Re: Fw: [OpenAFS-devel] openafs / opendfs collaboration

[Steven French]

> is it time to consider splitting the cache manager out of individual filesystem clients?
> If the interfaces are abstract enough, we should be able to have multiple
> distributed fs's using the same cache manager API.  Yes, there's tons of
> little details to be worked out (e.g. credential management, access
> control, etc.)

I am pleased with the recent addition of the credential keyring to the kernel, thanks to AFS users, which will be helpful as soon as I figure out what the user space tools are saving there at logon time - and how to hook in kernel the plaintext password or kerberos ticket that winbind or pam_kerberos get at logon (CIFS client has to get Kerberos tickets to authenticate to Samba, Windows, Netapp etc.).  I don't want to be prompting for passwords as CIFS users traverse a DFS junction.

The credential management needs improvement in the kernel to handle CIFS, NFSv4 and AFS (very similar problems) but the other parts o you comment is puzzling, since at least for Linux the client cache is common (for all but two major filesystems) and led to much of the improvement between 2.4 and 2.6 Linux kernels (and there is no distinct server cache as all of the servers run on stock filesystems).   CIFS client, NFS client etc. all use the common mm cache and the CIFS client handles the primitive delegations (oplock), somewhat similar to what NFSv4 will be doing.   The in kernel AFS client offerred a client cache to disk patch IIRC which would be mildly helpful for everyone to standardize on - and I will be happy to integrate support for that on the CIFS client side.

Where we could really use improvement is mapping the missing pieces of the server side of the AFS API to a set of generic operations - to construct a list of what is needed to be added to the kernel VFS so JFS, EXT3, XFS etc. can replicate, move, backup, snapshot etc. better.  There has been enormous progress in the 2.6 kernel, but Samba 4, NFSv4 have protocol support (which currently can not be implemented) that could plug into many of these already.


Steve French
Senior Software Engineer
Linux Technology Center - IBM Austin
phone: 512-838-2294
email: sfrench at-sign us dot ibm dot com