Squashfs: add a decompressor framework

This adds a decompressor framework which allows multiple compression
algorithms to be cleanly supported.

Also update zlib wrapper and other code to use the new framework.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

fs/squashfs/Makefile

@@ -4,4 +4,4 @@
 
 obj-$(CONFIG_SQUASHFS) += squashfs.o
 squashfs-y += block.o cache.o dir.o export.o file.o fragment.o id.o inode.o
-squashfs-y += namei.o super.o symlink.o zlib_wrapper.o
+squashfs-y += namei.o super.o symlink.o zlib_wrapper.o decompressor.o

fs/squashfs/block.c

@@ -36,6 +36,7 @@
 #include "squashfs_fs_sb.h"
 #include "squashfs_fs_i.h"
 #include "squashfs.h"
+#include "decompressor.h"
 
 /*
  * Read the metadata block length, this is stored in the first two
@@ -151,7 +152,7 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
 	}
 
 	if (compressed) {
-		length = squashfs_zlib_uncompress(msblk, buffer, bh, b, offset,
+		length = squashfs_decompress(msblk, buffer, bh, b, offset,
 			 length, srclength, pages);
 		if (length < 0)
 			goto read_failure;

fs/squashfs/decompressor.c

@@ -0,0 +1,58 @@
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
+ * Phillip Lougher <phillip@lougher.demon.co.uk>
+ *
+ * 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.
+ *
+ * decompressor.c
+ */
+
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/buffer_head.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs_fs_i.h"
+#include "decompressor.h"
+#include "squashfs.h"
+
+/*
+ * This file (and decompressor.h) implements a decompressor framework for
+ * Squashfs, allowing multiple decompressors to be easily supported
+ */
+
+static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
+	NULL, NULL, NULL, 0, "unknown", 0
+};
+
+static const struct squashfs_decompressor *decompressor[] = {
+	&squashfs_zlib_comp_ops,
+	&squashfs_unknown_comp_ops
+};
+
+
+const struct squashfs_decompressor *squashfs_lookup_decompressor(int id)
+{
+	int i;
+
+	for (i = 0; decompressor[i]->id; i++)
+		if (id == decompressor[i]->id)
+			break;
+
+	return decompressor[i];
+}

fs/squashfs/decompressor.h

@@ -0,0 +1,55 @@
+#ifndef DECOMPRESSOR_H
+#define DECOMPRESSOR_H
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
+ * Phillip Lougher <phillip@lougher.demon.co.uk>
+ *
+ * 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.
+ *
+ * decompressor.h
+ */
+
+struct squashfs_decompressor {
+	void	*(*init)(struct squashfs_sb_info *);
+	void	(*free)(void *);
+	int	(*decompress)(struct squashfs_sb_info *, void **,
+		struct buffer_head **, int, int, int, int, int);
+	int	id;
+	char	*name;
+	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)
+{
+	if (msblk->decompressor)
+		msblk->decompressor->free(s);
+}
+
+static inline int squashfs_decompress(struct squashfs_sb_info *msblk,
+	void **buffer, struct buffer_head **bh, int b, int offset, int length,
+	int srclength, int pages)
+{
+	return msblk->decompressor->decompress(msblk, buffer, bh, b, offset,
+		length, srclength, pages);
+}
+#endif

fs/squashfs/squashfs.h

@@ -51,6 +51,9 @@ extern struct squashfs_cache_entry *squashfs_get_datablock(struct super_block *,
 				u64, int);
 extern int squashfs_read_table(struct super_block *, void *, u64, int);
 
+/* decompressor.c */
+extern const struct squashfs_decompressor *squashfs_lookup_decompressor(int);
+
 /* export.c */
 extern __le64 *squashfs_read_inode_lookup_table(struct super_block *, u64,
 				unsigned int);
@@ -70,14 +73,8 @@ extern struct inode *squashfs_iget(struct super_block *, long long,
 				unsigned int);
 extern int squashfs_read_inode(struct inode *, long long);
 
