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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 <asm/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)
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
78struct fsnotify_group;
79struct fsnotify_event;
80struct fsnotify_mark;
81struct 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 - this means that a mark has been flagged to die when everything
92 * finishes using it. The function is supplied with what must be a
93 * valid group and inode to use to clean up.
94 */
95struct fsnotify_ops {
96 bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode,
97 struct fsnotify_mark *inode_mark,
98 struct fsnotify_mark *vfsmount_mark,
99 __u32 mask, void *data, int data_type);
100 int (*handle_event)(struct fsnotify_group *group,
101 struct fsnotify_mark *inode_mark,
102 struct fsnotify_mark *vfsmount_mark,
103 struct fsnotify_event *event);
104 void (*free_group_priv)(struct fsnotify_group *group);
105 void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
106 void (*free_event_priv)(struct fsnotify_event_private_data *priv);
107};
108
109/*
110 * A group is a "thing" that wants to receive notification about filesystem
111 * events. The mask holds the subset of event types this group cares about.
112 * refcnt on a group is up to the implementor and at any moment if it goes 0
113 * everything will be cleaned up.
114 */
115struct fsnotify_group {
116 /*
117 * How the refcnt is used is up to each group. When the refcnt hits 0
118 * fsnotify will clean up all of the resources associated with this group.
119 * As an example, the dnotify group will always have a refcnt=1 and that
120 * will never change. Inotify, on the other hand, has a group per
121 * inotify_init() and the refcnt will hit 0 only when that fd has been
122 * closed.
123 */
124 atomic_t refcnt; /* things with interest in this group */
125
126 const struct fsnotify_ops *ops; /* how this group handles things */
127
128 /* needed to send notification to userspace */
129 struct mutex notification_mutex; /* protect the notification_list */
130 struct list_head notification_list; /* list of event_holder this group needs to send to userspace */
131 wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */
132 unsigned int q_len; /* events on the queue */
133 unsigned int max_events; /* maximum events allowed on the list */
134 /*
135 * Valid fsnotify group priorities. Events are send in order from highest
136 * priority to lowest priority. We default to the lowest priority.
137 */
138 #define FS_PRIO_0 0 /* normal notifiers, no permissions */
139 #define FS_PRIO_1 1 /* fanotify content based access control */
140 #define FS_PRIO_2 2 /* fanotify pre-content access */
141 unsigned int priority;
142
143 /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
144 spinlock_t mark_lock; /* protect marks_list */
145 atomic_t num_marks; /* 1 for each mark and 1 for not being
146 * past the point of no return when freeing
147 * a group */
148 struct list_head marks_list; /* all inode marks for this group */
149
150 /* groups can define private fields here or use the void *private */
151 union {
152 void *private;
153#ifdef CONFIG_INOTIFY_USER
154 struct inotify_group_private_data {
155 spinlock_t idr_lock;
156 struct idr idr;
157 u32 last_wd;
158 struct fasync_struct *fa; /* async notification */
159 struct user_struct *user;
160 } inotify_data;
161#endif
162#ifdef CONFIG_FANOTIFY
163 struct fanotify_group_private_data {
164#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
165 /* allows a group to block waiting for a userspace response */
166 struct mutex access_mutex;
167 struct list_head access_list;
168 wait_queue_head_t access_waitq;
169 atomic_t bypass_perm;
170#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
171 int f_flags;
172 unsigned int max_marks;
173 struct user_struct *user;
174 } fanotify_data;
175#endif /* CONFIG_FANOTIFY */
176 };
177};
178
179/*
180 * A single event can be queued in multiple group->notification_lists.
181 *
182 * each group->notification_list will point to an event_holder which in turns points
183 * to the actual event that needs to be sent to userspace.
184 *
185 * Seemed cheaper to create a refcnt'd event and a small holder for every group
186 * than create a different event for every group
187 *
188 */
189struct fsnotify_event_holder {
190 struct fsnotify_event *event;
191 struct list_head event_list;
192};
193
194/*
195 * Inotify needs to tack data onto an event. This struct lets us later find the
196 * correct private data of the correct group.
197 */
198struct fsnotify_event_private_data {
199 struct fsnotify_group *group;
200 struct list_head event_list;
201};
202
203/*
204 * all of the information about the original object we want to now send to
205 * a group. If you want to carry more info from the accessing task to the
206 * listener this structure is where you need to be adding fields.
207 */
208struct fsnotify_event {
209 /*
210 * If we create an event we are also likely going to need a holder
211 * to link to a group. So embed one holder in the event. Means only
212 * one allocation for the common case where we only have one group
213 */
214 struct fsnotify_event_holder holder;
215 spinlock_t lock; /* protection for the associated event_holder and private_list */
216 /* to_tell may ONLY be dereferenced during handle_event(). */
217 struct inode *to_tell; /* either the inode the event happened to or its parent */
218 /*
219 * depending on the event type we should have either a path or inode
220 * We hold a reference on path, but NOT on inode. Since we have the ref on
221 * the path, it may be dereferenced at any point during this object's
222 * lifetime. That reference is dropped when this object's refcnt hits
223 * 0. If this event contains an inode instead of a path, the inode may
224 * ONLY be used during handle_event().
