xfs: split iop_unlock

The iop_unlock method is called when comitting or cancelling a
transaction.  In the latter case, the transaction may or may not be
aborted.  While there is no known problem with the current code in
practice, this implementation is limited in that any log item
implementation that might want to differentiate between a commit and a
cancellation must rely on the aborted state.  The aborted bit is only
set when the cancelled transaction is dirty, however.  This means that
there is no way to distinguish between a commit and a clean transaction
cancellation.

For example, intent log items currently rely on this distinction.  The
log item is either transferred to the CIL on commit or released on
transaction cancel. There is currently no possibility for a clean intent
log item in a transaction, but if that state is ever introduced a cancel
of such a transaction will immediately result in memory leaks of the
associated log item(s).  This is an interface deficiency and landmine.

To clean this up, replace the iop_unlock method with an iop_release
method that is specific to transaction cancel.  The existing
iop_committing method occurs at the same time as iop_unlock in the
commit path and there is no need for two separate callbacks here.
Overload the iop_committing method with the current commit time
iop_unlock implementations to eliminate the need for the latter and
further simplify the interface.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 003d916904d2..261c51486d7a 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -780,9 +780,8 @@ xfs_trans_free_items(
 		xfs_trans_del_item(lip);
 		if (abort)
 			set_bit(XFS_LI_ABORTED, &lip->li_flags);
-
-		if (lip->li_ops->iop_unlock)
-			lip->li_ops->iop_unlock(lip);
+		if (lip->li_ops->iop_release)
+			lip->li_ops->iop_release(lip);
 	}
 }
 
@@ -815,7 +814,7 @@ xfs_log_item_batch_insert(
  *
  * If we are called with the aborted flag set, it is because a log write during
  * a CIL checkpoint commit has failed. In this case, all the items in the
- * checkpoint have already gone through iop_committed and iop_unlock, which
+ * checkpoint have already gone through iop_committed and iop_committing, which
  * means that checkpoint commit abort handling is treated exactly the same
  * as an iclog write error even though we haven't started any IO yet. Hence in
  * this case all we need to do is iop_committed processing, followed by an