1 /*
2 * Filesystem access notification for Linux
3 *
4 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
5 */
6
7 #ifndef __LINUX_FSNOTIFY_BACKEND_H
8 #define __LINUX_FSNOTIFY_BACKEND_H
9
10 #ifdef __KERNEL__
11
12 #include <linux/idr.h> /* inotify uses this */
13 #include <linux/fs.h> /* struct inode */
14 #include <linux/list.h>
15 #include <linux/path.h> /* struct path */
16 #include <linux/spinlock.h>
17 #include <linux/types.h>
18
19 #include <linux/atomic.h>
20
21 /*
22 * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
23 * convert between them. dnotify only needs conversion at watch creation
24 * so no perf loss there. fanotify isn't defined yet, so it can use the
25 * wholes if it needs more events.
26 */
27 #define FS_ACCESS 0x00000001 /* File was accessed */
28 #define FS_MODIFY 0x00000002 /* File was modified */
29 #define FS_ATTRIB 0x00000004 /* Metadata changed */
30 #define FS_CLOSE_WRITE 0x00000008 /* Writtable file was closed */
31 #define FS_CLOSE_NOWRITE 0x00000010 /* Unwrittable file closed */
32 #define FS_OPEN 0x00000020 /* File was opened */
33 #define FS_MOVED_FROM 0x00000040 /* File was moved from X */
34 #define FS_MOVED_TO 0x00000080 /* File was moved to Y */
35 #define FS_CREATE 0x00000100 /* Subfile was created */
36 #define FS_DELETE 0x00000200 /* Subfile was deleted */
37 #define FS_DELETE_SELF 0x00000400 /* Self was deleted */
38 #define FS_MOVE_SELF 0x00000800 /* Self was moved */
39
40 #define FS_UNMOUNT 0x00002000 /* inode on umount fs */
41 #define FS_Q_OVERFLOW 0x00004000 /* Event queued overflowed */
42 #define FS_IN_IGNORED 0x00008000 /* last inotify event here */
43
44 #define FS_OPEN_PERM 0x00010000 /* open event in an permission hook */
45 #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */
46
47 #define FS_EXCL_UNLINK 0x04000000 /* do not send events if object is unlinked */
48 #define FS_ISDIR 0x40000000 /* event occurred against dir */
49 #define FS_IN_ONESHOT 0x80000000 /* only send event once */
50
51 #define FS_DN_RENAME 0x10000000 /* file renamed */
52 #define FS_DN_MULTISHOT 0x20000000 /* dnotify multishot */
53
54 /* This inode cares about things that happen to its children. Always set for
55 * dnotify and inotify. */
56 #define FS_EVENT_ON_CHILD 0x08000000
57
58 /* This is a list of all events that may get sent to a parernt based on fs event
59 * happening to inodes inside that directory */
60 #define FS_EVENTS_POSS_ON_CHILD (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
61 FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
62 FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
63 FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM)
64
65 #define FS_MOVE (FS_MOVED_FROM | FS_MOVED_TO)
66
67 #define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM)
68
69 #define ALL_FSNOTIFY_EVENTS (FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
70 FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN | \
71 FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
72 FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
73 FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
74 FS_OPEN_PERM | FS_ACCESS_PERM | FS_EXCL_UNLINK | \
75 FS_ISDIR | FS_IN_ONESHOT | FS_DN_RENAME | \
76 FS_DN_MULTISHOT | FS_EVENT_ON_CHILD)
77
78 struct fsnotify_group;
79 struct fsnotify_event;
80 struct fsnotify_mark;
81 struct fsnotify_event_private_data;
82
83 /*
84 * Each group much define these ops. The fsnotify infrastructure will call
85 * these operations for each relevant group.
86 *
87 * should_send_event - given a group, inode, and mask this function determines
88 * if the group is interested in this event.
89 * handle_event - main call for a group to handle an fs event
90 * free_group_priv - called when a group refcnt hits 0 to clean up the private union
91 * freeing_mark - called when a mark is being destroyed for some reason. The group
92 * MUST be holding a reference on each mark and that reference must be
93 * dropped in this function. inotify uses this function to send
94 * userspace messages that marks have been removed.
95 */
96 struct fsnotify_ops {
97 bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode,
98 struct fsnotify_mark *inode_mark,
99 struct fsnotify_mark *vfsmount_mark,
100 __u32 mask, void *data, int data_type);
101 int (*handle_event)(struct fsnotify_group *group,
102 struct fsnotify_mark *inode_mark,
103 struct fsnotify_mark *vfsmount_mark,
104 struct fsnotify_event *event);
105 void (*free_group_priv)(struct fsnotify_group *group);
106 void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
107 void (*free_event_priv)(struct fsnotify_event_private_data *priv);
108 };
109
110 /*
111 * A group is a "thing" that wants to receive notification about filesystem
112 * events. The mask holds the subset of event types this group cares about.
