xref: /linux/include/linux/fsnotify_backend.h (revision 67f5f11cdf5081af9b592d8ab24d054a0d681b2f)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * Filesystem access notification for Linux
4  *
5  *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
6  */
7 
8 #ifndef __LINUX_FSNOTIFY_BACKEND_H
9 #define __LINUX_FSNOTIFY_BACKEND_H
10 
11 #ifdef __KERNEL__
12 
13 #include <linux/idr.h> /* inotify uses this */
14 #include <linux/fs.h> /* struct inode */
15 #include <linux/list.h>
16 #include <linux/path.h> /* struct path */
17 #include <linux/spinlock.h>
18 #include <linux/types.h>
19 #include <linux/atomic.h>
20 #include <linux/user_namespace.h>
21 #include <linux/refcount.h>
22 #include <linux/mempool.h>
23 #include <linux/sched/mm.h>
24 
25 /*
26  * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
27  * convert between them.  dnotify only needs conversion at watch creation
28  * so no perf loss there.  fanotify isn't defined yet, so it can use the
29  * wholes if it needs more events.
30  */
31 #define FS_ACCESS		0x00000001	/* File was accessed */
32 #define FS_MODIFY		0x00000002	/* File was modified */
33 #define FS_ATTRIB		0x00000004	/* Metadata changed */
34 #define FS_CLOSE_WRITE		0x00000008	/* Writable file was closed */
35 #define FS_CLOSE_NOWRITE	0x00000010	/* Unwritable file closed */
36 #define FS_OPEN			0x00000020	/* File was opened */
37 #define FS_MOVED_FROM		0x00000040	/* File was moved from X */
38 #define FS_MOVED_TO		0x00000080	/* File was moved to Y */
39 #define FS_CREATE		0x00000100	/* Subfile was created */
40 #define FS_DELETE		0x00000200	/* Subfile was deleted */
41 #define FS_DELETE_SELF		0x00000400	/* Self was deleted */
42 #define FS_MOVE_SELF		0x00000800	/* Self was moved */
43 #define FS_OPEN_EXEC		0x00001000	/* File was opened for exec */
44 
45 #define FS_UNMOUNT		0x00002000	/* inode on umount fs */
46 #define FS_Q_OVERFLOW		0x00004000	/* Event queued overflowed */
47 #define FS_ERROR		0x00008000	/* Filesystem Error (fanotify) */
48 
49 /*
50  * FS_IN_IGNORED overloads FS_ERROR.  It is only used internally by inotify
51  * which does not support FS_ERROR.
52  */
53 #define FS_IN_IGNORED		0x00008000	/* last inotify event here */
54 
55 #define FS_OPEN_PERM		0x00010000	/* open event in an permission hook */
56 #define FS_ACCESS_PERM		0x00020000	/* access event in a permissions hook */
57 #define FS_OPEN_EXEC_PERM	0x00040000	/* open/exec event in a permission hook */
58 /* #define FS_DIR_MODIFY	0x00080000 */	/* Deprecated (reserved) */
59 
60 #define FS_PRE_ACCESS		0x00100000	/* Pre-content access hook */
61 
62 #define FS_MNT_ATTACH		0x01000000	/* Mount was attached */
63 #define FS_MNT_DETACH		0x02000000	/* Mount was detached */
64 #define FS_MNT_MOVE		(FS_MNT_ATTACH | FS_MNT_DETACH)
65 
66 /*
67  * Set on inode mark that cares about things that happen to its children.
68  * Always set for dnotify and inotify.
69  * Set on inode/sb/mount marks that care about parent/name info.
70  */
71 #define FS_EVENT_ON_CHILD	0x08000000
72 
73 #define FS_RENAME		0x10000000	/* File was renamed */
74 #define FS_DN_MULTISHOT		0x20000000	/* dnotify multishot */
75 #define FS_ISDIR		0x40000000	/* event occurred against dir */
76 
77 #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)
78 
79 /*
80  * Directory entry modification events - reported only to directory
81  * where entry is modified and not to a watching parent.
82  * The watching parent may get an FS_ATTRIB|FS_EVENT_ON_CHILD event
83  * when a directory entry inside a child subdir changes.
84  */
85 #define ALL_FSNOTIFY_DIRENT_EVENTS (FS_CREATE | FS_DELETE | FS_MOVE | FS_RENAME)
86 
87 /* Mount namespace events */
88 #define FSNOTIFY_MNT_EVENTS (FS_MNT_ATTACH | FS_MNT_DETACH)
89 
90 /* Content events can be used to inspect file content */
91 #define FSNOTIFY_CONTENT_PERM_EVENTS (FS_OPEN_PERM | FS_OPEN_EXEC_PERM | \
92 				      FS_ACCESS_PERM)
93 /* Pre-content events can be used to fill file content */
94 #define FSNOTIFY_PRE_CONTENT_EVENTS  (FS_PRE_ACCESS)
95 
96 #define ALL_FSNOTIFY_PERM_EVENTS (FSNOTIFY_CONTENT_PERM_EVENTS | \
97 				  FSNOTIFY_PRE_CONTENT_EVENTS)
98 
99 /*
100  * This is a list of all events that may get sent to a parent that is watching
101  * with flag FS_EVENT_ON_CHILD based on fs event on a child of that directory.
102  */
103 #define FS_EVENTS_POSS_ON_CHILD   (ALL_FSNOTIFY_PERM_EVENTS | \
104 				   FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
105 				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | \
106 				   FS_OPEN | FS_OPEN_EXEC)
107 
108 /*
109  * This is a list of all events that may get sent with the parent inode as the
110  * @to_tell argument of fsnotify().
