From owner-freebsd-arch@FreeBSD.ORG Fri Dec 19 20:12:06 2014 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 926BC8F4 for ; Fri, 19 Dec 2014 20:12:06 +0000 (UTC) Received: from hergotha.csail.mit.edu (wollman-1-pt.tunnel.tserv4.nyc4.ipv6.he.net [IPv6:2001:470:1f06:ccb::2]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4E8232126 for ; Fri, 19 Dec 2014 20:12:06 +0000 (UTC) Received: from hergotha.csail.mit.edu (localhost [127.0.0.1]) by hergotha.csail.mit.edu (8.14.9/8.14.9) with ESMTP id sBJKC2Lu086110; Fri, 19 Dec 2014 15:12:03 -0500 (EST) (envelope-from wollman@hergotha.csail.mit.edu) Received: (from wollman@localhost) by hergotha.csail.mit.edu (8.14.9/8.14.4/Submit) id sBJKC1rW086109; Fri, 19 Dec 2014 15:12:01 -0500 (EST) (envelope-from wollman) Date: Fri, 19 Dec 2014 15:12:01 -0500 (EST) From: Garrett Wollman Message-Id: <201412192012.sBJKC1rW086109@hergotha.csail.mit.edu> To: jilles@stack.nl Subject: Re: Change default VFS timestamp precision? X-Newsgroups: mit.lcs.mail.freebsd-arch References: <201412161348.41219.jhb@freebsd.org> <77322.1418933100@critter.freebsd.dk> <77371.1418933642@critter.freebsd.dk> <7567696.mqJ3jgzJgL@ralph.baldwin.cx> <82135.1419010861@critter.freebsd.dk> <20141219194800.GA29107@stack.nl> Organization: none X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.4.3 (hergotha.csail.mit.edu [127.0.0.1]); Fri, 19 Dec 2014 15:12:03 -0500 (EST) X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED autolearn=disabled version=3.4.0 X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on hergotha.csail.mit.edu Cc: freebsd-arch@freebsd.org X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 19 Dec 2014 20:12:06 -0000 In article <20141219194800.GA29107@stack.nl>, jilles@stack.nl writes: >Because there is no API to set timestamps with nanosecond resolution, >and therefore a cp -p copy of a file will appear older than the original >with 99.9% probability. I think that is undesirable. But that's something we can easily fix -- and should have done, years ago. Why don't we just *do* that? Of course, in the case of NFS clients, where this issue is most severe, the RPCs are already defined. The underlying VOP_SETATTR has no trouble with nanoseconds, either. It's just a matter of providing a standard library interface (and associated system call(s)) to do it, and since Linux has already implemented this, we can just implement that interface and applications will get it "for free". -GAWollman