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, 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         struct mutex notification_mutex;        /* 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
 152         /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
 153         struct mutex mark_mutex;        /* protect marks_list */
 154         atomic_t num_marks;             /* 1 for each mark and 1 for not being
 155                                          * past the point of no return when freeing
 156                                          * a group */
 157         struct list_head marks_list;    /* all inode marks for this group */
 158
 159         struct fasync_struct *fsn_fa;    /* async notification */
 160
 161         struct fsnotify_event *overflow_event;  /* Event we queue when the
 162                                                  * notification list is too
 163                                                  * full */
 164
 165         /* groups can define private fields here or use the void *private */
 166         union {
 167                 void *private;
 168 #ifdef CONFIG_INOTIFY_USER
 169                 struct inotify_group_private_data {
 170                         spinlock_t      idr_lock;
 171                         struct idr      idr;
 172                         struct user_struct      *user;
 173                 } inotify_data;
 174 #endif
 175 #ifdef CONFIG_FANOTIFY
 176                 struct fanotify_group_private_data {
 177 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 178                         /* allows a group to block waiting for a userspace response */
 179                         spinlock_t access_lock;
 180                         struct list_head access_list;
 181                         wait_queue_head_t access_waitq;
 182                         atomic_t bypass_perm;
 183 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 184                         int f_flags;
 185                         unsigned int max_marks;
 186                         struct user_struct *user;
 187                 } fanotify_data;
 188 #endif /* CONFIG_FANOTIFY */
 189         };
 190 };
 191
 192 /* when calling fsnotify tell it if the data is a path or inode */
 193 #define FSNOTIFY_EVENT_NONE     0
 194 #define FSNOTIFY_EVENT_PATH     1
 195 #define FSNOTIFY_EVENT_INODE    2
 196
 197 /*
 198  * A mark is simply an object attached to an in core inode which allows an
 199  * fsnotify listener to indicate they are either no longer interested in events
 200  * of a type matching mask or only interested in those events.
 201  *
 202  * These are flushed when an inode is evicted from core and may be flushed
 203  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify
 204  * users (such as dnotify) will flush these when the open fd is closed and not
 205  * at inode eviction or modification.
 206  *
 207  * Text in brackets is showing the lock(s) protecting modifications of a
 208  * particular entry. obj_lock means either inode->i_lock or
 209  * mnt->mnt_root->d_lock depending on the mark type.
 210  */
 211 struct fsnotify_mark {
 212         /* Mask this mark is for [mark->lock, group->mark_mutex] */
 213         __u32 mask;
 214         /* We hold one for presence in g_list. Also one ref for each 'thing'
 215          * in kernel that found and may be using this mark. */
 216         atomic_t refcnt;
 217         /* Group this mark is for. Set on mark creation, stable until last ref
 218          * is dropped */
 219         struct fsnotify_group *group;
 220         /* List of marks by group->i_fsnotify_marks. Also reused for queueing
 221          * mark into destroy_list when it's waiting for the end of SRCU period
 222          * before it can be freed. [group->mark_mutex] */
 223         union {
 224                 struct list_head g_list;
 225                 struct rcu_head g_rcu;
 226         };
 227         /* Protects inode / mnt pointers, flags, masks */
 228         spinlock_t lock;
 229         /* List of marks for inode / vfsmount [obj_lock] */
 230         struct hlist_node obj_list;
 231         union { /* Object pointer [mark->lock, group->mark_mutex] */
 232                 struct inode *inode;    /* inode this mark is associated with */
 233                 struct vfsmount *mnt;   /* vfsmount this mark is associated with */
 234         };
 235         /* Events types to ignore [mark->lock, group->mark_mutex] */
 236         __u32 ignored_mask;
 237 #define FSNOTIFY_MARK_FLAG_INODE                0x01
 238 #define FSNOTIFY_MARK_FLAG_VFSMOUNT             0x02
 239 #define FSNOTIFY_MARK_FLAG_OBJECT_PINNED        0x04
 240 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x08
 241 #define FSNOTIFY_MARK_FLAG_ALIVE                0x10
 242 #define FSNOTIFY_MARK_FLAG_ATTACHED             0x20
 243         unsigned int flags;             /* flags [mark->lock] */
 244         void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
 245 };
 246
 247 #ifdef CONFIG_FSNOTIFY
 248
 249 /* called from the vfs helpers */
 250
 251 /* main fsnotify call to send events */
 252 extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 253                     const unsigned char *name, u32 cookie);
 254 extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
 255 extern void __fsnotify_inode_delete(struct inode *inode);
 256 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 257 extern u32 fsnotify_get_cookie(void);
 258
 259 static inline int fsnotify_inode_watches_children(struct inode *inode)
 260 {
 261         /* FS_EVENT_ON_CHILD is set if the inode may care */
 262         if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 263                 return 0;
 264         /* this inode might care about child events, does it care about the
 265          * specific set of events that can happen on a child? */
 266         return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 267 }
 268
 269 /*
 270  * Update the dentry with a flag indicating the interest of its parent to receive
 271  * filesystem events when those events happens to this dentry->d_inode.
