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

[Wendy Cheng <wcheng@redhat.com>]

Robert Rappaport wrote:

> [snip]
> ....   This is because the vfs running on the same node where the
> samba server is running is not necessarily aware of all accesses to
> the file on which it is granting a lease.  Since vfs does not
> currently inform file systems about the granting and rescinding of
> leases, a clustered file system cannot allow a samba server to support
> OpLocks on its files and this has a negative impact on performance.
>
> What I think is needed is to add a file systems defined
> file_operations function, that would be invoked when vfs is
> considering the granting of a lease on a file associated with an
> inode.  Such an enhancement would allow a file system to be come aware
> of vfs lease activity and allow it to support this activity.
>
NFS has similar issues because Linux NLM-VFS does not invoke server side 
filesystem specific lock method. This implies NFS client applications is 
not able to use posix locks to coordinate file access across different 
nodes  with a cluster filesystem, even the cluster filesystem itself 
does support posix locking. IBM Research and University of Michigan CITI 
group have worked out a set of patches to remedy the issue:

http://www.opensubscriber.com/message/linux-fsdevel@vger.kernel.org/5527833.html

-- Wendy