From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 E52233F54B6; Thu, 16 Jul 2026 13:53:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784210012; cv=none; b=sFKqpEHT2eqiU4n3wIpiI9GXAX/AbyMn5GqqySzumQ3+E8uOtu37lcV1VOaohz8KKeWx/XGt7dNuhHosMAbYa9xJdBtu1HGl3qX+op2OoOq23OiBt/R35AxjlhGZ5dPbqfH3zaBAFM8hmYBBQ6LWpTc33gtJsD5pUe05WCKPOvw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784210012; c=relaxed/simple; bh=o2FMYpRHS+zhsw2qdQBfeWS5YsMyIw7aMRtPcXZRFCA=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=G8QsFYgmmlNRSRKzAjdgyiiVeWmXaQ4XLvkso5Eomabc8AdXTlOQDKN3SAj8gN6a0CeN+sukYfewzEiuxZOv7TGjlY4HS38kxWG/9ofFr7l+cLBgximBt6pA7U21pB8eHn5nJX6jBZnLQdiEncfAmcIaB1LglBIt75fwcnLKwQY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BTTAgX1w; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BTTAgX1w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F41F91F00A3A; Thu, 16 Jul 2026 13:53:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784210010; bh=eEtiy5RcvunMEYeq/F+MrWWi428oKufCgwRjxTU2YSA=; h=Subject:From:To:Cc:Date:In-Reply-To:References; b=BTTAgX1wPqLgVJJm5aBSv/z1nAgbGfYrKOAhshHz790K8xr2F5LTEfNv5ceohjAfv QfQq2T7354fXt93IQemu2UiMdVIvUF8QYeJToD+iSxGmykNftt5q98Xp+yyyMmJuR9 64uccJ2ACZfqd+cfuoJlGNpYnF+6D7yZ1KIVUUkY5OYlDs0eBaD/a9q/vBgSQ23PjY +SWPaT3My3tt9GQlVYiNZLFwOpgssaYTLjxbXnyLlGy/YWIGIjV/KGKkS45ct4YwEz +kEQZKpe2MAQOOPrmwbo6zpv9aK15Lf4N12VEfILN1wfVNpgacMYyXvyFkCZoWiJrn 6yXyLkBBw+Q5A== Message-ID: <4ef6dd5a13bfb51f72452aa30f59c89a54037404.camel@kernel.org> Subject: Re: [PATCH v6 3/6] nfsd: implement server-stats-get netlink handler From: Jeff Layton To: Chuck Lever , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: Trond Myklebust , Anna Schumaker , Steve Dickson , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 16 Jul 2026 09:53:28 -0400 In-Reply-To: <8173debc-96fb-4354-ba11-dff99b772523@app.fastmail.com> References: <20260619-exportd-netlink-v6-0-ddef3499793c@kernel.org> <20260619-exportd-netlink-v6-3-ddef3499793c@kernel.org> <8173debc-96fb-4354-ba11-dff99b772523@app.fastmail.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv 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linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2026-06-19 at 16:40 -0400, Chuck Lever wrote: >=20 > On Fri, Jun 19, 2026, at 11:26 AM, Jeff Layton wrote: > > Implement nfsd_nl_server_stats_get_dumpit() which exposes the > > NFS server statistics currently available via /proc/net/rpc/nfsd > > through the nfsd generic netlink family. >=20 > A couple of questions on the dump design and one on the commit message, > then some smaller items. >=20 > The commit message says: >=20 > > - First message: all scalar stats (reply cache, filehandle, > > IO, network, RPC) plus per-version procedure counts > > (proc2/3/4-ops) using per-netns vs_count arrays. > >=20 > > - Subsequent messages: NFSv4 per-operation counts > > (proc4ops-ops), one entry per message, using cb->args[0] > > to track the current operation index across dump calls. >=20 > The code does not stream across subsequent messages. The proc4ops-ops > nests are emitted in the first message, inside the same "if (start =3D=3D= 0)" > block as the scalars, and cb->args[0] only ever holds 0 or -1, never an > operation index. The function's own kerneldoc