Date: Fri, 22 Sep 2023 12:21:08 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Chuck Lever III <chuck.lever@...cle.com>
Cc: Lorenzo Bianconi <lorenzo@...nel.org>, Linux NFS Mailing List
 <linux-nfs@...r.kernel.org>, Lorenzo Bianconi
 <lorenzo.bianconi@...hat.com>,  Neil Brown <neilb@...e.de>,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] NFSD: convert write_threads and write_v4_end_grace to
 netlink commands

On Fri, 2023-09-22 at 16:06 +0000, Chuck Lever III wrote:
> 
> > On Sep 22, 2023, at 12:04 PM, Jeff Layton <jlayton@...nel.org> wrote:
> > 
> > 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@...nel.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!
> 
> No argument.
> 
> But I thought you could echo a negative number of threads in /proc/fs/nfsd/threads
> to reduce the thread count. Maybe this field should be an s32?
> 

Yuck! I think I'd rather see this implemented as a declarative field.

Let's have this specify an explicit number of threads with 0 meaning
shutdown. If someone wants to reduce the number, they can do the math in
userland. That also jives better with the SERVICE_STATUS_GET...

> 
> > > +      -
> > > +        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@...nel.org>
> 
> 
> --
> Chuck Lever
> 
> 

-- 
Jeff Layton <jlayton@...nel.org>

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