[PATCH v2 12/13] sunrpc: add SUNRPC_CMD_CACHE_FLUSH netlink command

[Jeff Layton <jlayton@kernel.org>]

Add a new SUNRPC_CMD_CACHE_FLUSH generic netlink command that allows
userspace to flush the sunrpc auth caches (ip_map and unix_gid) without
writing to /proc/net/rpc/*/flush.

An optional SUNRPC_A_CACHE_FLUSH_MASK u32 attribute selects which caches
to flush (bit 1 = ip_map, bit 2 = unix_gid). If the attribute is
omitted, all sunrpc caches are flushed.

This is used by exportfs to replace its /proc-based cache_flush() with a
netlink equivalent, with /proc fallback for older kernels.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 Documentation/netlink/specs/sunrpc_cache.yaml | 17 ++++++++++++++
 include/uapi/linux/sunrpc_netlink.h           |  8 +++++++
 net/sunrpc/netlink.c                          | 12 ++++++++++
 net/sunrpc/netlink.h                          |  1 +
 net/sunrpc/svcauth_unix.c                     | 32 +++++++++++++++++++++++++++
 5 files changed, 70 insertions(+)

diff --git a/Documentation/netlink/specs/sunrpc_cache.yaml b/Documentation/netlink/specs/sunrpc_cache.yaml
index ed0ddb61ebcf22b6ad889b0760f8a6f470295dbd..55dabc914dbc8693e10a8765a654b11021b32872 100644
--- a/Documentation/netlink/specs/sunrpc_cache.yaml
+++ b/Documentation/netlink/specs/sunrpc_cache.yaml
@@ -76,6 +76,14 @@ attribute-sets:
         type: nest
         nested-attributes: unix-gid
         multi-attr: true
+  -
+    name: cache-flush
+    attributes:
+      -
+        name: mask
+        type: u32
+        enum: cache-type
+        enum-as-flags: true
 
 operations:
   list:
@@ -123,6 +131,15 @@ operations:
           request:
             attributes:
               - requests
+    -
+      name: cache-flush
+      doc: Flush sunrpc caches (ip_map and/or unix_gid)
+      attribute-set: cache-flush
+      flags: [admin-perm]
+      do:
+        request:
+          attributes:
+            - mask
 
 mcast-groups:
   list:
diff --git a/include/uapi/linux/sunrpc_netlink.h b/include/uapi/linux/sunrpc_netlink.h
index d71c623e92aba4566e3114cc23d0aa553cbdb885..34677f0ec2f958961f1f460c1dc81c8377cc5157 100644
--- a/include/uapi/linux/sunrpc_netlink.h
+++ b/include/uapi/linux/sunrpc_netlink.h
@@ -59,12 +59,20 @@ enum {
 	SUNRPC_A_UNIX_GID_REQS_MAX = (__SUNRPC_A_UNIX_GID_REQS_MAX - 1)
 };
 
+enum {
+	SUNRPC_A_CACHE_FLUSH_MASK = 1,
+
+	__SUNRPC_A_CACHE_FLUSH_MAX,
+	SUNRPC_A_CACHE_FLUSH_MAX = (__SUNRPC_A_CACHE_FLUSH_MAX - 1)
+};
+
 enum {
 	SUNRPC_CMD_CACHE_NOTIFY = 1,
 	SUNRPC_CMD_IP_MAP_GET_REQS,
 	SUNRPC_CMD_IP_MAP_SET_REQS,
 	SUNRPC_CMD_UNIX_GID_GET_REQS,
 	SUNRPC_CMD_UNIX_GID_SET_REQS,
+	SUNRPC_CMD_CACHE_FLUSH,
 
 	__SUNRPC_CMD_MAX,
 	SUNRPC_CMD_MAX = (__SUNRPC_CMD_MAX - 1)
diff --git a/net/sunrpc/netlink.c b/net/sunrpc/netlink.c
index 3ac6b0cac5fece964f6e6591f90d074f40e96af1..5ccf0967809c4d3cbc58fde5dd20279e1ec29301 100644
--- a/net/sunrpc/netlink.c
+++ b/net/sunrpc/netlink.c
@@ -49,6 +49,11 @@ static const struct nla_policy sunrpc_unix_gid_set_reqs_nl_policy[SUNRPC_A_UNIX_
 	[SUNRPC_A_UNIX_GID_REQS_REQUESTS] = NLA_POLICY_NESTED(sunrpc_unix_gid_nl_policy),
 };
 