-/* zlib_wrapper.c */
-extern void *squashfs_zlib_init(void);
-extern void squashfs_zlib_free(void *);
-extern int squashfs_zlib_uncompress(struct squashfs_sb_info *, void **,
-				struct buffer_head **, int, int, int, int, int);
-
 /*
- * Inodes and files operations
+ * Inodes, files and decompressor operations
  */
 
 /* dir.c */
@@ -94,3 +91,6 @@ extern const struct inode_operations squashfs_dir_inode_ops;
 
 /* symlink.c */
 extern const struct address_space_operations squashfs_symlink_aops;
+
+/* zlib_wrapper.c */
+extern const struct squashfs_decompressor squashfs_zlib_comp_ops;

fs/squashfs/squashfs_fs_sb.h

@@ -52,25 +52,26 @@ struct squashfs_cache_entry {
 };
 
 struct squashfs_sb_info {
-	int			devblksize;
-	int			devblksize_log2;
-	struct squashfs_cache	*block_cache;
-	struct squashfs_cache	*fragment_cache;
-	struct squashfs_cache	*read_page;
-	int			next_meta_index;
-	__le64			*id_table;
-	__le64			*fragment_index;
-	unsigned int		*fragment_index_2;
-	struct mutex		read_data_mutex;
-	struct mutex		meta_index_mutex;
-	struct meta_index	*meta_index;
-	void			*stream;
-	__le64			*inode_lookup_table;
-	u64			inode_table;
-	u64			directory_table;
-	unsigned int		block_size;
-	unsigned short		block_log;
-	long long		bytes_used;
-	unsigned int		inodes;
+	const struct squashfs_decompressor	*decompressor;
+	int					devblksize;
+	int					devblksize_log2;
+	struct squashfs_cache			*block_cache;
+	struct squashfs_cache			*fragment_cache;
+	struct squashfs_cache			*read_page;
+	int					next_meta_index;
+	__le64					*id_table;
+	__le64					*fragment_index;
+	unsigned int				*fragment_index_2;
+	struct mutex				read_data_mutex;
+	struct mutex				meta_index_mutex;
+	struct meta_index			*meta_index;
+	void					*stream;
+	__le64					*inode_lookup_table;
+	u64					inode_table;
+	u64					directory_table;
+	unsigned int				block_size;
+	unsigned short				block_log;
+	long long				bytes_used;
+	unsigned int				inodes;
 };
 #endif

fs/squashfs/super.c

@@ -41,27 +41,35 @@
 #include "squashfs_fs_sb.h"
 #include "squashfs_fs_i.h"
 #include "squashfs.h"
+#include "decompressor.h"
 
 static struct file_system_type squashfs_fs_type;
 static const struct super_operations squashfs_super_ops;
 
-static int supported_squashfs_filesystem(short major, short minor, short comp)
+static const struct squashfs_decompressor *supported_squashfs_filesystem(short
+	major, short minor, short id)
 {
+	const struct squashfs_decompressor *decompressor;
+
 	if (major < SQUASHFS_MAJOR) {
 		ERROR("Major/Minor mismatch, older Squashfs %d.%d "
 			"filesystems are unsupported\n", major, minor);
-		return -EINVAL;
+		return NULL;
 	} else if (major > SQUASHFS_MAJOR || minor > SQUASHFS_MINOR) {
 		ERROR("Major/Minor mismatch, trying to mount newer "
 			"%d.%d filesystem\n", major, minor);
 		ERROR("Please update your kernel\n");
-		return -EINVAL;
+		return NULL;
 	}
 
-	if (comp != ZLIB_COMPRESSION)
-		return -EINVAL;
+	decompressor = squashfs_lookup_decompressor(id);
+	if (!decompressor->supported) {
+		ERROR("Filesystem uses \"%s\" compression. This is not "
+			"supported\n", decompressor->name);
+		return NULL;
+	}
 
-	return 0;
+	return decompressor;
 }
 
 
@@ -86,10 +94,6 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	}
 	msblk = sb->s_fs_info;
 
-	msblk->stream = squashfs_zlib_init();
-	if (msblk->stream == NULL)
-		goto failure;
-
 	sblk = kzalloc(sizeof(*sblk), GFP_KERNEL);
 	if (sblk == NULL) {
 		ERROR("Failed to allocate squashfs_super_block\n");
@@ -116,25 +120,25 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed_mount;
 	}
 
