Date: Tue, 26 Sep 2023 23:09:14 +0000
From: Chuck Lever III <chuck.lever@...cle.com>
To: Neil Brown <neilb@...e.de>
CC: Lorenzo Bianconi <lorenzo@...nel.org>,
        Linux NFS Mailing List
	<linux-nfs@...r.kernel.org>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>,
        Jeff Layton <jlayton@...nel.org>,
        "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
Subject: Re: [PATCH v3] NFSD: convert write_threads, write_maxblksize and
 write_maxconn to netlink commands



> On Sep 26, 2023, at 7:05 PM, NeilBrown <neilb@...e.de> wrote:
> 
> 
> Hi,
> thanks for doing this.  I had a hunt through the patch largely to help
> improve my own understanding of netlink.  A few things stood out.  Not
> necessarily problems with the patch, but things that seemed worth
> mentioning. 
> 
> Firstly, and rather trivially, the word "convert" in the subject lead
> me to think that the old approach was being converted to a new
> approach.  I see that isn't correct - you are just introducing a new
> option.
> 
> On Wed, 27 Sep 2023, 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@...nel.org>
>> ---
>> Changes since v2:
>> - use u32 to store nthreads in nfsd_nl_threads_set_doit
>> - rename server-attr in control-plane in nfsd.yaml specs
>> 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                      | 141 ++++++++++++++++++++++++++
>> include/uapi/linux/nfsd_netlink.h     |  15 +++
>> 5 files changed, 279 insertions(+)
>> 
>> diff --git a/Documentation/netlink/specs/nfsd.yaml b/Documentation/netlink/specs/nfsd.yaml
>> index 403d3e3a04f3..c6af1653bc1d 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: control-plane
>> +    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: control-plane
>> +      flags: [ admin-perm ]
>> +      do:
>> +        request:
>> +          attributes:
>> +            - threads
>> +    -
>> +      name: threads-get
>> +      doc: dump the number of running threads
>> +      attribute-set: control-plane
>> +      dump:
>> +        reply:
>> +          attributes:
>> +            - threads
>> +    -
>> +      name: max-blksize-set
>> +      doc: set the nfs block size
>> +      attribute-set: control-plane
>> +      flags: [ admin-perm ]
>> +      do:
>> +        request:
>> +          attributes:
>> +            - max-blksize
>> +    -
>> +      name: max-blksize-get
>> +      doc: dump the nfs block size
>> +      attribute-set: control-plane
>> +      dump:
>> +        reply:
>> +          attributes:
>> +            - max-blksize
>> +    -
>> +      name: max-conn-set
>> +      doc: set the max number of connections
>> +      attribute-set: control-plane
>> +      flags: [ admin-perm ]
>> +      do:
>> +        request:
>> +          attributes:
>> +            - max-conn
>> +    -
>> +      name: max-conn-get
>> +      doc: dump the max number of connections
>> +      attribute-set: control-plane
>> +      dump:
>> +        reply:
>> +          attributes:
>> +            - max-conn
>> diff --git a/fs/nfsd/netlink.c b/fs/nfsd/netlink.c
>> index 0e1d635ec5f9..8f7d72ae60d6 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_CONTROL_PLANE_THREADS + 1] = {
>> + [NFSD_A_CONTROL_PLANE_THREADS] = { .type = NLA_U32, },
>> +};
> 
> This array, and the following arrays, is sized exactly large enough to
> hold the last element.  In that case you don't need to explicitly set
> the size:
> 
> +static const struct nla_policy nfsd_threads_set_nl_policy[] = {
> + [NFSD_A_CONTROL_PLANE_THREADS] = { .type = NLA_U32, },
> +};
> 
> I at first assumed you were following a standard practice, but other
> places that declare nla_policy use a variety of different approaches.
> I prefer the [] approach, but it is up to you.

FYI, here and below, this code was generated by a Python
script from the nfsd netlink protocol specification in
Documentation/netlink/specs/nfsd.yaml.