225 */
226 union {
227 struct path path;
228 struct inode *inode;
229 };
230/* when calling fsnotify tell it if the data is a path or inode */
231#define FSNOTIFY_EVENT_NONE 0
232#define FSNOTIFY_EVENT_PATH 1
233#define FSNOTIFY_EVENT_INODE 2
234 int data_type; /* which of the above union we have */
235 atomic_t refcnt; /* how many groups still are using/need to send this event */
236 __u32 mask; /* the type of access, bitwise OR for FS_* event types */
237
238 u32 sync_cookie; /* used to corrolate events, namely inotify mv events */
239 const unsigned char *file_name;
240 size_t name_len;
241 struct pid *tgid;
242
243#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
244 __u32 response; /* userspace answer to question */
245#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
246
247 struct list_head private_data_list; /* groups can store private data here */
248};
249
250/*
251 * Inode specific fields in an fsnotify_mark
252 */
253struct fsnotify_inode_mark {
254 struct inode *inode; /* inode this mark is associated with */
255 struct hlist_node i_list; /* list of marks by inode->i_fsnotify_marks */
256 struct list_head free_i_list; /* tmp list used when freeing this mark */
257};
258
259/*
260 * Mount point specific fields in an fsnotify_mark
261 */
262struct fsnotify_vfsmount_mark {
263 struct vfsmount *mnt; /* vfsmount this mark is associated with */
264 struct hlist_node m_list; /* list of marks by inode->i_fsnotify_marks */
265 struct list_head free_m_list; /* tmp list used when freeing this mark */
266};
267
268/*
269 * a mark is simply an object attached to an in core inode which allows an
270 * fsnotify listener to indicate they are either no longer interested in events
271 * of a type matching mask or only interested in those events.
272 *
273 * these are flushed when an inode is evicted from core and may be flushed
274 * when the inode is modified (as seen by fsnotify_access). Some fsnotify users
275 * (such as dnotify) will flush these when the open fd is closed and not at
276 * inode eviction or modification.
277 */
278struct fsnotify_mark {
279 __u32 mask; /* mask this mark is for */
280 /* we hold ref for each i_list and g_list. also one ref for each 'thing'
281 * in kernel that found and may be using this mark. */
282 atomic_t refcnt; /* active things looking at this mark */
283 struct fsnotify_group *group; /* group this mark is for */
284 struct list_head g_list; /* list of marks by group->i_fsnotify_marks */
285 spinlock_t lock; /* protect group and inode */
286 union {
287 struct fsnotify_inode_mark i;
288 struct fsnotify_vfsmount_mark m;
289 };
290 struct list_head free_g_list; /* tmp list used when freeing this mark */
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 */
307extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
308 const unsigned char *name, u32 cookie);
309extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
310extern void __fsnotify_inode_delete(struct inode *inode);
311extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
312extern u32 fsnotify_get_cookie(void);
313
314static 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 */
328static 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 */
351static 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/* get a reference to an existing or create a new group */
364extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
365/* drop reference on a group from fsnotify_alloc_group */
366extern void fsnotify_put_group(struct fsnotify_group *group);
367
368/* take a reference to an event */
369extern void fsnotify_get_event(struct fsnotify_event *event);
370extern void fsnotify_put_event(struct fsnotify_event *event);
371/* find private data previously attached to an event and unlink it */
372extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
373 struct fsnotify_event *event);
374
375/* attach the event to the group notification queue */
376extern struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
377 struct fsnotify_event *event,
378 struct fsnotify_event_private_data *priv,
379 struct fsnotify_event *(*merge)(struct list_head *,
380 struct fsnotify_event *));
381/* true if the group notification queue is empty */
382extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
383/* return, but do not dequeue the first event on the notification queue */
384extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
385/* return AND dequeue the first event on the notification queue */
386extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
387
388/* functions used to manipulate the marks attached to inodes */
389
390/* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
391extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
392/* run all marks associated with an inode and update inode->i_fsnotify_mask */
393extern void fsnotify_recalc_inode_mask(struct inode *inode);
394extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
395/* find (and take a reference) to a mark associated with group and inode */
396extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
397/* find (and take a reference) to a mark associated with group and vfsmount */
398extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
399/* copy the values from old into new */
400extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
401/* set the ignored_mask of a mark */
402extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
403/* set the mask of a mark (might pin the object into memory */
404extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
405/* attach the mark to both the group and the inode */
406extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
407 struct inode *inode, struct vfsmount *mnt, int allow_dups);
408/* given a mark, flag it to be freed when all references are dropped */
409extern void fsnotify_destroy_mark(struct fsnotify_mark *mark);
410/* run all the marks in a group, and clear all of the vfsmount marks */
411extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
412/* run all the marks in a group, and clear all of the inode marks */
413extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
414/* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
415extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
416/* run all the marks in a group, and flag them to be freed */
417extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
418extern void fsnotify_get_mark(struct fsnotify_mark *mark);
419extern void fsnotify_put_mark(struct fsnotify_mark *mark);
420extern void fsnotify_unmount_inodes(struct list_head *list);
421
422/* put here because inotify does some weird stuff when destroying watches */
423extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
424 void *data, int data_is,
425 const unsigned char *name,
426 u32 cookie, gfp_t gfp);
427
428/* fanotify likes to change events after they are on lists... */
429extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
430extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
431 struct fsnotify_event *new_event);
432
433#else
434
435static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
436 const unsigned char *name, u32 cookie)
437{
438 return 0;
439}
440
441static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
442{
443 return 0;
444}
445
446static inline void __fsnotify_inode_delete(struct inode *inode)
447{}
448
449static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
450{}
451
452static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
453{}
454
455static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
456{}
457
458static inline u32 fsnotify_get_cookie(void)
459{
460 return 0;
461}
462
463static inline void fsnotify_unmount_inodes(struct list_head *list)
464{}
465
466#endif /* CONFIG_FSNOTIFY */
467
468#endif /* __KERNEL __ */
469
470#endif /* __LINUX_FSNOTIFY_BACKEND_H */