2 * Filesystem access notification for Linux
4 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
7 #ifndef __LINUX_FSNOTIFY_BACKEND_H
8 #define __LINUX_FSNOTIFY_BACKEND_H
12 #include <linux/fs.h> /* struct inode */
13 #include <linux/list.h>
14 #include <linux/path.h> /* struct path */
15 #include <linux/spinlock.h>
16 #include <linux/types.h>
18 #include <asm/atomic.h>
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.
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 */
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 */
43 #define FS_IN_ISDIR 0x40000000 /* event occurred against dir */
44 #define FS_IN_ONESHOT 0x80000000 /* only send event once */
46 #define FS_DN_RENAME 0x10000000 /* file renamed */
47 #define FS_DN_MULTISHOT 0x20000000 /* dnotify multishot */
49 /* This inode cares about things that happen to its children. Always set for
50 * dnotify and inotify. */
51 #define FS_EVENT_ON_CHILD 0x08000000
53 /* This is a list of all events that may get sent to a parernt based on fs event
54 * happening to inodes inside that directory */
55 #define FS_EVENTS_POSS_ON_CHILD (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
56 FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
57 FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
60 /* listeners that hard code group numbers near the top */
61 #define DNOTIFY_GROUP_NUM UINT_MAX
63 struct fsnotify_group;
64 struct fsnotify_event;
65 struct fsnotify_mark_entry;
68 * Each group much define these ops. The fsnotify infrastructure will call
69 * these operations for each relevant group.
71 * should_send_event - given a group, inode, and mask this function determines
72 * if the group is interested in this event.
73 * handle_event - main call for a group to handle an fs event
74 * free_group_priv - called when a group refcnt hits 0 to clean up the private union
75 * freeing-mark - this means that a mark has been flagged to die when everything
76 * finishes using it. The function is supplied with what must be a
77 * valid group and inode to use to clean up.
80 bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode, __u32 mask);
81 int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
82 void (*free_group_priv)(struct fsnotify_group *group);
83 void (*freeing_mark)(struct fsnotify_mark_entry *entry, struct fsnotify_group *group);
87 * A group is a "thing" that wants to receive notification about filesystem
88 * events. The mask holds the subset of event types this group cares about.
89 * refcnt on a group is up to the implementor and at any moment if it goes 0
90 * everything will be cleaned up.
92 struct fsnotify_group {
94 * global list of all groups receiving events from fsnotify.
95 * anchored by fsnotify_groups and protected by either fsnotify_grp_mutex
96 * or fsnotify_grp_srcu depending on write vs read.
98 struct list_head group_list;
101 * Defines all of the event types in which this group is interested.
102 * This mask is a bitwise OR of the FS_* events from above. Each time
103 * this mask changes for a group (if it changes) the correct functions
104 * must be called to update the global structures which indicate global
105 * interest in event types.
110 * How the refcnt is used is up to each group. When the refcnt hits 0
111 * fsnotify will clean up all of the resources associated with this group.
112 * As an example, the dnotify group will always have a refcnt=1 and that
113 * will never change. Inotify, on the other hand, has a group per
114 * inotify_init() and the refcnt will hit 0 only when that fd has been
117 atomic_t refcnt; /* things with interest in this group */
118 unsigned int group_num; /* simply prevents accidental group collision */
120 const struct fsnotify_ops *ops; /* how this group handles things */
122 /* needed to send notification to userspace */
123 struct mutex notification_mutex; /* protect the notification_list */
124 struct list_head notification_list; /* list of event_holder this group needs to send to userspace */
125 wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */
126 unsigned int q_len; /* events on the queue */
127 unsigned int max_events; /* maximum events allowed on the list */
129 /* stores all fastapth entries assoc with this group so they can be cleaned on unregister */
130 spinlock_t mark_lock; /* protect mark_entries list */
131 atomic_t num_marks; /* 1 for each mark entry and 1 for not being
132 * past the point of no return when freeing
134 struct list_head mark_entries; /* all inode mark entries for this group */
136 /* prevents double list_del of group_list. protected by global fsnotify_grp_mutex */
139 /* groups can define private fields here or use the void *private */
146 * A single event can be queued in multiple group->notification_lists.
148 * each group->notification_list will point to an event_holder which in turns points
149 * to the actual event that needs to be sent to userspace.
151 * Seemed cheaper to create a refcnt'd event and a small holder for every group
152 * than create a different event for every group
155 struct fsnotify_event_holder {
156 struct fsnotify_event *event;
157 struct list_head event_list;
161 * all of the information about the original object we want to now send to
162 * a group. If you want to carry more info from the accessing task to the
163 * listener this structure is where you need to be adding fields.
165 struct fsnotify_event {
167 * If we create an event we are also likely going to need a holder
168 * to link to a group. So embed one holder in the event. Means only
169 * one allocation for the common case where we only have one group
171 struct fsnotify_event_holder holder;
172 spinlock_t lock; /* protection for the associated event_holder and private_list */
173 /* to_tell may ONLY be dereferenced during handle_event(). */
174 struct inode *to_tell; /* either the inode the event happened to or its parent */
176 * depending on the event type we should have either a path or inode
177 * We hold a reference on path, but NOT on inode. Since we have the ref on
178 * the path, it may be dereferenced at any point during this object's
179 * lifetime. That reference is dropped when this object's refcnt hits
180 * 0. If this event contains an inode instead of a path, the inode may
181 * ONLY be used during handle_event().
