Return-Path: Received: from cn.fujitsu.com ([222.73.24.84]:52379 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754611Ab0ETJqK (ORCPT ); Thu, 20 May 2010 05:46:10 -0400 Message-ID: <4BF504DE.7010804@cn.fujitsu.com> Date: Thu, 20 May 2010 17:46:06 +0800 From: Mi Jinlong To: "J. Bruce Fields" CC: Trond Myklebust , Jeff Layton , NFSv3 list , linux-fsdevel@vger.kernel.org, ebiederm@xmission.com, adobriyan@gmail.com, viro@ZenIV.linux.org.uk, jamie@shareable.org Subject: Re: [PATCH] VFS: Unlink should revoke all outstanding leases on file References: <4BED195F.3070504@cn.fujitsu.com> <20100514055844.109d2fdc@tlielax.poochiereds.net> <1273857471.4732.7.camel@localhost.localdomain> <20100514133819.5e383485@tlielax.poochiereds.net> <1273859968.4732.22.camel@localhost.localdomain> <1273861872.4732.34.camel@localhost.localdomain> <20100514192327.GA20192@fieldses.org> <4BF3B36F.80209@cn.fujitsu.com> <20100519155700.GE4581@fieldses.org> In-Reply-To: <20100519155700.GE4581@fieldses.org> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 J. Bruce Fields : > On Wed, May 19, 2010 at 05:46:23PM +0800, Mi Jinlong wrote: >> >> J. Bruce Fields : >>> On Fri, May 14, 2010 at 02:31:12PM -0400, Trond Myklebust wrote: >>>> On Fri, 2010-05-14 at 13:59 -0400, Trond Myklebust wrote: >>>>> Note that the server should also recall the delegation if someone >>>>> attempts to violate the guarantees that are listed in section 9.4: Open >>>>> Delegation >>>>> >>>>> When a client has a read open delegation, it may not make any changes >>>>> to the contents or attributes of the file but it is assured that no >>>>> other client may do so. When a client has a write open delegation, >>>>> it may modify the file data since no other client will be accessing >>>>> the file's data. The client holding a write delegation may only >>>>> affect file attributes which are intimately connected with the file >>>>> data: size, time_modify, change. >>>>> >>>>> IOW: even if you hold a write delegation you are not allowed to change >>>>> the file mode bits, owner, group or acls... >>>> ...or the nlink value. So technically, we should also recall the >>>> delegation when someone creates or deletes a hard link. I think I need >>>> to remind Tom that he should add that to the RFC3530bis draft... >>> Yep. And fixing all these cases is required before our the server's >>> NFSv4 server is ready for much of anything. >>> >>> I'm not sure ading break_lease() to may_delete() is right, but maybe >>> it's better than nothing. >> Agree with you. >> >>> One problem is that there's a race: nothing I can see stops anyone from >>> getting another lease after may_delete() but before the delete happens. >> Yes. >> The problem will exist, but there isn't some better methods to avoid it. >> Is there a lease lock exist in kernel? >> If that's true, the problem will be fixed simply. > > I don't know of any existing lock that does exactly what we want. > > Somebody at citi worked on a better lease implementation for a while, > but I don't think we ever really got it right; the last version I can > find is here: > > git://linux-nfs.org/~bfields/linux-topics.git leases When reading the code of the git, i found a patch which try to fix the lease's problem, but only for unlink. commit id: d5a08e556116c66fb60a448f805a40bf54314634 msg: "leases: break file leases on unlink." In this patch, it seems only add break_lease() and some other functions but seems don't avoid the problem of race. Or there is some different at break_lease() with the community's kernel. Can you give me some message about the new lease? Thanks. thanks, Mi Jinlong