Re: [PATCH v2] NFSD: convert write_threads, write_maxblksize and write_maxconn to netlink commands

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On Sun, Sep 24, 2023 at 03:52:28PM +0200, Lorenzo Bianconi wrote:
> Introduce write_threads, write_maxblksize and write_maxconn netlink
> commands similar to the ones available through the procfs.
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
> ---
> Changes since v1:
> - remove write_v4_end_grace command
> - add write_maxblksize and write_maxconn netlink commands
> 
> This patch can be tested with user-space tool reported below:
> https://github.com/LorenzoBianconi/nfsd-netlink.git
> ---
>  Documentation/netlink/specs/nfsd.yaml |  63 ++++++++++++
>  fs/nfsd/netlink.c                     |  51 ++++++++++
>  fs/nfsd/netlink.h                     |   9 ++
>  fs/nfsd/nfsctl.c                      | 139 ++++++++++++++++++++++++++
>  include/uapi/linux/nfsd_netlink.h     |  15 +++
>  5 files changed, 277 insertions(+)

This looks pretty close to me. A couple of comments below.


> diff --git a/Documentation/netlink/specs/nfsd.yaml b/Documentation/netlink/specs/nfsd.yaml
> index 403d3e3a04f3..10214fcec8a5 100644
> --- a/Documentation/netlink/specs/nfsd.yaml
> +++ b/Documentation/netlink/specs/nfsd.yaml
> @@ -62,6 +62,18 @@ attribute-sets:
>          name: compound-ops
>          type: u32
>          multi-attr: true
> +  -
> +    name: server-attr

Or, say, "control-plane" ? "server-attr" doesn't seem very self-
explanatory or specific.


> +    attributes:
> +      -
> +        name: threads
> +        type: u32
> +      -
> +        name: max-blksize
> +        type: u32
> +      -
> +        name: max-conn
> +        type: u32
>  
>  operations:
>    list:
> @@ -72,3 +84,54 @@ 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: threads-get
> +      doc: dump the number of running threads
> +      attribute-set: server-attr
> +      dump:
> +        reply:
> +          attributes:
> +            - threads
> +    -
> +      name: max-blksize-set
> +      doc: set the nfs block size
> +      attribute-set: server-attr
> +      flags: [ admin-perm ]
> +      do:
> +        request:
> +          attributes:
> +            - max-blksize
> +    -
> +      name: max-blksize-get
> +      doc: dump the nfs block size
> +      attribute-set: server-attr
> +      dump:
> +        reply:
> +          attributes:
> +            - max-blksize
> +    -
> +      name: max-conn-set
> +      doc: set the max number of connections
> +      attribute-set: server-attr
> +      flags: [ admin-perm ]
> +      do:
> +        request:
> +          attributes:
> +            - max-conn
> +    -
> +      name: max-conn-get
> +      doc: dump the max number of connections
> +      attribute-set: server-attr
> +      dump:
> +        reply:
> +          attributes:
> +            - max-conn
> diff --git a/fs/nfsd/netlink.c b/fs/nfsd/netlink.c
> index 0e1d635ec5f9..f3dde1b1e162 100644
> --- a/fs/nfsd/netlink.c
> +++ b/fs/nfsd/netlink.c
> @@ -10,6 +10,21 @@
>  
>  #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_U32, },
> +};
> +
> +/* NFSD_CMD_MAX_BLKSIZE_SET - do */
> +static const struct nla_policy nfsd_max_blksize_set_nl_policy[NFSD_A_SERVER_ATTR_MAX_BLKSIZE + 1] = {
> +	[NFSD_A_SERVER_ATTR_MAX_BLKSIZE] = { .type = NLA_U32, },
> +};
> +
> +/* NFSD_CMD_MAX_CONN_SET - do */
> +static const struct nla_policy nfsd_max_conn_set_nl_policy[NFSD_A_SERVER_ATTR_MAX_CONN + 1] = {
> +	[NFSD_A_SERVER_ATTR_MAX_CONN] = { .type = NLA_U32, },
> +};
> +
>  /* Ops table for nfsd */
>  static const struct genl_split_ops nfsd_nl_ops[] = {
>  	{
> @@ -19,6 +34,42 @@ 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_THREADS_GET,
> +		.dumpit	= nfsd_nl_threads_get_dumpit,
> +		.flags	= GENL_CMD_CAP_DUMP,
> +	},
> +	{
> +		.cmd		= NFSD_CMD_MAX_BLKSIZE_SET,
> +		.doit		= nfsd_nl_max_blksize_set_doit,
> +		.policy		= nfsd_max_blksize_set_nl_policy,
> +		.maxattr	= NFSD_A_SERVER_ATTR_MAX_BLKSIZE,
> +		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
> +	},
> +	{
> +		.cmd	= NFSD_CMD_MAX_BLKSIZE_GET,
> +		.dumpit	= nfsd_nl_max_blksize_get_dumpit,
> +		.flags	= GENL_CMD_CAP_DUMP,
> +	},
> +	{
> +		.cmd		= NFSD_CMD_MAX_CONN_SET,
> +		.doit		= nfsd_nl_max_conn_set_doit,
> +		.policy		= nfsd_max_conn_set_nl_policy,
> +		.maxattr	= NFSD_A_SERVER_ATTR_MAX_CONN,
> +		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
> +	},
> +	{
> +		.cmd	= NFSD_CMD_MAX_CONN_GET,
> +		.dumpit	= nfsd_nl_max_conn_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..41b95651c638 100644
> --- a/fs/nfsd/netlink.h
> +++ b/fs/nfsd/netlink.h
> @@ -16,6 +16,15 @@ 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_dumpit(struct sk_buff *skb,
> +			       struct netlink_callback *cb);
> +int nfsd_nl_max_blksize_set_doit(struct sk_buff *skb, struct genl_info *info);
> +int nfsd_nl_max_blksize_get_dumpit(struct sk_buff *skb,
> +				   struct netlink_callback *cb);
> +int nfsd_nl_max_conn_set_doit(struct sk_buff *skb, struct genl_info *info);
> +int nfsd_nl_max_conn_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..0167b7fd0d63 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -1694,6 +1694,145 @@ 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_u32(info->attrs[NFSD_A_SERVER_ATTR_THREADS]);

