[PATCH v2 3/4] nfsd: implement server-stats-get netlink handler

[Jeff Layton]

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.

The handler uses a dump operation to stream statistics across
multiple netlink messages:

  - 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.

  - 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.

This allows nfsstat to retrieve server statistics via netlink
with a procfs fallback for older kernels.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
 Documentation/netlink/specs/nfsd.yaml | 105 +++++++++++++++++
 fs/nfsd/netlink.c                     |   5 +
 fs/nfsd/netlink.h                     |   2 +
 fs/nfsd/nfsctl.c                      | 213 ++++++++++++++++++++++++++++++++++
 include/uapi/linux/nfsd_netlink.h     |  35 ++++++
 5 files changed, 360 insertions(+)

diff --git a/Documentation/netlink/specs/nfsd.yaml b/Documentation/netlink/specs/nfsd.yaml
index 8f36fadd68f7..2a89d355ee7b 100644
--- a/Documentation/netlink/specs/nfsd.yaml
+++ b/Documentation/netlink/specs/nfsd.yaml
@@ -330,6 +330,86 @@ attribute-sets:
           of which client holds the state. Intended for use after
           all clients have been unexported from a given path,
           enabling the underlying filesystem to be unmounted.
+  -
+    name: server-proc-entry
+    attributes:
+      -
+        name: op
+        type: u32
+      -
+        name: count
+        type: u64
+      -
+        name: pad
+        type: pad
+  -
+    name: server-stats
+    attributes:
+      -
+        name: rc-hits
+        type: u64
+      -
+        name: rc-misses
+        type: u64
+      -
+        name: rc-nocache
+        type: u64
+      -
+        name: pad
+        type: pad
+      -
+        name: fh-stale
+        type: u64
+      -
+        name: io-read
+        type: u64
+      -
+        name: io-write
+        type: u64
+      -
+        name: netcnt
+        type: u32
+      -
+        name: netudpcnt
+        type: u32
+      -
+        name: nettcpcnt
+        type: u32
+      -
+        name: nettcpconn
+        type: u32
+      -
+        name: rpccnt
+        type: u32
+      -
+        name: rpcbadfmt
+        type: u32
+      -
+        name: rpcbadauth
+        type: u32
+      -
+        name: rpcbadclnt
+        type: u32
+      -
+        name: proc2-ops
+        type: nest
+        nested-attributes: server-proc-entry
+        multi-attr: true
+      -
+        name: proc3-ops
+        type: nest
+        nested-attributes: server-proc-entry
+        multi-attr: true
+      -
+        name: proc4-ops
+        type: nest
+        nested-attributes: server-proc-entry
+        multi-attr: true
+      -
+        name: proc4ops-ops
+        type: nest
+        nested-attributes: server-proc-entry
+        multi-attr: true
 
 operations:
   list:
@@ -516,6 +596,31 @@ operations:
         request:
           attributes:
             - path
+    -
+      name: server-stats-get
+      doc: dump NFS server statistics
+      attribute-set: server-stats
+      dump:
+        reply:
+          attributes:
+            - rc-hits
+            - rc-misses
+            - rc-nocache
+            - fh-stale
+            - io-read
+            - io-write
+            - netcnt
+            - netudpcnt
+            - nettcpcnt
+            - nettcpconn
+            - rpccnt
+            - rpcbadfmt
+            - rpcbadauth
+            - rpcbadclnt
+            - proc2-ops
+            - proc3-ops
+            - proc4-ops
+            - proc4ops-ops
 
 mcast-groups:
   list:
diff --git a/fs/nfsd/netlink.c b/fs/nfsd/netlink.c
index fbee3676d253..eba8b353f412 100644
--- a/fs/nfsd/netlink.c
+++ b/fs/nfsd/netlink.c
@@ -225,6 +225,11 @@ static const struct genl_split_ops nfsd_nl_ops[] = {
 		.maxattr	= NFSD_A_UNLOCK_EXPORT_PATH,
 		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
 	},
+	{
+		.cmd	= NFSD_CMD_SERVER_STATS_GET,
+		.dumpit	= nfsd_nl_server_stats_get_dumpit,
+		.flags	= GENL_CMD_CAP_DUMP,
+	},
 };
 
 static const struct genl_multicast_group nfsd_nl_mcgrps[] = {
diff --git a/fs/nfsd/netlink.h b/fs/nfsd/netlink.h
index af41aa0d4a65..027e2953db26 100644
--- a/fs/nfsd/netlink.h
+++ b/fs/nfsd/netlink.h
@@ -42,6 +42,8 @@ int nfsd_nl_cache_flush_doit(struct sk_buff *skb, struct genl_info *info);
 int nfsd_nl_unlock_ip_doit(struct sk_buff *skb, struct genl_info *info);
 int nfsd_nl_unlock_filesystem_doit(struct sk_buff *skb, struct genl_info *info);
 int nfsd_nl_unlock_export_doit(struct sk_buff *skb, struct genl_info *info);
+int nfsd_nl_server_stats_get_dumpit(struct sk_buff *skb,
+				    struct netlink_callback *cb);
 
 enum {
 	NFSD_NLGRP_NONE,
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 3aaa67b322d5..751864d8e34e 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -2261,6 +2261,219 @@ int nfsd_nl_cache_flush_doit(struct sk_buff *skb, struct genl_info *info)
 	return 0;
 }
 
