A 'lease_direct' lease requires that the vma have a valid MAP_DIRECT
mapping established. For xfs we establish a new lease and then check if
the MAP_DIRECT mapping has been broken. We want to be sure that the
process will receive notification that the MAP_DIRECT mapping is being
torn down so it knows why other code paths are throwing failures.

For example in the RDMA/ibverbs case we want ibv_reg_mr() to fail if the
MAP_DIRECT mapping is invalid or in the process of being invalidated.

Cc: Jan Kara <redacted>
Cc: Jeff Moyer <redacted>
Cc: Christoph Hellwig <redacted>
Cc: Dave Chinner <redacted>
Cc: "Darrick J. Wong" <redacted>
Cc: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: Jeff Layton <redacted>
Cc: "J. Bruce Fields" <redacted>
Signed-off-by: Dan Williams <redacted>
---
 fs/xfs/xfs_file.c |   28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index e35518600e28..823b65f17429 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c

@@ -1166,6 +1166,33 @@ xfs_filemap_direct_close(
 	put_map_direct_vma(vma->vm_private_data);
 }
 
+static struct lease_direct *
+xfs_filemap_direct_lease(
+	struct vm_area_struct	*vma,
+	void			(*break_fn)(void *),
+	void			*owner)
+{
+	struct lease_direct	*ld;
+
+	ld = map_direct_lease(vma, break_fn, owner);
+
+	if (IS_ERR(ld))
+		return ld;
+
+	/*
+	 * We now have an established lease while the base MAP_DIRECT
+	 * lease was not broken. So, we know that the "lease holder" will
+	 * receive a SIGIO notification when the lease is broken and
+	 * take any necessary cleanup actions.
+	 */
+	if (!is_map_direct_broken(vma->vm_private_data))
+		return ld;
+
+	map_direct_lease_destroy(ld);
+
+	return ERR_PTR(-ENXIO);