111  * It may include events that can be sent to an inode/sb/mount mark, but cannot
112  * be sent to a parent watching children.
113  */
114 #define FS_EVENTS_POSS_TO_PARENT (FS_EVENTS_POSS_ON_CHILD)
115 
116 /* Events that can be reported to backends */
117 #define ALL_FSNOTIFY_EVENTS (ALL_FSNOTIFY_DIRENT_EVENTS | \
118 			     FSNOTIFY_MNT_EVENTS | \
119 			     FS_EVENTS_POSS_ON_CHILD | \
120 			     FS_DELETE_SELF | FS_MOVE_SELF | \
121 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
122 			     FS_ERROR)
123 
124 /* Extra flags that may be reported with event or control handling of events */
125 #define ALL_FSNOTIFY_FLAGS  (FS_ISDIR | FS_EVENT_ON_CHILD | FS_DN_MULTISHOT)
126 
127 #define ALL_FSNOTIFY_BITS   (ALL_FSNOTIFY_EVENTS | ALL_FSNOTIFY_FLAGS)
128 
129 struct fsnotify_group;
130 struct fsnotify_event;
131 struct fsnotify_mark;
132 struct fsnotify_event_private_data;
133 struct fsnotify_fname;
134 struct fsnotify_iter_info;
135 
136 struct mem_cgroup;
137 
138 /*
139  * Each group much define these ops.  The fsnotify infrastructure will call
140  * these operations for each relevant group.
141  *
142  * handle_event - main call for a group to handle an fs event
143  * @group:	group to notify
144  * @mask:	event type and flags
145  * @data:	object that event happened on
146  * @data_type:	type of object for fanotify_data_XXX() accessors
147  * @dir:	optional directory associated with event -
148  *		if @file_name is not NULL, this is the directory that
149  *		@file_name is relative to
150  * @file_name:	optional file name associated with event
151  * @cookie:	inotify rename cookie
152  * @iter_info:	array of marks from this group that are interested in the event
153  *
154  * handle_inode_event - simple variant of handle_event() for groups that only
155  *		have inode marks and don't have ignore mask
156  * @mark:	mark to notify
157  * @mask:	event type and flags
158  * @inode:	inode that event happened on
159  * @dir:	optional directory associated with event -
160  *		if @file_name is not NULL, this is the directory that
161  *		@file_name is relative to.
162  *		Either @inode or @dir must be non-NULL.
163  * @file_name:	optional file name associated with event
164  * @cookie:	inotify rename cookie
165  *
166  * free_group_priv - called when a group refcnt hits 0 to clean up the private union
167  * freeing_mark - called when a mark is being destroyed for some reason.  The group
168  *		MUST be holding a reference on each mark and that reference must be
169  *		dropped in this function.  inotify uses this function to send
170  *		userspace messages that marks have been removed.
171  */
172 struct fsnotify_ops {
173 	int (*handle_event)(struct fsnotify_group *group, u32 mask,
174 			    const void *data, int data_type, struct inode *dir,
175 			    const struct qstr *file_name, u32 cookie,
176 			    struct fsnotify_iter_info *iter_info);
177 	int (*handle_inode_event)(struct fsnotify_mark *mark, u32 mask,
178 			    struct inode *inode, struct inode *dir,
179 			    const struct qstr *file_name, u32 cookie);
180 	void (*free_group_priv)(struct fsnotify_group *group);
181 	void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
182 	void (*free_event)(struct fsnotify_group *group, struct fsnotify_event *event);
183 	/* called on final put+free to free memory */
184 	void (*free_mark)(struct fsnotify_mark *mark);
185 };
186 
187 /*
188  * all of the information about the original object we want to now send to
189  * a group.  If you want to carry more info from the accessing task to the
190  * listener this structure is where you need to be adding fields.
191  */
192 struct fsnotify_event {
193 	struct list_head list;
194 };
195 
196 /*
197  * fsnotify group priorities.
198  * Events are sent in order from highest priority to lowest priority.
199  */
200 enum fsnotify_group_prio {
201 	FSNOTIFY_PRIO_NORMAL = 0,	/* normal notifiers, no permissions */
202 	FSNOTIFY_PRIO_CONTENT,		/* fanotify permission events */
203 	FSNOTIFY_PRIO_PRE_CONTENT,	/* fanotify pre-content events */
204 	__FSNOTIFY_PRIO_NUM
205 };
206 
207 /*
208  * A group is a "thing" that wants to receive notification about filesystem
209  * events.  The mask holds the subset of event types this group cares about.
210  * refcnt on a group is up to the implementor and at any moment if it goes 0
211  * everything will be cleaned up.
212  */
213 struct fsnotify_group {
214 	const struct fsnotify_ops *ops;	/* how this group handles things */
215 
216 	/*
217 	 * How the refcnt is used is up to each group.  When the refcnt hits 0
218 	 * fsnotify will clean up all of the resources associated with this group.
219 	 * As an example, the dnotify group will always have a refcnt=1 and that
220 	 * will never change.  Inotify, on the other hand, has a group per
221 	 * inotify_init() and the refcnt will hit 0 only when that fd has been
222 	 * closed.
