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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * inode.c - part of tracefs, a pseudo file system for activating tracing4 *5 * Based on debugfs by: Greg Kroah-Hartman <greg@kroah.com>6 *7 * Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>8 *9 * tracefs is the file system that is used by the tracing infrastructure.10 */11 12#include <linux/module.h>13#include <linux/fs.h>14#include <linux/fs_context.h>15#include <linux/fs_parser.h>16#include <linux/kobject.h>17#include <linux/namei.h>18#include <linux/tracefs.h>19#include <linux/fsnotify.h>20#include <linux/security.h>21#include <linux/seq_file.h>22#include <linux/magic.h>23#include <linux/slab.h>24#include "internal.h"25 26#define TRACEFS_DEFAULT_MODE 070027static struct kmem_cache *tracefs_inode_cachep __ro_after_init;28 29static struct vfsmount *tracefs_mount;30static int tracefs_mount_count;31static bool tracefs_registered;32 33/*34 * Keep track of all tracefs_inodes in order to update their35 * flags if necessary on a remount.36 */37static DEFINE_SPINLOCK(tracefs_inode_lock);38static LIST_HEAD(tracefs_inodes);39 40static struct inode *tracefs_alloc_inode(struct super_block *sb)41{42 struct tracefs_inode *ti;43 unsigned long flags;44 45 ti = alloc_inode_sb(sb, tracefs_inode_cachep, GFP_KERNEL);46 if (!ti)47 return NULL;48 49 spin_lock_irqsave(&tracefs_inode_lock, flags);50 list_add_rcu(&ti->list, &tracefs_inodes);51 spin_unlock_irqrestore(&tracefs_inode_lock, flags);52 53 return &ti->vfs_inode;54}55 56static void tracefs_free_inode(struct inode *inode)57{58 struct tracefs_inode *ti = get_tracefs(inode);59 60 kmem_cache_free(tracefs_inode_cachep, ti);61}62 63static void tracefs_destroy_inode(struct inode *inode)64{65 struct tracefs_inode *ti = get_tracefs(inode);66 unsigned long flags;67 68 spin_lock_irqsave(&tracefs_inode_lock, flags);69 list_del_rcu(&ti->list);70 spin_unlock_irqrestore(&tracefs_inode_lock, flags);71}72 73static ssize_t default_read_file(struct file *file, char __user *buf,74 size_t count, loff_t *ppos)75{76 return 0;77}78 79static ssize_t default_write_file(struct file *file, const char __user *buf,80 size_t count, loff_t *ppos)81{82 return count;83}84 85static const struct file_operations tracefs_file_operations = {86 .read = default_read_file,87 .write = default_write_file,88 .open = simple_open,89 .llseek = noop_llseek,90};91 92static struct tracefs_dir_ops {93 int (*mkdir)(const char *name);94 int (*rmdir)(const char *name);95} tracefs_ops __ro_after_init;96 97static char *get_dname(struct dentry *dentry)98{99 const char *dname;100 char *name;101 int len = dentry->d_name.len;102 103 dname = dentry->d_name.name;104 name = kmalloc(len + 1, GFP_KERNEL);105 if (!name)106 return NULL;107 memcpy(name, dname, len);108 name[len] = 0;109 return name;110}111 112static int tracefs_syscall_mkdir(struct mnt_idmap *idmap,113 struct inode *inode, struct dentry *dentry,114 umode_t mode)115{116 struct tracefs_inode *ti;117 char *name;118 int ret;119 120 name = get_dname(dentry);121 if (!name)122 return -ENOMEM;123 124 /*125 * This is a new directory that does not take the default of126 * the rootfs. It becomes the default permissions for all the127 * files and directories underneath it.128 */129 ti = get_tracefs(inode);130 ti->flags |= TRACEFS_INSTANCE_INODE;131 ti->private = inode;132 133 /*134 * The mkdir call can call the generic functions that create135 * the files within the tracefs system. It is up to the individual136 * mkdir routine to handle races.137 */138 inode_unlock(inode);139 ret = tracefs_ops.mkdir(name);140 inode_lock(inode);141 142 kfree(name);143 144 return ret;145}146 147static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)148{149 char *name;150 int ret;151 152 name = get_dname(dentry);153 