1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
4 */
5
6#include <linux/dcache.h>
7#include <linux/fs.h>
8#include <linux/gfp.h>
9#include <linux/init.h>
10#include <linux/module.h>
11#include <linux/mount.h>
12#include <linux/srcu.h>
13
14#include <linux/fsnotify_backend.h>
15#include "fsnotify.h"
16
17/*
18 * Clear all of the marks on an inode when it is being evicted from core
19 */
20void __fsnotify_inode_delete(struct inode *inode)
21{
22 fsnotify_clear_marks_by_inode(inode);
23}
24EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
25
26void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
27{
28 fsnotify_clear_marks_by_mount(mnt);
29}
30
31/**
32 * fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
33 * @sb: superblock being unmounted.
34 *
35 * Called during unmount with no locks held, so needs to be safe against
36 * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
37 */
38static void fsnotify_unmount_inodes(struct super_block *sb)
39{
40 struct inode *inode, *iput_inode = NULL;
41
42 spin_lock(lock: &sb->s_inode_list_lock);
43 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
44 /*
45 * We cannot __iget() an inode in state I_FREEING,
46 * I_WILL_FREE, or I_NEW which is fine because by that point
47 * the inode cannot have any associated watches.
48 */
49 spin_lock(lock: &inode->i_lock);
50 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
51 spin_unlock(lock: &inode->i_lock);
52 continue;
53 }
54
55 /*
56 * If i_count is zero, the inode cannot have any watches and
57 * doing an __iget/iput with SB_ACTIVE clear would actually
58 * evict all inodes with zero i_count from icache which is
59 * unnecessarily violent and may in fact be illegal to do.
60 * However, we should have been called /after/ evict_inodes
61 * removed all zero refcount inodes, in any case. Test to
62 * be sure.
63 */
64 if (!atomic_read(v: &inode->i_count)) {
65 spin_unlock(lock: &inode->i_lock);
66 continue;
67 }
68
69 __iget(inode);
70 spin_unlock(lock: &inode->i_lock);
71 spin_unlock(lock: &sb->s_inode_list_lock);
72
73 iput(iput_inode);
74
75 /* for each watch, send FS_UNMOUNT and then remove it */
76 fsnotify_inode(inode, FS_UNMOUNT);
77
78 fsnotify_inode_delete(inode);
79
80 iput_inode = inode;
81
82 cond_resched();
83 spin_lock(lock: &sb->s_inode_list_lock);
84 }
85 spin_unlock(lock: &sb->s_inode_list_lock);
86
87 iput(iput_inode);
88}
89
90void fsnotify_sb_delete(struct super_block *sb)
91{
92 fsnotify_unmount_inodes(sb);
93 fsnotify_clear_marks_by_sb(sb);
94 /* Wait for outstanding object references from connectors */
95 wait_var_event(&sb->s_fsnotify_connectors,
96 !atomic_long_read(&sb->s_fsnotify_connectors));
97}
98
99/*
100 * Given an inode, first check if we care what happens to our children. Inotify
101 * and dnotify both tell their parents about events. If we care about any event
102 * on a child we run all of our children and set a dentry flag saying that the
103 * parent cares. Thus when an event happens on a child it can quickly tell
104 * if there is a need to find a parent and send the event to the parent.
105 */
106void __fsnotify_update_child_dentry_flags(struct inode *inode)
107{
108 struct dentry *alias;
109 int watched;
110
111 if (!S_ISDIR(inode->i_mode))
112 return;
113
114 /* determine if the children should tell inode about their events */
115 watched = fsnotify_inode_watches_children(inode);
116
117 spin_lock(lock: &inode->i_lock);
118 /* run all of the dentries associated with this inode. Since this is a
119 * directory, there damn well better only be one item on this list */
120 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
121 struct dentry *child;
122
123 /* run all of the children of the original inode and fix their
124 * d_flags to indicate parental interest (their parent is the
125 * original inode) */
126 spin_lock(lock: &alias->d_lock);
127 hlist_for_each_entry(child, &alias->d_children, d_sib) {
128 if (!child->d_inode)
129 continue;
130
131 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
132 if (watched)
133 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
134 else
135 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
136 spin_unlock(lock: &child->d_lock);
137 }
138 spin_unlock(lock: &alias->d_lock);
139 }
140 spin_unlock(lock: &inode->i_lock);
141}
142
143/* Are inode/sb/mount interested in parent and name info with this event? */
144static bool fsnotify_event_needs_parent(struct inode *inode, __u32 mnt_mask,
145 __u32 mask)
146{
147 __u32 marks_mask = 0;
148
149 /* We only send parent/name to inode/sb/mount for events on non-dir */
150 if (mask & FS_ISDIR)
151 return false;
152
153 /*
154 * All events that are possible on child can also may be reported with
155 * parent/name info to inode/sb/mount. Otherwise, a watching parent
156 * could result in events reported with unexpected name info to sb/mount.
