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_IN_ISDIR             0x40000000      /* event occurred against dir */
  45 #define FS_IN_ONESHOT           0x80000000      /* only send event once */
  46
  47 #define FS_DN_RENAME            0x10000000      /* file renamed */
  48 #define FS_DN_MULTISHOT         0x20000000      /* dnotify multishot */
  49
  50 /* This inode cares about things that happen to its children.  Always set for
  51  * dnotify and inotify. */
  52 #define FS_EVENT_ON_CHILD       0x08000000
  53
  54 /* This is a list of all events that may get sent to a parernt based on fs event
  55  * happening to inodes inside that directory */
  56 #define FS_EVENTS_POSS_ON_CHILD   (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
  57                                    FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
  58                                    FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
  59                                    FS_DELETE)
  60
  61 #define FS_MOVE                 (FS_MOVED_FROM | FS_MOVED_TO)
  62
  63 struct fsnotify_group;
  64 struct fsnotify_event;
  65 struct fsnotify_mark;
  66 struct fsnotify_event_private_data;
  67
  68 /*
  69  * Each group much define these ops.  The fsnotify infrastructure will call
  70  * these operations for each relevant group.
  71  *
  72  * should_send_event - given a group, inode, and mask this function determines
  73  *              if the group is interested in this event.
  74  * handle_event - main call for a group to handle an fs event
  75  * free_group_priv - called when a group refcnt hits 0 to clean up the private union
  76  * freeing-mark - this means that a mark has been flagged to die when everything
  77  *              finishes using it.  The function is supplied with what must be a
  78  *              valid group and inode to use to clean up.
  79  */
  80 struct fsnotify_ops {
  81         bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode,
  82                                   struct vfsmount *mnt, __u32 mask, void *data,
  83                                   int data_type);
  84         int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
  85         void (*free_group_priv)(struct fsnotify_group *group);
  86         void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
  87         void (*free_event_priv)(struct fsnotify_event_private_data *priv);
  88 };
  89
  90 /*
  91  * A group is a "thing" that wants to receive notification about filesystem
  92  * events.  The mask holds the subset of event types this group cares about.
  93  * refcnt on a group is up to the implementor and at any moment if it goes 0
  94  * everything will be cleaned up.
  95  */
  96 struct fsnotify_group {
  97         /*
  98          * global list of all groups receiving events from fsnotify.
  99          * anchored by fsnotify_inode_groups and protected by either fsnotify_grp_mutex
 100          * or fsnotify_grp_srcu depending on write vs read.
 101          */
 102         struct list_head inode_group_list;
 103         /*
 104          * same as above except anchored by fsnotify_vfsmount_groups
 105          */
 106         struct list_head vfsmount_group_list;
 107
 108         /*
 109          * Defines all of the event types in which this group is interested.
 110          * This mask is a bitwise OR of the FS_* events from above.  Each time
 111          * this mask changes for a group (if it changes) the correct functions
 112          * must be called to update the global structures which indicate global
 113          * interest in event types.
 114          */
 115         __u32 mask;
 116
 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         /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
 137         spinlock_t mark_lock;           /* protect marks_list */
 138         atomic_t num_marks;             /* 1 for each mark and 1 for not being
 139                                          * past the point of no return when freeing
 140                                          * a group */
 141         struct list_head marks_list;    /* all inode marks for this group */
 142
 143         /* prevents double list_del of group_list.  protected by global fsnotify_grp_mutex */
 144         bool on_inode_group_list;
 145         bool on_vfsmount_group_list;
 146
 147         /* groups can define private fields here or use the void *private */
 148         union {
 149                 void *private;
 150 #ifdef CONFIG_INOTIFY_USER
 151                 struct inotify_group_private_data {
 152                         spinlock_t      idr_lock;
 153                         struct idr      idr;
 154                         u32             last_wd;
 155                         struct fasync_struct    *fa;    /* async notification */
 156                         struct user_struct      *user;
 157                 } inotify_data;
 158 #endif
 159         };
 160 };
 161
 162 /*
 163  * A single event can be queued in multiple group->notification_lists.
 164  *
 165  * each group->notification_list will point to an event_holder which in turns points
 166  * to the actual event that needs to be sent to userspace.
 167  *
 168  * Seemed cheaper to create a refcnt'd event and a small holder for every group
 169  * than create a different event for every group
 170  *
 171  */
 172 struct fsnotify_event_holder {
 173         struct fsnotify_event *event;
 174         struct list_head event_list;
 175 };
 176
 177 /*
 178  * Inotify needs to tack data onto an event.  This struct lets us later find the
 179  * correct private data of the correct group.
