mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-06 02:24:14 +08:00
5f55dbc0c5
Restructure squashfs_readpage() splitting it into separate functions for datablocks, fragments and sparse blocks. Move the memcpying (from squashfs cache entry) implementation of squashfs_readpage_block into file_cache.c This allows different implementations to be supported. Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk> Reviewed-by: Minchan Kim <minchan@kernel.org>
504 lines
14 KiB
C
504 lines
14 KiB
C
/*
|
|
* Squashfs - a compressed read only filesystem for Linux
|
|
*
|
|
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
|
|
* Phillip Lougher <phillip@squashfs.org.uk>
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License
|
|
* as published by the Free Software Foundation; either version 2,
|
|
* or (at your option) any later version.
|
|
*
|
|
* 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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
|
|
*
|
|
* file.c
|
|
*/
|
|
|
|
/*
|
|
* This file contains code for handling regular files. A regular file
|
|
* consists of a sequence of contiguous compressed blocks, and/or a
|
|
* compressed fragment block (tail-end packed block). The compressed size
|
|
* of each datablock is stored in a block list contained within the
|
|
* file inode (itself stored in one or more compressed metadata blocks).
|
|
*
|
|
* To speed up access to datablocks when reading 'large' files (256 Mbytes or
|
|
* larger), the code implements an index cache that caches the mapping from
|
|
* block index to datablock location on disk.
|
|
*
|
|
* The index cache allows Squashfs to handle large files (up to 1.75 TiB) while
|
|
* retaining a simple and space-efficient block list on disk. The cache
|
|
* is split into slots, caching up to eight 224 GiB files (128 KiB blocks).
|
|
* Larger files use multiple slots, with 1.75 TiB files using all 8 slots.
|
|
* The index cache is designed to be memory efficient, and by default uses
|
|
* 16 KiB.
|
|
*/
|
|
|
|
#include <linux/fs.h>
|
|
#include <linux/vfs.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/string.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/mutex.h>
|
|
|
|
#include "squashfs_fs.h"
|
|
#include "squashfs_fs_sb.h"
|
|
#include "squashfs_fs_i.h"
|
|
#include "squashfs.h"
|
|
|
|
/*
|
|
* Locate cache slot in range [offset, index] for specified inode. If
|
|
* there's more than one return the slot closest to index.
|
|
*/
|
|
static struct meta_index *locate_meta_index(struct inode *inode, int offset,
|
|
int index)
|
|
{
|
|
struct meta_index *meta = NULL;
|
|
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
|
|
int i;
|
|
|
|
mutex_lock(&msblk->meta_index_mutex);
|
|
|
|
TRACE("locate_meta_index: index %d, offset %d\n", index, offset);
|
|
|
|
if (msblk->meta_index == NULL)
|
|
goto not_allocated;
|
|
|
|
for (i = 0; i < SQUASHFS_META_SLOTS; i++) {
|
|
if (msblk->meta_index[i].inode_number == inode->i_ino &&
|
|
msblk->meta_index[i].offset >= offset &&
|
|
msblk->meta_index[i].offset <= index &&
|
|
msblk->meta_index[i].locked == 0) {
|
|
TRACE("locate_meta_index: entry %d, offset %d\n", i,
|
|
msblk->meta_index[i].offset);
|
|
meta = &msblk->meta_index[i];
|
|
offset = meta->offset;
|
|
}
|
|
}
|
|
|
|
if (meta)
|
|
meta->locked = 1;
|
|
|
|
not_allocated:
|
|
mutex_unlock(&msblk->meta_index_mutex);
|
|
|
|
return meta;
|
|
}
|
|
|
|
|
|
/*
|
|
* Find and initialise an empty cache slot for index offset.
