tracing: Convert the tracing facility over to use tracefs

debugfs was fine for the tracing facility as a quick way to get
an interface. Now that tracing has matured, it should separate itself
from debugfs such that it can be mounted separately without needing
to mount all of debugfs with it. That is, users resist using tracing
because it requires mounting debugfs. Having tracing have its own file
system lets users get the features of tracing without needing to bring
in the rest of the kernel's debug infrastructure.

Another reason for tracefs is that debubfs does not support mkdir.
Currently, to create instances, one does a mkdir in the tracing/instance
directory. This is implemented via a hack that forces debugfs to do
something it is not intended on doing. By converting over to tracefs, this
hack can be removed and mkdir can be properly implemented. This patch does
not address this yet, but it lays the ground work for that to be done.

Signed-off-by: Steven Rostedt <[e-mail]>

kernel/trace/ftrace.c

···
 #include <linux/kallsyms.h>
 #include <linux/seq_file.h>
 #include <linux/suspend.h>
-#include <linux/debugfs.h>
+#include <linux/tracefs.h>
 #include <linux/hardirq.h>
 #include <linux/kthread.h>
 #include <linux/uaccess.h>
···
 	.stat_show	= function_stat_show
 };
 
-static __init void ftrace_profile_debugfs(struct dentry *d_tracer)
+static __init void ftrace_profile_tracefs(struct dentry *d_tracer)
 {
 	struct ftrace_profile_stat *stat;
 	struct dentry *entry;
···
 		}
 	}
 
-	entry = debugfs_create_file("function_profile_enabled", 0644,
+	entry = tracefs_create_file("function_profile_enabled", 0644,
 				    d_tracer, NULL, &ftrace_profile_fops);
 	if (!entry)
-		pr_warning("Could not create debugfs "
+		pr_warning("Could not create tracefs "
 			   "'function_profile_enabled' entry\n");
 }
 
 #else /* CONFIG_FUNCTION_PROFILER */
-static __init void ftrace_profile_debugfs(struct dentry *d_tracer)
+static __init void ftrace_profile_tracefs(struct dentry *d_tracer)
 {
 }
 #endif /* CONFIG_FUNCTION_PROFILER */
···
 	mutex_unlock(&ftrace_lock);
 }
 
-static __init int ftrace_init_dyn_debugfs(struct dentry *d_tracer)
+static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer)
 {
 
 	trace_create_file("available_filter_functions", 0444,
···
 }
 core_initcall(ftrace_nodyn_init);
 
-static inline int ftrace_init_dyn_debugfs(struct dentry *d_tracer) { return 0; }
+static inline int ftrace_init_dyn_tracefs(struct dentry *d_tracer) { return 0; }
 static inline void ftrace_startup_enable(int command) { }
 static inline void ftrace_startup_all(int command) { }
 /* Keep as macros so we do not need to define the commands */
···
 	.release	= ftrace_pid_release,
 };
 
-static __init int ftrace_init_debugfs(void)
+static __init int ftrace_init_tracefs(void)
 {
 	struct dentry *d_tracer;
 
···
 	if (IS_ERR(d_tracer))
 		return 0;
 
-	ftrace_init_dyn_debugfs(d_tracer);
+	ftrace_init_dyn_tracefs(d_tracer);
 
 	trace_create_file("set_ftrace_pid", 0644, d_tracer,
 			    NULL, &ftrace_pid_fops);
 
-	ftrace_profile_debugfs(d_tracer);
+	ftrace_profile_tracefs(d_tracer);
 
 	return 0;
 }
-fs_initcall(ftrace_init_debugfs);
+fs_initcall(ftrace_init_tracefs);
 
 /**
  * ftrace_kill - kill ftrace

kernel/trace/trace.c

···
 #include <linux/notifier.h>
 #include <linux/irqflags.h>
 #include <linux/debugfs.h>
+#include <linux/tracefs.h>
 #include <linux/pagemap.h>
 #include <linux/hardirq.h>
 #include <linux/linkage.h>
···
 
 static struct dentry *tracing_get_dentry(struct trace_array *tr)
 {
+	if (WARN_ON(!tr->dir))
+		return ERR_PTR(-ENODEV);
+
+	/* Top directory uses NULL as the parent */
+	if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
+		return NULL;
+
+	/* All sub buffers have a descriptor */
 	return tr->dir;
 }
 
···
 	if (IS_ERR(d_tracer))
 		return NULL;
 
-	tr->percpu_dir = debugfs_create_dir("per_cpu", d_tracer);
+	tr->percpu_dir = tracefs_create_dir("per_cpu", d_tracer);
 
