Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753350AbcDOAvG (ORCPT ); Thu, 14 Apr 2016 20:51:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60378 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753194AbcDOAvD (ORCPT ); Thu, 14 Apr 2016 20:51:03 -0400 Date: Fri, 15 Apr 2016 02:50:54 +0200 From: Mateusz Guzik To: Florian Margaine Cc: Alexander Viro , Jeff Layton , "J. Bruce Fields" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] fs: add the FIGETFROZEN ioctl call Message-ID: <20160415005052.6734gfnt7kjpwxyc@mguzik> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0.1 (2016-04-01) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 15 Apr 2016 00:51:02 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 672 Lines: 17 On Thu, Apr 14, 2016 at 09:57:07AM +0200, Florian Margaine wrote: > This lets userland get the filesystem freezing status, aka whether the > filesystem is frozen or not. This is so that an application can know if > it should freeze the filesystem or if it isn't necessary when taking a > snapshot. The feature may be useful in general, I don't know. However, I'm confused why programs would depend on it. If you froze a particular subsystem, you don't have to check. If you did not, what prevents whoever originaly froze it from unfreezing as you access it? As such, maybe the feature you are looking for would count how many times the fs is frozen. -- Mateusz Guzik