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a3f94cb99a
Previously in squashfs_readpage() when copying data into the page cache, it used the length of the datablock read from the filesystem (after decompression). However, if the filesystem has been corrupted this data block may be short, which will leave pages unfilled. The fix for this is to compute the expected number of bytes to copy from the inode size, and use this to detect if the block is short. Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk> Tested-by: Willy Tarreau <w@1wt.eu> Cc: Анатолий Тросиненко <anatoly.trosinenko@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
514 lines
14 KiB
C
514 lines
14 KiB
C
/*
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* Squashfs - a compressed read only filesystem for Linux
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*
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* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
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* Phillip Lougher <phillip@squashfs.org.uk>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2,
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* or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* file.c
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*/
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/*
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* This file contains code for handling regular files. A regular file
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* consists of a sequence of contiguous compressed blocks, and/or a
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* compressed fragment block (tail-end packed block). The compressed size
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* of each datablock is stored in a block list contained within the
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* file inode (itself stored in one or more compressed metadata blocks).
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*
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* To speed up access to datablocks when reading 'large' files (256 Mbytes or
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* larger), the code implements an index cache that caches the mapping from
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* block index to datablock location on disk.
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*
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* The index cache allows Squashfs to handle large files (up to 1.75 TiB) while
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* retaining a simple and space-efficient block list on disk. The cache
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* is split into slots, caching up to eight 224 GiB files (128 KiB blocks).
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* Larger files use multiple slots, with 1.75 TiB files using all 8 slots.
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* The index cache is designed to be memory efficient, and by default uses
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* 16 KiB.
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*/
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#include <linux/fs.h>
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#include <linux/vfs.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/pagemap.h>
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#include <linux/mutex.h>
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#include "squashfs_fs.h"
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#include "squashfs_fs_sb.h"
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#include "squashfs_fs_i.h"
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#include "squashfs.h"
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/*
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* Locate cache slot in range [offset, index] for specified inode. If
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* there's more than one return the slot closest to index.
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*/
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static struct meta_index *locate_meta_index(struct inode *inode, int offset,
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int index)
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{
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struct meta_index *meta = NULL;
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struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
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int i;
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mutex_lock(&msblk->meta_index_mutex);
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TRACE("locate_meta_index: index %d, offset %d\n", index, offset);
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if (msblk->meta_index == NULL)
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goto not_allocated;
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for (i = 0; i < SQUASHFS_META_SLOTS; i++) {
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if (msblk->meta_index[i].inode_number == inode->i_ino &&
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msblk->meta_index[i].offset >= offset &&
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msblk->meta_index[i].offset <= index &&
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msblk->meta_index[i].locked == 0) {
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TRACE("locate_meta_index: entry %d, offset %d\n", i,
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msblk->meta_index[i].offset);
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meta = &msblk->meta_index[i];
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offset = meta->offset;
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}
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}
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if (meta)
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meta->locked = 1;
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not_allocated:
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mutex_unlock(&msblk->meta_index_mutex);
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return meta;
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}
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/*
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* Find and initialise an empty cache slot for index offset.
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*/
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static struct meta_index *empty_meta_index(struct inode *inode, int offset,
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int skip)
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{
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struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
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struct meta_index *meta = NULL;
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int i;
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mutex_lock(&msblk->meta_index_mutex);
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TRACE("empty_meta_index: offset %d, skip %d\n", offset, skip);
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if (msblk->meta_index == NULL) {
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/*
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* First time cache index has been used, allocate and
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* initialise. The cache index could be allocated at
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* mount time but doing it here means it is allocated only
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* if a 'large' file is read.
