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* Filesystem access notification for Linux
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <>
#ifdef __KERNEL__
#include <linux/idr.h> /* inotify uses this */
#include <linux/fs.h> /* struct inode */
#include <linux/list.h>
#include <linux/path.h> /* struct path */
#include <linux/spinlock.h>
#include <linux/types.h>
#include <asm/atomic.h>
* IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
* convert between them. dnotify only needs conversion at watch creation
* so no perf loss there. fanotify isn't defined yet, so it can use the
* wholes if it needs more events.
#define FS_ACCESS 0x00000001 /* File was accessed */
#define FS_MODIFY 0x00000002 /* File was modified */
#define FS_ATTRIB 0x00000004 /* Metadata changed */
#define FS_CLOSE_WRITE 0x00000008 /* Writtable file was closed */
#define FS_CLOSE_NOWRITE 0x00000010 /* Unwrittable file closed */
#define FS_OPEN 0x00000020 /* File was opened */
#define FS_MOVED_FROM 0x00000040 /* File was moved from X */
#define FS_MOVED_TO 0x00000080 /* File was moved to Y */
#define FS_CREATE 0x00000100 /* Subfile was created */
#define FS_DELETE 0x00000200 /* Subfile was deleted */
#define FS_DELETE_SELF 0x00000400 /* Self was deleted */
#define FS_MOVE_SELF 0x00000800 /* Self was moved */
#define FS_UNMOUNT 0x00002000 /* inode on umount fs */
#define FS_Q_OVERFLOW 0x00004000 /* Event queued overflowed */
#define FS_IN_IGNORED 0x00008000 /* last inotify event here */
#define FS_OPEN_PERM 0x00010000 /* open event in an permission hook */
#define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */
#define FS_EXCL_UNLINK 0x04000000 /* do not send events if object is unlinked */
#define FS_ISDIR 0x40000000 /* event occurred against dir */
#define FS_IN_ONESHOT 0x80000000 /* only send event once */
#define FS_DN_RENAME 0x10000000 /* file renamed */
#define FS_DN_MULTISHOT 0x20000000 /* dnotify multishot */
/* This inode cares about things that happen to its children. Always set for
* dnotify and inotify. */
#define FS_EVENT_ON_CHILD 0x08000000
/* This is a list of all events that may get sent to a parernt based on fs event
* happening to inodes inside that directory */
struct fsnotify_group;
struct fsnotify_event;
struct fsnotify_mark;
struct fsnotify_event_private_data;
* Each group much define these ops. The fsnotify infrastructure will call
* these operations for each relevant group.
* should_send_event - given a group, inode, and mask this function determines
* if the group is interested in this event.
* handle_event - main call for a group to handle an fs event
* free_group_priv - called when a group refcnt hits 0 to clean up the private union
* freeing-mark - this means that a mark has been flagged to die when everything
* finishes using it. The function is supplied with what must be a
* valid group and inode to use to clean up.
struct fsnotify_ops {
bool (*should_send_event)(struct fsnotify_group *group, struct inode *inode,
struct fsnotify_mark *inode_mark,
struct fsnotify_mark *vfsmount_mark,
__u32 mask, void *data, int data_type);
int (*handle_event)(struct fsnotify_group *group,
struct fsnotify_mark *inode_mark,
struct fsnotify_mark *vfsmount_mark,
struct fsnotify_event *event);
void (*free_group_priv)(struct fsnotify_group *group);
void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
void (*free_event_priv)(struct fsnotify_event_private_data *priv);
* A group is a "thing" that wants to receive notification about filesystem
* events. The mask holds the subset of event types this group cares about.
* refcnt on a group is up to the implementor and at any moment if it goes 0
* everything will be cleaned up.
struct fsnotify_group {
* How the refcnt is used is up to each group. When the refcnt hits 0
* fsnotify will clean up all of the resources associated with this group.
* As an example, the dnotify group will always have a refcnt=1 and that
* will never change. Inotify, on the other hand, has a group per
* inotify_init() and the refcnt will hit 0 only when that fd has been
* closed.
atomic_t refcnt; /* things with interest in this group */
const struct fsnotify_ops *ops; /* how this group handles things */
/* needed to send notification to userspace */
struct mutex notification_mutex; /* protect the notification_list */
struct list_head notification_list; /* list of event_holder this group needs to send to userspace */
wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */
unsigned int q_len; /* events on the queue */
unsigned int max_events; /* maximum events allowed on the list */
* Valid fsnotify group priorities. Events are send in order from highest
* priority to lowest priority. We default to the lowest priority.