|
|
*/
|
|
static struct meta_index *empty_meta_index(struct inode *inode, int offset,
|
|
int skip)
|
|
{
|
|
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
|
|
struct meta_index *meta = NULL;
|
|
int i;
|
|
|
|
mutex_lock(&msblk->meta_index_mutex);
|
|
|
|
TRACE("empty_meta_index: offset %d, skip %d\n", offset, skip);
|
|
|
|
if (msblk->meta_index == NULL) {
|
|
/*
|
|
* First time cache index has been used, allocate and
|
|
* initialise. The cache index could be allocated at
|
|
* mount time but doing it here means it is allocated only
|
|
* if a 'large' file is read.
|
|
*/
|
|
msblk->meta_index = kcalloc(SQUASHFS_META_SLOTS,
|
|
sizeof(*(msblk->meta_index)), GFP_KERNEL);
|
|
if (msblk->meta_index == NULL) {
|
|
ERROR("Failed to allocate meta_index\n");
|
|
goto failed;
|
|
}
|
|
for (i = 0; i < SQUASHFS_META_SLOTS; i++) {
|
|
msblk->meta_index[i].inode_number = 0;
|
|
msblk->meta_index[i].locked = 0;
|
|
}
|
|
msblk->next_meta_index = 0;
|
|
}
|
|
|
|
for (i = SQUASHFS_META_SLOTS; i &&
|
|
msblk->meta_index[msblk->next_meta_index].locked; i--)
|
|
msblk->next_meta_index = (msblk->next_meta_index + 1) %
|
|
SQUASHFS_META_SLOTS;
|
|
|
|
if (i == 0) {
|
|
TRACE("empty_meta_index: failed!\n");
|
|
goto failed;
|
|
}
|
|
|
|
TRACE("empty_meta_index: returned meta entry %d, %p\n",
|
|
msblk->next_meta_index,
|
|
&msblk->meta_index[msblk->next_meta_index]);
|
|
|
|
meta = &msblk->meta_index[msblk->next_meta_index];
|
|
msblk->next_meta_index = (msblk->next_meta_index + 1) %
|
|
SQUASHFS_META_SLOTS;
|
|
|
|
meta->inode_number = inode->i_ino;
|
|
meta->offset = offset;
|
|
meta->skip = skip;
|
|
meta->entries = 0;
|
|
meta->locked = 1;
|
|
|
|
failed:
|
|
mutex_unlock(&msblk->meta_index_mutex);
|
|
return meta;
|
|
}
|
|
|
|
|
|
static void release_meta_index(struct inode *inode, struct meta_index *meta)
|
|
{
|
|
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
|
|
mutex_lock(&msblk->meta_index_mutex);
|
|
meta->locked = 0;
|
|
mutex_unlock(&msblk->meta_index_mutex);
|
|
}
|
|
|
|
|
|
/*
|
|
* Read the next n blocks from the block list, starting from
|
|
* metadata block <start_block, offset>.
|
|
*/
|
|
static long long read_indexes(struct super_block *sb, int n,
|
|
u64 *start_block, int *offset)
|
|
{
|
|
int err, i;
|
|
long long block = 0;
|
|
__le32 *blist = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL);
|
|
|
|
if (blist == NULL) {
|
|
ERROR("read_indexes: Failed to allocate block_list\n");
|
|
return -ENOMEM;
|
|
}
|
|
|
|
while (n) {
|
|
int blocks = min_t(int, n, PAGE_CACHE_SIZE >> 2);
|
|
|
|
err = squashfs_read_metadata(sb, blist, start_block,
|
|
offset, blocks << 2);
|
|
if (err < 0) {
|
|
ERROR("read_indexes: reading block [%llx:%x]\n",
|
|
*start_block, *offset);
|
|
goto failure;
|
|
}
|
|
|
|
for (i = 0; i < blocks; i++) {
|
|
int size = le32_to_cpu(blist[i]);
|
|
block += SQUASHFS_COMPRESSED_SIZE_BLOCK(size);
|
|
}
|
|
n -= blocks;
|
|
}
|
|
|
|
kfree(blist);
|
|
return block;
|
|
|
|
failure:
|
|
kfree(blist);
|
|
return err;
|
|
}
|
|
|
|
|
|
/*
|
|
* Each cache index slot has SQUASHFS_META_ENTRIES, each of which
|
|
* can cache one index -> datablock/blocklist-block mapping. We wish
|
|
* to distribute these over the length of the file, entry[0] maps index x,
|
|
* entry[1] maps index x + skip, entry[2] maps index x + 2 * skip, and so on.