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*/
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msblk->meta_index = kcalloc(SQUASHFS_META_SLOTS,
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sizeof(*(msblk->meta_index)), GFP_KERNEL);
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if (msblk->meta_index == NULL) {
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ERROR("Failed to allocate meta_index\n");
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goto failed;
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}
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for (i = 0; i < SQUASHFS_META_SLOTS; i++) {
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msblk->meta_index[i].inode_number = 0;
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msblk->meta_index[i].locked = 0;
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}
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msblk->next_meta_index = 0;
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}
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for (i = SQUASHFS_META_SLOTS; i &&
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msblk->meta_index[msblk->next_meta_index].locked; i--)
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msblk->next_meta_index = (msblk->next_meta_index + 1) %
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SQUASHFS_META_SLOTS;
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if (i == 0) {
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TRACE("empty_meta_index: failed!\n");
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goto failed;
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}
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TRACE("empty_meta_index: returned meta entry %d, %p\n",
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msblk->next_meta_index,
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&msblk->meta_index[msblk->next_meta_index]);
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meta = &msblk->meta_index[msblk->next_meta_index];
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msblk->next_meta_index = (msblk->next_meta_index + 1) %
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SQUASHFS_META_SLOTS;
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meta->inode_number = inode->i_ino;
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meta->offset = offset;
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meta->skip = skip;
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meta->entries = 0;
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meta->locked = 1;
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failed:
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mutex_unlock(&msblk->meta_index_mutex);
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return meta;
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}
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static void release_meta_index(struct inode *inode, struct meta_index *meta)
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{
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struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
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mutex_lock(&msblk->meta_index_mutex);
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meta->locked = 0;
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mutex_unlock(&msblk->meta_index_mutex);
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}
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/*
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* Read the next n blocks from the block list, starting from
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* metadata block <start_block, offset>.
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*/
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static long long read_indexes(struct super_block *sb, int n,
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u64 *start_block, int *offset)
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{
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int err, i;
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long long block = 0;
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__le32 *blist = kmalloc(PAGE_SIZE, GFP_KERNEL);
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if (blist == NULL) {
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ERROR("read_indexes: Failed to allocate block_list\n");
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return -ENOMEM;
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}
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while (n) {
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int blocks = min_t(int, n, PAGE_SIZE >> 2);
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err = squashfs_read_metadata(sb, blist, start_block,
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offset, blocks << 2);
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if (err < 0) {
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ERROR("read_indexes: reading block [%llx:%x]\n",
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*start_block, *offset);
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goto failure;
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}
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for (i = 0; i < blocks; i++) {
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int size = squashfs_block_size(blist[i]);
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if (size < 0) {
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err = size;
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goto failure;
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}
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block += SQUASHFS_COMPRESSED_SIZE_BLOCK(size);
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}
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n -= blocks;
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}
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kfree(blist);
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return block;
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failure:
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kfree(blist);
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return err;
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}
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/*
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* Each cache index slot has SQUASHFS_META_ENTRIES, each of which
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* can cache one index -> datablock/blocklist-block mapping. We wish
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* to distribute these over the length of the file, entry[0] maps index x,
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* entry[1] maps index x + skip, entry[2] maps index x + 2 * skip, and so on.
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* The larger the file, the greater the skip factor. The skip factor is
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* limited to the size of the metadata cache (SQUASHFS_CACHED_BLKS) to ensure
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* the number of metadata blocks that need to be read fits into the cache.
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* If the skip factor is limited in this way then the file will use multiple
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* slots.
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*/
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static inline int calculate_skip(int blocks)
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{
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int skip = blocks / ((SQUASHFS_META_ENTRIES + 1)
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* SQUASHFS_META_INDEXES);
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return min(SQUASHFS_CACHED_BLKS - 1, skip + 1);
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}
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/*
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* Search and grow the index cache for the specified inode, returning the
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* on-disk locations of the datablock and block list metadata block
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* <index_block, index_offset> for index (scaled to nearest cache index).
