Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933024AbcKVKjd (ORCPT ); Tue, 22 Nov 2016 05:39:33 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53268 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932451AbcKVKjc (ORCPT ); Tue, 22 Nov 2016 05:39:32 -0500 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20161119224331.GE31101@dastard> References: <20161119224331.GE31101@dastard> <20161118220744.GC31101@dastard> <147938969703.13574.10295364502230379833.stgit@warthog.procyon.org.uk> <147938970382.13574.11581172952175034619.stgit@warthog.procyon.org.uk> <20161117234047.GE28177@dastard> <11317.1479509642@warthog.procyon.org.uk> To: Dave Chinner Cc: dhowells@redhat.com, Andreas Dilger , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] statx: Add a system call to make enhanced file info available MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <9045.1479811169.1@warthog.procyon.org.uk> Date: Tue, 22 Nov 2016 10:39:29 +0000 Message-ID: <9047.1479811169@warthog.procyon.org.uk> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Tue, 22 Nov 2016 10:39:31 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 586 Lines: 15 Dave Chinner wrote: > No. Just provide a 64 bit high resoultion field, and define it to > contain nanoseconds. When we need higher resolution to be exported > to userspace, we use a /feature flag/ to indicate that is contains > something like attoseconds or the like. That sounds suspiciously like a bad idea - if you're talking about a flag with a currently undefined meaning that the kernel can inflict on userspace without warning to change the meaning of the nanoseconds field to something we haven't defined yet. Userspace would have to ask for it. David