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-rw-r--r--include/linux/fsnotify_backend.h387
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diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
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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_IN_ISDIR 0x40000000 /* event occurred against dir */
45#define FS_IN_ONESHOT 0x80000000 /* only send event once */
46
47#define FS_DN_RENAME 0x10000000 /* file renamed */
48#define FS_DN_MULTISHOT 0x20000000 /* dnotify multishot */
49
50/* This inode cares about things that happen to its children. Always set for
51 * dnotify and inotify. */
52#define FS_EVENT_ON_CHILD 0x08000000
53
54/* This is a list of all events that may get sent to a parernt based on fs event
55 * happening to inodes inside that directory */
56#define FS_EVENTS_POSS_ON_CHILD (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
57 FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
58 FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
59 FS_DELETE)
60
61/* listeners that hard code group numbers near the top */
62#define DNOTIFY_GROUP_NUM UINT_MAX
63#define INOTIFY_GROUP_NUM (DNOTIFY_GROUP_NUM-1)
64
65struct fsnotify_group;
66struct fsnotify_event;
67struct fsnotify_mark_entry;
68struct fsnotify_event_private_data;
69
70/*
71 * Each group much define these ops. The fsnotify infrastructure will call
72 * these operations for each relevant group.
73 *
74 * should_send_event - given a group, inode, and mask this function determines
75 * if the group is interested in this event.
76 * handle_event - main call for a group to handle an fs event
77 * free_group_priv - called when a group refcnt hits 0 to clean up the private union
78 * freeing-mark - this means that a mark has been flagged to die when everything
79 * finishes using it. The function is supplied with what must be a
80 * valid group and inode to use to clean up.
81 */
82struct fsnotify_ops {
83 bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode, __u32 mask);
84 int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
85 void (*free_group_priv)(struct fsnotify_group *group);
86 void (*freeing_mark)(struct fsnotify_mark_entry *entry, struct fsnotify_group *group);
87 void (*free_event_priv)(struct fsnotify_event_private_data *priv);
88};
89
90/*
91 * A group is a "thing" that wants to receive notification about filesystem
92 * events. The mask holds the subset of event types this group cares about.
93 * refcnt on a group is up to the implementor and at any moment if it goes 0
94 * everything will be cleaned up.
95 */
96struct fsnotify_group {
97 /*
98 * global list of all groups receiving events from fsnotify.
99 * anchored by fsnotify_groups and protected by either fsnotify_grp_mutex
100 * or fsnotify_grp_srcu depending on write vs read.
101 */
102 struct list_head group_list;
103
104 /*
105 * Defines all of the event types in which this group is interested.
106 * This mask is a bitwise OR of the FS_* events from above. Each time
107 * this mask changes for a group (if it changes) the correct functions
108 * must be called to update the global structures which indicate global
109 * interest in event types.
110 */
111 __u32 mask;
112
113 /*
114 * How the refcnt is used is up to each group. When the refcnt hits 0
115 * fsnotify will clean up all of the resources associated with this group.
116 * As an example, the dnotify group will always have a refcnt=1 and that
117 * will never change. Inotify, on the other hand, has a group per
118 * inotify_init() and the refcnt will hit 0 only when that fd has been
119 * closed.
120 */
121 atomic_t refcnt; /* things with interest in this group */
122 unsigned int group_num; /* simply prevents accidental group collision */
123
124 const struct fsnotify_ops *ops; /* how this group handles things */
125
126 /* needed to send notification to userspace */
127 struct mutex notification_mutex; /* protect the notification_list */
128 struct list_head notification_list; /* list of event_holder this group needs to send to userspace */
129 wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */
130 unsigned int q_len; /* events on the queue */
131 unsigned int max_events; /* maximum events allowed on the list */
132
133 /* stores all fastapth entries assoc with this group so they can be cleaned on unregister */
134 spinlock_t mark_lock; /* protect mark_entries list */
135 atomic_t num_marks; /* 1 for each mark entry and 1 for not being
136 * past the point of no return when freeing
137 * a group */
138 struct list_head mark_entries; /* all inode mark entries for this group */
139
140 /* prevents double list_del of group_list. protected by global fsnotify_grp_mutex */
141 bool on_group_list;
142
143 /* groups can define private fields here or use the void *private */
144 union {
145 void *private;
146#ifdef CONFIG_INOTIFY_USER
147 struct inotify_group_private_data {
148 spinlock_t idr_lock;
149 struct idr idr;
150 u32 last_wd;
151 struct fasync_struct *fa; /* async notification */
152 struct user_struct *user;
153 } inotify_data;
154#endif
155 };
156};
157
158/*
159 * A single event can be queued in multiple group->notification_lists.
