linux/include/linux/fsnotify_backend.h
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   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 - this means that a mark has been flagged to die when everything
  92 *              finishes using it.  The function is supplied with what must be a
  93 *              valid group and inode to use to clean up.
  94 */
  95struct fsnotify_ops {
  96        bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode,
  97                                  struct fsnotify_mark *inode_mark,
  98                                  struct fsnotify_mark *vfsmount_mark,
  99                                  __u32 mask, void *data, int data_type);
 100        int (*handle_event)(struct fsnotify_group *group,
 101                            struct fsnotify_mark *inode_mark,
 102                            struct fsnotify_mark *vfsmount_mark,
 103                            struct fsnotify_event *event);
 104        void (*free_group_priv)(struct fsnotify_group *group);
 105        void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
 106        void (*free_event_priv)(struct fsnotify_event_private_data *priv);
 107};
 108
 109/*
 110 * A group is a "thing" that wants to receive notification about filesystem
 111 * events.  The mask holds the subset of event types this group cares about.
 112 * refcnt on a group is up to the implementor and at any moment if it goes 0
 113 * everything will be cleaned up.
 114 */
 115struct fsnotify_group {
 116        /*
 117         * How the refcnt is used is up to each group.  When the refcnt hits 0
 118         * fsnotify will clean up all of the resources associated with this group.
 119         * As an example, the dnotify group will always have a refcnt=1 and that
 120         * will never change.  Inotify, on the other hand, has a group per
 121         * inotify_init() and the refcnt will hit 0 only when that fd has been
 122         * closed.
 123         */
 124        atomic_t refcnt;                /* things with interest in this group */
 125
 126        const struct fsnotify_ops *ops; /* how this group handles things */
 127
 128        /* needed to send notification to userspace */
 129        struct mutex notification_mutex;        /* protect the notification_list */
 130        struct list_head notification_list;     /* list of event_holder this group needs to send to userspace */
 131        wait_queue_head_t notification_waitq;   /* read() on the notification file blocks on this waitq */
 132        unsigned int q_len;                     /* events on the queue */
 133        unsigned int max_events;                /* maximum events allowed on the list */
 134        /*
 135         * Valid fsnotify group priorities.  Events are send in order from highest
 136         * priority to lowest priority.  We default to the lowest priority.
 137         */
 138        #define FS_PRIO_0       0 /* normal notifiers, no permissions */
 139        #define FS_PRIO_1       1 /* fanotify content based access control */
 140        #define FS_PRIO_2       2 /* fanotify pre-content access */
 141        unsigned int priority;
 142
 143        /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
 144        spinlock_t mark_lock;           /* protect marks_list */
 145        atomic_t num_marks;             /* 1 for each mark and 1 for not being
 146                                         * past the point of no return when freeing
 147                                         * a group */
 148        struct list_head marks_list;    /* all inode marks for this group */
 149
 150        /* groups can define private fields here or use the void *private */
 151        union {
 152                void *private;
 153#ifdef CONFIG_INOTIFY_USER
 154                struct inotify_group_private_data {
 155                        spinlock_t      idr_lock;
 156                        struct idr      idr;
 157                        u32             last_wd;
 158                        struct fasync_struct    *fa;    /* async notification */
 159                        struct user_struct      *user;
 160                } inotify_data;
 161#endif
 162#ifdef CONFIG_FANOTIFY
 163                struct fanotify_group_private_data {
 164#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 165                        /* allows a group to block waiting for a userspace response */
 166                        struct mutex access_mutex;
 167                        struct list_head access_list;
 168                        wait_queue_head_t access_waitq;
 169                        atomic_t bypass_perm;
 170#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 171                        int f_flags;
 172                        unsigned int max_marks;
 173                        struct user_struct *user;
 174                } fanotify_data;
 175#endif /* CONFIG_FANOTIFY */
 176        };
 177};
 178
 179/*
 180 * A single event can be queued in multiple group->notification_lists.
 181 *
 182 * each group->notification_list will point to an event_holder which in turns points
 183 * to the actual event that needs to be sent to userspace.
