Squashfs: Add XZ compression configuration option

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

fs/squashfs/Kconfig

@@ -53,6 +53,21 @@ config SQUASHFS_LZO
 
 	  If unsure, say N.
 
+config SQUASHFS_XZ
+	bool "Include support for XZ compressed file systems"
+	depends on SQUASHFS
+	select XZ_DEC
+	help
+	  Saying Y here includes support for reading Squashfs file systems
+	  compressed with XZ compresssion.  XZ gives better compression than
+	  the default zlib compression, at the expense of greater CPU and
+	  memory overhead.
+
+	  XZ is not the standard compression used in Squashfs and so most
+	  file systems will be readable without selecting this option.
+
+	  If unsure, say N.
+
 config SQUASHFS_EMBEDDED
 	bool "Additional option for memory-constrained systems"
 	depends on SQUASHFS

fs/squashfs/Makefile

@@ -7,3 +7,4 @@ 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 decompressor.o
 squashfs-$(CONFIG_SQUASHFS_XATTR) += xattr.o xattr_id.o
 squashfs-$(CONFIG_SQUASHFS_LZO) += lzo_wrapper.o
+squashfs-$(CONFIG_SQUASHFS_XZ) += xz_wrapper.o

fs/squashfs/decompressor.c

@@ -46,6 +46,12 @@ static const struct squashfs_decompressor squashfs_lzo_unsupported_comp_ops = {
 };
 #endif
 
+#ifndef CONFIG_SQUASHFS_XZ
+static const struct squashfs_decompressor squashfs_xz_comp_ops = {
+	NULL, NULL, NULL, XZ_COMPRESSION, "xz", 0
+};
+#endif
+
 static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
 	NULL, NULL, NULL, 0, "unknown", 0
 };
@@ -58,6 +64,7 @@ static const struct squashfs_decompressor *decompressor[] = {
 #else
 	&squashfs_lzo_unsupported_comp_ops,
 #endif
+	&squashfs_xz_comp_ops,
 	&squashfs_unknown_comp_ops
 };
 

fs/squashfs/decompressor.h

@@ -52,4 +52,9 @@ static inline int squashfs_decompress(struct squashfs_sb_info *msblk,
 	return msblk->decompressor->decompress(msblk, buffer, bh, b, offset,
 		length, srclength, pages);
 }
+
+#ifdef CONFIG_SQUASHFS_XZ
+extern const struct squashfs_decompressor squashfs_xz_comp_ops;
+#endif
+
 #endif