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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(&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(&inode->i_lock);
50 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
51 spin_unlock(&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(&inode->i_count)) {
65 spin_unlock(&inode->i_lock);
66 continue;
67 }
68
69 __iget(inode);
70 spin_unlock(&inode->i_lock);
71 spin_unlock(&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(&sb->s_inode_list_lock);
84 }
85 spin_unlock(&sb->s_inode_list_lock);
86
87 iput(iput_inode);
88}
89
90void fsnotify_sb_delete(struct super_block *sb)
91{
92 struct fsnotify_sb_info *sbinfo = fsnotify_sb_info(sb);
93
94 /* Were any marks ever added to any object on this sb? */
95 if (!sbinfo)
96 return;
97
98 fsnotify_unmount_inodes(sb);
99 fsnotify_clear_marks_by_sb(sb);
100 /* Wait for outstanding object references from connectors */
101 wait_var_event(fsnotify_sb_watched_objects(sb),
102 !atomic_long_read(fsnotify_sb_watched_objects(sb)));
103 WARN_ON(fsnotify_sb_has_priority_watchers(sb, FSNOTIFY_PRIO_CONTENT));
104 WARN_ON(fsnotify_sb_has_priority_watchers(sb,
105 FSNOTIFY_PRIO_PRE_CONTENT));
106}
107
108void fsnotify_sb_free(struct super_block *sb)
109{
110 kfree(sb->s_fsnotify_info);
111}
112
113/*
114 * Given an inode, first check if we care what happens to our children. Inotify
115 * and dnotify both tell their parents about events. If we care about any event
116 * on a child we run all of our children and set a dentry flag saying that the
117 * parent cares. Thus when an event happens on a child it can quickly tell
118 * if there is a need to find a parent and send the event to the parent.
119 */
120void fsnotify_set_children_dentry_flags(struct inode *inode)
121{
122 struct dentry *alias;
123
124 if (!S_ISDIR(inode->i_mode))
125 return;
126
127 spin_lock(&inode->i_lock);
128 /* run all of the dentries associated with this inode. Since this is a
129 * directory, there damn well better only be one item on this list */
130 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
131 struct dentry *child;
132
133 /* run all of the children of the original inode and fix their
134 * d_flags to indicate parental interest (their parent is the
135 * original inode) */
136 spin_lock(&alias->d_lock);
137 hlist_for_each_entry(child, &alias->d_children, d_sib) {
138 if (!child->d_inode)
139 continue;
140
141 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
142 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
143 spin_unlock(&child->d_lock);
144 }
145 spin_unlock(&alias->d_lock);
146 }
147 spin_unlock(&inode->i_lock);
148}
149
150/*
151 * Lazily clear false positive PARENT_WATCHED flag for child whose parent had
152 * stopped watching children.
153 */
154static void fsnotify_clear_child_dentry_flag(struct inode *pinode,
155 struct dentry *dentry)
156{
157 spin_lock(&dentry->d_lock);
158 /*
159 * d_lock is a sufficient barrier to prevent observing a non-watched
160 * parent state from before the fsnotify_set_children_dentry_flags()
161 * or fsnotify_update_flags() call that had set PARENT_WATCHED.
162 */
163 if (!fsnotify_inode_watches_children(pinode))
164 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
165 spin_unlock(&dentry->d_lock);
166}
167
168/* Are inode/sb/mount interested in parent and name info with this event? */
169static bool fsnotify_event_needs_parent(struct inode *inode, __u32 mnt_mask,
170 __u32 mask)
171{
172 __u32 marks_mask = 0;
173
174 /* We only send parent/name to inode/sb/mount for events on non-dir */
175 if (mask & FS_ISDIR)
176 return false;
177
178 /*
179 * All events that are possible on child can also may be reported with
180 * parent/name info to inode/sb/mount. Otherwise, a watching parent
181 * could result in events reported with unexpected name info to sb/mount.
