LXR linux/include/linux/fsnotify

   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 <linux/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_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 | FS_OPEN_PERM | FS_ACCESS_PERM)
  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_ISDIR | FS_IN_ONESHOT | FS_DN_RENAME | \
  76                             FS_DN_MULTISHOT | FS_EVENT_ON_CHILD)
  77
  78struct fsnotify_group;
  79struct fsnotify_event;
  80struct fsnotify_mark;
  81struct 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 - 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 */
  96struct fsnotify_ops {
  97        bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode,
  98                                  struct fsnotify_mark *inode_mark,
  99                                  struct fsnotify_mark *vfsmount_mark,
 100                                  __u32 mask, void *data, int data_type);
 101        int (*handle_event)(struct fsnotify_group *group,
 102                            struct fsnotify_mark *inode_mark,
 103                            struct fsnotify_mark *vfsmount_mark,
 104                            struct fsnotify_event *event);
 105        void (*free_group_priv)(struct fsnotify_group *group);
 106        void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
 107        void (*free_event_priv)(struct fsnotify_event_private_data *priv);
 108};
 109
 110/*
 111 * A group is a "thing" that wants to receive notification about filesystem
 112 * events.  The mask holds the subset of event types this group cares about.
 113 * refcnt on a group is up to the implementor and at any moment if it goes 0
 114 * everything will be cleaned up.
 115 */
 116struct fsnotify_group {
 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         * Valid fsnotify group priorities.  Events are send in order from highest
 137         * priority to lowest priority.  We default to the lowest priority.
 138         */
 139        #define FS_PRIO_0       0 /* normal notifiers, no permissions */
 140        #define FS_PRIO_1       1 /* fanotify content based access control */
 141        #define FS_PRIO_2       2 /* fanotify pre-content access */
 142        unsigned int priority;
 143
 144        /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
 145        struct mutex mark_mutex;        /* protect marks_list */
 146        atomic_t num_marks;             /* 1 for each mark and 1 for not being
 147                                         * past the point of no return when freeing
 148                                         * a group */
 149        struct list_head marks_list;    /* all inode marks for this group */
 150
 151        struct fasync_struct    *fsn_fa;    /* async notification */
 152
 153        /* groups can define private fields here or use the void *private */
 154        union {
 155                void *private;
 156#ifdef CONFIG_INOTIFY_USER
 157                struct inotify_group_private_data {
 158                        spinlock_t      idr_lock;
 159                        struct idr      idr;
 160                        struct user_struct      *user;
 161                } inotify_data;
 162#endif
 163#ifdef CONFIG_FANOTIFY
 164                struct fanotify_group_private_data {
 165#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 166                        /* allows a group to block waiting for a userspace response */
 167                        struct mutex access_mutex;
 168                        struct list_head access_list;
 169                        wait_queue_head_t access_waitq;
 170                        atomic_t bypass_perm;
 171#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 172                        int f_flags;
 173                        unsigned int max_marks;
 174                        struct user_struct *user;
 175                } fanotify_data;
 176#endif /* CONFIG_FANOTIFY */
 177        };
 178};
 179
 180/*
 181 * A single event can be queued in multiple group->notification_lists.
 182 *
 183 * each group->notification_list will point to an event_holder which in turns points
 184 * to the actual event that needs to be sent to userspace.
 185 *
 186 * Seemed cheaper to create a refcnt'd event and a small holder for every group
 187 * than create a different event for every group
 188 *
 189 */
 190struct fsnotify_event_holder {
 191        struct fsnotify_event *event;
 192        struct list_head event_list;
 193};
 194
 195/*
 196 * Inotify needs to tack data onto an event.  This struct lets us later find the
 197 * correct private data of the correct group.
 198 */
 199struct fsnotify_event_private_data {
 200        struct fsnotify_group *group;
 201        struct list_head event_list;
 202};
 203
 204/*
 205 * all of the information about the original object we want to now send to
 206 * a group.  If you want to carry more info from the accessing task to the
 207 * listener this structure is where you need to be adding fields.
 208 */
 209struct fsnotify_event {
 210        /*
 211         * If we create an event we are also likely going to need a holder
 212         * to link to a group.  So embed one holder in the event.  Means only
 213         * one allocation for the common case where we only have one group
 214         */
 215        struct fsnotify_event_holder holder;
 216        spinlock_t lock;        /* protection for the associated event_holder and private_list */
 217        /* to_tell may ONLY be dereferenced during handle_event(). */
 218        struct inode *to_tell;  /* either the inode the event happened to or its parent */
 219        /*
 220         * depending on the event type we should have either a path or inode
 221         * We hold a reference on path, but NOT on inode.  Since we have the ref on
 222         * the path, it may be dereferenced at any point during this object's
 223         * lifetime.  That reference is dropped when this object's refcnt hits
 224         * 0.  If this event contains an inode instead of a path, the inode may
 225         * ONLY be used during handle_event().
