Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linuxgrafted

Pull I3C updates from Alexandre Belloni:
 "A new driver this cycle, for the AMD AXI I3C controller.

  There are also new features such as IBI wakeup support, SETAASA device
  discovery and ACPI support for the the DAA methods, meaning we can now
  communicate with the SPD devices on DDR5 modules.

  New driver:
   - AMD AXI I3C master controller

  Subsystem:
   - I3C Common Command Code (CCC) handling improvements, especially
     around GET CCCs
   - SETAASA device discovery support
   - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as
     well as I2C devices on I3C bus
   - IBI-based wakeup support

  Drivers:
   - dw: SETAASA support
   - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C
     controller support, PIO queue management support for HCI v1.2
   - renesas: improve suspend to RAM support, add runtime PM support"

* tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits)
  i3c: dw: reduce do_daa time if there's no client
  i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller
  i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2
  i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode
  i3c: dw: rename "pclk" to "apb" to match dt-binding
  i3c: dw: make struct dw_i3c_cmd smaller
  i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding
  i3c: renesas: Don't register devices when ENTDAA times out
  i3c: master: dw-i3c-master: fix OD timing for first broadcast
  i3c: mipi-i3c-hci: Advertise IBI wakeup capability
  i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()
  i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI
  i3c: master: Reject IBI requests from non-IBI-capable devices
  i3c: master: Add helper to query bus wakeup requirements
  i3c: master: Report wakeup events for IBIs
  i3c: master: Support IBI-based wakeup capability
  i3c: master: Fix potential UAF in i3c_device_match()
  i3c: master: Fix potential UAF in i3c_device_uevent()
  i3c: Make dev->desc locking assumptions explicit
  i3c: master: Fix use-after-free of master->this
  ...

4 files changed, 1825 insertions, 0 deletions

diff --git a/fs/tracefs/Makefile b/fs/tracefs/Makefile
new file mode 100644
index 000000000..73c56da8e
--- /dev/null
+++ b/fs/tracefs/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+tracefs-objs	:= inode.o
+tracefs-objs	+= event_inode.o
+
+obj-$(CONFIG_TRACING)	+= tracefs.o
+
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
new file mode 100644
index 000000000..604ba3e84
--- /dev/null
+++ b/fs/tracefs/event_inode.c
@@ -0,0 +1,928 @@
+// 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 <rostedt@goodmis.org>
+ *  Copyright (C) 2020-23 VMware Inc, author: Ajay Kaher <akaher@vmware.com>
+ *  Copyright (C) 2023 Google, author: Steven Rostedt <rostedt@goodmis.org>
+ *
+ *  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"
+
+/*
+ * eventfs_mutex protects the eventfs_inode (ei) dentry. Any access
+ * to the ei->dentry must be done under this mutex and after checking
+ * if ei->is_freed is not set. When ei->is_freed is set, the dentry
+ * is on its way to being freed after the last dput() is made on it.
+ */
+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)
+{
+	if (!ei->ino) {
+		ei->ino = get_next_ino();
+		/* Must not have the file inode number */
+		if (ei->ino == EVENTFS_FILE_INODE_INO)
+			ei->ino = get_next_ino();
+	}
+
+	return ei->ino;
+}
+
+/*
+ * The eventfs_inode (ei) itself is protected by SRCU. It is released from
+ * its parent's list and will have is_freed set (under eventfs_mutex).
+ * After the SRCU grace period is over and the last dput() is called
+ * the ei is freed.
+ */
+DEFINE_STATIC_SRCU(eventfs_srcu);
+
+/* Mode is unsigned short, use the upper bits for flags */
+enum {
+	EVENTFS_SAVE_MODE	= BIT(16),
+	EVENTFS_SAVE_UID	= BIT(17),
+	EVENTFS_SAVE_GID	= BIT(18),
+};
+
+#define EVENTFS_MODE_MASK	(EVENTFS_SAVE_MODE - 1)
+
+static void free_ei_rcu(struct rcu_head *rcu)
+{
+	struct eventfs_inode *ei = container_of(rcu, struct eventfs_inode, rcu);
+	struct eventfs_root_inode *rei;
+
+	kfree(ei->entry_attrs);
+	kfree_const(ei->name);
+	if (ei->is_events) {
+		rei = get_root_inode(ei);
+		kfree(rei);
+	} else {
+		kfree(ei);
+	}
+}
+
+/*
+ * eventfs_inode reference count management.
+ *
+ * NOTE! We count only references from dentries, in the
+ * form 'dentry->d_fsdata'. There are also references from
+ * directory inodes ('ti->private'), but the dentry reference
+ * count is always a superset of the inode reference count.
+ */
+static void release_ei(struct kref *ref)
+{
+	struct eventfs_inode *ei = container_of(ref, struct eventfs_inode, kref);
+	const struct eventfs_entry *entry;
+
+	WARN_ON_ONCE(!ei->is_freed);
+
+	for (int i = 0; i < ei->nr_entries; i++) {
+		entry = &ei->entries[i];
+		if (entry->release)
+			entry->release(entry->name, ei->data);
+	}
+
+	call_srcu(&eventfs_srcu, &ei->rcu, free_ei_rcu);
+}
+
+static inline void put_ei(struct eventfs_inode *ei)
+{
+	if (ei)
+		kref_put(&ei->kref, release_ei);
+}
+
+static inline void free_ei(struct eventfs_inode *ei)
+{
+	if (ei) {
+		/* The ei should have no children if it is being freed. */
+		WARN_ON_ONCE(!list_empty(&ei->children));
+		ei->is_freed = 1;
+		/*
+		 * The SRCU iteration has a smp_rmb() to make sure it
+		 * sees a child (that may have already been freed)
+		 * before it reads is_free. If is_free is set, it must
+		 * not use the child it acquired from ei->children, as
+		 * the list may be used for SRCU.
+		 */
+		smp_wmb();
+		put_ei(ei);
+	}
+}
+
+/*
+ * Called when creation of an ei fails, do not call release() functions.
+ */
+static inline void cleanup_ei(struct eventfs_inode *ei)
+{
+	if (ei) {
+		/* Set nr_entries to 0 to prevent release() function being called */
+		ei->nr_entries = 0;
+		free_ei(ei);
+	}
+}
+
+static inline struct eventfs_inode *get_ei(struct eventfs_inode *ei)
+{
+	if (ei)
+		kref_get(&ei->kref);
+	return ei;
+}
+
+static struct dentry *eventfs_root_lookup(struct inode *dir,
+					  struct dentry *dentry,
+					  unsigned int flags);
+static int eventfs_iterate(struct file *file, struct dir_context *ctx);
+
+static void update_attr(struct eventfs_attr *attr, struct iattr *iattr)
+{
+	unsigned int ia_valid = iattr->ia_valid;
+
+	if (ia_valid & ATTR_MODE) {
+		attr->mode = (attr->mode & ~EVENTFS_MODE_MASK) |
+			(iattr->ia_mode & EVENTFS_MODE_MASK) |
+			EVENTFS_SAVE_MODE;
+	}
+	if (ia_valid & ATTR_UID) {
+		attr->mode |= EVENTFS_SAVE_UID;
+		attr->uid = iattr->ia_uid;
+	}
+	if (ia_valid & ATTR_GID) {
+		attr->mode |= EVENTFS_SAVE_GID;
+		attr->gid = iattr->ia_gid;
+	}
+}
+
+static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
+			    struct iattr *iattr)
+{
+	const struct eventfs_entry *entry;
+	struct eventfs_inode *ei;
+	const char *name;
+	int ret;
+
+	guard(mutex)(&eventfs_mutex);
+	ei = dentry->d_fsdata;
+	/* Do not allow changes if the event is about to be removed. */
+	if (ei->is_freed)
+		return -ENODEV;
+
+	/* Preallocate the children mode array if necessary */
+	if (!(dentry->d_inode->i_mode & S_IFDIR)) {
+		if (!ei->entry_attrs) {
+			ei->entry_attrs = kzalloc_objs(*ei->entry_attrs,
+						       ei->nr_entries, GFP_NOFS);
+			if (!ei->entry_attrs)
+				return -ENOMEM;
+		}
+	}
+
+	ret = simple_setattr(idmap, dentry, iattr);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * If this is a dir, then update the ei cache, only the file
+	 * mode is saved in the ei->m_children, and the ownership is
+	 * determined by the parent directory.
