mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
238 lines
6.8 KiB
238 lines
6.8 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
|
/* |
|
* Squashfs - a compressed read only filesystem for Linux |
|
* |
|
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 |
|
* Phillip Lougher <[email protected]> |
|
* |
|
* namei.c |
|
*/ |
|
|
|
/* |
|
* This file implements code to do filename lookup in directories. |
|
* |
|
* Like inodes, directories are packed into compressed metadata blocks, stored |
|
* in a directory table. Directories are accessed using the start address of |
|
* the metablock containing the directory and the offset into the |
|
* decompressed block (<block, offset>). |
|
* |
|
* Directories are organised in a slightly complex way, and are not simply |
|
* a list of file names. The organisation takes advantage of the |
|
* fact that (in most cases) the inodes of the files will be in the same |
|
* compressed metadata block, and therefore, can share the start block. |
|
* Directories are therefore organised in a two level list, a directory |
|
* header containing the shared start block value, and a sequence of directory |
|
* entries, each of which share the shared start block. A new directory header |
|
* is written once/if the inode start block changes. The directory |
|
* header/directory entry list is repeated as many times as necessary. |
|
* |
|
* Directories are sorted, and can contain a directory index to speed up |
|
* file lookup. Directory indexes store one entry per metablock, each entry |
|
* storing the index/filename mapping to the first directory header |
|
* in each metadata block. Directories are sorted in alphabetical order, |
|
* and at lookup the index is scanned linearly looking for the first filename |
|
* alphabetically larger than the filename being looked up. At this point the |
|
* location of the metadata block the filename is in has been found. |
|
* The general idea of the index is ensure only one metadata block needs to be |
|
* decompressed to do a lookup irrespective of the length of the directory. |
|
* This scheme has the advantage that it doesn't require extra memory overhead |
|
* and doesn't require much extra storage on disk. |
|
*/ |
|
|
|
#include <linux/fs.h> |
|
#include <linux/vfs.h> |
|
#include <linux/slab.h> |
|
#include <linux/string.h> |
|
#include <linux/dcache.h> |
|
#include <linux/xattr.h> |
|
|
|
#include "squashfs_fs.h" |
|
#include "squashfs_fs_sb.h" |
|
#include "squashfs_fs_i.h" |
|
#include "squashfs.h" |
|
#include "xattr.h" |
|
|
|
/* |
|
* Lookup name in the directory index, returning the location of the metadata |
|
* block containing it, and the directory index this represents. |
|
* |
|
* 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_name(struct super_block *sb, |
|
u64 *next_block, int *next_offset, u64 index_start, |
|
int index_offset, int i_count, const char *name, |
|
int len) |
|
{ |
|
struct squashfs_sb_info *msblk = sb->s_fs_info; |
|
int i, length = 0, err; |
|
unsigned int size; |
|
struct squashfs_dir_index *index; |
|
char *str; |
|
|
|
TRACE("Entered get_dir_index_using_name, i_count %d\n", i_count); |
|
|
|
index = kmalloc(sizeof(*index) + SQUASHFS_NAME_LEN * 2 + 2, GFP_KERNEL); |
|
if (index == NULL) { |
|
ERROR("Failed to allocate squashfs_dir_index\n"); |
|
goto out; |
|
} |
|
|
|
str = &index->name[SQUASHFS_NAME_LEN + 1]; |
|
strncpy(str, name, len); |
|
str[len] = '\0'; |
|
|
|
for (i = 0; i < i_count; i++) { |
|
err = squashfs_read_metadata(sb, index, &index_start, |
|
&index_offset, sizeof(*index)); |
|
if (err < 0) |
|
break; |
|
|
|
|
|
size = le32_to_cpu(index->size) + 1; |
|
if (size > SQUASHFS_NAME_LEN) |
|
break; |
|
|
|
