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 #include <linux/atomic.h>
  19
  20 /*
  21  * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
  22  * convert between them.  dnotify only needs conversion at watch creation
  23  * so no perf loss there.  fanotify isn't defined yet, so it can use the
  24  * wholes if it needs more events.
  25  */
  26 #define FS_ACCESS               0x00000001      /* File was accessed */
  27 #define FS_MODIFY               0x00000002      /* File was modified */
  28 #define FS_ATTRIB               0x00000004      /* Metadata changed */
  29 #define FS_CLOSE_WRITE          0x00000008      /* Writtable file was closed */
  30 #define FS_CLOSE_NOWRITE        0x00000010      /* Unwrittable file closed */
  31 #define FS_OPEN                 0x00000020      /* File was opened */
  32 #define FS_MOVED_FROM           0x00000040      /* File was moved from X */
  33 #define FS_MOVED_TO             0x00000080      /* File was moved to Y */
  34 #define FS_CREATE               0x00000100      /* Subfile was created */
  35 #define FS_DELETE               0x00000200      /* Subfile was deleted */
  36 #define FS_DELETE_SELF          0x00000400      /* Self was deleted */
  37 #define FS_MOVE_SELF            0x00000800      /* Self was moved */
  38
  39 #define FS_UNMOUNT              0x00002000      /* inode on umount fs */
  40 #define FS_Q_OVERFLOW           0x00004000      /* Event queued overflowed */
  41 #define FS_IN_IGNORED           0x00008000      /* last inotify event here */
  42
  43 #define FS_OPEN_PERM            0x00010000      /* open event in an permission hook */
  44 #define FS_ACCESS_PERM          0x00020000      /* access event in a permissions hook */
  45
  46 #define FS_EXCL_UNLINK          0x04000000      /* do not send events if object is unlinked */
  47 #define FS_ISDIR                0x40000000      /* event occurred against dir */
  48 #define FS_IN_ONESHOT           0x80000000      /* only send event once */
  49
  50 #define FS_DN_RENAME            0x10000000      /* file renamed */
  51 #define FS_DN_MULTISHOT         0x20000000      /* dnotify multishot */
  52
  53 /* This inode cares about things that happen to its children.  Always set for
  54  * dnotify and inotify. */
  55 #define FS_EVENT_ON_CHILD       0x08000000
  56
  57 /* This is a list of all events that may get sent to a parernt based on fs event
  58  * happening to inodes inside that directory */
  59 #define FS_EVENTS_POSS_ON_CHILD   (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
  60                                    FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
  61                                    FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
  62                                    FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM)
  63
  64 #define FS_MOVE                 (FS_MOVED_FROM | FS_MOVED_TO)
  65
  66 #define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM)
  67
  68 #define ALL_FSNOTIFY_EVENTS (FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
  69                              FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN | \
  70                              FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
  71                              FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
  72                              FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
  73                              FS_OPEN_PERM | FS_ACCESS_PERM | FS_EXCL_UNLINK | \
  74                              FS_ISDIR | FS_IN_ONESHOT | FS_DN_RENAME | \
  75                              FS_DN_MULTISHOT | FS_EVENT_ON_CHILD)
  76
  77 struct fsnotify_group;
  78 struct fsnotify_event;
  79 struct fsnotify_mark;
  80 struct fsnotify_event_private_data;
  81 struct fsnotify_fname;
  82
  83 /*
  84  * Each group much define these ops.  The fsnotify infrastructure will call
  85  * these operations for each relevant group.
  86  *
  87  * should_send_event - given a group, inode, and mask this function determines
  88  *              if the group is interested in this event.
  89  * handle_event - main call for a group to handle an fs event
  90  * free_group_priv - called when a group refcnt hits 0 to clean up the private union
  91  * freeing_mark - called when a mark is being destroyed for some reason.  The group
  92  *              MUST be holding a reference on each mark and that reference must be
  93  *              dropped in this function.  inotify uses this function to send
  94  *              userspace messages that marks have been removed.