157 */
158 BUILD_BUG_ON(FS_EVENTS_POSS_ON_CHILD & ~FS_EVENTS_POSS_TO_PARENT);
159
160 /* Did either inode/sb/mount subscribe for events with parent/name? */
161 marks_mask |= fsnotify_parent_needed_mask(mask: inode->i_fsnotify_mask);
162 marks_mask |= fsnotify_parent_needed_mask(mask: inode->i_sb->s_fsnotify_mask);
163 marks_mask |= fsnotify_parent_needed_mask(mask: mnt_mask);
164
165 /* Did they subscribe for this event with parent/name info? */
166 return mask & marks_mask;
167}
168
169/* Are there any inode/mount/sb objects that are interested in this event? */
170static inline bool fsnotify_object_watched(struct inode *inode, __u32 mnt_mask,
171 __u32 mask)
172{
173 __u32 marks_mask = inode->i_fsnotify_mask | mnt_mask |
174 inode->i_sb->s_fsnotify_mask;
175
176 return mask & marks_mask & ALL_FSNOTIFY_EVENTS;
177}
178
179/*
180 * Notify this dentry's parent about a child's events with child name info
181 * if parent is watching or if inode/sb/mount are interested in events with
182 * parent and name info.
183 *
184 * Notify only the child without name info if parent is not watching and
185 * inode/sb/mount are not interested in events with parent and name info.
186 */
187int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
188 int data_type)
189{
190 const struct path *path = fsnotify_data_path(data, data_type);
191 __u32 mnt_mask = path ? real_mount(mnt: path->mnt)->mnt_fsnotify_mask : 0;
192 struct inode *inode = d_inode(dentry);
193 struct dentry *parent;
194 bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED;
195 bool parent_needed, parent_interested;
196 __u32 p_mask;
197 struct inode *p_inode = NULL;
198 struct name_snapshot name;
199 struct qstr *file_name = NULL;
200 int ret = 0;
201
202 /* Optimize the likely case of nobody watching this path */
203 if (likely(!parent_watched &&
204 !fsnotify_object_watched(inode, mnt_mask, mask)))
205 return 0;
206
207 parent = NULL;
208 parent_needed = fsnotify_event_needs_parent(inode, mnt_mask, mask);
209 if (!parent_watched && !parent_needed)
210 goto notify;
211
212 /* Does parent inode care about events on children? */
213 parent = dget_parent(dentry);
214 p_inode = parent->d_inode;
215 p_mask = fsnotify_inode_watches_children(inode: p_inode);
216 if (unlikely(parent_watched && !p_mask))
217 __fsnotify_update_child_dentry_flags(inode: p_inode);
218
219 /*
220 * Include parent/name in notification either if some notification
221 * groups require parent info or the parent is interested in this event.