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*/
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static int fill_meta_index(struct inode *inode, int index,
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u64 *index_block, int *index_offset, u64 *data_block)
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{
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struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
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int skip = calculate_skip(i_size_read(inode) >> msblk->block_log);
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int offset = 0;
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struct meta_index *meta;
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struct meta_entry *meta_entry;
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u64 cur_index_block = squashfs_i(inode)->block_list_start;
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int cur_offset = squashfs_i(inode)->offset;
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u64 cur_data_block = squashfs_i(inode)->start;
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int err, i;
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/*
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* Scale index to cache index (cache slot entry)
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*/
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index /= SQUASHFS_META_INDEXES * skip;
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while (offset < index) {
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meta = locate_meta_index(inode, offset + 1, index);
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if (meta == NULL) {
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meta = empty_meta_index(inode, offset + 1, skip);
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if (meta == NULL)
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goto all_done;
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} else {
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offset = index < meta->offset + meta->entries ? index :
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meta->offset + meta->entries - 1;
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meta_entry = &meta->meta_entry[offset - meta->offset];
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cur_index_block = meta_entry->index_block +
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msblk->inode_table;
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cur_offset = meta_entry->offset;
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cur_data_block = meta_entry->data_block;
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TRACE("get_meta_index: offset %d, meta->offset %d, "
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"meta->entries %d\n", offset, meta->offset,
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meta->entries);
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TRACE("get_meta_index: index_block 0x%llx, offset 0x%x"
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" data_block 0x%llx\n", cur_index_block,
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cur_offset, cur_data_block);
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}
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/*
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* If necessary grow cache slot by reading block list. Cache
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* slot is extended up to index or to the end of the slot, in
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* which case further slots will be used.
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*/
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for (i = meta->offset + meta->entries; i <= index &&
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i < meta->offset + SQUASHFS_META_ENTRIES; i++) {
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int blocks = skip * SQUASHFS_META_INDEXES;
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long long res = read_indexes(inode->i_sb, blocks,
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&cur_index_block, &cur_offset);
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if (res < 0) {
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if (meta->entries == 0)
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/*
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* Don't leave an empty slot on read
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* error allocated to this inode...
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*/
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meta->inode_number = 0;
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err = res;
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goto failed;
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}
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cur_data_block += res;
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meta_entry = &meta->meta_entry[i - meta->offset];
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meta_entry->index_block = cur_index_block -
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msblk->inode_table;
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meta_entry->offset = cur_offset;
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meta_entry->data_block = cur_data_block;
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meta->entries++;
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offset++;
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}
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TRACE("get_meta_index: meta->offset %d, meta->entries %d\n",
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meta->offset, meta->entries);
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release_meta_index(inode, meta);
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}
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all_done:
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*index_block = cur_index_block;
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*index_offset = cur_offset;
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*data_block = cur_data_block;
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/*
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* Scale cache index (cache slot entry) to index
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*/
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return offset * SQUASHFS_META_INDEXES * skip;
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failed:
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release_meta_index(inode, meta);
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return err;
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}
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/*
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* Get the on-disk location and compressed size of the datablock
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* specified by index. Fill_meta_index() does most of the work.
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*/
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static int read_blocklist(struct inode *inode, int index, u64 *block)
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{
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u64 start;
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long long blks;
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int offset;
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__le32 size;
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int res = fill_meta_index(inode, index, &start, &offset, block);
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TRACE("read_blocklist: res %d, index %d, start 0x%llx, offset"
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" 0x%x, block 0x%llx\n", res, index, start, offset,
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*block);
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if (res < 0)
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return res;
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/*
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* res contains the index of the mapping returned by fill_meta_index(),
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* this will likely be less than the desired index (because the
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* meta_index cache works at a higher granularity). Read any
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* extra block indexes needed.
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*/
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if (res < index) {
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blks = read_indexes(inode->i_sb, index - res, &start, &offset);
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if (blks < 0)
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return (int) blks;
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*block += blks;
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}
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/*
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* Read length of block specified by index.