 	WARN_ONCE(!tr->percpu_dir,
-		  "Could not create debugfs directory 'per_cpu/%d'\n", cpu);
+		  "Could not create tracefs directory 'per_cpu/%d'\n", cpu);
 
 	return tr->percpu_dir;
 }
···
 }
 
 static void
-tracing_init_debugfs_percpu(struct trace_array *tr, long cpu)
+tracing_init_tracefs_percpu(struct trace_array *tr, long cpu)
 {
 	struct dentry *d_percpu = tracing_dentry_percpu(tr, cpu);
 	struct dentry *d_cpu;
···
 		return;
 
 	snprintf(cpu_dir, 30, "cpu%ld", cpu);
-	d_cpu = debugfs_create_dir(cpu_dir, d_percpu);
+	d_cpu = tracefs_create_dir(cpu_dir, d_percpu);
 	if (!d_cpu) {
-		pr_warning("Could not create debugfs '%s' entry\n", cpu_dir);
+		pr_warning("Could not create tracefs '%s' entry\n", cpu_dir);
 		return;
 	}
 
···
 {
 	struct dentry *ret;
 
-	ret = debugfs_create_file(name, mode, parent, data, fops);
+	ret = tracefs_create_file(name, mode, parent, data, fops);
 	if (!ret)
-		pr_warning("Could not create debugfs '%s' entry\n", name);
+		pr_warning("Could not create tracefs '%s' entry\n", name);
 
 	return ret;
 }
···
 	if (IS_ERR(d_tracer))
 		return NULL;
 
-	tr->options = debugfs_create_dir("options", d_tracer);
+	tr->options = tracefs_create_dir("options", d_tracer);
 	if (!tr->options) {
-		pr_warning("Could not create debugfs directory 'options'\n");
+		pr_warning("Could not create tracefs directory 'options'\n");
 		return NULL;
 	}
 
···
 		return;
 
 	for (cnt = 0; topts[cnt].opt; cnt++)
-		debugfs_remove(topts[cnt].entry);
+		tracefs_remove(topts[cnt].entry);
 
 	kfree(topts);
 }
···
 struct dentry *trace_instance_dir;
 
 static void
-init_tracer_debugfs(struct trace_array *tr, struct dentry *d_tracer);
+init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer);
 
 static int
 allocate_trace_buffer(struct trace_array *tr, struct trace_buffer *buf, int size)
···
 	if (allocate_trace_buffers(tr, trace_buf_size) < 0)
 		goto out_free_tr;
 
-	tr->dir = debugfs_create_dir(name, trace_instance_dir);
+	tr->dir = tracefs_create_dir(name, trace_instance_dir);
 	if (!tr->dir)
 		goto out_free_tr;
 
 	ret = event_trace_add_tracer(tr->dir, tr);
 	if (ret) {
-		debugfs_remove_recursive(tr->dir);
+		tracefs_remove_recursive(tr->dir);
 		goto out_free_tr;
 	}
 
-	init_tracer_debugfs(tr, tr->dir);
+	init_tracer_tracefs(tr, tr->dir);
 
 	list_add(&tr->list, &ftrace_trace_arrays);
 
···
 		return -ENOENT;
 
 	/*
-	 * The inode mutex is locked, but debugfs_create_dir() will also
+	 * The inode mutex is locked, but tracefs_create_dir() will also
 	 * take the mutex. As the instances directory can not be destroyed
 	 * or changed in any other way, it is safe to unlock it, and
 	 * let the dentry try. If two users try to make the same dir at
···
 	mutex_unlock(&dentry->d_inode->i_mutex);
 
 	/*
-	 * The inode mutex is locked, but debugfs_create_dir() will also
+	 * The inode mutex is locked, but tracefs_create_dir() will also
 	 * take the mutex. As the instances directory can not be destroyed
 	 * or changed in any other way, it is safe to unlock it, and
 	 * let the dentry try. If two users try to make the same dir at
···
 
 static __init void create_trace_instances(struct dentry *d_tracer)
 {
-	trace_instance_dir = debugfs_create_dir("instances", d_tracer);
+	trace_instance_dir = tracefs_create_dir("instances", d_tracer);
 	if (WARN_ON(!trace_instance_dir))
 		return;
 
···
 }
 
 static void
-init_tracer_debugfs(struct trace_array *tr, struct dentry *d_tracer)
+init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
 {
 	int cpu;
 
