[PATCH 23/24] filelock: default to returning -EINVAL when ->setlease operation is NULL

[Jeff Layton]

Now that most filesystems where we expect to need lease support have
their ->setlease() operations explicitly set, change kernel_setlease()
to return -EINVAL when the setlease is a NULL pointer.

Also update the Documentation/ with info about this change.

Signed-off-by: Jeff Layton <jlayton at kernel.org>
---
 Documentation/filesystems/porting.rst | 9 +++++++++
 Documentation/filesystems/vfs.rst     | 9 ++++++---
 fs/locks.c                            | 3 +--
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 3397937ed838e5e7dfacc6379a9d71481cc30914..c0f7103628ab5ed70d142a5c7f6d95ca4734c741 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1334,3 +1334,12 @@ end_creating() and the parent will be unlocked precisely when necessary.
 
 kill_litter_super() is gone; convert to DCACHE_PERSISTENT use (as all
 in-tree filesystems have done).
+
+---
+
+**mandatory**
+
+The ->setlease() file_operation must now be explicitly set in order to provide
+support for leases. When set to NULL, the kernel will now return -EINVAL to
+attempts to set a lease. Filesystems that wish to use the kernel-internal lease
+implementation should set it to generic_setlease().
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index 670ba66b60e4964927164a57e68adc0edfc681ee..21dc8921dd9ebedeafc4c108de7327f172138b6e 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -1180,9 +1180,12 @@ otherwise noted.
 	method is used by the splice(2) system call
 
 ``setlease``
-	called by the VFS to set or release a file lock lease.  setlease
-	implementations should call generic_setlease to record or remove
-	the lease in the inode after setting it.
+	called by the VFS to set or release a file lock lease.  Local
+	filesystems that wish to use the kernel-internal lease implementation
+	should set this to generic_setlease(). Other setlease implementations
+	should call generic_setlease() to record or remove the lease in the inode
+	after setting it. When set to NULL, attempts to set or remove a lease will
+	return -EINVAL.
 
 ``fallocate``
 	called by the VFS to preallocate blocks or punch a hole.
diff --git a/fs/locks.c b/fs/locks.c
index e2036aa4bd3734be415296f9157d8f17166878aa..ea38a18f373c2202ba79e8e37125f8d32a0e2d42 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2016,8 +2016,7 @@ kernel_setlease(struct file *filp, int arg, struct file_lease **lease, void **pr
 		setlease_notifier(arg, *lease);
 	if (filp->f_op->setlease)
 		return filp->f_op->setlease(filp, arg, lease, priv);
-	else
-		return generic_setlease(filp, arg, lease, priv);
+	return -EINVAL;
 }
 EXPORT_SYMBOL_GPL(kernel_setlease);
 

-- 
2.52.0