222 */
223 parent_interested = mask & p_mask & ALL_FSNOTIFY_EVENTS;
224 if (parent_needed || parent_interested) {
225 /* When notifying parent, child should be passed as data */
226 WARN_ON_ONCE(inode != fsnotify_data_inode(data, data_type));
227
228 /* Notify both parent and child with child name info */
229 take_dentry_name_snapshot(&name, dentry);
230 file_name = &name.name;
231 if (parent_interested)
232 mask |= FS_EVENT_ON_CHILD;
233 }
234
235notify:
236 ret = fsnotify(mask, data, data_type, dir: p_inode, name: file_name, inode, cookie: 0);
237
238 if (file_name)
239 release_dentry_name_snapshot(&name);
240 dput(parent);
241
242 return ret;
243}
244EXPORT_SYMBOL_GPL(__fsnotify_parent);
245
246static int fsnotify_handle_inode_event(struct fsnotify_group *group,
247 struct fsnotify_mark *inode_mark,
248 u32 mask, const void *data, int data_type,
249 struct inode *dir, const struct qstr *name,
250 u32 cookie)
251{
252 const struct path *path = fsnotify_data_path(data, data_type);
253 struct inode *inode = fsnotify_data_inode(data, data_type);
254 const struct fsnotify_ops *ops = group->ops;
255
256 if (WARN_ON_ONCE(!ops->handle_inode_event))
257 return 0;
258
259 if (WARN_ON_ONCE(!inode && !dir))
260 return 0;
261
262 if ((inode_mark->flags & FSNOTIFY_MARK_FLAG_EXCL_UNLINK) &&
263 path && d_unlinked(dentry: path->dentry))
264 return 0;
265
266 /* Check interest of this mark in case event was sent with two marks */
267 if (!(mask & inode_mark->mask & ALL_FSNOTIFY_EVENTS))
268 return 0;
269
270 return ops->handle_inode_event(inode_mark, mask, inode, dir, name, cookie);
271}
272
273static int fsnotify_handle_event(struct fsnotify_group *group, __u32 mask,
274 const void *data, int data_type,
275 struct inode *dir, const struct qstr *name,
276 u32 cookie, struct fsnotify_iter_info *iter_info)
277{
278 struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
279 struct fsnotify_mark *parent_mark = fsnotify_iter_parent_mark(iter_info);
280 int ret;
281
282 if (WARN_ON_ONCE(fsnotify_iter_sb_mark(iter_info)) ||
283 WARN_ON_ONCE(fsnotify_iter_vfsmount_mark(iter_info)))
284 return 0;
285
286 /*
287 * For FS_RENAME, 'dir' is old dir and 'data' is new dentry.
288 * The only ->handle_inode_event() backend that supports FS_RENAME is
289 * dnotify, where it means file was renamed within same parent.
290 */
291 if (mask & FS_RENAME) {
292 struct dentry *moved = fsnotify_data_dentry(data, data_type);
293
294 if (dir != moved->d_parent->d_inode)
295 return 0;
296 }
297
298 if (parent_mark) {
299 ret = fsnotify_handle_inode_event(group, inode_mark: parent_mark, mask,
300 data, data_type, dir, name, cookie: 0);
301 if (ret)
302 return ret;
303 }
304
305 if (!inode_mark)
306 return 0;
307
308 if (mask & FS_EVENT_ON_CHILD) {
309 /*
310 * Some events can be sent on both parent dir and child marks
311 * (e.g. FS_ATTRIB). If both parent dir and child are
312 * watching, report the event once to parent dir with name (if
313 * interested) and once to child without name (if interested).
314 * The child watcher is expecting an event without a file name
315 * and without the FS_EVENT_ON_CHILD flag.
316 */
317 mask &= ~FS_EVENT_ON_CHILD;
318 dir = NULL;
319 name = NULL;
320 }
321
322 return fsnotify_handle_inode_event(group, inode_mark, mask, data, data_type,
323 dir, name, cookie);
324}
325
326static int send_to_group(__u32 mask, const void *data, int data_type,
327 struct inode *dir, const struct qstr *file_name,
328 u32 cookie, struct fsnotify_iter_info *iter_info)
329{
330 struct fsnotify_group *group = NULL;
331 __u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
332 __u32 marks_mask = 0;
333 __u32 marks_ignore_mask = 0;
334 bool is_dir = mask & FS_ISDIR;
335 struct fsnotify_mark *mark;
336 int type;
337
338 if (!iter_info->report_mask)
339 return 0;
340
341 /* clear ignored on inode modification */
342 if (mask & FS_MODIFY) {
343 fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
344 if (!(mark->flags &
345 FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
346 mark->ignore_mask = 0;
347 }
348 }
349
350 /* Are any of the group marks interested in this event? */
351 fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
352 group = mark->group;
353 marks_mask |= mark->mask;
354 marks_ignore_mask |=
355 fsnotify_effective_ignore_mask(mark, is_dir, iter_type: type);
356 }
357
358 pr_debug("%s: group=%p mask=%x marks_mask=%x marks_ignore_mask=%x data=%p data_type=%d dir=%p cookie=%d\n",
359 __func__, group, mask, marks_mask, marks_ignore_mask,
360 data, data_type, dir, cookie);
361
362 if (!(test_mask & marks_mask & ~marks_ignore_mask))
363 return 0;
364
365 if (group->ops->handle_event) {
366 return group->ops->handle_event(group, mask, data, data_type, dir,
367 file_name, cookie, iter_info);
368 }
369
370 return fsnotify_handle_event(group, mask, data, data_type, dir,
371 name: file_name, cookie, iter_info);
372}
373
374static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
375{
376 struct fsnotify_mark_connector *conn;
377 struct hlist_node *node = NULL;
378
379 conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
380 if (conn)
381 node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);
382
383 return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
384}
385
386static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark)
387{
388 struct hlist_node *node = NULL;
389
390 if (mark)
391 node = srcu_dereference(mark->obj_list.next,
392 &fsnotify_mark_srcu);
393
394 return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
395}
396
397/*
398 * iter_info is a multi head priority queue of marks.