187 /* when calling fsnotify tell it if the data is a path or inode */
188 #define FSNOTIFY_EVENT_NONE 0
189 #define FSNOTIFY_EVENT_PATH 1
190 #define FSNOTIFY_EVENT_INODE 2
191 #define FSNOTIFY_EVENT_FILE 3
192 int data_type; /* which of the above union we have */
193 atomic_t refcnt; /* how many groups still are using/need to send this event */
194 __u32 mask; /* the type of access, bitwise OR for FS_* event types */
196 u32 sync_cookie; /* used to corrolate events, namely inotify mv events */
202 * a mark is simply an entry attached to an in core inode which allows an
203 * fsnotify listener to indicate they are either no longer interested in events
204 * of a type matching mask or only interested in those events.
206 * these are flushed when an inode is evicted from core and may be flushed
207 * when the inode is modified (as seen by fsnotify_access). Some fsnotify users
208 * (such as dnotify) will flush these when the open fd is closed and not at
209 * inode eviction or modification.
211 struct fsnotify_mark_entry {
212 __u32 mask; /* mask this mark entry is for */
213 /* we hold ref for each i_list and g_list. also one ref for each 'thing'
214 * in kernel that found and may be using this mark. */
215 atomic_t refcnt; /* active things looking at this mark */
216 struct inode *inode; /* inode this entry is associated with */
217 struct fsnotify_group *group; /* group this mark entry is for */
218 struct hlist_node i_list; /* list of mark_entries by inode->i_fsnotify_mark_entries */
219 struct list_head g_list; /* list of mark_entries by group->i_fsnotify_mark_entries */
220 spinlock_t lock; /* protect group, inode, and killme */
221 struct list_head free_i_list; /* tmp list used when freeing this mark */
222 struct list_head free_g_list; /* tmp list used when freeing this mark */
223 void (*free_mark)(struct fsnotify_mark_entry *entry); /* called on final put+free */
226 #ifdef CONFIG_FSNOTIFY
228 /* called from the vfs helpers */
230 /* main fsnotify call to send events */
231 extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
232 const char *name, u32 cookie);
233 extern void __fsnotify_parent(struct dentry *dentry, __u32 mask);
234 extern void __fsnotify_inode_delete(struct inode *inode);
235 extern u32 fsnotify_get_cookie(void);
237 static inline int fsnotify_inode_watches_children(struct inode *inode)
239 /* FS_EVENT_ON_CHILD is set if the inode may care */
240 if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
242 /* this inode might care about child events, does it care about the
243 * specific set of events that can happen on a child? */
244 return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
248 * Update the dentry with a flag indicating the interest of its parent to receive
249 * filesystem events when those events happens to this dentry->d_inode.
251 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
253 struct dentry *parent;
255 assert_spin_locked(&dcache_lock);
256 assert_spin_locked(&dentry->d_lock);
258 parent = dentry->d_parent;
259 if (fsnotify_inode_watches_children(parent->d_inode))
260 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
262 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
266 * fsnotify_d_instantiate - instantiate a dentry for inode
267 * Called with dcache_lock held.
269 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
274 assert_spin_locked(&dcache_lock);
276 spin_lock(&dentry->d_lock);
277 __fsnotify_update_dcache_flags(dentry);
278 spin_unlock(&dentry->d_lock);
281 /* called from fsnotify listeners, such as fanotify or dnotify */
283 /* must call when a group changes its ->mask */
284 extern void fsnotify_recalc_global_mask(void);
285 /* get a reference to an existing or create a new group */
286 extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num,
288 const struct fsnotify_ops *ops);
289 /* run all marks associated with this group and update group->mask */
290 extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
291 /* drop reference on a group from fsnotify_obtain_group */
292 extern void fsnotify_put_group(struct fsnotify_group *group);
294 /* take a reference to an event */
295 extern void fsnotify_get_event(struct fsnotify_event *event);
296 extern void fsnotify_put_event(struct fsnotify_event *event);
297 /* find private data previously attached to an event */
298 extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group,
299 struct fsnotify_event *event);
301 /* attach the event to the group notification queue */
302 extern int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event);
303 /* true if the group notification queue is empty */
304 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
305 /* return, but do not dequeue the first event on the notification queue */
306 extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
307 /* reutnr AND dequeue the first event on the notification queue */
308 extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
310 /* functions used to manipulate the marks attached to inodes */
312 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
313 extern void fsnotify_recalc_inode_mask(struct inode *inode);
314 extern void fsnotify_init_mark(struct fsnotify_mark_entry *entry, void (*free_mark)(struct fsnotify_mark_entry *entry));
315 /* find (and take a reference) to a mark associated with group and inode */
316 extern struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group, struct inode *inode);
317 /* attach the mark to both the group and the inode */
318 extern int fsnotify_add_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group, struct inode *inode);
319 /* given a mark, flag it to be freed when all references are dropped */
320 extern void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry);
321 /* run all the marks in a group, and flag them to be freed */
322 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
323 extern void fsnotify_get_mark(struct fsnotify_mark_entry *entry);
324 extern void fsnotify_put_mark(struct fsnotify_mark_entry *entry);
326 /* put here because inotify does some weird stuff when destroying watches */
327 extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
328 void *data, int data_is, const char *name,
333 static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
334 const char *name, u32 cookie)
337 static inline void __fsnotify_parent(struct dentry *dentry, __u32 mask)
340 static inline void __fsnotify_inode_delete(struct inode *inode)
343 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
346 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
349 static inline u32 fsnotify_get_cookie(void)
354 #endif /* CONFIG_FSNOTIFY */
356 #endif /* __KERNEL __ */
358 #endif /* __LINUX_FSNOTIFY_BACKEND_H */