/*
* Filesystem access notification for Linux
*
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
*/
#ifndef __LINUX_FSNOTIFY_BACKEND_H
#define __LINUX_FSNOTIFY_BACKEND_H
#ifdef __KERNEL__
#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_IN_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 */
struct fsnotify_group;
struct fsnotify_event;
/*
* Each group much define these ops. The fsnotify infrastructure will call
* these operations for each relevant group.
*
* 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
*/
struct fsnotify_ops {
int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
void (*free_group_priv)(struct fsnotify_group *group);
};
/*
* 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 {
/*
* global list of all groups receiving events from fsnotify.
* anchored by fsnotify_groups and protected by either fsnotify_grp_mutex
* or fsnotify_grp_srcu depending on write vs read.
*/
struct list_head group_list;
/*
* Defines all of the event types in which this group is interested.
* This mask is a bitwise OR of the FS_* events from above. Each time
* this mask changes for a group (if it changes) the correct functions
* must be called to update the global structures which indicate global
* interest in event types.
*/
__u32 mask;
/*
* 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 */
unsigned int group_num; /* simply prevents accidental group collision */
const struct fsnotify_ops *ops; /* how this group handles things */
/* prevents double list_del of group_list. protected by global fsnotify_gr_mutex */
bool on_group_list;
/* groups can define private fields here or use the void *private */
union {
void *private;
};
};
/*
* 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 {
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 */
#define FSNOTIFY_EVENT_NONE 0
#define FSNOTIFY_EVENT_PATH 1
#define FSNOTIFY_EVENT_INODE 2
#define FSNOTIFY_EVENT_FILE 3
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 */
};
#ifdef CONFIG_FSNOTIFY
/* called from the vfs helpers */
/* main fsnotify call to send events */
extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is);
/* called from fsnotify listeners, such as fanotify or dnotify */
/* must call when a group changes its ->mask */
extern void fsnotify_recalc_global_mask(void);
/* get a reference to an existing or create a new group */
extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num,
__u32 mask,
const struct fsnotify_ops *ops);
/* drop reference on a group from fsnotify_obtain_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 */
extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group,
struct fsnotify_event *event);
/* 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);
#else
static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is)
{}
#endif /* CONFIG_FSNOTIFY */
#endif /* __KERNEL __ */
#endif /* __LINUX_FSNOTIFY_BACKEND_H */
