GFS2: Don't "get" xattrs for ACLs when ACLs are turned off

This is to match ext3 behaviour. We should not allow getting of
xattrs relating to ACLs when ACLs are turned off.
Reported-by: NNate Straz <nstraz@redhat.com>
Signed-off-by: NSteven Whitehouse <swhiteho@redhat.com>

fs/gfs2/acl.c

@@ -236,10 +236,14 @@ static int gfs2_xattr_system_get(struct dentry *dentry, const char *name,
 				 void *buffer, size_t size, int xtype)
 {
 	struct inode *inode = dentry->d_inode;
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
 	struct posix_acl *acl;
 	int type;
 	int error;
 
+	if (!sdp->sd_args.ar_posix_acl)
+		return -EOPNOTSUPP;
+
 	type = gfs2_acl_type(name);
 	if (type < 0)
 		return type;