kernfs: Add support for always empty directories.
Add a new function kernfs_create_empty_dir that can be used to create
directory that can not be modified.
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.
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index 2da8493..756dd56 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -296,6 +296,8 @@
case KERNFS_DIR:
inode->i_op = &kernfs_dir_iops;
inode->i_fop = &kernfs_dir_fops;
+ if (kn->flags & KERNFS_EMPTY_DIR)
+ make_empty_dir_inode(inode);
break;
case KERNFS_FILE:
inode->i_size = kn->attr.size;