 180  */
 181 struct fsnotify_event_private_data {
 182         struct fsnotify_group *group;
 183         struct list_head event_list;
 184 };
 185
 186 /*
 187  * all of the information about the original object we want to now send to
 188  * a group.  If you want to carry more info from the accessing task to the
 189  * listener this structure is where you need to be adding fields.
 190  */
 191 struct fsnotify_event {
 192         /*
 193          * If we create an event we are also likely going to need a holder
 194          * to link to a group.  So embed one holder in the event.  Means only
 195          * one allocation for the common case where we only have one group
 196          */
 197         struct fsnotify_event_holder holder;
 198         spinlock_t lock;        /* protection for the associated event_holder and private_list */
 199         /* to_tell may ONLY be dereferenced during handle_event(). */
 200         struct inode *to_tell;  /* either the inode the event happened to or its parent */
 201         /*
 202          * depending on the event type we should have either a path or inode
 203          * We hold a reference on path, but NOT on inode.  Since we have the ref on
 204          * the path, it may be dereferenced at any point during this object's
 205          * lifetime.  That reference is dropped when this object's refcnt hits
 206          * 0.  If this event contains an inode instead of a path, the inode may
 207          * ONLY be used during handle_event().
 208          */
 209         union {
 210                 struct path path;
 211                 struct inode *inode;
 212         };
 213 /* when calling fsnotify tell it if the data is a path or inode */
 214 #define FSNOTIFY_EVENT_NONE     0
 215 #define FSNOTIFY_EVENT_PATH     1
 216 #define FSNOTIFY_EVENT_INODE    2
 217         int data_type;          /* which of the above union we have */
 218         atomic_t refcnt;        /* how many groups still are using/need to send this event */
 219         __u32 mask;             /* the type of access, bitwise OR for FS_* event types */
 220
 221         u32 sync_cookie;        /* used to corrolate events, namely inotify mv events */
 222         char *file_name;
 223         size_t name_len;
 224         struct pid *tgid;
 225
 226         struct list_head private_data_list;     /* groups can store private data here */
 227 };
 228
 229 /*
 230  * Inode specific fields in an fsnotify_mark
 231  */
 232 struct fsnotify_inode_mark {
 233         struct inode *inode;            /* inode this mark is associated with */
 234         struct hlist_node i_list;       /* list of marks by inode->i_fsnotify_marks */
 235         struct list_head free_i_list;   /* tmp list used when freeing this mark */
 236 };
 237
 238 /*
 239  * Mount point specific fields in an fsnotify_mark
 240  */
 241 struct fsnotify_vfsmount_mark {
 242         struct vfsmount *mnt;           /* vfsmount this mark is associated with */
 243         struct hlist_node m_list;       /* list of marks by inode->i_fsnotify_marks */
 244         struct list_head free_m_list;   /* tmp list used when freeing this mark */
 245 };
 246
 247 /*
 248  * a mark is simply an object attached to an in core inode which allows an
 249  * fsnotify listener to indicate they are either no longer interested in events
 250  * of a type matching mask or only interested in those events.
 251  *
 252  * these are flushed when an inode is evicted from core and may be flushed
 253  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify users
 254  * (such as dnotify) will flush these when the open fd is closed and not at
 255  * inode eviction or modification.
 256  */
 257 struct fsnotify_mark {
 258         __u32 mask;                     /* mask this mark is for */
 259         /* we hold ref for each i_list and g_list.  also one ref for each 'thing'
 260          * in kernel that found and may be using this mark. */
 261         atomic_t refcnt;                /* active things looking at this mark */
 262         struct fsnotify_group *group;   /* group this mark is for */
 263         struct list_head g_list;        /* list of marks by group->i_fsnotify_marks */
 264         spinlock_t lock;                /* protect group and inode */
 265         union {
 266                 struct fsnotify_inode_mark i;
 267                 struct fsnotify_vfsmount_mark m;
 268         };
 269         struct list_head free_g_list;   /* tmp list used when freeing this mark */
 270 #define FSNOTIFY_MARK_FLAG_INODE                0x01
 271 #define FSNOTIFY_MARK_FLAG_VFSMOUNT             0x02
 272 #define FSNOTIFY_MARK_FLAG_OBJECT_PINNED        0x04
 273         unsigned int flags;             /* vfsmount or inode mark? */
 274         void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
 275 };
 276
 277 #ifdef CONFIG_FSNOTIFY
 278
 279 /* called from the vfs helpers */
 280
 281 /* main fsnotify call to send events */
 282 extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 283                      const char *name, u32 cookie);
 284 extern void __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
 285 extern void __fsnotify_inode_delete(struct inode *inode);
 286 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 287 extern u32 fsnotify_get_cookie(void);
 288
 289 static inline int fsnotify_inode_watches_children(struct inode *inode)
 290 {
 291         /* FS_EVENT_ON_CHILD is set if the inode may care */
 292         if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 293                 return 0;
 294         /* this inode might care about child events, does it care about the
 295          * specific set of events that can happen on a child? */
 296         return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 297 }
 298
 299 /*
 300  * Update the dentry with a flag indicating the interest of its parent to receive
 301  * filesystem events when those events happens to this dentry->d_inode.
