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 <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 65 struct fsnotify_group; 66 struct fsnotify_event; 67 struct fsnotify_mark_entry; 68 struct 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 */ 82 struct 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 */ 96 struct 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 */ 168 struct 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 */ 177 struct 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 */ 187 struct 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 */ 235 struct 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 */ 255 extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is, 256 const char *name, u32 cookie); 257 extern void __fsnotify_parent(struct dentry *dentry, __u32 mask); 258 extern void __fsnotify_inode_delete(struct inode *inode); 259 extern u32 fsnotify_get_cookie(void); 260 261 static 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 */ 275 static 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 (parent->d_inode && 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 */ 293 static 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 */ 308 extern void fsnotify_recalc_global_mask(void); 309 /* get a reference to an existing or create a new group */ 310 extern 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 */ 314 extern void fsnotify_recalc_group_mask(struct fsnotify_group *group); 315 /* drop reference on a group from fsnotify_obtain_group */ 316 extern void fsnotify_put_group(struct fsnotify_group *group); 317 318 /* take a reference to an event */ 319 extern void fsnotify_get_event(struct fsnotify_event *event); 320 extern void fsnotify_put_event(struct fsnotify_event *event); 321 /* find private data previously attached to an event and unlink it */ 322 extern 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 */ 326 extern 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 */ 329 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group); 330 /* return, but do not dequeue the first event on the notification queue */ 331 extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group); 332 /* return AND dequeue the first event on the notification queue */ 333 extern 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 */ 338 extern void fsnotify_recalc_inode_mask(struct inode *inode); 339 extern 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 */ 341 extern 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 */ 343 extern 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 */ 345 extern 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 */ 347 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group); 348 extern void fsnotify_get_mark(struct fsnotify_mark_entry *entry); 349 extern void fsnotify_put_mark(struct fsnotify_mark_entry *entry); 350 extern void fsnotify_unmount_inodes(struct list_head *list); 351 352 /* put here because inotify does some weird stuff when destroying watches */ 353 extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, 354 void *data, int data_is, const char *name, 355 u32 cookie, gfp_t gfp); 356 357 #else 358 359 static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is, 360 const char *name, u32 cookie) 361 {} 362 363 static inline void __fsnotify_parent(struct dentry *dentry, __u32 mask) 364 {} 365 366 static inline void __fsnotify_inode_delete(struct inode *inode) 367 {} 368 369 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry) 370 {} 371 372 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode) 373 {} 374 375 static inline u32 fsnotify_get_cookie(void) 376 { 377 return 0; 378 } 379 380 static 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 */ 388