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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 <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
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 - 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 */
96struct 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 */
116struct 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 u32 last_wd;
161 struct user_struct *user;
162 } inotify_data;
163#endif
164#ifdef CONFIG_FANOTIFY
165 struct fanotify_group_private_data {
166#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
167 /* allows a group to block waiting for a userspace response */
168 struct mutex access_mutex;
169 struct list_head access_list;
170 wait_queue_head_t access_waitq;
171 atomic_t bypass_perm;
172#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
173 int f_flags;
174 unsigned int max_marks;
175 struct user_struct *user;
176 } fanotify_data;
177#endif /* CONFIG_FANOTIFY */
178 };
179};
180
181/*
182 * A single event can be queued in multiple group->notification_lists.
183 *
184 * each group->notification_list will point to an event_holder which in turns points
185 * to the actual event that needs to be sent to userspace.
186 *
187 * Seemed cheaper to create a refcnt'd event and a small holder for every group
188 * than create a different event for every group
189 *
190 */
191struct fsnotify_event_holder {
192 struct fsnotify_event *event;
193 struct list_head event_list;
194};
195
196/*
197 * Inotify needs to tack data onto an event. This struct lets us later find the
198 * correct private data of the correct group.
199 */
200struct fsnotify_event_private_data {
201 struct fsnotify_group *group;
202 struct list_head event_list;
203};
204
205/*
206 * all of the information about the original object we want to now send to
207 * a group. If you want to carry more info from the accessing task to the
208 * listener this structure is where you need to be adding fields.
209 */
210struct fsnotify_event {
211 /*
212 * If we create an event we are also likely going to need a holder
213 * to link to a group. So embed one holder in the event. Means only
214 * one allocation for the common case where we only have one group
215 */
216 struct fsnotify_event_holder holder;
217 spinlock_t lock; /* protection for the associated event_holder and private_list */
218 /* to_tell may ONLY be dereferenced during handle_event(). */
219 struct inode *to_tell; /* either the inode the event happened to or its parent */
220 /*
221 * depending on the event type we should have either a path or inode
222 * We hold a reference on path, but NOT on inode. Since we have the ref on
223 * the path, it may be dereferenced at any point during this object's
224 * lifetime. That reference is dropped when this object's refcnt hits
225 * 0. If this event contains an inode instead of a path, the inode may
226 * ONLY be used during handle_event().
227 */
228 union {
229 struct path path;
230 struct inode *inode;
231 };
232/* when calling fsnotify tell it if the data is a path or inode */
233#define FSNOTIFY_EVENT_NONE 0
234#define FSNOTIFY_EVENT_PATH 1
235#define FSNOTIFY_EVENT_INODE 2
236 int data_type; /* which of the above union we have */
237 atomic_t refcnt; /* how many groups still are using/need to send this event */
238 __u32 mask; /* the type of access, bitwise OR for FS_* event types */
239
240 u32 sync_cookie; /* used to corrolate events, namely inotify mv events */
241 const unsigned char *file_name;
242 size_t name_len;
243 struct pid *tgid;
244
245#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
246 __u32 response; /* userspace answer to question */
247#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
248
249 struct list_head private_data_list; /* groups can store private data here */
250};
251
252/*
253 * Inode specific fields in an fsnotify_mark
254 */
255struct fsnotify_inode_mark {
256 struct inode *inode; /* inode this mark is associated with */
257 struct hlist_node i_list; /* list of marks by inode->i_fsnotify_marks */
258 struct list_head free_i_list; /* tmp list used when freeing this mark */
259};
260
261/*
262 * Mount point specific fields in an fsnotify_mark
263 */
264struct fsnotify_vfsmount_mark {
265 struct vfsmount *mnt; /* vfsmount this mark is associated with */
266 struct hlist_node m_list; /* list of marks by inode->i_fsnotify_marks */
267 struct list_head free_m_list; /* tmp list used when freeing this mark */
268};
269
270/*
271 * a mark is simply an object attached to an in core inode which allows an
272 * fsnotify listener to indicate they are either no longer interested in events
273 * of a type matching mask or only interested in those events.
274 *
275 * these are flushed when an inode is evicted from core and may be flushed
276 * when the inode is modified (as seen by fsnotify_access). Some fsnotify users
277 * (such as dnotify) will flush these when the open fd is closed and not at
278 * inode eviction or modification.
279 */
280struct fsnotify_mark {
281 __u32 mask; /* mask this mark is for */
282 /* we hold ref for each i_list and g_list. also one ref for each 'thing'
283 * in kernel that found and may be using this mark. */
284 atomic_t refcnt; /* active things looking at this mark */
285 struct fsnotify_group *group; /* group this mark is for */
286 struct list_head g_list; /* list of marks by group->i_fsnotify_marks */
287 spinlock_t lock; /* protect group and inode */
288 union {
289 struct fsnotify_inode_mark i;
290 struct fsnotify_vfsmount_mark m;
291 };
292 __u32 ignored_mask; /* events types to ignore */
293#define FSNOTIFY_MARK_FLAG_INODE 0x01
294#define FSNOTIFY_MARK_FLAG_VFSMOUNT 0x02
295#define FSNOTIFY_MARK_FLAG_OBJECT_PINNED 0x04
296#define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY 0x08
297#define FSNOTIFY_MARK_FLAG_ALIVE 0x10
298 unsigned int flags; /* vfsmount or inode mark? */
299 struct list_head destroy_list;
300 void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
301};
302
303#ifdef CONFIG_FSNOTIFY
304
305/* called from the vfs helpers */
306
307/* main fsnotify call to send events */
308extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
309 const unsigned char *name, u32 cookie);
310extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
311extern void __fsnotify_inode_delete(struct inode *inode);
312extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
313extern u32 fsnotify_get_cookie(void);
314
315static inline int fsnotify_inode_watches_children(struct inode *inode)
316{
317 /* FS_EVENT_ON_CHILD is set if the inode may care */
318 if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
319 return 0;
320 /* this inode might care about child events, does it care about the
321 * specific set of events that can happen on a child? */
322 return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
323}
324
325/*
326 * Update the dentry with a flag indicating the interest of its parent to receive
327 * filesystem events when those events happens to this dentry->d_inode.
