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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * event_inode.c - part of tracefs, a pseudo file system for activating tracing
4 *
5 * Copyright (C) 2020-23 VMware Inc, author: Steven Rostedt <rostedt@goodmis.org>
6 * Copyright (C) 2020-23 VMware Inc, author: Ajay Kaher <akaher@vmware.com>
7 * Copyright (C) 2023 Google, author: Steven Rostedt <rostedt@goodmis.org>
8 *
9 * eventfs is used to dynamically create inodes and dentries based on the
10 * meta data provided by the tracing system.
11 *
12 * eventfs stores the meta-data of files/dirs and holds off on creating
13 * inodes/dentries of the files. When accessed, the eventfs will create the
14 * inodes/dentries in a just-in-time (JIT) manner. The eventfs will clean up
15 * and delete the inodes/dentries when they are no longer referenced.
16 */
17#include <linux/fsnotify.h>
18#include <linux/fs.h>
19#include <linux/namei.h>
20#include <linux/workqueue.h>
21#include <linux/security.h>
22#include <linux/tracefs.h>
23#include <linux/kref.h>
24#include <linux/delay.h>
25#include "internal.h"
26
27/*
28 * eventfs_mutex protects the eventfs_inode (ei) dentry. Any access
29 * to the ei->dentry must be done under this mutex and after checking
30 * if ei->is_freed is not set. When ei->is_freed is set, the dentry
31 * is on its way to being freed after the last dput() is made on it.
32 */
33static DEFINE_MUTEX(eventfs_mutex);
34
35/* Choose something "unique" ;-) */
36#define EVENTFS_FILE_INODE_INO 0x12c4e37
37
38struct eventfs_root_inode {
39 struct eventfs_inode ei;
40 struct dentry *events_dir;
41};
42
43static struct eventfs_root_inode *get_root_inode(struct eventfs_inode *ei)
44{
45 WARN_ON_ONCE(!ei->is_events);
46 return container_of(ei, struct eventfs_root_inode, ei);
47}
48
49/* Just try to make something consistent and unique */
50static int eventfs_dir_ino(struct eventfs_inode *ei)
51{
52 if (!ei->ino) {
53 ei->ino = get_next_ino();
54 /* Must not have the file inode number */
55 if (ei->ino == EVENTFS_FILE_INODE_INO)
56 ei->ino = get_next_ino();
57 }
58
59 return ei->ino;
60}
61
62/*
63 * The eventfs_inode (ei) itself is protected by SRCU. It is released from
64 * its parent's list and will have is_freed set (under eventfs_mutex).
65 * After the SRCU grace period is over and the last dput() is called
66 * the ei is freed.
67 */
68DEFINE_STATIC_SRCU(eventfs_srcu);
69
70/* Mode is unsigned short, use the upper bits for flags */
71enum {
72 EVENTFS_SAVE_MODE = BIT(16),
73 EVENTFS_SAVE_UID = BIT(17),
74 EVENTFS_SAVE_GID = BIT(18),
75};
76
77#define EVENTFS_MODE_MASK (EVENTFS_SAVE_MODE - 1)
78
79static void free_ei_rcu(struct rcu_head *rcu)
80{
81 struct eventfs_inode *ei = container_of(rcu, struct eventfs_inode, rcu);
82 struct eventfs_root_inode *rei;
83
84 kfree(objp: ei->entry_attrs);
85 kfree_const(x: ei->name);
86 if (ei->is_events) {
87 rei = get_root_inode(ei);
88 kfree(objp: rei);
89 } else {
90 kfree(objp: ei);
91 }
92}
93
94/*
95 * eventfs_inode reference count management.
96 *
97 * NOTE! We count only references from dentries, in the
98 * form 'dentry->d_fsdata'. There are also references from
99 * directory inodes ('ti->private'), but the dentry reference
100 * count is always a superset of the inode reference count.
