nfsd: add notifier to handle mount/unmount of rpc_pipefs sb

In the event that rpc_pipefs isn't mounted when nfsd starts, we
must register a notifier to handle creating the dentry once it
is mounted, and to remove the dentry on unmount.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

3 files changed, 53 insertions, 1 deletions

diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index 12e0cff435b4..66eac332bf8d 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -31,4 +31,5 @@ struct nfsd_net {
 };
 
 extern int nfsd_net_id;
+extern struct notifier_block nfsd4_cld_block;
 #endif /* __NFSD_NETNS_H__ */
diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index cec62ed2a064..6f13281635ba 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -38,6 +38,7 @@
 #include <linux/crypto.h>
 #include <linux/sched.h>
 #include <linux/fs.h>
+#include <linux/module.h>
 #include <net/net_namespace.h>
 #include <linux/sunrpc/rpc_pipe_fs.h>
 #include <linux/sunrpc/clnt.h>
@@ -982,3 +983,46 @@ nfsd4_record_grace_done(struct net *net, time_t boot_time)
         if (client_tracking_ops)
                 client_tracking_ops->grace_done(net, boot_time);
 }
+
+static int
+rpc_pipefs_event(struct notifier_block *nb, unsigned long event, void *ptr)
+{
+        struct super_block *sb = ptr;
+        struct net *net = sb->s_fs_info;
+        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+        struct cld_net *cn = nn->cld_net;
+        struct dentry *dentry;
+        int ret = 0;
+
+        if (!try_module_get(THIS_MODULE))
+                return 0;
+
+        if (!cn) {
+                module_put(THIS_MODULE);
+                return 0;
+        }
+
+        switch (event) {
+        case RPC_PIPEFS_MOUNT:
+                dentry = nfsd4_cld_register_sb(sb, cn->cn_pipe);
+                if (IS_ERR(dentry)) {
+                        ret = PTR_ERR(dentry);
+                        break;
+                }
+                cn->cn_pipe->dentry = dentry;
+                break;
+        case RPC_PIPEFS_UMOUNT:
+                if (cn->cn_pipe->dentry)
+                        nfsd4_cld_unregister_sb(cn->cn_pipe);
+                break;
+        default:
+                ret = -ENOTSUPP;
+                break;
+        }
+        module_put(THIS_MODULE);
+        return ret;
+}
+
+struct notifier_block nfsd4_cld_block = {
+        .notifier_call = rpc_pipefs_event,
+};
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 141197e04703..dee6c1bb9ba8 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -13,6 +13,7 @@
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/gss_api.h>
 #include <linux/sunrpc/gss_krb5_enctypes.h>
+#include <linux/sunrpc/rpc_pipe_fs.h>
 #include <linux/module.h>
 
 #include "idmap.h"
@@ -1136,9 +1137,12 @@ static int __init init_nfsd(void)
         int retval;
         printk(KERN_INFO "Installing knfsd (copyright (C) 1996 okir@monad.swb.de).\n");
 
+        retval = rpc_pipefs_notifier_register(&nfsd4_cld_block);
+        if (retval)
+                return retval;
         retval = register_pernet_subsys(&nfsd_net_ops);
         if (retval < 0)
-                return retval;
+                goto out_unregister_notifier;
         retval = nfsd4_init_slabs();
         if (retval)
                 goto out_unregister_pernet;
@@ -1181,6 +1185,8 @@ out_free_slabs:
         nfsd4_free_slabs();
 out_unregister_pernet:
         unregister_pernet_subsys(&nfsd_net_ops);
+out_unregister_notifier:
+        rpc_pipefs_notifier_unregister(&nfsd4_cld_block);
         return retval;
 }
 
@@ -1197,6 +1203,7 @@ static void __exit exit_nfsd(void)
         nfsd_fault_inject_cleanup();
         unregister_filesystem(&nfsd_fs_type);
         unregister_pernet_subsys(&nfsd_net_ops);
+        rpc_pipefs_notifier_unregister(&nfsd4_cld_block);
 }
 
 MODULE_AUTHOR("Olaf Kirch <okir@monad.swb.de>");