Re: File system awareness (or lack thereof) of vfs granting of leases

[David Teigland <teigland@redhat.com>]

On Tue, Feb 20, 2007 at 10:46:51AM -0500, Robert Rappaport wrote:
> Thank you both for your helpful replies.  In particular, the addition
> of the calls to file system specific functions in routines,
> fcntl_setlease() and break_lease(), as well as the modifications to
> the file_operations and inode_operations structures, pointed to by
> Bruce's reply, look exactly like the hooks that I would need to
> proceed to resolve my problems.  Is there any timetable established
> for these modifications to make it into a future release?  These hooks
> would clearly benefit any cluster file system that has to deal with
> leases.

We did an experimental distributed lease implementation in gfs(1) a while
ago.  It worked, but was so extremely expensive that there was no point in
considering it seriously.  The problem is that _every_ open and close of
every file requires a new dlm lock operation.  Leases require knowledge
about the cluster-wide opened/closed state of files, not only that but the
mode they're open in.

Dave