NFSD: Add NFSD_CMD_UNLOCK_FILESYSTEM netlink command

Add NFSD_CMD_UNLOCK_FILESYSTEM as a dedicated netlink command for
revoking NFS state under a filesystem path, providing a netlink
equivalent of /proc/fs/nfsd/unlock_fs.

The command requires a "path" string attribute containing the
filesystem path whose state should be released. The handler
resolves the path to its superblock, then cancels async copies,
releases NLM locks, and revokes NFSv4 state on that superblock.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

5 files changed, 77 insertions, 0 deletions

diff --git a/Documentation/netlink/specs/nfsd.yaml b/Documentation/netlink/specs/nfsd.yaml
index bf41682464c3..e121c54033a0 100644
--- a/Documentation/netlink/specs/nfsd.yaml
+++ b/Documentation/netlink/specs/nfsd.yaml
@@ -310,6 +310,13 @@ attribute-sets:
         doc: struct sockaddr_in or struct sockaddr_in6.
         checks:
           min-len: 16
+  -
+    name: unlock-filesystem
+    attributes:
+      -
+        name: path
+        type: string
+        doc: Filesystem path whose state should be released.
 
 operations:
   list:
@@ -473,6 +480,15 @@ operations:
         request:
           attributes:
             - address
+    -
+      name: unlock-filesystem
+      doc: revoke NFS state under a filesystem path
+      attribute-set: unlock-filesystem
+      flags: [admin-perm]
+      do:
+        request:
+          attributes:
+            - path
 
 mcast-groups:
   list:
diff --git a/fs/nfsd/netlink.c b/fs/nfsd/netlink.c
index 5830627c0288..63df3c4cf63a 100644
--- a/fs/nfsd/netlink.c
+++ b/fs/nfsd/netlink.c
@@ -108,6 +108,11 @@ static const struct nla_policy nfsd_unlock_ip_nl_policy[NFSD_A_UNLOCK_IP_ADDRESS
 	[NFSD_A_UNLOCK_IP_ADDRESS] = NLA_POLICY_MIN_LEN(16),
 };
 
+/* NFSD_CMD_UNLOCK_FILESYSTEM - do */
+static const struct nla_policy nfsd_unlock_filesystem_nl_policy[NFSD_A_UNLOCK_FILESYSTEM_PATH + 1] = {
+	[NFSD_A_UNLOCK_FILESYSTEM_PATH] = { .type = NLA_NUL_STRING, },
+};
+
 /* Ops table for nfsd */
 static const struct genl_split_ops nfsd_nl_ops[] = {
 	{
@@ -201,6 +206,13 @@ static const struct genl_split_ops nfsd_nl_ops[] = {
 		.maxattr	= NFSD_A_UNLOCK_IP_ADDRESS,
 		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
 	},
+	{
+		.cmd		= NFSD_CMD_UNLOCK_FILESYSTEM,
+		.doit		= nfsd_nl_unlock_filesystem_doit,
+		.policy		= nfsd_unlock_filesystem_nl_policy,
+		.maxattr	= NFSD_A_UNLOCK_FILESYSTEM_PATH,
+		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
+	},
 };
 
 static const struct genl_multicast_group nfsd_nl_mcgrps[] = {
diff --git a/fs/nfsd/netlink.h b/fs/nfsd/netlink.h
index 88edbbc68453..29bd5468d401 100644
--- a/fs/nfsd/netlink.h
+++ b/fs/nfsd/netlink.h
@@ -40,6 +40,7 @@ int nfsd_nl_expkey_get_reqs_dumpit(struct sk_buff *skb,
 int nfsd_nl_expkey_set_reqs_doit(struct sk_buff *skb, struct genl_info *info);
 int nfsd_nl_cache_flush_doit(struct sk_buff *skb, struct genl_info *info);
 int nfsd_nl_unlock_ip_doit(struct sk_buff *skb, struct genl_info *info);
+int nfsd_nl_unlock_filesystem_doit(struct sk_buff *skb, struct genl_info *info);
 
 enum {
 	NFSD_NLGRP_NONE,
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index cf246652e478..f7f104cc457d 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -2315,6 +2315,46 @@ int nfsd_nl_unlock_ip_doit(struct sk_buff *skb, struct genl_info *info)
 }
 
 /**
+ * nfsd_nl_unlock_filesystem_doit - revoke NFS state under a filesystem path
+ * @skb: reply buffer
+ * @info: netlink metadata and command arguments
+ *
+ * Return: 0 on success or a negative errno.
+ */
+int nfsd_nl_unlock_filesystem_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);
+	struct path path;
+	int error;
+
+	if (GENL_REQ_ATTR_CHECK(info, NFSD_A_UNLOCK_FILESYSTEM_PATH))
+		return -EINVAL;
+
+	trace_nfsd_ctl_unlock_fs(net,
+			nla_data(info->attrs[NFSD_A_UNLOCK_FILESYSTEM_PATH]));
+	error = kern_path(
+			nla_data(info->attrs[NFSD_A_UNLOCK_FILESYSTEM_PATH]),
+			0, &path);
+	if (error)
+		return error;
+
+	nfsd4_cancel_copy_by_sb(net, path.dentry->d_sb);
+	error = nlmsvc_unlock_all_by_sb(path.dentry->d_sb);
+
+	mutex_lock(&nfsd_mutex);
+	if (nn->nfsd_serv)
+		nfsd4_revoke_states(nn, path.dentry->d_sb);
+	else
+		error = -EINVAL;
+	mutex_unlock(&nfsd_mutex);
+
+	path_put(&path);
+	return error;
+}
+
+/**
  * 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 90ef1e686769..d01096c06d72 100644
--- a/include/uapi/linux/nfsd_netlink.h
+++ b/include/uapi/linux/nfsd_netlink.h
@@ -212,6 +212,13 @@ enum {
 };
 
 enum {
+	NFSD_A_UNLOCK_FILESYSTEM_PATH = 1,
+
+	__NFSD_A_UNLOCK_FILESYSTEM_MAX,
+	NFSD_A_UNLOCK_FILESYSTEM_MAX = (__NFSD_A_UNLOCK_FILESYSTEM_MAX - 1)
+};
+
+enum {
 	NFSD_CMD_RPC_STATUS_GET = 1,
 	NFSD_CMD_THREADS_SET,
 	NFSD_CMD_THREADS_GET,
@@ -228,6 +235,7 @@ enum {
 	NFSD_CMD_EXPKEY_SET_REQS,
 	NFSD_CMD_CACHE_FLUSH,
 	NFSD_CMD_UNLOCK_IP,
+	NFSD_CMD_UNLOCK_FILESYSTEM,
 
 	__NFSD_CMD_MAX,
 	NFSD_CMD_MAX = (__NFSD_CMD_MAX - 1)