if (!name)154 return -ENOMEM;155 156 /*157 * The rmdir call can call the generic functions that create158 * the files within the tracefs system. It is up to the individual159 * rmdir routine to handle races.160 * This time we need to unlock not only the parent (inode) but161 * also the directory that is being deleted.162 */163 inode_unlock(inode);164 inode_unlock(d_inode(dentry));165 166 ret = tracefs_ops.rmdir(name);167 168 inode_lock_nested(inode, I_MUTEX_PARENT);169 inode_lock(d_inode(dentry));170 171 kfree(name);172 173 return ret;174}175 176static void set_tracefs_inode_owner(struct inode *inode)177{178 struct tracefs_inode *ti = get_tracefs(inode);179 struct inode *root_inode = ti->private;180 kuid_t uid;181 kgid_t gid;182 183 uid = root_inode->i_uid;184 gid = root_inode->i_gid;185 186 /*187 * If the root is not the mount point, then check the root's188 * permissions. If it was never set, then default to the189 * mount point.190 */191 if (root_inode != d_inode(root_inode->i_sb->s_root)) {192 struct tracefs_inode *rti;193 194 rti = get_tracefs(root_inode);195 root_inode = d_inode(root_inode->i_sb->s_root);196 197 if (!(rti->flags & TRACEFS_UID_PERM_SET))198 uid = root_inode->i_uid;199 200 if (!(rti->flags & TRACEFS_GID_PERM_SET))201 gid = root_inode->i_gid;202 }203 204 /*205 * If this inode has never been referenced, then update206 * the permissions to the superblock.207 */208 if (!(ti->flags & TRACEFS_UID_PERM_SET))209 inode->i_uid = uid;210 211 if (!(ti->flags & TRACEFS_GID_PERM_SET))212 inode->i_gid = gid;213}214 215static int tracefs_permission(struct mnt_idmap *idmap,216 struct inode *inode, int mask)217{218 set_tracefs_inode_owner(inode);219 return generic_permission(idmap, inode, mask);220}221 222static int tracefs_getattr(struct mnt_idmap *idmap,223 const struct path *path, struct kstat *stat,224 u32 request_mask, unsigned int flags)225{226 struct inode *inode = d_backing_inode(path->dentry);227 228 set_tracefs_inode_owner(inode);229 generic_fillattr(idmap, request_mask, inode, stat);230 return 0;231}232 233static int tracefs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,234 struct iattr *attr)235{236 unsigned int ia_valid = attr->ia_valid;237 struct inode *inode = d_inode(dentry);238 struct tracefs_inode *ti = get_tracefs(inode);239 240 if (ia_valid & ATTR_UID)241 ti->flags |= TRACEFS_UID_PERM_SET;242 243 if (ia_valid & ATTR_GID)244 ti->flags |= TRACEFS_GID_PERM_SET;245 246 return simple_setattr(idmap, dentry, attr);247}248 249static const struct inode_operations tracefs_instance_dir_inode_operations = {250 .lookup = simple_lookup,251 .mkdir = tracefs_syscall_mkdir,252 .rmdir = tracefs_syscall_rmdir,253 .permission = tracefs_permission,254 .getattr = tracefs_getattr,255 .setattr = tracefs_setattr,256};257 258static const struct inode_operations tracefs_dir_inode_operations = {259 .lookup = simple_lookup,260 .permission = tracefs_permission,261 .getattr = tracefs_getattr,262 .setattr = tracefs_setattr,263};264 265static const struct inode_operations tracefs_file_inode_operations = {266 .permission = tracefs_permission,267 .getattr = tracefs_getattr,268 .setattr = tracefs_setattr,269};270 271struct inode *tracefs_get_inode(struct super_block *sb)272{273 struct inode *inode = new_inode(sb);274 if (inode) {275 inode->i_ino = get_next_ino();276 simple_inode_init_ts(inode);277 }278 return inode;279}280 281struct tracefs_fs_info {282 kuid_t uid;283 kgid_t gid;284 umode_t mode;285 /* Opt_* bitfield. */286 unsigned int opts;287};288 289enum {290 Opt_uid,291 Opt_gid,292 Opt_mode,293};294 295static const struct fs_parameter_spec tracefs_param_specs[] = {296 fsparam_gid ("gid", Opt_gid),297 fsparam_u32oct ("mode", Opt_mode),298 fsparam_uid ("uid", Opt_uid),299 {}300};301 302static int tracefs_parse_param(struct fs_context *fc, struct fs_parameter *param)303{304 struct tracefs_fs_info *opts = fc->s_fs_info;305 struct fs_parse_result result;306 int opt;307 308 opt = fs_parse(fc, tracefs_param_specs, param, &result);309 if (opt < 0)310 return opt;311 312 switch (opt) {313 case Opt_uid:314 opts->uid = result.uid;315 break;316 case Opt_gid:317 opts->gid = result.gid;318 break;319 case Opt_mode:320 opts->mode = result.uint_32 & S_IALLUGO;321 break;322 /*323 * We might like to report bad mount options here;324 * but traditionally tracefs has ignored all mount options325 */326 }327 328 opts->opts |= BIT(opt);329 330 return 0;331}332 333static int tracefs_apply_options(struct super_block *sb, bool remount)334{335 struct tracefs_fs_info *fsi = sb->s_fs_info;336 struct inode *inode = d_inode(sb->s_root);337 struct tracefs_inode *ti;338 bool update_uid, update_gid;339 umode_t tmp_mode;340 341 /*342 * On remount, only reset mode/uid/gid if they were provided as mount343 * options.344 */345 346 if (!remount || fsi->opts & BIT(Opt_mode)) {347 tmp_mode = READ_ONCE(inode->i_mode) & ~S_IALLUGO;348 tmp_mode |= fsi->mode;349 WRITE_ONCE(inode->i_mode, tmp_mode);350 }351 352 if (!remount || fsi->opts & BIT(Opt_uid))353 inode->i_uid = fsi->uid;354 355 if (!remount || fsi->opts & BIT(Opt_gid))356 inode->i_gid = fsi->gid;357 358 if (remount && (fsi->opts & BIT(Opt_uid) || fsi->opts & BIT(Opt_gid))) {359 360 update_uid = fsi->opts & BIT(Opt_uid);361 update_gid = fsi->opts & BIT(Opt_gid);362 363 rcu_read_lock();364 list_for_each_entry_rcu(ti, &tracefs_inodes, list) {365 if (update_uid) {366 ti->flags &= ~TRACEFS_UID_PERM_SET;367 ti->vfs_inode.i_uid = fsi->uid;368 }369 370 if (update_gid) {371 ti->flags &= ~TRACEFS_GID_PERM_SET;372 ti->vfs_inode.i_gid = fsi->gid;373 }374 375 /*376 * Note, the above ti->vfs_inode updates are377 * used in eventfs_remount() so they must come378 * before calling it.379 */380 if (ti->flags & TRACEFS_EVENT_INODE)381 eventfs_remount(ti, update_uid, update_gid);382 }383 rcu_read_unlock();384 }385 386 return 0;387}388 389static int tracefs_reconfigure(struct fs_context *fc)390{391 struct super_block *sb = fc->root->d_sb;392 struct tracefs_fs_info *sb_opts = sb->s_fs_info;393 struct tracefs_fs_info *new_opts = fc->s_fs_info;394 395 if (!new_opts)396 return 0;397 398 sync_filesystem(sb);399 /* structure copy of new mount options to sb */400 *sb_opts = *new_opts;401 402 return tracefs_apply_options(sb, true);403}404 405static int tracefs_show_options(struct seq_file *m, struct dentry *root)406{407 struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;408 409 if (!uid_eq(fsi->uid, GLOBAL_ROOT_UID))410 seq_printf(m, ",uid=%u",411 from_kuid_munged(&init_user_ns, fsi->uid));412 if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID))413 seq_printf(m, ",gid=%u",414 from_kgid_munged(&init_user_ns, fsi->gid));415 if (fsi->mode != TRACEFS_DEFAULT_MODE)416 seq_printf(m, ",mode=%o", fsi->mode);417 418 return 0;419}420 421static int tracefs_drop_inode(struct inode *inode)422{423 struct tracefs_inode *ti = get_tracefs(inode);424 425 /*426 * This inode is being freed and cannot be used for427 * eventfs. Clear the flag so that it doesn't call into428 * eventfs during the remount flag updates. The eventfs_inode429 * gets freed after an RCU cycle, so the content will still430 * be safe if the iteration is going on now.431 */432 ti->flags &= ~TRACEFS_EVENT_INODE;433 434 return 1;435}436 437static const struct super_operations tracefs_super_operations = {438 .alloc_inode = tracefs_alloc_inode,439 .free_inode = tracefs_free_inode,440 .destroy_inode = tracefs_destroy_inode,441 .drop_inode = tracefs_drop_inode,442 .statfs = simple_statfs,443 .show_options = tracefs_show_options,444};445 446/*447 * It would be cleaner if eventfs had its own dentry ops.448 *449 * Note that d_revalidate is called potentially under RCU,450 * so it can't take the eventfs mutex etc. It's fine - if451 * we open a file just as it's marked dead, things will452 * still work just fine, and just see the old stale case.453 */454static void tracefs_d_release(struct dentry *dentry)455{456 if (dentry->d_fsdata)457 eventfs_d_release(dentry);458}459 460static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags)461{462 struct eventfs_inode *ei = dentry->d_fsdata;463 464 return !