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 with-in
tracing folder.
eventfs_add_subsystem_dir() will adds the info of subsystem_dir to
eventfs and dynamically create subsystem_dir as and when requires.
eventfs_add_dir() will add the info of dir (which is with-in
subsystem_dir) to eventfs and dynamically create these dir as
and when requires.
Signed-off-by: Ajay Kaher <akaher@xxxxxxxxxx>
Co-developed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Tested-by: Ching-lin Yu <chinglinyu@xxxxxxxxxx>
---
fs/tracefs/Makefile | 1 +
fs/tracefs/event_inode.c | 252 +++++++++++++++++++++++++++++++++++++++
include/linux/tracefs.h | 29 +++++
kernel/trace/trace.h | 1 +
4 files changed, 283 insertions(+)
create mode 100644 fs/tracefs/event_inode.c
diff --git a/fs/tracefs/Makefile b/fs/tracefs/Makefile
index 7c35a282b..73c56da8e 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 000000000..82caba7e9
--- /dev/null
+++ b/fs/tracefs/event_inode.c
@@ -0,0 +1,252 @@
+// 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@xxxxxxxxxxx>
+ * Copyright (C) 2020-22 VMware Inc, author: Ajay Kaher <akaher@xxxxxxxxxx>
+ *
+ * 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/security.h>
+#include <linux/tracefs.h>
+#include <linux/kref.h>
+#include <linux/delay.h>
+#include "internal.h"
+
+/**
+ * eventfs_dentry_to_rwsem - Return corresponding eventfs_rwsem
+ * @dentry: a pointer to dentry
+ *
+ * helper function to return crossponding eventfs_rwsem for given dentry
+ */
+static struct rw_semaphore *eventfs_dentry_to_rwsem(struct dentry *dentry)
+{
+ if (S_ISDIR(dentry->d_inode->i_mode))
+ return (struct rw_semaphore *)dentry->d_inode->i_private;
+ else
+ return (struct rw_semaphore *)dentry->d_parent->d_inode->i_private;
+}
+
+/**
+ * eventfs_down_read - acquire read lock function
+ * @eventfs_rwsem: a pointer to rw_semaphore
+ *
+ * helper function to perform read lock, skip locking if caller task already
+ * own the lock. read lock requires for lookup(), release() and these also
+ * called with-in open(), remove() which already hold the read/write lock.
+ */
+static void eventfs_down_read(struct rw_semaphore *eventfs_rwsem)
+{
+ down_read_nested(eventfs_rwsem, SINGLE_DEPTH_NESTING);
+}
+
+/**
+ * eventfs_up_read - release read lock function
+ * @eventfs_rwsem: a pointer to rw_semaphore
+ *
+ * helper function to release eventfs_rwsem lock if locked
+ */
+static void eventfs_up_read(struct rw_semaphore *eventfs_rwsem)
+{
+ up_read(eventfs_rwsem);
+}
+
+/**
+ * eventfs_down_write - acquire write lock function
+ * @eventfs_rwsem: a pointer to rw_semaphore
+ *
+ * helper function to perform write lock on eventfs_rwsem
+ */
+static void eventfs_down_write(struct rw_semaphore *eventfs_rwsem)
+{
+ while (!down_write_trylock(eventfs_rwsem))
+ msleep(10);
+}
+
+/**
+ * eventfs_up_write - release write lock function
+ * @eventfs_rwsem: a pointer to rw_semaphore
+ *
+ * helper function to perform write lock on eventfs_rwsem
+ */
+static void eventfs_up_write(struct rw_semaphore *eventfs_rwsem)
+{
+ up_write(eventfs_rwsem);
+}
+
+static const struct file_operations eventfs_file_operations = {
+};
+
+static const struct inode_operations eventfs_root_dir_inode_operations = {
+};
+
+/**
+ * eventfs_create_events_dir - create the trace event structure
+ * @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.
+ * @eventfs_rwsem: a pointer to rw_semaphore
+ *
+ * This function creates the top of the trace event directory.
