proc: Allow creating permanently empty directories that serve as mount points

Add a new function proc_create_mount_point that when used to creates a
directory that can not be added to.

Add a new function is_empty_pde to test if a function is a mount
point.

Update the code to use make_empty_dir_inode when reporting
a permanently empty directory to the vfs.

Update the code to not allow adding to permanently empty directories.

Update /proc/openprom and /proc/fs/nfsd to be permanently empty directories.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/proc/root.c b/fs/proc/root.c
index 64e1ab64bde6..68feb0f70e63 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -179,10 +179,10 @@ void __init proc_root_init(void)
 #endif
         proc_mkdir("fs", NULL);
         proc_mkdir("driver", NULL);
-        proc_mkdir("fs/nfsd", NULL); /* somewhere for the nfsd filesystem to be mounted */
+        proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
         /* just give it a mountpoint */
-        proc_mkdir("openprom", NULL);
+        proc_create_mount_point("openprom");
 #endif
         proc_tty_init();
         proc_mkdir("bus", NULL);