223 	 */
224 	refcount_t refcnt;		/* things with interest in this group */
225 
226 	/* needed to send notification to userspace */
227 	spinlock_t notification_lock;		/* protect the notification_list */
228 	struct list_head notification_list;	/* list of event_holder this group needs to send to userspace */
229 	wait_queue_head_t notification_waitq;	/* read() on the notification file blocks on this waitq */
230 	unsigned int q_len;			/* events on the queue */
231 	unsigned int max_events;		/* maximum events allowed on the list */
232 	enum fsnotify_group_prio priority;	/* priority for sending events */
233 	bool shutdown;		/* group is being shut down, don't queue more events */
234 
235 #define FSNOTIFY_GROUP_USER	0x01 /* user allocated group */
236 #define FSNOTIFY_GROUP_DUPS	0x02 /* allow multiple marks per object */
237 	int flags;
238 	unsigned int owner_flags;	/* stored flags of mark_mutex owner */
239 
240 	/* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
241 	struct mutex mark_mutex;	/* protect marks_list */
242 	atomic_t user_waits;		/* Number of tasks waiting for user
243 					 * response */
244 	struct list_head marks_list;	/* all inode marks for this group */
245 
246 	struct fasync_struct *fsn_fa;    /* async notification */
247 
248 	struct fsnotify_event *overflow_event;	/* Event we queue when the
249 						 * notification list is too
250 						 * full */
251 
252 	struct mem_cgroup *memcg;	/* memcg to charge allocations */
253 	struct user_namespace *user_ns;	/* user ns where group was created */
254 
255 	/* groups can define private fields here or use the void *private */
256 	union {
257 		void *private;
258 #ifdef CONFIG_INOTIFY_USER
259 		struct inotify_group_private_data {
260 			spinlock_t	idr_lock;
261 			struct idr      idr;
262 			struct ucounts *ucounts;
263 		} inotify_data;
264 #endif
265 #ifdef CONFIG_FANOTIFY
266 		struct fanotify_group_private_data {
267 			/* Hash table of events for merge */
268 			struct hlist_head *merge_hash;
269 			/* allows a group to block waiting for a userspace response */
270 			struct list_head access_list;
271 			wait_queue_head_t access_waitq;
272 			int flags;           /* flags from fanotify_init() */
273 			int f_flags; /* event_f_flags from fanotify_init() */
274 			struct ucounts *ucounts;
275 			mempool_t error_events_pool;
276 			/* chained on perm_group_list */
277 			struct list_head perm_grp_list;
278 		} fanotify_data;
279 #endif /* CONFIG_FANOTIFY */
280 	};
281 };
282 
283 /*
284  * These helpers are used to prevent deadlock when reclaiming inodes with
285  * evictable marks of the same group that is allocating a new mark.
286  */
fsnotify_group_lock(struct fsnotify_group * group)287 static inline void fsnotify_group_lock(struct fsnotify_group *group)
288 {
289 	mutex_lock(&group->mark_mutex);
290 	group->owner_flags = memalloc_nofs_save();
291 }
292 
fsnotify_group_unlock(struct fsnotify_group * group)293 static inline void fsnotify_group_unlock(struct fsnotify_group *group)
294 {
295 	memalloc_nofs_restore(group->owner_flags);
296 	mutex_unlock(&group->mark_mutex);
297 }
298 
fsnotify_group_assert_locked(struct fsnotify_group * group)299 static inline void fsnotify_group_assert_locked(struct fsnotify_group *group)
300 {
301 	WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex));
302 	WARN_ON_ONCE(!(current->flags & PF_MEMALLOC_NOFS));
303 }
304 
305 /* When calling fsnotify tell it if the data is a path or inode */
306 enum fsnotify_data_type {
307 	FSNOTIFY_EVENT_NONE,
308 	FSNOTIFY_EVENT_FILE_RANGE,
309 	FSNOTIFY_EVENT_PATH,
310 	FSNOTIFY_EVENT_INODE,
311 	FSNOTIFY_EVENT_DENTRY,
312 	FSNOTIFY_EVENT_MNT,
313 	FSNOTIFY_EVENT_ERROR,
314 };
315 
316 struct fs_error_report {
317 	int error;
318 	struct inode *inode;
319 	struct super_block *sb;
320 };
321 
322 struct file_range {
323 	const struct path *path;
324 	loff_t pos;
325 	size_t count;
326 };
327 
file_range_path(const struct file_range * range)328 static inline const struct path *file_range_path(const struct file_range *range)
329 {
330 	return range->path;
331 }
332 
333 struct fsnotify_mnt {
334 	const struct mnt_namespace *ns;
335 	u64 mnt_id;
336 };
337 
fsnotify_data_inode(const void * data,int data_type)338 static inline struct inode *fsnotify_data_inode(const void *data, int data_type)
339 {
340 	switch (data_type) {
341 	case FSNOTIFY_EVENT_INODE:
342 		return (struct inode *)data;
343 	case FSNOTIFY_EVENT_DENTRY:
344 		return d_inode(data);
345 	case FSNOTIFY_EVENT_PATH:
346 		return d_inode(((const struct path *)data)->dentry);