182 */
183 BUILD_BUG_ON(FS_EVENTS_POSS_ON_CHILD & ~FS_EVENTS_POSS_TO_PARENT);
184
185 /* Did either inode/sb/mount subscribe for events with parent/name? */
186 marks_mask |= fsnotify_parent_needed_mask(
187 READ_ONCE(inode->i_fsnotify_mask));
188 marks_mask |= fsnotify_parent_needed_mask(
189 READ_ONCE(inode->i_sb->s_fsnotify_mask));
190 marks_mask |= fsnotify_parent_needed_mask(mnt_mask);
191
192 /* Did they subscribe for this event with parent/name info? */
193 return mask & marks_mask;
194}
195
196/* Are there any inode/mount/sb objects that are interested in this event? */
197static inline bool fsnotify_object_watched(struct inode *inode, __u32 mnt_mask,
198 __u32 mask)
199{
200 __u32 marks_mask = READ_ONCE(inode->i_fsnotify_mask) | mnt_mask |
201 READ_ONCE(inode->i_sb->s_fsnotify_mask);
202
203 return mask & marks_mask & ALL_FSNOTIFY_EVENTS;
204}
205
206/*
207 * Notify this dentry's parent about a child's events with child name info
208 * if parent is watching or if inode/sb/mount are interested in events with
209 * parent and name info.
210 *
211 * Notify only the child without name info if parent is not watching and
212 * inode/sb/mount are not interested in events with parent and name info.
213 */
214int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
215 int data_type)
216{
217 const struct path *path = fsnotify_data_path(data, data_type);
218 __u32 mnt_mask = path ?
219 READ_ONCE(real_mount(path->mnt)->mnt_fsnotify_mask) : 0;
220 struct inode *inode = d_inode(dentry);
221 struct dentry *parent;
222 bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED;
223 bool parent_needed, parent_interested;
224 __u32 p_mask;
225 struct inode *p_inode = NULL;
226 struct name_snapshot name;
227 struct qstr *file_name = NULL;
228 int ret = 0;
229
230 /* Optimize the likely case of nobody watching this path */
231 if (likely(!parent_watched &&
232 !fsnotify_object_watched(inode, mnt_mask, mask)))
233 return 0;
234
235 parent = NULL;
236 parent_needed = fsnotify_event_needs_parent(inode, mnt_mask, mask);
237 if (!parent_watched && !parent_needed)
238 goto notify;
239
240 /* Does parent inode care about events on children? */
241 parent = dget_parent(dentry);
242 p_inode = parent->d_inode;
243 p_mask = fsnotify_inode_watches_children(p_inode);
244 if (unlikely(parent_watched && !p_mask))
245 fsnotify_clear_child_dentry_flag(p_inode, dentry);
246
247 /*
248 * Include parent/name in notification either if some notification
249 * groups require parent info or the parent is interested in this event.
250 */
251 parent_interested = mask & p_mask & ALL_FSNOTIFY_EVENTS;
252 if (parent_needed || parent_interested) {
253 /* When notifying parent, child should be passed as data */
254 WARN_ON_ONCE(inode != fsnotify_data_inode(data, data_type));
255
256 /* Notify both parent and child with child name info */
257 take_dentry_name_snapshot(&name, dentry);
258 file_name = &name.name;
259 if (parent_interested)
260 mask |= FS_EVENT_ON_CHILD;
261 }
262
263notify:
264 ret = fsnotify(mask, data, data_type, p_inode, file_name, inode, 0);
265
266 if (file_name)
267 release_dentry_name_snapshot(&name);
268 dput(parent);
269
270 return ret;
271}
272EXPORT_SYMBOL_GPL(__fsnotify_parent);
273
274static int fsnotify_handle_inode_event(struct fsnotify_group *group,
275 struct fsnotify_mark *inode_mark,
276 u32 mask, const void *data, int data_type,
277 struct inode *dir, const struct qstr *name,
278 u32 cookie)
279{
280 const struct path *path = fsnotify_data_path(data, data_type);
281 struct inode *inode = fsnotify_data_inode(data, data_type);
282 const struct fsnotify_ops *ops = group->ops;
283
284 if (WARN_ON_ONCE(!ops->handle_inode_event))
285 return 0;
286
287 if (WARN_ON_ONCE(!inode && !dir))
288 return 0;
289
290 if ((inode_mark->flags & FSNOTIFY_MARK_FLAG_EXCL_UNLINK) &&
291 path && d_unlinked(path->dentry))
292 return 0;
293
294 /* Check interest of this mark in case event was sent with two marks */
295 if (!(mask & inode_mark->mask & ALL_FSNOTIFY_EVENTS))
296 return 0;
297
298 return ops->handle_inode_event(inode_mark, mask, inode, dir, name, cookie);
299}
300
301static int fsnotify_handle_event(struct fsnotify_group *group, __u32 mask,
302 const void *data, int data_type,
303 struct inode *dir, const struct qstr *name,
304 u32 cookie, struct fsnotify_iter_info *iter_info)
305{
306 struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
307 struct fsnotify_mark *parent_mark = fsnotify_iter_parent_mark(iter_info);
308 int ret;
309
310 if (WARN_ON_ONCE(fsnotify_iter_sb_mark(iter_info)) ||
311 WARN_ON_ONCE(fsnotify_iter_vfsmount_mark(iter_info)))
312 return 0;
313
314 /*
315 * For FS_RENAME, 'dir' is old dir and 'data' is new dentry.