101 */
102static void release_ei(struct kref *ref)
103{
104 struct eventfs_inode *ei = container_of(ref, struct eventfs_inode, kref);
105 const struct eventfs_entry *entry;
106
107 WARN_ON_ONCE(!ei->is_freed);
108
109 for (int i = 0; i < ei->nr_entries; i++) {
110 entry = &ei->entries[i];
111 if (entry->release)
112 entry->release(entry->name, ei->data);
113 }
114
115 call_srcu(ssp: &eventfs_srcu, head: &ei->rcu, func: free_ei_rcu);
116}
117
118static inline void put_ei(struct eventfs_inode *ei)
119{
120 if (ei)
121 kref_put(kref: &ei->kref, release: release_ei);
122}
123
124static inline void free_ei(struct eventfs_inode *ei)
125{
126 if (ei) {
127 ei->is_freed = 1;
128 put_ei(ei);
129 }
130}
131
132/*
133 * Called when creation of an ei fails, do not call release() functions.
134 */
135static inline void cleanup_ei(struct eventfs_inode *ei)
136{
137 if (ei) {
138 /* Set nr_entries to 0 to prevent release() function being called */
139 ei->nr_entries = 0;
140 free_ei(ei);
141 }
142}
143
144static inline struct eventfs_inode *get_ei(struct eventfs_inode *ei)
145{
146 if (ei)
147 kref_get(kref: &ei->kref);
148 return ei;
149}
150
151static struct dentry *eventfs_root_lookup(struct inode *dir,
152 struct dentry *dentry,
153 unsigned int flags);
154static int eventfs_iterate(struct file *file, struct dir_context *ctx);
155
156static void update_attr(struct eventfs_attr *attr, struct iattr *iattr)
157{
158 unsigned int ia_valid = iattr->ia_valid;
159
160 if (ia_valid & ATTR_MODE) {
161 attr->mode = (attr->mode & ~EVENTFS_MODE_MASK) |
162 (iattr->ia_mode & EVENTFS_MODE_MASK) |
163 EVENTFS_SAVE_MODE;
164 }
165 if (ia_valid & ATTR_UID) {
166 attr->mode |= EVENTFS_SAVE_UID;
167 attr->uid = iattr->ia_uid;
168 }
169 if (ia_valid & ATTR_GID) {
170 attr->mode |= EVENTFS_SAVE_GID;
171 attr->gid = iattr->ia_gid;
172 }
173}
174
175static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
176 struct iattr *iattr)
177{
178 const struct eventfs_entry *entry;
179 struct eventfs_inode *ei;
180 const char *name;
181 int ret;
182
183 mutex_lock(&eventfs_mutex);
184 ei = dentry->d_fsdata;
185 if (ei->is_freed) {
186 /* Do not allow changes if the event is about to be removed. */
187 mutex_unlock(lock: &eventfs_mutex);
188 return -ENODEV;
189 }
190
191 /* Preallocate the children mode array if necessary */
192 if (!(dentry->d_inode->i_mode & S_IFDIR)) {
193 if (!ei->entry_attrs) {
194 ei->entry_attrs = kcalloc(ei->nr_entries, sizeof(*ei->entry_attrs),
195 GFP_NOFS);
196 if (!ei->entry_attrs) {
197 ret = -ENOMEM;
198 goto out;
199 }
200 }
201 }
202
203 ret = simple_setattr(idmap, dentry, iattr);
204 if (ret < 0)
205 goto out;
206
207 /*
208 * If this is a dir, then update the ei cache, only the file
209 * mode is saved in the ei->m_children, and the ownership is
210 * determined by the parent directory.
