include/linux/fsnotify_backend.h

   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 #include <linux/atomic.h>
  19
  20 /*
  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.
  25  */
  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 */
  38
  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 */
  42
  43 #define FS_OPEN_PERM            0x00010000      /* open event in an permission hook */
  44 #define FS_ACCESS_PERM          0x00020000      /* access event in a permissions hook */
  45
  46 #define FS_EXCL_UNLINK          0x04000000      /* do not send events if object is unlinked */
  47 #define FS_ISDIR                0x40000000      /* event occurred against dir */
  48 #define FS_IN_ONESHOT           0x80000000      /* only send event once */
  49
  50 #define FS_DN_RENAME            0x10000000      /* file renamed */
  51 #define FS_DN_MULTISHOT         0x20000000      /* dnotify multishot */
  52
  53 /* This inode cares about things that happen to its children.  Always set for
  54  * dnotify and inotify. */
  55 #define FS_EVENT_ON_CHILD       0x08000000
  56
  57 /* This is a list of all events that may get sent to a parernt based on fs event
  58  * happening to inodes inside that directory */
  59 #define FS_EVENTS_POSS_ON_CHILD   (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
  60                                    FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
  61                                    FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
  62                                    FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM)
  63
  64 #define FS_MOVE                 (FS_MOVED_FROM | FS_MOVED_TO)
  65
  66 #define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM)
  67
  68 #define ALL_FSNOTIFY_EVENTS (FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
  69                              FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN | \
  70                              FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
  71                              FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
  72                              FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
  73                              FS_OPEN_PERM | FS_ACCESS_PERM | FS_EXCL_UNLINK | \
  74                              FS_ISDIR | FS_IN_ONESHOT | FS_DN_RENAME | \
  75                              FS_DN_MULTISHOT | FS_EVENT_ON_CHILD)
  76
  77 struct fsnotify_group;
  78 struct fsnotify_event;
  79 struct fsnotify_mark;
  80 struct fsnotify_event_private_data;
  81 struct fsnotify_fname;
  82
  83 /*
  84  * Each group much define these ops.  The fsnotify infrastructure will call
  85  * these operations for each relevant group.
  86  *
  87  * handle_event - main call for a group to handle an fs event
  88  * free_group_priv - called when a group refcnt hits 0 to clean up the private union
  89  * freeing_mark - called when a mark is being destroyed for some reason.  The group
  90  *              MUST be holding a reference on each mark and that reference must be
  91  *              dropped in this function.  inotify uses this function to send
  92  *              userspace messages that marks have been removed.
  93  */
  94 struct fsnotify_ops {
  95         int (*handle_event)(struct fsnotify_group *group,
  96                             struct inode *inode,
  97                             struct fsnotify_mark *inode_mark,
  98                             struct fsnotify_mark *vfsmount_mark,
  99                             u32 mask, const void *data, int data_type,
 100                             const unsigned char *file_name, u32 cookie);
 101         void (*free_group_priv)(struct fsnotify_group *group);
 102         void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
 103         void (*free_event)(struct fsnotify_event *event);
 104 };
 105
 106 /*
 107  * all of the information about the original object we want to now send to
 108  * a group.  If you want to carry more info from the accessing task to the
 109  * listener this structure is where you need to be adding fields.
 110  */
 111 struct fsnotify_event {
 112         struct list_head list;
 113         /* inode may ONLY be dereferenced during handle_event(). */
 114         struct inode *inode;    /* either the inode the event happened to or its parent */
 115         u32 mask;               /* the type of access, bitwise OR for FS_* event types */
 116 };
 117
 118 /*
 119  * A group is a "thing" that wants to receive notification about filesystem
 120  * events.  The mask holds the subset of event types this group cares about.
 121  * refcnt on a group is up to the implementor and at any moment if it goes 0
 122  * everything will be cleaned up.
 123  */
 124 struct fsnotify_group {
 125         /*
 126          * How the refcnt is used is up to each group.  When the refcnt hits 0
 127          * fsnotify will clean up all of the resources associated with this group.
 128          * As an example, the dnotify group will always have a refcnt=1 and that
 129          * will never change.  Inotify, on the other hand, has a group per
 130          * inotify_init() and the refcnt will hit 0 only when that fd has been
 131          * closed.
 132          */
 133         atomic_t refcnt;                /* things with interest in this group */
 134
 135         const struct fsnotify_ops *ops; /* how this group handles things */
 136
 137         /* needed to send notification to userspace */
 138         spinlock_t notification_lock;           /* protect the notification_list */
 139         struct list_head notification_list;     /* list of event_holder this group needs to send to userspace */
 140         wait_queue_head_t notification_waitq;   /* read() on the notification file blocks on this waitq */
 141         unsigned int q_len;                     /* events on the queue */
 142         unsigned int max_events;                /* maximum events allowed on the list */
 143         /*
 144          * Valid fsnotify group priorities.  Events are send in order from highest
 145          * priority to lowest priority.  We default to the lowest priority.