316 * The only ->handle_inode_event() backend that supports FS_RENAME is
317 * dnotify, where it means file was renamed within same parent.
318 */
319 if (mask & FS_RENAME) {
320 struct dentry *moved = fsnotify_data_dentry(data, data_type);
321
322 if (dir != moved->d_parent->d_inode)
323 return 0;
324 }
325
326 if (parent_mark) {
327 ret = fsnotify_handle_inode_event(group, parent_mark, mask,
328 data, data_type, dir, name, 0);
329 if (ret)
330 return ret;
331 }
332
333 if (!inode_mark)
334 return 0;
335
336 /*
337 * Some events can be sent on both parent dir and child marks (e.g.
338 * FS_ATTRIB). If both parent dir and child are watching, report the
339 * event once to parent dir with name (if interested) and once to child
340 * without name (if interested).
341 *
342 * In any case regardless whether the parent is watching or not, the
343 * child watcher is expecting an event without the FS_EVENT_ON_CHILD
344 * flag. The file name is expected if and only if this is a directory
345 * event.
346 */
347 mask &= ~FS_EVENT_ON_CHILD;
348 if (!(mask & ALL_FSNOTIFY_DIRENT_EVENTS)) {
349 dir = NULL;
350 name = NULL;
351 }
352
353 return fsnotify_handle_inode_event(group, inode_mark, mask, data, data_type,
354 dir, name, cookie);
355}
356
357static int send_to_group(__u32 mask, const void *data, int data_type,
358 struct inode *dir, const struct qstr *file_name,
359 u32 cookie, struct fsnotify_iter_info *iter_info)
360{
361 struct fsnotify_group *group = NULL;
362 __u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
363 __u32 marks_mask = 0;
364 __u32 marks_ignore_mask = 0;
365 bool is_dir = mask & FS_ISDIR;
366 struct fsnotify_mark *mark;
367 int type;
368
369 if (!iter_info->report_mask)
370 return 0;
371
372 /* clear ignored on inode modification */
373 if (mask & FS_MODIFY) {
374 fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
375 if (!(mark->flags &
376 FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
377 mark->ignore_mask = 0;
378 }
379 }
380
381 /* Are any of the group marks interested in this event? */
382 fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
383 group = mark->group;
384 marks_mask |= mark->mask;
385 marks_ignore_mask |=
386 fsnotify_effective_ignore_mask(mark, is_dir, type);
387 }
388
389 pr_debug("%s: group=%p mask=%x marks_mask=%x marks_ignore_mask=%x data=%p data_type=%d dir=%p cookie=%d\n",
390 __func__, group, mask, marks_mask, marks_ignore_mask,
391 data, data_type, dir, cookie);
392
393 if (!(test_mask & marks_mask & ~marks_ignore_mask))
394 return 0;
395
396 if (group->ops->handle_event) {
397 return group->ops->handle_event(group, mask, data, data_type, dir,
398 file_name, cookie, iter_info);
399 }
400
401 return fsnotify_handle_event(group, mask, data, data_type, dir,
402 file_name, cookie, iter_info);
403}
404
405static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
406{
407 struct fsnotify_mark_connector *conn;
408 struct hlist_node *node = NULL;
409
410 conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
411 if (conn)
412 node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);
413
414 return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
415}
416
417static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark)
418{
419 struct hlist_node *node = NULL;
420
421 if (mark)
422 node = srcu_dereference(mark->obj_list.next,
423 &fsnotify_mark_srcu);
424
425 return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
426}
427
428/*
429 * iter_info is a multi head priority queue of marks.