(ei && ei->is_freed);465}466 467static const struct dentry_operations tracefs_dentry_operations = {468 .d_revalidate = tracefs_d_revalidate,469 .d_release = tracefs_d_release,470};471 472static int tracefs_fill_super(struct super_block *sb, struct fs_context *fc)473{474 static const struct tree_descr trace_files[] = {{""}};475 int err;476 477 err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);478 if (err)479 return err;480 481 sb->s_op = &tracefs_super_operations;482 sb->s_d_op = &tracefs_dentry_operations;483 484 return 0;485}486 487static int tracefs_get_tree(struct fs_context *fc)488{489 int err = get_tree_single(fc, tracefs_fill_super);490 491 if (err)492 return err;493 494 return tracefs_reconfigure(fc);495}496 497static void tracefs_free_fc(struct fs_context *fc)498{499 kfree(fc->s_fs_info);500}501 502static const struct fs_context_operations tracefs_context_ops = {503 .free = tracefs_free_fc,504 .parse_param = tracefs_parse_param,505 .get_tree = tracefs_get_tree,506 .reconfigure = tracefs_reconfigure,507};508 509static int tracefs_init_fs_context(struct fs_context *fc)510{511 struct tracefs_fs_info *fsi;512 513 fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);514 if (!fsi)515 return -ENOMEM;516 517 fsi->mode = TRACEFS_DEFAULT_MODE;518 519 fc->s_fs_info = fsi;520 fc->ops = &tracefs_context_ops;521 return 0;522}523 524static struct file_system_type trace_fs_type = {525 .owner = THIS_MODULE,526 .name = "tracefs",527 .init_fs_context = tracefs_init_fs_context,528 .parameters = tracefs_param_specs,529 .kill_sb = kill_litter_super,530};531MODULE_ALIAS_FS("tracefs");532 533struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)534{535 struct dentry *dentry;536 int error;537 538 pr_debug("tracefs: creating file '%s'\n",name);539 540 error = simple_pin_fs(&trace_fs_type, &tracefs_mount,541 &tracefs_mount_count);542 if (error)543 return ERR_PTR(error);544 545 /* If the parent is not specified, we create it in the root.546 * We need the root dentry to do this, which is in the super547 * block. A pointer to that is in the struct vfsmount that we548 * have around.549 */550 if (!parent)551 parent = tracefs_mount->mnt_root;552 553 inode_lock(d_inode(parent));554 if (unlikely(IS_DEADDIR(d_inode(parent))))555 dentry = ERR_PTR(-ENOENT);556 else557 dentry = lookup_one_len(name, parent, strlen(name));558 if (!IS_ERR(dentry) && d_inode(dentry)) {559 dput(dentry);560 dentry = ERR_PTR(-EEXIST);561 }562 563 if (IS_ERR(dentry)) {564 inode_unlock(d_inode(parent));565 simple_release_fs(&tracefs_mount, &tracefs_mount_count);566 }567 568 return dentry;569}570 571struct dentry *tracefs_failed_creating(struct dentry *dentry)572{573 inode_unlock(d_inode(dentry->d_parent));574 dput(dentry);575 simple_release_fs(&tracefs_mount, &tracefs_mount_count);576 return NULL;577}578 579struct dentry *tracefs_end_creating(struct dentry *dentry)580{581 inode_unlock(d_inode(dentry->d_parent));582 return dentry;583}584 585/* Find the inode that this will use for default */586static struct inode *instance_inode(struct dentry *parent, struct inode *inode)587{588 struct tracefs_inode *ti;589 590 /* If parent is NULL then use root inode */591 if (!parent)592 return d_inode(inode->i_sb->s_root);593 594 /* Find the inode that is flagged as an instance or the root inode */595 while (!IS_ROOT(parent)) {596 