···
 #endif
 
 	for_each_tracing_cpu(cpu)
-		tracing_init_debugfs_percpu(tr, cpu);
+		tracing_init_tracefs_percpu(tr, cpu);
 
 }
 
···
 		return ERR_PTR(-ENOMEM);
 	}
 
-	return tr->dir;
+	return NULL;
 }
 
-static __init int tracer_init_debugfs(void)
+static __init int tracer_init_tracefs(void)
 {
 	struct dentry *d_tracer;
 
···
 	if (IS_ERR(d_tracer))
 		return 0;
 
-	init_tracer_debugfs(&global_trace, d_tracer);
+	init_tracer_tracefs(&global_trace, d_tracer);
 
 	trace_create_file("tracing_thresh", 0644, d_tracer,
 			&global_trace, &tracing_thresh_fops);
···
 	return 0;
 }
 
-fs_initcall(tracer_init_debugfs);
+fs_initcall(tracer_init_tracefs);
 late_initcall(clear_boot_tracer);

kernel/trace/trace.h

···
 
 
 /**
- * struct tracer - a specific tracer and its callbacks to interact with debugfs
+ * struct tracer - a specific tracer and its callbacks to interact with tracefs
  * @name: the name chosen to select it on the available_tracers file
  * @init: called when one switches to this tracer (echo name > current_tracer)
  * @reset: called when one switches to another tracer

kernel/trace/trace_events.c

···
 #include <linux/workqueue.h>
 #include <linux/spinlock.h>
 #include <linux/kthread.h>
-#include <linux/debugfs.h>
+#include <linux/tracefs.h>
 #include <linux/uaccess.h>
 #include <linux/module.h>
 #include <linux/ctype.h>
···
 		return;
 
 	if (!--dir->nr_events) {
-		debugfs_remove_recursive(dir->entry);
+		tracefs_remove_recursive(dir->entry);
 		list_del(&dir->list);
 		__put_system_dir(dir);
 	}
···
 		}
 		spin_unlock(&dir->d_lock);
 
-		debugfs_remove_recursive(dir);
+		tracefs_remove_recursive(dir);
 	}
 
 	list_del(&file->list);
···
 	} else
 		__get_system(system);
 
-	dir->entry = debugfs_create_dir(name, parent);
+	dir->entry = tracefs_create_dir(name, parent);
 	if (!dir->entry) {
 		pr_warn("Failed to create system directory %s\n", name);
 		__put_system(system);
···
 	dir->subsystem = system;
 	file->system = dir;
 
-	entry = debugfs_create_file("filter", 0644, dir->entry, dir,
+	entry = tracefs_create_file("filter", 0644, dir->entry, dir,
 				    &ftrace_subsystem_filter_fops);
 	if (!entry) {
 		kfree(system->filter);
 		system->filter = NULL;
-		pr_warn("Could not create debugfs '%s/filter' entry\n", name);
+		pr_warn("Could not create tracefs '%s/filter' entry\n", name);
 	}
 
 	trace_create_file("enable", 0644, dir->entry, dir,
···
 		d_events = parent;
 
 	name = ftrace_event_name(call);
-	file->dir = debugfs_create_dir(name, d_events);
+	file->dir = tracefs_create_dir(name, d_events);
 	if (!file->dir) {
-		pr_warn("Could not create debugfs '%s' directory\n", name);
+		pr_warn("Could not create tracefs '%s' directory\n", name);
 		return -1;
 	}
 
···
 /*
  * The top level array has already had its ftrace_event_file
  * descriptors created in order to allow for early events to
- * be recorded. This function is called after the debugfs has been
+ * be recorded. This function is called after the tracefs has been
  * initialized, and we now have to create the files associated
  * to the events.
  */
···
 	struct dentry *d_events;
 	struct dentry *entry;
 
-	entry = debugfs_create_file("set_event", 0644, parent,
+	entry = tracefs_create_file("set_event", 0644, parent,
 				    tr, &ftrace_set_event_fops);
 	if (!entry) {
-		pr_warn("Could not create debugfs 'set_event' entry\n");
+		pr_warn("Could not create tracefs 'set_event' entry\n");
 		return -ENOMEM;
 	}
 
-	d_events = debugfs_create_dir("events", parent);
+	d_events = tracefs_create_dir("events", parent);
 	if (!d_events) {
-		pr_warn("Could not create debugfs 'events' directory\n");
+		pr_warn("Could not create tracefs 'events' directory\n");
 		return -ENOMEM;
 	}
 
