afs: Lay the groundwork for supporting network namespaces

Lay the groundwork for supporting network namespaces (netns) to the AFS
filesystem by moving various global features to a network-namespace struct
(afs_net) and providing an instance of this as a temporary global variable
that everything uses via accessor functions for the moment.

The following changes have been made:

 (1) Store the netns in the superblock info.  This will be obtained from
     the mounter's nsproxy on a manual mount and inherited from the parent
     superblock on an automount.

 (2) The cell list is made per-netns.  It can be viewed through
     /proc/net/afs/cells and also be modified by writing commands to that
     file.

 (3) The local workstation cell is set per-ns in /proc/net/afs/rootcell.
     This is unset by default.

 (4) The 'rootcell' module parameter, which sets a cell and VL server list
     modifies the init net namespace, thereby allowing an AFS root fs to be
     theoretically used.

 (5) The volume location lists and the file lock manager are made
     per-netns.

 (6) The AF_RXRPC socket and associated I/O bits are made per-ns.

The various workqueues remain global for the moment.

Changes still to be made:

 (1) /proc/fs/afs/ should be moved to /proc/net/afs/ and a symlink emplaced
     from the old name.

 (2) A per-netns subsys needs to be registered for AFS into which it can
     store its per-netns data.

 (3) Rather than the AF_RXRPC socket being opened on module init, it needs
     to be opened on the creation of a superblock in that netns.

 (4) The socket needs to be closed when the last superblock using it is
     destroyed and all outstanding client calls on it have been completed.
     This prevents a reference loop on the namespace.

 (5) It is possible that several namespaces will want to use AFS, in which
     case each one will need its own UDP port.  These can either be set
     through /proc/net/afs/cm_port or the kernel can pick one at random.
     The init_ns gets 7001 by default.

Other issues that need resolving:

 (1) The DNS keyring needs net-namespacing.

 (2) Where do upcalls go (eg. DNS request-key upcall)?

 (3) Need something like open_socket_in_file_ns() syscall so that AFS
     command line tools attempting to operate on an AFS file/volume have
     their RPC calls go to the right place.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 39 insertions, 43 deletions

diff --git a/fs/afs/server.c b/fs/afs/server.c
index c001b1f2455f..e47fd9bc0ddc 100644
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -15,32 +15,22 @@
 
 static unsigned afs_server_timeout = 10;	/* server timeout in seconds */
 
-static void afs_reap_server(struct work_struct *);
-
-/* tree of all the servers, indexed by IP address */
-static struct rb_root afs_servers = RB_ROOT;
-static DEFINE_RWLOCK(afs_servers_lock);
-
-/* LRU list of all the servers not currently in use */
-static LIST_HEAD(afs_server_graveyard);
-static DEFINE_SPINLOCK(afs_server_graveyard_lock);
-static DECLARE_DELAYED_WORK(afs_server_reaper, afs_reap_server);
-
 /*
  * install a server record in the master tree
  */
 static int afs_install_server(struct afs_server *server)
 {
 	struct afs_server *xserver;
+	struct afs_net *net = server->cell->net;
 	struct rb_node **pp, *p;
 	int ret;
 
 	_enter("%p", server);
 
-	write_lock(&afs_servers_lock);
+	write_lock(&net->servers_lock);
 
 	ret = -EEXIST;
-	pp = &afs_servers.rb_node;
+	pp = &net->servers.rb_node;
 	p = NULL;
 	while (*pp) {
 		p = *pp;
@@ -55,11 +45,11 @@ static int afs_install_server(struct afs_server *server)
 	}
 
 	rb_link_node(&server->master_rb, p, pp);
-	rb_insert_color(&server->master_rb, &afs_servers);
+	rb_insert_color(&server->master_rb, &net->servers);
 	ret = 0;
 
 error:
-	write_unlock(&afs_servers_lock);
+	write_unlock(&net->servers_lock);
 	return ret;
 }
 
@@ -150,9 +140,9 @@ found_server_quickly:
 	read_unlock(&cell->servers_lock);
 no_longer_unused:
 	if (!list_empty(&server->grave)) {
-		spin_lock(&afs_server_graveyard_lock);
+		spin_lock(&cell->net->server_graveyard_lock);
 		list_del_init(&server->grave);
-		spin_unlock(&afs_server_graveyard_lock);
+		spin_unlock(&cell->net->server_graveyard_lock);
 	}
 	_leave(" = %p{%d}", server, atomic_read(&server->usage));
 	return server;
@@ -178,7 +168,8 @@ server_in_two_cells:
 /*
  * look up a server by its IP address
  */
-struct afs_server *afs_find_server(const struct sockaddr_rxrpc *srx)
+struct afs_server *afs_find_server(struct afs_net *net,
+				   const struct sockaddr_rxrpc *srx)
 {
 	struct afs_server *server = NULL;
 	struct rb_node *p;
@@ -191,9 +182,9 @@ struct afs_server *afs_find_server(const struct sockaddr_rxrpc *srx)
 		return NULL;
 	}
 
