[for-next][PATCH 0/7] tracing: Add new filesystem tracefs

[for-next][PATCH 0/7] tracing: Add new filesystem tracefs

[Steven Rostedt]

Al,

I know that you do not like the releasing of the parent i_mutex lock.
But it is no different than what we do today, except that we move the
release out of the tracing code and into the tracefs code.

This still gives us the separate tracefs filesystem that will let
users mount it without needing to mount debugfs, so I want to get this
into 3.20.

These are the patches that I plan on submitting, and will soon be adding
to my linux-next branch, to be included in linux-next.

-- Steve


  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
ftrace/tracefs

Head SHA1: eae473581cf93dad94ca833aa961c033c6a43924


Steven Rostedt (Red Hat) (7):
      tracing: Only create tracer options files if directory exists
      tracing: Create cmdline tracer options on tracing fs init
      tracefs: Add new tracefs file system
      tracing: Convert the tracing facility over to use tracefs
      tracing: Automatically mount tracefs on debugfs/tracing
      tracefs: Add directory /sys/kernel/tracing
      tracing: Have mkdir and rmdir be part of tracefs

----
 fs/Makefile                          |   1 +
 fs/tracefs/Makefile                  |   4 +
 fs/tracefs/inode.c                   | 650 +++++++++++++++++++++++++++++++++++
 include/linux/tracefs.h              |  45 +++
 include/uapi/linux/magic.h           |   2 +
 kernel/trace/ftrace.c                |  22 +-
 kernel/trace/trace.c                 | 187 +++++-----
 kernel/trace/trace.h                 |   2 +-
 kernel/trace/trace_events.c          |  32 +-
 kernel/trace/trace_functions_graph.c |   7 +-
 kernel/trace/trace_kprobe.c          |  10 +-
 kernel/trace/trace_probe.h           |   2 +-
 kernel/trace/trace_stat.c            |  10 +-
 13 files changed, 832 insertions(+), 142 deletions(-)

[for-next][PATCH 1/7] tracing: Only create tracer options files if directory exists

[Steven Rostedt]

[-- Attachment #1: 0001-tracing-Only-create-tracer-options-files-if-director.patch --]
[-- Type: text/plain, Size: 1072 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

Do not bother creating tracer options if no tracing directory
exists. If a tracer is enabled via the command line, and is
started before the tracing directory is created, then it wont have
its tracer specific options created.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 38c613ede10d..d4627f15407a 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4172,8 +4172,11 @@ static int tracing_set_tracer(struct trace_array *tr, const char *buf)
 		free_snapshot(tr);
 	}
 #endif
-	/* Currently, only the top instance has options */
-	if (tr->flags & TRACE_ARRAY_FL_GLOBAL) {
+	/*
+	 * Only enable if the directory has been created already.
+	 * Currently, only the top instance has options
+	 */
+	if (tr->dir && tr->flags & TRACE_ARRAY_FL_GLOBAL) {
 		destroy_trace_option_files(topts);
 		topts = create_trace_option_files(tr, t);
 	}
-- 
2.1.4

[for-next][PATCH 2/7] tracing: Create cmdline tracer options on tracing fs init

[Steven Rostedt]

[-- Attachment #1: 0002-tracing-Create-cmdline-tracer-options-on-tracing-fs-.patch --]
[-- Type: text/plain, Size: 2229 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

The options for cmdline tracers are not created if the debugfs system
is not ready yet. If tracing has started before debugfs is up, then the
option files for the tracer are not created. Create them when creating
the tracing directory if the current tracer requires option files.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d4627f15407a..05e0e50539fc 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4105,9 +4105,24 @@ static void tracing_set_nop(struct trace_array *tr)
 	tr->current_trace = &nop_trace;
 }
 
-static int tracing_set_tracer(struct trace_array *tr, const char *buf)
+static void update_tracer_options(struct trace_array *tr, struct tracer *t)
 {
 	static struct trace_option_dentry *topts;
+
+	/* Only enable if the directory has been created already. */
+	if (!tr->dir)
+		return;
+
+	/* Currently, only the top instance has options */
+	if (!(tr->flags & TRACE_ARRAY_FL_GLOBAL))
+		return;
+
+	destroy_trace_option_files(topts);
+	topts = create_trace_option_files(tr, t);
+}
+
+static int tracing_set_tracer(struct trace_array *tr, const char *buf)
+{
 	struct tracer *t;
 #ifdef CONFIG_TRACER_MAX_TRACE
 	bool had_max_tr;
@@ -4172,14 +4187,7 @@ static int tracing_set_tracer(struct trace_array *tr, const char *buf)
 		free_snapshot(tr);
 	}
 #endif
-	/*
-	 * Only enable if the directory has been created already.
-	 * Currently, only the top instance has options
-	 */
-	if (tr->dir && tr->flags & TRACE_ARRAY_FL_GLOBAL) {
-		destroy_trace_option_files(topts);
-		topts = create_trace_option_files(tr, t);
-	}
+	update_tracer_options(tr, t);
 
 #ifdef CONFIG_TRACER_MAX_TRACE
 	if (t->use_max_tr && !had_max_tr) {
@@ -6578,6 +6586,10 @@ static __init int tracer_init_debugfs(void)
 
 	create_trace_options_dir(&global_trace);
 
+	/* If the tracer was started via cmdline, create options for it here */
+	if (global_trace.current_trace != &nop_trace)
+		update_tracer_options(&global_trace, global_trace.current_trace);
+
 	return 0;
 }
 
-- 
2.1.4

[for-next][PATCH 3/7] tracefs: Add new tracefs file system

[Steven Rostedt]

[-- Attachment #1: 0003-tracefs-Add-new-tracefs-file-system.patch --]
[-- Type: text/plain, Size: 17639 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

Add a separate file system to handle the tracing directory. Currently it
is part of debugfs, but that is starting to show its limits.

One thing is that in order to access the tracing infrastructure, you need
to mount debugfs. As that includes debugging from all sorts of sub systems
in the kernel, it is not considered advisable to mount such an all
encompassing debugging system.

Having the tracing system in its own file systems gives access to the
tracing sub system without needing to include all other systems.

