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_EVENTS (FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
  68                              FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN | \
  69                              FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
  70                              FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
  71                              FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
  72                              FS_OPEN_PERM | FS_ACCESS_PERM | FS_EXCL_UNLINK | \
  73                              FS_IN_ISDIR | FS_IN_ONESHOT | FS_DN_RENAME | \
  74                              FS_DN_MULTISHOT | FS_EVENT_ON_CHILD)
  75
  76 struct fsnotify_group;
  77 struct fsnotify_event;
  78 struct fsnotify_mark;
  79 struct fsnotify_event_private_data;
  80
  81 /*
  82  * Each group much define these ops.  The fsnotify infrastructure will call
  83  * these operations for each relevant group.
  84  *
  85  * should_send_event - given a group, inode, and mask this function determines
  86  *              if the group is interested in this event.
  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 - this means that a mark has been flagged to die when everything
  90  *              finishes using it.  The function is supplied with what must be a
  91  *              valid group and inode to use to clean up.
  92  */
  93 struct fsnotify_ops {
  94         bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode,
  95                                   struct fsnotify_mark *inode_mark,
  96                                   struct fsnotify_mark *vfsmount_mark,
  97                                   __u32 mask, void *data, int data_type);
  98         int (*handle_event)(struct fsnotify_group *group,
  99                             struct fsnotify_mark *inode_mark,
 100                             struct fsnotify_mark *vfsmount_mark,
 101                             struct fsnotify_event *event);
 102         void (*free_group_priv)(struct fsnotify_group *group);
 103         void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
 104         void (*free_event_priv)(struct fsnotify_event_private_data *priv);
 105 };
 106
 107 /*
 108  * A group is a "thing" that wants to receive notification about filesystem
 109  * events.  The mask holds the subset of event types this group cares about.
 110  * refcnt on a group is up to the implementor and at any moment if it goes 0
 111  * everything will be cleaned up.
 112  */
 113 struct fsnotify_group {
 114         /*
 115          * How the refcnt is used is up to each group.  When the refcnt hits 0
 116          * fsnotify will clean up all of the resources associated with this group.
 117          * As an example, the dnotify group will always have a refcnt=1 and that
 118          * will never change.  Inotify, on the other hand, has a group per
 119          * inotify_init() and the refcnt will hit 0 only when that fd has been
 120          * closed.
 121          */
 122         atomic_t refcnt;                /* things with interest in this group */
 123
 124         const struct fsnotify_ops *ops; /* how this group handles things */
 125
 126         /* needed to send notification to userspace */
 127         struct mutex notification_mutex;        /* protect the notification_list */
 128         struct list_head notification_list;     /* list of event_holder this group needs to send to userspace */
 129         wait_queue_head_t notification_waitq;   /* read() on the notification file blocks on this waitq */
 130         unsigned int q_len;                     /* events on the queue */
 131         unsigned int max_events;                /* maximum events allowed on the list */
 132
 133         /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
 134         spinlock_t mark_lock;           /* protect marks_list */
 135         atomic_t num_marks;             /* 1 for each mark and 1 for not being
 136                                          * past the point of no return when freeing
 137                                          * a group */
 138         struct list_head marks_list;    /* all inode marks for this group */
 139
 140         /* groups can define private fields here or use the void *private */
 141         union {
 142                 void *private;
 143 #ifdef CONFIG_INOTIFY_USER
 144                 struct inotify_group_private_data {
 145                         spinlock_t      idr_lock;
 146                         struct idr      idr;
 147                         u32             last_wd;
 148                         struct fasync_struct    *fa;    /* async notification */
 149                         struct user_struct      *user;
 150                 } inotify_data;
 151 #endif
 152 #ifdef CONFIG_FANOTIFY
 153                 struct fanotify_group_private_data {
 154 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 155                         /* allows a group to block waiting for a userspace response */
 156                         struct mutex access_mutex;
 157                         struct list_head access_list;
 158                         wait_queue_head_t access_waitq;
 159                         bool bypass_perm; /* protected by access_mutex */
 160 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 161                         int f_flags;
 162                 } fanotify_data;
 163 #endif /* CONFIG_FANOTIFY */
 164         };
 165 };
 166
 167 /*
 168  * A single event can be queued in multiple group->notification_lists.
 169  *
 170  * each group->notification_list will point to an event_holder which in turns points
 171  * to the actual event that needs to be sent to userspace.
 172  *
 173  * Seemed cheaper to create a refcnt'd event and a small holder for every group
 174  * than create a different event for every group
 175  *
 176  */
 177 struct fsnotify_event_holder {
 178         struct fsnotify_event *event;
 179         struct list_head event_list;
 180 };
 181
 182 /*
 183  * Inotify needs to tack data onto an event.  This struct lets us later find the
 184  * correct private data of the correct group.