#define FS_PRIO_0 0 /* normal notifiers, no permissions */
#define FS_PRIO_1 1 /* fanotify content based access control */
#define FS_PRIO_2 2 /* fanotify pre-content access */
unsigned int priority;
/* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
spinlock_t mark_lock; /* protect marks_list */
atomic_t num_marks; /* 1 for each mark and 1 for not being
* past the point of no return when freeing
* a group */
struct list_head marks_list; /* all inode marks for this group */
/* groups can define private fields here or use the void *private */
union {
void *private;
struct inotify_group_private_data {
spinlock_t idr_lock;
struct idr idr;
u32 last_wd;
struct fasync_struct *fa; /* async notification */
struct user_struct *user;
} inotify_data;
struct fanotify_group_private_data {
/* allows a group to block waiting for a userspace response */
struct mutex access_mutex;
struct list_head access_list;
wait_queue_head_t access_waitq;
atomic_t bypass_perm;
int f_flags;
unsigned int max_marks;
struct user_struct *user;
} fanotify_data;
#endif /* CONFIG_FANOTIFY */
* A single event can be queued in multiple group->notification_lists.
* each group->notification_list will point to an event_holder which in turns points
* to the actual event that needs to be sent to userspace.
* Seemed cheaper to create a refcnt'd event and a small holder for every group
* than create a different event for every group
struct fsnotify_event_holder {
struct fsnotify_event *event;
struct list_head event_list;
* Inotify needs to tack data onto an event. This struct lets us later find the
* correct private data of the correct group.
struct fsnotify_event_private_data {
struct fsnotify_group *group;
struct list_head event_list;
* all of the information about the original object we want to now send to
* a group. If you want to carry more info from the accessing task to the
* listener this structure is where you need to be adding fields.
struct fsnotify_event {
* If we create an event we are also likely going to need a holder
* to link to a group. So embed one holder in the event. Means only
* one allocation for the common case where we only have one group
struct fsnotify_event_holder holder;
spinlock_t lock; /* protection for the associated event_holder and private_list */
/* to_tell may ONLY be dereferenced during handle_event(). */
struct inode *to_tell; /* either the inode the event happened to or its parent */
* depending on the event type we should have either a path or inode
* We hold a reference on path, but NOT on inode. Since we have the ref on
* the path, it may be dereferenced at any point during this object's
* lifetime. That reference is dropped when this object's refcnt hits
* 0. If this event contains an inode instead of a path, the inode may
* ONLY be used during handle_event().
union {
struct path path;
struct inode *inode;
/* when calling fsnotify tell it if the data is a path or inode */
int data_type; /* which of the above union we have */
atomic_t refcnt; /* how many groups still are using/need to send this event */
__u32 mask; /* the type of access, bitwise OR for FS_* event types */
u32 sync_cookie; /* used to corrolate events, namely inotify mv events */
const unsigned char *file_name;
size_t name_len;
struct pid *tgid;
__u32 response; /* userspace answer to question */
struct list_head private_data_list; /* groups can store private data here */
* Inode specific fields in an fsnotify_mark
struct fsnotify_inode_mark {
struct inode *inode; /* inode this mark is associated with */
struct hlist_node i_list; /* list of marks by inode->i_fsnotify_marks */
struct list_head free_i_list; /* tmp list used when freeing this mark */
* Mount point specific fields in an fsnotify_mark
struct fsnotify_vfsmount_mark {
struct vfsmount *mnt; /* vfsmount this mark is associated with */
struct hlist_node m_list; /* list of marks by inode->i_fsnotify_marks */
struct list_head free_m_list; /* tmp list used when freeing this mark */
* a mark is simply an object attached to an in core inode which allows an
* fsnotify listener to indicate they are either no longer interested in events
* of a type matching mask or only interested in those events.