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*/
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res = squashfs_read_metadata(inode->i_sb, &size, &start, &offset,
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sizeof(size));
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if (res < 0)
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return res;
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return squashfs_block_size(size);
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}
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void squashfs_fill_page(struct page *page, struct squashfs_cache_entry *buffer, int offset, int avail)
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{
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int copied;
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void *pageaddr;
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pageaddr = kmap_atomic(page);
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copied = squashfs_copy_data(pageaddr, buffer, offset, avail);
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memset(pageaddr + copied, 0, PAGE_SIZE - copied);
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kunmap_atomic(pageaddr);
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flush_dcache_page(page);
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if (copied == avail)
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SetPageUptodate(page);
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else
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SetPageError(page);
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}
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/* Copy data into page cache */
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void squashfs_copy_cache(struct page *page, struct squashfs_cache_entry *buffer,
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int bytes, int offset)
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{
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struct inode *inode = page->mapping->host;
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struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
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int i, mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
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int start_index = page->index & ~mask, end_index = start_index | mask;
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/*
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* Loop copying datablock into pages. As the datablock likely covers
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* many PAGE_SIZE pages (default block size is 128 KiB) explicitly
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* grab the pages from the page cache, except for the page that we've
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* been called to fill.
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*/
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for (i = start_index; i <= end_index && bytes > 0; i++,
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bytes -= PAGE_SIZE, offset += PAGE_SIZE) {
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struct page *push_page;
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int avail = buffer ? min_t(int, bytes, PAGE_SIZE) : 0;
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TRACE("bytes %d, i %d, available_bytes %d\n", bytes, i, avail);
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push_page = (i == page->index) ? page :
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grab_cache_page_nowait(page->mapping, i);
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if (!push_page)
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continue;
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if (PageUptodate(push_page))
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goto skip_page;
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squashfs_fill_page(push_page, buffer, offset, avail);
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skip_page:
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unlock_page(push_page);
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if (i != page->index)
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put_page(push_page);
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}
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}
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/* Read datablock stored packed inside a fragment (tail-end packed block) */
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static int squashfs_readpage_fragment(struct page *page, int expected)
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{
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struct inode *inode = page->mapping->host;
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struct squashfs_cache_entry *buffer = squashfs_get_fragment(inode->i_sb,
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squashfs_i(inode)->fragment_block,
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squashfs_i(inode)->fragment_size);
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int res = buffer->error;
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if (res)
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ERROR("Unable to read page, block %llx, size %x\n",
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squashfs_i(inode)->fragment_block,
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squashfs_i(inode)->fragment_size);
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else
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squashfs_copy_cache(page, buffer, expected,
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squashfs_i(inode)->fragment_offset);
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squashfs_cache_put(buffer);
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return res;
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}
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static int squashfs_readpage_sparse(struct page *page, int expected)
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{
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squashfs_copy_cache(page, NULL, expected, 0);
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return 0;
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}
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static int squashfs_readpage(struct file *file, struct page *page)
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{
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struct inode *inode = page->mapping->host;
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struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
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int index = page->index >> (msblk->block_log - PAGE_SHIFT);
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int file_end = i_size_read(inode) >> msblk->block_log;
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int expected = index == file_end ?
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(i_size_read(inode) & (msblk->block_size - 1)) :
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msblk->block_size;
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int res;
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void *pageaddr;
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TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n",
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page->index, squashfs_i(inode)->start);
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if (page->index >= ((i_size_read(inode) + PAGE_SIZE - 1) >>
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PAGE_SHIFT))
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goto out;
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if (index < file_end || squashfs_i(inode)->fragment_block ==
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SQUASHFS_INVALID_BLK) {
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u64 block = 0;
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int bsize = read_blocklist(inode, index, &block);
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if (bsize < 0)
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goto error_out;
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if (bsize == 0)
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res = squashfs_readpage_sparse(page, expected);
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else
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res = squashfs_readpage_block(page, block, bsize, expected);
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} else
|
|
res = squashfs_readpage_fragment(page, expected);
|
|
|
|
if (!res)
|
|
return 0;
|
|
|
|
error_out:
|
|
SetPageError(page);
|
|
out:
|
|
pageaddr = kmap_atomic(page);
|
|
memset(pageaddr, 0, PAGE_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
|
|
};
|