ti = get_tracefs(d_inode(parent));597 if (ti->flags & TRACEFS_INSTANCE_INODE)598 break;599 parent = parent->d_parent;600 }601 602 return d_inode(parent);603}604 605/**606 * tracefs_create_file - create a file in the tracefs filesystem607 * @name: a pointer to a string containing the name of the file to create.608 * @mode: the permission that the file should have.609 * @parent: a pointer to the parent dentry for this file. This should be a610 * directory dentry if set. If this parameter is NULL, then the611 * file will be created in the root of the tracefs filesystem.612 * @data: a pointer to something that the caller will want to get to later613 * on. The inode.i_private pointer will point to this value on614 * the open() call.615 * @fops: a pointer to a struct file_operations that should be used for616 * this file.617 *618 * This is the basic "create a file" function for tracefs. It allows for a619 * wide range of flexibility in creating a file, or a directory (if you want620 * to create a directory, the tracefs_create_dir() function is621 * recommended to be used instead.)622 *623 * This function will return a pointer to a dentry if it succeeds. This624 * pointer must be passed to the tracefs_remove() function when the file is625 * to be removed (no automatic cleanup happens if your module is unloaded,626 * you are responsible here.) If an error occurs, %NULL will be returned.627 *628 * If tracefs is not enabled in the kernel, the value -%ENODEV will be629 * returned.630 */631struct dentry *tracefs_create_file(const char *name, umode_t mode,632 struct dentry *parent, void *data,633 const struct file_operations *fops)634{635 struct tracefs_inode *ti;636 struct dentry *dentry;637 struct inode *inode;638 639 if (security_locked_down(LOCKDOWN_TRACEFS))640 return NULL;641 642 if (!(mode & S_IFMT))643 mode |= S_IFREG;644 BUG_ON(!S_ISREG(mode));645 dentry = tracefs_start_creating(name, parent);646 647 if (IS_ERR(dentry))648 return NULL;649 650 inode = tracefs_get_inode(dentry->d_sb);651 if (unlikely(!inode))652 return tracefs_failed_creating(dentry);653 654 ti = get_tracefs(inode);655 ti->private = instance_inode(parent, inode);656 657 inode->i_mode = mode;658 inode->i_op = &tracefs_file_inode_operations;659 inode->i_fop = fops ? fops : &tracefs_file_operations;660 inode->i_private = data;661 inode->i_uid = d_inode(dentry->d_parent)->i_uid;662 inode->i_gid = d_inode(dentry->d_parent)->i_gid;663 d_instantiate(dentry, inode);664 fsnotify_create(d_inode(dentry->d_parent), dentry);665 return tracefs_end_creating(dentry);666}667 668static struct dentry *__create_dir(const char *name, struct dentry *parent,669 const struct inode_operations *ops)670{671 struct tracefs_inode *ti;672 struct dentry *dentry = tracefs_start_creating(name, parent);673 struct inode *inode;674 675 if (IS_ERR(dentry))676 return NULL;677 678 inode = tracefs_get_inode(dentry->d_sb);679 if (unlikely(!inode))680 return tracefs_failed_creating(dentry);681 682 /* Do not set bits for OTH */683 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;684 inode->i_op = ops;685 inode->i_fop = &simple_dir_operations;686 inode->i_uid = d_inode(dentry->d_parent)->i_uid;687 inode->i_gid = d_inode(dentry->d_parent)->i_gid;688 689 ti = get_tracefs(inode);690 ti->private = instance_inode(parent, inode);691 692 /* directory inodes start off with i_nlink == 2 (for "." entry) */693 inc_nlink(inode);694 d_instantiate(dentry, inode);695 inc_nlink(d_inode(dentry->d_parent));696 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);697 return tracefs_end_creating(dentry);698}699 700/**701 * tracefs_create_dir - create a directory in the tracefs filesystem702 * @name: a pointer to a string containing the name of the directory to703 * create.704 * @parent: a pointer to the parent dentry for