From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f46.google.com ([209.85.214.46]:37818 "EHLO mail-it0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754409AbdBNPaz (ORCPT ); Tue, 14 Feb 2017 10:30:55 -0500 Received: by mail-it0-f46.google.com with SMTP id x75so36710460itb.0 for ; Tue, 14 Feb 2017 07:30:49 -0800 (PST) Received: from [191.9.206.254] (rrcs-70-62-41-24.central.biz.rr.com. [70.62.41.24]) by smtp.gmail.com with ESMTPSA id l17sm454038ioi.60.2017.02.14.07.30.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 14 Feb 2017 07:30:46 -0800 (PST) To: linux-btrfs@vger.kernel.org From: "Austin S. Hemmelgarn" Subject: Unexpected behavior involving file attributes and snapshots. Message-ID: Date: Tue, 14 Feb 2017 10:30:43 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: I was just experimenting with snapshots on 4.9.0, and came across some unexpected behavior. The simple explanation is that if you snapshot a subvolume, any files in the subvolume that have the NOCOW attribute will not have that attribute in the snapshot. Some further testing indicates that this is the only file attribute that isn't preserved (I checked all the chattr flags that BTRFS supports). I'm kind of curious whether: 1. This is actually documented somewhere, as it's somewhat unexpected given that everything else is preserved when snapshotting. 2. This is intended behavior, or just happens to be a side effect of the implementation.