430 * Pick a subset of marks from queue heads, all with the same group
431 * and set the report_mask to a subset of the selected marks.
432 * Returns false if there are no more groups to iterate.
433 */
434static bool fsnotify_iter_select_report_types(
435 struct fsnotify_iter_info *iter_info)
436{
437 struct fsnotify_group *max_prio_group = NULL;
438 struct fsnotify_mark *mark;
439 int type;
440
441 /* Choose max prio group among groups of all queue heads */
442 fsnotify_foreach_iter_type(type) {
443 mark = iter_info->marks[type];
444 if (mark &&
445 fsnotify_compare_groups(max_prio_group, mark->group) > 0)
446 max_prio_group = mark->group;
447 }
448
449 if (!max_prio_group)
450 return false;
451
452 /* Set the report mask for marks from same group as max prio group */
453 iter_info->current_group = max_prio_group;
454 iter_info->report_mask = 0;
455 fsnotify_foreach_iter_type(type) {
456 mark = iter_info->marks[type];
457 if (mark && mark->group == iter_info->current_group) {
458 /*
459 * FSNOTIFY_ITER_TYPE_PARENT indicates that this inode
460 * is watching children and interested in this event,
461 * which is an event possible on child.
462 * But is *this mark* watching children?
463 */
464 if (type == FSNOTIFY_ITER_TYPE_PARENT &&
465 !(mark->mask & FS_EVENT_ON_CHILD) &&
466 !(fsnotify_ignore_mask(mark) & FS_EVENT_ON_CHILD))
467 continue;
468
469 fsnotify_iter_set_report_type(iter_info, type);
470 }
471 }
472
473 return true;
474}
475
476/*
477 * Pop from iter_info multi head queue, the marks that belong to the group of
478 * current iteration step.
479 */
480static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info)
481{
482 struct fsnotify_mark *mark;
483 int type;
484
485 /*
486 * We cannot use fsnotify_foreach_iter_mark_type() here because we
487 * may need to advance a mark of type X that belongs to current_group
488 * but was not selected for reporting.
489 */
490 fsnotify_foreach_iter_type(type) {
491 mark = iter_info->marks[type];
492 if (mark && mark->group == iter_info->current_group)
493 iter_info->marks[type] =
494 fsnotify_next_mark(iter_info->marks[type]);
495 }
496}
497
498/*
499 * fsnotify - This is the main call to fsnotify.
500 *
501 * The VFS calls into hook specific functions in linux/fsnotify.h.
502 * Those functions then in turn call here. Here will call out to all of the
503 * registered fsnotify_group. Those groups can then use the notification event
504 * in whatever means they feel necessary.
505 *
506 * @mask: event type and flags
507 * @data: object that event happened on
508 * @data_type: type of object for fanotify_data_XXX() accessors
509 * @dir: optional directory associated with event -
510 * if @file_name is not NULL, this is the directory that
511 * @file_name is relative to
512 * @file_name: optional file name associated with event
513 * @inode: optional inode associated with event -
514 * If @dir and @inode are both non-NULL, event may be
515 * reported to both.
516 * @cookie: inotify rename cookie
517 */
518int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
519 const struct qstr *file_name, struct inode *inode, u32 cookie)
520{
521 const struct path *path = fsnotify_data_path(data, data_type);
522 struct super_block *sb = fsnotify_data_sb(data, data_type);
523 struct fsnotify_sb_info *sbinfo = fsnotify_sb_info(sb);
524 struct fsnotify_iter_info iter_info = {};
525 struct mount *mnt = NULL;
526 struct inode *inode2 = NULL;
527 struct dentry *moved;
528 int inode2_type;
529 int ret = 0;
530 __u32 test_mask, marks_mask;
531
532 if (path)
533 mnt = real_mount(path->mnt);
534
535 if (!inode) {
536 /* Dirent event - report on TYPE_INODE to dir */
537 inode = dir;
538 /* For FS_RENAME, inode is old_dir and inode2 is new_dir */
539 if (mask & FS_RENAME) {
540 moved = fsnotify_data_dentry(data, data_type);
541 inode2 = moved->d_parent->d_inode;
542 inode2_type = FSNOTIFY_ITER_TYPE_INODE2;
543 }
544 } else if (mask & FS_EVENT_ON_CHILD) {
545 /*
546 * Event on child - report on TYPE_PARENT to dir if it is
547 * watching children and on TYPE_INODE to child.