  95  */
  96 struct fsnotify_ops {
  97         int (*handle_event)(struct fsnotify_group *group,
  98                             struct inode *inode,
  99                             struct fsnotify_mark *inode_mark,
 100                             struct fsnotify_mark *vfsmount_mark,
 101                             u32 mask, void *data, int data_type,
 102                             const unsigned char *file_name, u32 cookie);
 103         void (*free_group_priv)(struct fsnotify_group *group);
 104         void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
 105         void (*free_event)(struct fsnotify_event *event);
 106 };
 107
 108 /*
 109  * all of the information about the original object we want to now send to
 110  * a group.  If you want to carry more info from the accessing task to the
 111  * listener this structure is where you need to be adding fields.
 112  */
 113 struct fsnotify_event {
 114         struct list_head list;
 115         /* inode may ONLY be dereferenced during handle_event(). */
 116         struct inode *inode;    /* either the inode the event happened to or its parent */
 117         u32 mask;               /* the type of access, bitwise OR for FS_* event types */
 118 };
 119
 120 /*
 121  * A group is a "thing" that wants to receive notification about filesystem
 122  * events.  The mask holds the subset of event types this group cares about.
 123  * refcnt on a group is up to the implementor and at any moment if it goes 0
 124  * everything will be cleaned up.
 125  */
 126 struct fsnotify_group {
 127         /*
 128          * How the refcnt is used is up to each group.  When the refcnt hits 0
 129          * fsnotify will clean up all of the resources associated with this group.
 130          * As an example, the dnotify group will always have a refcnt=1 and that
 131          * will never change.  Inotify, on the other hand, has a group per
 132          * inotify_init() and the refcnt will hit 0 only when that fd has been
 133          * closed.
 134          */
 135         atomic_t refcnt;                /* things with interest in this group */
 136
 137         const struct fsnotify_ops *ops; /* how this group handles things */
 138
 139         /* needed to send notification to userspace */
 140         struct mutex notification_mutex;        /* protect the notification_list */
 141         struct list_head notification_list;     /* list of event_holder this group needs to send to userspace */
 142         wait_queue_head_t notification_waitq;   /* read() on the notification file blocks on this waitq */
 143         unsigned int q_len;                     /* events on the queue */
 144         unsigned int max_events;                /* maximum events allowed on the list */
 145         /*
 146          * Valid fsnotify group priorities.  Events are send in order from highest
 147          * priority to lowest priority.  We default to the lowest priority.
 148          */
 149         #define FS_PRIO_0       0 /* normal notifiers, no permissions */
 150         #define FS_PRIO_1       1 /* fanotify content based access control */
 151         #define FS_PRIO_2       2 /* fanotify pre-content access */
 152         unsigned int priority;
 153
 154         /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
 155         struct mutex mark_mutex;        /* protect marks_list */
 156         atomic_t num_marks;             /* 1 for each mark and 1 for not being
 157                                          * past the point of no return when freeing
 158                                          * a group */
 159         struct list_head marks_list;    /* all inode marks for this group */
 160
 161         struct fasync_struct *fsn_fa;    /* async notification */
 162
 163         struct fsnotify_event *overflow_event;  /* Event we queue when the
 164                                                  * notification list is too
 165                                                  * full */
 166
 167         /* groups can define private fields here or use the void *private */
 168         union {
 169                 void *private;
 170 #ifdef CONFIG_INOTIFY_USER
 171                 struct inotify_group_private_data {
 172                         spinlock_t      idr_lock;
 173                         struct idr      idr;
 174                         struct user_struct      *user;
 175                 } inotify_data;
 176 #endif
 177 #ifdef CONFIG_FANOTIFY
 178                 struct fanotify_group_private_data {
 179 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 180                         /* allows a group to block waiting for a userspace response */
 181                         spinlock_t access_lock;
 182                         struct list_head access_list;
 183                         wait_queue_head_t access_waitq;
 184                         atomic_t bypass_perm;
 185 #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 186                         int f_flags;
 187                         unsigned int max_marks;
 188                         struct user_struct *user;
 189                 } fanotify_data;
 190 #endif /* CONFIG_FANOTIFY */
 191         };
 192 };
 193
 194 /* when calling fsnotify tell it if the data is a path or inode */
 195 #define FSNOTIFY_EVENT_NONE     0
 196 #define FSNOTIFY_EVENT_PATH     1
 197 #define FSNOTIFY_EVENT_INODE    2
 198
 199 /*
 200  * Inode specific fields in an fsnotify_mark
 201  */
 202 struct fsnotify_inode_mark {
 203         struct inode *inode;            /* inode this mark is associated with */
 204         struct hlist_node i_list;       /* list of marks by inode->i_fsnotify_marks */
 205         struct list_head free_i_list;   /* tmp list used when freeing this mark */
 206 };
 207
 208 /*
 209  * Mount point specific fields in an fsnotify_mark
 210  */
 211 struct fsnotify_vfsmount_mark {
 212         struct vfsmount *mnt;           /* vfsmount this mark is associated with */
 213         struct hlist_node m_list;       /* list of marks by inode->i_fsnotify_marks */
 214         struct list_head free_m_list;   /* tmp list used when freeing this mark */
 215 };
 216
 217 /*
 218  * a mark is simply an object attached to an in core inode which allows an
 219  * fsnotify listener to indicate they are either no longer interested in events
 220  * of a type matching mask or only interested in those events.