+	 */
+	if (dentry->d_inode->i_mode & S_IFDIR) {
+		/* Just use the inode permissions for the events directory */
+		if (!ei->is_events)
+			update_attr(&ei->attr, iattr);
+
+	} else {
+		name = dentry->d_name.name;
+
+		for (int i = 0; i < ei->nr_entries; i++) {
+			entry = &ei->entries[i];
+			if (strcmp(name, entry->name) == 0) {
+				update_attr(&ei->entry_attrs[i], iattr);
+				break;
+			}
+		}
+	}
+	return ret;
+}
+
+static const struct inode_operations eventfs_dir_inode_operations = {
+	.lookup		= eventfs_root_lookup,
+	.setattr	= eventfs_set_attr,
+};
+
+static const struct inode_operations eventfs_file_inode_operations = {
+	.setattr	= eventfs_set_attr,
+};
+
+static const struct file_operations eventfs_file_operations = {
+	.read		= generic_read_dir,
+	.iterate_shared	= eventfs_iterate,
+	.llseek		= generic_file_llseek,
+};
+
+static void eventfs_set_attrs(struct eventfs_inode *ei, bool update_uid, kuid_t uid,
+			      bool update_gid, kgid_t gid, int level)
+{
+	struct eventfs_inode *ei_child;
+
+	lockdep_assert_held(&eventfs_mutex);
+
+	/* Update events/<system>/<event> */
+	if (WARN_ON_ONCE(level > 3))
+		return;
+
+	if (update_uid) {
+		ei->attr.mode &= ~EVENTFS_SAVE_UID;
+		ei->attr.uid = uid;
+	}
+
+	if (update_gid) {
+		ei->attr.mode &= ~EVENTFS_SAVE_GID;
+		ei->attr.gid = gid;
+	}
+
+	list_for_each_entry(ei_child, &ei->children, list) {
+		eventfs_set_attrs(ei_child, update_uid, uid, update_gid, gid, level + 1);
+	}
+
+	if (!ei->entry_attrs)
+		return;
+
+	for (int i = 0; i < ei->nr_entries; i++) {
+		if (update_uid) {
+			ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_UID;
+			ei->entry_attrs[i].uid = uid;
+		}
+		if (update_gid) {
+			ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_GID;
+			ei->entry_attrs[i].gid = gid;
+		}
+	}
+
+}
+
+/*
+ * On a remount of tracefs, if UID or GID options are set, then
+ * the mount point inode permissions should be used.
+ * Reset the saved permission flags appropriately.
+ */
+void eventfs_remount(struct tracefs_inode *ti, bool update_uid, bool update_gid)
+{
+	struct eventfs_inode *ei = ti->private;
+
+	/* Only the events directory does the updates */
+	if (!ei || !ei->is_events || ei->is_freed)
+		return;
+
+	eventfs_set_attrs(ei, update_uid, ti->vfs_inode.i_uid,
+			  update_gid, ti->vfs_inode.i_gid, 0);
+}
+
+static void update_inode_attr(struct inode *inode, umode_t mode,
+			      struct eventfs_attr *attr, struct eventfs_root_inode *rei)
+{
+	if (attr && attr->mode & EVENTFS_SAVE_MODE)
+		inode->i_mode = attr->mode & EVENTFS_MODE_MASK;
+	else
+		inode->i_mode = mode;
+
+	if (attr && attr->mode & EVENTFS_SAVE_UID)
+		inode->i_uid = attr->uid;
+	else
+		inode->i_uid = rei->ei.attr.uid;
+
+	if (attr && attr->mode & EVENTFS_SAVE_GID)
+		inode->i_gid = attr->gid;
+	else
+		inode->i_gid = rei->ei.attr.gid;
+}
+
+static struct inode *eventfs_get_inode(struct dentry *dentry, struct eventfs_attr *attr,
+				       umode_t mode,  struct eventfs_inode *ei)
+{
+	struct eventfs_root_inode *rei;
+	struct eventfs_inode *pei;
+	struct tracefs_inode *ti;
+	struct inode *inode;
+
+	inode = tracefs_get_inode(dentry->d_sb);
+	if (!inode)
+		return NULL;
+
+	ti = get_tracefs(inode);
+	ti->private = ei;
+	ti->flags |= TRACEFS_EVENT_INODE;
+
+	/* Find the top dentry that holds the "events" directory */
+	do {
+		dentry = dentry->d_parent;
+		/* Directories always have d_fsdata */
+		pei = dentry->d_fsdata;
+	} while (!pei->is_events);
+
+	rei = get_root_inode(pei);
+
+	update_inode_attr(inode, mode, attr, rei);
+
+	return inode;
+}
+
+/**
+ * lookup_file - look up a file in the tracefs filesystem
+ * @parent_ei: Pointer to the eventfs_inode that represents parent of the file
+ * @dentry: the dentry to look up
+ * @mode: the permission that the file should have.
+ * @attr: saved attributes changed by user
+ * @data: something that the caller will want to get to later on.
+ * @fop: struct file_operations that should be used for this file.
+ *
+ * This function creates a dentry that represents a file in the eventsfs_inode
+ * directory. The inode.i_private pointer will point to @data in the open()
+ * call.
+ */
+static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
+				  struct dentry *dentry,
+				  umode_t mode,
+				  struct eventfs_attr *attr,
+				  void *data,
+				  const struct file_operations *fop)
+{
+	struct inode *inode;
+
+	if (!(mode & S_IFMT))
+		mode |= S_IFREG;
+
+	if (WARN_ON_ONCE(!S_ISREG(mode)))
+		return ERR_PTR(-EIO);
+
+	/* Only directories have ti->private set to an ei, not files */
+	inode = eventfs_get_inode(dentry, attr, mode, NULL);
+	if (unlikely(!inode))
+		return ERR_PTR(-ENOMEM);
+
+	inode->i_op = &eventfs_file_inode_operations;
+	inode->i_fop = fop;
+	inode->i_private = data;
+
+	/* All files will have the same inode number */
+	inode->i_ino = EVENTFS_FILE_INODE_INO;
+
+	// Files have their parent's ei as their fsdata
+	dentry->d_fsdata = get_ei(parent_ei);
+
+	return d_splice_alias(inode, dentry);
+};
+
+/**
+ * lookup_dir_entry - look up a dir in the tracefs filesystem
+ * @dentry: the directory to look up
+ * @pei: Pointer to the parent eventfs_inode if available
+ * @ei: the eventfs_inode that represents the directory to create
+ *
+ * This function will look up a dentry for a directory represented by
+ * a eventfs_inode.
+ */
+static struct dentry *lookup_dir_entry(struct dentry *dentry,
+	struct eventfs_inode *pei, struct eventfs_inode *ei)
+{
+	struct inode *inode;
+	umode_t mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+
+	inode = eventfs_get_inode(dentry, &ei->attr, mode, ei);
+	if (unlikely(!inode))
+		return ERR_PTR(-ENOMEM);
+
+	inode->i_op = &eventfs_dir_inode_operations;
+	inode->i_fop = &eventfs_file_operations;
+
+	/* All directories will have the same inode number */
+	inode->i_ino = eventfs_dir_ino(ei);
+
+	dentry->d_fsdata = get_ei(ei);
+
+	return d_splice_alias(inode, dentry);
+}
+
+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_obj(*ei);
+	struct eventfs_inode *result;
+
+	if (!ei)
+		return NULL;
+
+	result = init_ei(ei, name);
+	if (!result)
+		kfree(ei);
+
+	return result;
+}
+
+static inline struct eventfs_inode *alloc_root_ei(const char *name)
+{
+	struct eventfs_root_inode *rei = kzalloc_obj(*rei);
+	struct eventfs_inode *ei;
+
+	if (!rei)
+		return NULL;
+
+	rei->ei.is_events = 1;
+	ei = init_ei(&rei->ei, name);
+	if (!ei)
+		kfree(rei);
+
+	return ei;
+}
+
+/**
+ * eventfs_d_release - dentry is going away
+ * @dentry: dentry which has the reference to remove.
+ *
+ * Remove the association between a dentry from an eventfs_inode.
+ */
+void eventfs_d_release(struct dentry *dentry)
+{
+	put_ei(dentry->d_fsdata);
+}
+
+/**
+ * lookup_file_dentry - create a dentry for a file of an eventfs_inode
+ * @dentry: The parent dentry under which the new file's dentry will be created
+ * @ei: the eventfs_inode that the file will be created under
+ * @idx: the index into the entry_attrs[] of the @ei
+ * @mode: The mode of the file.
+ * @data: The data to use to set the inode of the file with on open()
+ * @fops: The fops of the file to be created.
+ *
+ * This function creates a dentry for a file associated with an
+ * eventfs_inode @ei. It uses the entry attributes specified by @idx,
+ * if available. The file will have the specified @mode and its inode will be
+ * set up with @data upon open. The file operations will be set to @fops.
+ *
+ * Return: Returns a pointer to the newly created file's dentry or an error
+ * pointer.
+ */
+static struct dentry *
+lookup_file_dentry(struct dentry *dentry,
+		   struct eventfs_inode *ei, int idx,
+		   umode_t mode, void *data,
+		   const struct file_operations *fops)
+{
+	struct eventfs_attr *attr = NULL;
+
+	if (ei->entry_attrs)
+		attr = &ei->entry_attrs[idx];
+
+	return lookup_file(ei, dentry, mode, attr, data, fops);
+}
+
+/**
+ * eventfs_root_lookup - lookup routine to create file/dir
+ * @dir: in which a lookup is being done
+ * @dentry: file/dir dentry
+ * @flags: Just passed to simple_lookup()
+ *
+ * Used to create dynamic file/dir with-in @dir, search with-in @ei
+ * list, if @dentry found go ahead and create the file/dir
+ */
+
+static struct dentry *eventfs_root_lookup(struct inode *dir,
+					  struct dentry *dentry,
+					  unsigned int flags)
+{
+	struct eventfs_inode *ei_child;
+	struct tracefs_inode *ti;
+	struct eventfs_inode *ei;
+	const char *name = dentry->d_name.name;
+
+	ti = get_tracefs(dir);
+	if (WARN_ON_ONCE(!(ti->flags & TRACEFS_EVENT_INODE)))
+		return ERR_PTR(-EIO);
+
+	guard(mutex)(&eventfs_mutex);
+
+	ei = ti->private;
+	if (!ei || ei->is_freed)
+		return NULL;
+
+	list_for_each_entry(ei_child, &ei->children, list) {
+		if (strcmp(ei_child->name, name) != 0)
+			continue;
+		/* A child is freed and removed from the list at the same time */
+		if (WARN_ON_ONCE(ei_child->is_freed))
+			return NULL;
+		return lookup_dir_entry(dentry, ei, ei_child);
+	}
+
+	for (int i = 0; i < ei->nr_entries; i++) {
+		void *data;
+		umode_t mode;
+		const struct file_operations *fops;
+		const struct eventfs_entry *entry = &ei->entries[i];
+
+		if (strcmp(name, entry->name) != 0)
+			continue;
+
+		data = ei->data;
+		if (entry->callback(name, &mode, &data, &fops) <= 0)
+			return NULL;
+
+		return lookup_file_dentry(dentry, ei, i, mode, data, fops);
+
+	}
+	return NULL;
+}
+
+/*
+ * Walk the children of a eventfs_inode to fill in getdents().
+ */
+static int eventfs_iterate(struct file *file, struct dir_context *ctx)
+{
+	const struct file_operations *fops;
+	struct inode *f_inode = file_inode(file);
+	const struct eventfs_entry *entry;
+	struct eventfs_inode *ei_child;
+	struct tracefs_inode *ti;
+	struct eventfs_inode *ei;
+	const char *name;
+	umode_t mode;
+	int ino;
+	int i, r, c;
+
+	if (!dir_emit_dots(file, ctx))
+		return 0;
+
+	ti = get_tracefs(f_inode);
+	if (!(ti->flags & TRACEFS_EVENT_INODE))
+		return -EINVAL;
+
+	/* Logic should prevent ctx->pos from going out of range */
+	if (WARN_ON_ONCE(ctx->pos < 2 || ctx->pos > 0x7fffffffULL))
+		return -EINVAL;
+
+	c = ctx->pos - 2;
+
+	guard(srcu)(&eventfs_srcu);
+
+	scoped_guard(mutex, &eventfs_mutex) {
+		ei = READ_ONCE(ti->private);
+		if (!ei || ei->is_freed)
+			return -EINVAL;
+	}
+
+	/*
+	 * Need to create the dentries and inodes to have a consistent
+	 * inode number.
+	 */
+
+	/* Start at 'c' to jump over already read entries */
+	for (i = c; i < ei->nr_entries; i++, ctx->pos++) {
+		void *cdata = ei->data;
+
+		entry = &ei->entries[i];
+		name = entry->name;
+
+		/* If ei->is_freed then just bail here, nothing more to do */
+		scoped_guard(mutex, &eventfs_mutex) {
+			if (ei->is_freed)
+				return -EINVAL;
+			r = entry->callback(name, &mode, &cdata, &fops);
+		}
+		if (r <= 0)
+			continue;
+
+		ino = EVENTFS_FILE_INODE_INO;
+
+		if (!dir_emit(ctx, name, strlen(name), ino, DT_REG))
+			return -EINVAL;
+	}
+
+	/* Subtract the skipped entries above */
+	c -= min((unsigned int)c, (unsigned int)ei->nr_entries);
+
+	list_for_each_entry_srcu(ei_child, &ei->children, list,
+				 srcu_read_lock_held(&eventfs_srcu)) {
+
+		/*
+		 * If the ei is being freed, then the ei->children may be
+		 * being used as the rcu list, which means the next element
+		 * may be garbage. The ei->is_free is set before switching
+		 * the ei->children over to ei->rcu. The read memory barrier
+		 * here makes sure the ei_child is read before is_free is
+		 * updated.
+		 *
+		 * Matches the smp_wmb() in free_ei()
+		 */
+		smp_rmb();
+		if (ei->is_freed)
+			return -EINVAL;
+
+		if (c > 0) {
+			c--;
+			continue;
+		}
+
+		ctx->pos++;
+
+		if (ei_child->is_freed)
+			continue;
+
+		name = ei_child->name;
+
+		ino = eventfs_dir_ino(ei_child);
+
+		if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR)) {
+			/* Incremented ctx->pos without adding something, reset it */
+			ctx->pos--;
+			return -EINVAL;
+		}
+	}
+	return 1;
+}
+
+/**
+ * eventfs_create_dir - Create the eventfs_inode for this directory
+ * @name: The name of the directory to create.
+ * @parent: The eventfs_inode of the parent directory.
+ * @entries: A list of entries that represent the files under this directory
+ * @size: The number of @entries
+ * @data: The default data to pass to the files (an entry may override it).
+ *
+ * This function creates the descriptor to represent a directory in the
+ * eventfs. This descriptor is an eventfs_inode, and it is returned to be
+ * used to create other children underneath.
+ *
+ * The @entries is an array of eventfs_entry structures which has:
+ *	const char		 *name
+ *	eventfs_callback	callback;
+ *
+ * The name is the name of the file, and the callback is a pointer to a function
+ * that will be called when the file is reference (either by lookup or by
+ * reading a directory). The callback is of the prototype:
+ *
+ *    int callback(const char *name, umode_t *mode, void **data,
+ *		   const struct file_operations **fops);
+ *
+ * When a file needs to be created, this callback will be called with
+ *   name = the name of the file being created (so that the same callback
+ *          may be used for multiple files).
+ *   mode = a place to set the file's mode
+ *   data = A pointer to @data, and the callback may replace it, which will
+ *         cause the file created to pass the new data to the open() call.
+ *   fops = the fops to use for the created file.
+ *
+ * NB. @callback is called while holding internal locks of the eventfs
+ *     system. The callback must not call any code that might also call into
+ *     the tracefs or eventfs system or it will risk creating a deadlock.
+ */
+struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode *parent,
+					 const struct eventfs_entry *entries,
+					 int size, void *data)
+{
+	struct eventfs_inode *ei;
+
+	if (!parent)
+		return ERR_PTR(-EINVAL);
+
+	ei = alloc_ei(name);
+	if (!ei)
+		return ERR_PTR(-ENOMEM);
+
+	ei->entries = entries;
+	ei->nr_entries = size;
+	ei->data = data;
+	INIT_LIST_HEAD(&ei->children);
+	INIT_LIST_HEAD(&ei->list);
+
+	scoped_guard(mutex, &eventfs_mutex) {
+		if (!parent->is_freed)
+			list_add_tail_rcu(&ei->list, &parent->children);
+	}
+	/* Was the parent freed? */
+	if (list_empty(&ei->list)) {
+		cleanup_ei(ei);
+		ei = ERR_PTR(-EBUSY);
+	}
+	return ei;
+}
+
+/**
+ * eventfs_create_events_dir - create the top level events directory
+ * @name: The name of the top level directory to create.
+ * @parent: Parent dentry for this file in the tracefs directory.
+ * @entries: A list of entries that represent the files under this directory
+ * @size: The number of @entries
+ * @data: The default data to pass to the files (an entry may override it).
+ *
+ * This function creates the top of the trace event directory.
+ *
+ * See eventfs_create_dir() for use of @entries.
+ */
+struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry *parent,
+						const struct eventfs_entry *entries,
+						int size, void *data)
+{
+	struct dentry *dentry;
+	struct eventfs_root_inode *rei;
+	struct eventfs_inode *ei;
+	struct tracefs_inode *ti;
+	struct inode *inode;
+	kuid_t uid;
+	kgid_t gid;
+
+	if (security_locked_down(LOCKDOWN_TRACEFS))
+		return NULL;
+
+	dentry = tracefs_start_creating(name, parent);
+	if (IS_ERR(dentry))
+		return ERR_CAST(dentry);
+
+	ei = alloc_root_ei(name);
+	if (!ei)
+		goto fail;
+
+	inode = tracefs_get_inode(dentry->d_sb);
+	if (unlikely(!inode))
+		goto fail;
+
+	// Note: we have a ref to the dentry from tracefs_start_creating()
+	rei = get_root_inode(ei);
+	rei->events_dir = dentry;
+
+	ei->entries = entries;
+	ei->nr_entries = size;
+	ei->data = data;
+
+	/* Save the ownership of this directory */
+	uid = d_inode(dentry->d_parent)->i_uid;
+	gid = d_inode(dentry->d_parent)->i_gid;
+
+	/*
+	 * The ei->attr will be used as the default values for the
+	 * files beneath this directory.
+	 */
+	ei->attr.uid = uid;
+	ei->attr.gid = gid;
+
+	INIT_LIST_HEAD(&ei->children);
+	INIT_LIST_HEAD(&ei->list);
+
+	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_uid = uid;
+	inode->i_gid = gid;
+	inode->i_op = &eventfs_dir_inode_operations;
+	inode->i_fop = &eventfs_file_operations;
+
+	dentry->d_fsdata = get_ei(ei);
+
+	/*
+	 * Keep all eventfs directories with i_nlink == 1.
+	 * Due to the dynamic nature of the dentry creations and not
+	 * wanting to add a pointer to the parent eventfs_inode in the
+	 * eventfs_inode structure, keeping the i_nlink in sync with the
+	 * number of directories would cause too much complexity for
+	 * something not worth much. Keeping directory links at 1
+	 * tells userspace not to trust the link number.
+	 */
+	d_make_persistent(dentry, inode);
+	/* The dentry of the "events" parent does keep track though */
+	inc_nlink(dentry->d_parent->d_inode);
+	fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
+	tracefs_end_creating(dentry);
+
+	return ei;
+
+ fail:
+	cleanup_ei(ei);
+	tracefs_failed_creating(dentry);
+	return ERR_PTR(-ENOMEM);
+}
+
+/**
+ * eventfs_remove_rec - remove eventfs dir or file from list
+ * @ei: eventfs_inode to be removed.
+ * @level: prevent recursion from going more than 3 levels deep.
+ *
+ * This function recursively removes eventfs_inodes which
+ * contains info of files and/or directories.
+ */
+static void eventfs_remove_rec(struct eventfs_inode *ei, int level)
+{
+	struct eventfs_inode *ei_child, *tmp;
+
+	/*
+	 * Check recursion depth. It should never be greater than 3:
+	 * 0 - events/
+	 * 1 - events/group/
+	 * 2 - events/group/event/
+	 * 3 - events/group/event/file
+	 */
+	if (WARN_ON_ONCE(level > 3))
+		return;
+
+	/* search for nested folders or files */
+	list_for_each_entry_safe(ei_child, tmp, &ei->children, list)
+		eventfs_remove_rec(ei_child, level + 1);
+
+	list_del_rcu(&ei->list);
+	free_ei(ei);
+}
+
+/**
+ * eventfs_remove_dir - remove eventfs dir or file from list
+ * @ei: eventfs_inode to be removed.
+ *
+ * This function acquire the eventfs_mutex lock and call eventfs_remove_rec()
+ */
+void eventfs_remove_dir(struct eventfs_inode *ei)
+{
+	if (!ei)
+		return;
+
+	guard(mutex)(&eventfs_mutex);
+	eventfs_remove_rec(ei, 0);
+}
+
+/**
+ * eventfs_remove_events_dir - remove the top level eventfs directory
+ * @ei: the event_inode returned by eventfs_create_events_dir().
