Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753668Ab2EYQi5 (ORCPT ); Fri, 25 May 2012 12:38:57 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:64999 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751265Ab2EYQiz convert rfc822-to-8bit (ORCPT ); Fri, 25 May 2012 12:38:55 -0400 MIME-Version: 1.0 In-Reply-To: References: <20120525154249.GC2082@localhost.localdomain> Date: Fri, 25 May 2012 18:38:54 +0200 Message-ID: Subject: Re: atime and filesystems with snapshots (especially Btrfs) From: Alexander Block To: Andreas Dilger Cc: Josef Bacik , "linux-btrfs@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1000 Lines: 16 On Fri, May 25, 2012 at 6:28 PM, Andreas Dilger wrote: > On 2012-05-25, at 9:59, Alexander Block wrote: > > Are you talking about the atime for the primary copy, or the atime for the snapshots? ?IMHO, the atime should not be updated for a snapshot unless it is explicitly mounted r/w, or it isn't really a good snapshot. > Snapshots are by default r/w but can be created r/o explicitly. But that doesn't matter for the normal use case where you snapshot / and continue working on /. After snapshotting, all metadata is shared between the two subvolumes, but when a metadata block in one of both subvolume changes (no matter which one), this one metadata block get's cowed and unshared and uses up more space. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/