[PATCH 5.10 0/1] nfsd: Ensure knfsd shuts down when the "nfsd" pseudofs is unmounted

[PATCH 5.10 0/1] nfsd: Ensure knfsd shuts down when the "nfsd" pseudofs is unmounted

[Nikos Tsironis]

The bug that upstream commit c6c7f2a84da45 ("nfsd: Ensure knfsd shuts
down when the "nfsd" pseudofs is unmounted") fixes in kernel v5.13
exists in kernel v5.10 too.

That is, knfsd threads are left behind once the nfsd pseudofs is
unmounted, e.g. when the container is killed.

I backported the patch to kernel v5.10, and tested it.

Trond Myklebust (1):
  nfsd: Ensure knfsd shuts down when the "nfsd" pseudofs is unmounted

 fs/nfsd/netns.h     |  6 +++---
 fs/nfsd/nfs4state.c |  8 +-------
 fs/nfsd/nfsctl.c    | 14 ++------------
 fs/nfsd/nfsd.h      |  3 +--
 fs/nfsd/nfssvc.c    | 35 ++++++++++++++++++++++++++++++++++-
 5 files changed, 41 insertions(+), 25 deletions(-)

-- 
2.30.2

[PATCH 5.10 1/1] nfsd: Ensure knfsd shuts down when the "nfsd" pseudofs is unmounted

[Nikos Tsironis]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

commit c6c7f2a84da459bcc3714044e74a9cb66de31039 upstream.

In order to ensure that knfsd threads don't linger once the nfsd
pseudofs is unmounted (e.g. when the container is killed) we let
nfsd_umount() shut down those threads and wait for them to exit.

This also should ensure that we don't need to do a kernel mount of
the pseudofs, since the thread lifetime is now limited by the
lifetime of the filesystem.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com>
---
 fs/nfsd/netns.h     |  6 +++---
 fs/nfsd/nfs4state.c |  8 +-------
 fs/nfsd/nfsctl.c    | 14 ++------------
 fs/nfsd/nfsd.h      |  3 +--
 fs/nfsd/nfssvc.c    | 35 ++++++++++++++++++++++++++++++++++-
 5 files changed, 41 insertions(+), 25 deletions(-)

diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index 7346acda9d76..02d3d2f0e616 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -42,9 +42,6 @@ struct nfsd_net {
 	bool grace_ended;
 	time64_t boot_time;
 
-	/* internal mount of the "nfsd" pseudofilesystem: */
-	struct vfsmount *nfsd_mnt;
-
 	struct dentry *nfsd_client_dir;
 
 	/*
@@ -121,6 +118,9 @@ struct nfsd_net {
 	wait_queue_head_t ntf_wq;
 	atomic_t ntf_refcnt;
 
+	/* Allow umount to wait for nfsd state cleanup */
+	struct completion nfsd_shutdown_complete;
+
 	/*
 	 * clientid and stateid data for construction of net unique COPY
 	 * stateids.
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 9a47cc66963f..cb13a1649632 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -7394,14 +7394,9 @@ nfs4_state_start_net(struct net *net)
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 	int ret;
 
-	ret = get_nfsdfs(net);
-	if (ret)
-		return ret;
 	ret = nfs4_state_create_net(net);
-	if (ret) {
-		mntput(nn->nfsd_mnt);
+	if (ret)
 		return ret;
-	}
 	locks_start_grace(net, &nn->nfsd4_manager);
 	nfsd4_client_tracking_init(net);
 	if (nn->track_reclaim_completes && nn->reclaim_str_hashtbl_size == 0)
@@ -7471,7 +7466,6 @@ nfs4_state_shutdown_net(struct net *net)
 
 	nfsd4_client_tracking_exit(net);
 	nfs4_state_destroy_net(net);
-	mntput(nn->nfsd_mnt);
 }
 
 void
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index dedec4771ecc..c4b11560ac1b 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1417,6 +1417,8 @@ static void nfsd_umount(struct super_block *sb)
 {
 	struct net *net = sb->s_fs_info;
 
