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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#include <linux/atomic.h>
19
20/*
21 * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
22 * convert between them. dnotify only needs conversion at watch creation
23 * so no perf loss there. fanotify isn't defined yet, so it can use the
24 * wholes if it needs more events.
25 */
26#define FS_ACCESS 0x00000001 /* File was accessed */
27#define FS_MODIFY 0x00000002 /* File was modified */
28#define FS_ATTRIB 0x00000004 /* Metadata changed */
29#define FS_CLOSE_WRITE 0x00000008 /* Writtable file was closed */
30#define FS_CLOSE_NOWRITE 0x00000010 /* Unwrittable file closed */
31#define FS_OPEN 0x00000020 /* File was opened */
32#define FS_MOVED_FROM 0x00000040 /* File was moved from X */
33#define FS_MOVED_TO 0x00000080 /* File was moved to Y */
34#define FS_CREATE 0x00000100 /* Subfile was created */
35#define FS_DELETE 0x00000200 /* Subfile was deleted */
36#define FS_DELETE_SELF 0x00000400 /* Self was deleted */
37#define FS_MOVE_SELF 0x00000800 /* Self was moved */
38
39#define FS_UNMOUNT 0x00002000 /* inode on umount fs */
40#define FS_Q_OVERFLOW 0x00004000 /* Event queued overflowed */
41#define FS_IN_IGNORED 0x00008000 /* last inotify event here */
42
43#define FS_OPEN_PERM 0x00010000 /* open event in an permission hook */
44#define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */
45
46#define FS_EXCL_UNLINK 0x04000000 /* do not send events if object is unlinked */
47#define FS_ISDIR 0x40000000 /* event occurred against dir */
48#define FS_IN_ONESHOT 0x80000000 /* only send event once */
49
50#define FS_DN_RENAME 0x10000000 /* file renamed */
51#define FS_DN_MULTISHOT 0x20000000 /* dnotify multishot */
52
53/* This inode cares about things that happen to its children. Always set for
54 * dnotify and inotify. */
55#define FS_EVENT_ON_CHILD 0x08000000
56
57/* This is a list of all events that may get sent to a parernt based on fs event
58 * happening to inodes inside that directory */
59#define FS_EVENTS_POSS_ON_CHILD (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
60 FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
61 FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
62 FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM)
63
64#define FS_MOVE (FS_MOVED_FROM | FS_MOVED_TO)
65
66#define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM)
67
68#define ALL_FSNOTIFY_EVENTS (FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
69 FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN | \
70 FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
71 FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
72 FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
73 FS_OPEN_PERM | FS_ACCESS_PERM | FS_EXCL_UNLINK | \
74 FS_ISDIR | FS_IN_ONESHOT | FS_DN_RENAME | \
75 FS_DN_MULTISHOT | FS_EVENT_ON_CHILD)
76
77struct fsnotify_group;
78struct fsnotify_event;
79struct fsnotify_mark;
80struct fsnotify_event_private_data;
81struct fsnotify_fname;
82
83/*
84 * Each group much define these ops. The fsnotify infrastructure will call
85 * these operations for each relevant group.
86 *
87 * handle_event - main call for a group to handle an fs event
88 * free_group_priv - called when a group refcnt hits 0 to clean up the private union
89 * freeing_mark - called when a mark is being destroyed for some reason. The group
90 * MUST be holding a reference on each mark and that reference must be
91 * dropped in this function. inotify uses this function to send
92 * userspace messages that marks have been removed.
93 */
94struct fsnotify_ops {
95 int (*handle_event)(struct fsnotify_group *group,
96 struct inode *inode,
97 struct fsnotify_mark *inode_mark,
98 struct fsnotify_mark *vfsmount_mark,
99 u32 mask, void *data, int data_type,
100 const unsigned char *file_name, u32 cookie);
101 void (*free_group_priv)(struct fsnotify_group *group);
102 void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
103 void (*free_event)(struct fsnotify_event *event);
104};
105
106/*
107 * all of the information about the original object we want to now send to
108 * a group. If you want to carry more info from the accessing task to the
109 * listener this structure is where you need to be adding fields.
110 */
111struct fsnotify_event {
112 struct list_head list;
113 /* inode may ONLY be dereferenced during handle_event(). */
114 struct inode *inode; /* either the inode the event happened to or its parent */
115 u32 mask; /* the type of access, bitwise OR for FS_* event types */
116};
117
118/*
119 * A group is a "thing" that wants to receive notification about filesystem
120 * events. The mask holds the subset of event types this group cares about.
121 * refcnt on a group is up to the implementor and at any moment if it goes 0
122 * everything will be cleaned up.
123 */
124struct fsnotify_group {
125 /*
126 * How the refcnt is used is up to each group. When the refcnt hits 0
127 * fsnotify will clean up all of the resources associated with this group.