113 * refcnt on a group is up to the implementor and at any moment if it goes 0
114 * everything will be cleaned up.
115 */
116 struct fsnotify_group {
117 /*
118 * How the refcnt is used is up to each group. When the refcnt hits 0
119 * fsnotify will clean up all of the resources associated with this group.
120 * As an example, the dnotify group will always have a refcnt=1 and that
121 * will never change. Inotify, on the other hand, has a group per
122 * inotify_init() and the refcnt will hit 0 only when that fd has been
123 * closed.
124 */
125 atomic_t refcnt; /* things with interest in this group */
126
127 const struct fsnotify_ops *ops; /* how this group handles things */
128
129 /* needed to send notification to userspace */
130 struct mutex notification_mutex; /* protect the notification_list */
131 struct list_head notification_list; /* list of event_holder this group needs to send to userspace */
132 wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */
133 unsigned int q_len; /* events on the queue */
134 unsigned int max_events; /* maximum events allowed on the list */
135 /*
136 * Valid fsnotify group priorities. Events are send in order from highest
137 * priority to lowest priority. We default to the lowest priority.
138 */
139 #define FS_PRIO_0 0 /* normal notifiers, no permissions */
140 #define FS_PRIO_1 1 /* fanotify content based access control */
141 #define FS_PRIO_2 2 /* fanotify pre-content access */
142 unsigned int priority;
143
144 /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
145 struct mutex mark_mutex; /* protect marks_list */
146 atomic_t num_marks; /* 1 for each mark and 1 for not being
147 * past the point of no return when freeing
148 * a group */
149 struct list_head marks_list; /* all inode marks for this group */
150
151 struct fasync_struct *fsn_fa; /* async notification */
152
153 /* groups can define private fields here or use the void *private */
154 union {
155 void *private;
156 #ifdef CONFIG_INOTIFY_USER
157 struct inotify_group_private_data {
158 spinlock_t idr_lock;
159 struct idr idr;
160 struct user_struct *user;
161 } inotify_data;
162 #endif
163 #ifdef CONFIG_FANOTIFY
164 struct fanotify_group_private_data {
165 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
166 /* allows a group to block waiting for a userspace response */
167 struct mutex access_mutex;
168 struct list_head access_list;
169 wait_queue_head_t access_waitq;
170 atomic_t bypass_perm;
171 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
172 int f_flags;
173 unsigned int max_marks;
174 struct user_struct *user;
175 } fanotify_data;
176 #endif /* CONFIG_FANOTIFY */
177 };
178 };
179
180 /*
181 * A single event can be queued in multiple group->notification_lists.
182 *
183 * each group->notification_list will point to an event_holder which in turns points
184 * to the actual event that needs to be sent to userspace.
185 *
186 * Seemed cheaper to create a refcnt'd event and a small holder for every group
187 * than create a different event for every group
188 *
189 */
190 struct fsnotify_event_holder {
191 struct fsnotify_event *event;
192 struct list_head event_list;
193 };
194
195 /*
196 * Inotify needs to tack data onto an event. This struct lets us later find the
197 * correct private data of the correct group.
198 */
199 struct fsnotify_event_private_data {
200 struct fsnotify_group *group;
201 struct list_head event_list;
202 };
203
204 /*
205 * all of the information about the original object we want to now send to
206 * a group. If you want to carry more info from the accessing task to the
207 * listener this structure is where you need to be adding fields.
208 */
209 struct fsnotify_event {
210 /*
211 * If we create an event we are also likely going to need a holder
212 * to link to a group. So embed one holder in the event. Means only
213 * one allocation for the common case where we only have one group
214 */
215 struct fsnotify_event_holder holder;
216 spinlock_t lock; /* protection for the associated event_holder and private_list */
217 /* to_tell may ONLY be dereferenced during handle_event(). */
218 struct inode *to_tell; /* either the inode the event happened to or its parent */
219 /*
220 * depending on the event type we should have either a path or inode
221 * We hold a reference on path, but NOT on inode. Since we have the ref on
222 * the path, it may be dereferenced at any point during this object's
223 * lifetime. That reference is dropped when this object's refcnt hits
224 * 0. If this event contains an inode instead of a path, the inode may
225 * ONLY be used during handle_event().