 302  */
 303 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 304 {
 305         struct dentry *parent;
 306
 307         assert_spin_locked(&dcache_lock);
 308         assert_spin_locked(&dentry->d_lock);
 309
 310         parent = dentry->d_parent;
 311         if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
 312                 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 313         else
 314                 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 315 }
 316
 317 /*
 318  * fsnotify_d_instantiate - instantiate a dentry for inode
 319  * Called with dcache_lock held.
 320  */
 321 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 322 {
 323         if (!inode)
 324                 return;
 325
 326         assert_spin_locked(&dcache_lock);
 327
 328         spin_lock(&dentry->d_lock);
 329         __fsnotify_update_dcache_flags(dentry);
 330         spin_unlock(&dentry->d_lock);
 331 }
 332
 333 /* called from fsnotify listeners, such as fanotify or dnotify */
 334
 335 /* must call when a group changes its ->mask */
 336 extern void fsnotify_recalc_global_mask(void);
 337 /* get a reference to an existing or create a new group */
 338 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
 339 /* run all marks associated with this group and update group->mask */
 340 extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
 341 /* drop reference on a group from fsnotify_alloc_group */
 342 extern void fsnotify_put_group(struct fsnotify_group *group);
 343
 344 /* take a reference to an event */
 345 extern void fsnotify_get_event(struct fsnotify_event *event);
 346 extern void fsnotify_put_event(struct fsnotify_event *event);
 347 /* find private data previously attached to an event and unlink it */
 348 extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
 349                                                                            struct fsnotify_event *event);
 350
 351 /* attach the event to the group notification queue */
 352 extern int fsnotify_add_notify_event(struct fsnotify_group *group,
 353                                      struct fsnotify_event *event,
 354                                      struct fsnotify_event_private_data *priv,
 355                                      int (*merge)(struct list_head *, struct fsnotify_event *));
 356 /* true if the group notification queue is empty */
 357 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
 358 /* return, but do not dequeue the first event on the notification queue */
 359 extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
 360 /* return AND dequeue the first event on the notification queue */
 361 extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
 362
 363 /* functions used to manipulate the marks attached to inodes */
 364
 365 /* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
 366 extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
 367 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
 368 extern void fsnotify_recalc_inode_mask(struct inode *inode);
 369 extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
 370 /* find (and take a reference) to a mark associated with group and inode */
 371 extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
 372 /* find (and take a reference) to a mark associated with group and vfsmount */
 373 extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
 374 /* copy the values from old into new */
 375 extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
 376 /* set the mask of a mark (might pin the object into memory */
 377 extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 378 /* attach the mark to both the group and the inode */
 379 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
 380                              struct inode *inode, struct vfsmount *mnt, int allow_dups);
 381 /* given a mark, flag it to be freed when all references are dropped */
 382 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark);
 383 /* run all the marks in a group, and flag them to be freed */
 384 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
 385 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 386 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 387 extern void fsnotify_unmount_inodes(struct list_head *list);
 388
 389 /* put here because inotify does some weird stuff when destroying watches */
 390 extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
 391                                                     void *data, int data_is, const char *name,
 392                                                     u32 cookie, gfp_t gfp);
 393
 394 /* fanotify likes to change events after they are on lists... */
 395 extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
 396 extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
 397                                   struct fsnotify_event *new_event);
 398
 399 #else
 400
 401 static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 402                             const char *name, u32 cookie)
 403 {}
 404
 405 static inline void __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
 406 {}
 407
 408 static inline void __fsnotify_inode_delete(struct inode *inode)
 409 {}
 410
 411 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 412 {}
 413
 414 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 415 {}
 416
 417 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 418 {}
 419
 420 static inline u32 fsnotify_get_cookie(void)
 421 {
 422         return 0;
 423 }
 424
 425 static inline void fsnotify_unmount_inodes(struct list_head *list)
 426 {}
 427
 428 #endif  /* CONFIG_FSNOTIFY */
 429
 430 #endif  /* __KERNEL __ */
 431
 432 #endif  /* __LINUX_FSNOTIFY_BACKEND_H */