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 661D025A624; Sun, 26 Jan 2025 11:18:24 +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=1737890304; cv=none; b=AfgAez1fs0v6OxJP0Jz1on+SkiwSyMdCQHDtrhGbkQrXj+OitsR0YJ5v3DlqchjPOUYggsYX5Fna7obghYIcqqNcUt84Y6u9FmEBMB3xHEC/leD6jmMlvec16w04fRXsH0l0AJHpG3R88TpXRTzIoV1AHUXg3DMpuxE8dWIqeB4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737890304; c=relaxed/simple; bh=hrOUKmqCrVTpXsUOcQzsiqAb+RLwDDWzgsOzHFQRaP4=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=fWFQp9IfawFnLIgv/Ma4i0u74mCqoBNpYPZZjsWVm17BKlzozPcWqqXc1SiZJsYf9BVhtAOfyKC+jsIHRv9/oMH045EAjEkIZkvMJTmkFMnsCAzbdk96c756ZHEl4mT47wOqpbM7QZ3+gvXQch5e71K2fse8EhbjRSILovFBkHU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Mb/BOctZ; 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="Mb/BOctZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 64C9AC4CED3; Sun, 26 Jan 2025 11:18:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737890303; bh=hrOUKmqCrVTpXsUOcQzsiqAb+RLwDDWzgsOzHFQRaP4=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Mb/BOctZcse1z0vcVpBXEBXqzhC0mJVtIIpqk/xkKfbDLlI+IvQV9x7nEJ7NteO9a BhCpbtk8DdkZLZyPL15MwCQDYFtvQTfSwdnG414xvRao6obLs6GRtFWNHh6ggRzxXZ pDoZLT8nqLRuiwulGsEoMth8ONNF6QqvciUPyPMW9oIo3Kv+Waajs8gGQVRKBozQ2i 8pNHR1FcqUyStFnYWU6mYRj4JLC/Hd3/0xT1M1zsnQBByxTxCAbSfrWZQcAsyryqAX bb0qq1VmOX3rpkgRSW9BQaz7L2FiTGit3BuCR+yVwSUiF4wK4aja0h2zalcWa6BvLo bweW+zQk+qq1w== Message-ID: Subject: Re: [PATCH 1/8] nfsd: don't restart v4.1+ callback when RPC_SIGNALLED is set From: Jeff Layton To: NeilBrown Cc: Chuck Lever , Olga Kornievskaia , Dai Ngo , Tom Talpey , "J. Bruce Fields" , Kinglong Mee , Trond Myklebust , Anna Schumaker , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Date: Sun, 26 Jan 2025 06:18:21 -0500 In-Reply-To: <173784610046.22054.813567864998956753@noble.neil.brown.name> References: <20250123-nfsd-6-14-v1-0-c1137a4fa2ae@kernel.org> , <20250123-nfsd-6-14-v1-1-c1137a4fa2ae@kernel.org> <173784610046.22054.813567864998956753@noble.neil.brown.name> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn 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DfX/sn9XcfoVZIxMpCRE750zvJvcCUz9HojsrMQ1NFc7MFT1z3MOW2/RlzPcog7xvR5ENPH19ojRD CHqumUHRry+RF0lH00clzX/W8OrQJZtoBPXv9ahka/Vp7kEulcBJr1cH5Wz/WprhsIM7U9pse1f1g Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Sun, 2025-01-26 at 10:01 +1100, NeilBrown wrote: > On Fri, 24 Jan 2025, Jeff Layton wrote: > > This is problematic, since the RPC might have been entirely successful. > > There is no point in restarting a v4.1+ callback just because > > RPC_SIGNALLED is true. The v4.1+ error handling has other mechanisms fo= r > > detecting when it should retransmit the RPC. >=20 > But why might RPC_SIGNALLED() ever be true? > The flag RPC_TASK_SIGNALLED is only ever set by rpc_signal_task() which > is only called from rpc_killall_tasks() and __rpc_execute() for > non-async tasks which doesn't apply to nfsd callbacks as they are > started with rpc_call_async(). >=20 > rpc_killall_tasks() is called by fs/nfs/ which isn't relevant for us, > and from rpc_shutdown_client(). In those cases we certainly don't want > the request to be retried, though the nfsd4_process_cb_update() case is > a little interesting as we do want it to be retried, but in a different > client. > > So the code you are removing is either dead code because something else > will prevent the restart when a client is being shut down, or it is bad > code because it would delay rpc_shutdown_client() while the request is > retried.=20 >=20 > I haven't dug the extra step to figure out which, but either way I think > the code should go. >=20 >=20 Thanks. That was my analysis too. rpc_shutdown_client() is called when we tear down and rebuild the rpc_client. nfsd does this in setup_callback_client(), which gets called from nfsd4_process_cb_update() (basically when we detect that the backchannel is having problems). There are really only two states: We either got a reply from the server before the client went down, or we didn't. In the case where we got a reply, there is no need to retry anything. In the case where we didn't, the tk_status will be '1', so there is no need to check RPC_SIGNALLED() at all here. The existing code could lead to the call being retried when we had already gotten a perfectly valid reply. > >=20 > > Fixes: 7ba6cad6c88f ("nfsd: New helper nfsd4_cb_sequence_done() for pro= cessing more cb errors") > > Signed-off-by: Jeff Layton > > --- > > fs/nfsd/nfs4callback.c | 3 --- > > 1 file changed, 3 deletions(-) > >=20 > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c > > index 50e468bdb8d4838b5217346dcc2bd0fec1765c1a..e12205ef16ca932ffbcc86d= 67b0817aec2436c89 100644 > > --- a/fs/nfsd/nfs4callback.c > > +++ b/fs/nfsd/nfs4callback.c > > @@ -1403,9 +1403,6 @@ static bool nfsd4_cb_sequence_done(struct rpc_tas= k *task, struct nfsd4_callback > > } > > trace_nfsd_cb_free_slot(task, cb); > > nfsd41_cb_release_slot(cb); > > - > > - if (RPC_SIGNALLED(task)) > > - goto need_restart; > > out: > > return ret; > > retry_nowait: > >=20 > > --=20 > > 2.48.1 > >=20 > >=20 >=20 --=20 Jeff Layton