[PATCH v4 03/10] eventfs: Implement eventfs dir creation functions

Ajay Kaher
2023-07-13T11:34:11Z

Adding eventfs_file structure which will hold properties of file or dir.

Adding following functions to add dir in eventfs:

eventfs_create_events_dir() will directly create events dir within
tracing folder.

eventfs_add_subsystem_dir() adds the information of subsystem_dir
to eventfs, and dynamically creates subsystem_dir directories when
they are accessed.

eventfs_add_dir() adds the information of the dir, within a
subsystem_dir, to eventfs and dynamically creates these directories
when they are accessed.

Adding tracefs_inode structure, this will help eventfs to keep track
of inode, flags and pointer to private date.

Signed-off-by: Ajay Kaher <akaher@vmware.com>
Co-developed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Tested-by: Ching-lin Yu <chinglinyu@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202305051619.9a469a9a-yujie.liu@intel.com
---
fs/tracefs/Makefile | 1 +
fs/tracefs/event_inode.c | 217 +++++++++++++++++++++++++++++++++++++++
fs/tracefs/inode.c | 8 +-
fs/tracefs/internal.h | 25 +++++
include/linux/tracefs.h | 11 ++
5 files changed, 258 insertions(+), 4 deletions(-)
create mode 100644 fs/tracefs/event_inode.c
create mode 100644 fs/tracefs/internal.h

diff --git a/fs/tracefs/Makefile b/fs/tracefs/Makefile
index 7c35a282b484..73c56da8e284 100644
--- a/fs/tracefs/Makefile
+++ b/fs/tracefs/Makefile
@@ -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

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
new file mode 100644
index 000000000000..4e7a8eccaa0b
--- /dev/null
+++ b/fs/tracefs/event_inode.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * event_inode.c - part of tracefs, a pseudo file system for activating tracing
+ *
+ * Copyright (C) 2020-22 VMware Inc, author: Steven Rostedt (VMware) <rostedt@goodmis.org>
+ * Copyright (C) 2020-22 VMware Inc, author: Ajay Kaher <akaher@vmware.com>
+ *
+ * eventfs is used to show trace events with one set of dentries
+ *
+ * eventfs stores meta-data of files/dirs and skip to create object of
+ * inodes/dentries. As and when requires, eventfs will create the
+ * inodes/dentries for only required files/directories. Also eventfs
+ * would delete the inodes/dentries once no more requires but preserve
+ * the meta data.
+ */
+#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 {
+ const char *name;
+ struct dentry *d_parent;
+ struct dentry *dentry;
+ struct list_head list;
+ struct eventfs_inode *ei;
+ const struct file_operations *fop;
+ const struct inode_operations *iop;
+ union {
+ struct rcu_head rcu;
+ struct llist_node llist; /* For freeing after RCU */
+ };
+ void *data;
+ umode_t mode;
+ bool created;
+};
+
+static DEFINE_MUTEX(eventfs_mutex);
+
+static const struct file_operations eventfs_file_operations = {
+};
+
+static const struct inode_operations eventfs_root_dir_inode_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 | S_IRWXU | S_IRUGO | S_IXUGO,
+ &eventfs_file_operations,
+ &eventfs_root_dir_inode_operations, NULL);
+
+ if (IS_ERR(ef))
+ return ef;
+
+ mutex_lock(&eventfs_mutex);
+ list_add_tail(&ef->list, &ei_parent->e_top_files);
+ ef->d_parent = parent;
+ 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 | S_IRWXU | S_IRUGO | S_IXUGO,
+ &eventfs_file_operations,
+ &eventfs_root_dir_inode_operations, NULL);
+
+ if (IS_ERR(ef))
+ return ef;
+
+ mutex_lock(&eventfs_mutex);
+ list_add_tail(&ef->list, &ef_parent->ei->e_top_files);
+ ef->d_parent = ef_parent->dentry;
+ mutex_unlock(&eventfs_mutex);
+ return ef;
+}
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index b0348efc0238..7ef3a02766f5 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -127,7 +127,7 @@ static const struct inode_operations tracefs_dir_inode_operations = {
.rmdir = tracefs_syscall_rmdir,
};

-static struct inode *tracefs_get_inode(struct super_block *sb)
+struct inode *tracefs_get_inode(struct super_block *sb)
{
struct inode *inode = new_inode(sb);
if (inode) {
@@ -399,7 +399,7 @@ static struct file_system_type trace_fs_type = {
};
MODULE_ALIAS_FS("tracefs");

-static struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
+struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
{
struct dentry *dentry;
int error;
@@ -437,7 +437,7 @@ static struct dentry *tracefs_start_creating(const char *name, struct dentry *pa
return dentry;
}

-static struct dentry *tracefs_failed_creating(struct dentry *dentry)
+struct dentry *tracefs_failed_creating(struct dentry *dentry)
{
inode_unlock(d_inode(dentry->d_parent));
dput(dentry);
@@ -445,7 +445,7 @@ static struct dentry *tracefs_failed_creating(struct dentry *dentry)
return NULL;
}

-static struct dentry *tracefs_end_creating(struct dentry *dentry)
+struct dentry *tracefs_end_creating(struct dentry *dentry)
{
inode_unlock(d_inode(dentry->d_parent));
return dentry;
diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h
new file mode 100644
index 000000000000..c443a0c32a8c
--- /dev/null
+++ b/fs/tracefs/internal.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TRACEFS_INTERNAL_H
+#define _TRACEFS_INTERNAL_H
+
+enum {
+ TRACEFS_EVENT_INODE = BIT(1),
+};
+
+struct tracefs_inode {
+ unsigned long flags;
+ void *private;
+ struct inode vfs_inode;
+};
+
+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);
+
+#endif /* _TRACEFS_INTERNAL_H */
diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h
index 99912445974c..432e5e6f7901 100644
--- a/include/linux/tracefs.h
+++ b/include/linux/tracefs.h
@@ -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);
--
2.39.0