-	read_lock(&afs_servers_lock);
+	read_lock(&net->servers_lock);
 
-	p = afs_servers.rb_node;
+	p = net->servers.rb_node;
 	while (p) {
 		server = rb_entry(p, struct afs_server, master_rb);
 
@@ -211,7 +202,7 @@ struct afs_server *afs_find_server(const struct sockaddr_rxrpc *srx)
 
 	server = NULL;
 found:
-	read_unlock(&afs_servers_lock);
+	read_unlock(&net->servers_lock);
 	ASSERTIFCMP(server, server->addr.s_addr, ==, addr.s_addr);
 	_leave(" = %p", server);
 	return server;
@@ -223,6 +214,8 @@ found:
  */
 void afs_put_server(struct afs_server *server)
 {
+	struct afs_net *net = server->cell->net;
+
 	if (!server)
 		return;
 
@@ -239,14 +232,14 @@ void afs_put_server(struct afs_server *server)
 
 	afs_flush_callback_breaks(server);
 
-	spin_lock(&afs_server_graveyard_lock);
+	spin_lock(&net->server_graveyard_lock);
 	if (atomic_read(&server->usage) == 0) {
-		list_move_tail(&server->grave, &afs_server_graveyard);
+		list_move_tail(&server->grave, &net->server_graveyard);
 		server->time_of_death = ktime_get_real_seconds();
-		queue_delayed_work(afs_wq, &afs_server_reaper,
-				   afs_server_timeout * HZ);
+		queue_delayed_work(afs_wq, &net->server_reaper,
+				   net->live ? afs_server_timeout * HZ : 0);
 	}
-	spin_unlock(&afs_server_graveyard_lock);
+	spin_unlock(&net->server_graveyard_lock);
 	_leave(" [dead]");
 }
 
@@ -272,42 +265,45 @@ static void afs_destroy_server(struct afs_server *server)
 /*
  * reap dead server records
  */
-static void afs_reap_server(struct work_struct *work)
+void afs_reap_server(struct work_struct *work)
 {
 	LIST_HEAD(corpses);
 	struct afs_server *server;
+	struct afs_net *net = container_of(work, struct afs_net, server_reaper.work);
 	unsigned long delay, expiry;
 	time64_t now;
 
 	now = ktime_get_real_seconds();
-	spin_lock(&afs_server_graveyard_lock);
+	spin_lock(&net->server_graveyard_lock);
 
-	while (!list_empty(&afs_server_graveyard)) {
-		server = list_entry(afs_server_graveyard.next,
+	while (!list_empty(&net->server_graveyard)) {
+		server = list_entry(net->server_graveyard.next,
 				    struct afs_server, grave);
 
 		/* the queue is ordered most dead first */
-		expiry = server->time_of_death + afs_server_timeout;
-		if (expiry > now) {
-			delay = (expiry - now) * HZ;
-			mod_delayed_work(afs_wq, &afs_server_reaper, delay);
-			break;
+		if (net->live) {
+			expiry = server->time_of_death + afs_server_timeout;
+			if (expiry > now) {
+				delay = (expiry - now) * HZ;
+				mod_delayed_work(afs_wq, &net->server_reaper, delay);
+				break;
+			}
 		}
 
 		write_lock(&server->cell->servers_lock);
-		write_lock(&afs_servers_lock);
+		write_lock(&net->servers_lock);
 		if (atomic_read(&server->usage) > 0) {
 			list_del_init(&server->grave);
 		} else {
 			list_move_tail(&server->grave, &corpses);
 			list_del_init(&server->link);
-			rb_erase(&server->master_rb, &afs_servers);
+			rb_erase(&server->master_rb, &net->servers);
 		}
-		write_unlock(&afs_servers_lock);
+		write_unlock(&net->servers_lock);
 		write_unlock(&server->cell->servers_lock);
 	}
 
-	spin_unlock(&afs_server_graveyard_lock);
+	spin_unlock(&net->server_graveyard_lock);
 
 	/* now reap the corpses we've extracted */
 	while (!list_empty(&corpses)) {
@@ -318,10 +314,10 @@ static void afs_reap_server(struct work_struct *work)
 }
 
 /*
- * discard all the server records for rmmod
+ * Discard all the server records from a net namespace when it is destroyed or
+ * the afs module is removed.
  */
-void __exit afs_purge_servers(void)
+void __net_exit afs_purge_servers(struct afs_net *net)
 {
-	afs_server_timeout = 0;
-	mod_delayed_work(afs_wq, &afs_server_reaper, 0);
+	mod_delayed_work(afs_wq, &net->server_reaper, 0);
 }