548 */
549 inode2 = dir;
550 inode2_type = FSNOTIFY_ITER_TYPE_PARENT;
551 }
552
553 /*
554 * Optimization: srcu_read_lock() has a memory barrier which can
555 * be expensive. It protects walking the *_fsnotify_marks lists.
556 * However, if we do not walk the lists, we do not have to do
557 * SRCU because we have no references to any objects and do not
558 * need SRCU to keep them "alive".
559 */
560 if ((!sbinfo || !sbinfo->sb_marks) &&
561 (!mnt || !mnt->mnt_fsnotify_marks) &&
562 (!inode || !inode->i_fsnotify_marks) &&
563 (!inode2 || !inode2->i_fsnotify_marks))
564 return 0;
565
566 marks_mask = READ_ONCE(sb->s_fsnotify_mask);
567 if (mnt)
568 marks_mask |= READ_ONCE(mnt->mnt_fsnotify_mask);
569 if (inode)
570 marks_mask |= READ_ONCE(inode->i_fsnotify_mask);
571 if (inode2)
572 marks_mask |= READ_ONCE(inode2->i_fsnotify_mask);
573
574
575 /*
576 * If this is a modify event we may need to clear some ignore masks.
577 * In that case, the object with ignore masks will have the FS_MODIFY
578 * event in its mask.
579 * Otherwise, return if none of the marks care about this type of event.
580 */
581 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
582 if (!(test_mask & marks_mask))
583 return 0;
584
585 iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
586
587 if (sbinfo) {
588 iter_info.marks[FSNOTIFY_ITER_TYPE_SB] =
589 fsnotify_first_mark(&sbinfo->sb_marks);
590 }
591 if (mnt) {
592 iter_info.marks[FSNOTIFY_ITER_TYPE_VFSMOUNT] =
593 fsnotify_first_mark(&mnt->mnt_fsnotify_marks);
594 }
595 if (inode) {
596 iter_info.marks[FSNOTIFY_ITER_TYPE_INODE] =
597 fsnotify_first_mark(&inode->i_fsnotify_marks);
598 }
599 if (inode2) {
600 iter_info.marks[inode2_type] =
601 fsnotify_first_mark(&inode2->i_fsnotify_marks);
602 }
603
604 /*
605 * We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark
606 * ignore masks are properly reflected for mount/sb mark notifications.
607 * That's why this traversal is so complicated...
608 */
609 while (fsnotify_iter_select_report_types(&iter_info)) {
610 ret = send_to_group(mask, data, data_type, dir, file_name,
611 cookie, &iter_info);
612
613 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
614 goto out;
615
616 fsnotify_iter_next(&iter_info);
617 }
618 ret = 0;
619out:
620 srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx);
621
622 return ret;
623}
624EXPORT_SYMBOL_GPL(fsnotify);
625
626static __init int fsnotify_init(void)
627{
628 int ret;
629
630 BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23);
631
632 ret = init_srcu_struct(&fsnotify_mark_srcu);
633 if (ret)
634 panic("initializing fsnotify_mark_srcu");
635
636 fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector,
637 SLAB_PANIC);
638
639 return 0;
640}
641core_initcall(fsnotify_init);
1/*
2 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2, or (at your option)
7 * any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; see the file COPYING. If not, write to
16 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
17 */
18
19#include <linux/dcache.h>
20#include <linux/fs.h>
21#include <linux/gfp.h>
22#include <linux/init.h>
23#include <linux/module.h>
24#include <linux/mount.h>
25#include <linux/srcu.h>
26
27#include <linux/fsnotify_backend.h>
28#include "fsnotify.h"
29#include "../mount.h"
30
31/*
32 * Clear all of the marks on an inode when it is being evicted from core
33 */
34void __fsnotify_inode_delete(struct inode *inode)
35{
36 fsnotify_clear_marks_by_inode(inode);
37}
38EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
39
40void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
41{
42 fsnotify_clear_marks_by_mount(mnt);
43}
44
45/*
46 * Given an inode, first check if we care what happens to our children. Inotify
47 * and dnotify both tell their parents about events. If we care about any event
48 * on a child we run all of our children and set a dentry flag saying that the
49 * parent cares. Thus when an event happens on a child it can quickly tell if
50 * if there is a need to find a parent and send the event to the parent.
