Ocfs2: Handle deletion of reflinked oprhan inodes correctly.

The rule is that all inodes in the orphan dir have ORPHANED_FL,
otherwise we treated it as an ERROR.  This rule works well except
for some rare cases of reflink operation:

http://oss.oracle.com/bugzilla/show_bug.cgi?id=1215

The problem is caused by how reflink and our orphan_scan thread
interact.

 * The orphan scan pulls the orphans into a queue first, then runs the
   queue at a later time.  We only hold the orphan_dir's lock
   during scanning.

 * Reflink create a oprhaned target in orphan_dir as its first step.
   It removes the target and clears the flag as the final step.
   These two steps take the orphan_dir's lock, but it is not held for
   the duration.

Based on the above semantics, a reflink inode can be moved out of the
orphan dir and have its ORPHANED_FL cleared before the queue of orphans
is run.  This leads to a ERROR in ocfs2_query_wipde_inode().

This patch teaches ocfs2_query_wipe_inode() to detect previously
orphaned reflink targets.  If a reflink fails or a crash occurs during
the relfink operation, the inode will retain ORPHANED_FL and will be
properly wiped.

Signed-off-by: Tristan Ye <tristan.ye@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

fs/ocfs2/inode.c

@@ -891,6 +891,21 @@ static int ocfs2_query_inode_wipe(struct inode *inode,
 	/* Do some basic inode verification... */
 	di = (struct ocfs2_dinode *) di_bh->b_data;
 	if (!(di->i_flags & cpu_to_le32(OCFS2_ORPHANED_FL))) {
+		/*
+		 * Inodes in the orphan dir must have ORPHANED_FL.  The only
+		 * inodes that come back out of the orphan dir are reflink
+		 * targets. A reflink target may be moved out of the orphan
+		 * dir between the time we scan the directory and the time we
+		 * process it. This would lead to HAS_REFCOUNT_FL being set but
+		 * ORPHANED_FL not.
+		 */
+		if (di->i_dyn_features & cpu_to_le16(OCFS2_HAS_REFCOUNT_FL)) {
+			mlog(0, "Reflinked inode %llu is no longer orphaned.  "
+			     "it shouldn't be deleted\n",
+			     (unsigned long long)oi->ip_blkno);
+			goto bail;
+		}
+
 		/* for lack of a better error? */
 		status = -EEXIST;
 		mlog(ML_ERROR,