160 *
161 * each group->notification_list will point to an event_holder which in turns points
162 * to the actual event that needs to be sent to userspace.
163 *
164 * Seemed cheaper to create a refcnt'd event and a small holder for every group
165 * than create a different event for every group
166 *
167 */
168struct fsnotify_event_holder {
169 struct fsnotify_event *event;
170 struct list_head event_list;
171};
172
173/*
174 * Inotify needs to tack data onto an event. This struct lets us later find the
175 * correct private data of the correct group.
176 */
177struct fsnotify_event_private_data {
178 struct fsnotify_group *group;
179 struct list_head event_list;
180};
181
182/*
183 * all of the information about the original object we want to now send to
184 * a group. If you want to carry more info from the accessing task to the
185 * listener this structure is where you need to be adding fields.
186 */
187struct fsnotify_event {
188 /*
189 * If we create an event we are also likely going to need a holder
190 * to link to a group. So embed one holder in the event. Means only
191 * one allocation for the common case where we only have one group
192 */
193 struct fsnotify_event_holder holder;
194 spinlock_t lock; /* protection for the associated event_holder and private_list */
195 /* to_tell may ONLY be dereferenced during handle_event(). */
196 struct inode *to_tell; /* either the inode the event happened to or its parent */
197 /*
198 * depending on the event type we should have either a path or inode
199 * We hold a reference on path, but NOT on inode. Since we have the ref on
200 * the path, it may be dereferenced at any point during this object's
201 * lifetime. That reference is dropped when this object's refcnt hits
202 * 0. If this event contains an inode instead of a path, the inode may
203 * ONLY be used during handle_event().
204 */
205 union {
206 struct path path;
207 struct inode *inode;
208 };
209/* when calling fsnotify tell it if the data is a path or inode */
210#define FSNOTIFY_EVENT_NONE 0
211#define FSNOTIFY_EVENT_PATH 1
212#define FSNOTIFY_EVENT_INODE 2
213#define FSNOTIFY_EVENT_FILE 3
214 int data_type; /* which of the above union we have */
215 atomic_t refcnt; /* how many groups still are using/need to send this event */
216 __u32 mask; /* the type of access, bitwise OR for FS_* event types */
217
218 u32 sync_cookie; /* used to corrolate events, namely inotify mv events */
219 char *file_name;
220 size_t name_len;
221
222 struct list_head private_data_list; /* groups can store private data here */
223};
224
225/*
226 * a mark is simply an entry attached to an in core inode which allows an
227 * fsnotify listener to indicate they are either no longer interested in events
228 * of a type matching mask or only interested in those events.
229 *
230 * these are flushed when an inode is evicted from core and may be flushed
231 * when the inode is modified (as seen by fsnotify_access). Some fsnotify users
232 * (such as dnotify) will flush these when the open fd is closed and not at
233 * inode eviction or modification.
234 */
235struct fsnotify_mark_entry {
236 __u32 mask; /* mask this mark entry is for */
237 /* we hold ref for each i_list and g_list. also one ref for each 'thing'
238 * in kernel that found and may be using this mark. */
239 atomic_t refcnt; /* active things looking at this mark */
240 struct inode *inode; /* inode this entry is associated with */
241 struct fsnotify_group *group; /* group this mark entry is for */
242 struct hlist_node i_list; /* list of mark_entries by inode->i_fsnotify_mark_entries */
243 struct list_head g_list; /* list of mark_entries by group->i_fsnotify_mark_entries */
244 spinlock_t lock; /* protect group, inode, and killme */
245 struct list_head free_i_list; /* tmp list used when freeing this mark */
246 struct list_head free_g_list; /* tmp list used when freeing this mark */
247 void (*free_mark)(struct fsnotify_mark_entry *entry); /* called on final put+free */
248};
249
250#ifdef CONFIG_FSNOTIFY
251
252/* called from the vfs helpers */
253
254/* main fsnotify call to send events */
255extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
256 const char *name, u32 cookie);
257extern void __fsnotify_parent(struct dentry *dentry, __u32 mask);
258extern void __fsnotify_inode_delete(struct inode *inode);
259extern u32 fsnotify_get_cookie(void);
260
261static inline int fsnotify_inode_watches_children(struct inode *inode)
262{
263 /* FS_EVENT_ON_CHILD is set if the inode may care */
264 if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
265 return 0;
266 /* this inode might care about child events, does it care about the
267 * specific set of events that can happen on a child? */
268 return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
269}
270
271/*
272 * Update the dentry with a flag indicating the interest of its parent to receive
273 * filesystem events when those events happens to this dentry->d_inode.