211 */
212 if (dentry->d_inode->i_mode & S_IFDIR) {
213 /* Just use the inode permissions for the events directory */
214 if (!ei->is_events)
215 update_attr(attr: &ei->attr, iattr);
216
217 } else {
218 name = dentry->d_name.name;
219
220 for (int i = 0; i < ei->nr_entries; i++) {
221 entry = &ei->entries[i];
222 if (strcmp(name, entry->name) == 0) {
223 update_attr(attr: &ei->entry_attrs[i], iattr);
224 break;
225 }
226 }
227 }
228 out:
229 mutex_unlock(lock: &eventfs_mutex);
230 return ret;
231}
232
233static const struct inode_operations eventfs_dir_inode_operations = {
234 .lookup = eventfs_root_lookup,
235 .setattr = eventfs_set_attr,
236};
237
238static const struct inode_operations eventfs_file_inode_operations = {
239 .setattr = eventfs_set_attr,
240};
241
242static const struct file_operations eventfs_file_operations = {
243 .read = generic_read_dir,
244 .iterate_shared = eventfs_iterate,
245 .llseek = generic_file_llseek,
246};
247
248static void eventfs_set_attrs(struct eventfs_inode *ei, bool update_uid, kuid_t uid,
249 bool update_gid, kgid_t gid, int level)
250{
251 struct eventfs_inode *ei_child;
252
253 /* Update events/<system>/<event> */
254 if (WARN_ON_ONCE(level > 3))
255 return;
256
257 if (update_uid) {
258 ei->attr.mode &= ~EVENTFS_SAVE_UID;
259 ei->attr.uid = uid;
260 }
261
262 if (update_gid) {
263 ei->attr.mode &= ~EVENTFS_SAVE_GID;
264 ei->attr.gid = gid;
265 }
266
267 list_for_each_entry(ei_child, &ei->children, list) {
268 eventfs_set_attrs(ei: ei_child, update_uid, uid, update_gid, gid, level: level + 1);
269 }
270
271 if (!ei->entry_attrs)
272 return;
273
274 for (int i = 0; i < ei->nr_entries; i++) {
275 if (update_uid) {
276 ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_UID;
277 ei->entry_attrs[i].uid = uid;
278 }
279 if (update_gid) {
280 ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_GID;
281 ei->entry_attrs[i].gid = gid;
282 }
283 }
284
285}
286
287/*
288 * On a remount of tracefs, if UID or GID options are set, then
289 * the mount point inode permissions should be used.
290 * Reset the saved permission flags appropriately.
291 */
292void eventfs_remount(struct tracefs_inode *ti, bool update_uid, bool update_gid)
293{
294 struct eventfs_inode *ei = ti->private;
295
296 /* Only the events directory does the updates */
297 if (!ei || !ei->is_events || ei->is_freed)
298 return;
299
300 eventfs_set_attrs(ei, update_uid, uid: ti->vfs_inode.i_uid,
301 update_gid, gid: ti->vfs_inode.i_gid, level: 0);
302}
303
304static void update_inode_attr(struct inode *inode, umode_t mode,
305 struct eventfs_attr *attr, struct eventfs_root_inode *rei)
306{
307 if (attr && attr->mode & EVENTFS_SAVE_MODE)
308 inode->i_mode = attr->mode & EVENTFS_MODE_MASK;
309 else
310 inode->i_mode = mode;
311
312 if (attr && attr->mode & EVENTFS_SAVE_UID)
313 inode->i_uid = attr->uid;
314 else
315 inode->i_uid = rei->ei.attr.uid;
316
317 if (attr && attr->mode & EVENTFS_SAVE_GID)
318 inode->i_gid = attr->gid;
319 else
320 inode->i_gid = rei->ei.attr.gid;
321}
322
323static struct inode *eventfs_get_inode(struct dentry *dentry, struct eventfs_attr *attr,
324 umode_t mode, struct eventfs_inode *ei)
325{
326 struct eventfs_root_inode *rei;
327 struct eventfs_inode *pei;
328 struct tracefs_inode *ti;
329 struct inode *inode;
330
331 inode = tracefs_get_inode(sb: dentry->d_sb);
332 if (!inode)
333 return NULL;
334
335 ti = get_tracefs(inode);
336 ti->private = ei;
337 ti->flags |= TRACEFS_EVENT_INODE;
338
339 /* Find the top dentry that holds the "events" directory */
340 do {
341 dentry = dentry->d_parent;
342 /* Directories always have d_fsdata */
343 pei = dentry->d_fsdata;
344 } while (!pei->is_events);
345
346 rei = get_root_inode(ei: pei);
347
348 update_inode_attr(inode, mode, attr, rei);
349
350 return inode;
351}
352
353/**
354 * lookup_file - look up a file in the tracefs filesystem
355 * @parent_ei: Pointer to the eventfs_inode that represents parent of the file
356 * @dentry: the dentry to look up
357 * @mode: the permission that the file should have.
