summaryrefslogtreecommitdiffstats
path: root/fs/notify/fsnotify.c
blob: fde3a1115a170c905991b99b708befdade0220a3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
 */

#include <linux/dcache.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/srcu.h>

#include <linux/fsnotify_backend.h>
#include "fsnotify.h"

/*
 * Clear all of the marks on an inode when it is being evicted from core
 */
void __fsnotify_inode_delete(struct inode *inode)
{
	fsnotify_clear_marks_by_inode(inode);
}
EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);

void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
{
	fsnotify_clear_marks_by_mount(mnt);
}

/**
 * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
 * @sb: superblock being unmounted.
 *
 * Called during unmount with no locks held, so needs to be safe against
 * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
 */
static void fsnotify_unmount_inodes(struct super_block *sb)
{
	struct inode *inode, *iput_inode = NULL;

	spin_lock(&sb->s_inode_list_lock);
	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
		/*
		 * We cannot __iget() an inode in state I_FREEING,
		 * I_WILL_FREE, or I_NEW which is fine because by that point
		 * the inode cannot have any associated watches.
		 */
		spin_lock(&inode->i_lock);
		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
			spin_unlock(&inode->i_lock);
			continue;
		}

		/*
		 * If i_count is zero, the inode cannot have any watches and
		 * doing an __iget/iput with SB_ACTIVE clear would actually
		 * evict all inodes with zero i_count from icache which is
		 * unnecessarily violent and may in fact be illegal to do.
		 * However, we should have been called /after/ evict_inodes
		 * removed all zero refcount inodes, in any case.  Test to
		 * be sure.
		 */
		if (!atomic_read(&inode->i_count)) {
			spin_unlock(&inode->i_lock);
			continue;
		}

		__iget(inode);
		spin_unlock(&inode->i_lock);
		spin_unlock(&sb->s_inode_list_lock);

		if (iput_inode)
			iput(iput_inode);

		/* for each watch, send FS_UNMOUNT and then remove it */
		fsnotify_inode(inode, FS_UNMOUNT);

		fsnotify_inode_delete(inode);

		iput_inode = inode;

		cond_resched();
		spin_lock(&sb->s_inode_list_lock);
	}
	spin_unlock(&sb->s_inode_list_lock);

	if (iput_inode)
		iput(iput_inode);
}

void fsnotify_sb_delete(struct super_block *sb)
{
	fsnotify_unmount_inodes(sb);
	fsnotify_clear_marks_by_sb(sb);
	/* Wait for outstanding object references from connectors */
	wait_var_event(&sb->s_fsnotify_connectors,
		       !atomic_long_read(&sb->s_fsnotify_connectors));
}

/*
 * Given an inode, first check if we care what happens to our children.  Inotify
 * and dnotify both tell their parents about events.  If we care about any event
 * on a child we run all of our children and set a dentry flag saying that the
 * parent cares.  Thus when an event happens on a child it can quickly tell if
 * if there is a need to find a parent and send the event to the parent.
 */
void __fsnotify_update_child_dentry_flags(struct inode *inode)
{
	struct dentry *alias;
	int watched;

	if (!S_ISDIR(inode->i_mode))
		return;

	/* determine if the children should tell inode about their events */
	watched = fsnotify_inode_watches_children(inode);

	spin_lock(&inode->i_lock);
	/* run all of the dentries associated with this inode.  Since this is a
	 * directory, there damn well better only be one item on this list */
	hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
		struct dentry *child;

		/* run all of the children of the original inode and fix their
		 * d_flags to indicate parental interest (their parent is the
		 * original inode) */
		spin_lock(&alias->d_lock);
		list_for_each_entry(child, &alias->d_subdirs, d_child) {
			if (!child->d_inode)
				continue;

			spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
			if (watched)
				child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
			else
				child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
			spin_unlock(&child->d_lock);
		}
		spin_unlock(&alias->d_lock);
	}
	spin_unlock(&inode->i_lock);
}

/* Are inode/sb/mount interested in parent and name info with this event? */
static bool fsnotify_event_needs_parent(struct inode *inode, struct mount *mnt,
					__u32 mask)
{
	__u32 marks_mask = 0;

	/* We only send parent/name to inode/sb/mount for events on non-dir */
	if (mask & FS_ISDIR)
		return false;

	/*
	 * All events that are possible on child can also may be reported with
	 * parent/name info to inode/sb/mount.  Otherwise, a watching parent
	 * could result in events reported with unexpected name info to sb/mount.
	 */
	BUILD_BUG_ON(FS_EVENTS_POSS_ON_CHILD & ~FS_EVENTS_POSS_TO_PARENT);