+	err = -EINVAL;
+
 	/* Check it is a SQUASHFS superblock */
 	sb->s_magic = le32_to_cpu(sblk->s_magic);
 	if (sb->s_magic != SQUASHFS_MAGIC) {
 		if (!silent)
 			ERROR("Can't find a SQUASHFS superblock on %s\n",
 						bdevname(sb->s_bdev, b));
-		err = -EINVAL;
 		goto failed_mount;
 	}
 
-	/* Check the MAJOR & MINOR versions and compression type */
-	err = supported_squashfs_filesystem(le16_to_cpu(sblk->s_major),
+	/* Check the MAJOR & MINOR versions and lookup compression type */
+	msblk->decompressor = supported_squashfs_filesystem(
+			le16_to_cpu(sblk->s_major),
 			le16_to_cpu(sblk->s_minor),
 			le16_to_cpu(sblk->compression));
-	if (err < 0)
+	if (msblk->decompressor == NULL)
 		goto failed_mount;
 
-	err = -EINVAL;
-
 	/*
 	 * Check if there's xattrs in the filesystem.  These are not
 	 * supported in this version, so warn that they will be ignored.
@@ -201,6 +205,10 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 
 	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)
@@ -288,7 +296,7 @@ failed_mount:
 	squashfs_cache_delete(msblk->block_cache);
 	squashfs_cache_delete(msblk->fragment_cache);
 	squashfs_cache_delete(msblk->read_page);
-	squashfs_zlib_free(msblk->stream);
+	squashfs_decompressor_free(msblk, msblk->stream);
 	kfree(msblk->inode_lookup_table);
 	kfree(msblk->fragment_index);
 	kfree(msblk->id_table);
@@ -298,7 +306,6 @@ failed_mount:
 	return err;
 
 failure:
-	squashfs_zlib_free(msblk->stream);
 	kfree(sb->s_fs_info);
 	sb->s_fs_info = NULL;
 	return -ENOMEM;
@@ -342,7 +349,7 @@ static void squashfs_put_super(struct super_block *sb)
 		squashfs_cache_delete(sbi->block_cache);
 		squashfs_cache_delete(sbi->fragment_cache);
 		squashfs_cache_delete(sbi->read_page);
-		squashfs_zlib_free(sbi->stream);
+		squashfs_decompressor_free(sbi, sbi->stream);
 		kfree(sbi->id_table);
 		kfree(sbi->fragment_index);
 		kfree(sbi->meta_index);

fs/squashfs/zlib_wrapper.c

@@ -30,8 +30,9 @@
 #include "squashfs_fs_sb.h"
 #include "squashfs_fs_i.h"
 #include "squashfs.h"
+#include "decompressor.h"
 
-void *squashfs_zlib_init()
+static void *zlib_init(struct squashfs_sb_info *dummy)
 {
 	z_stream *stream = kmalloc(sizeof(z_stream), GFP_KERNEL);
 	if (stream == NULL)
@@ -50,7 +51,7 @@ failed:
 }
 
 
-void squashfs_zlib_free(void *strm)
+static void zlib_free(void *strm)
 {
 	z_stream *stream = strm;
 
@@ -60,7 +61,7 @@ void squashfs_zlib_free(void *strm)
 }
 
 
-int squashfs_zlib_uncompress(struct squashfs_sb_info *msblk, void **buffer,
+static int zlib_uncompress(struct squashfs_sb_info *msblk, void **buffer,
 	struct buffer_head **bh, int b, int offset, int length, int srclength,
 	int pages)
 {
@@ -137,3 +138,13 @@ release_mutex:
 
 	return -EIO;
 }
+
+const struct squashfs_decompressor squashfs_zlib_comp_ops = {
+	.init = zlib_init,
+	.free = zlib_free,
+	.decompress = zlib_uncompress,
+	.id = ZLIB_COMPRESSION,
+	.name = "zlib",
+	.supported = 1
+};
+