51 */
52void __fsnotify_update_child_dentry_flags(struct inode *inode)
53{
54 struct dentry *alias;
55 int watched;
56
57 if (!S_ISDIR(inode->i_mode))
58 return;
59
60 /* determine if the children should tell inode about their events */
61 watched = fsnotify_inode_watches_children(inode);
62
63 spin_lock(&inode->i_lock);
64 /* run all of the dentries associated with this inode. Since this is a
65 * directory, there damn well better only be one item on this list */
66 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
67 struct dentry *child;
68
69 /* run all of the children of the original inode and fix their
70 * d_flags to indicate parental interest (their parent is the
71 * original inode) */
72 spin_lock(&alias->d_lock);
73 list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
74 if (!child->d_inode)
75 continue;
76
77 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
78 if (watched)
79 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
80 else
81 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
82 spin_unlock(&child->d_lock);
83 }
84 spin_unlock(&alias->d_lock);
85 }
86 spin_unlock(&inode->i_lock);
87}
88
89/* Notify this dentry's parent about a child's events. */
90int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
91{
92 struct dentry *parent;
93 struct inode *p_inode;
94 int ret = 0;
95
96 if (!dentry)
97 dentry = path->dentry;
98
99 if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
100 return 0;
101
102 parent = dget_parent(dentry);
103 p_inode = parent->d_inode;
104
105 if (unlikely(!fsnotify_inode_watches_children(p_inode)))
106 __fsnotify_update_child_dentry_flags(p_inode);
107 else if (p_inode->i_fsnotify_mask & mask) {
108 /* we are notifying a parent so come up with the new mask which
109 * specifies these are events which came from a child. */
110 mask |= FS_EVENT_ON_CHILD;
111
112 if (path)
113 ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
114 dentry->d_name.name, 0);
115 else
116 ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
117 dentry->d_name.name, 0);
118 }
119
120 dput(parent);
121
122 return ret;
123}
124EXPORT_SYMBOL_GPL(__fsnotify_parent);
125
126static int send_to_group(struct inode *to_tell,
127 struct fsnotify_mark *inode_mark,
128 struct fsnotify_mark *vfsmount_mark,
129 __u32 mask, void *data,
130 int data_is, u32 cookie,
131 const unsigned char *file_name,
132 struct fsnotify_event **event)
133{
134 struct fsnotify_group *group = NULL;
135 __u32 inode_test_mask = 0;
136 __u32 vfsmount_test_mask = 0;
137
138 if (unlikely(!inode_mark && !vfsmount_mark)) {
139 BUG();
140 return 0;
141 }
142
143 /* clear ignored on inode modification */
144 if (mask & FS_MODIFY) {
145 if (inode_mark &&
146 !(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
147 inode_mark->ignored_mask = 0;
148 if (vfsmount_mark &&
149 !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
150 vfsmount_mark->ignored_mask = 0;
151 }
152
153 /* does the inode mark tell us to do something? */
154 if (inode_mark) {
155 group = inode_mark->group;
156 inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
157 inode_test_mask &= inode_mark->mask;
158 inode_test_mask &= ~inode_mark->ignored_mask;
159 }
160
161 /* does the vfsmount_mark tell us to do something? */
162 if (vfsmount_mark) {
163 vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
164 group = vfsmount_mark->group;
165 vfsmount_test_mask &= vfsmount_mark->mask;
166 vfsmount_test_mask &= ~vfsmount_mark->ignored_mask;
167 if (inode_mark)
168 vfsmount_test_mask &= ~inode_mark->ignored_mask;
169 }
170
171 pr_debug("%s: group=%p to_tell=%p mask=%x inode_mark=%p"
172 " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x"
173 " data=%p data_is=%d cookie=%d event=%p\n",
174 __func__, group, to_tell, mask, inode_mark,
175 inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
176 data_is, cookie, *event);
177
178 if (!inode_test_mask && !vfsmount_test_mask)
179 return 0;
180
181 if (group->ops->should_send_event(group, to_tell, inode_mark,
182 vfsmount_mark, mask, data,
183 data_is) == false)
184 return 0;
185
186 if (!*event) {
187 *event = fsnotify_create_event(to_tell, mask, data,
188 data_is, file_name,
189 cookie, GFP_KERNEL);
190 if (!*event)
191 return -ENOMEM;
192 }
193 return group->ops->handle_event(group, inode_mark, vfsmount_mark, *event);
194}
195
196/*
197 * This is the main call to fsnotify. The VFS calls into hook specific functions
198 * in linux/fsnotify.h. Those functions then in turn call here. Here will call
199 * out to all of the registered fsnotify_group. Those groups can then use the
200 * notification event in whatever means they feel necessary.
