afs: Display manually added cells in dynamic root mount

Alter the dynroot mount so that cells created by manipulation of
/proc/fs/afs/cells and /proc/fs/afs/rootcell and by specification of a root
cell as a module parameter will cause directories for those cells to be
created in the dynamic root superblock for the network namespace[*].

To this end:

 (1) Only one dynamic root superblock is now created per network namespace
     and this is shared between all attempts to mount it.  This makes it
     easier to find the superblock to modify.

 (2) When a dynamic root superblock is created, the list of cells is walked
     and directories created for each cell already defined.

 (3) When a new cell is added, if a dynamic root superblock exists, a
     directory is created for it.

 (4) When a cell is destroyed, the directory is removed.

 (5) These directories are created by calling lookup_one_len() on the root
     dir which automatically creates them if they don't exist.

[*] Inasmuch as network namespaces are currently supported here.

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

1 files changed, 8 insertions, 4 deletions

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index bb92b54d2a4a..f3d0bef16d78 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -15,6 +15,7 @@
 #include <linux/dns_resolver.h>
 #include <linux/sched.h>
 #include <linux/inet.h>
+#include <linux/namei.h>
 #include <keys/rxrpc-type.h>
 #include "internal.h"
 
@@ -531,9 +532,11 @@ static int afs_activate_cell(struct afs_net *net, struct afs_cell *cell)
 	ret = afs_proc_cell_setup(cell);
 	if (ret < 0)
 		return ret;
-	spin_lock(&net->proc_cells_lock);
+
+	mutex_lock(&net->proc_cells_lock);
 	list_add_tail(&cell->proc_link, &net->proc_cells);
-	spin_unlock(&net->proc_cells_lock);
+	afs_dynroot_mkdir(net, cell);
+	mutex_unlock(&net->proc_cells_lock);
 	return 0;
 }
 
@@ -546,9 +549,10 @@ static void afs_deactivate_cell(struct afs_net *net, struct afs_cell *cell)
 
 	afs_proc_cell_remove(cell);
 
-	spin_lock(&net->proc_cells_lock);
+	mutex_lock(&net->proc_cells_lock);
 	list_del_init(&cell->proc_link);
-	spin_unlock(&net->proc_cells_lock);
+	afs_dynroot_rmdir(net, cell);
+	mutex_unlock(&net->proc_cells_lock);
 
 #ifdef CONFIG_AFS_FSCACHE
 	fscache_relinquish_cookie(cell->cache, NULL, false);