From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Olszak Subject: Re: Optional switching off cow in overlayfs Date: Thu, 18 Jun 2015 16:43:03 +0200 Message-ID: <5582D8F7.1060700@samsung.com> References: <5582C6C1.8080602@samsung.com> <13405.1434634748@warthog.procyon.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mailout1.w1.samsung.com ([210.118.77.11]:51400 "EHLO mailout1.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752029AbbFROnH (ORCPT ); Thu, 18 Jun 2015 10:43:07 -0400 Received: from eucpsbgm1.samsung.com (unknown [203.254.199.244]) by mailout1.w1.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0NQ5006SPA7TDY40@mailout1.w1.samsung.com> for linux-unionfs@vger.kernel.org; Thu, 18 Jun 2015 15:43:05 +0100 (BST) In-reply-to: <13405.1434634748@warthog.procyon.org.uk> Sender: linux-unionfs-owner@vger.kernel.org List-Id: linux-unionfs@vger.kernel.org To: David Howells Cc: linux-unionfs@vger.kernel.org On 06/18/2015 03:39 PM, David Howells wrote: > Jan Olszak wrote: > >> I was wondering about a small improvement to overlayfs - optional, per file >> copy of write. >> >> 1. By default overlayfs would work as usual. >> 2. If a file in 'lower' filesystem has an xattr set >> (e.g. trusted.overlay.cow=n) the file would not be copied. >> >> What do you think? > Ummm. What's the use case? How do you handle the file being part of multiple > overlays? > > David > I wan't to achieve 'files' granularity in overlayfs instead of 'directory' granularity. It would be useful in Linux containers configuration. Sometimes you don't have the power to change the images that are run inside containers and in one folder you have both: - files that have to be copied - files that don't really need to be copied trusted.overlay.cow==n indicates switching off copying the file to the upper layer. So with multiple overlays you would always have only one file from the lower-most dir. Jan