gfs2: getlabel support

Add support for the GETFSLABEL ioctl in gfs2.
I tested this patch and it works as expected.
Signed-off-by: Steve Whitehouse <swhiteho@redhat.com>
Tested-by: Abhi Das <adas@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

fs/gfs2/file.c

@@ -314,6 +314,17 @@ static int gfs2_set_flags(struct file *filp, u32 __user *ptr)
 	return do_gfs2_set_flags(filp, gfsflags, mask);
 }
 
+static int gfs2_getlabel(struct file *filp, char __user *label)
+{
+	struct inode *inode = file_inode(filp);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
+
+	if (copy_to_user(label, sdp->sd_sb.sb_locktable, GFS2_LOCKNAME_LEN))
+		return -EFAULT;
+
+	return 0;
+}
+
 static long gfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	switch(cmd) {
@@ -323,7 +334,10 @@ static long gfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return gfs2_set_flags(filp, (u32 __user *)arg);
 	case FITRIM:
 		return gfs2_fitrim(filp, (void __user *)arg);
+	case FS_IOC_GETFSLABEL:
+		return gfs2_getlabel(filp, (char __user *)arg);
 	}
+
 	return -ENOTTY;
 }