ocfs2: fix a tiny case that inode can not removed.

When running dirop_fileop_racer we found a case that inode can not removed.

2 nodes, say Node A and Node B, mount the same ocfs2 volume. Create two dirs /race/1/ and /race/2/ in the filesystem.

Node A Node B
rm -r /race/2/

                                  mv /race/1/ /race/2/

call ocfs2_unlink(), get
the EX mode of /race/2/
wait for B unlock /race/2/
decrease i_nlink of /race/2/ to 0,
and add inode of /race/2/ into
orphan dir, unlock /race/2/
got EX mode of /race/2/. because /race/1/ is dir, so inc i_nlink of /race/2/ and update into disk, unlock /race/2/
because i_nlink of /race/2/
is not zero, this inode will
always remain in orphan dir

This patch fixes this case by test whether i_nlink of new dir is zero.

---
 fs/ocfs2/namei.c | 9 +++++++++
 1 file changed, 9 insertions(+)

index b5c3a5e..fd6db5b 100644
@@ -1291,6 +1291,15 @@ static int ocfs2_rename(struct inode *old_dir,
 	}
 	parents_locked = 1;
 
+	if (!new_dir->i_nlink) {
+		mlog(ML_ERROR, "new dir %llu has been removed, inode %llu "
+				"can not be moved into it.",
+				(unsigned long long)new_dir->i_ino,
+				(unsigned long long)old_inode->i_ino);
+		status = -EACCES;
+		goto bail;
+	}
+
 	/* make sure both dirs have bhs
 	 * get an extra ref on old_dir_bh if old==new */
 	if (!new_dir_bh) {

-- 1.8.3.4