 184 *
 185 * Seemed cheaper to create a refcnt'd event and a small holder for every group
 186 * than create a different event for every group
 187 *
 188 */
 189struct fsnotify_event_holder {
 190        struct fsnotify_event *event;
 191        struct list_head event_list;
 192};
 193
 194/*
 195 * Inotify needs to tack data onto an event.  This struct lets us later find the
 196 * correct private data of the correct group.
 197 */
 198struct fsnotify_event_private_data {
 199        struct fsnotify_group *group;
 200        struct list_head event_list;
 201};
 202
 203/*
 204 * all of the information about the original object we want to now send to
 205 * a group.  If you want to carry more info from the accessing task to the
 206 * listener this structure is where you need to be adding fields.
 207 */
 208struct fsnotify_event {
 209        /*
 210         * If we create an event we are also likely going to need a holder
 211         * to link to a group.  So embed one holder in the event.  Means only
 212         * one allocation for the common case where we only have one group
 213         */
 214        struct fsnotify_event_holder holder;
 215        spinlock_t lock;        /* protection for the associated event_holder and private_list */
 216        /* to_tell may ONLY be dereferenced during handle_event(). */
 217        struct inode *to_tell;  /* either the inode the event happened to or its parent */
 218        /*
 219         * depending on the event type we should have either a path or inode
 220         * We hold a reference on path, but NOT on inode.  Since we have the ref on
 221         * the path, it may be dereferenced at any point during this object's
 222         * lifetime.  That reference is dropped when this object's refcnt hits
 223         * 0.  If this event contains an inode instead of a path, the inode may
 224         * ONLY be used during handle_event().
 225         */
 226        union {
 227                struct path path;
 228                struct inode *inode;
 229        };
 230/* when calling fsnotify tell it if the data is a path or inode */
 231#define FSNOTIFY_EVENT_NONE     0
 232#define FSNOTIFY_EVENT_PATH     1
 233#define FSNOTIFY_EVENT_INODE    2
 234        int data_type;          /* which of the above union we have */
 235        atomic_t refcnt;        /* how many groups still are using/need to send this event */
 236        __u32 mask;             /* the type of access, bitwise OR for FS_* event types */
 237
 238        u32 sync_cookie;        /* used to corrolate events, namely inotify mv events */
 239        const unsigned char *file_name;
 240        size_t name_len;
 241        struct pid *tgid;
 242
 243#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 244        __u32 response; /* userspace answer to question */
 245#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
 246
 247        struct list_head private_data_list;     /* groups can store private data here */
 248};
 249
 250/*
 251 * Inode specific fields in an fsnotify_mark
 252 */
 253struct fsnotify_inode_mark {
 254        struct inode *inode;            /* inode this mark is associated with */
 255        struct hlist_node i_list;       /* list of marks by inode->i_fsnotify_marks */
 256        struct list_head free_i_list;   /* tmp list used when freeing this mark */
 257};
 258
 259/*
 260 * Mount point specific fields in an fsnotify_mark
 261 */
 262struct fsnotify_vfsmount_mark {
 263        struct vfsmount *mnt;           /* vfsmount this mark is associated with */
 264        struct hlist_node m_list;       /* list of marks by inode->i_fsnotify_marks */
 265        struct list_head free_m_list;   /* tmp list used when freeing this mark */
 266};
 267
 268/*
 269 * a mark is simply an object attached to an in core inode which allows an
 270 * fsnotify listener to indicate they are either no longer interested in events
 271 * of a type matching mask or only interested in those events.
 272 *
 273 * these are flushed when an inode is evicted from core and may be flushed
 274 * when the inode is modified (as seen by fsnotify_access).  Some fsnotify users
 275 * (such as dnotify) will flush these when the open fd is closed and not at
 276 * inode eviction or modification.
