From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E7BDA34A771; Wed, 14 Jan 2026 13:06:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768396021; cv=none; b=fzNvVPesYt9XS9IybPaICM1kOX7KDxqaf6inXgmqj36dGl1eghSnGvtqKRO81wl8KV0g3ozBemNTX9YyMndtUI50IoS/xlJiY3/Me2OGxbjscUBUFk3v8tqBgRoUWcgBnfQXJpIGMiNTzIyTt/Cnqk6V+YBqCtkVN+wtUAgT8JE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768396021; c=relaxed/simple; bh=swA2Z+cvI7i5nnmNw9LviIKuh4fmhAEhMcaz35sVbIE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UlJDm21/lq0s/5RKvuUEVZSKxvNE+lqDEW5S3AMXWdNj/e1Hq2gQvx+FxM19ij8w4aj7q8QpoL3vRxcnY3vm7G/N4iinQo7wKmR13wJnhFFei1LNYu+j5F8p50sgMRFSaUZJdjpomlVH8vSpm4qhk7AaWNrvo3mKyFRcgQqjOaY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=CsUTToet; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="CsUTToet" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=frpDmmp1i4r1AZelS3CVor2fKx/lP0Tq5j8/mhEG/8s=; b=CsUTToetKF+Id6BSRt8PfLBnAS Y0ul3yOPNvK2EqLosGUY3uqxb0rBGjpkb3pFkF+nzL0tn0KOBAl2xhlehcW9SbJloDYCaYos/fI+R /3mikrJStWJrWeOJzR2PeycF0eBRtBI6m7fleAVeDpZJmAWb5/mhUGXdyVHOSGGKP+FgMpRotCkGe U4rxrSW9vdcoJ/4xvbYl6nQLLy/pVnBBXwulC6bpAsoSvSw4Aw1pxxyPY2C1RxEdi/vm7DGCPqLOa XPJH2SpQwhbv/9XjUm+ADr7Kr9Po4kKl3x0XMHBhpwdVI/FJYFR2ISU4AMVB1IFKkKKX1rv/bPqoF Uf0wlX6w==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vg0Zb-00000009Gnt-0ut4; Wed, 14 Jan 2026 13:06:07 +0000 Date: Wed, 14 Jan 2026 05:06:07 -0800 From: Christoph Hellwig To: Amir Goldstein Cc: Christoph Hellwig , Jeff Layton , Christian Brauner , Chuck Lever , Jan Kara , Luis de Bethencourt , Salah Triki , Nicolas Pitre , Anders Larsen , Alexander Viro , David Sterba , Chris Mason , Gao Xiang , Chao Yu , Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li , Chunhai Guo , Jan Kara , Theodore Ts'o , Andreas Dilger , Jaegeuk Kim , OGAWA Hirofumi , David Woodhouse , Richard Weinberger , Dave Kleikamp , Ryusuke Konishi , Viacheslav Dubeyko , Konstantin Komarov , Mark Fasheh , Joel Becker , Joseph Qi , Mike Marshall , Martin Brandenburg , Miklos Szeredi , Phillip Lougher , Carlos Maiolino , Hugh Dickins , Baolin Wang , Andrew Morton , Namjae Jeon , Sungjong Seo , Yuezhang Mo , Alexander Aring , Andreas Gruenbacher , Jonathan Corbet , "Matthew Wilcox (Oracle)" , Eric Van Hensbergen , Latchesar Ionkov , Dominique Martinet , Christian Schoenebeck , Xiubo Li , Ilya Dryomov , Trond Myklebust , Anna Schumaker , Steve French , Paulo Alcantara , Ronnie Sahlberg , Shyam Prasad N , Tom Talpey , Bharath SM , Hans de Goede , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, jfs-discussion@lists.sourceforge.net, linux-nilfs@vger.kernel.org, ntfs3@lists.linux.dev, ocfs2-devel@lists.linux.dev, devel@lists.orangefs.org, linux-unionfs@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, gfs2@lists.linux.dev, linux-doc@vger.kernel.org, v9fs@lists.linux.dev, ceph-devel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org Subject: Re: [PATCH 00/24] vfs: require filesystems to explicitly opt-in to lease support Message-ID: References: <8af369636c32b868f83669c49aea708ca3b894ac.camel@kernel.org> <20260113-mondlicht-raven-82fc4eb70e9d@brauner> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Wed, Jan 14, 2026 at 10:34:04AM +0100, Amir Goldstein wrote: > On Wed, Jan 14, 2026 at 7:28 AM Christoph Hellwig wrote: > > > > On Tue, Jan 13, 2026 at 12:06:42PM -0500, Jeff Layton wrote: > > > Fair point, but it's not that hard to conceive of a situation where > > > someone inadvertantly exports cgroupfs or some similar filesystem: > > > > Sure. But how is this worse than accidentally exporting private data > > or any other misconfiguration? > > > > My POV is that it is less about security (as your question implies), and > more about correctness. I was just replying to Jeff. > The special thing about NFS export, as opposed to, say, ksmbd, is > open by file handle, IOW, the export_operations. > > I perceive this as a very strange and undesired situation when NFS > file handles do not behave as persistent file handles. That is not just very strange, but actually broken (discounting the obscure volatile file handles features not implemented in Linux NFS and NFSD). And the export ops always worked under the assumption that these file handles are indeed persistent. If they're not we do have a problem. > > cgroupfs, pidfs, nsfs, all gained open_by_handle_at() capability for > a known reason, which was NOT NFS export. > > If the author of open_by_handle_at() support (i.e. brauner) does not > wish to imply that those fs should be exported to NFS, why object? Because "want to export" is a stupid category. OTOH "NFS exporting doesn't actually properly work because someone overloaded export_ops with different semantics" is a valid category. > We could have the opt-in/out of NFS export fixes per EXPORT_OP_ > flags and we could even think of allowing admin to make this decision > per vfsmount (e.g. for cgroupfs). > > In any case, I fail to see how objecting to the possibility of NFS export > opt-out serves anyone. You're still think of it the wrong way. If we do have file systems that break the original exportfs semantics we need to fix that, and something like a "stable handles" flag will work well for that. But a totally arbitrary "is exportable" flag is total nonsense.