Revert "eventfs: Create eventfs_root_inode to store dentry"

This reverts commit e5c80b2352 which is
commit c3137ab631 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Id15d7f90e6e21d2fc148eb1b2abda5ecaff5aa94
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

fs/tracefs/event_inode.c

@@ -35,17 +35,6 @@ static DEFINE_MUTEX(eventfs_mutex);
 /* Choose something "unique" ;-) */
 #define EVENTFS_FILE_INODE_INO		0x12c4e37
 
-struct eventfs_root_inode {
-	struct eventfs_inode		ei;
-	struct dentry			*events_dir;
-};
-
-static struct eventfs_root_inode *get_root_inode(struct eventfs_inode *ei)
-{
-	WARN_ON_ONCE(!ei->is_events);
-	return container_of(ei, struct eventfs_root_inode, ei);
-}
-
 /* Just try to make something consistent and unique */
 static int eventfs_dir_ino(struct eventfs_inode *ei)
 {
@@ -83,18 +72,12 @@ enum {
 static void release_ei(struct kref *ref)
 {
 	struct eventfs_inode *ei = container_of(ref, struct eventfs_inode, kref);
-	struct eventfs_root_inode *rei;
 
 	WARN_ON_ONCE(!ei->is_freed);
 
 	kfree(ei->entry_attrs);
 	kfree_const(ei->name);
-	if (ei->is_events) {
+	kfree_rcu(ei, rcu);
-		rei = get_root_inode(ei);
-		kfree_rcu(rei, ei.rcu);
-	} else {
-		kfree_rcu(ei, rcu);
-	}
 }
 
 static inline void put_ei(struct eventfs_inode *ei)
@@ -435,43 +418,19 @@ static struct dentry *lookup_dir_entry(struct dentry *dentry,
 	return NULL;
 }
 
-static inline struct eventfs_inode *init_ei(struct eventfs_inode *ei, const char *name)
-{
-	ei->name = kstrdup_const(name, GFP_KERNEL);
-	if (!ei->name)
-		return NULL;
-	kref_init(&ei->kref);
-	return ei;
-}
-
 static inline struct eventfs_inode *alloc_ei(const char *name)
 {
 	struct eventfs_inode *ei = kzalloc(sizeof(*ei), GFP_KERNEL);
-	struct eventfs_inode *result;
 
 	if (!ei)
 		return NULL;
 
-	result = init_ei(ei, name);
+	ei->name = kstrdup_const(name, GFP_KERNEL);
-	if (!result)
+	if (!ei->name) {
 		kfree(ei);
-
-	return result;
-}
-
-static inline struct eventfs_inode *alloc_root_ei(const char *name)
-{
-	struct eventfs_root_inode *rei = kzalloc(sizeof(*rei), GFP_KERNEL);
-	struct eventfs_inode *ei;
-
-	if (!rei)
 		return NULL;
-
+	}
-	rei->ei.is_events = 1;
+	kref_init(&ei->kref);
-	ei = init_ei(&rei->ei, name);
-	if (!ei)
-		kfree(rei);
-
 	return ei;
 }
 
@@ -760,7 +719,6 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
 						int size, void *data)
 {
 	struct dentry *dentry = tracefs_start_creating(name, parent);
-	struct eventfs_root_inode *rei;
 	struct eventfs_inode *ei;
 	struct tracefs_inode *ti;
 	struct inode *inode;
@@ -773,7 +731,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
 	if (IS_ERR(dentry))
 		return ERR_CAST(dentry);
 
-	ei = alloc_root_ei(name);
+	ei = alloc_ei(name);
 	if (!ei)
 		goto fail;
 
@@ -782,11 +740,10 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
 		goto fail;
 
 	// Note: we have a ref to the dentry from tracefs_start_creating()
-	rei = get_root_inode(ei);
+	ei->events_dir = dentry;
-	rei->events_dir = dentry;
-
 	ei->entries = entries;
 	ei->nr_entries = size;
+	ei->is_events = 1;
 	ei->data = data;
 
 	/* Save the ownership of this directory */
@@ -889,15 +846,13 @@ void eventfs_remove_dir(struct eventfs_inode *ei)
  */
 void eventfs_remove_events_dir(struct eventfs_inode *ei)
 {
-	struct eventfs_root_inode *rei;
 	struct dentry *dentry;
 
-	rei = get_root_inode(ei);
+	dentry = ei->events_dir;
-	dentry = rei->events_dir;
 	if (!dentry)
 		return;
 
-	rei->events_dir = NULL;
+	ei->events_dir = NULL;
 	eventfs_remove_dir(ei);
 
 	/*

fs/tracefs/internal.h

@@ -39,6 +39,7 @@ struct eventfs_attr {
  * @children:	link list into the child eventfs_inode
  * @entries:	the array of entries representing the files in the directory
  * @name:	the name of the directory to create
+ * @events_dir: the dentry of the events directory
  * @entry_attrs: Saved mode and ownership of the @d_children
  * @data:	The private data to pass to the callbacks
  * @attr:	Saved mode and ownership of eventfs_inode itself
@@ -56,6 +57,7 @@ struct eventfs_inode {
 	struct list_head		children;
 	const struct eventfs_entry	*entries;
 	const char			*name;
+	struct dentry			*events_dir;
 	struct eventfs_attr		*entry_attrs;
 	void				*data;
 	struct eventfs_attr		attr;