 277 */
 278struct fsnotify_mark {
 279        __u32 mask;                     /* mask this mark is for */
 280        /* we hold ref for each i_list and g_list.  also one ref for each 'thing'
 281         * in kernel that found and may be using this mark. */
 282        atomic_t refcnt;                /* active things looking at this mark */
 283        struct fsnotify_group *group;   /* group this mark is for */
 284        struct list_head g_list;        /* list of marks by group->i_fsnotify_marks */
 285        spinlock_t lock;                /* protect group and inode */
 286        union {
 287                struct fsnotify_inode_mark i;
 288                struct fsnotify_vfsmount_mark m;
 289        };
 290        struct list_head free_g_list;   /* tmp list used when freeing this mark */
 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/* get a reference to an existing or create a new group */
 364extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
 365/* drop reference on a group from fsnotify_alloc_group */
 366extern void fsnotify_put_group(struct fsnotify_group *group);
 367
 368/* take a reference to an event */
 369extern void fsnotify_get_event(struct fsnotify_event *event);
 370extern void fsnotify_put_event(struct fsnotify_event *event);
 371/* find private data previously attached to an event and unlink it */
 372extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
 373                                                                           struct fsnotify_event *event);
 374
 375/* attach the event to the group notification queue */
 376extern struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
 377                                                        struct fsnotify_event *event,
 378                                                        struct fsnotify_event_private_data *priv,
 379                                                        struct fsnotify_event *(*merge)(struct list_head *,
 380                                                                                        struct fsnotify_event *));
 381/* true if the group notification queue is empty */
 382extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
 383/* return, but do not dequeue the first event on the notification queue */
 384extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
 385/* return AND dequeue the first event on the notification queue */
 386extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
 387
 388/* functions used to manipulate the marks attached to inodes */
 389
 390/* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
 391extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
 392/* run all marks associated with an inode and update inode->i_fsnotify_mask */
 393extern void fsnotify_recalc_inode_mask(struct inode *inode);
 394extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
 395/* find (and take a reference) to a mark associated with group and inode */
 396extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
 397/* find (and take a reference) to a mark associated with group and vfsmount */
 398extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
 399/* copy the values from old into new */
 400extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
 401/* set the ignored_mask of a mark */
 402extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 403/* set the mask of a mark (might pin the object into memory */
 404extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 405/* attach the mark to both the group and the inode */
 406extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
 407                             struct inode *inode, struct vfsmount *mnt, int allow_dups);
 408/* given a mark, flag it to be freed when all references are dropped */
 409extern void fsnotify_destroy_mark(struct fsnotify_mark *mark);
 410/* run all the marks in a group, and clear all of the vfsmount marks */
 411extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
 412/* run all the marks in a group, and clear all of the inode marks */
 413extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
 414/* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
 415extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
 416/* run all the marks in a group, and flag them to be freed */
 417extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
 418extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 419extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 420extern void fsnotify_unmount_inodes(struct list_head *list);
 421
 422/* put here because inotify does some weird stuff when destroying watches */
 423extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
 424                                                    void *data, int data_is,
 425                                                    const unsigned char *name,
 426                                                    u32 cookie, gfp_t gfp);
 427
 428/* fanotify likes to change events after they are on lists... */
 429extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
 430extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
 431                                  struct fsnotify_event *new_event);
 432
 433#else
 434
 435static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 436                           const unsigned char *name, u32 cookie)
 437{
 438        return 0;
 439}
 440
 441static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
 442{
 443        return 0;
 444}
 445
 446static inline void __fsnotify_inode_delete(struct inode *inode)
 447{}
 448
 449static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 450{}
 451
 452static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
 453{}
 454
 455static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
 456{}
 457
 458static inline u32 fsnotify_get_cookie(void)
 459{
 460        return 0;
 461}
 462
 463static inline void fsnotify_unmount_inodes(struct list_head *list)
 464{}
 465
 466#endif  /* CONFIG_FSNOTIFY */
 467
 468#endif  /* __KERNEL __ */
 469
 470#endif  /* __LINUX_FSNOTIFY_BACKEND_H */
 471
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