201 */
202int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
203 const unsigned char *file_name, u32 cookie)
204{
205 struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
206 struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
207 struct fsnotify_group *inode_group, *vfsmount_group;
208 struct fsnotify_event *event = NULL;
209 struct mount *mnt;
210 int idx, ret = 0;
211 /* global tests shouldn't care about events on child only the specific event */
212 __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
213
214 if (data_is == FSNOTIFY_EVENT_PATH)
215 mnt = real_mount(((struct path *)data)->mnt);
216 else
217 mnt = NULL;
218
219 /*
220 * if this is a modify event we may need to clear the ignored masks
221 * otherwise return if neither the inode nor the vfsmount care about
222 * this type of event.
223 */
224 if (!(mask & FS_MODIFY) &&
225 !(test_mask & to_tell->i_fsnotify_mask) &&
226 !(mnt && test_mask & mnt->mnt_fsnotify_mask))
227 return 0;
228
229 idx = srcu_read_lock(&fsnotify_mark_srcu);
230
231 if ((mask & FS_MODIFY) ||
232 (test_mask & to_tell->i_fsnotify_mask))
233 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
234 &fsnotify_mark_srcu);
235
236 if (mnt && ((mask & FS_MODIFY) ||
237 (test_mask & mnt->mnt_fsnotify_mask))) {
238 vfsmount_node = srcu_dereference(mnt->mnt_fsnotify_marks.first,
239 &fsnotify_mark_srcu);
240 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
241 &fsnotify_mark_srcu);
242 }
243
244 while (inode_node || vfsmount_node) {
245 inode_group = vfsmount_group = NULL;
246
247 if (inode_node) {
248 inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
249 struct fsnotify_mark, i.i_list);
250 inode_group = inode_mark->group;
251 }
252
253 if (vfsmount_node) {
254 vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu),
255 struct fsnotify_mark, m.m_list);
256 vfsmount_group = vfsmount_mark->group;
257 }
258
259 if (inode_group > vfsmount_group) {
260 /* handle inode */
261 ret = send_to_group(to_tell, inode_mark, NULL, mask, data,
262 data_is, cookie, file_name, &event);
263 /* we didn't use the vfsmount_mark */
264 vfsmount_group = NULL;
265 } else if (vfsmount_group > inode_group) {
266 ret = send_to_group(to_tell, NULL, vfsmount_mark, mask, data,
267 data_is, cookie, file_name, &event);
268 inode_group = NULL;
269 } else {
270 ret = send_to_group(to_tell, inode_mark, vfsmount_mark,
271 mask, data, data_is, cookie, file_name,
272 &event);
273 }
274
275 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
276 goto out;
277
278 if (inode_group)
279 inode_node = srcu_dereference(inode_node->next,
280 &fsnotify_mark_srcu);
281 if (vfsmount_group)
282 vfsmount_node = srcu_dereference(vfsmount_node->next,
283 &fsnotify_mark_srcu);
284 }
285 ret = 0;
286out:
287 srcu_read_unlock(&fsnotify_mark_srcu, idx);
288 /*
289 * fsnotify_create_event() took a reference so the event can't be cleaned
290 * up while we are still trying to add it to lists, drop that one.
291 */
292 if (event)
293 fsnotify_put_event(event);
294
295 return ret;
296}
297EXPORT_SYMBOL_GPL(fsnotify);
298
299static __init int fsnotify_init(void)
300{
301 int ret;
302
303 BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
304
305 ret = init_srcu_struct(&fsnotify_mark_srcu);
306 if (ret)
307 panic("initializing fsnotify_mark_srcu");
308
309 return 0;
310}
311core_initcall(fsnotify_init);