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

[Prabhakar Pujeri]

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
 	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)
-- 
2.54.0