	/* Did either inode/sb/mount subscribe for events with parent/name? */
	marks_mask |= fsnotify_parent_needed_mask(inode->i_fsnotify_mask);
	marks_mask |= fsnotify_parent_needed_mask(inode->i_sb->s_fsnotify_mask);
	if (mnt)
		marks_mask |= fsnotify_parent_needed_mask(mnt->mnt_fsnotify_mask);

	/* Did they subscribe for this event with parent/name info? */
	return mask & marks_mask;
}

/*
 * Notify this dentry's parent about a child's events with child name info
 * if parent is watching or if inode/sb/mount are interested in events with
 * parent and name info.
 *
 * Notify only the child without name info if parent is not watching and
 * inode/sb/mount are not interested in events with parent and name info.
 */
int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
		      int data_type)
{
	const struct path *path = fsnotify_data_path(data, data_type);
	struct mount *mnt = path ? real_mount(path->mnt) : NULL;
	struct inode *inode = d_inode(dentry);
	struct dentry *parent;
	bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED;
	bool parent_needed, parent_interested;
	__u32 p_mask;
	struct inode *p_inode = NULL;
	struct name_snapshot name;
	struct qstr *file_name = NULL;
	int ret = 0;

	/*
	 * Do inode/sb/mount care about parent and name info on non-dir?
	 * Do they care about any event at all?
	 */
	if (!inode->i_fsnotify_marks && !inode->i_sb->s_fsnotify_marks &&
	    (!mnt || !mnt->mnt_fsnotify_marks) && !parent_watched)
		return 0;

	parent = NULL;
	parent_needed = fsnotify_event_needs_parent(inode, mnt, mask);
	if (!parent_watched && !parent_needed)
		goto notify;

	/* Does parent inode care about events on children? */
	parent = dget_parent(dentry);
	p_inode = parent->d_inode;
	p_mask = fsnotify_inode_watches_children(p_inode);
	if (unlikely(parent_watched && !p_mask))
		__fsnotify_update_child_dentry_flags(p_inode);

	/*
	 * Include parent/name in notification either if some notification
	 * groups require parent info or the parent is interested in this event.
	 */
	parent_interested = mask & p_mask & ALL_FSNOTIFY_EVENTS;
	if (parent_needed || parent_interested) {
		/* When notifying parent, child should be passed as data */
		WARN_ON_ONCE(inode != fsnotify_data_inode(data, data_type));

		/* Notify both parent and child with child name info */
		take_dentry_name_snapshot(&name, dentry);
		file_name = &name.name;
		if (parent_interested)
			mask |= FS_EVENT_ON_CHILD;
	}

notify:
	ret = fsnotify(mask, data, data_type, p_inode, file_name, inode, 0);

	if (file_name)
		release_dentry_name_snapshot(&name);
	dput(parent);

	return ret;
}
EXPORT_SYMBOL_GPL(__fsnotify_parent);

static int fsnotify_handle_inode_event(struct fsnotify_group *group,
				       struct fsnotify_mark *inode_mark,
				       u32 mask, const void *data, int data_type,
				       struct inode *dir, const struct qstr *name,
				       u32 cookie)
{
	const struct path *path = fsnotify_data_path(data, data_type);
	struct inode *inode = fsnotify_data_inode(data, data_type);
	const struct fsnotify_ops *ops = group->ops;

	if (WARN_ON_ONCE(!ops->handle_inode_event))
		return 0;

	if ((inode_mark->mask & FS_EXCL_UNLINK) &&
	    path && d_unlinked(path->dentry))
		return 0;

	/* Check interest of this mark in case event was sent with two marks */
	if (!(mask & inode_mark->mask & ALL_FSNOTIFY_EVENTS))
		return 0;

	return ops->handle_inode_event(inode_mark, mask, inode, dir, name, cookie);
}

static int fsnotify_handle_event(struct fsnotify_group *group, __u32 mask,
				 const void *data, int data_type,
				 struct inode *dir, const struct qstr *name,
				 u32 cookie, struct fsnotify_iter_info *iter_info)
{
	struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
	struct fsnotify_mark *parent_mark = fsnotify_iter_parent_mark(iter_info);
	int ret;

	if (WARN_ON_ONCE(fsnotify_iter_sb_mark(iter_info)) ||
	    WARN_ON_ONCE(fsnotify_iter_vfsmount_mark(iter_info)))
		return 0;

