HP CIFS File Locking Interoperation

6.6 WINDOWS AND PC-NFS CLIENT ACCESS – Local

and NFS Mounted File Systems

The diagram above shows a Windows client and a PC-NFS client requesting concurrent file

access on the CIFS/9000 server to a local and/or NFS mounted file system. The key issue for

this configuration is that with PC-NFS, the locking interoperability is the same for a local or

NFS mounted file system, and even for PC-NFS direct access to the NFS file server – as

illustrated above.

PC-NFS implements Mandatory Share Mode (Open Mode) locking through the NFS Network

Lock Manager. This allows PC-NFS to place and honor Mandatory Share Mode locks with

other PC-NFS clients. CIFS/9000 has been enhanced to translate Windows

Mandatory Share Mode locks into byte range locks, thus providing locking

interoperation with the UNIX/NFS advisory locking protocol and reducing the risk

of data corruption. This enhancement works for PC-NFS because of the interoperation in

the NLM. Windows applications expect mandatory share mode locking to be enabled, so

share mode locking should remain enabled on the CIFS/9000 server.

Byte Range locking is implemented for concurrent Windows and PC-NFS access using the

NFS NLM. Since NFS NLM byte range locking is advisory, Windows applications that are

accessing the file must be properly coded to participate in the locking protocol. PC-NFS will

propagate the Windows byte range lock over the PC-NFS mount. The cooperating CIFS/9000

smbd process actually calls the UNIX fcntl function to implement Windows client byte range

locking. Thus, a Windows PC-NFS client accessing a file on a CIFS/9000 share using

CIFS/9000

File

NFS

Windows

UNIX

PC-NFS

CIFS/9000

Clients