 221  *
 222  * these are flushed when an inode is evicted from core and may be flushed
 223  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify users
 224  * (such as dnotify) will flush these when the open fd is closed and not at
 225  * inode eviction or modification.
 226  */
 227 struct fsnotify_mark {
 228         __u32 mask;                     /* mask this mark is for */
 229         /* we hold ref for each i_list and g_list.  also one ref for each 'thing'
 230          * in kernel that found and may be using this mark. */
 231         atomic_t refcnt;                /* active things looking at this mark */
 232         struct fsnotify_group *group;   /* group this mark is for */
 233         struct list_head g_list;        /* list of marks by group->i_fsnotify_marks */
 234         spinlock_t lock;                /* protect group and inode */
 235         union {
 236                 struct fsnotify_inode_mark i;
 237                 struct fsnotify_vfsmount_mark m;
 238         };
 239         __u32 ignored_mask;             /* events types to ignore */
 240 #define FSNOTIFY_MARK_FLAG_INODE                0x01
 241 #define FSNOTIFY_MARK_FLAG_VFSMOUNT             0x02
 242 #define FSNOTIFY_MARK_FLAG_OBJECT_PINNED        0x04
 243 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x08
 244 #define FSNOTIFY_MARK_FLAG_ALIVE                0x10
 245         unsigned int flags;             /* vfsmount or inode mark? */
 246         struct list_head destroy_list;
 247         void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
 248 };
 249
 250 #ifdef CONFIG_FSNOTIFY
 251
 252 /* called from the vfs helpers */
 253
 254 /* main fsnotify call to send events */
 255 extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 256                     const unsigned char *name, u32 cookie);
 257 extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
 258 extern void __fsnotify_inode_delete(struct inode *inode);
 259 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 260 extern u32 fsnotify_get_cookie(void);
 261
 262 static inline int fsnotify_inode_watches_children(struct inode *inode)
 263 {
 264         /* FS_EVENT_ON_CHILD is set if the inode may care */
 265         if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 266                 return 0;
 267         /* this inode might care about child events, does it care about the
 268          * specific set of events that can happen on a child? */
 269         return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 270 }
 271
 272 /*
 273  * Update the dentry with a flag indicating the interest of its parent to receive
 274  * filesystem events when those events happens to this dentry->d_inode.
 275  */
 276 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 277 {
 278         struct dentry *parent;
 279
 280         assert_spin_locked(&dentry->d_lock);
 281
 282         /*
 283          * Serialisation of setting PARENT_WATCHED on the dentries is provided
 284          * by d_lock. If inotify_inode_watched changes after we have taken
 285          * d_lock, the following __fsnotify_update_child_dentry_flags call will
 286          * find our entry, so it will spin until we complete here, and update
 287          * us with the new state.