	if (parent_mark) {
		/*
		 * parent_mark indicates that the parent inode is watching
		 * children and interested in this event, which is an event
		 * possible on child. But is *this mark* watching children and
		 * interested in this event?
		 */
		if (parent_mark->mask & FS_EVENT_ON_CHILD) {
			ret = fsnotify_handle_inode_event(group, parent_mark, mask,
							  data, data_type, dir, name, 0);
			if (ret)
				return ret;
		}
		if (!inode_mark)
			return 0;
	}

	if (mask & FS_EVENT_ON_CHILD) {
		/*
		 * Some events can be sent on both parent dir and child marks
		 * (e.g. FS_ATTRIB).  If both parent dir and child are
		 * watching, report the event once to parent dir with name (if
		 * interested) and once to child without name (if interested).
		 * The child watcher is expecting an event without a file name
		 * and without the FS_EVENT_ON_CHILD flag.
		 */
		mask &= ~FS_EVENT_ON_CHILD;
		dir = NULL;
		name = NULL;
	}

	return fsnotify_handle_inode_event(group, inode_mark, mask, data, data_type,
					   dir, name, cookie);
}

static int send_to_group(__u32 mask, const void *data, int data_type,
			 struct inode *dir, const struct qstr *file_name,
			 u32 cookie, struct fsnotify_iter_info *iter_info)
{
	struct fsnotify_group *group = NULL;
	__u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
	__u32 marks_mask = 0;
	__u32 marks_ignored_mask = 0;
	struct fsnotify_mark *mark;
	int type;

	if (WARN_ON(!iter_info->report_mask))
		return 0;

	/* clear ignored on inode modification */
	if (mask & FS_MODIFY) {
		fsnotify_foreach_obj_type(type) {
			if (!fsnotify_iter_should_report_type(iter_info, type))
				continue;
			mark = iter_info->marks[type];
			if (mark &&
			    !(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
				mark->ignored_mask = 0;
		}
	}

	fsnotify_foreach_obj_type(type) {
		if (!fsnotify_iter_should_report_type(iter_info, type))
			continue;
		mark = iter_info->marks[type];
		/* does the object mark tell us to do something? */
		if (mark) {
			group = mark->group;
			marks_mask |= mark->mask;
			marks_ignored_mask |= mark->ignored_mask;
		}
	}

	pr_debug("%s: group=%p mask=%x marks_mask=%x marks_ignored_mask=%x data=%p data_type=%d dir=%p cookie=%d\n",
		 __func__, group, mask, marks_mask, marks_ignored_mask,
		 data, data_type, dir, cookie);

	if (!(test_mask & marks_mask & ~marks_ignored_mask))
		return 0;

	if (group->ops->handle_event) {
		return group->ops->handle_event(group, mask, data, data_type, dir,
						file_name, cookie, iter_info);
	}

	return fsnotify_handle_event(group, mask, data, data_type, dir,
				     file_name, cookie, iter_info);
}

static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
{
	struct fsnotify_mark_connector *conn;
	struct hlist_node *node = NULL;

	conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
	if (conn)
		node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);

	return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
}

static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark)
{
	struct hlist_node *node = NULL;

	if (mark)
		node = srcu_dereference(mark->obj_list.next,
					&fsnotify_mark_srcu);

	return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
}

/*
 * iter_info is a multi head priority queue of marks.
 * Pick a subset of marks from queue heads, all with the
 * same group and set the report_mask for selected subset.
 * Returns the report_mask of the selected subset.
 */
static unsigned int fsnotify_iter_select_report_types(
		struct fsnotify_iter_info *iter_info)
{
	struct fsnotify_group *max_prio_group = NULL;
	struct fsnotify_mark *mark;
	int type;

	/* Choose max prio group among groups of all queue heads */
	fsnotify_foreach_obj_type(type) {
		mark = iter_info->marks[type];
		if (mark &&
		    fsnotify_compare_groups(max_prio_group, mark->group) > 0)
			max_prio_group = mark->group;
	}

	if (!max_prio_group)
		return 0;

	/* Set the report mask for marks from same group as max prio group */
	iter_info->report_mask = 0;
	fsnotify_foreach_obj_type(type) {
		mark = iter_info->marks[type];
		if (mark &&
		    fsnotify_compare_groups(max_prio_group, mark->group) == 0)
			fsnotify_iter_set_report_type(iter_info, type);
	}

	return iter_info->report_mask;
}

/*
 * Pop from iter_info multi head queue, the marks that were iterated in the
 * current iteration step.
 */
static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info)
{
	int type;

	fsnotify_foreach_obj_type(type) {
		if (fsnotify_iter_should_report_type(iter_info, type))
			iter_info->marks[type] =
				fsnotify_next_mark(iter_info->marks[type]);
	}
}

