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 #include <linux/user_namespace.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 struct fsnotify_fname;
  83 struct fsnotify_iter_info;
  84
  85 /*
  86  * Each group much define these ops.  The fsnotify infrastructure will call
  87  * these operations for each relevant group.
  88  *
  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         int (*handle_event)(struct fsnotify_group *group,
  98                             struct inode *inode,
  99                             struct fsnotify_mark *inode_mark,
 100                             struct fsnotify_mark *vfsmount_mark,
 101                             u32 mask, const void *data, int data_type,
 102                             const unsigned char *file_name, u32 cookie,
 103                             struct fsnotify_iter_info *iter_info);
 104         void (*free_group_priv)(struct fsnotify_group *group);
 105         void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
 106         void (*free_event)(struct fsnotify_event *event);
 107         /* called on final put+free to free memory */
 108         void (*free_mark)(struct fsnotify_mark *mark);
 109 };
 110
 111 /*
 112  * all of the information about the original object we want to now send to
 113  * a group.  If you want to carry more info from the accessing task to the
 114  * listener this structure is where you need to be adding fields.
 115  */
 116 struct fsnotify_event {
 117         struct list_head list;
 118         /* inode may ONLY be dereferenced during handle_event(). */
 119         struct inode *inode;    /* either the inode the event happened to or its parent */
 120         u32 mask;               /* the type of access, bitwise OR for FS_* event types */
 121 };
 122
 123 /*
 124  * A group is a "thing" that wants to receive notification about filesystem
 125  * events.  The mask holds the subset of event types this group cares about.
 126  * refcnt on a group is up to the implementor and at any moment if it goes 0
 127  * everything will be cleaned up.
 128  */
 129 struct fsnotify_group {
 130         /*
 131          * How the refcnt is used is up to each group.  When the refcnt hits 0
 132          * fsnotify will clean up all of the resources associated with this group.
 133          * As an example, the dnotify group will always have a refcnt=1 and that
 134          * will never change.  Inotify, on the other hand, has a group per
 135          * inotify_init() and the refcnt will hit 0 only when that fd has been
 136          * closed.
 137          */
 138         atomic_t refcnt;                /* things with interest in this group */
 139
 140         const struct fsnotify_ops *ops; /* how this group handles things */
 141
 142         /* needed to send notification to userspace */
 143         spinlock_t notification_lock;           /* protect the notification_list */
 144         struct list_head notification_list;     /* list of event_holder this group needs to send to userspace */
 145         wait_queue_head_t notification_waitq;   /* read() on the notification file blocks on this waitq */
 146         unsigned int q_len;                     /* events on the queue */
 147         unsigned int max_events;                /* maximum events allowed on the list */
 148         /*
 149          * Valid fsnotify group priorities.  Events are send in order from highest
 150          * priority to lowest priority.  We default to the lowest priority.
 151          */
 152         #define FS_PRIO_0       0 /* normal notifiers, no permissions */
 153         #define FS_PRIO_1       1 /* fanotify content based access control */
 154         #define FS_PRIO_2       2 /* fanotify pre-content access */
 155         unsigned int priority;
 156         bool shutdown;          /* group is being shut down, don't queue more events */
 157
 158         /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
 159         struct mutex mark_mutex;        /* protect marks_list */
 160         atomic_t num_marks;             /* 1 for each mark and 1 for not being
 161                                          * past the point of no return when freeing
 162                                          * a group */
 163         struct list_head marks_list;    /* all inode marks for this group */
 164
 165         struct fasync_struct *fsn_fa;    /* async notification */
 166
 167         struct fsnotify_event *overflow_event;  /* Event we queue when the
 168                                                  * notification list is too
 169                                                  * full */
 170         atomic_t user_waits;            /* Number of tasks waiting for user
 171                                          * response */
 172
 173         /* groups can define private fields here or use the void *private */
 174         union {
 175                 void *private;
 176 #ifdef CONFIG_INOTIFY_USER
 177                 struct inotify_group_private_data {
 178                         spinlock_t      idr_lock;
 179                         struct idr      idr;
 180                         struct ucounts *ucounts;
 181                 } inotify_data;
 182 #endif
 183 #ifdef CONFIG_FANOTIFY
 184                 struct fanotify_group_private_data {
 185 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 186                         /* allows a group to block waiting for a userspace response */
 187                         struct list_head access_list;
 188                         wait_queue_head_t access_waitq;
 189 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 190                         int f_flags;
 191                         unsigned int max_marks;
 192                         struct user_struct *user;
 193                 } fanotify_data;
 194 #endif /* CONFIG_FANOTIFY */
 195         };
 196 };
 197
 198 /* when calling fsnotify tell it if the data is a path or inode */
 199 #define FSNOTIFY_EVENT_NONE     0
 200 #define FSNOTIFY_EVENT_PATH     1
 201 #define FSNOTIFY_EVENT_INODE    2
 202
 203 /*
 204  * Inode / vfsmount point to this structure which tracks all marks attached to
 205  * the inode / vfsmount. The reference to inode / vfsmount is held by this
 206  * structure. We destroy this structure when there are no more marks attached
 207  * to it. The structure is protected by fsnotify_mark_srcu.