347 	case FSNOTIFY_EVENT_FILE_RANGE:
348 		return d_inode(file_range_path(data)->dentry);
349 	case FSNOTIFY_EVENT_ERROR:
350 		return ((struct fs_error_report *)data)->inode;
351 	default:
352 		return NULL;
353 	}
354 }
355 
fsnotify_data_dentry(const void * data,int data_type)356 static inline struct dentry *fsnotify_data_dentry(const void *data, int data_type)
357 {
358 	switch (data_type) {
359 	case FSNOTIFY_EVENT_DENTRY:
360 		/* Non const is needed for dget() */
361 		return (struct dentry *)data;
362 	case FSNOTIFY_EVENT_PATH:
363 		return ((const struct path *)data)->dentry;
364 	case FSNOTIFY_EVENT_FILE_RANGE:
365 		return file_range_path(data)->dentry;
366 	default:
367 		return NULL;
368 	}
369 }
370 
fsnotify_data_path(const void * data,int data_type)371 static inline const struct path *fsnotify_data_path(const void *data,
372 						    int data_type)
373 {
374 	switch (data_type) {
375 	case FSNOTIFY_EVENT_PATH:
376 		return data;
377 	case FSNOTIFY_EVENT_FILE_RANGE:
378 		return file_range_path(data);
379 	default:
380 		return NULL;
381 	}
382 }
383 
fsnotify_data_sb(const void * data,int data_type)384 static inline struct super_block *fsnotify_data_sb(const void *data,
385 						   int data_type)
386 {
387 	switch (data_type) {
388 	case FSNOTIFY_EVENT_INODE:
389 		return ((struct inode *)data)->i_sb;
390 	case FSNOTIFY_EVENT_DENTRY:
391 		return ((struct dentry *)data)->d_sb;
392 	case FSNOTIFY_EVENT_PATH:
393 		return ((const struct path *)data)->dentry->d_sb;
394 	case FSNOTIFY_EVENT_FILE_RANGE:
395 		return file_range_path(data)->dentry->d_sb;
396 	case FSNOTIFY_EVENT_ERROR:
397 		return ((struct fs_error_report *) data)->sb;
398 	default:
399 		return NULL;
400 	}
401 }
402 
fsnotify_data_mnt(const void * data,int data_type)403 static inline const struct fsnotify_mnt *fsnotify_data_mnt(const void *data,
404 							   int data_type)
405 {
406 	switch (data_type) {
407 	case FSNOTIFY_EVENT_MNT:
408 		return data;
409 	default:
410 		return NULL;
411 	}
412 }
413 
fsnotify_data_mnt_id(const void * data,int data_type)414 static inline u64 fsnotify_data_mnt_id(const void *data, int data_type)
415 {
416 	const struct fsnotify_mnt *mnt_data = fsnotify_data_mnt(data, data_type);
417 
418 	return mnt_data ? mnt_data->mnt_id : 0;
419 }
420 
fsnotify_data_error_report(const void * data,int data_type)421 static inline struct fs_error_report *fsnotify_data_error_report(
422 							const void *data,
423 							int data_type)
424 {
425 	switch (data_type) {
426 	case FSNOTIFY_EVENT_ERROR:
427 		return (struct fs_error_report *) data;
428 	default:
429 		return NULL;
430 	}
431 }
432 
fsnotify_data_file_range(const void * data,int data_type)433 static inline const struct file_range *fsnotify_data_file_range(
434 							const void *data,
435 							int data_type)
436 {
437 	switch (data_type) {
438 	case FSNOTIFY_EVENT_FILE_RANGE:
439 		return (struct file_range *)data;
440 	default:
441 		return NULL;
442 	}
443 }
444 
445 /*
446  * Index to merged marks iterator array that correlates to a type of watch.
447  * The type of watched object can be deduced from the iterator type, but not
448  * the other way around, because an event can match different watched objects
449  * of the same object type.
450  * For example, both parent and child are watching an object of type inode.
451  */
452 enum fsnotify_iter_type {
453 	FSNOTIFY_ITER_TYPE_INODE,
454 	FSNOTIFY_ITER_TYPE_VFSMOUNT,
455 	FSNOTIFY_ITER_TYPE_SB,
456 	FSNOTIFY_ITER_TYPE_PARENT,
457 	FSNOTIFY_ITER_TYPE_INODE2,
458 	FSNOTIFY_ITER_TYPE_MNTNS,
459 	FSNOTIFY_ITER_TYPE_COUNT
460 };
461 
462 /* The type of object that a mark is attached to */
463 enum fsnotify_obj_type {
464 	FSNOTIFY_OBJ_TYPE_ANY = -1,
465 	FSNOTIFY_OBJ_TYPE_INODE,
466 	FSNOTIFY_OBJ_TYPE_VFSMOUNT,
467 	FSNOTIFY_OBJ_TYPE_SB,
468 	FSNOTIFY_OBJ_TYPE_MNTNS,
469 	FSNOTIFY_OBJ_TYPE_COUNT,
470 	FSNOTIFY_OBJ_TYPE_DETACHED = FSNOTIFY_OBJ_TYPE_COUNT
471 };
472 
fsnotify_valid_obj_type(unsigned int obj_type)473 static inline bool fsnotify_valid_obj_type(unsigned int obj_type)
474 {
475 	return (obj_type < FSNOTIFY_OBJ_TYPE_COUNT);
476 }
477 
478 struct fsnotify_iter_info {
479 	struct fsnotify_mark *marks[FSNOTIFY_ITER_TYPE_COUNT];
480 	struct fsnotify_group *current_group;
481 	unsigned int report_mask;
482 	int srcu_idx;
483 };
484 
fsnotify_iter_should_report_type(struct fsnotify_iter_info * iter_info,int iter_type)485 static inline bool fsnotify_iter_should_report_type(
486 		struct fsnotify_iter_info *iter_info, int iter_type)