328 */
329static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
330{
331 struct dentry *parent;
332
333 assert_spin_locked(&dentry->d_lock);
334
335 /*
336 * Serialisation of setting PARENT_WATCHED on the dentries is provided
337 * by d_lock. If inotify_inode_watched changes after we have taken
338 * d_lock, the following __fsnotify_update_child_dentry_flags call will
339 * find our entry, so it will spin until we complete here, and update
340 * us with the new state.
341 */
342 parent = dentry->d_parent;
343 if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
344 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
345 else
346 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
347}
348
349/*
350 * fsnotify_d_instantiate - instantiate a dentry for inode
351 */
352static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
353{
354 if (!inode)
355 return;
356
357 spin_lock(&dentry->d_lock);
358 __fsnotify_update_dcache_flags(dentry);
359 spin_unlock(&dentry->d_lock);
360}
361
362/* called from fsnotify listeners, such as fanotify or dnotify */
363
364/* create a new group */
365extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
366/* get reference to a group */
367extern void fsnotify_get_group(struct fsnotify_group *group);
368/* drop reference on a group from fsnotify_alloc_group */
369extern void fsnotify_put_group(struct fsnotify_group *group);
370/* destroy group */
371extern void fsnotify_destroy_group(struct fsnotify_group *group);
372/* fasync handler function */
373extern int fsnotify_fasync(int fd, struct file *file, int on);
374/* take a reference to an event */
375extern void fsnotify_get_event(struct fsnotify_event *event);
376extern void fsnotify_put_event(struct fsnotify_event *event);
377/* find private data previously attached to an event and unlink it */
378extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
379 struct fsnotify_event *event);
380
381/* attach the event to the group notification queue */
382extern struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
383 struct fsnotify_event *event,
384 struct fsnotify_event_private_data *priv,
385 struct fsnotify_event *(*merge)(struct list_head *,
386 struct fsnotify_event *));
387/* true if the group notification queue is empty */
388extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
389/* return, but do not dequeue the first event on the notification queue */
390extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
391/* return AND dequeue the first event on the notification queue */
392extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
393
394/* functions used to manipulate the marks attached to inodes */
395
396/* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
397extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
398/* run all marks associated with an inode and update inode->i_fsnotify_mask */
399extern void fsnotify_recalc_inode_mask(struct inode *inode);
400extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
401/* find (and take a reference) to a mark associated with group and inode */
402extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
403/* find (and take a reference) to a mark associated with group and vfsmount */
404extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
405/* copy the values from old into new */
406extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
407/* set the ignored_mask of a mark */
408extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
409/* set the mask of a mark (might pin the object into memory */
410extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
411/* attach the mark to both the group and the inode */
412extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
413 struct inode *inode, struct vfsmount *mnt, int allow_dups);
414extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, struct fsnotify_group *group,
415 struct inode *inode, struct vfsmount *mnt, int allow_dups);
416/* given a group and a mark, flag mark to be freed when all references are dropped */
417extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
418 struct fsnotify_group *group);
419extern void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
420 struct fsnotify_group *group);
421/* run all the marks in a group, and clear all of the vfsmount marks */
422extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
423/* run all the marks in a group, and clear all of the inode marks */
424extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
425/* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
426extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
427/* run all the marks in a group, and flag them to be freed */
428extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
429extern void fsnotify_get_mark(struct fsnotify_mark *mark);
430extern void fsnotify_put_mark(struct fsnotify_mark *mark);
431extern void fsnotify_unmount_inodes(struct list_head *list);
432
433/* put here because inotify does some weird stuff when destroying watches */
434extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
435 void *data, int data_is,
436 const unsigned char *name,
437 u32 cookie, gfp_t gfp);
438
439/* fanotify likes to change events after they are on lists... */
440extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
441extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
442 struct fsnotify_event *new_event);
443
444#else
445
446static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
447 const unsigned char *name, u32 cookie)
448{
449 return 0;
450}
451
452static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
453{
454 return 0;
455}
456
457static inline void __fsnotify_inode_delete(struct inode *inode)
458{}
459
460static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
461{}
462
463static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
464{}
465
466static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
467{}
468
469static inline u32 fsnotify_get_cookie(void)
470{
471 return 0;
472}
473
474static inline void fsnotify_unmount_inodes(struct list_head *list)
475{}
476
477#endif /* CONFIG_FSNOTIFY */
478
479#endif /* __KERNEL __ */
480
481#endif /* __LINUX_FSNOTIFY_BACKEND_H */