 185  */
 186 struct fsnotify_event_private_data {
 187         struct fsnotify_group *group;
 188         struct list_head event_list;
 189 };
 190
 191 /*
 192  * all of the information about the original object we want to now send to
 193  * a group.  If you want to carry more info from the accessing task to the
 194  * listener this structure is where you need to be adding fields.
 195  */
 196 struct fsnotify_event {
 197         /*
 198          * If we create an event we are also likely going to need a holder
 199          * to link to a group.  So embed one holder in the event.  Means only
 200          * one allocation for the common case where we only have one group
 201          */
 202         struct fsnotify_event_holder holder;
 203         spinlock_t lock;        /* protection for the associated event_holder and private_list */
 204         /* to_tell may ONLY be dereferenced during handle_event(). */
 205         struct inode *to_tell;  /* either the inode the event happened to or its parent */
 206         /*
 207          * depending on the event type we should have either a path or inode
 208          * We hold a reference on path, but NOT on inode.  Since we have the ref on
 209          * the path, it may be dereferenced at any point during this object's
 210          * lifetime.  That reference is dropped when this object's refcnt hits
 211          * 0.  If this event contains an inode instead of a path, the inode may
 212          * ONLY be used during handle_event().
 213          */
 214         union {
 215                 struct path path;
 216                 struct inode *inode;
 217         };
 218 /* when calling fsnotify tell it if the data is a path or inode */
 219 #define FSNOTIFY_EVENT_NONE     0
 220 #define FSNOTIFY_EVENT_PATH     1
 221 #define FSNOTIFY_EVENT_INODE    2
 222         int data_type;          /* which of the above union we have */
 223         atomic_t refcnt;        /* how many groups still are using/need to send this event */
 224         __u32 mask;             /* the type of access, bitwise OR for FS_* event types */
 225
 226         u32 sync_cookie;        /* used to corrolate events, namely inotify mv events */
 227         const unsigned char *file_name;
 228         size_t name_len;
 229         struct pid *tgid;
 230
 231 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 232         __u32 response; /* userspace answer to question */
 233 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 234
 235         struct list_head private_data_list;     /* groups can store private data here */
 236 };
 237
 238 /*
 239  * Inode specific fields in an fsnotify_mark
 240  */
 241 struct fsnotify_inode_mark {
 242         struct inode *inode;            /* inode this mark is associated with */
 243         struct hlist_node i_list;       /* list of marks by inode->i_fsnotify_marks */
 244         struct list_head free_i_list;   /* tmp list used when freeing this mark */
 245 };
 246
 247 /*
 248  * Mount point specific fields in an fsnotify_mark
 249  */
 250 struct fsnotify_vfsmount_mark {
 251         struct vfsmount *mnt;           /* vfsmount this mark is associated with */
 252         struct hlist_node m_list;       /* list of marks by inode->i_fsnotify_marks */
 253         struct list_head free_m_list;   /* tmp list used when freeing this mark */
 254 };
 255
 256 /*
 257  * a mark is simply an object attached to an in core inode which allows an
 258  * fsnotify listener to indicate they are either no longer interested in events
 259  * of a type matching mask or only interested in those events.
 260  *
 261  * these are flushed when an inode is evicted from core and may be flushed
 262  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify users
 263  * (such as dnotify) will flush these when the open fd is closed and not at
 264  * inode eviction or modification.
 265  */
 266 struct fsnotify_mark {
 267         __u32 mask;                     /* mask this mark is for */
 268         /* we hold ref for each i_list and g_list.  also one ref for each 'thing'
 269          * in kernel that found and may be using this mark. */
 270         atomic_t refcnt;                /* active things looking at this mark */
 271         struct fsnotify_group *group;   /* group this mark is for */
 272         struct list_head g_list;        /* list of marks by group->i_fsnotify_marks */
 273         spinlock_t lock;                /* protect group and inode */
 274         union {
 275                 struct fsnotify_inode_mark i;
 276                 struct fsnotify_vfsmount_mark m;
 277         };
 278         __u32 ignored_mask;             /* events types to ignore */
 279         struct list_head free_g_list;   /* tmp list used when freeing this mark */
 280 #define FSNOTIFY_MARK_FLAG_INODE                0x01
 281 #define FSNOTIFY_MARK_FLAG_VFSMOUNT             0x02
 282 #define FSNOTIFY_MARK_FLAG_OBJECT_PINNED        0x04
 283 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x08
 284 #define FSNOTIFY_MARK_FLAG_ALIVE                0x10
 285         unsigned int flags;             /* vfsmount or inode mark? */
 286         struct list_head destroy_list;
 287         void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
 288 };
 289
 290 #ifdef CONFIG_FSNOTIFY
 291
 292 /* called from the vfs helpers */
 293
 294 /* main fsnotify call to send events */
 295 extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 296                     const unsigned char *name, u32 cookie);
 297 extern void __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
 298 extern void __fsnotify_inode_delete(struct inode *inode);
 299 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 300 extern u32 fsnotify_get_cookie(void);
 301
 302 static inline int fsnotify_inode_watches_children(struct inode *inode)
 303 {
 304         /* FS_EVENT_ON_CHILD is set if the inode may care */
 305         if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 306                 return 0;
 307         /* this inode might care about child events, does it care about the
 308          * specific set of events that can happen on a child? */
 309         return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 310 }
 311
 312 /*
 313  * Update the dentry with a flag indicating the interest of its parent to receive
 314  * filesystem events when those events happens to this dentry->d_inode.