487 {
488 	return (iter_info->report_mask & (1U << iter_type));
489 }
490 
fsnotify_iter_set_report_type(struct fsnotify_iter_info * iter_info,int iter_type)491 static inline void fsnotify_iter_set_report_type(
492 		struct fsnotify_iter_info *iter_info, int iter_type)
493 {
494 	iter_info->report_mask |= (1U << iter_type);
495 }
496 
fsnotify_iter_mark(struct fsnotify_iter_info * iter_info,int iter_type)497 static inline struct fsnotify_mark *fsnotify_iter_mark(
498 		struct fsnotify_iter_info *iter_info, int iter_type)
499 {
500 	if (fsnotify_iter_should_report_type(iter_info, iter_type))
501 		return iter_info->marks[iter_type];
502 	return NULL;
503 }
504 
fsnotify_iter_step(struct fsnotify_iter_info * iter,int type,struct fsnotify_mark ** markp)505 static inline int fsnotify_iter_step(struct fsnotify_iter_info *iter, int type,
506 				     struct fsnotify_mark **markp)
507 {
508 	while (type < FSNOTIFY_ITER_TYPE_COUNT) {
509 		*markp = fsnotify_iter_mark(iter, type);
510 		if (*markp)
511 			break;
512 		type++;
513 	}
514 	return type;
515 }
516 
517 #define FSNOTIFY_ITER_FUNCS(name, NAME) \
518 static inline struct fsnotify_mark *fsnotify_iter_##name##_mark( \
519 		struct fsnotify_iter_info *iter_info) \
520 { \
521 	return fsnotify_iter_mark(iter_info, FSNOTIFY_ITER_TYPE_##NAME); \
522 }
523 
524 FSNOTIFY_ITER_FUNCS(inode, INODE)
525 FSNOTIFY_ITER_FUNCS(parent, PARENT)
526 FSNOTIFY_ITER_FUNCS(vfsmount, VFSMOUNT)
527 FSNOTIFY_ITER_FUNCS(sb, SB)
528 
529 #define fsnotify_foreach_iter_type(type) \
530 	for (type = 0; type < FSNOTIFY_ITER_TYPE_COUNT; type++)
531 #define fsnotify_foreach_iter_mark_type(iter, mark, type) \
532 	for (type = 0; \
533 	     type = fsnotify_iter_step(iter, type, &mark), \
534 	     type < FSNOTIFY_ITER_TYPE_COUNT; \
535 	     type++)
536 
537 /*
538  * Inode/vfsmount/sb point to this structure which tracks all marks attached to
539  * the inode/vfsmount/sb. The reference to inode/vfsmount/sb is held by this
540  * structure. We destroy this structure when there are no more marks attached
541  * to it. The structure is protected by fsnotify_mark_srcu.
542  */
543 struct fsnotify_mark_connector {
544 	spinlock_t lock;
545 	unsigned char type;	/* Type of object [lock] */
546 	unsigned char prio;	/* Highest priority group */
547 #define FSNOTIFY_CONN_FLAG_IS_WATCHED	0x01
548 #define FSNOTIFY_CONN_FLAG_HAS_IREF	0x02
549 	unsigned short flags;	/* flags [lock] */
550 	union {
551 		/* Object pointer [lock] */
552 		void *obj;
553 		/* Used listing heads to free after srcu period expires */
554 		struct fsnotify_mark_connector *destroy_next;
555 	};
556 	struct hlist_head list;
557 };
558 
559 /*
560  * Container for per-sb fsnotify state (sb marks and more).
561  * Attached lazily on first marked object on the sb and freed when killing sb.
562  */
563 struct fsnotify_sb_info {
564 	struct fsnotify_mark_connector __rcu *sb_marks;
565 	/*
566 	 * Number of inode/mount/sb objects that are being watched in this sb.
567 	 * Note that inodes objects are currently double-accounted.
568 	 *
569 	 * The value in watched_objects[prio] is the number of objects that are
570 	 * watched by groups of priority >= prio, so watched_objects[0] is the
571 	 * total number of watched objects in this sb.
572 	 */
573 	atomic_long_t watched_objects[__FSNOTIFY_PRIO_NUM];
574 };
575 
fsnotify_sb_info(struct super_block * sb)576 static inline struct fsnotify_sb_info *fsnotify_sb_info(struct super_block *sb)
577 {
578 #ifdef CONFIG_FSNOTIFY
579 	return READ_ONCE(sb->s_fsnotify_info);
580 #else
581 	return NULL;
582 #endif
583 }
584 
fsnotify_sb_watched_objects(struct super_block * sb)585 static inline atomic_long_t *fsnotify_sb_watched_objects(struct super_block *sb)
586 {
587 	return &fsnotify_sb_info(sb)->watched_objects[0];
588 }
589 
590 /*
591  * A mark is simply an object attached to an in core inode which allows an
592  * fsnotify listener to indicate they are either no longer interested in events
593  * of a type matching mask or only interested in those events.
594  *
595  * These are flushed when an inode is evicted from core and may be flushed
596  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify
597  * users (such as dnotify) will flush these when the open fd is closed and not
598  * at inode eviction or modification.
599  *
600  * Text in brackets is showing the lock(s) protecting modifications of a
601  * particular entry. obj_lock means either inode->i_lock or
602  * mnt->mnt_root->d_lock depending on the mark type.