358 * @attr: saved attributes changed by user
359 * @data: something that the caller will want to get to later on.
360 * @fop: struct file_operations that should be used for this file.
361 *
362 * This function creates a dentry that represents a file in the eventsfs_inode
363 * directory. The inode.i_private pointer will point to @data in the open()
364 * call.
365 */
366static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
367 struct dentry *dentry,
368 umode_t mode,
369 struct eventfs_attr *attr,
370 void *data,
371 const struct file_operations *fop)
372{
373 struct inode *inode;
374
375 if (!(mode & S_IFMT))
376 mode |= S_IFREG;
377
378 if (WARN_ON_ONCE(!S_ISREG(mode)))
379 return ERR_PTR(error: -EIO);
380
381 /* Only directories have ti->private set to an ei, not files */
382 inode = eventfs_get_inode(dentry, attr, mode, NULL);
383 if (unlikely(!inode))
384 return ERR_PTR(error: -ENOMEM);
385
386 inode->i_op = &eventfs_file_inode_operations;
387 inode->i_fop = fop;
388 inode->i_private = data;
389
390 /* All files will have the same inode number */
391 inode->i_ino = EVENTFS_FILE_INODE_INO;
392
393 // Files have their parent's ei as their fsdata
394 dentry->d_fsdata = get_ei(ei: parent_ei);
395
396 d_add(dentry, inode);
397 return NULL;
398};
399
400/**
401 * lookup_dir_entry - look up a dir in the tracefs filesystem
402 * @dentry: the directory to look up
403 * @pei: Pointer to the parent eventfs_inode if available
404 * @ei: the eventfs_inode that represents the directory to create
405 *
406 * This function will look up a dentry for a directory represented by
407 * a eventfs_inode.
408 */
409static struct dentry *lookup_dir_entry(struct dentry *dentry,
410 struct eventfs_inode *pei, struct eventfs_inode *ei)
411{
412 struct inode *inode;
413 umode_t mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
414
415 inode = eventfs_get_inode(dentry, attr: &ei->attr, mode, ei);
416 if (unlikely(!inode))
417 return ERR_PTR(error: -ENOMEM);
418
419 inode->i_op = &eventfs_dir_inode_operations;
420 inode->i_fop = &eventfs_file_operations;
421
422 /* All directories will have the same inode number */
423 inode->i_ino = eventfs_dir_ino(ei);
424
425 dentry->d_fsdata = get_ei(ei);
426
427 d_add(dentry, inode);
428 return NULL;
429}
430
431static inline struct eventfs_inode *init_ei(struct eventfs_inode *ei, const char *name)
432{
433 ei->name = kstrdup_const(s: name, GFP_KERNEL);
434 if (!ei->name)
435 return NULL;
436 kref_init(kref: &ei->kref);
437 return ei;
438}
439
440static inline struct eventfs_inode *alloc_ei(const char *name)
441{
442 struct eventfs_inode *ei = kzalloc(sizeof(*ei), GFP_KERNEL);
443 struct eventfs_inode *result;
444
445 if (!ei)
446 return NULL;
447
448 result = init_ei(ei, name);
449 if (!result)
450 kfree(objp: ei);
451
452 return result;
453}
454
455static inline struct eventfs_inode *alloc_root_ei(const char *name)
456{
457 struct eventfs_root_inode *rei = kzalloc(sizeof(*rei), GFP_KERNEL);
458 struct eventfs_inode *ei;
459
460 if (!rei)
461 return NULL;
462
463 rei->ei.is_events = 1;
464 ei = init_ei(ei: &rei->ei, name);
465 if (!ei)
466 kfree(objp: rei);
467
468 return ei;
469}
470
471/**
472 * eventfs_d_release - dentry is going away
473 * @dentry: dentry which has the reference to remove.
