Re: [PATCH] NFSD: convert write_threads and write_v4_end_grace to netlink commands

[Jeff Layton <jlayton@kernel.org>]

On Fri, 2023-09-22 at 14:44 +0200, Lorenzo Bianconi wrote:
> Introduce write_threads and write_v4_end_grace netlink commands similar
> to the ones available through the procfs.
> Introduce nfsd_nl_server_status_get_dumpit netlink command in order to
> report global server metadata.
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
> This patch can be tested with user-space tool reported below:
> https://github.com/LorenzoBianconi/nfsd-netlink.git
> ---
>  Documentation/netlink/specs/nfsd.yaml | 33 +++++++++
>  fs/nfsd/netlink.c                     | 30 ++++++++
>  fs/nfsd/netlink.h                     |  5 ++
>  fs/nfsd/nfsctl.c                      | 98 +++++++++++++++++++++++++++
>  include/uapi/linux/nfsd_netlink.h     | 11 +++
>  5 files changed, 177 insertions(+)
> 
> diff --git a/Documentation/netlink/specs/nfsd.yaml b/Documentation/netlink/specs/nfsd.yaml
> index 403d3e3a04f3..fa1204892703 100644
> --- a/Documentation/netlink/specs/nfsd.yaml
> +++ b/Documentation/netlink/specs/nfsd.yaml
> @@ -62,6 +62,15 @@ attribute-sets:
>          name: compound-ops
>          type: u32
>          multi-attr: true
> +  -
> +    name: server-attr
> +    attributes:
> +      -
> +        name: threads
> +        type: u16

65k threads ought to be enough for anybody!

> +      -
> +        name: v4-grace
> +        type: u8
>  
>  operations:
>    list:
> @@ -72,3 +81,27 @@ operations:
>        dump:
>          pre: nfsd-nl-rpc-status-get-start
>          post: nfsd-nl-rpc-status-get-done
> +    -
> +      name: threads-set
> +      doc: set the number of running threads
> +      attribute-set: server-attr
> +      flags: [ admin-perm ]
> +      do:
> +        request:
> +          attributes:
> +            - threads
> +    -
> +      name: v4-grace-release
> +      doc: release the grace period for nfsd's v4 lock manager
> +      attribute-set: server-attr
> +      flags: [ admin-perm ]
> +      do:
> +        request:
> +          attributes:
> +            - v4-grace
> +    -
> +      name: server-status-get
> +      doc: dump server status info
> +      attribute-set: server-attr
> +      dump:
> +        pre: nfsd-nl-server-status-get-start
> diff --git a/fs/nfsd/netlink.c b/fs/nfsd/netlink.c
> index 0e1d635ec5f9..783a34e69354 100644
> --- a/fs/nfsd/netlink.c
> +++ b/fs/nfsd/netlink.c
> @@ -10,6 +10,16 @@
>  
>  #include <uapi/linux/nfsd_netlink.h>
>  
> +/* NFSD_CMD_THREADS_SET - do */
> +static const struct nla_policy nfsd_threads_set_nl_policy[NFSD_A_SERVER_ATTR_THREADS + 1] = {
> +	[NFSD_A_SERVER_ATTR_THREADS] = { .type = NLA_U16, },
> +};
> +
> +/* NFSD_CMD_V4_GRACE_RELEASE - do */
> +static const struct nla_policy nfsd_v4_grace_release_nl_policy[NFSD_A_SERVER_ATTR_V4_GRACE + 1] = {
> +	[NFSD_A_SERVER_ATTR_V4_GRACE] = { .type = NLA_U8, },
> +};
> +
>  /* Ops table for nfsd */
>  static const struct genl_split_ops nfsd_nl_ops[] = {
>  	{
> @@ -19,6 +29,26 @@ 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_ATTR_THREADS,
> +		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
> +	},
> +	{
> +		.cmd		= NFSD_CMD_V4_GRACE_RELEASE,
> +		.doit		= nfsd_nl_v4_grace_release_doit,
> +		.policy		= nfsd_v4_grace_release_nl_policy,
> +		.maxattr	= NFSD_A_SERVER_ATTR_V4_GRACE,
> +		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
> +	},
> +	{
> +		.cmd	= NFSD_CMD_SERVER_STATUS_GET,
> +		.start	= nfsd_nl_server_status_get_start,
> +		.dumpit	= nfsd_nl_server_status_get_dumpit,
> +		.flags	= GENL_CMD_CAP_DUMP,
> +	},
>  };
>  
>  struct genl_family nfsd_nl_family __ro_after_init = {
> diff --git a/fs/nfsd/netlink.h b/fs/nfsd/netlink.h
> index d83dd6bdee92..2e98061fbb0a 100644
> --- a/fs/nfsd/netlink.h
> +++ b/fs/nfsd/netlink.h
> @@ -12,10 +12,15 @@
>  #include <uapi/linux/nfsd_netlink.h>
>  
>  int nfsd_nl_rpc_status_get_start(struct netlink_callback *cb);
> +int nfsd_nl_server_status_get_start(struct netlink_callback *cb);
>  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_v4_grace_release_doit(struct sk_buff *skb, struct genl_info *info);
> +int nfsd_nl_server_status_get_dumpit(struct sk_buff *skb,
> +				     struct netlink_callback *cb);
>  
>  extern struct genl_family nfsd_nl_family;
>  
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index b71744e355a8..c631b59b7a4f 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -1694,6 +1694,104 @@ 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)
> +{
> +	u16 nthreads;
> +	int ret;
> +
> +	if (!info->attrs[NFSD_A_SERVER_ATTR_THREADS])
> +		return -EINVAL;
> +
> +	nthreads = nla_get_u16(info->attrs[NFSD_A_SERVER_ATTR_THREADS]);
> +
> +	ret = nfsd_svc(nthreads, genl_info_net(info), get_current_cred());
> +	return ret == nthreads ? 0 : ret;
> +}
> +
> +/**
> + * nfsd_nl_v4_grace_release_doit - release the nfs4 grace period
> + * @skb: reply buffer
> + * @info: netlink metadata and command arguments
> + *
> + * Return 0 on success or a negative errno.
> + */
> +int nfsd_nl_v4_grace_release_doit(struct sk_buff *skb, struct genl_info *info)
> +{
> +#ifdef CONFIG_NFSD_V4
> +	struct nfsd_net *nn = net_generic(genl_info_net(info), nfsd_net_id);
> +
> +	if (!info->attrs[NFSD_A_SERVER_ATTR_V4_GRACE])
> +		return -EINVAL;
> +
> +	if (nla_get_u8(info->attrs[NFSD_A_SERVER_ATTR_V4_GRACE]))
> +		nfsd4_end_grace(nn);
> +

