From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from atl4mhob12.myregisteredsite.com ([209.17.115.107]:33412 "EHLO atl4mhob12.myregisteredsite.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750857Ab3FGCvY (ORCPT ); Thu, 6 Jun 2013 22:51:24 -0400 Received: from mailpod1.hostingplatform.com ([10.30.71.116]) by atl4mhob12.myregisteredsite.com (8.14.4/8.14.4) with ESMTP id r572pMad026154 for ; Thu, 6 Jun 2013 22:51:22 -0400 Message-ID: <51B14AB0.4040906@chinilu.com> Date: Thu, 06 Jun 2013 19:51:28 -0700 From: George Mitchell Reply-To: george@chinilu.com MIME-Version: 1.0 To: linux-btrfs@vger.kernel.org Subject: How do I safely terminate COW on pre-existing files? Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: I want to eliminate the COW feature on all of my OS files. It is a nice feature for user files, but I don't see a clear benefit for the actual OS files. And I suspect that COW induced fragmentation is causing or aggravating problems with my system including the boot open_ctree problem. I had planned to recursively chattr these files to "nodatacow" status but then I ran into this cryptic warning on the chattr man page: (Note: For btrfs, the 'C' flag should be set on new or empty files. If it is set on a file which already has data blocks, it is undefined when the blocks assigned to the file will be fully stable. If the 'C' flag is set on a directory, it will have no effect on the directory, but new files created in that directory will the No_COW attribute.) So what exactly does that mean? Does it mean that it is unsafe? Or does it mean that it is simply unreliable? If I run a btrfs balance first will that clear out the COW snapshots and enable me to perform the recursive chattrs? What is the best way to approach this? Thanks for any tips, George