474 *
475 * Remove the association between a dentry from an eventfs_inode.
476 */
477void eventfs_d_release(struct dentry *dentry)
478{
479 put_ei(ei: dentry->d_fsdata);
480}
481
482/**
483 * lookup_file_dentry - create a dentry for a file of an eventfs_inode
484 * @dentry: The parent dentry under which the new file's dentry will be created
485 * @ei: the eventfs_inode that the file will be created under
486 * @idx: the index into the entry_attrs[] of the @ei
487 * @mode: The mode of the file.
488 * @data: The data to use to set the inode of the file with on open()
489 * @fops: The fops of the file to be created.
490 *
491 * This function creates a dentry for a file associated with an
492 * eventfs_inode @ei. It uses the entry attributes specified by @idx,
493 * if available. The file will have the specified @mode and its inode will be
494 * set up with @data upon open. The file operations will be set to @fops.
495 *
496 * Return: Returns a pointer to the newly created file's dentry or an error
497 * pointer.
498 */
499static struct dentry *
500lookup_file_dentry(struct dentry *dentry,
501 struct eventfs_inode *ei, int idx,
502 umode_t mode, void *data,
503 const struct file_operations *fops)
504{
505 struct eventfs_attr *attr = NULL;
506
507 if (ei->entry_attrs)
508 attr = &ei->entry_attrs[idx];
509
510 return lookup_file(parent_ei: ei, dentry, mode, attr, data, fop: fops);
511}
512
513/**
514 * eventfs_root_lookup - lookup routine to create file/dir
515 * @dir: in which a lookup is being done
516 * @dentry: file/dir dentry
517 * @flags: Just passed to simple_lookup()
518 *
519 * Used to create dynamic file/dir with-in @dir, search with-in @ei
520 * list, if @dentry found go ahead and create the file/dir
521 */
522
523static struct dentry *eventfs_root_lookup(struct inode *dir,
524 struct dentry *dentry,
525 unsigned int flags)
526{
527 struct eventfs_inode *ei_child;
528 struct tracefs_inode *ti;
529 struct eventfs_inode *ei;
530 const char *name = dentry->d_name.name;
531 struct dentry *result = NULL;
532
533 ti = get_tracefs(inode: dir);
534 if (WARN_ON_ONCE(!(ti->flags & TRACEFS_EVENT_INODE)))
535 return ERR_PTR(error: -EIO);
536
537 mutex_lock(&eventfs_mutex);
538
539 ei = ti->private;
540 if (!ei || ei->is_freed)
541 goto out;
542
543 list_for_each_entry(ei_child, &ei->children, list) {
544 if (strcmp(ei_child->name, name) != 0)
545 continue;
546 /* A child is freed and removed from the list at the same time */
547 if (WARN_ON_ONCE(ei_child->is_freed))
548 goto out;
549 result = lookup_dir_entry(dentry, pei: ei, ei: ei_child);
550 goto out;
551 }
552
553 for (int i = 0; i < ei->nr_entries; i++) {
554 void *data;
555 umode_t mode;
556 const struct file_operations *fops;
557 const struct eventfs_entry *entry = &ei->entries[i];
558
559 if (strcmp(name, entry->name) != 0)
560 continue;
561
562 data = ei->data;
563 if (entry->callback(name, &mode, &data, &fops) <= 0)
564 goto out;
565
566 result = lookup_file_dentry(dentry, ei, idx: i, mode, data, fops);
567 goto out;
568 }
569 out:
570 mutex_unlock(lock: &eventfs_mutex);
571 return result;
572}
573
574/*
575 * Walk the children of a eventfs_inode to fill in getdents().