 146          */
 147         #define FS_PRIO_0       0 /* normal notifiers, no permissions */
 148         #define FS_PRIO_1       1 /* fanotify content based access control */
 149         #define FS_PRIO_2       2 /* fanotify pre-content access */
 150         unsigned int priority;
 151         bool shutdown;          /* group is being shut down, don't queue more events */
 152
 153         /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
 154         struct mutex mark_mutex;        /* protect marks_list */
 155         atomic_t num_marks;             /* 1 for each mark and 1 for not being
 156                                          * past the point of no return when freeing
 157                                          * a group */
 158         struct list_head marks_list;    /* all inode marks for this group */
 159
 160         struct fasync_struct *fsn_fa;    /* async notification */
 161
 162         struct fsnotify_event *overflow_event;  /* Event we queue when the
 163                                                  * notification list is too
 164                                                  * full */
 165
 166         /* groups can define private fields here or use the void *private */
 167         union {
 168                 void *private;
 169 #ifdef CONFIG_INOTIFY_USER
 170                 struct inotify_group_private_data {
 171                         spinlock_t      idr_lock;
 172                         struct idr      idr;
 173                         struct user_struct      *user;
 174                 } inotify_data;
 175 #endif
 176 #ifdef CONFIG_FANOTIFY
 177                 struct fanotify_group_private_data {
 178 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 179                         /* allows a group to block waiting for a userspace response */
 180                         struct list_head access_list;
 181                         wait_queue_head_t access_waitq;
 182 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 183                         int f_flags;
 184                         unsigned int max_marks;
 185                         struct user_struct *user;
 186                 } fanotify_data;
 187 #endif /* CONFIG_FANOTIFY */
 188         };
 189 };
 190
 191 /* when calling fsnotify tell it if the data is a path or inode */
 192 #define FSNOTIFY_EVENT_NONE     0
 193 #define FSNOTIFY_EVENT_PATH     1
 194 #define FSNOTIFY_EVENT_INODE    2
 195
 196 /*
 197  * A mark is simply an object attached to an in core inode which allows an
 198  * fsnotify listener to indicate they are either no longer interested in events
 199  * of a type matching mask or only interested in those events.
 200  *
 201  * These are flushed when an inode is evicted from core and may be flushed
 202  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify
 203  * users (such as dnotify) will flush these when the open fd is closed and not
 204  * at inode eviction or modification.
 205  *
 206  * Text in brackets is showing the lock(s) protecting modifications of a
 207  * particular entry. obj_lock means either inode->i_lock or
 208  * mnt->mnt_root->d_lock depending on the mark type.
 209  */
 210 struct fsnotify_mark {
 211         /* Mask this mark is for [mark->lock, group->mark_mutex] */
 212         __u32 mask;
 213         /* We hold one for presence in g_list. Also one ref for each 'thing'
 214          * in kernel that found and may be using this mark. */
 215         atomic_t refcnt;
 216         /* Group this mark is for. Set on mark creation, stable until last ref
 217          * is dropped */
 218         struct fsnotify_group *group;
 219         /* List of marks by group->i_fsnotify_marks. Also reused for queueing
 220          * mark into destroy_list when it's waiting for the end of SRCU period
 221          * before it can be freed. [group->mark_mutex] */
 222         struct list_head g_list;
 223         /* Protects inode / mnt pointers, flags, masks */
 224         spinlock_t lock;
 225         /* List of marks for inode / vfsmount [obj_lock] */
 226         struct hlist_node obj_list;
 227         union { /* Object pointer [mark->lock, group->mark_mutex] */
 228                 struct inode *inode;    /* inode this mark is associated with */
 229                 struct vfsmount *mnt;   /* vfsmount this mark is associated with */
 230         };
 231         /* Events types to ignore [mark->lock, group->mark_mutex] */
 232         __u32 ignored_mask;
 233 #define FSNOTIFY_MARK_FLAG_INODE                0x01
 234 #define FSNOTIFY_MARK_FLAG_VFSMOUNT             0x02
 235 #define FSNOTIFY_MARK_FLAG_OBJECT_PINNED        0x04
 236 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x08
 237 #define FSNOTIFY_MARK_FLAG_ALIVE                0x10
 238 #define FSNOTIFY_MARK_FLAG_ATTACHED             0x20
 239         unsigned int flags;             /* flags [mark->lock] */
 240         void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
 241 };
 242
 243 #ifdef CONFIG_FSNOTIFY
 244
 245 /* called from the vfs helpers */
 246
 247 /* main fsnotify call to send events */
 248 extern int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
 249                     const unsigned char *name, u32 cookie);
 250 extern int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask);
 251 extern void __fsnotify_inode_delete(struct inode *inode);
 252 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 253 extern u32 fsnotify_get_cookie(void);
 254
 255 static inline int fsnotify_inode_watches_children(struct inode *inode)
 256 {
 257         /* FS_EVENT_ON_CHILD is set if the inode may care */
 258         if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 259                 return 0;
 260         /* this inode might care about child events, does it care about the
 261          * specific set of events that can happen on a child? */
 262         return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 263 }
 264
 265 /*
 266  * Update the dentry with a flag indicating the interest of its parent to receive
 267  * filesystem events when those events happens to this dentry->d_inode.
