@@ -1,5 +1,6 @@
# SPDX-License-Identifier: GPL-2.0-only
tracefs-objs := inode.o
+tracefs-objs += event_inode.o
obj-$(CONFIG_TRACING) += tracefs.o
new file mode 100644
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * event_inode.c - part of tracefs, a pseudo file system for activating tracing
+ *
+ * Copyright (C) 2020-23 VMware Inc, author: Steven Rostedt (VMware) <rostedt@goodmis.org>
+ * Copyright (C) 2020-23 VMware Inc, author: Ajay Kaher <akaher@vmware.com>
+ *
+ * eventfs is used to dynamically create inodes and dentries based on the
+ * meta data provided by the tracing system.
+ *
+ * eventfs stores the meta-data of files/dirs and holds off on creating
+ * inodes/dentries of the files. When accessed, the eventfs will create the
+ * inodes/dentries in a just-in-time (JIT) manner. The eventfs will clean up
+ * and delete the inodes/dentries when they are no longer referenced.
+ */
+#include <linux/fsnotify.h>
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/workqueue.h>
+#include <linux/security.h>
+#include <linux/tracefs.h>
+#include <linux/kref.h>
+#include <linux/delay.h>
+#include "internal.h"
+
+struct eventfs_inode {
+ struct list_head e_top_files;
+};
+
+/**
+ * struct eventfs_file - hold the properties of the eventfs files and
+ * directories.
+ * @name: the name of the file or directory to create
+ * @list: file or directory to be added to parent directory
+ * @ei: list of files and directories within directory
+ * @fop: file_operations for file or directory
+ * @iop: inode_operations for file or directory
+ * @data: something that the caller will want to get to later on
+ * @mode: the permission that the file or directory should have
+ */
+struct eventfs_file {
+ const char *name;
+ struct list_head list;
+ struct eventfs_inode *ei;
+ const struct file_operations *fop;
+ const struct inode_operations *iop;
+ void *data;
+ umode_t mode;
+};
+
+static DEFINE_MUTEX(eventfs_mutex);
+
+static const struct inode_operations eventfs_root_dir_inode_operations = {
+};
+
+static const struct file_operations eventfs_file_operations = {
+};
+
+/**
+ * eventfs_prepare_ef - helper function to prepare eventfs_file
+ * @name: the name of the file/directory to create.
+ * @mode: the permission that the file should have.
+ * @fop: struct file_operations that should be used for this file/directory.
+ * @iop: struct inode_operations that should be used for this file/directory.
+ * @data: something that the caller will want to get to later on. The
+ * inode.i_private pointer will point to this value on the open() call.
+ *
+ * This function allocates and fills the eventfs_file structure.
+ */
+static struct eventfs_file *eventfs_prepare_ef(const char *name, umode_t mode,
+ const struct file_operations *fop,
+ const struct inode_operations *iop,
+ void *data)
+{
+ struct eventfs_file *ef;
+
+ ef = kzalloc(sizeof(*ef), GFP_KERNEL);
+ if (!ef)
+ return ERR_PTR(-ENOMEM);
+
+ ef->name = kstrdup(name, GFP_KERNEL);
+ if (!ef->name) {
+ kfree(ef);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ if (S_ISDIR(mode)) {
+ ef->ei = kzalloc(sizeof(*ef->ei), GFP_KERNEL);
+ if (!ef->ei) {
+ kfree(ef->name);
+ kfree(ef);
+ return ERR_PTR(-ENOMEM);
+ }
+ INIT_LIST_HEAD(&ef->ei->e_top_files);
+ } else {
+ ef->ei = NULL;
+ }
+
+ ef->iop = iop;
+ ef->fop = fop;
+ ef->mode = mode;
+ ef->data = data;
+ return ef;
+}
+
+/**
+ * eventfs_create_events_dir - create the trace event structure
+ * @name: the name of the directory to create.
+ * @parent: parent dentry for this file. This should be a directory dentry
+ * if set. If this parameter is NULL, then the directory will be
+ * created in the root of the tracefs filesystem.
+ *
+ * This function creates the top of the trace event directory.