+ */
+struct dentry *eventfs_create_events_dir(const char *name,
+ struct dentry *parent,
+ struct rw_semaphore *eventfs_rwsem)
+{
+ 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_rwsem(eventfs_rwsem);
+ 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;
+ inode->i_private = eventfs_rwsem;
+
+ /* 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: a pointer to a string containing the name of the file to create.
+ * @parent: a pointer to the parent dentry for this dir.
+ * @eventfs_rwsem: a pointer to rw_semaphore
+ *
+ * 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 rw_semaphore *eventfs_rwsem)
+{
+ 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 = kzalloc(sizeof(*ef), GFP_KERNEL);
+ if (!ef)
+ return ERR_PTR(-ENOMEM);
+
+ ef->ei = kzalloc(sizeof(*ef->ei), GFP_KERNEL);
+ if (!ef->ei) {
+ kfree(ef);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ INIT_LIST_HEAD(&ef->ei->e_top_files);
+
+ ef->name = kstrdup(name, GFP_KERNEL);
+ if (!ef->name) {
+ kfree(ef->ei);
+ kfree(ef);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ ef->mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+ ef->iop = &eventfs_root_dir_inode_operations;
+ ef->fop = &eventfs_file_operations;
+ ef->dentry = NULL;
+ ef->created = false;
+ ef->d_parent = parent;
+ ef->data = eventfs_rwsem;
+
+ eventfs_down_write(eventfs_rwsem);
+ list_add_tail(&ef->list, &ei_parent->e_top_files);
+ eventfs_up_write(eventfs_rwsem);
+ return ef;
+}
+
+/**
+ * eventfs_add_dir - add eventfs dir to list to create later
+ * @name: a pointer to a string containing the name of the file to create.
+ * @ef_parent: a pointer to the parent eventfs_file for this dir.
+ * @eventfs_rwsem: a pointer to rw_semaphore
+ *
+ * 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 rw_semaphore *eventfs_rwsem)
+{
+ struct eventfs_file *ef;
+
+ if (!ef_parent)
+ return ERR_PTR(-EINVAL);
+
+ ef = kzalloc(sizeof(*ef), GFP_KERNEL);
+ if (!ef)
+ return ERR_PTR(-ENOMEM);
+
+ ef->ei = kzalloc(sizeof(*ef->ei), GFP_KERNEL);
+ if (!ef->ei) {
+ kfree(ef);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ INIT_LIST_HEAD(&ef->ei->e_top_files);
+
+ ef->name = kstrdup(name, GFP_KERNEL);
+ if (!ef->name) {
+ kfree(ef->ei);
+ kfree(ef);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ ef->mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+ ef->iop = &eventfs_root_dir_inode_operations;
+ ef->fop = &eventfs_file_operations;
+ ef->created = false;
+ ef->dentry = NULL;
+ ef->d_parent = NULL;
+ ef->data = eventfs_rwsem;
+
+ eventfs_down_write(eventfs_rwsem);
+ list_add_tail(&ef->list, &ef_parent->ei->e_top_files);
+ eventfs_up_write(eventfs_rwsem);
+ return ef;
+}
diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h
index 999124459..aeca6761f 100644
--- a/include/linux/tracefs.h
+++ b/include/linux/tracefs.h
@@ -21,6 +21,35 @@ struct file_operations;
#ifdef CONFIG_TRACING
+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;
+ void *data;
+ umode_t mode;
+ bool created;
+};
+
+struct dentry *eventfs_create_events_dir(const char *name,
+ struct dentry *parent,
+ struct rw_semaphore *eventfs_rwsem);
+
+struct eventfs_file *eventfs_add_subsystem_dir(const char *name,
+ struct dentry *parent,
+ struct rw_semaphore *eventfs_rwsem);
+
+struct eventfs_file *eventfs_add_dir(const char *name,
+ struct eventfs_file *ef_parent,
+ struct rw_semaphore *eventfs_rwsem);
+
struct dentry *tracefs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 616e1aa1c..3726725c8 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -359,6 +359,7 @@ struct trace_array {
struct dentry *options;
struct dentry *percpu_dir;
struct dentry *event_dir;
+ struct rw_semaphore eventfs_rwsem;
struct trace_options *topts;
struct list_head systems;
struct list_head events;
--
2.39.0