/*
 * fsnotify - This is the main call to fsnotify.
 *
 * The VFS calls into hook specific functions in linux/fsnotify.h.
 * Those functions then in turn call here.  Here will call out to all of the
 * registered fsnotify_group.  Those groups can then use the notification event
 * in whatever means they feel necessary.
 *
 * @mask:	event type and flags
 * @data:	object that event happened on
 * @data_type:	type of object for fanotify_data_XXX() accessors
 * @dir:	optional directory associated with event -
 *		if @file_name is not NULL, this is the directory that
 *		@file_name is relative to
 * @file_name:	optional file name associated with event
 * @inode:	optional inode associated with event -
 *		If @dir and @inode are both non-NULL, event may be
 *		reported to both.
 * @cookie:	inotify rename cookie
 */
int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
	     const struct qstr *file_name, struct inode *inode, u32 cookie)
{
	const struct path *path = fsnotify_data_path(data, data_type);
	struct super_block *sb = fsnotify_data_sb(data, data_type);
	struct fsnotify_iter_info iter_info = {};
	struct mount *mnt = NULL;
	struct inode *parent = NULL;
	int ret = 0;
	__u32 test_mask, marks_mask;

	if (path)
		mnt = real_mount(path->mnt);

	if (!inode) {
		/* Dirent event - report on TYPE_INODE to dir */
		inode = dir;
	} else if (mask & FS_EVENT_ON_CHILD) {
		/*
		 * Event on child - report on TYPE_PARENT to dir if it is
		 * watching children and on TYPE_INODE to child.
		 */
		parent = dir;
	}

	/*
	 * Optimization: srcu_read_lock() has a memory barrier which can
	 * be expensive.  It protects walking the *_fsnotify_marks lists.
	 * However, if we do not walk the lists, we do not have to do
	 * SRCU because we have no references to any objects and do not
	 * need SRCU to keep them "alive".
	 */
	if (!sb->s_fsnotify_marks &&
	    (!mnt || !mnt->mnt_fsnotify_marks) &&
	    (!inode || !inode->i_fsnotify_marks) &&
	    (!parent || !parent->i_fsnotify_marks))
		return 0;

	marks_mask = sb->s_fsnotify_mask;
	if (mnt)
		marks_mask |= mnt->mnt_fsnotify_mask;
	if (inode)
		marks_mask |= inode->i_fsnotify_mask;
	if (parent)
		marks_mask |= parent->i_fsnotify_mask;


	/*
	 * if this is a modify event we may need to clear the ignored masks
	 * otherwise return if none of the marks care about this type of event.
	 */
	test_mask = (mask & ALL_FSNOTIFY_EVENTS);
	if (!(mask & FS_MODIFY) && !(test_mask & marks_mask))
		return 0;

	iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);

	iter_info.marks[FSNOTIFY_OBJ_TYPE_SB] =
		fsnotify_first_mark(&sb->s_fsnotify_marks);
	if (mnt) {
		iter_info.marks[FSNOTIFY_OBJ_TYPE_VFSMOUNT] =
			fsnotify_first_mark(&mnt->mnt_fsnotify_marks);
	}
	if (inode) {
		iter_info.marks[FSNOTIFY_OBJ_TYPE_INODE] =
			fsnotify_first_mark(&inode->i_fsnotify_marks);
	}
	if (parent) {
		iter_info.marks[FSNOTIFY_OBJ_TYPE_PARENT] =
			fsnotify_first_mark(&parent->i_fsnotify_marks);
	}

	/*
	 * We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark
	 * ignore masks are properly reflected for mount/sb mark notifications.
	 * That's why this traversal is so complicated...
	 */
	while (fsnotify_iter_select_report_types(&iter_info)) {
		ret = send_to_group(mask, data, data_type, dir, file_name,
				    cookie, &iter_info);

		if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
			goto out;

		fsnotify_iter_next(&iter_info);
	}
	ret = 0;
out:
	srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx);

	return ret;
}
EXPORT_SYMBOL_GPL(fsnotify);

static __init int fsnotify_init(void)
{
	int ret;

	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);

	ret = init_srcu_struct(&fsnotify_mark_srcu);
	if (ret)
		panic("initializing fsnotify_mark_srcu");

	fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector,
						    SLAB_PANIC);

	return 0;
}
core_initcall(fsnotify_init);