It isn't the server's problem. There is no way the server has access to the Vfs opens as visible objects or as having the assignment of locks to such fine-grained opens. I'm kind of thinking that this shows we (Bruce, me, and rest of the working group) made a mistake in that sort of a design in which we do not allow multiple distinguished open objects for a given fh-owner pair. Anyway the problems that it caused are pretty minor and we don't know what problems would have been generated with an alternate design. I think this is something to look at in NFSv5 or the next NFSv4.1-style minor version, if any. -----Original Message----- From: J. Bruce Fields [mailto:bfields@xxxxxxxxxxxx] Sent: Thursday, August 19, 2010 12:45 PM To: Trond Myklebust Cc: Noveck, David; nfsv4@xxxxxxxx; linux-nfs@xxxxxxxxxxxxxxx Subject: Re: [nfsv4] OPEN_DOWNGRADE and posix byte range locking issue > > -----Original Message----- > > From: nfsv4-bounces@xxxxxxxx [mailto:nfsv4-bounces@xxxxxxxx] On Behalf > > Of Trond Myklebust > > Sent: Wednesday, July 07, 2010 7:30 PM > > To: nfsv4@xxxxxxxx > > Subject: [nfsv4] OPEN_DOWNGRADE and posix byte range locking issue > > > > Neither RFC3530, nor RFC5661 appear to list NFS4ERR_LOCKS_HELD as a > > valid response when the client calls OPEN_DOWNGRADE. > > > > The question is: what should the server then do if the NFS client holds > > a WRITE_LT lock, but then asks for an OPEN_DOWNGRADE to > > OPEN4_SHARE_ACCESS_READ. I understand that this is sanctioned in Windows > > server environments, but it should definitely be forbidden in a POSIX > > environment, and NFS4ERR_LOCKS_HELD would appear to fit the bill... A bizarre variation: the linux server associates vfs opens with stateid's. Locks are performed on vfs opens, and the vfs will complain if you attempt to close a file that still has locks associated with it. The sequence open RW lock R open R open downgrade to R would therefore be implemented at the vfs level as: open RW -> f lock R on f open R -> g close f Oops. We're stuck with ditching the lock (or erroring out) even though it's still compatible with the new config option. Well, I suppose this is my problem: either I should get a new vfs open for the use of the lock, or represent the original RW open by two vfs open's. It's not something a unix-like client could do, I think, but I don't think it's safe for me to assume I can reject it? --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
