT/foobar
   $XFS_IO_PROG -c "truncate 542872" $SCRATCH_MNT/foobar
   $XFS_IO_PROG -c "fsync" $SCRATCH_MNT/foobar

This results in the following file items in the fs tree:

   item 4 key (257 INODE_ITEM 0) itemoff 15879 itemsize 160
       inode generation 6 transid 6 size 542872 block group 0 mode 100600
   item 5 key (257 INODE_REF 256) itemoff 15863 itemsize 16
       inode ref index 2 namelen 6 name: foobar
   item 6 key (257 EXTENT_DATA 0) itemoff 15810 itemsize 53
       extent data disk byte 0 nr 0 gen 6
       extent data offset 0 nr 24576 ram 266240
       extent compression 0
   item 7 key (257 EXTENT_DATA 24576) itemoff 15757 itemsize 53
       prealloc data disk byte 12849152 nr 241664 gen 6
       prealloc data offset 0 nr 241664
   item 8 key (257 EXTENT_DATA 266240) itemoff 15704 itemsize 53
       extent data disk byte 12845056 nr 4096 gen 6
       extent data offset 0 nr 20480 ram 20480
       extent compression 2
   item 9 key (257 EXTENT_DATA 286720) itemoff 15651 itemsize 53
       prealloc data disk byte 13090816 nr 405504 gen 6
       prealloc data offset 0 nr 258048

The on disk extent at offset 266240 (which corresponds to 1 single disk block),
contains 5 compressed chunks of file data. Each of the first 4 compress 4096
bytes of file data, while the last one only compresses 3024 bytes of file data.
Therefore a read into the file region [285648 ; 286720[ (length = 4096 - 3024 =
1072 bytes) should always return zeroes (our next extent is a prealloc one).

The solution here is the compression code path to zero the remaining (untouched)
bytes of the last page it uncompressed data into, as the information about how
much space the file data consumes in the last page is not known in the upper layer
fs/btrfs/extent_io.c:__do_readpage(). In __do_readpage we were correctly zeroing
the remainder of the page but only if it corresponds to the last page of the inode
and if the inode's size is not a multiple of the page size.

This would cause not only returning random data on reads, but also permanently
storing random data when updating parts of the region that should be zeroed.
For the example above, it means updating a single byte in the region [285648 ; 286720[
would store that byte correctly but also store random data on disk.

A test case for xfstests follows soon.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>
2014-02-08 17:57:15 -08:00

1057 lines
27 KiB
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 "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 int btrfs_decompress_biovec(int type, struct page **pages_in,
u64 disk_start, struct bio_vec *bvec,
int vcnt, size_t srclen);
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 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);
csum = btrfs_csum_data(kaddr, csum, PAGE_CACHE_SIZE);
btrfs_csum_final(csum, (char *)&csum);
kunmap_atomic(kaddr);
if (csum != *cb_sum) {
btrfs_info(BTRFS_I(inode)->root->fs_info,
"csum failed ino %llu extent %llu csum %u wanted %u mirror %d",
btrfs_ino(inode), 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 void 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 */
}
/*
* 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 pg_index = 0;
struct page *page;
u64 first_byte = disk_start;
struct block_device *bdev;
int ret;
int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
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 (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
page = compressed_pages[pg_index];
page->mapping = inode->i_mapping;
if (bio->bi_size)
ret = io_tree->ops->merge_bio_hook(WRITE, 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); /* -ENOMEM */
if (!skip_sum) {
ret = btrfs_csum_one_bio(root, inode, bio,
start, 1);
BUG_ON(ret); /* -ENOMEM */
}
ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
BUG_ON(ret); /* -ENOMEM */
bio_put(bio);
bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
BUG_ON(!bio);
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) {
btrfs_info(BTRFS_I(inode)->root->fs_info,
"bytes left %lu compress len %lu nr %lu",
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); /* -ENOMEM */
if (!skip_sum) {
ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
BUG_ON(ret); /* -ENOMEM */
}
ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
BUG_ON(ret); /* -ENOMEM */
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 pg_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) {
pg_index = last_offset >> PAGE_CACHE_SHIFT;
if (pg_index > end_index)
break;
rcu_read_lock();
page = radix_tree_lookup(&mapping->page_tree, pg_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, pg_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);
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);
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);
memset(userpage + zero_offset, 0, zeros);
flush_dcache_page(page);
kunmap_atomic(userpage);
}
}
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);
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 pg_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;
int faili = 0;
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);
if (!em)
return -EIO;
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 (pg_index = 0; pg_index < nr_pages; pg_index++) {
cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
__GFP_HIGHMEM);
if (!cb->compressed_pages[pg_index]) {
faili = pg_index - 1;
ret = -ENOMEM;
goto fail2;
}
}
faili = nr_pages - 1;
cb->nr_pages = nr_pages;
/* In the parent-locked case, we only locked the range we are
* interested in. In all other cases, we can opportunistically
* cache decompressed data that goes beyond the requested range. */
if (!(bio_flags & EXTENT_BIO_PARENT_LOCKED))
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 (pg_index = 0; pg_index < nr_pages; pg_index++) {
page = cb->compressed_pages[pg_index];
page->mapping = inode->i_mapping;
page->index = em_start >> PAGE_CACHE_SHIFT;
if (comp_bio->bi_size)
ret = tree->ops->merge_bio_hook(READ, 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); /* -ENOMEM */
/*
* 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); /* -ENOMEM */
}
sums += (comp_bio->bi_size + root->sectorsize - 1) /
root->sectorsize;
ret = btrfs_map_bio(root, READ, comp_bio,
mirror_num, 0);
if (ret)
bio_endio(comp_bio, ret);
bio_put(comp_bio);
comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
GFP_NOFS);
BUG_ON(!comp_bio);
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); /* -ENOMEM */
if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
ret = btrfs_lookup_bio_sums(root, inode, comp_bio, sums);
BUG_ON(ret); /* -ENOMEM */
}
ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
if (ret)
bio_endio(comp_bio, ret);
bio_put(comp_bio);
return 0;
fail2:
while (faili >= 0) {
__free_page(cb->compressed_pages[faili]);
faili--;
}
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];
static struct btrfs_compress_op *btrfs_compress_op[] = {
&btrfs_zlib_compress,
&btrfs_lzo_compress,
};
void __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]);
}
}
/*
* 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:
smp_mb();
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.
*/
static 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 *pg_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[*pg_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);
memcpy(kaddr + *pg_offset, buf + buf_offset, bytes);
if (*pg_index == (vcnt - 1) && *pg_offset == 0)
memset(kaddr + bytes, 0, PAGE_CACHE_SIZE - bytes);
kunmap_atomic(kaddr);
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) {
(*pg_index)++;
if (*pg_index >= vcnt)
return 0;
page_out = bvec[*pg_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;
}