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 B23F1C5CFF1 for ; Tue, 12 Jun 2018 18:24:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5CB9A208B1 for ; Tue, 12 Jun 2018 18:24:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5CB9A208B1 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 S1754207AbeFLSYa (ORCPT ); Tue, 12 Jun 2018 14:24:30 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:35566 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752954AbeFLSY3 (ORCPT ); Tue, 12 Jun 2018 14:24:29 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.87 #1 (Red Hat Linux)) id 1fSnxv-0001ML-Fs; Tue, 12 Jun 2018 18:24:23 +0000 Date: Tue, 12 Jun 2018 19:24:23 +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: <20180612182423.GA30522@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> <20180612024029.GZ30522@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 11:24:39AM +0200, Miklos Szeredi wrote: > > 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? > > There's no change regarding how file_dentry() works. We've just > pushed these weird files (f_path points to overlay, f_inode points to > underlay) down into the guts of overlayfs and are not directly > referenced from the file table anymore. That shouldn't make *any* > difference from the lower fs's pov. *owwww* I'd managed to push that particular nest of horrors out of mind ;-/ Having dug out my notes from back then and grepped around... The real mess is not even /proc/*/maps - it's /proc/*/map_files/* and yes, the reasons for that kludge are still valid ;-/ Fuck. OK, so we want to get rid of ->f_path.dentry accesses and see that they don't come back. Leaving them around due to "it won't come anywhere near overlayfs" was a mistake of the same kind as leaving d_add() in ->lookup() instances where we'd been certain that filesystem would never get exported over NFS. Just as we'd got open-by-handle for e.g. NFS, we'd got nothing to prevent ecryptfs as lower layer in overlayfs... I hate it, but... consider path_open() objections withdrawn for now. Uses of ->vm_file (and rules for those) are too convoluted to untangle at the moment. I still would love to get that straightened out, but it's not this cycle fodder, more's the pity...