399 * Pick a subset of marks from queue heads, all with the same group
400 * and set the report_mask to a subset of the selected marks.
401 * Returns false if there are no more groups to iterate.
402 */
403static bool fsnotify_iter_select_report_types(
404 struct fsnotify_iter_info *iter_info)
405{
406 struct fsnotify_group *max_prio_group = NULL;
407 struct fsnotify_mark *mark;
408 int type;
409
410 /* Choose max prio group among groups of all queue heads */
411 fsnotify_foreach_iter_type(type) {
412 mark = iter_info->marks[type];
413 if (mark &&
414 fsnotify_compare_groups(a: max_prio_group, b: mark->group) > 0)
415 max_prio_group = mark->group;
416 }
417
418 if (!max_prio_group)
419 return false;
420
421 /* Set the report mask for marks from same group as max prio group */
422 iter_info->current_group = max_prio_group;
423 iter_info->report_mask = 0;
424 fsnotify_foreach_iter_type(type) {
425 mark = iter_info->marks[type];
426 if (mark && mark->group == iter_info->current_group) {
427 /*
428 * FSNOTIFY_ITER_TYPE_PARENT indicates that this inode
429 * is watching children and interested in this event,
430 * which is an event possible on child.
431 * But is *this mark* watching children?
432 */
433 if (type == FSNOTIFY_ITER_TYPE_PARENT &&
434 !(mark->mask & FS_EVENT_ON_CHILD) &&
435 !(fsnotify_ignore_mask(mark) & FS_EVENT_ON_CHILD))
436 continue;
437
438 fsnotify_iter_set_report_type(iter_info, iter_type: type);
439 }
440 }
441
442 return true;
443}
444
445/*
446 * Pop from iter_info multi head queue, the marks that belong to the group of
447 * current iteration step.
448 */
449static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info)
450{
451 struct fsnotify_mark *mark;
452 int type;
453
454 /*
455 * We cannot use fsnotify_foreach_iter_mark_type() here because we
456 * may need to advance a mark of type X that belongs to current_group
457 * but was not selected for reporting.
458 */
459 fsnotify_foreach_iter_type(type) {
460 mark = iter_info->marks[type];
461 if (mark && mark->group == iter_info->current_group)
462 iter_info->marks[type] =
463 fsnotify_next_mark(mark: iter_info->marks[type]);
464 }
465}
466
467/*
468 * fsnotify - This is the main call to fsnotify.
469 *
470 * The VFS calls into hook specific functions in linux/fsnotify.h.
471 * Those functions then in turn call here. Here will call out to all of the
472 * registered fsnotify_group. Those groups can then use the notification event
473 * in whatever means they feel necessary.
474 *
475 * @mask: event type and flags
476 * @data: object that event happened on
477 * @data_type: type of object for fanotify_data_XXX() accessors
478 * @dir: optional directory associated with event -
479 * if @file_name is not NULL, this is the directory that
480 * @file_name is relative to
481 * @file_name: optional file name associated with event
482 * @inode: optional inode associated with event -
483 * If @dir and @inode are both non-NULL, event may be
484 * reported to both.