603  */
604 struct fsnotify_mark {
605 	/* Mask this mark is for [mark->lock, group->mark_mutex] */
606 	__u32 mask;
607 	/* We hold one for presence in g_list. Also one ref for each 'thing'
608 	 * in kernel that found and may be using this mark. */
609 	refcount_t refcnt;
610 	/* Group this mark is for. Set on mark creation, stable until last ref
611 	 * is dropped */
612 	struct fsnotify_group *group;
613 	/* List of marks by group->marks_list. Also reused for queueing
614 	 * mark into destroy_list when it's waiting for the end of SRCU period
615 	 * before it can be freed. [group->mark_mutex] */
616 	struct list_head g_list;
617 	/* Protects inode / mnt pointers, flags, masks */
618 	spinlock_t lock;
619 	/* List of marks for inode / vfsmount [connector->lock, mark ref] */
620 	struct hlist_node obj_list;
621 	/* Head of list of marks for an object [mark ref] */
622 	struct fsnotify_mark_connector *connector;
623 	/* Events types and flags to ignore [mark->lock, group->mark_mutex] */
624 	__u32 ignore_mask;
625 	/* General fsnotify mark flags */
626 #define FSNOTIFY_MARK_FLAG_ALIVE		0x0001
627 #define FSNOTIFY_MARK_FLAG_ATTACHED		0x0002
628 	/* inotify mark flags */
629 #define FSNOTIFY_MARK_FLAG_EXCL_UNLINK		0x0010
630 #define FSNOTIFY_MARK_FLAG_IN_ONESHOT		0x0020
631 	/* fanotify mark flags */
632 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY	0x0100
633 #define FSNOTIFY_MARK_FLAG_NO_IREF		0x0200
634 #define FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS	0x0400
635 #define FSNOTIFY_MARK_FLAG_HAS_FSID		0x0800
636 #define FSNOTIFY_MARK_FLAG_WEAK_FSID		0x1000
637 	unsigned int flags;		/* flags [mark->lock] */
638 };
639 
640 #ifdef CONFIG_FSNOTIFY
641 
642 /* called from the vfs helpers */
643 
644 /* main fsnotify call to send events */
645 extern int fsnotify(__u32 mask, const void *data, int data_type,
646 		    struct inode *dir, const struct qstr *name,
647 		    struct inode *inode, u32 cookie);
648 extern int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
649 			   int data_type);
650 extern void __fsnotify_inode_delete(struct inode *inode);
651 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
652 extern void fsnotify_sb_delete(struct super_block *sb);
653 extern void __fsnotify_mntns_delete(struct mnt_namespace *mntns);
654 extern void fsnotify_sb_free(struct super_block *sb);
655 extern u32 fsnotify_get_cookie(void);
656 extern void fsnotify_mnt(__u32 mask, struct mnt_namespace *ns, struct vfsmount *mnt);
657 
fsnotify_parent_needed_mask(__u32 mask)658 static inline __u32 fsnotify_parent_needed_mask(__u32 mask)
659 {
660 	/* FS_EVENT_ON_CHILD is set on marks that want parent/name info */
661 	if (!(mask & FS_EVENT_ON_CHILD))
662 		return 0;
663 	/*
664 	 * This object might be watched by a mark that cares about parent/name
665 	 * info, does it care about the specific set of events that can be
666 	 * reported with parent/name info?
667 	 */
668 	return mask & FS_EVENTS_POSS_TO_PARENT;
669 }
670 
fsnotify_inode_watches_children(struct inode * inode)671 static inline int fsnotify_inode_watches_children(struct inode *inode)
672 {
673 	__u32 parent_mask = READ_ONCE(inode->i_fsnotify_mask);
674 
675 	/* FS_EVENT_ON_CHILD is set if the inode may care */
676 	if (!(parent_mask & FS_EVENT_ON_CHILD))
677 		return 0;
678 	/* this inode might care about child events, does it care about the
679 	 * specific set of events that can happen on a child? */
680 	return parent_mask & FS_EVENTS_POSS_ON_CHILD;
681 }
682 
683 /*
684  * Update the dentry with a flag indicating the interest of its parent to receive
685  * filesystem events when those events happens to this dentry->d_inode.
686  */
fsnotify_update_flags(struct dentry * dentry)687 static inline void fsnotify_update_flags(struct dentry *dentry)
688 {
689 	assert_spin_locked(&dentry->d_lock);
690 
691 	/*
692 	 * Serialisation of setting PARENT_WATCHED on the dentries is provided
693 	 * by d_lock. If inotify_inode_watched changes after we have taken
694 	 * d_lock, the following fsnotify_set_children_dentry_flags call will
695 	 * find our entry, so it will spin until we complete here, and update
696 	 * us with the new state.