Another problem with tracing using the debugfs system is that the
instances use mkdir to create sub buffers. debugfs does not support mkdir
from userspace so to implement it, special hacks were used. By controlling
the file system that the tracing infrastructure uses, this can be properly
done without hacks.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 fs/Makefile                |   1 +
 fs/tracefs/Makefile        |   4 +
 fs/tracefs/inode.c         | 522 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/tracefs.h    |  41 ++++
 include/uapi/linux/magic.h |   2 +
 5 files changed, 570 insertions(+)
 create mode 100644 fs/tracefs/Makefile
 create mode 100644 fs/tracefs/inode.c
 create mode 100644 include/linux/tracefs.h

diff --git a/fs/Makefile b/fs/Makefile
index bedff48e8fdc..d244b8d973ac 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -118,6 +118,7 @@ obj-$(CONFIG_HOSTFS)		+= hostfs/
 obj-$(CONFIG_HPPFS)		+= hppfs/
 obj-$(CONFIG_CACHEFILES)	+= cachefiles/
 obj-$(CONFIG_DEBUG_FS)		+= debugfs/
+obj-$(CONFIG_TRACING)		+= tracefs/
 obj-$(CONFIG_OCFS2_FS)		+= ocfs2/
 obj-$(CONFIG_BTRFS_FS)		+= btrfs/
 obj-$(CONFIG_GFS2_FS)           += gfs2/
diff --git a/fs/tracefs/Makefile b/fs/tracefs/Makefile
new file mode 100644
index 000000000000..82fa35b656c4
--- /dev/null
+++ b/fs/tracefs/Makefile
@@ -0,0 +1,4 @@
+tracefs-objs	:= inode.o
+
+obj-$(CONFIG_TRACING)	+= tracefs.o
+
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
new file mode 100644
index 000000000000..5b1547a452d8
--- /dev/null
+++ b/fs/tracefs/inode.c
@@ -0,0 +1,522 @@
+/*
+ *  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>
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License version
+ *	2 as published by the Free Software Foundation.
+ *
+ * tracefs is the file system that is used by the tracing infrastructure.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/tracefs.h>
+#include <linux/fsnotify.h>
+#include <linux/seq_file.h>
+#include <linux/parser.h>
+#include <linux/magic.h>
+#include <linux/slab.h>
+
+#define TRACEFS_DEFAULT_MODE	0700
+
+static struct vfsmount *tracefs_mount;
+static int tracefs_mount_count;
+static bool tracefs_registered;
+
+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 inode *tracefs_get_inode(struct super_block *sb)
+{
+	struct inode *inode = new_inode(sb);
+	if (inode) {
+		inode->i_ino = get_next_ino();
+		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+	}
+	return inode;
+}
+
+struct tracefs_mount_opts {
+	kuid_t uid;
+	kgid_t gid;
+	umode_t mode;
+};
+
+enum {
+	Opt_uid,
+	Opt_gid,
+	Opt_mode,
+	Opt_err
+};
+
+static const match_table_t tokens = {
+	{Opt_uid, "uid=%u"},
+	{Opt_gid, "gid=%u"},
+	{Opt_mode, "mode=%o"},
+	{Opt_err, NULL}
+};
+
+struct tracefs_fs_info {
+	struct tracefs_mount_opts mount_opts;
+};
+
+static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
+{
+	substring_t args[MAX_OPT_ARGS];
+	int option;
+	int token;
+	kuid_t uid;
+	kgid_t gid;
+	char *p;
+
+	opts->mode = TRACEFS_DEFAULT_MODE;
+
+	while ((p = strsep(&data, ",")) != NULL) {
+		if (!*p)
+			continue;
+
+		token = match_token(p, tokens, args);
+		switch (token) {
+		case Opt_uid:
+			if (match_int(&args[0], &option))
+				return -EINVAL;
+			uid = make_kuid(current_user_ns(), option);
+			if (!uid_valid(uid))
+				return -EINVAL;
+			opts->uid = uid;
+			break;
+		case Opt_gid:
+			if (match_int(&args[0], &option))
+				return -EINVAL;
+			gid = make_kgid(current_user_ns(), option);
+			if (!gid_valid(gid))
+				return -EINVAL;
+			opts->gid = gid;
+			break;
+		case Opt_mode:
+			if (match_octal(&args[0], &option))
+				return -EINVAL;
+			opts->mode = option & S_IALLUGO;
+			break;
+		/*
+		 * We might like to report bad mount options here;
+		 * but traditionally tracefs has ignored all mount options
+		 */
+		}
+	}
+
+	return 0;
+}
+
+static int tracefs_apply_options(struct super_block *sb)
+{
+	struct tracefs_fs_info *fsi = sb->s_fs_info;
+	struct inode *inode = sb->s_root->d_inode;
+	struct tracefs_mount_opts *opts = &fsi->mount_opts;
+
+	inode->i_mode &= ~S_IALLUGO;
+	inode->i_mode |= opts->mode;
+
+	inode->i_uid = opts->uid;
+	inode->i_gid = opts->gid;
+
+	return 0;
+}
+
+static int tracefs_remount(struct super_block *sb, int *flags, char *data)
+{
+	int err;
+	struct tracefs_fs_info *fsi = sb->s_fs_info;
+
+	sync_filesystem(sb);
+	err = tracefs_parse_options(data, &fsi->mount_opts);
+	if (err)
+		goto fail;
+
+	tracefs_apply_options(sb);
+
+fail:
+	return err;
+}
+
+static int tracefs_show_options(struct seq_file *m, struct dentry *root)
+{
+	struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
+	struct tracefs_mount_opts *opts = &fsi->mount_opts;
+
+	if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
+		seq_printf(m, ",uid=%u",
+			   from_kuid_munged(&init_user_ns, opts->uid));
+	if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
+		seq_printf(m, ",gid=%u",
+			   from_kgid_munged(&init_user_ns, opts->gid));
+	if (opts->mode != TRACEFS_DEFAULT_MODE)
+		seq_printf(m, ",mode=%o", opts->mode);
+
+	return 0;
+}
+
+static const struct super_operations tracefs_super_operations = {
+	.statfs		= simple_statfs,
+	.remount_fs	= tracefs_remount,
+	.show_options	= tracefs_show_options,
+};
+
+static int trace_fill_super(struct super_block *sb, void *data, int silent)
+{
+	static struct tree_descr trace_files[] = {{""}};
+	struct tracefs_fs_info *fsi;
+	int err;
+
+	save_mount_options(sb, data);
+
+	fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
+	sb->s_fs_info = fsi;
+	if (!fsi) {
+		err = -ENOMEM;
+		goto fail;
+	}
+
+	err = tracefs_parse_options(data, &fsi->mount_opts);
+	if (err)
+		goto fail;
+
+	err  =  simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
+	if (err)
+		goto fail;
+
+	sb->s_op = &tracefs_super_operations;
+
+	tracefs_apply_options(sb);
+
+	return 0;
+
+fail:
+	kfree(fsi);
+	sb->s_fs_info = NULL;
+	return err;
+}
+
+static struct dentry *trace_mount(struct file_system_type *fs_type,
+			int flags, const char *dev_name,
+			void *data)
+{
+	return mount_single(fs_type, flags, data, trace_fill_super);
+}
+
+static struct file_system_type trace_fs_type = {
+	.owner =	THIS_MODULE,
+	.name =		"tracefs",
+	.mount =	trace_mount,
+	.kill_sb =	kill_litter_super,
+};
+MODULE_ALIAS_FS("tracefs");
+
+static struct dentry *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;
+
+	mutex_lock(&parent->d_inode->i_mutex);
+	dentry = lookup_one_len(name, parent, strlen(name));
+	if (!IS_ERR(dentry) && dentry->d_inode) {
+		dput(dentry);
+		dentry = ERR_PTR(-EEXIST);
+	}
+	if (IS_ERR(dentry))
+		mutex_unlock(&parent->d_inode->i_mutex);
+	return dentry;
+}
+
+static struct dentry *failed_creating(struct dentry *dentry)
+{
+	mutex_unlock(&dentry->d_parent->d_inode->i_mutex);
+	dput(dentry);
+	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+	return NULL;
+}
+
+static struct dentry *end_creating(struct dentry *dentry)
+{
+	mutex_unlock(&dentry->d_parent->d_inode->i_mutex);
+	return dentry;
+}
+
+/**
+ * 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 dentry *dentry;
+	struct inode *inode;
+
+	if (!(mode & S_IFMT))
+		mode |= S_IFREG;
+	BUG_ON(!S_ISREG(mode));
+	dentry = start_creating(name, parent);
+
+	if (IS_ERR(dentry))
+		return NULL;
+
+	inode = tracefs_get_inode(dentry->d_sb);
+	if (unlikely(!inode))
+		return failed_creating(dentry);
+
+	inode->i_mode = mode;
+	inode->i_fop = fops ? fops : &tracefs_file_operations;
+	inode->i_private = data;
+	d_instantiate(dentry, inode);
+	fsnotify_create(dentry->d_parent->d_inode, dentry);
+	return 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)
+{
+	struct dentry *dentry = start_creating(name, parent);
+	struct inode *inode;
+
+	if (IS_ERR(dentry))
+		return NULL;
+
+	inode = tracefs_get_inode(dentry->d_sb);
+	if (unlikely(!inode))
+		return failed_creating(dentry);
+
+	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+	inode->i_op = &simple_dir_inode_operations;
+	inode->i_fop = &simple_dir_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 end_creating(dentry);
+}
+
+static inline int tracefs_positive(struct dentry *dentry)
+{
+	return dentry->d_inode && !d_unhashed(dentry);
+}
+
+static int __tracefs_remove(struct dentry *dentry, struct dentry *parent)
+{
+	int ret = 0;
+
+	if (tracefs_positive(dentry)) {
+		if (dentry->d_inode) {
+			dget(dentry);
+			switch (dentry->d_inode->i_mode & S_IFMT) {
+			case S_IFDIR:
+				ret = simple_rmdir(parent->d_inode, dentry);
+				break;
+			default:
+				simple_unlink(parent->d_inode, dentry);
+				break;
+			}
+			if (!ret)
+				d_delete(dentry);
+			dput(dentry);
+		}
+	}
+	return ret;
+}
+
+/**
+ * tracefs_remove - removes a file or directory from the tracefs filesystem
+ * @dentry: a pointer to a the dentry of the file or directory to be
+ *          removed.
+ *
+ * This function removes a file or directory 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)
+{
+	struct dentry *parent;
+	int ret;
+
+	if (IS_ERR_OR_NULL(dentry))
+		return;
+
+	parent = dentry->d_parent;
+	if (!parent || !parent->d_inode)
+		return;
+
+	mutex_lock(&parent->d_inode->i_mutex);
+	ret = __tracefs_remove(dentry, parent);
+	mutex_unlock(&parent->d_inode->i_mutex);
+	if (!ret)
+		simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+}
+
+/**
+ * tracefs_remove_recursive - 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_recursive(struct dentry *dentry)
+{
+	struct dentry *child, *parent;
+
+	if (IS_ERR_OR_NULL(dentry))
+		return;
+
+	parent = dentry->d_parent;
+	if (!parent || !parent->d_inode)
+		return;
+
+	parent = dentry;
+ down:
+	mutex_lock(&parent->d_inode->i_mutex);
+ loop:
+	/*
+	 * The parent->d_subdirs is protected by the d_lock. Outside that
+	 * lock, the child can be unlinked and set to be freed which can
+	 * use the d_u.d_child as the rcu head and corrupt this list.
+	 */
+	spin_lock(&parent->d_lock);
+	list_for_each_entry(child, &parent->d_subdirs, d_child) {
+		if (!tracefs_positive(child))
+			continue;
+
+		/* perhaps simple_empty(child) makes more sense */
+		if (!list_empty(&child->d_subdirs)) {
+			spin_unlock(&parent->d_lock);
+			mutex_unlock(&parent->d_inode->i_mutex);
+			parent = child;
+			goto down;
+		}
+
+		spin_unlock(&parent->d_lock);
+
+		if (!__tracefs_remove(child, parent))
+			simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+
+		/*
+		 * The parent->d_lock protects agaist child from unlinking
+		 * from d_subdirs. When releasing the parent->d_lock we can
+		 * no longer trust that the next pointer is valid.
+		 * Restart the loop. We'll skip this one with the
+		 * tracefs_positive() check.
+		 */
+		goto loop;
+	}
+	spin_unlock(&parent->d_lock);
+
+	mutex_unlock(&parent->d_inode->i_mutex);
+	child = parent;
+	parent = parent->d_parent;
+	mutex_lock(&parent->d_inode->i_mutex);
+
+	if (child != dentry)
+		/* go up */
+		goto loop;
+
+	if (!__tracefs_remove(child, parent))
+		simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+	mutex_unlock(&parent->d_inode->i_mutex);
+}
+
+/**
+ * tracefs_initialized - Tells whether tracefs has been registered
+ */
+bool tracefs_initialized(void)
+{
+	return tracefs_registered;
+}
+
+static int __init tracefs_init(void)
+{
+	int retval;
+
+	retval = register_filesystem(&trace_fs_type);
+	if (!retval)
+		tracefs_registered = true;
+
+	return retval;
+}
+core_initcall(tracefs_init);
diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h
new file mode 100644
index 000000000000..23e04ce21749
--- /dev/null
+++ b/include/linux/tracefs.h
@@ -0,0 +1,41 @@
+/*
+ *  tracefs.h - a pseudo file system for activating tracing
+ *
+ * Based on debugfs by: 2004 Greg Kroah-Hartman <greg@kroah.com>
+ *
+ *  Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License version
+ *	2 as published by the Free Software Foundation.
+ *
+ * tracefs is the file system that is used by the tracing infrastructure.
+ *
+ */
+
+#ifndef _TRACEFS_H_
+#define _TRACEFS_H_
+
+#include <linux/fs.h>
+#include <linux/seq_file.h>
+
+#include <linux/types.h>
+
+struct file_operations;
+
+#ifdef CONFIG_TRACING
+
+struct dentry *tracefs_create_file(const char *name, umode_t mode,
+				   struct dentry *parent, void *data,
+				   const struct file_operations *fops);
+
+struct dentry *tracefs_create_dir(const char *name, struct dentry *parent);
+
+void tracefs_remove(struct dentry *dentry);
+void tracefs_remove_recursive(struct dentry *dentry);
+
+bool tracefs_initialized(void);
+
+#endif /* CONFIG_TRACING */
+
+#endif
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index 7d664ea85ebd..7b1425a6b370 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -58,6 +58,8 @@
 
 #define STACK_END_MAGIC		0x57AC6E9D
 
+#define TRACEFS_MAGIC          0x74726163
+
 #define V9FS_MAGIC		0x01021997
 
 #define BDEVFS_MAGIC            0x62646576
-- 
2.1.4

Re: [for-next][PATCH 3/7] tracefs: Add new tracefs file system

[Namhyung Kim]

Hi Steve,

On Wed, Feb 04, 2015 at 09:34:23AM -0500, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
> 
> Add a separate file system to handle the tracing directory. Currently it
> is part of debugfs, but that is starting to show its limits.
> 
> One thing is that in order to access the tracing infrastructure, you need
> to mount debugfs. As that includes debugging from all sorts of sub systems
> in the kernel, it is not considered advisable to mount such an all
> encompassing debugging system.
> 
> Having the tracing system in its own file systems gives access to the
> tracing sub system without needing to include all other systems.
> 
> Another problem with tracing using the debugfs system is that the
> instances use mkdir to create sub buffers. debugfs does not support mkdir
> from userspace so to implement it, special hacks were used. By controlling
> the file system that the tracing infrastructure uses, this can be properly
> done without hacks.
> 
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---

[SNIP]
> +/**
> + * 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.

I cannot find where it returns -ENODEV.  AFAICS we cannot call tracefs
functions if tracing was not enabled.


> + */
> +struct dentry *tracefs_create_file(const char *name, umode_t mode,
> +				   struct dentry *parent, void *data,
> +				   const struct file_operations *fops)
> +{
> +	struct dentry *dentry;
> +	struct inode *inode;
> +
> +	if (!(mode & S_IFMT))
> +		mode |= S_IFREG;
> +	BUG_ON(!S_ISREG(mode));
> +	dentry = start_creating(name, parent);
> +
> +	if (IS_ERR(dentry))
> +		return NULL;
> +
> +	inode = tracefs_get_inode(dentry->d_sb);
> +	if (unlikely(!inode))
> +		return failed_creating(dentry);
> +
> +	inode->i_mode = mode;
> +	inode->i_fop = fops ? fops : &tracefs_file_operations;
> +	inode->i_private = data;
> +	d_instantiate(dentry, inode);
> +	fsnotify_create(dentry->d_parent->d_inode, dentry);
> +	return 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.

Ditto.

Thanks,
Namhyung


> + */
> +struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
> +{
> +	struct dentry *dentry = start_creating(name, parent);
> +	struct inode *inode;
> +
> +	if (IS_ERR(dentry))
> +		return NULL;
> +
> +	inode = tracefs_get_inode(dentry->d_sb);
> +	if (unlikely(!inode))
> +		return failed_creating(dentry);
> +
> +	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
> +	inode->i_op = &simple_dir_inode_operations;
> +	inode->i_fop = &simple_dir_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 end_creating(dentry);
> +}

Re: [for-next][PATCH 3/7] tracefs: Add new tracefs file system

[Steven Rostedt]

On Mon, 9 Feb 2015 14:56:19 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> Hi Steve,
> 
> On Wed, Feb 04, 2015 at 09:34:23AM -0500, Steven Rostedt wrote:
> > From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
> > 
> > Add a separate file system to handle the tracing directory. Currently it
> > is part of debugfs, but that is starting to show its limits.
> > 
> > One thing is that in order to access the tracing infrastructure, you need
> > to mount debugfs. As that includes debugging from all sorts of sub systems
> > in the kernel, it is not considered advisable to mount such an all
> > encompassing debugging system.
> > 
> > Having the tracing system in its own file systems gives access to the
> > tracing sub system without needing to include all other systems.
> > 
> > Another problem with tracing using the debugfs system is that the
> > instances use mkdir to create sub buffers. debugfs does not support mkdir
> > from userspace so to implement it, special hacks were used. By controlling
> > the file system that the tracing infrastructure uses, this can be properly
> > done without hacks.
> > 
> > Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> > ---
> 
> [SNIP]
> > +/**
> > + * 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.
> 
> I cannot find where it returns -ENODEV.  AFAICS we cannot call tracefs
> functions if tracing was not enabled.

Ah, originally I had it like debugfs, where these functions were stubs
that would return ENODEV when TRACING was not configured. But then, I
decided that nothing should be calling these functions when tracing is
not configured.

I'll nuke that comment.

> 
> 
> > + */
> > +struct dentry *tracefs_create_file(const char *name, umode_t mode,
> > +				   struct dentry *parent, void *data,
> > +				   const struct file_operations *fops)
> > +{
> > +	struct dentry *dentry;
> > +	struct inode *inode;
> > +
> > +	if (!(mode & S_IFMT))
> > +		mode |= S_IFREG;
> > +	BUG_ON(!S_ISREG(mode));
> > +	dentry = start_creating(name, parent);
> > +
> > +	if (IS_ERR(dentry))
> > +		return NULL;
> > +
> > +	inode = tracefs_get_inode(dentry->d_sb);
> > +	if (unlikely(!inode))
> > +		return failed_creating(dentry);
> > +
> > +	inode->i_mode = mode;
> > +	inode->i_fop = fops ? fops : &tracefs_file_operations;
> > +	inode->i_private = data;
> > +	d_instantiate(dentry, inode);
> > +	fsnotify_create(dentry->d_parent->d_inode, dentry);
> > +	return 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.
> 
> Ditto.

And that one too.

Thanks,

-- Steve

[for-next][PATCH 4/7] tracing: Convert the tracing facility over to use tracefs

[Steven Rostedt]

[-- Attachment #1: 0004-tracing-Convert-the-tracing-facility-over-to-use-tra.patch --]
[-- Type: text/plain, Size: 19838 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

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 <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c                | 22 +++++++--------
 kernel/trace/trace.c                 | 55 +++++++++++++++++++++---------------
 kernel/trace/trace.h                 |  2 +-
 kernel/trace/trace_events.c          | 32 ++++++++++-----------
 kernel/trace/trace_functions_graph.c |  7 ++---
 kernel/trace/trace_kprobe.c          | 10 +++----
 kernel/trace/trace_probe.h           |  2 +-
 kernel/trace/trace_stat.c            | 10 +++----
 8 files changed, 74 insertions(+), 66 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 45e5cb143d17..fcc0e7052a79 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -18,7 +18,7 @@
 #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>
@@ -1008,7 +1008,7 @@ static struct tracer_stat function_stats __initdata = {
 	.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;
@@ -1044,15 +1044,15 @@ static __init void ftrace_profile_debugfs(struct dentry *d_tracer)
 		}
 	}
 
-	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 */
@@ -4690,7 +4690,7 @@ void ftrace_destroy_filter_files(struct ftrace_ops *ops)
 	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,
@@ -4998,7 +4998,7 @@ static int __init ftrace_nodyn_init(void)
 }
 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 */
@@ -5451,7 +5451,7 @@ static const struct file_operations ftrace_pid_fops = {
 	.release	= ftrace_pid_release,
 };
 
-static __init int ftrace_init_debugfs(void)
+static __init int ftrace_init_tracefs(void)
 {
 	struct dentry *d_tracer;
 
@@ -5459,16 +5459,16 @@ static __init int ftrace_init_debugfs(void)
 	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
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 05e0e50539fc..6c4739bee4bb 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -20,6 +20,7 @@
 #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>
@@ -5828,6 +5829,14 @@ static inline __init int register_snapshot_cmd(void) { return 0; }
 
 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;
 }
 
@@ -5842,10 +5851,10 @@ static struct dentry *tracing_dentry_percpu(struct trace_array *tr, int cpu)
 	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;
 }
@@ -5862,7 +5871,7 @@ trace_create_cpu_file(const char *name, umode_t mode, struct dentry *parent,
 }
 
 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;
@@ -5872,9 +5881,9 @@ tracing_init_debugfs_percpu(struct trace_array *tr, long 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;
 	}
 
@@ -6026,9 +6035,9 @@ struct dentry *trace_create_file(const char *name,
 {
 	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;
 }
@@ -6045,9 +6054,9 @@ static struct dentry *trace_options_init_dentry(struct trace_array *tr)
 	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;
 	}
 
@@ -6116,7 +6125,7 @@ destroy_trace_option_files(struct trace_option_dentry *topts)
 		return;
 
 	for (cnt = 0; topts[cnt].opt; cnt++)
-		debugfs_remove(topts[cnt].entry);
+		tracefs_remove(topts[cnt].entry);
 
 	kfree(topts);
 }
@@ -6205,7 +6214,7 @@ static const struct file_operations rb_simple_fops = {
 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)
@@ -6321,17 +6330,17 @@ static int new_instance_create(const char *name)
 	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);
 
@@ -6404,7 +6413,7 @@ static int instance_mkdir (struct inode *inode, struct dentry *dentry, umode_t m
 		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
@@ -6434,7 +6443,7 @@ static int instance_rmdir(struct inode *inode, struct dentry *dentry)
 	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
@@ -6459,7 +6468,7 @@ static const struct inode_operations instance_dir_inode_operations = {
 
 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;
 
@@ -6468,7 +6477,7 @@ static __init void create_trace_instances(struct dentry *d_tracer)
 }
 
 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;
 
@@ -6522,7 +6531,7 @@ init_tracer_debugfs(struct trace_array *tr, struct dentry *d_tracer)
 #endif
 
 	for_each_tracing_cpu(cpu)
-		tracing_init_debugfs_percpu(tr, cpu);
+		tracing_init_tracefs_percpu(tr, cpu);
 
 }
 
@@ -6550,10 +6559,10 @@ struct dentry *tracing_init_dentry(void)
 		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;
 
@@ -6563,7 +6572,7 @@ static __init int tracer_init_debugfs(void)
 	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);
@@ -6925,5 +6934,5 @@ __init static int clear_boot_tracer(void)
 	return 0;
 }
 
-fs_initcall(tracer_init_debugfs);
+fs_initcall(tracer_init_tracefs);
 late_initcall(clear_boot_tracer);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index dd8205a35760..d951deddec89 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -334,7 +334,7 @@ struct tracer_flags {
 
 
 /**
- * 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
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index db54dda10ccc..0d2e47370ee7 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -13,7 +13,7 @@
 #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>
@@ -480,7 +480,7 @@ static void remove_subsystem(struct ftrace_subsystem_dir *dir)
 		return;
 
 	if (!--dir->nr_events) {
-		debugfs_remove_recursive(dir->entry);
+		tracefs_remove_recursive(dir->entry);
 		list_del(&dir->list);
 		__put_system_dir(dir);
 	}
@@ -499,7 +499,7 @@ static void remove_event_file_dir(struct ftrace_event_file *file)
 		}
 		spin_unlock(&dir->d_lock);
 
-		debugfs_remove_recursive(dir);
+		tracefs_remove_recursive(dir);
 	}
 
 	list_del(&file->list);
@@ -1526,7 +1526,7 @@ event_subsystem_dir(struct trace_array *tr, const char *name,
 	} 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);
@@ -1539,12 +1539,12 @@ event_subsystem_dir(struct trace_array *tr, const char *name,
 	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,
@@ -1585,9 +1585,9 @@ event_create_dir(struct dentry *parent, struct ftrace_event_file *file)
 		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;
 	}
 
@@ -2228,7 +2228,7 @@ static inline int register_event_cmds(void) { return 0; }
 /*
  * 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.
  */
@@ -2311,16 +2311,16 @@ create_event_toplevel_files(struct dentry *parent, struct trace_array *tr)
 	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;
 	}
 
@@ -2412,7 +2412,7 @@ int event_trace_del_tracer(struct trace_array *tr)
 
 	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;
@@ -2534,10 +2534,10 @@ static __init int event_trace_init(void)
 	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");
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 2d25ad1526bb..9cfea4c6d314 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -6,7 +6,6 @@
  * is Copyright (c) Steven Rostedt <srostedt@redhat.com>
  *
  */
-#include <linux/debugfs.h>
 #include <linux/uaccess.h>
 #include <linux/ftrace.h>
 #include <linux/slab.h>
@@ -151,7 +150,7 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
 	 * 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;
@@ -1432,7 +1431,7 @@ static const struct file_operations graph_depth_fops = {
 	.llseek		= generic_file_llseek,
 };
 
-static __init int init_graph_debugfs(void)
+static __init int init_graph_tracefs(void)
 {
 	struct dentry *d_tracer;
 
@@ -1445,7 +1444,7 @@ static __init int init_graph_debugfs(void)
 
 	return 0;
 }
-fs_initcall(init_graph_debugfs);
+fs_initcall(init_graph_tracefs);
 
 static __init int init_graph_trace(void)
 {
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index b4a00def88f5..c1c6655847c8 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1310,7 +1310,7 @@ static int unregister_kprobe_event(struct trace_kprobe *tk)
 	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;
@@ -1323,20 +1323,20 @@ static __init int init_kprobe_trace(void)
 	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;
 }
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 4f815fbce16d..19aff635841a 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -25,7 +25,7 @@
 #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>
diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
index 75e19e86c954..6cf935316769 100644
--- a/kernel/trace/trace_stat.c
+++ b/kernel/trace/trace_stat.c
@@ -12,7 +12,7 @@
 #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"
 
@@ -65,7 +65,7 @@ static void reset_stat_session(struct stat_session *session)
 
 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);
@@ -279,9 +279,9 @@ static int tracing_stat_init(void)
 	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;
 }
@@ -291,7 +291,7 @@ static int init_stat_file(struct stat_session *session)
 	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)
-- 
2.1.4

[for-next][PATCH 5/7] tracing: Automatically mount tracefs on debugfs/tracing

[Steven Rostedt]

[-- Attachment #1: 0005-tracing-Automatically-mount-tracefs-on-debugfs-traci.patch --]
[-- Type: text/plain, Size: 2682 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

As tools currently rely on the tracing directory in debugfs, we can not
just created a tracefs infrastructure and expect sysadmins to mount
the new tracefs to have their old tools work.

Instead, the debugfs tracing directory is still created and the tracefs
file system is mounted there when the debugfs filesystem is mounted.

No longer does the tracing infrastructure update the debugfs file system,
but instead interacts with the tracefs file system. But now, it still
appears to the user like nothing changed, except you also have the feature
of mounting just the tracing system without needing all of debugfs!

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 36 +++++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6c4739bee4bb..b4aa936509d2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -32,6 +32,7 @@
 #include <linux/splice.h>
 #include <linux/kdebug.h>
 #include <linux/string.h>
+#include <linux/mount.h>
 #include <linux/rwsem.h>
 #include <linux/slab.h>
 #include <linux/ctype.h>
@@ -6535,6 +6536,28 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
 
 }
 
+static struct vfsmount *trace_automount(void *ingore)
+{
+	struct vfsmount *mnt;
+	struct file_system_type *type;
+
+	/*
+	 * To maintain backward compatibility for tools that mount
+	 * debugfs to get to the tracing facility, tracefs is automatically
+	 * mounted to the debugfs/tracing directory.
+	 */
+	type = get_fs_type("tracefs");
+	if (!type)
+		return NULL;
+	mnt = vfs_kern_mount(type, 0, "tracefs", NULL);
+	put_filesystem(type);
+	if (IS_ERR(mnt))
+		return NULL;
+	mntget(mnt);
+
+	return mnt;
+}
+
 /**
  * tracing_init_dentry - initialize top level trace array
  *
@@ -6546,14 +6569,21 @@ struct dentry *tracing_init_dentry(void)
 {
 	struct trace_array *tr = &global_trace;
 
+	/* The top level trace array uses  NULL as parent */
 	if (tr->dir)
-		return tr->dir;
+		return NULL;
 
 	if (WARN_ON(!debugfs_initialized()))
 		return ERR_PTR(-ENODEV);
 
-	tr->dir = debugfs_create_dir("tracing", NULL);
-
+	/*
+	 * As there may still be users that expect the tracing
+	 * files to exist in debugfs/tracing, we must automount
+	 * the tracefs file system there, so older tools still
+	 * work with the newer kerenl.
+	 */
+	tr->dir = debugfs_create_automount("tracing", NULL,
+					   trace_automount, NULL);
 	if (!tr->dir) {
 		pr_warn_once("Could not create debugfs directory 'tracing'\n");
 		return ERR_PTR(-ENOMEM);
-- 
2.1.4

Re: [for-next][PATCH 5/7] tracing: Automatically mount tracefs on debugfs/tracing

[Namhyung Kim]

On Wed, Feb 04, 2015 at 09:34:25AM -0500, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
> 
> As tools currently rely on the tracing directory in debugfs, we can not
> just created a tracefs infrastructure and expect sysadmins to mount
> the new tracefs to have their old tools work.
> 
> Instead, the debugfs tracing directory is still created and the tracefs
> file system is mounted there when the debugfs filesystem is mounted.
> 
> No longer does the tracing infrastructure update the debugfs file system,
> but instead interacts with the tracefs file system. But now, it still
> appears to the user like nothing changed, except you also have the feature
> of mounting just the tracing system without needing all of debugfs!

One question.  Is it possible to have both of the old
/sys/kernel/debug/tracing and new /sys/kernel/tracing directories?


> 
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
>  kernel/trace/trace.c | 36 +++++++++++++++++++++++++++++++++---
>  1 file changed, 33 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 6c4739bee4bb..b4aa936509d2 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -32,6 +32,7 @@
>  #include <linux/splice.h>
>  #include <linux/kdebug.h>
>  #include <linux/string.h>
> +#include <linux/mount.h>
>  #include <linux/rwsem.h>
>  #include <linux/slab.h>
>  #include <linux/ctype.h>
> @@ -6535,6 +6536,28 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
>  
>  }
>  
> +static struct vfsmount *trace_automount(void *ingore)
> +{
> +	struct vfsmount *mnt;
> +	struct file_system_type *type;
> +
> +	/*
> +	 * To maintain backward compatibility for tools that mount
> +	 * debugfs to get to the tracing facility, tracefs is automatically
> +	 * mounted to the debugfs/tracing directory.
> +	 */
> +	type = get_fs_type("tracefs");
> +	if (!type)
> +		return NULL;
> +	mnt = vfs_kern_mount(type, 0, "tracefs", NULL);
> +	put_filesystem(type);
> +	if (IS_ERR(mnt))
> +		return NULL;
> +	mntget(mnt);
> +
> +	return mnt;
> +}
> +
>  /**
>   * tracing_init_dentry - initialize top level trace array
>   *
> @@ -6546,14 +6569,21 @@ struct dentry *tracing_init_dentry(void)
>  {
>  	struct trace_array *tr = &global_trace;
>  
> +	/* The top level trace array uses  NULL as parent */
>  	if (tr->dir)
> -		return tr->dir;
> +		return NULL;
>  
>  	if (WARN_ON(!debugfs_initialized()))
>  		return ERR_PTR(-ENODEV);
>  
> -	tr->dir = debugfs_create_dir("tracing", NULL);
> -
> +	/*
> +	 * As there may still be users that expect the tracing
> +	 * files to exist in debugfs/tracing, we must automount
> +	 * the tracefs file system there, so older tools still
> +	 * work with the newer kerenl.

s/kerenl/kernel/

Thanks,
Namhyung


> +	 */
> +	tr->dir = debugfs_create_automount("tracing", NULL,
> +					   trace_automount, NULL);
>  	if (!tr->dir) {
>  		pr_warn_once("Could not create debugfs directory 'tracing'\n");
>  		return ERR_PTR(-ENOMEM);
> -- 
> 2.1.4
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Re: [for-next][PATCH 5/7] tracing: Automatically mount tracefs on debugfs/tracing

[Steven Rostedt]

On Mon, 9 Feb 2015 15:00:02 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> On Wed, Feb 04, 2015 at 09:34:25AM -0500, Steven Rostedt wrote:
> > From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
> > 
> > As tools currently rely on the tracing directory in debugfs, we can not
> > just created a tracefs infrastructure and expect sysadmins to mount
> > the new tracefs to have their old tools work.
> > 
> > Instead, the debugfs tracing directory is still created and the tracefs
> > file system is mounted there when the debugfs filesystem is mounted.
> > 
> > No longer does the tracing infrastructure update the debugfs file system,
> > but instead interacts with the tracefs file system. But now, it still
> > appears to the user like nothing changed, except you also have the feature
> > of mounting just the tracing system without needing all of debugfs!
> 
> One question.  Is it possible to have both of the old
> /sys/kernel/debug/tracing and new /sys/kernel/tracing directories?

Yes. In fact it's required. Because we must stay backward compatible
with older tools, we can not get rid of the debug/tracing directory.


> > +	/*
> > +	 * As there may still be users that expect the tracing
> > +	 * files to exist in debugfs/tracing, we must automount
> > +	 * the tracefs file system there, so older tools still
> > +	 * work with the newer kerenl.
> 
> s/kerenl/kernel/

Thanks, will fix.

-- Steve

[for-next][PATCH 6/7] tracefs: Add directory /sys/kernel/tracing

[Steven Rostedt]

[-- Attachment #1: 0006-tracefs-Add-directory-sys-kernel-tracing.patch --]
[-- Type: text/plain, Size: 1184 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

When tracefs is configured, have the directory /sys/kernel/tracing appear
just like /sys/kernel/debug appears when debugfs is configured.

