From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 60E293081DC; Mon, 10 Nov 2025 13:33:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762781638; cv=none; b=NBjww0kWXcnDLRcboX3ORKUFjuAsmPb1lZmjRfR+qEMQ0uTRgVf+aQuOuO98fYEuqeGsbh5fqcjoYQlBlzQbcDzzxD3UmVNT316u4ViGokZpdH2D/R5Ka578+aDD+qETMPpIXyxX7C0Rn7xHeEAc4Klo1+P3d5EhZWODF2T9jWw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762781638; c=relaxed/simple; bh=KrJ2YKSsIzH6nVo1MlcOu41RTn1gmKSelMYjAFxZ1Kw=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=WENx1hvyxzfpZFWpcNDyYANxA3MHaEKmax+Dlz6EVBD75Awv6EmoaijnHQh8CkM8WragF8eQydbIfVuP5nBdSMuWxSL7KVrb7zn4mntbdjXZEJksKuMN8Sbr6GIgCwKPbOOlGvHOG4/5Ddwe7y97pj5N8Yvh0Eeu9rMTk9VYCwo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=P0dUDWXH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="P0dUDWXH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD371C116D0; Mon, 10 Nov 2025 13:33:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762781638; bh=KrJ2YKSsIzH6nVo1MlcOu41RTn1gmKSelMYjAFxZ1Kw=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=P0dUDWXHQAvfCZU96S6hWjTpUdjmy7990xsJAOgF2CPwPSMXSVRsm34nvItduBqJo 5r6TiGqARZw7Eg0NAlv4hqXVkXnXR00yU81y+/1hssGhBP2QnhBuRTd1rKsa0bEBMj Hbu9pBb4VNRUzzjGtGbADEFn8xpzAfqli27LuNHV+W1vU/p0H5rBF1hs0ok6kNmnTL crvtwFCEpLMFhTP4xj/4kINe9DpW3ESB89iBfn/UcT3kalqScrRhUX9l/r2VL2Sfo7 S1SSj+epa2IdhMzEMmaVnXBOJL7zpDBnytMGuYkPIaWyE6V3o/PavzUg5H/3e1tdD5 Hw8dDCjhkWaFA== Message-ID: Subject: Re: RFC: NFSD administrative interface to prevent offering NFSv4 delegation From: Jeff Layton To: Chuck Lever , Benjamin Coddington Cc: Linux NFS Mailing List , Linux FS Devel Date: Mon, 10 Nov 2025 08:33:56 -0500 In-Reply-To: <26959e66-f04f-4e6e-a8ce-a44c4362d99f@oracle.com> References: <8918ca00-11cb-4a39-855a-e4b727cb63b8@oracle.com> <2602B6D3-C892-4D5A-98E7-299095BD245F@hammerspace.com> <26959e66-f04f-4e6e-a8ce-a44c4362d99f@oracle.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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Benjamin Coddington wrote: > > On 4 Nov 2025, at 10:54, Chuck Lever wrote: > >=20 > > > NFSD has long had some ability to disable NFSv4 delegation, by disabl= ing > > > fs leases. > > >=20 > > > However it would be nice to have more fine-grained control, for examp= le > > > in cases where read delegation seems to work well but the newer forms > > > of delegation (directory, or attribute) might have bugs or performanc= e > > > problems, and need to be disabled. There are also testing scenarios > > > where a unit test might focus specifically on one type of delegation. > > >=20 > > > A little brainstorming: > > >=20 > > > * Controls would be per net namespace > > > * Allow read delegations, or read and write > > > * Control attribute delegations too? Perhaps yes. > > > * Ignore the OPEN_XOR_DELEG flag? Either that, or mask off the > > > advertised feature flag. > > > * Change of setting would cause immediate behavior change; no > > > server restart needed > > > * Control directory delegations too (when they arrive) > > >=20 > > > Is this for NFSD only, or also for local accessors (via the VFS) on t= he > > > NFS server? > > >=20 I agree with all of the above bullet points. I think we should just implement the more fine-grained controls for nfsd (at least initially). OPEN_XOR_DELEG and attribute delegs don't have any relevance at the VFS layer, so if we want to control all of these then it makes more sense to do it in nfsd. We could consider adding more fine-grained VFS layer controls later if that's needed though. > > > Should this be plumbed into NFSD netlink, or into /sys ? > > >=20 > > > Any thoughts/opinions/suggestions are welcome at this point. > >=20 > > Happy to read this. > >=20 > > I think this would be most welcomed by the distros - there's been a lot= of > > instances of "disable delegations" with the big knob > > /proc/sys/fs/leases-enable > >=20 > > I'd also like to be able to twiddle these bits for clients as well, and > > lacking a netlink tool to do it for the client the logical place might = be > > the client's sysfs interface. >=20 > Jeff is working on a system call API that disables delegation on the > client, to write unit tests against. Trond also proposed one, years ago. > On the client you might want to disable delegation per file. >=20 Not exactly. I'm just adding fcntl() commands that allow you to set/get delegations from userland: https://lore.kernel.org/linux-nfs/20251105-dir-deleg-ro-v5-17-7ebc168a88ac@= kernel.org/T/#u The main reason I wanted these was for testing purposes (so we can ensure that later VFS changes don't subtly break delegations). >=20 > > Would you also look to grain these settings per-client? The server's > > per-client interface in proc has been fantastic. > >=20 > > Ben >=20 > The issue with per-client control is that, if the client hasn't already > contacted the server, we don't know how to identify that client to > the server administrator. We can't use the client's IP address because > the client could be multi-homed or DHCP-configured. >=20 > So, per client, the settings would have to be done every time the client > contacts the server after either one has rebooted (I think). >=20 > If we're doing per net-namespace on the server, that becomes easier to > implement and document. Each container instance has its own settings > that apply to all exports from that container. >=20 Agreed. I don't think we can reasonably do this on a per-client basis, because we don't have any stable long-term persistent record of clients on the server. If the client disappears for a while, the server will just forget about it. --=20 Jeff Layton