+	nfsd_shutdown_threads(net);
+
 	kill_litter_super(sb);
 	put_net(net);
 }
@@ -1429,18 +1431,6 @@ static struct file_system_type nfsd_fs_type = {
 };
 MODULE_ALIAS_FS("nfsd");
 
-int get_nfsdfs(struct net *net)
-{
-	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-	struct vfsmount *mnt;
-
-	mnt =  vfs_kern_mount(&nfsd_fs_type, SB_KERNMOUNT, "nfsd", NULL);
-	if (IS_ERR(mnt))
-		return PTR_ERR(mnt);
-	nn->nfsd_mnt = mnt;
-	return 0;
-}
-
 #ifdef CONFIG_PROC_FS
 static int create_proc_exports_entry(void)
 {
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index cb742e17e04a..4362d295ed34 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -85,13 +85,12 @@ int		nfsd_get_nrthreads(int n, int *, struct net *);
 int		nfsd_set_nrthreads(int n, int *, struct net *);
 int		nfsd_pool_stats_open(struct inode *, struct file *);
 int		nfsd_pool_stats_release(struct inode *, struct file *);
+void		nfsd_shutdown_threads(struct net *net);
 
 void		nfsd_destroy(struct net *net);
 
 bool		i_am_nfsd(void);
 
-int get_nfsdfs(struct net *);
-
 struct nfsdfs_client {
 	struct kref cl_ref;
 	void (*cl_release)(struct kref *kref);
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index c7fffe1453bd..2e61a565cdbd 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -600,6 +600,37 @@ static const struct svc_serv_ops nfsd_thread_sv_ops = {
 	.svo_module		= THIS_MODULE,
 };
 
+static void nfsd_complete_shutdown(struct net *net)
+{
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
+	WARN_ON(!mutex_is_locked(&nfsd_mutex));
+
+	nn->nfsd_serv = NULL;
+	complete(&nn->nfsd_shutdown_complete);
+}
+
+void nfsd_shutdown_threads(struct net *net)
+{
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+	struct svc_serv *serv;
+
+	mutex_lock(&nfsd_mutex);
+	serv = nn->nfsd_serv;
+	if (serv == NULL) {
+		mutex_unlock(&nfsd_mutex);
+		return;
+	}
+
+	svc_get(serv);
+	/* Kill outstanding nfsd threads */
+	serv->sv_ops->svo_setup(serv, NULL, 0);
+	nfsd_destroy(net);
+	mutex_unlock(&nfsd_mutex);
+	/* Wait for shutdown of nfsd_serv to complete */
+	wait_for_completion(&nn->nfsd_shutdown_complete);
+}
+
 bool i_am_nfsd(void)
 {
 	return kthread_func(current) == nfsd;
@@ -622,11 +653,13 @@ int nfsd_create_serv(struct net *net)
 						&nfsd_thread_sv_ops);
 	if (nn->nfsd_serv == NULL)
 		return -ENOMEM;
+	init_completion(&nn->nfsd_shutdown_complete);
 
 	nn->nfsd_serv->sv_maxconn = nn->max_connections;
 	error = svc_bind(nn->nfsd_serv, net);
 	if (error < 0) {
 		svc_destroy(nn->nfsd_serv);
+		nfsd_complete_shutdown(net);
 		return error;
 	}
 
@@ -675,7 +708,7 @@ void nfsd_destroy(struct net *net)
 		svc_shutdown_net(nn->nfsd_serv, net);
 	svc_destroy(nn->nfsd_serv);
 	if (destroy)
-		nn->nfsd_serv = NULL;
+		nfsd_complete_shutdown(net);
 }
 
 int nfsd_set_nrthreads(int n, int *nthreads, struct net *net)
-- 
2.30.2