ceph: dereference pointer after checking for NULL

moved dereference after BUG_ON
Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>

fs/ceph/inode.c

@@ -851,11 +851,12 @@ static void ceph_set_dentry_offset(struct dentry *dn)
 {
 	struct dentry *dir = dn->d_parent;
 	struct inode *inode = dir->d_inode;
-	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_inode_info *ci;
 	struct ceph_dentry_info *di;
 
 	BUG_ON(!inode);
 
+	ci = ceph_inode(inode);
 	di = ceph_dentry(dn);
 
 	spin_lock(&ci->i_ceph_lock);