 208  */
 209 struct fsnotify_mark_connector {
 210         spinlock_t lock;
 211 #define FSNOTIFY_OBJ_TYPE_INODE         0x01
 212 #define FSNOTIFY_OBJ_TYPE_VFSMOUNT      0x02
 213 #define FSNOTIFY_OBJ_ALL_TYPES          (FSNOTIFY_OBJ_TYPE_INODE | \
 214                                          FSNOTIFY_OBJ_TYPE_VFSMOUNT)
 215         unsigned int flags;     /* Type of object [lock] */
 216         union { /* Object pointer [lock] */
 217                 struct inode *inode;
 218                 struct vfsmount *mnt;
 219         };
 220         union {
 221                 struct hlist_head list;
 222                 /* Used listing heads to free after srcu period expires */
 223                 struct fsnotify_mark_connector *destroy_next;
 224         };
 225 };
 226
 227 /*
 228  * A mark is simply an object attached to an in core inode which allows an
 229  * fsnotify listener to indicate they are either no longer interested in events
 230  * of a type matching mask or only interested in those events.
 231  *
 232  * These are flushed when an inode is evicted from core and may be flushed
 233  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify
 234  * users (such as dnotify) will flush these when the open fd is closed and not
 235  * at inode eviction or modification.
 236  *
 237  * Text in brackets is showing the lock(s) protecting modifications of a
 238  * particular entry. obj_lock means either inode->i_lock or
 239  * mnt->mnt_root->d_lock depending on the mark type.
 240  */
 241 struct fsnotify_mark {
 242         /* Mask this mark is for [mark->lock, group->mark_mutex] */
 243         __u32 mask;
 244         /* We hold one for presence in g_list. Also one ref for each 'thing'
 245          * in kernel that found and may be using this mark. */
 246         atomic_t refcnt;
 247         /* Group this mark is for. Set on mark creation, stable until last ref
 248          * is dropped */
 249         struct fsnotify_group *group;
 250         /* List of marks by group->i_fsnotify_marks. Also reused for queueing
 251          * mark into destroy_list when it's waiting for the end of SRCU period
 252          * before it can be freed. [group->mark_mutex] */
 253         struct list_head g_list;
 254         /* Protects inode / mnt pointers, flags, masks */
 255         spinlock_t lock;
 256         /* List of marks for inode / vfsmount [connector->lock, mark ref] */
 257         struct hlist_node obj_list;
 258         /* Head of list of marks for an object [mark ref] */
 259         struct fsnotify_mark_connector *connector;
 260         /* Events types to ignore [mark->lock, group->mark_mutex] */
 261         __u32 ignored_mask;
 262 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x01
 263 #define FSNOTIFY_MARK_FLAG_ALIVE                0x02
 264 #define FSNOTIFY_MARK_FLAG_ATTACHED             0x04
 265         unsigned int flags;             /* flags [mark->lock] */
 266 };
 267
 268 #ifdef CONFIG_FSNOTIFY
 269
 270 /* called from the vfs helpers */
 271
 272 /* main fsnotify call to send events */
 273 extern int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
 274                     const unsigned char *name, u32 cookie);
 275 extern int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask);
 276 extern void __fsnotify_inode_delete(struct inode *inode);
 277 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 278 extern u32 fsnotify_get_cookie(void);
 279
 280 static inline int fsnotify_inode_watches_children(struct inode *inode)
 281 {
 282         /* FS_EVENT_ON_CHILD is set if the inode may care */
 283         if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 284                 return 0;
 285         /* this inode might care about child events, does it care about the
 286          * specific set of events that can happen on a child? */
 287         return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 288 }
 289
 290 /*
 291  * Update the dentry with a flag indicating the interest of its parent to receive
 292  * filesystem events when those events happens to this dentry->d_inode.
