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, 12 insertions, 3 deletions

diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index b6c684ea56c1..e9da8274bf31 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -595,7 +595,7 @@ xfs_buf_item_put(
  * free the item.
  */
 STATIC void
-xfs_buf_item_unlock(
+xfs_buf_item_release(
 	struct xfs_log_item	*lip)
 {
 	struct xfs_buf_log_item	*bip = BUF_ITEM(lip);
@@ -610,7 +610,7 @@ xfs_buf_item_unlock(
 						   &lip->li_flags);
 #endif
 
-	trace_xfs_buf_item_unlock(bip);
+	trace_xfs_buf_item_release(bip);
 
 	/*
 	 * The bli dirty state should match whether the blf has logged segments
@@ -640,6 +640,14 @@ xfs_buf_item_unlock(
 	xfs_buf_relse(bp);
 }
 
+STATIC void
+xfs_buf_item_committing(
+	struct xfs_log_item	*lip,
+	xfs_lsn_t		commit_lsn)
+{
+	return xfs_buf_item_release(lip);
+}
+
 /*
  * This is called to find out where the oldest active copy of the
  * buf log item in the on disk log resides now that the last log
@@ -680,7 +688,8 @@ static const struct xfs_item_ops xfs_buf_item_ops = {
 	.iop_format	= xfs_buf_item_format,
 	.iop_pin	= xfs_buf_item_pin,
 	.iop_unpin	= xfs_buf_item_unpin,
-	.iop_unlock	= xfs_buf_item_unlock,
+	.iop_release	= xfs_buf_item_release,
+	.iop_committing	= xfs_buf_item_committing,
 	.iop_committed	= xfs_buf_item_committed,
 	.iop_push	= xfs_buf_item_push,
 };