this file. This should be a705 * directory dentry if set. If this parameter is NULL, then the706 * directory will be created in the root of the tracefs filesystem.707 *708 * This function creates a directory in tracefs with the given name.709 *710 * This function will return a pointer to a dentry if it succeeds. This711 * pointer must be passed to the tracefs_remove() function when the file is712 * to be removed. If an error occurs, %NULL will be returned.713 *714 * If tracing is not enabled in the kernel, the value -%ENODEV will be715 * returned.716 */717struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)718{719 if (security_locked_down(LOCKDOWN_TRACEFS))720 return NULL;721 722 return __create_dir(name, parent, &tracefs_dir_inode_operations);723}724 725/**726 * tracefs_create_instance_dir - create the tracing instances directory727 * @name: The name of the instances directory to create728 * @parent: The parent directory that the instances directory will exist729 * @mkdir: The function to call when a mkdir is performed.730 * @rmdir: The function to call when a rmdir is performed.731 *732 * Only one instances directory is allowed.733 *734 * The instances directory is special as it allows for mkdir and rmdir735 * to be done by userspace. When a mkdir or rmdir is performed, the inode736 * locks are released and the methods passed in (@mkdir and @rmdir) are737 * called without locks and with the name of the directory being created738 * within the instances directory.739 *740 * Returns the dentry of the instances directory.741 */742__init struct dentry *tracefs_create_instance_dir(const char *name,743 struct dentry *parent,744 int (*mkdir)(const char *name),745 int (*rmdir)(const char *name))746{747 struct dentry *dentry;748 749 /* Only allow one instance of the instances directory. */750 if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))751 return NULL;752 753 dentry = __create_dir(name, parent, &tracefs_instance_dir_inode_operations);754 if (!dentry)755 return NULL;756 757 tracefs_ops.mkdir = mkdir;758 tracefs_ops.rmdir = rmdir;759 760 return dentry;761}762 763static void remove_one(struct dentry *victim)764{765 simple_release_fs(&tracefs_mount, &tracefs_mount_count);766}767 768/**769 * tracefs_remove - recursively removes a directory770 * @dentry: a pointer to a the dentry of the directory to be removed.771 *772 * This function recursively removes a directory tree in tracefs that773 * was previously created with a call to another tracefs function774 * (like tracefs_create_file() or variants thereof.)775 */776void tracefs_remove(struct dentry *dentry)777{778 if (IS_ERR_OR_NULL(dentry))779 return;780 781 simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);782 simple_recursive_removal(dentry, remove_one);783 simple_release_fs(&tracefs_mount, &tracefs_mount_count);784}785 786/**787 * tracefs_initialized - Tells whether tracefs has been registered788 */789bool tracefs_initialized(void)790{791 return tracefs_registered;792}793 794static void init_once(void *foo)795{796 struct tracefs_inode *ti = (struct tracefs_inode *) foo;797 798 /* inode_init_once() calls memset() on the vfs_inode portion */799 inode_init_once(&ti->vfs_inode);800 801 /* Zero out the rest */802 memset_after(ti, 0, vfs_inode);803}804 805static int __init tracefs_init(void)806{807 int retval;808 809 tracefs_inode_cachep = kmem_cache_create("tracefs_inode_cache",810 sizeof(struct tracefs_inode),811 0, (SLAB_RECLAIM_ACCOUNT|812 SLAB_ACCOUNT),813 init_once);814 if (!tracefs_inode_cachep)815 return -ENOMEM;816 817 retval = sysfs_create_mount_point(kernel_kobj, "tracing");818 if (retval)819 return -EINVAL;820 821 retval = register_filesystem(&trace_fs_type);822 if (!retval)823 tracefs_registered = true;824 825 return retval;826}827core_initcall(tracefs_init);828