[PATCH 2/6] locks: provide a file lease method enabling cluster-coherent leases

["J. Bruce Fields" <bfields@fieldses.org>]

From: J. Bruce Fields <bfields@fieldses.org>

Currently leases are only kept locally, so there's no way for a distributed
filesystem to enforce them against multiple clients.  We're particularly
interested in the case of nfsd exporting a cluster filesystem, in which
case nfsd needs cluster-coherent leases in order to implement delegations
correctly.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
---
 fs/locks.c         |    7 +++++--
 include/linux/fs.h |    1 +
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index 6ad3c7b..8fa4420 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1442,7 +1442,10 @@ int setlease(struct file *filp, long arg, struct file_lock **lease)
 	int error;
 
 	lock_kernel();
-	error = __setlease(filp, arg, lease);
+	if (filp->f_op && filp->f_op->setlease)
+		error = filp->f_op->setlease(filp, arg, lease);
+        else
+		error = __setlease(filp, arg, lease);
 	unlock_kernel();
 
 	return error;
@@ -1474,7 +1477,7 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
 
 	lock_kernel();
 
-	error = __setlease(filp, arg, &flp);
+	error = setlease(filp, arg, &flp);
 	if (error || arg == F_UNLCK)
 		goto out_unlock;
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6a41f4c..4fbbc7f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1113,6 +1113,7 @@ struct file_operations {
 	int (*flock) (struct file *, int, struct file_lock *);
 	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
 	ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
+	int (*setlease)(struct file *, long, struct file_lock **);
 };
 
 struct inode_operations {
-- 
1.5.2.58.g98ee