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Squashfs: directory readdir operations
Signed-off-by: Phillip Lougher <[email protected]>
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Phillip Lougher
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Jan 5, 2009
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/* | ||
* Squashfs - a compressed read only filesystem for Linux | ||
* | ||
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 | ||
* Phillip Lougher <[email protected]> | ||
* | ||
* 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. | ||
* | ||
* dir.c | ||
*/ | ||
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/* | ||
* This file implements code to read directories from disk. | ||
* | ||
* See namei.c for a description of directory organisation on disk. | ||
*/ | ||
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#include <linux/fs.h> | ||
#include <linux/vfs.h> | ||
#include <linux/slab.h> | ||
#include <linux/zlib.h> | ||
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#include "squashfs_fs.h" | ||
#include "squashfs_fs_sb.h" | ||
#include "squashfs_fs_i.h" | ||
#include "squashfs.h" | ||
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static const unsigned char squashfs_filetype_table[] = { | ||
DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK | ||
}; | ||
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/* | ||
* Lookup offset (f_pos) in the directory index, returning the | ||
* metadata block containing it. | ||
* | ||
* If we get an error reading the index then return the part of the index | ||
* (if any) we have managed to read - the index isn't essential, just | ||
* quicker. | ||
*/ | ||
static int get_dir_index_using_offset(struct super_block *sb, | ||
u64 *next_block, int *next_offset, u64 index_start, int index_offset, | ||
int i_count, u64 f_pos) | ||
{ | ||
struct squashfs_sb_info *msblk = sb->s_fs_info; | ||
int err, i, index, length = 0; | ||
struct squashfs_dir_index dir_index; | ||
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TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n", | ||
i_count, f_pos); | ||
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/* | ||
* Translate from external f_pos to the internal f_pos. This | ||
* is offset by 3 because we invent "." and ".." entries which are | ||
* not actually stored in the directory. | ||
*/ | ||
if (f_pos < 3) | ||
return f_pos; | ||
f_pos -= 3; | ||
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for (i = 0; i < i_count; i++) { | ||
err = squashfs_read_metadata(sb, &dir_index, &index_start, | ||
&index_offset, sizeof(dir_index)); | ||
if (err < 0) | ||
break; | ||
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index = le32_to_cpu(dir_index.index); | ||
if (index > f_pos) | ||
/* | ||
* Found the index we're looking for. | ||
*/ | ||
break; | ||
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err = squashfs_read_metadata(sb, NULL, &index_start, | ||
&index_offset, le32_to_cpu(dir_index.size) + 1); | ||
if (err < 0) | ||
break; | ||
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length = index; | ||
*next_block = le32_to_cpu(dir_index.start_block) + | ||
msblk->directory_table; | ||
} | ||
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*next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE; | ||
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/* | ||
* Translate back from internal f_pos to external f_pos. | ||
*/ | ||
return length + 3; | ||
} | ||
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static int squashfs_readdir(struct file *file, void *dirent, filldir_t filldir) | ||
{ | ||
struct inode *inode = file->f_dentry->d_inode; | ||
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; | ||
u64 block = squashfs_i(inode)->start + msblk->directory_table; | ||
int offset = squashfs_i(inode)->offset, length = 0, dir_count, size, | ||
type, err; | ||
unsigned int inode_number; | ||
struct squashfs_dir_header dirh; | ||
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); | ||
if (dire == NULL) { | ||
ERROR("Failed to allocate squashfs_dir_entry\n"); | ||
goto finish; | ||
} | ||
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/* | ||
* Return "." and ".." entries as the first two filenames in the | ||
* directory. To maximise compression these two entries are not | ||
* stored in the directory, and so we invent them here. | ||
* | ||
* It also means that the external f_pos is offset by 3 from the | ||
* on-disk directory f_pos. | ||
*/ | ||
while (file->f_pos < 3) { | ||
char *name; | ||
int i_ino; | ||
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if (file->f_pos == 0) { | ||
name = "."; | ||
size = 1; | ||
i_ino = inode->i_ino; | ||
} else { | ||
name = ".."; | ||
size = 2; | ||
i_ino = squashfs_i(inode)->parent; | ||
} | ||
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TRACE("Calling filldir(%p, %s, %d, %lld, %d, %d)\n", | ||
dirent, name, size, file->f_pos, i_ino, | ||
squashfs_filetype_table[1]); | ||
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if (filldir(dirent, name, size, file->f_pos, i_ino, | ||
squashfs_filetype_table[1]) < 0) { | ||
TRACE("Filldir returned less than 0\n"); | ||
goto finish; | ||
} | ||
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file->f_pos += size; | ||
} | ||
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length = get_dir_index_using_offset(inode->i_sb, &block, &offset, | ||
squashfs_i(inode)->dir_idx_start, | ||
squashfs_i(inode)->dir_idx_offset, | ||
squashfs_i(inode)->dir_idx_cnt, | ||
file->f_pos); | ||
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while (length < i_size_read(inode)) { | ||
/* | ||
* Read directory header | ||
*/ | ||
err = squashfs_read_metadata(inode->i_sb, &dirh, &block, | ||
&offset, sizeof(dirh)); | ||
if (err < 0) | ||
goto failed_read; | ||
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length += sizeof(dirh); | ||
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dir_count = le32_to_cpu(dirh.count) + 1; | ||
while (dir_count--) { | ||
/* | ||
* Read directory entry. | ||
*/ | ||
err = squashfs_read_metadata(inode->i_sb, dire, &block, | ||
&offset, sizeof(*dire)); | ||
if (err < 0) | ||
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, | ||
&block, &offset, size); | ||
if (err < 0) | ||
goto failed_read; | ||
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length += sizeof(*dire) + size; | ||
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if (file->f_pos >= length) | ||
continue; | ||
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dire->name[size] = '\0'; | ||
inode_number = le32_to_cpu(dirh.inode_number) + | ||
((short) le16_to_cpu(dire->inode_number)); | ||
type = le16_to_cpu(dire->type); | ||
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TRACE("Calling filldir(%p, %s, %d, %lld, %x:%x, %d, %d)" | ||
"\n", dirent, dire->name, size, | ||
file->f_pos, | ||
le32_to_cpu(dirh.start_block), | ||
le16_to_cpu(dire->offset), | ||
inode_number, | ||
squashfs_filetype_table[type]); | ||
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if (filldir(dirent, dire->name, size, file->f_pos, | ||
inode_number, | ||
squashfs_filetype_table[type]) < 0) { | ||
TRACE("Filldir returned less than 0\n"); | ||
goto finish; | ||
} | ||
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file->f_pos = length; | ||
} | ||
} | ||
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finish: | ||
kfree(dire); | ||
return 0; | ||
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failed_read: | ||
ERROR("Unable to read directory block [%llx:%x]\n", block, offset); | ||
kfree(dire); | ||
return 0; | ||
} | ||
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const struct file_operations squashfs_dir_ops = { | ||
.read = generic_read_dir, | ||
.readdir = squashfs_readdir | ||
}; |