485 * @cookie: inotify rename cookie
486 */
487int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
488 const struct qstr *file_name, struct inode *inode, u32 cookie)
489{
490 const struct path *path = fsnotify_data_path(data, data_type);
491 struct super_block *sb = fsnotify_data_sb(data, data_type);
492 struct fsnotify_iter_info iter_info = {};
493 struct mount *mnt = NULL;
494 struct inode *inode2 = NULL;
495 struct dentry *moved;
496 int inode2_type;
497 int ret = 0;
498 __u32 test_mask, marks_mask;
499
500 if (path)
501 mnt = real_mount(mnt: path->mnt);
502
503 if (!inode) {
504 /* Dirent event - report on TYPE_INODE to dir */
505 inode = dir;
506 /* For FS_RENAME, inode is old_dir and inode2 is new_dir */
507 if (mask & FS_RENAME) {
508 moved = fsnotify_data_dentry(data, data_type);
509 inode2 = moved->d_parent->d_inode;
510 inode2_type = FSNOTIFY_ITER_TYPE_INODE2;
511 }
512 } else if (mask & FS_EVENT_ON_CHILD) {
513 /*
514 * Event on child - report on TYPE_PARENT to dir if it is
515 * watching children and on TYPE_INODE to child.
516 */
517 inode2 = dir;
518 inode2_type = FSNOTIFY_ITER_TYPE_PARENT;
519 }
520
521 /*
522 * Optimization: srcu_read_lock() has a memory barrier which can
523 * be expensive. It protects walking the *_fsnotify_marks lists.
524 * However, if we do not walk the lists, we do not have to do
525 * SRCU because we have no references to any objects and do not
526 * need SRCU to keep them "alive".
527 */
528 if (!sb->s_fsnotify_marks &&
529 (!mnt || !mnt->mnt_fsnotify_marks) &&
530 (!inode || !inode->i_fsnotify_marks) &&
531 (!inode2 || !inode2->i_fsnotify_marks))
532 return 0;
533
534 marks_mask = sb->s_fsnotify_mask;
535 if (mnt)
536 marks_mask |= mnt->mnt_fsnotify_mask;
537 if (inode)
538 marks_mask |= inode->i_fsnotify_mask;
539 if (inode2)
540 marks_mask |= inode2->i_fsnotify_mask;
541
542
543 /*
544 * If this is a modify event we may need to clear some ignore masks.
545 * In that case, the object with ignore masks will have the FS_MODIFY
546 * event in its mask.
547 * Otherwise, return if none of the marks care about this type of event.
548 */
549 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
550 if (!(test_mask & marks_mask))
551 return 0;
552
553 iter_info.srcu_idx = srcu_read_lock(ssp: &fsnotify_mark_srcu);
554
555 iter_info.marks[FSNOTIFY_ITER_TYPE_SB] =
556 fsnotify_first_mark(connp: &sb->s_fsnotify_marks);
557 if (mnt) {
558 iter_info.marks[FSNOTIFY_ITER_TYPE_VFSMOUNT] =
559 fsnotify_first_mark(connp: &mnt->mnt_fsnotify_marks);
560 }
561 if (inode) {
562 iter_info.marks[FSNOTIFY_ITER_TYPE_INODE] =
563 fsnotify_first_mark(connp: &inode->i_fsnotify_marks);
564 }
565 if (inode2) {
566 iter_info.marks[inode2_type] =
567 fsnotify_first_mark(connp: &inode2->i_fsnotify_marks);
568 }
569
570 /*
571 * We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark
572 * ignore masks are properly reflected for mount/sb mark notifications.
573 * That's why this traversal is so complicated...
574 */
575 while (fsnotify_iter_select_report_types(iter_info: &iter_info)) {
576 ret = send_to_group(mask, data, data_type, dir, file_name,
577 cookie, iter_info: &iter_info);
578
579 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
580 goto out;
581
582 fsnotify_iter_next(iter_info: &iter_info);
583 }
584 ret = 0;
585out:
586 srcu_read_unlock(ssp: &fsnotify_mark_srcu, idx: iter_info.srcu_idx);
587
588 return ret;
589}
590EXPORT_SYMBOL_GPL(fsnotify);
591
592static __init int fsnotify_init(void)
593{
594 int ret;
595
596 BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23);
597
598 ret = init_srcu_struct(&fsnotify_mark_srcu);
599 if (ret)
600 panic(fmt: "initializing fsnotify_mark_srcu");
601
602 fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector,
603 SLAB_PANIC);
604
605 return 0;
606}
607core_initcall(fsnotify_init);
608

source code of linux/fs/notify/fsnotify.c