3. SQUASHFS FILESYSTEM DESIGN
-----------------------------
-A squashfs filesystem consists of a maximum of eight parts, packed together on a byte
-alignment:
+A squashfs filesystem consists of a maximum of nine parts, packed together on a
+byte alignment:
---------------
| superblock |
|---------------|
+ | compression |
+ | options |
+ |---------------|
| datablocks |
| & fragments |
|---------------|
written the completed inode, directory, fragment, export and uid/gid lookup
tables are written.
-3.1 Inodes
+3.1 Compression options
+-----------------------
+
+Compressors can optionally support compression specific options (e.g.
+dictionary size). If non-default compression options have been used, then
+these are stored here.
+
+3.2 Inodes
----------
Metadata (inodes and directories) are compressed in 8Kbyte blocks. Each
regular files and directories, and extended types where extra
information has to be stored.
-3.2 Directories
+3.3 Directories
---------------
Like inodes, directories are packed into compressed metadata blocks, stored
This scheme has the advantage that it doesn't require extra memory overhead
and doesn't require much extra storage on disk.
-3.3 File data
+3.4 File data
-------------
Regular files consist of a sequence of contiguous compressed blocks, and/or a
The index cache is designed to be memory efficient, and by default uses
16 KiB.
-3.4 Fragment lookup table
+3.5 Fragment lookup table
-------------------------
Regular files can contain a fragment index which is mapped to a fragment
speed of access (and because it is small) is read at mount time and cached
in memory.
-3.5 Uid/gid lookup table
+3.6 Uid/gid lookup table
------------------------
For space efficiency regular files store uid and gid indexes, which are
locate these. This second index table for speed of access (and because it
is small) is read at mount time and cached in memory.
-3.6 Export table
+3.7 Export table
----------------
To enable Squashfs filesystems to be exportable (via NFS etc.) filesystems
used to locate these. This second index table for speed of access (and because
it is small) is read at mount time and cached in memory.
-3.7 Xattr table
+3.8 Xattr table
---------------
The xattr table contains extended attributes for each inode. The xattrs
help
Saying Y here includes support for SquashFS 4.0 (a Compressed
Read-Only File System). Squashfs is a highly compressed read-only
- filesystem for Linux. It uses zlib/lzo compression to compress both
- files, inodes and directories. Inodes in the system are very small
- and all blocks are packed to minimise data overhead. Block sizes
- greater than 4K are supported up to a maximum of 1 Mbytes (default
- block size 128K). SquashFS 4.0 supports 64 bit filesystems and files
- (larger than 4GB), full uid/gid information, hard links and
+ filesystem for Linux. It uses zlib, lzo or xz compression to
+ compress both files, inodes and directories. Inodes in the system
+ are very small and all blocks are packed to minimise data overhead.
+ Block sizes greater than 4K are supported up to a maximum of 1 Mbytes
+ (default block size 128K). SquashFS 4.0 supports 64 bit filesystems
+ and files (larger than 4GB), full uid/gid information, hard links and
timestamps.
