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;
66 struct fsnotify_event_private_data;
69 * Each group much define these ops. The fsnotify infrastructure will call
70 * these operations for each relevant group.
72 * should_send_event - given a group, inode, and mask this function determines
73 * if the group is interested in this event.
74 * handle_event - main call for a group to handle an fs event
75 * free_group_priv - called when a group refcnt hits 0 to clean up the private union
76 * freeing-mark - this means that a mark has been flagged to die when everything
77 * finishes using it. The function is supplied with what must be a
78 * valid group and inode to use to clean up.
81 bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode, __u32 mask);
82 int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
83 void (*free_group_priv)(struct fsnotify_group *group);
84 void (*freeing_mark)(struct fsnotify_mark_entry *entry, struct fsnotify_group *group);
85 void (*free_event_priv)(struct fsnotify_event_private_data *priv);
89 * A group is a "thing" that wants to receive notification about filesystem
90 * events. The mask holds the subset of event types this group cares about.
91 * refcnt on a group is up to the implementor and at any moment if it goes 0
92 * everything will be cleaned up.
94 struct fsnotify_group {
96 * global list of all groups receiving events from fsnotify.
97 * anchored by fsnotify_groups and protected by either fsnotify_grp_mutex
98 * or fsnotify_grp_srcu depending on write vs read.
100 struct list_head group_list;
103 * Defines all of the event types in which this group is interested.
104 * This mask is a bitwise OR of the FS_* events from above. Each time
105 * this mask changes for a group (if it changes) the correct functions
106 * must be called to update the global structures which indicate global
107 * interest in event types.
112 * How the refcnt is used is up to each group. When the refcnt hits 0
113 * fsnotify will clean up all of the resources associated with this group.
114 * As an example, the dnotify group will always have a refcnt=1 and that
115 * will never change. Inotify, on the other hand, has a group per
116 * inotify_init() and the refcnt will hit 0 only when that fd has been
119 atomic_t refcnt; /* things with interest in this group */
120 unsigned int group_num; /* simply prevents accidental group collision */
122 const struct fsnotify_ops *ops; /* how this group handles things */
124 /* needed to send notification to userspace */
125 struct mutex notification_mutex; /* protect the notification_list */
126 struct list_head notification_list; /* list of event_holder this group needs to send to userspace */
127 wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */
128 unsigned int q_len; /* events on the queue */
129 unsigned int max_events; /* maximum events allowed on the list */
131 /* stores all fastapth entries assoc with this group so they can be cleaned on unregister */
132 spinlock_t mark_lock; /* protect mark_entries list */
133 atomic_t num_marks; /* 1 for each mark entry and 1 for not being
134 * past the point of no return when freeing
136 struct list_head mark_entries; /* all inode mark entries for this group */
138 /* prevents double list_del of group_list. protected by global fsnotify_grp_mutex */
141 /* groups can define private fields here or use the void *private */
148 * A single event can be queued in multiple group->notification_lists.
150 * each group->notification_list will point to an event_holder which in turns points
151 * to the actual event that needs to be sent to userspace.
153 * Seemed cheaper to create a refcnt'd event and a small holder for every group
154 * than create a different event for every group
157 struct fsnotify_event_holder {
158 struct fsnotify_event *event;
159 struct list_head event_list;
163 * Inotify needs to tack data onto an event. This struct lets us later find the
164 * correct private data of the correct group.
166 struct fsnotify_event_private_data {
167 struct fsnotify_group *group;
168 struct list_head event_list;
172 * all of the information about the original object we want to now send to
173 * a group. If you want to carry more info from the accessing task to the
174 * listener this structure is where you need to be adding fields.
176 struct fsnotify_event {
178 * If we create an event we are also likely going to need a holder
179 * to link to a group. So embed one holder in the event. Means only
180 * one allocation for the common case where we only have one group
182 struct fsnotify_event_holder holder;
183 spinlock_t lock; /* protection for the associated event_holder and private_list */
184 /* to_tell may ONLY be dereferenced during handle_event(). */
185 struct inode *to_tell; /* either the inode the event happened to or its parent */
187 * depending on the event type we should have either a path or inode
188 * We hold a reference on path, but NOT on inode. Since we have the ref on
189 * the path, it may be dereferenced at any point during this object's
190 * lifetime. That reference is dropped when this object's refcnt hits
191 * 0. If this event contains an inode instead of a path, the inode may
192 * ONLY be used during handle_event().
198 /* when calling fsnotify tell it if the data is a path or inode */
199 #define FSNOTIFY_EVENT_NONE 0
200 #define FSNOTIFY_EVENT_PATH 1
201 #define FSNOTIFY_EVENT_INODE 2
202 #define FSNOTIFY_EVENT_FILE 3
203 int data_type; /* which of the above union we have */
204 atomic_t refcnt; /* how many groups still are using/need to send this event */
205 __u32 mask; /* the type of access, bitwise OR for FS_* event types */
207 u32 sync_cookie; /* used to corrolate events, namely inotify mv events */
211 struct list_head private_data_list; /* groups can store private data here */
215 * a mark is simply an entry attached to an in core inode which allows an
216 * fsnotify listener to indicate they are either no longer interested in events
217 * of a type matching mask or only interested in those events.
