On Tue, Jan 17, 2012 at 11:00:23AM -0500, J. Bruce Fields wrote: > From: "J. Bruce Fields" <bfields@xxxxxxxxxx> > > NFSv4 delegations are currently implemented as leases. However, leases > don't have quite the same semantics, which means that delegations are > currently enforced correctly only for conflicts between NFSv4 clients. > > I previously attempted to address this by "fixing" the existing lease > behavior, assuming it was a bug--but from further investigation it looks > like that would be the wrong thing to do for Samba. > > So instead I'm defining a new FL_DELEG flag to mark NFSv4 delegations, > and varying behavior based on that. Delegations aren't meant to be > available to userspace for now--nfsd is the only user. > > In theory this code allows both read and write delegations, but I'm only > using read delegations for now--write delegations are a project for > another day. (At which point write leases will probably need some > fixing while we're at it.) > > Still to do: if OPEN(dirfd, name) returns a delegation to the client, > then the client should be guaranteed that the opened file is still > linked as (dirfd, name). But the current nfsd code allows a rename or > unlink to intervene between the lookup and the request for a delegation. OK, I decided I could fix that in the nfsd4 open code by retrying the lookup after obtaining the delegation, and just dropping the delegation (they're always optional) if it turned out there'd been a race. I'll post revised vfs patches (without that extra nfsd stuff). --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
