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
  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 */