We don't have control over its style or unused elements.


>> +
>> +/* NFSD_CMD_MAX_BLKSIZE_SET - do */
>> +static const struct nla_policy nfsd_max_blksize_set_nl_policy[NFSD_A_CONTROL_PLANE_MAX_BLKSIZE + 1] = {
>> + [NFSD_A_CONTROL_PLANE_MAX_BLKSIZE] = { .type = NLA_U32, },
>> +};
>> +
>> +/* NFSD_CMD_MAX_CONN_SET - do */
>> +static const struct nla_policy nfsd_max_conn_set_nl_policy[NFSD_A_CONTROL_PLANE_MAX_CONN + 1] = {
>> + [NFSD_A_CONTROL_PLANE_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_CONTROL_PLANE_THREADS,
> 
> maxattr is *always* the largest index for the policy array.
> I think it would aid reading to have something like
> 
> #define NLA_POLICY(_pol) .policy = _pol, .maxattr = ARRAY_SIZE(_pol) - 1
> 
> then you could have
> .doit  = nfsd_nl_thread_set_doit,
> NLA_POLICY(nfsd_thread_set_nl_policy),
> 
> and be certain that all the maxattr values are correct.
> 
>> + .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_CONTROL_PLANE_MAX_BLKSIZE,
>> + .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
>> + },
> 
> it is a little weird that the dumpit sections are indented differently
> to the doit section.  But that is probably intentional and I might even
> grow to like it...
> 
>> + {
>> + .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_CONTROL_PLANE_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..07e7a09e28e3 100644
>> --- a/fs/nfsd/nfsctl.c
>> +++ b/fs/nfsd/nfsctl.c
>> @@ -1694,6 +1694,147 @@ 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)
>> +{
>> + u32 nthreads;
>> + int ret;
>> +
>> + if (!info->attrs[NFSD_A_CONTROL_PLANE_THREADS])
>> + return -EINVAL;
>> +
>> + nthreads = nla_get_u32(info->attrs[NFSD_A_CONTROL_PLANE_THREADS]);
>> +
>> + 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_CONTROL_PLANE_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);
>> + struct nlattr *attr = info->attrs[NFSD_A_CONTROL_PLANE_MAX_BLKSIZE];
>> + int ret = 0;
>> +
>> + if (!attr)
>> + return -EINVAL;
>> +
>> + mutex_lock(&nfsd_mutex);
>> + if (nn->nfsd_serv) {
>> + ret = -EBUSY;
>> + goto out;
>> + }
> 
> This code is wrong... but then the original in write_maxblksize is wrong
> to, so you can't be blamed.
> nfsd_max_blksize applies to nfsd in ALL network namespaces.  So if we
> need to check there are no active services in one namespace, we need to
> check the same for *all* namespaces.
> 
> I think we should make nfsd_max_blksize a per-namespace value.
> 
>> +
>> + nfsd_max_blksize = nla_get_u32(attr);
>> + 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_CONTROL_PLANE_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);
>> + struct nlattr *attr = info->attrs[NFSD_A_CONTROL_PLANE_MAX_CONN];
>> +
>> + if (!attr)
>> + return -EINVAL;
>> +
>> + nn->max_connections = nla_get_u32(attr);
>> +
>> + 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_CONTROL_PLANE_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..145f4811f3d9 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_CONTROL_PLANE_THREADS = 1,
>> + NFSD_A_CONTROL_PLANE_MAX_BLKSIZE,
>> + NFSD_A_CONTROL_PLANE_MAX_CONN,
>> +
>> + __NFSD_A_CONTROL_PLANE_MAX,
>> + NFSD_A_CONTROL_PLANE_MAX = (__NFSD_A_CONTROL_PLANE_MAX - 1)
> 
> This last value is never used.  Is it needed?
> 
> 
> Thanks,
> NeilBrown
> 
>> +};
>> +
>> 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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