576 */
577static int eventfs_iterate(struct file *file, struct dir_context *ctx)
578{
579 const struct file_operations *fops;
580 struct inode *f_inode = file_inode(f: file);
581 const struct eventfs_entry *entry;
582 struct eventfs_inode *ei_child;
583 struct tracefs_inode *ti;
584 struct eventfs_inode *ei;
585 const char *name;
586 umode_t mode;
587 int idx;
588 int ret = -EINVAL;
589 int ino;
590 int i, r, c;
591
592 if (!dir_emit_dots(file, ctx))
593 return 0;
594
595 ti = get_tracefs(inode: f_inode);
596 if (!(ti->flags & TRACEFS_EVENT_INODE))
597 return -EINVAL;
598
599 c = ctx->pos - 2;
600
601 idx = srcu_read_lock(ssp: &eventfs_srcu);
602
603 mutex_lock(&eventfs_mutex);
604 ei = READ_ONCE(ti->private);
605 if (ei && ei->is_freed)
606 ei = NULL;
607 mutex_unlock(lock: &eventfs_mutex);
608
609 if (!ei)
610 goto out;
611
612 /*
613 * Need to create the dentries and inodes to have a consistent
614 * inode number.
615 */
616 ret = 0;
617
618 /* Start at 'c' to jump over already read entries */
619 for (i = c; i < ei->nr_entries; i++, ctx->pos++) {
620 void *cdata = ei->data;
621
622 entry = &ei->entries[i];
623 name = entry->name;
624
625 mutex_lock(&eventfs_mutex);
626 /* If ei->is_freed then just bail here, nothing more to do */
627 if (ei->is_freed) {
628 mutex_unlock(lock: &eventfs_mutex);
629 goto out;
630 }
631 r = entry->callback(name, &mode, &cdata, &fops);
632 mutex_unlock(lock: &eventfs_mutex);
633 if (r <= 0)
634 continue;
635
636 ino = EVENTFS_FILE_INODE_INO;
637
638 if (!dir_emit(ctx, name, strlen(name), ino, DT_REG))
639 goto out;
640 }
641
642 /* Subtract the skipped entries above */
643 c -= min((unsigned int)c, (unsigned int)ei->nr_entries);
644
645 list_for_each_entry_srcu(ei_child, &ei->children, list,
646 srcu_read_lock_held(&eventfs_srcu)) {
647
648 if (c > 0) {
649 c--;
650 continue;
651 }
652
653 ctx->pos++;
654
655 if (ei_child->is_freed)
656 continue;
657
658 name = ei_child->name;
659
660 ino = eventfs_dir_ino(ei: ei_child);
661
662 if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR))
663 goto out_dec;
664 }
665 ret = 1;
666 out:
667 srcu_read_unlock(ssp: &eventfs_srcu, idx);
668
669 return ret;
670
671 out_dec:
672 /* Incremented ctx->pos without adding something, reset it */
673 ctx->pos--;
674 goto out;
675}
676
677/**
678 * eventfs_create_dir - Create the eventfs_inode for this directory
679 * @name: The name of the directory to create.
680 * @parent: The eventfs_inode of the parent directory.
681 * @entries: A list of entries that represent the files under this directory
682 * @size: The number of @entries
683 * @data: The default data to pass to the files (an entry may override it).
684 *
685 * This function creates the descriptor to represent a directory in the
686 * eventfs. This descriptor is an eventfs_inode, and it is returned to be
687 * used to create other children underneath.
