From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J. Bruce Fields" Subject: Re: [PATCH 0/2] locks: allow mandatory locking to work with file-private locks Date: Mon, 10 Mar 2014 15:21:46 -0400 Message-ID: <20140310192146.GE28006@fieldses.org> References: <1394458607-23579-1-git-send-email-jlayton@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, trond.myklebust@primarydata.com, Andy Lutomirski To: Jeff Layton Return-path: Received: from fieldses.org ([174.143.236.118]:40195 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752357AbaCJTVr (ORCPT ); Mon, 10 Mar 2014 15:21:47 -0400 Content-Disposition: inline In-Reply-To: <1394458607-23579-1-git-send-email-jlayton@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, Mar 10, 2014 at 09:36:45AM -0400, Jeff Layton wrote: > This patchset fixes the problems that Trond pointed out last week, > namely that you can end up deadlocking yourself if you set a > file-private lock on a file and then do some I/O on the same. > > With this set, mandatory locking should work more or less as you'd > expect with file-private locks. If you set a lock on an open file > and then do some I/O on it, it won't block. If you try to lock and > do I/O on different open files, then the I/O may end up blocked. > > Note that this approach is just as racy as the existing mandatory > lock implementation, but I don't think it makes anything worse there. As another alternative, could we declare file-private locks to never be mandatory? The mandatory bit has only ever applied to traditional posix locks, so I don't think there's necessarily a presumption they'd apply to this new lock type as well. That doesn't necessarily simplify the locks_mandatory_area case as it then needs __posix_lock_file to be able to ignore traditional posix locks. --b.