+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 = 0; j < nproc; j++) {
+		unsigned long count = 0;
+
+		for_each_possible_cpu(k)
+			count += per_cpu(counts[j], k);
+
+		nest = 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
+ *
+ * cb->args[0] tracks the current NFSv4 operation index for proc4ops.
+ * A value of 0 means we haven't started yet. We emit all scalar stats
+ * and per-version procedure counts in the first message, then emit
+ * proc4ops entries filling as many as will fit per message.
+ *
+ * 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 = sock_net(skb->sk);
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+	struct svc_stat *statp = &nn->nfsd_svcstats;
+	struct svc_program *prog = statp->program;
+	int start = cb->args[0];
+	void *hdr;
+	int ret;
+
+	/*
+	 * cb->args[0] == 0: first call, emit scalar stats + procN counts
+	 * cb->args[0] > 0: emit proc4ops entries starting from args[0] - 1
+	 * cb->args[0] < 0: done
+	 */
+	if (start < 0)
+		return 0;
+
+	if (start == 0) {
+		hdr = 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;
+
+		/* Reply cache stats */
+		{
+			u64 hits, misses, nocache;
+
+			hits = percpu_counter_sum_positive(&nn->counter[NFSD_STATS_RC_HITS]);
+			misses = percpu_counter_sum_positive(&nn->counter[NFSD_STATS_RC_MISSES]);
+			nocache = percpu_counter_sum_positive(&nn->counter[NFSD_STATS_RC_NOCACHE]);
+			ret = nla_put_u64_64bit(skb, NFSD_A_SERVER_STATS_RC_HITS,
+					hits, NFSD_A_SERVER_STATS_PAD) ||
+			      nla_put_u64_64bit(skb, NFSD_A_SERVER_STATS_RC_MISSES,
+					misses, NFSD_A_SERVER_STATS_PAD) ||
+			      nla_put_u64_64bit(skb, NFSD_A_SERVER_STATS_RC_NOCACHE,
+					nocache, NFSD_A_SERVER_STATS_PAD);
+		}
+		if (ret)
+			goto err_cancel;
+
+		/* Filehandle stats */
+		ret = nla_put_u64_64bit(skb, NFSD_A_SERVER_STATS_FH_STALE,
+				percpu_counter_sum_positive(&nn->counter[NFSD_STATS_FH_STALE]),
+				NFSD_A_SERVER_STATS_PAD);
+		if (ret)
+			goto err_cancel;
+
+		/* IO stats */
+		{
+			u64 rd, wr;
+
+			rd = percpu_counter_sum_positive(&nn->counter[NFSD_STATS_IO_READ]);
+			wr = percpu_counter_sum_positive(&nn->counter[NFSD_STATS_IO_WRITE]);
+			ret = nla_put_u64_64bit(skb, NFSD_A_SERVER_STATS_IO_READ,
+					rd, NFSD_A_SERVER_STATS_PAD) ||
+			      nla_put_u64_64bit(skb, NFSD_A_SERVER_STATS_IO_WRITE,
+					wr, NFSD_A_SERVER_STATS_PAD);
+		}
+		if (ret)
+			goto err_cancel;
+
+		/* Network stats */
+		ret = nla_put_u32(skb, NFSD_A_SERVER_STATS_NETCNT,
+				  statp->netcnt) ||
+		      nla_put_u32(skb, NFSD_A_SERVER_STATS_NETUDPCNT,
+				  statp->netudpcnt) ||
+		      nla_put_u32(skb, NFSD_A_SERVER_STATS_NETTCPCNT,
+				  statp->nettcpcnt) ||
+		      nla_put_u32(skb, NFSD_A_SERVER_STATS_NETTCPCONN,
+				  statp->nettcpconn);
+		if (ret)
+			goto err_cancel;
+
+		/* RPC stats */
+		ret = nla_put_u32(skb, NFSD_A_SERVER_STATS_RPCCNT,
+				  statp->rpccnt) ||
+		      nla_put_u32(skb, NFSD_A_SERVER_STATS_RPCBADFMT,
+				  statp->rpcbadfmt) ||
+		      nla_put_u32(skb, NFSD_A_SERVER_STATS_RPCBADAUTH,
+				  statp->rpcbadauth) ||
+		      nla_put_u32(skb, NFSD_A_SERVER_STATS_RPCBADCLNT,
+				  statp->rpcbadclnt);
+		if (ret)
+			goto err_cancel;
+
+		/* Per-version procedure counts */
+		if (statp->vs_count) {
+			static const int proc_attrs[] = {
+				[2] = NFSD_A_SERVER_STATS_PROC2_OPS,
+				[3] = NFSD_A_SERVER_STATS_PROC3_OPS,
+				[4] = NFSD_A_SERVER_STATS_PROC4_OPS,
+			};
+			unsigned int i;
+
+			for (i = 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;
+				ret = nfsd_nl_fill_proc_ops(skb,
+						proc_attrs[i],
+						statp->vs_count[i],
+						prog->pg_vers[i]->vs_nproc);
+				if (ret)
+					goto err_cancel;
+			}
+		}
+
+		genlmsg_end(skb, hdr);
+		cb->args[0] = 1;
+	}
+
+#ifdef CONFIG_NFSD_V4
+	/* NFSv4 individual operation counts */
+	{
+		int i = (start > 0) ? start - 1 : 0;
+
+		for (; i <= LAST_NFS4_OP; i++) {
+			struct percpu_counter *ctr;
+			struct nlattr *nest;
+			u64 cnt;
+
+			ctr = &nn->counter[NFSD_STATS_NFS4_OP(i)];
+			cnt = percpu_counter_sum_positive(ctr);
+
+			hdr = 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) {
+				cb->args[0] = i + 1;
+				goto out;
+			}
+
+			nest = nla_nest_start(skb,
+					NFSD_A_SERVER_STATS_PROC4OPS_OPS);
+			if (!nest) {
+				genlmsg_cancel(skb, hdr);
+				cb->args[0] = i + 1;
+				goto out;
+			}
+			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);
+				genlmsg_cancel(skb, hdr);
+				cb->args[0] = i + 1;
+				goto out;
+			}
+			nla_nest_end(skb, nest);
+			genlmsg_end(skb, hdr);
+		}
+	}
+#endif
+
+	cb->args[0] = -1;
+out:
+	return skb->len;
+
+err_cancel:
+	genlmsg_cancel(skb, hdr);
+	return ret;
+}
+
 int nfsd_cache_notify(struct cache_detail *cd, struct cache_head *h, u32 cache_type)
 {
 	struct genlmsghdr *hdr;
diff --git a/include/uapi/linux/nfsd_netlink.h b/include/uapi/linux/nfsd_netlink.h
index f5b75d5caba9..3d076d173b1d 100644
--- a/include/uapi/linux/nfsd_netlink.h
+++ b/include/uapi/linux/nfsd_netlink.h
@@ -225,6 +225,40 @@ enum {
 	NFSD_A_UNLOCK_EXPORT_MAX = (__NFSD_A_UNLOCK_EXPORT_MAX - 1)
 };
 
