Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752177AbcCKUjZ (ORCPT ); Fri, 11 Mar 2016 15:39:25 -0500 Received: from mail-qk0-f173.google.com ([209.85.220.173]:35536 "EHLO mail-qk0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750953AbcCKUjV (ORCPT ); Fri, 11 Mar 2016 15:39:21 -0500 Subject: Re: Variant symlink filesystem To: Richard Weinberger , Cole References: <56E327FF.1010103@nod.at> <56E3298A.1040008@nod.at> Cc: LKML From: "Austin S. Hemmelgarn" Message-ID: <56E32CD3.1010705@gmail.com> Date: Fri, 11 Mar 2016 15:38:43 -0500 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <56E3298A.1040008@nod.at> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Antivirus: avast! (VPS 160311-1, 2016-03-11), Outbound message X-Antivirus-Status: Clean Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1127 Lines: 21 On 2016-03-11 15:24, Richard Weinberger wrote: > Am 11.03.2016 um 21:22 schrieb Cole: >> If I remember correctly, when we were testing the fuse version, we hard coded >> the path to see if that solved the problem, and the difference between >> the env lookup >> code and the hard coded path was almost the same, but substantially slower than >> the native file system. > > And where exactly as the performance problem? > > Anyway, if you submit your filesystem also provide a decent use case for it. :-) > I don't know that this qualifies as a use case, but I've seen a number of capability based systems that have a similar concept they usually refer to as 'context dependent symbolic links'. In such cases, the resolution is usually based on what capabilities you posses, and is more of a mapping than a value expansion most of the time, but such usage could be emulated (albeit much less securely) with this. If this could be extended to expand other values (for example, process bit width, or SELinux context, or even what namespace the process is in), it could provide the same functionality almost as securely.