Squashfs is intended for general read-only filesystem use, for
#include <linux/types.h>
#include <linux/mutex.h>
+#include <linux/slab.h>
#include <linux/buffer_head.h>
#include "squashfs_fs.h"
return decompressor[i];
}
+
+
+void *squashfs_decompressor_init(struct super_block *sb, unsigned short flags)
+{
+ struct squashfs_sb_info *msblk = sb->s_fs_info;
+ void *strm, *buffer = NULL;
+ int length = 0;
+
+ /*
+ * Read decompressor specific options from file system if present
+ */
+ if (SQUASHFS_COMP_OPTS(flags)) {
+ buffer = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL);
+ if (buffer == NULL)
+ return ERR_PTR(-ENOMEM);
+
+ length = squashfs_read_data(sb, &buffer,
+ sizeof(struct squashfs_super_block), 0, NULL,
+ PAGE_CACHE_SIZE, 1);
+
+ if (length < 0) {
+ strm = ERR_PTR(length);
+ goto finished;
+ }
+ }
+
+ strm = msblk->decompressor->init(msblk, buffer, length);
+
+finished:
+ kfree(buffer);
+
+ return strm;
+}
*/
struct squashfs_decompressor {
- void *(*init)(struct squashfs_sb_info *);
+ void *(*init)(struct squashfs_sb_info *, void *, int);
void (*free)(void *);
int (*decompress)(struct squashfs_sb_info *, void **,
struct buffer_head **, int, int, int, int, int);
int supported;
};
-static inline void *squashfs_decompressor_init(struct squashfs_sb_info *msblk)
-{
- return msblk->decompressor->init(msblk);
-}
-
static inline void squashfs_decompressor_free(struct squashfs_sb_info *msblk,
void *s)
{
length += sizeof(dirh);
dir_count = le32_to_cpu(dirh.count) + 1;
+
+ /* dir_count should never be larger than 256 */
+ if (dir_count > 256)
+ goto failed_read;
+
while (dir_count--) {
/*
* Read directory entry.
size = le16_to_cpu(dire->size) + 1;
+ /* size should never be larger than SQUASHFS_NAME_LEN */
+ if (size > SQUASHFS_NAME_LEN)
+ goto failed_read;
+
err = squashfs_read_metadata(inode->i_sb, dire->name,
&block, &offset, size);
if (err < 0)
void *output;
};
-static void *lzo_init(struct squashfs_sb_info *msblk)
+static void *lzo_init(struct squashfs_sb_info *msblk, void *buff, int len)
{
int block_size = max_t(int, msblk->block_size, SQUASHFS_METADATA_SIZE);
failed:
ERROR("Failed to allocate lzo workspace\n");
kfree(stream);
- return NULL;
+ return ERR_PTR(-ENOMEM);
}
length += sizeof(dirh);
dir_count = le32_to_cpu(dirh.count) + 1;
+
+ /* dir_count should never be larger than 256 */
+ if (dir_count > 256)
+ goto data_error;
+
while (dir_count--) {
/*
* Read directory entry.
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)
d_add(dentry, inode);
return ERR_PTR(0);
+data_error:
+ err = -EIO;
+
read_failure:
ERROR("Unable to read directory block [%llx:%x]\n",
squashfs_i(dir)->start + msblk->directory_table,
/* decompressor.c */
extern const struct squashfs_decompressor *squashfs_lookup_decompressor(int);
+extern void *squashfs_decompressor_init(struct super_block *, unsigned short);
/* export.c */
extern __le64 *squashfs_read_inode_lookup_table(struct super_block *, u64,
#define SQUASHFS_ALWAYS_FRAG 5
#define SQUASHFS_DUPLICATE 6
#define SQUASHFS_EXPORT 7
+#define SQUASHFS_COMP_OPT 10
#define SQUASHFS_BIT(flag, bit) ((flag >> bit) & 1)
#define SQUASHFS_EXPORTABLE(flags) SQUASHFS_BIT(flags, \
SQUASHFS_EXPORT)
+#define SQUASHFS_COMP_OPTS(flags) SQUASHFS_BIT(flags, \
+ SQUASHFS_COMP_OPT)
+
/* Max number of types and file types */
#define SQUASHFS_DIR_TYPE 1
#define SQUASHFS_REG_TYPE 2
err = -ENOMEM;
- msblk->stream = squashfs_decompressor_init(msblk);