219 * these are flushed when an inode is evicted from core and may be flushed
220 * when the inode is modified (as seen by fsnotify_access). Some fsnotify users
221 * (such as dnotify) will flush these when the open fd is closed and not at
222 * inode eviction or modification.
224 struct fsnotify_mark_entry {
225 __u32 mask; /* mask this mark entry is for */
226 /* we hold ref for each i_list and g_list. also one ref for each 'thing'
227 * in kernel that found and may be using this mark. */
228 atomic_t refcnt; /* active things looking at this mark */
229 struct inode *inode; /* inode this entry is associated with */
230 struct fsnotify_group *group; /* group this mark entry is for */
231 struct hlist_node i_list; /* list of mark_entries by inode->i_fsnotify_mark_entries */
232 struct list_head g_list; /* list of mark_entries by group->i_fsnotify_mark_entries */
233 spinlock_t lock; /* protect group, inode, and killme */
234 struct list_head free_i_list; /* tmp list used when freeing this mark */
235 struct list_head free_g_list; /* tmp list used when freeing this mark */
236 void (*free_mark)(struct fsnotify_mark_entry *entry); /* called on final put+free */
239 #ifdef CONFIG_FSNOTIFY
241 /* called from the vfs helpers */
243 /* main fsnotify call to send events */
244 extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
245 const char *name, u32 cookie);
246 extern void __fsnotify_parent(struct dentry *dentry, __u32 mask);
247 extern void __fsnotify_inode_delete(struct inode *inode);
248 extern u32 fsnotify_get_cookie(void);
250 static inline int fsnotify_inode_watches_children(struct inode *inode)
252 /* FS_EVENT_ON_CHILD is set if the inode may care */
253 if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
255 /* this inode might care about child events, does it care about the
256 * specific set of events that can happen on a child? */
257 return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
261 * Update the dentry with a flag indicating the interest of its parent to receive
262 * filesystem events when those events happens to this dentry->d_inode.
264 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
266 struct dentry *parent;
268 assert_spin_locked(&dcache_lock);
269 assert_spin_locked(&dentry->d_lock);
271 parent = dentry->d_parent;
272 if (fsnotify_inode_watches_children(parent->d_inode))
273 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
275 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
279 * fsnotify_d_instantiate - instantiate a dentry for inode
280 * Called with dcache_lock held.
282 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
287 assert_spin_locked(&dcache_lock);
289 spin_lock(&dentry->d_lock);
290 __fsnotify_update_dcache_flags(dentry);
291 spin_unlock(&dentry->d_lock);
294 /* called from fsnotify listeners, such as fanotify or dnotify */
296 /* must call when a group changes its ->mask */
297 extern void fsnotify_recalc_global_mask(void);
298 /* get a reference to an existing or create a new group */
299 extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num,
301 const struct fsnotify_ops *ops);
302 /* run all marks associated with this group and update group->mask */
303 extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
304 /* drop reference on a group from fsnotify_obtain_group */
305 extern void fsnotify_put_group(struct fsnotify_group *group);
307 /* take a reference to an event */
308 extern void fsnotify_get_event(struct fsnotify_event *event);
309 extern void fsnotify_put_event(struct fsnotify_event *event);
310 /* find private data previously attached to an event and unlink it */
311 extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
312 struct fsnotify_event *event);
314 /* attach the event to the group notification queue */
315 extern int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
316 struct fsnotify_event_private_data *priv);
317 /* true if the group notification queue is empty */
318 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
319 /* return, but do not dequeue the first event on the notification queue */
320 extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
321 /* return AND dequeue the first event on the notification queue */
322 extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
324 /* functions used to manipulate the marks attached to inodes */
326 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
327 extern void fsnotify_recalc_inode_mask(struct inode *inode);
328 extern void fsnotify_init_mark(struct fsnotify_mark_entry *entry, void (*free_mark)(struct fsnotify_mark_entry *entry));
329 /* find (and take a reference) to a mark associated with group and inode */
330 extern struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group, struct inode *inode);
331 /* attach the mark to both the group and the inode */
332 extern int fsnotify_add_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group, struct inode *inode);
333 /* given a mark, flag it to be freed when all references are dropped */
334 extern void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry);
335 /* run all the marks in a group, and flag them to be freed */
336 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
337 extern void fsnotify_get_mark(struct fsnotify_mark_entry *entry);
338 extern void fsnotify_put_mark(struct fsnotify_mark_entry *entry);
339 extern void fsnotify_unmount_inodes(struct list_head *list);
341 /* put here because inotify does some weird stuff when destroying watches */
342 extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
343 void *data, int data_is, const char *name,
348 static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
349 const char *name, u32 cookie)
352 static inline void __fsnotify_parent(struct dentry *dentry, __u32 mask)
355 static inline void __fsnotify_inode_delete(struct inode *inode)
358 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
361 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
364 static inline u32 fsnotify_get_cookie(void)
369 static inline void fsnotify_unmount_inodes(struct list_head *list)
372 #endif /* CONFIG_FSNOTIFY */
374 #endif /* __KERNEL __ */
376 #endif /* __LINUX_FSNOTIFY_BACKEND_H */