 268  */
 269 static inline void fsnotify_update_flags(struct dentry *dentry)
 270 {
 271         assert_spin_locked(&dentry->d_lock);
 272
 273         /*
 274          * Serialisation of setting PARENT_WATCHED on the dentries is provided
 275          * by d_lock. If inotify_inode_watched changes after we have taken
 276          * d_lock, the following __fsnotify_update_child_dentry_flags call will
 277          * find our entry, so it will spin until we complete here, and update
 278          * us with the new state.
 279          */
 280         if (fsnotify_inode_watches_children(dentry->d_parent->d_inode))
 281                 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 282         else
 283                 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 284 }
 285
 286 /* called from fsnotify listeners, such as fanotify or dnotify */
 287
 288 /* create a new group */
 289 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
 290 /* get reference to a group */
 291 extern void fsnotify_get_group(struct fsnotify_group *group);
 292 /* drop reference on a group from fsnotify_alloc_group */
 293 extern void fsnotify_put_group(struct fsnotify_group *group);
 294 /* group destruction begins, stop queuing new events */
 295 extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);
 296 /* destroy group */
 297 extern void fsnotify_destroy_group(struct fsnotify_group *group);
 298 /* fasync handler function */
 299 extern int fsnotify_fasync(int fd, struct file *file, int on);
 300 /* Free event from memory */
 301 extern void fsnotify_destroy_event(struct fsnotify_group *group,
 302                                    struct fsnotify_event *event);
 303 /* attach the event to the group notification queue */
 304 extern int fsnotify_add_event(struct fsnotify_group *group,
 305                               struct fsnotify_event *event,
 306                               int (*merge)(struct list_head *,
 307                                            struct fsnotify_event *));
 308 /* true if the group notification queue is empty */
 309 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
 310 /* return, but do not dequeue the first event on the notification queue */
 311 extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group);
 312 /* return AND dequeue the first event on the notification queue */
 313 extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);
 314
 315 /* functions used to manipulate the marks attached to inodes */
 316
 317 /* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
 318 extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
 319 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
 320 extern void fsnotify_recalc_inode_mask(struct inode *inode);
 321 extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
 322 /* find (and take a reference) to a mark associated with group and inode */
 323 extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
 324 /* find (and take a reference) to a mark associated with group and vfsmount */
 325 extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
 326 /* set the ignored_mask of a mark */
 327 extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 328 /* set the mask of a mark (might pin the object into memory */
 329 extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 330 /* attach the mark to both the group and the inode */
 331 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
 332                              struct inode *inode, struct vfsmount *mnt, int allow_dups);
 333 extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, struct fsnotify_group *group,
 334                                     struct inode *inode, struct vfsmount *mnt, int allow_dups);
 335 /* given a group and a mark, flag mark to be freed when all references are dropped */
 336 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
 337                                   struct fsnotify_group *group);
 338 /* detach mark from inode / mount list, group list, drop inode reference */
 339 extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
 340 /* free mark */
 341 extern void fsnotify_free_mark(struct fsnotify_mark *mark);
 342 /* run all the marks in a group, and clear all of the vfsmount marks */
 343 extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
 344 /* run all the marks in a group, and clear all of the inode marks */
 345 extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
 346 /* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
 347 extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
 348 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 349 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 350 extern void fsnotify_unmount_inodes(struct super_block *sb);
 351
 352 /* put here because inotify does some weird stuff when destroying watches */
 353 extern void fsnotify_init_event(struct fsnotify_event *event,
 354                                 struct inode *to_tell, u32 mask);
 355
 356 #else
 357
 358 static inline int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
 359                            const unsigned char *name, u32 cookie)
 360 {
 361         return 0;
 362 }
 363
 364 static inline int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask)
 365 {
 366         return 0;
 367 }
 368
 369 static inline void __fsnotify_inode_delete(struct inode *inode)
 370 {}
 371
 372 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 373 {}
 374
 375 static inline void fsnotify_update_flags(struct dentry *dentry)
 376 {}
 377
 378 static inline u32 fsnotify_get_cookie(void)
 379 {
 380         return 0;
 381 }
 382
 383 static inline void fsnotify_unmount_inodes(struct super_block *sb)
 384 {}
 385
 386 #endif  /* CONFIG_FSNOTIFY */
 387
 388 #endif  /* __KERNEL __ */
 389
 390 #endif  /* __LINUX_FSNOTIFY_BACKEND_H */