+ *
+ * This function removes the events main directory
+ */
+void eventfs_remove_events_dir(struct eventfs_inode *ei)
+{
+	struct eventfs_root_inode *rei;
+	struct dentry *dentry;
+
+	rei = get_root_inode(ei);
+	dentry = rei->events_dir;
+	if (!dentry)
+		return;
+
+	rei->events_dir = NULL;
+	eventfs_remove_dir(ei);
+
+	/*
+	 * Matches the dget() done by tracefs_start_creating()
+	 * in eventfs_create_events_dir() when it the dentry was
+	 * created. In other words, it's a normal dentry that
+	 * sticks around while the other ei->dentry are created
+	 * and destroyed dynamically.
+	 */
+	d_invalidate(dentry);
+	d_make_discardable(dentry);
+}
+
+int eventfs_remount_lock(void)
+{
+	mutex_lock(&eventfs_mutex);
+	return srcu_read_lock(&eventfs_srcu);
+}
+
+void eventfs_remount_unlock(int srcu_idx)
+{
+	srcu_read_unlock(&eventfs_srcu, srcu_idx);
+	mutex_unlock(&eventfs_mutex);
+}
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
new file mode 100644
index 000000000..f3d6188a3
--- /dev/null
+++ b/fs/tracefs/inode.c
@@ -0,0 +1,809 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  inode.c - part of tracefs, a pseudo file system for activating tracing
+ *
+ * Based on debugfs by: Greg Kroah-Hartman <greg@kroah.com>
+ *
+ *  Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>
+ *
+ * tracefs is the file system that is used by the tracing infrastructure.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include <linux/kobject.h>
+#include <linux/namei.h>
+#include <linux/tracefs.h>
+#include <linux/fsnotify.h>
+#include <linux/security.h>
+#include <linux/seq_file.h>
+#include <linux/magic.h>
+#include <linux/slab.h>
+#include "internal.h"
+
+#define TRACEFS_DEFAULT_MODE	0700
+static struct kmem_cache *tracefs_inode_cachep __ro_after_init;
+
+static struct vfsmount *tracefs_mount;
+static int tracefs_mount_count;
+static bool tracefs_registered;
+
+/*
+ * Keep track of all tracefs_inodes in order to update their
+ * flags if necessary on a remount.
+ */
+static DEFINE_SPINLOCK(tracefs_inode_lock);
+static LIST_HEAD(tracefs_inodes);
+
+static struct inode *tracefs_alloc_inode(struct super_block *sb)
+{
+	struct tracefs_inode *ti;
+	unsigned long flags;
+
+	ti = alloc_inode_sb(sb, tracefs_inode_cachep, GFP_KERNEL);
+	if (!ti)
+		return NULL;
+
+	spin_lock_irqsave(&tracefs_inode_lock, flags);
+	list_add_rcu(&ti->list, &tracefs_inodes);
+	spin_unlock_irqrestore(&tracefs_inode_lock, flags);
+
+	return &ti->vfs_inode;
+}
+
+static void tracefs_free_inode(struct inode *inode)
+{
+	struct tracefs_inode *ti = get_tracefs(inode);
+
+	kmem_cache_free(tracefs_inode_cachep, ti);
+}
+
+static void tracefs_destroy_inode(struct inode *inode)
+{
+	struct tracefs_inode *ti = get_tracefs(inode);
+	unsigned long flags;
+
+	spin_lock_irqsave(&tracefs_inode_lock, flags);
+	list_del_rcu(&ti->list);
+	spin_unlock_irqrestore(&tracefs_inode_lock, flags);
+}
+
+static ssize_t default_read_file(struct file *file, char __user *buf,
+				 size_t count, loff_t *ppos)
+{
+	return 0;
+}
+
+static ssize_t default_write_file(struct file *file, const char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	return count;
+}
+
+static const struct file_operations tracefs_file_operations = {
+	.read =		default_read_file,
+	.write =	default_write_file,
+	.open =		simple_open,
+	.llseek =	noop_llseek,
+};
+
+static struct tracefs_dir_ops {
+	int (*mkdir)(const char *name);
+	int (*rmdir)(const char *name);
+} tracefs_ops __ro_after_init;
+
+static struct dentry *tracefs_syscall_mkdir(struct mnt_idmap *idmap,
+					    struct inode *inode, struct dentry *dentry,
+					    umode_t mode)
+{
+	struct tracefs_inode *ti;
+	struct name_snapshot name;
+	int ret;
+
+	/*
+	 * This is a new directory that does not take the default of
+	 * the rootfs. It becomes the default permissions for all the
+	 * files and directories underneath it.
+	 */
+	ti = get_tracefs(inode);
+	ti->flags |= TRACEFS_INSTANCE_INODE;
+	ti->private = inode;
+
+	/*
+	 * The mkdir call can call the generic functions that create
+	 * the files within the tracefs system. It is up to the individual
+	 * mkdir routine to handle races.
+	 */
+	take_dentry_name_snapshot(&name, dentry);
+	inode_unlock(inode);
+	ret = tracefs_ops.mkdir(name.name.name);
+	inode_lock(inode);
+	release_dentry_name_snapshot(&name);
+
+	return ERR_PTR(ret);
+}
+
+static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
+{
+	struct name_snapshot name;
+	int ret;
+
+	/*
+	 * The rmdir call can call the generic functions that create
+	 * the files within the tracefs system. It is up to the individual
+	 * rmdir routine to handle races.
+	 * This time we need to unlock not only the parent (inode) but
+	 * also the directory that is being deleted.
+	 */
+	take_dentry_name_snapshot(&name, dentry);
+	inode_unlock(inode);
+	inode_unlock(d_inode(dentry));
+
+	ret = tracefs_ops.rmdir(name.name.name);
+
+	inode_lock_nested(inode, I_MUTEX_PARENT);
+	inode_lock(d_inode(dentry));
+	release_dentry_name_snapshot(&name);
+
+	return ret;
+}
+
+static void set_tracefs_inode_owner(struct inode *inode)
+{
+	struct tracefs_inode *ti = get_tracefs(inode);
+	struct inode *root_inode = ti->private;
+	kuid_t uid;
+	kgid_t gid;
+
+	uid = root_inode->i_uid;
+	gid = root_inode->i_gid;
+
+	/*
+	 * If the root is not the mount point, then check the root's
+	 * permissions. If it was never set, then default to the
+	 * mount point.
+	 */
+	if (root_inode != d_inode(root_inode->i_sb->s_root)) {
+		struct tracefs_inode *rti;
+
+		rti = get_tracefs(root_inode);
+		root_inode = d_inode(root_inode->i_sb->s_root);
+
+		if (!(rti->flags & TRACEFS_UID_PERM_SET))
+			uid = root_inode->i_uid;
+
+		if (!(rti->flags & TRACEFS_GID_PERM_SET))
+			gid = root_inode->i_gid;
+	}
+
+	/*
+	 * If this inode has never been referenced, then update
+	 * the permissions to the superblock.