128 * As an example, the dnotify group will always have a refcnt=1 and that
129 * will never change. Inotify, on the other hand, has a group per
130 * inotify_init() and the refcnt will hit 0 only when that fd has been
131 * closed.
132 */
133 atomic_t refcnt; /* things with interest in this group */
134
135 const struct fsnotify_ops *ops; /* how this group handles things */
136
137 /* needed to send notification to userspace */
138 spinlock_t notification_lock; /* protect the notification_list */
139 struct list_head notification_list; /* list of event_holder this group needs to send to userspace */
140 wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */
141 unsigned int q_len; /* events on the queue */
142 unsigned int max_events; /* maximum events allowed on the list */
143 /*
144 * Valid fsnotify group priorities. Events are send in order from highest
145 * priority to lowest priority. We default to the lowest priority.
146 */
147 #define FS_PRIO_0 0 /* normal notifiers, no permissions */
148 #define FS_PRIO_1 1 /* fanotify content based access control */
149 #define FS_PRIO_2 2 /* fanotify pre-content access */
150 unsigned int priority;
151 bool shutdown; /* group is being shut down, don't queue more events */
152
153 /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
154 struct mutex mark_mutex; /* protect marks_list */
155 atomic_t num_marks; /* 1 for each mark and 1 for not being
156 * past the point of no return when freeing
157 * a group */
158 struct list_head marks_list; /* all inode marks for this group */
159
160 struct fasync_struct *fsn_fa; /* async notification */
161
162 struct fsnotify_event *overflow_event; /* Event we queue when the
163 * notification list is too
164 * full */
165
166 /* groups can define private fields here or use the void *private */
167 union {
168 void *private;
169#ifdef CONFIG_INOTIFY_USER
170 struct inotify_group_private_data {
171 spinlock_t idr_lock;
172 struct idr idr;
173 struct user_struct *user;
174 } inotify_data;
175#endif
176#ifdef CONFIG_FANOTIFY
177 struct fanotify_group_private_data {
178#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
179 /* allows a group to block waiting for a userspace response */
180 struct list_head access_list;
181 wait_queue_head_t access_waitq;
182#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
183 int f_flags;
184 unsigned int max_marks;
185 struct user_struct *user;
186 } fanotify_data;
187#endif /* CONFIG_FANOTIFY */
188 };
189};
190
191/* when calling fsnotify tell it if the data is a path or inode */
192#define FSNOTIFY_EVENT_NONE 0
193#define FSNOTIFY_EVENT_PATH 1
194#define FSNOTIFY_EVENT_INODE 2
195
196/*
197 * A mark is simply an object attached to an in core inode which allows an
198 * fsnotify listener to indicate they are either no longer interested in events
199 * of a type matching mask or only interested in those events.
200 *
201 * These are flushed when an inode is evicted from core and may be flushed
202 * when the inode is modified (as seen by fsnotify_access). Some fsnotify
203 * users (such as dnotify) will flush these when the open fd is closed and not
204 * at inode eviction or modification.
205 *
206 * Text in brackets is showing the lock(s) protecting modifications of a
207 * particular entry. obj_lock means either inode->i_lock or
208 * mnt->mnt_root->d_lock depending on the mark type.
209 */
210struct fsnotify_mark {
211 /* Mask this mark is for [mark->lock, group->mark_mutex] */
212 __u32 mask;
213 /* We hold one for presence in g_list. Also one ref for each 'thing'
214 * in kernel that found and may be using this mark. */
215 atomic_t refcnt;
216 /* Group this mark is for. Set on mark creation, stable until last ref
217 * is dropped */
218 struct fsnotify_group *group;
219 /* List of marks by group->i_fsnotify_marks. Also reused for queueing
220 * mark into destroy_list when it's waiting for the end of SRCU period
221 * before it can be freed. [group->mark_mutex] */
222 struct list_head g_list;
223 /* Protects inode / mnt pointers, flags, masks */
224 spinlock_t lock;
225 /* List of marks for inode / vfsmount [obj_lock] */
226 struct hlist_node obj_list;
227 union { /* Object pointer [mark->lock, group->mark_mutex] */
228 struct inode *inode; /* inode this mark is associated with */
229 struct vfsmount *mnt; /* vfsmount this mark is associated with */
230 };
231 /* Events types to ignore [mark->lock, group->mark_mutex] */
232 __u32 ignored_mask;
233#define FSNOTIFY_MARK_FLAG_INODE 0x01
234#define FSNOTIFY_MARK_FLAG_VFSMOUNT 0x02
235#define FSNOTIFY_MARK_FLAG_OBJECT_PINNED 0x04
236#define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY 0x08
237#define FSNOTIFY_MARK_FLAG_ALIVE 0x10
238#define FSNOTIFY_MARK_FLAG_ATTACHED 0x20
239 unsigned int flags; /* flags [mark->lock] */
240 void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
241};
242
243#ifdef CONFIG_FSNOTIFY
244
245/* called from the vfs helpers */
246
247/* main fsnotify call to send events */
248extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
249 const unsigned char *name, u32 cookie);
250extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
251extern void __fsnotify_inode_delete(struct inode *inode);
252extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
253extern u32 fsnotify_get_cookie(void);
254
255static inline int fsnotify_inode_watches_children(struct inode *inode)
256{
257 /* FS_EVENT_ON_CHILD is set if the inode may care */
258 if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
259 return 0;
260 /* this inode might care about child events, does it care about the
261 * specific set of events that can happen on a child? */
262 return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
263}
264
265/*
266 * Update the dentry with a flag indicating the interest of its parent to receive
267 * filesystem events when those events happens to this dentry->d_inode.