226 */
227 union {
228 struct path path;
229 struct inode *inode;
230 };
231 /* when calling fsnotify tell it if the data is a path or inode */
232 #define FSNOTIFY_EVENT_NONE 0
233 #define FSNOTIFY_EVENT_PATH 1
234 #define FSNOTIFY_EVENT_INODE 2
235 int data_type; /* which of the above union we have */
236 atomic_t refcnt; /* how many groups still are using/need to send this event */
237 __u32 mask; /* the type of access, bitwise OR for FS_* event types */
238
239 u32 sync_cookie; /* used to corrolate events, namely inotify mv events */
240 const unsigned char *file_name;
241 size_t name_len;
242 struct pid *tgid;
243
244 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
245 __u32 response; /* userspace answer to question */
246 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
247
248 struct list_head private_data_list; /* groups can store private data here */
249 };
250
251 /*
252 * Inode specific fields in an fsnotify_mark
253 */
254 struct fsnotify_inode_mark {
255 struct inode *inode; /* inode this mark is associated with */
256 struct hlist_node i_list; /* list of marks by inode->i_fsnotify_marks */
257 struct list_head free_i_list; /* tmp list used when freeing this mark */
258 };
259
260 /*
261 * Mount point specific fields in an fsnotify_mark
262 */
263 struct fsnotify_vfsmount_mark {
264 struct vfsmount *mnt; /* vfsmount this mark is associated with */
265 struct hlist_node m_list; /* list of marks by inode->i_fsnotify_marks */
266 struct list_head free_m_list; /* tmp list used when freeing this mark */
267 };
268
269 /*
270 * a mark is simply an object attached to an in core inode which allows an
271 * fsnotify listener to indicate they are either no longer interested in events
272 * of a type matching mask or only interested in those events.
273 *
274 * these are flushed when an inode is evicted from core and may be flushed
275 * when the inode is modified (as seen by fsnotify_access). Some fsnotify users
276 * (such as dnotify) will flush these when the open fd is closed and not at
277 * inode eviction or modification.
278 */
279 struct fsnotify_mark {
280 __u32 mask; /* mask this mark is for */
281 /* we hold ref for each i_list and g_list. also one ref for each 'thing'
282 * in kernel that found and may be using this mark. */
283 atomic_t refcnt; /* active things looking at this mark */
284 struct fsnotify_group *group; /* group this mark is for */
285 struct list_head g_list; /* list of marks by group->i_fsnotify_marks */
286 spinlock_t lock; /* protect group and inode */
287 union {
288 struct fsnotify_inode_mark i;
289 struct fsnotify_vfsmount_mark m;
290 };
291 __u32 ignored_mask; /* events types to ignore */
292 #define FSNOTIFY_MARK_FLAG_INODE 0x01
293 #define FSNOTIFY_MARK_FLAG_VFSMOUNT 0x02
294 #define FSNOTIFY_MARK_FLAG_OBJECT_PINNED 0x04
295 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY 0x08
296 #define FSNOTIFY_MARK_FLAG_ALIVE 0x10
297 unsigned int flags; /* vfsmount or inode mark? */
298 struct list_head destroy_list;
299 void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
300 };
301
302 #ifdef CONFIG_FSNOTIFY
303
304 /* called from the vfs helpers */
305
306 /* main fsnotify call to send events */
307 extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
308 const unsigned char *name, u32 cookie);
309 extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
310 extern void __fsnotify_inode_delete(struct inode *inode);
311 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
312 extern u32 fsnotify_get_cookie(void);
313
fsnotify_inode_watches_children(struct inode * inode)314 static inline int fsnotify_inode_watches_children(struct inode *inode)
315 {
316 /* FS_EVENT_ON_CHILD is set if the inode may care */
317 if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
318 return 0;
319 /* this inode might care about child events, does it care about the
320 * specific set of events that can happen on a child? */
321 return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
322 }
323
324 /*
325 * Update the dentry with a flag indicating the interest of its parent to receive
326 * filesystem events when those events happens to this dentry->d_inode.
327 */
__fsnotify_update_dcache_flags(struct dentry * dentry)328 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
329 {
330 struct dentry *parent;
331
332 assert_spin_locked(&dentry->d_lock);
333
334 /*
335 * Serialisation of setting PARENT_WATCHED on the dentries is provided
336 * by d_lock. If inotify_inode_watched changes after we have taken
337 * d_lock, the following __fsnotify_update_child_dentry_flags call will
338 * find our entry, so it will spin until we complete here, and update
339 * us with the new state.
340 */
341 parent = dentry->d_parent;
342 if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
343 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
344 else
345 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
346 }
347
348 /*
349 * fsnotify_d_instantiate - instantiate a dentry for inode
350 */
__fsnotify_d_instantiate(struct dentry * dentry,struct inode * inode)351 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
352 {
353 if (!inode)
354 return;
355
356 spin_lock(&dentry->d_lock);
357 __fsnotify_update_dcache_flags(dentry);
358 spin_unlock(&dentry->d_lock);
359 }
360
361 /* called from fsnotify listeners, such as fanotify or dnotify */
362
363 /* create a new group */
364 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
365 /* get reference to a group */
366 extern void fsnotify_get_group(struct fsnotify_group *group);
367 /* drop reference on a group from fsnotify_alloc_group */
368 extern void fsnotify_put_group(struct fsnotify_group *group);
369 /* destroy group */
370 extern void fsnotify_destroy_group(struct fsnotify_group *group);
371 /* fasync handler function */
372 extern int fsnotify_fasync(int fd, struct file *file, int on);
373 /* take a reference to an event */
374 extern void fsnotify_get_event(struct fsnotify_event *event);
375 extern void fsnotify_put_event(struct fsnotify_event *event);
376 /* find private data previously attached to an event and unlink it */
377 extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
378 struct fsnotify_event *event);
379
380 /* attach the event to the group notification queue */
381 extern struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
382 struct fsnotify_event *event,
383 struct fsnotify_event_private_data *priv,
384 struct fsnotify_event *(*merge)(struct list_head *,
385 struct fsnotify_event *));
386 /* true if the group notification queue is empty */
387 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
388 /* return, but do not dequeue the first event on the notification queue */
389 extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
390 /* return AND dequeue the first event on the notification queue */
391 extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
392
393 /* functions used to manipulate the marks attached to inodes */
394
395 /* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
396 extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
397 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
398 extern void fsnotify_recalc_inode_mask(struct inode *inode);
399 extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
400 /* find (and take a reference) to a mark associated with group and inode */
401 extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
402 /* find (and take a reference) to a mark associated with group and vfsmount */
403 extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
404 /* copy the values from old into new */
405 extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
406 /* set the ignored_mask of a mark */
407 extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
408 /* set the mask of a mark (might pin the object into memory */
409 extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
410 /* attach the mark to both the group and the inode */
411 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
412 struct inode *inode, struct vfsmount *mnt, int allow_dups);
413 extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, struct fsnotify_group *group,
414 struct inode *inode, struct vfsmount *mnt, int allow_dups);
415 /* given a group and a mark, flag mark to be freed when all references are dropped */
416 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
417 struct fsnotify_group *group);
418 extern void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
419 struct fsnotify_group *group);
420 /* run all the marks in a group, and clear all of the vfsmount marks */
421 extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
422 /* run all the marks in a group, and clear all of the inode marks */
423 extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
424 /* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
425 extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
426 /* run all the marks in a group, and flag them to be freed */
427 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
428 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
429 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
430 extern void fsnotify_unmount_inodes(struct list_head *list);
431
432 /* put here because inotify does some weird stuff when destroying watches */
433 extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
434 void *data, int data_is,
435 const unsigned char *name,
436 u32 cookie, gfp_t gfp);
437
438 /* fanotify likes to change events after they are on lists... */
439 extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
440 extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
441 struct fsnotify_event *new_event);
442
443 #else
444
fsnotify(struct inode * to_tell,__u32 mask,void * data,int data_is,const unsigned char * name,u32 cookie)445 static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
446 const unsigned char *name, u32 cookie)
447 {
448 return 0;
449 }
450
__fsnotify_parent(struct path * path,struct dentry * dentry,__u32 mask)451 static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
452 {
453 return 0;
454 }
455
__fsnotify_inode_delete(struct inode * inode)456 static inline void __fsnotify_inode_delete(struct inode *inode)
457 {}
458
__fsnotify_vfsmount_delete(struct vfsmount * mnt)459 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
460 {}
461
__fsnotify_update_dcache_flags(struct dentry * dentry)462 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
463 {}
464
__fsnotify_d_instantiate(struct dentry * dentry,struct inode * inode)465 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
466 {}
467
fsnotify_get_cookie(void)468 static inline u32 fsnotify_get_cookie(void)
469 {
470 return 0;
471 }
472
fsnotify_unmount_inodes(struct list_head * list)473 static inline void fsnotify_unmount_inodes(struct list_head *list)
474 {}
475
476 #endif /* CONFIG_FSNOTIFY */
477
478 #endif /* __KERNEL __ */
479
480 #endif /* __LINUX_FSNOTIFY_BACKEND_H */
481