Squashfs: directory readdir operations
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
This commit is contained in:
Phillip Lougher
parent
c88da2c979
commit
07972dde75
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/*
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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@lougher.demon.co.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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* dir.c
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*/
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/*
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* This file implements code to read directories from disk.
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*
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* See namei.c for a description of directory organisation on disk.
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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/slab.h>
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#include <linux/zlib.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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static const unsigned char squashfs_filetype_table[] = {
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DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK
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};
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/*
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* Lookup offset (f_pos) in the directory index, returning the
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* metadata block containing it.
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*
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* If we get an error reading the index then return the part of the index
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* (if any) we have managed to read - the index isn't essential, just
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* quicker.
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*/
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static int get_dir_index_using_offset(struct super_block *sb,
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u64 *next_block, int *next_offset, u64 index_start, int index_offset,
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int i_count, u64 f_pos)
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{
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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int err, i, index, length = 0;
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struct squashfs_dir_index dir_index;
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TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n",
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i_count, f_pos);
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/*
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* Translate from external f_pos to the internal f_pos. This
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* is offset by 3 because we invent "." and ".." entries which are
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* not actually stored in the directory.
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*/
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if (f_pos < 3)
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return f_pos;
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f_pos -= 3;
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for (i = 0; i < i_count; i++) {
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err = squashfs_read_metadata(sb, &dir_index, &index_start,
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&index_offset, sizeof(dir_index));
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if (err < 0)
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break;
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index = le32_to_cpu(dir_index.index);
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if (index > f_pos)
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/*
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* Found the index we're looking for.
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*/
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break;
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err = squashfs_read_metadata(sb, NULL, &index_start,
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&index_offset, le32_to_cpu(dir_index.size) + 1);
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if (err < 0)
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break;
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length = index;
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*next_block = le32_to_cpu(dir_index.start_block) +
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msblk->directory_table;
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}
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*next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
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/*
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* Translate back from internal f_pos to external f_pos.
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*/
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return length + 3;
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}
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static int squashfs_readdir(struct file *file, void *dirent, filldir_t filldir)
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{
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struct inode *inode = file->f_dentry->d_inode;
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struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
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u64 block = squashfs_i(inode)->start + msblk->directory_table;
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int offset = squashfs_i(inode)->offset, length = 0, dir_count, size,
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type, err;
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unsigned int inode_number;
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struct squashfs_dir_header dirh;
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struct squashfs_dir_entry *dire;
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TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset);
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dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
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if (dire == NULL) {
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ERROR("Failed to allocate squashfs_dir_entry\n");
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goto finish;
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}
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/*
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* Return "." and ".." entries as the first two filenames in the
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* directory. To maximise compression these two entries are not
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* stored in the directory, and so we invent them here.
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*
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* It also means that the external f_pos is offset by 3 from the
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* on-disk directory f_pos.
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*/
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while (file->f_pos < 3) {
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char *name;
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int i_ino;
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if (file->f_pos == 0) {
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name = ".";
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size = 1;
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i_ino = inode->i_ino;
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} else {
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name = "..";
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size = 2;
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i_ino = squashfs_i(inode)->parent;
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}
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TRACE("Calling filldir(%p, %s, %d, %lld, %d, %d)\n",
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dirent, name, size, file->f_pos, i_ino,
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squashfs_filetype_table[1]);
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if (filldir(dirent, name, size, file->f_pos, i_ino,
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squashfs_filetype_table[1]) < 0) {
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TRACE("Filldir returned less than 0\n");
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goto finish;
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}
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file->f_pos += size;
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}
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length = get_dir_index_using_offset(inode->i_sb, &block, &offset,
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squashfs_i(inode)->dir_idx_start,
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squashfs_i(inode)->dir_idx_offset,
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squashfs_i(inode)->dir_idx_cnt,
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file->f_pos);
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while (length < i_size_read(inode)) {
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/*
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* Read directory header
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*/
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err = squashfs_read_metadata(inode->i_sb, &dirh, &block,
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&offset, sizeof(dirh));
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if (err < 0)
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goto failed_read;
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length += sizeof(dirh);
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dir_count = le32_to_cpu(dirh.count) + 1;
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while (dir_count--) {
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/*
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* Read directory entry.
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*/
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err = squashfs_read_metadata(inode->i_sb, dire, &block,
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&offset, sizeof(*dire));
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if (err < 0)
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goto failed_read;
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size = le16_to_cpu(dire->size) + 1;
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err = squashfs_read_metadata(inode->i_sb, dire->name,
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&block, &offset, size);
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if (err < 0)
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goto failed_read;
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length += sizeof(*dire) + size;
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if (file->f_pos >= length)
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continue;
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dire->name[size] = '\0';
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inode_number = le32_to_cpu(dirh.inode_number) +
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((short) le16_to_cpu(dire->inode_number));
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type = le16_to_cpu(dire->type);
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TRACE("Calling filldir(%p, %s, %d, %lld, %x:%x, %d, %d)"
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"\n", dirent, dire->name, size,
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file->f_pos,
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le32_to_cpu(dirh.start_block),
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le16_to_cpu(dire->offset),
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inode_number,
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squashfs_filetype_table[type]);
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if (filldir(dirent, dire->name, size, file->f_pos,
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inode_number,
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squashfs_filetype_table[type]) < 0) {
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TRACE("Filldir returned less than 0\n");
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goto finish;
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}
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file->f_pos = length;
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}
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}
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finish:
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kfree(dire);
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return 0;
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failed_read:
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ERROR("Unable to read directory block [%llx:%x]\n", block, offset);
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kfree(dire);
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return 0;
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}
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const struct file_operations squashfs_dir_ops = {
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.read = generic_read_dir,
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.readdir = squashfs_readdir
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};
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