 226         */
 227        union {
 228                struct path path;
 229                struct inode *inode;
 230        };
 231/* when calling fsnotify tell it if the data is a path or inode */
 232#define FSNOTIFY_EVENT_NONE     0
 233#define FSNOTIFY_EVENT_PATH     1
 234#define FSNOTIFY_EVENT_INODE    2
 235        int data_type;          /* which of the above union we have */
 236        atomic_t refcnt;        /* how many groups still are using/need to send this event */
 237        __u32 mask;             /* the type of access, bitwise OR for FS_* event types */
 238
 239        u32 sync_cookie;        /* used to corrolate events, namely inotify mv events */
 240        const unsigned char *file_name;
 241        size_t name_len;
 242        struct pid *tgid;
 243
 244#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 245        __u32 response; /* userspace answer to question */
 246#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 247
 248        struct list_head private_data_list;     /* groups can store private data here */
 249};
 250
 251/*
 252 * Inode specific fields in an fsnotify_mark
 253 */
 254struct fsnotify_inode_mark {
 255        struct inode *inode;            /* inode this mark is associated with */
 256        struct hlist_node i_list;       /* list of marks by inode->i_fsnotify_marks */
 257        struct list_head free_i_list;   /* tmp list used when freeing this mark */
 258};
 259
 260/*
 261 * Mount point specific fields in an fsnotify_mark
 262 */
 263struct fsnotify_vfsmount_mark {
 264        struct vfsmount *mnt;           /* vfsmount this mark is associated with */
 265        struct hlist_node m_list;       /* list of marks by inode->i_fsnotify_marks */
 266        struct list_head free_m_list;   /* tmp list used when freeing this mark */
 267};
 268
 269/*
 270 * a mark is simply an object attached to an in core inode which allows an
 271 * fsnotify listener to indicate they are either no longer interested in events
 272 * of a type matching mask or only interested in those events.
 273 *
 274 * these are flushed when an inode is evicted from core and may be flushed
 275 * when the inode is modified (as seen by fsnotify_access).  Some fsnotify users
 276 * (such as dnotify) will flush these when the open fd is closed and not at
 277 * inode eviction or modification.
 278 */
 279struct fsnotify_mark {
 280        __u32 mask;                     /* mask this mark is for */
 281        /* we hold ref for each i_list and g_list.  also one ref for each 'thing'
 282         * in kernel that found and may be using this mark. */
 283        atomic_t refcnt;                /* active things looking at this mark */
 284        struct fsnotify_group *group;   /* group this mark is for */
 285        struct list_head g_list;        /* list of marks by group->i_fsnotify_marks */
 286        spinlock_t lock;                /* protect group and inode */
 287        union {
 288                struct fsnotify_inode_mark i;
 289                struct fsnotify_vfsmount_mark m;
 290        };
 291        __u32 ignored_mask;             /* events types to ignore */
 292#define FSNOTIFY_MARK_FLAG_INODE                0x01
 293#define FSNOTIFY_MARK_FLAG_VFSMOUNT             0x02
 294#define FSNOTIFY_MARK_FLAG_OBJECT_PINNED        0x04
 295#define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x08
 296#define FSNOTIFY_MARK_FLAG_ALIVE                0x10
 297        unsigned int flags;             /* vfsmount or inode mark? */
 298        struct list_head destroy_list;
 299        void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
 300};
 301
 302#ifdef CONFIG_FSNOTIFY
 303
 304/* called from the vfs helpers */
 305
 306/* main fsnotify call to send events */
 307extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 308                    const unsigned char *name, u32 cookie);
 309extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
 310extern void __fsnotify_inode_delete(struct inode *inode);
 311extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 312extern u32 fsnotify_get_cookie(void);
 313
 314static inline int fsnotify_inode_watches_children(struct inode *inode)
 315{
 316        /* FS_EVENT_ON_CHILD is set if the inode may care */
 317        if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 318                return 0;
 319        /* this inode might care about child events, does it care about the
 320         * specific set of events that can happen on a child? */
 321        return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 322}
 323
 324/*
 325 * Update the dentry with a flag indicating the interest of its parent to receive
 326 * filesystem events when those events happens to this dentry->d_inode.