268 */
269static inline void fsnotify_update_flags(struct dentry *dentry)
270{
271 assert_spin_locked(&dentry->d_lock);
272
273 /*
274 * Serialisation of setting PARENT_WATCHED on the dentries is provided
275 * by d_lock. If inotify_inode_watched changes after we have taken
276 * d_lock, the following __fsnotify_update_child_dentry_flags call will
277 * find our entry, so it will spin until we complete here, and update
278 * us with the new state.
279 */
280 if (fsnotify_inode_watches_children(dentry->d_parent->d_inode))
281 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
282 else
283 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
284}
285
286/* called from fsnotify listeners, such as fanotify or dnotify */
287
288/* create a new group */
289extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
290/* get reference to a group */
291extern void fsnotify_get_group(struct fsnotify_group *group);
292/* drop reference on a group from fsnotify_alloc_group */
293extern void fsnotify_put_group(struct fsnotify_group *group);
294/* group destruction begins, stop queuing new events */
295extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);
296/* destroy group */
297extern void fsnotify_destroy_group(struct fsnotify_group *group);
298/* fasync handler function */
299extern int fsnotify_fasync(int fd, struct file *file, int on);
300/* Free event from memory */
301extern void fsnotify_destroy_event(struct fsnotify_group *group,
302 struct fsnotify_event *event);
303/* attach the event to the group notification queue */
304extern int fsnotify_add_event(struct fsnotify_group *group,
305 struct fsnotify_event *event,
306 int (*merge)(struct list_head *,
307 struct fsnotify_event *));
308/* true if the group notification queue is empty */
309extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
310/* return, but do not dequeue the first event on the notification queue */
311extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group);
312/* return AND dequeue the first event on the notification queue */
313extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);
314
315/* functions used to manipulate the marks attached to inodes */
316
317/* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
318extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
319/* run all marks associated with an inode and update inode->i_fsnotify_mask */
320extern void fsnotify_recalc_inode_mask(struct inode *inode);
321extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
322/* find (and take a reference) to a mark associated with group and inode */
323extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
324/* find (and take a reference) to a mark associated with group and vfsmount */
325extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
326/* copy the values from old into new */
327extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
328/* set the ignored_mask of a mark */
329extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
330/* set the mask of a mark (might pin the object into memory */
331extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
332/* attach the mark to both the group and the inode */
333extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
334 struct inode *inode, struct vfsmount *mnt, int allow_dups);
335extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, struct fsnotify_group *group,
336 struct inode *inode, struct vfsmount *mnt, int allow_dups);
337/* given a group and a mark, flag mark to be freed when all references are dropped */
338extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
339 struct fsnotify_group *group);
340/* detach mark from inode / mount list, group list, drop inode reference */
341extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
342/* free mark */
343extern void fsnotify_free_mark(struct fsnotify_mark *mark);
344/* run all the marks in a group, and clear all of the vfsmount marks */
345extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
346/* run all the marks in a group, and clear all of the inode marks */
347extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
348/* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
349extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
350extern void fsnotify_get_mark(struct fsnotify_mark *mark);
351extern void fsnotify_put_mark(struct fsnotify_mark *mark);
352extern void fsnotify_unmount_inodes(struct super_block *sb);
353
354/* put here because inotify does some weird stuff when destroying watches */
355extern void fsnotify_init_event(struct fsnotify_event *event,
356 struct inode *to_tell, u32 mask);
357
358#else
359
360static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
361 const unsigned char *name, u32 cookie)
362{
363 return 0;
364}
365
366static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
367{
368 return 0;
369}
370
371static inline void __fsnotify_inode_delete(struct inode *inode)
372{}
373
374static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
375{}
376
377static inline void fsnotify_update_flags(struct dentry *dentry)
378{}
379
380static inline u32 fsnotify_get_cookie(void)
381{
382 return 0;
383}
384
385static inline void fsnotify_unmount_inodes(struct super_block *sb)
386{}
387
388#endif /* CONFIG_FSNOTIFY */
389
390#endif /* __KERNEL __ */
391
392#endif /* __LINUX_FSNOTIFY_BACKEND_H */