[PATCH 14/14] nfsd: add NFSD_CMD_CACHE_FLUSH netlink command

Jeff Layton
2026-03-16T15:15:27Z

Add a new NFSD_CMD_CACHE_FLUSH generic netlink command that allows
userspace to flush the nfsd export caches (svc_export and expkey)
without writing to /proc/net/rpc/*/flush.

An optional NFSD_A_CACHE_FLUSH_MASK u32 attribute selects which caches
to flush (bit 1 = svc_export, bit 2 = expkey). If the attribute is
omitted, all nfsd 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/nfsd.yaml | 17 +++++++++++++++++
fs/nfsd/netlink.c | 12 ++++++++++++
fs/nfsd/netlink.h | 1 +
fs/nfsd/nfsctl.c | 32 ++++++++++++++++++++++++++++++++
include/uapi/linux/nfsd_netlink.h | 8 ++++++++
5 files changed, 70 insertions(+)

diff --git a/Documentation/netlink/specs/nfsd.yaml b/Documentation/netlink/specs/nfsd.yaml
index 65fd9caf6bf66abca9302ffa3b947b589dbf0dd3..09faeff3b7c20032cd61c992170f1e81f922605e 100644
--- a/Documentation/netlink/specs/nfsd.yaml
+++ b/Documentation/netlink/specs/nfsd.yaml
@@ -303,6 +303,14 @@ attribute-sets:
type: nest
nested-attributes: expkey
multi-attr: true
+ -
+ name: cache-flush
+ attributes:
+ -
+ name: mask
+ type: u32
+ enum: cache-type
+ enum-as-flags: true

operations:
list:
@@ -448,6 +456,15 @@ operations:
request:
attributes:
- requests
+ -
+ name: cache-flush
+ doc: Flush nfsd caches (svc_export and/or expkey)
+ attribute-set: cache-flush
+ flags: [admin-perm]
+ do:
+ request:
+ attributes:
+ - mask

mcast-groups:
list:
diff --git a/fs/nfsd/netlink.c b/fs/nfsd/netlink.c
index 394230e250a5b07fa0bb6a5b76f7282758e94565..30c4f8be3df98d8ae98ecddbfac488b5f997ab2f 100644
--- a/fs/nfsd/netlink.c
+++ b/fs/nfsd/netlink.c
@@ -108,6 +108,11 @@ static const struct nla_policy nfsd_expkey_set_reqs_nl_policy[NFSD_A_EXPKEY_REQS
[NFSD_A_EXPKEY_REQS_REQUESTS] = NLA_POLICY_NESTED(nfsd_expkey_nl_policy),
};

+/* NFSD_CMD_CACHE_FLUSH - do */
+static const struct nla_policy nfsd_cache_flush_nl_policy[NFSD_A_CACHE_FLUSH_MASK + 1] = {
+ [NFSD_A_CACHE_FLUSH_MASK] = NLA_POLICY_MASK(NLA_U32, 0x3),
+};
+
/* Ops table for nfsd */
static const struct genl_split_ops nfsd_nl_ops[] = {
{
@@ -191,6 +196,13 @@ static const struct genl_split_ops nfsd_nl_ops[] = {
.maxattr = NFSD_A_EXPKEY_REQS_REQUESTS,
.flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
},
+ {
+ .cmd = NFSD_CMD_CACHE_FLUSH,
+ .doit = nfsd_nl_cache_flush_doit,
+ .policy = nfsd_cache_flush_nl_policy,
+ .maxattr = NFSD_A_CACHE_FLUSH_MASK,
+ .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 f5b3387772850692b220bbbf8a66bc416b67801e..cc89732ed71bd77c1eee011dd07f130c6909462b 100644
--- a/fs/nfsd/netlink.h
+++ b/fs/nfsd/netlink.h
@@ -38,6 +38,7 @@ int nfsd_nl_svc_export_set_reqs_doit(struct sk_buff *skb,
int nfsd_nl_expkey_get_reqs_dumpit(struct sk_buff *skb,
struct netlink_callback *cb);
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);

enum {
NFSD_NLGRP_NONE,
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 7edcbe4504a91966db4805a099368edb92ca38ee..98eeb2be56ce4b826611ba378074c522d761cb1e 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -10,6 +10,7 @@
#include <linux/ctype.h>
#include <linux/fs_context.h>

+#include <linux/sunrpc/cache.h>
#include <linux/sunrpc/svcsock.h>
#include <linux/lockd/bind.h>
#include <linux/sunrpc/addr.h>
@@ -2215,6 +2216,37 @@ int nfsd_nl_pool_mode_get_doit(struct sk_buff *skb, struct genl_info *info)
return err;
}

+/**
+ * nfsd_nl_cache_flush_doit - flush nfsd caches via netlink
+ * @skb: reply buffer
+ * @info: netlink metadata and command arguments
+ *
+ * Flush the svc_export and/or expkey caches. If NFSD_A_CACHE_FLUSH_MASK
+ * is provided, only flush the caches indicated by the bitmask (bit 0 =
+ * svc_export, bit 1 = expkey). If omitted, flush both.
+ *
+ * Return 0 on success or a negative errno.
+ */
+int nfsd_nl_cache_flush_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);
+ u32 mask = ~0U;
+
+ if (info->attrs[NFSD_A_CACHE_FLUSH_MASK])
+ mask = nla_get_u32(info->attrs[NFSD_A_CACHE_FLUSH_MASK]);
+
+ if ((mask & NFSD_CACHE_TYPE_SVC_EXPORT) &&
+ nn->svc_export_cache)
+ cache_purge(nn->svc_export_cache);
+
+ if ((mask & NFSD_CACHE_TYPE_EXPKEY) &&
+ nn->svc_expkey_cache)
+ cache_purge(nn->svc_expkey_cache);
+
+ return 0;
+}
+
int nfsd_cache_notify(struct cache_detail *cd, struct cache_head *h, u32 cache_type)
{
struct genlmsghdr *hdr;
diff --git a/include/uapi/linux/nfsd_netlink.h b/include/uapi/linux/nfsd_netlink.h
index e96cc1d23366bce13624084fd476dda65aef140a..08b8a77179f88f596d482d7a2ec5c19ee98b2e77 100644
--- a/include/uapi/linux/nfsd_netlink.h
+++ b/include/uapi/linux/nfsd_netlink.h
@@ -198,6 +198,13 @@ enum {
NFSD_A_EXPKEY_REQS_MAX = (__NFSD_A_EXPKEY_REQS_MAX - 1)
};

+enum {
+ NFSD_A_CACHE_FLUSH_MASK = 1,
+
+ __NFSD_A_CACHE_FLUSH_MAX,
+ NFSD_A_CACHE_FLUSH_MAX = (__NFSD_A_CACHE_FLUSH_MAX - 1)
+};
+
enum {
NFSD_CMD_RPC_STATUS_GET = 1,
NFSD_CMD_THREADS_SET,
@@ -213,6 +220,7 @@ enum {
NFSD_CMD_SVC_EXPORT_SET_REQS,
NFSD_CMD_EXPKEY_GET_REQS,
NFSD_CMD_EXPKEY_SET_REQS,
+ NFSD_CMD_CACHE_FLUSH,

__NFSD_CMD_MAX,
NFSD_CMD_MAX = (__NFSD_CMD_MAX - 1)

--
2.53.0