|
|
* The larger the file, the greater the skip factor. The skip factor is
|
|
* limited to the size of the metadata cache (SQUASHFS_CACHED_BLKS) to ensure
|
|
* the number of metadata blocks that need to be read fits into the cache.
|
|
* If the skip factor is limited in this way then the file will use multiple
|
|
* slots.
|
|
*/
|
|
static inline int calculate_skip(int blocks)
|
|
{
|
|
int skip = blocks / ((SQUASHFS_META_ENTRIES + 1)
|
|
* SQUASHFS_META_INDEXES);
|
|
return min(SQUASHFS_CACHED_BLKS - 1, skip + 1);
|
|
}
|
|
|
|
|
|
/*
|
|
* Search and grow the index cache for the specified inode, returning the
|
|
* on-disk locations of the datablock and block list metadata block
|
|
* <index_block, index_offset> for index (scaled to nearest cache index).
|
|
*/
|
|
static int fill_meta_index(struct inode *inode, int index,
|
|
u64 *index_block, int *index_offset, u64 *data_block)
|
|
{
|
|
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
|
|
int skip = calculate_skip(i_size_read(inode) >> msblk->block_log);
|
|
int offset = 0;
|
|
struct meta_index *meta;
|
|
struct meta_entry *meta_entry;
|
|
u64 cur_index_block = squashfs_i(inode)->block_list_start;
|
|
int cur_offset = squashfs_i(inode)->offset;
|
|
u64 cur_data_block = squashfs_i(inode)->start;
|
|
int err, i;
|
|
|
|
/*
|
|
* Scale index to cache index (cache slot entry)
|
|
*/
|
|
index /= SQUASHFS_META_INDEXES * skip;
|
|
|
|
while (offset < index) {
|
|
meta = locate_meta_index(inode, offset + 1, index);
|
|
|
|
if (meta == NULL) {
|
|
meta = empty_meta_index(inode, offset + 1, skip);
|
|
if (meta == NULL)
|
|
goto all_done;
|
|
} else {
|
|
offset = index < meta->offset + meta->entries ? index :
|
|
meta->offset + meta->entries - 1;
|
|
meta_entry = &meta->meta_entry[offset - meta->offset];
|
|
cur_index_block = meta_entry->index_block +
|
|
msblk->inode_table;
|
|
cur_offset = meta_entry->offset;
|
|
cur_data_block = meta_entry->data_block;
|
|
TRACE("get_meta_index: offset %d, meta->offset %d, "
|
|
"meta->entries %d\n", offset, meta->offset,
|
|
meta->entries);
|
|
TRACE("get_meta_index: index_block 0x%llx, offset 0x%x"
|
|
" data_block 0x%llx\n", cur_index_block,
|
|
cur_offset, cur_data_block);
|
|
}
|
|
|
|
/*
|
|
* If necessary grow cache slot by reading block list. Cache
|
|
* slot is extended up to index or to the end of the slot, in
|
|
* which case further slots will be used.
|
|
*/
|
|
for (i = meta->offset + meta->entries; i <= index &&
|
|
i < meta->offset + SQUASHFS_META_ENTRIES; i++) {
|
|
int blocks = skip * SQUASHFS_META_INDEXES;
|
|
long long res = read_indexes(inode->i_sb, blocks,
|
|
&cur_index_block, &cur_offset);
|
|
|
|
if (res < 0) {
|
|
if (meta->entries == 0)
|
|
/*
|
|
* Don't leave an empty slot on read
|
|
* error allocated to this inode...
