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 vfsmount *mnt, __u32 mask, void *data,
  96                                   int data_type);
  97         int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
  98         void (*free_group_priv)(struct fsnotify_group *group);
  99         void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
 100         void (*free_event_priv)(struct fsnotify_event_private_data *priv);
 101 };
 102
 103 /*
 104  * A group is a "thing" that wants to receive notification about filesystem
 105  * events.  The mask holds the subset of event types this group cares about.
 106  * refcnt on a group is up to the implementor and at any moment if it goes 0
 107  * everything will be cleaned up.
 108  */
 109 struct fsnotify_group {
 110         /*
 111          * global list of all groups receiving events from fsnotify.
 112          * anchored by fsnotify_inode_groups and protected by either fsnotify_grp_mutex
 113          * or fsnotify_grp_srcu depending on write vs read.
 114          */
 115         struct list_head inode_group_list;
 116         /*
 117          * same as above except anchored by fsnotify_vfsmount_groups
 118          */
 119         struct list_head vfsmount_group_list;
 120
 121         /*
 122          * Defines all of the event types in which this group is interested.
 123          * This mask is a bitwise OR of the FS_* events from above.  Each time
 124          * this mask changes for a group (if it changes) the correct functions
 125          * must be called to update the global structures which indicate global
 126          * interest in event types.
 127          */
 128         __u32 mask;
 129
 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         struct mutex notification_mutex;        /* 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         /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
 150         spinlock_t mark_lock;           /* protect marks_list */
 151         atomic_t num_marks;             /* 1 for each mark and 1 for not being
 152                                          * past the point of no return when freeing
 153                                          * a group */
 154         struct list_head marks_list;    /* all inode marks for this group */
 155
 156         /* prevents double list_del of group_list.  protected by global fsnotify_grp_mutex */
 157         bool on_inode_group_list;
 158         bool on_vfsmount_group_list;
 159
 160         /* groups can define private fields here or use the void *private */
 161         union {
 162                 void *private;
 163 #ifdef CONFIG_INOTIFY_USER
 164                 struct inotify_group_private_data {
 165                         spinlock_t      idr_lock;
 166                         struct idr      idr;
 167                         u32             last_wd;
 168                         struct fasync_struct    *fa;    /* async notification */
 169                         struct user_struct      *user;
 170                 } inotify_data;
 171 #endif
 172 #ifdef CONFIG_FANOTIFY
 173                 struct fanotify_group_private_data {
 174 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 175                         /* allows a group to block waiting for a userspace response */
 176                         struct mutex access_mutex;
 177                         struct list_head access_list;
 178                         wait_queue_head_t access_waitq;
 179 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 180                         int f_flags;
 181                 } fanotify_data;
 182 #endif /* CONFIG_FANOTIFY */
 183         };
 184 };
 185
 186 /*
 187  * A single event can be queued in multiple group->notification_lists.
 188  *
 189  * each group->notification_list will point to an event_holder which in turns points
 190  * to the actual event that needs to be sent to userspace.
 191  *
 192  * Seemed cheaper to create a refcnt'd event and a small holder for every group
 193  * than create a different event for every group
 194  *
 195  */
 196 struct fsnotify_event_holder {
 197         struct fsnotify_event *event;
 198         struct list_head event_list;
 199 };
 200
 201 /*
 202  * Inotify needs to tack data onto an event.  This struct lets us later find the
 203  * correct private data of the correct group.
 204  */
 205 struct fsnotify_event_private_data {
 206         struct fsnotify_group *group;
 207         struct list_head event_list;
 208 };
 209
 210 /*
 211  * all of the information about the original object we want to now send to
 212  * a group.  If you want to carry more info from the accessing task to the
 213  * listener this structure is where you need to be adding fields.
