new primitive: debugfs_create_automount()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 53 insertions, 0 deletions

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 1219dff8e18f..957c40ce09f6 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -175,6 +175,18 @@ static const struct super_operations debugfs_super_operations = {
         .show_options   = debugfs_show_options,
 };
 
+static struct vfsmount *debugfs_automount(struct path *path)
+{
+        struct vfsmount *(*f)(void *);
+        f = (struct vfsmount *(*)(void *))path->dentry->d_fsdata;
+        return f(path->dentry->d_inode->i_private);
+}
+
+static const struct dentry_operations debugfs_dops = {
+        .d_delete = always_delete_dentry,
+        .d_automount = debugfs_automount,
+};
+
 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 {
         static struct tree_descr debug_files[] = {{""}};
@@ -199,6 +211,7 @@ static int debug_fill_super(struct super_block *sb, void *data, int silent)
                 goto fail;
 
         sb->s_op = &debugfs_super_operations;
+        sb->s_d_op = &debugfs_dops;
 
         debugfs_apply_options(sb);
 
@@ -368,6 +381,41 @@ struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 
 /**
+ * debugfs_create_automount - create automount point in the debugfs filesystem
+ * @name: a pointer to a string containing the name of the file to create.
+ * @parent: a pointer to the parent dentry for this file.  This should be a
+ *          directory dentry if set.  If this parameter is NULL, then the
+ *          file will be created in the root of the debugfs filesystem.
+ * @f: function to be called when pathname resolution steps on that one.
+ * @data: opaque argument to pass to f().
+ *
+ * @f should return what ->d_automount() would.
+ */
+struct dentry *debugfs_create_automount(const char *name,
+                                        struct dentry *parent,
+                                        struct vfsmount *(*f)(void *),
+                                        void *data)
+{
+        struct dentry *dentry = start_creating(name, parent);
+        struct inode *inode;
+
+        if (IS_ERR(dentry))
+                return NULL;
+
+        inode = debugfs_get_inode(dentry->d_sb);
+        if (unlikely(!inode))
+                return failed_creating(dentry);
+
+        inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+        inode->i_flags |= S_AUTOMOUNT;
+        inode->i_private = data;
+        dentry->d_fsdata = (void *)f;
+        d_instantiate(dentry, inode);
+        return end_creating(dentry);
+}
+EXPORT_SYMBOL(debugfs_create_automount);
+
+/**
  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
  * @name: a pointer to a string containing the name of the symbolic link to
  *        create.
diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index da4c4983adbe..ea149a24a1f2 100644
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -56,6 +56,11 @@ struct dentry *debugfs_create_dir(const char *name, struct dentry *parent);
 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
                                       const char *dest);
 
+struct dentry *debugfs_create_automount(const char *name,
+                                        struct dentry *parent,
+                                        struct vfsmount *(*f)(void *),
+                                        void *data);
+
 void debugfs_remove(struct dentry *dentry);
 void debugfs_remove_recursive(struct dentry *dentry);