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

From: Lorenzo Bianconi <[email-masked]>
Date: Mon, 25 Sep 2023 16:31:57 +0200

On Sep 25, Chuck Lever wrote:
> 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 <[email-masked]>
> > ---
> > 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.

ack, fine to me..naming is always hard :)

> 
> 
> > +    attributes:
> > +      -
> > +        name: threads
> > +        type: u32
> > +      -
> > +        name: max-blksize
> > +        type: u32
> > +      -
> > +        name: max-conn
> > +        type: u32
> >  
> >  operations:
> >    list:
> > @@ -72,3 +84,54 @@ operations:
> >        dump:
[...]
> >  
> > +/**
> > + * 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?

actually this is a leftover of the previous patch. I will fix it in v3.

Regards,
Lorenzo

> 
> 
> > +	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