+	 */
+	if (!(ti->flags & TRACEFS_UID_PERM_SET))
+		inode->i_uid = uid;
+
+	if (!(ti->flags & TRACEFS_GID_PERM_SET))
+		inode->i_gid = gid;
+}
+
+static int tracefs_permission(struct mnt_idmap *idmap,
+			      struct inode *inode, int mask)
+{
+	set_tracefs_inode_owner(inode);
+	return generic_permission(idmap, inode, mask);
+}
+
+static int tracefs_getattr(struct mnt_idmap *idmap,
+			   const struct path *path, struct kstat *stat,
+			   u32 request_mask, unsigned int flags)
+{
+	struct inode *inode = d_backing_inode(path->dentry);
+
+	set_tracefs_inode_owner(inode);
+	generic_fillattr(idmap, request_mask, inode, stat);
+	return 0;
+}
+
+static int tracefs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+			   struct iattr *attr)
+{
+	unsigned int ia_valid = attr->ia_valid;
+	struct inode *inode = d_inode(dentry);
+	struct tracefs_inode *ti = get_tracefs(inode);
+
+	if (ia_valid & ATTR_UID)
+		ti->flags |= TRACEFS_UID_PERM_SET;
+
+	if (ia_valid & ATTR_GID)
+		ti->flags |= TRACEFS_GID_PERM_SET;
+
+	return simple_setattr(idmap, dentry, attr);
+}
+
+static const struct inode_operations tracefs_instance_dir_inode_operations = {
+	.lookup		= simple_lookup,
+	.mkdir		= tracefs_syscall_mkdir,
+	.rmdir		= tracefs_syscall_rmdir,
+	.permission	= tracefs_permission,
+	.getattr	= tracefs_getattr,
+	.setattr	= tracefs_setattr,
+};
+
+static const struct inode_operations tracefs_dir_inode_operations = {
+	.lookup		= simple_lookup,
+	.permission	= tracefs_permission,
+	.getattr	= tracefs_getattr,
+	.setattr	= tracefs_setattr,
+};
+
+static const struct inode_operations tracefs_file_inode_operations = {
+	.permission	= tracefs_permission,
+	.getattr	= tracefs_getattr,
+	.setattr	= tracefs_setattr,
+};
+
+struct inode *tracefs_get_inode(struct super_block *sb)
+{
+	struct inode *inode = new_inode(sb);
+	if (inode) {
+		inode->i_ino = get_next_ino();
+		simple_inode_init_ts(inode);
+	}
+	return inode;
+}
+
+struct tracefs_fs_info {
+	kuid_t uid;
+	kgid_t gid;
+	umode_t mode;
+	/* Opt_* bitfield. */
+	unsigned int opts;
+};
+
+enum {
+	Opt_uid,
+	Opt_gid,
+	Opt_mode,
+};
+
+static const struct fs_parameter_spec tracefs_param_specs[] = {
+	fsparam_gid	("gid",		Opt_gid),
+	fsparam_u32oct	("mode",	Opt_mode),
+	fsparam_uid	("uid",		Opt_uid),
+	{}
+};
+
+static int tracefs_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct tracefs_fs_info *opts = fc->s_fs_info;
+	struct fs_parse_result result;
+	int opt;
+
+	opt = fs_parse(fc, tracefs_param_specs, param, &result);
+	if (opt < 0)
+		return opt;
+
+	switch (opt) {
+	case Opt_uid:
+		opts->uid = result.uid;
+		break;
+	case Opt_gid:
+		opts->gid = result.gid;
+		break;
+	case Opt_mode:
+		opts->mode = result.uint_32 & S_IALLUGO;
+		break;
+	/*
+	 * We might like to report bad mount options here;
+	 * but traditionally tracefs has ignored all mount options
+	 */
+	}
+
+	opts->opts |= BIT(opt);
+
+	return 0;
+}
+
+static int tracefs_apply_options(struct super_block *sb, bool remount)
+{
+	struct tracefs_fs_info *fsi = sb->s_fs_info;
+	struct inode *inode = d_inode(sb->s_root);
+	struct tracefs_inode *ti;
+	bool update_uid, update_gid;
+	int srcu_idx;
+	umode_t tmp_mode;
+
+	/*
+	 * On remount, only reset mode/uid/gid if they were provided as mount
+	 * options.
+	 */
+
+	if (!remount || fsi->opts & BIT(Opt_mode)) {
+		tmp_mode = READ_ONCE(inode->i_mode) & ~S_IALLUGO;
+		tmp_mode |= fsi->mode;
+		WRITE_ONCE(inode->i_mode, tmp_mode);
+	}
+
+	if (!remount || fsi->opts & BIT(Opt_uid))
+		inode->i_uid = fsi->uid;
+
+	if (!remount || fsi->opts & BIT(Opt_gid))
+		inode->i_gid = fsi->gid;
+
+	if (remount && (fsi->opts & BIT(Opt_uid) || fsi->opts & BIT(Opt_gid))) {
+
+		update_uid = fsi->opts & BIT(Opt_uid);
+		update_gid = fsi->opts & BIT(Opt_gid);
+
+		srcu_idx = eventfs_remount_lock();
+		rcu_read_lock();
+		list_for_each_entry_rcu(ti, &tracefs_inodes, list) {
+			if (update_uid) {
+				ti->flags &= ~TRACEFS_UID_PERM_SET;
+				ti->vfs_inode.i_uid = fsi->uid;
+			}
+
+			if (update_gid) {
+				ti->flags &= ~TRACEFS_GID_PERM_SET;
+				ti->vfs_inode.i_gid = fsi->gid;
+			}
+
+			/*
+			 * Note, the above ti->vfs_inode updates are
+			 * used in eventfs_remount() so they must come
+			 * before calling it.
+			 */
+			if (ti->flags & TRACEFS_EVENT_INODE)
+				eventfs_remount(ti, update_uid, update_gid);
+		}
+		rcu_read_unlock();
+		eventfs_remount_unlock(srcu_idx);
+	}
+
+	return 0;
+}
+
+static int tracefs_reconfigure(struct fs_context *fc)
+{
+	struct super_block *sb = fc->root->d_sb;
+	struct tracefs_fs_info *sb_opts = sb->s_fs_info;
+	struct tracefs_fs_info *new_opts = fc->s_fs_info;
+
+	if (!new_opts)
+		return 0;
+
+	sync_filesystem(sb);
+	/* structure copy of new mount options to sb */
+	*sb_opts = *new_opts;
+
+	return tracefs_apply_options(sb, true);
+}
+
+static int tracefs_show_options(struct seq_file *m, struct dentry *root)
+{
+	struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
+
+	if (!uid_eq(fsi->uid, GLOBAL_ROOT_UID))
+		seq_printf(m, ",uid=%u",
+			   from_kuid_munged(&init_user_ns, fsi->uid));
+	if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID))
+		seq_printf(m, ",gid=%u",
+			   from_kgid_munged(&init_user_ns, fsi->gid));
+	if (fsi->mode != TRACEFS_DEFAULT_MODE)
+		seq_printf(m, ",mode=%o", fsi->mode);
+
+	return 0;
+}
+
+static int tracefs_drop_inode(struct inode *inode)
+{
+	struct tracefs_inode *ti = get_tracefs(inode);
+
+	/*
+	 * This inode is being freed and cannot be used for
+	 * eventfs. Clear the flag so that it doesn't call into
+	 * eventfs during the remount flag updates. The eventfs_inode
+	 * gets freed after an SRCU cycle, so the content will still
+	 * be safe if the iteration is going on now.
+	 */
+	ti->flags &= ~TRACEFS_EVENT_INODE;
+
+	return 1;
+}
+
+static const struct super_operations tracefs_super_operations = {
+	.alloc_inode    = tracefs_alloc_inode,
+	.free_inode     = tracefs_free_inode,
+	.destroy_inode  = tracefs_destroy_inode,
+	.drop_inode     = tracefs_drop_inode,
+	.statfs		= simple_statfs,
+	.show_options	= tracefs_show_options,
+};
+
+/*
+ * It would be cleaner if eventfs had its own dentry ops.