err = squashfs_read_metadata(sb, index->name, &index_start, |
|
&index_offset, size); |
|
if (err < 0) |
|
break; |
|
|
|
index->name[size] = '\0'; |
|
|
|
if (strcmp(index->name, str) > 0) |
|
break; |
|
|
|
length = le32_to_cpu(index->index); |
|
*next_block = le32_to_cpu(index->start_block) + |
|
msblk->directory_table; |
|
} |
|
|
|
*next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE; |
|
kfree(index); |
|
|
|
out: |
|
/* |
|
* Return index (f_pos) of the looked up metadata block. Translate |
|
* from internal f_pos to external f_pos which is offset by 3 because |
|
* we invent "." and ".." entries which are not actually stored in the |
|
* directory. |
|
*/ |
|
return length + 3; |
|
} |
|
|
|
|
|
static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry, |
|
unsigned int flags) |
|
{ |
|
const unsigned char *name = dentry->d_name.name; |
|
int len = dentry->d_name.len; |
|
struct inode *inode = NULL; |
|
struct squashfs_sb_info *msblk = dir->i_sb->s_fs_info; |
|
struct squashfs_dir_header dirh; |
|
struct squashfs_dir_entry *dire; |
|
u64 block = squashfs_i(dir)->start + msblk->directory_table; |
|
int offset = squashfs_i(dir)->offset; |
|
int err, length; |
|
unsigned int dir_count, size; |
|
|
|
TRACE("Entered squashfs_lookup [%llx:%x]\n", block, offset); |
|
|
|
dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL); |
|
if (dire == NULL) { |
|
ERROR("Failed to allocate squashfs_dir_entry\n"); |
|
return ERR_PTR(-ENOMEM); |
|
} |
|
|
|
if (len > SQUASHFS_NAME_LEN) { |
|
err = -ENAMETOOLONG; |
|
goto failed; |
|
} |
|
|
|
length = get_dir_index_using_name(dir->i_sb, &block, &offset, |
|
squashfs_i(dir)->dir_idx_start, |
|
squashfs_i(dir)->dir_idx_offset, |
|
squashfs_i(dir)->dir_idx_cnt, name, len); |
|
|
|
while (length < i_size_read(dir)) { |
|
/* |
|
* Read directory header. |
|
*/ |
|
err = squashfs_read_metadata(dir->i_sb, &dirh, &block, |
|
&offset, sizeof(dirh)); |
|
if (err < 0) |
|
goto read_failure; |
|
|
|
length += sizeof(dirh); |
|
|
|
dir_count = le32_to_cpu(dirh.count) + 1; |
|
|
|
if (dir_count > SQUASHFS_DIR_COUNT) |
|
goto data_error; |
|
|
|
while (dir_count--) { |
|
/* |
|
* Read directory entry. |
|
*/ |
|
err = squashfs_read_metadata(dir->i_sb, dire, &block, |
|
&offset, sizeof(*dire)); |
|
if (err < 0) |
|
goto read_failure; |
|
|
|
size = le16_to_cpu(dire->size) + 1; |
|
|
|
/* size should never be larger than SQUASHFS_NAME_LEN */ |
|
if (size > SQUASHFS_NAME_LEN) |
|
goto data_error; |
|
|
|
err = squashfs_read_metadata(dir->i_sb, dire->name, |
|
&block, &offset, size); |
|
if (err < 0) |
|
goto read_failure; |
|
|
|
length += sizeof(*dire) + size; |
|
|
|
if (name[0] < dire->name[0]) |
|
goto exit_lookup; |
|
|
|
if (len == size && !strncmp(name, dire->name, len)) { |
|
unsigned int blk, off, ino_num; |
|
long long ino; |
|
blk = le32_to_cpu(dirh.start_block); |
|
off = le16_to_cpu(dire->offset); |
|
ino_num = le32_to_cpu(dirh.inode_number) + |
|
(short) le16_to_cpu(dire->inode_number); |
|
ino = SQUASHFS_MKINODE(blk, off); |
|
|
|
TRACE("calling squashfs_iget for directory " |
|
"entry %s, inode %x:%x, %d\n", name, |
|
blk, off, ino_num); |
|
|
|
inode = squashfs_iget(dir->i_sb, ino, ino_num); |
|
goto exit_lookup; |
|
} |
|
} |
|
} |
|
|
|
exit_lookup: |
|
kfree(dire); |
|
return d_splice_alias(inode, dentry); |
|
|
|
data_error: |
|
err = -EIO; |
|
|
|
read_failure: |
|
ERROR("Unable to read directory block [%llx:%x]\n", |
|
squashfs_i(dir)->start + msblk->directory_table, |
|
squashfs_i(dir)->offset); |
|
failed: |
|
kfree(dire); |
|
return ERR_PTR(err); |
|
} |
|
|
|
|
|
const struct inode_operations squashfs_dir_inode_ops = { |
|
.lookup = squashfs_lookup, |
|
.listxattr = squashfs_listxattr |
|
};
|
|
|