 327 */
 328static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 329{
 330        struct dentry *parent;
 331
 332        assert_spin_locked(&dentry->d_lock);
 333
 334        /*
 335         * Serialisation of setting PARENT_WATCHED on the dentries is provided
 336         * by d_lock. If inotify_inode_watched changes after we have taken
 337         * d_lock, the following __fsnotify_update_child_dentry_flags call will
 338         * find our entry, so it will spin until we complete here, and update
 339         * us with the new state.
 340         */
 341        parent = dentry->d_parent;
 342        if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
 343                dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 344        else
 345                dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 346}
 347
 348/*
 349 * fsnotify_d_instantiate - instantiate a dentry for inode
 350 */
 351static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 352{
 353        if (!inode)
 354                return;
 355
 356        spin_lock(&dentry->d_lock);
 357        __fsnotify_update_dcache_flags(dentry);
 358        spin_unlock(&dentry->d_lock);
 359}
 360
 361/* called from fsnotify listeners, such as fanotify or dnotify */
 362
 363/* create a new group */
 364extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
 365/* get reference to a group */
 366extern void fsnotify_get_group(struct fsnotify_group *group);
 367/* drop reference on a group from fsnotify_alloc_group */
 368extern void fsnotify_put_group(struct fsnotify_group *group);
 369/* destroy group */
 370extern void fsnotify_destroy_group(struct fsnotify_group *group);
 371/* fasync handler function */
 372extern int fsnotify_fasync(int fd, struct file *file, int on);
 373/* take a reference to an event */
 374extern void fsnotify_get_event(struct fsnotify_event *event);
 375extern void fsnotify_put_event(struct fsnotify_event *event);
 376/* find private data previously attached to an event and unlink it */
 377extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
 378                                                                           struct fsnotify_event *event);
 379
 380/* attach the event to the group notification queue */
 381extern struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
 382                                                        struct fsnotify_event *event,
 383                                                        struct fsnotify_event_private_data *priv,
 384                                                        struct fsnotify_event *(*merge)(struct list_head *,
 385                                                                                        struct fsnotify_event *));
 386/* true if the group notification queue is empty */
 387extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
 388/* return, but do not dequeue the first event on the notification queue */
 389extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
 390/* return AND dequeue the first event on the notification queue */
 391extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
 392
 393/* functions used to manipulate the marks attached to inodes */
 394
 395/* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
 396extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
 397/* run all marks associated with an inode and update inode->i_fsnotify_mask */
 398extern void fsnotify_recalc_inode_mask(struct inode *inode);
 399extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
 400/* find (and take a reference) to a mark associated with group and inode */
 401extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
 402/* find (and take a reference) to a mark associated with group and vfsmount */
 403extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
 404/* copy the values from old into new */
 405extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
 406/* set the ignored_mask of a mark */
 407extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 408/* set the mask of a mark (might pin the object into memory */
 409extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 410/* attach the mark to both the group and the inode */
 411extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
 412                             struct inode *inode, struct vfsmount *mnt, int allow_dups);
 413extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, struct fsnotify_group *group,
 414                                    struct inode *inode, struct vfsmount *mnt, int allow_dups);
 415/* given a group and a mark, flag mark to be freed when all references are dropped */
 416extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
 417                                  struct fsnotify_group *group);
 418extern void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
 419                                         struct fsnotify_group *group);
 420/* run all the marks in a group, and clear all of the vfsmount marks */
 421extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
 422/* run all the marks in a group, and clear all of the inode marks */
 423extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
 424/* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
 425extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
 426/* run all the marks in a group, and flag them to be freed */
 427extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
 428extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 429extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 430extern void fsnotify_unmount_inodes(struct list_head *list);
 431
 432/* put here because inotify does some weird stuff when destroying watches */
 433extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
 434                                                    void *data, int data_is,
 435                                                    const unsigned char *name,
 436                                                    u32 cookie, gfp_t gfp);
 437
 438/* fanotify likes to change events after they are on lists... */
 439extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
 440extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
 441                                  struct fsnotify_event *new_event);
 442
 443#else
 444
 445static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 446                           const unsigned char *name, u32 cookie)
 447{
 448        return 0;
 449}
 450
 451static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
 452{
 453        return 0;
 454}
 455
 456static inline void __fsnotify_inode_delete(struct inode *inode)
 457{}
 458
 459static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 460{}
 461
 462static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 463{}
 464
 465static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 466{}
 467
 468static inline u32 fsnotify_get_cookie(void)
 469{
 470        return 0;
 471}
 472
 473static inline void fsnotify_unmount_inodes(struct list_head *list)
 474{}
 475
 476#endif  /* CONFIG_FSNOTIFY */
 477
 478#endif  /* __KERNEL __ */
 479
 480#endif  /* __LINUX_FSNOTIFY_BACKEND_H */
 481