+/* SUNRPC_CMD_CACHE_FLUSH - do */
+static const struct nla_policy sunrpc_cache_flush_nl_policy[SUNRPC_A_CACHE_FLUSH_MASK + 1] = {
+	[SUNRPC_A_CACHE_FLUSH_MASK] = NLA_POLICY_MASK(NLA_U32, 0x3),
+};
+
 /* Ops table for sunrpc */
 static const struct genl_split_ops sunrpc_nl_ops[] = {
 	{
@@ -79,6 +84,13 @@ static const struct genl_split_ops sunrpc_nl_ops[] = {
 		.maxattr	= SUNRPC_A_UNIX_GID_REQS_REQUESTS,
 		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
 	},
+	{
+		.cmd		= SUNRPC_CMD_CACHE_FLUSH,
+		.doit		= sunrpc_nl_cache_flush_doit,
+		.policy		= sunrpc_cache_flush_nl_policy,
+		.maxattr	= SUNRPC_A_CACHE_FLUSH_MASK,
+		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
+	},
 };
 
 static const struct genl_multicast_group sunrpc_nl_mcgrps[] = {
diff --git a/net/sunrpc/netlink.h b/net/sunrpc/netlink.h
index 2aec57d27a586e4c6b2fc65c7b4505b0996d9577..2c1012303d48bcbaad01192eca1c306790a4522b 100644
--- a/net/sunrpc/netlink.h
+++ b/net/sunrpc/netlink.h
@@ -23,6 +23,7 @@ int sunrpc_nl_unix_gid_get_reqs_dumpit(struct sk_buff *skb,
 				       struct netlink_callback *cb);
 int sunrpc_nl_unix_gid_set_reqs_doit(struct sk_buff *skb,
 				     struct genl_info *info);
+int sunrpc_nl_cache_flush_doit(struct sk_buff *skb, struct genl_info *info);
 
 enum {
 	SUNRPC_NLGRP_NONE,
diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 7703523d424617a6033fa7ab48e25728b4c14abb..64a2658faddbe6c217f548c565a3a434b5573a76 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -818,6 +818,38 @@ int sunrpc_nl_unix_gid_set_reqs_doit(struct sk_buff *skb,
 	return ret;
 }
 
+/**
+ * sunrpc_nl_cache_flush_doit - flush sunrpc caches via netlink
+ * @skb: reply buffer
+ * @info: netlink metadata and command arguments
+ *
+ * Flush the ip_map and/or unix_gid caches. If SUNRPC_A_CACHE_FLUSH_MASK
+ * is provided, only flush the caches indicated by the bitmask (bit 1 =
+ * ip_map, bit 2 = unix_gid). If omitted, flush both.
+ *
+ * Return 0 on success or a negative errno.
+ */
+int sunrpc_nl_cache_flush_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct sunrpc_net *sn;
+	u32 mask = ~0U;
+
+	sn = net_generic(genl_info_net(info), sunrpc_net_id);
+
+	if (info->attrs[SUNRPC_A_CACHE_FLUSH_MASK])
+		mask = nla_get_u32(info->attrs[SUNRPC_A_CACHE_FLUSH_MASK]);
+
+	if ((mask & SUNRPC_CACHE_TYPE_IP_MAP) &&
+	    sn->ip_map_cache)
+		cache_purge(sn->ip_map_cache);
+
+	if ((mask & SUNRPC_CACHE_TYPE_UNIX_GID) &&
+	    sn->unix_gid_cache)
+		cache_purge(sn->unix_gid_cache);
+
+	return 0;
+}
+
 static const struct cache_detail unix_gid_cache_template = {
 	.owner		= THIS_MODULE,
 	.hash_size	= GID_HASHMAX,

-- 
2.53.0