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/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