Date: Fri, 22 Sep 2023 17:25:10 +0000
From: Chuck Lever III <chuck.lever@...cle.com>
To: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
CC: Jeff Layton <jlayton@...nel.org>, Lorenzo Bianconi <lorenzo@...nel.org>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        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 Sep 22, 2023, at 12:20 PM, Lorenzo Bianconi <lorenzo.bianconi@...hat.com> 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!
> 
> maybe u8 is fine here :)

32-bit is the usual for this kind of interface. I don't think we need to go with 16-bit.


>>> +      -
>>> +        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
> 
> I tried to be aligned with write_v4_end_grace() here but supporting just 1 (or
> any other non-zero value) and skipping 'Y/y'. If we send 0 it should skip the
> release action.
> 
>> matter at all. Do we have to send down a value at all?
> 
> I am not sure if ynl supports a doit operation with a request with no parameters.
> @Chuck, Jakub: any input here?

I think it does, I might have done something like that for one of the
handshake protocol commands.

But I think Jeff's right, end_grace might be better postponed. Pick any of
the others that you think might be easy to implement instead.


> Regards,
> Lorenzo
> 
>> 
>>> + 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

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