+enum {
+	NFSD_A_SERVER_PROC_ENTRY_OP = 1,
+	NFSD_A_SERVER_PROC_ENTRY_COUNT,
+	NFSD_A_SERVER_PROC_ENTRY_PAD,
+
+	__NFSD_A_SERVER_PROC_ENTRY_MAX,
+	NFSD_A_SERVER_PROC_ENTRY_MAX = (__NFSD_A_SERVER_PROC_ENTRY_MAX - 1)
+};
+
+enum {
+	NFSD_A_SERVER_STATS_RC_HITS = 1,
+	NFSD_A_SERVER_STATS_RC_MISSES,
+	NFSD_A_SERVER_STATS_RC_NOCACHE,
+	NFSD_A_SERVER_STATS_PAD,
+	NFSD_A_SERVER_STATS_FH_STALE,
+	NFSD_A_SERVER_STATS_IO_READ,
+	NFSD_A_SERVER_STATS_IO_WRITE,
+	NFSD_A_SERVER_STATS_NETCNT,
+	NFSD_A_SERVER_STATS_NETUDPCNT,
+	NFSD_A_SERVER_STATS_NETTCPCNT,
+	NFSD_A_SERVER_STATS_NETTCPCONN,
+	NFSD_A_SERVER_STATS_RPCCNT,
+	NFSD_A_SERVER_STATS_RPCBADFMT,
+	NFSD_A_SERVER_STATS_RPCBADAUTH,
+	NFSD_A_SERVER_STATS_RPCBADCLNT,
+	NFSD_A_SERVER_STATS_PROC2_OPS,
+	NFSD_A_SERVER_STATS_PROC3_OPS,
+	NFSD_A_SERVER_STATS_PROC4_OPS,
+	NFSD_A_SERVER_STATS_PROC4OPS_OPS,
+
+	__NFSD_A_SERVER_STATS_MAX,
+	NFSD_A_SERVER_STATS_MAX = (__NFSD_A_SERVER_STATS_MAX - 1)
+};
+
 enum {
 	NFSD_CMD_RPC_STATUS_GET = 1,
 	NFSD_CMD_THREADS_SET,
@@ -244,6 +278,7 @@ enum {
 	NFSD_CMD_UNLOCK_IP,
 	NFSD_CMD_UNLOCK_FILESYSTEM,
 	NFSD_CMD_UNLOCK_EXPORT,
+	NFSD_CMD_SERVER_STATS_GET,
 
 	__NFSD_CMD_MAX,
 	NFSD_CMD_MAX = (__NFSD_CMD_MAX - 1)

-- 
2.54.0