697 	 */
698 	if (fsnotify_inode_watches_children(dentry->d_parent->d_inode))
699 		dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
700 	else
701 		dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
702 }
703 
704 /* called from fsnotify listeners, such as fanotify or dnotify */
705 
706 /* create a new group */
707 extern struct fsnotify_group *fsnotify_alloc_group(
708 				const struct fsnotify_ops *ops,
709 				int flags);
710 /* get reference to a group */
711 extern void fsnotify_get_group(struct fsnotify_group *group);
712 /* drop reference on a group from fsnotify_alloc_group */
713 extern void fsnotify_put_group(struct fsnotify_group *group);
714 /* group destruction begins, stop queuing new events */
715 extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);
716 /* destroy group */
717 extern void fsnotify_destroy_group(struct fsnotify_group *group);
718 /* fasync handler function */
719 extern int fsnotify_fasync(int fd, struct file *file, int on);
720 /* Free event from memory */
721 extern void fsnotify_destroy_event(struct fsnotify_group *group,
722 				   struct fsnotify_event *event);
723 /* attach the event to the group notification queue */
724 extern int fsnotify_insert_event(struct fsnotify_group *group,
725 				 struct fsnotify_event *event,
726 				 int (*merge)(struct fsnotify_group *,
727 					      struct fsnotify_event *),
728 				 void (*insert)(struct fsnotify_group *,
729 						struct fsnotify_event *));
730 
fsnotify_add_event(struct fsnotify_group * group,struct fsnotify_event * event,int (* merge)(struct fsnotify_group *,struct fsnotify_event *))731 static inline int fsnotify_add_event(struct fsnotify_group *group,
732 				     struct fsnotify_event *event,
733 				     int (*merge)(struct fsnotify_group *,
734 						  struct fsnotify_event *))
735 {
736 	return fsnotify_insert_event(group, event, merge, NULL);
737 }
738 
739 /* Queue overflow event to a notification group */
fsnotify_queue_overflow(struct fsnotify_group * group)740 static inline void fsnotify_queue_overflow(struct fsnotify_group *group)
741 {
742 	fsnotify_add_event(group, group->overflow_event, NULL);
743 }
744 
fsnotify_is_overflow_event(u32 mask)745 static inline bool fsnotify_is_overflow_event(u32 mask)
746 {
747 	return mask & FS_Q_OVERFLOW;
748 }
749 
fsnotify_notify_queue_is_empty(struct fsnotify_group * group)750 static inline bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group)
751 {
752 	assert_spin_locked(&group->notification_lock);
753 
754 	return list_empty(&group->notification_list);
755 }
756 
757 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
758 /* return, but do not dequeue the first event on the notification queue */
759 extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group);
760 /* return AND dequeue the first event on the notification queue */
761 extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);
762 /* Remove event queued in the notification list */
763 extern void fsnotify_remove_queued_event(struct fsnotify_group *group,
764 					 struct fsnotify_event *event);
765 
766 /* functions used to manipulate the marks attached to inodes */
767 
768 /*
769  * Canonical "ignore mask" including event flags.
770  *
771  * Note the subtle semantic difference from the legacy ->ignored_mask.
772  * ->ignored_mask traditionally only meant which events should be ignored,
773  * while ->ignore_mask also includes flags regarding the type of objects on
774  * which events should be ignored.
775  */
fsnotify_ignore_mask(struct fsnotify_mark * mark)776 static inline __u32 fsnotify_ignore_mask(struct fsnotify_mark *mark)
777 {
778 	__u32 ignore_mask = mark->ignore_mask;
779 
780 	/* The event flags in ignore mask take effect */
781 	if (mark->flags & FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS)
782 		return ignore_mask;
783 
784 	/*
785 	 * Legacy behavior:
786 	 * - Always ignore events on dir
787 	 * - Ignore events on child if parent is watching children
788 	 */
789 	ignore_mask |= FS_ISDIR;
790 	ignore_mask &= ~FS_EVENT_ON_CHILD;
791 	ignore_mask |= mark->mask & FS_EVENT_ON_CHILD;
792 
793 	return ignore_mask;
794 }
795 
796 /* Legacy ignored_mask - only event types to ignore */
fsnotify_ignored_events(struct fsnotify_mark * mark)797 static inline __u32 fsnotify_ignored_events(struct fsnotify_mark *mark)
798 {
799 	return mark->ignore_mask & ALL_FSNOTIFY_EVENTS;
800 }
801 
802 /*
803  * Check if mask (or ignore mask) should be applied depending if victim is a
804  * directory and whether it is reported to a watching parent.
805  */
fsnotify_mask_applicable(__u32 mask,bool is_dir,int iter_type)806 static inline bool fsnotify_mask_applicable(__u32 mask, bool is_dir,
807 					    int iter_type)
808 {
809 	/* Should mask be applied to a directory? */
810 	if (is_dir && !(mask & FS_ISDIR))
811 		return false;
812 
813 	/* Should mask be applied to a child? */
814 	if (iter_type == FSNOTIFY_ITER_TYPE_PARENT &&
815 	    !(mask & FS_EVENT_ON_CHILD))
816 		return false;
817 
818 	return true;
819 }
820 
821 /*
822  * Effective ignore mask taking into account if event victim is a
823  * directory and whether it is reported to a watching parent.
824  */
fsnotify_effective_ignore_mask(struct fsnotify_mark * mark,bool is_dir,int iter_type)825 static inline __u32 fsnotify_effective_ignore_mask(struct fsnotify_mark *mark,
826 						   bool is_dir, int iter_type)
827 {
828 	__u32 ignore_mask = fsnotify_ignored_events(mark);
829 
830 	if (!ignore_mask)
831 		return 0;
832 
833 	/* For non-dir and non-child, no need to consult the event flags */
834 	if (!is_dir && iter_type != FSNOTIFY_ITER_TYPE_PARENT)
835 		return ignore_mask;
836 
837 	ignore_mask = fsnotify_ignore_mask(mark);
838 	if (!fsnotify_mask_applicable(ignore_mask, is_dir, iter_type))
839 		return 0;
840 
841 	return ignore_mask & ALL_FSNOTIFY_EVENTS;
842 }
843 
844 /* Get mask for calculating object interest taking ignore mask into account */
fsnotify_calc_mask(struct fsnotify_mark * mark)845 static inline __u32 fsnotify_calc_mask(struct fsnotify_mark *mark)
846 {
847 	__u32 mask = mark->mask;
848 
849 	if (!fsnotify_ignored_events(mark))
850 		return mask;
851 
852 	/* Interest in FS_MODIFY may be needed for clearing ignore mask */
853 	if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
854 		mask |= FS_MODIFY;
855 
856 	/*
857 	 * If mark is interested in ignoring events on children, the object must
858 	 * show interest in those events for fsnotify_parent() to notice it.
