ceph: fix leak of dentry in ceph_init_dentry() error path

If we fail to allocate a ceph_dentry_info, don't leak the dn reference.
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/inode.c

@@ -1199,8 +1199,10 @@ int ceph_readdir_prepopulate(struct ceph_mds_request *req,
 				goto out;
 			}
 			err = ceph_init_dentry(dn);
-			if (err < 0)
+			if (err < 0) {
+				dput(dn);
 				goto out;
+			}
 		} else if (dn->d_inode &&
 			   (ceph_ino(dn->d_inode) != vino.ino ||
 			    ceph_snap(dn->d_inode) != vino.snap)) {