274 */
275static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
276{
277 struct dentry *parent;
278
279 assert_spin_locked(&dcache_lock);
280 assert_spin_locked(&dentry->d_lock);
281
282 parent = dentry->d_parent;
283 if (fsnotify_inode_watches_children(parent->d_inode))
284 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
285 else
286 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
287}
288
289/*
290 * fsnotify_d_instantiate - instantiate a dentry for inode
291 * Called with dcache_lock held.
292 */
293static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
294{
295 if (!inode)
296 return;
297
298 assert_spin_locked(&dcache_lock);
299
300 spin_lock(&dentry->d_lock);
301 __fsnotify_update_dcache_flags(dentry);
302 spin_unlock(&dentry->d_lock);
303}
304
305/* called from fsnotify listeners, such as fanotify or dnotify */
306
307/* must call when a group changes its ->mask */
308extern void fsnotify_recalc_global_mask(void);
309/* get a reference to an existing or create a new group */
310extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num,
311 __u32 mask,
312 const struct fsnotify_ops *ops);
313/* run all marks associated with this group and update group->mask */
314extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
315/* drop reference on a group from fsnotify_obtain_group */
316extern void fsnotify_put_group(struct fsnotify_group *group);
317
318/* take a reference to an event */
319extern void fsnotify_get_event(struct fsnotify_event *event);
320extern void fsnotify_put_event(struct fsnotify_event *event);
321/* find private data previously attached to an event and unlink it */
322extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
323 struct fsnotify_event *event);
324
325/* attach the event to the group notification queue */
326extern int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
327 struct fsnotify_event_private_data *priv);
328/* true if the group notification queue is empty */
329extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
330/* return, but do not dequeue the first event on the notification queue */
331extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
332/* return AND dequeue the first event on the notification queue */
333extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
334
335/* functions used to manipulate the marks attached to inodes */
336
337/* run all marks associated with an inode and update inode->i_fsnotify_mask */
338extern void fsnotify_recalc_inode_mask(struct inode *inode);
339extern void fsnotify_init_mark(struct fsnotify_mark_entry *entry, void (*free_mark)(struct fsnotify_mark_entry *entry));
340/* find (and take a reference) to a mark associated with group and inode */
341extern struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group, struct inode *inode);
342/* attach the mark to both the group and the inode */
343extern int fsnotify_add_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group, struct inode *inode);
344/* given a mark, flag it to be freed when all references are dropped */
345extern void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry);
346/* run all the marks in a group, and flag them to be freed */
347extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
348extern void fsnotify_get_mark(struct fsnotify_mark_entry *entry);
349extern void fsnotify_put_mark(struct fsnotify_mark_entry *entry);
350extern void fsnotify_unmount_inodes(struct list_head *list);
351
352/* put here because inotify does some weird stuff when destroying watches */
353extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
354 void *data, int data_is, const char *name,
355 u32 cookie);
356
357#else
358
359static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
360 const char *name, u32 cookie)
361{}
362
363static inline void __fsnotify_parent(struct dentry *dentry, __u32 mask)
364{}
365
366static inline void __fsnotify_inode_delete(struct inode *inode)
367{}
368
369static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
370{}
371
372static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
373{}
374
375static inline u32 fsnotify_get_cookie(void)
376{
377 return 0;
378}
379
380static inline void fsnotify_unmount_inodes(struct list_head *list)
381{}
382
383#endif /* CONFIG_FSNOTIFY */
384
385#endif /* __KERNEL __ */
386
387#endif /* __LINUX_FSNOTIFY_BACKEND_H */
generated by cgit v1.2.2 (git 2.25.0) at 2025-02-03 21:04:11 -0500