From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from resqmta-ch2-03v.sys.comcast.net ([69.252.207.35]:56468 "EHLO resqmta-ch2-03v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932234AbaJVUIw (ORCPT ); Wed, 22 Oct 2014 16:08:52 -0400 Message-ID: <54480ED0.9070703@pobox.com> Date: Wed, 22 Oct 2014 13:08:48 -0700 From: Robert White MIME-Version: 1.0 To: Btrfs BTRFS Subject: NOCOW and Swap Files? Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: So the documentation is clear that you can't mount a swap file through BTRFS (unless you use a loop device). Why isn't a NOCOW file that has been fully pre-allocated -- as with fallocate(1) -- not suitable for swapping? I found one reference to an unimplemented feature necessary for swap, but wouldn't it be reasonable for that feature to exist for NOCOW files? (or does this relate to my previous questions about the COW operation that happens after a snapshot?)