 272  */
 273 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 274 {
 275         struct dentry *parent;
 276
 277         assert_spin_locked(&dentry->d_lock);
 278
 279         /*
 280          * Serialisation of setting PARENT_WATCHED on the dentries is provided
 281          * by d_lock. If inotify_inode_watched changes after we have taken
 282          * d_lock, the following __fsnotify_update_child_dentry_flags call will
 283          * find our entry, so it will spin until we complete here, and update
 284          * us with the new state.
 285          */
 286         parent = dentry->d_parent;
 287         if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
 288                 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 289         else
 290                 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 291 }
 292
 293 /*
 294  * fsnotify_d_instantiate - instantiate a dentry for inode
 295  */
 296 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 297 {
 298         if (!inode)
 299                 return;
 300
 301         spin_lock(&dentry->d_lock);
 302         __fsnotify_update_dcache_flags(dentry);
 303         spin_unlock(&dentry->d_lock);
 304 }
 305
 306 /* called from fsnotify listeners, such as fanotify or dnotify */
 307
 308 /* create a new group */
 309 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
 310 /* get reference to a group */
 311 extern void fsnotify_get_group(struct fsnotify_group *group);
 312 /* drop reference on a group from fsnotify_alloc_group */
 313 extern void fsnotify_put_group(struct fsnotify_group *group);
 314 /* destroy group */
 315 extern void fsnotify_destroy_group(struct fsnotify_group *group);
 316 /* fasync handler function */
 317 extern int fsnotify_fasync(int fd, struct file *file, int on);
 318 /* Free event from memory */
 319 extern void fsnotify_destroy_event(struct fsnotify_group *group,
 320                                    struct fsnotify_event *event);
 321 /* attach the event to the group notification queue */
 322 extern int fsnotify_add_event(struct fsnotify_group *group,
 323                               struct fsnotify_event *event,
 324                               int (*merge)(struct list_head *,
 325                                            struct fsnotify_event *));
 326 /* Remove passed event from groups notification queue */
 327 extern void fsnotify_remove_event(struct fsnotify_group *group, struct fsnotify_event *event);
 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_first_event(struct fsnotify_group *group);
 332 /* return AND dequeue the first event on the notification queue */
 333 extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);
 334
 335 /* functions used to manipulate the marks attached to inodes */
 336
 337 /* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
 338 extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
 339 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
 340 extern void fsnotify_recalc_inode_mask(struct inode *inode);
 341 extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
 342 /* find (and take a reference) to a mark associated with group and inode */
 343 extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
 344 /* find (and take a reference) to a mark associated with group and vfsmount */
 345 extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
 346 /* copy the values from old into new */
 347 extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
 348 /* set the ignored_mask of a mark */
 349 extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 350 /* set the mask of a mark (might pin the object into memory */
 351 extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 352 /* attach the mark to both the group and the inode */
 353 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
 354                              struct inode *inode, struct vfsmount *mnt, int allow_dups);
 355 extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, struct fsnotify_group *group,
 356                                     struct inode *inode, struct vfsmount *mnt, int allow_dups);
 357 /* given a group and a mark, flag mark to be freed when all references are dropped */
 358 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
 359                                   struct fsnotify_group *group);
 360 /* detach mark from inode / mount list, group list, drop inode reference */
 361 extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
 362 /* free mark */
 363 extern void fsnotify_free_mark(struct fsnotify_mark *mark);
 364 /* run all the marks in a group, and clear all of the vfsmount marks */
 365 extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
 366 /* run all the marks in a group, and clear all of the inode marks */
 367 extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
 368 /* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
 369 extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
 370 /* run all the marks in a group, and flag them to be freed */
 371 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
 372 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 373 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 374 extern void fsnotify_unmount_inodes(struct super_block *sb);
 375
 376 /* put here because inotify does some weird stuff when destroying watches */
 377 extern void fsnotify_init_event(struct fsnotify_event *event,
 378                                 struct inode *to_tell, u32 mask);
 379
 380 #else
 381
 382 static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 383                            const unsigned char *name, u32 cookie)
 384 {
 385         return 0;
 386 }
 387
 388 static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
 389 {
 390         return 0;
 391 }
 392
 393 static inline void __fsnotify_inode_delete(struct inode *inode)
 394 {}
 395
 396 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 397 {}
 398
 399 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 400 {}
 401
 402 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 403 {}
 404
 405 static inline u32 fsnotify_get_cookie(void)
 406 {
 407         return 0;
 408 }
 409
 410 static inline void fsnotify_unmount_inodes(struct super_block *sb)
 411 {}
 412
 413 #endif  /* CONFIG_FSNOTIFY */
 414
 415 #endif  /* __KERNEL __ */
 416
 417 #endif  /* __LINUX_FSNOTIFY_BACKEND_H */