xfs: use internal dfops in cow blocks cancel

All callers either explicitly initialize a dfops or pass a
transaction with an internal dfops. Drop the hacky old dfops
replacement logic and use the one associated with the transaction.

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

fs/xfs/xfs_reflink.c

@@ -483,8 +483,6 @@ xfs_reflink_cancel_cow_blocks(
 	struct xfs_ifork		*ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
 	struct xfs_bmbt_irec		got, del;
 	struct xfs_iext_cursor		icur;
-	struct xfs_defer_ops		dfops;
-	struct xfs_defer_ops		*odfops = (*tpp)->t_dfops;
 	int				error = 0;
 
 	if (!xfs_is_reflink_inode(ip))
@@ -511,7 +509,8 @@ xfs_reflink_cancel_cow_blocks(
 			if (error)
 				break;
 		} else if (del.br_state == XFS_EXT_UNWRITTEN || cancel_real) {
-			xfs_defer_init(*tpp, &dfops);
+			ASSERT((*tpp)->t_dfops);
+			ASSERT((*tpp)->t_firstblock == NULLFSBLOCK);
 
 			/* Free the CoW orphan record. */
 			error = xfs_refcount_free_cow_extent(ip->i_mount,
@@ -553,7 +552,6 @@ next_extent:
 	/* clear tag if cow fork is emptied */
 	if (!ifp->if_bytes)
 		xfs_inode_clear_cowblocks_tag(ip);
-	(*tpp)->t_dfops = odfops;
 	return error;
 }