- if (msblk->stream == NULL)
- goto failed_mount;
-
msblk->block_cache = squashfs_cache_init("metadata",
SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
if (msblk->block_cache == NULL)
goto failed_mount;
}
+ msblk->stream = squashfs_decompressor_init(sb, flags);
+ if (IS_ERR(msblk->stream)) {
+ err = PTR_ERR(msblk->stream);
+ msblk->stream = NULL;
+ goto failed_mount;
+ }
+
/* Allocate and read id index table */
msblk->id_table = squashfs_read_id_index_table(sb,
le64_to_cpu(sblk->id_table_start), le16_to_cpu(sblk->no_ids));
}
-static struct dentry *squashfs_mount(struct file_system_type *fs_type, int flags,
- const char *dev_name, void *data)
+static struct dentry *squashfs_mount(struct file_system_type *fs_type,
+ int flags, const char *dev_name, void *data)
{
return mount_bdev(fs_type, flags, dev_name, data, squashfs_fill_super);
}
#include <linux/buffer_head.h>
#include <linux/slab.h>
#include <linux/xz.h>
+#include <linux/bitops.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
-#include "squashfs_fs_i.h"
#include "squashfs.h"
#include "decompressor.h"
struct xz_buf buf;
};
-static void *squashfs_xz_init(struct squashfs_sb_info *msblk)
+struct comp_opts {
+ __le32 dictionary_size;
+ __le32 flags;
+};
+
+static void *squashfs_xz_init(struct squashfs_sb_info *msblk, void *buff,
+ int len)
{
- int block_size = max_t(int, msblk->block_size, SQUASHFS_METADATA_SIZE);
+ struct comp_opts *comp_opts = buff;
+ struct squashfs_xz *stream;
+ int dict_size = msblk->block_size;
+ int err, n;
+
+ if (comp_opts) {
+ /* check compressor options are the expected length */
+ if (len < sizeof(*comp_opts)) {
+ err = -EIO;
+ goto failed;
+ }
- struct squashfs_xz *stream = kmalloc(sizeof(*stream), GFP_KERNEL);
- if (stream == NULL)
+ dict_size = le32_to_cpu(comp_opts->dictionary_size);
+
+ /* the dictionary size should be 2^n or 2^n+2^(n+1) */
+ n = ffs(dict_size) - 1;
+ if (dict_size != (1 << n) && dict_size != (1 << n) +
+ (1 << (n + 1))) {
+ err = -EIO;
+ goto failed;
+ }
+ }
+
+ dict_size = max_t(int, dict_size, SQUASHFS_METADATA_SIZE);
+
+ stream = kmalloc(sizeof(*stream), GFP_KERNEL);
+ if (stream == NULL) {
+ err = -ENOMEM;
goto failed;
+ }
- stream->state = xz_dec_init(XZ_PREALLOC, block_size);
- if (stream->state == NULL)
+ stream->state = xz_dec_init(XZ_PREALLOC, dict_size);
+ if (stream->state == NULL) {
+ kfree(stream);
+ err = -ENOMEM;
goto failed;
+ }
return stream;
failed:
- ERROR("Failed to allocate xz workspace\n");
- kfree(stream);
- return NULL;
+ ERROR("Failed to initialise xz decompressor\n");
+ return ERR_PTR(err);
}
#include <linux/buffer_head.h>
#include <linux/slab.h>
#include <linux/zlib.h>
+#include <linux/vmalloc.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs.h"
#include "decompressor.h"
-static void *zlib_init(struct squashfs_sb_info *dummy)
+static void *zlib_init(struct squashfs_sb_info *dummy, void *buff, int len)
{
z_stream *stream = kmalloc(sizeof(z_stream), GFP_KERNEL);
if (stream == NULL)
goto failed;
- stream->workspace = kmalloc(zlib_inflate_workspacesize(),
- GFP_KERNEL);
+ stream->workspace = vmalloc(zlib_inflate_workspacesize());
if (stream->workspace == NULL)
goto failed;
failed:
ERROR("Failed to allocate zlib workspace\n");
kfree(stream);
- return NULL;
+ return ERR_PTR(-ENOMEM);
}
z_stream *stream = strm;
if (stream)
- kfree(stream->workspace);
+ vfree(stream->workspace);
kfree(stream);
}
git.openpandora.org / pandora-kernel.git / commitdiff