859 	 */
860 	return mask | mark->ignore_mask;
861 }
862 
863 /* Get mask of events for a list of marks */
864 extern __u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn);
865 /* Calculate mask of events for a list of marks */
866 extern void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn);
867 extern void fsnotify_init_mark(struct fsnotify_mark *mark,
868 			       struct fsnotify_group *group);
869 /* Find mark belonging to given group in the list of marks */
870 struct fsnotify_mark *fsnotify_find_mark(void *obj, unsigned int obj_type,
871 					 struct fsnotify_group *group);
872 /* attach the mark to the object */
873 int fsnotify_add_mark(struct fsnotify_mark *mark, void *obj,
874 		      unsigned int obj_type, int add_flags);
875 int fsnotify_add_mark_locked(struct fsnotify_mark *mark, void *obj,
876 			     unsigned int obj_type, int add_flags);
877 
878 /* attach the mark to the inode */
fsnotify_add_inode_mark(struct fsnotify_mark * mark,struct inode * inode,int add_flags)879 static inline int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
880 					  struct inode *inode,
881 					  int add_flags)
882 {
883 	return fsnotify_add_mark(mark, inode, FSNOTIFY_OBJ_TYPE_INODE,
884 				 add_flags);
885 }
fsnotify_add_inode_mark_locked(struct fsnotify_mark * mark,struct inode * inode,int add_flags)886 static inline int fsnotify_add_inode_mark_locked(struct fsnotify_mark *mark,
887 						 struct inode *inode,
888 						 int add_flags)
889 {
890 	return fsnotify_add_mark_locked(mark, inode, FSNOTIFY_OBJ_TYPE_INODE,
891 					add_flags);
892 }
893 
fsnotify_find_inode_mark(struct inode * inode,struct fsnotify_group * group)894 static inline struct fsnotify_mark *fsnotify_find_inode_mark(
895 						struct inode *inode,
896 						struct fsnotify_group *group)
897 {
898 	return fsnotify_find_mark(inode, FSNOTIFY_OBJ_TYPE_INODE, group);
899 }
900 
901 /* given a group and a mark, flag mark to be freed when all references are dropped */
902 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
903 				  struct fsnotify_group *group);
904 /* detach mark from inode / mount list, group list, drop inode reference */
905 extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
906 /* free mark */
907 extern void fsnotify_free_mark(struct fsnotify_mark *mark);
908 /* Wait until all marks queued for destruction are destroyed */
909 extern void fsnotify_wait_marks_destroyed(void);
910 /* Clear all of the marks of a group attached to a given object type */
911 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
912 					  unsigned int obj_type);
913 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
914 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
915 extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
916 extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);
917 
fsnotify_init_event(struct fsnotify_event * event)918 static inline void fsnotify_init_event(struct fsnotify_event *event)
919 {
920 	INIT_LIST_HEAD(&event->list);
921 }
922 int fsnotify_pre_content(const struct path *path, const loff_t *ppos,
923 			 size_t count);
924 
925 #else
926 
fsnotify_pre_content(const struct path * path,const loff_t * ppos,size_t count)927 static inline int fsnotify_pre_content(const struct path *path,
928 				       const loff_t *ppos, size_t count)
929 {
930 	return 0;
931 }
932 
fsnotify(__u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * name,struct inode * inode,u32 cookie)933 static inline int fsnotify(__u32 mask, const void *data, int data_type,
934 			   struct inode *dir, const struct qstr *name,
935 			   struct inode *inode, u32 cookie)
936 {
937 	return 0;
938 }
939 
__fsnotify_parent(struct dentry * dentry,__u32 mask,const void * data,int data_type)940 static inline int __fsnotify_parent(struct dentry *dentry, __u32 mask,
941 				  const void *data, int data_type)
942 {
943 	return 0;
944 }
945 
__fsnotify_inode_delete(struct inode * inode)946 static inline void __fsnotify_inode_delete(struct inode *inode)
947 {}
948 
__fsnotify_vfsmount_delete(struct vfsmount * mnt)949 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
950 {}
951 
fsnotify_sb_delete(struct super_block * sb)952 static inline void fsnotify_sb_delete(struct super_block *sb)
953 {}
954 
__fsnotify_mntns_delete(struct mnt_namespace * mntns)955 static inline void __fsnotify_mntns_delete(struct mnt_namespace *mntns)
956 {}
957 
fsnotify_sb_free(struct super_block * sb)958 static inline void fsnotify_sb_free(struct super_block *sb)
959 {}
960 
fsnotify_update_flags(struct dentry * dentry)961 static inline void fsnotify_update_flags(struct dentry *dentry)
962 {}
963 
fsnotify_get_cookie(void)964 static inline u32 fsnotify_get_cookie(void)
965 {
966 	return 0;
967 }
968 
fsnotify_unmount_inodes(struct super_block * sb)969 static inline void fsnotify_unmount_inodes(struct super_block *sb)
970 {}
971 
fsnotify_mnt(__u32 mask,struct mnt_namespace * ns,struct vfsmount * mnt)972 static inline void fsnotify_mnt(__u32 mask, struct mnt_namespace *ns, struct vfsmount *mnt)
973 {}
974 
975 #endif	/* CONFIG_FSNOTIFY */
976 
977 #endif	/* __KERNEL __ */
978 
979 #endif	/* __LINUX_FSNOTIFY_BACKEND_H */
980