+ *
+ * Note that d_revalidate is called potentially under RCU,
+ * so it can't take the eventfs mutex etc. It's fine - if
+ * we open a file just as it's marked dead, things will
+ * still work just fine, and just see the old stale case.
+ */
+static void tracefs_d_release(struct dentry *dentry)
+{
+	if (dentry->d_fsdata)
+		eventfs_d_release(dentry);
+}
+
+static int tracefs_d_revalidate(struct inode *inode, const struct qstr *name,
+				struct dentry *dentry, unsigned int flags)
+{
+	struct eventfs_inode *ei = dentry->d_fsdata;
+
+	return !(ei && ei->is_freed);
+}
+
+static int tracefs_d_delete(const struct dentry *dentry)
+{
+	/*
+	 * We want to keep eventfs dentries around but not tracefs
+	 * ones. eventfs dentries have content in d_fsdata.
+	 * Use d_fsdata to determine if it's a eventfs dentry or not.
+	 */
+	return dentry->d_fsdata == NULL;
+}
+
+static const struct dentry_operations tracefs_dentry_operations = {
+	.d_revalidate = tracefs_d_revalidate,
+	.d_release = tracefs_d_release,
+	.d_delete = tracefs_d_delete,
+};
+
+static int tracefs_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+	static const struct tree_descr trace_files[] = {{""}};
+	int err;
+
+	err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
+	if (err)
+		return err;
+
+	sb->s_op = &tracefs_super_operations;
+	tracefs_apply_options(sb, false);
+	set_default_d_op(sb, &tracefs_dentry_operations);
+
+	return 0;
+}
+
+static int tracefs_get_tree(struct fs_context *fc)
+{
+	int err = get_tree_single(fc, tracefs_fill_super);
+
+	if (err)
+		return err;
+
+	return tracefs_reconfigure(fc);
+}
+
+static void tracefs_free_fc(struct fs_context *fc)
+{
+	kfree(fc->s_fs_info);
+}
+
+static const struct fs_context_operations tracefs_context_ops = {
+	.free		= tracefs_free_fc,
+	.parse_param	= tracefs_parse_param,
+	.get_tree	= tracefs_get_tree,
+	.reconfigure	= tracefs_reconfigure,
+};
+
+static int tracefs_init_fs_context(struct fs_context *fc)
+{
+	struct tracefs_fs_info *fsi;
+
+	fsi = kzalloc_obj(struct tracefs_fs_info);
+	if (!fsi)
+		return -ENOMEM;
+
+	fsi->mode = TRACEFS_DEFAULT_MODE;
+
+	fc->s_fs_info = fsi;
+	fc->ops = &tracefs_context_ops;
+	return 0;
+}
+
+static struct file_system_type trace_fs_type = {
+	.owner =	THIS_MODULE,
+	.name =		"tracefs",
+	.init_fs_context = tracefs_init_fs_context,
+	.parameters	= tracefs_param_specs,
+	.kill_sb =	kill_anon_super,
+};
+MODULE_ALIAS_FS("tracefs");
+
+struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
+{
+	struct dentry *dentry;
+	int error;
+
+	pr_debug("tracefs: creating file '%s'\n",name);
+
+	error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
+			      &tracefs_mount_count);
+	if (error)
+		return ERR_PTR(error);
+
+	/* If the parent is not specified, we create it in the root.
+	 * We need the root dentry to do this, which is in the super
+	 * block. A pointer to that is in the struct vfsmount that we
+	 * have around.
+	 */
+	if (!parent)
+		parent = tracefs_mount->mnt_root;
+
+	dentry = simple_start_creating(parent, name);
+	if (IS_ERR(dentry))
+		simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+
+	return dentry;
+}
+
+struct dentry *tracefs_failed_creating(struct dentry *dentry)
+{
+	simple_done_creating(dentry);
+	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+	return NULL;
+}
+
+struct dentry *tracefs_end_creating(struct dentry *dentry)
+{
+	simple_done_creating(dentry);
+	return dentry;	// borrowed
+}
+
+/* Find the inode that this will use for default */
+static struct inode *instance_inode(struct dentry *parent, struct inode *inode)
+{
+	struct tracefs_inode *ti;
+
+	/* If parent is NULL then use root inode */
+	if (!parent)
+		return d_inode(inode->i_sb->s_root);
+
+	/* Find the inode that is flagged as an instance or the root inode */
+	while (!IS_ROOT(parent)) {
+		ti = get_tracefs(d_inode(parent));
+		if (ti->flags & TRACEFS_INSTANCE_INODE)
+			break;
+		parent = parent->d_parent;
+	}
+
+	return d_inode(parent);
+}
+
+/**
+ * tracefs_create_file - create a file in the tracefs filesystem
+ * @name: a pointer to a string containing the name of the file to create.
+ * @mode: the permission that the file should have.
+ * @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 tracefs filesystem.
+ * @data: a pointer to 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.
+ * @fops: a pointer to a struct file_operations that should be used for
+ *        this file.
+ *
+ * This is the basic "create a file" function for tracefs.  It allows for a
+ * wide range of flexibility in creating a file, or a directory (if you want
+ * to create a directory, the tracefs_create_dir() function is
+ * recommended to be used instead.)
+ *
+ * This function will return a pointer to a dentry if it succeeds.  This
+ * pointer must be passed to the tracefs_remove() function when the file is
+ * to be removed (no automatic cleanup happens if your module is unloaded,
+ * you are responsible here.)  If an error occurs, %NULL will be returned.
+ *
+ * If tracefs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ */
+struct dentry *tracefs_create_file(const char *name, umode_t mode,
+				   struct dentry *parent, void *data,
+				   const struct file_operations *fops)
+{
+	struct tracefs_inode *ti;
+	struct dentry *dentry;
+	struct inode *inode;
+
+	if (security_locked_down(LOCKDOWN_TRACEFS))
+		return NULL;
+
+	if (!(mode & S_IFMT))
+		mode |= S_IFREG;
+	BUG_ON(!S_ISREG(mode));
+	dentry = tracefs_start_creating(name, parent);
+
+	if (IS_ERR(dentry))
+		return NULL;
+
+	inode = tracefs_get_inode(dentry->d_sb);
+	if (unlikely(!inode))
+		return tracefs_failed_creating(dentry);
+
+	ti = get_tracefs(inode);
+	ti->private = instance_inode(parent, inode);
+
+	inode->i_mode = mode;
+	inode->i_op = &tracefs_file_inode_operations;
+	inode->i_fop = fops ? fops : &tracefs_file_operations;
+	inode->i_private = data;
+	inode->i_uid = d_inode(dentry->d_parent)->i_uid;
+	inode->i_gid = d_inode(dentry->d_parent)->i_gid;
+	d_make_persistent(dentry, inode);
+	fsnotify_create(d_inode(dentry->d_parent), dentry);
+	return tracefs_end_creating(dentry);
+}
+EXPORT_SYMBOL_GPL(tracefs_create_file);
+
+static struct dentry *__create_dir(const char *name, struct dentry *parent,
+				   const struct inode_operations *ops)
+{
+	struct tracefs_inode *ti;
+	struct dentry *dentry = tracefs_start_creating(name, parent);
+	struct inode *inode;
+
+	if (IS_ERR(dentry))
+		return NULL;
+
+	inode = tracefs_get_inode(dentry->d_sb);
+	if (unlikely(!inode))
+		return tracefs_failed_creating(dentry);
+
+	/* Do not set bits for OTH */
+	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;
+	inode->i_op = ops;
+	inode->i_fop = &simple_dir_operations;
+	inode->i_uid = d_inode(dentry->d_parent)->i_uid;
+	inode->i_gid = d_inode(dentry->d_parent)->i_gid;
+
+	ti = get_tracefs(inode);
+	ti->private = instance_inode(parent, inode);
+
+	/* directory inodes start off with i_nlink == 2 (for "." entry) */
+	inc_nlink(inode);
+	d_make_persistent(dentry, inode);
+	inc_nlink(d_inode(dentry->d_parent));
+	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
+	return tracefs_end_creating(dentry);
+}
+
+/**
+ * tracefs_create_dir - create a directory in the tracefs filesystem
+ * @name: a pointer to a string containing the name of the directory 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
+ *          directory will be created in the root of the tracefs filesystem.
