Re: [PATCH v1 1/3] nfsd: report NFSv4 grace state through Netlink

[Jeff Layton]

On Tue, 2026-08-25 at 06:51 +0000, Prabhakar Pujeri wrote:
> Operational tooling needs to distinguish a server that is accepting
> normal NFSv4 state operations from one that is still accepting only
> recovery requests. The existing Netlink threads query reports
> server-wide configuration, but recovery state is available only through
> the nfsd filesystem.
> 
> Add an in-grace value to the threads-get reply. Return it in every reply
> so user space can distinguish a server that is not in grace from an older
> kernel that does not provide the attribute.
> 
> Signed-off-by: Prabhakar Pujeri <prabhakar.pujeri@xxxxxxxx>
> ---
>  Documentation/admin-guide/nfs/nfsd-admin-interfaces.rst | 3 +++
>  Documentation/netlink/specs/nfsd.yaml                   | 6 ++++++
>  fs/nfsd/nfsctl.c                                        | 9 ++++++++-
>  include/uapi/linux/nfsd_netlink.h                       | 1 +
>  4 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/nfs/nfsd-admin-interfaces.rst b/Documentation/admin-guide/nfs/nfsd-admin-interfaces.rst
> index c05926f79054..35c174000ab3 100644
> --- a/Documentation/admin-guide/nfs/nfsd-admin-interfaces.rst
> +++ b/Documentation/admin-guide/nfs/nfsd-admin-interfaces.rst
> @@ -25,6 +25,9 @@ udp and one tcp listener at port 2049 (see nfsd_init_socks).
>  On startup, nfsd and lockd grace periods start. nfsd is shut down by a write of
>  0 to nfsd/threads.  All locks and state are thrown away at that point.
>  
> +The ``in-grace`` value in the ``threads-get`` Generic Netlink reply reports
> +whether the NFSv4 server's recovery grace period is still active.
> +
>  Between startup and shutdown, the number of threads may be adjusted up
>  or down by additional writes to nfsd/threads or by writes to
>  nfsd/pool_threads.
> diff --git a/Documentation/netlink/specs/nfsd.yaml b/Documentation/netlink/specs/nfsd.yaml
> index 642268819c6f..d01d93f39392 100644
> --- a/Documentation/netlink/specs/nfsd.yaml
> +++ b/Documentation/netlink/specs/nfsd.yaml
> @@ -130,6 +130,11 @@ attribute-sets:
>          type: binary
>          checks:
>              exact-len: 16
> +      -
> +        name: in-grace
> +        type: u8
> +        doc: One while the NFSv4 server is in its recovery grace period,
> +             otherwise zero.
>    -
>      name: version
>      attributes:
> @@ -464,6 +469,7 @@ operations:
>              - leasetime
>              - scope
>              - min-threads
> +            - in-grace
>      -
>        name: version-set
>        doc: set nfs enabled versions
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index 6e63950a99e1..7ea865b372cc 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -1775,6 +1775,7 @@ 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);
> +	bool in_grace = false;
>  	void *hdr;
>  	int err;
>  
> @@ -1790,6 +1791,11 @@ int nfsd_nl_threads_get_doit(struct sk_buff *skb, struct genl_info *info)
>  
>  	mutex_lock(&nfsd_mutex);
>  
> +#ifdef CONFIG_NFSD_V4
> +	in_grace = nfsd_vers(nn, 4, NFSD_TEST) &&
> +		test_bit(NFSD_NET_UP, &nn->flags) &&
> +		!test_bit(NFSD_NET_GRACE_ENDED, &nn->flags);
> +#endif


What's your interest in reporting this info?

Just because the v4 recovery is done does not mean that you will be
able to access files. The overall system grace period is a union of
both the NLM and v4 grace periods.

This patch is reporting just the v4 one. If the goal is for the admin
to reliably tell when the grace period has been lifted, then this won't
tell us that.

Maybe this should just return the result of locks_in_grace() instead?

Or, do you plan to add similar functionality to lockd? Then you can
just do the union in userland to figure out if it has been lifted.

>  	err = nla_put_u32(skb, NFSD_A_SERVER_GRACETIME,
>  			  nn->nfsd4_grace) ||
>  	      nla_put_u32(skb, NFSD_A_SERVER_LEASETIME,
> @@ -1797,7 +1803,8 @@ int nfsd_nl_threads_get_doit(struct sk_buff *skb, struct genl_info *info)
>  	      nla_put_u32(skb, NFSD_A_SERVER_MIN_THREADS,
>  			  nn->min_threads) ||
>  	      nla_put_string(skb, NFSD_A_SERVER_SCOPE,
> -			  nn->nfsd_name);
> +			  nn->nfsd_name) ||
> +	      nla_put_u8(skb, NFSD_A_SERVER_IN_GRACE, in_grace);
>  	if (err)
>  		goto err_unlock;
>  
> diff --git a/include/uapi/linux/nfsd_netlink.h b/include/uapi/linux/nfsd_netlink.h
> index 87da1d0bb21e..e1fc2db00046 100644
> --- a/include/uapi/linux/nfsd_netlink.h
> +++ b/include/uapi/linux/nfsd_netlink.h
> @@ -84,6 +84,7 @@ enum {
>  	NFSD_A_SERVER_SCOPE,
>  	NFSD_A_SERVER_MIN_THREADS,
>  	NFSD_A_SERVER_FH_KEY,
> +	NFSD_A_SERVER_IN_GRACE,
>  
>  	__NFSD_A_SERVER_MAX,
>  	NFSD_A_SERVER_MAX = (__NFSD_A_SERVER_MAX - 1)

-- 
Jeff Layton <jlayton@xxxxxxxxxx>