agrees: "The entire > server-stats object is emitted in a single netlink message on the first > invocation." >=20 > Should the commit message be reworded to match the code, or should the co= de > move to the streaming design the message describes? That second option t= ies > into the next question. >=20 > > diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c > > index 601301e34fc7..f0514d8149cd 100644 > > --- a/fs/nfsd/nfsctl.c > > +++ b/fs/nfsd/nfsctl.c > > @@ -2329,6 +2329,185 @@ int nfsd_nl_cache_flush_doit(struct sk_buff *sk= b, struct genl_info *info) > > return 0; > > } > >=20 > > +static int nfsd_nl_fill_proc_ops(struct sk_buff *skb, int attr, > > + unsigned long __percpu *counts, > > + unsigned int nproc) > > +{ > > + struct nlattr *nest; > > + unsigned int j; > > + int k; > > + > > + for (j =3D 0; j < nproc; j++) { > > + unsigned long count =3D 0; > > + > > + for_each_possible_cpu(k) > > + count +=3D per_cpu(counts[j], k); > > + > > + nest =3D nla_nest_start(skb, attr); > > + if (!nest) > > + return -EMSGSIZE; > > + if (nla_put_u32(skb, NFSD_A_SERVER_PROC_ENTRY_OP, j) || > > + nla_put_u64_64bit(skb, NFSD_A_SERVER_PROC_ENTRY_COUNT, > > + count, NFSD_A_SERVER_PROC_ENTRY_PAD)) { > > + nla_nest_cancel(skb, nest); > > + return -EMSGSIZE; > > + } > > + nla_nest_end(skb, nest); > > + } > > + > > + return 0; > > +} > > + > > +/** > > + * nfsd_nl_server_stats_get_dumpit - dump NFS server statistics > > + * @skb: reply buffer > > + * @cb: netlink metadata and command arguments > > + * > > + * The entire server-stats object is emitted in a single netlink messa= ge on > > + * the first invocation. cb->args[0] is set to -1 afterwards so that t= he next > > + * invocation terminates the dump. > > + * > > + * Returns the size of the reply or a negative errno. > > + */ > > +int nfsd_nl_server_stats_get_dumpit(struct sk_buff *skb, > > + struct netlink_callback *cb) > > +{ > > + struct net *net =3D sock_net(skb->sk); > > + struct nfsd_net *nn =3D net_generic(net, nfsd_net_id); > > + struct svc_stat *statp =3D &nn->nfsd_svcstats; > > + struct svc_program *prog =3D statp->program; > > + int start =3D cb->args[0]; > > + void *hdr; > > + > > + /* > > + * cb->args[0] =3D=3D 0: first call, emit the full server-stats objec= t > > + * cb->args[0] < 0: dump already complete > > + */ > > + if (start < 0) > > + return 0; > > + > > + if (start =3D=3D 0) { > > + hdr =3D genlmsg_put(skb, NETLINK_CB(cb->skb).portid, > > + cb->nlh->nlmsg_seq, &nfsd_nl_family, > > + NLM_F_MULTI, NFSD_CMD_SERVER_STATS_GET); > > + if (!hdr) > > + return -ENOBUFS; > > + >=20 > This handler assembles the entire server-stats object -- all scalars, the > proc2/3/4-ops nests, and one proc4ops-ops nest per NFSv4 operation -- in = one > message under "if (start =3D=3D 0)", then sets cb->args[0] =3D -1 so the = next call > ends the dump. >=20 > Does that hold up once the assembled message no longer fits the dump buff= er? > A dump skb is allocated at max(cb->min_dump_alloc, NLMSG_GOODSIZE), and t= his > handler sets neither cb->min_dump_alloc nor a .start callback, so the flo= or > is NLMSG_GOODSIZE, which is SKB_WITH_OVERHEAD(PAGE_SIZE), roughly 3.7k on= a > 4k-page host. A larger skb is allocated only when userspace has previous= ly > grown its receive