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 14A82153BF7; Fri, 24 Jan 2025 16:04:55 +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=1737734695; cv=none; b=pkgpPuuRUc26GdqB4bI9Rcdjsxmdn9COJnG7J4BVpPVkh1Z5Ow3LAF+wuqnau671UaIUsaqK0eMg3kBEQkRVXGjsEbcouW94+8m2CKBsGC4f84Ps9o1AncGTZqbnQvksHNKO7awNwDGikGxPauDdCeaQRQu1C+tk8g3XYs4QykY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737734695; c=relaxed/simple; bh=TPA434fY7lux6XnYf1clstY4nCFfIk5DH1SOpMjVHVI=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=WfFQSGGAbpRuPMgNBcsXN8rFVLw60gMvve+0ukFDO2HKCMSeNMv8id7nRdb611T6gb/K4zKwR54L0lZ5L/klIvIi4ENmNQ7vOocN5DFdQTvu6oyrsNhP7C+JUIf+BNI5WJSUcDKBOlyavK0w6yPhEVfVv49A28d2Wl8cUsFRr4w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KCevB+Ns; 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="KCevB+Ns" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69460C4CED2; Fri, 24 Jan 2025 16:04:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737734694; bh=TPA434fY7lux6XnYf1clstY4nCFfIk5DH1SOpMjVHVI=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=KCevB+Ns2FRk7n1PoeY9NsTiTg90kWA+kmsmeOvo7mnD3CfaSF5twxpQAKIXJhNMc b3rn6nNuoIbJe3saF8Jn2WRm82ufKmBnmCqg5oeD/xixd7t1RcLfQHDVAKat9YAvOT 9+b/EPvSVHFaBrhCOD7JMddzNtEYNJCaqw3ebGyUeIR5p9zpe4EP8u1wLcusaAAPs1 bNAzgCMCT5vHssZ4lTA/1j2uJKidce2ur/YKZM/8WPF9cfi+4Ve0G6xYLhIKE+/NpX Ox2TSDJLjaaLomDPZJP9DkVnhe0zAlClfyE/bh9tDN17OpuxTEgE/YdTyGPUBxzRKk 13PZJBxH63rqA== Message-ID: <9237d52f30f63cbe6450fcbbbeaf259250554814.camel@kernel.org> Subject: Re: [PATCH 2/8] nfsd: fix CB_SEQUENCE error handling of NFS4ERR_{BADSLOT,BADSESSION,SEQ_MISORDERED} From: Jeff Layton To: Chuck Lever , Neil Brown , 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 Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Date: Fri, 24 Jan 2025 11:04:52 -0500 In-Reply-To: References: <20250123-nfsd-6-14-v1-0-c1137a4fa2ae@kernel.org> <20250123-nfsd-6-14-v1-2-c1137a4fa2ae@kernel.org> <66e5e5e74487a274a069539dc14fb10d7832044f.camel@kernel.org> 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 VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ 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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 Fri, 2025-01-24 at 10:31 -0500, Chuck Lever wrote: > On 1/24/25 9:46 AM, Jeff Layton wrote: > > On Fri, 2025-01-24 at 09:32 -0500, Chuck Lever wrote: > > > On 1/23/25 3:25 PM, Jeff Layton wrote: > > > > The current error handling has some problems: > > > >=20 > > > > BADSLOT and BADSESSION: don't release the slot before retrying the = call > > > >=20 > > > > SEQ_MISORDERED: does some sketchy resetting of the seqid? I can't f= ind any > > > > recommendation about doing that in the spec, and it seems wrong. > > >=20 > > > Random thought: You might use the Linux NFS client's forechannel sess= ion > > > implementation as a code reference. > > >=20 > > >=20 > > > > Handle all three errors the same way: release the slot, but then ha= ndle > > > > it just like we would as if we hadn't gotten a reply; mark the sess= ion > > > > as faulty, and retry the call. > > >=20 > > > Some questions: > > >=20 > > > Why does it matter whether NFSD keeps the slot if both sides plan to > > > destroy the session? > > >=20 > >=20 > > It may not be required, but there is no reason to hold onto the slot in > > these cases. >=20 > In the BADSLOT case, if the slot is released, then another session > consumer on the NFS server can use it and will encounter the same error. > Best to keep it in the penalty box, IMO. >=20 > If there are other slots, they are likely still usable. An > implementation can choose to continue using the session rather than > scuttling it immediately. In the past, with a single backchannel slot, > NFSD had no choice but to replace the session. But now it can be more > conservative. >=20 It may still be usable, but if we got BADSLOT, then it's still indicative