Date: Sat, 12 Apr 2008 13:53:13 -1000 (HST) From: Jeff Roberson <jroberson@jroberson.net> To: Alfred Perlstein <alfred@freebsd.org> Cc: Kirk McKusick <mckusick@mckusick.com>, arch@freebsd.org Subject: Re: VOP_LEASE Message-ID: <20080412135135.V43186@desktop> In-Reply-To: <20080412234547.GZ95731@elvis.mu.org> References: <200804121703.m3CH3StJ081660@chez.mckusick.com> <41ED3941-E5E6-45F0-B880-C1B2861FDE32@rabson.org> <20080412131017.S43186@desktop> <20080412234547.GZ95731@elvis.mu.org>
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On Sat, 12 Apr 2008, Alfred Perlstein wrote: > * Jeff Roberson <jroberson@jroberson.net> [080412 16:13] wrote: >> On Sat, 12 Apr 2008, Doug Rabson wrote: >> >>> >>> On 12 Apr 2008, at 18:03, Kirk McKusick wrote: >>> >>>>> Date: Sat, 12 Apr 2008 02:13:15 -1000 (HST) >>>>> From: Jeff Roberson <jroberson@jroberson.net> >>>>> To: arch@freebsd.org >>>>> Subject: VOP_LEASE >>>>> >>>>> As far as I can tell this has never been used. Unless someone can show >>>>> me >>>>> otherwise I'm going to go ahead and remove it. >>>>> >>>>> Thanks, >>>>> Jeff >>>> >>>> VOP_LEASE is used by NQNFS and NFSv4. It notifies them when a file >>>> is modified locally so that they know to update any outstanding >>>> leases (e.g., evict any write lease for the file and do callbacks >>>> for any read leases for the file). Deleting VOP_LEASE would break >>>> NFS big time. >>> >>> I think our NQNFS support might have been removed some time ago - I can't >>> see any calls to VOP_LEASE in the code right now. Something like VOP_LEASE >>> would certainly be useful for a hypothetical future NFSv4 server. I >>> believe that samba could use it too for its oplocks feature which appears >>> to be similar to NQNFS's leases and NFSv4's delegations. >> >> So the idea with delegations is that close() doesn't actually release the >> file entirely to make future access cheaper? >> >> My issue with VOP_LEASE is only that there are no in kernel >> implementations of the VOP. I doubt it is applied regularly in syscalls. >> It also seems odd that it is called without a lock. >> >> Is the intent that the server will trap all accesses to a local vnode in >> order to invalidate the client leases? > > VOP_LEASE is supposed to implemented by a filesystem client. > > For insance, NFS client with NQNFS would implement the VOP_LEASE > and trap those accesses to manage the lease with the remote server. > > The remote server would get "lease RPCs" from the client and manage > the cache appropriately. So why isn't this done within the actual VOP? If the lease expires between calling VOP_LEASE and vn_lock(), VOP_READ() you have to do that work all over again anyway. I don't yet see why this is in filesystem independent code. I'm not asserting that it doesn't need to be. I'd just like to understand it better. Thanks, Jeff > > -- > - Alfred Perlstein >
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