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 D0CBA7C6E6; Fri, 24 Jan 2025 14:11:26 +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=1737727886; cv=none; b=WTfPebfASYu/OVP/mtMyGchldwNr+eZd/5fV0ZEp421RFG15+W0M5PCgjOuzDo8nyhZQASYjb/OAmTc7NqfjMc+vRq3CFmmzm3uDdtN7TTsaRwjIEBzU/HHZWUvnhs1TmNGV83LyB5sTdWJb/iKBnI37OQZ44wgKcnJtHO0KRB8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737727886; c=relaxed/simple; bh=jAvqWJ7yhUiFZNafZTKzScdFt8IoxWPnx39/7EcBfJQ=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Wt5fwNwDZ5c8sCT+wrYrarYAaWGb8chS3/2Bkc7JzzIS5I9VWJ88BEtnb036OtkblJSY2NhoWnpWT8ZDRjH+JVs7pBUwY5EflxE0Rz508TlrEOgynUyAAizy7U9yGjsIr9HIrrcqBZeyFkG68uDGQbYYRwzA4WsrWT/CDYB+eEY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ny4d+A4b; 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="Ny4d+A4b" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37961C4CED2; Fri, 24 Jan 2025 14:11:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737727886; bh=jAvqWJ7yhUiFZNafZTKzScdFt8IoxWPnx39/7EcBfJQ=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Ny4d+A4bnA1U5HWq7uK6iXLlTBG+O8YQNhb3oisEJTA3mIXTc6Tq2rVHpA3YLxkFG YM2tObwQcZjAoxnfJdvXygqdaW7HoRfVcjgSQ4GLCS3hJOBOFphi07zeP4PaMLH3f/ qohcYEm01SdxFMUHPzZ61Y0Gbub3876qiBtRgepYokBeJzPBlRgXFMzp4ISYeiQAAB lSBVCN5hyM3wpOHOxl5PxWBhzAx7dN//4OTUIt3Sv/5ed52XUj6d1Iu7LAcFcda6d5 5QvMTZL7Z0BlNARAEV6gpU0GKBdKi1w/IwG6kQ98Vl6cDt1xUCCDT8kkBIZZRFn8Ib Mo/G5tk5n5XZw== Message-ID: <8314a4b3823ead3dc08411dd48da70e5dcf6b2ae.camel@kernel.org> Subject: Re: [PATCH 3/8] nfsd: when CB_SEQUENCE gets NFS4ERR_DELAY, release the slot From: Jeff Layton To: "J. Bruce Fields" Cc: Chuck Lever , Neil Brown , Olga Kornievskaia , Dai Ngo , Tom Talpey , 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: Fri, 24 Jan 2025 09:11:24 -0500 In-Reply-To: References: <20250123-nfsd-6-14-v1-0-c1137a4fa2ae@kernel.org> <20250123-nfsd-6-14-v1-3-c1137a4fa2ae@kernel.org> <4f89125253d82233b5b14c6e0c4fd7565b1824e0.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 09:00 -0500, J. Bruce Fields wrote: > On Thu, Jan 23, 2025 at 06:20:08PM -0500, Jeff Layton wrote: > > On Thu, 2025-01-23 at 17:18 -0500, Chuck Lever wrote: > > > On 1/23/25 3:25 PM, Jeff Layton wrote: > > > > RFC8881, 15.1.1.3 says this about NFS4ERR_DELAY: > > > >=20 > > > > "For any of a number of reasons, the replier could not process this > > > > operation in what was deemed a reasonable time. The client should= wait > > > > and then try the request with a new slot and sequence value." > > >=20 > > > A little farther down, Section 15.1.1.3 says this: > > >=20 > > > "If NFS4ERR_DELAY is returned on a SEQUENCE operation, the request is > > > retried in full with the SEQUENCE operation containing the same slo= t > > > and sequence values." > > >=20 > > > And: > > >=20 > > > "If NFS4ERR_DELAY is returned on an operation other than the first in > > > the request, the request when retried MUST contain a SEQUENCE opera= tion > > > that is different than the original one, with either the slot ID or= the > > > sequence value different from that in the original request." > > >=20 > > > My impression is that the slot needs to be held and used again only i= f > > > the server responded with NFS4ERR_DELAY on the SEQUENCE operation. If > > > the NFS4ERR_DELAY was the status of the 2nd or later operation in the > > > COMPOUND, then yes, a different slot, or the same slot with a bumped > > > sequence number, must be used. > > >=20 > > > The current code in nfsd4_cb_sequence_done() appears to be correct in > > > this regard. > > >=20 > >=20 > > Ok! I stand corrected. We should be able to just drop this patch, but > > some of the later patches may need some trivial merge conflicts fixed > > up. > >=20 > > Any idea why SEQUENCE is different in this regard? >=20 > Isn't DELAY on SEQUENCE an indication that the operation is still in > progress? The difference between retrying the same slot or not is > whether you're asking the server again for the result of the previous > operation, or whether you're asking it to perform a new one. >=20 > If you get DELAY on a later op and then keep retrying with the same > seqid/slot then I'd expect you to get stuck in an infinite loop getting > a DELAY response out of the reply cache. >=20 Hi Bruce! That may be the case. From RFC8881, section 2.10.6.2: "A retry might be sent while the original request is still in progress on the replier. The replier SHOULD deal with the issue by returning NFS4ERR_DELAY as the reply to SEQUENCE or CB_SEQUENCE operation, but implementations MAY return NFS4ERR_MISORDERED. Since errors from SEQUENCE and CB_SEQUENCE are never recorded in the reply cache, this approach allows the results of the execution of the original request to be properly recorded in the reply cache (assuming that the requester specified the reply to be cached)." >=20 >=20 > > This rule seems a > > bit arbitrary. If the response is NFS4ERR_DELAY, then why would it > > matter which slot you use when retransmitting? The responder is just > > saying "go away and come back later". > >=20 > > What if the responder repeatedly returns NFS4ERR_DELAY (maybe because > > it's under resource pressure), and also shrinks the slot table in the > > meantime? It seems like that might put the requestor in an untenable > > position. > >=20 > > Maybe we should lobby to get this changed in the spec? > >=20 > > >=20 > > > > This is CB_SEQUENCE, but I believe the same rule applies. Release t= he > > > > slot before submitting the delayed RPC. > > > >=20 > > > > Fixes: 7ba6cad6c88f ("nfsd: New helper nfsd4_cb_sequence_done() for= processing more cb errors") > > > > Signed-off-by: Jeff Layton > > > > --- > > > > fs/nfsd/nfs4callback.c | 1 + > > > > 1 file changed, 1 insertion(+) > > > >=20 > > > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c > > > > index bfc9de1fcb67b4f05ed2f7a28038cd8290809c17..c26ccb9485b95499fc9= 08833a384d741e966a8db 100644 > > > > --- a/fs/nfsd/nfs4callback.c > > > > +++ b/fs/nfsd/nfs4callback.c > > > > @@ -1392,6 +1392,7 @@ static bool nfsd4_cb_sequence_done(struct rpc= _task *task, struct nfsd4_callback > > > > goto need_restart; > > > > case -NFS4ERR_DELAY: > > > > cb->cb_seq_status =3D 1; > > > > + nfsd41_cb_release_slot(cb); > > > > if (!rpc_restart_call(task)) > > > > goto out; > > > > =20 > > > >=20 > > >=20 > > >=20 > >=20 > > --=20 > > Jeff Layton --=20 Jeff Layton