To be clear here. Issuing this with anything but 0 will end the grace
period. A value of 0 is ignored. It might be best to make the value not
matter at all. Do we have to send down a value at all?

> +	return 0;
> +#else
> +	return -EOPNOTSUPP;
> +#endif /* CONFIG_NFSD_V4 */
> +}
> +
> +/**
> + * nfsd_nl_server_status_get_start - Prepare server_status_get dumpit
> + * @cb: netlink metadata and command arguments
> + *
> + * Return values:
> + *   %0: The server_status_get command may proceed
> + *   %-ENODEV: There is no NFSD running in this namespace
> + */
> +int nfsd_nl_server_status_get_start(struct netlink_callback *cb)
> +{
> +	struct nfsd_net *nn = net_generic(sock_net(cb->skb->sk), nfsd_net_id);
> +
> +	return nn->nfsd_serv ? 0 : -ENODEV;
> +}
> +
> +/**
> + * nfsd_nl_server_status_get_dumpit - dump server status info
> + * @skb: reply buffer
> + * @cb: netlink metadata and command arguments
> + *
> + * Returns the size of the reply or a negative errno.
> + */
> +int nfsd_nl_server_status_get_dumpit(struct sk_buff *skb,
> +				     struct netlink_callback *cb)
> +{
> +	struct net *net = sock_net(skb->sk);
> +#ifdef CONFIG_NFSD_V4
> +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> +#endif /* CONFIG_NFSD_V4 */
> +	void *hdr;
> +
> +	if (cb->args[0]) /* already consumed */
> +		return 0;
> +
> +	hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
> +			  &nfsd_nl_family, NLM_F_MULTI,
> +			  NFSD_CMD_SERVER_STATUS_GET);
> +	if (!hdr)
> +		return -ENOBUFS;
> +
> +	if (nla_put_u16(skb, NFSD_A_SERVER_ATTR_THREADS, nfsd_nrthreads(net)))
> +		return -ENOBUFS;
> +#ifdef CONFIG_NFSD_V4
> +	if (nla_put_u8(skb, NFSD_A_SERVER_ATTR_V4_GRACE, !nn->grace_ended))
> +		return -ENOBUFS;
> +#endif /* CONFIG_NFSD_V4 */
> +
> +	genlmsg_end(skb, hdr);
> +	cb->args[0] = 1;
> +
> +	return skb->len;
> +}
> +
>  /**
>   * 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 c8ae72466ee6..b82fbc53d336 100644
> --- a/include/uapi/linux/nfsd_netlink.h
> +++ b/include/uapi/linux/nfsd_netlink.h
> @@ -29,8 +29,19 @@ enum {
>  	NFSD_A_RPC_STATUS_MAX = (__NFSD_A_RPC_STATUS_MAX - 1)
>  };
>  
> +enum {
> +	NFSD_A_SERVER_ATTR_THREADS = 1,
> +	NFSD_A_SERVER_ATTR_V4_GRACE,
> +
> +	__NFSD_A_SERVER_ATTR_MAX,
> +	NFSD_A_SERVER_ATTR_MAX = (__NFSD_A_SERVER_ATTR_MAX - 1)
> +};
> +
>  enum {
>  	NFSD_CMD_RPC_STATUS_GET = 1,
> +	NFSD_CMD_THREADS_SET,
> +	NFSD_CMD_V4_GRACE_RELEASE,
> +	NFSD_CMD_SERVER_STATUS_GET,
>  
>  	__NFSD_CMD_MAX,
>  	NFSD_CMD_MAX = (__NFSD_CMD_MAX - 1)

-- 
Jeff Layton <jlayton@kernel.org>