Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-ie0-f178.google.com ([209.85.223.178]:61815 "EHLO mail-ie0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750872Ab3CKOAA (ORCPT ); Mon, 11 Mar 2013 10:00:00 -0400 MIME-Version: 1.0 In-Reply-To: <51364285.4040406@samba.org> References: <1362065133-9490-1-git-send-email-piastry@etersoft.ru> <512FD1D5.3010106@mit.edu> <20130304211923.GI20389@fieldses.org> <5135250A.30604@samba.org> <20130305181306.GA15816@fieldses.org> <51364285.4040406@samba.org> Date: Mon, 11 Mar 2013 17:59:59 +0400 Message-ID: Subject: Re: [PATCH v3 0/7] Add O_DENY* support for VFS and CIFS/NFS From: Pavel Shilovsky To: Simo Cc: "J. Bruce Fields" , Al Viro , linux-kernel@vger.kernel.org, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, wine-devel@winehq.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-nfs-owner@vger.kernel.org List-ID: 2013/3/5 Simo : > On 03/05/2013 01:13 PM, J. Bruce Fields wrote: >> >> On Mon, Mar 04, 2013 at 05:49:46PM -0500, Simo wrote: >>> >>> On 03/04/2013 04:19 PM, J. Bruce Fields wrote: >>>> I'm a little more worried: these are mandatory locks, and applications >>>> that use them are used to the locks being enforced correctly. Are we >>>> sure that an application that opens a file O_DENYWRITE won't crash if it >>>> sees the file data change while it holds the open? >>> >>> The redirector may simply assume it has full control of that part of >>> the file and not read nor send data until the lock is released too, >>> so you get conflicting views of the file contents between different >>> clients if you let a mandatory lock not be mandatory. >>> >>>> In general the idea of making a mandatory lock opt-in makes me nervous. >>>> I'd prefer something like a mount option, so that we know that everyone >>>> on that one filesystem is playing by the same rules, but we can still >>>> mount filesystems like / without the option. >>> >>> +1 >>> >>>> But I'll admit I'm definitely not an expert on Windows locking and may >>>> be missing something about how these locks are meant to work. >>> >>> Mandatory locks really are mandatory in Windows. >>> That may not be nice to a Unix system but what can you do ? >> >> I wonder if we could repurpose the existing -omand mount option? >> >> That would be a problem for anyone that wants to allow mandatory fcntl >> locks without allowing share locks. I doubt anyone sane actually uses >> mandatory fcntl locks, but still I suppose it would probably be better >> to play it safe and use a new mount option. > > > Maybe we should have a -o win_semantics option :-) > > /me runs > (CC'ing Al Viro, since these patches should go through his tree) I don't mind to introduce a new mount option for turning this feature on/off - something like '-o denylock' to make it mathing names of new flags would be ok. Al, what do you think about this feature overall? -- Best regards, Pavel Shilovsky.