+ */
+struct dentry *eventfs_create_events_dir(const char *name,
+ struct dentry *parent)
+{
+ struct dentry *dentry = tracefs_start_creating(name, parent);
+ struct eventfs_inode *ei;
+ struct tracefs_inode *ti;
+ struct inode *inode;
+
+ if (IS_ERR(dentry))
+ return dentry;
+
+ ei = kzalloc(sizeof(*ei), GFP_KERNEL);
+ if (!ei)
+ return ERR_PTR(-ENOMEM);
+ inode = tracefs_get_inode(dentry->d_sb);
+ if (unlikely(!inode)) {
+ kfree(ei);
+ tracefs_failed_creating(dentry);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ INIT_LIST_HEAD(&ei->e_top_files);
+
+ ti = get_tracefs(inode);
+ ti->flags |= TRACEFS_EVENT_INODE;
+ ti->private = ei;
+
+ inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+ inode->i_op = &eventfs_root_dir_inode_operations;
+ inode->i_fop = &eventfs_file_operations;
+
+ /* directory inodes start off with i_nlink == 2 (for "." entry) */
+ inc_nlink(inode);
+ d_instantiate(dentry, inode);
+ inc_nlink(dentry->d_parent->d_inode);
+ fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
+ return tracefs_end_creating(dentry);
+}
+
+/**
+ * eventfs_add_subsystem_dir - add eventfs subsystem_dir to list to create later
+ * @name: the name of the file to create.
+ * @parent: parent dentry for this dir.
+ *
+ * This function adds eventfs subsystem dir to list.
+ * And all these dirs are created on the fly when they are looked up,
+ * and the dentry and inodes will be removed when they are done.
+ */
+struct eventfs_file *eventfs_add_subsystem_dir(const char *name,
+ struct dentry *parent)
+{
+ struct tracefs_inode *ti_parent;
+ struct eventfs_inode *ei_parent;
+ struct eventfs_file *ef;
+
+ if (!parent)
+ return ERR_PTR(-EINVAL);
+
+ ti_parent = get_tracefs(parent->d_inode);
+ ei_parent = ti_parent->private;
+
+ ef = eventfs_prepare_ef(name, S_IFDIR, NULL, NULL, NULL);
+ if (IS_ERR(ef))
+ return ef;
+
+ mutex_lock(&eventfs_mutex);
+ list_add_tail(&ef->list, &ei_parent->e_top_files);
+ mutex_unlock(&eventfs_mutex);
+ return ef;
+}
+
+/**
+ * eventfs_add_dir - add eventfs dir to list to create later
+ * @name: the name of the file to create.
+ * @ef_parent: parent eventfs_file for this dir.
+ *
+ * This function adds eventfs dir to list.
+ * And all these dirs are created on the fly when they are looked up,
+ * and the dentry and inodes will be removed when they are done.
+ */
+struct eventfs_file *eventfs_add_dir(const char *name,
+ struct eventfs_file *ef_parent)
+{
+ struct eventfs_file *ef;
+
+ if (!ef_parent)
+ return ERR_PTR(-EINVAL);
+
+ ef = eventfs_prepare_ef(name, S_IFDIR, NULL, NULL, NULL);
+ if (IS_ERR(ef))
+ return ef;
+
+ mutex_lock(&eventfs_mutex);
+ list_add_tail(&ef->list, &ef_parent->ei->e_top_files);
+ mutex_unlock(&eventfs_mutex);
+ return ef;
+}
@@ -2,6 +2,10 @@
#ifndef _TRACEFS_INTERNAL_H
#define _TRACEFS_INTERNAL_H
+enum {
+ TRACEFS_EVENT_INODE = BIT(1),
+};
+
struct tracefs_inode {
unsigned long flags;
void *private;
@@ -21,6 +21,17 @@ struct file_operations;
#ifdef CONFIG_TRACING
+struct eventfs_file;
+
+struct dentry *eventfs_create_events_dir(const char *name,
+ struct dentry *parent);
+
+struct eventfs_file *eventfs_add_subsystem_dir(const char *name,
+ struct dentry *parent);
+
+struct eventfs_file *eventfs_add_dir(const char *name,
+ struct eventfs_file *ef_parent);
+
struct dentry *tracefs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops);