linux/fs/tracefs/inode.c
Linus Torvalds 31e5f934ff Tracing updates for v6.7:
- Remove eventfs_file descriptor
 
   This is the biggest change, and the second part of making eventfs
   create its files dynamically.
 
   In 6.6 the first part was added, and that maintained a one to one
   mapping between eventfs meta descriptors and the directories and
   file inodes and dentries that were dynamically created. The
   directories were represented by a eventfs_inode and the files
   were represented by a eventfs_file.
 
   In v6.7 the eventfs_file is removed. As all events have the same
   directory make up (sched_switch has an "enable", "id", "format",
   etc files), the handing of what files are underneath each leaf
   eventfs directory is moved back to the tracing subsystem via a
   callback. When a event is added to the eventfs, it registers
   an array of evenfs_entry's. These hold the names of the files and
   the callbacks to call when the file is referenced. The callback gets
   the name so that the same callback may be used by multiple files.
   The callback then supplies the filesystem_operations structure needed
   to create this file.
 
   This has brought the memory footprint of creating multiple eventfs
   instances down by 2 megs each!
 
 - User events now has persistent events that are not associated
   to a single processes. These are privileged events that hang around
   even if no process is attached to them.
 
 - Clean up of seq_buf.
   There's talk about using seq_buf more to replace strscpy() and friends.
   But this also requires some minor modifications of seq_buf to be
   able to do this.
 
 - Expand instance ring buffers individually
   Currently if boot up creates an instance, and a trace event is
   enabled on that instance, the ring buffer for that instance and the
   top level ring buffer are expanded (1.4 MB per CPU). This wastes
   memory as this happens when nothing is using the top level instance.
 
 - Other minor clean ups and fixes.
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Merge tag 'trace-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing updates from Steven Rostedt:

 - Remove eventfs_file descriptor

   This is the biggest change, and the second part of making eventfs
   create its files dynamically.

   In 6.6 the first part was added, and that maintained a one to one
   mapping between eventfs meta descriptors and the directories and file
   inodes and dentries that were dynamically created. The directories
   were represented by a eventfs_inode and the files were represented by
   a eventfs_file.

   In v6.7 the eventfs_file is removed. As all events have the same
   directory make up (sched_switch has an "enable", "id", "format", etc
   files), the handing of what files are underneath each leaf eventfs
   directory is moved back to the tracing subsystem via a callback.

   When an event is added to the eventfs, it registers an array of
   evenfs_entry's. These hold the names of the files and the callbacks
   to call when the file is referenced. The callback gets the name so
   that the same callback may be used by multiple files. The callback
   then supplies the filesystem_operations structure needed to create
   this file.

   This has brought the memory footprint of creating multiple eventfs
   instances down by 2 megs each!

 - User events now has persistent events that are not associated to a
   single processes. These are privileged events that hang around even
   if no process is attached to them

 - Clean up of seq_buf

   There's talk about using seq_buf more to replace strscpy() and
   friends. But this also requires some minor modifications of seq_buf
   to be able to do this

 - Expand instance ring buffers individually

   Currently if boot up creates an instance, and a trace event is
   enabled on that instance, the ring buffer for that instance and the
   top level ring buffer are expanded (1.4 MB per CPU). This wastes
   memory as this happens when nothing is using the top level instance

 - Other minor clean ups and fixes

* tag 'trace-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (34 commits)
  seq_buf: Export seq_buf_puts()
  seq_buf: Export seq_buf_putc()
  eventfs: Use simple_recursive_removal() to clean up dentries
  eventfs: Remove special processing of dput() of events directory
  eventfs: Delete eventfs_inode when the last dentry is freed
  eventfs: Hold eventfs_mutex when calling callback functions
  eventfs: Save ownership and mode
  eventfs: Test for ei->is_freed when accessing ei->dentry
  eventfs: Have a free_ei() that just frees the eventfs_inode
  eventfs: Remove "is_freed" union with rcu head
  eventfs: Fix kerneldoc of eventfs_remove_rec()
  tracing: Have the user copy of synthetic event address use correct context
  eventfs: Remove extra dget() in eventfs_create_events_dir()
  tracing: Have trace_event_file have ref counters
  seq_buf: Introduce DECLARE_SEQ_BUF and seq_buf_str()
  eventfs: Fix typo in eventfs_inode union comment
  eventfs: Fix WARN_ON() in create_file_dentry()
  powerpc: Remove initialisation of readpos
  tracing/histograms: Simplify last_cmd_set()
  seq_buf: fix a misleading comment
  ...
2023-11-03 07:41:18 -10:00

782 lines
20 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* inode.c - part of tracefs, a pseudo file system for activating tracing
*
* Based on debugfs by: Greg Kroah-Hartman <greg@kroah.com>
*
* Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>
*
* tracefs is the file system that is used by the tracing infrastructure.
*/
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/tracefs.h>
#include <linux/fsnotify.h>
#include <linux/security.h>
#include <linux/seq_file.h>
#include <linux/parser.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include "internal.h"
#define TRACEFS_DEFAULT_MODE 0700
static struct kmem_cache *tracefs_inode_cachep __ro_after_init;
static struct vfsmount *tracefs_mount;
static int tracefs_mount_count;
static bool tracefs_registered;
static struct inode *tracefs_alloc_inode(struct super_block *sb)
{
struct tracefs_inode *ti;
ti = kmem_cache_alloc(tracefs_inode_cachep, GFP_KERNEL);
if (!ti)
return NULL;
ti->flags = 0;
return &ti->vfs_inode;
}
static void tracefs_free_inode(struct inode *inode)
{
kmem_cache_free(tracefs_inode_cachep, get_tracefs(inode));
}
static ssize_t default_read_file(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
return 0;
}
static ssize_t default_write_file(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
return count;
}
static const struct file_operations tracefs_file_operations = {
.read = default_read_file,
.write = default_write_file,
.open = simple_open,
.llseek = noop_llseek,
};
static struct tracefs_dir_ops {
int (*mkdir)(const char *name);
int (*rmdir)(const char *name);
} tracefs_ops __ro_after_init;
static 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 mnt_idmap *idmap,
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.
*/
inode_unlock(inode);
ret = tracefs_ops.mkdir(name);
inode_lock(inode);
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.
*/
inode_unlock(inode);
inode_unlock(d_inode(dentry));
ret = tracefs_ops.rmdir(name);
inode_lock_nested(inode, I_MUTEX_PARENT);
inode_lock(d_inode(dentry));
kfree(name);
return ret;
}
static const struct inode_operations tracefs_dir_inode_operations = {
.lookup = simple_lookup,
.mkdir = tracefs_syscall_mkdir,
.rmdir = tracefs_syscall_rmdir,
};
struct inode *tracefs_get_inode(struct super_block *sb)
{
struct inode *inode = new_inode(sb);
if (inode) {
inode->i_ino = get_next_ino();
simple_inode_init_ts(inode);
}
return inode;
}
struct tracefs_mount_opts {
kuid_t uid;
kgid_t gid;
umode_t mode;
/* Opt_* bitfield. */
unsigned int opts;
};
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 void change_gid(struct dentry *dentry, kgid_t gid)
{
if (!dentry->d_inode)
return;
dentry->d_inode->i_gid = gid;
}
/*
* Taken from d_walk, but without he need for handling renames.
* Nothing can be renamed while walking the list, as tracefs
* does not support renames. This is only called when mounting
* or remounting the file system, to set all the files to
* the given gid.
*/
static void set_gid(struct dentry *parent, kgid_t gid)
{
struct dentry *this_parent;
struct list_head *next;
this_parent = parent;
spin_lock(&this_parent->d_lock);
change_gid(this_parent, gid);
repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
next = tmp->next;
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
change_gid(dentry, gid);
if (!list_empty(&dentry->d_subdirs)) {
spin_unlock(&this_parent->d_lock);
spin_release(&dentry->d_lock.dep_map, _RET_IP_);
this_parent = dentry;
spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
goto repeat;
}
spin_unlock(&dentry->d_lock);
}
/*
* All done at this level ... ascend and resume the search.
*/
rcu_read_lock();
ascend:
if (this_parent != parent) {
struct dentry *child = this_parent;
this_parent = child->d_parent;
spin_unlock(&child->d_lock);
spin_lock(&this_parent->d_lock);
/* go into the first sibling still alive */
do {
next = child->d_child.next;
if (next == &this_parent->d_subdirs)
goto ascend;
child = list_entry(next, struct dentry, d_child);
} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
rcu_read_unlock();
goto resume;
}
rcu_read_unlock();
spin_unlock(&this_parent->d_lock);
return;
}
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->opts = 0;
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
*/
}
opts->opts |= BIT(token);
}
return 0;
}
static int tracefs_apply_options(struct super_block *sb, bool remount)
{
struct tracefs_fs_info *fsi = sb->s_fs_info;
struct inode *inode = d_inode(sb->s_root);
struct tracefs_mount_opts *opts = &fsi->mount_opts;
umode_t tmp_mode;
/*
* On remount, only reset mode/uid/gid if they were provided as mount
* options.
*/
if (!remount || opts->opts & BIT(Opt_mode)) {
tmp_mode = READ_ONCE(inode->i_mode) & ~S_IALLUGO;
tmp_mode |= opts->mode;
WRITE_ONCE(inode->i_mode, tmp_mode);
}
if (!remount || opts->opts & BIT(Opt_uid))
inode->i_uid = opts->uid;
if (!remount || opts->opts & BIT(Opt_gid)) {
/* Set all the group ids to the mount option */
set_gid(sb->s_root, 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, true);
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 = {
.alloc_inode = tracefs_alloc_inode,
.free_inode = tracefs_free_inode,
.drop_inode = generic_delete_inode,
.statfs = simple_statfs,
.remount_fs = tracefs_remount,
.show_options = tracefs_show_options,
};
static void tracefs_dentry_iput(struct dentry *dentry, struct inode *inode)
{
struct tracefs_inode *ti;
if (!dentry || !inode)
return;
ti = get_tracefs(inode);
if (ti && ti->flags & TRACEFS_EVENT_INODE)
eventfs_set_ei_status_free(ti, dentry);
iput(inode);
}
static const struct dentry_operations tracefs_dentry_operations = {
.d_iput = tracefs_dentry_iput,
};
static int trace_fill_super(struct super_block *sb, void *data, int silent)
{
static const struct tree_descr trace_files[] = {{""}};
struct tracefs_fs_info *fsi;
int err;
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;
sb->s_d_op = &tracefs_dentry_operations;
tracefs_apply_options(sb, false);
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");
struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
{
struct dentry *dentry;
int error;
pr_debug("tracefs: creating file '%s'\n",name);
error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
&tracefs_mount_count);
if (error)
return ERR_PTR(error);
/* If the parent is not specified, we create it in the root.
* We need the root dentry to do this, which is in the super
* block. A pointer to that is in the struct vfsmount that we
* have around.
*/
if (!parent)
parent = tracefs_mount->mnt_root;
inode_lock(d_inode(parent));
if (unlikely(IS_DEADDIR(d_inode(parent))))
dentry = ERR_PTR(-ENOENT);
else
dentry = lookup_one_len(name, parent, strlen(name));
if (!IS_ERR(dentry) && d_inode(dentry)) {
dput(dentry);
dentry = ERR_PTR(-EEXIST);
}
if (IS_ERR(dentry)) {
inode_unlock(d_inode(parent));
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
}
return dentry;
}
struct dentry *tracefs_failed_creating(struct dentry *dentry)
{
inode_unlock(d_inode(dentry->d_parent));
dput(dentry);
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
return NULL;
}
struct dentry *tracefs_end_creating(struct dentry *dentry)
{
inode_unlock(d_inode(dentry->d_parent));
return dentry;
}
/**
* eventfs_start_creating - start the process of creating a dentry
* @name: Name of the file created for the dentry
* @parent: The parent dentry where this dentry will be created
*
* This is a simple helper function for the dynamically created eventfs
* files. When the directory of the eventfs files are accessed, their
* dentries are created on the fly. This function is used to start that
* process.
*/
struct dentry *eventfs_start_creating(const char *name, struct dentry *parent)
{
struct dentry *dentry;
int error;
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;
if (unlikely(IS_DEADDIR(parent->d_inode)))
dentry = ERR_PTR(-ENOENT);
else
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))
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
return dentry;
}
/**
* eventfs_failed_creating - clean up a failed eventfs dentry creation
* @dentry: The dentry to clean up
*
* If after calling eventfs_start_creating(), a failure is detected, the
* resources created by eventfs_start_creating() needs to be cleaned up. In
* that case, this function should be called to perform that clean up.
*/
struct dentry *eventfs_failed_creating(struct dentry *dentry)
{
dput(dentry);
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
return NULL;
}
/**
* eventfs_end_creating - Finish the process of creating a eventfs dentry
* @dentry: The dentry that has successfully been created.
*
* This function is currently just a place holder to match
* eventfs_start_creating(). In case any synchronization needs to be added,
* this function will be used to implement that without having to modify
* the callers of eventfs_start_creating().
*/
struct dentry *eventfs_end_creating(struct dentry *dentry)
{
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 (security_locked_down(LOCKDOWN_TRACEFS))
return NULL;
if (!(mode & S_IFMT))
mode |= S_IFREG;
BUG_ON(!S_ISREG(mode));
dentry = tracefs_start_creating(name, parent);
if (IS_ERR(dentry))
return NULL;
inode = tracefs_get_inode(dentry->d_sb);
if (unlikely(!inode))
return tracefs_failed_creating(dentry);
inode->i_mode = mode;
inode->i_fop = fops ? fops : &tracefs_file_operations;
inode->i_private = data;
inode->i_uid = d_inode(dentry->d_parent)->i_uid;
inode->i_gid = d_inode(dentry->d_parent)->i_gid;
d_instantiate(dentry, inode);
fsnotify_create(d_inode(dentry->d_parent), dentry);
return tracefs_end_creating(dentry);
}
static struct dentry *__create_dir(const char *name, struct dentry *parent,
const struct inode_operations *ops)
{
struct dentry *dentry = tracefs_start_creating(name, parent);
struct inode *inode;
if (IS_ERR(dentry))
return NULL;
inode = tracefs_get_inode(dentry->d_sb);
if (unlikely(!inode))
return tracefs_failed_creating(dentry);
/* Do not set bits for OTH */
inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;
inode->i_op = ops;
inode->i_fop = &simple_dir_operations;
inode->i_uid = d_inode(dentry->d_parent)->i_uid;
inode->i_gid = d_inode(dentry->d_parent)->i_gid;
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
d_instantiate(dentry, inode);
inc_nlink(d_inode(dentry->d_parent));
fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
return tracefs_end_creating(dentry);
}
/**
* tracefs_create_dir - create a directory in the tracefs filesystem
* @name: a pointer to a string containing the name of the directory to
* create.
* @parent: a pointer to the parent dentry for this file. This should be a
* directory dentry if set. If this parameter is NULL, then the
* directory will be created in the root of the tracefs filesystem.
*
* This function creates a directory in tracefs with the given name.
*
* This function will return a pointer to a dentry if it succeeds. This
* pointer must be passed to the tracefs_remove() function when the file is
* to be removed. If an error occurs, %NULL will be returned.
*
* If tracing is not enabled in the kernel, the value -%ENODEV will be
* returned.
*/
struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
{
if (security_locked_down(LOCKDOWN_TRACEFS))
return NULL;
return __create_dir(name, parent, &simple_dir_inode_operations);
}
/**
* tracefs_create_instance_dir - create the tracing instances directory
* @name: The name of the instances directory to create
* @parent: The parent directory that the instances directory will exist
* @mkdir: The function to call when a mkdir is performed.
* @rmdir: The function to call when a rmdir is performed.
*
* Only one instances directory is allowed.
*
* The instances directory is special as it allows for mkdir and rmdir
* to be done by userspace. When a mkdir or rmdir is performed, the inode
* locks are released and the methods passed in (@mkdir and @rmdir) are
* called without locks and with the name of the directory being created
* within the instances directory.
*
* Returns the dentry of the instances directory.
*/
__init struct dentry *tracefs_create_instance_dir(const char *name,
struct dentry *parent,
int (*mkdir)(const char *name),
int (*rmdir)(const char *name))
{
struct dentry *dentry;
/* Only allow one instance of the instances directory. */
if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
return NULL;
dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
if (!dentry)
return NULL;
tracefs_ops.mkdir = mkdir;
tracefs_ops.rmdir = rmdir;
return dentry;
}
static void remove_one(struct dentry *victim)
{
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
}
/**
* tracefs_remove - recursively removes a directory
* @dentry: a pointer to a the dentry of the directory to be removed.
*
* This function recursively removes a directory tree in tracefs that
* was previously created with a call to another tracefs function
* (like tracefs_create_file() or variants thereof.)
*/
void tracefs_remove(struct dentry *dentry)
{
if (IS_ERR_OR_NULL(dentry))
return;
simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
simple_recursive_removal(dentry, remove_one);
simple_release_fs(&tracefs_mount, &tracefs_mount_count);
}
/**
* tracefs_initialized - Tells whether tracefs has been registered
*/
bool tracefs_initialized(void)
{
return tracefs_registered;
}
static void init_once(void *foo)
{
struct tracefs_inode *ti = (struct tracefs_inode *) foo;
inode_init_once(&ti->vfs_inode);
}
static int __init tracefs_init(void)
{
int retval;
tracefs_inode_cachep = kmem_cache_create("tracefs_inode_cache",
sizeof(struct tracefs_inode),
0, (SLAB_RECLAIM_ACCOUNT|
SLAB_MEM_SPREAD|
SLAB_ACCOUNT),
init_once);
if (!tracefs_inode_cachep)
return -ENOMEM;
retval = sysfs_create_mount_point(kernel_kobj, "tracing");
if (retval)
return -EINVAL;
retval = register_filesystem(&trace_fs_type);
if (!retval)
tracefs_registered = true;
return retval;
}
core_initcall(tracefs_init);