nfsd: add netlink upcall for the svc_export cache

Add netlink-based cache upcall support for the svc_export (nfsd.export)
cache to Documentation/netlink/specs/nfsd.yaml and regenerate the
resulting files.

Implement nfsd_cache_notify() which sends a NFSD_CMD_CACHE_NOTIFY
multicast event to the "exportd" group, carrying the cache type so
userspace knows which cache has pending requests.

Implement nfsd_nl_svc_export_get_reqs_dumpit() which snapshots
pending svc_export cache requests and sends each entry's seqno,
client name, and path over netlink.

Implement nfsd_nl_svc_export_set_reqs_doit() which parses svc_export
cache responses from userspace (client, path, expiry, flags, anon
uid/gid, fslocations, uuid, secinfo, xprtsec, fsid, or negative
flag) and updates the cache via svc_export_lookup() /
svc_export_update().

Wire up the svc_export_notify() callback in svc_export_cache_template
so cache misses trigger NFSD_CMD_CACHE_NOTIFY multicast events with
NFSD_CACHE_TYPE_SVC_EXPORT.

Note that the export-flags and xprtsec-mode enums are organized to match
their counterparts in include/uapi/linux/nfsd/export.h. The intent is
that future export options will only be added to the netlink headers,
which should eliminate the need to keep so much in sync.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: jtlayton

Documentation/netlink/specs/nfsd.yaml

@@ -6,7 +6,51 @@ uapi-header: linux/nfsd_netlink.h
 
 doc: NFSD configuration over generic netlink.
 
+definitions:
+  -
+    type: flags
+    name: cache-type
+    entries: [svc_export]
+  -
+    type: flags
+    name: export-flags
+    doc: These flags are ordered to match the NFSEXP_* flags in include/linux/nfsd/export.h
+    entries:
+      - readonly
+      - insecure-port
+      - rootsquash
+      - allsquash
+      - async
+      - gathered-writes
+      - noreaddirplus
+      - security-label
+      - sign-fh
+      - nohide
+      - nosubtreecheck
+      - noauthnlm
+      - msnfs
+      - fsid
+      - crossmount
+      - noacl
+      - v4root
+      - pnfs
+  -
+    type: flags
+    name: xprtsec-mode
+    doc: These flags are ordered to match the NFSEXP_XPRTSEC_* flags in include/linux/nfsd/export.h
+    entries:
+      - none
+      - tls
+      - mtls
+
 attribute-sets:
+  -
+    name: cache-notify
+    attributes:
+      -
+        name: cache-type
+        type: u32
+        enum: cache-type
   -
     name: rpc-status
     attributes:
@@ -132,6 +176,91 @@ attribute-sets:
       -
         name: npools
         type: u32
+  -
+    name: fslocation
+    attributes:
+      -
+        name: host
+        type: string
+      -
+        name: path
+        type: string
+  -
+    name: fslocations
+    attributes:
+      -
+        name: location
+        type: nest
+        nested-attributes: fslocation
+        multi-attr: true
+  -
+    name: auth-flavor
+    attributes:
+      -
+        name: pseudoflavor
+        type: u32
+      -
+        name: flags
+        type: u32
+        enum: export-flags
+        enum-as-flags: true
+  -
+    name: svc-export
+    attributes:
+      -
+        name: seqno
+        type: u64
+      -
+        name: client
+        type: string
+      -
+        name: path
+        type: string
+      -
+        name: negative
+        type: flag
+      -
+        name: expiry
+        type: u64
+      -
+        name: anon-uid
+        type: u32
+      -
+        name: anon-gid
+        type: u32
+      -
+        name: fslocations
+        type: nest
+        nested-attributes: fslocations
+      -
+        name: uuid
+        type: binary
+      -
+        name: secinfo
+        type: nest
+        nested-attributes: auth-flavor
+        multi-attr: true
+      -
+        name: xprtsec
+        type: u32
+        enum: xprtsec-mode
+        multi-attr: true
+      -
+        name: flags
+        type: u32
+        enum: export-flags
+        enum-as-flags: true
+      -
+        name: fsid
+        type: s32
+  -
+    name: svc-export-reqs
+    attributes:
+      -
+        name: requests
+        type: nest
+        nested-attributes: svc-export
+        multi-attr: true
 
 operations:
   list:
@@ -233,3 +362,36 @@ operations:
           attributes:
             - mode
             - npools
+    -
+      name: cache-notify
+      doc: Notification that there are cache requests that need servicing
+      attribute-set: cache-notify
+      mcgrp: exportd
+      event:
+        attributes:
+          - cache-type
+    -
+      name: svc-export-get-reqs
+      doc: Dump all pending svc_export requests
+      attribute-set: svc-export-reqs
+      flags: [admin-perm]
+      dump:
+          request:
+            attributes:
+              - requests
+    -
+      name: svc-export-set-reqs
+      doc: Respond to one or more svc_export requests
+      attribute-set: svc-export-reqs
+      flags: [admin-perm]
+      do:
+          request:
+            attributes:
+              - requests
+
+mcast-groups:
+  list:
+    -
+      name: none
+    -
+      name: exportd