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/* SPDX-License-Identifier: GPL-2.0 */
* 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 <linux/atomic.h>
#include <linux/user_namespace.h>
#include <linux/refcount.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;
struct fsnotify_fname;
struct fsnotify_iter_info;
struct mem_cgroup;
* 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
* freeing_mark - called when a mark is being destroyed for some reason. The group
* MUST be holding a reference on each mark and that reference must be
* dropped in this function. inotify uses this function to send
* userspace messages that marks have been removed.
struct fsnotify_ops {
int (*handle_event)(struct fsnotify_group *group,
struct inode *inode,
u32 mask, const void *data, int data_type,
const unsigned char *file_name, u32 cookie,
struct fsnotify_iter_info *iter_info);
void (*free_group_priv)(struct fsnotify_group *group);
void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
void (*free_event)(struct fsnotify_event *event);
/* called on final put+free to free memory */
void (*free_mark)(struct fsnotify_mark *mark);
* 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 {
struct list_head list;
/* inode may ONLY be dereferenced during handle_event(). */
struct inode *inode; /* either the inode the event happened to or its parent */
u32 mask; /* the type of access, bitwise OR for FS_* event types */
* 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 {
const struct fsnotify_ops *ops; /* how this group handles things */
* 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.
refcount_t refcnt; /* things with interest in this group */
/* needed to send notification to userspace */
spinlock_t notification_lock; /* 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;
bool shutdown; /* group is being shut down, don't queue more events */
/* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
struct mutex mark_mutex; /* 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 */
atomic_t user_waits; /* Number of tasks waiting for user
* response */
struct list_head marks_list; /* all inode marks for this group */
struct fasync_struct *fsn_fa; /* async notification */
struct fsnotify_event *overflow_event; /* Event we queue when the
* notification list is too
* full */
struct mem_cgroup *memcg; /* memcg to charge allocations */
/* 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;
struct ucounts *ucounts;
} inotify_data;
struct fanotify_group_private_data {
/* allows a group to block waiting for a userspace response */
struct list_head access_list;
wait_queue_head_t access_waitq;
int f_flags;
unsigned int max_marks;
struct user_struct *user;
bool audit;
} fanotify_data;
#endif /* CONFIG_FANOTIFY */
/* when calling fsnotify tell it if the data is a path or inode */
enum fsnotify_obj_type {
static inline bool fsnotify_valid_obj_type(unsigned int type)
return (type < FSNOTIFY_OBJ_TYPE_COUNT);
struct fsnotify_iter_info {
struct fsnotify_mark *marks[FSNOTIFY_OBJ_TYPE_COUNT];
unsigned int report_mask;
int srcu_idx;
static inline bool fsnotify_iter_should_report_type(
struct fsnotify_iter_info *iter_info, int type)
return (iter_info->report_mask & (1U << type));
static inline void fsnotify_iter_set_report_type(
struct fsnotify_iter_info *iter_info, int type)
iter_info->report_mask |= (1U << type);
static inline void fsnotify_iter_set_report_type_mark(
struct fsnotify_iter_info *iter_info, int type,
struct fsnotify_mark *mark)
iter_info->marks[type] = mark;
iter_info->report_mask |= (1U << type);
static inline struct fsnotify_mark *fsnotify_iter_##name##_mark( \
struct fsnotify_iter_info *iter_info) \
{ \
return (iter_info->report_mask & FSNOTIFY_OBJ_TYPE_##NAME##_FL) ? \
iter_info->marks[FSNOTIFY_OBJ_TYPE_##NAME] : NULL; \
#define fsnotify_foreach_obj_type(type) \
for (type = 0; type < FSNOTIFY_OBJ_TYPE_COUNT; type++)
* fsnotify_connp_t is what we embed in objects which connector can be attached
* to. fsnotify_connp_t * is how we refer from connector back to object.
struct fsnotify_mark_connector;
typedef struct fsnotify_mark_connector __rcu *fsnotify_connp_t;
* Inode / vfsmount point to this structure which tracks all marks attached to
* the inode / vfsmount. The reference to inode / vfsmount is held by this
* structure. We destroy this structure when there are no more marks attached
* to it. The structure is protected by fsnotify_mark_srcu.
struct fsnotify_mark_connector {
spinlock_t lock;
unsigned int type; /* Type of object [lock] */
union {
/* Object pointer [lock] */
fsnotify_connp_t *obj;
/* Used listing heads to free after srcu period expires */
struct fsnotify_mark_connector *destroy_next;
struct hlist_head list;
* 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.