buffer. >=20 > With LAST_NFS4_OP at 75, the proc4ops-ops loop alone emits 76 nests of ab= out > 28 bytes each (~2.1k); the proc2 and proc3 nests plus the scalar block br= ing > the total to roughly 3.5k -- already within a few hundred bytes of the fl= oor, > and growing by one nest for every NFSv4 operation added later. >=20 > [ ... scalar puts for reply cache, fh, io, net, rpc snipped ... ] >=20 > > + /* Per-version procedure counts */ > > + if (statp->vs_count) { > > + static const int proc_attrs[] =3D { > > + [2] =3D NFSD_A_SERVER_STATS_PROC2_OPS, > > + [3] =3D NFSD_A_SERVER_STATS_PROC3_OPS, > > + [4] =3D NFSD_A_SERVER_STATS_PROC4_OPS, > > + }; > > + unsigned int i; > > + > > + for (i =3D 0; i < prog->pg_nvers && > > + i < ARRAY_SIZE(proc_attrs); i++) { > > + if (!prog->pg_vers[i] || > > + !statp->vs_count[i]) > > + continue; > > + if (!proc_attrs[i]) > > + continue; > > + if (nfsd_nl_fill_proc_ops(skb, > > + proc_attrs[i], > > + statp->vs_count[i], > > + prog->pg_vers[i]->vs_nproc)) > > + goto err_cancel; > > + } > > + } > > + > > +#ifdef CONFIG_NFSD_V4 > > + /* NFSv4 individual operation counts */ > > + for (int i =3D 0; i <=3D LAST_NFS4_OP; i++) { > > + struct nlattr *nest; > > + u64 cnt; > > + > > + cnt =3D percpu_counter_sum_positive( > > + &nn->counter[NFSD_STATS_NFS4_OP(i)]); > > + > > + nest =3D nla_nest_start(skb, > > + NFSD_A_SERVER_STATS_PROC4OPS_OPS); > > + if (!nest) > > + goto err_cancel; > > + if (nla_put_u32(skb, NFSD_A_SERVER_PROC_ENTRY_OP, i) || > > + nla_put_u64_64bit(skb, NFSD_A_SERVER_PROC_ENTRY_COUNT, > > + cnt, NFSD_A_SERVER_PROC_ENTRY_PAD)) { > > + nla_nest_cancel(skb, nest); > > + goto err_cancel; > > + } > > + nla_nest_end(skb, nest); > > + } > > +#endif >=20 > This loop open-codes the same nest that nfsd_nl_fill_proc_ops() builds ju= st > above -- nla_nest_start(), nla_put_u32(PROC_ENTRY_OP), > nla_put_u64_64bit(PROC_ENTRY_COUNT), nla_nest_end() -- into the same > NFSD_A_SERVER_STATS_PROC4OPS_OPS attribute. Could the helper be generali= zed > to take the per-op counter source so this is not a second copy of the sam= e > code? >=20 > The per-version block above skips empty versions: >=20 > if (!prog->pg_vers[i] || !statp->vs_count[i]) > continue; >=20 > but this loop emits an entry for every op 0..LAST_NFS4_OP, zero-count ops > included. Is that difference intentional? Skipping zero counts here wou= ld > also trim the worst-case message size above. >=20 > There is also a counter that this dump does not emit. /proc/net/rpc/nfsd > prints a wdeleg_getattr line after proc4ops: >=20 > seq_printf(seq, "\nwdeleg_getattr %lld", > percpu_counter_sum_positive(&nn->counter[NFSD_STATS_WDELEG_GETATTR])); >=20 > incremented by nfsd_stats_wdeleg_getattr_inc(). Since the goal is to exp= ose > the statistics currently available via /proc/net/rpc/nfsd, should > wdeleg_getattr get an attribute here too, so nfsstat over netlink does no= t > drop it relative to the procfs path? >=20 The only thing in this review that is not addressed in my current series is the above comment, and I think we had agreed in an earlier email thread that this was approximately the same value as the counter for CB_GETATTR calls and so it's good enough for this purpose. Are you still ok with this approach? --=20 Jeff Layton