 315  */
 316 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 317 {
 318         struct dentry *parent;
 319
 320         assert_spin_locked(&dcache_lock);
 321         assert_spin_locked(&dentry->d_lock);
 322
 323         parent = dentry->d_parent;
 324         if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
 325                 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 326         else
 327                 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 328 }
 329
 330 /*
 331  * fsnotify_d_instantiate - instantiate a dentry for inode
 332  * Called with dcache_lock held.
 333  */
 334 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 335 {
 336         if (!inode)
 337                 return;
 338
 339         assert_spin_locked(&dcache_lock);
 340
 341         spin_lock(&dentry->d_lock);
 342         __fsnotify_update_dcache_flags(dentry);
 343         spin_unlock(&dentry->d_lock);
 344 }
 345
 346 /* called from fsnotify listeners, such as fanotify or dnotify */
 347
 348 /* get a reference to an existing or create a new group */
 349 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
 350 /* drop reference on a group from fsnotify_alloc_group */
 351 extern void fsnotify_put_group(struct fsnotify_group *group);
 352
 353 /* take a reference to an event */
 354 extern void fsnotify_get_event(struct fsnotify_event *event);
 355 extern void fsnotify_put_event(struct fsnotify_event *event);
 356 /* find private data previously attached to an event and unlink it */
 357 extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
 358                                                                            struct fsnotify_event *event);
 359
 360 /* attach the event to the group notification queue */
 361 extern struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
 362                                                         struct fsnotify_event *event,
 363                                                         struct fsnotify_event_private_data *priv,
 364                                                         struct fsnotify_event *(*merge)(struct list_head *,
 365                                                                                         struct fsnotify_event *));
 366 /* true if the group notification queue is empty */
 367 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
 368 /* return, but do not dequeue the first event on the notification queue */
 369 extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
 370 /* return AND dequeue the first event on the notification queue */
 371 extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
 372
 373 /* functions used to manipulate the marks attached to inodes */
 374
 375 /* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
 376 extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
 377 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
 378 extern void fsnotify_recalc_inode_mask(struct inode *inode);
 379 extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
 380 /* find (and take a reference) to a mark associated with group and inode */
 381 extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
 382 /* find (and take a reference) to a mark associated with group and vfsmount */
 383 extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
 384 /* copy the values from old into new */
 385 extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
 386 /* set the ignored_mask of a mark */
 387 extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 388 /* set the mask of a mark (might pin the object into memory */
 389 extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 390 /* attach the mark to both the group and the inode */
 391 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
 392                              struct inode *inode, struct vfsmount *mnt, int allow_dups);
 393 /* given a mark, flag it to be freed when all references are dropped */
 394 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark);
 395 /* run all the marks in a group, and clear all of the vfsmount marks */
 396 extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
 397 /* run all the marks in a group, and clear all of the inode marks */
 398 extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
 399 /* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
 400 extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
 401 /* run all the marks in a group, and flag them to be freed */
 402 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
 403 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 404 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 405 extern void fsnotify_unmount_inodes(struct list_head *list);
 406
 407 /* put here because inotify does some weird stuff when destroying watches */
 408 extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
 409                                                     void *data, int data_is,
 410                                                     const unsigned char *name,
 411                                                     u32 cookie, gfp_t gfp);
 412
 413 /* fanotify likes to change events after they are on lists... */
 414 extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
 415 extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
 416                                   struct fsnotify_event *new_event);
 417
 418 #else
 419
 420 static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 421                            const unsigned char *name, u32 cookie)
 422 {
 423         return 0;
 424 }
 425
 426 static inline void __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
 427 {}
 428
 429 static inline void __fsnotify_inode_delete(struct inode *inode)
 430 {}
 431
 432 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 433 {}
 434
 435 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 436 {}
 437
 438 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 439 {}
 440
 441 static inline u32 fsnotify_get_cookie(void)
 442 {
 443         return 0;
 444 }
 445
 446 static inline void fsnotify_unmount_inodes(struct list_head *list)
 447 {}
 448
 449 #endif  /* CONFIG_FSNOTIFY */
 450
 451 #endif  /* __KERNEL __ */
 452
 453 #endif  /* __LINUX_FSNOTIFY_BACKEND_H */