* Text in brackets is showing the lock(s) protecting modifications of a
* particular entry. obj_lock means either inode->i_lock or
* mnt->mnt_root->d_lock depending on the mark type.
struct fsnotify_mark {
/* Mask this mark is for [mark->lock, group->mark_mutex] */
__u32 mask;
/* We hold one for presence in g_list. Also one ref for each 'thing'
* in kernel that found and may be using this mark. */
refcount_t refcnt;
/* Group this mark is for. Set on mark creation, stable until last ref
* is dropped */
struct fsnotify_group *group;
/* List of marks by group->marks_list. Also reused for queueing
* mark into destroy_list when it's waiting for the end of SRCU period
* before it can be freed. [group->mark_mutex] */
struct list_head g_list;
/* Protects inode / mnt pointers, flags, masks */
spinlock_t lock;
/* List of marks for inode / vfsmount [connector->lock, mark ref] */
struct hlist_node obj_list;
/* Head of list of marks for an object [mark ref] */
struct fsnotify_mark_connector *connector;
/* Events types to ignore [mark->lock, group->mark_mutex] */
__u32 ignored_mask;
unsigned int flags; /* flags [mark->lock] */
/* called from the vfs helpers */
/* main fsnotify call to send events */
extern int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
const unsigned char *name, u32 cookie);
extern int __fsnotify_parent(const 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_flags(struct dentry *dentry)
* Serialisation of setting PARENT_WATCHED on the dentries is provided
* by d_lock. If inotify_inode_watched changes after we have taken
* d_lock, the following __fsnotify_update_child_dentry_flags call will
* find our entry, so it will spin until we complete here, and update
* us with the new state.
if (fsnotify_inode_watches_children(dentry->d_parent->d_inode))
/* called from fsnotify listeners, such as fanotify or dnotify */
/* create a new group */
extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
/* get reference to a group */
extern void fsnotify_get_group(struct fsnotify_group *group);
/* drop reference on a group from fsnotify_alloc_group */
extern void fsnotify_put_group(struct fsnotify_group *group);
/* group destruction begins, stop queuing new events */
extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);
/* destroy group */
extern void fsnotify_destroy_group(struct fsnotify_group *group);
/* fasync handler function */
extern int fsnotify_fasync(int fd, struct file *file, int on);
/* Free event from memory */
extern void fsnotify_destroy_event(struct fsnotify_group *group,
struct fsnotify_event *event);
/* attach the event to the group notification queue */
extern int fsnotify_add_event(struct fsnotify_group *group,
struct fsnotify_event *event,
int (*merge)(struct list_head *,
struct fsnotify_event *));
/* Queue overflow event to a notification group */
static inline void fsnotify_queue_overflow(struct fsnotify_group *group)
fsnotify_add_event(group, group->overflow_event, NULL);
/* 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_first_event(struct fsnotify_group *group);
/* return AND dequeue the first event on the notification queue */
extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);
/* functions used to manipulate the marks attached to inodes */
/* Get mask of events for a list of marks */
extern __u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn);
/* Calculate mask of events for a list of marks */
extern void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn);
extern void fsnotify_init_mark(struct fsnotify_mark *mark,
struct fsnotify_group *group);
/* Find mark belonging to given group in the list of marks */
extern struct fsnotify_mark *fsnotify_find_mark(fsnotify_connp_t *connp,
struct fsnotify_group *group);
/* attach the mark to the object */
extern int fsnotify_add_mark(struct fsnotify_mark *mark,
fsnotify_connp_t *connp, unsigned int type,
int allow_dups);
extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
fsnotify_connp_t *connp, unsigned int type,
int allow_dups);
/* attach the mark to the inode */
static inline int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
struct inode *inode,
int allow_dups)
return fsnotify_add_mark(mark, &inode->i_fsnotify_marks,
static inline int fsnotify_add_inode_mark_locked(struct fsnotify_mark *mark,
struct inode *inode,
int allow_dups)
return fsnotify_add_mark_locked(mark, &inode->i_fsnotify_marks,
/* given a group and a mark, flag mark to be freed when all references are dropped */
extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
struct fsnotify_group *group);
/* detach mark from inode / mount list, group list, drop inode reference */
extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
/* free mark */
extern void fsnotify_free_mark(struct fsnotify_mark *mark);
/* run all the marks in a group, and clear all of the marks attached to given object type */
extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group, unsigned int type);
/* run all the marks in a group, and clear all of the vfsmount marks */
static inline void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group)
fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_VFSMOUNT_FL);
/* run all the marks in a group, and clear all of the inode marks */
static inline void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_INODE_FL);
extern void fsnotify_get_mark(struct fsnotify_mark *mark);
extern void fsnotify_put_mark(struct fsnotify_mark *mark);
extern void fsnotify_unmount_inodes(struct super_block *sb);
extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);
/* put here because inotify does some weird stuff when destroying watches */
extern void fsnotify_init_event(struct fsnotify_event *event,
struct inode *to_tell, u32 mask);
static inline int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
const unsigned char *name, u32 cookie)
return 0;
static inline int __fsnotify_parent(const 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_flags(struct dentry *dentry)
static inline u32 fsnotify_get_cookie(void)
return 0;
static inline void fsnotify_unmount_inodes(struct super_block *sb)
#endif /* CONFIG_FSNOTIFY */
#endif /* __KERNEL __ */