fs/reiserfs: return f_fsid for statfs(2)

Make reiserfs3 return f_fsid info for statfs(2).  By Andreas' suggestion,
this patch populates a persistent f_fsid between boots/mounts with help of
on-disk uuid record.

Randy Dunlap reported a compiling error from v2 patch like:
    fs/built-in.o: In function `reiserfs_statfs':
    super.c:(.text+0x7332b): undefined reference to `crc32_le'
    super.c:(.text+0x7333f): undefined reference to `crc32_le'
Also he provided helpful solution to fix this error. The modification of v3
patch is based on Randy's suggestion, add 'select CRC32' in fs/reiserfs/Kconfig.

Signed-off-by: Coly Li <coly.li@suse.de>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/reiserfs/Kconfig

@@ -1,5 +1,6 @@
 config REISERFS_FS
 	tristate "Reiserfs support"
+	select CRC32
 	help
 	  Stores not just filenames but the files themselves in a balanced
 	  tree.  Uses journalling.

fs/reiserfs/super.c

@@ -27,6 +27,7 @@
 #include <linux/mnt_namespace.h>
 #include <linux/mount.h>
 #include <linux/namei.h>
+#include <linux/crc32.h>
 
 struct file_system_type reiserfs_fs_type;
 
@@ -1904,6 +1905,10 @@ static int reiserfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_bsize = dentry->d_sb->s_blocksize;
 	/* changed to accommodate gcc folks. */
 	buf->f_type = REISERFS_SUPER_MAGIC;
+	buf->f_fsid.val[0] = (u32)crc32_le(0, rs->s_uuid, sizeof(rs->s_uuid)/2);
+	buf->f_fsid.val[1] = (u32)crc32_le(0, rs->s_uuid + sizeof(rs->s_uuid)/2,
+				sizeof(rs->s_uuid)/2);
+
 	return 0;
 }