688 *
689 * The @entries is an array of eventfs_entry structures which has:
690 * const char *name
691 * eventfs_callback callback;
692 *
693 * The name is the name of the file, and the callback is a pointer to a function
694 * that will be called when the file is reference (either by lookup or by
695 * reading a directory). The callback is of the prototype:
696 *
697 * int callback(const char *name, umode_t *mode, void **data,
698 * const struct file_operations **fops);
699 *
700 * When a file needs to be created, this callback will be called with
701 * name = the name of the file being created (so that the same callback
702 * may be used for multiple files).
703 * mode = a place to set the file's mode
704 * data = A pointer to @data, and the callback may replace it, which will
705 * cause the file created to pass the new data to the open() call.
706 * fops = the fops to use for the created file.
707 *
708 * NB. @callback is called while holding internal locks of the eventfs
709 * system. The callback must not call any code that might also call into
710 * the tracefs or eventfs system or it will risk creating a deadlock.
711 */
712struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode *parent,
713 const struct eventfs_entry *entries,
714 int size, void *data)
715{
716 struct eventfs_inode *ei;
717
718 if (!parent)
719 return ERR_PTR(error: -EINVAL);
720
721 ei = alloc_ei(name);
722 if (!ei)
723 return ERR_PTR(error: -ENOMEM);
724
725 ei->entries = entries;
726 ei->nr_entries = size;
727 ei->data = data;
728 INIT_LIST_HEAD(list: &ei->children);
729 INIT_LIST_HEAD(list: &ei->list);
730
731 mutex_lock(&eventfs_mutex);
732 if (!parent->is_freed)
733 list_add_tail(new: &ei->list, head: &parent->children);
734 mutex_unlock(lock: &eventfs_mutex);
735
736 /* Was the parent freed? */
737 if (list_empty(head: &ei->list)) {
738 cleanup_ei(ei);
739 ei = ERR_PTR(error: -EBUSY);
740 }
741 return ei;
742}
743
744/**
745 * eventfs_create_events_dir - create the top level events directory
746 * @name: The name of the top level directory to create.
747 * @parent: Parent dentry for this file in the tracefs directory.
748 * @entries: A list of entries that represent the files under this directory
749 * @size: The number of @entries
750 * @data: The default data to pass to the files (an entry may override it).
751 *
752 * This function creates the top of the trace event directory.
753 *
754 * See eventfs_create_dir() for use of @entries.
755 */
756struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry *parent,
757 const struct eventfs_entry *entries,
758 int size, void *data)
759{
760 struct dentry *dentry;
761 struct eventfs_root_inode *rei;
762 struct eventfs_inode *ei;
763 struct tracefs_inode *ti;
764 struct inode *inode;
765 kuid_t uid;
766 kgid_t gid;
767
768 if (security_locked_down(what: LOCKDOWN_TRACEFS))
769 return NULL;
770
771 dentry = tracefs_start_creating(name, parent);
772 if (IS_ERR(ptr: dentry))
773 return ERR_CAST(ptr: dentry);
774
775 ei = alloc_root_ei(name);
776 if (!ei)
777 goto fail;
778
779 inode = tracefs_get_inode(sb: dentry->d_sb);
780 if (unlikely(!inode))
781 goto fail;
782
783 // Note: we have a ref to the dentry from tracefs_start_creating()
784 rei = get_root_inode(ei);
785 rei->events_dir = dentry;
786
787 ei->entries = entries;
788 ei->nr_entries = size;
789 ei->data = data;
790
791 /* Save the ownership of this directory */
792 uid = d_inode(dentry: dentry->d_parent)->i_uid;
793 gid = d_inode(dentry: dentry->d_parent)->i_gid;
794
795 /*
796 * The ei->attr will be used as the default values for the
797 * files beneath this directory.
