Re: [PATCH v8 2/6] NFSD: convert write_threads to netlink command

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2024-04-17 at 08:28 +1000, NeilBrown wrote:
> On Tue, 16 Apr 2024, Lorenzo Bianconi wrote:
> > 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>
> > Co-developed-by: Jeff Layton <jlayton@kernel.org>
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > ---
> >  Documentation/netlink/specs/nfsd.yaml |  33 ++++++++
> >  fs/nfsd/netlink.c                     |  19 +++++
> >  fs/nfsd/netlink.h                     |   2 +
> >  fs/nfsd/nfsctl.c                      | 104 ++++++++++++++++++++++++++
> >  include/uapi/linux/nfsd_netlink.h     |  11 +++
> >  5 files changed, 169 insertions(+)
> > 
> > diff --git a/Documentation/netlink/specs/nfsd.yaml b/Documentation/netlink/specs/nfsd.yaml
> > index 05acc73e2e33..cbe6c5fd6c4d 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-worker
> > +    attributes:
> > +      -
> > +        name: threads
> > +        type: u32
> > +      -
> > +        name: gracetime
> > +        type: u32
> > +      -
> > +        name: leasetime
> > +        type: u32
> 
> Another thought: I would be really happy if the "scope" were another
> optional argument here.  The mechanism of setting the scope by user the
> hostname works but is ugly.  I'm inclined to ignore the hostname
> completely when netlink is used, but I'm not completely sure about that.
> (aside - I think using the hostname for the default scope was a really
> bad idea.  It should have been a fixed string like "Linux").
> 

I'd be ok with that.

I replicated how rpc.nfsd does this in the userland tool, but I also
thought it was pretty ugly. I think all that it does currently is make
this work in nfsd_svc() since it overrides the nodename in the new
namespace:

        strscpy(nn->nfsd_name, utsname()->nodename,
                sizeof(nn->nfsd_name));

If we make that a new optional parameter, we could pass the scope in as
a new const char * argument to nfsd_svc. Then we'd just copy that into
nfsd_name instead of the nodename when it's provided.

I wonder too if we ought to rename this particular operations too. It's
becoming less of a "set threads" interface and more of a generic server
setup.

> 
> 
> >  
> >  operations:
> >    list:
> > @@ -87,3 +99,24 @@ 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
> > +            - gracetime
> > +            - leasetime
> > +    -
> > +      name: threads-get
> > +      doc: get the number of running threads
> > +      attribute-set: server-worker
> > +      do:
> > +        reply:
> > +          attributes:
> > +            - threads
> > +            - gracetime
> > +            - leasetime
> > diff --git a/fs/nfsd/netlink.c b/fs/nfsd/netlink.c
> > index 0e1d635ec5f9..20a646af0324 100644
> > --- a/fs/nfsd/netlink.c
> > +++ b/fs/nfsd/netlink.c
> > @@ -10,6 +10,13 @@
> >  
> >  #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_LEASETIME + 1] = {
> > +	[NFSD_A_SERVER_WORKER_THREADS] = { .type = NLA_U32, },
> > +	[NFSD_A_SERVER_WORKER_GRACETIME] = { .type = NLA_U32, },
> > +	[NFSD_A_SERVER_WORKER_LEASETIME] = { .type = NLA_U32, },
> > +};
> > +
> >  /* Ops table for nfsd */
> >  static const struct genl_split_ops nfsd_nl_ops[] = {
> >  	{
> > @@ -19,6 +26,18 @@ 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_LEASETIME,
> > +		.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 f2e442d7fe16..38a5df03981b 100644
> > --- a/fs/nfsd/nfsctl.c
> > +++ b/fs/nfsd/nfsctl.c
> > @@ -1653,6 +1653,110 @@ 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)
> > +{
> > +	struct net *net = genl_info_net(info);
> > +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> > +	int ret = -EBUSY;
> > +	u32 nthreads;
> > +
> > +	if (GENL_REQ_ATTR_CHECK(info, NFSD_A_SERVER_WORKER_THREADS))
> > +		return -EINVAL;
> > +
> > +	nthreads = nla_get_u32(info->attrs[NFSD_A_SERVER_WORKER_THREADS]);
> > +
> > +	mutex_lock(&nfsd_mutex);
> > +	if (info->attrs[NFSD_A_SERVER_WORKER_GRACETIME] ||
> > +	    info->attrs[NFSD_A_SERVER_WORKER_LEASETIME]) {
> > +		const struct nlattr *attr;
> > +
> > +		if (nn->nfsd_serv && nn->nfsd_serv->sv_nrthreads)
> > +			goto out_unlock;
> > +
> > +		ret = -EINVAL;
> > +		attr = info->attrs[NFSD_A_SERVER_WORKER_GRACETIME];
> > +		if (attr) {
> > +			u32 gracetime = nla_get_u32(attr);
> > +
> > +			if (gracetime < 10 || gracetime > 3600)
> > +				goto out_unlock;
> > +
> > +			nn->nfsd4_grace = gracetime;
> > +		}
> > +
> > +		attr = info->attrs[NFSD_A_SERVER_WORKER_LEASETIME];
> > +		if (attr) {
> > +			u32 leasetime = nla_get_u32(attr);
> > +
> > +			if (leasetime < 10 || leasetime > 3600)
> > +				goto out_unlock;
> > +
> > +			nn->nfsd4_lease = leasetime;
> > +		}
> > +	}
> > +
> > +	ret = nfsd_svc(nthreads, net, get_current_cred());
> > +out_unlock:
> > +	mutex_unlock(&nfsd_mutex);
> > +
> > +	return ret == nthreads ? 0 : ret;
> > +}
> > +
> > +/**
> > + * 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)
> > +{
> > +	struct net *net = genl_info_net(info);
> > +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> > +	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;
> > +	}
> > +
> > +	mutex_lock(&nfsd_mutex);
> > +	err = nla_put_u32(skb, NFSD_A_SERVER_WORKER_GRACETIME,
> > +			  nn->nfsd4_grace) ||
> > +	      nla_put_u32(skb, NFSD_A_SERVER_WORKER_LEASETIME,
> > +			  nn->nfsd4_lease) ||
> > +	      nla_put_u32(skb, NFSD_A_SERVER_WORKER_THREADS,
> > +			  nn->nfsd_serv ? nn->nfsd_serv->sv_nrthreads : 0);
> > +	mutex_unlock(&nfsd_mutex);
> > +
> > +	if (err) {
> > +		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..ccc78a5ee650 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_WORKER_THREADS = 1,
> > +	NFSD_A_SERVER_WORKER_GRACETIME,
> > +	NFSD_A_SERVER_WORKER_LEASETIME,
> > +
> > +	__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
> > 
> > 
> 

-- 
Jeff Layton <jlayton@kernel.org>