[XFS] fix one more set of transaction callback ordering issues,

this was always there, but exposed by the last change in
this area and made much more likely.

SGI Modid: 2.5.x-xfs:slinx:139655a

fs/xfs/xfs_log.c

@@ -378,17 +378,26 @@ xfs_log_notify(xfs_mount_t	  *mp,		/* mount of partition */
 		iclog->ic_callback_tail = &(cb->cb_next);
 	}
 	LOG_UNLOCK(log, spl);
-	if (!abortflg) {
-		if (xlog_state_release_iclog(log, iclog)) {
-			xfs_force_shutdown(mp, XFS_LOG_IO_ERROR);
-			return EIO;
-		}
-	} else {
+	if (abortflg) {
 		cb->cb_func(cb->cb_arg, abortflg);
 	}
 	return 0;
 }	/* xfs_log_notify */
 
+int
+xfs_log_release_iclog(xfs_mount_t *mp,
+		      void	  *iclog_hndl)
+{
+	xlog_t *log = mp->m_log;
+	xlog_in_core_t	  *iclog = (xlog_in_core_t *)iclog_hndl;
+
+	if (xlog_state_release_iclog(log, iclog)) {
+		xfs_force_shutdown(mp, XFS_LOG_IO_ERROR);
+		return(EIO);
+	}
+
+	return 0;
+}
 
 /*
  * Initialize log manager data.	 This routine is intended to be called when

fs/xfs/xfs_log.h

@@ -164,6 +164,8 @@ void	  xfs_log_move_tail(struct xfs_mount	*mp,
 int	  xfs_log_notify(struct xfs_mount	*mp,
 			 void			*iclog,
 			 xfs_log_callback_t	*callback_entry);
+int	  xfs_log_release_iclog(struct xfs_mount *mp,
+			 void			 *iclog_hndl);
 int	  xfs_log_reserve(struct xfs_mount *mp,
 			  int		   length,
 			  int		   count,

fs/xfs/xfs_trans.c

@@ -808,19 +808,6 @@ xfs_trans_commit(
 		return XFS_ERROR(EIO);
 	}
 
-	/*
-	 * Once all the items of the transaction have been copied
-	 * to the in core log we can release them.  Do that here.
-	 * This will free descriptors pointing to items which were
-	 * not logged since there is nothing more to do with them.
-	 * For items which were logged, we will keep pointers to them
-	 * so they can be unpinned after the transaction commits to disk.
-	 * This will also stamp each modified meta-data item with
-	 * the commit lsn of this transaction for dependency tracking
-	 * purposes.
-	 */
-	xfs_trans_unlock_items(tp, commit_lsn);
-
 	/*
 	 * Once the transaction has committed, unused
 	 * reservations need to be released and changes to
@@ -856,12 +843,36 @@ xfs_trans_commit(
 	tp->t_logcb.cb_arg = tp;
 
 	/* We need to pass the iclog buffer which was used for the
-	 * transaction commit record into this function, attach
-	 * the callback to it, and then release it. This will guarantee
-	 * that we do callbacks on the transaction in the correct order.
+	 * transaction commit record into this function, and attach
+	 * the callback to it. The callback must be attached before
+	 * the items are unlocked to avoid racing with other threads
+	 * waiting for an item to unlock.
 	 */
 	error = xfs_log_notify(mp, commit_iclog, &(tp->t_logcb));
 #endif
+
+	/*
+	 * Once all the items of the transaction have been copied
+	 * to the in core log and the callback is attached, the
+	 * items can be unlocked.
+	 *
+	 * This will free descriptors pointing to items which were
+	 * not logged since there is nothing more to do with them.
+	 * For items which were logged, we will keep pointers to them
+	 * so they can be unpinned after the transaction commits to disk.
+	 * This will also stamp each modified meta-data item with
+	 * the commit lsn of this transaction for dependency tracking
+	 * purposes.
+	 */
+	xfs_trans_unlock_items(tp, commit_lsn);
+
+	/*
+	 * Now that the xfs_trans_committed callback has been attached,
+	 * and the items are released we can finally allow the iclog to
+	 * go to disk.
+	 */
+	error = xfs_log_release_iclog(mp, commit_iclog);
+
 	/*
 	 * If the transaction needs to be synchronous, then force the
 	 * log out now and wait for it.