798 */
799 ei->attr.uid = uid;
800 ei->attr.gid = gid;
801
802 INIT_LIST_HEAD(list: &ei->children);
803 INIT_LIST_HEAD(list: &ei->list);
804
805 ti = get_tracefs(inode);
806 ti->flags |= TRACEFS_EVENT_INODE;
807 ti->private = ei;
808
809 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
810 inode->i_uid = uid;
811 inode->i_gid = gid;
812 inode->i_op = &eventfs_dir_inode_operations;
813 inode->i_fop = &eventfs_file_operations;
814
815 dentry->d_fsdata = get_ei(ei);
816
817 /*
818 * Keep all eventfs directories with i_nlink == 1.
819 * Due to the dynamic nature of the dentry creations and not
820 * wanting to add a pointer to the parent eventfs_inode in the
821 * eventfs_inode structure, keeping the i_nlink in sync with the
822 * number of directories would cause too much complexity for
823 * something not worth much. Keeping directory links at 1
824 * tells userspace not to trust the link number.
825 */
826 d_make_persistent(dentry, inode);
827 /* The dentry of the "events" parent does keep track though */
828 inc_nlink(inode: dentry->d_parent->d_inode);
829 fsnotify_mkdir(dir: dentry->d_parent->d_inode, dentry);
830 tracefs_end_creating(dentry);
831
832 return ei;
833
834 fail:
835 cleanup_ei(ei);
836 tracefs_failed_creating(dentry);
837 return ERR_PTR(error: -ENOMEM);
838}
839
840/**
841 * eventfs_remove_rec - remove eventfs dir or file from list
842 * @ei: eventfs_inode to be removed.
843 * @level: prevent recursion from going more than 3 levels deep.
844 *
845 * This function recursively removes eventfs_inodes which
846 * contains info of files and/or directories.
847 */
848static void eventfs_remove_rec(struct eventfs_inode *ei, int level)
849{
850 struct eventfs_inode *ei_child;
851
852 /*
853 * Check recursion depth. It should never be greater than 3:
854 * 0 - events/
855 * 1 - events/group/
856 * 2 - events/group/event/
857 * 3 - events/group/event/file
858 */
859 if (WARN_ON_ONCE(level > 3))
860 return;
861
862 /* search for nested folders or files */
863 list_for_each_entry(ei_child, &ei->children, list)
864 eventfs_remove_rec(ei: ei_child, level: level + 1);
865
866 list_del_rcu(entry: &ei->list);
867 free_ei(ei);
868}
869
870/**
871 * eventfs_remove_dir - remove eventfs dir or file from list
872 * @ei: eventfs_inode to be removed.
873 *
874 * This function acquire the eventfs_mutex lock and call eventfs_remove_rec()
875 */
876void eventfs_remove_dir(struct eventfs_inode *ei)
877{
878 if (!ei)
879 return;
880
881 mutex_lock(&eventfs_mutex);
882 eventfs_remove_rec(ei, level: 0);
883 mutex_unlock(lock: &eventfs_mutex);
884}
885
886/**
887 * eventfs_remove_events_dir - remove the top level eventfs directory
888 * @ei: the event_inode returned by eventfs_create_events_dir().
889 *
890 * This function removes the events main directory
891 */
892void eventfs_remove_events_dir(struct eventfs_inode *ei)
893{
894 struct eventfs_root_inode *rei;
895 struct dentry *dentry;
896
897 rei = get_root_inode(ei);
898 dentry = rei->events_dir;
899 if (!dentry)
900 return;
901
902 rei->events_dir = NULL;
903 eventfs_remove_dir(ei);
904
905 /*
906 * Matches the dget() done by tracefs_start_creating()
907 * in eventfs_create_events_dir() when it the dentry was
908 * created. In other words, it's a normal dentry that
909 * sticks around while the other ei->dentry are created
910 * and destroyed dynamically.
911 */
912 d_invalidate(dentry);
913 d_make_discardable(dentry);
914}
915

source code of linux/fs/tracefs/event_inode.c