···
 
 	down_write(&trace_event_sem);
 	__trace_remove_event_dirs(tr);
-	debugfs_remove_recursive(tr->event_dir);
+	tracefs_remove_recursive(tr->event_dir);
 	up_write(&trace_event_sem);
 
 	tr->event_dir = NULL;
···
 	if (IS_ERR(d_tracer))
 		return 0;
 
-	entry = debugfs_create_file("available_events", 0444, d_tracer,
+	entry = tracefs_create_file("available_events", 0444, d_tracer,
 				    tr, &ftrace_avail_fops);
 	if (!entry)
-		pr_warn("Could not create debugfs 'available_events' entry\n");
+		pr_warn("Could not create tracefs 'available_events' entry\n");
 
 	if (trace_define_common_fields())
 		pr_warn("tracing: Failed to allocate common fields");

kernel/trace/trace_functions_graph.c

···
  * is Copyright (c) Steven Rostedt <[e-mail]>
  *
  */
-#include <linux/debugfs.h>
 #include <linux/uaccess.h>
 #include <linux/ftrace.h>
 #include <linux/slab.h>
···
 	 * The curr_ret_stack is initialized to -1 and get increased
 	 * in this function.  So it can be less than -1 only if it was
 	 * filtered out via ftrace_graph_notrace_addr() which can be
-	 * set from set_graph_notrace file in debugfs by user.
+	 * set from set_graph_notrace file in tracefs by user.
 	 */
 	if (current->curr_ret_stack < -1)
 		return -EBUSY;
···
 	.llseek		= generic_file_llseek,
 };
 
-static __init int init_graph_debugfs(void)
+static __init int init_graph_tracefs(void)
 {
 	struct dentry *d_tracer;
 
···
 
 	return 0;
 }
-fs_initcall(init_graph_debugfs);
+fs_initcall(init_graph_tracefs);
 
 static __init int init_graph_trace(void)
 {

kernel/trace/trace_kprobe.c

···
 	return ret;
 }
 
-/* Make a debugfs interface for controlling probe points */
+/* Make a tracefs interface for controlling probe points */
 static __init int init_kprobe_trace(void)
 {
 	struct dentry *d_tracer;
···
 	if (IS_ERR(d_tracer))
 		return 0;
 
-	entry = debugfs_create_file("kprobe_events", 0644, d_tracer,
+	entry = tracefs_create_file("kprobe_events", 0644, d_tracer,
 				    NULL, &kprobe_events_ops);
 
 	/* Event list interface */
 	if (!entry)
-		pr_warning("Could not create debugfs "
+		pr_warning("Could not create tracefs "
 			   "'kprobe_events' entry\n");
 
 	/* Profile interface */
-	entry = debugfs_create_file("kprobe_profile", 0444, d_tracer,
+	entry = tracefs_create_file("kprobe_profile", 0444, d_tracer,
 				    NULL, &kprobe_profile_ops);
 
 	if (!entry)
-		pr_warning("Could not create debugfs "
+		pr_warning("Could not create tracefs "
 			   "'kprobe_profile' entry\n");
 	return 0;
 }

kernel/trace/trace_probe.h

···
 #include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/smp.h>
-#include <linux/debugfs.h>
+#include <linux/tracefs.h>
 #include <linux/types.h>
 #include <linux/string.h>
 #include <linux/ctype.h>

kernel/trace/trace_stat.c

···
 #include <linux/list.h>
 #include <linux/slab.h>
 #include <linux/rbtree.h>
-#include <linux/debugfs.h>
+#include <linux/tracefs.h>
 #include "trace_stat.h"
 #include "trace.h"
 
···
 
 static void destroy_session(struct stat_session *session)
 {
-	debugfs_remove(session->file);
+	tracefs_remove(session->file);
 	__reset_stat_session(session);
 	mutex_destroy(&session->stat_mutex);
 	kfree(session);
···
 	if (IS_ERR(d_tracing))
 		return 0;
 
-	stat_dir = debugfs_create_dir("trace_stat", d_tracing);
+	stat_dir = tracefs_create_dir("trace_stat", d_tracing);
 	if (!stat_dir)
-		pr_warning("Could not create debugfs "
+		pr_warning("Could not create tracefs "
 			   "'trace_stat' entry\n");
 	return 0;
 }
···
 	if (!stat_dir && tracing_stat_init())
 		return -ENODEV;
 
-	session->file = debugfs_create_file(session->ts->name, 0644,
+	session->file = tracefs_create_file(session->ts->name, 0644,
 					    stat_dir,
 					    session, &tracing_stat_fops);
 	if (!session->file)