of a faulty session. Best to mark it as such, IMO. It's worth noting that these things should really _never_ happen, so being somewhat heavy-handed in this situation seems reasonable. >=20 > > Also, at this point, only nfsd has declared that it needs > > a new session (see below). >=20 > If the client's backchannel service has returned BADSESSION, then the > client already knows this session is unusable. >=20 Fair point. I still think it's reasonable to mark it CB_FAULT in that case. That status is also displayed via the client_info file, so that's helpful info. >=20 > > > Also, AFAICT marking CB_FAULT does not destroy the session, it simply > > > tries to recreate backchannel's rpc_clnt. Perhaps NFSD's callback cod= e > > > should actively destroy the session and let the client drive a fresh > > > CREATE_SESSION to recover? > > >=20 > >=20 > > Marking it with a fault just sets the cl_cb_state to NFSD4_CB_FAULT. > > Then, on the next SEQUENCE call, that makes nfsd set > > SEQ4_STATUS_BACKCHANNEL_FAULT, which should make the client recreate > > the session. Obviously, there is some delay involved there since we > > might have to wait for the client to do a lease renewal before this > > happens. > >=20 > > >=20 > > > > Fixes: 7ba6cad6c88f ("nfsd: New helper nfsd4_cb_sequence_done() for= processing more cb errors") > > > > Signed-off-by: Jeff Layton > > > > --- > > > > fs/nfsd/nfs4callback.c | 27 +++++++++++---------------- > > > > 1 file changed, 11 insertions(+), 16 deletions(-) > > > >=20 > > > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c > > > > index e12205ef16ca932ffbcc86d67b0817aec2436c89..bfc9de1fcb67b4f05ed= 2f7a28038cd8290809c17 100644 > > > > --- a/fs/nfsd/nfs4callback.c > > > > +++ b/fs/nfsd/nfs4callback.c > > > > @@ -1371,17 +1371,24 @@ static bool nfsd4_cb_sequence_done(struct r= pc_task *task, struct nfsd4_callback > > > > nfsd4_mark_cb_fault(cb->cb_clp); > > > > ret =3D false; > > > > break; > > > > + case -NFS4ERR_BADSESSION: > > > > + case -NFS4ERR_BADSLOT: > > > > + case -NFS4ERR_SEQ_MISORDERED: > > > > + /* > > > > + * These errors indicate that something has gone wrong > > > > + * with the server and client's synchronization. Release > > > > + * the slot, but handle it as if we hadn't gotten a reply. > > > > + */ > > > > + nfsd41_cb_release_slot(cb); > > > > + fallthrough; > > > > case 1: > > > > /* > > > > * cb_seq_status remains 1 if an RPC Reply was never > > > > * received. NFSD can't know if the client processed > > > > * the CB_SEQUENCE operation. Ask the client to send a > > > > - * DESTROY_SESSION to recover. > > > > + * DESTROY_SESSION to recover, but keep the slot. > > > > */ > > > > - fallthrough; > > > > - case -NFS4ERR_BADSESSION: > > > > nfsd4_mark_cb_fault(cb->cb_clp); > > > > - ret =3D false; > > > > goto need_restart; > > > > case -NFS4ERR_DELAY: > > > > cb->cb_seq_status =3D 1; > > > > @@ -1390,14 +1397,6 @@ static bool nfsd4_cb_sequence_done(struct rp= c_task *task, struct nfsd4_callback > > > > =20 > > > > rpc_delay(task, 2 * HZ); > > > > return false; > > > > - case -NFS4ERR_BADSLOT: > > > > - goto retry_nowait; > > > > - case -NFS4ERR_SEQ_MISORDERED: > > > > - if (session->se_cb_seq_nr[cb->cb_held_slot] !=3D 1) { > > > > - session->se_cb_seq_nr[cb->cb_held_slot] =3D 1; > > > > - goto retry_nowait; > > > > - } > > > > - break; > > > > default: > > > > nfsd4_mark_cb_fault(cb->cb_clp); > > > > } > > > > @@ -1405,10 +1404,6 @@ static bool nfsd4_cb_sequence_done(struct rp= c_task *task, struct nfsd4_callback > > > > nfsd41_cb_release_slot(cb); > > > > out: > > > > return ret; > > > > -retry_nowait: > > > > - if (rpc_restart_call_prepare(task)) > > > > - ret =3D false; > > > > - goto out; > > > > need_restart: > > > > if (!test_bit(NFSD4_CLIENT_CB_KILL, &clp->cl_flags)) { > > > > trace_nfsd_cb_restart(clp, cb); > > > >=20 > > >=20 > > >=20 > >=20 >=20 >=20 --=20 Jeff Layton