This will give a consistent place for system admins to mount tracefs.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 fs/tracefs/inode.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 5b1547a452d8..0b9cf5cf24c9 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -16,6 +16,7 @@
 #include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/mount.h>
+#include <linux/kobject.h>
 #include <linux/namei.h>
 #include <linux/tracefs.h>
 #include <linux/fsnotify.h>
@@ -509,10 +510,16 @@ bool tracefs_initialized(void)
 	return tracefs_registered;
 }
 
+static struct kobject *trace_kobj;
+
 static int __init tracefs_init(void)
 {
 	int retval;
 
+	trace_kobj = kobject_create_and_add("tracing", kernel_kobj);
+	if (!trace_kobj)
+		return -EINVAL;
+
 	retval = register_filesystem(&trace_fs_type);
 	if (!retval)
 		tracefs_registered = true;
-- 
2.1.4

[for-next][PATCH 7/7] tracing: Have mkdir and rmdir be part of tracefs

[Steven Rostedt]

[-- Attachment #1: 0007-tracing-Have-mkdir-and-rmdir-be-part-of-tracefs.patch --]
[-- Type: text/plain, Size: 10771 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

The tracing "instances" directory can create sub tracing buffers
with mkdir, and remove them with rmdir. As a mkdir will also create
all the files and directories that control the sub buffer the inode
mutexes need to be released before this is done, to avoid deadlocks.
It is better to let the tracing system unlock the inode mutexes before
calling the functions that create the files within the new directory
(or deletes the files from the one being destroyed).

Now that tracing has been converted over to tracefs, the tracefs file
system can be modified to accommodate this feature. It still releases
the locks, but the filesystem itself can take care of the ugly
business and let the user just do what it needs.

The tracing system now attaches a descriptor to the directory dentry
that can have userspace create or remove sub directories. If this
descriptor does not exist for a dentry, then that dentry can not be
used to create other directories. This descriptor holds a mkdir and
rmdir method that only takes a character string as an argument.

The tracefs file system will first make a copy of the dentry name
before releasing the locks. Then it will pass the copied name to the
methods. It is up to the tracing system that supplied the methods to
handle races with duplicate names and such as all the inode mutexes
would be released when the functions are called.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 fs/tracefs/inode.c      | 151 +++++++++++++++++++++++++++++++++++++++++++-----
 include/linux/tracefs.h |   4 ++
 kernel/trace/trace.c    |  75 ++----------------------
 3 files changed, 145 insertions(+), 85 deletions(-)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 0b9cf5cf24c9..d92bdf3b079a 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -50,6 +50,84 @@ static const struct file_operations tracefs_file_operations = {
 	.llseek =	noop_llseek,
 };
 
+static struct tracefs_dir_ops {
+	int (*mkdir)(const char *name);
+	int (*rmdir)(const char *name);
+} tracefs_ops;
+
+static char *get_dname(struct dentry *dentry)
+{
+	const char *dname;
+	char *name;
+	int len = dentry->d_name.len;
+
+	dname = dentry->d_name.name;
+	name = kmalloc(len + 1, GFP_KERNEL);
+	if (!name)
+		return NULL;
+	memcpy(name, dname, len);
+	name[len] = 0;
+	return name;
+}
+
+static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umode_t mode)
+{
+	char *name;
+	int ret;
+
+	name = get_dname(dentry);
+	if (!name)
+		return -ENOMEM;
+
+	/*
+	 * 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.
+	 */
+	mutex_unlock(&inode->i_mutex);
+	ret = tracefs_ops.mkdir(name);
+	mutex_lock(&inode->i_mutex);
+
+	kfree(name);
+
+	return ret;
+}
+
+static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
+{
+	char *name;
+	int ret;
+
+	name = get_dname(dentry);
+	if (!name)
+		return -ENOMEM;
+
+	/*
+	 * 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.
+	 */
+	mutex_unlock(&inode->i_mutex);
+	mutex_unlock(&dentry->d_inode->i_mutex);
+
+	ret = tracefs_ops.rmdir(name);
+
+	mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
+	mutex_lock(&dentry->d_inode->i_mutex);
+
+	kfree(name);
+
+	return ret;
+}
+
+static const struct inode_operations tracefs_dir_inode_operations = {
+	.lookup		= simple_lookup,
+	.mkdir		= tracefs_syscall_mkdir,
+	.rmdir		= tracefs_syscall_rmdir,
+};
+
 static struct inode *tracefs_get_inode(struct super_block *sb)
 {
 	struct inode *inode = new_inode(sb);
@@ -334,6 +412,31 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
 	return end_creating(dentry);
 }
 
+static struct dentry *__create_dir(const char *name, struct dentry *parent,
+				   const struct inode_operations *ops)
+{
+	struct dentry *dentry = start_creating(name, parent);
+	struct inode *inode;
+
+	if (IS_ERR(dentry))
+		return NULL;
+
+	inode = tracefs_get_inode(dentry->d_sb);
+	if (unlikely(!inode))
+		return failed_creating(dentry);
+
+	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+	inode->i_op = ops;
+	inode->i_fop = &simple_dir_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 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
@@ -353,26 +456,44 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
  */
 struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
 {
-	struct dentry *dentry = start_creating(name, parent);
-	struct inode *inode;
+	return __create_dir(name, parent, &simple_dir_inode_operations);
+}
 
-	if (IS_ERR(dentry))
+/**
+ * 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
+ * to be done by userspace. When a mkdir or rmdir is performed, the inode
+ * locks are released and the methhods 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.
+ */
+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;
 
-	inode = tracefs_get_inode(dentry->d_sb);
-	if (unlikely(!inode))
-		return failed_creating(dentry);
+	dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
+	if (!dentry)
+		return NULL;
 
-	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
-	inode->i_op = &simple_dir_inode_operations;
-	inode->i_fop = &simple_dir_operations;
+	tracefs_ops.mkdir = mkdir;
+	tracefs_ops.rmdir = rmdir;
 
-	/* 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 end_creating(dentry);
+	return dentry;
 }
 
 static inline int tracefs_positive(struct dentry *dentry)
diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h
index 23e04ce21749..5b727a17beee 100644
--- a/include/linux/tracefs.h
+++ b/include/linux/tracefs.h
@@ -34,6 +34,10 @@ struct dentry *tracefs_create_dir(const char *name, struct dentry *parent);
 void tracefs_remove(struct dentry *dentry);
 void tracefs_remove_recursive(struct dentry *dentry);
 
+struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent,
+					   int (*mkdir)(const char *name),
+					   int (*rmdir)(const char *name));
+
 bool tracefs_initialized(void);
 
 #endif /* CONFIG_TRACING */
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b4aa936509d2..3c8913bac204 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6292,7 +6292,7 @@ static void free_trace_buffers(struct trace_array *tr)
 #endif
 }
 
-static int new_instance_create(const char *name)
+static int instance_mkdir(const char *name)
 {
 	struct trace_array *tr;
 	int ret;
@@ -6362,7 +6362,7 @@ static int new_instance_create(const char *name)
 
