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 4A08E23504C for ; Tue, 10 Jun 2025 17:01:48 +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=1749574908; cv=none; b=gE7oivUym8wRcKm1zjmZ8sBpGNY5JMD4WBwfoNLEmjqGzjDqUqLu+WSBb8UaUusuZCideErJmNV40IQNhk6dEgswZBPoAmobaQbw3W25wJsBucq+DDu6icxycl/j76ZQPr0qvZ+0+DNPV0jLS5g7W8eFTzaibrJtFcfNPeCsbOM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749574908; c=relaxed/simple; bh=or+U/v6zYYMSY/pzcgD97UzYtCbS4pUqtXxf18N519A=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=GwGEIZ4bjXk//OKW1UTWg+cfdRsdArbPOYfVikuzz1fZao79DuesbqCK5GS9DpHGMInsEjD2EpxiGPXnb8Ier9yTLo79D1JVHbYi6ao5hFeXtwrKSUEEPNIfxQZa2f47FnXS3sbCxhTZ0AO/j6rjvOb2rC54830CZgvBUw/m2ak= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dd67YFqi; 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="dd67YFqi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C37AC4CEED; Tue, 10 Jun 2025 17:01:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1749574907; bh=or+U/v6zYYMSY/pzcgD97UzYtCbS4pUqtXxf18N519A=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=dd67YFqiD3DgW6IuyukCLkROaB9Cf+VNbfOOoHgjp8lUP+ddSEv6DwB+rXWys4Ggz 1VufIO1AkxdYRDUjnt8l45HKyckOYrdcsLxnCI93pWL9OBYrUBC/Ox4x0uNTYNlDnU yX1TX97ktPiv3S0VqYHEPINXDgPr9iKJNttKbiAMzaxLe/RqV2gPyYQnQEmCxfhqxE xWXBIemGuoO55H88cBdNO7xCvrQKl2RPGV2Odkshp+5BzTiSI7OSGKYKkz22YKkhYB WOo+2ruajQCunsApysnKfgLHly8ORnHMBNoRM4IYbCwIjwUCEII4vgHJfnzMdgRXIj 1X/3YxxE+QguQ== Message-ID: <2155635c72f3bf440d25f74fd7924694389fb378.camel@kernel.org> Subject: Re: [RFC PATCH 3/3] NFSD: Remove the cap on number of operations per NFSv4 COMPOUND From: Jeff Layton To: Chuck Lever , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-nfs@vger.kernel.org, Chuck Lever Date: Tue, 10 Jun 2025 13:01:46 -0400 In-Reply-To: <20250610160509.97599-4-cel@kernel.org> References: <20250610160509.97599-1-cel@kernel.org> <20250610160509.97599-4-cel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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This limit has always been a sanity check; in nearly all cases a > large COMPOUND is a sign of a malfunctioning client. The only real > limit on COMPOUND size and complexity is the size of NFSD's send > and receive buffers. >=20 > However, there are a few cases where a large COMPOUND is sane. For > example, when a client implementation wants to walk down a long file > pathname in a single round trip. >=20 > A small risk is that now a client can construct a COMPOUND request > that can keep a single nfsd thread busy for quite some time. >=20 You're right about the risk there. I wonder what we could do to mitigate that? Maybe get a timestamp at the start of the compound and then check vs. that after every operation? If the compound is taking longer than a some timeout, give up and return an error on the next operation? Also, while I did suggest it, we should consider not removing this limit altogether, and rather just increase it to something like a max practical limit: For instance, we have limits in the channel_attrs for ca_maxrequestsize and ca_maxresponsesize. What's the smallest operation? If we had a compound comprised of just those operations, how many would fit? That would at least act as a sanity check against compounds that are clearly nonsensical. =20 > Suggested-by: Jeff Layton > Signed-off-by: Chuck Lever > --- > fs/nfsd/nfs4proc.c | 14 ++------------ > fs/nfsd/nfs4state.c | 1 - > fs/nfsd/nfs4xdr.c | 4 +--- > fs/nfsd/nfsd.h | 3 --- > fs/nfsd/xdr4.h | 1 - > 5 files changed, 3 insertions(+), 20 deletions(-) >=20 > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c > index f13abbb13b38..f4edf222e00e 100644 > --- a/fs/nfsd/nfs4proc.c > +++ b/fs/nfsd/nfs4proc.c > @@ -2842,20 +2842,10 @@ nfsd4_proc_compound(struct svc_rqst *rqstp) > =20 > rqstp->rq_lease_breaker =3D (void **)&cstate->clp; > =20 > - trace_nfsd_compound(rqstp, args->tag, args->taglen, args->client_opcnt)= ; > + trace_nfsd_compound(rqstp, args->tag, args->taglen, args->opcnt); > while (!status && resp->opcnt < args->opcnt) { > op =3D &args->ops[resp->opcnt++]; > =20 > - if (unlikely(resp->opcnt =3D=3D NFSD_MAX_OPS_PER_COMPOUND)) { > - /* If there are still more operations to process, > - * stop here and report NFS4ERR_RESOURCE. */ > - if (cstate->minorversion =3D=3D 0 && > - args->client_opcnt > resp->opcnt) { > - op->status =3D nfserr_resource; > - goto encode_op; > - } > - } > - > /* > * The XDR decode routines may have pre-set op->status; > * for example, if there is a miscellaneous XDR error > @@ -2932,7 +2922,7 @@ nfsd4_proc_compound(struct svc_rqst *rqstp) > status =3D op->status; > } > =20 > - trace_nfsd_compound_status(args->client_opcnt, resp->opcnt, > + trace_nfsd_compound_status(args->opcnt, resp->opcnt, > status, nfsd4_op_name(op->opnum)); > =20 > nfsd4_cstate_clear_replay(cstate); > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index d5694987f86f..4b6ae8e54cd2 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -3872,7 +3872,6 @@ static __be32 check_forechannel_attrs(struct nfsd4_= channel_attrs *ca, struct nfs > ca->headerpadsz =3D 0; > ca->maxreq_sz =3D min_t(u32, ca->maxreq_sz, maxrpc); > ca->maxresp_sz =3D min_t(u32, ca->maxresp_sz, maxrpc); > - ca->maxops =3D min_t(u32, ca->maxops, NFSD_MAX_OPS_PER_COMPOUND); > ca->maxresp_cached =3D min_t(u32, ca->maxresp_cached, > NFSD_SLOT_CACHE_SIZE + NFSD_MIN_HDR_SEQ_SZ); > ca->maxreqs =3D min_t(u32, ca->maxreqs, NFSD_MAX_SLOTS_PER_SESSION); > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c > index 3afcdbed6e14..ea91bad4eee2 100644 > --- a/fs/nfsd/nfs4xdr.c > +++ b/fs/nfsd/nfs4xdr.c > @@ -2500,10 +2500,8 @@ nfsd4_decode_compound(struct nfsd4_compoundargs *a= rgp) > =20 > if (xdr_stream_decode_u32(argp->xdr, &argp->minorversion) < 0) > return false; > - if (xdr_stream_decode_u32(argp->xdr, &argp->client_opcnt) < 0) > + if (xdr_stream_decode_u32(argp->xdr, &argp->opcnt) < 0) > return false; > - argp->opcnt =3D min_t(u32, argp->client_opcnt, > - NFSD_MAX_OPS_PER_COMPOUND); > =20 > if (argp->opcnt > ARRAY_SIZE(argp->iops)) { > argp->ops =3D vcalloc(argp->opcnt, sizeof(*argp->ops)); > diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h > index 570065285e67..54a96042f5ac 100644 > --- a/fs/nfsd/nfsd.h > +++ b/fs/nfsd/nfsd.h > @@ -57,9 +57,6 @@ struct readdir_cd { > __be32 err; /* 0, nfserr, or nfserr_eof */ > }; > =20 > -/* Maximum number of operations per session compound */ > -#define NFSD_MAX_OPS_PER_COMPOUND 50 > - > struct nfsd_genl_rqstp { > struct sockaddr rq_daddr; > struct sockaddr rq_saddr; > diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h > index aa2a356da784..a23bc56051ca 100644 > --- a/fs/nfsd/xdr4.h > +++ b/fs/nfsd/xdr4.h > @@ -870,7 +870,6 @@ struct nfsd4_compoundargs { > char * tag; > u32 taglen; > u32 minorversion; > - u32 client_opcnt; > u32 opcnt; > bool splice_ok; > struct nfsd4_op *ops; --=20 Jeff Layton