 293  */
 294 static inline void fsnotify_update_flags(struct dentry *dentry)
 295 {
 296         assert_spin_locked(&dentry->d_lock);
 297
 298         /*
 299          * Serialisation of setting PARENT_WATCHED on the dentries is provided
 300          * by d_lock. If inotify_inode_watched changes after we have taken
 301          * d_lock, the following __fsnotify_update_child_dentry_flags call will
 302          * find our entry, so it will spin until we complete here, and update
 303          * us with the new state.
 304          */
 305         if (fsnotify_inode_watches_children(dentry->d_parent->d_inode))
 306                 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 307         else
 308                 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 309 }
 310
 311 /* called from fsnotify listeners, such as fanotify or dnotify */
 312
 313 /* create a new group */
 314 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
 315 /* get reference to a group */
 316 extern void fsnotify_get_group(struct fsnotify_group *group);
 317 /* drop reference on a group from fsnotify_alloc_group */
 318 extern void fsnotify_put_group(struct fsnotify_group *group);
 319 /* group destruction begins, stop queuing new events */
 320 extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);
 321 /* destroy group */
 322 extern void fsnotify_destroy_group(struct fsnotify_group *group);
 323 /* fasync handler function */
 324 extern int fsnotify_fasync(int fd, struct file *file, int on);
 325 /* Free event from memory */
 326 extern void fsnotify_destroy_event(struct fsnotify_group *group,
 327                                    struct fsnotify_event *event);
 328 /* attach the event to the group notification queue */
 329 extern int fsnotify_add_event(struct fsnotify_group *group,
 330                               struct fsnotify_event *event,
 331                               int (*merge)(struct list_head *,
 332                                            struct fsnotify_event *));
 333 /* true if the group notification queue is empty */
 334 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
 335 /* return, but do not dequeue the first event on the notification queue */
 336 extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group);
 337 /* return AND dequeue the first event on the notification queue */
 338 extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);
 339
 340 /* functions used to manipulate the marks attached to inodes */
 341
 342 /* Calculate mask of events for a list of marks */
 343 extern void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn);
 344 extern void fsnotify_init_mark(struct fsnotify_mark *mark,
 345                                struct fsnotify_group *group);
 346 /* Find mark belonging to given group in the list of marks */
 347 extern struct fsnotify_mark *fsnotify_find_mark(
 348                                 struct fsnotify_mark_connector __rcu **connp,
 349                                 struct fsnotify_group *group);
 350 /* attach the mark to the inode or vfsmount */
 351 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct inode *inode,
 352                              struct vfsmount *mnt, int allow_dups);
 353 extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
 354                                     struct inode *inode, struct vfsmount *mnt, int allow_dups);
 355 /* given a group and a mark, flag mark to be freed when all references are dropped */
 356 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
 357                                   struct fsnotify_group *group);
 358 /* detach mark from inode / mount list, group list, drop inode reference */
 359 extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
 360 /* free mark */
 361 extern void fsnotify_free_mark(struct fsnotify_mark *mark);
 362 /* run all the marks in a group, and clear all of the marks attached to given object type */
 363 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group, unsigned int type);
 364 /* run all the marks in a group, and clear all of the vfsmount marks */
 365 static inline void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group)
 366 {
 367         fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_VFSMOUNT);
 368 }
 369 /* run all the marks in a group, and clear all of the inode marks */
 370 static inline void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
 371 {
 372         fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_INODE);
 373 }
 374 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 375 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 376 extern void fsnotify_unmount_inodes(struct super_block *sb);
 377 extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
 378 extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);
 379
 380 /* put here because inotify does some weird stuff when destroying watches */
 381 extern void fsnotify_init_event(struct fsnotify_event *event,
 382                                 struct inode *to_tell, u32 mask);
 383
 384 #else
 385
 386 static inline int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
 387                            const unsigned char *name, u32 cookie)
 388 {
 389         return 0;
 390 }
 391
 392 static inline int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask)
 393 {
 394         return 0;
 395 }
 396
 397 static inline void __fsnotify_inode_delete(struct inode *inode)
 398 {}
 399
 400 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 401 {}
 402
 403 static inline void fsnotify_update_flags(struct dentry *dentry)
 404 {}
 405
 406 static inline u32 fsnotify_get_cookie(void)
 407 {
 408         return 0;
 409 }
 410
 411 static inline void fsnotify_unmount_inodes(struct super_block *sb)
 412 {}
 413
 414 #endif  /* CONFIG_FSNOTIFY */
 415
 416 #endif  /* __KERNEL __ */
 417
 418 #endif  /* __LINUX_FSNOTIFY_BACKEND_H */