|
|
*/
|
|
meta->inode_number = 0;
|
|
err = res;
|
|
goto failed;
|
|
}
|
|
|
|
cur_data_block += res;
|
|
meta_entry = &meta->meta_entry[i - meta->offset];
|
|
meta_entry->index_block = cur_index_block -
|
|
msblk->inode_table;
|
|
meta_entry->offset = cur_offset;
|
|
meta_entry->data_block = cur_data_block;
|
|
meta->entries++;
|
|
offset++;
|
|
}
|
|
|
|
TRACE("get_meta_index: meta->offset %d, meta->entries %d\n",
|
|
meta->offset, meta->entries);
|
|
|
|
release_meta_index(inode, meta);
|
|
}
|
|
|
|
all_done:
|
|
*index_block = cur_index_block;
|
|
*index_offset = cur_offset;
|
|
*data_block = cur_data_block;
|
|
|
|
/*
|
|
* Scale cache index (cache slot entry) to index
|
|
*/
|
|
return offset * SQUASHFS_META_INDEXES * skip;
|
|
|
|
failed:
|
|
release_meta_index(inode, meta);
|
|
return err;
|
|
}
|
|
|
|
|
|
/*
|
|
* Get the on-disk location and compressed size of the datablock
|
|
* specified by index. Fill_meta_index() does most of the work.
|
|
*/
|
|
static int read_blocklist(struct inode *inode, int index, u64 *block)
|
|
{
|
|
u64 start;
|
|
long long blks;
|
|
int offset;
|
|
__le32 size;
|
|
int res = fill_meta_index(inode, index, &start, &offset, block);
|
|
|
|
TRACE("read_blocklist: res %d, index %d, start 0x%llx, offset"
|
|
" 0x%x, block 0x%llx\n", res, index, start, offset,
|
|
*block);
|
|
|
|
if (res < 0)
|
|
return res;
|
|
|
|
/*
|
|
* res contains the index of the mapping returned by fill_meta_index(),
|
|
* this will likely be less than the desired index (because the
|
|
* meta_index cache works at a higher granularity). Read any
|
|
* extra block indexes needed.
|
|
*/
|
|
if (res < index) {
|
|
blks = read_indexes(inode->i_sb, index - res, &start, &offset);
|
|
if (blks < 0)
|
|
return (int) blks;
|
|
*block += blks;
|
|
}
|
|
|
|
/*
|
|
* Read length of block specified by index.
|
|
*/
|
|
res = squashfs_read_metadata(inode->i_sb, &size, &start, &offset,
|
|
sizeof(size));
|
|
if (res < 0)
|
|
return res;
|
|
return le32_to_cpu(size);
|
|
}
|
|
|
|
/* Copy data into page cache */
|
|
void squashfs_copy_cache(struct page *page, struct squashfs_cache_entry *buffer,
|
|
int bytes, int offset)
|
|
{
|
|
struct inode *inode = page->mapping->host;
|
|
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
|
|
void *pageaddr;
|
|
int i, mask = (1 << (msblk->block_log - PAGE_CACHE_SHIFT)) - 1;
|
|
int start_index = page->index & ~mask, end_index = start_index | mask;
|
|
|
|
/*
|
|
* Loop copying datablock into pages. As the datablock likely covers
|
|
* many PAGE_CACHE_SIZE pages (default block size is 128 KiB) explicitly
|
|
* grab the pages from the page cache, except for the page that we've
|
|
* been called to fill.