+ *
+ * This function creates a directory in tracefs with the given name.
+ *
+ * This function will return a pointer to a dentry if it succeeds.  This
+ * pointer must be passed to the tracefs_remove() function when the file is
+ * to be removed. If an error occurs, %NULL will be returned.
+ *
+ * If tracing is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ */
+struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
+{
+	if (security_locked_down(LOCKDOWN_TRACEFS))
+		return NULL;
+
+	return __create_dir(name, parent, &tracefs_dir_inode_operations);
+}
+
+/**
+ * tracefs_create_instance_dir - create the tracing instances directory
+ * @name: The name of the instances directory to create
+ * @parent: The parent directory that the instances directory will exist
+ * @mkdir: The function to call when a mkdir is performed.
+ * @rmdir: The function to call when a rmdir is performed.
+ *
+ * Only one instances directory is allowed.
+ *
+ * The instances directory is special as it allows for mkdir and rmdir
+ * to be done by userspace. When a mkdir or rmdir is performed, the inode
+ * locks are released and the methods passed in (@mkdir and @rmdir) are
+ * called without locks and with the name of the directory being created
+ * within the instances directory.
+ *
+ * Returns the dentry of the instances directory.
+ */
+__init struct dentry *tracefs_create_instance_dir(const char *name,
+					  struct dentry *parent,
+					  int (*mkdir)(const char *name),
+					  int (*rmdir)(const char *name))
+{
+	struct dentry *dentry;
+
+	/* Only allow one instance of the instances directory. */
+	if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
+		return NULL;
+
+	dentry = __create_dir(name, parent, &tracefs_instance_dir_inode_operations);
+	if (!dentry)
+		return NULL;
+
+	tracefs_ops.mkdir = mkdir;
+	tracefs_ops.rmdir = rmdir;
+
+	return dentry;
+}
+
+static void remove_one(struct dentry *victim)
+{
+	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+}
+
+/**
+ * tracefs_remove - recursively removes a directory
+ * @dentry: a pointer to a the dentry of the directory to be removed.
+ *
+ * This function recursively removes a directory tree in tracefs that
+ * was previously created with a call to another tracefs function
+ * (like tracefs_create_file() or variants thereof.)
+ */
+void tracefs_remove(struct dentry *dentry)
+{
+	if (IS_ERR_OR_NULL(dentry))
+		return;
+
+	simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
+	simple_recursive_removal(dentry, remove_one);
+	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+}
+
+/**
+ * tracefs_initialized - Tells whether tracefs has been registered
+ */
+bool tracefs_initialized(void)
+{
+	return tracefs_registered;
+}
+
+static void init_once(void *foo)
+{
+	struct tracefs_inode *ti = (struct tracefs_inode *) foo;
+
+	/* inode_init_once() calls memset() on the vfs_inode portion */
+	inode_init_once(&ti->vfs_inode);
+
+	/* Zero out the rest */
+	memset_after(ti, 0, vfs_inode);
+}
+
+static int __init tracefs_init(void)
+{
+	int retval;
+
+	tracefs_inode_cachep = kmem_cache_create("tracefs_inode_cache",
+						 sizeof(struct tracefs_inode),
+						 0, (SLAB_RECLAIM_ACCOUNT|
+						     SLAB_ACCOUNT),
+						 init_once);
+	if (!tracefs_inode_cachep)
+		return -ENOMEM;
+
+	retval = sysfs_create_mount_point(kernel_kobj, "tracing");
+	if (retval)
+		return -EINVAL;
+
+	retval = register_filesystem(&trace_fs_type);
+	if (!retval)
+		tracefs_registered = true;
+
+	return retval;
+}
+core_initcall(tracefs_init);
diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h
new file mode 100644
index 000000000..c61481d04
--- /dev/null
+++ b/fs/tracefs/internal.h
@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TRACEFS_INTERNAL_H
+#define _TRACEFS_INTERNAL_H
+
+enum {
+	TRACEFS_EVENT_INODE		= BIT(1),
+	TRACEFS_GID_PERM_SET		= BIT(2),
+	TRACEFS_UID_PERM_SET		= BIT(3),
+	TRACEFS_INSTANCE_INODE		= BIT(4),
+};
+
+struct tracefs_inode {
+	struct inode            vfs_inode;
+	/* The below gets initialized with memset_after(ti, 0, vfs_inode) */
+	struct list_head	list;
+	unsigned long           flags;
+	void                    *private;
+};
+
+/*
+ * struct eventfs_attr - cache the mode and ownership of a eventfs entry
+ * @mode:	saved mode plus flags of what is saved
+ * @uid:	saved uid if changed
+ * @gid:	saved gid if changed
+ */
+struct eventfs_attr {
+	int				mode;
+	kuid_t				uid;
+	kgid_t				gid;
+};
+
+/*
+ * struct eventfs_inode - hold the properties of the eventfs directories.
+ * @list:	link list into the parent directory
+ * @rcu:	Union with @list for freeing
+ * @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
+ * @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
+ * @is_freed:	Flag set if the eventfs is on its way to be freed
+ *                Note if is_freed is set, then dentry is corrupted.
+ * @is_events:	Flag set for only the top level "events" directory
+ * @nr_entries: The number of items in @entries
+ * @ino:	The saved inode number
+ */
+struct eventfs_inode {
+	struct list_head	list;
+	union {
+		struct list_head	children;
+		struct rcu_head		rcu;
+	};
+	const struct eventfs_entry	*entries;
+	const char			*name;
+	struct eventfs_attr		*entry_attrs;
+	void				*data;
+	struct eventfs_attr		attr;
+	struct kref			kref;
+	unsigned int			is_freed:1;
+	unsigned int			is_events:1;
+	unsigned int			nr_entries:30;
+	unsigned int			ino;
+};
+
+static inline struct tracefs_inode *get_tracefs(const struct inode *inode)
+{
+	return container_of(inode, struct tracefs_inode, vfs_inode);
+}
+
+struct dentry *tracefs_start_creating(const char *name, struct dentry *parent);
+struct dentry *tracefs_end_creating(struct dentry *dentry);
+struct dentry *tracefs_failed_creating(struct dentry *dentry);
+struct inode *tracefs_get_inode(struct super_block *sb);
+
+void eventfs_remount(struct tracefs_inode *ti, bool update_uid, bool update_gid);
+void eventfs_d_release(struct dentry *dentry);
+
+int eventfs_remount_lock(void);
+void eventfs_remount_unlock(int srcu_idx);
+
+#endif /* _TRACEFS_INTERNAL_H */