 }
 
-static int instance_delete(const char *name)
+static int instance_rmdir(const char *name)
 {
 	struct trace_array *tr;
 	int found = 0;
@@ -6403,78 +6403,13 @@ static int instance_delete(const char *name)
 	return ret;
 }
 
-static int instance_mkdir (struct inode *inode, struct dentry *dentry, umode_t mode)
-{
-	struct dentry *parent;
-	int ret;
-
-	/* Paranoid: Make sure the parent is the "instances" directory */
-	parent = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
-	if (WARN_ON_ONCE(parent != trace_instance_dir))
-		return -ENOENT;
-
-	/*
-	 * 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
-	 * the same time, then the new_instance_create() will determine the
-	 * winner.
-	 */
-	mutex_unlock(&inode->i_mutex);
-
-	ret = new_instance_create(dentry->d_iname);
-
-	mutex_lock(&inode->i_mutex);
-
-	return ret;
-}
-
-static int instance_rmdir(struct inode *inode, struct dentry *dentry)
-{
-	struct dentry *parent;
-	int ret;
-
-	/* Paranoid: Make sure the parent is the "instances" directory */
-	parent = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
-	if (WARN_ON_ONCE(parent != trace_instance_dir))
-		return -ENOENT;
-
-	/* The caller did a dget() on dentry */
-	mutex_unlock(&dentry->d_inode->i_mutex);
-
-	/*
-	 * 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
-	 * the same time, then the instance_delete() will determine the
-	 * winner.
-	 */
-	mutex_unlock(&inode->i_mutex);
-
-	ret = instance_delete(dentry->d_iname);
-
-	mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
-	mutex_lock(&dentry->d_inode->i_mutex);
-
-	return ret;
-}
-
-static const struct inode_operations instance_dir_inode_operations = {
-	.lookup		= simple_lookup,
-	.mkdir		= instance_mkdir,
-	.rmdir		= instance_rmdir,
-};
-
 static __init void create_trace_instances(struct dentry *d_tracer)
 {
-	trace_instance_dir = tracefs_create_dir("instances", d_tracer);
+	trace_instance_dir = tracefs_create_instance_dir("instances", d_tracer,
+							 instance_mkdir,
+							 instance_rmdir);
 	if (WARN_ON(!trace_instance_dir))
 		return;
-
-	/* Hijack the dir inode operations, to allow mkdir */
-	trace_instance_dir->d_inode->i_op = &instance_dir_inode_operations;
 }
 
 static void
-- 
2.1.4

Re: [for-next][PATCH 7/7] tracing: Have mkdir and rmdir be part of tracefs

[Namhyung Kim]

On Wed, Feb 04, 2015 at 09:34:27AM -0500, Steven Rostedt wrote:
> +static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umode_t mode)
> +{
> +	char *name;
> +	int ret;
> +
> +	name = get_dname(dentry);
> +	if (!name)
> +		return -ENOMEM;
> +
> +	/*
> +	 * The mkdir call can call the generic functions that create

	   The mkdir can call ... ?


> +	 * the files within the tracefs system. It is up to the individual
> +	 * mkdir routine to handle races.
> +	 */
> +	mutex_unlock(&inode->i_mutex);
> +	ret = tracefs_ops.mkdir(name);
> +	mutex_lock(&inode->i_mutex);
> +
> +	kfree(name);
> +
> +	return ret;
> +}
> +
> +static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
> +{
> +	char *name;
> +	int ret;
> +
> +	name = get_dname(dentry);
> +	if (!name)
> +		return -ENOMEM;
> +
> +	/*
> +	 * The rmdir call can call the generic functions that create

Ditto.


> +	 * 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.
> +	 */
> +	mutex_unlock(&inode->i_mutex);
> +	mutex_unlock(&dentry->d_inode->i_mutex);
> +
> +	ret = tracefs_ops.rmdir(name);
> +
> +	mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
> +	mutex_lock(&dentry->d_inode->i_mutex);
> +
> +	kfree(name);
> +
> +	return ret;
> +}
> +

[SNIP]
> +/**
> + * 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
> + * to be done by userspace. When a mkdir or rmdir is performed, the inode
> + * locks are released and the methhods passed in (@mkdir and @rmdir) are

s/methhods/methods/

Thanks,
Namhyung


> + * called without locks and with the name of the directory being created
> + * within the instances directory.
> + *
> + * Returns the dentry of the instances directory.
> + */
> +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;
>  
> -	inode = tracefs_get_inode(dentry->d_sb);
> -	if (unlikely(!inode))
> -		return failed_creating(dentry);
> +	dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
> +	if (!dentry)
> +		return NULL;
>  
> -	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
> -	inode->i_op = &simple_dir_inode_operations;
> -	inode->i_fop = &simple_dir_operations;
> +	tracefs_ops.mkdir = mkdir;
> +	tracefs_ops.rmdir = rmdir;
>  
> -	/* 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 end_creating(dentry);
> +	return dentry;
>  }

Re: [for-next][PATCH 7/7] tracing: Have mkdir and rmdir be part of tracefs

[Steven Rostedt]

On Mon, 9 Feb 2015 15:07:22 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> On Wed, Feb 04, 2015 at 09:34:27AM -0500, Steven Rostedt wrote:
> > +static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umode_t mode)
> > +{
> > +	char *name;
> > +	int ret;
> > +
> > +	name = get_dname(dentry);
> > +	if (!name)
> > +		return -ENOMEM;
> > +
> > +	/*
> > +	 * The mkdir call can call the generic functions that create
> 
> 	   The mkdir can call ... ?

Actually, that wasn't a typo. "mkdir call" is the subject.

> 
> 
> > +	 * the files within the tracefs system. It is up to the individual
> > +	 * mkdir routine to handle races.
> > +	 */
> > +	mutex_unlock(&inode->i_mutex);
> > +	ret = tracefs_ops.mkdir(name);
> > +	mutex_lock(&inode->i_mutex);
> > +
> > +	kfree(name);
> > +
> > +	return ret;
> > +}
> > +
> > +static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
> > +{
> > +	char *name;
> > +	int ret;
> > +
> > +	name = get_dname(dentry);
> > +	if (!name)
> > +		return -ENOMEM;
> > +
> > +	/*
> > +	 * The rmdir call can call the generic functions that create
> 
> Ditto.
> 

"rmdir call" is also the subject.

> 
> > +	 * 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.
> > +	 */
> > +	mutex_unlock(&inode->i_mutex);
> > +	mutex_unlock(&dentry->d_inode->i_mutex);
> > +
> > +	ret = tracefs_ops.rmdir(name);
> > +
> > +	mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
> > +	mutex_lock(&dentry->d_inode->i_mutex);
> > +
> > +	kfree(name);
> > +
> > +	return ret;
> > +}
> > +
> 
> [SNIP]
> > +/**
> > + * 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
> > + * to be done by userspace. When a mkdir or rmdir is performed, the inode
> > + * locks are released and the methhods passed in (@mkdir and @rmdir) are
> 
> s/methhods/methods/

I must have been on meth ;-)

Thanks.

-- Steve