nfs: disable leases over NFS

As Peter Staubach says elsewhere
(http://marc.info/?l=linux-kernel&m=118113649526444&w=2):

> The problem is that some file system such as NFSv2 and NFSv3 do
> not have sufficient support to be able to support leases correctly.
> In particular for these two file systems, there is no over the wire
> protocol support.
>
> Currently, these two file systems fail the fcntl(F_SETLEASE) call
> accidentally, due to a reference counting difference.  These file
> systems should fail more consciously, with a proper error to
> indicate that the call is invalid for them.

Define an nfs setlease method that just returns -EINVAL.

If someone can demonstrate a real need, perhaps we could reenable
them in the presence of the "nolock" mount option.

Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Cc: Peter Staubach <staubach@redhat.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 8689b736fdd9..13ac6fa2b62b 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -53,6 +53,7 @@ static int  nfs_fsync(struct file *, struct dentry *dentry, int datasync);
 static int nfs_check_flags(int flags);
 static int nfs_lock(struct file *filp, int cmd, struct file_lock *fl);
 static int nfs_flock(struct file *filp, int cmd, struct file_lock *fl);
+static int nfs_setlease(struct file *file, long arg, struct file_lock **fl);
 
 const struct file_operations nfs_file_operations = {
         .llseek         = nfs_file_llseek,
@@ -69,6 +70,7 @@ const struct file_operations nfs_file_operations = {
         .flock          = nfs_flock,
         .splice_read    = nfs_file_splice_read,
         .check_flags    = nfs_check_flags,
+        .setlease       = nfs_setlease,
 };
 
 const struct inode_operations nfs_file_inode_operations = {
@@ -558,3 +560,13 @@ static int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
                 return do_unlk(filp, cmd, fl);
         return do_setlk(filp, cmd, fl);
 }
+
+static int nfs_setlease(struct file *file, long arg, struct file_lock **fl)
+{
+        /*
+         * There is no protocol support for leases, so we have no way
+         * to implement them correctly in the face of opens by other
+         * clients.
+         */
+        return -EINVAL;
+}