ufs: permit mounting of BorderWare filesystems

I recently had to recover some files from an old broken machine that was
running BorderWare Document Gateway.  It's basically a drop in web server
for sharing files.  From the look of the init process and using strings on
of a few files it seems to be based on FreeBSD 3.3.

The process turned out to be more difficult than I imagined, but to cut a
long story short BorderWare in their wisdom use a nonstandard magic number
in their UFS (ufstype=44bsd) file systems.  Thus Linux refuses to mount
the file systems in order to recover the data.  After a bit of hunting I
was able to make a quick fix to fs/ufs/super.c in order to detect the new
magic number.

I assume that this number is the same for all installations.  It's quite
easy to find out from ufs_fs.h.  The superblock sits 8k into the block
device and the magic number its 1372 bytes into the superblock struct.

# dd if=/dev/sda5 skip=$(( 8192 + 1372 )) bs=1 count=4 2> /dev/null | hd
00000000  97 26 24 0f                                       |.&$.|
#

Signed-off-by: Thomas Stewart <thomas@stewarts.org.uk>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ufs/super.c

@@ -918,6 +918,7 @@ again:
 	sbi->s_bytesex = BYTESEX_LE;
 	switch ((uspi->fs_magic = fs32_to_cpu(sb, usb3->fs_magic))) {
 		case UFS_MAGIC:
+		case UFS_MAGIC_BW:
 		case UFS2_MAGIC:
 		case UFS_MAGIC_LFN:
 	        case UFS_MAGIC_FEA:
@@ -927,6 +928,7 @@ again:
 	sbi->s_bytesex = BYTESEX_BE;
 	switch ((uspi->fs_magic = fs32_to_cpu(sb, usb3->fs_magic))) {
 		case UFS_MAGIC:
+		case UFS_MAGIC_BW:
 		case UFS2_MAGIC:
 		case UFS_MAGIC_LFN:
 	        case UFS_MAGIC_FEA:

fs/ufs/ufs_fs.h

@@ -48,6 +48,7 @@ typedef __u16 __bitwise __fs16;
 #define UFS_SECTOR_SIZE 512
 #define UFS_SECTOR_BITS 9
 #define UFS_MAGIC  0x00011954
+#define UFS_MAGIC_BW 0x0f242697
 #define UFS2_MAGIC 0x19540119
 #define UFS_CIGAM  0x54190100 /* byteswapped MAGIC */