From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0A3AC433E2 for ; Sat, 29 Aug 2020 18:04:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C65D0206B5 for ; Sat, 29 Aug 2020 18:04:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728411AbgH2SE6 (ORCPT ); Sat, 29 Aug 2020 14:04:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57662 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728265AbgH2SE6 (ORCPT ); Sat, 29 Aug 2020 14:04:58 -0400 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E9094C061236 for ; Sat, 29 Aug 2020 11:04:57 -0700 (PDT) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kC5Dc-0077NX-5a; Sat, 29 Aug 2020 18:04:48 +0000 Date: Sat, 29 Aug 2020 19:04:48 +0100 From: Al Viro To: Miklos Szeredi Cc: Matthew Wilcox , Dave Chinner , Christian Schoenebeck , "Dr. David Alan Gilbert" , Greg Kurz , linux-fsdevel@vger.kernel.org, Stefan Hajnoczi , Miklos Szeredi , Vivek Goyal , Giuseppe Scrivano , Daniel J Walsh , Chirantan Ekbote Subject: Re: xattr names for unprivileged stacking? Message-ID: <20200829180448.GQ1236603@ZenIV.linux.org.uk> References: <20200812143323.GF2810@work-vm> <27541158.PQPtYaGs59@silver> <20200816225620.GA28218@dread.disaster.area> <20200816230908.GI17456@casper.infradead.org> <20200817002930.GB28218@dread.disaster.area> <20200827152207.GJ14765@casper.infradead.org> <20200827222457.GB12096@dread.disaster.area> <20200829160717.GS14765@casper.infradead.org> <20200829161358.GP1236603@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Sat, Aug 29, 2020 at 07:51:47PM +0200, Miklos Szeredi wrote: > On Sat, Aug 29, 2020 at 6:14 PM Al Viro wrote: > > > > On Sat, Aug 29, 2020 at 05:07:17PM +0100, Matthew Wilcox wrote: > > > > > > > The fact that ADS inodes would not be in the dentry cache and hence > > > > not visible to pathwalks at all then means that all of the issues > > > > such as mounting over them, chroot, etc don't exist in the first > > > > place... > > > > > > Wait, you've now switched from "this is dentry cache infrastructure" > > > to "it should not be in the dentry cache". So I don't understand what > > > you're arguing for. > > > > Bloody wonderful, that. So now we have struct file instances with no dentry > > associated with them? Which would have to be taken into account all over > > the place... > > It could have a temporary dentry allocated for the lifetime of the > file and dropped on last dput. I.e. there's a dentry, but no cache. > Yeah, yeah, d_path() issues, however that one will have to be special > cased anyway. d_path() is the least of the problems, actually. Directory tree structure on those, OTOH, is a serious problem. If you want to have getdents(2) on that shite, you want an opened descriptor that looks like a directory. And _that_ opens a large can of worms. Because now you have fchdir(2) to cope with, lookups going through /proc/self/fd//..., etc., etc. Al, fully expecting "we'll special-case our way out of everything - how hard could that be?" in response...