 214  */
 215 struct fsnotify_event {
 216         /*
 217          * If we create an event we are also likely going to need a holder
 218          * to link to a group.  So embed one holder in the event.  Means only
 219          * one allocation for the common case where we only have one group
 220          */
 221         struct fsnotify_event_holder holder;
 222         spinlock_t lock;        /* protection for the associated event_holder and private_list */
 223         /* to_tell may ONLY be dereferenced during handle_event(). */
 224         struct inode *to_tell;  /* either the inode the event happened to or its parent */
 225         /*
 226          * depending on the event type we should have either a file or inode
 227          * We hold a reference on file, but NOT on inode.  Since we have the ref on
 228          * the file, it may be dereferenced at any point during this object's
 229          * lifetime.  That reference is dropped when this object's refcnt hits
 230          * 0.  If this event contains an inode instead of a file, the inode may
 231          * ONLY be used during handle_event().
 232          */
 233         union {
 234                 struct file *file;
 235                 struct inode *inode;
 236         };
 237 /* when calling fsnotify tell it if the data is a path or inode */
 238 #define FSNOTIFY_EVENT_NONE     0
 239 #define FSNOTIFY_EVENT_FILE     1
 240 #define FSNOTIFY_EVENT_INODE    2
 241         int data_type;          /* which of the above union we have */
 242         atomic_t refcnt;        /* how many groups still are using/need to send this event */
 243         __u32 mask;             /* the type of access, bitwise OR for FS_* event types */
 244
 245         u32 sync_cookie;        /* used to corrolate events, namely inotify mv events */
 246         const unsigned char *file_name;
 247         size_t name_len;
 248         struct pid *tgid;
 249
 250 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 251         __u32 response; /* userspace answer to question */
 252 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 253
 254         struct list_head private_data_list;     /* groups can store private data here */
 255 };
 256
 257 /*
 258  * Inode specific fields in an fsnotify_mark
 259  */
 260 struct fsnotify_inode_mark {
 261         struct inode *inode;            /* inode this mark is associated with */
 262         struct hlist_node i_list;       /* list of marks by inode->i_fsnotify_marks */
 263         struct list_head free_i_list;   /* tmp list used when freeing this mark */
 264 };
 265
 266 /*
 267  * Mount point specific fields in an fsnotify_mark
 268  */
 269 struct fsnotify_vfsmount_mark {
 270         struct vfsmount *mnt;           /* vfsmount this mark is associated with */
 271         struct hlist_node m_list;       /* list of marks by inode->i_fsnotify_marks */
 272         struct list_head free_m_list;   /* tmp list used when freeing this mark */
 273 };
 274
 275 /*
 276  * a mark is simply an object attached to an in core inode which allows an
 277  * fsnotify listener to indicate they are either no longer interested in events
 278  * of a type matching mask or only interested in those events.
 279  *
 280  * these are flushed when an inode is evicted from core and may be flushed
 281  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify users
 282  * (such as dnotify) will flush these when the open fd is closed and not at
 283  * inode eviction or modification.
 284  */
 285 struct fsnotify_mark {
 286         __u32 mask;                     /* mask this mark is for */
 287         /* we hold ref for each i_list and g_list.  also one ref for each 'thing'
 288          * in kernel that found and may be using this mark. */
 289         atomic_t refcnt;                /* active things looking at this mark */
 290         struct fsnotify_group *group;   /* group this mark is for */
 291         struct list_head g_list;        /* list of marks by group->i_fsnotify_marks */
 292         spinlock_t lock;                /* protect group and inode */
 293         union {
 294                 struct fsnotify_inode_mark i;
 295                 struct fsnotify_vfsmount_mark m;
 296         };
 297         __u32 ignored_mask;             /* events types to ignore */
 298         struct list_head free_g_list;   /* tmp list used when freeing this mark */
 299 #define FSNOTIFY_MARK_FLAG_INODE                0x01
 300 #define FSNOTIFY_MARK_FLAG_VFSMOUNT             0x02
 301 #define FSNOTIFY_MARK_FLAG_OBJECT_PINNED        0x04
 302 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x08
 303         unsigned int flags;             /* vfsmount or inode mark? */
 304         void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
 305 };
 306
 307 #ifdef CONFIG_FSNOTIFY
 308
 309 /* called from the vfs helpers */
 310
 311 /* main fsnotify call to send events */
 312 extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 313                     const unsigned char *name, u32 cookie);
 314 extern void __fsnotify_parent(struct file *file, struct dentry *dentry, __u32 mask);
 315 extern void __fsnotify_inode_delete(struct inode *inode);
 316 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 317 extern u32 fsnotify_get_cookie(void);
 318
 319 static inline int fsnotify_inode_watches_children(struct inode *inode)
 320 {
 321         /* FS_EVENT_ON_CHILD is set if the inode may care */
 322         if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 323                 return 0;
 324         /* this inode might care about child events, does it care about the
 325          * specific set of events that can happen on a child? */
 326         return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 327 }
 328
 329 /*
 330  * Update the dentry with a flag indicating the interest of its parent to receive
 331  * filesystem events when those events happens to this dentry->d_inode.