|
|
*/
|
|
for (i = start_index; i <= end_index && bytes > 0; i++,
|
|
bytes -= PAGE_CACHE_SIZE, offset += PAGE_CACHE_SIZE) {
|
|
struct page *push_page;
|
|
int avail = buffer ? min_t(int, bytes, PAGE_CACHE_SIZE) : 0;
|
|
|
|
TRACE("bytes %d, i %d, available_bytes %d\n", bytes, i, avail);
|
|
|
|
push_page = (i == page->index) ? page :
|
|
grab_cache_page_nowait(page->mapping, i);
|
|
|
|
if (!push_page)
|
|
continue;
|
|
|
|
if (PageUptodate(push_page))
|
|
goto skip_page;
|
|
|
|
pageaddr = kmap_atomic(push_page);
|
|
squashfs_copy_data(pageaddr, buffer, offset, avail);
|
|
memset(pageaddr + avail, 0, PAGE_CACHE_SIZE - avail);
|
|
kunmap_atomic(pageaddr);
|
|
flush_dcache_page(push_page);
|
|
SetPageUptodate(push_page);
|
|
skip_page:
|
|
unlock_page(push_page);
|
|
if (i != page->index)
|
|
page_cache_release(push_page);
|
|
}
|
|
}
|
|
|
|
/* Read datablock stored packed inside a fragment (tail-end packed block) */
|
|
static int squashfs_readpage_fragment(struct page *page)
|
|
{
|
|
struct inode *inode = page->mapping->host;
|
|
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
|
|
struct squashfs_cache_entry *buffer = squashfs_get_fragment(inode->i_sb,
|
|
squashfs_i(inode)->fragment_block,
|
|
squashfs_i(inode)->fragment_size);
|
|
int res = buffer->error;
|
|
|
|
if (res)
|
|
ERROR("Unable to read page, block %llx, size %x\n",
|
|
squashfs_i(inode)->fragment_block,
|
|
squashfs_i(inode)->fragment_size);
|
|
else
|
|
squashfs_copy_cache(page, buffer, i_size_read(inode) &
|
|
(msblk->block_size - 1),
|
|
squashfs_i(inode)->fragment_offset);
|
|
|
|
squashfs_cache_put(buffer);
|
|
return res;
|
|
}
|
|
|
|
static int squashfs_readpage_sparse(struct page *page, int index, int file_end)
|
|
{
|
|
struct inode *inode = page->mapping->host;
|
|
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
|
|
int bytes = index == file_end ?
|
|
(i_size_read(inode) & (msblk->block_size - 1)) :
|
|
msblk->block_size;
|
|
|
|
squashfs_copy_cache(page, NULL, bytes, 0);
|
|
return 0;
|
|
}
|
|
|
|
static int squashfs_readpage(struct file *file, struct page *page)
|
|
{
|
|
struct inode *inode = page->mapping->host;
|
|
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
|
|
int index = page->index >> (msblk->block_log - PAGE_CACHE_SHIFT);
|
|
int file_end = i_size_read(inode) >> msblk->block_log;
|
|
int res;
|
|
void *pageaddr;
|
|
|
|
TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n",
|
|
page->index, squashfs_i(inode)->start);
|
|
|
|
if (page->index >= ((i_size_read(inode) + PAGE_CACHE_SIZE - 1) >>
|
|
PAGE_CACHE_SHIFT))
|
|
goto out;
|
|
|
|
if (index < file_end || squashfs_i(inode)->fragment_block ==
|
|
SQUASHFS_INVALID_BLK) {
|
|
u64 block = 0;
|
|
int bsize = read_blocklist(inode, index, &block);
|
|
if (bsize < 0)
|
|
goto error_out;
|
|
|
|
if (bsize == 0)
|
|
res = squashfs_readpage_sparse(page, index, file_end);
|
|
else
|
|
res = squashfs_readpage_block(page, block, bsize);
|
|
} else
|
|
res = squashfs_readpage_fragment(page);
|
|
|
|
if (!res)
|
|
return 0;
|
|
|
|
error_out:
|
|
SetPageError(page);
|
|
out:
|
|
pageaddr = kmap_atomic(page);
|
|
memset(pageaddr, 0, PAGE_CACHE_SIZE);
|
|
kunmap_atomic(pageaddr);
|
|
flush_dcache_page(page);
|
|
if (!PageError(page))
|
|
SetPageUptodate(page);
|
|
unlock_page(page);
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
const struct address_space_operations squashfs_aops = {
|
|
.readpage = squashfs_readpage
|
|
};
|