[PATCH v7 1/5] NFSD: convert write_threads to netlink command

[Lorenzo Bianconi <lorenzo@kernel.org>]

Introduce write_threads netlink command similar to the one available
through the procfs.

Tested-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 Documentation/netlink/specs/nfsd.yaml | 23 ++++++++++
 fs/nfsd/netlink.c                     | 17 ++++++++
 fs/nfsd/netlink.h                     |  2 +
 fs/nfsd/nfsctl.c                      | 60 +++++++++++++++++++++++++++
 include/uapi/linux/nfsd_netlink.h     |  9 ++++
 5 files changed, 111 insertions(+)

diff --git a/Documentation/netlink/specs/nfsd.yaml b/Documentation/netlink/specs/nfsd.yaml
index 05acc73e2e33..c92e1425d316 100644
--- a/Documentation/netlink/specs/nfsd.yaml
+++ b/Documentation/netlink/specs/nfsd.yaml
@@ -62,6 +62,12 @@ attribute-sets:
         name: compound-ops
         type: u32
         multi-attr: true
+  -
+    name: server-worker
+    attributes:
+      -
+        name: threads
+        type: u32
 
 operations:
   list:
@@ -87,3 +93,20 @@ operations:
             - sport
             - dport
             - compound-ops
+    -
+      name: threads-set
+      doc: set the number of running threads
+      attribute-set: server-worker
+      flags: [ admin-perm ]
+      do:
+        request:
+          attributes:
+            - threads
+    -
+      name: threads-get
+      doc: get the number of running threads
+      attribute-set: server-worker
+      do:
+        reply:
+          attributes:
+            - threads
diff --git a/fs/nfsd/netlink.c b/fs/nfsd/netlink.c
index 0e1d635ec5f9..1a59a8e6c7e2 100644
--- a/fs/nfsd/netlink.c
+++ b/fs/nfsd/netlink.c
@@ -10,6 +10,11 @@
 
 #include <uapi/linux/nfsd_netlink.h>
 
+/* NFSD_CMD_THREADS_SET - do */
+static const struct nla_policy nfsd_threads_set_nl_policy[NFSD_A_SERVER_WORKER_THREADS + 1] = {
+	[NFSD_A_SERVER_WORKER_THREADS] = { .type = NLA_U32, },
+};
+
 /* Ops table for nfsd */
 static const struct genl_split_ops nfsd_nl_ops[] = {
 	{
@@ -19,6 +24,18 @@ static const struct genl_split_ops nfsd_nl_ops[] = {
 		.done	= nfsd_nl_rpc_status_get_done,
 		.flags	= GENL_CMD_CAP_DUMP,
 	},
+	{
+		.cmd		= NFSD_CMD_THREADS_SET,
+		.doit		= nfsd_nl_threads_set_doit,
+		.policy		= nfsd_threads_set_nl_policy,
+		.maxattr	= NFSD_A_SERVER_WORKER_THREADS,
+		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
+	},
+	{
+		.cmd	= NFSD_CMD_THREADS_GET,
+		.doit	= nfsd_nl_threads_get_doit,
+		.flags	= GENL_CMD_CAP_DO,
+	},
 };
 
 struct genl_family nfsd_nl_family __ro_after_init = {
diff --git a/fs/nfsd/netlink.h b/fs/nfsd/netlink.h
index d83dd6bdee92..4137fac477e4 100644
--- a/fs/nfsd/netlink.h
+++ b/fs/nfsd/netlink.h
@@ -16,6 +16,8 @@ int nfsd_nl_rpc_status_get_done(struct netlink_callback *cb);
 
 int nfsd_nl_rpc_status_get_dumpit(struct sk_buff *skb,
 				  struct netlink_callback *cb);
+int nfsd_nl_threads_set_doit(struct sk_buff *skb, struct genl_info *info);
+int nfsd_nl_threads_get_doit(struct sk_buff *skb, struct genl_info *info);
 
 extern struct genl_family nfsd_nl_family;
 
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 93c87587e646..71608744e67f 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1651,6 +1651,66 @@ int nfsd_nl_rpc_status_get_done(struct netlink_callback *cb)
 	return 0;
 }
 
+/**
+ * nfsd_nl_threads_set_doit - set the number of running threads
+ * @skb: reply buffer
+ * @info: netlink metadata and command arguments
+ *
+ * Return 0 on success or a negative errno.
+ */
+int nfsd_nl_threads_set_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	u32 nthreads;
+	int ret;
+
+	if (GENL_REQ_ATTR_CHECK(info, NFSD_A_SERVER_WORKER_THREADS))
+		return -EINVAL;
+
+	nthreads = nla_get_u32(info->attrs[NFSD_A_SERVER_WORKER_THREADS]);
+	ret = nfsd_svc(nthreads,
+		       genl_info_net(info), get_current_cred());
+
+	return ret == nthreads ? 0 : -EINVAL;
+}
+
+/**
+ * nfsd_nl_threads_get_doit - get the number of running threads
+ * @skb: reply buffer
+ * @info: netlink metadata and command arguments
+ *
+ * Return 0 on success or a negative errno.
+ */
+int nfsd_nl_threads_get_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	void *hdr;
+	int err;
+
+	skb = genlmsg_new(GENLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!skb)
+		return -ENOMEM;
+
+	hdr = genlmsg_iput(skb, info);
+	if (!hdr) {
+		err = -EMSGSIZE;
+		goto err_free_msg;
+	}
+
+	if (nla_put_u32(skb, NFSD_A_SERVER_WORKER_THREADS,
+			nfsd_nrthreads(genl_info_net(info)))) {
+		err = -EINVAL;
+		goto err_free_msg;
+	}
+
+	genlmsg_end(skb, hdr);
+
+	return genlmsg_reply(skb, info);
+
+err_free_msg:
+	nlmsg_free(skb);
+
+	return err;
+}
+
 /**
  * nfsd_net_init - Prepare the nfsd_net portion of a new net namespace
  * @net: a freshly-created network namespace
diff --git a/include/uapi/linux/nfsd_netlink.h b/include/uapi/linux/nfsd_netlink.h
index 3cd044edee5d..1b6fe1f9ed0e 100644
--- a/include/uapi/linux/nfsd_netlink.h
+++ b/include/uapi/linux/nfsd_netlink.h
@@ -29,8 +29,17 @@ enum {
 	NFSD_A_RPC_STATUS_MAX = (__NFSD_A_RPC_STATUS_MAX - 1)
 };
 
+enum {
+	NFSD_A_SERVER_WORKER_THREADS = 1,
+
+	__NFSD_A_SERVER_WORKER_MAX,
+	NFSD_A_SERVER_WORKER_MAX = (__NFSD_A_SERVER_WORKER_MAX - 1)
+};
+
 enum {
 	NFSD_CMD_RPC_STATUS_GET = 1,
+	NFSD_CMD_THREADS_SET,
+	NFSD_CMD_THREADS_GET,
 
 	__NFSD_CMD_MAX,
 	NFSD_CMD_MAX = (__NFSD_CMD_MAX - 1)
-- 
2.44.0