NFS: make nfs_volume_list per net ns

This patch splits global list of NFS servers into per-net-ns array of lists.
This looks more strict and clearer.
BTW, this patch also makes "/proc/fs/nfsfs/volumes" content depends on /proc
mount owner pid namespace. See below for details.

NOTE: few words about how was /proc/fs/nfsfs/ entries content show per network
namespace done. This is a little bit tricky and not the best is could be. But
it's cheap (proper fix for /proc conteinerization is a hard nut to crack).
The idea is simple: take proper network namespace from pid namespace
child reaper nsproxy of /proc/ mount creator.
This actually means, that if there are 2 containers with different net
namespace sharing pid namespace, then read of /proc/fs/nfsfs/ entries will
always return content, taken from net namespace of pid namespace creator task
(and thus second namespace set wil be unvisible).
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/client.c

@@ -56,7 +56,6 @@
 #define NFSDBG_FACILITY		NFSDBG_CLIENT
 
 DEFINE_SPINLOCK(nfs_client_lock);
-static LIST_HEAD(nfs_volume_list);
 static DECLARE_WAIT_QUEUE_HEAD(nfs_client_active_wq);
 #ifdef CONFIG_NFS_V4
 static DEFINE_IDR(cb_ident_idr); /* Protected by nfs_client_lock */
@@ -1036,10 +1035,11 @@ static void nfs_server_copy_userdata(struct nfs_server *target, struct nfs_serve
 static void nfs_server_insert_lists(struct nfs_server *server)
 {
 	struct nfs_client *clp = server->nfs_client;
+	struct nfs_net *nn = net_generic(clp->net, nfs_net_id);
 
 	spin_lock(&nfs_client_lock);
 	list_add_tail_rcu(&server->client_link, &clp->cl_superblocks);
-	list_add_tail(&server->master_link, &nfs_volume_list);
+	list_add_tail(&server->master_link, &nn->nfs_volume_list);
 	clear_bit(NFS_CS_STOP_RENEW, &clp->cl_res_state);
 	spin_unlock(&nfs_client_lock);
 
@@ -1764,6 +1764,7 @@ void nfs_clients_init(struct net *net)
 	struct nfs_net *nn = net_generic(net, nfs_net_id);
 
 	INIT_LIST_HEAD(&nn->nfs_client_list);
+	INIT_LIST_HEAD(&nn->nfs_volume_list);
 }
 
 #ifdef CONFIG_PROC_FS
@@ -1900,13 +1901,15 @@ static int nfs_volume_list_open(struct inode *inode, struct file *file)
 {
 	struct seq_file *m;
 	int ret;
+	struct pid_namespace *pid_ns = file->f_dentry->d_sb->s_fs_info;
+	struct net *net = pid_ns->child_reaper->nsproxy->net_ns;
 
 	ret = seq_open(file, &nfs_volume_list_ops);
 	if (ret < 0)
 		return ret;
 
 	m = file->private_data;
-	m->private = PDE(inode)->data;
+	m->private = net;
 
 	return 0;
 }
@@ -1916,9 +1919,11 @@ static int nfs_volume_list_open(struct inode *inode, struct file *file)
  */
 static void *nfs_volume_list_start(struct seq_file *m, loff_t *_pos)
 {
+	struct nfs_net *nn = net_generic(m->private, nfs_net_id);
+
 	/* lock the list against modification */
 	spin_lock(&nfs_client_lock);
-	return seq_list_start_head(&nfs_volume_list, *_pos);
+	return seq_list_start_head(&nn->nfs_volume_list, *_pos);
 }
 
 /*
@@ -1926,7 +1931,9 @@ static void *nfs_volume_list_start(struct seq_file *m, loff_t *_pos)
  */
 static void *nfs_volume_list_next(struct seq_file *p, void *v, loff_t *pos)
 {
-	return seq_list_next(v, &nfs_volume_list, pos);
+	struct nfs_net *nn = net_generic(p->private, nfs_net_id);
+
+	return seq_list_next(v, &nn->nfs_volume_list, pos);
 }
 
 /*
@@ -1945,9 +1952,10 @@ static int nfs_volume_list_show(struct seq_file *m, void *v)
 	struct nfs_server *server;
 	struct nfs_client *clp;
 	char dev[8], fsid[17];
+	struct nfs_net *nn = net_generic(m->private, nfs_net_id);
 
 	/* display header on line 1 */
-	if (v == &nfs_volume_list) {
+	if (v == &nn->nfs_volume_list) {
 		seq_puts(m, "NV SERVER   PORT DEV     FSID              FSC\n");
 		return 0;
 	}

fs/nfs/netns.h

@@ -8,6 +8,7 @@ struct nfs_net {
 	struct cache_detail *nfs_dns_resolve;
 	struct rpc_pipe *bl_device_pipe;
 	struct list_head nfs_client_list;
+	struct list_head nfs_volume_list;
 };
 
 extern int nfs_net_id;