1 /* 2 * Filesystem access notification for Linux 3 * 4 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <[email protected]> 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 78 struct fsnotify_group; 79 struct fsnotify_event; 80 struct fsnotify_mark; 81 struct 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 */ 96 struct 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 */ 116 struct 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 */ 191 struct 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 */ 200 struct 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 */ 210 struct 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 */ 255 struct 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 */ 264 struct 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 */ 280 struct 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 */ 308 extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is, 309 const unsigned char *name, u32 cookie); 310 extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask); 311 extern void __fsnotify_inode_delete(struct inode *inode); 312 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt); 313 extern u32 fsnotify_get_cookie(void); 314 315 static 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 */ 329 static 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 */ 352 static 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 */ 365 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops); 366 /* get reference to a group */ 367 extern void fsnotify_get_group(struct fsnotify_group *group); 368 /* drop reference on a group from fsnotify_alloc_group */ 369 extern void fsnotify_put_group(struct fsnotify_group *group); 370 /* destroy group */ 371 extern void fsnotify_destroy_group(struct fsnotify_group *group); 372 /* fasync handler function */ 373 extern int fsnotify_fasync(int fd, struct file *file, int on); 374 /* take a reference to an event */ 375 extern void fsnotify_get_event(struct fsnotify_event *event); 376 extern void fsnotify_put_event(struct fsnotify_event *event); 377 /* find private data previously attached to an event and unlink it */ 378 extern 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 */ 382 extern 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 */ 388 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group); 389 /* return, but do not dequeue the first event on the notification queue */ 390 extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group); 391 /* return AND dequeue the first event on the notification queue */ 392 extern 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 */ 397 extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt); 398 /* run all marks associated with an inode and update inode->i_fsnotify_mask */ 399 extern void fsnotify_recalc_inode_mask(struct inode *inode); 400 extern 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 */ 402 extern 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 */ 404 extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt); 405 /* copy the values from old into new */ 406 extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old); 407 /* set the ignored_mask of a mark */ 408 extern 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 */ 410 extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask); 411 /* attach the mark to both the group and the inode */ 412 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group, 413 struct inode *inode, struct vfsmount *mnt, int allow_dups); 414 extern 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 */ 417 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark, 418 struct fsnotify_group *group); 419 extern 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 */ 422 extern 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 */ 424 extern 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*/ 426 extern 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 */ 428 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group); 429 extern void fsnotify_get_mark(struct fsnotify_mark *mark); 430 extern void fsnotify_put_mark(struct fsnotify_mark *mark); 431 extern void fsnotify_unmount_inodes(struct list_head *list); 432 433 /* put here because inotify does some weird stuff when destroying watches */ 434 extern 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... */ 440 extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event); 441 extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder, 442 struct fsnotify_event *new_event); 443 444 #else 445 446 static 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 } 451 452 static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask) 453 { 454 return 0; 455 } 456 457 static inline void __fsnotify_inode_delete(struct inode *inode) 458 {} 459 460 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt) 461 {} 462 463 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry) 464 {} 465 466 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode) 467 {} 468 469 static inline u32 fsnotify_get_cookie(void) 470 { 471 return 0; 472 } 473 474 static 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 */ 482