* these are flushed when an inode is evicted from core and may be flushed
* when the inode is modified (as seen by fsnotify_access). Some fsnotify users
* (such as dnotify) will flush these when the open fd is closed and not at
* inode eviction or modification.
struct fsnotify_mark {
__u32 mask; /* mask this mark is for */
/* we hold ref for each i_list and g_list. also one ref for each 'thing'
* in kernel that found and may be using this mark. */
atomic_t refcnt; /* active things looking at this mark */
struct fsnotify_group *group; /* group this mark is for */
struct list_head g_list; /* list of marks by group->i_fsnotify_marks */
spinlock_t lock; /* protect group and inode */
union {
struct fsnotify_inode_mark i;
struct fsnotify_vfsmount_mark m;
struct list_head free_g_list; /* tmp list used when freeing this mark */
__u32 ignored_mask; /* events types to ignore */
unsigned int flags; /* vfsmount or inode mark? */
struct list_head destroy_list;
void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
/* called from the vfs helpers */
/* main fsnotify call to send events */
extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
const unsigned char *name, u32 cookie);
extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
extern void __fsnotify_inode_delete(struct inode *inode);
extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
extern u32 fsnotify_get_cookie(void);
static inline int fsnotify_inode_watches_children(struct inode *inode)
/* FS_EVENT_ON_CHILD is set if the inode may care */
if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
return 0;
/* this inode might care about child events, does it care about the
* specific set of events that can happen on a child? */
return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
* Update the dentry with a flag indicating the interest of its parent to receive
* filesystem events when those events happens to this dentry->d_inode.
static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
struct dentry *parent;
parent = dentry->d_parent;
if (parent->d_inode && fsnotify_inode_watches_children(parent->d_inode))
* fsnotify_d_instantiate - instantiate a dentry for inode
* Called with dcache_lock held.
static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
if (!inode)
/* called from fsnotify listeners, such as fanotify or dnotify */
/* get a reference to an existing or create a new group */
extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
/* drop reference on a group from fsnotify_alloc_group */
extern void fsnotify_put_group(struct fsnotify_group *group);
/* take a reference to an event */
extern void fsnotify_get_event(struct fsnotify_event *event);
extern void fsnotify_put_event(struct fsnotify_event *event);
/* find private data previously attached to an event and unlink it */
extern struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group,
struct fsnotify_event *event);
/* attach the event to the group notification queue */
extern struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
struct fsnotify_event *event,
struct fsnotify_event_private_data *priv,
struct fsnotify_event *(*merge)(struct list_head *,
struct fsnotify_event *));
/* true if the group notification queue is empty */
extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
/* return, but do not dequeue the first event on the notification queue */
extern struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group);
/* return AND dequeue the first event on the notification queue */
extern struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group);
/* functions used to manipulate the marks attached to inodes */
/* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
/* run all marks associated with an inode and update inode->i_fsnotify_mask */
extern void fsnotify_recalc_inode_mask(struct inode *inode);
extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
/* find (and take a reference) to a mark associated with group and inode */
extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
/* find (and take a reference) to a mark associated with group and vfsmount */
extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
/* copy the values from old into new */
extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
/* set the ignored_mask of a mark */
extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
/* set the mask of a mark (might pin the object into memory */
extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
/* attach the mark to both the group and the inode */
extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
struct inode *inode, struct vfsmount *mnt, int allow_dups);
/* given a mark, flag it to be freed when all references are dropped */
extern void fsnotify_destroy_mark(struct fsnotify_mark *mark);
/* run all the marks in a group, and clear all of the vfsmount marks */
extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
/* run all the marks in a group, and clear all of the inode marks */
extern void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group);
/* run all the marks in a group, and clear all of the marks where mark->flags & flags is true*/
extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, unsigned int flags);
/* run all the marks in a group, and flag them to be freed */
extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group);
extern void fsnotify_get_mark(struct fsnotify_mark *mark);
extern void fsnotify_put_mark(struct fsnotify_mark *mark);
extern void fsnotify_unmount_inodes(struct list_head *list);
/* put here because inotify does some weird stuff when destroying watches */
extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
void *data, int data_is,
const unsigned char *name,
u32 cookie, gfp_t gfp);
/* fanotify likes to change events after they are on lists... */
extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
struct fsnotify_event *new_event);
static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
const unsigned char *name, u32 cookie)
return 0;
static inline int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
return 0;
static inline void __fsnotify_inode_delete(struct inode *inode)
static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
static inline void __fsnotify_update_dcache_flags(struct dentry *dentry)
static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
static inline u32 fsnotify_get_cookie(void)
return 0;
static inline void fsnotify_unmount_inodes(struct list_head *list)
#endif /* CONFIG_FSNOTIFY */
#endif /* __KERNEL __ */