Re: [PATCH v4 0/6] nfsd: overhaul the client name tracking code

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Jan 23, 2012 at 03:01:01PM -0500, Jeff Layton wrote:
> This is the fourth iteration of this patchset. I had originally asked
> Bruce to take the last one for 3.3, but decided at the last minute to
> wait on it a bit. I knew there would be some changes needed in the
> upcall, so by waiting we can avoid needing to deal with those in code
> that has already shipped. I would like to see this patchset considered
> for 3.4 however.
> 
> The previous patchset can be viewed here. That set also contains a
> more comprehensive description of the rationale for this:
> 
>     http://www.spinics.net/lists/linux-nfs/msg26324.html
> 
> There have been a number of significant changes since the last set:
> 
> - the remove/expire upcall is now gone. In a clustered environment, the
> records would need to be refcounted in order to handle that properly. That
> becomes a sticky problem when you could have nodes rebooting. We don't
> really need to remove these records individually however. Cleaning them
> out only when the grace period ends should be sufficient.

I don't think so:

	1. Client establishes state with server.
	2. Network goes down.
	3. A lease period passes without the client being able to renew.
	   The server expires the client and grants conflicting locks to
	   other clients.
	3. Server reboots.
	4. Network comes back up.

At this point, the client sees that the server has rebooted and is in
its grace period, and reclaims.  Ooops.

The server needs to be able to tell the client "nope, you're not allowed
to reclaim any more" at this point.

So we need some sort of remove/expire upcall.

--b.

> - an "init" upcall has been added. When knfsd starts, it will upcall to
> userspace for a boot_generation value. This will replace the boot time
> in the scheme that generates clientid4's. By doing this, we eliminate
> a potential problem with clientid4 collisions in clustered setups.
> 
> - a "client index" has been added to the create and check upcalls. The
> kernel ignores this value for now, but eventually we'll need to use it
> to help establish what clients own which locks in a clustered setup.
> 
> - a number of the client_tracking functions have been changed to void
> return functions. Since the callers all ignore the return codes of those
> functions, there was little benefit in passing them back.
> 
> Comments and suggestions are welcome...
> 
> Jeff Layton (6):
>   nfsd: add nfsd4_client_tracking_ops struct and a way to set it
>   sunrpc: create nfsd dir in rpc_pipefs
>   nfsd: convert nfs4_client->cl_cb_flags to a generic flags field
>   nfsd: add a header describing upcall to nfsdcld
>   nfsd: add the infrastructure to handle the cld upcall
>   nfsd: get boot generation number from upcall instead of boot_time
> 
>  fs/nfsd/nfs4callback.c   |   12 +-
>  fs/nfsd/nfs4recover.c    |  480 +++++++++++++++++++++++++++++++++++++++++++++-
>  fs/nfsd/nfs4state.c      |   63 +++----
>  fs/nfsd/state.h          |   22 ++-
>  include/linux/nfsd/cld.h |   58 ++++++
>  net/sunrpc/rpc_pipe.c    |    5 +
>  6 files changed, 581 insertions(+), 59 deletions(-)
>  create mode 100644 include/linux/nfsd/cld.h
> 
> -- 
> 1.7.7.5
>