I worry about what happens if someone sends down a value larger than
64K. While not a likely scenario, the behavior is not well defined,
and I don't think the implicit type conversions are necessary.

Can nthreads be u32?


> +	ret = nfsd_svc(nthreads, genl_info_net(info), get_current_cred());
> +	return ret == nthreads ? 0 : ret;
> +}
> +
> +static int nfsd_nl_get_dump(struct sk_buff *skb, struct netlink_callback *cb,
> +			    int cmd, int attr, u32 val)
> +{
> +	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, cmd);
> +	if (!hdr)
> +		return -ENOBUFS;
> +
> +	if (nla_put_u32(skb, attr, val))
> +		return -ENOBUFS;
> +
> +	genlmsg_end(skb, hdr);
> +	cb->args[0] = 1;
> +
> +	return skb->len;
> +}
> +
> +/**
> + * nfsd_nl_threads_get_dumpit - dump the number of running threads
> + * @skb: reply buffer
> + * @cb: netlink metadata and command arguments
> + *
> + * Returns the size of the reply or a negative errno.
> + */
> +int nfsd_nl_threads_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
> +{
> +	return nfsd_nl_get_dump(skb, cb, NFSD_CMD_THREADS_GET,
> +				NFSD_A_SERVER_ATTR_THREADS,
> +				nfsd_nrthreads(sock_net(skb->sk)));
> +}
> +
> +/**
> + * nfsd_nl_max_blksize_set_doit - set the nfs block size
> + * @skb: reply buffer
> + * @info: netlink metadata and command arguments
> + *
> + * Return 0 on success or a negative errno.
> + */
> +int nfsd_nl_max_blksize_set_doit(struct sk_buff *skb, struct genl_info *info)
> +{
> +	struct nfsd_net *nn = net_generic(genl_info_net(info), nfsd_net_id);
> +	int ret = 0;
> +
> +	if (!info->attrs[NFSD_A_SERVER_ATTR_MAX_BLKSIZE])
> +		return -EINVAL;
> +
> +	mutex_lock(&nfsd_mutex);
> +	if (nn->nfsd_serv) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	nfsd_max_blksize = nla_get_u32(info->attrs[NFSD_A_SERVER_ATTR_MAX_BLKSIZE]);
> +	nfsd_max_blksize = max_t(int, nfsd_max_blksize, 1024);
> +	nfsd_max_blksize = min_t(int, nfsd_max_blksize, NFSSVC_MAXBLKSIZE);
> +	nfsd_max_blksize &= ~1023;
> +out:
> +	mutex_unlock(&nfsd_mutex);
> +
> +	return ret;
> +}
> +
> +/**
> + * nfsd_nl_max_blksize_get_dumpit - dump the nfs block size
> + * @skb: reply buffer
> + * @cb: netlink metadata and command arguments
> + *
> + * Returns the size of the reply or a negative errno.
> + */
> +int nfsd_nl_max_blksize_get_dumpit(struct sk_buff *skb,
> +				   struct netlink_callback *cb)
> +{
> +	return nfsd_nl_get_dump(skb, cb, NFSD_CMD_MAX_BLKSIZE_GET,
> +				NFSD_A_SERVER_ATTR_MAX_BLKSIZE,
> +				nfsd_max_blksize);
> +}
> +
> +/**
> + * nfsd_nl_max_conn_set_doit - set the max number of connections
> + * @skb: reply buffer
> + * @info: netlink metadata and command arguments
> + *
> + * Return 0 on success or a negative errno.
> + */
> +int nfsd_nl_max_conn_set_doit(struct sk_buff *skb, struct genl_info *info)
> +{
> +	struct nfsd_net *nn = net_generic(genl_info_net(info), nfsd_net_id);
> +
> +	if (!info->attrs[NFSD_A_SERVER_ATTR_MAX_CONN])
> +		return -EINVAL;
> +
> +	nn->max_connections = nla_get_u32(info->attrs[NFSD_A_SERVER_ATTR_MAX_CONN]);
> +
> +	return 0;
> +}
> +
> +/**
> + * nfsd_nl_max_conn_get_dumpit - dump the max number of connections
> + * @skb: reply buffer
> + * @cb: netlink metadata and command arguments
> + *
> + * Returns the size of the reply or a negative errno.
> + */
> +int nfsd_nl_max_conn_get_dumpit(struct sk_buff *skb,
> +				struct netlink_callback *cb)
> +{
> +	struct nfsd_net *nn = net_generic(sock_net(cb->skb->sk), nfsd_net_id);
> +
> +	return nfsd_nl_get_dump(skb, cb, NFSD_CMD_MAX_CONN_GET,
> +				NFSD_A_SERVER_ATTR_MAX_CONN,
> +				nn->max_connections);
> +}
> +
>  /**
>   * 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..59d0aa22ba94 100644
> --- a/include/uapi/linux/nfsd_netlink.h
> +++ b/include/uapi/linux/nfsd_netlink.h
> @@ -29,8 +29,23 @@ enum {
>  	NFSD_A_RPC_STATUS_MAX = (__NFSD_A_RPC_STATUS_MAX - 1)
>  };
>  
> +enum {
> +	NFSD_A_SERVER_ATTR_THREADS = 1,
> +	NFSD_A_SERVER_ATTR_MAX_BLKSIZE,
> +	NFSD_A_SERVER_ATTR_MAX_CONN,
> +
> +	__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_THREADS_GET,
> +	NFSD_CMD_MAX_BLKSIZE_SET,
> +	NFSD_CMD_MAX_BLKSIZE_GET,
> +	NFSD_CMD_MAX_CONN_SET,
> +	NFSD_CMD_MAX_CONN_GET,
>  
>  	__NFSD_CMD_MAX,
>  	NFSD_CMD_MAX = (__NFSD_CMD_MAX - 1)
> -- 
> 2.41.0
> 

-- 
Chuck Lever



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