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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id 0E337C004E4 for ; Tue, 12 Jun 2018 02:40:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BB92A208AF for ; Tue, 12 Jun 2018 02:40:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB92A208AF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ZenIV.linux.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935152AbeFLCkd (ORCPT ); Mon, 11 Jun 2018 22:40:33 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:42444 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935004AbeFLCkc (ORCPT ); Mon, 11 Jun 2018 22:40:32 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.87 #1 (Red Hat Linux)) id 1fSZEU-0006yj-1U; Tue, 12 Jun 2018 02:40:30 +0000 Date: Tue, 12 Jun 2018 03:40:30 +0100 From: Al Viro To: Miklos Szeredi Cc: Miklos Szeredi , overlayfs , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: [PATCH 14/39] ovl: stack file ops Message-ID: <20180612024029.GZ30522@ZenIV.linux.org.uk> References: <20180529144339.16538-1-mszeredi@redhat.com> <20180529144339.16538-15-mszeredi@redhat.com> <20180610041243.GJ30522@ZenIV.linux.org.uk> <20180612022926.GY30522@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180612022926.GY30522@ZenIV.linux.org.uk> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 12, 2018 at 03:29:26AM +0100, Al Viro wrote: > It might (or might not) work for the filesystems you'd been testing > on, but it's a lot of trouble waiting to happen. Hell, try and use > ecryptfs as lower layer, see how fast it'll blow up. Sure, it's > a dumb testcase, but I don't see how to check if something more > realistic is trouble-free. > > I'd been trying to come up with some way to salvage that kludge of yours, > but I don't see any solutions. We don't have good proxies for "this > filesystem might be unsafe as lower layer" ;-/ Note that anything that uses file_dentry() anywhere near ->open(), ->read_iter() or ->write_iter() is an instant trouble with your scheme. Such as int nfs_open(struct inode *inode, struct file *filp) { struct nfs_open_context *ctx; ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode, filp); if (IS_ERR(ctx)) return PTR_ERR(ctx); nfs_file_set_open_context(filp, ctx); put_nfs_open_context(ctx); nfs_fscache_open_file(inode, filp); return 0; } You do want to support NFS for lower layers, right?