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 <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_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_IN_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)
  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_IN_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 - this means that a mark has been flagged to die when everything
  92  *              finishes using it.  The function is supplied with what must be a
  93  *              valid group and inode to use to clean up.
  94  */
  95 struct fsnotify_ops {
  96         bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode,
  97                                   struct fsnotify_mark *inode_mark,
  98                                   struct fsnotify_mark *vfsmount_mark,
  99                                   __u32 mask, void *data, int data_type);
 100         int (*handle_event)(struct fsnotify_group *group,
 101                             struct fsnotify_mark *inode_mark,
 102                             struct fsnotify_mark *vfsmount_mark,
 103                             struct fsnotify_event *event);
 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_priv)(struct fsnotify_event_private_data *priv);
 107 };
 108
 109 /*
 110  * A group is a "thing" that wants to receive notification about filesystem
 111  * events.  The mask holds the subset of event types this group cares about.
 112  * refcnt on a group is up to the implementor and at any moment if it goes 0
 113  * everything will be cleaned up.
 114  */
 115 struct fsnotify_group {
 116         /*
 117          * How the refcnt is used is up to each group.  When the refcnt hits 0
 118          * fsnotify will clean up all of the resources associated with this group.
 119          * As an example, the dnotify group will always have a refcnt=1 and that
 120          * will never change.  Inotify, on the other hand, has a group per
 121          * inotify_init() and the refcnt will hit 0 only when that fd has been
 122          * closed.
 123          */
 124         atomic_t refcnt;                /* things with interest in this group */
 125
 126         const struct fsnotify_ops *ops; /* how this group handles things */
 127
 128         /* needed to send notification to userspace */
 129         struct mutex notification_mutex;        /* protect the notification_list */
 130         struct list_head notification_list;     /* list of event_holder this group needs to send to userspace */
 131         wait_queue_head_t notification_waitq;   /* read() on the notification file blocks on this waitq */
 132         unsigned int q_len;                     /* events on the queue */
 133         unsigned int max_events;                /* maximum events allowed on the list */
 134         /*
 135          * Valid fsnotify group priorities.  Events are send in order from highest
 136          * priority to lowest priority.  We default to the lowest priority.
 137          */
 138         #define FS_PRIO_0       0 /* normal notifiers, no permissions */
 139         #define FS_PRIO_1       1 /* fanotify content based access control */
 140         #define FS_PRIO_2       2 /* fanotify pre-content access */
 141         unsigned int priority;
 142
 143         /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
 144         spinlock_t mark_lock;           /* protect marks_list */
 145         atomic_t num_marks;             /* 1 for each mark and 1 for not being
 146                                          * past the point of no return when freeing
 147                                          * a group */
 148         struct list_head marks_list;    /* all inode marks for this group */
 149
 150         /* groups can define private fields here or use the void *private */
 151         union {
 152                 void *private;
 153 #ifdef CONFIG_INOTIFY_USER
 154                 struct inotify_group_private_data {
 155                         spinlock_t      idr_lock;
 156                         struct idr      idr;
 157                         u32             last_wd;
 158                         struct fasync_struct    *fa;    /* async notification */
 159                         struct user_struct      *user;
 160                 } inotify_data;
 161 #endif
 162 #ifdef CONFIG_FANOTIFY
 163                 struct fanotify_group_private_data {
 164 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 165                         /* allows a group to block waiting for a userspace response */
 166                         struct mutex access_mutex;
 167                         struct list_head access_list;
 168                         wait_queue_head_t access_waitq;
 169                         bool bypass_perm; /* protected by access_mutex */
 170 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 171                         int f_flags;
 172                 } fanotify_data;
 173 #endif /* CONFIG_FANOTIFY */
 174         };
 175 };
 176
 177 /*
 178  * A single event can be queued in multiple group->notification_lists.
 179  *
 180  * each group->notification_list will point to an event_holder which in turns points
 181  * to the actual event that needs to be sent to userspace.
 182  *
 183  * Seemed cheaper to create a refcnt'd event and a small holder for every group
 184  * than create a different event for every group
 185  *
 186  */
 187 struct fsnotify_event_holder {
 188         struct fsnotify_event *event;
 189         struct list_head event_list;
 190 };
 191
 192 /*
 193  * Inotify needs to tack data onto an event.  This struct lets us later find the
 194  * correct private data of the correct group.
 195  */
 196 struct fsnotify_event_private_data {
 197         struct fsnotify_group *group;
 198         struct list_head event_list;
 199 };
 200
 201 /*
 202  * all of the information about the original object we want to now send to
 203  * a group.  If you want to carry more info from the accessing task to the
 204  * listener this structure is where you need to be adding fields.
