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

Jeff Layton
2026-03-25T14:41:11Z

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