 288          */
 289         parent = dentry->d_parent;
 290         if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
 291                 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 292         else
 293                 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 294 }
 295
 296 /*
 297  * fsnotify_d_instantiate - instantiate a dentry for inode
 298  */
 299 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 300 {
 301         if (!inode)
 302                 return;
 303
 304         spin_lock(&dentry->d_lock);
 305         __fsnotify_update_dcache_flags(dentry);
 306         spin_unlock(&dentry->d_lock);
 307 }
 308
 309 /* called from fsnotify listeners, such as fanotify or dnotify */
 310
 311 /* create a new group */
 312 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
 313 /* get reference to a group */
 314 extern void fsnotify_get_group(struct fsnotify_group *group);
 315 /* drop reference on a group from fsnotify_alloc_group */
 316 extern void fsnotify_put_group(struct fsnotify_group *group);
 317 /* destroy group */
 318 extern void fsnotify_destroy_group(struct fsnotify_group *group);
 319 /* fasync handler function */
 320 extern int fsnotify_fasync(int fd, struct file *file, int on);
 321 /* Free event from memory */
 322 extern void fsnotify_destroy_event(struct fsnotify_group *group,
 323                                    struct fsnotify_event *event);
 324 /* attach the event to the group notification queue */
 325 extern int fsnotify_add_event(struct fsnotify_group *group,
 326                               struct fsnotify_event *event,
 327                               int (*merge)(struct list_head *,
 328                                            struct fsnotify_event *));
 329 /* Remove passed event from groups notification queue */
 330 extern void fsnotify_remove_event(struct fsnotify_group *group, struct fsnotify_event *event);
 331 /* true if the group notification queue is empty */
 332 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
 333 /* return, but do not dequeue the first event on the notification queue */
 334 extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group);
 335 /* return AND dequeue the first event on the notification queue */
 336 extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);
 337
 338 /* functions used to manipulate the marks attached to inodes */
 339
 340 /* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
 341 extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
 342 /* run all marks associated with an inode and update inode->i_fsnotify_mask */
 343 extern void fsnotify_recalc_inode_mask(struct inode *inode);
 344 extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
 345 /* find (and take a reference) to a mark associated with group and inode */
 346 extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
 347 /* find (and take a reference) to a mark associated with group and vfsmount */
 348 extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
 349 /* copy the values from old into new */
 350 extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
 351 /* set the ignored_mask of a mark */
 352 extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 353 /* set the mask of a mark (might pin the object into memory */
 354 extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 355 /* attach the mark to both the group and the inode */
 356 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
 357                              struct inode *inode, struct vfsmount *mnt, int allow_dups);
 358 extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, struct fsnotify_group *group,
 359                                     struct inode *inode, struct vfsmount *mnt, int allow_dups);
 360 /* given a group and a mark, flag mark to be freed when all references are dropped */
 361 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
 362                                   struct fsnotify_group *group);
 363 extern void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
 364                                          struct fsnotify_group *group);
 365 /* run all the marks in a group, and clear all of the vfsmount marks */
 366 extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
 367 /* run all the marks in a group, and clear all of the inode marks */
 368 extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
 369 /* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
 370 extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
 371 /* run all the marks in a group, and flag them to be freed */
 372 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
 373 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 374 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 375 extern void fsnotify_unmount_inodes(struct list_head *list);
 376
 377 /* put here because inotify does some weird stuff when destroying watches */
 378 extern void fsnotify_init_event(struct fsnotify_event *event,
 379                                 struct inode *to_tell, u32 mask);
 380
 381 #else
 382
 383 static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 384                            const unsigned char *name, u32 cookie)
 385 {
 386         return 0;
 387 }
 388
 389 static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
 390 {
 391         return 0;
 392 }
 393
 394 static inline void __fsnotify_inode_delete(struct inode *inode)
 395 {}
 396
 397 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 398 {}
 399
 400 static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 401 {}
 402
 403 static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 404 {}
 405
 406 static inline u32 fsnotify_get_cookie(void)
 407 {
 408         return 0;
 409 }
 410
 411 static inline void fsnotify_unmount_inodes(struct list_head *list)
 412 {}
 413
 414 #endif  /* CONFIG_FSNOTIFY */
 415
 416 #endif  /* __KERNEL __ */
 417
 418 #endif  /* __LINUX_FSNOTIFY_BACKEND_H */