eventfs: Do not differentiate the toplevel events directory

The toplevel events directory is really no different than the events
directory of instances. Having the two be different caused
inconsistencies and made it harder to fix the permissions bugs.

Make all events directories act the same.

Link: https://lore.kernel.org/linux-trace-kernel/20240502200905.846448710@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 8186fff7 ("tracefs/eventfs: Use root and instance inodes as default ownership")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

fs/tracefs/event_inode.c

@@ -68,7 +68,6 @@ enum {
 	EVENTFS_SAVE_MODE	= BIT(16),
 	EVENTFS_SAVE_UID	= BIT(17),
 	EVENTFS_SAVE_GID	= BIT(18),
-	EVENTFS_TOPLEVEL	= BIT(19),
 };
 
 #define EVENTFS_MODE_MASK	(EVENTFS_SAVE_MODE - 1)
@@ -239,14 +238,10 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
 	return ret;
 }
 
-static void update_top_events_attr(struct eventfs_inode *ei, struct super_block *sb)
+static void update_events_attr(struct eventfs_inode *ei, struct super_block *sb)
 {
 	struct inode *root;
 
-	/* Only update if the "events" was on the top level */
-	if (!ei || !(ei->attr.mode & EVENTFS_TOPLEVEL))
-		return;
-
 	/* Get the tracefs root inode. */
 	root = d_inode(sb->s_root);
 	ei->attr.uid = root->i_uid;
@@ -259,10 +254,10 @@ static void set_top_events_ownership(struct inode *inode)
 	struct eventfs_inode *ei = ti->private;
 
 	/* The top events directory doesn't get automatically updated */
-	if (!ei || !ei->is_events || !(ei->attr.mode & EVENTFS_TOPLEVEL))
+	if (!ei || !ei->is_events)
 		return;
 
-	update_top_events_attr(ei, inode->i_sb);
+	update_events_attr(ei, inode->i_sb);
 
 	if (!(ei->attr.mode & EVENTFS_SAVE_UID))
 		inode->i_uid = ei->attr.uid;
@@ -291,7 +286,7 @@ static int eventfs_permission(struct mnt_idmap *idmap,
 	return generic_permission(idmap, inode, mask);
 }
 
-static const struct inode_operations eventfs_root_dir_inode_operations = {
+static const struct inode_operations eventfs_dir_inode_operations = {
 	.lookup		= eventfs_root_lookup,
 	.setattr	= eventfs_set_attr,
 	.getattr	= eventfs_get_attr,
@@ -359,7 +354,7 @@ static struct eventfs_inode *eventfs_find_events(struct dentry *dentry)
 		// Walk upwards until you find the events inode
 	} while (!ei->is_events);
 
-	update_top_events_attr(ei, dentry->d_sb);
+	update_events_attr(ei, dentry->d_sb);
 
 	return ei;
 }
@@ -465,7 +460,7 @@ static struct dentry *lookup_dir_entry(struct dentry *dentry,
 	update_inode_attr(dentry, inode, &ei->attr,
 			  S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO);
 
-	inode->i_op = &eventfs_root_dir_inode_operations;
+	inode->i_op = &eventfs_dir_inode_operations;
 	inode->i_fop = &eventfs_file_operations;
 
 	/* All directories will have the same inode number */
@@ -845,14 +840,6 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
 	uid = d_inode(dentry->d_parent)->i_uid;
 	gid = d_inode(dentry->d_parent)->i_gid;
 
-	/*
-	 * If the events directory is of the top instance, then parent
-	 * is NULL. Set the attr.mode to reflect this and its permissions will
-	 * default to the tracefs root dentry.
-	 */
-	if (!parent)
-		ei->attr.mode = EVENTFS_TOPLEVEL;
-
 	/* This is used as the default ownership of the files and directories */
 	ei->attr.uid = uid;
 	ei->attr.gid = gid;
@@ -861,13 +848,13 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
 	INIT_LIST_HEAD(&ei->list);
 
 	ti = get_tracefs(inode);
-	ti->flags |= TRACEFS_EVENT_INODE | TRACEFS_EVENT_TOP_INODE;
+	ti->flags |= TRACEFS_EVENT_INODE;
 	ti->private = ei;
 
 	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
 	inode->i_uid = uid;
 	inode->i_gid = gid;
-	inode->i_op = &eventfs_root_dir_inode_operations;
+	inode->i_op = &eventfs_dir_inode_operations;
 	inode->i_fop = &eventfs_file_operations;
 
 	dentry->d_fsdata = get_ei(ei);

fs/tracefs/internal.h

@@ -4,10 +4,9 @@
 
 enum {
 	TRACEFS_EVENT_INODE		= BIT(1),
-	TRACEFS_EVENT_TOP_INODE		= BIT(2),
-	TRACEFS_GID_PERM_SET		= BIT(3),
-	TRACEFS_UID_PERM_SET		= BIT(4),
-	TRACEFS_INSTANCE_INODE		= BIT(5),
+	TRACEFS_GID_PERM_SET		= BIT(2),
+	TRACEFS_UID_PERM_SET		= BIT(3),
+	TRACEFS_INSTANCE_INODE		= BIT(4),
 };
 
 struct tracefs_inode {