From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fieldses.org ([174.143.236.118]:34110 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751526Ab1HUQud (ORCPT ); Sun, 21 Aug 2011 12:50:33 -0400 Date: Sun, 21 Aug 2011 12:50:29 -0400 From: "J. Bruce Fields" To: Jamie Lokier Cc: Volker Lendecke , linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, samba-technical@lists.samba.org, Casey Bodley Subject: Re: [PATCH] locks: breaking read lease should not block read open Message-ID: <20110821165029.GA9296@fieldses.org> References: <20110609231606.GB22215@fieldses.org> <20110610134859.GA27837@fieldses.org> <20110721000758.GD27871@fieldses.org> <20110819190829.GD11512@jl-vm1.vm.bytemark.co.uk> Content-Type: text/plain; charset=us-ascii In-Reply-To: <20110819190829.GD11512@jl-vm1.vm.bytemark.co.uk> Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Fri, Aug 19, 2011 at 08:08:29PM +0100, Jamie Lokier wrote: > J. Bruce Fields wrote: > > I'm not sure how to approach the lease code. > > > > On the one hand, I've never seen any evidence that anyone outside Samba > > and NFSv4 has ever used it, and both currently make extremely limited > > use of it. So we could probably get away with "fixing" the lease code > > to do whatever both of us need. > > I've never used it, but I've _nearly_ used it (project took a > different direction), in a web application framework. > > Pretty much the way CIFS/NFS use it, to keep other things (remote > state, database state, derived files) transactionally coherent with > changes to file contents by programs that only know about the files > they access. > > The SIGIO stuff is a horrible interface. > I could still see me trying to use it sometime in the future. > In which case I really don't mind if you make the semantics saner :-) > > Now we have fanotify which does something very similar and could have > generalised leases, but unfortunately fanotify came from such a > different motivation that it's not well suited for ordinary user > applications. I'm not sure what you mean by that--mainly just because I'm not as familiar with fanotify as I should be. For my case the important difference between leases and the various notification interfaces is that leases are synchronous--the lease-holder is notified and has a chance to clean up before releasing its lease and allowing the conflicting operation to continue--whereas the the various notification interfaces tell you "tough luck, something just happened". --b.