 332  */
 333 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 334 {
 335         struct dentry *parent;
 336
 337         assert_spin_locked(&dcache_lock);
 338         assert_spin_locked(&dentry->d_lock);
 339
 340         parent = dentry->d_parent;
 341         if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
 342                 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 343         else
 344                 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 345 }
 346
 347 /*
 348  * fsnotify_d_instantiate - instantiate a dentry for inode
 349  * Called with dcache_lock held.
 350  */
 351 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 352 {
 353         if (!inode)
 354                 return;
 355
 356         assert_spin_locked(&dcache_lock);
 357
 358         spin_lock(&dentry->d_lock);
 359         __fsnotify_update_dcache_flags(dentry);
 360         spin_unlock(&dentry->d_lock);
 361 }
 362
 363 /* called from fsnotify listeners, such as fanotify or dnotify */
 364
 365 /* must call when a group changes its ->mask */
 366 extern void fsnotify_recalc_global_mask(void);
 367 /* get a reference to an existing or create a new group */
 368 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
 369 /* run all marks associated with this group and update group->mask */
 370 extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
 371 /* drop reference on a group from fsnotify_alloc_group */
 372 extern void fsnotify_put_group(struct fsnotify_group *group);
 373
 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 /* given a mark, flag it to be freed when all references are dropped */
 415 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark);
 416 /* run all the marks in a group, and clear all of the vfsmount marks */
 417 extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
 418 /* run all the marks in a group, and clear all of the inode marks */
 419 extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
 420 /* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
 421 extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
 422 /* run all the marks in a group, and flag them to be freed */
 423 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
 424 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 425 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 426 extern void fsnotify_unmount_inodes(struct list_head *list);
 427
 428 /* put here because inotify does some weird stuff when destroying watches */
 429 extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
 430                                                     void *data, int data_is,
 431                                                     const unsigned char *name,
 432                                                     u32 cookie, gfp_t gfp);
 433
 434 /* fanotify likes to change events after they are on lists... */
 435 extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
 436 extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
 437                                   struct fsnotify_event *new_event);
 438
 439 #else
 440
 441 static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 442                            const unsigned char *name, u32 cookie)
 443 {
 444         return 0;
 445 }
 446
 447 static inline void __fsnotify_parent(struct file *file, struct dentry *dentry, __u32 mask)
 448 {}
 449
 450 static inline void __fsnotify_inode_delete(struct inode *inode)
 451 {}
 452
 453 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 454 {}
 455
 456 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 457 {}
 458
 459 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 460 {}
 461
 462 static inline u32 fsnotify_get_cookie(void)
 463 {
 464         return 0;
 465 }
 466
 467 static inline void fsnotify_unmount_inodes(struct list_head *list)
 468 {}
 469
 470 #endif  /* CONFIG_FSNOTIFY */
 471
 472 #endif  /* __KERNEL __ */
 473
 474 #endif  /* __LINUX_FSNOTIFY_BACKEND_H */