From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:36580 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750922AbaBLHgy (ORCPT ); Wed, 12 Feb 2014 02:36:54 -0500 Message-ID: <52FB2490.1030207@oracle.com> Date: Wed, 12 Feb 2014 15:36:48 +0800 From: Anand Jain MIME-Version: 1.0 To: Duncan <1i5t5.duncan@cox.net> CC: linux-btrfs@vger.kernel.org Subject: Re: btrfs multiple mounts stacked on the same mount point References: <52F9DCBA.1010002@oracle.com> <52FAEC7F.4050707@oracle.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: > BTW, another (general) reason over-mounts are sometimes used is to > deliberately obscure what's underneath. It's worth noting that anything > with a file already open on the underlying filesystem still has access to > that file after something else is mounted over top, and that fact is > sometimes used to control access to certain files/filesystems, by > starting whatever it is that needs to access them and letting them open > the files they need, then over-mounting a different filesystem, often > empty, so no other applications can access the under-mounted files. Thanks. Makes sense theoretically. Any eg of real practical application ? Any product in the market using it that way ? looks btrfs-progs shouldn't depend on the mnt-point driven ioctls to manage the FS. Now that's a set of challenges. Thanks, Anand