 205  */
 206 struct fsnotify_event {
 207         /*
 208          * If we create an event we are also likely going to need a holder
 209          * to link to a group.  So embed one holder in the event.  Means only
 210          * one allocation for the common case where we only have one group
 211          */
 212         struct fsnotify_event_holder holder;
 213         spinlock_t lock;        /* protection for the associated event_holder and private_list */
 214         /* to_tell may ONLY be dereferenced during handle_event(). */
 215         struct inode *to_tell;  /* either the inode the event happened to or its parent */
 216         /*
 217          * depending on the event type we should have either a path or inode
 218          * We hold a reference on path, but NOT on inode.  Since we have the ref on
 219          * the path, it may be dereferenced at any point during this object's
 220          * lifetime.  That reference is dropped when this object's refcnt hits
 221          * 0.  If this event contains an inode instead of a path, the inode may
 222          * ONLY be used during handle_event().
 223          */
 224         union {
 225                 struct path path;
 226                 struct inode *inode;
 227         };
 228 /* when calling fsnotify tell it if the data is a path or inode */
 229 #define FSNOTIFY_EVENT_NONE     0
 230 #define FSNOTIFY_EVENT_PATH     1
 231 #define FSNOTIFY_EVENT_INODE    2
 232         int data_type;          /* which of the above union we have */
 233         atomic_t refcnt;        /* how many groups still are using/need to send this event */
 234         __u32 mask;             /* the type of access, bitwise OR for FS_* event types */
 235
 236         u32 sync_cookie;        /* used to corrolate events, namely inotify mv events */
 237         const unsigned char *file_name;
 238         size_t name_len;
 239         struct pid *tgid;
 240
 241 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 242         __u32 response; /* userspace answer to question */
 243 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 244
 245         struct list_head private_data_list;     /* groups can store private data here */
 246 };
 247
 248 /*
 249  * Inode specific fields in an fsnotify_mark
 250  */
 251 struct fsnotify_inode_mark {
 252         struct inode *inode;            /* inode this mark is associated with */
 253         struct hlist_node i_list;       /* list of marks by inode->i_fsnotify_marks */
 254         struct list_head free_i_list;   /* tmp list used when freeing this mark */
 255 };
 256
 257 /*
 258  * Mount point specific fields in an fsnotify_mark
 259  */
 260 struct fsnotify_vfsmount_mark {
 261         struct vfsmount *mnt;           /* vfsmount this mark is associated with */
 262         struct hlist_node m_list;       /* list of marks by inode->i_fsnotify_marks */
 263         struct list_head free_m_list;   /* tmp list used when freeing this mark */
 264 };
 265
 266 /*
 267  * a mark is simply an object attached to an in core inode which allows an
 268  * fsnotify listener to indicate they are either no longer interested in events
 269  * of a type matching mask or only interested in those events.
 270  *
 271  * these are flushed when an inode is evicted from core and may be flushed
 272  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify users
 273  * (such as dnotify) will flush these when the open fd is closed and not at
 274  * inode eviction or modification.
 275  */
 276 struct fsnotify_mark {
 277         __u32 mask;                     /* mask this mark is for */
 278         /* we hold ref for each i_list and g_list.  also one ref for each 'thing'
 279          * in kernel that found and may be using this mark. */
 280         atomic_t refcnt;                /* active things looking at this mark */
 281         struct fsnotify_group *group;   /* group this mark is for */
 282         struct list_head g_list;        /* list of marks by group->i_fsnotify_marks */
 283         spinlock_t lock;                /* protect group and inode */
 284         union {
 285                 struct fsnotify_inode_mark i;
 286                 struct fsnotify_vfsmount_mark m;
 287         };
 288         __u32 ignored_mask;             /* events types to ignore */
 289         struct list_head free_g_list;   /* tmp list used when freeing this mark */
 290 #define FSNOTIFY_MARK_FLAG_INODE                0x01
 291 #define FSNOTIFY_MARK_FLAG_VFSMOUNT             0x02
 292 #define FSNOTIFY_MARK_FLAG_OBJECT_PINNED        0x04
 293 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x08
 294 #define FSNOTIFY_MARK_FLAG_ALIVE                0x10
 295         unsigned int flags;             /* vfsmount or inode mark? */
 296         struct list_head destroy_list;
 297         void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
 298 };
 299
 300 #ifdef CONFIG_FSNOTIFY
 301
 302 /* called from the vfs helpers */
 303
 304 /* main fsnotify call to send events */
 305 extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 306                     const unsigned char *name, u32 cookie);
 307 extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
 308 extern void __fsnotify_inode_delete(struct inode *inode);
 309 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 310 extern u32 fsnotify_get_cookie(void);
 311
 312 static inline int fsnotify_inode_watches_children(struct inode *inode)
 313 {
 314         /* FS_EVENT_ON_CHILD is set if the inode may care */
 315         if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 316                 return 0;
 317         /* this inode might care about child events, does it care about the
 318          * specific set of events that can happen on a child? */
 319         return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 320 }
 321
 322 /*
 323  * Update the dentry with a flag indicating the interest of its parent to receive
 324  * filesystem events when those events happens to this dentry->d_inode.
 325  */
 326 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 327 {
 328         struct dentry *parent;
 329
 330         assert_spin_locked(&dcache_lock);
 331         assert_spin_locked(&dentry->d_lock);
 332
 333         parent = dentry->d_parent;
 334         if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
 335                 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 336         else
 337                 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 338 }
 339
 340 /*
 341  * fsnotify_d_instantiate - instantiate a dentry for inode
 342  * Called with dcache_lock held.
 343  */
 344 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 345 {
 346         if (!inode)
 347                 return;
 348
 349         assert_spin_locked(&dcache_lock);
 350
 351         spin_lock(&dentry->d_lock);
 352         __fsnotify_update_dcache_flags(dentry);
 353         spin_unlock(&dentry->d_lock);
 354 }
 355
 356 /* called from fsnotify listeners, such as fanotify or dnotify */
 357
 358 /* get a reference to an existing or create a new group */
 359 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
 360 /* drop reference on a group from fsnotify_alloc_group */
 361 extern void fsnotify_put_group(struct fsnotify_group *group);
 362
 363 /* take a reference to an event */
 364 extern void fsnotify_get_event(struct fsnotify_event *event);
 365 extern void fsnotify_put_event(struct fsnotify_event *event);
 366 /* find private data previously attached to an event and unlink it */
 367 extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
 368                                                                            struct fsnotify_event *event);
 369
 370 /* attach the event to the group notification queue */
 371 extern struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
 372                                                         struct fsnotify_event *event,
 373                                                         struct fsnotify_event_private_data *priv,
 374                                                         struct fsnotify_event *(*merge)(struct list_head *,
 375                                                                                         struct fsnotify_event *));
 376 /* true if the group notification queue is empty */
 377 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
 378 /* return, but do not dequeue the first event on the notification queue */
 379 extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
 380 /* return AND dequeue the first event on the notification queue */
 381 extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
 382
 383 /* functions used to manipulate the marks attached to inodes */
 384
 385 /* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
 386 extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
 387 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
 388 extern void fsnotify_recalc_inode_mask(struct inode *inode);
 389 extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
 390 /* find (and take a reference) to a mark associated with group and inode */
 391 extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
 392 /* find (and take a reference) to a mark associated with group and vfsmount */
 393 extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
 394 /* copy the values from old into new */
 395 extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
 396 /* set the ignored_mask of a mark */
 397 extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 398 /* set the mask of a mark (might pin the object into memory */
 399 extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 400 /* attach the mark to both the group and the inode */
 401 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
 402                              struct inode *inode, struct vfsmount *mnt, int allow_dups);
 403 /* given a mark, flag it to be freed when all references are dropped */
 404 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark);
 405 /* run all the marks in a group, and clear all of the vfsmount marks */
 406 extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
 407 /* run all the marks in a group, and clear all of the inode marks */
 408 extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
 409 /* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
 410 extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
 411 /* run all the marks in a group, and flag them to be freed */
 412 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
 413 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 414 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 415 extern void fsnotify_unmount_inodes(struct list_head *list);
 416
 417 /* put here because inotify does some weird stuff when destroying watches */
 418 extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
 419                                                     void *data, int data_is,
 420                                                     const unsigned char *name,
 421                                                     u32 cookie, gfp_t gfp);
 422
 423 /* fanotify likes to change events after they are on lists... */
 424 extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
 425 extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
 426                                   struct fsnotify_event *new_event);
 427
 428 #else
 429
 430 static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 431                            const unsigned char *name, u32 cookie)
 432 {
 433         return 0;
 434 }
 435
 436 static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
 437 {
 438         return 0;
 439 }
 440
 441 static inline void __fsnotify_inode_delete(struct inode *inode)
 442 {}
 443
 444 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 445 {}
 446
 447 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 448 {}
 449
 450 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 451 {}
 452
 453 static inline u32 fsnotify_get_cookie(void)
 454 {
 455         return 0;
 456 }
 457
 458 static inline void fsnotify_unmount_inodes(struct list_head *list)
 459 {}
 460
 461 #endif  /* CONFIG_FSNOTIFY */
 462
 463 #endif  /* __KERNEL __ */
 464
 465 #endif  /* __LINUX_FSNOTIFY_BACKEND_H */